Geology and Mineral Resources of the

Hailey I°x2° Quadrangle and the

Western Part of the Idaho Falls

I°x2° Quadrangle, Idaho

* , ,

» Prepare/ in *VG}'erati(>ttaw$i the faho Geological Survey 

Idaffo Stat^Universitv, 'and th&Jr "ni\'ersity of Idaho

U.S. GEOLOGICAL SURVEY BULLETIN~2064-rA-R
Cover. Looking south at the Mackay stock, southwest of Mackay, Idaho. The Eocene 

Mackay stock (center of photograph; is made up of granite, quartz monzonite, leucogranite porphyry, and felsic dike rocks. It is flanked by Paleozoic sedimentary rocks, including 

the Lower Mississippian McGowan Creek Formation and the Upper Mississippian White 

Knob Limestone. The Mackay mineralized area includes polymetallic skarn deposits. 

Photograph by Ronald G.. Worl, 1987.
Geology and Mineral Resources of the 

Hailey I°x2° Quadrangle and the 

Western Part of the Idaho Falls 

I°x2° Quadrangle, Idaho

Edited by Ronald G. Worl, Paul K. Link, Gary R. Winkler, and Kathleen M. Johnson

U.S. GEOLOGICAL SURVEY BULLETIN 2064

Prepared in cooperation with the Idaho Geological Survey, 

Idaho State University, and the University of Idaho

Volume 1 (chapters A-R) contains regional information and 

a discussion of mineral deposit types hosted by sedimentary 

rocks. These chapters are issued together and are not 

available separately

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

Published in the Central Region, Denver, Colorado

Manuscript approved for publication November 4, 1993

Edited by Judith Stoeser

Graphic design by Patricia L. Wilber

Cartography by David M. Caster, Joseph A. Romero,

and JRG Computer Graphics 

Tables prepared by Judith Stoeser 

Photocomposition by Carol Quesenberry 

Cover design by Art Isom

For sale by U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

Library of Congress Cataloging in Publication Data

Geology and mineral resources of the Hailey 1 °x2° quadrangle and the western part of the 

Idaho Falls I°x2° quadrangle, Idaho / edited by Ronald G. Worl... [et al.]. 

p. cm. (U.S. Geological Survey bulletin ; 2064)

"Prepared in cooperation with the Idaho Geological Survey, Idaho State University, 

and the University of Idaho."

Includes bibliographical references.

Supt. of Docs, no.: I 19.3:2064 A-R

1. Geology Idaho. 2. Mines and mineral resources Idaho. 

I. Worl, Ronald G. II. Idaho Geological Survey. III. Idaho State University. 

IV. University of Idaho. V. Series. 

QE75.B9 no. 2064 

[QE103] 

557.3 s dc20

[557.96] 93^4574

CIP
PREFACE

The U.S. Geological Survey Conterminous United States Mineral Assessment Program (CUSMAP) was initiated in 1977 to provide up-to-date assessments of the mineral 

potential of the Nation's public lands in the conterminous United States. A major objective 

of CUSMAP is the development and application of new concepts for the identification of 

mineral resource potential in heretofore untested but possibly mineralized areas. CUSMAP 

is providing new information on present and potential mineral supplies and is producing 

important data to guide national mineral policy, land-use planning by Federal, State, and 

local governments, and mineral exploration by the private sector.

This CUSMAP project was a cooperative venture with the Idaho Geological Survey 

and the Departments of Geology at Idaho State University and the University of Idaho. 

Project personnel interacted closely with concurrent research investigations in the area supported by National Science Foundation Grant RUIEAR 86-18629 and an Idaho State 

Board of Education Economic Incentive Grant to Idaho State University. Project participants came from several branches of the U.S. Geological Survey, Idaho Geological Survey, 

Idaho State University, University of Idaho, Boise State University, Bureau of Land Management, U.S. Forest Service, U.S. Bureau of Mines, Rice University, and Western Washington University.

Wayne Hall and Thor Kiilsgaard proposed the Hailey I°x2° quadrangle as a CUSMAP project and as the founding fathers were sources of guidance and inspiration for all 

who served on the project. Wayne spent many years prior to this CUSMAP project developing an understanding of the black shale terrane and associated mineral deposits (Hall,

1985). His work laid the foundation for studies in the black shale terrane, and his concepts 

on the genesis of the mineral deposits provided the guidance for many of the studies 

reported in volume 1 of this bulletin. Thor has actively studied the mineral deposits of central Idaho for many years starting during a period when many of the mines were still operational (Anderson and others, 1950). His first-hand knowledge and understanding of the 

important ore deposits in the region proved invaluable to the success of this project. In 

recent years, Thor has been recognized as an expert on the Trans-Challis fault system and 

on precious-metal deposits hosted by rocks of the Idaho batholith (Kiilsgaard and others,

1986). His work has provided new insight into this important class of mineral deposits and 

provided the foundation for many of the studies that will be reported in volume 2 of this 

bulletin.

Those who served include:

Ron Worl Earl Bennett Thor Kiilsgaard 

Paul Link Reed Lewis Brian Mahoney 

Sandy Soulliere Betty Skipp Kate Johnson 

Wayne Hall Gary Winkler Falma Moye 

Bill Hackett Cole Smith Anna Wilson 

Jim Erdman Dean Kleinkopf Keegan Schmidt 

Rick Sanford Nancy Milton Scott Southworth 

Larry Snee Brad Burton Larry Snider 

Barbara Eiswerth Dave Stewart Shelly Whitman 

Larry Dee Joe Wooden Tony Gibbons
PREFACE

Dan Bruner Ed Ratchford Craig Wavra 

Ryan McDermott J.P. O'Brien John Montgomery 

Micheline Doyle Norio Honjo Bill Leeman 

Chris Clark Jeff Jones Bruce Doe 

Mark Stowman Betty Bailey Bob Criss 

Flint Hall Ann McCafferty Spencer Wood 

Bob Darling John Blakley Helen Whitney 

Marty Power Brenan Jordan Victoria Mitchell 

Walt Baweic Dick Hardyman Kevin Kunkel 

John Finnegsmeir Will Park Darlene Batatian 

Audrey Huerta 

And companions:

Blue Minos Nooky 

Earl's Yorkies Joe Gretchen 

Annie Brittany Mollie 

Zonker Minnie Moore Mutts Basho Kitty 

Investigations of the Hailey CUSMAP project expanded on previous mineral resource 

assessments of nearby areas in Idaho and Montana. Studies in the Hailey CUSMAP project 

began in 1986 and fieldwork was completed in 1989. Preliminary results were presented in 

May 1988 during oral and poster sessions at the 41st Annual Meeting of the Rocky Mountain Section, Geological Society of America, Sun Valley, Idaho (Link and Hackett, 1988), 

and on December 7, 1989, at the Northwest Mining Association 95th Annual Convention 

and Trade Show in Spokane, Washington (Winkler and others, 1989). A preliminary geologic map of the Hailey quadrangle was jointly prepared and released by the U.S. Geological Survey and the Idaho Geological Survey (Worl and others, 1991), and an aeromagnetic 

anomaly map of the Hailey quadrangle and the western part of the Idaho Falls quadrangle 

was released by the U.S. Geological Survey (McCafferty and Abrams, 1991).

REFERENCES CITED

Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 1950, Detailed geology of certain areas in

the Mineral Hill and Warm Springs mining districts, Blaine County, Idaho: Idaho Bureau of

Mines and Geology Pamphlet 90, 73 p. 

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle and upper Paleozoic rocks of the

black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology and

mineral deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin

1658-J, p. 117-132. 

Kiilsgaard, T.H., Fisher, F.S., and Bennett, E.H., 1986, The trans-Challis fault system and associated

precious metal deposits, Idaho: Economic Geology and the Bulletin of the Society of Economic

Geologists, v. 81, no. 3, p. 721-724. 

Link, P.K., and Hackett, W.R., eds., 1988, Guidebook to the geology of central and southern Idaho:

Idaho Geological Survey Bulletin 27, 319 p. 

McCafferty, A.E., and Abrams, G.A., 1991, Aeromagnetic anomaly map of the Hailey and western

part of the Idaho Falls I°x2° quadrangle, Idaho: U.S. Geological Survey Miscellaneous Field

Studies Map MF-2160-A, scale 1:250,000. 

Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 1989, Geology and mineral

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey

Open-File Report 89-639, 140 p.
CONTENTS

A. Geology and Mineral Deposits of the Hailey I°x2° Quadrangle and the Western Part of 

the Idaho Falls I°x2° Quadrangle, South-Central Idaho An Overview

By Ronald G. Worl and Kathleen M. Johnson

B. Structural Framework of Mineral Deposits Hosted by Paleozoic Rocks in the 

Northeastern Part of the Hailey I°x2° Quadrangle, South-Central Idaho

By David W. Rodgers, Paul Karl Link, and Audrey D. Huerta

C. Stratigraphic Setting of Sediment-Hosted Mineral Deposits in the Eastern Part of the 

Hailey I°x2° Quadrangle and Part of the Southern Part of the Challis I°x2° Quadrangle, 

South-Central Idaho

By Paul Karl Link, J. Brian Mahoney, Daniel J. Bruner, L. Darlene Batatian, Eric Wilson, 

and Felicie J.C. Williams

D. Mineral Deposits of the Muldoon-Star Hope Area, Southern Pioneer Mountains, SouthCentral Idaho

By Gary R. Winkler, Kevin W. Kunkel, Richard F. Sanford, Ronald G. Worl, and Falma 

J. Moye

E. Structural and Stratigraphic Setting of the Triumph Stratiform Zinc-Lead-Silver Deposit, 

Devonian Milligen Formation, Central Idaho

By Robert J. W. Turner and Brace R. Otto

F. Structural Setting of Ore Deposits in the Lake Creek Mineralized Area, Blaine County, 

South-Central Idaho

By Bradford R. Burton and Paul Karl Link

G. Geologic Setting of Mineral Deposits in the Washington Basin Area, Custer County, 

South-Central Idaho

By J. Brian Mahoney

H. Mineral Deposits at Leadbelt, Lava Creek Mining District, South-Central Idaho 

By Sandra J. Soulliere, Anna B. Wilson, and Betty Skipp

I. Mineral Deposits of the Mackay and Copper Basin Mineralized Areas, White Knob 

Mountains, South-Central Idaho

By Anna B. Wilson, Sandra J. Soulliere, and Betty Skipp

J. Jasperoid-Associated Precious-Metal Deposits in the Northwestern Part of the Idaho Falls 

I°x2° Quadrangle, South-Central Idaho

By Sandra J. Soulliere, Anna B. Wilson, and Betty Skipp
CONTENTS

K. Tertiary Sedimentary Rocks of the Payette Formation (Miocene) and the Lower Part 

(Miocene and Pliocene) of the Idaho Group, Hailey I°x2° Quadrangle and Vicinity, 

West-Central Idaho

By Anthony B. Gibbons

L. Interpretation of the Regional Geochemistry of the Hailey I°x2° Quadrangle, SouthCentral Idaho

By Cole L. Smith

M. Lead-Isotope Characteristics of Ore Systems in Central Idaho 

By Brace R. Doe and Richard F. Sanford

N. Sources of Lead in Ore Deposits of Central Idaho 

By Richard F. Sanford and Joseph L. Wooden

O. Geochemical Evidence for Epithermal Metallization in Mississippian Turbidites of the 

McGowan Creek Formation, Lava Creek Mining District, South-Central Idaho

By James A. Erdman, Falma J. Moye, Betty Skipp, and Paul K. Theobald

P. Petrogenesis of Silver-Lead-Zinc Veins on the Eastern Margin of the Idaho Batholith in 

the Carrietown Mineralized Area, Blaine and Camas Counties, South-Central Idaho

By Robert S. Darling, Harry W. Campbell, and Paul Karl Link

Q. Metamorphism and Deformation on the Eastern Margin of the Idaho Batholith, Blaine 

and Camas Counties, South-Central Idaho

By Shelly K. Whitman

R. Regional Geophysical Studies Applied to Mineral Resource Assessment of the Hailey 

I°x2° Quadrangle and the Western Part of the Idaho Falls I°x2° Quadrangle, SouthCentral Idaho

By M. Dean Kleinkopf, Anne E. McCafferty, and Gerda A. Abrams

METRIC CONVERSION FACTORS

Multiply By To obtain

Miles 1.609 Kilometers

Feet 0.3048 Meters

Inches 2.54 Centimeters

Tons 1.016 Metric tons

Short tons 0.907 Metric tons

Troy ounces 31.103 Grams

Ounces 28.35 Grams
Geology and Mineral Deposits of the Hailey I°x2° 

Quadrangle and the Western Part of the Idaho Falls 

I°x2° Quadrangle, South-Central Idaho An Overview

By Ronald G. Worl and Kathleen M. Johnson

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-A

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Summary............................................................................................................................... Al

Introduction........................................................................................................................... 1

Geologic Terranes................................................................................................................. 1

Structural Features................................................................................................................ 2

Mineralized Areas................................................................................................................. 2

Mineral Deposit Types ......................................................................................................... 2

Tungsten Stockworks and Veins .................................................................................. 9

Tertiary Molybdenum Stockworks............................................................................... 10

Tertiary Polymetallic Veins.......................................................................................... 11

Epithermal Precious-Metal Veins................................................................................. 11

Tertiary Polymetallic Replacements............................................................................. 12

Copper Skarn................................................................................................................ 13

Cretaceous Molybdenum Stockworks.......................................................................... 14

Polymetallic Quartz Veins and Lodes .......................................................................... 14

Cretaceous Polymetallic Veins..................................................................................... 16

Cretaceous Polymetallic Replacements........................................................................ 17

Metallogenic Events............................................................................................................. 17

Paleozoic Events........................................................................................................... 18

Cretaceous Events......................................................................................................... 19

Eocene Events............................................................................................................... 19

Miocene and Younger Events....................................................................................... 19

Pleistocene to Holocene Events.................................................................................... 19

References Cited................................................................................................................... 20

PLATE

[Plate is in pocket]

1. Map showing geologic terranes of the Hailey I°x2° quadrangle and the western part of the 

Idaho Falls I°x2° quadrangle, south-central Idaho.

FIGURE

1. Map showing generalized geologic terranes and location of mineralized areas in the Hailey I°x2° quadrangle

and the western part of the Idaho Falls I°x2° quadrangle, south-central Idaho............................................................ A3

TABLES

1. Mineralized areas in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle............. A4

2. Mineral deposit types thought to be present in the Hailey I°x2° quadrangle and the western part of the

Idaho Falls I°x2° quadrangle......................................................................................................................................... 9

3. Metallogenic events in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle......... 18
Geology and Mineral Deposits of the Hailey I°x2° Quadrangle

and the Western Part of the Idaho Falls I°x2° Quadrangle,

South-Central Idaho An Overview

By Ronald G. Worl 1 and Kathleen M. Johnson1

SUMMARY

The area of the Hailey 1 °x2° quadrangle and the western 

part of the Idaho Falls I°x2° quadrangle, Idaho, is characterized by a wide variety of geologic terranes and mineral 

deposit types. The eastern part of the area is a region of folded 

and faulted Paleozoic sedimentary rocks, covered in part by 

rocks of the Eocene Challis volcanic field. Much of the western part is underlain by the southern part of the Atlanta lobe 

of the Cretaceous Idaho batholith. Hypabyssal to epizonal 

bodies of Eocene intrusive rocks crop out throughout the 

area. Miocene and younger volcanic and sedimentary rocks 

cover much of the southern part of the area, and large areas 

of Quaternary sedimentary rocks are common.

The Paleozoic sedimentary rocks are complexly folded 

and faulted along major low-angle thrust faults, detachment 

faults, and high-angle normal faults. Wide shear zones are 

common in Cretaceous and Eocene plutonic rocks.

Mineral deposits of numerous types are hosted in the 

diverse geologic terranes of the area. Important deposit types 

include polymetallic quartz veins and lodes, polymetallic 

veins, polymetallic replacements, epithermal precious-metal 

veins, copper skarn, tungsten skarn, and gold placers. Significant amounts of silver, gold, lead, copper, zinc, tungsten, 

and antimony have been produced from these deposits. 

Other deposit types are prospective for a variety of elements.

Forty-six distinct mineralized areas have been defined 

in the Hailey quadrangle and the western part of the Idaho 

Falls quadrangle. These areas are based on geographic groupings of mineral deposits of similar geologic characteristics, 

origin, or age. They include large areas of past mineral production and areas prospective for a variety of deposit types.

At least five metallogenic events are represented in the 

mineral deposits of the Hailey quadrangle and the western 

part of the Idaho Falls quadrangle. The earliest event was 

syngenetic deposition of metals in oxygen-depleted basins 

during much of Paleozoic time, especially during the Middle

'U.S. Geological Survey, W. 904 Riverside Avenue, Spokane, Washington 99201.

to Late Devonian. Igneous and hydrothermal activity related 

to formation of the Cretaceous and Paleocene intrusive rocks 

of the Idaho batholith and its satellite plutons was the driving 

force for the second metallogenic event. The third event was 

associated with regional extensional tectonism and widespread plutonic and volcanic activity that started about 50 

Ma. Miocene to Recent hydrothermal activity and the movement of groundwater constituted the fourth event. The most 

recent metallogenic event was the mechanical concentration 

of placer deposits during Quaternary time.

INTRODUCTION

Mineral deposits are common in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle (lat 43°-44° N., long 113°15'-116° W.) and were a major 

factor in the settlement and development of the area. Deposits containing base-, precious-, and ferrous-metals are hosted 

in a variety of geologic terranes and were formed during a 

series of metallogenic events. This chapter summarizes the 

geologic terranes, mineralized areas, mineral deposit types, 

and metallogenic history of the quadrangles and is meant to 

provide background information for the more detailed 

reports that follow.

GEOLOGIC TERRANES

Mineral resource information in this chapter, as well as 

in those that follow, includes descriptions of geologic settings of mineral deposit types in terms of geologic terranes, 

interaction of geologic terranes, and major structural features. For this project, a geologic terrane was defined as the 

area in which a particular assemblage of rock types crops out.

The study area is underlain by six major terranes: 

Middle Proterozoic metamorphic rocks, Paleozoic sedimentary rocks, Cretaceous intrusive rocks, Tertiary intrusive 

rocks, Tertiary volcanic rocks, and Quaternary deposits (pi. 

1). These terranes were originally defined by Worl and 

others (1991).

Al
A2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Middle Proterozoic metamorphic rocks are present in 

the Pioneer Mountains core complex and are mainly layered 

quartzo-feldspathic gneiss, quartzitic gneiss, mafic gneiss, 

and calc-silicate marble. Paleozoic sedimentary rocks, which 

range in age from Late Cambrian to Early Permian, constitute four terranes, each characterized by a particular rock 

assemblage: quartzite, carbonate rock, flysch, or black shale. 

Rocks of the quartzite terrane are of limited extent, present 

mainly as narrow lenses in other terranes. Rocks of the carbonate, flysch, and black shale terranes underlie extensive 

areas in the eastern part of the study area, in roughly parallel 

north-northwest-trending belts (pi. 1).

Cretaceous intrusive rocks constitute three terranes, 

each characterized by a particular rock type: granite, granodiorite, or tonalite. Rocks in these terranes are part of the 

Idaho batholith and satellitic plutons. The Idaho batholith 

underlies much of the western part of the area, and its eastern 

edge intrudes Paleozoic black shale terrane. Tertiary intrusive rocks constitute three terranes: rhyolite, granite, and 

diorite complex. Tertiary intrusive rocks are present 

throughout the area but are most prevalent in the western 

part. They intrude all older rock types, either as large plutons 

and batholiths, where they intrude Cretaceous intrusive 

rocks, or as smaller plutonic or hypabyssal bodies, where 

they intrude Paleozoic sedimentary rocks.

Tertiary volcanic rocks constitute two major terranes: 

Eocene and Miocene-Pliocene. The Eocene volcanic rock 

terrane consists of rocks of the Challis Volcanic Group in 

large tracts in the eastern part of the area, where rocks of the 

terrane overlie rocks of the Paleozoic sedimentary rock terranes. The Challis Volcanic Group is principally intermediate to mafic potassium-rich lava flow rocks and lesser 

amounts of volcaniclastic material. Locally the rocks are 

predominantly rhyolitic lava flow rocks and ash-flow tuff or 

volcaniclastic sedimentary rocks.

The Miocene-Pliocene volcanic rock terrane consists of 

the Idavada Volcanics, Banbury Basalt, and rocks of the 

Magic Mountain eruptive center and underlies much of the 

southern part of the area along the north edge of the Snake 

River Plain. The terrane is predominantly basaltic to rhyolitic lava flow rocks and tuff, rhyolite domes, and intercalated sedimentary rocks. The Quaternary deposits terrane 

includes lava flow rocks and intercalated sedimentary rocks, 

terrace gravels, glacial deposits, and stream gravels.

STRUCTURAL FEATURES

The structural setting of the Hailey quadrangle and the 

western part of the Idaho Falls quadrangle was developed 

during several events including the late Paleozoic Antler 

orogeny, the Mesozoic Cordilleran orogeny, Paleogene 

extensional tectonism, and Neogene basin and range extension and development of the Snake River Plain (Rodgers 

and others, this volume). The Antler orogeny is recorded in 

this area only in the stratigraphic record. Features of the

Cordilleran orogeny include a major fold and thrust belt in 

the Paleozoic sedimentary rocks in the eastern part of the 

area. Several thrust plates formed from east-directed compression during the Cordilleran orogeny (Skipp, 1987). In 

the black shale belt these thrust plates were the loci of Cretaceous-Paleocene mineralization. Ductile deformation and 

metamorphism accompanied this event and are best 

recorded in rocks of the Pioneer Mountains core complex.

Paleogene extension was accompanied by the Eocene 

Challis magmatic episode (Moye, in press). The northeasttrending Trans-Challis fault system, exposed in the northwestern part of the study area, is a prominent regional feature 

that localized Eocene plutonic and volcanic activity. Numerous northeast-, north-, and northwest-trending brittle fracture 

systems developed during this episode and helped to localize 

Tertiary mineralization. Detachments in the Pioneer Mountains core complex and low-angle normal faults in the black 

shale terrane developed during Paleogene extension. Paleogene structures in some areas represent reactivation of structures formed during the Cordilleran orogeny (Rodgers and 

others, this volume).

Neogene basin and range extension coincided with volcanism on the Snake River Plain. Many Neogene faults are 

present in the study area, and, although their trends are 

diverse, the most obvious are of northwest orientation. Several of the major faults host hot springs, and in some areas 

they host precious-metal-bearing hot-springs deposits. 

Faulting continues to the present along some of the rangefront faults in the region, most notably the range-bounding 

fault on the west side of the Lost River Range.

MINERALIZED AREAS

Mineralized areas in the Hailey quadangle and the western part of the Idaho Falls quadrangle have been defined on 

the basis of geologic characteristics (fig. 1, table 1). These 

mineralized areas are geographic groupings of mineral 

deposits or terranes of similar character and do not represent 

mining districts or other political entities. The mineralized 

areas were defined primarily for descriptive purposes and to 

assist in the integration of resource, geochemical, and geophysical data for assessment of potential for undiscovered 

resources. Table 1 contains a summary of the geologic terranes, major structural features, and the descriptive mineral 

deposit types thought to be present in each mineralized area. 

An interpretation of the regional geochemistry of the mineralized areas in the Hailey quadrangle is provided in Smith 

(this volume).

MINERAL DEPOSIT TYPES

Mineral deposit types described in this section are 

based on characteristics of known and inferred deposits 

within or close to the study area. The descriptions of the
44°00'

0 10 20 30 KILOMETERS

EXPLANATION

Quaternary terrane 

Tertiary volcanic rock terranes 

Miocene-Pliocene terrane

Eocene terrane

Tertiary intrusive rock terrane 

Cretaceous intrusive rock terrane

Paleozoic sedimentary rock terranes 

Black shale terraneFlysch terrane 

Carbonate terrane

Middle Proterozoic

metamorphic rock terrane

Contact Major fault 

Mineralized Area

1. Quartzburg

2. Idaho City3. Swanholm

4. Black Warrior

5. Atlanta6. Rocky Bar

7. Neal

8. Pine9. Volcano

10. Marshall Peak

11. Vienna

12. Rooks Creek stock13. Deer Creek stock14. Croesus stock

15. Hailey gold belt

16. Soldier17. Middle Fork Boise River

18. Corral Creek19. Sawtooth

20. Smoky Mountains21. Carrietown

MINERALIZED AREAS

22. Bullion23. Bunker Hill24. Minnie Moore25. Bellevue26. Wood River27. Triumph28. East Fork Wood River

29. Lake Creek 30. Galena 

31. Washington Basin 32. Baker Creek 

33. Boulder Basin 34. East Fork Salmon 

35. Summit

36. Muldoon 37. Lead Belt 38. Lava Creek 39. Champagne Creek 

40. Lake Creek stock 41. Copper Basin 42. Mackay

43. Burma Road 44. Pioneer 

45. Magic 

46. Elk Creek

O§atn70 

>a

ow po <1

Figure 1. Map showing generalized geologic terranes and location of mineralized areas in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, 

south-central Idaho.
Table 1. Mineralized areas in the Hailey I°x2° quadrangle and the western part of the Idaho Falls 1 °x2° quadrangle, south-central Idaho. 

[Shown by number in figure 1]

Mineralized

No. area

1 Quartzburg

2 Idaho City

3 Swanholm

4 Black

Warrior

5 Atlanta

6 Rocky Bar

7 Neal

Mineral deposit types having

Geologic terrane(s)

Cretaceous granite, Tertiarydiorite complex, Quaternary

cover rock

Cretaceous granodiorite, Tertiary

diorite complex, MiocenePliocene volcanic rock,

Quaternary cover rock

Cretaceous granite, Cretaceous

granodiorite

Cretaceous granite, Cretaceous

granodiorite, Tertiary granite

Cretaceous granodiorite,

Cretaceous granite

Cretaceous granodiorite

Cretaceous granodiorite, Tertiary

rhyolite

Major structural features

Trans-Challis fault systemTrans-Challis fault systemNorthwest-trendingfracture systems

North- to northwesttrending fracture systems

Intersection of regionalnorthwest- and northeasttrending fracture systems

Intersection of regional

northwest- and northeasttrending fracture systems

Northeast-trendingfracture systems

significant production

Tertiary epithermal

precious-metal veins,

Quaternary gold placersTertiary epithermal

precious-metal veins,polymetallic quartz

veins and lodes,

Quaternary gold placers

None

Polymetallic quartzveins and lodes (gold

and base-metalvarieties)

Polymetallic quartz

veins and lodes (goldvariety)

Polymetallic quartz

veins and lodes (goldvariety)

Precious-metal veins

Other mineral

deposit types

Tertiary polymetallic

veins, polymetallic quartz

veins and lodes

NonePolymetallic quartz veinsand lodes (stibnite rich)

Tertiary epithermal

precious-metal veins,

Tertiary polymetallic

veins

None

Tertiary epithermalprecious-metal veins,

Tertiary polymetallicveinsNone

Comments

NoneNoneNoneNone

Polymetallic quartz veins and

lodes may have importantTertiary component. Thesedeposits are target ofcontinuing (1991) exploration

Polymetallic quartz veins and

lodes are target of continuing(1991) exploration

Veins are either polymetallic

quartz veins and lodes (gold

References

Kiilsgaard, Scanlan,

and Stewart (inpress).

Kiilsgaard, Scanlan,and Stewart (in

press).Popoff(1953).

Kiilsgaard andothers (1970),

Kiilsgaard andothers (1983).Kiilsgaard andBacon (in press).

Bennett (in press).

Bennett (in press).

A4 GEOLOG A

^ZO1tn

po

r70tn

C/3Opo

ntn

O

HX tn

I;>Ctn

;>zOBnc o

r

V)

O

>

8 Pine Cretaceous granite, Tertiary

diorite complex, Tertiary granite

9 Volcano Tertiary rhyolite, Tertiary granite, 

Cretaceous granodiorite, 

Cretaceous granite

Northeast- and northwest- Base- and precioustrending fracture systems metal veins

East- and northeasttrending fracture systems Polymetallic quartz veins and lodes (gold 

variety)

None

None

variety) or Tertiary 

epithermal precious-metal veins. Continuing exploration 

(1991) for precious metalsVeins are either polymetallic quartz veins and lodes or 

Tertiary polymetallic veins

Polymetallic quartz veins and lodes may have Tertiary 

component

Bennett (in press).

Bennett (in press).

ao

GC/3
10 Marshall 

Peak

11 Vienna

Cretaceous granodiorite

12

13

Rooks Creek 

stock

Deer Creek 

stock

14 Croesus 

stock

15 Haileygold 

belt

16 Soldier

17 Middle Fork 

Boise River

18 Corral Creek

19 Sawtooth

Cretaceous granodiorite

Cretaceous granodiorite, 

Cretaceous tonalite, Paleozoic 

black shale, Tertiary rhyolite

Cretaceous tonalite, Paleozoic 

black shale

Cretaceous tonalite, Paleozoic 

black shale

Cretaceous tonalite, MiocenePliocene volcanic rock

Cretaceous granodiorite, 

Cretaceous tonalite, Tertiary 

diorite complex, Eocene volcanic 

rock, Miocene-Pliocene volcanic 

rock

Tertiary granite, Tertiary diorite 

complex, Cretaceous granodiorite

Tertiary rhyolite, Tertiary granite, 

Tertiary diorite complex, 

Cretaceous granite, Cretaceous 

granodiorite

Tertiary granite, Cretaceous 

granite, Cretaceous granodiorite

Regional northeast- and 

northwest-trending shear 

zones

Northwest-trending 

fractures and later 

regional northeasttrending shear zones

None

None

West-trending low-angle 

and northwest-trending 

high- angle fracture 

systems

West- and northwesttrending low-angle 

fracture systems

Northwest-trending 

fracture systems

None

Major northeast-trending 

fracture systems

None

None

Polymetallic quartz 

veins and lodes (silver 

variety)

Polymetallic quartz 

veins and lodes (gold 

variety)

None

Polymetallic quartz 

veins and lodes (gold 

and base-metal 

varieties)

Polymetallic quartz 

veins and lodes (gold 

and base-metal 

varieties)

Polymetallic quartz 

veins and lodes (gold 

and base-metal 

varieties)

None

None

None

Polymetallic quartz veins 

and lodes (gold and basemetal varieties), Tertiary 

epithermal precious-metal 

veins, Tertiary 

polymetallic veins

None

Cretaceous polymetallic 

replacements

Polymetallic quartz veins 

and lodes (gold and basemetal varieties), 

Cretaceous polymetallic 

replacements

Polymetallic replacements

None

None

None

Relative importance of 

production from Creta

and Tertiary veins is 

unknown

Veins deposits are hos

mainly in northwest- tr

fractures

None

None

Important replacement 

deposits close to this a

Minnie Moore mineral

area (area 24)

Small hot springs depo

containing traces of go

uranium may be presen

None

Prospects and geochem

anomalies suggest Tert

quartz stockworks con

molybdenum, tin, or tu

Tungsten stockworks and None 

veins

Quartz stockworks 

containing Be, Sn, Mo, 

Ag, or Bi

None
Table 1. Mineralized areas in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, south-central Idaho Continued.

No.

20

21

22

23

24

25

26

27

28

29

Mineralized 

area

Smoky

Mountains

Carrietown

Bullion

Bunker Hill

Minnie

Moore

Bellevue

Wood River

Triumph

East Fork

Wood River

Lake Creek

Geologic terrane(s)

Tertiary granite, Tertiary diorite

complex, Paleozoic black shale,

Eocene volcanic rock

Paleozoic black shale, Cretaceous

granodiorite, Cretaceous tonalite,

Eocene volcanic rock

Paleozoic black shale

Paleozoic black shale, Cretaceous

tonalite

Paleozoic black shale (primarily

argillaceous rock), Cretaceous

tonalite

Paleozoic black shale (primarily

argillaceous rock)

Paleozoic black shale (primarily

argillaceous rock), Eocene

volcanic rock

Paleozoic black shale (primarily

argillaceous rock)

Paleozoic black shale

Paleozoic black shale

Mineral deposit types having 

Major structural features significant production

North-trending faults on

east edge of Idaho

batholith

Northwest- and northeasttrending fracture systems

on east edge of Idaho

batholith

Major northwest-trending

fracture systems on east

edge of Idaho batholith

Major northwest-trending

fracture systems on east

edge of Idaho batholith

Low- and high-angle,

northwest-trending

fracture systems in

Mesozoic fold and thrust

belt

Major northwest- trending

fracture systems in

Mesozoic fold and thrust

belt

Mesozoic fold and thrust

belt

Low- and high-angle,

northwest-trending

fracture systems in

Mesozoic fold and thrust

belt

Northwest-trending lowangle fracture systems in

Mesozoic fold and thrust

belt

Major low- and highangle northwest-trending

None

Cretaceous polymetallic

veins, Cretaceous

polymetallic

replacements

Cretaceous polymetallic

veins

None

Cretaceous polymetallic

veins, Cretaceous

polymetallic

replacements

None

Stratabound barite

Cretaceous polymetallic

veins, Cretaceous

polymetallic

replacements, possible

Paleozoic stratabound

zinc-lead deposits

None

Tertiary polymetallic

veins and replacements

Other mineral 

deposit types Comments

Tertiary polymetallic None

replacements, Tertiary

polymetallic veins

None None

None None

Cretaceous polymetallic None

veins, Cretaceous

polymetallic replacements

None None

Cretaceous polymetallic None

veins

Cretaceous polymetallic None

veins

Tertiary(?) gold skarn Some Cretaceous or

Paleozoic deposits m

Tertiary overprint

Cretaceous polymetallic None

veins

None Some Tertiary depos

represent material

fracture systems in 

Mesozoic fold and thrust 

belt

remobilized from Cr

vein deposits
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A7

talh'c NoneLink others(thii and 

volume). is 

in

2 § IP.! a

II f > 1

CO g>'g 3 « 

0 r° 3 0

4J C H 0 4) o " - p y cd co co H e<J

Jfitl U > u D- rt

%

1£-*

5P t»

Major northeast-trendin 

fracture insystems 

fold Mesozoic andthru 

belt

:> *

Paleozoic black shale(primaril; 

argillaceous rock)

ct

1O

tallic A Cretaceous molybdenum Mahoney (this 

north ofstockwork just the volume). ents, 

polyme )us id replacem

8 §

1.1

u £

§

z

t«

Northeast- andnorthwe trending low- high- and 

CO

3 4)

Paleozoic blackshale, Cretacec granodiorite, tonalil Cretaceous 

I

bO

I'i« a

^ «

Hailey quadrangle has knownenum 

resources

 o 

x>

^'o

s

i-a 1^11U to

c «

angle fracture isystems fold Mesozoic andthru; 

belt

Geochemistry and fieldErdman others 

geology undiscovered (this volume). suggest 

Tertiary epithermal preciousdeposits metal 

None Ratchford (in press)

1

Z

4)

§

Z

>13

Fracture thatsystems m 

be caldera ofpart 

complex

volcanic Eocene rck, 

intrusive rock

M

*H

u

Ic§

«

go

a

£ S U3 e

1|

If'o c

^ s

-^ c

b a

.s t*

4) 'S

H >

CO

Northwest- andnorthea trending low- andhighangle fracture systems

* o-a

Paleozoic blackshale, Tertiary granite, Tertiary diorite comple rhyolite, Tertiary volcai Ecene 

rock

JS1-s S S

M M

alh'c Noneand othersSewart 

(in press). ents 

S s

18

£t £-0

11

(2 S

4)

§

Z

to1 a

Northeast- andnorthwe trending fracture systn

granite, dioritf Tertiary 

complex, Tertiary rhyolite, Paleozoic blackshale, Eocene 

volcanic rock

^c

i

e§ "rt W on

None Linkand others(his im 

volume), :n 

ns

9 y-> .*H § a^ 2 § § ^ 3 

O of co e-9-a

p», 0 0

III u o o

H to to

CO = 1

3 1 Q> Q

S3 ^

1&0 C

a- T3 & S b « 

.3 co

§ §

H >

P u

Major low-angle fractui and northeast- systems and northwest-trending 

high- anglefracture 

all inMesozoii systems, 

fold anthrust bel

o

Paleozoic blackshale, Paleozoi 

flysch, granite Tertiary 

«

§

5

co

The significant Tertiary Winkler adothers more 

polymetallic veins and(this volume), 

replacements hosted inare 

iund barite

o

 9 

1on

«T

of

^ g 13

rs l|lP -a

O > « CL, CL.-O 0

>, s ;>»

.3 « .3

£ 'S 1

H > H

a

North- andnorthwest- trending fracture systn in fold Mesozoic and

£

Paleozoic flysch, graniTertiary 

Eocene volcanic rock

|

2'a

S

Drummond MineLimestone 

of MemberBasin Copper 

Formation. Veinsand 

replacements of target are 

continuing (1991) exploration 

for metals precious 

ic There hasbeenase- Soulliere andothers some 

CO

_C'53

1

s

CO

.2

U

&

thrust bel

i

H j>* "3 

a. § 

I

1

Z

bO 

e

Major northwest-trendij

Paleozoic flysch, Paleozoic

'3

M "S

CQ

J

lermal andprecious-metal (thisvolume), 

production from bothknown is 

deposit types

11 

^3rt o

1 1 r-1 3

CO .2 .S £ 

£ B,

^

low-angle fracture and north-systems trending high-angle 

fracture allinsystems, Mesozoic foldanthru;

M

carbonate, Eocene volcanic roc

1
Table 1. Mineralized areas in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, south-central Idaho Continued.

No.

38

39

40

41

42

43

44

45

46

Mineralized 

area

Lava Creek

Champagne 

Creek

Lake Creek 

stock

Copper 

Basin

Mackay

Burma Road

Pioneer

Magic

Elk Creek

Geologic terrane(s)

Paleozoic flysch, Paleozoic 

carbonate, Tertiary granite

Eocene volcanic rock

Paleozgic flysch, Eocene 

volcanic rock

Tertiary diorite complex, 

Paleozoic flysch, Eocene 

volcanic rock

Paleozoic flysch, Tertiary 

rhyolite, Tertiary granite

Tertiary granite, Paleozoic flysch, 

Paleozoic carbonate, Tertiary 

rhyolite

Eocene volcanic rock

Proterozoic metamorphic rock, 

Tertiary granite, Paleozoic

quartzite

Cretaceous granodiorite, Eocene 

volcanic rock, Miocene-Pliocene 

volcanic rock

Cretaceous granodiorite, Tertiary

Mineral deposit types having 

Major structural features significant production

North- to northwesttrending fracture systems 

in Mesozoic fold and 

thrust belt

North-trending fracture 

systems

Northeast-trending 

fracture systems

Northeast-trending 

fracture systems

Northeast-trending 

fracture systems

Northeast- and northwesttrending fracture systems

Pioneer Mountains core 

complex

None

Northwest- and northeastTertiary polymetallic 

veins and replacements

Tertiary polymetallic 

veins, Tertiary 

epithermal preciousmetal veins, hot-springs 

precious-metal deposits

None

None

Copper skarn

None

Tungsten skarn

None

None

Other mineral 

deposit types

Tertiary tungsten 

stockworks and veins, 

Tertiary epithermal 

precious-metal veins

None

Tertiary polymetallic 

veins and replacements

Copper skarn, Tertiary 

polymetallic 

replacements, Tertiary 

polymetallic veins

Tertiary polymetallic 

replacements, Tertiary 

polymetallic veins, 

tungsten skarn

Tertiary antimony veins, 

Tertiary epithermal 

precious-metal veins

Polymetallic replacements

Precious-metal-bearing 

hot-springs deposits

Precious-metal-bearing

Comments

None

Hot-springs deposits are 

currently (1991) being m

for gold

None

Area is target of recent 

exploration for precious

metal deposits

Some lead and zinc 

production from polyme

veins

Area is target for contin

(1990) exploration for 

precious-metal deposits

None

Active hot springs are in 

general area

Active hot springs are i

diorite complex, Eocene volcanic 

rock, Miocene-Pliocene volcanic 

rock

trending fracture systems hot-springs deposits general area
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A9

mineral deposit types are presented in the format of the mineral deposit models defined by Cox and Singer (1986), and 

the applicable mineral deposit model of Cox and Singer is 

indicated (referred to as USGS model analog). Examples of 

deposits listed in the Hailey descriptive models are from 

central Idaho; those examples within the Hailey quadrangle 

and the western part of the Idaho Falls quadrangles are 

referred to the relevant mineralized area. Table 2 lists all 

mineral deposit types thought to be present in the study area. 

Detailed descriptive models follow for deposit types for 

which adequate information is available.

TUNGSTEN STOCKWORKS AND VEINS

Approximate Synonym

Quartz-wolframite veins

USGS Model Analog

Tungsten veins (15a) (Cox and Singer, 1986, p. 64)

Summary Description

Fissure-filled quartz veins, commonly in a stockwork 

pattern, are along major fractures or in and just above felsic 

porphyritic intrusions.

Commodities

Major. Tungsten

Byproducts. Antimony, gold, silver, and molybdenum

Geologic Environment

Rock types. Deposits are in altered granitic plutons and 

calcareous and quartzitic sedimentary and metasedimentary 

rocks.

Depositional environment. Tungsten was apparently 

deposited within or just above small epizonal granitic plutons that formed during the late stages of both the Cretaceous 

and Tertiary episodes of plutonism.

Tectonic setting. Deposition was as fissure fillings in 

regional fracture systems.

Associated deposit types. Related deposits include molybdenum stockworks and tungsten skarns. Cretaceous tungsten 

stockworks and veins may be part of a family of vein deposits that includes Cretaceous polymetallic veins and polymetallic quartz veins and lodes.

Deposits

Description. Quartz veins and stockworks contain local 

concentrations of wolframite or scheelite. The economically 

important deposits are above molybdenum stockwork deposits.

Mineralogy. Ore minerals include wolframite (ferberite 

and huebnerite) and some scheelite, molybdenite, stibnite, 

gold, and silver. The bulk of the vein material is quartz; variable amounts of fluorite, arsenopyrite, calcite, rhodochrosite,

Table 2. Mineral deposit types thought to be present in the 

Hailey I°x2° quadrangle and the western part of the Idaho Falls 

I°x2° quadrangle, south-central Idaho.

[Deposit types enclosed in parentheses are those for which not enough is 

known to develop descriptive models]

Age of

mineralization__________Mineral deposit type_________ 

Quaternary (Gold placers)

(Radioactive black-sand placers)

(Hot springs deposits)

Tertiary (Tungsten skarn)

Tungsten stockworks and veins

(Stockwork deposits containing molybdenum, 

tungsten, tin, or beryllium)

Copper skarn

Polymetallic replacements

(Gold-bearing skarn)

Molybdenum stockworks

Epithermal precious-metal veins

Polymetallic veins

(Carbonate-hosted, jasperoid-associated, preciousmetal deposits)

(Antimony veins)

Polymetallic veins

Cretaceous (Tungsten skarn)

Tungsten stockworks and veins 

Molybdenum stockworks 

Polymetallic replacements 

Polymetallic veins 

Polymetallic quartz veins and lodes

Paleozoic (Sedimentary stratabound lead-zinc deposits) 

(Stratabound barite)

sericite, feldspar, pyrite, sphalerite, chalcopyrite, tetrahedrite, galena, and cinnabar are also present. Manganese 

oxide minerals are ubiquitous.

Texture/structure. Deposits are in veins and veinlets of fissure-filling massive quartz and as lenses and pods of sulfide 

minerals.

Alteration. Silicification, as shown by cavities lined with 

chalcedonic quartz and drusy quartz, is common near the 

deposits; argillic and sericitic alteration of feldspar is common in igneous host rocks.

Ore controls. Deposits are in swarms of quartz veins in 

fracture zones close to granite pluton contacts; important 

deposits may be at intersections of major structures. 

Age range. Both Cretaceous and Eocene deposits are 

known.

Orebodies. Individual orebodies are irregular in shape but 

tend to be elongate along fracture systems or form envelopes 

parallel with plutonic contacts. Orebodies range in size from 

less than 2 ft in width and 100 ft in length to as much as 35 

ft in width and 1,700 ft in length. Grades average 0.5-5 percent WO3, 0.05-6.0 percent antimony, 0.01-0.10 ounces of 

gold per ton, and 0.01-1.75 ounces of silver per ton.
A10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Geochemical Signature

A stream-sediment sample collected below the Ima mine 

(Worl and others, 1989) contained anomalous concentrations of copper, lead, antimony, and tungsten. A geochemical signature commonly associated with tungsten veins is W, 

Mo, Sn, Bi, As, Cu, Pb, Be, and F.

Geophysical Signature

The deposits themselves have no geophysical expression, 

but the major fracture zones and related intrusions correspond to anomalies in regional magnetic and gravity data.

Examples

Most deposits in the Corral Creek mineralized area (fig. 1) 

Big and Little Falls prospects (Summit mineralized area,

fig. 1)

Blizzard Mountain prospect (Lava Creek mineralized area,

fig- 1)

Ima mine (Mitchell and others, 1981)

Tungsten Jim (Mitchell and others, 1986)

Comment

These deposits probably could be separated into Cretaceous 

and Tertiary types.

References

Callaghan and Lemon (1941) 

Cook (1956)

TERTIARY MOLYBDENUM STOCKWORKS

Approximate Synonym

Calc-alkaline stockwork

USGS Model Analog

None

Summary Description

Vein stockworks and disseminations of molybdenite are in 

or near hypabyssal rocks of Eocene age.

Commodities

Major. Molybdenum 

Byproducts. Copper and tungsten 

Trace. Antimony

Geologic Environment

Rock types. Host rocks include Paleozoic sedimentary 

rocks of the black shale terrane, granodiorite of the Idaho 

batholith, and Eocene hypabyssal intrusive rocks. 

Depositional environment. Deposits are within and above 

late phases of multiple-phase intrusions. 

Tectonic setting. Deposits are localized along deep-seated 

fracture systems, including the Trans-Challis fault system.

Associated deposit types. Related deposits include fluorspar deposits and tungsten veins and skarns.

Deposits

Description. Two general deposit types are recognized: 

deposits within and next to rhyolite dikes in shear zones and 

deposits within small epizonal plutons. Stockworks of 

molybdenite-bearing quartz veinlets and disseminations of 

molybdenite are characteristic of both types. Most of the 

molybdenite is in intrusive rock, although some extends 

along fractures into country rock.

Mineralogy. Ore minerals include molybdenite and chalcopyrite and locally scheelite and stibnite. Gangue is quartz 

and pyrite and locally pyrrhotite and arsenopyrite. 

Texture/structure. Deposits consist of flakes and rosettes 

of molybdenite in veins and veinlets of quartz and as disseminations in altered rock.

Alteration. Intense alteration consisting of a siliceous core 

surrounded by envelopes of argillized, sericitized, and chloritized rocks is common. Pyrite zone may overprint other 

alteration types.

Ore controls. Deposits are associated with rhyolite dikes 

within major fractures of the Trans-Challis fault system or 

with later phases of multiple-phase plutons. 

Age range. Deposits are Eocene or younger. 

Orebodies. The orebodies range from small isolated pods 

of low-grade ore within intrusive bodies to orebodies containing 0.1 percent MoS2 and as much as 1 billion tons of ore. 

Orebodies associated with rhyolite dikes are elongate in the 

direction of the host shear zones and dikes. 

Weathering. Oxidized pyrite gives outcrops a reddishbrown color.

Geochemical Signature

Stream sediments and soils contain anomalous amounts of 

molybdenum and copper, and some stream sediments also 

contain anomalous amounts of silver.

Geophysical Signature

The deposits themselves may be detectable using electrical 

methods, and buried intrusions are detectable using aeromagnetic data.

Examples

Rhyolite- and shear-zone-hosted deposits

Cumo prospect (Mitchell and others, 1986)

Little Falls prospect (Mitchell and others, 1986)

Red Mountain (Mitchell and others, 1986)

Pluton-hosted deposits

Walton-White Mountain prospect (Summit mineralized

area, fig. 1)

Ima mine (Mitchell and others, 1981)

References

Rostad (1967)

Tucheck and Ridenour (1981)
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW All

TERTIARY POLYMETALLIC VEINS

Approximate Synonyms

Lead-silver-zinc-antimony-tin veins, base-metal veins

USGS Model Analog

None

Summary Description

Base- and precious-metal veins are hosted by several terranes in the vicinity of Eocene plutonic or volcanic rocks.

Commodities

Major. Silver, lead, and zinc

Byproduct. Gold

Trace. Antimony, copper, tin, tungsten, and bismuth

Geologic Environment

Rock types. Deposits are in many types of host rock including sheared Cretaceous intrusive rocks; quartzite, argillite, 

and carbonate beds of the black shale terrane; argillite and 

carbonate beds of the flysch terrane; and carbonate beds of 

the carbonate terrane.

Depositional environment. Deposits formed in fracture 

systems that also localized Eocene intrusions. 

Tectonic setting. Many deposits are in or near major shear 

zones in Cretaceous intrusive rocks or regional faults in the 

Paleozoic sedimentary rock terranes. 

Associated deposit types. Related deposits include Tertiary 

polymetallic replacement deposits and epithermal preciousmetal veins.

Deposits

Description. Deposits in base- and precious-metal veins 

are characterized by open-space filling textures, cryptocrystalline quartz, trace to significant amounts of gold, silver, 

lead, and zinc, and trace amounts of antimony, copper, tungsten, bismuth, and tin.

Mineralogy. Ore minerals include galena, sphalerite, and 

silver-bearing tetrahedrite in a gangue of quartz, siderite, 

calcite, pyrite, arsenopyrite, pyrrhotite, and cryptocrystalline quartz. Locally the ore contains minor amounts of 

bornite, bournonite, chalcopyrite, enargite, silver telluride 

(hessite?), cassiterite, zincian stannite, and silver sulfantimonide minerals.

Texture/structure. Deposits are characterized by sheared 

and broken zones in which quartz bodies are broken and 

pulled apart. Fault gouge and highly sheared rock are common.

Alteration. Carbonate country rocks are metamorphosed to 

hornfels and skarn, and most host rocks show some degree 

of silicification.

Ore controls. Fissures and shear zones provided permeability for mineralizing solutions driven by Eocene volcanic 

and plutonic activity.

Age range. Most deposits are Tertiary or have a Tertiary 

overprint.

Orebodies. Deposits generally are small lenses, pods, or 

irregular bodies along tabular linear veins. Size of individual 

orebodies ranges from a few feet in length and depth to as 

much as 200 ft in length, 300 ft in depth, and 7 ft in width. 

Grades range from trace to 6 ounces of silver per ton, 2 to 8 

percent lead, 2 to 5 percent zinc, and trace to 1 ounce of gold 

per ton. Known deposits of this type in shear zones in Cretaceous intrusive rocks are small but may represent higher 

grade zones in a large area of low-grade mineralized rock. 

Weathering. Zones that contain pyrite or pyrrhotite form 

conspicuous gossans, but zones that contain only silver, lead, 

and zinc minerals have inconspicuous outcrop. Secondary 

lead, zinc, and antimony minerals are common in the weathered zones.

Geochemical Signature

Rocks and stream sediments in the vicinity of deposits in the 

black shale belt are anomalous in Sn, As, Sb, Cd, Zn, Pb, Au, 

and Ag; the best geochemical indicators are probably Zn, Pb, 

Sb, As, Ag, and Cu.

Geophysical Signature

The deposits themselves have no direct geophysical expression, but some intrusions and major structures can be recognized by prominent anomalies and steep gradient zones in 

the magnetic and gravity data.

Examples

Most deposits in the Galena, Boulder Basin, Lake Creek, and 

Lead Belt mineralized areas and some deposits in the Marshall Peak, Mackay, Copper Basin, Lava Creek, and Muldoon mineralized areas (fig. 1)

References

Anderson (1929, 1947a) 

Anderson and Wagner (1946a) 

Federspiel and others (1987) 

Tucheck and Ridenour (1981)

EPITHERMAL PRECIOUS-METAL VEINS

Approximate Synonym

Epithermal gold (quartz-adularia)

USGS Model Analog

Comstock epithermal veins (25c) (Cox and Singer, 1986, 

p. 150)

Summary Description

Epithermal gold and silver quartz veins are within or close to 

Eocene volcanic or hypabyssal rocks, commonly within 

major deep-seated regional fracture systems.
A12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Commodities

Major. Gold and silver 

Byproducts. Lead, zinc, and copper 

Trace. Antimony and bismuth

Geologic Environment

Rock types. Host rocks include units of the Idaho batholith 

and siliceous Eocene extrusive and intrusive rocks. 

Depositional environment. Hydrothermal systems are 

associated with Eocene calc-alkaline peraluminous volcanism and associated intrusive activity. 

Tectonic setting. Major deposits are aligned along extensional regional fracture systems, including the Trans-Challis 

fault system.

Associated deposit types. Related deposits include fluorspar veins, Tertiary antimony veins, and Tertiary polymetallic veins and replacements.

Deposits

Description. Deposits are in banded and crustified veins 

and stockworks of veinlets that formed mainly by openspace filling in altered and silicified rocks. 

Mineralogy. Ore minerals include auriferous pyrite, native 

gold, native silver, electrum, tetrahedrite, pyrargyrite, proustite, argentite, stephanite, galena, chalcopyrite, enargite, 

sphalerite, and aikinite and other bismuth sulfide minerals. 

Gangue includes quartz (cryptocrystalline to coarsely crystalline), pyrite, calcite, adularia, siderite, barite, pyrrhotite, 

and arsenopyrite.

Texture/structure. Veins are characterized by open-spacefilling textures in fissures and breccias; sheared rock and 

fault gouge are common in and along ore shoots. Ore minerals are in clusters, thin layers, lenses, and disseminations. 

Alteration. Sericitized and silicified zones are closer to the 

veins, and wide propylitized zones are farther away. 

Ore controls. Most of the deposits are along high-angle 

fractures in the vicinity of hypabyssal dikes, stocks, and 

plugs.

Age range. Deposits are Eocene or younger. 

Orebodies. Deposits are generally small lenticular pods as 

much as 100 ft in strike length, 100 ft in dip length, and 3 ft 

or more in thickness. Ore values are very irregular even 

within a single orebody and range from trace to 23 ounces of 

gold per ton and trace to 2,500 ounces of silver per ton. 

Weathering. Weathering includes bleached country rock 

and iron-stained outcrops.

Geochemical Signature

Bismuth is associated with gold in the Quartzburg, Idaho 

City, Lava Creek and Champagne Creek mineralized areas 

(fig. 1); heavy-mineral concentrates in some areas contain 

anomalous amounts of Au, Ag, Sn, Ba, Bi, Cu, Mo, and Pb.

Geophysical Signature

The deposits themselves have no geophysical expression, 

but the ore-controlling faults might be detected by detailed

magnetic surveys and intensely altered zones might be 

detected by resistivity surveys. Regional magnetic data show 

the northeast-trending structures of the Trans-Challis fault 

system. Some mines are at intersections of strong east-west 

and northeast linear magnetic trends.

Examples

Gold Hill mine (Quartzburg mineralized area, fig. 1) 

Volcanic rock-hosted deposits in the Muldoon, Lava Creek, 

and Champagne Creek mineralized areas (fig. 1)

Reference

Anderson (1929, 1947a, b)

TERTIARY POLYMETALLIC 

REPLACEMENTS

Approximate Synonyms

Distal skarn, irregular replacements of base- and preciousmetals

USGS Model Analog

Zinc-lead skarns (18c) (Cox and Singer, 1986, p. 90)

Summary Description

Carbonate strata are partly to completely replaced by silicate 

and sulfide minerals.

Commodities

Major. Silver, lead, and zinc 

Byproducts. Copper, gold, and antimony

Geologic Environment

Rock types. Host rocks are calcareous or dolomitic units in 

flysch and carbonate terranes.

Depositional environment. Deposits formed by replacement of carbonate-bearing units by solutions following highangle and bedding-parallel fracture systems in the vicinity of 

hypabyssal intrusive bodies.

Tectonic setting. Deposits are generally near high-angle 

faults that host hypabyssal bodies.

Associated deposit types. Related deposits include Tertiary 

poly metallic veins and epithermal precious-metal veins.

Deposits

Description. Deposits are tabular to elongate lenses or 

ovoid, pipelike, stratabound bodies of silicate and sulfide 

minerals.

Mineralogy. Sulfide minerals include galena, sphalerite, 

pyrite, chalcopyrite, arsenopyrite, marcasite, and complex 

antimonide minerals. Oxidized zones contain cerussite, 

anglesite, scorodite, malachite, and iron oxide minerals. 

Gangue minerals include calcite, quartz, sericitized feldspar, 

fluorite, and several calc-silicate minerals.
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A13

Texture/structure. Deposits are generally coarse grained 

mosaics of silicate, sulfide, and carbonate minerals. 

Alteration. Alteration effects are not extensive in carbonate 

rocks; they consist of some minor bleaching and silicification. Extensive silicification and sericitic alteration are 

present in siliceous igneous rocks.

Ore controls. Deposits formed along permeable zones 

within receptive host rock close to hypabyssal intrusive 

bodies.

Age range. Known deposits are probably Eocene. 

Orebodies. Numerous sulfide seams and stringers are in 

bodies that are as much as 1,000 ft long, 120 ft wide, and 20 

ft thick. Grades range from 6 to 12 ounces of silver per ton, 

5 to 10 percent lead, 3 to 7 percent zinc, 0.1 to 1.0 percent 

copper, and trace to 0.3 ounces of gold per ton. Some pockets 

of high-grade ore were mined from the oxidized zone. 

Weathering. Secondary lead and zinc minerals are common in the weathered zone.

Geochemical Signature

Stream-sediment samples contain anomalous amounts of 

Ag, As, Ba, Cu, Pb, Sb, and Zn. Most barren rock samples 

from the same stratigraphic unit that hosts the orebodies 

contain anomalous amounts of barium, and many contain 

anomalous amounts of boron and zinc (Winkler and others, 

this volume).

Geophysical Signature

No geophysical signatures are known, but local detailed 

electrical surveys might detect individual orebodies.

Examples

Eagle Bird mine area (Muldoon mineralized area, fig. 1) 

Phi Kappa mine (Summit mineralized area, fig. 1)

References

Anderson and Wagner (1946a) 

Tucheck and Ridenour (1981)

COPPER SKARN

Approximate Synonyms

Base-metal skarn, polymetallic skarn

USGS Model Analog

Copper skarn (18b) (Cox and Singer, 1986, p. 86)

Summary Description

Chalcopyrite-rich lenses, pods, and disseminations of sulfide 

minerals are in calc-silicate contact metasomatic rocks.

Commodities

Major. Copper, lead, zinc, and silver 

Byproducts. Gold, molybdenum, and iron 

Trace. Tungsten and fluorine

Geologic Environment

Rock types. Host rocks are skarn composed of Ca-Fe-MgMn-silicate minerals within carbonate-bearing sedimentary 

rocks at the contact with Tertiary granite and leucogranite 

porphyry.

Depositional environment. Deposits are in thermal and 

chemical aureoles of Tertiary plutons intruding carbonatebearing rocks.

Tectonic setting. Plutons are most commonly along northeast- or northwest-trending regional structures. Deposits are 

in faulted margins of plutons.

Associated deposit types. Outer zones of these skarns contain polymetallic veins and local iron skarns.

Deposits

Description. Skarn deposits contain significant copper 

minerals. The orebodies are pipelike, chimney-, or podshaped and are along the contacts of intrusive rock and skarn, 

along the contacts of skarn and carbonate-bearing sedimentary rock, and along joints, breccias, faults, and bedding 

planes within skarn. Peripheral to and, in some cases, overlapping the skarn deposits are replacement veins containing 

silver, lead, and zinc minerals. The two deposit types are 

genetically related.

Mineralogy. Historic ore production was mainly from 

oxidized ore containing chrysocolla, malachite, azurite, and 

tenorite in a gangue of calc-silicate minerals and iron 

hydroxide. Primary ore contains chalcopyrite, local concentrations of molybdenite, sphalerite, and bornite, and rare 

fluorite and scheelite associated with pyrite, pyrrhotite, calcite, quartz, magnetite, and specularite in a matrix of calcsilicate minerals.

Texture/structure. The ore-bearing skarn is coarse to very 

coarse grained and, in general, coarser grained than surrounding barren skarn. Copper sulfide minerals are massive 

to disseminated; the other sulfide minerals are disseminated 

and interstitial to the calc-silicate minerals. 

Alteration. Skarn formation.

Ore controls. Deposits are related to receptive carbonatebearing beds, Eocene felsic plutons, and permeable areas 

within the metasomatic zone.

Age range. All known occurrences are associated with 

Eocene plutonic rocks.

Orebodies. Individual orebodies are 15-200 ft long, 5-55 

ft wide, and as much as 600 ft deep. Grades range from 2 to 

6 percent copper in oxidized ore and are 2.5 percent or less 

copper in sulfide ore.

Weathering. Exposures have been described as calc-silicate rock carrying disseminations and spongelike aggregates of metallic minerals. Secondary copper and iron 

minerals are common.

Geochemical Signature

Stream-sediment samples in the vicinity of the Empire 

mine contain anomalous amounts of copper (Worl and 

others, 1989).
A14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Geophysical Signature

Magnetic anomalies may indicate buried intrusive bodies in 

Paleozoic carbonate rocks. Local detailed electrical surveys 

might detect individual orebodies.

Examples

Most deposits in the Mackay and Copper Basin mineralized 

areas (fig. 1)

Reference

Umpleby (1917)

CRETACEOUS MOLYBDENUM 

STOCKWORKS

Approximate Synonym

Calc-alkaline stockwork

USGS Model Analog

Porphyry molybdenum, low-fluorine (21b) (Cox and Singer, 

1986, p. 120)

Summary Description

Vein stockworks and disseminations of molybdenite are in 

or near plutonic rocks of Cretaceous age.

Commodities

Major. Molybdenum 

Byproducts. Silver and tungsten

Geologic Environment

Rock types. The deposits are within or associated with 

compositionally zoned stocks of Cretaceous biotite granodiorite and porphyritic biotite granite. 

Depositional environment. The intrusions are outliers of 

the Idaho batholith and are within a late Mesozoic-Tertiary 

magmatic arc in the western North American Cordillera that 

hosts many economically significant molybdenum stockwork deposits associated with fluorine-deficient, I-type, 

compositionally zoned granitoid plutons that are probably 

subduction related.

Tectonic setting. Known deposits are on the eastern edge of 

the Idaho batholith.

Associated deposit types. Related deposits include tungsten veins and stockworks and tungsten skarn.

Deposits

Description. Deposits are stockworks of veins and veinlets 

of quartz, biotite, potassium feldspar, and white mica in 

which sulfide minerals other than molybdenite are rare. 

Mineralogy. Ore minerals include molybdenite and locally 

scheelite, chalcopyrite, galena, and silver minerals. Gangue 

includes biotite, potassium feldspar, and white mica.

Texture/structure. Molybdenite is present as rosettes,

flakes, fracture fillings, intercalations with secondary micas,

and selvages.

Alteration. Central potassic zone grades outward through

phyllic, argillic, and probably propylitic zones.

Ore controls. Deposits are in quartz stockworks in and

above compositionally zoned plutons.

Age range. Cretaceous.

Orebodies. Mineralized areas range in size from a few feet

in diameter to bodies as much as 11,100 ft in length, 3,000 ft

in width, and more than 2,200 ft in thickness.

Weathering. Yellow ferrimolybdite, after molybdenite, is

present locally.

Geochemical Signature

Stream-sediment and heavy-mineral-fraction samples in the 

vicinity of the Thompson Creek mine contain anomalous 

amounts of tungsten, molybdenum, bismuth, and copper; 

stream sediments also contain anomalous amounts silver, 

and the heavy-mineral fraction contains anomalous amounts 

of lead, antimony, boron, and thorium (Worl and others, 

1989). A reconnaissance biogeochemical survey in 1979 

included wood samples from two Douglas fir trees from the 

window overlying the orebody at Thompson Creek. These 

samples yielded silver concentrations of 300 and 500 ppm, 

as compared to a norm of about 20 ppm. Anomalous molybdenum concentrations were also measured (J. Erdman, U.S. 

Geological Survey, unpublished data, 1992).

Geophysical Signature

Known deposits are on the flanks of positive magnetic 

anomalies that probably indicate buried granitic plutons.

Examples

Thompson Creek mine (Mitchell and others, 1986) 

Cabin Creek deposit (Mitchell and others, 1986) 

Virginia-Bern deposit (Mitchell and others, 1986) 

Little Boulder Creek (mainly a skarn deposit) (Mitchell and 

others, 1986)

References

Cavanaugh(1979) 

Hall and others (1984)

POLYMETALLIC QUARTZ VEINS 

AND LODES

Approximate Synonym

Mixed base- and precious-metal veins

USGS Model Analog

Mixed base- and precious-metal veins (James D. Bliss, U.S. 

Geological Survey, Tucson, Arizona, written commun., 

1991)
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A15

Summary Description

Quartz veins and lodes locally enriched in precious- or basemetals are within or close to the Idaho batholith.

Commodities

Major. Gold and silver; locally antimony, copper, lead or

zinc

Byproducts. Gold and silver where other metals dominant

Trace. Molybdenum and tungsten

Geologic Environment

Rock types. Host rocks include all lithologic phases of the 

Idaho batholith and siliceous and calcareous sedimentary 

and metamorphic rocks near the batholith. 

Depositional environment. Mineralization occurred during 

and directly following formation of the Idaho batholith and 

prior to Eocene volcanism.

Tectonic setting. Deposits are in fractures that formed during cooling of the Idaho batholith; regionally, this was a 

period of change from a dominantly compressive to a dominantly tensional structural environment. 

Associated deposit types. These veins and lodes represent 

the quartz-gold-rich end member of a family of vein deposits 

that were emplaced during and directly following batholith 

formation. The other end member of this family is represented 

by the polymetallic veins that are present in the black shale 

terrane next to the batholith. Cretaceous tungsten stockworks 

and veins may also be part of this family of vein deposits and 

closely related to the polymetallic quartz veins and lodes.

Deposits

Description. The deposits are multistage quartz veins and 

lodes within shear zones and fault fissures. They are spatially 

and genetically related to the Idaho batholith and are in rocks 

of the batholith and in nearby siliceous and calcareous rocks. 

Several varieties of deposits are recognized; they reflect in 

part gradations between the two end members and in part 

mineral or metal zoning within the polymetallic quartz veins 

and lodes. Subtypes include base-metal veins, gold veins, 

antimony veins, and silver veins.

Base-metal veins are characterized by multistage quartz 

and siderite or calcite gangue and locally abundant galena, 

tetrahedrite, and sphalerite. The carbonate minerals commonly are present as fracture fillings in brecciated quartz and 

the sulfide minerals as replacements of carbonate minerals. 

Production from these veins was mainly for silver, lead, and 

zinc. Examples are in the Croesus mine (Croesus stock mineralized area, fig. 1).

Gold veins are characterized by several stages of quartz 

including early massive columnar and late vuggy cockscomb 

varieties and generally minor amounts of pyrite, chalcopyrite, pyrrhotite, and (or) arsenopyrite. Sericite is present in 

most veins and vein selvages. Production from these veins 

was mainly for gold and locally for copper. Examples 

include deposits in the Hailey gold belt, Rocky Bar, and 

Atlanta mineralized areas (fig. 1).

Antimony veins are characterized by vuggy cockscomb 

quartz and locally abundant stibnite; other sulfide minerals 

may be present. Production from these veins was mainly for 

antimony, but some veins may have significant preciousmetal content as well. Examples include deposits in the 

Swanholm mineralized area (fig. 1).

Silver veins are characterized by vuggy banded 

cockscomb quartz, ruby silver minerals, and an absence of 

arsenopyrite, pyrrhotite, or sphalerite; stibnite may be 

present. Production from these veins was mainly for silver. 

The silver veins may grade into gold veins at depth. Examples include deposits in the Vienna mineralized area (fig. 1). 

Mineralogy. Quartz is dominant in all deposits. Other nonsulfide gangue minerals include siderite, calcite, and sparse 

barite, sericite, albite, adularia(?), epidote, magnetite, and 

fluorite. Sulfide gangue minerals are mostly insignificant 

and include pyrite, arsenopyrite, and pyrrhotite. Ore minerals are chalcopyrite, galena, sphalerite, tetrahedrite, pyrargyrite, stibnite, huebnerite, and scheelite. Silver is mostly 

associated with galena, tetrahedrite, or pyrargyrite, and gold 

is associated with chalcopyrite or pyrite. 

Texture/structure. The deposits include massive single 

veins of quartz in fissures and zones of many veins, veinlets, 

breccia fillings, and disseminations of quartz in large areas 

of broken, sheared, and crushed country rock. Both syn- and 

post-mineral deformation is evident in most deposits. Much 

of the quartz is barren or metal-deficient massive and columnar varieties. Generally, metal-enriched veins and lodes have 

a late quartz stage with drusy, cockscomb, coliform, and 

vuggy textures. Sulfide minerals are present as bands, pods, 

and disseminations within the quartz. 

Alteration. Alteration is mostly confined to the zone of 

broken, sheared, and crushed country rock. Argillic and 

sericitic alteration is pervasive through the sheared zones, 

and pyritic alteration and silicification are present next to the 

veins and lodes.

Ore controls. The deposits are in shear zones and fracture 

systems, and groups of deposits commonly have similar orientations, but there is no apparent regional control to their 

location. Deposits in parts of the batholith are genetically 

related to the muscovite-biotite granite phase. Deposits 

formed at or near the edges or tops of batholith phases. 

Age range. Deposits range from Late Cretaceous to Paleocene in age.

Orebodies. Individual veins and lodes are from tens of feet 

to several miles in length, a few feet to a few tens of feet in 

width, and hundreds to thousands of feet in depth. Individual 

orebodies are lenticular pipelike ore shoots within the veins 

or lodes and are characterized by consistency through large 

vertical extents. Some of the larger orebodies have strike 

lengths of as much as 300 ft, dip lengths of more than 700 ft, 

and thicknesses of a few inches to 8 ft. Grades vary considerably; recorded averages range from trace to 1 ounce of 

gold per ton, trace to 15 ounces of silver per ton, 0.01 to 4.5 

percent copper, 2 to 8 percent lead, and 4 to 9 percent zinc.
A16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Weathering. Abundant quartz chips and placer gold concentrations are in soils and stream sediments; local minor 

lenses of gossan, manganese-oxide stain, and malachite or 

azurite stain are present.

Geochemical Signature

Anomalous amounts of arsenic, gold, silver, and antimony 

and locally tungsten, lead, copper, and zinc are in streamsediment and heavy-mineral-fraction samples.

Geophysical Signature

High-angle shear zones and fractures, where mineralized, can 

be mapped using detailed magnetic and electrical surveys.

Examples

Many deposits hosted by rocks of the Idaho batholith including, in the Hailey quadrangle, most deposits from the 

Atlanta, Rocky Bar, Black Warrior, Swanholm, Volcano, 

Vienna, Hailey gold belt, and Croesus stock mineralized 

areas (fig. 1)

References

Alien (1952) 

Anderson(1939, 1943) 

Anderson and others (1950) 

Anderson and Wagner (1946b) 

Kiilsgaard and others (1970) 

Popoff(1953) 

Ross (1927)

CRETACEOUS POLYMETALLIC VEINS

Approximate Synonyms

Wood River lead-silver veins, lead-silver-zinc-antimony 

veins

USGS Model Analog

Polymetallic veins (22c) (Cox and Singer, 1986, p. 125)

Summary Description

Deposits are rich siderite-silver-lead veins in the Idaho black 

shale belt.

Commodities

Major. Silver

Byproducts. Lead, zinc, and gold

Trace. Antimony and copper

Geologic Environment

Rock types. Carbonaceous micritic limestone and black 

argillite are the most common hosts, but deposits are also 

present in siltite, siltstone, shale, quartzite, and sandy limestone.

Depositional environment. Deposition was along major 

fracture systems in the black shale terrane within the thermal 

aureoles of Cretaceous granodioritic to granitic intrusions. 

Tectonic setting. Many deposits are in or near major 

regional low-angle faults.

Associated deposit type. These veins represent the sideritesilver-lead-rich end member of a family of vein deposits 

emplaced during and directly following batholith formation. 

The other end member of this family is represented by polymetallic quartz veins and lodes hosted by rocks of the Cretaceous intrusive terrane.

Deposits

Description. Deposits comprise multistage veins characterized by siderite and quartz gangue. Deposits formed along 

fracture systems in black shale terrane through a combination of open-space filling and replacement of carbonate beds. 

Veins have simple mineralogy and contain few trace metals; 

they are mainly in argillaceous rocks of the black shale terrane, grade into polymetallic replacement deposits, and are 

within the metamorphic and metasomatic influence of the 

Cretaceous intrusive rocks.

Mineralogy. Ore minerals are argentiferous galena, 

sphalerite, and silver-bearing tetrahedrite in a gangue of siderite, calcite, and quartz. Variable amounts of pyrite, arsenopyrite, and chalcopyrite are present in the ore. 

Texture/structure. Coarse-grained sulfide minerals are 

present as bands, pods, and disseminations within siderite 

and crushed country rock.

Alteration. The country rocks are metamorphosed and 

metasomatized to hornfels and skarn. Alteration, mainly formation of sericite, extends only a few inches from individual 

fractures and is not a conspicuous feature. 

Ore controls. Fissures and shear zones close to Cretaceous 

igneous rock intruding black shale terrane provided permeability for metal-bearing solutions.

Age range. Most deposits are probably Cretaceous and 

Paleocene, although some may have an Eocene overprint. 

Orebodies. Small lenses, pods, or tabular veins and large 

irregular bodies. Size ranges from a few tons to 200,000 tons 

for a single orebody. Average grades range from 5 to 45 

ounces of silver per ton, 5 to 20 percent lead, and 5 to 13 percent zinc; trace amounts of gold are present. The very rich 

ores resulted from secondary enrichment. 

Weathering. Zones that contain pyrite or pyrrhotite form 

conspicuous gossans, but zones that contain only silver, lead, 

and zinc minerals have inconspicuous outcrop. Secondary 

lead, zinc, and antimony minerals are common in the weathered zones. Reported gold production was from gossans 

derived from pyrite-rich veins.

Geochemical Signature

Best geochemical indicators are probably Zn, Pb, Sb, As, 

Ag, Cu, and organic carbon.
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A17

Geophysical Signature

The deposits themselves have no direct geophysical expression, but some intrusions and major structures exhibit prominent anomalies and steep gradient zones in the magnetic and 

gravity data.

Examples

Livingston mine (Mitchell and others, 1986)

Hoodoo mine (Mitchell and others, 1986)

Triumph mine (Triumph mineralized area, fig. 1)

Minnie Moore mine (Minnie Moore mineralized area, fig. 1)

Most deposits in the Bullion mineralized area (fig. 1)

References

Anderson and others (1950) 

Umpleby and others (1930) 

Van Noy and others (1986)

CRETACEOUS POLYMETALLIC 

REPLACEMENTS

Approximate Synonym

Irregular replacements of base- and precious-metals

USGS Model Analog

Polymetallic replacement deposits (19a) (Cox and Singer, 

1986, p. 99)

Summary Description

Deposits formed by selective replacement by silicate and 

sulfide minerals of carbonate strata in Paleozoic black shale 

terrane.

Commodities

Major. Silver, lead, and zinc 

Byproducts. Copper and gold

Geologic Environment

Rock types. Host rocks are generally sandy or silty calcareous or dolomitic rock interbedded with black carbonaceous 

argillite of the black shale terrane.

Depositional environment. Solutions emanating from Cretaceous intrusive rocks and moving along fracture systems 

replaced receptive host rocks.

Tectonic setting. Most of the richer deposits are at the intersections of the host rocks and steep faults. Regional fold 

structures and low-angle faults may have helped localize ore. 

Associated deposit type. Cretaceous polymetallic veins 

commonly are in the same location, but they are thought to 

be slightly younger.

Deposits

Description. Deposits of tabular to irregular-shaped bodies 

are in part stratabound but locally crosscut strata. In some

areas the deposits may represent local reconcentration of 

metals.

Mineralogy. Ore minerals include galena, sphalerite, tetrahedrite, and chalcopyrite; gangue includes siderite, quartz, 

pyrite, and arsenopyrite. Deposits are characterized by the 

presence of siderite gangue and jamesonite. 

Texture/structure. Deposits are generally coarse grained; 

ore minerals are present as pods, veinlets, irregular masses, 

and disseminations.

Alteration. Dolomitization(?), silicification, and serialization occurred around some of the deposits. 

Ore controls. Mineralization was controlled by location of 

major fracture systems cutting receptive carbonate rocks 

within the influence of Cretaceous igneous intrusions. 

Age range. Deposits are mostly Cretaceous in age; they 

may be Paleocene in part.

Orebodies. Orebodies are generally irregular, discontinuous, elongate lenses or ovoid pipelike bodies that follow bedding in the host rock. Orebodies range from a few tons to 

more than 200,000 tons. Grades range from a few percent 

lead and zinc and less than an ounce of silver per ton to 

30-40 percent lead and 40-60 ounces of silver per ton. Some 

of the richer orebodies mined in the past were in the secondary enrichment zone.

Weathering. Secondary lead and zinc minerals are common in the weathered zone.

Geochemical Signature

Stream-sediment samples from the vicinity of the Clayton 

Silver mine (Mitchell and others, 1986) contain anomalous 

amounts of B, Ag, Cu, Zn, Pb, and As, and heavy-mineral 

concentrates contain anomalous amounts of B, Ag, Cu, Zn, 

Pb, Ba, Mo, Cd, Sn, and W (Worl and others, 1989).

Geophysical Signature

No geophysical signature is known, but local detailed electrical surveys might detect individual orebodies.

Examples

Some deposits in the Minnie Moore, Triumph, Bullion, 

Rooks Creek stock, and Deer Creek stock mineralized areas

(fig. 1)

Clayton Silver mine (Mitchell and others, 1986)

References

Anderson and others (1950) 

Hall and others (1978) 

Ross (1937)

METALLOGENIC EVENTS

Mineralizing events recognized in the rocks of the 

Hailey quadrangle and the western part of the Idaho Falls 

quadrangle include (1) sedimentation in marine basins that
A18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

were oxygen depleted during much of Paleozoic time, (2) 

igneous and hydrothermal activity related to formation of the 

Cretaceous Idaho batholith, (3) igneous and hydrothermal 

activity during formation of Eocene granitic intrusions and 

the Eocene Chain's volcanic field, (4) hydrothermal activity 

related to Miocene and younger volcanic activity, and (5) 

Pleistocene to Holocene weathering and erosion. These 

events are listed in table 3 and described below.

PALEOZOIC EVENTS

The earliest recorded event was stratabound concentration of metals in black shales during most of the Paleozoic, 

especially during the Middle Devonian. Metals concentrated 

include Ag, Ba, Cu, Mo, Va, Pb, Zn, and Ni. The metals 

entered the basin as emanations directly onto the sea floor

and in detritus derived from weathering of pre-existing 

deposits in the sediment source area (Sanford and Wooden, 

this volume). Metal concentrations took the form of lenses, 

stringers, and disseminations of sulfide minerals and probably metal-bearing nonsulfide minerals. The metal-enriched 

rocks are mainly black carbonaceous argillite, siltite, shale, 

and micritic limestone, which are shown as argillaceous 

rocks within the black shale terrane on plate 1. Known syngenetic metal deposits include stratabound zinc deposits at 

the Hoodoo and Livingston mines in the Boulder Creek district just north of the Hailey quadrangle (Hall, 1985) and 

some of the stratabound zinc-lead orebodies in the Triumph 

mineralized area (Turner and Otto, this volume) (fig. 1). 

Numerous other deposits in the black shale terrane are 

thought to be stratabound in part. In addition to the stratabound deposits that are known to be present or may be 

present, the carbonaceous rocks (black shale) constitute an 

enormous possible low-grade resource of metals.

Table 3. Metallogenic events in the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, south-central 

Idaho.

Age Metallogenic event(s)

Pleistocene and Holocene 

Miocene to present

50-40 Ma

78-57 Ma

74(7) Ma

90-80 Ma

Late Pennsylvanian and Permian

Early Mississippian 

Middle and Late Devonian

Ordovician and Devonian

Mechanical concentration of gold and heavy minerals into placer deposits.

Hydrothermal cells associated with volcanism developed hot springs deposits containing gold and locally 

containing uranium.

Mineralization associated with Eocene extensional and igneous activity included:

Veins and veinlets along major deep-seated, high-angle fault systems containing Au, Ag, Bi, Sb, Pb, Zn,

Cu, fluorspar, and Ba; 

Disseminations and stockworks containing molybdenum and tungsten within and above granitic and

rhyolitic intrusions; 

Replacement deposits including skarns and distal skarns containing Pb, Zn, Ag, W, and Au in the vicinity

of granitic-rhyolitic intrusions; 

Greisens and pegmatitic pods containing molybdenum, tungsten, beryllium, or tin in and just above the tops

of pink granite intrusions; and 

Remobilization of pre-existing ores, mainly affecting vein and massive deposits of lead, silver, and zinc and

massive quartz veins containing gold and silver.

Mineralization during transition from dominantly compressional to dominantly extensional tectonism 

developed a family of deposits characterized by several generations of quartz and containing some combination 

of Au, Ag, Sb, As, Pb, Cu, W, and Zn. Deposits formed in Paleozoic black shale terrane were enriched in 

silver, lead, and zinc and those formed in Cretaceous intrusive rocks and siliceous metamorphic rocks were 

enriched in gold and locally silver, antimony, or tungsten.

Intrusion of leucogranitic phase of Idaho batholith developed disseminations and stockworks containing 

molybdenum, tungsten, and antimony (?) within and surrounding the plutonic bodies.

Intrusion of Idaho batholith border phases formed lead-, zinc-, and silver-enriched massive replacement bodies 

in carbonate country rocks; metals were derived, in part, from older deposits and enrichments.

Metalliferous sedimentation concentrated barium, lead, silver, and zinc in carbonaceous sediments; metals were 

derived, in part, from detrital material from older deposits.

Metalliferous sedimentation concentrated barium, lead, silver, and zinc in turbidite beds.

Significant concentration of silver, lead, and zinc in stratiform lenses and disseminations of sulfide minerals 

interbedded with calcareous mudrock, chert, and limestone; the source of metals was metalliferous solutions 

discharging on the sea floor.

Metalliferous sedimentation concentrated Pb, Ag, Zn, V, Mo, Ba, Cu, Ni, and possibly other metals in 

carbonaceous sediments.
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A19

CRETACEOUS EVENTS

Emplacement of the Idaho batholith during Cretaceous 

and Paleocene time resulted in many of the important mineral deposits in the area. Three physical types of deposits 

formed during this event: replacement deposits, stockworks 

of veinlets, and large veins and lodes. Polymetallic replacement deposits, most notable in the Minnie Moore and Carrietown mineralized areas (fig. 1), have been mined for their 

silver, lead, and zinc content. These are stratabound to irregular-shaped, massive deposits of galena and sphalerite that 

formed by replacement of carbonate-bearing members of the 

black shale sequence near its contacts with intrusive rocks of 

the Idaho batholith and satellite bodies.

Stockwork deposits formed during this event concentrated molybdenum, tungsten, and some copper. Known 

deposits of this type in the region include Thompson 

Creek, a producing world-class molybdenum deposit north 

of the study area in the Challis quadrangle, and the Little 

Boulder Creek molybdenum prospect, just north of the 

Hailey quadrangle.

A variety of vein deposits formed during the late stages 

of batholith formation (about 78-57 Ma; L.W. Snee, U.S. 

Geological Survey, 1992, unpublished data), during a period 

of transition from dominantly compressional to dominantly 

extensional tectonism. Two general types are recognized: 

polymetallic veins and polymetallic quartz veins and lodes. 

Cretaceous polymetallic veins, characterized by quartz-siderite gangue, are mainly within the black shale terrane and 

have produced silver, lead, and zinc. Notable examples are 

in the Minnie Moore, Triumph, and Bullion mineralized 

areas (fig. 1). Polymetallic quartz veins and lodes are characterized by several generations of quartz and limited sulfide 

minerals. They are mainly within rocks of the Idaho batholith 

or in siliceous and calcareous sedimentary rocks within or 

close to the batholith and have produced principally gold and 

silver. Most deposits in the Atlanta, Rocky Bar, and Hailey 

gold belt mineralized areas (fig. 1) are of this type.

EOCENE EVENTS

Tertiary igneous and hydrothermal activity and attendant metallization started about 50 Ma during regional 

extension characterized by deep-seated high-angle fractures 

and rift structures. Metals introduced during this event 

include Au, Ag, Mo, W, Be, Sn, Sb, Bi, F, Pb, Cu, and Zn. 

Solutions transporting these metals also may have mobilized 

and reconcentrated metals from earlier deposits. Tertiary 

metal concentrations are of three general types: replacement 

of sedimentary carbonate rocks, stockworks of veins and 

veinlets, and vein systems.

Tertiary replacement deposits, including skarn, concentrated copper, lead, zinc, silver, and gold, formed in carbonate-bearing sedimentary rocks around Tertiary intrusive

bodies. Replacement deposits in the Mackay mineralized 

area (fig. 1) are typical copper skarns mined mainly for copper. Replacement deposits in the Summit and Muldoon mineralized areas (fig. 1), hosted by the Drummond Mine 

Limestone Member of the Copper Basin Formation (pi. 1), 

have produced some lead and silver and may be distal zinclead skarns.

Stockwork deposits of Eocene age concentrated molybdenum and tungsten within or close to plutonic bodies. 

Examples are in the Summit mineralized area (fig. 1). Eocene 

granite batholiths in this area are enriched in beryllium, 

molybdenum, tungsten, and tin; it is possible that greisens 

formed during some of the later crystallization stages (Smith, 

this volume).

Hydrothermal activity, starting about 50 Ma and continuing intermittently to the present, produced a variety of 

vein deposits. Polymetallic veins that have produced some 

silver, lead, and zinc formed in open fractures and breccia 

zones in the vicinity of Tertiary plutons in all terranes. 

Examples in the Mackay mineralized area (fig. 1) are in carbonate terrane; those in the Lead Belt, Lava Creek, and Muldoon mineralized areas (fig. 1) are in flysch terrane; and 

those in the Summit mineralized area (fig. 1) are in black 

shale terrane.

Epithermal precious-metal veins, some of which have 

been major gold producers, formed from hydrothermal cells 

in areas of volcanism. Most of these deposits are hosted by, 

or are closely associated with, Eocene volcanic and hypabyssal rocks. Examples are in the Quartzburg, Lava Creek, and 

Burma Road mineralized areas (fig. 1).

MIOCENE AND YOUNGER EVENTS

A few gold- and uranium-bearing deposits that are 

related to hot-springs systems formed during Miocene to 

Holocene time. Examples are in the Magic and Elk Creek 

mineralized areas (fig. 1). Hydrothermal solutions coursing 

along major high-angle fracture systems formed large bodies 

of jasperoid in Paleozoic carbonate, flysch, and black shale 

terranes and in altered rock in Tertiary volcanic terranes. 

Some of these solutions may have been metal bearing, in 

which case large low-grade sediment- and volcanic-hosted 

epithermal precious-metal deposits may have formed (Soulliere and others, this volume).

PLEISTOCENE TO HOLOCENE EVENTS

During Pleistocene and Holocene time, radioactive 

black-sand and gold placers formed. Minerals concentrated 

in the late-stage crystallization products of the Cretaceous 

Idaho batholith and Eocene granitic plutons were the sources 

for the minerals in the radioactive black-sand placer deposits. Lode deposits were sources for the placer gold.
A20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

REFERENCES CITED

Alien, R.M., Jr.. 1952, Geology and mineralization of the Volcano

district, Elmore County, Idaho: Moscow, University of Idaho,

M.S. thesis, 55 p. 

Anderson, A.L., 1929, Geology and ore deposits of the Lava Creek

district, Idaho: Idaho Bureau of Mines and Geology Pamphlet

32, 70 p.

 1939, Geology and ore deposits of the Atlanta district, 

Elmore County, Idaho: Idaho Bureau of Mines and Geology 

Pamphlet 49, 71 p.

 1943, Geology of the gold-bearing lodes of the Rocky Bar 

district, Elmore County, Idaho: Idaho Bureau of Mines and 

Geology Pamphlet 65, 39 p.

 1947a, Epithermal mineralization at the Last Chance and 

Horn Silver Mines, Lava Creek District, Butte County, Idaho: 

Geological Society of America Bulletin, v. 56, p. 451-482.

 1947b, Geology and ore deposits of Boise Basin, Idaho:

U.S. Geological Survey Bulletin 944-C, 319 p.

Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 1950, 

Detailed geology of certain areas in the Mineral Hill and Warm 

Springs mining districts, Blaine County, Idaho: Idaho Bureau 

of Mines and Geology Pamphlet 90, 73 p.

Anderson, A.L., and Wagner, W.R., 1946a, A geological reconnaissance in the Little Wood River (Muldoon) district, Blaine 

County, Idaho: Idaho Bureau of Mines and Geology Pamphlet 

75, 22 p.

 1946b, A geologic reconnaissance of the Hailey gold belt 

(Camas district), Blaine County, Idaho: Idaho Bureau of Mines 

and Geology Pamphlet 76, 26 p.

Bennett, E.H., in press, Geology and mineral deposits of part of the 

western half of the Hailey I°x2° quadrangle, Idaho, with a section on the Neal mining district by Thor H. Kiilsgaard and Earl 

H. Bennett and a section on the Dixie mining district by Thomas M. Jacob: U.S. Geological Survey Bulletin 2064-W.

Callaghan, Eugene, and Lemmon, D.M., 1941, Tungsten resources 

of the Blue Wing district, Lemhi County, Idaho: U.S. Geological Survey Bulletin 931-A, 21 p.

Cavanaugh, P.C., 1979, The geology of the Little Boulder Creek 

molybdenum deposit, Custer County, Idaho: Missoula, University of Montana, M.S. thesis, 100 p.

Cook, E.F., 1956. Tungsten deposits of south-central Idaho: Idaho 

Bureau of Mines and Geology Pamphlet 108, 40 p.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Federspiel, F.E., Gabby, P.N., Neumann, T.N., and Leszcykowski, 

A.M., 1987, Mineral resources of the South Boise Yuba Study 

Area and additions, Blaine, Camas, and Elmore Counties, 

Idaho: U.S. Bureau of Mines Open-File Report MLA 64-87, 

117p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed.. Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658, p. 117-132.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Hall, W.E., Schmidt, E.A., Howe, S.S., and Broch, M.J., 1984, The 

Thompson Creek, Idaho, porphyry molybdenum deposit An 

example of a fluorine-deficient molybdenum deposit: Proceedings of the Sixth Quadrennial IAGOD Symposium, v. 6, 1, p. 

349-357.

Kiilsgaard, T.H., and Bacon, L.D., in press, Geology and mineral 

deposits of the Atlanta Hill area, Idaho: U.S. Geological Survey Bulletin 2064-Z.

Kiilsgaard, T.H., Benham, J.R. and Avery, D.W., 1983, Mineral 

resource potential of the Ten Mile West Roadless Area, Boise 

and Elmore Counties, Idaho: U.S. Geological Survey Miscellaneous Field Studies Map MF-1500-C, scale 1:62,500.

Kiilsgaard, T.H., Freeman, V.L., and Coffman, J.S., 1970, Mineral 

resources of the Sawtooth Primitive Area, Idaho: U.S. Geological Survey Bulletin 1319-D, 174 p.

Kiilsgaard, T.H., Lewis, R.S., and Bennett, E.H., in press, Plutonic 

and hypabyssal rocks of the Hailey I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 2064-U.

Kiilsgaard, T.H., Scanlan, T.M. and Stewart, D.E., in press, Geology and mineral deposits of the Boise Basin area, Boise and Ada 

Counties, Idaho: U.S. Geological Survey Bulletin 2064-BB.

Kiilsgaard, T.H., and Smith, C.L., in press, Geology, geochemistry, 

and mineral resources of the lower part of the Middle Fork Boise River drainage basin, Boise and Elmore Counties, Idaho: 

U.S. Geological Survey Bulletin 2064-AA.

Leeman, W.P., 1982, Geology of the Magic Reservoir area, Snake 

River Plain, Idaho, in Bonnichsen, Bill, and Breckenridge, 

R.M., eds., Cenozoic geology of Idaho: Idaho Bureau of Mines 

and Geology Bulletin 26, p. 369-376.

Lewis, R.S., in press, Alteration and mineralization in the eastern 

part of the Soldier Mountains, Camas County, Idaho: U.S. 

Geological Survey Bulletin 2064-V.

Link P.K., and Worl, R.G., in press. Geology and mineral deposits 

of the Minnie Moore and Bullion mineralized areas, Blaine 

County, Idaho: U.S. Geological Survey Bulletin 2064-Y.

Mahoney, J.B., and Horn, M.C., in press, Geology of the Vienna 

mineralized area, Blaine and Camas Counties, Idaho: U.S. 

Geological Survey Bulletin 2064-DD.

Mitchell, V.E., Strowd, W.B., Hustedde, G.S., and Bennett, E.H., 

1981, Mines and prospects of the Dubois quadrangle, Idaho: 

Idaho Bureau of Mines and Geology, Mines and Prospects 

Map Series, scale 1:250,000, 22 p.

 1986, Mines and prospects of the Challis quadrangle, Idaho 

(2nd ed.): Idaho Bureau of Mines and Geology, Mines and 

Prospects Map Series, scale 1:250,000, 56 p.

Moye, F.J., in press, The southeastern Challis volcanic field, central 

Idaho Mineral deposit models: U.S. Geological Survey Bulletin 2064-FF.

Park, W.A., in press, The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-CC.

Popoff, C.C., 1953, Hermada antimony deposit, Elmore County, 

Idaho: U.S. Bureau of Mines Report of Investigations 4950, 

28 p.

Ratchford, M.E., in press, Epigenetic lead-tin-silver-antimony-gold 

veins in Boulder Basin, Blaine and Custer Counties, Idaho Potential for economic tin mineralization: U.S. Geological Survey Bulletin 2064-JJ.
GEOLOGY AND MINERAL DEPOSITS AN OVERVIEW A21

Ross, C.P., 1927, Ore deposits in Tertiary lava in the Salmon River 

Mountains, Idaho: Idaho Bureau of Mines and Geology Pamphlet 25, 20 p.

Rostad, O.H., 1967, Geochemical case history at the Little Falls 

molybdenite prospect, Boise County, Idaho, in Symposium on 

geochemical prospecting: Canadian Geological Survey Paper 

66-54, p. 249-252.

Skipp, Betty, 1987, Basement thrust sheet in the Clearwater orogenic zone, central Idaho and western Montana: Geology, v. 

15, no. 3, p. 220-224.

Stewart, D.E., Schmidt, K.L., Moye, F.J., Mahoney, J.B., and Link, 

P.K., in press. Eocene intrusive complexes in the Smoky and 

Boulder Mountains, south-central Idaho: U.S. Geological Survey Bulletin 2064-HH.

Tuchek, E.T., and Ridenour, James, 1981, Economic appraisal of 

the Boulder-Pioneer Wilderness Study Area, Blaine and Custer 

Counties, Idaho, in Mineral resources of the Boulder-Pioneer 

Wilderness Study Area, Blaine and Custer Counties, Idaho: 

U.S. Geological Survey Bulletin 1497, p. 181-292.

Umpleby, J.B., 1917, Geology and ore deposits of the Mackay 

region, Idaho: U.S. Geological Survey Professional Paper 97, 

scale 1:375,000, 129 p.

Umpleby, J.B., Westgate, L.G., and Ross, C.P., 1930, Geology and 

ore deposits of the Wood River region, Idaho: U.S. Geological 

Survey Bulletin 814, 250 p.

Van Noy, R.M., Ridenour, James, Zilka, N.T., Federspiel, F.E., 

Evans, R.K., Tuchek, E.T., and McMahan, A.B., 1986, Economic appraisal of the eastern part of the Sawtooth National 

Recreation Area, Idaho: U.S. Geological Survey Bulletin 

1545-E, p. 232-472.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Worl, R.G., and Lewis, R.S., in press, Vein deposits hosted by plutonic rocks in the Croesus stock and Hailey gold belt mineralized areas, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-X.

Worl, R.G., Wilson, A.B., Smith, C.L., Kleinkopf, M.D., and 

Sykes, R.C., 1989, Mineral resource potential and geology of 

the Challis National Forest, Idaho: U.S. Geological Survey 

Bulletin 1873, 101 p.

Structural Framework of Mineral Deposits 

Hosted by Paleozoic Rocks in the 

Northeastern Part of the Hailey I°x2° Quadrangle, 

South-Central Idaho

By David W. Rodgers, Paul Karl Link, and Audrey D. Huerta

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-B

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Bl

Introduction........................................................................................................................... 1

Paleozoic Syngenetic Stratiform Mineralization and the Antler Orogeny........................... 3

Pennsylvanian-Permian Wood River Basin.......................................................................... 4

Mesozoic Shortening............................................................................................................ 5

Structural Style and Geometry...................................................................................... 5

Amount of Shortening .................................................................................................. 8

Timing of Deformation................................................................................................. 8

Cretaceous Structures and Mineralization.................................................................... 8

Cretaceous to Eocene Exhumation....................................................................................... 9

Early Eocene(?) to Oligocene Deformation.......................................................................... 10

Early Eocene(?) Dextral-Normal Faulting.................................................................... 10

Style and Geometry of Faults............................................................................... 10

Amount of Offset.................................................................................................. 11

Timing of Faulting................................................................................................ 11

Middle Eocene to Oligocene Extension ....................................................................... 13

Structural Style and Geometry.............................................................................. 13

Pioneer Mountains Metamorphic Core Complex................................................. 13

Amount of Extension............................................................................................ 14

Timing of Magmatism and Extension .................................................................. 14

Early Eocene(?)-Oligocene Mineralization.................................................................. 14

Neogene Basin and Range Extension................................................................................... 15

Structural Style and Geometry...................................................................................... 15

Amount and Timing of Extension ................................................................................ 15

References Cited................................................................................................................... 15

PLATE

[Plate is in pocket] 

1. Geologic map of the northeastern part of the Hailey 1 °x2° quadrangle, south-central Idaho.

FIGURES

1. Index map showing location of 7.5-minute quadrangles for the northeastern part of the Hailey quadrangle............... B2

2. Map showing Cretaceous(?) fold-axis orientations in Paleozoic strata across the central part of the study area......... 7

3. Map showing structure contours and slip vector of the Lake Creek fault..................................................................... 12
Structural Framework of Mineral Deposits Hosted by 

Paleozoic Rocks in the Northeastern Part of the 

Hailey I°x2° Quadrangle, South-Central Idaho

By David W. Rodgers, 1 Paul Karl Link, 1 and Audrey D. Huerta 1

ABSTRACT

The style, geometry, and timing of structures in the 

northeastern part of the Hailey I°x2° quadrangle, south-central Idaho, has had a strong influence on mineralization of 

Paleozoic rocks. Polyphase deformation has produced a 

myriad of faults and folds and resulted in significant shortening, extension, and differential uplift. Devonian rift-related 

faults may have influenced syngenetic silver-lead-zinc mineralization in the Milligen Formation. The Late Devonian 

and Early Mississippian Antler orogeny was characterized 

by folding and thrusting of lower Paleozoic siliceous deepwater strata over coeval carbonate platform rocks. Crustal 

warping probably related to the Middle Pennsylvanian 

Ancestral Rockies orogeny is manifested by uplift of the 

Copper Basin highland relative to the subsiding Wood River 

Basin to the west.

During the Late Jurassic to Cretaceous Sevier orogeny, 

folds and thrusts formed and the Atlanta lobe of the Idaho 

batholith was emplaced. Open, upright, north-trending folds 

are present in the Smoky Mountains, whereas tight, overturned, northwest-trending folds are present to the east in the 

Pioneer and Boulder Mountains. Map-scale folds accommodated at least 25 percent shortening, whereas pressure solution, small-scale folding, and shearing resulted in additional 

unmeasured shortening. Of the many thrust faults previously 

identified, only the Pioneer thrust fault and possibly the Trail 

Creek fault are interpreted as major; these have inferred topto-the-east-northeast slip of several tens of kilometers. Silverlead-zinc veins in the Triumph mine formed in minor thrust 

faults above inferred Late Cretaceous intrusive bodies. Vein 

deposits of the Minnie Moore area are hosted by northweststriking, steeply dipping shear zones that formed shortly after 

intrusion of plutons about 90 Ma. In the Carrietown mineralized area, smaller shear-zone-hosted silver-lead-zinc veins 

formed about 80 Ma adjacent to the Idaho batholith.

'Department of Geology, Idaho State University, Pocatello, Idaho 

83209.

During the Late Cretaceous to Eocene, the southeastern 

Idaho batholith and adjacent country rock were exhumed 

8-12 km, after which occurred an extended period of early 

Eocene(?) to middle Oligocene deformation. In the early 

stages of this tectonism top-to-the-northwest slip occurred 

along low-angle faults including the Lake Creek and Trail 

Creek faults in the Pioneer and Boulder Mountains. The 

Lake Creek fault slipped about 18 km in a dextral-normal 

sense; most slip occurred before 51-48 Ma. Shear zones 

along the Lake Creek fault contain silver-lead veins, and in 

the Triumph and Minnie Moore mineralized areas low-angle 

faults offset Cretaceous veins. During and after eruption of 

the main body of the Challis Volcanic Group (48^4-7 Ma), 

northeast-striking high-angle faults and dikes formed; northwest-southeast extension of perhaps 6-25 percent probably 

was accommodated by faulting. Some fault zones near volcanic vents show silicification and alteration. In the middle 

Eocene and middle Oligocene, the Pioneer Mountains metamorphic core complex was uplifted. Uplift was probably 

associated with 17-23 km of top-to-the-northwest slip along 

the Wildhorse detachment fault.

Neogene basin and range faulting produced northweststriking northeast-tilted fault blocks. The amount of southwest-northeast extension is probably about 10-15 percent. 

Existing mineral deposits were offset, but no new deposits 

formed near the surface.

INTRODUCTION

The location of mineral deposits hosted by Paleozoic 

rocks in south-central Idaho is influenced by structures that 

formed during several erogenic events. Ore deposits are concentrated in joints, shear zones, fault zones, and the cores of 

folds and are offset by high- and low-angle faults that have 

meters to tens of kilometers of slip. The area is part of the 

"central Idaho black-shale mineral belt," as defined by Hall 

(1985) to include carbonaceous mudrock of various ages 

along the southeastern edge of the Idaho batholith.

Bl
B2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

We focus herein on the structural framework of mineralized Paleozoic strata in the northeastern part of the Hailey 

I°x2° quadrangle in south-central Idaho. The framework of 

mineralization and the mineralized areas are described by 

Worl and Johnson (this volume). Details of Paleozoic 

stratigraphy are described by Link and others (this volume), 

and more detailed discussions of mineral genesis and remobilization are presented by Burton and Link (this volume), 

Darling and others (this volume), Mahoney (this volume), 

Turner and Otto (this volume), Winkler and others (this volume), Link and Worl (in press), Mahoney and Horn (in 

press), and Park (in press).

The study area is bisected by the northwest-trending 

Wood River valley, along which are the towns of Ketchum, 

Hailey, and Bellevue. To the west of the Wood River valley 

are the Smoky Mountains, to the north are the Boulder 

Mountains, and to the northeast are the Pioneer Mountains. 

The headwaters of the Salmon River are in the northern 

Smoky Mountains, the headwaters of the East Fork Salmon 

River are in the northern Boulder Mountains, and the Big 

Lost River flows through the eastern Pioneer Mountains and 

Boulder Mountains. Major mineralized areas include the Triumph area in the western Pioneer Mountains near Hailey and 

Ketchum, the Minnie Moore area west of Bellevue, the Bullion area west of Hailey, and the Carrietown area in the 

southern Smoky Mountains. The location of individual 7.5- 

minute quadrangles in the study area is shown in figure 1.

The distribution of rocks in the study area is complex, 

but a general northwest-trending outcrop pattern is shown 

by most major rock units (plate 1). From southwest to 

northeast, the major rock units are the Cretaceous Idaho 

batholith, the upper Paleozoic Sun Valley Group (Dollarhide, Grand Prize, and Wood River Formations), lower 

Paleozoic strata (Milligen Formation and unnamed Ordovician, Silurian, and Devonian strata), and the Mississippian 

Copper Basin Formation. Overlying all these units is the 

Eocene Challis Volcanic Group. Proterozoic to Paleozoic 

metasedimentary rocks and Eocene plutons crop out in the 

Pioneer Mountains metamorphic core complex in the central Pioneer Mountains. Structurally, Paleozoic strata 

throughout the area are involved in map-scale folds that 

have north- to north west-trending hinges. Four types of 

map-scale faults are present: (1) thrust faults such as the 

north-northwest-striking Pioneer thrust fault in the eastern 

Boulder Mountains and northern and eastern Pioneer 

Mountains; (2) dextral-normal faults including the northwest-striking Lake Creek and Trail Creek faults in the 

western Boulder and Pioneer Mountains and the arched 

Wildhorse detachment fault of the Pioneer Mountains core 

complex; (3) northeast-striking normal faults exposed 

throughout the map area, most notably the White Mountain 

fault within the south-central Pioneer Mountains; and (4) 

north-northwest striking normal faults exposed throughout 

the area.

114 44° 

00'

45' 30' 15' 114°00' 113°45'

45'

30'

,4

GANNET

43°15' L

LITTLE

WOOD

RIVER

RES

,

4"

Figure 1. Index map showing location of 7.5-minute quadrangles for the northeastern part of the Hailey I°x2° quadrangle, 

south-central Idaho.

Paleozoic strata of south-central Idaho record a protracted erogenic history that has been unraveled in large part 

by previous workers (Lindgren, 1900; Umpleby and others, 

1930; Anderson and others, 1950; Nilsen, 1977; Hall, Rye, 

and Doe, 1978; Skipp and others, 1979; Dover, 1981, 1983; 

Hall, 1985; Link and others, 1988). We briefly review this 

history before describing the structural evolution of the area 

in more detail.

Subsidence during the latest Proterozoic of Early Proterozoic crystalline rocks and overlying Middle Proterozoic 

strata (exposed in the core of the Pioneer Mountains) produced a west-facing passive continental margin that persisted until the end of the Silurian. Isolated exposures of 

lower Paleozoic shelf strata of this passive margin crop out 

east of the Cretaceous Pioneer thrust fault, and coeval deepwater (siliceous) strata are exposed west of the Pioneer thrust 

fault from Trail Creek north to the North Fork of the Big Lost 

River. A pulse of Devonian rifting, subsidence, and stratiform syngenetic silver-lead-zinc mineralization is recorded 

within the Milligen Formation, which is extensively exposed 

east of the Wood River valley near Hailey and Ketchum and 

in the Boulder Mountains. The Lower Mississippian part of 

the Copper Basin Formation accumulated during and after 

the Late Devonian-Early Mississippian Antler orogeny in a 

foreland basin-flysch trough to the east of a thrusted Antler 

highland, and the upper part of the formation is interpreted to 

be a marginal-marine facies that represents filling of the 

foreland basin. Pennsylvanian and Permian crustal warping, 

possibly associated with formation of the Ancestral Rockies,
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B3

is reflected by relative uplift of the area now east of the Pioneer thrust fault to form the Copper Basin highland and relative subsidence of the area now west of the Pioneer thrust 

fault to form the epicratonic Wood River Basin in which the 

Sun Valley Group was deposited.

During the Late Jurassic to Cretaceous Sevier orogeny. 

Paleozoic and older strata were metamorphosed, folded, 

thrust eastward, and intruded by granitoid rocks of the 

Atlanta lobe of the Idaho batholith. North- to northwesttrending, east-vergent folds accommodated most of the 

shortening. A smaller, but unresolved amount of shortening 

was accommodated along thrust faults, primarily the Pioneer 

thrust. Late Cretaceous granitoid rocks are exposed in the 

Smoky Mountains and include the Atlanta lobe and three satellite plutons (Rooks Creek, Deer Creek, and Croesus 

stocks) near Hailey and Bellevue. The historically productive Minnie Moore and Triumph mines near Hailey contain 

shear-zone-hosted silver-lead-zinc veins that formed during 

late stages of Cretaceous intrusive activity.

Significant exhumation of the Atlanta lobe and adjacent 

Paleozoic strata occurred during the Late Cretaceous and 

early Tertiary. By the middle Eocene, rocks formerly at 8-12 

km depth were at the surface.

Paleozoic rocks were extensively deformed in early 

Eocene(?) to middle Oligocene time, before, during, and 

after eruption of the middle Eocene Challis Volcanic Group. 

Slippage occurred on several low-angle faults including the 

Lake Creek and Trail Creek faults. Northeast-striking highangle normal faults and dikes throughout the area are structurally parallel with the Trans-Challis fault system. The Pioneer Mountains metamorphic core complex formed during 

this time and was episodically uplifted along the Wildhorse 

detachment fault. Remobilization and introduction of metals 

accompanied these deformational events.

Neogene development of the Basin and Range province 

is manifested by differential uplift and northeast tilting along 

north- to northwest-striking normal faults. The study area is 

characterized by rugged topography that formed as a result 

of erosion by Quaternary glaciers and streams and has a 

present-day maximum elevation greater than 3,500 m.

Acknowledgments. This synthesis reflects knowledge 

obtained by many geologists during the course of the U.S. 

Geological Survey Conterminous United States Mineral 

Assessment Program (CUSMAP) in the Hailey quadrangle 

and the Idaho Initiative project of the Idaho Geological Survey. In particular, we would like to thank Idaho State University graduate students who have attacked the area with 

inquisitive minds and youthful vigor: L.D. Batatian, B.R. 

Burton, R.S. Darling, J.K. Geslin, B.T. Jordan, J.B. 

Mahoney, J.P. O'Brien, D.E. Stewart, S.K. Whitman, and 

Eric Wilson. Their mapping, stratigraphic, structural, and 

petrologic studies have been invaluable contributions to our 

understanding of the geologic history of the area. Other 

assistance was provided by Kevin Greer, who first compiled 

and interpreted folded bedding attitudes. B.R. Burton, J.B.

Mahoney, and S.E. Box are thanked for excellent reviews of 

the manuscript and figures. Errors of omission or fact may 

remain, however, and we take full responsibility for them.

PALEOZOIC SYNGENETIC

STRATIFORM MINERALIZATION

AND THE ANTLER OROGENY

Fine-grained carbonaceous Devonian strata including 

the Milligen Formation and correlative units (parts of the 

Salmon River assemblage and unnamed Silurian and Devonian units) were deposited over much of the eastern part of 

the Hailey I°x2° quadrangle and the eastern part of the Challis I°x2° quadrangle to the north. Turner and Otto (this volume) and Link and others (this volume) describe the 

stratigraphy of these Devonian rocks. At the Triumph mine 

east of Ketchum (and at the Livingston and HooDoo mines 

in the Challis quadrangle), these strata contain stratiform silver-lead-zinc mineral deposits that have demonstrable syngenetic texture (Hall, 1985). By comparison with other large 

Devonian mineral deposits in Canada, these deposits are 

thought to have formed in a transtensional or extensional 

strain regime (Turner and Otto, this volume). In the Milligen 

Formation, the stratiform ore deposits may have been concentrated in small fault-bounded deep-water basins that were 

subject to exhalation of hydrothermal fluids enriched in metals (Hall, 1985; Turner and Otto, 1988, this volume). Turner 

and Otto (1988, this volume) identified possible tuffs and 

mafic sills in the Milligen Formation in the Triumph mineralized area; however, the absence of faults and Devonian 

radiometric ages has so far prevented a direct tie between 

these metal concentrations and sedimentary exhalative processes. These stratiform deposits are broadly constrained as 

Middle Devonian (Eifelian) in age (Link and others, this volume). Devonian ore deposits may be a significant source of 

metals that were remobilized during Cretaceous and Eocene 

magmatic activity and are now in Paleozoic rocks of various 

ages in the black shale mineral belt (Hall, Rye, and Doe, 

1978; Hall, 1985, 1987; Sanford and Wooden, this volume).

Based on recognition of soft-sediment folds of 

inferred tectonic origin in the Milligen Formation (Turner 

and Otto, 1988, this volume), Milligen deposition may have 

been concurrent with, or closely followed by, early compressional phases of the Late Devonian to Early Mississippian Antler orogeny. The transition from basin formation 

and associated rifting to compressional deformation and, 

indeed, the details of Antler deformation in south-central 

Idaho are not well understood.

The later phases of the Antler orogeny produced axial 

planar cleavage and tight to isoclinal folds in the Milligen 

Formation in the Triumph area and in the Boulder Mountains (Davis, 1984; Turner and Otto, 1988, this volume), 

complex folds in the Milligen Formation in the Lake Creek
B4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

area (Burton and Link, this volume), and regional tilting of 

the Milligen Formation below a Middle Pennsylvanian 

unconformity in the northern Boulder Mountains (Batatian, 

1991; Burton and Link, this volume). These structures are 

attributed to the Antler orogeny because they have only 

been found in pre-Mississippian rocks and were overprinted by northeast-vergent folds during the Mesozoic 

Sevier orogeny. Although some outcrop belts of Milligen 

Formation west of the Trail Creek fault show clear polydeformational structures, only one fabric can be demonstrated 

in other areas. Polydeformational fabrics have not been 

identified east of the Trail Creek fault in the Lower Ordovician to Middle Silurian Phi Kappa Formation, Middle Silurian Trail Creek Formation, Devonian Milligen 

Formation, and unnamed Silurian and Devonian units. Our 

observation is that an Antler fabric is present in many, but 

not all, outcrops of Devonian and older strata west of the 

Trail Creek fault but is not present east of the fault. The 

presence of an Antler fabric in central Idaho has been long 

debated (Dover, 1980), and the nature of such a fabric 

requires further study.

Based on the presence of a Mississippian-age flysch 

trough (Copper Basin Formation) containing clasts derived 

from the Milligen Formation, Skipp and Hall (1975) and 

Nilsen (1977) suggested that the Milligen Formation was 

thrust eastward to form a highland during the Late Devonian 

to Early Mississippian Antler orogeny. The thrust fault that 

accommodated this shortening cannot, however, be conclusively located in south-central Idaho (Dover, 1980). If it is 

present in the Hailey I°x2° quadrangle, it may be concealed 

beneath the outcrop belt of upper Paleozoic Wood River Formation in the Boulder Mountains (Roberts and Thomasson, 

1964), or it may have been reactivated to become the Cretaceous Pioneer thrust fault (Wust, 1986) or the early 

Eocene(?) Trail Creek fault. The Pioneer thrust fault is an 

unlikely candidate because it contains Mississippian flysch 

in its hanging wall (Link and others, this volume). We 

observe that the Trail Creek fault forms the eastern boundary 

of a demonstrable Antler fabric in the Milligen Formation 

and that the fault zone shows several stages of deformation, 

especially in its footwall where the Milligen Formation is 

tightly folded and northwest of Trail Creek where the fault 

zone is a mylonitic zone tens of meters wide (Dover, 1983). 

Similar stratigraphic members of the Milligen Formation are 

present in the footwall and hanging wall of the Trail Creek 

fault (Bruner, 1991; Link and others, this volume), and thus 

any Antler-age slip along the Trail Creek fault would be less 

than the distance over which facies changes occurred in the 

original Milligen basin.

Latest Devonian to Early Mississippian uplift of the 

Antler highland in Nevada and Idaho produced a source for 

elastics that formed a wedge of chert-rich flysch and molasse 

which becomes finer grained and more carbonate-rich

eastward (Poole and Sandberg, 1991). Within central Idaho 

these strata comprise the eastward-fining Mississippian Copper Basin Formation, which was deposited in the foreland 

basin east of the Antler highland. With the exception of a few 

isolated exposures in the hanging wall of the Pioneer thrust 

fault (Link and others, this volume), the Copper Basin Formation now crops out east of the Pioneer thrust fault (Nilsen, 

1977; Skipp and others, 1979; Skipp and Hall, 1980; Dover, 

1983; Link and others, this volume). Black and gray chert 

and cleaved argillite clasts in the Copper Basin Formation 

that were derived from the Devonian Milligen Formation 

suggest that the Milligen was deformed prior to Early 

Mississippian time and was part of the western Antler highland (Davis, 1984).

PENNSYLVANIAN-PERMIAN WOOD 

RIVER BASIN

Middle Pennsylvanian to Early Permian subsidence of 

the Wood River Basin produced a depositional site for 

thick sequences (more than 3,000 m) of fine-grained mixed 

carbonate-siliciclastic strata of the Sun Valley Group 

(Mahoney and others, 1991). The Sun Valley Group contains the Wood River, Grand Prize, and Dollarhide Formations, each of which on plate 1 is divided into lower and 

upper units.

The Sun Valley Group contains two upward-fining 

stratigraphic cycles interpreted to represent two periods of 

tectonic subsidence (Mahoney and others, 1991). Subsidence during the lower cycle (Desmoinesian to Missourian, 

Middle to Late Pennsylvanian) provided accommodation 

space for the Hailey Member and correlative strata that 

make up the basal part of the Sun Valley Group. These 

units were deposited in a southwest-flowing braid-delta 

system and adjacent deep-water slope. The braid delta 

drained the Copper Basin highland (now the eastern Pioneer Mountains) where the Copper Basin Formation 

cropped out (Winsor, 1981). The Copper Basin highland 

may have been uplifted along an east-dipping reverse 

fault, as suggested by Mahoney and others (1991), but the 

location of this fault has not been identified. Uplift of the 

Copper Basin highland and coeval subsidence of the 

Wood River Basin to the southwest was probably related 

to the Ancestral Rockies orogeny (Skipp and Hall, 1980; 

Kluth, 1986; Mahoney and others, 1991; Link and others, 

this volume).

During the second cycle of subsidence (Virgilian to 

Wolfcampian, Late Pennsylvanian to Early Permian), the 

Copper Basin highland ceased to be a significant source of 

sediment. Fine-grained carbonate detritus derived from the
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B5

Snaky Canyon Formation (now exposed 100 km to the east) 

may have washed over the site of the former highland on its 

way to the Wood River Basin. This second phase of subsidence may be related to crustal loading by thrust plates to the 

west (Geslin, 1993) or, possibly, to accretion of terranes 

along the western margin of the continent. Such loading may 

have produced the Dry Mountain orogenic phase in east-central Nevada (Trexler and others, 1991) that was synchronous 

with the Virgilian-Wolfcampian time of most rapid subsidence in the Wood River Basin (Mahoney and others, 1991).

MESOZOIC SHORTENING

Shortening of sedimentary rocks during the Late Jurassic to Cretaceous Sevier orogeny was accommodated by 

folding and to a lesser extent by thrusting and cleavage 

development. North-trending folds are upright to east-overturned, and slip along thrusts was generally top-to-the-east. 

Shortening of rocks now exposed in the core of the Pioneer 

Mountains metamorphic core complex is manifested by ductile shear zones and folds of all scales. The geology of the 

core of the Pioneer Mountains has been described by Dover 

(1981, 1983), O'Neill and Pavlis (1988), and Silverberg 

(1988, 1990a, b).

STRUCTURAL STYLE AND GEOMETRY

The presence of far-traveled Mesozoic thrust plates in 

the study area has long been the accepted tectonic model 

(Umpleby and others, 1930; Hal, Rye, and Doe, 1978; Hall, 

1985; Link and others, 1988). Numerous faults have been 

previously identified as thrusts based on the criteria of brittle 

shear zones, gentle fault dips, and stratigraphic juxtaposition. Slip along the thrust faults was inferred to be perpendicular to fold hinges, generally top-to-the-east-northeast. 

Recent mapping (Mahoney and others, 1991; Worl and others, 1991; Mahoney, 1992; Mahoney and Link, 1992; Stewart and others, 1992) and reconstruction of sedimentary 

facies of the Sun Valley Group (Mahoney and others, 1991; 

Link and others, this volume) indicate, however, that many 

of these faults are not thrust faults but instead are (1) shear 

zones with little slip, (2) gently dipping faults characterized 

by normal and strike-slip displacement to the northwest, or 

(3) facies transitions between formations of the Sun Valley 

Group. With our improved understanding of the regional 

geology, we now consider a fault a thrust only if it places 

older rocks on top of younger rocks and (or) preserves evidence of west-southwest-east-northeast slip. All thrust faults 

shown on plate 1 show one or both of these criteria. Following Silverberg (1990b), we have modified Dover's (1981, 

1983) mapping of the lower plate of the Pioneer Mountains 

core complex to show only older-over-younger thrust faults.

The paucity of thrust faults shown on plate 1 represents a significant reinterpretation of the structural geology.

The Pioneer thrust fault places the Ordovician and Silurian Phi Kappa and Silurian Trail Creek Formations or the 

Devonian Milligen Formation and correlative strata over the 

Mississippian Copper Basin Formation (Skipp and Hall, 

1975; Skipp and Hait, 1977; Dover, 1981, 1983; Link and 

others, 1988). The fault strikes north, dips west, and is somewhat discontinuously exposed in the northeastern part of the 

map area (plate 1). Along most of its exposed trace, the thrust 

fault shows a hanging wall that is flat through the Phi Kappa 

Formation; a buried footwall-flat most likely is present in the 

same unit. Several faults immediately west of the trace of the 

Pioneer thrust fault repeat lower Paleozoic strata and are 

interpreted to be imbricate splays that merge into the Pioneer 

thrust fault at depth (Dover, 1981, 1983). This imbricate system of thrusts was shown by Dover as placing both older-onyounger and younger-on-older strata, but based on the structural style to the west (see Wood River thrust discussion 

below) we interpret younger-on-older juxtapositions near the 

Pioneer thrust as locally sheared depositional contacts and 

show a simpler imbricate system in cross section C-C (plate 

1). The direction of slip along the Pioneer thrust fault is 

assumed to be east-northeast, perpendicular to numerous 

fold hinges in its hanging wall and footwall.

The Glide Mountain thrust of Dover (1981, 1983) 

places coarse-grained siliciclastic facies of the Copper Basin 

Formation (unit Mcu, plate 1) over approximately coeval, 

finer grained, more carbonate rich facies of the Copper Basin 

Formation (unit Mcl, plate 1). Dover showed the Glide 

Mountain thrust fault as a continuous structure to the north, 

east, and south of the Pioneer Mountains core complex, but 

the fault as mapped is unusual because it cuts both up- and 

down-section in all directions and eliminates and repeats 

section and because the fault surface displays irregular 

changes in orientation. To explain these features, Dover 

invoked map-scale folding before and after thrusting. An 

alternative interpretation prepared by Wilson (1992, 1994) 

and Wilson and Rodgers (1993), based on new mapping, is 

that the mapped Glide Mountain thrust of Dover is not a 

regionally extensive fault. It is, instead, a depositional contact in Muldoon Canyon (just east of the map area) and Phi 

Kappa Creek, a thrust fault having about 200 m of eastnortheast slip along the East Fork of the Big Lost River, and 

a gently northwest-dipping normal fault having about 800 m 

of top-to-the-northwest slip in Big Fall Creek. In Big Fall 

Creek the Glide Mountain fault decapitates the 48-Ma Summit Creek stock, indicating a 48-Ma or younger age of movement. Plate 1 shows the Glide Mountain fault as mapped and 

interpreted by Wilson (1994).

The Wood River thrust fault of Hall, Rye, and Doe 

(1978) and Dover (1983) was placed by them at the contact 

between the Devonian Milligen Formation and overlying 

Pennsylvanian and Permian strata of the Wood River
B6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Formation, about 5-15 km west of the Pioneer thrust fault, 

but we do not show it on plate 1. Reinvestigation of the 

contact (Skipp and others, 1986; Link and others, 1988; 

Burton and others, 1989; Mahoney and others, 1991; Worl 

and others, 1991; Burton and Link, this volume) suggests 

instead that at least three geologic relations are present 

across it (see cross sections, plate 1): (1) an undisturbed 

unconformity with the Milligen Formation depositionally 

overlain by the Hailey Member or the Eagle Creek Member; (2) an unconformity across which the Hailey Member 

has been sheared, boudinaged, and locally eliminated, with 

east-northeast-trending striations and mineralized quartz 

veins locally preserved along the shear zones; and (3) a 

dextral-normal fault characterized by stratigraphic elimination, typically with Eagle Creek and Wilson Creek Members of the Wood River Formation placed over Milligen 

Formation (Trail Creek and Lake Creek faults, cross sections C-C', D-D', plate 1). Thus, only where the Wood 

River-Milligen contact is sheared to the east-northeast 

could it be a thrust fault (having a hanging wall-flat over 

footwall-flat geometry), but even this type of contact could 

be the result of flexural slip during folding. We do not 

recognize the Wood River thrust fault.

The Trail Creek fault (plate 1) is present from the 

North Fork of the Big Lost River southeastward to the Pioneer Mountains core complex. In the eastern Boulder 

Mountains, the fault places little-deformed Wilson Creek 

Member of the Wood River Formation on complexly 

folded Devonian and older strata. Dover (1983) mapped 

this younger-on-older fault relation as part of the "Wood 

River thrust system." At least two interpretations are possible for this fault. First, it may be a thrust fault of Sevier age 

that was reactivated as an Eocene dextral-normal fault 

(whose structural style is described later). This possibility 

is suggested by the intensity of folding in the footwall 

(interpreted to reflect unusually high strain near the thrust 

fault), as well as by the present relation of younger rocks on 

older. Alternatively, it may be only an Eocene dextral-normal fault, and the intense folding of footwall rocks may be 

unrelated to slip along the fault. Detailed study of the fault 

is needed to clarify its kinematic history.

Several thrust faults having older-on-younger stratigraphic relations are present west of the Pioneer thrust fault 

in its hanging wall, but they have relatively short fault traces 

and minor amounts of slip. The Deer Creek and Murdock 

Creek thrust faults are in the cores of map-scale folds; if this 

structural style is typical, then unrecognized blind thrust 

faults may be associated with other east-vergent folds. Identified minor thrust faults include:

1. The Deer Creek thrust fault west of Hailey, which 

places the lower member of the Dollarhide Formation on the 

Eagle Creek Member of the Wood River Formation (Skipp 

and others, 1994).

2. The Boulder Peak thrust fault in the southern Boulder Mountains, which places the Milligen Formation over 

the Eagle Creek Member of the Wood River Formation 

(Ratchford, 1989).

3. The Washington Basin thrust fault, near the northwestern corner of the map area (plate 1), which places the 

Eagle Creek Member of the Wood River Formation over 

member 2 of the Grand Prize Formation (Mahoney, this 

volume).

4. The Murdock Creek thrust fault, exposed in the 

southern Boulder Mountains between the East Fork of the 

North Fork of the Wood River and Eagle Creek, which places 

the Milligen Formation above the Eagle Creek Member of 

the Wood River Formation, and passes southeastward into 

the core of a northeast-overturned anticline (Batatian, 1991).

5. Four thrust faults that repeat sections of the Milligen Formation in the Triumph area (Turner and Otto, this 

volume).

Shortening during the Sevier orogeny was accommodated by northwest- to north-northeast-trending map-scale 

folding. Folds are open to tight; anticlines are tighter and 

more angular than synclines, and fold wavelengths are commonly several kilometers. Folds are generally symmetric and 

upright west of the Wood River valley but asymmetric and 

east-vergent east of the Wood River valley (cross sections 

C-C', D-D', plate 1). Mesoscopic folds are uncommon in the 

coarser grained Grand Prize and Wood River Formations, 

more common in the fine-grained Dollarhide and Milligen 

Formations, and quite common in lower Paleozoic strata 

near the Pioneer thrust fault. These differences suggest that 

folding was facilitated by high strain, deep burial depths, and 

large variations in lithology and hence rheology.

Map- and outcrop-scale fold hinges trend north-northeast to northwest and plunge gently to subhorizontally north 

or south (plate 1, fig. 2). Three general variations in fold orientation were recognized within the Pennsylvanian and Permian Sun Valley Group. First, within the Carrietown 

mineralized area (Dollarhide Mountain quadrangle, fig. 2) 

isoclinal folds and cleavage are present in the lower member 

of the Dollarhide Formation adjacent to the southeastern 

edge of the Idaho batholith (Whitman, 1990, this volume). 

The folds are tight to isoclinal, and their hinges plunge moderately to the east-northeast, orthogonal to the regional trend 

of fold hinges. A first cleavage is sparsely preserved, 

whereas a second cleavage is well preserved and axial planar 

to numerous mesoscopic folds. The anomalous trend of fold 

hinges is interpreted to be the result of high shear strain, in 

which fold hinges having an initial northwest trend were passively rotated to an east-northeast trend, parallel with the 

overall shear strain direction (Whitman, 1990, this volume). 

Formation of the isoclinal folds only adjacent to the batholith 

suggests that the high strain resulted from lower rock 

strength during contact metamorphism.

A second variation in fold-hinge trend is a counterclockwise rotation from west to east, from S. 4° E. in the Boyle
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B7

114°00'

TRAIL 

LAKE CREEK CREEK 

FAULT -- -

43° 30'

"12

n=56

EXPLANATION 

Average trend and plunge

(in degrees) of fold axis 

Number of poles to bedding

plotted 43° 15'

Figure 2. Cretaceous(?) fold-axis orientations in Paleozoic strata across the central part of 

the study area, Hailey 1 °x2° quadrangle. See text for discussion of data. Folds west of the Trail 

Creek fault involve the Middle Pennsylvanian to Lower Permian Sun Valley Group, folds between the Trail Creek fault and Pioneer thrust fault involve Ordovician to Devonian strata, and 

folds east of the Pioneer thrust fault involve the Mississippian Copper Basin Formation. To 

construct the figure, (1) structural domains (dashed lines) were selected using 7.5-minute quadrangles (fig. 1), major faults, or local map areas as boundaries, (2) all Paleozoic bedding attitudes within each domain were plotted on a lower hemisphere equal-area projection, and (3) an 

average fold axis was measured according to the great-circle distribution of poles to bedding. 

The derived fold-axis attitude and observed outcrop and map-scale fold-hinge attitudes are 

consistent within each domain (see also plate 1). Sources of data include Batatian (1991), 

Batchelder and Hall (1978), Burton (1988), Hall, Batchelder, and Tschanz (1978), Whitman 

(1990), O'Brien and others (1993), P.K. Link (unpublished mapping, Boyle Mountain, Griffin 

Butte, and Seamans Creek quadrangles, 1986-1989), and W. Hall and C. Wavra (unpublished 

mapping. Amber Lakes quadrangle, 1980-1985).

Mountain and Griffin Butte quadrangles to S. 22°-29° E. in 

the Amber Lakes, Sun Valley, and Hailey quadrangles, to an 

extreme rotation of S. 53° E. in the Rock Roll Canyon and 

Phi Kappa quadrangles (fig. 2). We are unsure of the reason 

for this pattern, but it may be related to (1) an increase in 

strain caused by greater heating and (or) proximity to the

Pioneer thrust fault resulting in the rotation of fold axes 

toward the east-northeast transport direction, (2) buttressing 

against the northeastern edge of the Wood River Basin as the 

hanging wall of the Pioneer thrust fault moved eastward, or 

(3) buttressing against concealed footwall ramps in the 

Pioneer thrust fault system. The rotation cannot be attributed
B8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

to superimposed rotation accommodated by younger faults 

because fold-hinge trends do not vary across faults such as 

the Lake Creek and Trail Creek (fig. 2). The first two hypotheses do not satisfactorily explain the observed variations 

because strata directly against the Pioneer thrust fault (which 

also demarcates the edge of the Sun Valley Group) have foldhinge trends of S. 26° E. to S. 20° E., significantly less rotation than fold hinges west of the thrust fault and the edge of 

the Sun Valley Group outcrop belt. Thus, fold-hinge trends 

may reflect patterns of footwall ramps in the Pioneer thrust 

fault or some other, as yet unrecognized, phenomena.

The third trend in fold-hinge orientations is a consistent increase in southeasterly plunge from north to south, 

from the Ryan Peak quadrangle in the northwestern corner 

of the study area to the Grays Peak quadrangle in the southeastern corner. In the Ryan Peak quadrangle fold hinges 

plunge 9° NE. and in the Rock Roll Canyon and Hyndman 

Peak quadrangles fold hinges plunge 14°-16° SE., whereas 

in the Grays Peak quadrangle fold hinges plunge 28° SE. 

The southward tilting of fold hinges may reflect (1) tilting 

of strata along a broad, south-facing lateral ramp beneath 

the Pioneer thrust fault, (2) doming of the Pioneer Mountains core complex, or (3) southward tilting of strata due to 

Neogene downwarping of the Snake River Plain. The first 

option is the preferred hypothesis because doming would 

cause radial tilting of fold hinges away from the core, a feature that is not recognized (fig. 2), and the Snake River 

Plain downwarp extends only a few tens of kilometers 

north of the plain (Zentner, 1989).

AMOUNT OF SHORTENING

The total amount of shortening by folding and thrusting 

is difficult to estimate because of the absence of pinpoints 

across the Pioneer thrust fault, the possibility that flexural 

flow was an important process of fold formation, and the 

variable but unknown extent of pressure dissolution during 

cleavage formation. Skipp and Hait (1977) proposed that 

130-150 km of slip occurred along the Pioneer thrust fault 

because the fault places lower Paleozoic continental slope 

strata over coeval cratonal strata. This amount of slip is 

greater than need be, especially if fades juxtaposition 

occurred by slip along a concealed Late Devonian Antler 

thrust fault rather than along the Cretaceous Pioneer thrust 

fault. If the Pioneer thrust fault is similar to better understood 

Cretaceous thrust faults in the Sevier foreland, only a few 

tens of kilometers of slip may have occurred along it. In the 

hanging wall of the Pioneer thrust fault, a minimum of 10 

km, or 25 percent, of east-northeast-directed shortening is 

evident when folds and thrusts in cross section C-C (plate 

1) are restored, but this is only an estimate because several 

folds in this cross section are schematic. Significantly more 

shortening occurred as a result of small-scale folding, cleavage development, and internal shearing. East of the Pioneer

thrust fault, about 25 percent shortening by folding is evident 

in the Copper Basin Formation (using the cross sections of 

Dover, 1983).

TIMING OF DEFORMATION

Folds and thrust faults formed by the end of the Cretaceous. According to Skipp and others (1994), the Deer Creek 

thrust fault in the Mahoney Butte quadrangle (fig. 1) cut the 

core of an anticline prior to emplacement of the Deer Creek 

stock, dated at 94.4±0.3 Ma using the 40Ar/39Ar technique on 

hornblende (L.W. Snee, U.S. Geological Survey, unpublished data, 1992). Whitman (1990, this volume) identified 

coeval folding, cleavage development, and metamorphism in 

the lower part of the Dollarhide Formation near the Buttercup 

mine (plate 1) and obtained a whole-rock K-Ar age of 

83.9±3.4 Ma from a carbonaceous argillite (R.L. Armstrong, 

written commun., 1990). Just north of the study area, the 

83.0±2.8-Ma (K-Ar, biotite) White Cloud stock intrudes 

north-trending folds, as does an unnamed and undated stock 

in Washington Basin (Mahoney, 1992). A foliated gneissose 

granodiorite in the core of the Pioneer Mountains core complex yielded a hornblende K-Ar age of 67.6±1.6 Ma (Dover, 

1983), and hornblende from a schist in the complex yielded 

a 40Ar/39Ar plateau age of 79.3±1.1 Ma (Silverberg, 1990b). 

All of the ages are best interpreted as ages of cooling below 

the argon retention temperature of the mineral analyzed and, 

as such, are minimum ages of metamorphism and plutonism. 

Thus, available age constraints indicate that deformation had 

ceased by about 79 Ma, but the actual ages of shortening 

remain unconstrained. Regionally, the Atlanta lobe of the 

Idaho batholith was emplaced between about 95 and 75 Ma 

(Johnson and others, 1988); if shortening was approximately 

synchronous with magmatism, then it was a Late 

Cretaceous event.

CRETACEOUS STRUCTURES 

AND MINERALIZATION

Intrusion of the Idaho batholith and satellite plutons produced the most historically productive mineral deposits in the 

Wood River region. Shear-zone-hosted silver-lead-zinc veins 

having a gangue of quartz or siderite are present in several 

mineralized areas. These mesothermal veins developed during faulting that was synchronous with or followed intrusive 

activity and were filled by mineral deposition from hydrothermal systems driven by the Cretaceous intrusive activity. 

East of the Wood River these veins occupy thrust faults and 

sheared stratigraphic contacts. In the southern Smoky Mountains, the dominant strike of these veins is parallel with Mesozoic fold hinges and sheared axial zones. The mineralized 

areas (plate 1) (Worl and Johnson, this volume; Link and
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B9

others, this volume) include Triumph, Minnie Moore, Bullion, Bellevue, Hailey gold belt, Bunker Hill, Deer Creek 

stock, Rooks Creek stock, Croesus stock, Carrietown, 

Vienna, and Washington Basin.

Host structures for the Cretaceous vein deposits 

include:

1. Thrust faults and sheared areas along the unconformity between the Milligen Formation and the Hailey 

Member of the Wood River Formation. In the Triumph 

area, much of the lead-silver-zinc ore was produced from 

shear-zone-hosted veins along thrust faults. The mineralized Fissure fault at the Triumph mine and the ore zone at 

the North Star mine are interpreted to be the same structure 

offset by a normal fault (Turner and Otto, this volume). In 

the Triumph mineralized area the mineralized thrusts are 

intruded by granitic (quartz porphyry) and andesitic dikes 

(Kiilsgaard, in Anderson and others, 1950) that are displaced by low-angle normal faults, including the Triumph 

Shaft flat fault (Turner and Otto, this volume). The sheared 

unconformity between the Milligen and Wood River Formations hosts quartz veins that contain small lead-zinc 

deposits in the Wood River and Lake Creek mineralized 

areas (Burton and Link, this volume).

2. North west-striking high-angle normal faults. 

These control locations of veins in the Minnie Moore and 

Bullion mineralized areas, west of Bellevue and Hailey 

(Link and Worl, in press). These faults, though generally 

parallel with earlier fold axes, cut the Croesus and Deer 

Creek stocks (intruded about 90 Ma) and may represent a 

period of extension during initial uplift of the stocks. The 

shear-zone-hosted veins are interpreted as Cretaceous in 

age because they contain mesothermal mineral assemblages 

and fluid inclusions and because there are no Eocene intrusive rocks exposed nearby.

3. High-angle faults and minor fractures parallel with 

Mesozoic fold hinges. These are especially important in the 

Rooks Creek stock mineralized area (Park, 1990, in press) 

and the Washington Basin area (Mahoney, this volume). In 

the Rooks Creek mineralized area, the mineralized veins 

strike northeast and contain sericite dated by 40Ar/39Ar at 

about 91 Ma (Park, in press).

Mineralization of the Carrietown, Vienna, and Marshall 

Peak mineralized areas is associated with intrusion of the 

main-phase batholith about 80 Ma (Darling and others, this 

volume; Mahoney and Horn, in press). The Marshall Peak 

and Vienna areas are not shown on plate 1 but are directly 

west and north of Galena Summit, in the northwestern part 

of the map area. The host structures are northwest- and 

northeast-striking shear zones that developed after intrusion 

of the batholith in the Vienna area but may have been inherited from the pre-intrusion compressional structures in the 

Carrietown area.

CRETACEOUS TO EOCENE 

EXHUMATION

Exhumation of the Atlanta lobe and adjacent country 

rock occurred during Late Cretaceous to Eocene time, during and (or) after folding, thrusting, and batholith emplacement. Evidence for exhumation includes isotopic and 

geochronologic data from the batholith (Jordan, 1994) and 

the unconformable contact of the Challis volcanic group on 

batholith rocks. Distinct lateral and vertical trends have been 

observed in both the alteration and the apparent K-Ar ages 

of biotite from Cretaceous plutons in the southern Atlanta 

lobe, mostly just west of the study area (Criss and others, 

1982). These trends were attributed to postemplacement 

exhumation and reheating of the batholith, including exhumation during the Late Cretaceous to early Paleogene at a 

rate of about 120 m/m.y., arching during the middle Eocene 

(and perhaps earlier) about a north-trending axis in the eastcentral part of the batholith, and reheating during the middle 

Eocene, with the intensity of reheating increasing toward the 

east-central part of the core, with depth, and near individual 

Eocene plutons. Second, in the Smoky Mountains the Idaho 

batholith was emplaced at a depth of 8-12 km (Whitman, 

1990), but basal lavas of the Eocene Challis Volcanic Group 

unconformably overlie the batholith and its country rock. 

Thus a cumulative uplift of 8-12 km occurred between 84 

Ma, the minimum age of metamorphism and mineralization 

(Darling, 1987; Whitman, 1990, this volume), and 51 Ma, 

the approximate age of initial eruption of Challis volcanic 

rocks (Moye and others, in press).

Exhumation is indirectly indicated by Upper Cretaceous to Eocene sedimentary deposits. In the Boulder and 

Pioneer Mountains, the conglomerate of Smiley Creek 

(Paull, 1974) is sparsely preserved beneath the basal Challis 

lavas (on plate 1 the Smiley Creek is included with the 

Challis Volcanic Group). The conglomerate is an alluvial fan 

deposit containing clasts of subjacent Paleozoic formations 

that suggests well-developed topographic relief within the 

area. Paull (1974) and Dover (1981, 1983) suggested that the 

conglomerate could be as old as Cretaceous or as young as 

Eocene. Burton and Blakley (1988) documented a 

conformable transition from conglomerate to tuffaceous 

sandstone and lahar deposits of the Eocene Challis Volcanic 

Group that suggests deposition occurred just prior to Eocene 

volcanism, about 51 Ma. The lack of a sedimentologic tie 

between the Idaho batholith and the conglomerate of Smiley 

Creek makes it unclear, however, if this deposit reflects 

uplift of the batholith. In Oregon and California, Eocene 

arkosic sandstone is interpreted to reflect exhumation of the 

Idaho batholith. The Idaho batholith and Eocene Tyee 

Formation of western Oregon show similar Nd-Sm, Rb-Sr, 

K-Ar, 18O- 16O, and D/H isotopic values (Heller and others, 

1985), evidence that the batholith was the major source of 

sediment for the Tyee Formation (although the isotopic
BIO GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

variation of the batholith is not sufficient to uniquely identify 

which lobe provided sediment). Similarly, the Upper Cretaceous to lower middle Eocene Montgomery Creek Formation of northern California contains detrital muscovite that 

has Cretaceous to Eocene 40Ar/39Ar ages unlike those from 

nearby crystalline rocks but similar to those in the Idaho 

batholith (Renne and others, 1990).

Based on the relatively long duration and slow, steady 

rate of Late Cretaceous to Paleogene exhumation, Criss and 

others (1982) proposed that exhumation was related to 

regional isostatic uplift. Late Cretaceous to Paleogene 

drainage patterns and pollen indicate that mountains once 

capped the Idaho batholith (Axelrod, 1968; Heller and others, 1985; Renne and others, 1990), mountains that probably formed in response to crustal heating and thickening. 

Erosion of the mountains and consequent isostatic uplift 

would have caused exhumation of the deep-seated batholith 

(England and Molnar, 1990; Jordan, 1994). In contrast, 

Eocene exhumation may reflect more localized isostatic 

uplift that was a response to more localized Challis magmatism and extension (Criss and others, 1982).

EARLY EOCENE(?) TO OLIGOCENE 

DEFORMATION

Most faults in the study area are normal and strike-slip 

faults that accommodated northwest-southeast slip during 

the Paleogene. Major fault sets and associated structures 

include low-angle faults, high-angle normal faults, dikes, 

and the Pioneer Mountains metamorphic core complex. 

Recent studies by Kim (1986), Wust (1986), O'Neill and 

Pavlis (1988), Silverberg (1988, 1990a, b), Huerta (1992), 

and Wilson (1994) significantly improve our kinematic 

understanding of these structures and reveal that tectonic 

activity occurred episodically for more than 15 m.y., before, 

during, and after eruption of the middle Eocene Challis Volcanic Group. In the following section we discuss low-angle 

faults first because available age constraints indicate that 

movement on most low-angle faults occurred prior to formation of the other structures.

EARLY EOCENE(?) DEXTRAL-NORMAL 

FAULTING

Several northwest-striking, gently southwest dipping 

faults that accommodated dextral-normal slip formed at 

some time after Cretaceous folding and prior to or during the 

early stages of Eocene Challis volcanism. We infer that most 

slip occurred in the early Eocene, but more data are needed 

to document the precise age(s) of faulting.

STYLE AND GEOMETRY OF FAULTS

Several low-angle faults are exposed in the Boulder, 

Pioneer, and Smoky Mountains (Kim, 1986; Burton, 1988; 

Batatian, 1991; Worl and others, 1991; Burton and Link, this 

volume). The faults generally strike northwest and dip 

4°^5° SW. A concentration of fault striations that trend and 

plunge gently west-northwest to northwest indicate predominantly strike slip displacement, and along at least one fault, 

the Lake Creek fault, the sense of slip is dextral (Huerta, 

1992). The faults have strike lengths of from 1 to more than 

40 km and are typically characterized by stratigraphic elimination. The faults are expressed as sharp contacts or brecciated zones several centimeters to meters thick, and in some 

places, notably at the head of Lake Creek and Trail Creek in 

the Boulder Mountains, the fault zones are filled with 1-2 m 

of quartz veins.

Two major low-angle, top-to-the-northwest faults, the 

Trail Creek and Lake Creek faults, in the northern Boulder 

Mountains (plate 1) (Batatian, 1991; Burton and Link, this 

volume) were previously mapped as Mesozoic thrust faults 

by Umpleby and others (1930) and Dover (1981, 1983) but 

have been reinterpreted by us as dextral-normal faults 

because they cut across folds, generally eliminate stratigraphic section, and locally have northwest-trending striations. The trace of the better studied Lake Creek fault 

extends for more than 40 km from the central Boulder Mountains to the western Pioneer Mountains (plate 1). The fault 

strikes N. 45°-52° W. and dips 20°-30° SW. (Huerta, 1992). 

In most places the fault places younger rocks on older rocks, 

but in a few places the reverse is true because the rocks were 

folded prior to faulting.

Numerous other low-angle faults having northwest slip 

have been identified within the study area. Kim (1986) measured northwest-trending striations on the Pioneer thrust 

fault system, the Glide Mountain thrust of Dover (1983), and 

several unnamed low-angle faults north and west of the core. 

The Glide Mountain fault north of Summit Creek clearly displays a top-to-the-northwest fabric (Wilson, 1992, 1994). 

Turner and Otto (this volume) mapped four subhorizontal 

faults having northwest striations that cut Challis volcanic 

rocks in the Triumph mineralized area just west of the 

exposed core complex. In the central and southern Smoky 

Mountains low-angle normal faults have been mapped in 

several places, including in the Mahoney Butte quadrangle 

(Skipp and others, 1994), in Colorado Gulch southwest of 

Hailey (Link and others, 1988; Link and Worl, in press), and 

in the central Smoky Mountains near Baker Peak (Stewart, 

1987; Stewart and others, 1992). The low-angle Rockwell 

fault displaces the Minnie vein in the Minnie Moore mine 

(Anderson and others, 1950; Link and Worl, this volume), 

and a low-angle fault places Wood River Formation above 

Dollarhide Formation in the Bullion mineralized area (Skipp 

and others, 1994; Link and Worl, in press).
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS Bll

In order to determine if the gentle dips of low-angle 

faults are due to superimposed tilting, the attitudes of other 

structures and contacts were compared to their expected initial attitudes. Middle Eocene volcaniclastic rocks are variably tilted as much as 20°, more consistently northeast than 

other directions (Worl and others, 1991), and the regional 

outcrop patterns of subplanar volcanic and hypabyssal contacts (for example, Mahoney, 1987) suggest that 10°-15° of 

tilting to the northeast has occurred, probably in association 

with basin and range faulting. North-northwest-trending 

Cretaceous fold hinges consistently plunge less than 16° (fig. 

2), except near the Idaho batholith and just south of the Pioneer Mountains core complex, and northeast-striking middle 

Eocene dikes throughout the region and rare northwest-striking dikes are subvertical. These attitudes are typical of those 

for untilted hinges and dikes. Finally, the deformational style 

along major low-angle faults does not vary along strike. For 

instance, along its 40-km length (subparallel with its slip 

direction) the Lake Creek fault shows no evidence of ductile 

shear, though ductile fabrics would be expected if the fault 

had been tilted southeast by more than about 15°. Taken 

together, the data suggest that low-angle faults have been 

tilted less than 15°, making them originally low-angle faults.

AMOUNT OF OFFSET

The offset on most low-angle faults has not been 

determined. One exception is the Lake Creek fault, the offset of which was determined by restoring piercing points 

defined by the intersection of a map-scale synclinal trough 

and the fault surface (Huerta, 1992). Devonian and Pennsylvanian-Permian strata within both the hanging wall and 

footwall of the fault are folded into northwest-trending, 

map-scale, overturned synclines (plate 1). The synclines 

extend along the entire length of the fault, but the fault cuts 

obliquely across them. Two piercing points are located 

where the planar contact of the Wilson Creek and Eagle 

Creek Members of the Wood River Formation is folded 

into a linear trough and intersects the Lake Creek fault surface (fig. 3). The vector between these piercing points 

trends N. 50° W., plunges 2° NW., and is 18 km long. This 

slip vector is corroborated by the unique geometries of the 

synclines. To the northwest both synclines are overturned, 

whereas to the southeast both synclines are upright, and 

restoration of 15 km slip juxtaposes overturned parts and 

upright parts of the folds (fig. 3). The calculated slip vector 

indicates that displacement along the Lake Creek fault 

involved significant dextral slip and minor normal slip.

Turner and Otto (this volume) estimate a minimum of 

several hundred meters of northwest-directed slip along lowangle faults near the Triumph mine southeast of Ketchum.

TIMING OF FAULTING

The age of dextral-normal faulting is bracketed by 

crosscutting relations with the Challis Volcanic Group. 

Regionally, intermediate volcanism occurred from 51 to 48 

Ma and silicic volcanism occurred from 48 to 44 Ma (Moye 

and others, in press; L.W. Snee, U.S. Geological Survey, 

unpublished data, 1992).

1. The low-angle normal fault near Big Fall Creek 

previously identified as the Glide Mountain thrust fault by 

Dover (1981, 1983) was thought by Dover to be pinned by 

the Summit Creek stock. New mapping by Wilson (1994) 

indicates that the fault decapitates the stock, which was 

emplaced 48.5±2.0 Ma (K-Ar, hornblende) (Zartman, 

unpublished data in Silverberg, 1990b). Porphyroblasts in 

the contact aureole of the stock are sheared in the normal 

fault zone, further evidence that some slip occurred after 

stock emplacement (Wilson, 1992).

2. Near their northern terminations the Lake Creek 

and Trail Creek faults encounter a dacite-rhyolite hypabyssal center that was uplifted 450 m along a steeply south 

dipping normal fault (plate 1, cross section A-A') (Batatian, 

1991). The hypabyssal center extends across the low-angle 

faults, indicating that emplacement the center broadly postdates slip along the faults. Within the center all rhyolite 

dikes pin the faults, whereas many dacite dikes are offset a 

few to at least several tens of meters (Batatian, 1991; oral 

commun., 1992). Dacite was dated at 50.2±1.8 Ma using 

the K-Ar technique (Fisher and others, 1983), and hornblende from a rhyolite porphyry 2 km north of the center 

was dated at 47.2 Ma using the K-Ar technique (Dover, 

1981). This, and the fact that the Lake Creek fault to the 

south is overlain by undated Eocene volcanic breccia, is 

interpreted to indicate that most slip along the Lake Creek 

and Trail Creek faults occurred prior to Challis volcanism 

but that minor slip was coeval with early Challis volcanism.

3. Near Baker Peak a low-angle fault is intruded by 

dacite porphyry dikes 48 m.y. old (K-Ar age, whole rock) 

(Stewart and others, 1992, in press).

4. Low-angle normal faults cut dacite lava in the Triumph area southeast of Ketchum (Turner and Otto, this volume) and at several other locations, and they cut dacite and 

rhyolite volcanic rocks in the Easley Hot Springs quadrangle 

(Ratchford, 1989).

In summary, it is likely that the majority of movement 

on the Lake Creek and Trail Creek faults was prior to intermediate volcanism (51-48 Ma), that movement on other 

faults was at some time prior to silicic volcanism (48^4 

Ma), and that movement on a few faults was after silicic volcanism. We theorize that the pre-Challis dextral-normal 

faults formed just prior to Challis magmatism, not well 

before it, because in the Challis 1 °x2° quadrangle northweststriking dextral strike-slip faults are associated with a northwest alignment of early Challis volcanic vents (Mclntyre and 

others, 1982).
114°22'30' 

43°52'30"4-

B B

Hanging wall of 

Lake Creek fault

BB 

VERTICAL EXAGGERATION 

TICK INCREMENT=300 FE

Hanging wall of 

Lake Creek fault

A

AA AA'

VERTICAL EXAGGERATION X5 

TICK INCREMENT=300 FEET
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B13

MIDDLE EOCENE TO OLIGOCENE 

EXTENSION

Widespread middle Eocene to middle Oligocene extension is manifested by high-angle faults, ductile shear zones, 

boudinage, and dike swarms. Extension was coeval with and 

postdated the main phase of eruption of the Challis Volcanic 

Group and resulted in uplift of the Pioneer Mountains metamorphic core complex.

STRUCTURAL STYLE AND GEOMETRY

Dike swarms associated with Challis volcanism have 

been mapped in several places, notably in the northern Boulder Mountains (Tschanz and others, 1986; Batatian, 1991; 

Schmidt, 1994; Moye and others, in press) and in the Smoky 

Mountains west of the area of plate 1 (Worl and others, 1991; 

Stewart and others, in press). Individual dikes are present 

throughout the study area but are too small to show on plate 

1. Dike swarms are more common to the west and east of the 

study area, where substantial exposures of plutonic and volcanic rocks are present. All dike swarms and most individual 

dikes strike northeast and dip almost vertically.

Normal faults that strike northeast, dip moderately to 

steeply southeast or northwest, and extend for several hundreds to several thousands of meters are present throughout 

the study area (plate 1). Stratigraphic juxtapositions indicate 

dip-slip displacements of a few hundred to rarely a few thousand meters. Most of these faults are unnamed, but one, the 

White Mountains fault, forms the southeast boundary of the 

Pioneer Mountain core complex (Dover, 1981, 1983) (plate 

1, cross section A-A'}. Because the high-angle fault set is distributed throughout the study area and is parallel with the 

Trans-Challis fault system in central Idaho (Bennett, 1986), 

it is inferred to be part of that system.

Figure 3 (facing page). Map view showing structure contours 

and slip vector of the Lake Creek fault. Contour interval 300 ft (91 

m); contours are dashed where extrapolated. Slip vector of N. 50° 

W., plunge 2°, and 18 km long is based on displacement of piercing points where trough of a Mesozoic syncline pierces the fault 

surface. Solid circles indicate well-constrained locations; x's indicate poorly constrained locations. Bar and ball on fault line indicates minor normal fault. Cross sections show geometry of Lake 

Creek fault and of contact between the Wilson Creek Member of 

the Wood River Formation (Pwu) and the Eagle Creek and Hailey 

Members of the Wood River Formation (PPwl) (not shown in 

map view) in the hanging wall (A-A', B-B') and the footwall 

(AA-AA', BB-BB') of the fault. Stacking of cross sections shows 

the inferred fold geometry after restoration of 18 km of slip along 

fault. Modified from Huerta (1992).

PIONEER MOUNTAINS METAMORPHIC 

CORE COMPLEX

The Pioneer Mountains metamorphic core complex 

includes a core of Early Proterozoic gneiss separated by the 

Hyndman ductile shear zone from Middle Proterozoic and 

lower Paleozoic metasedimentary rocks and intruded by 

Cretaceous(?) and Tertiary plutons. The core is separated by 

the Wildhorse detachment fault from overlying, internally 

faulted Paleozoic and Eocene rocks (plate 1). Dover (1981, 

1983) mapped the core and surrounding cover rocks, and Silverberg (1988, 1990a, b) studied the metamorphic, structural, and geochronologic history of the core. Wust (1986) 

studied the Wildhorse detachment fault, and O'Neill and 

Pavlis (1988) studied the detachment kinematics in some 

detail. Kirn (1986), Burton (1988), Burton and others (1989), 

Huerta (1992), Wilson (1994), and Burton and Link (this 

volume) described the geometry and kinematics of faults in 

the upper plate. We refer the reader to these studies for 

detailed discussions of the core and here only briefly review 

the structural geology of the detachment and upper plate.

The Wildhorse detachment fault (plate 1) is a brittle 

fault zone several meters thick that flanks the core on three 

sides (Dover, 1981, 1983; Wust, 1986). The fault surface is 

not planar but takes the shape of a map-scale kink fold that 

plunges northwest. The kink axis is along the northwest corner of the core and plunges about 25° NW., whereas the sides 

of the fault dip 45°-70° to the northeast and southwest, away 

from the core (Wust, 1986). In all places, the detachment 

fault shows west-northwest- to northwest-trending striations 

(Wust, 1986), making it a dextral-normal or sinistral-normal 

fault, except along the kink axis where it is a dip-slip normal 

fault. The fault overlies and (or) cuts across a 5-100-m-thick 

ductile shear zone, characterized by mylonitic gneiss, marble, and quartzite, that has kinematic indicators also indicating top-to-the-northwest shear strain (Wust, 1986; O'Neill 

and Pavlis, 1988; Silverberg, 1990b). 40Ar/39Ar analysis of 

minerals in the shear zone indicates that the zone cooled rapidly during the early Oligocene (36-33 Ma); Silverberg 

(1990a, b) interpreted the cooling to reflect tectonic unroofing due to slip along the shear zone.

The upper plate of the Pioneer Mountains core complex 

extends in all directions away from the core and has no definite outer boundary. The upper plate contains two main sets 

of Eocene(?) to Oligocene faults having northwest-southeast 

slip. Previously described low-angle faults (Trail Creek, and 

Lake Creek faults) accommodated top-to-the-northwest slip 

after Cretaceous folding and before the main phase of Challis volcanic activity. The previously described northeaststriking high-angle normal fault set was active during and 

(or) after the middle Eocene. The role of these faults in core 

complex formation and uplift is not clear. The Pioneer and 

Trail Creek faults are cut by the Wildhorse detachment fault 

(Dover, 1981, 1983) (plate 1), whereas the crosscutting relation between the detachment fault and the Lake Creek fault
B14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

is not known. High-angle normal faults may be temporally 

related to core complex development, but the small offset 

accommodated by them contrasts with upper plate fault patterns typical of core complexes. Upper plate rocks in the 

study area are not significantly tilted by faulting, in contrast 

to many other core complexes where upper plate strata are 

strongly tilted by domino-style faulting. At this point in our 

studies we have not documented significant upper plate 

extension that is temporally related to uplift of the core complex.

AMOUNT OF EXTENSION

Slip along the Wildhorse detachment fault was estimated by Wust (1986) as at least 17 km based on two lines 

of evidence: first, upper plate rocks in the Boulder Mountains northwest of the core originated southeast of the core, 

and second, the Summit Creek stock north of the core might 

be the beheaded equivalent of an Eocene pluton in the eastern half of the core. There is no stratigraphic evidence, however, that strata northwest and southeast of the core were 

originally contiguous, and a gravity study of the Summit 

Creek stock was unable to resolve whether the stock is 

rooted (Wust, 1986). Silverberg (1990a, b) presented evidence that the core rose as much as 8.4 km during the middle 

Eocene and proposed 23 km of horizontal displacement 

along the Wildhorse detachment fault, if it accommodated 

the 8.4 km of uplift and dipped 20° NW.

Slip along most high-angle faults has not been measured, but the steep dips and relatively small displacements 

of the faults suggest that the faults individually accommodated small amounts of extension as compared to that along 

more gently dipping faults. However, because of the large 

number of high-angle faults, the total north west-southeast 

extension accomplished along them may be significant. As 

an estimate of the approximate cumulative extension, each 

fault is assumed to dip 70° and show dip-slip displacement 

of 100 m. If the faults are spaced at a 250-m interval across 

a fault zone 100 km wide (measured northwest-southeast), 

the total northwest-southeast extension is about 14 km. 

Slightly modifying these assumptions (dips of 60°-80°, slips 

of 50-200 m, fault spacing of 200-400 m) yields estimates 

of extension ranging from 5 to 20 km, a cumulative extension of from 6 to 25 percent across the fault zone.

TIMING OF MAGMATISM AND EXTENSION

The ages of most structures are incompletely known at 

this time, but age constraints indicated by crosscutting textures and radiometric dating include the following:

1. Northeast-trending Challis dikes are dated, or 

served as feeders to volcanic flows that are dated, between

Ma for intermediate compositions and 48^4 Ma for 

silicic compositions (Moye and others, in press).

2. High-angle normal faults associated with the TransChallis system cut most dikes and rocks of the Challis Volcanic Group and cut low-angle faults having dextral-normal 

or indeterminate slip directions (Kim, 1986). The high-angle 

White Mountains fault cuts the Wildhorse detachment fault.

3. Silverberg (1988, 1990a, b) used 40Ar/39Ar geochronology on the lower plate of the Pioneer Mountains 

metamorphic core complex to document two phases of rapid 

cooling, at 48-45 Ma and at 36-33 Ma. The first phase was 

associated with 8.4 km of uplift, but the fault(s) that accommodated uplift is not known. The second phase reflects 4 km 

of uplift along the Wildhorse detachment fault.

According to these data, northwest-southeast extension occurred in the middle Eocene and the middle Oligocene. In the middle Eocene, dikes formed and one or 

more low-angle faults (the Wildhorse detachment?) must 

have slipped to produce 8 km of lower plate uplift. The Pioneer Mountains core complex was uplifted in two stages; 

the Wildhorse detachment fault was active during at least 

the second stage. The age(s) of high-angle faulting is not 

certain: the structurally parallel Trans-Challis fault zone 

formed in the middle Eocene (Bennett, 1986), but at least 

one high-angle fault in the study area cuts the middle Oligocene Wildhorse detachment fault.

EARLY EOCENE(?)-OLIGOCENE 

MINERALIZATION

Mineralized areas affected by hydrothermal cells generated during Challis magmatism and associated faulting 

include much of the Galena, Boulder Basin, Lake Creek, 

Smoky Mountains, Summit, and East Fork Salmon River 

areas. Regionally in south-central Idaho, Eocene gold-bearing epithermal ore deposits are associated with silicification along Trans-Challis fault zones formed during 

northwest-directed crustal extension. Generally the deposits are associated with extensive argillic and sericitic alteration of wallrock.

Most Eocene mineral deposits in Paleozoic rocks of the 

northeastern Hailey I°x2° quadrangle are in the Boulder and 

Smoky Mountains. The deposits are associated with 

hypabyssal intrusive rocks, especially granite and rhyolite, 

that make up the final Eocene intrusive phase, dated about 

48-44 Ma (L.W. Snee, U.S. Geological Survey, unpublished 

data, 1992; Stewart and others, in press).

Deposits in the Summit mineralized area of the northern 

Pioneer Mountains are associated with Eocene granodiorite 

of the Summit Creek stock and include skarns and veins in 

the Phi Kappa mine, molybdenum stockwork deposits in the 

Summit Creek stock in Fall Creek, and epithermal veins in 

unnamed Silurian and Devonian units in the East Fork of 

Trail Creek and Bear Canyon (Bruner, 1991).
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B15

The Lake Creek mineralized area in the Boulder Mountains (Burton and Link, this volume) contains silver-leadzinc veins at the Homestake and Long Grade prospects. 

These veins are in northwest-striking normal faults interpreted to be splays of the underlying Lake Creek dextral-normal fault. Intrusive rocks in the area include Eocene dacite 

porphyry dikes; larger stocks may be present at depth.

A variety of mineral deposits in the Boulder Basin, 

Galena, and Smoky Mountains areas are associated with 

Eocene silicic intrusive complexes. Deposits contain polymetallic veins and replacements in calcareous wallrock of 

the Milligen Formation and Sun Valley Group (Ratchford, 

in press).

The main period of mineralization in the Triumph mineralized area was interpreted by Kiilsgaard (in Anderson and 

others, 1950) to have occurred in the early Tertiary. The mineralization was interpreted to have been postbatholith and 

prevolcanic and associated with postbatholith andesite dikes. 

In contrast, Umpleby and others (1930), Hall, Rye, and Doe 

(1978), and Turner and Otto (this volume) interpreted the 

main period of mineralization to have been associated with 

Cretaceous intrusive activity and Eocene intrusive rocks in 

the Triumph mineralized area to postdate mineralization.

(plate 1, cross section B-B') (Mahoney, 1992; Stewart and 

others, 1992). Offset along these faults was accompanied by 

10°-15° of tilting to the northeast, as shown by regional outcrop patterns of subplanar volcanic and hypabyssal contacts 

(for example, Mahoney, 1987) and a few measurements of 

the attitudes of Challis Group volcaniclastic rocks.

Field observation (Umpleby and others, 1930) and analysis of aerial photographs and satellite imagery (Southworth, 

1988) demonstrate two prominent sets of lineaments, trending northeast and north-northwest, that control topography 

and cut rocks of all ages in the study area. One prominent 

northeast lineament is aligned with the East Fork of the 

Wood River. Turner and Otto (this volume) describe northeast-striking, steeply dipping faults, having tens of meters of 

apparent right-lateral displacement, that may be related to 

the formation of northeast-trending lineaments. Although 

the northeast-striking faults and lineaments are oriented perpendicular to basin and range faults, crosscutting relations 

suggest at least some postdate basin and range faults (Turner 

and Otto, this volume).

AMOUNT AND TIMING OF EXTENSION

NEOGENE BASIN AND RANGE 

EXTENSION

Neogene tectonic activity in the Wood River area is 

manifested by the development of northwest-striking basin 

and range normal faults. No near-surface remobilization of 

metals can be attributed to these faults, although they influence the locations of active hot springs and possible metal 

remobilization and deposition at depth. The young faults also 

cut mineral deposits, locally terminating minable ore shoots.

STRUCTURAL STYLE AND GEOMETRY

In the Smoky and Boulder Mountains, Neogene basin 

and range faults have broken the crust into gently northeast 

tilted blocks (plate 1, cross section B-B'} (Mahoney, 1987; 

Stewart and others, in press). The faults have north to northwest strikes, steep to moderate dips, and relatively long continuous map traces and cut across almost all other faults, 

folds, and pre-Quaternary rocks. Major faults include the 

Sun Valley fault zone, which strikes north along the east side 

of the Wood River valley (plate 1, cross sections B-B', C-C', 

D-D') and cuts Quaternary sediments near Sun Valley (Hall, 

Batchelder, and Tschanz, 1978), the Boulder front fault, 

which strikes northwest along the front of the Boulder 

Mountains (Tschanz and others, 1986; Mahoney and Link, 

1992), and the Big Smoky fault, which strikes north through 

much of the Smoky Mountains along Big Smoky Creek

The amount of northeast-southwest extension accommodated by basin and range faults is about 10 percent, if 

basin and range faults in cross section B-B' or C-C' (plate 1) 

are restored. Other unmapped faults having lesser offsets are 

present, making this estimate a minimum, but the true 

amount of extension probably is not substantially larger.

Little is known about the age of basin and range extension in the study area. The age of initial basin and range 

extension is not known because the oldest sediments in the 

Wood River valley are concealed beneath younger basin fill. 

Some recent slip is indicated by a fault scarp in Quaternary 

sediments near Sun Valley (Hall, Batchelder, and Tschanz, 

1978). In southern Idaho, basin and range faulting probably 

began in the early Miocene and continued sporadically to the 

present (Allmendinger, 1982; Rodgers and others, 1990), 

and a similar age span is likely for the northeastern part of 

the Hailey quadrangle.

REFERENCES CITED

Allmendinger, R.W., 1982, Sequence of late Cenozoic deformation 

in the Blackfoot Mountains, southeastern Idaho, in 

Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic 

geology of Idaho: Idaho Bureau of Mines and Geology 

Bulletin 26, p. 505-516.

Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 1950, 

Detailed geology of certain areas in the Mineral Hill and Warm 

Springs mining districts, Blaine County, Idaho: Idaho Bureau 

of Mines and Geology Pamphlet 90, 73 p.
B16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Axelrod, D.I., 1968, Tertiary floras and topographic history of the 

Snake River Basin, Idaho: Geological Society of America Bulletin^. 79, p. 713-734.

Batatian, L.D., 1991, Paleozoic stratigraphy and Cenozoic structure, central Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 85 p.

Batchelder, J.N., and Hall, W.E., 1978, Preliminary geologic map 

of the Hailey 7.5 minute quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 78-545, scale 1:24,000.

Bennett, E.H., 1986, Relationship of the trans-Challis fault system 

in central Idaho to Eocene and Basin and Range extension: 

Geology, v. 14, p. 481-484.

Bruner, D.J., 1991, Origina of mineralizationwithin Devonian-Silurian sedimentary breccias, northeastern Boulder Mountains, 

Custer County, south-central Idaho: Pocatello, Idaho State 

University, M.S. thesis, 118 p.

Burton, B.R., 1988, Stratigraphy of the Wood River Formation in 

the eastern Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 165 p.

Burton, B.R., and Blakley, J.B., 1988, The basal Challis conglomerate, Custer County, south-central Idaho Implications for 

the initiation of Challis volcanism: Geological Society of 

America Abstracts with Programs, v. 20, no. 6, p. 408-409.

Burton, B.R., Link, P.K., and Rodgers, D.W., 1989, Death of the 

Wood River thrust Structural relations in the Pioneer and 

Boulder Mountains, south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 21, no. 5, p. 62.

Criss, R.E., Lanphere, M.A., and Taylor, H.P., Jr., 1982, Effects of 

regional uplift, deformation and meteoric-hydrothermal metamorphism on K-Ar ages of biotites in the southern half of the 

Idaho batholith: Journal of Geophysical Research, v. 87, p. 

7029-7046.

Darling, R.S., 1987, The geology and ore deposits of the Carrietown 

silver-lead-zinc district, Blaine and Camas Counties, Idaho: 

Pocatello, Idaho State University, M.S. thesis, 168 p.

 1989, Geologic map and cross-sections of the northern half 

of the Dollarhide Mountain quadrangle: Idaho Geological Survey Technical Report 89-1, 1 plate.

Davis, S., 1984, A microstructural perspective of orogenesis in the 

Pioneer Mountains, central Idaho: Missoula, University of 

Montana, M.S. thesis, 55 p.

Dover, J.H., 1980, Status of Antler orogeny in central Idaho, clarification and constraints from the Pioneer Mountains, in Fouch, 

T.D., and Magathan, E.R., eds.. Paleozoic paleogeography of 

the West-Central United States: Rocky Mountain Section, 

Society of Economic Paleontologists and Mineralogists, WestCentral United States Paleogeography Symposium 1, p. 

371-381.

 1981, Geology of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho, in Mineral resources 

of the Boulder-Pioneer Wilderness Study Area, Blaine and 

Custer Counties, Idaho: U.S. Geological Survey Bulletin 

1497-A,p. 1-75.

 1983, Geologic map and sections of the central Pioneer 

Mountains, Blaine and Custer Counties, central Idaho: U.S. 

Geological Survey Miscellaneous Investigations Series Map 

1-1319, scale 1:48,000.

England, P., and Molnar, P., 1990, Surface uplift, uplift, and exhumation of rocks: Geology, v. 18, p. 1173-1177.

Fisher, F.S., May, G.C., and Johnson, F.L., 1983, Mineral resource 

potential, geology, and geochemistry of part of the White 

Cloud-Boulder Roadless Area, Custer County, Idaho: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1580, scale 1:62.500.

Gehlen, W.T., 1983, The geology and mineralization of the eastern 

part of the Little Smoky Creek mining district, Camas County, 

Idaho: Moscow, University of Idaho, M.S. thesis, 116 p.

Geslin, J.K., 1993, Evolution of the Pennsylvanian-Permian 

Oquirrh-Wood River Basin, southern Idaho: Los Angeles, 

University of California, Los Angeles, Ph.D. dissertation, 

272 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed.. Symposium on the geology 

and mineral deposits of the Challis 1 °x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

 1987, Stratiform syngenetic deposits of precious and base 

metals in argillic rocks and micritic limestone, in Fisher, F.S., 

and Johnson, K.M., eds., 1987, Preliminary manuscript for 

"Mineral-resource assessment and geology of the Challis 

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87-480, p. 205-208.

Hall, W.E., and Batchelder, J.N., 1979, Preliminary geologic map 

of the Baugh Creek Southwest ll/2 minute quadrangle, Idaho: 

U.S. Geological Survey Open-File Report 79-1617, scale 

1:24,000.

Hall, W.E., Batchelder, J.N., and Tschanz, C.M., 1978, Geologic 

map of the Sun Valley 7.5-minute quadrangle, Blaine County, 

Idaho: U.S. Geological Survey Open-File Report 78-1058, 

scale 1:24,000.

Hall, W.E., Rye, R.O, and Doe, B.R., 1978, Wood River mining 

district Intrusion-related lead-silver deposits derived from 

country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Heller, P.L., Peterman, Z.E., O'Neill, J.R., Shafiqullah, M., 1985, 

Isotopic provenance of sandstone from the Eocene Tyee Formation, Oregon Coast Range: Geological Society of America 

Bulletin, v. 96, p. 770-780.

Huerta, A.D., 1992, Lake Creek fault Evidence of pre-Challis 

shear within south-central Idaho: Pocatello, Idaho State University, M.S. thesis, 57 p.

Johnson, K.M., Lewis, R.S., Bennett, E.H., and Kiilsgaard, T.H., 

1988, Cretaceous and Tertiary intrusive rocks of south-central 

Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the 

geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 55-86.

Jordan, B.T., 1994, Emplacement and exhumation of the southeastern Atlanta lobe of the Idaho batholith and outlying stocks, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 110 p.

Kirn, A.Y.H., 1986, The kinematics of brittle polyphase deformation within the Pioneer metamorphic core complex, Pioneer 

Mountains, Idaho: Bethlehem, Pa., Lehigh University, M.S. 

thesis, 130 p.

Kluth, C.F., 1986, Plate tectonics of the ancestral Rocky Mountains, in Peterson, J.A., ed., Paleotectonics and sedimentation 

in the Rocky Mountain region, United States: American Association of Petroleum Geologists Memoir 41, p. 353- 369.
STRUCTURAL FRAMEWORK OF MINERAL DEPOSITS HOSTED BY PALEOZOIC ROCKS B17

Lewis, R.S., 1991, Geologic map and geochemical data of the eastern part of the Soldier Mountains, Camas County, Idaho: Idaho 

Geological Survey Technical Report 91-1, scale 1:24,000.

Lindgren, W., 1900, The gold and silver veins of Silver City, 

DeLamar, and other mining districts in Idaho: U.S. Geological 

Survey 20th Annual Report, pt. 3, p. 65-256.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke, Susanne, and 

Burton, B.R., 1988, Structural and stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knob, Pioneer, Boulder, and Smoky Mountains, in Link, 

P.K., and Hackett, W.R., eds., Guidebook to the geology of 

central and southern Idaho: Idaho Geological Survey Bulletin 

27, p. 5- 42.

Link, P.K., and Worl, R.G., in press, Geology and mineral deposits 

of the Minnie Moore and Bullion mineralized areas, Blaine 

County, Idaho: U.S. Geological Survey Bulletin 2064-Y.

Mahoney, J.B., 1987, The geology of the northern Smoky Mountains and stratigraphy of a portion of the Lower Permian Grand 

Prize Formation, Blaine and Camas Counties, Idaho: Pocatello, 

Idaho State University, M.S. thesis, 143 p.

 1992, Geologic map of the Frenchman Peak quadrangle, 

Blaine and Camas Counties, Idaho: Idaho Geological Survey 

Technical Report 92-2, scale 1:24,000.

Mahoney, J.B.. and Horn, M.C, in press, Geology and mineral 

deposits of the Vienna mineralized area, Blaine and Camas 

Counties, Idaho: U.S. Geological Survey Bulletin 2064-DD.

Mahoney, J.B., and Link, P.K., 1992, Geologic map of the Galena 

quadrangle, Blaine and Camas Counties, Idaho: Idaho Geological Survey Technical Report 92-3, scale 1:24,000.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvanian and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J.D., and 

Stevens, C.H., eds., Paleozoic paleogeography of the Western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-580.

Mclntyre, D.H., Ekren, E.B., and Hardyman, R.F., 1982, Stratigraphic and structural framework of the Chain's volcanics in 

the eastern half of the Challis I°x2° quadrangle, in 

Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic 

geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 

26, p. 3-22.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-EE.

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds., Paleozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 275-299.

O'Brien, J.P., Lewis, R.S., Link, P.K., Geslin, J.K., Whitman, S.K., 

and Schmidt, K.L.. 1993, Geologic map of the Buttercup 

Mountain quadrangle, Blaine and Camas Counties, Idaho: Idaho Geological Survey Technical Report 93-1, scale 1:24,000.

O'Neill, R.L., and Pavlis, T.L., 1988, Superposition of Cenozoic 

extension on Mesozoic compressional structures in the Pioneer 

Mountains metamorphic core complex, central Idaho: Geological Society of America Bulletin, v. 100, p. 1833-1845.

Park, W.A., 1990, The geology and ore deposits of the Rooks Creek 

stock, Blaine County, Idaho: Pocatello, Idaho State University, 

M.S. thesis, 135 p.

 in press, The geology and ore deposits of the Rooks Creek 

stock, Blaine County, Idaho: U.S. Geological Survey Bulletin 

2064-CC.

Paull, R.A., 1974, Upper Cretaceous(?) to lower Eocene post-orogenic conglomerate, south-central Idaho: Geological Society 

of America Abstracts with Programs, v. 6, no. 5, p. 466.

Poole, F.G., and Sandberg, C.A., 1991, Mississippian paleogeography and conodont biostratigraphy of the Western United 

States, in Cooper, J.D., and Stevens, C.H., eds., Paleozoic 

paleogeography of the Western United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, 

Publication 67, v. l,p. 107-136.

Ratchford, M.E., 1989, Geology of the Boulder Basin, Blaine and 

Custer Counties, Idaho: Moscow, University of Idaho, M.S. 

thesis, 154 p.

 in press, Epigenetic lead-tin-silver-antimony-gold veins in 

Boulder Basin, Blaine and Custer Counties, Idaho Potential 

for economic tin mineralization: U.S. Geological Survey Bulletin 2064-JJ.

Renne, P.R., Becker, T.A., and Swapp, S.M., 1990, 40Ar/39Ar laserprobe dating of detrital micas from the Montgomery Creek 

Formation, northern California Clues to provenance, tectonics, and weathering processes: Geology, v. 18, p. 563-566.

Roberts, R.J., and Thomasson, M.R., 1964, Comparison of late 

Paleozoic depositional history of northern Nevada and central 

Idaho: U.S. Geological Survey Professional Paper 475-D, p. 

D1-D6.

Rodgers, D.W., Hackett, W.R., and Ore, H.T., 1990, Extension of 

the Owyhee Plateau, eastern Snake River Plain, and Yellowstone Plateau: Geology, v. 18, p. 1138-1141.

Sanford, R.F., Whitney, H.A., McCafferty, A.E., and Gese, D.D., 

1989, Mineral resources of the Little Wood River Wilderness 

Study Area, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 1721-D, 15 p.

Schmidt, D.L., 1962, Quaternary geology of the Bellevue area in 

Blaine and Camas Counties, Idaho: U.S. Geological Survey 

Open-File Report 62-0120, 134 p.

Schmidt, K.L., 1994, Geology and petrology of the Ibex Canyon 

igneous complex, Blaine and Custer Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 177 p.

Silverberg, D.S., 1988, Petrologic, 40Ar/39Ar isotopic and structural 

constraints on the Tertiary tectonic evolution of the Pioneer 

core complex, south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 20, no. 7, p. A18.

 1990a, Denudation rates and timing of diachronous Paleogene extension in south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 22, p. 330.

 1990b, The tectonic evolution of the Pioneer metamorphic

core complex, south-central Idaho: Cambridge, Massachusetts 

Institute of Technology, Ph.D. dissertation, 280 p.

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River Plain, Idaho: Wyoming 

Geological Association Guidebook, Twenty-Ninth Annual 

Field Conference, p. 499-515.

Skipp, Betty, and Hall, W.E., 1975, Structure and Paleozoic stratigraphy of a complex of thrust plates in the Fish Creek Reservoir
B18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

area, south-central Idaho: U.S. Geological Survey Journal of 

Research, v. 3, no. 6, p. 671-689.

-1980, Upper Paleozoic paleotectonics and paleogeography

of Idaho, in Fouch, T.D., and Magathan, E.R., eds.. Paleozoic 

paleogeography of the West-Central United States: Rocky 

Mountain Section, Society of Economic Paleontologists and 

Mineralogists, West-Central United States Paleogeography 

Symposium 1, p. 387-422.

Skipp, Betty, Hall, W.E., and Link, P.K., 1986, Pre-middle Eocene 

extension in south-central Idaho The Wood River allochthon: Geological Society of America Abstracts with Programs, 

v. 18, p. 753.

 1994, Geologic map of the Mahoney Butte quadrangle, 

Blaine County, Idaho: U.S. Geological Survey Geologic Quadrangle Map GQ-1742, scale 1:24,000.

Skipp, Betty, Sando, W.J., and Hall, W.E., 1979, The Mississippian 

and Pennsylvanian (Carboniferous) Systems in the United 

States-Idaho: U.S. Geological Survey Professional Paper 

1110-AA, p. AA1-AA43.

Southworth, C.S., 1988, Preliminary lineament map of the Hailey, 

Idaho, and west half of the Idaho Falls, Idaho, I°x2° quadrangles, with inset of regional image mosaic and geologic structures: U.S. Geological Survey Open-File Report 88-640, scale 

1:250,000.

Stewart, D.E., 1987, Geology of the northern half of the Baker Peak 

quadrangle, Blaine and Camas Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 113 p.

Stewart, D.E., Mahoney, J.B., Geslin, J.G., Darling, R.S., and Link, 

P.K., 1992, Geologic map of the Baker Peak quadrangle, 

Blaine and Camas Counties, Idaho: Idaho Geological Survey 

Technical Report 92-1, scale 1:24,000.

Stewart, D.E., Schmidt, K.L., Moye, F.J., Mahoney, J.B., and Link, 

P.K., in press. Eocene intrusive complexes in the Smoky and 

Boulder Mountains, south-central Idaho: U.S. Geological Survey Bulletin 2064-HH.

Trexler, J.H., Jr., Snyder, W.S., Cashman, P.M., Gallegos, D.M., 

and Spinosa, C., 1991, Mississippian through Permian orogenesis in eastern Nevada: Post-Antler, pre-Sonoma tectonics of 

the western Cordillera, in Cooper, J.D., and Stevens, C.H., 

eds., Paleozoic paleogeography of the Western United 

States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 1. p. 317-330, v. 2, 

p. 551-579.

Tschanz, C.M., Kiilsgaard, T.H., and Seeland, D.A., 1986, Geology 

of the eastern part of the Sawtooth National Recreation Area, 

Idaho, in Mineral resources of the eastern part of the Sawtooth 

National Recreation Area, Custer and Blaine Counties, Idaho: 

U.S. Geological Survey Bulletin 1545-A, p. 17-43.

Turner, R.J.W., and Otto, B.R., 1988, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho, in Link, P.K., 

and Hackett, W.R., eds.. Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

153-167.

Umpleby, J.B., Westgate, L.G., and Ross, C.P., 1930, Geology and 

ore deposits of the Wood River region, Idaho: U.S. Geological 

Survey Bulletin 814, 250 p.

Whitman, S.K., 1990, Metamorphic petrology and structural geology of the Pennsylvanian-Permian Dollarhide Formation, 

Blaine and Camas Counties, south-central Idaho: Pocatello, 

Idaho State University, M.S. thesis, 108 p.

Wilson, Eric, 1992, Mesozoic compression and Cenozoic extension along the Glide Mountain fault, south-central Idaho: 

Geological Society of America Abstracts with Programs, v. 

24, no. 6, p. 68.

 1994, Demise of the Glide Mountain thrust fault, Pioneer 

Mountains, Blaine and Custer Counties, south-central Idaho: 

Pocatello, Idaho State University, M.S. thesis, 188 p.

Wilson, Eric, and Rodgers, D.W., 1993, Demise of the Glide Mountain thrust, Pioneer Mountains, south-central Idaho: Geological 

Society of America, Abstracts with Programs, v. 25, no. 4, 

p. 164.

Winsor, H.C., 1981, The paleogeography and paleoenvironments 

of the Middle Pennsylvanian part of the Wood River Formation 

in south-central Idaho: San Jose, Calif., San Jose State University, M.S. thesis, 81 p.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Wust, S.L., 1986, Extensional deformation with northwest vergence, Pioneer core complex, central Idaho: Geology, v. 14, p. 

712-714.

Zentner, N.C., 1989, Neogene normal faults related to the structural 

origin of the eastern Snake River Plain, Idaho: Pocatello, Idaho 

State University, M.S. thesis, 48 p.
Stratigraphic Setting of Sediment-Hosted 

Mineral Deposits in the Eastern Part of the 

Hailey Fx2° Quadrangle and Part of the 

Southern Part of the Challis I°x2° Quadrangle, 

South-Central Idaho

By Paul Karl Link, J. Brian Mahoney, Daniel J. Bruner, L. Darlene Batatian, 

Eric Wilson, and Felicie J.C. Williams

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-C

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995

CONTENTS

Abstract................................................................................................................................. Cl

Introduction.......................................................................................................................... 2

Previous Work...................................................................................................................... 2

Stratigraphy.......................................................................................................................... 2

Ordovician, Silurian, and Devonian Shelf-Facies Strata.............................................. 3

Ordovician and Silurian Phi Kappa and Silurian Trail Creek Formations................... 3

Silurian and Devonian Argillaceous Strata.................................................................. 3

Devonian Milligen Formation.............................................................................. 3

Unnamed Silurian and Devonian Rocks............................................................... 7

Miller Canyon Area...................................................................................... 9

Kent Peak Area............................................................................................. 10

Summary of Proposed Correlations of Silurian and Devonian Strata.................. 11

Upper Contact of Unnamed Silurian and Devonian Rocks.................................. 12

Paleozoic Salmon River Assemblage................................................................... 12

Mineral Deposits in Silurian and Devonian Rocks .............................................. 12

Mississippian Copper Basin Formation........................................................................ 13

Mineral Deposits in the Copper Basin Formation................................................ 14

Pennsylvanian and Permian Sun Valley Group............................................................ 14

Wood River Formation......................................................................................... 18

Mineral Deposits in the Wood River Formation.......................................... 24

Dollarhide Formation........................................................................................... 24

Mineral Deposits in the Dollarhide Formation............................................. 25

Grand Prize Formation......................................................................................... 25

Mineral Deposits in the Grand Prize Formation........................................... 25

Relations Between Formations of the Sun Valley Group..................................... 26

Mineral Deposit Models Applicable to Paleozoic Rocks of the Eastern Part of the

Hailey I°x2° Quadrangle ................................................................................................. 26

Geologic Complexity.................................................................................................... 26

Mineral Deposit Models............................................................................................... 26

Skarn Deposits...................................................................................................... 27

Polymetallic Replacement Deposits..................................................................... 27

Polymetallic Veins................................................................................................ 28

Cretaceous Vein Deposits............................................................................. 28

Eocene Vein Deposits................................................................................... 28

Syngenetic Stratabound Silver-Lead-Zinc Deposits............................................. 28

Devonian Milligen Formation...................................................................... 28

Salmon River Assemblage ........................................................................... 29

Ore Textures in Silurian and Devonian Strata, Miller Canyon Area............ 29

Possible Syngenetic Mineral Deposits in the Dollarhide Formation............ 29

Exploration Prospects................................................................................................... 30

References Cited................................................................................................................... 30
CONTENTS

PLATE

[Plate is in pocket]

1. Geologic map of outcrop areas of sedimentary units in the eastern part of the Hailey 1 °x2° quadrangle and part of the 

southern part of the Challis 1 °x2° quadrangle, south-central Idaho.

FIGURES

1. Map showing generalized geology and mineralized areas in the Hailey quadrangle and part of

the southern part of the Challis quadrangle................................................................................................................ C4

2, 3. Correlation charts for:

2. Paleozoic rocks of the eastern part of the Hailey quadrangle and the western part of the

Idaho Falls quadrangle ........................................................................................................................................ 6

3. Silurian through Devonian rocks in the eastern Boulder Mountains .................................................................. 8

4. Composite stratigraphic column of unnamed Silurian and Devonian rocks west of Miller Canyon,

eastern Boulder Mountains, and their correlation with the Devonian Milligen Formation........................................ 10

5. Photographs of unnamed Devonian strata east of Kent Peak..................................................................................... 11

6. Generalized stratigraphic columns of the Sun Valley Group...................................................................................... 15

7. Correlation chart for Middle Pennsylvanian to Lower Permian rocks of the Sun Valley Group............................... 17

8. Schematic diagram showing facies changes within the Sun Valley Group across the Wood River Basin................. 18

9. Photographs of reference sections of the Wood River Formation northeast of Ketchum.......................................... 19

TABLES

1. Graptolites from the Phi Kappa Formation ................................................................................................................ C7

2. Descriptions of type sections for three members of the Wood River Formation ....................................................... 20

3. Measured stratigraphic reference sections of the Pennsylvanian and Permian Sun Valley Group ............................ 22
Stratigraphic Setting of Sediment-Hosted Mineral Deposits

in the Eastern Part of the Hailey I°x2° Quadrangle and 

Part of the Southern Part of the Challis I°x2° Quadrangle,

South-Central Idaho

By Paul Karl Link, 1 J. Brian Mahoney,2 Daniel J. B rimer,3 L. Darlene Batatian,3 

Eric Wilson,3 and Felicie J.C. Williams4

ABSTRACT

The central Idaho black-shale mineral belt includes 

most of the outcrop area of Paleozoic strata in the eastern part 

of the Hailey I°x2° quadrangle and part of the southern part 

of the Challis 1 °x2° quadrangle. Syngenetic deposits of silver, lead, and zinc are present in the Devonian Milligen Formation, unnamed Silurian and Devonian strata, and the 

Devonian part of the Salmon River assemblage. Remobilization of these metals during Cretaceous and Eocene deformation and magmatism produced a variety of epigenetic mineral 

deposits including shear-zone-hosted veins, replacement 

deposits, and skarns. The most important time of mineralization probably was the Late Cretaceous (about 90-80 Ma), 

when folding and thrust faulting within the Sevier orogenic 

belt temporally and spatially overlapped intrusion of the 

Atlanta lobe of the Idaho batholith and satellite plutons to the 

east. Structures that host silver-lead-zinc veins include 

sheared unconformities, northwest- and northeast-striking 

Cretaceous high-angle faults, northwest-striking low-angle 

oblique-slip Paleogene faults, and northeast-striking highangle normal Eocene faults associated with the Trans-Challis 

fault system. Replacement deposits are present in calcareous 

rocks that are adjacent to mineralized structures and along 

silicification fronts produced during fluid migration. Skarn 

deposits are hosted by calcareous rocks adjacent to plutons.

'U.S. Geological Survey and Department of Geology, Idaho State 

University, Pocatello, Idaho 83209.

2U.S. Geological Survey and University of British Columbia, Vancouver, British Columbia V6T 1Z4.

^Department of Geology, Idaho State University, Pocatello, Idaho 

83209.

4Westmont Mining Inc., N. 10220 Nevada Street, Suite 140, Spokane, 

Washington 99218.

Mapping of informal members within the Devonian 

Milligen Formation (lower argillite, quartzite of Cait, 

argillite of Triumph, limestone of Lucky Coin, and 

sandstone of Independence) suggests that the formation is 

present in the Minnie Moore, Bellevue, Triumph, Lake 

Creek stock, and Summit mineralized areas where the Milligen Formation is interpreted to pass by facies change into 

unnamed Silurian and Devonian strata. Because the same 

Stratigraphic units are present from west to east within the 

Mesozoic Pioneer thrust plate, it is doubtful that the plate 

contains an older (Antler) thrust fault having significant 

(tens of kilometers) displacement.

The Mississippian Copper Basin Formation contains 

west-derived siliciclastic turbidite and east-derived calciclastic turbidite strata. The formation is present east of the 

Pioneer thrust fault and also in apparent Stratigraphic continuity with rocks of the Pioneer thrust plate. Calciclastic silty 

turbidites of the medial Drummond Mine Limestone Member are host to skarn and vein deposits in the Phi Kappa mine 

area south of Summit Creek.

The Pennsylvanian and Permian Sun Valley Group 

(Wood River, Dollarhide, and Grand Prize Formations) 

includes strata previously thought to be present in different 

thrust plates. The contacts between these formations are 

generally facies changes rather than structural contacts. The 

basal Hailey Member of the Wood River Formation hosts 

vein deposits along its sheared unconformity with the 

underlying Devonian Milligen Formation. This relationship 

was previously mapped as the "Wood River thrust." The 

medial Eagle Creek and the upper Wilson Creek Members 

of the Wood River Formation host vein, replacement, and 

skarn deposits adjacent to the Rooks Creek stock and in 

several areas east of the Wood River valley. Carbonaceous 

micritic siltstone of the lower and upper members of the 

Dollarhide Formation contains shear-zone-hosted veins in 

the Minnie Moore, Bullion, Deer Creek stock, Bunker Hill, 

and Smoky Mountains mineralized areas. In the Deer Creek

ci
C2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

stock area, the lower member of the Dollarhide Formation 

contains a laminated barite deposit. In the Carrietown area, 

adjacent to the Atlanta lobe of the Idaho batholith, mineralized veins are near the contact between foliated banded 

quartzite and carbonaceous marble within the lower 

member of the Dollarhide Formation. The four members of 

the Grand Prize Formation are host to skarn, replacement, 

and vein deposits in the Washington Basin, Smiley Creek, 

and Galena mineralized areas in the White Cloud Peaks, 

Smoky Mountains, and northern Boulder Mountains.

INTRODUCTION

This report provides a synthesis of the stratigraphic 

setting of sediment-hosted mineral deposits in the eastern 

half of the Hailey 1 °x2° quadrangle and part of the southern part of the Chain's I°x2° quadrangle (fig. 1, plate 1) and 

a summary of the present understanding of the Paleozoic 

stratigraphy of the area. The sediment-hosted mineral 

deposits are in the "central Idaho black-shale mineral belt" 

of Hall (1985) and have produced primarily silver, lead, 

and zinc and small amounts of gold. The deposits are 

included within mineralized areas defined by Worl and 

Johnson (this volume) (fig. 1).

Research summarized in this report has resolved some 

long-standing problems of stratigraphy but only scratched 

the surface of others. In particular, we understand the Pennsylvanian and Permian part of the stratigraphic section far 

better than we understand the lower Paleozoic units, especially the Silurian, Devonian, and Mississippian units. We 

therefore present this summary as a progress report.

Acknowledgments. Work on the Paleozoic rocks of 

south-central Idaho was supported by the Hailey project of 

the U.S. Geological Survey Conterminous United States 

Mineral Assessment Program (CUSMAP), Idaho State 

Board of Education Grant 89-56 to P.K. Link, and the Idaho 

Initiative project of the Idaho Geological Survey. This 

manuscript benefitted from review by S.J. Soulliere, Betty 

Skipp, David Seeland, and B.R. Burton.

PREVIOUS WORK

The mineral deposits of the Wood River area were first 

documented by Lindgren (1900) and have been more 

recently described by W.E. Hall and colleagues of the U.S. 

Geological Survey (Hall and Czamanske, 1972; Hall and 

others, 1978; Hall, 1985; Howe and Hall, 1985; Hall, 1987a, 

b; Hall and Hobbs, 1987). Hall concluded that many of the 

deposits were formed by hydrothermal circulation systems 

developed during both Cretaceous and Tertiary magmatism. 

These hydrothermal systems were thought to have derived 

metals from a country rock source (the lower Paleozoic 

black shales of the Milligen Formation and Salmon River 

assemblage). In the Wood River area, ore mineral deposition 

was thought to be localized near intrusive bodies and below 

regional thrust faults that acted as a permeability barrier to

mineralizing solutions. Hall (1985) also suggested that the 

Paleozoic black shales hosted syngenetic stratabound 

mineral deposits, particularly in the Paleozoic Salmon River 

assemblage at the Hoodoo mine (plate 1), the Devonian Milligen Formation in the Triumph mineralized area, and the 

Middle Pennsylvanian to Lower Permian Dollarhide Formation at the Deer Creek barite deposit, 12 km west of Hailey.

Recent work has modified some facets of these models. 

Syngenetic stratabound mineral deposits are believed to be 

present mainly in lower Paleozoic, primarily Devonian, 

strata but not in upper Paleozoic rocks. Lead isotope data 

suggest that the source of the metals in polymetallic vein 

deposits is remobilized Devonian syngenetic sulfide deposits 

and Precambrian continental crust (Sanford and Wooden, 

this volume). The concept of ore concentration below 

regional thrust faults is rejected. Many contacts previously 

mapped as thrust faults are now mapped as stratigraphic contacts, sheared unconformities, or low-angle oblique-slip 

faults (Skipp and others, 1986; Burton and others, 1989; 

Mahoney and others, 1991; Burton and Link, this volume; 

Rodgers and others, this volume).

This report is a synthesis of the stratigraphic setting of 

mineral deposits in the eastern part of the Hailey I°x2° quadrangle. For studies of individual mines and mineral districts 

that include maps, the reader is referred to Lindgren (1900), 

Umpleby (1915), Umpleby and others (1930), Anderson and 

others (1950), Tuchek and Ridenour (1981), and Van Noy 

and others (1986) and to reports in this volume and the second volume of this bulletin (in press).

STRATIGRAPHY

This report contains a summary of Paleozoic stratigraphy of the eastern part of the Hailey and part of the southern 

part of the Challis I°x2° quadrangles and emphasizes new 

developments. We discuss only the Paleozoic rocks structurally above the Wildhorse detachment fault, which forms the 

upper boundary of metamorphic and intrusive rocks of the 

Pioneer Mountains core complex (fig. 1). Proterozoic and 

Paleozoic metasedimentary strata of the core are discussed 

by Dover (1969, 1981, 1983). Our work is grounded in, but 

differs in detail from, the reports of Hall and others (1974), 

Skipp and Hall (1975, 1980), Sandberg and others (1975), 

Skipp, Sando, and Hall, (1979), Dover (1981, 1983), Hall 

(1985), Hall and Hobbs (1987), Mahoney and Sengebush 

(1988), and Link and others (1988).

Allochthonous Ordovician through Lower Permian 

strata in the eastern part of the Hailey 1 °x2° quadrangle are 

generally of three lithologic types: dark-colored carbonaceous argillite, light-colored calcareous sandstone, siltstone, and limestone, and pebble and cobble conglomerate. 

Because the rocks are mostly unfossiliferous and lithologically similar, formations of different ages have been difficult 

to differentiate with confidence. Age assignments have been, 

and remain, contentious.
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C3

Although we have made significant progress in understanding the Pennsylvanian and Permian parts of the section, the Devonian rocks are less well understood. They are 

structurally complex and have only recently been subdivided stratigraphically (Turner and Otto, 1988, this volume; Bruner, 1991). Biostratigraphic studies in the 

Milligen Formation and correlative lower Paleozoic units 

are especially needed.

ORDOVICIAN, SILURIAN, AND DEVONIAN 

SHELF-FACIES STRATA

Calcareous and quartzitic shelf-facies strata of early 

Paleozoic age are exposed in two structural inliers in Dry 

Canyon and Wildhorse Creek in the northeastern part of the 

Hailey I°x2° quadrangle (Dover, 1981, 1983) (figs. 1, 2, 

plate 1). Kim (1986) mapped the upper boundaries of these 

inliers as west-dipping low-angle normal faults. Dover 

(1981, 1983) showed these contacts as thrust faults. Wilson 

(1994) interpreted these contacts as unconformable.

Formations mapped within the Wildhorse inlier include 

the Middle and Upper Ordovician Hanson Creek Formation 

(cherty dolomite, more than 64 m thick), an unnamed Middle 

Silurian limestone unit (40-120 m thick) containing a prominent bed of black dolomite and black chert, the Silurian 

Roberts Mountains Formation (calcareous to dolomitic siltstone, about 600 m thick), and an unnamed carbonate and 

conglomerate and breccia unit of Devonian age (more than 

10 m thick). The lower contact of this sequence is not 

exposed. The upper contact is a fault or an unconformable 

contact with the Lower Mississippian lower part of the Copper Basin Formation.

The Dry Canyon inlier contains a partial section of the 

Lower and Middle Devonian Carey Dolomite (thickness 

unknown), the Upper Devonian Jefferson Formation (cliffforming, medium-bedded to massive, finely crystalline dolomitic limestone, dolomite, and bioclastic limestone and local 

intraformational conglomerate, about 350 m thick) and the 

Upper Devonian Picabo Formation (sandstone, at least 6 m 

thick). The lower contact of this sequence is not exposed. 

The upper contact is an unconformity with the Lower Mississippian part of the Copper Basin Formation. Near Fish 

Creek Reservoir in the Idaho Falls 1 °x2° quadrangle, to the 

east of the study area, the Picabo Formation lies unconformably below the Lower Mississippian part of the Copper 

Basin Formation (Link and others, 1988).

No mineral deposits are hosted by the carbonate rocks 

of these structural inliers.

ORDOVICIAN AND SILURIAN

PHI KAPPA AND SILURIAN 

TRAIL CREEK FORMATIONS

The Lower Ordovician to Middle Silurian Phi Kappa 

and Middle Silurian Trail Creek Formations are imbricated 

in a series of thrust-bounded slices in the hanging wall of the

Pioneer thrust fault in the headwaters of Trail Creek, east of 

Ketchum (Dover and others, 1980) (figs. 1, 2, plate 1). The 

Pioneer thrust fault places lower Paleozoic rocks above the 

Mississippian Copper Basin Formation.

The Phi Kappa and Trail Creek Formations were 

defined by Umpleby and others (1930). Their structural repetition was demonstrated by Churkin (1963) and Carter and 

Churkin (1977). The units were revised by Dover and others 

(1980). The Phi Kappa Formation is 240 m thick and consists 

of the basal massive, gray, fine-grained Basin Gulch Quartzite Member (55 m thick) overlain by 165 m of dark-gray, 

red-weathering, carbonaceous, locally silicified shale and 

argillite of the "main body" of the formation (Dover, 1983). 

Thin limestone beds are present in the middle of the formation. A rich graptolite fauna reveals that the Phi Kappa Formation contains Lower to Upper Ordovician strata 

gradationally overlain by 17 m of Lower to Middle Silurian 

strata of the upper member of the formation (Dover and others, 1980; Dover, 1981, 1983) (table 1).

The Trail Creek Formation (revised by Dover and others, 1980) is at least 100 m thick and contains buff-weathering, banded tan and white siliceous metasiltstone and very 

fine grained quartzite. The base of the Trail Creek Formation 

is gradational over a few meters with the underlying argillaceous Middle Silurian beds of the upper part of the Phi 

Kappa Formation, but biostratigraphic control is lacking in 

the Trail Creek Formation (Dover and others, 1980; Dover. 

1983). As mapped by Dover (1983), the top of the Trail 

Creek Formation is everywhere a thrust fault.

The map of Dover (1983) shows the contacts between 

the Phi Kappa and Trail Creek Formations and unnamed Silurian and Devonian units to be thrust faults. Our work suggests that some of these contacts may be sheared 

stratigraphic contacts, implying stratigraphic continuity 

between these units (discussed following).

No significant mineral deposits are hosted by the Phi 

Kappa or Trail Creek Formations. The Basin Gulch Member 

of the Phi Kappa Formation is quarried for building stone in 

the headwaters of Summit Creek.

SILURIAN AND DEVONIAN 

ARGILLACEOUS STRATA

DEVONIAN MILLIGEN FORMATION

The Lower to Upper Devonian Milligen Formation is 

the host for rich silver-lead-zinc ores in the historically productive Minnie Moore and Triumph mineralized areas near 

Hailey and Bellevue (fig. 1). The Milligen Formation was 

named by Umpleby and others (1930) for carbonaceous and 

argillaceous rocks originally included in the lower part of the 

Wood River Formation by Lindgren (1900). As described by 

Sandberg and others (1975), Dover (1981), and Turner and 

Otto (1988, this volume), the Devonian Milligen Formation
C4

44°15'

44°00' 

43°30'

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°45' 30' 15' 114°00'

HORSE 

DETATCHMENT 

FAULT

43°15'
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C5

EXPLANATION

Quaternary, Eocene, and Cretaceous rocks, undifferentiated 

Wood River Formation (Permian and Pennsylvanian) 

Grand Prize Formation (Permian and Pennsylvanian) 

Dollarhide Formation (Permian and Pennsylvanian)

Copper Basin Formation, west of Pioneer thrust 

(Mississippian)

Copper Basin Formation (Mississippian) 

Milligen Formation (Devonian)

Carbonate rocks of Wildhorse and Dry Canyon windows 

(Devonian, Silurian, and Ordovician)

Carbonate and underlying quartzite (Ordovician)

Lower Paleozoic shale and argillite (Devonian, Silurian, and 

Ordovician) Includes Salmon River assemblage (unit Pzsr) 

(Devonian and Cambrian)

Metamorphic rocks of the Pioneer Mountains core complex 

(Eocene to Early Proterozoic)

- Contact 

Thrust fault Sawteeth on upper plate

Low-angle fault Locally places younger rocks over older rocks 

(reactiviated thrust ?). Open sawteeth on upper plate

 Low-angle oblique-normal fault Hachured on downthrown side 

Normal fault Bar and ball on downthrown side

Figure 1 (above and facing page). Generalized geologic map of 

the eastern part of the Hailey I°x2° quadrangle and part of the 

southern part of the Challis I°x2° quadrangle, south-central Idaho 

(modified from Mahoney and others, 1991, and Batatian, 1991). 

Mineralized areas (Worl and Johnson, this volume), referred to by 

number, are shown in red: 10, Marshall Peak; 12, Rooks Creek 

stock; 13, Deer Creek stock; 14, Croesus stock: 15, Hailey gold belt; 

20, Smoky Mountains (a) Smiley Creek, (b) West Fork Big 

Smoky Creek, (c) Norton-Baker Peaks, (d) Baker Creek; 21, Carrietown (a) Carrietown, (b) Buttercup mine; 22, Bullion; 23, Bunker Hill; 24, Minnie Moore; 25, Bellevue (a) Slaughterhouse 

Gulch, (b) Vorberg Gulch; 26, Wood River (a) Quigley Gulch, 

(b) Carbonate Mountain, (c) Greenhorn Gulch, (d) Warm Springs 

Creek; 27, Triumph: 28. East Fork Wood River; 30, Galena; 

31, Washington Basin; 33, Boulder Basin; 34, East Fork 

Salmon (a) East Fork Salmon River, (b) Ryan Peak; 35, Summit; 

40, Lake Creek stock; 44, Pioneer.

contains more than 1,200 m of unfossiliferous, fine-grained, 

locally carbonaceous strata that are poorly exposed on sagebrush- and grass-covered slopes in the Boulder and Pioneer 

Mountains east of the Wood River. The base of the Milligen 

Formation has not been observed in detailed mapping of the 

Triumph mine area or on the western side of the Boulder 

Mountains (Dover, 1983; Turner and Otto, this volume). The 

upper contact varies along strike and is locally an unconformity below the Middle Pennsylvanian Hailey Member of the

Wood River Formation, a possibly conformable contact with 

strata mapped as Mississippian Copper Basin Formation, or 

a fault against Pennsylvanian and Permian strata of the Sun 

Valley Group.

Though Umpleby and others (1930) thought that the 

bulk of the Milligen Formation was Mississippian in age, 

Sandberg and others (1975) restricted the age of the formation in the type area of Milligen Gulch southeast of Ketchum 

(plate 1) to Devonian, based on the presence of sparse Eifelian, Frasnian, and Famennian conodonts (fig. 3). Dark-colored Lower Mississippian rocks in the Idaho Falls I°x2° 

quadrangle to the east, originally included in the Milligen 

Formation by Umpleby and others (1930) and many subsequent workers, were renamed the McGowan Creek Formation by Sandberg (1975). Dover (1969, p. 29; 1981, p. 34) 

and Sandberg (1975) cautioned against using the name Milligen Formation beyond the type area originally defined in 

the Boulder and Pioneer Mountains east of the Wood River.

A stratigraphic division of the Milligen Formation in 

the area near the Triumph mine (Turner and Otto, 1988, this 

volume) (fig. 3) includes, as informal members, (1) a lower 

argillite member (130+ m thick), which locally contains 

diamictite or is chert- or sandstone-rich, (2) the limestone 

member of Lucky Coin (50-250 m thick), which contains 

limestone turbidite, black argillite, and diamictite, (3) the 

quartzite member of Cait (lenses of variable thickness, usually less than 10 m), which contains carbonaceous coarsegrained sandstone, diamictite, and black argillite, (4) the 

argillite member of Triumph (0-150 m thick), which contains black argillite, locally cherty, and interbedded sandstone, and (5) the sandstone member of Independence (150+ 

m thick), which contains interbedded sandstone and limestone turbidite. Diamictite in the lower argillite member, 

coarse-grained sandstone in the quartzite of Cait, and calciclastic turbidite of the limestone of Lucky Coin represent 

distinctive markers that allow correlation of the Milligen 

Formation across structurally complex areas.

In the areas of the Triumph and Minnie Moore mines, 

the Milligen Formation is present in northeast-vergent 

overturned folds that have southwest-dipping limbs. 

Inferred syngenetic stratabound mineral deposits in these 

areas are in distinctive stratigraphic units in the middle part 

of the formation (limestone member of Lucky Coin and 

quartzite member of Cait).

Our recent work suggests several changes in understanding of the Milligen Formation. These revisions are 

grounded in geologic mapping and stratigraphic studies 

(Batatian, 1991; Bruner, 1991; Worl and others, 1991). Several of the revisions await confirmation from further biostratigraphic studies. These revisions include the following:
^5 H "a ^-03 § f»Q h* ^ a §. 3: ==_|33 ^o 3 °sSs^-g-gn 

-g-8.8 s-^^5»

s § 0?^-^ o^^E.00^3

lZ§.'5-^i'oPffffl

_., s. _. o *^ n n o S vo=?o &"C< 2«^p3 l^§ = g^Qoa-*o ^ O\g &3vo CL g. js. 3- s^? 8 s^sgs,^ s ?i&^r>sS;^^^ 0 ^ O O j-^ -? c/> X u^-1 § ^ ^^^ f-S|

& 2|'^g^g| S ^ Q -5" s' i § ?'! §" « 

-v^^ 5' 3 Q. - g. 3 .3 "^ '* N ^^ ^ r^\ "^ CTQ oHlffSIIII!

MISSISSIPPIAN

LOWER UPPER

^ o

Little Coppr 

Member 1,120+

"''

Drummond Mine Limestone Member L

795

Drummond Mine mestone Member 

795 |

Lower Copper Basin Formation

Upper clastic unit

(lower part of Muldoon Canyon (l°wer 

Formation (345+) andh°r

Scorpion Mountain Formation HC (1,100) ofPaull andGruber, 1977) a" ° °

Upper clastic unitpart of Muldoon Canyontion (345+), GreenLake tone Member (33-130), rpion Mountain Formation )f Paull andGruber, 1977)

-n r- ~n 

_ o _ 5' o en ;r _ 33" = 3 £" 'D a 

i; ro S °° aj T3 .S o" -= => ft |fp > i|0 i|i 

-E^ 1^33. s£l ^igi sip 2=1111 g si 3~!5 *t!f 8 Itafi in s^i

ofa B««|i j?t| y |l^ § ° = i ! s? ~' » *' "o"

si -E-3 a s 1?! |i |*ga g s ||

Muldoon Canyon-Iron Bog

Creek area East 

(Idaho Flls 1°x 2quadrangle) (Hailey

Fork, BigLost Riverf 1°x 2°quadrangle)

" i | m gO 3) ro <S i g 0 £ >0 H

Salmon Ri

-D3"

^

01 D 

ro"g°°

D)5

D

S." (S vA=

5(Q 5- Om DO-<3-n:: r ~~ \ 

^ Sii§D^ffffi|g3|O

-§ Iflls^liilllli 

+ pi3^fH8|l4|Sg 5130 » 2 o g^ V \ 2- S M * y^7? ^ X V 

__ \

-o I 9

.* P o 1 J | 8 " S -1 ? «

0 _, S. 3" 3- O Q) + 5 3 m s1 S 3

TO D- " 2. Q, ii 2 o ° 

S 0 Q. 

^ ff

^ § i 1 S 1

ver assemblage 2,000+

^^^^^ ^°Picabo Formation 5

Milligen o ^^^^^~^^^ 

Formation |+Jefferson Formation 

o; ° Carey Dolomite 30

1,000+ |"" Mil INiiii'iiiiin

Trail Ceek 3j

Formation 100l^U ^, ,JJxl U|

loberts Mountain Formatio ^1-iaTts^nTireSk^Bfffiafiofr Saturday Mountain Formati

S^^S ' S! » 

+/§/=" « \ X + N-j-zzLJ i 

_____ 

1 ________ MISSISSIPPIAN S z. ^ c/5 r" r; c -< ^ 9 ^ ^ I ^5 1 1 33 33 ^ *- 

> z. 

^°V 

/

^\ S1 ^ \ w - -/-/ / w o§ ?H"

^it 4 " 

|jl 

4

^ Copper Basin -. / Formation 3^ 

r- H'" 

o -5- J = $ § =^S 

-n» -n® =ISoo 5 0 ,,,50 "^> 

Sll- ill : 

+ 5-5 * 0' <B 

= CO =00 

ai a> « M 

5 5 

} ^ Wm , Tl 7T q s 0 < 

II - 5! 

^

tr§ Is Ur II l& 11 : :

+ 7T + 

5' 

S 3 i

GEOLOGY ANDMINERAL RESOURCES OFTHEH/

p

ULEY ANDIDAHO FALLS QUADF

COPPER BASIN

ONEER THRUST PLATE PLATE

WANGLES

GROUSE 

THRUST PLATE
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C7

Table 1. Graptolites from Phi Kappa Formation, south-central Idaho.

[Collected by D.J. Bruner and colleagues, identified by Claire Carter, U.S. Geological Survey, 1990 and 1991]

82PL89A Probably Early or Middle Ordovician but could be Silurian. Right fork of Trail Creek, elevation 8,200 ft, west of 

creek, unsurveyed, T. 7 N., R. 18 E., Rock Roll Canyon quadrangle, Blaine County, Idaho.

82PL89B Orthograptus sp; probably Middle or Late Ordovician. West side of Squib Canyon, elevation 8,700 ft, northwest of 

peak 10,284, unsurveyed T. 7 N., R. 18 E., Meridian Peak quadrangle, Custer County, Idaho.

82PL89C Diplograptids and Dicranograptus sp.; Middle Ordovician. In right fork of right fork of Trail Creek, elevation 

9,000 ft, unsurveyed T. 7 N. R. 18 E., Meridian Peak quadrangle, Blaine County, Idaho.

DJB-G2-90 Climacograptus spiniferus Ruedemann, Orthograptus!; Middle Ordovician zone of C. spiniferus. West side of 

Miller Canyon, northeast of 9413, elevation 8,400 ft, T. 7 N., R. 18 E., Meridian Peak quadrangle, Custer County, 

Idaho.

DJB-G3-90 Climacograptus caudatus Lapworth, Amplexograptusl, Orthograptus!', Middle Ordovician zone of C. spiniferus. 

East fork of Squib Canyon, elevation 8,600 ft, T. 7 N., R. 18 E.; Meridian Peak quadrangle, Custer County, Idaho.

DJB-G4-90 Climacograptus bicornis (Hall), Glossograptus ciliatus Emmons, unidentifiable diplograptid; Middle Ordovician 

zone of C. bicornis. Head of Miller Canyon, elevation 9,800 ft, northwest of peak 10,356, sec. 35, T. 7 N., R. 18 

E., Meridian Peak quadrangle, Custer County, Idaho.

DJB 25A 90 Climacograptus cf. C. tubuliferus Lapworth, C. sp. (small), C. cf C. spiniferus Ruedemann, Orthograptus!,

Glyptograptus!, Dicellograptus sp.; Middle Ordovician zone of C. spiniferus. Upper Bear Creek, elevation 8,600 

___________ft, sec. 34, T. 7 N., R. 18 E., Meridian Peak quadrangle, Custer County, Idaho._____________________

1. The contact of the Milligen Formation with the 

overlying Pennsylvanian and Permian Wood River Formation is not a regional thrust fault but rather is a locally 

sheared unconformity or a low-angle normal fault (Burton 

and others, 1989; Batatian, 1991; Mahoney and others, 

1991; Burton and Link, this volume; Rodgers and others, 

this volume).

2. Pending biostratigraphic verification, the informal 

members of the Milligen Formation from the type area can 

be recognized east of Kent Peak and in the Miller Canyon 

area on the east slope of the Boulder Mountains near the head 

of the North Fork of the Big Lost River (Batatian, 1991; 

Bruner, 1991; B. Otto, written commun., 1991).

3. The base of the Milligen Formation in the eastern 

Boulder Mountains may be gradational with underlying calcareous siltstone that contains Silurian (Ludlovian), as well 

as Early Devonian (Lochkovian and Pragian) conodonts 

(Brennan, 1987; Batatian, 1991) (fig. 3).

4. In the Boulder Mountains, Devonian argillite, 

apparently stratigraphically above the upper part of the Milligen Formation exposed in the Triumph mine area, appears 

to be locally conformably overlain by argillite and lithic 

wacke mapped as the upper part of the lower Copper Basin 

Formation (Lower Mississippian) (Bruner, 1991; Huerta and 

others, 1991) (fig. 2).

UNNAMED SILURIAN AND DEVONIAN ROCKS

Unnamed Silurian and Devonian rocks including 

black, siliceous to carbonaceous argillite (map unit DSa of 

Dover, 1983), tan, calcareous, dolomitic, or siliceous siltstone (map unit DSs of Dover, 1983), and bioclastic limestone (map unit DS1 of Dover, 1983) are tectonically 

imbricated with the Phi Kappa and Trail Creek Formations 

in steep grassy slopes at the head of Trail Creek and in the 

North Fork of the Big Lost River northeast of Ketchum 

(fig. 1, plate 1). The rocks were originally included in the 

Phi Kappa and Trail Creek Formations by Umpleby and 

others (1930) but were redefined based on biostratigraphy 

by Dover (1981, 1983). Structural complexity and poor 

exposure prevented Dover (1981, 1983) and previous workers from dividing this sequence into formations. Limestone 

(mapped as unit DS1 by Dover, 1983) in the unnamed Silurian and Devonian rocks contains Middle Devonian (Eifelian) conodonts (Dover and others, 1980; Dover, 1981, 

1983; Brennan, 1987) (fig. 3). Limestone beds in a siltstone 

unit (unit DSs of Dover, 1983) exposed in the headwaters 

of the North Fork of the Big Lost River contain Upper Silurian (Ludlovian) and Lower Devonian (Lochkovian and 

Pragian) conodonts (Dover, 1983; Brennan, 1987) (fig. 3).

We show the contact between undifferentiated Ordovician, Silurian, and Devonian rocks and the Milligen
C8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Headwaters North FrkRiver Big Lost Brennan 

(1987)

Headwaters Creek ofTrail 

North Frk, and 

River Big Lost Dover (1983)

Kent ofEasPeak 

Batatian (1991)

C i_

a, o CD cu «-

 >- CU c CD

 C C U 0) 

5 CD CO t. ,_ 

«= Q CO ~-

Wood EastFork River Triumph Mine area Otto Turner and

(1988)

Sandberg and others (1975)

T

CONODONT ZONES

1^*~

cu

Q. 

Q.

D

CO 

C/3 

Q

H^

=

3 

CD 

CO 

Q

=

=

=

cu

Q. 

Q.

D

cu

Q.

a.

D

CO 

CO 

Q

Black argillite 

chert unit

CD CU

Q o

CD ___

00 

CM

(£86 L) JS/\OQ p uoijeaijoj J8A|y poo/y\ ^

I

(A

CO 

Q

cu

£-5 g

o i- ^ ^ 

1 E |Q ~~ ^

CD g CO

C

in

m

CO 

Q

T\\

Q I

i

^ ^ s ^

z*

*

k

0 ' -

L " '

CJ

E "Q

*^ 

U 1 D

> 

< " " co I

<East >-ir* A

Argillite 

of member Triumph 

(Dmt^_ ^__^ 

<D

CO 

Q

1

CN

m

CO 

Q,

Limestone (Dmlc) 

~V" member of

 ^ Coin Lucky " / 

" 

C

 4

:

 o

5

. in

Lower calcareous

tn cu 

0 1

cu 

cu

c5??6 Q co 

cc

K

unit siltstone 

o

Formation

ro ^' 

CO 

O

/~^ Quartzite member of

Cait er (Dmc) ite 

H 11 1 _ O ro

 - = E

2 5

h- LL. 

^

(V

CO C

a. Q.'*: o 'P

CO CO ^

* E S. IF °

Q- LL

^^

CD C 

Q.O D.'^'Z? 

CO CO ^

- ^ t Q. 

" £°

 / ml ° '? « Q

juojjeLUJO-j U36;|]i|/\|

 o>

tn o-i 

g « fc °° r^ 

§ =6 -o «> 

ro 'E f. m

-^ ^ c "* CD ^ E CO 

0 CM

l jequjeai ainii6jB

uojieuuo-1 U86j||!|/\|

D

8

P 8 J

iili

c i 

1 !

-&.S

co a

c 

c .2 w o 

S § .2 o 2 E

^)T3 £ 3 "C d)W

llillfi.l 1 |1

^SlJl-ISi | |'8

5w« fcs-"-"°i3 a & «>

.(..ricotototoMj^ O3

3.ISS-8-&S-&! J |f 

^l&ossssg1 | -S&

2oSoD"o"o"oC ilflllljl 1 o 11o^ 3<xcoo.a.a.a.a.< a. «

NVINN3IAIVJ NVINSVHd

y3ddn

3

0

§ 

3 

^

f

NVI13AIO

^//

ft 

k'/<

^ // ^

^ 

^

Tortodus kockelianus australis

srn^oufirf/cy sn/njocf snjDjsco 

(NVn3dl3)

3iaaiiAi

sn^jouSrt/oj snuijojas sni^DuBrf/cy iBjgquojS 

NVIS1AI3

Sn^JDU5rf/OJ SU33Sll[3p 

snjoa/ns '3 dsqns -u 

snjoa/ns snpoi^ouScg

'OVdd V

sapio/;apojrfau\/ oj/ap 

vuipoyjvzQ sisuavydjng 

OIHOlT

y3MOi

NVINOA3Q

1

r^-

/

T3 CU 

tn 

0 

Q. 

X CU

(I

.

tn

CO 

CO

'Uppermost ^ Ozarkodina 

eosteinhornensis

ouipoyjozQ sisuamo^uiajsoa Pelekysgnathus index fauna

Ozarkodina crispa Pedavis latialata 

Polygnathoides siluricus

Nvnoaidd NVIAO

y3ddn

Ozarkodina crassaOzarkodina sagtta Kockelella patula

iam '^DcnNS/1

3iaaii/^

Polygnathus amorphognathoidei 5 

_o

1 

|

I

1

iA'AOQNVIl

J U 3MO1

Nvmmis

«* 
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C9

Figure 3 (facing page). Correlation chart for Silurian through 

Devonian rocks in the eastern Boulder Mountains, south-central 

Idaho. Modified from Batatian (1991) and Bruner (1991). Solid triangles indicate chert, and open irregular rectangles indicate intrabasinal clasts. Conodont zonation for Devonian System is as 

presented in Brennan (1987) based on sections in the Roberts 

Mountains, Nevada, and at Cellon, Carnic Alps, Austria (after Walliser, 1964; Klapper and Murphy, 1974; and Sandberg, 1979). Complete data for collections 1 through 9 are given in Sandberg and 

others (1975): 1, Sawmill Gulch, SAW-1; 2, Trail Creek, USGS 

8928-SD; 3, Slaughterhouse Creek, AXE-510; 4, Slaughterhouse 

Creek, BLV-3; 5, Fisher Canyon, FIC-1; 6, Fisher Canyon, FIC-2; 

7, Milligen Gulch (principal reference section), C-189; 8, Milligen 

Gulch (principal reference section), C-58; 9, North Fork Big Lost 

River, location uncertain, collected by R. Paull. 10, Bioclastic limestone in unit DSs of Dover (1983), no specific location given; Ludlovian conodonts (A.G. Harris, written commun., 1975, to J.H. 

Dover). 11, Silty limestone, possibly equivalent to number 10 

above; unit DSs?, tributary North Fork Big Lost River (C. Sandberg, oral commun., in Dover, 1983). 12, Dover 74-5209 (USGS 

loc. 9496-SD), middle to late Eifelian, unit DSa of Dover (1983), 

bioclastic phosphatic limestone. In stream cut draining small cirque 

east of Kent Peak in headwaters of North Fork of Big Lost River. In 

intensely sheared dominantly argillite section immediately below 

Wood River thrust fault (J.H. Dover, written commun., 1990). P elements Polygnathus linguiformis linguiformis, P elements P. costatus costatus Klapper, I element Icriodus cf. /. stelcki Chatterton, I 

element I. nodosus (Huddle), I element /. espansus Branson and 

Mehl, Pryantodus elements, Hindeodella element, Angulodus elements, Spathodnathodus cf. S. bipennatus Bischoff and Ziegler; 

conodonts identified by A.G. Epstein (Harris), 1974. 13, Dover 

74-5226 (USGS loc. 9497-SD), Eifelian, unit DS1 of Dover 

(1983), bioclastic phosphatic limestone. East side of south fork of 

North Fork of Big Lost River in chiefly argillite section (J.H. Dover, written commun., 1990). P elements of Polygnathus linguiformis linguiformis, P. elements of P. costatus costatus Klapper, I 

elements of Icriodus nodosus (Huddle), I elements of /. expansus 

Branson and Mehl transitional to /. stelcki Chatterton, Angulodus 

elements, Spathognathodus element, Ligonodina elements, Lonchodina element, Neoprioniodus element. Identified by A.G. Epstein (Harris), 1974. 14, Samples NF-8, NF-12, NF-13, NF-27, 

NF-29 of Brennan (1987), Ludlovian, lower part of calcareous siltstone unit (lower DSs unit of Dover, 1983, correlated with Trail 

Creek Formation by Spoelhof, 1972). Meadow in east fork of headwaters of the North Fork of the Big Lost River. Polygnathus siluricus, P. latialata, Anacoradella ploekensis. Identified by B.D. 

Brennan. 15, Samples NF-10, NF-11 of Brennan (1987), Lochkovian, upper part of calcareous siltstone unit (upper part of lower 

unit DSs of Dover, 1983). Ancyrodelloides delta. Identified by B.D. 

Brennan. 16, Sample NF-14 identified by Brennan (1987), Pragian, 

lower part of cherty argillite unit with thin limestone beds (unit DSa 

of Dover, 1983; lower argillite member of fig. 6, this paper (Bruner, 

1991), equivalent to lower argillite member of Milligen Formation 

of Turner and Otto (this volume). Eognathodus sulcatus. Identified 

by B.D. Brennan. 17, Sample NF-37 of Brennan (1987), Famennian. East side, North Fork Big Lost River, limestone (unit DS1 of Dover, 1983). Polygnathus styriacus(f). Identified by B.D. Brennan.

Formation as a gradational line of facies change in the area 

east of the Trail Creek fault from east of Kent Peak south to 

the Pioneer Mountains core complex (plate 1). In discussion 

of the unnamed Silurian and Devonian rocks, Dover (1981, 

p. 35) suggested that "at least some of these rocks are equivalent in lithology, conodont fauna, and age with the Milligen 

Formation [although] other parts of the sequence seem to 

have closer affinity in lithology and age to the Silurian Trail 

Creek Formation than to the Milligen." Furthermore, he suggested that "structural continuity in the subsurface [between 

the unnamed Silurian and Devonian rocks and the main Milligen outcrop belt] is probable."

MILLER CANYON AREA

Bruner (1991) described more than 1,200 m of 

unnamed Silurian and Devonian rocks from measured stratigraphic sections and drill core in the northeastern Boulder 

Mountains west of Miller Canyon (fig. 4, plate 1).

In the Miller Canyon area, graptolitic shale of the 

Lower Ordovician to Middle Silurian Phi Kappa Formation 

(table 1) forms the lowest exposed stratigraphic interval. 

The Phi Kappa Formation is exposed in imbricate fault 

slices (with apparent younger-over-older relations) below a 

folded thrust plate of tan dolomitic siltstone of the unnamed 

Silurian and Devonian rocks (unit DSs, fig. 4). The Middle 

Silurian Trail Creek Formation was not observed in the 

area and is apparently sheared out along the younger-overolder faults.

The unnamed Silurian and Devonian rocks structurally 

overlying the Phi Kappa Formation west of Miller Canyon 

are subdivided into three informal members: lower argillite, 

middle siltstone, and upper argillite (Bruner, 1991) (fig. 4). 

The lower argillite (unit DSa I, at least 630 m thick) contains 

five subunits (DSal1-DSal5, figs. 3, 4). A basal contact of 

the lower argillite member has not been observed. The lowest exposed subunit (104+ m thick) is black cherty argillite 

containing laminae of white chert. The second subunit (224 

m thick) contains black cherty argillite and interbeds of limestone, distinctive coarse-grained quartz sandstone, and pebble to boulder diamictite or sedimentary breccia (fig. 5). 

Diamictite beds are host to stratabound, inferred syngenetic, 

sulfide mineral deposits that are described later. The third 

subunit of the lower argillite unit (106 m thick) is siliceous 

siltstone, the fourth (45 m thick) is a black ribbon chert, and 

the fifth (151m thick) is black cherty argillite. Gradationally 

overlying the lower argillite member is 234 m of orangeweathering bioturbated siltstone of the middle siltstone 

member (unit DSs, figs. 3, 4). The upper argillite member 

(unit Dsau, figs. 3, 4) conformably overlies the middle siltstone member and contains at least 300 m of phyllitic cherty 

argillite. The upper argillite member may be stratigraphically overlain by Mississippian Copper Basin Formation
CIO GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

METERS 

1,200

1,100

1.000

c 

o

CD

Q

T3

C 

CO

c

A A

A A

A A

1

A A

A A

A A

A A

55

800 -

700 -

600

500

400 H 

300

200

100

DSau . Upper 

f argillite 

member

DSs

Middle siltstone member 

and the correlative 

sandstone member of 

Independence of 

Turner and Otto (1988)

DSal-5

DSal-4

DSal-3

S2' DSal-2

S2-

DSal-1

Lower 

argillite 

member

conglomerate west of the East Fork of Trail Creek (plate 1) 

(Huerta and others, 1991).

Strata in the Miller Canyon area are correlative with 

strata in the headwaters of the North Fork of the Big Lost 

River (fig. 1), where conodonts of Silurian and Devonian 

ages have been recovered (Dover, 1983; Brennan, 1987) 

(fig- 3).

The unnamed strata exposed near Miller Canyon may 

be lithologically correlative with the Devonian Milligen Formation as shown in figure 3 (Bruner, 1991). The lower argillite in Miller Canyon is interpreted to correlate with the 

lower argillite member and the argillite member of Triumph 

of the Milligen Formation because subunit 2 of the lower 

argillite in Miller Canyon (unit DSal2, fig. 4) contains distinctive diamictite and coarse-grained sandstone beds characteristic of the quartzite member of Cait. Thin limestone 

beds recognized in drill core from the lower argillite member 

may represent the limestone member of Lucky Coin.

The middle siltstone member (unit DSs, fig. 4) may correlate with the sandstone member of Independence. Note 

that this siltstone member is the stratigraphically higher of 

two siltstone units mapped as unit DSs by Dover (1983). The 

lower siltstone unit of Dover (1983), exposed in the headwaters of the Big Lost River east of Kent Peak, may correlate 

with the Trail Creek Formation but is not exposed in the 

Miller Canyon area (fig. 3).

The upper argillite member of the unnamed Silurian 

and Devonian rocks (unit DSau, fig. 4) may contain strata 

younger than any exposed in the Milligen Formation in the 

Triumph area.

A A

EXPLANATION 

Ribbon chert Interbeds of chert

Cherty argillite Local interbeds of sandstone and breccia 

Micritic dolomitic siltstone

Siliceous sandstone Interbeds of argillite, sandstone, and breccia 

Siliceous, medium-grained sandstone

Sedimentary breccia or diamictite Interbeds of coarse-grained 

sandstone; clasts mainly cherty argillite and quartzite. Dmc 

is quartzite member of Cait

Graded bedding

Thin bedded

Planar cross lamination

Bioturbation

Load structures

Disseminated pyrite

Sulfide rich

Laminae of white bedded chert

Sand

Breccia and coarse-grained sandstone beds, 0.1-1.5 m thick

KENT PEAK AREA

On the east side of Kent Peak, in the headwaters of 

the North Fork of the Big Lost River, Batatian (1991) reinterpreted strata mapped by Dover (1983) as "unnamed 

Devonian and Silurian" rocks and as Pennsylvanian and 

Permian Wood River Formation to be correlative with several of the informal members of the Milligen Formation 

(Turner and Otto, 1988, this volume). These correlations 

are based on lithologic similarity and require biostratigraphic confirmation.

Figure 4. Composite stratigraphic column of unnamed Silurian 

and Devonian rocks exposed in the area west of Miller Canyon, 

eastern Boulder Mountains, Custer County, Idaho, and their correlation with the Devonian Milligen Formation. Modified from 

Bruner (1991). Unit Dmc is quartzite member of Cait of Turner 

and Otto (1988).
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS Cll

Batatian (1991) mapped the cirque east of Kent Peak 

(plate 1 ) as containing a folded but continuous stratigraphic 

section of Silurian and Devonian rocks. Diamictite identical 

with that in the lower argillite member of the unnamed Silurian and Devonian strata in the Miller Canyon area, and 

containing very coarse quartz sand grains similar to the 

quartzite of Cait of the Milligen Formation, is present southeast of Kent Peak (plate 1). Batatian (1991) suggested that 

the strata are correlative with the Milligen Formation and 

that the lower argillite member, limestone of Lucky Coin, 

and sandstone of Independence are present (fig. 4).

Dover (1983) mapped some of the rocks east of Kent 

Peak as the upper part of the Wood River Formation and others as unnamed Silurian and Devonian argillite and siltstone. 

He mapped a low-angle fault (the "Wood River thrust") 

between Silurian and Devonian strata and the questionable 

strata in the cirque east of Kent Peak. He noted that argillite 

in the unit mapped as Wood River Formation contains "thick 

layers and lenses of dark chert pebble conglomerate [and] 

includes unit 7 of Hall and others (1974) and probably 

younger beds as well." Our observations suggest that these 

mixed carbonate-siliciclastic strata contain trace fossils 

(Taenidium and Zoophycos; Burton and Link, 1991) identical to those in the Wilson Creek Member of the Wood River 

Formation, supporting Dover's (1983) interpretation.

East of the problematic rocks in the cirque east of Kent 

Peak, and apparently downsection from them, is light-colored silicified banded siltstone (mapped as a lower interval 

of unit DSs by Dover, 1983) (fig. 3) that has yielded Silurian 

conodonts (Brennan, 1987) (fig. 5). These siltstone strata 

resemble the Silurian Trail Creek Formation, which is 

exposed along strike to the southwest in Park Creek and on 

Trail Creek Summit (Dover, 1983).

SUMMARY OF PROPOSED CORRELATIONS 

OF SILURIAN AND DEVONIAN STRATA

We suggest that some of the unnamed Silurian and 

Devonian strata in the North Fork of the Big Lost River correlate with the Trail Creek Formation and the informal members of the Milligen Formation as shown in figure 3. In 

particular, the lower interval of unit DSs (Dover, 1983; 

Batatian, 1991) may correlate with the Trail Creek Formation. The lower argillite member of the Milligen Formation 

(unit DMla of Batatian, 1991) may be present both in the 

Miller Canyon area and east of Kent Peak. This unit contains 

layers of diamictite (sedimentary breccia) and coarsegrained sandstone that correlate with the quartzite member 

of Cait, which is host to syngenetic stratabound mineral 

deposits. The limestone member of Lucky Coin may be 

present as thin interbeds in the lower argillite member of the

Figure 5. Unnamed Devonian strata east of Kent Peak. A, Graded 

bed of pebble breccia (Ta turbidite interval). Intrabasinal dark chert 

clasts float in matrix of calcareous silt at the base. Top of pebble bed 

contains extrabasinal quartz pebbles and granules. Overlying medium-grained calcareous sandstone is wavy parallel-laminated (Tc) 

interval. Coin shown for scale. B, Ungraded bed of pebble breccia 

containing intrabasinal dark cherty argillite clasts and coarsegrained sandstone clasts (ss). Knife shown for scale.

unnamed Silurian and Devonian rocks in the Miller Canyon 

area (Bruner, 1991) and may be correlative with an approximately 70-m-thick limestone interval east of Kent Peak 

(Batatian, 1991). If these correlations are correct, the argillite member of Triumph, which is present above the diamictite and sandstone beds of the quartzite member of Cait in the 

Triumph mine area (Turner and Otto, this volume), may be 

present as unit DSIa5 in the Miller Canyon area but thin or 

missing in the Kent Peak area. Strata correlative with the 

sandstone of Independence are present in both areas. The 

upper argillite member in the Miller Canyon area (unit 

DSau) may represent strata younger than any exposed in the 

Milligen Formation in the Triumph area.
C12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

UPPER CONTACT OF UNNAMED 

SILURIAN AND DEVONIAN ROCKS

The upper contact of the unnamed Silurian and Devonian rocks may be an unconformity with the Mississippian 

Copper Basin Formation. In the East Fork of Trail Creek, 

rocks mapped as unit DSa by Dover (1983) contain darkgray and brown carbonaceous argillite and dark-gray to 

black, coarse-grained quartzite. West of the East Fork of 

Trail Creek (plate 1), these rocks are apparently conformably 

overlain by sandy and conglomeratic argillite and granule to 

boulder conglomerate shown as the upper part of the lower 

Copper Basin Formation (Lower Mississippian) (Huerta and 

others, 1991; Rodgers and others, this volume). Biostratigraphic studies are required to confirm this interpretation.

PALEOZOIC SALMON RIVER ASSEMBLAGE

The Paleozoic Salmon River assemblage (Hobbs, 1985) 

is exposed in the southern part of the Challis I°x2° quadrangle directly to the north of the Hailey I°x2° quadrangle. The 

Salmon River assemblage contains isoclinally folded slices 

of dark-colored argillite, lighter colored siltstone, limestone, 

and quartzite. The assemblage may be about 2,000 m thick, 

but isoclinal folds and faults make this estimate tenuous 

(Hall and Hobbs, 1987). Samples collected in situ from the 

Salmon River assemblage contain Late Cambrian and Late 

Devonian conodonts; however, the Late Cambrian fauna 

were derived from carbonaceous limestone within what is 

interpreted to be a tectonic slice at the base of the assemblage 

(Hall, 1985). Fossils in two blocks of limestone float found 

north of the Salmon River contain Late Mississippian fossils 

(Nilsen, 1977; Hobbs, 1985). The Salmon River assemblage 

is described as Late Mississippian by Nilsen (1977) and 

Tschanz and others (1986) and as simply Paleozoic by Fisher 

and others (1983). The Mississippian age assignment for the 

assemblage is doubtful because bioclastic limestone beds 

similar to those that yielded the Late Mississippian fossils 

are unrecognized within Salmon River assemblage stratigraphy. It is our opinion that the majority of the Salmon River 

assemblage is Devonian in age.

The Salmon River assemblage occupies a structural 

position similar to the entire Ordovician through Devonian 

section in the Boulder Mountains west of the Pioneer thrust 

fault. On the west side of the White Cloud Peaks it underlies 

the Pennsylvanian and Permian Grand Prize Formation 

along a sheared unconformity that had formerly been interpreted as a regional thrust fault similar to the "Wood River 

thrust" (Sengebush, 1984; Hall, 1985; Hall and Hobbs, 1987; 

Mahoney and Sengebush, 1988; Mahoney and others, 1991; 

Mahoney, this volume). On the east side of the outcrop belt 

the Salmon River assemblage is thrust over Ordovician carbonate and quartzite strata including the Clayton Mine 

Quartzite, Ella Marble, Kinnikinic Quartzite, and Saturday

Mountain Formation (Hobbs, 1985; Hall and Hobbs, 1987) 

(fig. 1, plate 1).

In the Washington Basin mineralized area (Mahoney, 

this volume) (fig. 1) of the White Cloud Peaks, the Salmon 

River assemblage underlies sheared conglomerate boudins 

of the basal Grand Prize Formation. These boudins are similar to those of the Hailey Member of the Wood River Formation along the sheared contact between the Wood River 

and Milligen Formations. The map of Tschanz and others 

(1986) shows this unconformable relationship, though it 

includes rocks now recognized as Grand Prize Formation 

within the Wood River Formation and assigns a Mississippian age to the Salmon River assemblage.

The bulk of the Salmon River assemblage south of the 

Salmon River in the White Cloud Peaks (fig. 1, plate 1) contains dark-colored argillite, siltite, and sandstone that yield 

Late Devonian fossils. The Paleozoic Salmon River assemblage and the Devonian Milligen Formation are similar lithologically and stratigraphically in that both contain thick 

sections of homogeneous black argillite, abundant thin-bedded fine-grained turbidite sequences, and intercalated bluegray, locally tremolitic, limestone. The Salmon River assemblage and the Milligen Formation both host inferred syngenetic sulfide deposits that have identical lead-isotope 

signatures (Sanford and Wooden, this volume). We suggest 

that the Salmon River assemblage in the White Cloud Peaks 

area mostly correlates with the Milligen Formation. Hall 

(1985, p. 121) noted that the Salmon River assemblage contains a fracture cleavage almost parallel with bedding and 

differs from that of the Milligen, "which has a penetrative 

shear cleavage that is at a large angle to bedding, has a much 

higher metamorphic grade, and has a phyllitic sheen." Our 

mapping has not revealed a systematic difference in degree 

of deformation between the two units.

MINERAL DEPOSITS IN SILURIAN 

AND DEVONIAN ROCKS

Correlation of the Milligen Formation with the 

unnamed Silurian and Devonian strata of the North Fork of 

the Big Lost River and the Salmon River assemblage to the 

north in the White Cloud Peaks area suggests stratigraphic 

and structural continuity between these areas. This continuity has important implications for mineral resource potential. 

The entire area underlain by the Milligen Formation, the 

unnamed Silurian and Devonian units, and the Salmon River 

assemblage has potential for the occurrence of syngenetic 

stratabound silver-lead-zinc deposits. Syngenetic stratabound zinc and barite deposits within the Salmon River 

assemblage at the Hoodoo mine in Slate Creek have textures 

and lead-isotope signatures similar to inferred syngenetic silver-lead-zinc deposits in the Milligen Formation in parts of 

the Triumph mine (Hall, 1985; Hall and Hobbs, 1987; Sanford and Wooden, this volume) (plate 1). Syngenetic textures
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C13

are also present in lead-zinc sulfide minerals in the lower 

argillite member of the unnamed Silurian and Devonian 

rocks in the Miller Canyon area, as described later (Bruner, 

1991). In addition, epigenetic poly metallic veins are present 

in the Milligen Formation and correlative units and in 

younger formations that are in stratigraphic or structural contact with lower Paleozoic strata.

Mineral exploration activity has been sporadic, and 

continues, in the Slate Creek, Washington Basin, and North 

Fork of the Big Lost River drainages (fig. 1). Unnamed Silurian and Devonian strata in the Summit mineralized area 

near Miller Canyon (fig. 1) host sulfide-mineralized rocks. 

Structurally complex areas near Miller Canyon have been 

explored since the mid-1980's for syngenetic stratabound 

silver-lead-zinc mineral deposits. Bruner (1991) documented textures in polished sections and in hand samples 

indicative of both syngenetic sedimentary exhalative and 

epigenetic sulfide mineralization. These textures are 

described in the section on mineral deposit models.

MISSISSIPPIAN COPPER 

BASIN FORMATION

The Lower and Upper Mississippian Copper Basin Formation crops out extensively in the northeastern part of the 

Hailey I°x2° quadrangle, in the headwaters of the East and 

North Forks of the Big Lost River (fig. 1). The Copper Basin 

Formation was named by Ross (1962) for a thick sequence 

of coarse-grained siliciclastic strata in the Pioneer Mountains. Paull and others (1972) raised the formation to group 

rank and defined six formations within the Copper Basin 

Group. Paull and Gruber (1977) revised the definition of the 

Copper Basin Group. Nilsen (1977) and most subsequent 

workers (Skipp, Sando, and Hall, 1979; Dover, 1981, 1983) 

recognized stratigraphic and structural complications within 

these Mississippian strata, including structural repetition by 

the Glide Mountain thrust fault, and retained the name Copper Basin Formation after Ross (1962) (fig. 2). Wilson 

(1994) questioned the premise that the Copper Basin Formation occupies two thrust sheets and reaffirmed that, in the 

type area, the stratigraphy is essentially as described by Paull 

and others (1972) and Paull and Gruber (1977). Wilson and 

othes (1994) reviewed the stratigraphy and facies relations of 

the Copper Basin Formation.

The Copper Basin Formation contains graded beds of 

cobble and pebble conglomerate, as well as sand- and siltsize siliciclastic turbidite and argillite. Clasts in conglomerate include dark-colored chert and argillite similar to rocks of 

the Devonian Milligen Formation, as well as a large proportion of light-colored quartzite clasts of uncertain provenance.

The lower part of the Copper Basin Formation is of 

Early Mississippian age (Kinderhookian and Osagean) and 

is at least 3,000 m thick. As mapped by Nilsen (1977) and 

Dover (1981, 1983), these Lower Mississippian strata are 

exposed in two thrust sheets separated by the Glide Mountain thrust fault. Detailed examination of the Glide Mountain

thrust fault by Wilson (1994; Wilson and others, 1994) suggests that the mapped structure is variously a stratigraphic 

contact (locally sheared), a normal fault, and thrust fault. For 

further discussion see Rodgers and others (this volume).

According to Wilson (1994), in the Hailey I°x2° quadrangle the exposed Copper Basin Formation is solely of 

Early Mississippian age. Because the formation is internally 

sheared and locally tightly folded, thickness estimates are 

structural. The basal contact drapes older rocks in the Wildhorse inlier. As divided on plate 1, the formation consists of 

a lower interval (unit Mcl) that contains a basal of dark:gray 

argillite, siltite, and granule conglomerate turbidite (the Little Copper Member, from 0 to more than 660 m thick) overlain by a discontinuous, but generally eastward thickening 

wedge of fine-grained mixed carbonate-siliciclastic turbidite 

(Drummond Mine Limestone Member, 0-910 m thick). An 

upper unit (unit Mcu) of pebble and cobble conglomerate, 

sandstone, and argillite (more than 1,150 m thick) is mapped 

on plate 1. This upper unit includes the Scorpion Mountain 

Formation of Paull and Gruber (1977), the lower part of the 

Muldoon Canyon Formation of Paull and Gruber (1977), and 

the beds mapped as Green Lake Limestone Member of Copper Basin Formation north of Dry Canyon along the East 

Fork of the Big Lost River by Dover (1981).

The upper part of the Copper Basin Formation (Upper 

Mississippian, Meramecian and Chesterian) is not exposed 

in the map area of plate 1. In figure 2 it is shown as the upper 

Copper Basin Formation and includes at least 580 m of shallow-water sandstone and mudstone exposed in the western 

part of the Idaho Falls I°x2° quadrangle (Skipp, Sando, and 

Hall, 1979; Skipp, 1989) and including the Iron Bog Creek 

Formation of Paull and Gruber (1977) (fig. 2).

The siliciclastic parts of the Copper Basin Formation 

contain rare marine fossils. The primary age control on the 

Copper Basin Formation is from the intervals of limestone 

turbidite (the Drummond Mine Limestone Member and the 

lenticular Green Lake Limestone Member), which have 

yielded several identical assemblages of upper Kinderhookian conodonts (Sandberg, 1975; Skipp, Sando, and 

Hall, 1979; Dover, 1981; Wilson, 1993). Deep-water ichnofossils in these mixed carbonate-siliciclastic turbidites 

include Taenidium, Phycosiphon, Phyllodocites, Cosmorhaphe, and Chondrites.

The upper part of the Copper Basin Formation along 

Iron Bog Creek in the Idaho Falls I°x2° quadrangle, 17 km 

east of the east edge of the Hailey quadrangle, is dated as 

Chesterian in age by several macrofossil collections (Skipp, 

Sando, and Hall, 1979; Skipp, 1989).

The Copper Basin Formation is thought to represent 

Lower Mississippian flysch and overlying Upper Mississippian molasse that filled a foreland basin east of an emergent 

highland of the Antler erogenic belt (Poole, 1974; Nilsen, 

1977; Poole and Sandberg, 1977, 1991). Paleogeographic 

reconstructions (Poole and Sandberg, 1991) show that the 

Copper Basin Formation mainly represents deposits of a 

westward-derived, siliciclastic Scorpion Mountain-Brockie 

Lake submarine fan system, although recent work (Wilson
C14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

and others, 1994) suggests that a fault-bounded southern 

source area provided the bulk of the coarse detritus to unit 

Mcu. During a relative sea-level highstand in late Kinderhookian time the eastward-derived calciclastic Drummond 

Mine fan or ramp system prograded westward into the 

basin. The Upper Mississippian part of the formation is 

interpreted to be a marginal-marine facies that represents 

filling of the Antler foreland basin (Nilsen, 1977; Skipp, 

Sando, and Hall, 1979).

The majority of the Copper Basin Formation is exposed 

east of the Pioneer thrust fault, though there are small outcrops west of the Pioneer thrust fault (Rodgers and others, 

this volume). The Pioneer thrust fault places Lower Ordovician to Middle Silurian Phi Kappa and Middle Silurian Trail 

Creek Formations and an unnamed Silurian and Devonian 

argillite unit over the upper part of the lower Copper Basin 

Formation. The Pioneer thrust fault is the westernmost major 

Mesozoic thrust fault in south-central Idaho (Dover, 1981, 

1983; Rodgers and others, this volume) (fig. 1).

West of the Pioneer thrust fault (from the East Fork of 

Trail Creek north across the North Fork of the Big Lost 

River) are several outcrops of undated conglomeratic rocks 

mapped as Copper Basin Formation (Dover, 1983). A poorly 

exposed contact west of the East Fork of Trail Creek separates undated argillite and quartzite mapped as undifferentiated Silurian and Devonian argillite (unit Dsa of Dover, 

1983) from overlying undated argillite, siltstone, finegrained lithic wacke, quartzite, and channel-fill conglomerate mapped as Copper Basin Formation (plate 1). Although 

Dover (1983) mapped this contact as a thrust fault, the contact probably is gradational because bedding attitudes are 

consistent across it and stratigraphic tops are consistently to 

the west (Huerta and others, 1991). This relation implies that 

in Early Mississippian Osagean (?) time the western part of 

the Copper Basin flysch trough may have onlapped Devonian argillaceous rocks in stratigraphic continuity with Milligen Formation strata thought to have composed the Antler 

highland. The relation is consistent with the identification of 

terrigenous and shallow-water facies in western outcrops of 

the Copper Basin Formation (Dover, 1981). Below this contact, approximately 300 m to the east, is the Lower Ordovician Basin Gulch Quartzite Member, the basal unit of the Phi 

Kappa Formation. This relation indicates that several hundred meters of Devonian and (or) Silurian strata has been 

faulted out, but the stratigraphic location of this fault is 

unclear. More detailed geologic mapping and biostratigraphic study is needed to adequately document this relation.

East of the Pioneer thrust fault, in the Dry Canyon and 

Wildhorse inliers of the northeastern part of the Hailey 1 °x2° 

quadrangle, lower Paleozoic shelf carbonate rocks are 

exposed beneath the Copper Basin Formation. The contacts 

were interpreted to be thrust faults by Dover (1981, 1983), 

low-angle normal faults by Kim (1986), and locally sheared 

angular unconformities by Wilson (1994). To the southeast, 

in the Idaho Falls I°x2° quadrangle, the Middle Devonian 

Carey Dolomite unconformably underlies the Copper Basin 

Formation near Garfield Canyon (Kunkel, 1989) and the 

Upper Devonian Picabo Formation unconformably underlies

the Copper Basin Formation near Fish Creek Reservoir (Link 

and others, 1988). Farther to the east, in the White Knob 

Mountains, the Copper Basin Formation of the Copper Basin 

plate is thrust over finer grained coeval strata (Lower Mississippian McGowan Creek Formation) of the Grouse thrust 

plate (Link and others, 1988; Skipp and others, 1990) (fig. 2). 

In at least two locations, strata of the Copper Basin Formation have been transported along Eocene low-angle normal faults. In the headwaters of Summit Creek, a block of 

Copper Basin Formation conglomerate lies in low-angle normal fault contact above Wood River Formation and 

unnamed Devonian strata (Huerta and others, 1991). This 

contact was shown as a thrust fault by Dover (1983). Tectonic slices of Mississippian-age siltstone are also present 

between the Middle Pennsylvanian and Lower Permian 

Wood River Formation and the Devonian Milligen Formation in the Rock Roll Canyon quadrangle (C.M. Tschanz, 

U.S. Geological Survey, unpublished data, 1987).

MINERAL DEPOSITS IN THE 

COPPER BASIN FORMATION

Lead-silver skarn, replacement, and vein deposits are 

present in laminated calc-turbidites of the Drummond Mine 

Limestone Member in the Summit mineralized area (fig. 1) 

in the Phi Kappa mine (Winkler and others, this volume) and 

at several locations in the Idaho Falls I°x2° quadrangle to 

the east. Characteristics of these deposits are summarized in 

the section on mineral deposit models.

PENNSYLVANIAN AND PERMIAN 

SUN VALLEY GROUP

Hall (1985) recognized three lithologically similar 

upper Paleozoic formations in south-central Idaho: the 

Wood River, Dollarhide, and Grand Prize Formations. Each 

of these consists of generally fine grained, locally carbonaceous, mixed carbonate-siliciclastic strata. Link and others 

(1988) proposed that these strata were deposited in the epicratonic Wood River Basin during Pennsylvanian and Permian time. Mahoney and others (1991) formally defined the 

Sun Valley Group to include these formations and, using 

new paleontological collections, established that all three 

formations are of Middle Pennsylvanian to Early Permian 

age (figs. 6, 7).

Hall (1985) proposed that the formations now included 

in the Sun Valley Group belonged to distinct thrust complexes or tectonic stacks and that their mutual boundaries 

were everywhere thrust faults of significant lateral displacement. Recent geologic mapping and measurement of stratigraphic sections (Mahoney and others, 1991; O'Brien, 1991; 

Worl and others, 1991) demonstrate that boundaries between 

formations of the Sun Valley Group in most places represent 

facies changes rather than structural contacts (fig. 8). Faulted 

contacts are also present (plate 1). The three formations of the 

Sun Valley Group are mappable lateral variations of originally continuous strata deposited in the Wood River Basin.
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C15

METERS 

3,400 T

3,200

3,000 -

2,800 '

2,600 -

2,400 

2,200 

2,000 -

1,800 -

1,600 -

1,400 -

1,200 -

1,000 -

800 -

600 -

400 -

200 -

0 -

-TOOTEXPLANATION

Noncalcareous siltstone p | Micritic sandstone

Banded siltstone and sandstone [ | | j |' Sandy micrite

Carbonaceous, calcareous, banded siltstone tSS5?SiJ:| Siliceous sandstone

Carbonaceous siltstone tip:;x: '^"j Sandstone, micritic in part

Silty micrite K^'kV'"] Pebble layer or pebbly rock

Silty dolomicrite Ko^9;d Conglomerate

Argillaceous micrite \/^sS \ Phyllite

Limestone v ' ^ '1 Plutonic rock

2ZZ 

ML

Chert

Parallel laminated

Crosslaminated

Crossbedded

Massive

Channel

Graded bedding

Slump folded, convolute bedding

Load cast

Flute cast

Burrowed

Covered or float

Figure 6. Generalized stratigraphic columns of the Sun Valley Group, south-central Idaho. Numbers next to Wood River Formation 

column indicate informal units of Hall and others (1974). Modified from Mahoney and others (1991, fig. 3).
C16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 7 (facing page). Correlation chart for Middle Pennsylvanian to Lower Permian rocks of the Sun Valley Group, south-central 

Idaho. Modified from Mahoney and others (1991, fig. 2). Bars with 

numbers indicate ranges of previously published and new biostratigraphic collections. Ranges for fusulinids are based on Loeblich and 

Tappan (1988). Circled numbers indicate stratigraphic position of 

the collection. Identified taxa and name of biostratigrapher are as 

follows. Grand Prize Formation: 1, Conodont elements of Adetognathus sp., elements of Hindeodus cf. H. Ninutus (Ellison), elements of Idiognathosus sp., (late Morrowan to Wolfcampian), 

Member 2? or 3?, Peach Creek, identified by A.G. Harris (Hall, 

1985, p. 125); 2, Conodont Neogondelella idahoensis (middle and 

late Leonardian), member 3 or 4, Pole Creek, identified by B.R. 

Wardlaw (Hall, 1985, p. 125). Wood River Formation: 3, Wedekindellina (late Atokan(?) to Desmoinesian), Hailey Member limestone, north of Seamans Creek in principal reference section, 

(Bostwick, 1955) and Pseudozaphrentoides (Middle Pennsylvanian 

brachiopod), Eagle Creek Member (unit 3), Wilson Creek section 

(Thomasson, 1959); 4, Beedeina and numerous brachiopods (Desmoinesian), Hailey Member limestone, north of Seamans Creek in 

principal reference section (Bostwick, 1955; Hall and others, 1974, 

p. 91); 5, Beedeina (Desmoinesian), Eagle Creek Member (unit 3), 

north of Seamans Creek in principal reference section (Hall and others (1974, p. 91); 6, Triticites, Pseudofusulinella sp. and Triticites 

sp. aff cullomensis Dunbar and Condra (Virgilian), Eagle Creek 

Member (unit 4), Seamans Creek in principal reference section 

(Hall and others, 1974, p. 92); 7, Triticites sp. (Missourian to Wolfcampian), Eagle Creek Member (unit 5), north of Seamans Creek in 

principal reference section (Hall and others, 1974, p. 93.); 8, Schubertella and Staffella, unit 6 north of Seamans Creek in principal 

reference section (Hall and others, 1974, p. 94), as well as Triticites 

cullomensis (Wolfcampian), Eagle Creek Member, mid-upper unit 

6, Wilson Creek Ridge type section (Burton, 1988), identified by 

C.A. Ross (1988); 9, Pseudofusulinella (Desmoinesian to Wolfcampian), Eagle Creek Member, limestone at top of unit 6, Wilson 

Creek Ridge type section (Burton, 1988), identified by C.A. Ross 

(1988); 10, Triticites confertus, T. pinguis, T. meeki, T. cellamagnus, Pseudofusulinella utahensis, P. grandensis, P. elkoensis, 

(Wolfcampian), Wilson Creek Member, lower unit 7, Basin Gulch 

type section (Burton, 1988), identified by C.A. Ross (1988); 11, 

Pseudofusulina grandensis, P. elkoensis, P. wellsensis, Schwagerina, Paraschwagerina (Wolfcampian), Wilson Creek Member, upper unit 7 or 8, Basin Gulch type section (Burton, 1988), identified

by C.A. Ross (1988); this collection is thought to be from the same 

upper limestone bed tentatively assigned to Leonardian and Guadalupian(?) by Hall and others (1978, p. 581); 12, Bioclastic limestone east of summit of Kent Peak (Batatian, 1991). The unit 

yielded conodont collection Neogondolella sp. (not N. idahoensis), 

Drepanodus-like sp., and Sweetognathus sp. indicating a Late 

Pennsylvanian to Early Permian age (D. Van Hofwegan, C. Spinsoa, written commun., 1991) and macrofossils including Chaetetes 

sp. indicating a Desmoinesian (Middle Pennsylvanian) age (D.E. 

Fortsch, oral commun., 1991). Elevation 10,800 ft, ridge northeast 

of the summit of Kent Peak, Ryan Peak quadrangle, lat 45°53'35" 

N., long 114°23'32" W. Dollarhide Formation (14 through 18 are 

reported in Mahoney and others (1991) and O'Brien (1991): 13, 

Conodonts Idiognathodus delicatus (Gunnell) and Neognathodus 

dilatus (Stauffer and Plummer), Desmoinesian (Middle Pennsylvanian), lower member Dollarhide Formation, NWV^SW1/^ sec. 25, T. 

3 N., R. 17 E., Mahoney Butte 7.5-minute quadrangle, Blaine 

County, Idaho, lat 43°33.75' N., long 114°24.00' W., collected by 

Betty Skipp, identified by R.G. Stamm and B.R. Wardlaw (written 

commun., 1990, in Skipp and others, in press). USGS collection 

number 31400-PC; 14, Fusulinids, possibly Triticites (Missourian 

to Wolfcampian), lower member?, Sky Ranch flat, west of Bellevue, collected by P.K. Link, identified by R.C. Douglass (written 

commun., 1988); 15, Fusulinids Schwagerina sp. (Wolfcampian to 

mid-Leonardian), lower member, Sky Ranch flat, west of Bellevue, 

two collections, by P.K. Link and R.S. Lewis, identified by C.A. 

Ross (written commun., 1988) and D.A. Myers (written commun., 

1989); 16, Fusulinids, possibly Pseudofusulina (Wolfcampian to 

Leonardian), lower member, Wolf Tone Creek, R.C. Douglass 

(written commun., 1978, in Hall, 1985, p. 124); 17, Fusulinids suggestive of Schwagerina (Virgilian and Wolfcampian), elevation 

8,640 ft on ridge at northern headwaters of Deer Creek, SE1/^ sec. 

29, T. 3 N., R. 16 E., Buttercup Mountain 7.5-minute quadrangle, 

collected by J.P. O'Brien, identified by D.A. Myers (written commun., 1989); 18, Fusulinid Bartramella sp. Eelevation 8,640 ft on 

ridge at northern headwaters of Deer Creek, SE'/4 sec. 29, T. 3 N., 

R. 16 E., Buttercup Mountain 7.5-minute quadrangle, collected by 

R.S. Lewis, identified by D.A. Myers (written commun., 1989). Because this locality yielded both Bartramella and Schwagerina (collection 15 above), the collection may be B. heglarensis, which is 

associated with Schwagerina sublettensis (Wolfcampian) in the 

Sublett Range of southern Idaho (Thompson and others, 1958).
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C17

White Cloud Peaks,

North Boulder 

Mountains (Hall, 

1985; Mahoney 

and Sengebush, 

1988; this study)

South Boulder and

Pioneer Mountains east

Smoky Mountains (Hall

and others, 1974;

Hall and others,

1978; this study)

- Sun Valley Group 

West Smoky 

Mountains (Hall, 

1985; Wavra and

others, 1986; 

this study)

Lost River, Lemhi,

Beaverhead 

Ranges (Breuninger

and others, 1988; 

Verville and others, 1990)

£3U 

255 

260 

265 

270 

275 

280 

285 

ooc /ob 

+6

290 

295 

300 

305 

310 

5 Ma 

c

CO

E

CD 

0-

c

CO 'c

CO

>

>

CO

c 

c

CD

Q_

CO

0

_l

CO 

Q.

D.

=>

 o^

^

i

0

_l

Guadalupian 

(part)

Leonardian

Wolfcampian

Virgilian

Missourian

Desmoinesian

Atokan

Morrowan

i

c

 ^o

CO

E

o

LL

CD

N

£.

-o

C 

CO

O

'

,

Member 4 ^\

X

X

X

X w~"~

X

/

X

Member 3 ~f

~?~

©

Member 2

-?-

Member 1

-?-

1

c 

O

"co

E

- o

LL 

CD

£

~O

O

o

c

8

Wilson 

Creek 

Member

7

(j 

6

5

4

3

2

1

(H

)

(ii) 1

(10)

T

s '

f 1

I]2S

Eagle 

Creek 

Member

 

Hailey

^

C)

(e

5 j

©

Memben i (^ 

02!

Tl 1

" T 1 !~{

i

__

c

_o

TO

O 

LL

0

T3 

"I

_co

"5 

D

\ 

j

/

_______

--

(

Upper 

member

m;

7

Middle 

member

7

n

Lower 

member

@

4)

-1-

T

1

®

 

-> . -L

Park City 

and

Phosphoria

Formations

1

t

CO 

_Q.

C

o

CO

E 

o

LL

C

o

c

CO

O

CO

c

CO

Juniper 

Gulch 

Member

Gallagher 

Peak Member

Bloom 

Member

f

1

(part)

)

]

\ Section 

\ locations

\V ^

1 2 4

3

1
CIS GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

The Sun Valley Group contains eight lithofacies conglomerate, bioclastic limestone, micritic sandstone, banded micritic sandstone-siltstone, graded silty 

micritic limestone, silty micritic limestone, sandy micritic 

limestone, and carbonaceous siltstone described by 

Mahoney and others (1991). The Middle Pennsylvanian 

part of the Sun Valley Group (Hailey Member of the Wood 

River Formation and correlative Grand Prize Formation, 

member 1) consists mostly of proximally derived chert- and 

quartzite-pebble conglomerate and interbedded biostromal 

limestone deposited on a braid delta and adjacent slope. 

The Middle Pennsylvanian to Lower Permian part of the 

group (Eagle Creek and Wilson Creek Members of the 

Wood River Formation, all of the Dollarhide Formation, 

and the upper three members of the Grand Prize Formation) 

comprises fine-grained mixed carbonate and siliciclastic 

rocks deposited in a south-sloping ramp-apron system with 

distal (carbonate bank and cratonal) provenance.

Hall (1985) defined the Grand Prize and Dollarhide 

Formations as distinct from the long-recognized (Lindgren, 

1900) Wood River Formation on the basis of lithologic variations, carbon content (as demonstrated by color), and metamorphic overprint. The Grand Prize Formation, in addition 

to being sandier and coarser grained than the other formations, has undergone metamorphic silicification. The Dollarhide Formation is characteristically darker colored, more 

carbonaceous, and finer grained than the Wood River or 

Grand Prize Formations. Specific relations between the formations are described after the following stratigraphic discussion, modified from Mahoney and others (1991).

WOOD RIVER FORMATION

The Wood River Formation, as named by Lindgren 

(1900), included all Paleozoic rocks exposed near the Wood 

River Valley. Umpleby and others (1930) restricted the formation to light-colored rocks of Pennsylvanian and Permian 

age. The formation is now known to contain rocks of Desmoinesian to Leonardian age (Bostwick, 1955; Ross, 1960; 

Hall and others, 1974; Mahoney and others, 1991) (fig. 6) 

but may include rocks as young as Guadalupian (Hall and 

others, 1978; Skipp and Hall, 1980).

The Wood River Formation is divided into three formal 

members (Mahoney and othei s, 1991) (figs. 6, 7), the Hailey 

Member (basal 200 m), the Eagle Creek Member (middle 

880+ m), and the Wilson Creek Member (upper 800+ m). 

The principal reference section of the Wood River Formation, east of Bellevue (section W5, plate 1 ), which includes 

the type section of the Hailey Member at its base, was measured by Hall and others (1974). Mahoney and others (1991) 

designated several supplemental reference sections. The

GRAND PRIZE DOLLARHIDE 

FORMATION

Lower Paleozoic strata

EXPLANATION

Conglomerate

Intraformational conglomerate 

Sandstone

Figure 8. Schematic diagram showing facies changes within the 

Sun Valley Group across the Wood River Basin, south-central 

Idaho. Unpatterned areas represent mixed siliciclastic and carbonate rocks, and light-shaded areas indicate prograding wedges of 

medium- and fine-grained sand. Solid sawtooth line indicates observed transition between formations; dashed sawtooth line indicates inferred transition; double-ended arrow indicates sheared 

unconformity at base of Sun Valley Group; and dashed line between units Pg3 and Pg4 indicates that age of boundary is uncertain. Grand Prize Formation: Pg1, member 1, PPg2, member 2, 

Pg3, member 3, Pg4, member 4. Wood River Formation: Pwh, 

Hailey Member, PPwe, Eagle Creek Member, Pww, Wilson 

Creek Member. Dollarhide Formation: PPdl, lower member, Pdm, 

middle member, Pdu, upper member.

Wilson Creek section (section W4, fig. 9B, plate 1), exposed 

on the ridge crest north of Wilson Creek, contains the type 

section of the Eagle Creek Member. The Basin Gulch section 

(section W3, fig. 9A, plate 1), exposed on steep slopes northeast of the head of Lake Creek and on the ridge crest to the 

northeast, contains the type section of the Wilson Creek 

Member. Descriptions of these stratigraphic sections are 

contained in table 2. Two other reference sections that contain exposures of the entire formation are on the ridge north 

of Lake Creek (section W2, fig. 9C, plate 1) and on the ridge 

north of Murdock Creek (section Wl, plate 1). Precise locations of these sections are described in table 3.

The basal Hailey Member of the Wood River Formation, as defined by Mahoney and others (1991), consists of 

the Hailey Conglomerate Member and the bioclastic limestone of unit 2 of the Wood River Formation, as described
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C19

by Hall and others (1974). Unit 2 is vertically and laterally 

gradational with the conglomerate (Burton, 1988; Mahoney 

and others, 1991). The Eagle Creek Member consists of 

units 3 through 6 of Hall and others (1974), and the Wilson 

Creek Member consists of units 7 and 8 of Hall and others 

(1974, 1978).

The Hailey Member is 0-200 m thick and consists of 

0-180 m of light-brown to light-gray conglomerate gradationally overlain by 15-30 m of bluish-gray bioclastic limestone (fig. 6). The member is primarily exposed east of the 

Wood River in the Pioneer and Boulder Mountains, although 

it is exposed in a few areas west of the Wood River near 

Hailey (plate 1). To the east, near Fish Creek Reservoir in the 

Idaho Falls I°x2° quadrangle, the Hailey Member contains 

180 m of calcareous sandstone and dispersed chert-pebble 

conglomerate and bioclastic beds (Link and others, 1988). 

The Hailey Member may have been deposited on an irregular topographic surface and is locally depositionally absent 

(Winsor, 1981).

The basal contact of the Hailey Member is a locally 

sheared unconformity with the underlying Devonian Milligen Formation (Burton, 1988; Burton and others, 1989; 

Ratchford, 1989, in press; Mahoney and others, 1991; Burton and Link, this volume). In many areas interstratal slip 

along the unconformity has produced a shear zone in which 

the Hailey Member is present as kilometer-scale boudins, or 

is attenuated, particularly in fold limbs, or is thickened in

Figure 9. Reference sections of the Wood River Formation northeast of Ketchum, Idaho. Locations of sections shown on plate 1 and 

described in table 3. A, Basin Gulch section (W3), upper part within 

Wilson Creek Member, on the near ridge. Section was measured in 

southwest-dipping beds up to axis of eastward-overturned anticline. 

Upper part of the section is repeated in folded rocks to the northeast. 

View is looking southeast from west of the left fork of upper Trail 

Creek, toward the Pioneer Mountains core complex on horizon. 

Traces of Wildhorse detachment fault and Lake Creek fault on peak 

10,458 are shown. B, Wilson Creek ridge section (W4), view looking southeast from ridge west of Trail Creek. Complete section of 

Wood River Formation (Pwh, Hailey Member; PPwe, Eagle Creek 

Member; Pww, Wilson Creek Member) below the Lake Creek fault 

is present in overturned southwest-dipping beds from sheared unconformity with Devonian Milligen Formation (Dm) to axis of 

northeast-overturned syncline. In distance is the lower plate of the 

Wildhorse detachment fault, the core of the Pioneer Mountains core 

complex. C, Lake Creek ridge section (W2), view looking northwest from ridge west of Trail Creek. Complete section of Wood 

River Formation (Pwh, Hailey Member; PPwe, Eagle Creek Member; Pww, Wilson Creek Member) above the Lake Creek fault is 

present in overturned southwest-dipping beds from sheared unconformity with Devonian Milligen Formation (Dm) to axis of northeast-overturned syncline.
C20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 2. Descriptions of type sections for three members of the Wood River Formation, south-central Idaho. 

[Modified from Mahoney and others (1991, table 2)]

TYPE SECTION OF THE HAILEY MEMBER OF THE WOOD RIVER FORMATION

Measured by Hall and others (1974) east of Bellevue on the ridge north of Seamans Creek in northeast-dipping beds from 6,390 to 

6,600 ft elevation, SW1A sec. 28, T. 2 N., R. 19 E., Seamans Creek quadrangle (section W5, fig. 2).

Thickness 

(meters)

Conformable contact to Eagle Creek Member (unit 3) 

Top of Hailey Member

Unit 2 of Hall and others (1974)

Limestone, bluish-gray, medium- to thick-bedded, fine-grained, locally abundant crinoidal debris, bryozoa,

and brachiopod fragments. Contains 5-10 percent detrital quartz grains...................................................... 15.0

Conformable contact to unit 2 

Unitl

Chert-pebble conglomerate, light-gray, siliceous cement.................................................................................... 1.5

Limestone, brown, fine-grained, algal; chert-pebble conglomerate, beds 0.3-0.6 m thick.................................. 12.5

Chert-pebble conglomerate, as above.................................................................................................................. 0.3

Limestone, brown, fine-grained, algal; 10 percent fine-grained quartzite beds 1.3-2.5 cm thick........................ 16.2

Chert-pebble conglomerate, light-gray and brownish-gray, as above.................................................................. 64.0

Limestone, micritic, brown, silty, in part silicified.............................................................................................. 0.6

Chert-pebble conglomerate, light-gray, chalcedonic matrix ................................................................................ 3.7

Limestone, brown, fine-grained, sandy................................................................................................................ 1.5

Chert-pebble conglomerate, siliceous matrix, chert and quartzite clasts; quartzite, light-green, fine-grained,

thick-bedded................................................................................................................................................... 16.8

Limestone, sandy, brown..................................................................................................................................... 0.3

Chert-pebble conglomerate, light-gray, thick-bedded, siliceous cement, a few well-rounded light-brown

limestone and white quartzite clasts, subrounded chert pebbles 1-2.5 cm long............................................. 31.0

Total thickness Hailey Member......................................................................................................................................_____135.5

TYPE SECTION OF THE EAGLE CREEK MEMBER OF THE WOOD RIVER FORMATION

Measured on ridge north of Wilson Creek, in northeast-dipping beds from 6,600 to 8,800 ft elevation, NEV4 sec. 14 and SWV4 sec. 12, 

T. 5 N., R. 18 E., Rock Roll Canyon quadrangle (Burton, 1988) (section W4, fig. 2).

Thickness 

(meters)

Wilson Creek Member (gradational contact) 

Top of Eagle Creek Member

Unit 6 of Hall and others (1974)

Micritic sandstone, medium-gray, weathering brown, fine-grained trough cross-laminated, syndepositional

convolute laminae, thin-bedded, interbedded with silty micrite..................................................................... 20

Micritic sandstone (quartzarenite), gray, weathering brown, thick-bedded to massive, fine- to coarse-grained, 

fractured; sparse trough cross lamination, load casts and flute casts; Arenicolites. Section is cut by fault 

at 470 m.......................................................................................................................................................... 483

Unit 5 of Hall and others (1974)

Fine sandstone (quartzarenite), siliceous or partly calcareous, light-brown, well-indurated, thickly bedded to

massive; crude parallel laminae, dish structures, intensely fractured.............................................................. 160

Unit 4 of Hall and others (1974)

Silty micrite to fine micritic sandstone, brown, thin- to medium-bedded, trough cross- and convolutelaminated, weakly graded beds....................................................................................................................... 160

Silty micrite, dark-gray, weathering gray-brown, wavy parallel laminae; interbeds of dark-gray micritic

mudshale... ...................................................................................................................................................... 40

Very fine micritic sandstone, dark-brown, thin-bedded, convolute laminae, load casts, micritic mudstone

partings; Scalarituba.. .................................................................................................................................... 20

Unit 3 of Hall and others (1974)

Silty micrite and mudshale, dark-brown to purple-gray, pink-gray weathering, moderately bioturbated,

crudely fissile; Neonereites, Scalarituba, Phycosiphon, Zoophycos.............................................................. 175

Silty micrite, gray-brown and dark-brown, thin-bedded, wavy parallel laminae, burrowed to intensely 

bioturbated; contains interbeds as much as 1.5 m thick of silty allochem limestone containing crinoid, 

brachiopod, and rugose coral bioclasts, Neonereites, Scalarituba, Muensteria?, Spirophycos?.................... 85

Top of Hailey Member (bioclastic packstone of unit 2 of Hall and others, 1974)

Total thickness Eagle Creek Member............................................................................................................................. 1,143
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C21

Table 2. Descriptions of type sections for three members of the Wood River Formation, south-central Idaho Continued. 

[Modified from Mahoney and others (1991, table 2)]

TYPE SECTION OF THE WILSON CREEK MEMBER OF THE WOOD RIVER FORMATION

Measured southwest to northeast across ridge northeast of the head of Lake Creek; from 9,200 ft elevation across 10,200-foot ridge 

crest to 9,200-foot knob on ridge southwest of 9,677 ft, north of Basin Gulch; starts in NW1^ sec. 3, T. 5 N., R. 18 E. and continues into 

NEV4 sec. 34, T. 6 N., R. 18 E., Rock Roll Canyon quadrangle (Burton, 1988) (section W3, fig. 2).

Thickness 

(meters)

Top of measured section: hinge of tight syncline 

Unit 7 of Hall and others (1974)

Fine sandy micrite, medium-brown, weathering dark-brown, thin-bedded, partly silicified and dolomitic;

arranged in fining-upward cyclic packets 8-17 m thick of massive siliceous micrite in lower 2-3 m, overlain

by thin-bedded dolomicrite containing trough cross and convolute laminae, overlain by intensely

bioturbated carbonaceous silty micrite................................................................................................................. 175

Sandy and coarse silty micrite, thin-bedded, siliceous, trough cross- and convolute-laminated; mottled gray

orange to brown black; Neonereites.... ................................................................................................................. 180

Allochemic sandy micrite, medium- to dark-gray; bioclasts include crinoid columnals, scaphopods?,

cephalopods, bryozoa, fusulinids......................................................................................................................... 30

Micritic mudshale, very dark brown, silty, bioturbated; Neonereites, Phycosiphon, Paleophycus?......................... 20

Fine micritic sandstone (quartzarenite), medium-gray, weathering brown, calcareous, thick-bedded to massive .... 20

Interbedded coarse silty micrite and fine micritic sandstone, medium-gray to brown, silty micrite parts

bioturbated........................................................................................................................................................... 67

Micritic mudshale, very dark brown, silty, bioturbated; Neonereites, Phycosiphon, Paleophycus?......................... 8

Silty micrite and very fine sandy micrite, medium-gray, weathering light-gray to yellow-brown; arranged in 

thinning- and fining-upward sequences (15-25 m thick) containing complete turbidites at the base passing 

upward to partial (base-cutout) Tace and TC(je turbidites and to thin, very dark brown, intensely silicified 

Tdef turbidites at the top; basal sequences are intensely bioturbated.................................................................... 252

Silty micrite and micritic sandstone, medium-gray to light-brown; medium beds contain Taccje silt turbidite

sequences; Neonereites, Scalarituba, Phycosiphon, Zoophycos, Planolites..... ................................................... 35

Fine sandy micrite, medium-gray, weathering medium-brown, thin- to medium-bedded, brown micritic

mudstone partings................................................................................................................................................ 8

Fine micritic sandstone, medium-gray, thin-bedded, micritic mudstone partings, load casts, Scalarituba............... 5

Conformable contact, top of Eagle Creek Member (micritic sandstone, unit 6 of Hall and others, 1974)

Total thickness Wilson Creek Member.......................................................................................................................... 800+

fold hinges. Silver-lead-zinc vein deposits are present locally coarse-grained carbonaceous bioclastic limestone and

along this sheared unconformity (Burton and Link, this vol- resembles bioclastic beds in the Wilson Creek Member

ume). The upper contact of the Hailey Member is placed at (David Seeland, U.S. Geological Survey, written commun.,

the first appearance of the distinctive light-purple silty 1992). The unit yielded conodonts (collection 12, fig. 7) that

micrite of the Eagle Creek Member (table 2, fig. 6). The age indicate a Late Pennsylvanian to Early Permian age and

of the Hailey Member is Desmoinesian, based on the bios- macrofossils, including Chaetetes sp., that indicate a (Middle

tratigraphy of coral, fusulinid, and phylloid green algae Pennsylvanian) Desmoinesian age (D.E. Fortsch, Idaho State

occurrences (Bostwick, 1955; Hall and others, 1974) (fig. 9). University, oral commun., 1991). If the Desmoinesian age is

The Eagle Creek Member of the Wood River Formation correct, the beds may be the carbonaceous equivalent of 

(upper Desmoinesian to Wolfcampian) is 880-1,300 m thick limestone in the upper part of the Hailey Member. The facies 

and consists of 260m of light-purple silty micritic limestone resembles bioclastic parts of the Bloom Member of the 

overlain by 620-1,140m of light-brown micritic sandstone, Snaky Canyon Formation (Chesterian to Missourian) 

light-gray sandy micritic limestone, and subordinate quartz- exposed 55 km to the east across several thrust faults in the 

arenite (fig. 6). The Eagle Creek Member forms the bulk of Lost River Range (Skipp, Kuntz, and Morgan, 1979) (fig. 7). 

the outcrop area of the Wood River Formation both east and The Wilson Creek Member (Wolfcampian to Leonardwest of the Wood River. It is best exposed on the high ridges jan) consists of more than 800 m of dark-gray carbonaceous 

of the Boulder Mountains (fig. 9). siltstone and sandstone, thin-bedded light-brown graded

About 250 m of anomalous carbonate-rich facies silty micritic limestone, light-brown silty micritic limeassigned to the Eagle Creek Member by Batatian (1991) stone, light- to dark-gray sandy micritic limestone, and subcrops out just east of the summit of Kent Peak. The rock is ordinate light-brown medium-bedded micritic sandstone
C22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 3. Measured stratigraphic reference sections of the Pennsylvanian and Permian Sun Valley Group, south-central Idaho. 

[Diagrammatic stratigraphic columns for these sections are shown in Mahoney and others (1991, figs. 4-6). Locations of sections listed below are 

shown in fig. 2)]

__________________________________Wood River Formation_________________________________ 

Section Wl Murdock Creek (unconformable base of Hailey Member to hinge of syncline in upper part of Wilson Creek

Member, described by Burton, 1988). Measured in northeast-dipping beds on the ridge between Murdock Creek 

and the East Fork of the North Fork of the Wood River, Amber Lakes 7.5-minute quadrangle, starting just 

southwest of peak 8,635 and proceeding northeastward along long ridge line to peak 9,783. NEU sec. 27, 

through sec. 23, to SW»4 sec. 13, T. 6 N. R. 17 E., Blaine County, Idaho. Base of section lat 43°40'23" N., long 

114°24'22"W.

Section W2 Lake Creek section (unconformable base of Hailey Member to hinge of fold in lower part of Wilson Creek 

Member, described by Burton, 1988). Measured southwest to northeast along ridge between Lake and Eagle 

Creeks in northeast-dipping beds, Rock Roll Canyon 7.5-minute quadrangle; from 9,040 to 9,000 ft elevation, 

across peak 9,675; NWU sec. 8 to NE14 sec. 5, T. 5 N., R. 18 E., Blaine County, Idaho. Base of section lat 

43°46'56" N., long 114°20'34" W;

Section W3 Basin Gulch section; includes type section of Wilson Creek Member (unconformable base of Hailey Member to 

hinge of syncline in upper part of Wilson Creek Member, described by Burton, 1988). Measured southwest to 

northeast along ridge northeast of the head of Lake Creek in northeast-dipping beds, Rock Roll Canyon 7.5- 

minute quadrangle; measured from 7,960 ft elevation to peak 9,677, across 10,200 ft ridge crest; SW14 sec. 3, T. 

6 N., R. 18 E. and NE14 sec. 34, T. 6 N., R. 18 E., Blaine County and Custer Counties, Idaho. Base of section 

lat 43°47'58" N., long 114°18'45" W.

Section W4 Wilson Creek Ridge; includes type section of Eagle Creek Member (unconformable base of Hailey Member to 

hinge of syncline in upper part of Eagle Creek Member, described by Burton, 1988). Measured from southwest 

to northeast on the ridge between Wilson Creek and Trail Creek in northeast-dipping beds, Phi Kappa Mountain 

and Rock Roll Canyon 7.5-minute quadrangles. Hailey Member measured about 500 m east of the base of the 

ridge on the west bank of Wilson Creek, NW14 sec. 13, T. 5 N., R. 19 E. Eagle Creek and Wilson Creek 

Members measured along the ridge from 6,600 ft elevation to swale at 9,000 ft elevation in NE14 sec. 14 and 

SWl/4 sec. 12, T. 5 N., R. 18 E. Blaine County, Idaho. Base of section lat 43°46'13" N., long 114°16'18" W.

Section W5 Bellevue (principal reference section of the Wood River Formation and type section of Hailey Member),

unconformable base of Hailey Member to topographic surface in upper part of Wilson Creek Member, described 

by Hall and others (1974). Composite section; units 1-6 (Hailey and Eagle Creek Members) measured 

southwest to northeast along ridge north of Seamans Creek, Seamans Creek 7.5-minute quadrangle, from 6,390 

ft elevation to top of ridge; base of section lat 43°29'30" N., long 114°14'00" W.; unit 7 (Wilson Creek Member) 

measured on Quigley Creek in sec. 21, T. 3 N., R. 19 E., starting 2,300 ft north of the southwest corner of 

section 21 and measured toward the east up the ridge from 6,640 to 7,300 ft elevation, base of section lat

_____________43°34'30" N., long 114°12'30" W. Blaine County, Idaho._______________________________

Grand Prize Formation

Section Gl

Section G2

Section G3

Hoodoo Mine section (lower part of member 2 to lower part of member 3). Measured on east flank of peak 

10,050, west of Hoodoo Lake in west-dipping beds; section measured from 8,820 to 10,050 ft, Robinson Bar 

7.5-minute quadrangle, Custer County, Idaho. Base of section lat 44°10'35" N., long 114°38'15" W.

Fourth of July Creek section (composite reference section, unconformable base of member 1 to topographic 

surface in upper part of member 4; also shown in Mahoney and Sengebush, 1988). Composite section. Interval 

from 0 to 500 m measured in east-dipping beds, Strawberry Basin, north of Blackman Peak, from 9,800 to 

10,111 ft elevation, Washington Peak 7.5-minute quadrangle; base of section lat 44°04'28"N, long 114°39'32" 

W. Interval from 550 to 2,500 m measured from west to east in steeply west dipping overturned beds on ridge 

north of Fourth of July Creek, from 7,800 to 9,200 ft elevation, Obsidian and Washington Peak 7.5-minute 

quadrangles, Custer County, Idaho. Base of section lat 44°03'18"N, long 114°43'48" W.

Washington Basin section (sheared base of member 1 to topographic surface in lower part of member 3). 

Measured from east to west in steeply west dipping beds on east flank of peak 10,519, section starts at 10,200 ft 

and goes along sawtooth ridge to top of peak 10,519, Washington Peak quadrangle, Custer County, Idaho. Base 

of section lat 44°15'00", long 114°39'38".
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C23

Table 3. Measured stratigraphic reference sections of the Pennsylvanian and Permian Sun Valley Group, south-central Idaho 

Continued.

Grand Prize Formation Continued

Section G4 Champion Lakes section (lower part of member 2 to topographic surface in upper part of member 4). Measured 

on ridge south of Champion Lakes Basin, measured from east to west in steeply west dipping beds; section starts 

at 9,920 ft, southeast of peak 10,167, and continues along ridge to west side of Champion Lakes Basin, to north 

of peak 10,081, Horton Peak and Washington Peak 7.5-minute quadrangles, Custer County, Idaho. Base of 

section lat 43°58'53"N, long 114°40'00" W.

Section G5 Contains two sections (G5a and G5b of Mahoney and others, 1991) repeated across normal fault and containing 

parts of members 3 and 4. Comprises the type section of Grand Prize Formation of Hall (1985). Measured in 

northwest-dipping beds on north side of Pole Creek, near its confluence with Grand Prize Gulch, on south flank 

of peak 10,166, from 7,970 to 9,560 ft elevation, Horton Peak 7.5-minute quadrangle, Custer County, Idaho. 

Base of section lat 43°56'27" N., long 114°41'00" W.

Section G5b Pole Creek section 2, separated from Pole Creek section 1 by low-angle fault. Type section of Hall (1985) 

crosses this fault. Section continues from 9,560 to 10,166 ft elevation above section G5a, Horton Peak 7.5- 

minute quadrangle, Custer County, Idaho. Base of section lat 43°56'28" N., long 114°41'00" W.

Section G6 Salmon River Headwaters section (partial sections of members 2 and 3, described in Mahoney, 1987).

Measured on west side of Salmon River, on east flank of peak 9,423 in northwest-dipping beds, from 7,800 to 

9,423 ft elevation, Frenchman Creek 7.5-minute quadrangle, Camas County, Idaho. Base of section lat

_____________43°48'45" N., long 114°46'33" W.____________________________________________

Dollarhide Formation

Section Dl

Section D2

Section D3

Willow Creek section (principal reference section, intrusive contact at exposed base of lower member to 

topographic surface in upper part of upper member) described by Geslin (1986) and O'Brien (1991). Measured 

from southwest to northeast in northeast-dipping beds along ridge due west of Cup knob (benchmark 9,147); 

lower part measured from 7,245 ft (contact with Idaho batholith) to fault at knob 7,856, S1A sec. 36, T. 3 N., R. 

15 E.; base of section lat 43°32'49" N., long 114°37'00" W. Upper part of section measured 0.6 mi to the north 

of peak 7,856, from elevation 7,000 ft in creek bottom to knob 7,852, NEV4 sec. 36 to SEV4 sec. 25, T. 3 N., R. 

15 E. (O'Brien, 1991), Buttercup Mountain 7.5-minute quadrangle, Camas County, Idaho. Base of section lat 

43°33'35" N., long 114°37'25" W. Lower section may be continued above knob 7,856 into the middle and upper 

members up to knob "Cup" 9,147, although it is structurally thickened.

Dry Gulch-Bear Gulch section (intrusive contact in upper part of lower member to axis of syncline in upper 

member, described by O'Brien, 1991). Composite section. Lower 400 m measured on north slope of Dry Gulch, 

in northeast-dipping beds from contact with Cretaceous stock at 7,000-8,380 ft elevation; NE14 sec. 3, NW14 

sec. 4, T. 2 N., R. 16 E. and SWV4 sec. 35, T. 3 N., R. 16 E., Buttercup Mountain 7.5-minute quadrangle, Blaine 

County, Idaho. Base of section lat 43°32'25" N., long 1140 31'35" W. Upper 900 m measured in west-dipping 

beds in the central headwaters of Bear Gulch, on the east side of knob "Cup" (9,147) from 7,400 ft elevation to 

core of syncline at 8,900 ft, NVi2 sec. 32, T. 3 N., R. 16 E. Base of section lat 43°34'38" N., long 114°32'50" W.

Wolf Tone Creek section (covered interval in lower part of lower member to poorly exposed interval near top of 

middle member, described by Wavra and others, 1986). Measured along northwest side of Wolf Tone Creek in 

southwest-dipping beds. Section starts at stream fork at 6,058 ft and proceeds upstream to 6,280 ft, opposite 

prominent stream entering Wolf Tone Creek from the south; SWV4 sec. 8, SEV4 sec. 7, and NEV4 sec. 18, T. 2 N., 

R. 17 E., Mahoney Butte 7.5-minute quadrangle, Blaine County, Idaho. Base of section lat 43°31'25" N., long 

114°27'33"W.
C24 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

(fig. 6). The member forms slopes and is sparsely exposed 

east of Bellevue and Hailey, although it is well exposed in 

alpine ridges of the Boulder Mountains northeast of 

Ketchum (figs. 1, 9, plate 1). The fine-grained, thin-bedded 

silty micritic limestone of the Wilson Creek Member 

weathers to a characteristic reddish-brown regolith. The 

upper part of the member is dolomitic in part and contains 

diagenetic chert. The Wilson Creek Member contains a 

diverse assemblage of bathyal trace fossils that has been 

interpreted to reflect oxygenation levels controlled by turbidite depositional facies (Burton and Link, 1991). The 

upper contact of the Wilson Creek Member is eroded below 

an unconformity with the Eocene Chain's Volcanic Group 

or the present-day topographic surface (fig. 8).

MINERAL DEPOSITS IN THE WOOD RIVER FORMATION

A variety of mineral deposit types are present in the 

Wood River Formation. The Hailey Member hosts zincbearing veins in the Lake Creek mineralized area (Burton 

and Link, this volume) (fig. 1). Brittle sandstone of the 

Eagle Creek Member hosts vein deposits in the Boulder 

Basin (Ratchford, 1989), Galena, and Lake Creek areas 

(fig. 1). Limestone of the Eagle Creek Member hosts 

replacement deposits in the Wood River area (fig. 1). Carbonaceous siltstone of the Wilson Creek Member hosts 

shear-zone vein deposits in the Lake Creek area (Burton 

and Link, this volume) (fig. 1).

DOLLARHIDE FORMATION

The Dollarhide Formation comprises the southern and 

southwestern exposures of the Sun Valley Group. Complexly folded Dollarhide Formation is intruded by the Idaho 

batholith and associated stocks in the Smoky Mountains, 

west of the Wood River (Whitman, 1990, this volume; Darling and others, this volume) (fig. 1, plate 1). The formation 

was named by Hall (1985) for a sequence of dark-colored 

("sooty") carbonaceous limestone, siltite, fine-grained 

quartzite, and granule conglomerate exposed on Dollarhide 

Summit, west of Ketchum (plate 1), but a type section was 

not designated. Mahoney and others (1991) and O'Brien 

(1991), following Wavra (1985), Geslin (1986), and Wavra 

and others (1986), recognized three informal members and 

designated the principal reference section for the Dollarhide Formation to be east of Willow Creek (section Dl, 

plate 1). Other reference sections for the Dollarhide Formation are south of Wolf Tone Creek (lower and middle members, section D3, plate 1) and at the head of Deer Creek 

north of Buttercup Mountain (middle and upper members, 

section D2, plate 1).

Skipp and Hall (1980), Geslin (1986), Darling (1988), 

and Link and others (1988) described the metasedimentary

"Carrietown sequence" as being in thrust contact below the 

lower member of the Dollarhide Formation in the Smoky 

Mountains near the edge of the Idaho batholith (fig. 1, plate 

1). Whitman (1990, this volume) recognized that this contact is not structural but is a lithologic change accentuated 

by metamorphism. These metasedimentary rocks are now 

interpreted as foliated parts of the lower member of the 

Dollarhide Formation, marginal to the Idaho batholith 

(Whitman, 1990, this volume; Mahoney and others, 1991; 

Darling and others, this volume). The name "Carrietown 

sequence" is abandoned.

The lower member of the Dollarhide Formation (Desmoinesian to lower Wolfcampian) is at least 800 m thick and 

consists of rhythmically interbedded dark-gray carbonaceous silty micritic limestone and very fine grained lightgray to light-brown micritic sandstone and subordinate 

medium- to thick-bedded light-brown micritic sandstone and 

light- to dark-gray lenticular conglomerate containing 

mainly intrabasinal clasts of siltstone and bioclastic limestone. Extrabasinal clasts (vitreous quartzite and finegrained sandstone) are rare. The lower member of the Dollarhide Formation includes at the base a minimum of 175 m 

of quartzite, phyllite, and calc-silicate hornfels formerly 

assigned to the "Carrietown sequence." The lower member 

is exposed in the southern Smoky Mountains, where it forms 

dark-colored slopes punctuated by thin ridges of resistant 

micritic sandstone. The base of the lower member either is a 

fault or is masked by the Idaho batholith, and the upper contact is placed above a mappable dark-gray carbonaceous 

limestone and below thick light-brown micritic sandstone of 

the middle member (O'Brien, 1991) (fig. 6).

The middle member of the Dollarhide Formation 

(lower Wolfcampian) consists of about 300 m of finegrained light-brown micritic sandstone and light-gray sandy 

micritic limestone and subordinate dark-gray to black carbonaceous siltstone and lenticular conglomerate (fig. 6). The 

middle member forms prominent light-colored cliffs 

throughout the central and southern Smoky Mountains. 

North of Deer Creek (plate 1) it is interpreted to grade into 

thick sandstone beds of the Eagle Creek Member of the 

Wood River Formation.

The upper member of the Dollarhide Formation (Wolfcampian and Leonardian) is approximately 900 m thick and 

is composed of thin-bedded to laminated dark-gray carbonaceous siltstone and light-gray silty micritic limestone and 

minor light-brown micritic sandstone and conglomerate (fig. 

6). The upper member gradationally overlies the middle 

member, and the upper boundary is not recognized due to 

erosion. The upper member weathers to a dark-gray regolith, 

is poorly exposed, and forms slopes throughout the Smoky 

Mountains, which, as a result, contain large areas of sparsely 

vegetated "black-shale" regolith (Wavra and Hall, 1989) 

(fig. 1, plate 1).
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C25

MINERAL DEPOSITS IN THE DOLLARHIDE FORMATION

The lower member of the Dollarhide Formation hosts 

vein and replacement mineral deposits in the Bullion, Carrietown, and Deer Creek stock mineralized areas (fig. 1) and a 

laminated barite deposit in the northern part of the Bullion 

area. Sheared vein and replacement mineral deposits are 

present in the upper member of the Dollarhide Formation in 

the Bunker Hill and Carrietown mineralized areas (fig. 1). 

The middle member of the Dollarhide Formation, dominated 

by sandstone or quartzite, does not host mineral deposits.

Wavra and Hall (1989) designated most dark-colored 

outcrops of Paleozoic rocks in the southern Smoky Mountains as upper member, Dollarhide Formation (including 

rocks we map as Milligen Formation in the Minnie Moore 

mine area) and presented a model whereby the upper member is host to syngenetic mineral deposits including the Deer 

Creek barite deposit (plate 1). Recent work based on measured sections of the Dollarhide Formation and recognition 

of distinctive members of the Milligen Formation at the Minnie Moore mine (O'Brien, 1991; Worl and others, 1991; 

O'Brien and others, 1993; Skipp and others, 1994; Link and 

Worl, in press) suggests that restriction of mineral deposits 

to the upper member of the Dollarhide Formation is incorrect. Mineral deposits in the southern Smoky Mountains are 

hosted by the Milligen Formation, as well as by the lower 

and upper members of the Dollarhide Formation.

GRAND PRIZE FORMATION

The Grand Prize Formation comprises the northern 

exposures of the Sun Valley Group and is exposed primarily 

north of Pole Creek in the White Cloud Peaks area (fig. 1, 

plate 1). The formation was named by Hall (1985) for a 

1,450-meter-thick sequence of light-brown fine-grained 

quartzite, brown limy siltstone, banded light- and dark-gray 

siltite, and dark-gray to black carbonaceous silty limestone 

exposed north of Grand Prize Gulch, a tributary to Pole 

Creek (section G5, plate 1). Rocks of the Grand Prize Formation had previously been included in the Pole Creek 

sequence (Skipp and Hall, 1980; Fisher and others, 1983; 

Sengebush, 1984) or the Wood River Formation (Tschanz 

and others, 1986). Mahoney and Sengebush (1988) 

expanded and revised Hall's definition of the Grand Prize 

Formation, subdivided the formation into four informal 

members, and designated a composite reference section for 

the formation north of Fourth of July Creek (section G2, fig. 

6, plate 1). Mahoney and others (1991) slightly modified 

member boundaries within the Grand Prize Formation and 

described additional reference sections (plate 1) for the formation near the Hoodoo mine (section Gl), west of Washington Basin (section G3), above Champion Lakes north of 

Pole Creek (section G4), and at the headwaters of the Salmon 

River (section G6).

Member 1 (Desmoinesian) of the Grand Prize Formation is 0^00 m thick and consists of 0-350 m of light-brown 

to light-gray polymict conglomerate and sandstone overlain 

by 30-50 m of medium-gray bioclastic limestone (fig. 6). 

Member 1 is resistant and forms conspicuous cliffs and 

ledges. The lower contact of member 1 is an erosional 

unconformity with the underlying Paleozoic Salmon River 

assemblage. This contact was strongly sheared during Mesozoic compression, and the original stratigraphic thickness of 

the basal conglomerate is generally not preserved.

Member 2 (Desmoinesian to Wolfcampian) of the 

Grand Prize Formation consists of 500-1,100 m of thickbedded to massive light-brown micritic sandstone and subordinate light-gray sandy micritic limestone and gray carbonaceous siltstone. Member 2 gradationally overlies member 1; 

the contact is placed above the bioclastic limestone of member 1. Member 2 forms discontinuous cliffs and ledges in the 

northern Smoky Mountains and in the White Cloud Peaks. 

Member 3 (Wolfcampian to Leonardian) of the Grand Prize 

Formation consists of 650-1,700 m of fine-grained sandstone and siltstone arranged in rhythmically interbedded 

couplets 30 cm-3 m thick. The distinctive banded appearance of the member is produced by these couplets of lightgray fine-grained micritic sandstone gradationally overlain 

by dark-gray carbonaceous siltstone. Interbedded with the 

couplets is thick-bedded light-brown micritic sandstone and 

light-gray sandy micritic limestone (fig. 6). Member 3 gradationally overlies member 2. Member 3 has an irregular 

weathering pattern; the sandier intervals are exposed in bold 

relief against the more easily weathered finer grained intervals. The member forms distinctly banded light-gray cliffs 

throughout the White Cloud Peaks area.

Member 4 (Wolfcampian to Leonardian) of the Grand 

Prize Formation consists of more than 450 m of thin- to 

medium-bedded carbonaceous siltstone, sandy to silty 

micrite, and minor micritic sandstone (fig. 6). Carbonaceous 

siltstone of member 4 gradationally overlies banded sandstone and siltstone of member 3. Member 4 weathers to a 

dark-gray regolith and forms slopes in the southern part of 

the White Cloud Peaks area.

MINERAL DEPOSITS IN THE 

GRAND PRIZE FORMATION

Members 1, 2, and 3 of the Grand Prize Formation host 

polymetallic vein deposits in Washington Basin (fig. 1). 

Member 3 hosts a tungsten skarn deposit in the Smiley Creek 

drainage of the Smoky Mountains mineralized area (fig. 1). 

Micritic sandstone and sandy micrite of members 2 and 3 

host replacement deposits in the Pole Creek and Washington 

Basin areas (fig. 1). Limestones of member 4 also have 

potential for replacement deposits in the Galena area.
C26 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

RELATIONS BETWEEN FORMATIONS 

OF THE SUN VALLEY GROUP

Our work suggests that the formations of the Sun Valley Group in most places grade laterally and vertically into 

each other by facies change (fig. 8, plate 1) rather than occupying thrust-fault bounded allochthons. We recognize that, 

in places, contacts shown as facies changes on figure 2 may 

appear on the ground to arbitrarily punctuate gradual transitions in color, grain size, or type of cement. Specific relationships between formations are outlined following (after 

Mahoney and others, 1991).

The Dollarhide Formation-Wood River Formation contact may be observed at five locations:

1. In the Picabo Hills, dark-gray limestone and siltstone of the upper part of the lower member of the Dollarhide Formation grade eastward over a distance of about 2 

km into light-gray silty limestone of the Eagle Creek Member of the Wood River Formation, across a set of southwest-vergent folds.

2. Along Deer Creek west of Hailey (Skipp and others, 1994), dark siltstone and limestone of the lower member 

of the Dollarhide Formation are thrust over light-brown 

sandstone and limestone of the Eagle Creek Member along 

the Deer Creek thrust fault.

3. On Kelly Mountain, at the head of Wolf Tone 

Creek, a section of silicified quartzarenite and light-gray 

silty limestone of the Eagle Creek Member of the Wood 

River Formation, several hundreds of meters thick, lies 

above dark- and light-gray siltstone and sandstone of the 

middle and lower members of the Dollarhide Formation on 

a low-angle normal fault.

4. North of Deer Creek, the middle member of the 

Dollarhide Formation is mapped south of the Challis Volcanic Group near Mahoney Butte, but the Eagle Creek Member 

of the Wood River Formation is mapped in probably continuous strata to the north. In this area, the middle member of 

the Dollarhide Formation is a tongue of partially silicified 

micritic sandstone, petrographically identical to micritic 

sandstone of the Eagle Creek Member (fig. 8).

5. North of Baker Creek, light-brown calcareous 

sandstone of the Eagle Creek Member overlies dark-gray 

siltstone and limestone of the lower member of the Dollarhide Formation along a low-angle normal fault (Stewart, 

1987; Stewart and others, 1992).

The Wood River Formation grades northward into the 

Grand Prize Formation. This contact may be observed in 

two places and is shown as a line of facies change on plate 1.

1. North of Pole Creek, massive micritic sandstone of 

the Eagle Creek Member intertongues with thick-bedded 

micritic sandstone assigned to member 2 of the Grand Prize 

Formation. This relation was previously shown as a thrust 

fault by Hall (1985).

2. In Galena Gulch, medium-bedded micritic sandstone, thin-bedded sandy micritic limestone, and silty

micritic limestone of the Wilson Creek Member of the Wood 

River Formation are gradationally overlain by black carbonaceous siltstone and sandy to silty micrite assigned to member 4 of the Grand Prize Formation (fig. 8).

The contact between the upper member of the Dollarhide Formation and member 4 of the Grand Prize Formation 

is obscured by an Eocene dacite porphyry intrusive body 

west of the headwaters of the Salmon River (Mahoney, 

1992) (plate 1). The upper member of the Dollarhide Formation and member 4 of the Grand Prize Formation are lithologically identical carbonaceous siltstone and are interpreted 

as lateral equivalents (fig. 8).

MINERAL DEPOSIT MODELS

APPLICABLE TO PALEOZOIC ROCKS

OF THE EASTERN PART OF THE

HAILEY I°x2° QUADRANGLE

GEOLOGIC COMPLEXITY

The deformational and magmatic history of the eastern 

part of the Hailey I°x2° quadrangle is complex (Rodgers and 

others, this volume). Mineral deposits hosted by Paleozoic 

strata are of three distinct ages: (1) Devonian syngenetic 

stratabound deposits, (2) Cretaceous polymetallic veins and 

skarns associated with intrusion of the Idaho batholith, and 

(3) Tertiary polymetallic veins and skarn deposits associated 

with the Challis magmatic episode.

Probable syngenetic metal deposits are in the Devonian 

Milligen Formation, the Salmon River assemblage, and 

unnamed Silurian and Devonian strata east of the Boulder 

Mountains (Hall, 1985, 1987b; Turner and Otto, 1988, this 

volume; Bruner, 1991; Sanford and Wooden, this volume). 

These deposits may have formed by hydrothermal circulation systems and normal faults that developed during early 

phases of the Devonian and Mississippian Antler orogeny 

(Turner and Otto, this volume).

Magmatically driven hydrothermal systems were active 

in Late Cretaceous and Eocene time. These hydrothermal 

systems caused epigenetic recrystallization and remobilization of metals first concentrated in Devonian time. They also 

tapped new sources of metals in Precambrian granitic basement (Sanford and Wooden, this volume). Several generations of Mesozoic and Tertiary faults cut Paleozoic strata, 

and ore deposits in almost all districts are cut by postmineralization faults.

MINERAL DEPOSIT MODELS

Several of the mineral deposit models compiled in 

Cox and Singer (1986) and modified by Worl and Johnson 

(this volume) are applicable to the central Idaho black-shale
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C27

mineral belt. The following discussion, although neither a 

rigorous coverage of the models nor a mine-by-mine 

review of each mineral district, is meant to summarize 

present understanding. Complete descriptions of mines and 

production are contained in Lindgren (1900), Umpleby 

(1915), Umpleby and others (1930), Anderson and others 

(1950), Tuchek and Ridenour (1981), Van Noy and others 

(1986), Mclntyre (1985), and Fisher and Johnson (1987).

SKARN DEPOSITS

Skarns have not been major ore producers in the Wood 

River area, but gold, lead-zinc, and tungsten skarn deposits 

are present in several places where Paleozoic limestone is 

intruded by Tertiary or Cretaceous stocks.

At the June Day mine, in Parker Gulch of the Triumph 

mineralized area (fig. 1), southeast of Ketchum, a gold-bearing skarn is developed in the limestone member of Lucky 

Coin in the Milligen Formation. The silicified limestone 

"tactile" contains diopsidp, garnet, wollastonite, scapolite, 

clinozoisite, zoisite, and vesuvianite and hosts disseminated 

gold (Anderson and others, 1950). The intrusive rock is an 

Eocene dacite porphyry stock.

The Phi Kappa mine of the Summit mineralized area 

(fig. 1) contains zinc-silver skarn deposits in the Drummond 

Mine Limestone Member of the Copper Basin Formation 

(Winkler and others, this volume). Skarn minerals include 

diopside and grossularite. Sulfide minerals, present in tactile 

zones, include, in order of decreasing abundance, galena, 

sphalerite, pyrite, and chalcopyrile (Tuchek and Ridenour, 

1981). These skarns are associaled wilh granodiorile of Ihe 

Eocene Summil Creek slock, which crops oul lo Ihe wesl 

across Phi Kappa Creek.

Tungsten skarn deposils hosted by members 2 and 3 of 

the Grand Prize Formalion are in Ihe Ura group prospecis on 

Smiley Creek (Mahoney and Horn, in press) (fig. 1). Taclile 

is composed of red garnel, epidole, wollaslonile, quartz, and 

fine-grained scheelile (Van Noy and olhers, 1986).

Gold-bearing skarns may be presenl, associaled wilh 

gold-bearing veins and gossan, in the Black Rock claims of 

the Washington Basin area (Van Noy and others, 1986) (fig. 

1). Granodiorite, of probable Cretaceous age, intrudes limestone, micritic sandstone, and sandy micrile of Grand Prize 

Formalion members 1, 2, and 3 near Ihese claims (Mahoney, 

ihis volume).

Skarns are present west of Hailey and Bellevue in Ihe 

Bunker Hill, Deer Creek slock, and Rooks Creek slock 

mineralized areas (fig. 1). Silver-lead-zinc deposits in these 

areas formed during intrusion of Late Cretaceous (about 90 

Ma) potassium-rich plutons (Rooks Creek stock. Deer 

Creek stock, Croesus stock (fig. 1, plate 1) (Link and Worl, 

in press; Park, in press). These plutons were emplaced easl 

of, and earlier than, the main Atlanta lobe of the Idaho 

batholith to the west (Lewis, 1989). Tactile in contact

metamorphic deposits in the Wood River and Dollarhide 

Formations conlains argentiferous galena in a gangue of 

grossularite and epidote (Lindgren, 1900; Umpleby and 

others, 1930; Anderson and others, 1950). Skarns in the 

Rooks Creek stock area contain disseminated gold and 

sphalerite in a gangue of garnet and pyroxene (Anderson 

and olhers, 1950; Park, in press).

POLYMETALLIC REPLACEMENT DEPOSITS

Calcareous strata in several formations are hosts for 

replacement deposits. The limestone member of Lucky Coin 

(Milligen Formation) hosts polymetallic replacement ore in 

the Triumph and Minnie Moore mineralized areas (fig. 1) 

(Turner and Otlo, this volume; Link and Worl, in press). 

These lode deposits contain sphalerite, galena, tetrahedrite, 

and chalcopyrite. They are localized in calcareous beds suitable for replacemenl and proximal lo a fault thai acted as a 

pathway for mineralizing fluids (Kiilsgaard, 1950).

The Dollarhide Formation hosls replacement deposits 

in several areas west of the Wood River. In the Carrietown 

mineralized area (fig. 1), the host rock is limestone of the 

lower member of the Dollarhide Formalion (Darling and olhers, this volume). In the Bunker Hill mineralized area (fig. 1) 

Ihe hosl is limestone of the upper member of the Dollarhide 

Formation. Ore minerals in these areas, both in replacement 

and vein deposits, are galena, sphalerite, tetrahedrite, pyrite, 

arsenopyrite, pyrrhotite, and chalcopyrile.

In the Boulder Basin mineralized area on the west side 

of the Boulder Mountains (fig. 1), the replaced host is calcareous sandstone or quartzite of the Eagle Creek Member of 

the Wood River Formation. Intrusion of Eocene dikes probably generated ore-bearing circulation systems that deposited pyrite, galena, tetrahedrite, chalcopyrite, and sphalerite 

(Van Noy and olhers, 1986; Ralchford, 1989, in press).

In the northern part of the Galena mineralized area, 

along Pole Creek (fig. 1), calcareous sandstone of member 3 

of the Grand Prize Formation is replaced. Gossan provides 

an exploration guide. Ore minerals include sphalerite, 

galena, and chalcopyrite (Van Noy and others, 1986). 

Micritic sandstone and sandy micrite of members 2 and 3 of 

the Grand Prize Formation host replacement deposits containing delrilal quartz grains within a fine-grained to aphanilic galena matrix in the Washington Basin area (Mahoney, 

this volume) (fig. 1).

Replacement deposits may be present in any calcareous 

stratum. Thus, such deposits potentially could be present in 

the limestone member of Lucky Coin of the Milligen Formation, the lower member of the Dollarhide Formation, Grand 

Prize Formation members 1 to 4, the Hailey, Eagle Creek 

and Wilson Creek Members of the Wood River Formation, 

and the Drummond Mine Limestone Member of the Copper 

Basin Formation.
C28 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

POLYMETALLIC VEINS

Polymetallic vein mineral deposits in the eastern part of 

the Hailey quadrangle are commonly associated with, and 

locally difficult to distinguish from, polymetallic replacement deposits. Vein deposits have been the largest producers 

and are present throughout the black-shale mineral belt. 

Generally, veins hosted by carbonaceous siltstone and argillite ("black shale1 ') have siderite gangue, whereas veins in 

sandstone and quartzite host rock have quartz gangue. Generally, wallrock is not much altered, although some bleaching occurred with formation of sericite and addition of 

carbonate and pyrite.

CRETACEOUS VEIN DEPOSITS

In general, shear-zone-hosted veins of the KetchumHailey-Bellevue area follow fault systems or shear zones of 

Cretaceous age and are associated with Cretaceous plutonic 

activity. The polymetallic veins west of the Wood River 

were formed by hydrothermal systems driven by heat from 

the Late Cretaceous plutons that are border phases of the 

Idaho batholith (Lewis, 1989). These hydrothermal systems 

derived metals from remobilization of Devonian stratabound 

syngenetic mineral deposits and from underlying Precambrian crust (Sanford and Wooden, this volume).

In the East Fork Wood River, Bellevue, Minnie Moore, 

and Triumph mineralized areas (fig. 1), silver-lead-zinc vein 

deposits of probable Cretaceous age are present in black 

argillite of the argillite member of Triumph and limestone 

member of Lucky Coin of the Devonian Milligen Formation 

(Turner and Otto, 1988, this volume). In the Minnie Moore 

mineralized area, including the Minnie Moore and Silver 

Star Queens mines, shear-zone-hosted veins contain galena, 

pyrite, sphalerite, chalcopyrite, and arsenopyrite in a gangue 

of siderite, quartz, calcite, and crushed country rock (Anderson and others, 1950). These veins occupy northwest-striking reverse faults or shear zones that apparently formed 

shortly after intrusion of the adjacent Croesus quartz diorite 

stock about 90 Ma (Link and Worl, in press).

In the Bullion mineralized area (fig. 1), including the 

Mayflower and Red Elephant mines, northwest-striking Late 

Cretaceous veins are hosted by the lower member of the Dollarhide Formation (Link and Worl, in press). The most common ore minerals, in order of increasing abundance, are 

galena, sphalerite, and tetrahedrite. The most common 

gangue minerals are siderite, calcite, and quartz. Siderite 

gangue is associated with ore deposition (Fryklund, 1950).

Many of the areas listed above as containing replacement deposits also contain vein deposits. In general, ore minerals in veins are argentiferous galena, more or less abundant 

sphalerite and tetrahedrite, and subordinate and variable 

amounts of pyrite, arsenopyrite, and chalcopyrite (Umpleby 

and others, 1930; Anderson and others, 1950). The gangue

consists of altered and crushed country rock, siderite, calcite, 

and quartz.

Veins are hosted by both the upper and lower members 

of the Dollarhide Formation in the Carrietown mineralized 

area and by the upper member of the Dollarhide Formation 

in the Bunker Hill mineralized area (fig. 1.

In Washington Basin (fig. 1), polymetallic veins of 

probable Cretaceous age are present in northeast-trending 

shear zones or fractures localized along the axial plane of an 

east-vergent anticline (Mahoney, this volume).

EOCENE VEIN DEPOSITS

North and east of Ketchum, vein deposits of the Smoky 

Mountains, Galena, Lake Creek, and Summit mineralized 

areas (fig. 1) probably formed during Eocene plutonism. In 

the Galena district, mineralized silver-lead-zinc veins follow 

Tertiary shear zones that strike northeast and dip northwest. 

In the Lake Creek area, veins are within northwest-striking 

normal faults in the upper plate of a Paleogene detachment 

fault (Burton and Link, this volume). In both cases associated igneous rocks are dacite and rhyolite porphyry of 

Eocene age.

The ore-bearing vein and associated replacement 

deposits of the Livingston mine on Big Boulder Creek in the 

Challis I°x2° quadrangle (plate 1) contain metals likely 

remobilized from syngenetic stratabound minerals first 

deposited in the Salmon River assemblage during Devonian 

time (Hall, 1985). Eocene rhyolite porphyry dikes are associated with the veins. Ore minerals are jamesonite, galena, 

sphalerite, and tetrahedrite (Van Noy and others, 1986). The 

gangue is quartz that is locally iron stained.

SYNGENETIC STRATABOUND 

SILVER-LEAD-ZINC DEPOSITS

An ultimate syngenetic origin for many of the ore metals in the Wood River valley is suggested by location of 

mines in and near probable source rock of the Devonian 

Milligen Formation and correlative units, as well as by ore 

textures and isotopic data (Hall and others, 1972; Hall, 

1985; Howe and Hall, 1985). Sanford and Wooden (this 

volume) use lead-isotope data to suggest that the lead in 

mineral deposits of the Hailey I°x2° quadrangle was supplied both from syngenetic stratabound deposits within the 

Milligen Formation and Salmon River assemblage and 

from Precambrian crust, but not from detrital lead in Paleozoic black shale.

DEVONIAN MILLIGEN FORMATION

Turner and Otto (this volume) describe mineral deposits from the Milligen Formation in the Triumph mineralized
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C29

area (fig. 1), which is the best-documented example of syngenetic stratabound mineralization in the black-shale mineral belt. The Triumph stratiform sulfide bodies are within or 

at the top of the limestone member of Lucky Coin and are 

associated with limestone turbidite and diamictite. Hall 

(1985, p. 130) described the stratabound syngenetic ore from 

the Triumph mine as "fine-grained, thinly-bedded, darkgray, carbonaceous, micritic, silty limestone containing 

minute grains of sphalerite, galena, arsenopyrite, and pyrite 

disseminated along the bedding." The complex intrusive and 

deformational history of the region has produced a variety of 

epigenetic mineral deposits by remobilization of these stratabound Devonian sulfide deposits.

SALMON RIVER ASSEMBLAGE

Carbonaceous units of the Salmon River assemblage 

contain as much as 10,000 ppm V. At the Hoodoo mine on 

Slate Creek stratabound syngenetic deposits of zinc and barite are present in these rocks (Hall, 1985; Van Noy and others, 1986). The extensive workings follow a mineralized 

zone along the contact between Salmon River assemblage 

and member 1 of the Grand Prize Formation (designated as 

Hailey Conglomerate Member of the Wood River Formation 

by Van Noy and others, 1986, p. 262). Sphalerite and minor 

galena form concordant massive lenses from 0.3 to 12 m in 

thickness. Disseminations and veinlets in brecciated argillite, limestone, and quartzite are cemented by quartz and calcite. Smithsonite is the most abundant secondary mineral. 

Hall (1987b) speculated that during the time of sedimentation the belt of Salmon River assemblage now exposed along 

Slate Creek was downdropped and zinc-rich hydrothermal 

brines were concentrated there. Sphalerite and some galena 

and pyrite were deposited from these brines.

At several locations, original stratabound syngenetic 

sulfide deposits within the Salmon River assemblage are 

thought to have been recrystallized and remobilized by Cretaceous granodiorite plutons (Hall and Hobbs, 1987). Ore at 

the Livingston mine contains highly deformed black siliceous argillite containing bedded sphalerite, pyrite, and 

minor galena and jamesonite (Hall, 1985). These minerals 

are interpreted, based on light-stable-isotope characteristics, 

to have been syngenetic sulfides deposited with the black 

argillite (Howe and Hall, 1985). The rock was subsequently 

shattered and minerals remobilized during emplacement of 

Eocene rhyolite porphyry dikes. The minerals now occupy 

small veinlets and matrix between argillite fragments.

ORE TEXTURES IN SILURIAN AND 

DEVONIAN STRATA, MILLER CANYON AREA

Syngenetic textures suggesting sedimentary exhalative 

(SEDEX) mineralization are present in diamictite within 

the lower argillite unit (unit DSal-2 of figs. 3, 4), the

unnamed Silurian and Devonian rocks in the Miller Canyon 

area(Bruner, 1991).

Two types of pyrite were identified in polished sections: (1) dark, brassy, spongy looking pyrite having colloform, orbicular, and framboidal textures and (2) bright, 

subhedral to euhedral pyrite. The first type of pyrite is 

thought to be syngenetic because it is present (1) as concentrations in the matrix of breccias and (2) within broken argillite clasts. Its dark, spongy character is attributed to poor 

crystal development due to rapid growth in open spaces. 

Such textures are produced by syngenetic precipitates on the 

ocean floor or in epigenetic veinlets. The presence of these 

textures in sulfide-bearing argillite clasts in diamictite is 

strong indication of their syngenetic origin.

The second type of pyrite is thought to be epigenetic 

because it is present (1) as overgrowths on colloform and 

framboidal pyrite, (2) in massive occurrences lacking openspace filling textures, and (3) within calcite and quartz veinlets that crosscut all other fabrics in polished section.

Sphalerite, the second most abundant sulfide mineral, 

forms (1) colloform bands within colloform pyrite and 

galena and (2) reddish-brown blebs as much as 1.5 cm 

across within calcite veinlets. Micron-size chalcopyrite 

blebs are common within the sphalerite and are probably 

hydrothermal in origin, perhaps remobilized from syngenetic mineral deposits.

Galena, the third most abundant sulfide mineral, forms 

(1) colloform bands with spongy pyrite and (or) sphalerite in 

orbicular masses in sedimentary breccia clasts, (2) concordant and discordant veinlets, and (3) isolated anhedral blebs. 

Large blebs and veinlets of galena have curved cleavage 

planes that provide evidence of deformation. Deformed 

galena may have a magmatically driven hydrothermal origin, 

likely remobilized from syngenetic mineralization.

Pyrrhotite, the fourth most abundant sulfide mineral, 

forms (1) microscopic veinlets with quartz and (2) small 

blebs within quartz veinlets. Veinlets containing pyrrhotite 

crosscut all other sulfide mineral occurrences, indicating that 

it has a probable magmatically driven hydrothermal origin.

POSSIBLE SYNGENETIC MINERAL DEPOSITS 

IN THE DOLLARHIDE FORMATION

Hall (1985) and Wavra and Hall (1989) suggested that 

the presence of laminated barite in the northern part of the 

Bullion mineralized area (north of Deer Creek) indicates that 

syngenetic shale-hosted precious-metal deposits are present 

in the upper member of the Dollarhide Formation. Geologic 

mapping (Skipp and others, 1994) suggests that the Deer 

Creek barite deposit contains a lensoidal body of syngenetic 

or remobilized-syngenetic barite hosted by the lower member of the Dollarhide Formation. Sulfate analysis of the barite (Howe and Hall, 1985) yields a value close to Permian 

and Pennsylvanian seawater sulfate.
C30 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

EXPLORATION PROSPECTS

The complex tectonic, magmatic, and hydrothermal 

systems operative since Paleozoic time in the eastern part of 

the Hailey I°x2° quadrangle make exploration for Devonian 

syngenetic ore deposits difficult but afford the possibility 

that large mineral deposits remain to be discovered. Some 

recent models for exploration in the Milligen Formation, the 

Salmon River assemblage, and correlative unnamed Silurian 

and Devonian argillite invoke the presence of synsedimentary Devonian fault-bounded "third-order" basins, which 

during Devonian time were subject to restricted circulation 

of oceanic water and coeval hydrothermal activity (Turner 

and Otto, 1988, this volume; Bruner, 1991). Detailed stratigraphic analyses, including biostratigraphic studies, are 

needed to document Devonian basin evolution.

REFERENCES CITED

Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 1950, 

Detailed geology of certain areas in the Mineral Hill and Warm 

Springs mining districts, Blaine County, Idaho: Idaho Bureau 

of Mines and Geology Pamphlet 90, 73 p.

Batatian, L.D., 1991, Paleozoic stratigraphy and Cenozoic structure, central Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 85 p.

Bostwick, D.A., 1955, Stratigraphy of the Wood River Formation, 

south-central Idaho: Journal of Paleontology, v. 29, p. 

941-951.

Brennan, B.D., 1987, Silurian and Devonian rocks along the upper 

reaches of the North Fork of the Big Lost River, Custer County, 

Idaho: Milwaukee, University of Wisconsin, M.S. thesis, 72 p.

Breuninger, R.H., Canter, K.L., and Isaacson, P.E., 1988, Pennsylvanian-Permian Palaeoaplysina and algal buildups, Snaky 

Canyon Formation, south-central Idaho, U.S.A., in Geldsetzer, 

H.H.J., James, N.P., and Tebbut, G.E., eds., Reefs Canada 

and adjacent areas: Canadian Society of Petroleum Geologists 

Memoir 13, p. 631-637.

Bruner, D.J., 1991, Origin of mineralization within Devonian-Silurian sedimentary breccias, northeastern Boulder Mountains, 

Custer County, south-central Idaho: Pocatello, Idaho State 

University, M.S. thesis, 118 p.

Burton, B.R., 1988, Stratigraphy of the Wood River Formation in 

the eastern Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 165 p.

Burton, B.R., and Link, P.K., 1991, Ichnology of fine-grained 

mixed carbonate-siliciclastic turbidites. Wood River Formation, Pennsylvanian-Permian, south-central Idaho: Palaios, v. 

6, p. 291-301.

Burton, B.R., Link, P.K., and Rodgers, D.W., 1989, Death of the 

Wood River thrust Structural relations in the Pioneer and 

Boulder Mountains, south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 21, no. 5, p. 62.

Carter, Claire, and Churkin, Michael, Jr., 1977, Ordovician and Silurian graptolite succession in the Trail Creek area, central

Idaho A graptolite zone reference section: U.S. Geological 

Survey Professional Paper 1020, 37 p.

Churkin, Michael, Jr., 1963, Graptolite beds in thrust plates of central Idaho and their correlation with sequences in Nevada: 

American Association of Petroleum Geologists Bulletin, v. 47, 

p.1611-1623.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Darling, R.S., 1988, Ore deposits of the Carrietown silver-lead-zinc 

district, Blaine and Camas Counties, Idaho, in Link, P.K., and 

Hackett, W.R., eds., Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 

193-198.

Dover, J.H., 1969, Bedrock geology of the Pioneer Mountains, 

Blaine and Custer Counties, central Idaho: Idaho Bureau of 

Mines and Geology Pamphlet 142, 61 p.

 1981, Geology of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho, in Mineral resources 

of the Boulder-Pioneer Wilderness Study Area, Blaine and 

Custer Counties, Idaho: U.S. Geological Survey Bulletin 

1497-A, p. 1-75.

 1983, Geologic map and sections of the central Pioneer

Mountains, Blaine and Custer Counties, central Idaho: U.S. 

Geological Survey Miscellaneous Investigations Series Map 

1-1319, scale 1:48,000.

Dover, J.H., Berry, W.B.N., and Ross, R.J., Jr., 1980, Ordovician 

and Silurian Phi Kappa and Trail Creek Formations, Pioneer 

Mountains, central Idaho Stratigraphic and structural revisions, and new data on graptolite faunas: U.S. Geological Survey Professional Paper 1090, 54 p.

Fisher, F.S., and Johnson, K.M., eds., 1987, Preliminary manuscript 

for "Mineral-resource potential and geology of the Chain's 

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87^80, 251 p.

Fisher, F.S., Mclntyre, D.H., and Johnson, K.M., 1983, Geologic 

map of the Challis I°x2° quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 83-523, scale 1:250,000, 41 p.

Fryklund, V.C., Jr., 1950, The ore deposits of the Mayflower area, 

in Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 

Detailed geology of certain areas in the Mineral Hill and Warm 

Springs mining districts, Blaine County, Idaho: Idaho Bureau 

of Mines and Geology Pamphlet 90, p. 63-73.

Geslin, J.K., 1986, The Permian Dollarhide Formation and Paleozoic Carrietown sequence in the SW'/4 of the Buttercup Mountain quadrangle, Blaine and Camas Counties, Idaho: Pocatello, 

Idaho State University, M.S. thesis, 116 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

 1987a, Lead-silver-zinc-antimony-tin vein deposits, in 

Fisher, F.S., and Johnson, K.M., eds., 1987, Preliminary manuscript for "Mineral-resource assessment and geology of the 

Challis I°x2° quadrangle, Idaho": U.S. Geological Survey 

Open-File Report 87^80, p. 133-140.

 1987b, Stratiform syngenetic deposits of precious and base 

metals in argillic rocks and micritic limestone, in Fisher, F.S., 

and Johnson, K.M., eds., 1987, Preliminary manuscript for 

"Mineral-resource assessment and geology of the Challis
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C31

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87-480, p. 205-208.

Hall, W.E., Batchelder, J.H., and Douglass, R.D., 1974, Stratigraphic section of the Wood River Formation, Blaine County, 

Idaho: U.S. Geological Survey Journal of Research, v. 6, no. 5, 

p. 579-592.

Hall, W.E., and Czamanske, G.K., 1972, Mineralogy and trace element content of the Wood River lead-silver deposits, Blaine 

County, Idaho: Economic Geology, v. 67, p. 350-361. C

Hall, W.E., and Hobbs, S.W., 1987, Black shale terrane, in Fisher, 

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral-resource assessment and geology of the Chain's 

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87-480, p. 29-42.

Hall, W.E., Rye, R.O, and Doe, B.R., 1978, Wood River mining 

district Intrusion-related lead-silver deposits derived from 

country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Hobbs, S.W., 1985, Precambrian and Paleozoic sedimentary terranes in the Bayhorse area of the Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the geology and mineral 

deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-D, p. 59-68.

Howe, S.S., and Hall, W.E., 1985, Light-stable isotope characteristics of ore systems in central Idaho, in Mclntyre, D.H., ed., 

Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-P, p. 183-192.

Huerta, A.D., Lovejoy, F., and Link, P.K., 1991, Anomalous Mississippian(?) conglomerates near Summit Creek, northern 

Boulder Mountains, south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 23, no. 4, p. 34.

Kiilsgaard, T.H., 1950, Geology and ore deposits of the TriumphParker mine mineral belt, in Anderson, A.L., Kiilsgaard, T.H., 

and Fryklund, V.C., Jr., Detailed geology of certain areas in the 

Mineral Hill and Warm Springs mining districts, Blaine County, Idaho: Idaho Bureau of Mines and Geology Pamphlet 90, p. 

39-62.

Kim, A.Y.H., 1986, The kinematics of brittle polyphase deformation within the Pioneer metamorphic core complex, Pioneer 

Mountains, Idaho: Bethlehem, Pa., Lehigh University, M.S. 

thesis, 130 p.

Klapper, B., and Murphy, M.A., 1974, Silurian-Lower Devonian 

conodont sequence in the Roberts Mountains Formation of 

central Nevada: University of California Publications in Geological Sciences, v. 3, 62 p.

Kunkel, K.W., 1989, Geology and ore deposits of Garfield Canyon, 

Blaine County, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds.. Geology and mineral deposits 

of the Hailey and western Idaho Falls 1 °x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, p. 

92-94.

Lewis, R.S., 1989, Plutonic rocks in the southeastern part of the Idaho batholith and their relation to mineralization, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles: U.S. Geological Survey Open-File 

Report 89-639, p. 33-34.

Lindgren, W., 1900, The gold and silver veins of Silver City, 

DeLamar, and other mining districts in Idaho: U.S. Geological 

Survey 20th Annual Report, pt. 3, p. 65-256.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke, Susanne, and 

Burton, B.R., 1988, Structural and stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knob, Pioneer, Boulder, and Smoky Mountains, in Link, 

P.K.. and Hackett, W.R., eds., Guidebook to the geology of 

central and southern Idaho: Idaho Geological Survey Bulletin 

27, p. 5^2.

Link, P.K., and Worl, R.G., in press, Geology and mineral deposits 

of the Minnie Moore and Bullion mineralized areas, Blaine 

County, Idaho: U.S. Geological Survey Bulletin 2064-Y.

Loeblich, A.R., Jr., and Tappan, Helen, 1988, Foraminiferal genera and their classification: New York, Van Nostrand Reinhold, 970 p.

Mahoney, J.B., 1992, Geologic map of the Frenchman Creek quadrangle, Blaine and Camas Counties, Idaho: Idaho Geological 

Survey Technical Report 92-2, scale 1:24,000.

Mahoney, J.B., and Horn, M.C., in press, Geology of the Vienna 

mineralized area, Blaine and Camas Counties, Idaho: U.S. 

Geological Survey Bulletin 2064-DD.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvanian and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J.D., and 

Stevens, C.H., eds., Paleozoic paleogeography of the Western 

United States-II: Los Angeles, Pacific Section Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, 

p. 551-579.

Mahoney J.B., and Sengebush, R.M., 1988, Stratigraphy of the lower Permian Grand Prize Formation, south-central Idaho, in 

Link, P.K., and Hackett, W.R., eds., Guidebook to the geology 

of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 169-182.

Mclntyre, D.H., ed., 1985, Symposium on the geology and mineral 

deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658, 227 p.

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds., Paleozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium l,p. 275-299.

O'Brien, J.P., 1991, Stratigraphy of the Pennsylvanian-Permian 

Dollarhide Formation in the Buttercup Mountain quadrangle, 

Blaine and Camas Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 163 p.

O'Brien, J.P., Lewis, R.S., Link, P.K., Geolin, J.K., Whitman, S.K., 

and Schmidt, K.L., 1993, Geologic map of the Buttercup 

Mountain quadrangle, Blaine and Camas Counties, Idaho: Idaho Geological Survey Technical Report 93-1, scale 1:24,000.

Park, W.A., in press, The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-CC.

Paull, R.A., and Gruber, D.P., 1977, Little Copper Formation New name for lowest formation of Mississippian Copper 

Basin Group, Pioneer Mountains, south-central Idaho: American Association of Petroleum Geologists Bulletin, v. 61, no. 2, 

p. 256-262.
C32 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Paull, R.A., Wolbrink, M.A., Volkman, R.G., and Grover, R.L., 

1972, Stratigraphy of the Copper Basin Group, Pioneer Mountains, south-central Idaho: American Association of Petroleum 

Geologists Bulletin, v. 56, no. 8, p. 1370-1401.

Poole, F.G., 1974, Flysch deposits of the Antler foreland basin, 

western United States, in Dickinson, W.R., ed., Tectonics and 

sedimentation: Society of Economic Paleontologists and Mineralogists Special Publication 22, p. 58-82.

Poole, F.G., and Sandberg, C.A., 1991, Mississippian paleogeography and tectonics of the Western United States, in Stewart J.H., 

Stevens, C.H., and Fritsche, A.E., eds., Paleozoic paleogeography of the Western United States: Pacific Section, Society of 

Economic Paleontologists and Mineralogists, Pacific Coaast 

Paleogeography Symposium 1, p. 67-85.

 1991, Mississippian paleogeography and conodont biostratigraphy of the Western United States, in Cooper, J.D., and 

Stevens, C.H., eds., Paleozoic paleogeography of the Western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 1, p. 107-136.

Ratchford, M.E., 1989, Geology of the Boulder Basin, Blaine and 

Custer Counties, Idaho: Moscow, University of Idaho, M.S. 

thesis, 154 p.

 in press, Epigenetic lead-tin-silver, antimony-gold veins in 

Boulder Basin, Blaine and Custer Counties, Idaho Potential 

for economic tin mineralization: U.S. Geological Survey Bulletin 2064-JJ.

Ross, C.P., 1960, Diverse interfingering Carboniferous strata in the 

Mackay quadrangle, Idaho: U.S. Geological Survey Professional Paper 400-B, p. B232-B233.

 1962, Upper Paleozoic rocks in central Idaho: American 

Association of Petroleum Geologists Bulletin, v. 46, no. 3, p. 

384-387.

Sandberg, C.A., 1975, McGowan Creek Formation, new name for 

Lower Mississippian flysch sequence in east-central Idaho: 

U.S. Geological Survey Bulletin 1405-E, 11 p.

 1979, Devonian and Lower Mississippian conodont zonation of the Great Basin and Rocky Mountains: Brigham Young 

University Geology Studies, v. 26, pt. 3, p. 87-106.

Sandberg, C.A., Hall, W.E., Batchelder, J.N., and Axelson, Claus, 

1975, Stratigraphy, conodont dating, and paleotectonic interpretation of the type Milligen Formation (Devonian), Wood 

River area, Idaho: U.S. Geological Survey Journal of Research, 

v. 3, no. 6, p. 707-720.

Sengebush, R.M., 1984, The geology and tectonic history of the 

Fourth of July Creek area, White Cloud Peaks, Custer County, 

Idaho: Missoula, University of Montana, M.S. thesis, 79 p.

Skipp, Betty, 1989, Geologic map of the Mackay 4 (Grouse) NW 

quadrangle, Butte and Custer Counties, Idaho: U.S. Geological 

Survey Open-File Report 89-142, scale 1:24,000.

Skipp, Betty, and Hall, W.E., 1975, Structure and Paleozoic stratigraphy of a complex of thrust plates in the Fish Creek Reservoir 

area, south-central Idaho: U.S. Geological Survey Journal of 

Research, v. 3, no. 6, p. 671-689.

 1980, Upper Paleozoic paleotectonics and paleogeography 

of Idaho, in Fouch, T.D., and Magathan, E.R., eds., Paleozoic 

paleogeography of the West-Central United States: Rocky 

Mountain Section, Society of Economic Paleontologists and 

Mineralogists, West-Central United States Paleogeography 

Symposium 1, p. 387^22.

Skipp, Betty, Hall, W.E., and Link, P.K., 1986, Pre-middle Eocene 

extension in south-central Idaho The Wood River allochthon: Geological Society of America Abstracts with Programs, 

v. 18, p. 753.

 1994, Geologic map of the Mahoney Butte quadrangle, 

Blaine County, Idaho: U.S. Geological Survey Geologic Quadrangle Map GQ-1742, scale 1:24,000.

Skipp, Betty, Hoggan, R.D., Schleicher, D.L., and Douglass, R.C., 

1979, Upper Paleozoic carbonate bank in east-central Idaho Snaky Canyon, Bluebird Mountain, and Arco Hills Formations, and their paleotectonic significance: U.S. Geological 

Survey Bulletin 1496, 78 p.

Skipp, Betty, Kuntz, M.A., and Morgan, L.A., 1990, Geologic map 

of the Mackay 4 (Grouse) SE quadrangle, Butte County, Idaho: 

U.S. Geological Survey Open-File Report 89-431, scale 

1:24,000.

Skipp, Betty, Sando, W.J., and Hall, W.E., 1979, The Mississippian 

and Pennsylvanian (Carboniferous) systems in the United 

States-Idaho: U.S. Geological Survey Professional Paper 

1110-AA,p. AA1-AA43.

Spoelhof, R.A., 1972, Structure and stratigraphy of portions of the 

Meridian Peak and Herd Peak quadrangles, Custer County, 

south-central Idaho: Golden, Colorado School of Mines, M.S. 

thesis, 86 p.

Stewart, D.E., 1987, Geology of the northern half of the Baker Peak 

quadrangle, Blaine and Camas Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 113 p.

Stewart, D.E., Mahoney, J.B., Geslin, J.K., Darling, R.S., and Link, 

P.K., 1992, Geologic map of the Baker Peak quadrangle, 

Blaine and Camas Counties, Idaho: Idaho Geological Survey 

Technical Report 92-1, scale 1:24,000.

Thomasson, M.R., 1959, Late Paleozoic stratigraphy and paleotectonics of central and eastern Idaho: Madison, University of 

Wisconsin, Ph.D. dissertation, 244 p.

Thompson, M.L., Dodge, H.W., and Youngquist, W., 1958, 

Fusulinids from the Sublett Range, Idaho: Journal of Paleontology, v. 32, p. 113-125.

Tschanz, C.M., Kiilsgaard, T.H., and Seeland, D.A., 1986, Geology 

of the eastern part of the Sawtooth National Recreation Area, 

Idaho, in Mineral resources of the eastern part of the Sawtooth 

National Recreation Area, Custer and Blaine Counties, Idaho: 

U.S. Geological Survey Bulletin 1545-A, p. 17-43.

Tuchek, E.T., and Ridenour, James, 1981, Economic appraisal of 

the Boulder-Pioneer Wilderness Study Area, Blaine and Custer 

Counties, Idaho, in Mineral resources of the Boulder-Pioneer 

Wilderness Study Area, Blaine and Custer Counties, Idaho: 

U.S. Geological Survey Bulletin 1497, p. 181-292.

Turner, R.J.W., and Otto, B.R., 1988, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho, in Link, P.K., 

and Hackett, W.R., eds., Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

153-167.

Umpleby, J.B., 1915, Ore deposits in the Sawtooth quadrangle, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 580-K, p. 221-29.

Umpleby, J.B., Westgate, L.G., and Ross, C.P., 1930, Geology and 

ore deposits of the Wood River region, Idaho: U.S. Geological 

Survey Bulletin 814, 250 p.

Van Noy, R.M., Ridenour, James, Zilka, N.T., Federspiel, F.E., 

Evans, R.K., Tuchek, E.T., and McMahan, A.B., 1986,
STRATIGRAPHIC SETTING OF SEDIMENT-HOSTED MINERAL DEPOSITS C33

Economic appraisal of the eastern part of the Sawtooth National Recreation Area, Idaho: U.S. Geological Survey Bulletin 

1545-E, p. 232-472.

Verville, G.J., Sanderson, G.A., Baesemann, J.F., and Hampton, 

G.L., III, 1990, Pennsylvanian fusulinids from the Beaverhead 

Mountains, Morrison Lake area, Beaverhead County, Montana: The Mountain Geologist, v. 27, p. 47-55.

Walliser, O.H., 1964, Conodonten des Silurs: Abhandlungen des 

Hessischen Landesamtes fur Bodenforschung zu Wiesbaden, 

v. 41, 106 p.

Wavra, C.S., 1985, Structural geology and petrology of the SWVi of 

the Mahoney Butte quadrangle, Blaine County, Idaho: Moscow, University of Idaho, M.S. thesis, 103 p.

Wavra, C.S., and Hall, W.E., 1989, Potential for shale-hosted 

massive sulfides in the Permian Dollarhide Formation, southcentral Idaho: U.S. Geological Survey Open-File Report 

88-376, 9 p.

Wavra, C.S., Isaacson, P.E., and Hall, W.E., 1986, Studies of the 

Idaho black shale belt Stratigraphy, depositional environment, and economic geology of the Permian Dollarhide 

Formation: Geological Society of America Bulletin, v. 97, p. 

1504-1511.

Whitman, S.K., 1990, Metamorphic petrology and structural geology of the Pennsylvanian-Permian Dollarhide Formation, 

Blaine and Camas Counties, south-central Idaho: Pocatello, 

Idaho State University, M.S. thesis, 108 p.

Wilson, Eric, 1994, Demise of the Glide Mountain thrust, Pioneer 

Mountains, Blaine and Custer Counties, south-central Idaho: 

Pocatello, Idaho State University, M.S. thesis, 188 p.

Wilson, Eric, Preacher, J.M., and Link, P.K., 1994, New constraints 

on the nature of the Early Mississippian Antler sedimentary 

basin in Idaho, in Beauchamp, B., Embry, A.F., and Glass, G., 

eds., Pangea Global environments and resourses: Canadian 

Society of Petroleum Geologists Memoir 17.

Winsor, H.C., 1981, The paleogeography and paleoenvironments 

of the Middle Pennsylvanian part of the Wood River Formation 

in south-central Idaho: San Jose, Calif., San Jose State University, M.S. thesis, 81 p.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Mineral Deposits of the Muldoon-Star Hope Area, 

Southern Pioneer Mountains, South-Central Idaho

By Gary R. Winkler, Kevin W. Kunkel, Richard F. Sanford, 

Ronald G. Worl, and Falma J. Moye

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-D

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract.................................................................................................................................. Dl

Introduction........................................................................................................................... 2

Historical Perspective............................................................................................................ 2

Past Production.............................................................................................................. 2

Little Wood River District..................................................................................... 2

Copper Basin District............................................................................................ 5

Exploration Activity in the Little Wood River District................................................. 5

Geologic Setting.................................................................................................................... 6

Host Rocks..................................................................................................................... 7

Host Structures.............................................................................................................. 14

Mineral Deposits................................................................................................................... 15

Deposit Types................................................................................................................ 15

Polymetallic Replacement Deposits or Distal Skarns................................................... 15

Polymetallic Veins in Sedimentary Rocks.................................................................... 19

Polymetallic Veins in Igneous Rocks............................................................................ 20

Stratabound Replacement Deposits and Veins of Barite............................................... 21

Summary................................................................................................................................ 23

References Cited.................................................................................................................... 23

FIGURES

1. Map showing Muldoon-Star Hope areas in the eastern part of the Boulder-Pioneer Wilderness Study Area.............. D3

2. Map showing geology of the Muldoon-Star Hope area and location of selected mines and prospects........................ 4

3. Schematic stratigraphic section of the Copper Basin Formation in the Muldoon-Star Hope area................................ 14

TABLES

1. Major-element-oxide and minor-element composition, lithology, and approximate location of igneous rock

samples from the Muldoon-Star Hope area, southern Pioneer Mountains.................................................................... D8

2. Minor-element composition of unmineralized samples from the Little Copper, Drummond Mine Limestone, 

and Green Lake Limestone Members of the Mississippian Copper Basin Formation, Muldoon-Star Hope 

area, southern Pioneer Mountains................................................................................................................................... 10

3. Minor-element composition of mineralized samples from selected mines and prospects in the Muldoon-Star

Hope area, southern Pioneer Mountains......................................................................................................................... 16
Mineral Deposits of the Muldoon-Star Hope Area, 

Southern Pioneer Mountains, South-Central Idaho

By Gary R. Winkler, 1 Kevin W. Kunkel,2 Richard F. Sanford, 1 Ronald G. Worl,3

and Falma J. Moye4

ABSTRACT

Devonian and Mississippian carbonate and clastic rocks 

of the Milligen(?) Formation, Carey Dolostone, and Copper 

Basin Formation in the southern Pioneer Mountains host 

many vein, replacement, and distal skarn deposits of silverlead-zinc (+copper). In several places, the silver-base metal 

deposits are associated with stratabound veins and replacements of barite. Base- and precious-metal veins also are 

present locally in Eocene stocks that intrude the Paleozoic 

sequence and in rocks of the comagmatic Challis Volcanic 

Group that overlie the Paleozoic sequence.

The deposits are included in the Little Wood River 

and Copper Basin mining districts, which were formed in 

the early 1880's when the first significant discoveries and 

initial production occurred. The richest metal deposits were 

mined principally in the 1880's and 1890's and again in the 

1940's and 1950's. The richest barite bodies were mined 

only in the 1950's and 1960's. No mining has taken place 

in either district for the past 25 years; however, substantial 

resources have been identified or inferred, and exploration 

has been renewed in the middle 1970's, the early 1980's, 

and the late 1980's.

The locations of the silver-base metal deposits are governed by the presence of carbonaceous pelitic source rocks, 

chemically reactive calcareous trap rocks, concordant and 

discordant structures that provided channelways for solutions, and intrusive rocks that provided heat and fluids for 

metasomatism. Argillaceous rocks of the Little Copper 

Member of the Copper Basin Formation, which are significantly enriched in barium and slightly enriched in several 

metals, host numerous small and discontinuous veins that

'U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

Department of Geology, Idaho State University, Pocatello, Idaho 

83209.

3U.S. Geological Survey, W. 904 Riverside Avenue, Spokane, Washington 99201.

4Box 1145, Challis, Idaho 83226.

show spotty values for silver, lead, zinc, copper, and gold. 

The best examples are in the vicinity of the Mutual mine; 

however, such veins seldom were mined. The largest and 

richest metal deposits are polymetallic replacements or 

skarns in impure calcareous rocks of the Drummond Mine 

Limestone Member of the Copper Basin Formation, which 

overlies the Little Copper Member. The deposits are at several stratigraphic horizons and generally are within 1-3 km 

of quartz monzonite stocks or swarms of dikes. The best 

example is the Eagle Bird mine, where high-grade material 

remains underground in tabular lenses extending 100 m or 

more along bedding. In addition to the silver, lead, zinc, copper, and gold, some replacements and skarns also contain 

significant antimony or tin, but none is known to have been 

produced. Where polymetallic replacements are cut at high 

angles by faults or fractures, they generally have associated 

veins. Veins at the Solid Muldoon and Star Hope properties 

were unusually rich in silver and thus were mined during the 

early years in the districts.

Significant resources of base- and precious-metals and 

barite remain in the Muldoon-Star Hope area. Although 

most individual occurrences are likely to be small, they may 

be of high grade and closely spaced. Thus, the metal values 

of a group of occurrences might constitute collectively a 

minable resource in the future. Furthermore, lower grade 

resources, particularly of barite, but also of metals, may be 

relatively widespread in the Copper Basin Formation. Favorable areas for additional exploration include several (or all) 

of the following features: (1) calcareous, or mixed calcareous and siliceous host rocks; (2) Eocene leucocratic intrusive 

rocks; (3) carbonaceous pelitic rocks having elevated metal 

values; (4) ground structurally prepared by steep faults, particularly where associated with bedding-plane flexures or 

faults; (5) widespread geochemical anomalies of preciousand base-metals and associated elements; and, if available, 

(6) elevated electrical conductivity measurements, which 

might indicate the presence of metal-bearing sulfide minerals at shallow depth.

Dl
D2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

INTRODUCTION

In the Muldoon Creek, Garfield Canyon, and Star Hope 

Creek areas of Blaine and Custer Counties in south-central 

Idaho (fig. 1), Devonian and Mississippian carbonate and 

clastic rocks of the Milligen(?) Formation, Carey Dolostone, 

and Copper Basin Formation host numerous polymetallic 

deposits containing silver, lead, zinc, copper, and gold. 

Base- and precious-metal veins also are present in porphyritic quartz monzonite stocks that intrude Paleozoic sedimentary rocks in Muldoon Creek and Garfield Canyon and 

in rocks of the Eocene Challis Volcanic Group that overlie 

the Paleozoic sedimentary rocks at the confluence of Copper 

Creek and Blackspar Canyon. The deposits are present on 

both flanks of the southeastern Pioneer Mountains, which 

divide tributaries of the Little Wood River from those of the 

East Fork of the Big Lost River in Copper Basin. The precious- and base-metals are in vein, replacement, skarn, and 

stratabound deposits that in several places are associated 

with stratabound veins and replacements of barite.

HISTORICAL PERSPECTIVE 

PAST PRODUCTION

Although prospecting apparently began in the area in 

the 1860's, the first significant deposits were located in 

1881, with the discoveries of silver-base metal deposits at 

the Muldoon (or Solid Muldoon) and Star Hope claims (fig. 

2) on opposite sides of the drainage divide (Umpleby, 

1917). Within a few seasons, numerous additional discoveries were made nearby in both drainages. The claims were 

included in the separate Little Wood River and Copper 

Basin mining districts, inasmuch as normal access to them 

was by seasonal roads from Bellevue (or Carey) and 

Mackay, respectively. Most production in the districts was 

in the 1880's and again in the 1940's and 1950's, although 

U.S. Bureau of Mines records indicate some production in 

every decade from the 1900's through the 1960's (Tuchek 

and Ridenour, 1981). No mining has taken place in either 

district for the past 25 years.

LITTLE WOOD RIVER DISTRICT

Most deposits in the district are in a northwest-trending 

belt about 2 km wide that extends from near the mouth of 

Muldoon Creek to a short distance north of Little Copper 

Creek (fig. 2). Clusters of silver-base metal deposits are 

along upper Muldoon Creek, in Garfield Canyon, in Deep, 

Boundary, and Mutual Gulches, in the Little Copper Creek 

drainages, and in Argosy Creek. Base- and precious-metal 

veins in rocks of the Challis Volcanic Group along Copper 

Creek and Blackspar Canyon are west of this belt.

The Solid Muldoon claims were located in 1881 and 

patented in 1886. A concentrating mill and two 40-ton

smelters were erected near the claims in late 1881 and early 

1882 (E.H. Finch, in Umpleby, 1917). About $200,000 in 

silver-lead ore was produced from the claims between 1881 

and 1884 (Wells, 1983). Additional ore-grade material was 

stockpiled intermittently until 1908, when completion of a 

new 100-ton mill allowed minor additional production from 

1908 to 1911. By late 1911, Muldoon's mining machinery 

was consigned to another mill near Ketchum (Wells, 1983); 

however, U.S. Bureau of Mines records show minor additional production until 1948, which probably was chiefly 

from reprocessed tailings (Tuchek and Ridenour, 1981).

The Idaho Muldoon property on the east side of Muldoon Creek was located in 1908 and was rehabilitated in the 

1940's (Anderson and Wagner, 1946). No production 

records exist, although small shipments of lead-silver ore 

were sent to mills in Utah for testing. High-grade material 

remains in underground workings and in surface cuts that 

extend more than 100 ft south from the main portal (Anderson and Wagner, 1946).

The Eagle Bird claim in Garfield Canyon was located in 

1883 and patented in 1889. Numerous nearby claims were 

located (and some were patented) during the same decade. 

From 1929 to 1965, the Eagle Bird and nearby claims produced lead, zinc, silver, copper, and gold worth approximately $130,000 (Tuchek and Ridenour, 1981); value of 

earlier production, if any, is unknown. High-grade material 

remains in underground workings, and known shoots have 

not been explored extensively downdip. There are no records 

of production of base- or precious-metals from the numerous 

claims between the Solid Muldoon and Eagle Bird mines in 

Deep, Boundary, and Mutual Gulches. Minor production is 

likely inasmuch as several dumps are quite extensive, and 

material apparently has been removed from slopes underground (Tuchek and Ridenour, 1981).

Little published information exists on the Black Spar 

properties, at the confluence of Blackspar Canyon with Copper Creek. The deposit was discovered in 1887, and more 

than 300 tons of ore had been mined through 1888 (Wells, 

1983). No records of subsequent production exist; however, 

the survey for patent of 19 claims in 1923 indicates that there 

are more than 4,500 ft of underground workings, including 

two shafts, but apparently no stopes (J.J. Jones, U.S. Forest 

Service, written commun., 1988). There are no records of 

post-1900 production, although at least one of the tunnels 

was rehabilitated in the 1960's.

During a renewed pulse of exploration in the Muldoon-Star Hope area in the late 1950's. and 1960's, barite 

deposits in Deep Gulch were discovered, and a large shipment was made to the Atomic Energy Commission's 

research facilities near Arco for use as shielding material in 

nuclear reactors (Tuchek and Ridenour, 1981). Nearby 

base-metal-bearing veins were explored at the same time. 

Although the Deep Gulch barite claims were being 

developed actively in the mid-1970's and additional barite 

deposits between Muldoon and Argosy Creeks were 

explored during this time, no production has occurred since 

the 1970's.
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D3

/ToMackav 113°45'

I I I 

0 50 100 150 MILES 

0 100 200 KILOMETERS

Little Wood

River drainage

system

/ To Bellevue

0 1 5 MILES

To Carey/.

I I I I 1

01234 5 KILOMETERS

Figure 1 . Index map of the Muldoon-Star Hope area in the eastern part of the Boulder-Pioneer Wilderness 

Study Area, south-central Idaho.
D4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

113°55'

43°40' 

43°35'

R21E R22E

2 MILES 

J

I

3 KILOMETERS
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D5

CORRELATION OF MAP UNITS

Eocene

/ Upper Mississippian

> Lower Mississippian

Middle and Lower Devonian

> QUATERNARY

> TERTIARY

 MISSISSIPPIAN

DEVONIAN

DESCRIPTION OF MAP UNITS

Mcu

Mcd

Mcc

DC

Dm

Surficial deposits, undifferentiated 

Hypabyssal intrusive rocks (Eocene) 

Quartz monzonite stocks (Eocene) 

Challis Volcanic Group (Eocene)

GLIDE MOUNTAIN PLATE

Clastic rocks of the Copper Basin Formation 

(Upper and Lower Mississippian)

Green Lake Limestone of the Copper Basin

Formation (Lower Mississippian) *

COPPER BASIN PLATE

Upper clastic unit of the Copper Basin 

Formation (Upper Mississippian)

Drummond Mine Limestone Member of the

Copper Basin Formation (Lower Mississippian)

Little Copper Member of the Copper Basin Formation 

(Lower Mississippian)

Carey Dolostone (Middle and Lower Devonian) 

Milligen(?) Formation (Devonian)

-V 22

Contact

High-angle fault Dotted where concealed. Bar and

ball on downthrown side 

Thrust fault Queried where location is uncertain, dotted where

concealed. Sawteeth on upper plate. GMT is Glide Mountain

thrust fault 

Mine

Prospect

MINES AND PROSPECTS

1. American mine prospect 16. Idaho Muldoon mine

2. Black Spar mine

3. Blue Sky prospect

4. Boundary Gulch prospect

5. Candy Cane (south)

6. Champion prospect

7. Contact prospect

8. Copper Bell Group

9. Deep Gulch mine

10. Drummond mine

11. Eagle Bird mine

12. Frisco Gulch propects

13. Garfield Group

14. Gray Eagle prospects

15. Hecla-Carrier

17. Logan Tunnel

18. Lucky Boy (west)

19. Lucky Boy (east)

20. Mackinaw Group

21. Muldoon Creek prospects

22. Mutual mine

23. Rippeto claims

24. Scorpion Antimony

25. Scorpion Group

26. Silver Eagle

27. Silver Mint

28. Smuggler

29. Solid Muldoon mine

30. Star Hope mine

Figure 2 (above and facing page). Geology of the Muldoon-Star Hope area, south-central Idaho. Locations of selected mines 

and prospects are shown in red. Location of map area is shown in figure 1. Modified from Dover (1981) and Kunkel (1989). Base 

from U.S. Geological Survey Muldoon (1974) and Star Hope Mine (1974) 7.5-minute quadrangles.

COPPER BASIN DISTRICT

Sulfide-bearing vein deposits of silver, lead, zinc, and 

copper were discovered beginning in 1881 in the Star Hope 

Creek drainage in the southwestern corner of Copper Basin 

(fig. 2). The most promising claims near the head of Star 

Hope Gulch were patented in 1889. Most development was 

during the 1890's, when the properties apparently produced 

approximately $50,000 of lead-silver ore (Umpleby, 1917; 

Tuchek and Ridenour, 1981). Additional claims were made 

(and some were patented) in the main drainage between 

1899 and 1913. U.S. Bureau of Mines records show latest 

production, worth about $7,500, in the Star Hope area in 

1954, and additional earlier production is inferred from the 

size of slopes (Tuchek and Ridenour, 1981). There was

renewed exploration in the vicinity of the Star Hope properties in 1984, and some claims were staked (A.B. Wilson and 

S.J. Soulliere, U.S. Geological Survey, written commun., 

1990). No additional detailed site evaluation or development 

has been performed subsequently.

EXPLORATION ACTIVITY IN THE LITTLE 

WOOD RIVER DISTRICT

Following field work in 1973 and 1974, geologists of 

the U.S. Bureau of Mines estimated minimum resources of 

80,000 tons of high-grade material in the Eagle Bird, Rippeto, Silver Eagle, and nearby claims in Garfield Canyon 

and recommended that the claims and possible extensions be
D6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

explored (Tuchek and Ridenour, 1981). U.S. Bureau of 

Mines assays of samples from these properties contain 3-8 

percent Pb, 1-2.5 percent Zn, 3.3-9.4 ounces of silver per 

ton, and nil to 0.02 ounces of gold per ton (Tuchek and Ridenour, 1981). In the early 1980's, according to documents in 

the International Archive of Economic Geology at the University of Wyoming, Anaconda Mining Company conducted 

a regional exploration program for gold that included some 

sampling in the Muldoon-Star Hope area. In 1987-1989, 

Hecla Mining Company conducted exploration in Garfield 

Canyon for precious- and base-metal lodes and skarns. The 

exploration included detailed geologic mapping and surface 

geophysical surveys to test the extent and grade of deposits 

that crop out widely in the canyon through a vertical range of 

more than 600 m.

GEOLOGIC SETTING

Rocks in the Muldoon-Star Hope area include three 

fault-bounded Paleozoic sedimentary sequences that are 

overlain unconformably by flows of the Eocene Challis Volcanic Group (fig. 2). A western sequence of Paleozoic rocks 

consists of silicified argillaceous rocks that Dover (1981) 

mapped as the Milligen(?) Formation. These rocks, which 

comprise the structurally lowest allochthonous sequence 

above the Pioneer fault system, are undated in the Muldoon-Star Hope area but are correlated with the Milligen 

Formation of the type area east of the Triumph mine near 

Ketchum, Idaho, because of their similar strong deformation 

and suite of rocks. A medial Paleozoic sequence consists of 

siliceous and calcareous marine basinal facies assemblages 

of Mississippian age that were deposited unconformably on 

thinly laminated limy dolomite of Devonian age. An eastern 

Paleozoic sequence consists of siliceous, shallow-marine to 

partly terrigenous, basin-margin facies assemblages of Mississippian age and contains only minor calcareous rocks. The 

Mississippian rocks of the medial and eastern sequences 

constitute the Copper Basin Formation, and they are roughly 

coeval; however, they have been juxtaposed by the Glide 

Mountain thrust fault, which transposed the shallow-marine 

and nonmarine assemblages onto the basinal assemblages 

during the Cretaceous Sevier orogeny (Dover, 1981). The 

tight folding and well-developed axial planar cleavage in 

Mississippian rocks of the upper Glide Mountain plate are 

distinct from the generally open folds and homoclinal dips in 

rocks of the lower Copper Basin plate. The contrast in intensity of deformation may reflect a tectonic transport of upper 

plate rocks from an original position farther to the west than 

rocks in the lower plate.

Late Cretaceous and (or) early Tertiary uplift, erosion, 

and deposition of conglomerate preceded onset of Challis 

volcanism, which began about 49 Ma. The Eocene magmatic 

event included coeval volcanism and emplacement of 

hypabyssal stocks and dikes. The Paleozoic sequences are

intruded by porphyritic stocks and by dike swarms and single dikes inferred to be feeders to flows within rocks of the 

Challis Volcanic Group. Stocks exposed in Garfield Canyon 

and Muldoon Creek (fig. 2) are strongly discordant porphyritic hornblende-biotite (with or without pyroxene) quartz 

monzonite having no internal fabric. Biotite from the main 

phase of the Garfield stock has been dated by 40Ar/39Ar at 

48.72±0.15 Ma (Moye and others, this volume) and biotite 

from the Muldoon stock has been dated by K-Ar at 47.0 Ma 

(R.F. Zartman, in Dover, 1981). The two stocks are elongated northwest-southeast. A zone of high magnetic intensity enclosing the stocks indicates that they are connected at 

depth (Mabey, 1981). A concentrated swarm of dikes and 

associated locally intense alteration between Muldoon Canyon and Deadman Creek in the Star Hope area is believed to 

indicate a subjacent pluton at shallow depth (Dover, 1981). 

Dikes are texturally and compositionally more diverse than 

the stocks and range from porphyritic high-potassium rhyolite to high-potassium basalt (table 1). Dikes and wallrocks 

locally are strongly altered. The dikes commonly are oriented parallel with north-northwest and east-northeast fracture systems. In a few places, dikes intrude the stocks; 

intrusion of the stocks probably was coeval with earlier 

Challis volcanism.

Throughout the Muldoon-Star Hope area, the largest 

silver-base metal deposits are in calcareous rocks within 1 

km of quartz monzonite stocks (fig. 2). Apparently, weak 

hydrothermal cells were established during intrusion of the 

stocks. Analyses of fluid inclusions from quartz and calcite 

veins in Garfield Canyon indicate a temperature gradient 

centered on the stock: filling temperatures of fluid inclusions 

from mineralized veins at the margin of the stock are in 

excess of 425°C, whereas fluid inclusions in deposits farther 

from the stock filled at temperatures between 245°C and 

280°C (K.W. Kunkel, Idaho State University, unpub. data, 

1991). Low salinity values of 2-8 weight percent NaCl indicate dominantly meteoric fluids. Rudimentary zoning of sulfide minerals and alteration assemblages around the Garfield 

stock may indicate that mineralization was concurrent with 

intrusion. Chalcopyrite and pyrite are more abundant near 

the stock and are uncommon at greater distances (Kunkel, 

1989). Argillic alteration assemblages (kaolinite-sericite) 

are present near the stock, whereas propylitic assemblages 

(chlorite-zeolite) are present outward; however, the assemblages generally are developed only along faults, and 

unfaulted host rocks generally show little or no alteration.

In many places in the Muldoon-Star Hope area, silverbase metal deposits are in calcareous rocks several kilometers 

or more from exposed plutons. Although these deposits generally are smaller than those close to plutons, they contain the 

same equally coarse grained sulfide-mineral assemblages.

All host rocks are intruded by scattered to abundant 

dikes that probably are coeval with the stocks. In many 

places, dikes make up more than 10 percent of the outcrop. 

The dikes apparently occupy structures having the same
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D7

orientation as those that host mineral deposits. North- to 

northwest-trending dikes are roughly parallel in strike with 

enclosing strata but generally dip more steeply. East-northeast-trending dikes generally are almost vertical. Umpleby 

(1917) doubted whether the dikes alone could have supplied enough heat and introduced enough material to produce the orebodies and metasomatism of the host rocks; 

however, the dikes and the exposed stocks may have emanated from the same large magma chamber at depth that 

would have imposed a regional hydrothermal system 

throughout the Muldoon-Star Hope area.

Steep faults cut the Paleozoic sequences in many 

places; locally, they cut rocks of the Challis Volcanic 

Group. The steep faults tend to have three orientations, 

about N. 20° W., N. 50° E., or N. 80° E., which also are the 

dominant trends of Eocene dikes. The east-northeast-trending faults and dikes are roughly parallel with the TransChallis fault system and likely formed during Eocene 

regional extension and magmatism. North-northwest-trending faults generally have been attributed to Neogene Basin 

and Range extension, but their approximate parallelism with 

trends of some Eocene dikes may indicate an earlier ancestry as a conjugate set to faults that trend about N. 50° E.

HOST ROCKS

In the Muldoon-Star Hope area, a few silver-base metal 

deposits are in the Devonian Milligen(?) Formation and 

Carey Dolostone and in the Eocene Challis Volcanic Group, 

but most deposits having significant resources are hosted by 

the Mississippian Copper Basin Formation. In the lower 

reaches of Little Copper Creek, Deadman Creek, and 

Garfield Canyon, weakly mineralized pyrite-arsenopyritechalcopyrite-bearing quartz veins are in argillaceous rocks 

of the Milligen(?) Formation near porphyritic rhyolite dikes. 

Near the bottom of Garfield Canyon just east of the Copper 

Creek fault, silicified limy dolomite of the Carey Dolostone 

hosts tabular quartz veins and replacements containing 

galena, pyrite, chalcopyrite, and sphalerite. The sulfide minerals are most abundant at intersections of bedding-parallel 

and steep north-northwest-trending faults. The latter are subparallel with the Copper Creek fault. The steep faults are 

marked by mineralized gouge zones as much as 0.5 m wide.

Numerous silver-base metal deposits are present in the 

Copper Basin Formation (fig. 3), particularly within the 

marine basinal assemblages, which are designated the Little 

Copper and Drummond Mine Limestone Members. The 

members consist chiefly of argillaceous and micritic turbidites, respectively. The Little Copper Member is dominantly 

a thin- to medium-bedded, blocky weathering, dark-gray 

argillite and contains some interbeds of medium-gray sandstone and granule conglomerate (Paull and Gruber, 1977). 

It is 1,100 m or more thick. Analyses of samples from a 

regional geochemical survey of the Pioneer Mountains

indicate that all argillaceous rocks in the Little Copper 

Member are significantly enriched in barium, many are 

enriched in boron, and many are slightly enriched in cobalt 

and manganese (Simons, 1981). Analyses of additional 

samples from the Muldoon-Star Hope area (table 2) indicate that, in many places, the Little Copper Member also is 

slightly enriched in zinc. The ubiquity and abundance of 

barium in the Little Copper imply syngenetic deposition of 

barite; however, primary detrital or chemical-precipitation 

textures of barite have not been recognized in the field or in 

thin sections. Stratabound barite is present as coarsely crystalline, light-colored, bedding-parallel and discordant 

stringers and lenses at several zones in the Little Copper 

Member, as well as in the overlying Drummond Mine 

Limestone Member (fig. 3). In the Hailey and Ketchum 

areas to the west, data for lead and sulfur isotopes from 

deposits in argillaceous rocks of the Devonian Milligen 

Formation have been interpreted as indicating derivation of 

metals from enclosing host rocks (Hall and others, 1978). 

By analogy, the inference has been made that the Little 

Copper Member may have provided a source for metals in 

mineral deposits higher in the stratigraphic sequence; however, lead-isotope ratios of galena samples from the Mackinaw, Muldoon Barium, and Star Hope mines hosted in the 

Copper Basin Formation apparently indicate that the primary source of lead is extraformational (Sanford, Wooden, 

and others, 1989; Sanford and Wooden, this volume). The 

actual source is speculative at present. Most of the lead is 

nonradiogenic and may have been derived from a depleted 

source in the lower crust or upper mantle or from igneous 

rocks, such as Eocene intrusive rocks, that were derived 

from them. The lead-isotope ratios for samples from the 

Muldoon-Star Hope area exhibit characteristics similar to 

those of samples from the Alta and Lava Creek mining districts 35 km to the northwest and 30 km to the southeast, 

respectively. The alignment of the three areas coincides 

with magnetic and gravity anomalies (Kleinkopf and others, 1989) that extend northwestward from the Great Rift 

shear zone in the Snake River Plain. This coincidence suggests that intrusive rocks along structures subparallel with, 

but older than, Neogene basin and range faults may have 

been sources for the lead.

Impure calcareous rocks in the Drummond Mine 

Limestone Member host the highest grade silver-base metal 

deposits in the Copper Basin Formation. In the 

Muldoon-Star Hope area, the Drummond Mine Member is 

approximately 800 m thick. The lower third of the member 

consists of medium-to thick-bedded impure micritic limestone and a few thin beds of argillite, chert, and granule 

conglomerate. The upper two-thirds consists of thin- to 

medium-bedded micritic limestone and interbedded argillite, calcareous siltstone, and fine-grained calcareous sandstone (Paull and others, 1972). The proportion of limestone 

in the unit decreases southward, and thick beds of mediumto coarse-grained sandstone and finer grained clastic rocks
D8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 1. Major-element-oxide and minor-element composition, lithology, and approximate location of igneous rock samples from the 

Muldoon-Star Hope area, southern Pioneer Mountains, Idaho.

[Analyses by U.S. Geological Survey, Lakewood, Colo. Major element oxides (weight percent, volatile free) by X-ray spectroscopy; analysts, J.E. 

Taggart, A.J. Bartel, and D.F. Siems. Fe2O3 * is total iron as Fe2O3 ; LOI (in weight percent) is loss on ignition, 900°C. Minor elements (parts per 

million) by optical spectroscopy; analyst, D.L. Fey. < indicates element was detected, but amount is less than lower limit of detection. Elements 

analyzed for but below limit of detection (given in parentheses, in parts per million) in all samples: Ag (2), Au (8), Bi (10), Cd (2), Ho (4), Mo (2), Sn 

(10), Ta (40), U (100)]

Sample no. Wk3A Wk4A Wk7A Wk7B Wkl4A Wkl8F Wkl8G

Major-element oxides

Si02 

A1203 

Fe203* 

MgO 

CaO

Na2O 

K20 

TiO2

MnO

63.9 78.8 61.6 63.2 62.8 

15.9 12.9 14.7 15.0 15.0 

5.90 0.51 6.34 6.01 6.05 

3.22 0.27 4.58 3.39 3.43 

3.07 1.82 4.44 3.46 4.85

3.43 0.17 3.10 3.17 3.78 

3.51 5.38 4.11 4.75 3.05 

0.76 0.10 0.75 0.69 0.67 

0.30 <0.05 0.34 0.33 0.28

0.07 0.02 0.09 0.09 0.09

64.1 

15.8 

5.92 

2.42 

3.33

3.54 

3.90 

0.72 

0.24

0.08

53.2 

12.1 

9.30 

9.96 

9.85

1.77 

2.66 

0.72 

0.27

0.15

Volatiles

LOI 4.14 3.59 2.14 2.20 3.84 2.75 4.47

Minor elements

As

Ba

Be

Ce

Co

Cr

Cu

Eu

Ga

La

Li

Nb

Nd

Ni

Pb

Sc

Sr

Th

V

Y

Yb

Zn

Wk3A 

Wk4A 

Wk7A 

Wk7B 

Wkl4A 

WklSF 

WklSG

<10 <10 <10 <10 <10

3,700 

26232

1,260 639 1,880 2,330 1

142 43 97 102 92

25 3 27 22 23

81 2 205 110 139

14 3 40 38 25

2 <2 <2 <2 <2

21 18 19 20 20

87 23 59 61 56

16 32 18 19 22

18 22 22 21 13

59 16 42 43 41

36 6 85 36 42

24 37 16 22 20

11 <2 14 13 12

641 55 604 635 662

13 34 19 21 19

97 5 116 108 98

15 

23222

22 21 21 20

691 20 72 70 72

<10

,590

2

95

18

36

18

<2

21

58

22

21

40

15

19

11

681

23

102

22

2

66

<10

1,960

2

41

51

527

90

<2

17

26

53

<4

25

155

14

34

331

4

179

15

2

56

Plagioclase feldspar-hornblende porphyritic dacite dike, ridge above Mutual mine. 

Coarse-grained quartz-potassium feldspar porphyritic rhyolite dike, ridge south of Garfield Canyon. 

Equigranular hornblende-biotite granodiorite, ridge between Garfield and Muldoon Canyons. 

Plagioclase feldspar-biotite dacite porphyry pluton, ridge between Garfield and Muldoon Canyons. 

Plagioclase feldspar-biotite-hornblende porphyritic dacite dike, Muldoon Ridge. 

Hornblende-biotite-plagioclase feldspar porphyritic dacite dike, near Muldoon Creek barite prospect. 

Holocrystalline mafic dike (cuts 18F), near Muldoon Creek barite prospect.
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D9

Table 1. Major-element-oxide and minor-element composition, lithology, and approximate location of igneous rock samples from the 

Muldoon-Star Hope area, southern Pioneer Mountains, Idaho Continued.

[Analyses by U.S. Geological Survey, Lakewood, Colo. Major element oxides (weight percent, volatile free) by X-ray spectroscopy; analysts, J.E. 

Taggart, A.J. Bartel, and D.F. Siems. Fe2O3 * is total iron as Fe2O3 ; LOI (in weight percent) is loss on ignition, 900°C. Minor elements (parts per 

million) by optical spectroscopy; analyst, D.L. Fey. < indicates element was detected, but amount is less than lower limit of detection. Elements 

analyzed for but below limit of detection (given in parentheses, in parts per million) in all samples: Ag (2), Au (8), Bi (10), Cd (2), Ho (4), Mo (2), Sn 

(10), Ta (40), U (100)]

Sample no.Wk27A Wk33C Wk40A Wk40C Wk44A Wk47C Wk48C Wk49B

Major-element oxides

SiO2

A12O3

Fe2O3 *

MgO

CaO

Na2

K2

TiO2

P2^5

MnO

77.4 40.0 58.3 66.3 75.0

12.7 10.4 12.6 15.0 14.1

0.98 10.7 8.23 4.61 1.93

0.12 13.1 6.06 2.21 0.54

0.33 15.0 7.02 3.23 0.20

3.22 1.13 2.34 3.73 2.95

5.13 4.67 4.05 4.08 4.91

0.03 2.56 0.89 0.57 0.25

<0.05 2.32 0.40 0.57 0.08

<0.02 0.17 0.10 0.08 <0.02

77.4

12.8

0.89

<0.10

0.22

3.40

5.12

0.03

<0.05

0.02

64.4

15.0

3.72

4.20

5.00

3.41

3.57

0.53

0.19

0.04

62.4

15.7

6.21

3.34

4.30

3.72

2.93

0.94

0.36

0.07

Volatiles

LOI 0.99 9.83 4.72 0.54 1.66 0.60 0.66 2.25

Minor elements

As

Ba

Be

Ce

Co

Cr

Cu

Eu

Ga

La

Li

Nb

Nd

Ni

Pb

Sc

Sr

Th

V

Y

Yb

Zn

Wk27A

Wk33C

Wk40A

Wk40C

Wk44A

Wk47C

Wk48C

Wk49B

<10 <10 <10 <10 <10

138 

22333

3,890 1,140 1,330 1,660

25 337 81 107 60

<1 55 32 14 5

8 460 374 65 8

2 85 70 32 7

<2 6 2 <2 <2

16 17 18 20 20

12 187 46 67 37

24 27 55 25 13

22 120 7 15 12

12 152 44 42 23

<2 242 63 25 8

22 10 21 31 25

<2 26 22 9 2

50 2,660 597 514 122

21 14 11 30 25

<2 209 160 79 14

19 

22321

22 24 20 11

23 75 82 81 207

Quartz porphyritic rhyolite dike, ridge above Rippeto claim.

Biotite-bearing lamprophyric dike, ridge north of Eagle Bird mine.

Fine-grained, holocrystalline intermediate dike, upper Muldoon Creek.

Coarse-grained, equigranular, fresh quartz monzonite (Muldoon stock),

<10

252 2

2

35

<1

4

4

<2

15

19

11

16

17

<2

22

<2

49

21

<2

16

2

10

upper Muldoon Creek.

10

,560

2

81

16

235

18

<2

20

51

14

14

34

66

24

12

781

11

83

14

2

63

<10

1,430

2

105

22

122

6

2

21

64

72

10

44

44

8

11

667

10

104

15

2

66

Weakly porphyritic rhyolite dike with biotite-bearing groundmass, ridge north of Little Copper Creek.

Quartz porphyritic rhyolite dike, Bent Pine Tree claim (Star Hope Creek).

Plagioclase feldspar porphyritic dacite dike, head of Star Hope Creek.

Plagioclase feldspar, coarsely porphyritic dacite dike (cuts porphyritic rhyolite dikes of sample 47C), north of

Drummond mine.
Table 2. Minor-element composition of unmineralized samples from the Little Copper, Drummond Mine Limestone, and Green Lake Limestone Membe

Copper Basin Formation, Muldoon-Star Hope area, southern Pioneer Mountains, Idaho.

[Most samples are composite surface samples from a short interval of stratigraphic section. Results in parts per million. Analyses by U.S. Geological Survey, Lakewood, C

absorption; analyst, B. Roushey. Ag, As, Bi, Cd, Cu, Mo, Pb, Sb, and Zn by partial inductively coupled plasma-atomic emission spectrometry; other elements by total indu

emission spectrometry; analysts: D.L. Fey and J.M. Motooka. N indicates analysis was performed, but element was not detected (lower limit of detection given in parenthe

detected, but amount is less than lower limit of detection. Elements present but below detection limits in all samples (lower limit of detection given in parentheses): Au (0

(20), Ta (80), U (200), Yb (2)]

Sample no

Mn

Ag

As

Ba

Be

Cd

Ce

Co

Cr

Cu

Ga

La

Li

Mo

Nb

Nd

Ni

Pb

Sb

Sc

Sr

Th

V

Y

Zn

Wk2A

Wk3A

Wk8A

Wk8B

Wk8C

Wk8D

Wk9A

Wk9B

Wk9C

Wk9E

WklOA

Wkl4B

Wkl4C

. Wk2A Wk3B Wk8A Wk8B Wk8C Wk8D

217 139 76 27 23 38

0.06 0.35 0.19 0.23 0.24 1.1

17 22 17 15 12 17

2,390 3,390 12,000 5,380 4,870 3,410

<2 <2 <2 3 2 <2

12 1.3 0.052 0.099 0.032 0.084

10 16 <8 49 44 <8

8 8 14 8 7 5

58 55 3 104 98 31

19 40 160 28 24 14

<8 <8 <8 14 12 <8

13 12 <4 29 28 6

<4 5 <4 <4 <4 6

1.2 0.55 0.67 1.1 1.3 0.60

<8 <8 <8 9 16 <8

12 14 <8 25 23 <8

27 17 10 21 24 15

150 77 34 6.1 9.1 30

4.0 1.6 2.7 3.6 2.9 2.2

6 5 <4 8 9 <4

233 215 585 59 77 126

<8 <8 <8 8 <8 <8

101 118 14 260 247 80

11 11 <4 14 10 <4

600 110 8.7 12 2.1 15

Wk9A

35

0.17

19

3,020

<2

N(0.030)

45

6

75

15

10

28

<4

1.3

<8

19

18

4.9

2.0

6

44

<8

165

7

0.085

Wk9B

241

0.16

18

12,200

<2

0.090

17

17

44

31

<8

10

7

0.97

<8

13

32

18

1.7

<4

259

<8

108

8

14

Wk9C

164

0.14

9.4

10,600

<2

0.050

9

13

25

19

<8

7

<4

0.89

<8

<8

13

11

0.72

<4

64

<8

51

5

8.4

Wk9E

149

0.26

22

2,220

<2

0.091

35

9

52

31

<8

20

7

1.5

<8

17

36

6.8

3.5

4

31

<8

130

9

37

WklOA

66

0.27

28

3,060

<2

0.14

31

4

64

22

9

17

7

1.5

<8

16

21

11

6.2

6

43

<8

164

9

51

Sandstone sample from near top of Little Copper Member, roadcut on north side of Mutual Gulch.

Composite sample, lower third of Drummond Mine Limestone Member, upsection from sample 2A.

Barite veins in upper third, Little Copper Member, roadcut on ridge between Garfield Canyon and Mutual Gulch.

Upper third, Little Copper Member, downsection from sample 8A.

Upper third, Little Copper Member, downsection from sample 8B.

Upper third, Little Copper Member, downsection from sample 8C.

Middle third, Little Copper Member, downsection from sample 8C.

Middle third, Little Copper Member, upsection from sample 9A.

Middle third, Little Copper Member, upsection from sample 9B.

Upper third, Little Copper Member, upsection from sample 9C.

Upper third, Little Copper Member, hillside outcrops 0.5 km east of Scorpion Antimony prospect.

Middle third, Drummond Mine Limestone Member, Muldoon Ridge at head of Deep Gulch.

Middle third, Drummond Mine Limestone Member, downsection from sample 14B.
Sample no. WklSA WklSB

Mn

Ag

As

Ba

Be

Cd

Ce

Co

Cr

Cu

Ga

La

Li

Mo

Nb

Nd

Ni

Pb

Sb

Sc

Sr

Th

V

Y

Zn

WklSA

WklSB

Wkl6A

Wkl6B

Wkl7A

WklSA

WklSB

WklSC

WklSE

Wkl9A

Wk22B

Wk23A

Wk23B

71 20

0.36 0.61

3.8 3.4

728 2,150

<2 <2

0.30 0.086

42 27

7 <2

42 71

20 16

<8 9

18 19

8 4

1.4 2.2

<8 <8

14 15

43 11

12 64

0.83 0.82

<4 6

24 21

<8 <8

108 213

11 7

120 14

Wkl6A

201

0.12

11

1,060

<2

0.96

20

7

35

21

<8

17

6

3.1

<8

18

76

12

1.5

4

235

<8

115

12

84

Wkl6B

186

0.080

2.8

904

<2

0.17

13

5

26

6.9

<8

12

5

0.66

27

12

14

14

0.82

<4

338

<8

48

8

44

Wkl7A WklSA WklSB

141 463 393

0.13 N(0.045) 0.059

4.6 8.2 1 1 ^

958 4,990 4,200

<2 <2 <2

0.17 4.8 0.45

11 11 13

498

42 30 33

16 9.7 24

<8 <8 <8

9 11 13

6 8 14

0.66 0.73 0.37

<8 <8 <8

10 12 11

18 16 13

13 37 21

0.91 N(0.60) 0.66

4 <4 <4

58 189 159

<8 <8 <8

106 70 86

8 7 11

63 810 200

WklSC

217

0.12

9.2

17,800

<2

0.39

27

23

75

17

9

17

11

0.62

<8

18

76

12

0.61

4

235

<8

115

12

84

WklSE

581

0.046

5.0

563

<2

0.55

<8

3

11

4.8

<8

10

<4

0.17

<8

15

9

35

N(0.60)

<4

345

<8

14

7

120

Wkl9A

183

0.23

7.7

1,730

<2

0.93

10

6

28

58

<8

13

5

0.33

<8

17

12

26

1.5

4

770

<8

70

9

130

Wk22B

35

0.36

11

2,250

<2

0.39

14

5

42

6.3

<8

12

<4

5.8

<8

12

28

27

1.4

<4

94

<8

234

6

12

Middle third, Drummond Mine Limestone Member, downsection from sample 14C.

Lower third, Drummond Mine Limestone Member, downsection from sample ISA.

Lower third, Drummond Mine Limestone Member, spur ridge between Boundary Gulch and Deep Gulch.

Lower third, Drummond Mine Limestone Member, downsection from sample 16 A.

Upper third, Little Copper Member, downsection from sample 16B.

Laminated limestone in upper third, Drummond Mine Limestone Member, upsection from upper barite prospect on east side of Muldoon C

Dark siliceous limestone in Drummond Mine Limestone Member immediately above barite lenses at upper prospect, east side of Muldoon 

Barite-bearing turbidite in upper third of Drummond Mine Limestone Member, upper prospect, east of Muldoon Creek.

Pyritized limestone downsection from barite lenses at upper prospect, east side of Muldoon Creek.

Calcareous siltstone in upper third of Drummond Mine Limestone Member, lower barite prospect, east side of Muldoon Creek.

"Sooty" pyritic argillite in lower third of Drummond Mine Limestone Member, near upper adit, Boundary Gulch.

Upper third, Little Copper Member, ridge between Mutual Gulch and Boundary Gulch.

Upper third, Little Copper Member, downsection from sample 23 A.
D12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

c

S <§ g

G o tj5 *- 0

'&, S 5 t>

ct 2 § S ^?

"» S "a."" 3

"55 c _- ^ W

c« J3 <u -5 r

 ^ CH »-H Cd i^1 5? a< <-> o

3 I § 1 1

o of I 

u> O o "i O

JS U 3 u §

g -a 1 ~ ^

1 s -5 1 < ^ qj .£3 O O- «-^ ---"N ^

a -3 >^.S o 

S -3 £ g 8

1 ^141

H-3 r5 ^ O Q- on rr; .;; CD . i " " n

la .3 J Q 'c

O O "O .>;

CD O ^. O ^^

g O o '3 §

0 c* § 1 o

 O . p ~ u

 >-, 0 ^ *° if -Q ex o *Q

§ i § ^ |

S 

C2 

ts^S C *3 ^* (^

1 O "^ ^

 u 0 CD s .y o -2,

I iiaji

*^H C cd i> CXt

"O ^ cd G S S a c w o 3 a. 5 o «

| « S 1 § 3 

| o gt-^'S.S 

2 0 ^^ S a

Q -3 O* JQ --a 1-1 co 3 . a

£^l s il laatll

U « c u y "

JJ _C _O 3 CX,^

±3 ^ u a ^ >

j g s r * |

,u 5 u .2 .« u

J3 ^1 2 tj ^ -0

" r^i p. co O -t-»

| |f |ll

<u eu " -o u 2

| g ° s 1 g

ta r; > X5 1-7- <u co 3 ti on f-> c

-0 S ^ j= J §

S S - s £ J2 w 

^ gf 2 ^ 1 e

composition of unminei Muldoon-Star Hope ar< , surface samples from sieahey. Ag,Bi, Cd,AsuIS 

and D.L.Fey J.M. Meysts: than lowerimit ofdetectio 

2)]

"S g 'S a 1 £ ^ u .2 o o S u ;P

3+3 CX Pti ^ -- >H

4n S O PQ H 'Zl O1 v g ° ~- « § o 

l.||f|l&

2 ca *p ?^ 5 o1

. CQ g a" co ^ oo_

S cl « '§ 1 ^ ^

_Q f^j^ S? Q tfl y ^^

^2 5T^ O * -^ QJ ''^ CQ O ^ ^ H -Jr* O

H U ^j "§ S T3 ^

<

g^

3

Qm

^1^"

CQ m

m

^

m

^

U

CN

^

^

03

(N

m

o

m

U 

£

pa

1

CN

CO

Wk24A

g

_o

S

on

en 

cs 22

ON 9

CN O

<^ 2

-H O

in

^> S ! ^ ^ J

CN O

OO oo >_l

(N O

S f^

ZH O

en T*

^ s

-H O

m JQ

-H O

HH O

r^ °

o

^H °°

12 o

w ^j

^»^ *^C

CN

~1 CN CN "1 00

oo in V O ^H

oo en 2

 ON CN ^1 rON ON V O ^H

^ S CN ° 0

-H ON V O CN

*~l ^ rsl '"'

00 00 V O CS

o

cs m

2 3 v S 2

o

r-^ !3" ^ S °°

f~ oo V O » i

O CS

O

r- o

CN -H" V O en

o 

O ON

O

O 

VO CN

,_ i fvf V o in

co ca o "O o

< PQ PQ 0 0

2 vo

csenoovoo T:1.ooin>nen r: i<tr-oo^H ON

vOeni i V < i » i O V' '< l ' 'CS V^t VvOON 1^

vO

!£2 _. d oo envooovo-^-^Toovooo^^-'tf't-^oooN oo in en i i V' I^HO V^H" ir-^Z V-<* Vr^oo-<*

Th S ^

< i . oo oo .oor-^in-^t. r~~ oo cs > IT- i

vOenr~ V > i r~ O V^H^H^H^HTJ-I/-, Vin^HT}-

^J i/-, ^*

oo en i i V' I^HO V -^ cs i i T-H v-^t Vr^^Hvo

inenoorn ooo> iONTtTt^iSooI'1 5

^ "tcN V ON ^ V ^ ^ en ,_; v2 V^^JH;

rt >n ,-.

f^OOOOvO-t^ HVOr^^^^CNOOO-HCN

^en^ V-H^O V^CNON'O VCN Voo^in

^VOCS^CN^HO VcsencNr~ l° i<* V^^^HCS 

"^incs VcN 00 ^ v2einoden ln r>J V^^r-

- ? o 2 « 2 ^ o, 2 oo - ^ ^ oo oo g o g

r-oooor- ^oor-^oo^ enoo^ rCN no en ON O

oo en i i cs ^ i < VcNcN> ics'^en V * ' * ' ' '

Ol_i3caiTl O J3 -Q .^ _O _Q ,-1 J-H

OOOOJ^S222pHV5wwP>>HN

d

o

^U

ca T-I

"1

G n CD

iS ^

o "H ^

"§5 s

ca CD B*

^ u O

8 u o

o s -S

^r? ^

O CH

U g 2

3 J PQ U <i * Q >, . St+HCNeNenen^ H 

j Oenenen ^^ 53

t*-i^cDcD<U' i<uO

^flf 1-l SS !-' If l^S3o§ gssss^s-i

rgS-<t>nin «^ri<«1lllllll o pjiwc,.,^ c«_ p,

SS'2'3'2B*gSg|l|

ii|f|l!l!lll!

^"cococoUOgfie^Sj;,

|||llatlll4lt ^~* ^~^ f^ f^j f)"| *^3 * ^ * ^ * * ,r * 

llill?lllllll WUUOO-OSSSS^WCD 

co co CD CD CD C'«3 1^ 1«3^-i,e5'«5 1^; ccggggSSSS^Sg

^^SSS-^WWiUiUcfDD

 8 ,-.""'cocOcococD' § 1 1 1 1 1 1 1 1 9, % i?co1

1

rt^cDcDCDcDCDCDCDCDSlicD ^^SSS^^^ocrSeS . , ^H ^^1 f-4 *^t «1-H «*M «1-H «1-H ^^ r 1^ «1-H

S CD «- >H UU5I555I255I 2,0.0 CD o g'<'«S'!5'< Tj^'< 

R-R-cxcxS &"§"§"§"§ S^"§

r9r9oOO&0000§0§

^^OOOoagggSflg 

^ S«^^«SSgg||l ^ ^ .s « .s « a s a a 5 2 a

J^JJ^JQQQQQQQ

"§^§"H'2"2'H-2-2-2-2.'§'2-H

'S'S-S'S^gj-j-ji'jgj-'S^j-

*-. *-. '*~^ '*~^ '*~^ -t-t -t-t -t-t -t-t -t-t - . +-* 4 CJ CJ i i t CD i

' l-^RRrjl-l>HUlUlWHr-=H«WH -3'^CDcDCD<U4)4}cDCDT3 (U CD 

MM O O O O<O<O<CXQjS O CX

 gf* pQ -^ ^q r_^ <t^ ^q r_j <f| pr^ f) <f| <f| 

 ^ ^tinininocNcNenenenTj-in

cNcscNcscNenenenenenenenen

^^^^^^^^^^^^^
Sample no.

Mn

Ag

As

Ba

Be

Cd

Ce

Co

Cr

Cu

Ga

La

Li

Mo

Nb

Nd

Ni

Pb

Sb

Sc

Sr

Th

V

Y

Zn

Wk35B

Wk36A

Wk36B

Wk37A

Wk37B

Wk37C

Wk46A

Wk46B

Wk48A

Wk48B

Wk49A

Wk51A

Wk35B Wk36A Wk36B Wk37A Wk37B Wk37C Wk46A

220 218 248 339 174 253 211

0.13 0.066 0.17 0.091 0.22 0.13 0.090

6.8 6.7 2.6 25 11 82 4.7

1,800 1,190 1,380 2,110 1,960 2,000 2,220

<2 <2 <2 <2 <2 2 <2

0.14 0.18 0.23 0.073 0.069 N(0.030) 0.13

37 20 29 40 28 26 29

7 7 7 7 8 10 8

53 42 59 79 81 91 58

13 7.2 12 18 40 26 13

<8 <8 <8 12 13 13 8

25 19 20 24 18 15 22

14 15 18 21 32 53 14

0.53 0.23 0.49 1.6 1.1 1.0 0.49

<8 <8 <8 <8 <8 <8 <8

27 18 24 20 19 15 23

21 14 19 30 36 54 21

5.1 8.6 7.9 4.6 14 6.3 5.3

0.88 0.79 N(0.60) 4.0 3.2 3.5 0.70

55 78997

701 964 691 67 100 117 577

<8 <8 <8 9 <8 9 <8

104 69 107 204 216 227 118

11 12 14 10 10 10 13

43 36 32 46 36 19 64

Upper third, Drummond Mine Limestone Member, downsection from sample 3 5 A.

Middle third, Drummond Mine Limestone Member, downsection from sample 35B.

Lower third, Drummond Mine Limestone Member, downsection from sample 36A.

Upper third, Little Copper Member, downsection from sample 36B.

Upper third, Little Copper Member, downsection from sample 37A.

Middle third, Little Copper Member, downsection from sample 37B.

Upper half, Green Lake Limestone Member, Copper Basin Formation, west of Green Lake.

Lower half, Green Lake Limestone Member, downsection from sample 46A.

Upper third, Drummond Mine Limestone Member, head of Star Hope Creek.

Upper third, Drummond Mine Limestone Member, downsection from sample 48A.

Middle third, Drummond Mine Limestone Member, downsection from sample 48B.

Wk46B

339

0.17

1.2

9,210

<2

0.16

37

13

83

26

12

23

20

0.79

<8

21

33

9.9

N(0.60)

8

118

<8

155

16

88

Iron-stained argillite of Glide Mountain sequence, Copper Basin Formation near Blue Sky prospect,

Wk48A

159

0.12

6.7

1,650

<2

0.13

20

7

51

21

<8

18

12

0.58

<8

18

25

10

N(0.60)

5

569

<8

120

12

17

Wk48B

166

0.30

21

3,410

<2

0.90

36

11

81

50

10

25

12

0.94

<8

20

38

37

N(0.60)

7

454

<8

218

13

120

Wk49

247

0.099

5.6

1,960

<2

0.16

26

8

60

16

9

22

16

0.29

<8

21

20

11

N(0.60

7

942

<8

105

11

31

western tributary to upper Muldoon C
D14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

are present in the middle part of the Drummond Mine 

Member (Dover, 1981). Geochemical analyses of unmineralized samples (table 2) indicate that, in many places, the 

member is significantly enriched in barium and zinc, particularly in its lower and upper parts. Analyses of mineralized 

samples (K.W. Kunkel, Idaho State University, written 

commun., 1990) (table 3) indicate that, in general, gold and 

silver and their companion elements bismuth, antimony, 

and selenium are more abundant near the base of the Drummond Mine Limestone Member. Silver-base metal deposits 

in the unit are, however, stratabound at several horizons 

(fig. 3). Although mi critic limestone beds are favored hosts, 

no particular micrite horizon is especially favorable. In 

detail, deposits are localized or enriched where beddingplane and crosscutting steep faults intersect, and deposits 

may extend along faults of either orientation. Many deposits contain coarse-grained sulfide and calc-silicate minerals 

in contact with virtually unrecrystallized strata, characteristic of zinc-lead skarns that are distant from known or suspected intrusions (Einaudi and others, 1981).

The Lower Mississippian Drummond Mine Limestone 

Member of the Copper Basin Formation is overlain gradationally by an upper clastic unit more than 1,400 m thick 

consisting of gritty sandstone, granule conglomerate, and 

argillite (fig. 3). According to Nilsen (1977), the upper clastic unit includes the Scorpion Mountain Formation and the 

lower part of the Muldoon Canyon Formation of Paull and 

others (1972). In the vicinity of the Star Hope mine, the basal 

part of this unit, which hosts the deposits, consists of carbonaceous argillite and quartzite and thin calcareous interbeds. 

The strata are strongly folded, brecciated, and silicified and 

are intruded by swarms of aplite and quartz porphyry dikes 

that trend northeast.

At the Black Spar properties, brecciated and sheared 

light-gray andesite flows of the Challis Volcanic Group host 

weakly mineralized silver-base metal veins. Because the 

underground workings have been mostly inaccessible for 

decades, it was not possible during this study to reexamine 

the character of the host rocks at the main mineralized zones.

HOST STRUCTURES

Mineral deposits in the Muldoon-Star Hope area are 

localized by superimposed structures of Cretaceous and Tertiary age. The older structures include asymmetric folds and 

thrust faults that presumably formed during episodes of eastdirected compression of the Cretaceous Sevier orogeny 

(Dover, 1981). Strata in the hanging wall of the Pioneer fault 

(the Milligen(?) Formation) and the underlying Copper 

Basin plate form a broad anticline trends north-northwest. 

Regionally, broad and gentle folds are typical of the Copper 

Basin thrust plate. Widespread small-scale flexures that have 

the same vergence and bedding-parallel faults, which are 

themselves folded, are probably also Cretaceous in age. The

Star Hope

Gray Eagle * 

Idaho Muldoon *

X Ba 

Solid Muldoon *

Drummond 

(Prince Pine)

Eagle Bird 

Deep Gulch X Ba

X Ba - ^_

Carey Dolostone 3,013 

(Devonian)

Figure 3. Schematic stratigraphy of the Copper Basin Formation 

in the Muldoon-Star Hope area, south-central Idaho. Asterisk (*) 

indicates approximate stratigraphic level of named mine or prospect; xBa indicates approximate level of barite mine or prospect. 

Locations of mines and prospects are shown in figure 2.

overlying Glide Mountain plate of the Copper Basin Formation is characterized by pervasive folding on small and intermediate scales (Dover, 1981). These folds also generally 

trend north-northwest, are asymmetrical or overturned to the 

east, and are probably related to the thrusting. In many places 

the base of the Glide Mountain plate is a broad zone of 

intense shearing, tight folding, and silicification, and it 

locally contains slices and rolled blocks of structurally 

underlying rocks. At the Blue Sky prospect southwest of 

Muldoon Canyon (fig. 2), the Glide Mountain fault zone 

incorporates strongly deformed blocks of Drummond Mine 

Limestone Member. Fractured fold hinges, bedding-parallel 

faults, and thrust zones of Cretaceous age provided extensive 

"prepared ground" for subsequent mineral deposition.

Younger, steep faults cut the folded and thrusted Paleozoic sequences in many places; locally, they also displace 

rocks of the Challis Volcanic Group. Most are of small to 

intermediate oblique-slip displacement. The steep faults 

tend to follow one of three orientations, about N. 20° W., 

N. 50° E., or N. 80° E., which also are the dominant trends 

of Eocene dikes that cut the Paleozoic rocks. The faults and 

dikes likely formed during Eocene regional extension and
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D15

magmatism. North-northwest-trending faults such as the 

Copper Creek fault generally have been attributed to Neogene Basin and Range extension, but their approximate parallelism with trends of some Eocene dikes may indicate an 

earlier ancestry. In addition, the trace of the Copper Creek 

fault is cut at almost right angles by dikes of probable 

Eocene age (Nelson and Ross, 1969). Anderson and Wagner (1946) first noted that many silver-base metal deposits 

in the Little Wood River district are near intersections of 

steep faults and bedding-plane reverse faults; recent work 

in Garfield Canyon (Kunkel, 1989) indicates that highest 

grade replacement ore at the Eagle Bird mine and nearby 

deposits (fig. 2) is invariably at intersections of beddingplane and east-northeast-trending steep faults. Lower grade 

deposits may extend considerable distances along steep 

fault surfaces away from the richer, but discontinuous 

replacement deposits.

MINERAL DEPOSITS 

DEPOSIT TYPES

Mineral deposits in the Muldoon-Star Hope area are 

diverse but can be characterized generally as (1) polymetallic replacements or distal skarns (chiefly in carbonate 

rocks), (2) base- and precious-metal veins and replacements 

(which can be further subdivided, based on whether the 

host rock lithology is volcanic, intrusive, or calcareous, 

arenaceous, or pelitic sedimentary), and (3) bedded replacements and veins of barite. All gradations between these idealized types are present locally. For example, the largest 

replacement bodies are along structural or lithologic pathways tens to hundreds of meters from intrusive rocks, but 

in their calc-silicate mineralogy and coarse-grained texture 

many of the replacement bodies are similar to distal skarns. 

In addition, in many places where polymetallic replacements have been sheared, base- and precious-metal veins 

extend into the crosscutting shears.

POLYMETALLIC REPLACEMENT DEPOSITS 

OR DISTAL SKARNS

Description. The largest and highest grade deposits in 

the Muldoon-Star Hope area are polymetallic replacements 

or skarns. These deposits form tabular elongate lenses or 

ovoid, pipelike bodies that follow bedding-parallel faults in 

host rocks. Hosts generally are chemically reactive calcareous rocks, although the largest orebodies at the Solid Muldoon mine replaced sandstone in the footwall and 

porphyritic rhyolite in the hanging wall. In detail, the deposits are very irregular and discontinuous. At the Eagle Bird 

mine, replacement by sulfide minerals apparently is more 

complete where dips of controlling beds and structures are 

flexed and thus less steep (Anderson and Wagner, 1946). At

other deposits, bedding-parallel replacement deposits dip as 

steeply as 70°. The primary ore is present as massive or partial replacement of country rock, closely spaced veinlets, 

breccia fillings, or disseminations of sulfide minerals; all primary ore has been oxidized. The deposits have produced (in 

order of value) silver, lead, zinc, copper, and gold. As much 

as 4 percent Sb is present in some ore, but no production of 

antimony has been recorded.

Type example. Eagle Bird mine, Little Wood River 

district

Other examples. Little Wood River district: Drummond mine, Gray Eagle prospect, Hecla-Carrier, Idaho Muldoon mine, and Solid Muldoon (in part). Copper Basin 

district: Blue Sky prospect and Mackinaw Group

Mineralogy and texture. Sulfide minerals include 

galena, sphalerite, pyrite, chalcopyrite, arsenopyrite, marcasite, and complex antimonides. Pyrrhotite may be present in 

a few deposits. Preliminary electron microprobe data indicate that silver apparently resides principally in galena, 

although minor tetrahedrite and other discrete silver-bearing 

minerals may be present locally. Oxidized minerals include 

cerussite, anglesite, scorodite, malachite, and iron oxides. 

Gangue minerals include calcite, quartz, diopside, grossularite, epidote, idocrase, augite, sericitized feldspar, and fluorite. In many of the deposits, the sulfide, silicate, and 

carbonate minerals form very coarse grained euhedral or 

subhedral mosaics in favorable calcareous beds, whereas 

adjacent, more argillaceous beds are only slightly silicified 

and virtually unrecrystallized. In other deposits, the texture 

is granular, few ore minerals are euhedral, and the wallrocks 

are bleached and sericitized. Such is the case at the Solid 

Muldoon, where porphyritic rhyolite wallrocks are silicified 

and sericitized. In deposits near the margin of the Garfield 

stock, early formed sulfide minerals such as galena are thoroughly brecciated, whereas later sulfide phases are not.

Characteristics. Only very limited modern analytical 

information is available for mineral deposits of the Muldoon-Star Hope area. In general, pyrite and arsenopyrite are 

paragenetically older and are followed, in sequence, by 

sphalerite, galena, and chalcopyrite. Preliminary isotopic 

analyses of galena from replacement and vein deposits indicate a nonsedimentary source for the lead (Sanford, Wooden, 

and others, 1989; Sanford and Wooden, this volume). As discussed previously in the section on host rocks, the most 

likely source of lead is the Eocene plutonic rocks that were 

intruded into the sedimentary rocks. At most replacement 

deposits, alteration is not extensive in calcareous host rocks, 

although the rocks may be bleached and silicified. Where 

host rocks include siliceous igneous rocks, such as at the 

Solid Muldoon and Star Hope mines, quartz and sericite 

alteration is widespread. Although no geothermometric or 

geochronologic measurements have been made on minerals 

from the replacement deposits, the relative age of mineralization can be constrained by observations at two deposits. 

At the Blue Sky prospect, blocks of Lower Mississippian
D16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 3. Minor-element composition of mineralized samples from selected mines and prospects in the Muldoon-Star Hope area, 

southern Pioneer Mountains, Idaho.

[All samples are composite surface samples from "best" material exposed in workings or on dumps. In parts per million unless otherwise indicated. 

Analyses by U.S. Geological Survey, Lakewood, Colo. (P) indicates element by partial inductively coupled plasma-atomic emission spectrometry; 

all other elements except Au by optical spectroscopy (analysts: D.L. Fey, J.M. Motooka, and P.H. Briggs); Au by flame atomic absorption (analysts: 

B. Roushey, R.M. O'Leary, and R.H. Hill). N indicates analysis wasperformed, but element wasnot detected (lower limit of detection in 

parentheses). < indicates element was detected, but amount is less than lower limit of detection. Elements analyzed for but below limit of detection 

(given in parentheses, in parts per million) in all samples: Eu (4), Ho (8), Sn (20), Ta (80), U (200), Yb (2)]

Sample no. Wkll Wk20 Wk21A Wk22A

Mn

Ag

As

Ba

Be

Bi

Cd

Ce

Co

Cr

Cu

Ga

La

Li

Mo

Nb

Nd

Ni

Pb

Sc

Sn

Sr

V

Y

Zn

Ag(P)

As(P)

Bi(P)

Cd(P)

Cu(P)

Mo(P)

Pb(P)

Sb(P)

Zn(P)

Au

Pt

Pd

Rh

Ru

Ir

Wkll A

Wk20

Wk21A

Wk22A

125 78 176 28

62 291 <4 759

25,000 12,100 230 35,600

18 471 56 924

<2 <2 <2 <2

<20 30 <20 150

85 9 <4 4

<8 <8 <8 22

48 9 <2 25

18 27 19 56

994 2,290 19 2,170

<8 <8 <8 <8

<4 <4 <4 14

5 <4 7 6

<4 5 <4 47

<8 <8 <8 <8

<8 <8 <8 11

12 4 4 49

20,000 83,500 360 135,000

<4 <4 <4 <4

<20 <20 <20 40

10 23 20 59

49 55 42 82

<4 <4 <4 <4

10,800 988 42 1,010

N(1.5) 200 2.9 540

>24,000 68 190 30,000

N(20) N(6.6) N(0.60) 81

56 6.4 0.24 1.2

300 1,800 19 1,600

N(3.0) N(0.99) 1.0 52

30,000 13,000 820 18,000

N(20) 160 3.6 320

9700 N(0.33) 34 790

0.40 0.50 N(0.05) 0.10

<10 <2 1.7 <5

<20 7.0 <0.8 16

<10 3.0 <0.5 5.0

<10 <6 <2 <20

<10 <2 <0.5 10

Wk34B

14

61

340,000

27

<2

<20

16

<8

<2

9

638

<8

<4

<4

<8

<8

6

5,950

<4

20

4

18

<4

771

N(1.5)

>24,000

N(20)

N(l.O)

N(l.O)

N(3.0)

8,600

290

530

0.15

<50

<80

10.0

170

<50

Wk40B

2,000

329

1,000

277

<2

20

381

17

13

61

354

<8

12

14

<4

<8

12

13

92,400

4

<20

225

74

9

55,800

240

290

N(6.6)

370

230

N(0.99)

14,000

160

1700

<0.05

<5

<8

<5

<20

<5

Wk40C

582

816

300

787

<2

20

926

23

17

50

798

9

13

4

<4

9

12

18

137,000

<4

<20

131

82

11

125,000

540

N(6.6)

N(6.6)

926

200

N(0.99)

18,000

410

70

0.05

<5

<8

<5

<3

<5

Idaho Muldoon mine, open cut that extends south from adits. Coarse-grained galena- and arsenopyrite-bearing skarn that has thick

scorodite coatings; host rock is calcareous turbidite.

Lucky Boy mine, west side of Argosy Creek: vuggy, sulfide-bearing quartz-carbonate veins; host rock is fractured calcareous and

arenaceous turbidite cut by pyritized rhyolite porphyry dikes.

Surface pits, east side of Argosy Creek, opposite Lucky Boy mine. Weakly iron stained quartz veins in calcareous sandstone that

contains widely disseminated galena.

Boundary Gulch, highest adit.Granular and vuggy iron- and copper-stained quartz gangue containing abudant galena and arsenopyrite;

host rocks are highly cleaved carbonaceous argillite and calcareous siltstone cut by dacite dikes.

Wk34B

Wk40B

Eagle Bird mine. Coarse-grained to granular, vuggy to massive, sulfide-rich material including galena and arsenopyrite, heavily coated

with scorodite; host rock is calcareous turbidite containing patchy silicification.

Grey Eagle claims, upper workings. Multiple horizons of coarse-grained to granular galena- and sphalerite-rich skarn; host rock is thinbedded, locally silicified calcareous turbidite that is cut by porphyritic rhyolite dikes.

Wk40C Grey Eagle claims, lower adit. Coarse-grained, massive galena- and sphalerite-rich material; host rock is calcareous turbidite intruded by

microdiorite dike.
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA

Table 3. Minor-element composition of mineralized samples from selected mines and prospects in the Muldoon-Star Hope area, 

southern Pioneer Mountains, Idaho Continued.

D17

Sample no.

Mn

Ag

As

Ba

Be

Cd

Ce

Co

Cr

Cu

Ga

La

Li

Mo

Nb

Nd

Ni

Pb

Sc

Sn

Sr

Th

V

Y

Zn

Ag(P)

As(P)

Bi(P)

Cd(P)

Cu(P)

Mo(P)

Pb(P)

Sb(P)

Zn(P)

Au

Pt

Pd

Rh

Ru

Wk45A

169

<4

110

1,010

<2

<4

53

19

76

100

9

29

17

<4

8

26

78

230

7

<20

95

<8

166

18

140

0.87

93

N(0.60)

1.0

83

2.1

400

1.6

140

N(0.05)

<2

<3

<2

<6

Wk47A

21,100

71

20

222

12

162

16

11

30

35

37

14

45

<4

<8

12

22

17,000

<4

300

127

<8

65

10

20,100

45

380

120

150

N(l.O)

9.1

25,000

N(20)

17,000

N(0.05)

<1

<2

<1

<3

WkSOA

6,270

<4

70

571

<2

<4

20

10

65

1,180

23

18

6

5

<8

12

17

64

7

250

243

<8

117

16

238

1.5

54

1.1

0.95

980

0.31

110

1.2

160

N(0.05)

0.8

1.7

<0.5

<2

Wk53A

249

9

30

520

<2

<4

<8

26

22

1,570

<8

6

9

<4

<8

<8

42

1,860

<4

<20

63

<8

83

<4

156

3.3

1,000

N(20)

N(l.O)

1,200

3.9

2,900

N(20)

43

N(0.05)

<5

<8

<5

<20

RW88-49

170

<4

60

2,000

<2

<4

21

8

120

41

<8

15

14

53

<8

15

130

100

7

<20

71

<8

580

13

550

N(0.05)

RW88-53

170

170

2300

400

<2

12

21

2

70

460

12

13

15

33

<8

13

12

32,000

5

70

41

9

140

<4

1,000

0.15

RW88-59

200

<4

100

2,100

<2

<4

26

9

78

35

12

17

12

<4

<8

17

34

110

8

<20

140

8

200

14

130

N(0.05)

Wk45A Main (north) adit, Candy Cane claim group. Weakly iron stained dense argillite, no visible sulfide minerals; adit follows microdiorite

dike that cuts contact between argillite and overlying calcareous strata of Green Lake Limestone Member of Copper Basin Formation. 

Wk47A Adit at end of jeep road on east side of Star Hope Creek, opposite Bent Pine Tree claim. "Sooty" granular galena- and sphalerite-bearing

material; adit follows contact between porphyritic rhyodacite dike and dark, silicified calcareous turbidite; disseminated chalcopyrite and

weak copper staining at contact. 

WkSOA Blue Sky prospect. Coarse-grained, sulfide-bearing calc-silicate skarn showing conspicuous copper staining; host rock is strongly folded

and partly silicified tectonic lenses of calcareous turbidite cut by porphyritic rhyolite dikes. 

Wk53A High (south) adit, Candy Cane claim group. Granular pyrite, chalcopyrite, arsenopyrite, and galena in quartz gangue; ore minerals are

present as small lenses and fracture coatings along steep shears in silicified lithic sandstone immediately above contact with

carbonaceous siltite and argillite. 

RW88-49 Solid Muldoon mine. Chip sample from second dump from bottom, which is composed mainly of dark carbonaceous argillite and very

minor amounts of vein quartz and sulfide minerals. 

RW88-53 Solid Muldoon mine. Chip sample from uppermost large dump, which is light colored and composed of silicified and bleached rock and

abundant vein quartz. Altered rock contains disseminated pyrite, and vein quartz contains minor amounts of galena. 

RW88-58 Mutual mine. Composite chip sample from lower large dump, which contains a mixture of carbonaceous argillite and altered felsic dike

rocks.
D18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Drummond Mine Limestone Member as large as 50 m have 

been incorporated in the Sevier-age Glide Mountain thrust 

zone. The blocks are strongly deformed but have been partly 

silicified and partly replaced by coarse-grained mosaics of 

sulfide and silicate minerals, indicating that mineralization 

postdates Cretaceous emplacement of the thrust. At the Solid 

Muldoon mine, leucocratic dike rocks are strongly altered 

and weakly mineralized, whereas intermediate dike rocks are 

virtually unaltered. Although neither set of dikes has been 

dated isotopically, each is almost certainly Eocene, roughly 

the same age as the Muldoon stock (47 Ma, K-Ar on biotite; 

R.E. Zartman, in Dover, 1981). Hence, the orebodies likely 

are also of Eocene age.

Orebodies. The sulfide replacement bodies generally 

are short, small, and irregular and form thin tabular seams 

and stringers of ore-grade material. Typical dimensions are 

on the order of 10-20 cm thick and a few meters long, but 

several bodies might be located in close proximity either vertically or laterally where structural and lithologic conditions 

are favorable. The main orebody at the Eagle Bird mine, 

which has not been explored completely, is exceptionally 

large. It consists of several bands and stringers that are, in 

aggregate, more than 3 m thick, and it extends more than 30 

m downdip (Anderson and Wagner, 1946). The outcropping orebody at the Solid Muldoon mine is reported to have 

been 3.5-6 m thick (E.H. Finch, in Umpleby, 1917). It was 

developed through seven levels totaling more than 610 m of 

drifts and 275 m of crosscuts that have been inaccessible 

since early this century (Tuchek and Ridenour, 1981). One 

slope on the No. 4 level was more than 3 m wide, 15m long, 

and 60 m high (Anderson and Wagner, 1946), a shape that 

may indicate that mineralization was controlled by a steep 

fault. The orebody (or a series of overlapping bodies) may 

have extended through the entire vertical distance of workings, 300 m; however, the tenor decreased in lower levels. 

The Idaho Muldoon mine has two separate replacement 

deposits, one 0.3-1 m thick and at least 30 m long (Anderson 

and Wagner, 1946), and a second averaging 0.3 m thick and 

about 46 m long (Tuchek and Ridenour, 1981). The total tonnage of individual replacement bodies is not large; each of 

the two orebodies on the Idaho Muldoon property totals 

approximately 1,000 tons. The Eagle Bird mine deposit is 

estimated to contain about 33,000 tons (4,436 tons produced 

to date and 28,500 tons in inferred reserves; Tuchek and 

Ridenour, 1981), exceptionally large by district standards 

but small by world standards (Mosier and others, 1986).

The proportion of contained metals varies widely from 

deposit to deposit. Typical grades are 6-12 ounces of silver 

per ton, 5-10 percent Pb, 3-7 percent Zn, 0.1-1 percent Cu, 

and a trace to 0.3 ounces of gold per ton. Several orebodies 

contain as much as 5 percent As, and the Eagle Bird mine 

contains as much as 4 percent Sb. Production grades from the 

Eagle Bird mine were 8.8 ounces of silver per ton, 0.2 percent Cu, 7.6 percent Pb, 3.5 percent Zn, and 0.005 ounces of 

gold per ton (Tuchek and Ridenour, 1981). Production of ore

containing more than 40 ounces of silver per ton and 40 percent Pb from the Solid Muldoon and Mutual mines, and more 

than 28 percent Cu from the Drummond mine, was exceptional and could not be matched today without hand sorting.

Geochemical signature. The Muldoon-Star Hope 

area is within the boundary of a geochemical survey conducted for the Boulder-Pioneer Wilderness Study Area (fig. 

1) (Simons, 1981). Many samples of sediments from streams 

draining the area contained anomalous amounts of Ag, As, 

Ba, Cu, Pb, Sb, and Zn. Most unmineralized rock samples 

contained anomalous amounts of barium, many contained 

anomalous amounts of boron and zinc, and a few contained 

anomalous amounts of gold, cobalt, copper, and manganese. 

Each of these elements may be present in a geochemical signature that commonly is associated with polymetallic 

replacements or skarns.

Chemical analyses of selected sulfide-bearing samples 

collected during this study from deposits in the Muldoon-Star Hope area (particularly those that are hosted in 

the Drummond Mine Limestone Member) indicate the following range in metal enrichments: almost all samples contain anomalous amounts of lead (360-137,000 ppm) and 

zinc (238-125,000 ppm). The majority of samples contain 

silver (61-816 ppm), copper (354-2,290 ppm), arsenic 

(300-250,000 ppm), and detectable gold (trace-0.50 ppm). 

Several samples are enriched in antimony (160-410 ppm) 

and tin (20-300 ppm); these samples are from deposits that 

are hosted by, or adjacent to, argillaceous rocks. Barium 

(727-1,010 ppm) and manganese (2,000-21,100 ppm) each 

are slightly enriched in three separate samples, and cadmium is enriched in three samples from deposits that are 

cut by dikes. Bismuth (150-170 ppm) is enriched in two 

samples, only one of which contains detectable gold. 

Molybdenum is enriched (47 ppm) in a selected sample 

from the highest dump in Boundary Gulch; this sample has 

the broadest spectrum of elevated metal values in the analyzed suite and consists of sulfide minerals in argillaceous 

rock. Two samples from the upper and lower adits of the 

Star Hope mine also are enriched in molybdenum (100 and 

20 ppm, respectively; Bullock and others, 1990) and were 

collected from veins cutting arenite.

The chemistry of three composite dump samples 

reflects the main component of dump material in each of the 

sampled dumps. Two samples, RGW88-49 and RGW88-58 

(table 3), from dumps containing mostly argillite, have metal 

contents similar to those of unmineralized samples except 

for higher Zn and slightly higher As, Li, Mo, Ni, Pb, and V. 

A composite sample from an upper dump at the Solid Muldoon mine that consisted mainly of mineralized and altered 

rock was significantly enriched in Ag, As, Cd, Cu, Mo, Pb, 

Th, and Zn and slightly depleted in Ba and Y, as compared 

to unmineralized samples.

Geophysical signature. No specific geophysical signatures of polymetallic replacement deposits are known from 

the Muldoon-Star Hope area, but it is probable that local
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D19

detailed electrical surveys would detect individual orebodies, 

which are known to contain conductive sulfide minerals.

Genesis and ore controls. The locations of polymetallic replacement deposits and skarns are governed by chemically reactive host rocks (principally the Drummond Mine 

Limestone Member) that are cut by concordant and 

discordant faults and fractures. The intersections of beddingparallel northwest-trending faults and steep northeast-trending faults and fractures created open spaces that became sites 

of later mineral deposition. It is possible that carbonaceous 

pelitic rocks stratigraphically beneath mineralized horizons 

provided a source for some of the metals, although available 

information is equivocal. Stocks and dikes, which are 

exposed near the deposits, probably provided heat and fluids 

for metasomatism, although specific isotopic information 

that would fingerprint their influence is lacking. Locally, silification and serialization of intrusive and host rocks indicates hydrothermal activity. In addition, many of the 

polymetallic replacements are coarse-grained mosaics of 

sulfide, silicate, arid carbonate minerals, a characteristic feature of distal skarns. This skarnlike texture and mineralogy 

is one line of evidence that plutons may be present at shallow 

depth beneath the workings of most polymetallic deposits.

Exploration guides. Numerous polymetallic deposits 

are known in the Drummond Mine Limestone Member, particularly in its southern outcrops in the Muldoon-Star Hope 

district and in its northern outcrops in the Alta district 

approximately 30 km to the northwest. Because fault intersections principally localized these deposits, most orebodies 

are likely to be small, although they may be of high grade. 

Lower grade polymetallic veins and replacement deposits 

may extend along high-angle faults away from higher grade 

deposits for considerable distances, but the likelihood for 

large-tonnage deposits is low. In specific places where calcareous strata are particularly susceptible to replacement, 

high-grade orebodies may extend as tabular lenses for 100 m 

or more along bedding. At the Phi Kappa mine in the Alta 

district, the main replacement orebody in the Drummond 

Mine Limestone Member extends almost continuously for 

more than 1,200 m along strike and is believed to extend at 

least 300 m down dip (Tuchek and Ridenour, 1981). A concealed orebody of these dimensions in the Muldoon-Star 

Hope area should be detectable at considerable depth by 

careful surface electrical surveys. Smaller bodies will be difficult to detect. The proximity of the Phi Kappa mine to the 

Summit Creek quartz monzonite stock suggests an important 

magmatic influence on deposit formation. Similarly, the 

proximity of the Eagle Bird and Solid Muldoon mines to the 

Garfield and Muldoon stocks is regarded as more than fortuitous, as are the locations of the Star Hope, Mackinaw, and 

Drummond mines near concentrations of dikes. Thus, additional exploration in the central area of Drummond Mine 

Limestone Member outcrops between the Star Hope and Phi 

Kappa mines may not be fruitful, even in areas of northeasttrending high-angle faults, inasmuch as there are no known

dike swarms or extensive areas of silicification or bleaching 

that might indicate leucocratic plutons at shallow depths.

POLYMETALLIC VEINS IN 

SEDIMENTARY ROCKS

Description. Polymetallic veins are present in dark, 

argillaceous rocks of the Milligen(?) Formation and the Little Copper Member of the Copper Basin Formation, in calcareous rocks of the Carey Dolostone and the Drummond 

Mine Limestone and Green Lake Limestone Members of 

the Copper Basin Formation, and in arenaceous rocks of the 

upper clastic units of the Copper Basin Formation (fig. 2). 

The deposits include small discontinuous lenses, stringers, 

and pods along steep east-northeast- and north-northwesttrending faults, fractures, and brecciated zones. In places, 

the veins follow narrow contact metamorphic aureoles 

close to felsic intrusive bodies. Weathering of the veins 

forms conspicuous gossans in many places. Where host 

rocks are calcareous, the veins generally are associated 

with polymetallic replacements and in places extend along 

high-angle faults and fractures that cut bedding-parallel 

replacements. This type of vein is a hybrid and generally 

incorporates less gangue and therefore is chemically more 

enriched than veins in noncalcareous rocks. Where host 

rocks are noncalcareous, the veins generally are quartz rich 

but also may contain calc-silicate minerals or barite. High 

metal values in veins of this type are generally very spotty. 

The silver-rich veins at the Star Hope mine were a notable 

exception. Polymetallic veins have produced (in order of 

value) silver, lead, zinc, copper, and gold.

Type example. Polymetallic veins in carbonate rocks: 

Rippeto claim, Little Wood River district

Other examples. Little Wood River district: American mine prospect, Garfield group, Lucky Boy (east), Silver 

Eagle, Silver Mint, and Smuggler

Type example. Polymetallic veins in sandstone: Star 

Hope, Copper Basin district

Other examples. Little Wood River district: Champion prospect, Logan tunnel, Lucky Boy (west), and Solid 

Muldoon (part?). Copper Basin district: Candy Cane (south)

Type example. Polymetallic veins in argillite: Mutual 

mine, Little Wood River district

Other examples. Little Wood River district: Copper 

Bell group, Frisco Gulch prospects, and Scorpion Antimony

Mineralogy and texture. Sulfide minerals include 

galena, chalcopyrite, sphalerite, pyrite, and arsenopyrite. Silver values are higher in ore that is rich in galena, although 

discrete silver minerals including tetrahedrite were identified 

at the Solid Muldoon and Star Hope mines. Oxidized minerals include anglesite, cerussite, malachite, smithsonite, and 

iron oxides. Quartz is the predominant gangue mineral in 

most veins, but clay minerals, calcite, and calc-silicate minerals are present in a few veins.
D20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Characteristics. No modern laboratory data are available for polymetallic veins of the Muldoon-Star Hope area. 

The veins share many characteristics with the polymetallic 

replacements or skarns, however, and probably are coeval 

and cogenetic.

Orebodies. Most veins are thin and discontinuous. 

Typical thicknesses are 0.3-1.0 m, although thinner veins are 

not uncommon. A mineralized vein 3 m thick in Mutual 

Gulch (Tuchek and Ridenour, 1981) is exceptionally thick. 

Typical lengths of veins are 10-30 m; however, the main vein 

at the Rippeto claim can be followed for 150 m, the main zone 

at the Silver Eagle claim for 120 m, and a mineralized shear 

at the Champion property for 140 m (Tuchek and Ridenour, 

1981). The inferred tonnages of individual vein deposits are 

small. Resources on the Rippeto claim, which are exceptionally large for the Muldoon-Star Hope area, were inferred by 

Tuchek and Ridenour (1981) to be approximately 35,000 

tons grading 4.4 ounces of silver per ton, 4.91 percent Pb, 0.9 

percent Zn, and a trace of gold. Resources on the Silver Eagle 

claim are inferred to be 15,000 tons grading 3.3 ounces of silver per ton, 2.83 percent Pb, 2.53 percent Zn, and traces of 

gold. Other known polymetallic veins have comparable 

grades but significantly less tonnage; however, the aggregate 

tonnage in the Scorpion group of claims on the south side of 

Garfield Canyon (about 15,000 tons) and in the host of claims 

in Mutual Gulch (about 18,000 tons) each may constitute a 

minable resource collectively.

Geochemical and geophysical signatures. In the surrounding region, a geochemical signature commonly associated with polymetallic veins, regardless of host rock, is Zn, 

Cu, Pb, As, Au, Ag, Mn, Ba, Sb, and Bi (Worl and others, 

1989). Many rock and stream-sediment samples from the 

Muldoon-Star Hope area contain anomalous amounts of one 

or more of these elements (Simons, 1981). The vein deposits 

have no direct geophysical expression in the regional magnetic and gravity data available for the Muldoon-Star Hope 

area. Major steep faults and shallow stocks that may influence localization of some veins are delineated, however, by 

prominent anomalies and steep gradient zones.

Genesis and ore controls. East-northeast- and northnorthwest-trending steep faults apparently exert the strongest control on the locations of polymetallic veins by providing permeable zones through reactive rocks. Fault offsets of 

4 m or less were sufficient to create channelways (Kunkel, 

1989). At the Star Hope property, some shallowly dipping 

veins may follow fractures parallel with the Glide Mountain 

thrust fault. Silicification and serialization generally are 

more intense within the fault zones but in a few places extend 

laterally a few meters into susceptible country rocks. The 

most laterally continuous veins in the Muldoon-Star Hope 

area, those at the Rippeto, Silver Eagle, Champion, and Star 

Hope properties, are near contacts with quartz monzonite 

stocks or leucocratic dike swarms believed to emanate from 

subjacent plutons. The igneous rocks probably provided heat 

and fluids for metasomatism, although their role has not been

substantiated by isotopic or fluid-inclusion analyses. A subtle zoning of sulfide minerals, present in both replacement 

and vein deposits, probably indicates a hydrothermal influence on ore deposition. Arsenopyrite, pyrite, pyrrhotite, and 

chalcopyrite are more abundant closer to the Garfield and 

Muldoon stocks and to the inferred buried stock beneath the 

Star Hope mine, whereas those sulfide minerals that form at 

cooler temperatures (galena and sphalerite) are more abundant farther from the igneous rocks.

Exploration guides. In the Muldoon-Star Hope area, 

the coincidence of the triad (1) calcareous, or mixed calcareous and siliceous sedimentary host rocks, (2) east-northeast- or north-northwest-trending steep faults, and (3) 

Tertiary leucocratic igneous rocks indicates prospective 

ground. Fault control is fundamental for the vein deposits. 

The veins typically are small and may show only inconspicuous gossans. They are unlikely to have pronounced geophysical expression, although very detailed electrical 

surveys might detect sulfide-bearing veins hosted in steep 

fault zones.

POLYMETALLIC VEINS IN 

IGNEOUS ROCKS

Description. Polymetallic veins are present near the 

margin of the Muldoon stock at the Contact prospect along 

the west side of upper Muldoon Creek and also may be 

present along the west margin of the Garfield stock in 

Garfield Canyon. Precious- and base-metal veins also are 

present in rocks of the Challis Volcanic Group at the Black 

Spar mine west of Copper Creek (fig. 2). Almost no information has been published on these occurrences. At the Contact 

prospect, a vein occupies a shear zone at the contact of the 

quartz monzonite stock and interbedded calcareous and 

argillaceous rocks of the Drummond Mine Limestone Member, and sulfide minerals also are in irregular pods along 

joints in the stock. At the Black Spar mine near the confluence of Blackspar Canyon and Copper Creek, extensive 

workings explore shear zones in rocks of the Challis Volcanic Group. To the west in the Little Wood River area (Sanford, 1988; Sanford, Whitney, and others, 1989), to the south 

in the Lake Hills (Moye and others, 1988), and to the east in 

the Grouse quadrangle (Skipp, 1989), andesite, dacite, and 

rhyodacite flows, breccias, and tuffs constitute the southern 

field of the Challis Volcanic Group. In the Copper Creek 

area, rocks of the Challis Volcanic Group consist almost 

entirely of thick interlayered andesitic tuff-breccias and 

flows that form the basal Challis unit. About 1.6 km west of 

the Black Spar mine, these andesitic rocks are overlain by 

dacitic flows and minor welded ash-flow tuff. The basal 

andesitic rocks are cut by leucocratic dikes of two orientations: one set trends roughly north-south, and the second 

trends roughly east-west. The Black Spar underground 

workings, which are inaccessible, apparently follow
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D21

silicified shear zones parallel with these trends. West of the 

Muldoon townsite in the southwestern part of the area, a conspicuous swarm of north-trending sanidine-bearing rhyolite 

dikes cuts the andesitic rocks (fig. 2); no workings are known 

to be associated with these dikes.

Mineralogy and texture. In veins hosted by intrusive 

rocks, pyrite is the predominant sulfide mineral, but galena, 

sphalerite, and chalcopyrite also are present. Gossans are 

weakly developed, and sparse malachite is present. In volcanic-hosted veins., pyrite, galena, sphalerite, and chalcopyrite are present, together with quartz and siderite gangue. 

Bleaching, silicification, and pyritization extend 2-3 m 

from veins, and textures in volcanic host rocks are completely obliterated.

Characteristics. Neither laboratory nor analytical 

information is available for either type of vein occurrence. 

At the Contact prospect, the age of mineralization must be 

Eocene or younger inasmuch as mineralized rock occupies 

joints within the Muldoon stock, which has been dated at 47 

Ma. Although mineralized veins at the Black Spar property 

are in rocks of the Challis Volcanic Group, they trend northnorthwest and east-northeast, similar to faults, dikes, and 

veins in the underlying Devonian and Mississippian sedimentary rocks. Furthermore, leucocratic dike rocks are 

slightly to strongly altered, whereas intermediate dike rocks 

are virtually unaltered. Hence, the age of mineralization is 

about the same as the age of the dikes, probably Eocene. This 

age is consistent with ages inferred for volcanic-hosted 

deposits elsewhere in the Challis volcanic field. According 

to Moye and others (1989), the deposits are related spatially 

and temporally to waning stages of volcanism at local centers late in the Eocene.

Orebodies. At the Contact prospect, the pyritized 

shear zone is 0.6-1.5 m thick and extends along strike at least 

46 m (Tuchek and Ridenour, 1981). Pyrite pods along joints 

in the Muldoon stock are not extensive but are as thick as 0.9 

m. The extent of veins at the Black Spar property is 

unknown, but the veins are likely to be very irregular and 

thin, occupying fissures and brecciated zones within the 

complexly fractured volcanic rocks.

Geochemical and geophysical signatures. The Contact and Black Spar properties are at the edges of the 

regional geochemical and aeromagnetic surveys of the 

Boulder-Pioneer Wilderness Study Area (Mabey, 1981; 

Simons, 1981) and were not sampled adequately; however, 

the geochemical sampling included one rock sample near 

each property and one stream-sediment sample, which was 

collected near the mouth of Blackspar Canyon. Only lead 

and uranium shov/ed slightly elevated values near the Contact prospect, and only chromium was slightly enriched in 

the stream-sediment sample from Blackspar Canyon. Additional rock samples collected in 1987 near the Black Spar 

property show slightly elevated values of barium, chromium, and manganese but only background values of other 

elements commonly associated with polymetallic veins

(Bullock and others, 1990). A geochemical signature of 

polymetallic veins normally includes several of the elements Zn, Cu, Pb, As, Au, Ag, Mn, Ba, Sb, and Bi.

Regional magnetic values in the Blackspar Canyon area 

show a smooth eastward increase toward a positive anomaly 

in the Garfield Canyon area that is inferred to indicate the 

subsurface connection and extent of the Garfield and Muldoon stocks. The concealed part of the pluton apparently 

does not extend westward beneath Blackspar Canyon. A 

similar, smaller positive aeromagnetic anomaly, west of the 

former townsite of Muldoon, approximately 6 km south of 

Blackspar Canyon, also is inferred to indicate a concealed 

stock (Mabey, 1981) but does not appear to extend northward as far as Blackspar Canyon.

Genesis and ore controls. Polymetallic veins in igneous rocks almost certainly formed during accumulation of 

the southern Challis volcanic field, probably during late rhyolitic activity. The genesis of the veins apparently is analogous to that of veins in adjacent Paleozoic sedimentary 

rocks, and structural controls particularly intersections of 

east-northeast- and north-northwest-trending faults and fractures provided pathways for metal-bearing fluids. The 

extent of hydrothermal alteration in the Blackspar Canyon 

area is unknown. It is possible that shallow intermediate to 

siliceous intrusions are present in rocks of the Challis Volcanic Group of the Blackspar Canyon area, as they are in the 

Lava Creek district 30 km to the east-southeast. In the latter 

area, polymetallic vein deposits in rocks of the Challis Volcanic Group are hosted both by the intrusive rocks and the 

volcanic country rocks and have elevated gold and silver values (Moye and others, 1989). The deposits in the Lava Creek 

district formed during epithermal brecciation and silicification and have been exposed by younger high-angle faulting.

Exploration guides. Inasmuch as formation of polymetallic veins accompanied polymetallic replacement in 

chemically receptive rocks, the search for undiscovered 

veins in igneous rocks can best follow some of the same 

guidelines. Most orebodies in igneous rocks are likely to be 

at or near intersections of steep east-northeast- and northnorthwest-trending faults. The relative favorability of the 

two trends is unknown. If detailed mapping of the Challis 

Volcanic Group shows shallow, complex intrusive centers, 

exploration should be expanded to include intrusion margins 

as well as throughgoing steep faults. The coincidence of 

magnetic anomalies, leucocratic dikes, and propylitic or 

argillic alteration suggestive of hydrothermal circulation is 

highly favorable.

STRATABOUND REPLACEMENT DEPOSITS 

AND VEINS OF BARITE

Description. Stratabound barite is present as 

coarsely crystalline, light-colored, bedding-parallel lenses 

and stringers in both the Little Copper and Drummond
D22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Mine Limestone Members of the Copper Basin Formation. 

In many places, veins of barite cut across bedding to connect separate bedding-parallel lenses. Barite is present in 

several stratigraphic zones in a sequence approximately 

1,000 m thick (fig. 3). Argillaceous rocks in the upper 200 

m of the Little Copper Member host thin lenses and stringers of barite at many places between Garfield Canyon and 

Deep Gulch. In the vicinity of the Muldoon Barium Company Deep Gulch mine, several thick replacement deposits 

of barite are present in thin-bedded calcareous rocks at the 

contact of the Little Copper and Drummond Mine Limestone Members and in the lower 100 m of the Drummond 

Mine Limestone Member to the east. Silver-base metal 

veins are present in the same stratigraphic sequence as the 

barite replacement deposits but have not been observed in 

contact with them. Along Muldoon Ridge and to the east of 

the Eagle Bird mine, thin bedding-parallel stringers and 

lenses of barite are present in several stratigraphic horizons 

in thin-bedded calcareous rocks of the Drummond Mine 

Limestone Member. East of Muldoon Creek, thin and thick 

barite replacement deposits are within mixed calcareous 

and noncalcareous rocks in the uppermost 100 m of the 

Drummond Mine Limestone Member. These deposits are at 

approximately the same stratigraphic level as polymetallic 

replacement deposits at the Idaho Muldoon mine and crop 

out within 0.8 km, but no contact relations have been 

observed. Thin stringers and lenses of barite are in thinbedded calcareous and noncalcareous rocks at the Lucky 

Boy (east) prospects on the east side of Argosy Creek at 

approximately the same stratigraphic level. Most barite outcrops are weakly iron or copper stained, and analyses show 

the presence of a few percent zinc, lead, or copper, and 

traces of silver.

Type example. Deep Gulch mine, Little Wood River 

district

Other examples. Little Wood River district: Lucky 

Boy group (east) and Muldoon Creek prospects

Mineralogy, texture, and characteristics. Most 

replacement deposits and veins contain almost pure barite 

and only minor carbonate or clastic impurities; however, the 

deposits develop weak gossans that contain traces of sulfide 

minerals including pyrite, galena, sphalerite, chalcopyrite, 

and arsenopyrite. Oxidized minerals include limonite and 

malachite. The barite is coarse grained, milky white, and 

almost pure. Although beds adjacent to massive or weakly 

laminated barite are not obviously recrystallized, chemical 

analyses of them include significant barium. Measurements 

of stable isotopes that might pinpoint crystallization conditions of barite are not available.

Orebodies. Barite replacement deposits and veins 

are irregular. They form tabular seams and stringers that 

generally are parallel with bedding in enclosing calcareous 

or argillaceous host rocks but may abruptly cut across bedding or terminate. The barite bodies are from a few centimeters to 4.3 m in thickness, but most are less than 1 m

thick. Intervals in which closely spaced thin barite bodies 

are present may be as thick as 50 m. One replacement at the 

Deep Gulch mine may be 1.6 km long (Tuchek and Ridenour, 1981). The barite bodies generally are very pure, 

from 65 to 95 percent BaSO4, but most assays are greater 

than 90 percent (Tuchek and Ridenour, 1981). No estimates 

have been published of the total resources of barite on the 

Deep Gulch claims, but hundreds of thousands of tons of 

ore are present, and significant resources also are present in 

the claims east of Muldoon Creek.

Geochemical signature. The geochemical survey of 

the Boulder-Pioneer Wilderness Study Area (Simons, 1981) 

included the Deep Gulch, Muldoon Creek, and Argosy 

Creek areas in which barite replacements and veins crop out. 

Samples of sediments from streams draining these areas contained anomalous amounts of barium, as well as silver, lead, 

and zinc, elements that are associated with polymetallic 

replacement deposits and veins. Unmineralized rock samples also contained anomalous amounts of barium, and a few 

contained anomalous amounts of arsenic, beryllium, and 

manganese. More extensive sampling of unmineralized 

rocks from throughout the Little Copper and Drummond 

Mine Limestone Members indicates anomalous values of 

barium at all stratigraphic levels and locally anomalous values of arsenic and zinc. These latter analyses indicate that the 

average background level of barium for the Little Copper 

Member is 2,750 ppm and for the Drummond Mine Limestone Member 1,460 ppm (table 2).

Genesis and ore controls. The origin of the stratabound barite deposits is uncertain. Although the texture of 

the deposits and their local discordances with bedding indicate replacement of country rock sometime after lithification, it is possible that the deposits formed by 

recrystallization of original syngenetic barite and local 

remobilization into fractures. The intrinsic richness in barium of the Little Copper and the Drummond Mine Limestone Members of the Copper Basin Formation implies a 

formational control on barite distribution.

A recent review of stratiform barite in Paleozoic rocks 

of the Western United States (Poole, 1988) demonstrates that 

bedding-parallel barite deposits are common in rocks of 

Cambrian through Pennsylvanian age in the Antler orogenic 

belt in central Nevada. Barite deposits in Mississippian rocks 

are among the most easterly barite occurrences in Nevada, a 

tectonic setting similar to the Idaho occurrences. For the 

Nevada occurrences, barite deposition is thought to have 

occurred from the discharge of barium-bearing hydrothermal 

solutions at the seafloor in marine-basinal or continental-rise 

settings (Poole, 1988). The barite-rich chemical sediments 

were subsequently resedimented by turbidity currents. By 

analogy, deposits in the Muldoon-Star Hope area also may 

have formed syngenetically; however, their white, coarse 

crystallinity indicates that they were remobilized during 

postdepositional deformation and heating, probably during
MINERAL DEPOSITS OF THE MULDOON-STAR HOPE AREA D23

the same Cretaceous and Tertiary events that affected the 

nearby silver-base metal deposits.

Exploration guides. Although barite replacement 

deposits and veins are present in a stratigraphic interval of 

approximately 1,000 m, the thickest and most continuous 

known bodies are confined to the uppermost Little Copper 

and lowermost Drummond Mine Limestone Member in the 

vicinity of Deep Gulch and to the uppermost Drummond 

Mine Limestone Member between Muldoon and Argosy 

Creeks. No stratigraphically confined debris flows, slump 

features, or hydrothermal haloes that might indicate syndepositional fault systems or the location of exhalative vents have 

been recognized in either area; however, available information is only reconnaissance in scale. The recognition of such 

features would be a powerful aid in exploring for stratabound 

polymetallic deposits as well as barite deposits.

SUMMARY

Numerous mines in the Muldoon-Star Hope area of the 

southern Pioneer Mountains of south-central Idaho produced 

silver, lead, copper, zinc, gold, and barium from replacement 

and vein deposits in Mississippian and Devonian carbonate 

and clastic rocks; minor production also may have come 

from vein deposits in igneous rocks that intrude the sedimentary host rocks. The richest metal deposits were mined principally in the 1880's and 1890's and again in the 1940's and 

1950's. The richest barite bodies were mined only in the 

1950's. and 1960's. Some orebodies were not mined completely, and some known deposits were not explored thoroughly during the episodic activity.

Most mineral deposits are in micritic and argillaceous 

turbidites of the Mississippian Copper Basin Formation, 

which are designated the Drummond Mine Limestone and 

Little Copper Members, respectively. The dark, carbonaceous pelites of the lower member, the Little Copper, are 

significantly enriched in barium and boron and slightly 

enriched in cobalt, chromium, manganese, lead, and zinc. 

These argillaceous rocks contain bedding-parallel stringers 

and lenses of barite at several stratigraphic horizons and may 

have served as sources for some metals in mineral deposits 

in the overlying impure calcareous rocks of the Drummond 

Mine Limestone M ember. The Drummond Mine Limestone 

Member hosts numerous high-grade sulfide replacement 

bodies at several stratigraphic levels. These bodies generally 

are lenticular and of small tonnage; however, they are 

enriched where bedding-plane and crosscutting faults intersect. This apparent stratigraphic control may indicate some 

syngenetic metal deposition an implication that lower 

grade resources may be relatively widespread in the Copper 

Basin Formation.

Quartz monzonite stocks and related dike swarms of 

Eocene age intrude the Copper Basin Formation in many 

places. Mineral deposits are numerous around the

peripheries of several stocks; a crude zoning of sulfide minerals and metal values in these deposits indicates that the 

intrusions probably provided heat and fluids for metasomatism in bordering rocks. Where chemically reactive calcareous rocks are intruded, the presence of skarn deposits, as 

well as replacements, merits evaluation.

Significant resources of base- and precious-metals may 

remain in the Muldoon-Star Hope area. Although most individual occurrences are likely to be small, they may be of high 

grade and closely spaced. Favorable areas for additional 

exploration are indicated by the association of some or all of 

the following features: (1) calcareous or mixed calcareous 

and siliceous sedimentary host rocks; (2) Tertiary leucocratic igneous rocks; (3) carbonaceous pelitic source rocks 

having elevated metal values; (4) ground structurally prepared by steep east-northeast- or north-northwest-trending 

faults, particularly where associated with bedding-plane 

flexures or faults; and (5) widespread geochemical anomalies of precious- and base-metals and associated elements.

REFERENCES CITED

Anderson, A.L., and Wagner, W.R., 1946, A geological reconnaissance in the Little Wood River (Muldoon) district, Blaine 

County, Idaho: Idaho Bureau of Mines and Geology Pamphlet 

75, 22 p.

Bullock, J.H., Jr., Wilson, A.B., and Soulliere, S.J., 1990, Analytical results and sample locality maps of rock samples from the 

northwestern Idaho Falls and the northeastern Hailey I°x2° 

quadrangles, Idaho: U.S. Geological Survey Open-File Report 

90-645, 20 p.

Dover, J.H., 1981, Geology of the Boulder-Pioneer Wilderness 

Study Area, Blaine and Custer Counties, Idaho, in Mineral 

resources of the Boulder-Pioneer Wilderness Study Area, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 1497-A, p. 15-75.

Einaudi, M.T., Newberry, R.J., and Meinert, L.D., 1981, Skarn 

deposits, in Sims, P.K., and Skinner, B.J., eds., Economic 

Geology Seventy-fifth anniversary volume 1905-1980: El 

Paso, Texas, The Economic Geology Publishing Company, p. 

317-391.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Kleinkopf, M.D., Bankey, Vicki, and McCafferty, A.E., 1989, 

Gravity and magnetic anomaly patterns applied to mineral 

resource exploration, Hailey I°x2° quadrangle, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and Idaho Falls 

I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File 

Report 89-639, p. 26-32.

Kunkel, K.W., 1989, Geology and ore deposits of Garfield Canyon, Blaine County, Idaho, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2°
D24 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

quadrangles, Idaho: U.S. Geological Survey Open-File Report 

89-639, p. 92-94.

Mabey, D.R., 1981, Aeromagnetic studies of the Boulder-Pioneer 

Wilderness Study Area, Blaine and Custer Counties, Idaho: 

U.S. Geological Survey Bulletin 1497-B, p. 77-83.

Mosier, D.L., Morris, H.T., and Singer, D.A., 1986, Grade and tonnage model of polymetallic replacement deposits, in Cox, D.P., 

and Singer, D.A., eds.. Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 101-104.

Moye, F.J., Hackett, W.R., Blakley, J.D., and Snider, L.G., 1988, 

Regional geologic setting and volcanic stratigraphy of the 

Challis volcanic field, central Idaho, in Link, P.K., and Hackett, W.R., eds.. Guidebook to the geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 87-98.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-FF.

Moye, F.J., Sanford, R.F., Erdman, J.A., and Johnson, K.M., 1989, 

Volcanic-hosted and intrusion-related mineral deposits in the 

Hailey and western Idaho Falls quadrangles, Idaho, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 70-71.

Nelson, W.H., and Ross, C.P., 1969, Geologic map of the Mackay 

quadrangle, south-central Idaho: U.S. Geological Survey Miscellaneous Geologic Investigations Series Map 1-580, scale 

1:125,000.

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds., Paleozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 275-299.

Paull, R.A., and Gruber, D.P., 1977, Little Copper Formation New name for lowest formation of Mississippian Copper 

Basin Group, Pioneer Mountains, south-central Idaho: American Association of Petroleum Geologists Bulletin, v. 61, no. 2, 

p. 256-262.

Paull, R.A., Wolbrink, M.A., Volkmann, R.G., and Grover, R.L., 

1972, Stratigraphy of the Copper Basin Group, Pioneer Mountains, south-central Idaho: American Association of Petroleum 

Geologists Bulletin, v. 56, no. 8, p. 1370-1401.

Poole, F.G., 1988, Stratiform barite in Paleozoic rocks of the western United States: International Association on the Geology of 

Ore Deposits, Proceedings of the Seventh Quadrennial Symposium, p. 309-319.

Sanford, R.F., 1988, Challis Volcanics, Quaternary basalts, and a 

Quaternary lake, Little Wood River area, south-central Idaho: 

Geological Society of America Abstracts with Programs, v. 

20, p. 467.

Sanford, R.F., Whitney, H.A., McCafferty, A.E., and Gese, D.D., 

1989, Mineral resources of the Little Wood River Wilderness 

Study Area, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 1721-D, 15 p.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Simons, F.S., 1981, A geological and geochemical evaluation of the 

mineral resources of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho: U.S. Geological Survey Bulletin 1497-C, p. 85-180.

Skipp, Betty, 1989, Geologic map of Mackay 4 (Grouse) NW quadrangle, Butte and Custer Counties, Idaho: U.S. Geological Survey Open-File Report 89-142, scale 1:24,000.

Tuchek, E.T., and Ridenour, James, 1981, Economic appraisal of 

the Boulder-Pioneer Wilderness Study Area, Blaine and Custer 

Counties, Idaho, in Mineral resources of the Boulder-Pioneer 

Wilderness Study Area, Blaine and Custer Counties, Idaho: 

U.S. Geological Survey Bulletin 1497, p. 181-292.

Umpleby, J.B., 1917, Geology and ore deposits of the Mackay 

region, Idaho: U.S. Geological Survey Professional Paper 97, 

scale 1:375,000, 129 p.

Wells, M.W., 1983, Gold camps and silver cities (2nd ed.): Idaho 

Bureau of Mines and Geology Bulletin 22, 165 p.

Worl, R.G., Wilson, A.B., Smith, C.L., Kleinkopf, M.D., and 

Sykes, R.C., 1989, Mineral resource potential and geology of 

the Challis National Forest, Idaho: U.S. Geological Survey 

Bulletin 1873, 101 p.
Structural and Stratigraphic Setting of the 

Triumph Stratiform Zinc-Lead-Silver Deposit, 

Devonian Milligen Formation, Central Idaho

By Robert J.W. Turner and Bruce R. Otto

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-E

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995

CONTENTS

Abstract................................................................................................................................. El

Introduction.......................................................................................................................... 2

Geologic Setting................................................................................................................... 2

Regional Setting of the Milligen Formation, Central Idaho......................................... 2

Geologic Setting of the Milligen Formation, East Fork Wood River Valley............... 3

Geologic Setting of the Triumph Deposit..................................................................... 3

Milligen Formation............................................................................................................... 3

Lower Argillite Unit..................................................................................................... 5

Lucky Coin Limestone Facies...................................................................................... 5

Limestone Lithotypes........................................................................................... 7

Massive Carbonaceous Micrite .................................................................... 7

Thin- to Medium-Bedded Limestone and Argillite...................................... 7

Foliated Limestone and Marble.................................................................... 7

Diamictite............................................................................................................. 7

Volcanic Tuff Beds....................................................................................................... 9

Mafic Sills, Flows, and Dikes....................................................................................... 12

Cait Quartzite Facies .................................................................................................... 12

Triumph Argillite Unit.................................................................................................. 13

Independence Sandstone Unit...................................................................................... 14

Triumph Mine Area.............................................................................................. 15

East Fork Valley................................................................................................... 15

Wood River Formation......................................................................................................... 16

Granite Dikes........................................................................................................................ 16

Andesite Dikes...................................................................................................................... 16

Chain's Volcanic Group........................................................................................................ 16

Contact Metamorphism and Alteration in the Triumph Mine Area..................................... 16

Structure of the Triumph Mine Area.................................................................................... 17

General Structure.......................................................................................................... 17

Ductile Deformation..................................................................................................... 17

Thrust Fault Array........................................................................................................ 19

Independence Thrust Fault................................................................................... 20

Fissure Thrust Fault.............................................................................................. 20

Annie Thrust Fault................................................................................................ 20

Challenger Thrust Fault........................................................................................ 20

Low-Angle Normal Faults............................................................................................ 20

Triumph Shaft Fault............................................................................................. 21

Porphyry Peak-Wood River Faults...................................................................... 21

Challis Fault.......................................................................................................... 21

Steeply Dipping Oblique-Slip Faults............................................................................ 21

Triumph Orebody................................................................................................................. 22

History of Mine Development...................................................................................... 22

Structure and Stratigraphy of Stratiform Orebody....................................................... 22

Fissure Ore.................................................................................................................... 22
CONTENTS

Devonian Setting of Stratiform Sulfide Ores........................................................................ 23

Depositional Setting of Regional Milligen Strata......................................................... 23

Exhalative Origin and Depositional Setting of Stratiform Sulfide Body ..................... 24

East Fork Graben and Associated Stratiform Zinc-Lead Sulfide Deposits.................. 24

Paleotectonic Setting of the Milligen Formation.......................................................... 24

Deformation and Metamorphism of the Triumph Orebody.................................................. 25

Early Mississippian Antler Orogeny (Dl).................................................................... 25

Mesozoic Folding and Thrusting (D2).......................................................................... 25

Silver-Lead-Zinc Vein Mineralization and Contact Metamorphism............................ 25

Tertiary Extensional Faulting (D3)............................................................................... 26

References Cited................................................................................................................... 26

FIGURES

1-3. Maps showing geology of:

1. Wood River valley area ....................................................................................................................................... E4

2. Central part of Milligen belt within drainage of East Fork Wood River............................................................. 6

3. Triumph mine area............................................................................................................................................... 8

4. Structural cross sections, Triumph mine area............................................................................................................. 10

5. Diagram showing lithostratigraphic correlation of informal units in the Milligen Formation,

EastFork Wood River valley...................................................................................................................................... 11

6-8. Photographs of the Milligen Formation showing:

6. Rock units and alteration types............................................................................................................................ 12

7. Rock units............................................................................................................................................................ 14

8. Alteration types and structures............................................................................................................................ 18
Structural and Stratigraphic Setting of the

Triumph Stratiform Zinc-Lead-Silver Deposit,

Devonian Milligen Formation, Central Idaho

By Robert J.W. Turner 1 and Bruce R. Otto2

ABSTRACT

The Triumph mine in central Idaho was an important 

producer of lead, zinc, silver, and gold from 1927 to 1957. 

The bulk of base-rnetal production was from stratiform sediment-hosted zinc-lead siilfide bodies interbedded with carbonaceous argillite, limestone, chert, and diamictite of the 

Devonian Milligen Formation. Near the Triumph deposit, 

the Milligen Formation is divided into three informal units: 

lower argillite (black argillite, sandstone, chert), Triumph 

argillite (black argillite), and Independence sandstone (sandstone and limestone turbidite). Two intertonguing facies are 

in the transitional contact between the lower argillite and 

Triumph argillite units; these are the Lucky Coin limestone 

facies (limestone turbidite, black argillite, diamictite) and 

the Cait quartzite facies (quartzite turbidite, black argillite).

The Triumph stratiform sulfide bodies are within or at 

the top of the Lucky Coin limestone unit; structural complication makes their exact Stratigraphic position unclear. Near 

the Stratigraphic level of the stratiform sulfide bodies are 

limestone turbidite, black argillite, diamictite, thin tuff beds, 

and mafic sills. Diamictite is present as discontinuous lenses 

that are thickest near the stratiform sulfide body. The poorly 

sorted nature and similar composition of clasts to underlying 

Milligen strata suggest local resedimentation of Milligen 

strata. A contact rnetamorphic aureole extending northward 

from the Triumph mine area reflects a buried intrusion. Thinbedded calcareous units are altered to a quartz, tremolite, clinopyroxene, feldspar, and chloritoid assemblage, whereas 

mudrock units are variably hornfelsed to a quartz and biotite 

assemblage. Calc-silicate and hornfels alteration postdates 

cleavage-forming deformation and obscures sedimentary 

textures and cleavage.

'Geological Survey of Canada, 100 W. Fender Street, Vancouver, British Columbia V6B 1R8.

2333 Provident Drive, Boise, Idaho 83706.

In the Triumph mine area, Milligen strata generally 

strike N. 55°-65° W. and dip 30° SW. Milligen strata are 

deformed into tight to isoclinal folds associated with a variably developed early cleavage (Dl). Locally, the early cleavage is folded by east-vergent folds (D2). Southwest-dipping 

thrust faults repeat Milligen strata; some of these thrust 

faults host sheared lead-zinc-silver veins and are intruded by 

granitic and andesitic dikes. The Triumph stratiform orebody 

is immediately above the Fissure thrust fault in the overturned limb of an east-vergent anticline (Dl). Low-angle 

normal faults (D3) displace Milligen strata and thrust faults 

to the southwest and juxtapose Milligen rocks against structurally higher Pennsylvanian-Permian Wood River Formation and Eocene Challis Volcanic Group. Northeast-trending 

high-angle faults offset strata as young as the Challis Volcanic Group. Dl deformation may correlate with either the 

Early Mississippian Antler orogeny or the Sevier orogeny of 

Late Jurassic to Cretaceous age, D2 deformation with the 

Sevier orogeny, and D3 deformation with Eocene extension.

The Triumph stratiform sulfide body is composed of 

two types of ore known locally as complex ore and siliceous 

ore. Complex ore is laminated or banded fine-grained pyrite, 

sphalerite, and galena interbedded with carbonaceous pyritic 

chert, shale, and siltstone. Siliceous ore is mostly medium 

grained siderite, sphalerite, and galena interbedded with 

argillite or carbonate rocks. Along the Fissure thrust zone 

underlying the stratiform sulfide body, ore known as fissure 

ore is present as lenses and pods of sheared siderite-quartzsphalerite-galena within gouge and crushed rock.

Milligen strata record an anoxic depositional basin 

dominated by hemipelagic and pelagic sedimentation (lower 

argillite, Triumph argillite) punctuated by two periods of turbidite influx: a Middle to Late Devonian event composed of 

a carbonate channel complex (Lucky Coin limestone) to the 

west of a quartz-sand channel system (Cait quartzite), and a 

more widespread Late Devonian event of mixed siliciclastic 

and carbonate detritus (Independence sandstone). The

El
E2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Triumph stratiform sulfide body was deposited within the 

Lucky Coin carbonate fan and is associated with diamictite 

derived from the submarine scarp of an inferred syndepositional fault. This fault is invoked as the conduit for metalliferous fluids that exhaled on the seafloor to form the Triumph 

stratiform sulfide body.

INTRODUCTION

The Triumph zinc-lead-silver deposit, the major producer in the Warm Springs mining district of central Idaho, 

has long been recognized as mineralogically and texturally 

distinct from silver-lead vein deposits in the district 

(Umpleby and others, 1930; C.W. Merriam and C.N. Bozian, 

written commun., 1942; Anderson and others, 1950). Bedded ores of the Triumph deposit were interpreted by these 

authors as replacements of limestone beds adjacent to mineralizing fissures. More recently, the deposit has been reinterpreted as a syngenetic or syndiagenetic deposit coeval with 

deposition of host Devonian black shale and limestone 

(Smith, 1977; Hall, 1985). Herein, we describe the structure 

and stratigraphy of the Devonian Milligen Formation that 

hosts the Triumph deposit. Our studies are based on exploration field studies from 1983 to 1987 investigating Milligen 

strata east of Ketchum for Westley Mines Ltd., Mintek 

Resources Ltd., and Noranda Exploration Inc. (Otto, 1984; 

Turner and Michelson, 1984; Turner, 1985; Turner and others, 1986). Much of this work was in the Triumph mine area.

The Triumph deposit is in south-central Idaho, approximately 6 mi north of Hailey and 3 mi southeast of 

Ketchum on the north side of the East Fork of the Wood 

River (fig. 1). Our studies of the Triumph deposit included 

the area within the drainages of Triumph, North Star and 

Courier Gulches, and Independence Canyon, and we refer 

to this area as the Triumph mine area (fig. 2). Access to the 

area is by paved all-weather road up the East Fork valley 

and then by gravel road to the North Star mine in North 

Star Gulch and to the old Triumph and Independence mines 

via Triumph Gulch. There is also access to the Independence mine area by gravel road up Independence Canyon 

from the Elkhorn resort area. Elevations within the mine 

area vary from 6,000 ft along the East Fork valley to ridges 

more than 8,000 ft high on the north side of the area. The 

steep valley sides are mostly sage and grass covered; small 

groves of aspen are in some valley bottoms.

The surface outcrop of the Triumph orebody in North 

Star Gulch was discovered in 1881. Mining in the area began 

at the Independence mine in 1885. The Triumph mine produced from 1927 until 1957. Between 1936 and 1945 the Triumph mine produced about 100,000 tons per year and was 

the second largest silver producer in Idaho. Production 

records are incomplete, but from 1936 to 1948 the mine produced 1.06 million tons, and between 1941 and 1948 production averaged 6.57 percent zinc, 4.02 percent lead, 7.8

ounces of silver per ton, and 0.071 ounces of gold per ton 

(C.W. Merriam and C.N. Bozian, written commun., 1942).

Early access to the Triumph deposit was through the 

North Star mine at the head of North Star Gulch and a 700- 

foot-deep shaft of the "Old Triumph mine" in eastern part 

of upper Triumph Gulch (fig. 3). The mine was worked to 

the 900-foot level (level elevations are the distance below 

the collar of the shaft). Ore was taken by aerial tram to the 

Gimlet railway siding in the Wood River valley, 5 mi to the 

west. In 1943, a 6,500-foot-long haulage tunnel (Plummer 

tunnel) was completed connecting the 700-foot level of the 

mine with the North Star mill in the East Fork valley near 

the village of Triumph (fig. 3). The Plummer tunnel also 

provided access to the lower part of the Independence 

mine. By the 1950's, the high-grade bedded ores were 

exhausted, and work concentrated on developing reserves 

within the Fissure shear zone in the lower levels of the 

northwestern part of the mine.

The possibility of large additional base-metal reserves 

at the Triumph mine followed the recognition by Clyde 

Smith that the Triumph deposit was a member of the stratiform sediment-hosted lead-zinc class of ore deposits. Subsequent surface drill programs were conducted by Bear Creek 

Mining Company in 1978-79, Venture West Minerals in 

1981, and Getty Resources in 1984.

Acknowledgments. We would like to thank Victor 

Jones of Westley Mines and Rupert House of the Triumph 

Mining Company for permission to publish this study of the 

Triumph mine area. This work was conducted under the 

direction of Dr. Clyde Smith of Westley Mines Ltd., who 

first recognized the syngenetic nature of the Triumph deposit 

and who developed a three-dimensional model of the Triumph orebody from mine data. We thank Clyde for his 

insight and continued encouragement. We were ably assisted 

in the field by Carl Michelson, Dave Smith, Mary Fitch, Ken 

Loos, Pat Okita, and Greg Kuzma. James W. Whipple, Don 

Murphy, Charlie Jefferson, and Clyde Smith provided valuable critiques of the paper that considerably improved its 

content and style. This paper is GSC Contribution 49790.

GEOLOGIC SETTING

REGIONAL SETTING OF THE MILLIGEN 

FORMATION, CENTRAL IDAHO

Black argillite and interbedded limestone, sandstone, 

and chert of the Lower to Upper Devonian Milligen Formation is exposed east of the Wood River valley and U.S. Highway 75 in a belt 35 mi long and as wide as 6 mi (fig. 1). The 

exposures lie between Cretaceous intrusive rocks of the 

Idaho batholith to the west and high-grade metamorphic and 

intrusive rocks of the Eocene Pioneer Mountains core complex to the east. Milligen strata are in thrust contact with the 

Lower and Upper Mississippian Copper Basin Formation to
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E3

the east and are structurally overlain by Middle Pennsylvanian to Lower Permian Wood River Formation and Eocene 

Challis Volcanic Group to the west. This fault-bound package of Milligen strata was named the Pioneer allochthon by 

Dover (1980).

The Milligen Formation, along with black argillite, 

chert, and siltstone of the Lower Ordovician to Middle Silurian Phi Kappa and Middle Silurian Trail Creek Formations and an unnamed Silurian and Devonian unit, is 

interpreted as part of the Roberts Mountains allochthon, a 

sequence of outer continental margin strata thrust eastward 

over the continental margin during the Early Mississippian 

Antler orogeny (Roberts and Thomasson, 1964; Dover, 

1980). The sandstone turbidite facies of the Mississippian 

Copper Basin Formation that is exposed east of the Pioneer 

Mountains core complex is inferred to have been derived 

from the exposed Roberts Mountains allochthon ("Antler 

highlands") to the west (Nilsen, 1977; Poole and Sandberg, 

1977). A phyllitic fabric in some clasts within the Copper 

Basin Formation suggests pre-Mississippian deformation 

within the strata of the Roberts Mountains allochthon 

(Davis, 1984). Pennsylvanian and Permian Wood River 

Formation limestone, siltstone, shale, sandstone, and basal 

chert conglomerate are inferred to represent the post-Antler 

overlap assemblage (Poole and Sandberg, 1977). To the 

north of the Milligen belt rocks of the Challis volcanic field 

of Eocene age are widespread.

Paleozoic strata are weakly metamorphosed, folded by 

north- to northwest-trending, east-vergent folds, and cut by 

east-vergent thrust faults of Mesozoic age (Dover, 1980, 

1981). These Mesozoic structures are offset by low-angle 

extensional faults related to development of the Eocene Pioneer Mountains core complex. Within the Pioneer Mountains, Precambrian and Ordovician metasedimentary rocks 

and Cretaceous and Eocene plutonic rocks are separated by 

a low-angle fault from the overlying Paleozoic sedimentary 

rocks and Eocene volcanic rocks (Wust, 1986; O'Neill and 

Pavlis, 1988). The direction of displacement of upper plate 

rocks is N. 65° W. (Wust, 1986).

Zinc-lead-silver deposits and prospects in the Wood 

River area of the Warm Springs mining district are hosted by 

the Devonian Milligen Formation and, subordinately, by 

Cretaceous and Tertiary intrusive rocks and the Pennsylvanian and Permian Wood River Formation. Past production 

history and geologic setting of these deposits has been 

described by various authors (Umpleby and others, 1930; 

Anderson and others, 1950; Hall, Rye, and Doe, 1978).

GEOLOGIC SETTING OF THE

MILLIGEN FORMATION, EAST FORK

WOOD RIVER VALLEY

The drainage area of the East Fork Wood River is 

underlain primarily by faulted and folded Milligen strata. 

On the western margin of the Milligen belt, near the

Triumph mine, an overturned sequence of Milligen strata is 

repeated by northwest-trending thrust faults. Both lower 

and upper parts of the Milligen Formation are exposed. To 

the east, a central belt of open, east-vergent folds exposes 

only the upper part of the Milligen Formation, and thrust 

faults have not been recognized. On the eastern margin of 

the Milligen belt, Milligen strata are in fault contact with 

Wood River Formation.

Within the Milligen belt, a regionally extensive lowangle fault or series of faults separates the Milligen strata 

into lower and upper structural plates (fig. 2). This fault or 

fault array offsets earlier northwest-trending thrust and folds 

and can be mapped throughout an area of 30^40 mi2. Rocks 

of the lower plate crop out throughout much of the East Fork 

valley; upper plate strata cap high northeast-trending ridges 

of the East Fork valley, creating a map pattern of elongate 

northeast-trending klippe of upper plate Milligen strata. 

Klippe of Wood River Formation and Challis Volcanic 

Group overlie Milligen strata of the upper plate above lowangle normal faults.

GEOLOGIC SETTING OF THE 

TRIUMPH DEPOSIT

The Triumph stratiform lead-zinc-silver-gold deposit is 

within the Milligen Formation along the western margin of 

the outcrop belt of Milligen strata. Near the Triumph mine, 

the Milligen Formation is a structurally complex sequence of 

argillite, limestone, and sandstone (figs. 2, 3). Stratiform 

lead-zinc-silver ore of the Triumph mine is interbedded with 

carbonaceous shale, limestone, and diamictite. The Milligen 

strata strike northwest, dip southwest, and are folded, 

cleaved, and repeated by a series of southwest-dipping thrust 

faults (figs. 3, 4). These thrust faults locally host sheared 

lead-zinc-silver-bearing veins. Local calc-silicate alteration 

and silicification of calcareous beds and induration of fissile 

shales to nonfissile argillite within Milligen strata is interpreted to represent the metamorphic aureole of an intrusive 

body that underlies the Triumph mine area (Hall, Batchelder, 

and Tschanz, 1978). Low-angle normal faults offset Milligen strata and thrust faults and juxtapose Milligen rocks 

against younger limestone, quartzite, and conglomerate of 

the Wood River Formation and andesite of the Challis Volcanics. Klippe of Wood River Formation cap some of the 

higher ridges in the area. West of the Triumph deposit, the 

Milligen Formation is structurally overlain by rocks of the 

Challis Volcanic Group.

MILLIGEN FORMATION

Umpleby and others (1930) gave the name Milligen 

Formation to weakly metamorphosed dark-colored argillaceous rocks of supposed Devonian age in the Wood River
E4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°30' 114°00'

44°45' 

44°30' 

WILDHORSE 

DETACHMENT FAULT

PIONEER MOUNTAINS 

CORE COMPLEX

Figure 1 (above and facing column). Geologic map of the Wood River valley area, central Idaho, showing location of the Triumph 

mine and other lead-zinc-silver mines and prospects within the Milligen Formation. Area of figure 2 is also shown. Modified from Link 

and Mahoney( 1989).
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E5

EXPLANATION

Challis Volcanic Group (Tertiary)

Granodiorite and granite (Tertiary to Cretaceous)

Wood River Formation and Dollarhide Formation 

(Permian-Pennsylvanian)

Copper Basin Formation (Mississippian) 

Milligen Formation (Devonian)

Phi Kappa and Trail Creek Formations and unamed 

Silurian-Devonian rocks (Devonian to Ordovican)

 Contact Approximately located

* Lead-zinc mine or prospect, labeled or referred to by number

1. Independence mine

2. Baltimore mine

3. Parker mine

4. Cait prospect

5. Mascot mine

6. North Star mine

7. Minnie Moore mine

8. Snoose mine

9. Silver Star Queen mine

area. The formation is present as a fault-bound allochthon 

(Dover, 1980), and stratigraphic contacts between the Milligen Formation and older or younger strata have not been recognized. The internal stratigraphy of the Milligen Formation 

is poorly understood due to structural complexity, poor 

exposure of rock units, and paucity of fossils. Umpleby and 

others (1930) named the formation after strata exposed in 

Milligan Gulch, about half a mile east of the Triumph mine. 

Sandberg and others (1975) divided the Milligen Formation 

into a thick lower argillite member containing thin quartzite 

beds (Lower and Middle Devonian) and a thin upper calcareous turbidite member (Upper Devonian). The age determination was based on conodont collections from several 

measured sections including one in Milligan Gulch.

Otto and Turner (1987) and Turner and Otto (1988) 

recognized five lithostratigraphic units within Milligen 

strata exposed in the East Fork Wood River drainage. 

These were informally named, in ascending order, (1) 

lower argillite, (2) Lucky Coin limestone, (3) Cait quartzite, (4) Triumph argillite, and (5) Independence sandstone. 

As noted in this report, however, the Lucky Coin limestone 

and Cait quartzite are locally developed lithofacies and not 

always piesent (fig. 5). Where the Lucky Coin limestone 

and Cait quartzite are present, they can have an intertonguing relationship with the Triumph argillite and lower argillite. Therefore, we divide these lithostratigraphic units into 

three informal units (lower argillite, Triumph argillite, 

Independence sandstone) and two intertonguing facies 

(Lucky Coin limestone, Cait quartzite).

Stratiform sulfide ore of the Triumph mine is interbedded with limestone and argillite interpreted as an intertonguing zone of Lucky Coin limestone and Triumph argillite;

however, structural complications obscure the exact stratigraphic position of the stratiform sulfide orebody.

LOWER ARGILLITE UNIT

The lower argillite unit consists of siliceous black argillite and minor interbedded sandstone and chert. The lower 

argillite is best exposed near the Triumph mine where it 

crops out as resistant ribs between Triumph and North Star 

gulches (figs. 3, 4C). The argillite is massive and characterized by a well-developed southwest-dipping cleavage. Bedding is rarely preserved and typically transposed by 

cleavage. White chert beds or tremolitic sandstone beds are 

present locally. The base of the lower argillite is everywhere 

faulted, and a stratigraphic contact with older strata has not 

been observed. Our understanding of the lower argillite is 

hampered by strong cleavage development and limited area 

of exposure. The lower argillite is distinguished from the 

Triumph argillite by stratigraphic position with respect to the 

Lucky Coin limestone or Cait quartzite and by a lack of sooty 

organic-rich argillite.

Drilling at the Cait property in eastern East Fork valley 

(fig. 1) intersected a thick sequence of thin-bedded calcareous to noncalcareous, fine-grained sandstone, black argillite, 

and thin tuff beds below the Lucky Coin limestone (Otto and 

Turner, 1987). This unit is interpreted as a sand-rich facies of 

the lower argillite.

LUCKY COIN LIMESTONE FACIES

The Lucky Coin limestone facies is named after wellexposed interbedded limestone and black argillite near the 

Lucky Coin adit in the lower part of Independence Canyon 

(fig. 3). In Independence Canyon, the structural thickness of 

the Lucky Coin limestone exceeds 1,000 ft. Interbedded 

limestone and argillite below the Fissure fault and exposed 

on the ridge east of the North Star mine is at least 700 ft 

thick. Above the Fissure fault, limestone beds are more 

deformed and some are foliated marbles, precluding an estimate of original stratigraphic thickness.

Early workers in the Triumph mine recognized a lower 

and upper tremolitic limestone and noted their close association with the lead-zinc-silver ores (C.W. Merriam and 

C.N. Bozian, written commun., 1942). Kiilsgaard (in 

Anderson and others, 1950) mapped three discontinuous 

northwest-trending, southwest-dipping limestone units over 

a distance of 4 mi between the Triumph and Parker mines. 

Kiilsgaard's threefold subdivision was defined in Independence Canyon, a section we recognize as overturned and 

cut by faults that repeat the limestone units. Hence
E6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

44°40' 

Tc 

OLD TRIUMPH MINE

Area of figure 3

EXPLANATION

Challis Volcanic Group (Eocene) Andesite to 

rhyodacite flows, breccia, and tuff

Wood River Formation (Lower Permian to 

Middle Pennsylvanian) Sandstone, 

siltstone, bioclastic limestone, chert, and 

conglomerate

Milligen Formation (Upper to Lower Devonian)

Milligen Formation, undifferentiated

Independence sandstone unit Sandstone, 

argillite, and limestone

Triumph argillite unit Siliceous argillite and (or) 

carbonaceous argillite, sandstone, limestone, 

and diamictite

Cait quartzite facies Interbedded quartzite 

and argillite

Lucky Coin limestone facies Interbedded 

limestone and argillite

Lower argillite unit Siliceous argillite and 

chert and locally thin bedded sandstone

Contact Approximately located

Normal fault, low angle Sawteeth on 

downthrown side

Normal fault, high angle Ball and bar on 

downthrown side; dashed where inferred

Thrust fault Sawteeth on upper plate; 

dashed where inferred

Fold trace of synform 

Fold trace of antiform

Lead-zinc mine or prospect, labeled or 

referred to by number

1. Independence mine

2. Baltimore mine

3. Parker mine

4. Cait prospect

Line of lithostratigraphic correlation shown in 

figure 5 Locations of stratigraphic sections 

are also shown

Figure 2. Geologic map of the central part of the Milligen belt within the drainage area of the East Fork Wood River, Idaho. Location 

of map area is shown in figure 1.
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E7

Kiilsgaard's "Lower Limestone" lies stratigraphically 

above his "Middle Limestone" unit, and his "Upper Limestone" is a fault repetition of his "Lower Limestone" (fig. 

3). The disappearance and reappearance of individual limestone units along strike reflects offset by low-angle normal 

faults, as in the gulch immediately north of the Triumph 

shaft (compare Kiilsgaard, fig. 16, with fig. 3, this paper).

We apply the term Lucky Coin limestone throughout 

the East Fork Wood River valley to a sequence of interbedded limestone and argillite underlying and interfingering 

with the Triumph argillite and interfingering with the Cait 

quartzite (fig. 5). On the Cait property in eastern East Fork 

valley, the Lucky Coin limestone is a 5-20-foot-thick bed 

overlying a thin bed of coarse-grained quartzite (Cait quartzite) and within a sequence of argillite.

LIMESTONE LITHOTYPES

The Lucky Coin limestone in the Triumph area is composed of three limestone lithotypes: (1) massive carbonaceous micrite, (2) thin- to medium-bedded limestone and 

argillite, and (3) foliated limestone or marble.

MASSIVE CARBONACEOUS MICRITE

Massive dark-gray-weathering carbonaceous micrite 

beds as thick as 40 ft are exposed in the lower part of Independence Canyon, east of the Triumph shaft, and in upper 

North Star Gulch (fig. 3). In Independence Canyon, angular 

fragments of mudstone as much as 2 ft in diameter within 

the micrite suggest a sediment gravity flow origin (Bouma, 

1962). Thin interbeds of mud-chip bioclastic conglomerate 

suggest that the thick micrite units represent deposition of 

several gravity flow events that deposited a basal lag overlain by carbonate mud. Micrite is composed of fine-grained 

calcite and an abundance of disseminated micron-size carbonaceous grains. Angular detrital grains of quartz, plagioclase, potassium feldspar, and calcite as much as 0.2 mm in 

diameter are abundant in some beds. Scattered skeletal 

poikioblastic diamond-shaped tremolite and lathlike porphyroblastic chloritoid as long as 2 mm are in micritic 

limestone beds exposed in Triumph and North Star Gulches 

(fig- 6A).

siltite, commonly having a coarse basal arenite lamination 

(Tbde turbidites), are as thick as 2 ft. These limestone beds 

are composed of carbonate and quartz grains in a lime silt 

and mud matrix.

Units as thick as 50 ft of thin-bedded micritic limestone crop out below the uppermost portal (Boiler level) at 

the North Star mine. These limestone beds are in the footwall of the Fissure fault and are composed of a basal lamina of medium-grained quartz as thick as 5 mm overlain by 

massive micrite.

A 150-foot-thick overturned and faulted section of 

Lucky Coin limestone was intersected below the Fissure 

fault (between 238 and 502 ft, fig. 4) in drill hole 81-2, 400 

ft northeast of the Triumph mine shaft (Old Triumph mine in 

fig. 3). Three sequences, each as much as 50 ft thick, are 

composed of thinning-upward sandstone beds interbedded 

with carbonaceous chert and argillite. Sandstone beds, commonly 2-10 in. thick but as thick as 7 ft, have load cast bases 

and minor cross lamination and are interpreted to be Tabd, 

Tad, and Tj,d turbidites. These sandstone beds, metamorphosed to a calc-silicate assemblage and referred to as "footwall quartzites" by the miners, are described by Kiilsgaard 

(in Anderson, 1950) as pyritic, fine-grained calcareous 

quartzite 750 ft thick or more.

FOLIATED LIMESTONE AND MARBLE

Foliated, banded marble and limestone units are in the 

lower part of Independence Canyon, west and north of the 

Triumph shaft along the road to Independence Canyon, and 

on the ridge east of the lower part of Triumph Gulch. Banded 

marble units are composed of medium- to coarse-grained 

calcite and concordant and discordant lenses, pods, and veins 

of coarser calcite and quartz. Some marble units are composed of cigar-shaped calcite grains elongate to the northeast 

that suggest the principal stretching direction during deformation was in this direction. Banded marble units are transitional; a striped limestone unit is composed of an 

anastomosing network of pale-colored coarse-grained calcite bands that cut dark-colored fine-grained limestone. 

Where foliated limestone exhibits calc-silicate alteration, 

delicate porphyroblasts of tremolite and chloritoid extend 

undeformed across foliation, indicating calc-silicate mineral 

growth after deformation (fig. 6A).

THIN- TO MEDIUM-BEDDED LIMESTONE AND ARGILLITE

An overturned sequence of rhythmically interbedded 

medium-bedded limestone and calcareous and noncalcareous shale and argillite underlies the ridge east of North Star 

Gulch and extends west to the Fissure fault in the North Star 

mine area (figs. 3, 4A). This limestone sequence is well 

exposed on the access road in upper North Star Gulch (fig. 

7A). Massive to plane-laminated limestone arenite and

DIAMICTITE

Diamictite in the Triumph area is present as discontinuous lenses within the Lucky Coin limestone and lower part 

of the Triumph argillite (figs. 3, 5). Diamictite units are as 

thick as 50 ft and composed of polymict fragments within a 

silty mud matrix. Clasts are subangular to subrounded, typically less than an inch in diameter (fig. 7C), and composed
E8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

R18E

Figure 3 (above and facing column). Generalized geologic map of Triumph mine area, Idaho. Location of map area is shown in figure 

2. Numbers refer to mines or prospects listed in figure I. Lines of sections shown in figure 5 are also indicated. Base is U.S. Geological 

Survey Sun Valley 7.5-minute topographic quadangle (1967).
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E9

EXPLANATION

Challis Volcanic Group (Eocene) Andesite porphyry lava 

flows

Wood River Formation (Lower Permian to Middle 

Pennsylvanian) Quartzite, bioclastic limestone, and conglomerate 

Milligen Formation (Upper to Lower Devonian)

Independence sandstone unit Sandstone and argillite

Triumph argillite unit Siliceous and (or) carbonaceous argillite, 

sandstone, and limestone

Cait quartzite facies Argillite and quartzite 

Diamictite Mixed fragments in argillaceous matrix 

Bedded gossan Bedded sulfide, ferroan carbonate 

Bedded siliceous exhalite

Lucky Coin limestone facies Limestone and argillite, locally 

strongly foliated

Lower argillite unit Siliceous argillite and chert

 Contact Approximately located

A /'A Low-angle normal fault Showing dip; sawteeth on downdropped side

 * * Thrust fault Sawteeth on upper plate

Strike and dip of beds 

35X Upright

4^ Overturned

3 3V Strike and dip of foliation

73^ Strike and dip of flow banding

 Diamond drill-hole collar

a Mine shaft

v- Adit

intersected seventeen feet of diamictite at the stratigraphic 

base of the overturned stratiform sulfide body (fig. 4). Fragments in this diamictite are predominantly calcite cemented 

quartz sandstone fragments and minor rounded black chert 

fragments floating within a calcareous mud matrix. About 

1,500 ft southeast of the North Star mine area, and just above 

the Annie thrust fault (fig. 3), diamictite composed of quartzite and sandstone fragments in an argillite matrix overlies 

with angular discordance bedded argillite and quartzite. 

Diamictite interbedded with limestone, carbonaceous argillite, hydrothermal chert, and tremolitic limestone is exposed 

in a trench in the uppermost part of Triumph Gulch near the 

faulted contact between the Milligen Formation and Challis 

Volcanic Group.

Special significance is attached to diamictite because it 

is present at or near the stratigraphic level of the stratiform 

sulfide body, is thickest near the orebody, and may be related 

to syndepositional faults that localized ore formation. The 

poorly sorted nature and restricted composition of clasts suggest local resedimentation of Milligen sediments as slumps 

or debris flows, possibly related to the submarine scarps of 

syndepositional faults. Similar diamictite units are associated with other stratiform sediment-hosted zinc-lead deposits (see, for example, Abbott and Turner, 1990; Turner, 

1990). These diamictites are interpreted to represent aprons 

of seafloor debris shed from syndepositional faults that were 

also conduits for metalliferous hydrothermal fluids that 

formed the sulfide deposits.

VOLCANIC TUFF BEDS

of clasts of calcite-cemented quartz sandstone, tremolitic 

sandstone, argillite, quartz siltstone, feldspar-sericite rock, 

black chert, and white chert. The lithology of clasts is similar 

to strata in the Lucky Coin limestone and lower argillite. 

Quartz-tremolite-clinopyroxene fragments are interpreted as 

altered calcareous quartz sandstone fragments of the Lucky 

Coin limestone. Plagioclase-sericite-quartz clasts may represent altered mafic sills or tuffs.

Diamictite lenses are immediately below the stratigraphic level of stratiform sulfides of the Triumph mine (fig. 

5). A diamictite more than 20 ft thick is exposed in uppermost North Star Gulch. Based on drill core, this diamictite 

bed thins rapidly to the south, and a stratigraphically lower 

diamictite is interbedded with chert and limestone (fig. 5). 

The lower diamictite is composed of fragments of tremolitic 

sandstone, argillite, and minor pale chert. Twelve hundred 

feet north northwest of the Triumph shaft, drill hole 81-1

Thin, pale limonitic beds as much as an inch or so thick 

are exposed as interbeds within the Lucky Coin limestone on 

the east slope of North Star Gulch. These beds are distinct 

from interbedded quartzose siltstone and sandstone and are 

interpreted to be volcanic tuffs because of the abundance of 

plagioclase and potassium feldspar, sericite, and pyrite, the 

presence of minor amounts of chlorite, rutile, and tourmaline, and the absence of carbonaceous matter.

Tuff beds as thick as 1 ft within the lower argillite have 

been intersected in drill core at the Cait prospect in the eastern East Fork valley (Turner and Otto, 1988). These palegreen tuff beds are banded to laminated, contain argillite 

fragments and disseminated pyrite, chalcopyrite, and 

sphalerite, and are folded by Fl folds. They are composed of 

an intergrowth of sericite and felsitic plagioclase and lesser 

amounts of quartz, tourmaline, and altered glass. No primary 

volcanic textures were recognized.
E10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

SW NE

B1"

EXPLANATION

Dcq

Challis Volcanic Group (Eocene) Andesite porphyry 

lava flows

Milligen Formation (Upper to Lower Devonian) 

Independence sandstone unit Sandstone and argillite

Triumph argillite unit Siliceous and (or) carbonaceous 

argillite, sandstone, and limestone

Cait quartzite facies Argillite and quartzite 

Diamictite Mixed fragments in argillaceous matrix 

Bedded gossan Bedded sulfide, ferroan carbonate 

Bedded siliceous exhalite

Lucky Coin limestone facies Limestone and argillite, 

locally strongly foliated

Lower argillite unit Siliceous argillite and chert

Contact Queried (?) where uncertain

~= Normal fault Dotted where projected; arrows indicate 

direction of movement

^ Thrust fault Dotted where projected; arrows indicate 

direction of movement

<= SOD Mine working Number indicates depth (in feet) below 

collar of shaft

Figure 4. Structural cross sections, Triumph mine area, Idaho. Lines of section are shown in figure 3. A A', North of Triumph mine (Independence mine area). B-B', B"-B'", Across the northern part of Triumph mine (Triumph shaft area). C-C', Through the southern Triumph 

mine (North Star mine area).
w

FEET INDEPENDENCE 

2,000- CANYON

MILLIGEN 

GULCH SAWMILL 

GULCH

1,600 

CAIT 

PROSPECT

1,200 

800 

400 

0 

SANDSTONE

Early

Middle

Devonian

EXPLANATIONStratiform sulfide Quartzite, coarse-grained 

Diamictite Carbonaceous chert, 

local white chert

Quartz sandstone, siltstone; 

locally dolomitic

Limestone, thick-bedded, 

carbonaceous, micritic

ositional 

;ault

Carbonaceous argillite and 

chert, phyllitic shale

Limestone, thin-bedded, 

silty

Mafic sill, biotite-amphibolebearing

Fossil locality

Figure 5. Lithostratigraphic correlation of informal units in the Milligen Formation, East Fork Wood River valley, Idaho. No horizontal scale implied. Dark shaded areas 

indicate extent of diamictite. Locations of stratigraphic sections are shown in figure 2.

O 70

N

n

wD 

c/3

r 

I

D W3!/3

H
E12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 6 (above and facing page). Rock units and alteration types in the Milligen Formation, Triumph mine area, Idaho. A, Lucky Coin 

limestone facies. Randomly oriented tremolite grains (dark gray) in micritic limestone, Triumph mill area. Pen is shown for scale. B, Independence sandstone unit. Thin-bedded, fine-grained sandstone and argillite with wavy parallel laminations, upper part of Courier Gulch area. 

Hammer is shown for scale. C, Independence sandstone unit. Tremolitic calc-silicate alteration (white) as pods, bands, and discordant zones 

along fractures within calc-turbidite bed (gray), upper Independence Canyon. Pencil is shown for scale. D, Independence sandstone unit. 

Zones of silicification (dark gray) associated with thin quartz veins (white) cut calc-silicate-altered, thick-bedded, calcareous sandstone, 

Independence Canyon. Pencil is shown for scale.

MAFIC SILLS, FLOWS, AND DIKES

Concordant and discordant mafic igneous units as 

thick as 4 ft are present within Lucky Coin limestone strata 

on the east slope of North Star Gulch (fig. ID). Mafic igneous dikes contain hornblende phenocrysts and plagioclase 

and hornblende microlites in a carbonate-altered matrix and 

minor amygdules filled with sparry carbonate, quartz, 

albite, and chlorite. An assemblage of sericite, carbonate, 

quartz, pyrite, leucoxene, and rutile is present in sheared 

dike margins. Concordant mafic units commonly display 

perlitic devitrification textures along one or both of their 

contacts, lack evidence of contact hornfels in adjacent 

strata, and may represent volcanic flows or sills. Some 

mafic units are folded and cut by cleavage and predate at

least Mesozoic deformation. If these units are sills, the 

presence of devitrified glassy margins may indicate 

emplacement into wet unlithified sediments and hence a 

Devonian age. The occurrence of thin tuff beds in this same 

section lends support for an interpreted Devonian age of 

these mafic rocks.

CAIT QUARTZITE FACIES

The Cait quartzite facies was named for excellent 

exposures of coarse-grained, dark-gray quartzite and interbedded black argillite on the Cait lode mining claims in and 

near Sawmill Gulch east of the Triumph mine (fig. 2). The 

quartzite is composed of well-rounded quartz grains as
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E13

much as 1 mm in diameter cemented by quartz. The thickness of the Cait quartzite varies markedly in the East Fork 

valley area. At the Cait property the Cait quartzite is a single discontinuous bed less than 3 ft thick, whereas in the 

Sawmill Gulch area individual quartzite beds are more than 

30 ft thick and the sequence is more than 300 ft thick.

In the Triumph area, the Cait quartzite is composed of 

black argillite and subordinate thin quartzite beds; it is thickest to the south and east in the area of Courier Gulch (fig. 3). 

On the ridge east of Courier Gulch, an overturned Cait 

quartzite sequence is composed of interbedded black carbonaceous argillite, quartzite beds as thick as 3 ft, minor chert 

conglomerate, and limestone. Flute marks on the base of 

some quartzite beds suggest transport to the southwest as turbidity flows. The Cait quartzite thins rapidly to the north and 

west toward the Triumph mine area where it intertongues 

with tremolitic sandstone and limestone of the Lucky Coin 

limestone, massive sulfide, and diamictite (fig. 5). The Cait 

quartzite probably pinches out northwest of the Triumph 

shaft, possibly reflecting a channel margin controlled by 

syndepositional faults (fig. 5).

TRIUMPH ARGILLITE UNIT

The Triumph argillite unit is a black argillite unit 

between the Lucky Coin limestone and younger Independence sandstone units. The Triumph argillite includes black 

argillite, carbonaceous siliceous shale, chert, limestone and 

tremolitic calc-silicate beds, and diamictite lenses (fig. IB). 

The Triumph argillite is exposed in a northwest-trending belt 

in the area of the Triumph mine (fig. 5). Poor exposure and 

structural complexity limit our understanding of the internal 

stratigraphy and true thickness of the Triumph argillite. The 

best stratigraphic section of the Triumph argillite is exposed 

along an old road cut at the base of the south slope of Independence Canyon. Here the Triumph argillite is about 500 ft 

thick and conformably underlies the Lucky Coin limestone 

and overlies the Independence sandstone.

The dominant lithology of the member is a black, massive, weakly cleaved, siliceous argillite. In thin section, 

argillite laminae commonly have a microlenticular texture of 

aligned 0.05-0.1-millimeter-thick lenticles of turbid, cryptocrystalline chert rimmed by abundant carbonaceous material. Less common is microlaminated argillite composed of
E14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 7 (above and facing page). Rock units of the Milligen Formation, Triumph mine area, Idaho. A, Lucky Coin limestone facies. 

Overturned interbedded limestone and calcareous argillite, North Star mine portal access road. Hammer is shown or scale. B, Triumph argillite unit. Thin-bedded black chert, North Star portal area. Hammer is shown for scale. C, Diamictite composed of mixed fragments of calcareous sandstone, sandstone and chert. Cait property, East Fork valley. Coin is shown for scale. D, Mafic sill within overturned sequence 

of calcareous turbidites. Lucky Coin limestone facies, North Star mine portal access road. Hammer is shown for scale.

interlaminated carbonaceous material and chert or quartzfeldspar-silt.

The lower part of the Triumph argillite contains very 

carbonaceous argillite and chert, lenses of diamictite, minor 

white, gray, and buff chert beds, and the stratiform sulfide 

body of the Triumph mine. The lower part is exposed at the 

upper portal of the North Star mine where it is interbedded 

with bedded gossan of the Triumph orebody, near the pass 

between Independence Canyon and Triumph Gulch, northwest of the Triumph mine shaft, on the ridge between 

North Star mine portals and Triumph mine shaft, and on the 

ridge south of the North Star portal area above the Annie 

fault (fig. 3).

Near the Triumph mine, the Triumph argillite is more 

siliceous and indurated and displays less cleavage development than Triumph strata elsewhere in the Milligen belt. 

This textural difference may reflect a more siliceous nature

of the mudrock in the Triumph area but more likely reflects 

increased induration by contact metamorphism.

INDEPENDENCE SANDSTONE UNIT

The Independence sandstone unit is the uppermost 

stratigraphic member recognized in the Milligen Formation 

(Turner and Otto, 1988). The Independence sandstone is 

named after an overturned sequence of sandstone 1,000 ft or 

more thick exposed in upper Independence Canyon (fig. 3). 

The top of the unit is everywhere in fault contact with other 

Milligen or younger strata. The Independence sandstone is 

composed of buff- to reddish-brown-weathering, finegrained sandstone, black to gray-green argillite, silty and 

locally bioclastic limestone, and minor chert-pebble 

conglomerate.
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E15

 +-'M J^^i4 v -

^V rW^S»w«l'i^-<' * . ^Vr- -5V - 

^

Sandberg and others (1975) identified early Late Devonian (Frasnian) conodonts from bioclastic limestone conglomerate within argillaceous limestone exposed on the 

ridge east of Milligan Gulch; we correlate these strata with 

similar pale-gray limestone beds within the Independence 

sandstone and therefore suggest that the age of the Independence sandstone is Late Devonian.

TRIUMPH MINE AREA

Drill hole 81-1 (1,200 ft north-northwest of Triumph 

shaft) intersected a faulted upright section of Independence 

sandstone (between 70 and 400 ft thick) above the Fissure 

fault just north of the Triumph mine shaft (Old Triumph mine 

of fig. 3). A sandstone-rich section composed of two upwardthinning turbidite sequences, each about 80 ft thick, is overlain by carbonaceous chert and minor thin-bedded sandstone 

beds. The thinning-upward sequences are composed of sandstone beds as thick as 2 ft interbedded with lesser carbonaceous argillite and chert. Ball-and-pillow structures are 

common at the base of sandstone beds. Sandstone mineralogy

is a calc-silicate assemblage of quartz-clinopyroxene-tremolite/actinolite-pyrite-plagioclase-calcite, relict detrital quartz 

(0.1-0.5 mm), and minor plagioclase.

The Independence sandstone is well exposed on the east 

side of the ridge northeast of the Triumph mine shaft in the 

upper part of Courier Gulch (fig. 4). In this area, sandstone 

beds as thick as 4 ft display planar lamination, climbing ripples, ball-and-pillow structures, and cross lamination and are

interpreted as , and Tc turbidites.

EAST FORK VALLEY

The lower part of the Independence sandstone exposed 

on the east side of Milligan Gulch includes crinoid-rich bioclastic limestone, micritic sandy to silty limestone, quartzite, 

calcareous sandstone, siltite, argillite, and pebble conglomerate. Sandberg and others (1975) reported an early Frasnian 

(Late Devonian) fossil assemblage from these beds.

In the eastern part of the East Fork valley, the Independence sandstone is dominated by reddish-brown-weathering, thin-bedded, pyritic sandstone and argillite and lesser
E16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

interbedded silty limestone and chert conglomerate. Sandstone displays abundant planar lamination, graded bedding, 

ball-and-pillow structures, and climbing ripples. The color 

of interbedded argillite is transitional from black near the 

base upward to pale green. The reddish-brown-weathering 

color is due to the oxidation of disseminated pyrite, which 

commonly makes up as much as 5 percent of the rock.

Chert-pebble conglomerate lenses as thick as 75 ft are 

locally present at the contact between the Independence 

sandstone and underlying Triumph argillite. Conglomerate 

is composed of white and gray chert, black argillite, and 

sandstone clasts as much as 1 in. in diameter and lesser 

fine- to medium-grained quartz. Thin beds as thick as 1 ft 

of lithologically similar conglomerate that is interbedded 

with Cait quartzite have also been noted on the ridge east of 

Courier gulch.

Limestone units as thick as 20 ft are composed of amalgamated, thin to medium beds of silty limestone.

WOOD RIVER FORMATION

In the area of the Triumph mine, the Wood River Formation is juxtaposed against Milligen strata along shallow, 

west-dipping normal faults. Wood River strata are exposed 

as bold outcrops at the mouths of Triumph Gulch and Independence Canyon and as fault klippe capping the peak northwest of North Star mine and the ridge north of Independence 

Canyon. The Wood River Formation includes blue-gray, 

sandy bioclastic limestone, gray quartzite, and chert conglomerate (Hall, Batchelder, andTschanz, 1978). Kiilsgaard 

(in Anderson, 1950) described crinoids, productids, bryozoa, 

tabulate corals, and fusilinids from bioclastic limestone on 

North Star Peak. No base-metal-mineralized rocks are 

present within the Wood River Formation in the area of the 

Triumph mine.

GRANITE DIKES

Altered granitic dikes are present along the Fissure 

fault and are well exposed at the portal of the North Star 

mine. Granite dikes or small stocks within hornfelsed and 

calc-silicate Milligen strata have been drilled below the Triumph mine (fig. 4). These dikes contain coarse feldspar 

altered to sericite and clay, about 15 percent anhedral 

quartz grains (<10 mm), 10 percent biotite (<4 mm), and 

minor hornblende pseudomorphed by chlorite and pyrite. 

Elsewhere, similar dikes are highly altered to a granular 

intergrowth of quartz, muscovite, plagioclase, and as much 

as 15 percent pyrite. Plagioclase and quartz are intergrown 

with sutured margins. Muscovite grains (0.05-0.1 mm) are 

randomly oriented. Veinlike segregations of quartz and 

lesser pyrite, sphalerite, galena, rutile, and sphene are 

within the altered dikes.

ANDESITE DIKES

Biotite-hornblende andesite porphyry dikes, similar in 

composition to rocks of the Challis Volcanic Group, intrude 

Milligen strata. The dikes are composed of plagioclase 

(10-20 percent), hornblende (5-20 percent), and biotite (0-2 

percent) phenocrysts in an aphanitic matrix. Kiilsgaard (in 

Anderson, 1950) noted that dikes commonly are within 

northwest-trending, southwest-dipping shear zones and are 

commonly dismembered, sheared, and variably altered, suggesting that intrusion was prior to last fault movement. In 

drill hole 81-1 immediately north of Triumph mine shaft, a 

weakly altered andesite porphyry in contact with highly 

altered quartz-feldspar porphyry within the Fissure fault 

zone suggests that intrusion of the andesite dike postdates 

the emplacement and hydrothermal alteration of the felsic 

dike. Similar andesite dikes also cut Wood River Formation 

strata, granitic rocks of the Idaho batholith west of Bellevue 

(Kiilsgaard in Anderson, 1950), and Challis volcanic rocks. 

Mafic dikes in the nearby Pioneer Mountains dominantly 

trend N. 50°-70° E. (Dover, 1981).

CHALLIS VOLCANIC GROUP

Andesitic flow rocks of the Challis Volcanic Group 

structurally overlie Milligen and Wood River strata west of 

the Triumph mine. These rocks are predominantly darkgreenish-gray hornblende-andesite that weathers rusty 

brown. Primary layering is rarely observed except immediately west of the saddle between Triumph Gulch and Independence Canyon where vesicle layers and elongate lithic 

fragments trend north and dip steeply east and west.

CONTACT METAMORPHISM

AND ALTERATION IN THE

TRIUMPH MINE AREA

A contact metamorphic aureole in Milligen strata first 

mapped by Batchelder and Hall (1978) extends from the Triumph mine 2 mi north to the Parker mine (fig. 1). In the Triumph mine area, the metamorphic aureole extends to the 

north from the North Star portal area and to the west to the 

Challis contact. Contact metamorphism is weak or absent in 

lower Courier Gulch and lower North Star Gulch. Metamorphosed thin limestone beds contain an assemblage of quartz, 

tremolite, clinopyroxene, feldspar, and chloritoid. Mudrock 

is metamorphosed to a massive argillite that locally contains 

a tremolite-biotite assemblage.

Drilling below the Fissure fault west of the Triumph 

mine intersected granite dikes as thick as 30 ft that cut 

bleached pink and green hornfels rock. Similar granitic 

dikes are within the Fissure fault zone in the area of the
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E17

Triumph mine. Within calcareous beds, a commonly noted 

increase in abundance of clinopyroxene relative to tremolite with increasing depth suggests increasing metamorphic 

grade. It is likely that the northwest-trending contact metamorphic halo is related to a similarly trending buried granitic intrusion.

Metamorphism is most pervasive and destructive of 

primary textures in thin-bedded calcareous turbidite. Tremolite, quartz, clinopyroxene, and calcite, variable amounts 

of muscovite, orthoclase, and minor sphene and pyrite are 

present as pods, bands, and massive replacement of calcareous turbidite beds (fig. 6C). On a microscopic scale, randomly oriented, radial, sheaflike masses of elongate 

poikilitic tremolite (0.1-1.0 mm) form a semicontinuous 

matrix for fine-grained carbonate minerals and orthoclase. 

Prismatic or irregular clinopyroxene and calcite grains 

(0.1-0.5 mm long) are intergrown with patchlike aggregates of muscovite (as much as 2 mm across), subhedral 

equant grains of orthoclase (0.1-0.3 mm long), and scattered amoeboid grains of sphene (0.05-0.5 mm). Calc-silicate altered rock is locally cut by zones of silicification and 

quartz veining (fig. 6D). Contacts between limestone and 

calc-silicate rock are commonly sharp. Metamorphism of 

thick micritic limestone units is limited to scattered darkcolored porphyroblasts of skeletal poikiloblastic and diamond-shaped tremolite or lath-shaped chloritoid grains (fig. 

6A). These porphyroblasts are as long as 2 mm and may 

constitute as much as 5 percent of the rock.

Metamorphism of mudrocks includes silicification, 

calc-silicate alteration, and biotite hornfelsing. Mudrock 

altered to biotite hornfels at the head of Courier Gulch is 

composed of a cryptocrystalline aggregate of quartz, feldspar, and as much as 30 percent biotite and is cut by minor 

veinlets of potassium feldspar, biotite, and pyrrhotite. Above 

the Fissure fault northwest of the North Star portal area, 

mudrock is altered to a fine-grained assemblage of quartz, 

potassium feldspar, and tremolite and veinlets of tremolite 

and albite. Interbedded calc-turbidites are converted to calcsilicate assemblages.

Sandstone beds in the Independence sandstone unit are 

altered to an assemblage of quartz-tremolite-actinolite-clinopyroxene-calcite-pyrite. Tremolite is the dominant calcsilicate mineral. In drill hole 81-1 northwest of the Triumph mine shaft, abundant quartz, clinopyroxene, and actinolite are associated with veinlets of quartz and minor 

clinopyroxene, actinolite, pyrite, and calcite and trace 

sphalerite and galena.

Mineral textures indicate that metamorphism occurred 

after the earliest cleavage-forming deformation. Tremolite is 

characterized by randomly oriented radial and sheathlike 

aggregates that cross cleavage. Growth of calc-silicate minerals along cleavage supports a syn- or post-deformation 

timing of metamorphism (fig. 8A). The abrupt disappearance 

of calc-silicate alteration across the Fissure fault in the upper 

part of North Star Gulch suggests that some of the fault 

movement postdates metamorphism.

STRUCTURE OF THE 

TRIUMPH MINE AREA

GENERAL STRUCTURE

Three major deformational events are recorded in the 

Milligen strata of the East Fork valley (Turner and Otto, 

1988). An early deformation event (Dl) that includes tight 

to isoclinal folds and axial planar cleavage subparallel with 

bedding may be related to the Early Mississippian Antler 

orogeny or to younger Mesozoic deformation. Map-scale, 

northwest-trending, east-vergent folds (D2) that show variably developed cleavage deform Dl structures, as well as 

Pennsylvanian and Permian strata. Northwest-trending, 

southwest-dipping thrust faults are likely associated with 

D2 folds. Gently and steeply dipping extensional faults 

(D3) offset strata as young as Eocene age and are inferred 

to be related to formation of the nearby Pioneer Mountains 

core complex.

In the Triumph mine area, Milligen strata generally 

strike N. 55°-65° W. and dip 30°-60° SW. Although casual 

observation of this area suggests a simple homoclinal structure, the rocks are intensely faulted, tightly to isoclinally 

folded (fig. 8fi), and generally on the overturned limb of a 

large east-vergent fold. Locally, Dl cleavage is folded by 

east-vergent folds (fig. 8Q. A set of southwest-dipping 

thrust faults (D2) repeats Milligen strata; some of these 

thrust faults host sheared lead-zinc-silver vein mineralization. The Triumph stratiform orebody is immediately above 

a thrust (Fissure fault). Low-angle normal faults displace 

Milligen strata and thrust faults from east to west and juxtapose Milligen rocks against structurally higher Wood River 

Formation and Challis Volcanic Group.

DUCTILE DEFORMATION

A penetrative cleavage (Dl) associated with tight to 

isoclinal folds is variably developed in the Triumph mine 

area. The cleavage generally strikes N. 55°-65° W., dips 

30°-60° SW., and cuts bedding at a low angle. Dl cleavage 

is best developed in unmetamorphosed massive limestone 

and calcareous shale of the Lucky Coin limestone, shale of 

the Triumph argillite, and thin-bedded sandstone and shale 

of the Independence sandstone. Within the contact aureole, 

this cleavage is commonly absent, presumably due to mineral growth and recrystallization. A lack of similar cleavage 

within Pennsylvanian and Permian Wood River strata in the 

Triumph mine area suggests a pre-Pennsylvanian age for 

the cleavage; however, it may reflect the different rheology 

of massive limestone and quartzite in the Wood River Formation.

A belt of northwest-trending, southwest-dipping beds 

of foliated marble and cleaved argillite (Dl) is west of the 

Triumph mine. Most of these highly deformed rocks are
E18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 8 (above and facing page). Alteration types and structures in the Milligen Formation, Triumph mine area, Idaho. A, Folded bed 

of calcareous sandstone interbedded with black argillite. Tremolitic calc-silicate alteration has preferentially developed along cleavage 

axial planar to fold indicating tremolite formation is younger than deformation. Hammer is shown for scale. B, Dl fold. Asymmetric fold 

in interbedded white and black chert, lower part of Triumph Gulch. Key is shown for scale. C, D2 fold. Dl cleavage in calcareous argillite 

folded into east-vergent fold, North Star Gulch. Coin is shown for scale. D, D3 fault. Talus block with slickensides on a polished quartz 

fault surface, Cait prospect. Similar fault surfaces with northeast-trending slickensides are typical of D3 low-angle faults in the Triumph 

area and throughout the East Fork Wood River valley. Hammer is shown for scale.

above the Fissure fault. Foliated marble is inferred to have 

been the locus of early Dl ductile shearing and is truncated 

by later thrust faults (D2). Just west of the Triumph shaft, 

banded marble contains augen of coarse quartz and calcite 

and tightly folded calcite and quartz veins. Calcite grains 

within the marble strongly elongated in a northeasterly 

direction suggest that Dl deformation involved northeast 

transport. Within adjacent hornfelsed Triumph argillite, 

cleavage is axial planar to isoclinal folds of dismembered 

sandstone laminae.

Reversals of stratigraphic top direction in drill holes 

suggest that the structural hanging wall of the Triumph orebody is deformed by isoclinal folds having wavelengths of 

10-30 ft. The sense of asymmetry and the cleavage-bedding

relationships of outcrop-scale folds suggest that this 

sequence is on the overturned limb of an east-vergent fold.

Locally, small east-vergent folds deform the early 

cleavage (fig. 8C). Variations in dip of the cleavage, such as 

northeast-dipping cleavage on the west side of the upper part 

of Courier Gulch, may reflect folding by map-scale folds.

Interpretation of the structural history of the Triumph 

mine area is complicated by the contact metamorphic fabric 

that overprints older rock fabrics. Two interpretations are 

possible. Either both Dl folds and cleavage and D2 folds are 

Mesozoic, or the Dl cleavage is pre-Mesozoic (possibly 

Antler deformation) and younger minor D2 folds are Mesozoic. In the Triumph area there is no reason to believe that 

both ductile deformation events (Dl and D2) are not
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E19

Mesozoic in age; however, in the eastern East Fork valley 

near the Cait prospect, early Dl folds and cleavage are cut by 

a younger cleavage, and Turner and Otto (1988) interpreted 

the early deformation as Devonian Antler deformation based 

on its ductile soft-sediment style of deformation.

THRUST FAULT ARRAY

Four major northwest-trending, southwest-dipping 

thrust faults repeat Milligen strata in the area of the Triumph 

mine. From northeast to southwest and from lower to higher 

structural position, these faults are the Independence, Fissure, Annie and Challenger thrusts (figs. 3,5), and the bodies 

of rock above each thrust fault are referred to as the Independence, Fissure, Annie, and Challenger blocks, respectively. 

Kiilsgaard (in Anderson, 1950) interpreted a reverse sense of 

displacement on several of these faults based on underground observation of large-scale drag folds adjacent to 

shear zones, as well as evidence of stratigraphic offset. 

Although these observations suggest that these faults are 

thrusts, younger strata are placed on older in the Triumph 

mine area. This implies that faulting disrupted a previously

folded stratigraphic panel. Kiilsgaard also noted that shear 

zones associated with reverse faults are characterized by a 

sharp hanging wall fault plane that has slickensides suggesting oblique movement; these structures may reflect reactivation of thrust faults during Eocene extension.

The Challenger, Annie, and Fissure thrust faults are 

imbricate and converge in the southern part of North Star 

Gulch. Similar thrust faults have not been recognized outside 

the Triumph mine area, possibly because of a lack of detailed 

work in these areas. Regional mapping of Milligen strata to 

the east indicates that these strata are deformed by map-scale 

folds (fig. 2).

Much of the lead-zinc-silver ore mined in the ParkerTriumph belt was produced from mineralized thrust faults or 

"fissures" (Kiilsgaard in Anderson, 1950). Ore in the Independence, Baltimore, and Parker mines and the Fissure ore 

at the Triumph mine are present as pods, streaks, and stringers of vein-type ore within gouge or highly sheared rock. The 

fault zones were a locus of sulfide deposition, possibly remobilized from stratiform sulfide deposits; latest fault movement postdates mineralization. Thrust faults are offset by 

low-angle normal faults (figs. 3, 4) and northeast-trending 

steep normal faults (fig. 2).
E20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

INDEPENDENCE THRUST FAULT

The Independence thrust fault is the most northeasterly 

and structurally lowest fault in the Triumph-Parker thrust 

array (fig. 2). This important northwest-trending, southwestdipping structure was mined for lead-silver ore at both the 

Independence and Baltimore mines and can be traced from 

north of Independence Canyon to the lower part of Milligan 

Gulch, a distance of 4 mi (fig. 3). Contractional movement 

on the Independence fault is indicated by the juxtaposition of 

overturned strata of the Independence sandstone against 

underlying overturned argillite and quartzite of the Triumph 

argillite and Cait quartzite. The Independence fault is offset 

in several locations by low-angle normal faults. As a result, 

parts of the Independence fault are in three separate faultbound panels; the fault is offset progressively further to the 

west at successively higher structural levels (fig. 5).

The Independence mine was a significant producer of 

lead and silver and lesser gold from 1883 to about 1923. 

Umpleby and others (1930) described the Independence 

fault at the Independence mine as a variably striking zone 

that has a steplike profile of shallower (20° dip) and steeper 

(50° dip) segments consisting of crushed carbonaceous 

argillite. Ore was concentrated within the steeper parts of 

the structure.

FISSURE THRUST FAULT

The northwest-trending, southwest-dipping Fissure 

thrust fault subcrops on the west side of North Star Gulch, as 

well as within a structural window below the Triumph shaft 

low-angle fault near the Triumph shaft. Sheared and mineralized rock west of the saddle between Triumph Gulch and 

Independence Canyon may be associated with the Fissure 

fault, offset to the west by the Triumph shaft fault. Ore in the 

Triumph mine is within the Fissure fault ("Fissure ore") and 

as stratiform sulfides overlying the fault. Early miners interpreted the faults at the Triumph and North Star mines as separate structures; however, we interpret them as a single 

structure offset by a down-to-the-northwest normal fault 

shown on underground mine maps (Triumph Mining Company, unpublished maps).

C.W. Merriam and C.N. Bozian (written commun., 

1942) described the Fissure fault in the Triumph mine as a 

5-20-foot-thick zone of crushed rock, clay gouge, graphitic 

flour, and pods and fragments that have multiple slickensided surfaces and include sulfide-quartz-carbonate, altered 

quartz porphyry granite dikes, and altered mafic dikes. The 

hanging-wall surface of the fault zone is well defined and has 

mullion structure. Drag folds are numerous, and their fold 

sense suggests that the principal movement was reverse dipslip; however, slickenside striae suggest several directions of 

fault movement. The fault surface generally strikes northwest and dips 20°-40° SW., but in the northwestern part of

the Triumph mine the strike swings westerly and then northerly, forming a large-scale bend in the fault plane.

The Fissure fault has a complex history that includes 

early contractional movement, deposition of lead-zinc-silvergold ore, intrusion by granitic and andesitic dikes, and reactivation as a normal fault coincident with or following intrusion and mineralization (unpublished data). Contractional 

movement on the Fissure fault is suggested by repetition of 

the Lucky Coin limestone and Triumph argillite units, repetition of the Triumph stratiform sulfide body above the 200- 

foot level in the Triumph mine along imbricate splays of the 

fault, and small-displacement northeast-directed thrust faults 

noted in outcrop adjacent to the fault. Dikes and sulfidequartz-carbonate mineralized rocks within the Fissure fault 

are cut by normal faults and have foliated margins. The Fissure fault is offset by a series of northeast-trending, down-tothe-northwest normal faults.

ANNIE THRUST FAULT

The Annie thrust fault, exposed on the ridge between 

North Star and Triumph Gulches, juxtaposes overturned Cait 

quartzite and Lucky Coin limestone against lower argillite 

and Lucky Coin limestone (fig. 3). The more westerly trending Annie fault merges with the underlying Fissure fault in 

southern North Star Gulch. The Annie fault is cut by the Triumph shaft fault, a low-angle normal fault (fig. 4).

CHALLENGER THRUST FAULT

The Challenger thrust fault has the highest structural 

position of the four thrusts in the Triumph mine area. It is 

named for exposures in the Challenger tunnel in the lower 

part of Triumph Gulch where it is a 50-foot-wide zone of 

chloritic and graphitic slickensided gouge (fig. 4). Contractional movement on the Challenger fault is indicated by the 

juxtaposition of overturned strata of the Lucky Coin limestone and Independence sandstone units against underlying 

overturned lower argillite. The fault cuts upsection from 

southeast to northwest in the hanging wall.

LOW-ANGLE NORMAL FAULTS

A major contribution of this study has been recognition 

of the importance of low-angle normal faults. Three shallowly west dipping normal faults offset Milligen strata and 

older thrust faults and juxtapose younger rocks of the Wood 

River Formation and Challis Volcanic Group against Milligen strata. In successively higher structural position, these 

faults are the Triumph shaft, Porphyry Peak-Wood River, 

and Challis (figs. 3, 4). Offset of Milligen units and thrust 

faults indicates a net westerly displacement of upper plate
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E21

rocks on the Triumph Shaft and Porphyry Peak faults. Slickenside striae in adjacent parallel subsidiary faults indicate 

movement to the northwest (fig. 8D).

These low-angle faults are not mineralized, and they 

offset lead-zinc-silver-gold-bearing thrust faults. Low-angle 

faults both offset and are offset by northeast-trending highangle normal faults of small displacement.

TRIUMPH SHAFT FAULT

The Triumph Shaft fault, the structurally lowest major 

low-angle fault recognized in the Triumph area (fig. 4B), is 

partially exposed in the upper parts of North Star, Triumph 

and Independence drainages (fig. 3). The Triumph Shaft 

fault dips shallowly to the west at 5°-15° and appears to flatten to the east (fig. 4fi). The Triumph Shaft fault zone is 

poorly exposed, but subsidiary low-angle faults below the 

Triumph Shaft fault are well exposed in cliffs immediately 

northwest of the Triumph Shaft. Slickenside striae on these 

and other faults of the Triumph Shaft fault zone indicate a 

primary top-to-the-northwest sense of displacement and a 

secondary west-southwest trend of movement. The Independence thrust fault is offset more than 1,200 ft to the west by 

the Triumph Shaft fault; total offset could be considerably 

more than this westerly component of displacement (fig. 3). 

An updip portion of the Fissure fault and Triumph stratiform 

body is above the Triumph Shaft fault west of the saddle 

between Triumph and Independence drainages (figs. 3, 4B).

We correlate the Triumph shaft fault with a regionally 

extensive flat fault that can be traced to the northeast for 4 mi 

along the divide between Parker and Milligan Gulches (fig. 

2). This structure may be equivalent to structures exposed on 

similar northeast-trending ridges between Milligan Gulch 

and Hyndman Creek and between Hyndman Creek and East 

Fork of Wood River (fig. 2). If this correlation is correct, the 

areal extent of this structure exceeds 30-40 mi2.

PORPHYRY PEAK-WOOD RIVER FAULTS

The Porphyry Peak fault, about 300 ft above and subparallel with the Triumph shaft fault, subcrops on the ridgeline between the Independence, Triumph, and Courier 

drainages (figs. 3, 4A). The Porphyry Peak fault displaces 

strata of the Fissure and Independence blocks and the Independence fault 2,000-2,500 ft to the west. Given evidence 

for northwesterly displacement on other low-angle faults, we 

suspect a northwestly displacement on the Porphyry Peak 

fault; however, total displacement in a northwesterly direction is difficult to estimate because this direction is subparallel with the trend of Milligen strata and thrust faults.

The low-angle Wood River fault underlies a klippe of 

Wood River Formation on the peak south of the Triumph 

mine shaft ("Old Triumph mine" in fig. 3). South of Triumph

mine shaft this fault zone dips about 40° to the southwest, 

contains northwest-trending slickensides, and truncates the 

Fissure thrust fault. The Wood River fault has structural 

position similar to that of the Porphyry Peak fault. North of 

Independence Canyon near the Baltimore mine, Milligen 

Formation is in thrust contact with underlying Wood River 

Formation and both are truncated by the Wood River fault 

(M.E. Ratchford, University of Idaho, oral commun., 1989). 

Here the Wood River fault is a silicified and brecciated fault 

zone that has east-trending slickenside striae.

The Porphyry Peak and Wood River faults were originally considered different faults because of the differing rock 

types in the upper plate (Milligen Formation versus Wood 

River Formation); however, the occurrence of structurally 

juxtaposed Milligen and Wood River strata above the Wood 

River fault north of Independence Canyon suggests that what 

we refer to as the Wood River fault is the same structure as 

the Porphyry Peak fault.

CHALLIS FAULT

Rocks of the Chain's Volcanic Group of Eocene age are 

juxtaposed against underlying Milligen and Wood River 

strata on the west side of the Triumph mine area along the 

shallowly west dipping Challis fault (fig. 2). The Challis 

fault exposed in surface trenches in the upper part of Triumph Gulch is a broad zone of altered and brecciated volcanic rock above well-foliated Milligen argillite; overlying 

Challis volcanic rocks dip steeply into the fault zone. In a 

drill hole several hundred feet north of the trench, the Challis 

fault is a 3-foot-thick gouge zone that contains mixed Challis 

and Milligen fragments and is underlain by 30 ft of brecciated Milligen strata. Challis volcanic rocks are also faulted 

against Milligen strata in the lowest levels in the northwestern part of the Triumph mine (R. House, Hailey, Idaho, oral 

commun., 1985). This interpretation that the Milligen-Challis contact is a fault differs from that of Kiilsgaard (in Anderson, 1950), who interpreted the rubbly and weathered nature 

of the contact in the Lucky Coin adit and Triumph mine as 

an unconformity.

Small low-angle faults having west-trending slickenside striae were noted in several places within rocks of the 

Challis Volcanic Group.

STEEPLY DIPPING 

OBLIQUE-SLIP FAULTS

A widespread set of steeply dipping (60°-90°), northeast-trending (N. 55°-80° E.), small-displacement faults that 

offset low-angle normal faults may be the youngest structures in the Triumph mine area. Slickenside striae on nine 

such faults trend N. 40°-90° E. and plunge shallowly northeast. Offset of marker beds on some of these faults suggests
E22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

right-lateral oblique-slip displacement. In the Triumph mine, 

northeast-striking, steeply west dipping faults offset the orebody and the Fissure fault (C.W. Merriam and C.N. Bozian, 

written commun., 1942) with apparent down-to-the-north or 

right-lateral displacement. The largest such fault has an 

apparent normal offset of 200 ft and separates the Triumph 

orebody into the structurally higher North Star orebody to the 

southeast and the structurally lower Old Triumph orebody to 

the northwest. These faults parallel the lower drainage of the 

East Fork valley. Batchelder and Hall (1978) interpreted 

right-lateral offset on a fault under the lower East Fork valley 

based on apparent right-lateral offset of northwest-trending 

normal faults of the Wood River graben system.

TRIUMPH OREBODY 

HISTORY OF MINE DEVELOPMENT

The Triumph orebody includes a southwest-dipping 

stratiform sulfide body locally referred to as bedded "complex" and "siliceous" ores, as well as underlying faulted 

vein-mineralized rock or "fissure ore" within the southwestdipping Fissure fault zone. Early production was mostly 

from the high-grade "complex ores" of the stratiform sulfide 

body. With the exhaustion of those high-grade ores, production included lower grade "siliceous ores" and the widespread but discontinuous "fissure ores."

Production at the Triumph mine spanned thirty years 

from 1927 to 1957. Initial development of the Triumph orebody was from adits at the head of North Star Gulch (North 

Star mine) and in the eastern part of upper Triumph Gulch 

(Old Triumph mine). During the early years, production 

came from a 700-foot-deep shaft at the Old Triumph mine. 

Later, an interior shaft extended development to the 850-foot 

level (level elevations are the depth below the surface shaft 

collar). Ore was taken by aerial tram to the Gimlet railway 

siding, 5 mi to the west. In 1943 a 6,500-foot-long haulage 

tunnel (Plummer tunnel) was completed and connected the 

700-foot level of the mine with the North Star mill in the East 

Fork valley near the village of Triumph (fig. 3). A total of 10 

mi of tunnels, excluding slopes, was developed. By the 

1950's, the high-grade bedded ore was exhausted and work 

concentrated on developing "fissure ore" reserves in the 

deeper northwestern part of the mine.

STRUCTURE AND STRATIGRAPHY OF 

STRATIFORM OREBODY

The bulk of the production from the Triumph mine 

came from a stratiform deposit containing bedded pyritesphalerite-galena-ferroan carbonate-quartz ore. C.W. Merriam and C.N. Bozian (written commun., 1942) inferred this 

bedded ore to be the result of sulfide replacement of thin

limy partings interbedded with argillite beds. The stratiform 

sulfide body is more than 4,000 ft long along its northwest 

strike and is within an overturned sequence of interbedded 

limestone, carbonaceous argillite, and diamictite immediately above the Fissure fault. Strata younger than the bedded 

ores have been offset by the Fissure fault, and, because only 

thin, faulted slivers of argillite and limestone remain, the 

stratigraphic position of the Triumph deposit is somewhat 

ambiguous. It may lie within the Lucky Coin limestone, or, 

more probably, it is near the contact of the Lucky Coin limestone and overlying Triumph argillite.

Workers in the Triumph mine described two types of 

bedded ore: high-grade massive pyrite-sphalerite-galena 

"complex ores" and lower grade ferroan carbonate-quartzsphalerite-galena "siliceous ores" (C.W. Merriam and C.N. 

Bozian, written commun., 1942). The term complex ore, 

used to describe massive banded fine-grained pyrite, 

sphalerite, and galena, reflected the metallurgical problems 

associated with these zinc-rich ores. A typical assay of complex ore was 6-13 percent zinc, 3-6 percent lead, 6-7 ounces 

of silver per ton, and 0.01-0.02 ounces of gold per ton. C.W. 

Merriam and C.N. Bozian (written commun., 1942) 

described complex ore as commonly bedded or laminated, 

dense, fine-grained pyrite and lesser amounts of sphalerite 

and galena. Sulfide bands are interbedded with carbonaceous, pyritic chert and siltstone. Contacts between sulfide 

beds and interbeds are sharp to gradational. Major production from the Triumph mine was from complex ore. Kiilsgaard (in Anderson and others, 1950) described an ore shoot 

of complex ore in the Triumph mine that was 700 ft long, 170 

ft wide, and 6-50 ft thick.

Siliceous ore was described by C.W. Merriam and C.N. 

Bozian (written commun., 1942) as bedded siderite, galena, 

sphalerite, and quartz in argillite or limestone. Relative to 

complex ores from the Triumph mine, siliceous ore was 

commonly marginal in grade and had comparable zinc 

grades but below average gold, silver, and lead values. C.W. 

Merriam and C.N. Bozian (written commun., 1942) reported 

that the average grade of 30,000 tons of siliceous ore produced from the Triumph mine in 1942 was 6.4 percent zinc, 

3.4 percent lead, 4.1 ounces of silver per ton, and 0.01 

ounces of gold per ton.

FISSURE ORE

The fissure ore along the Fissure fault extended from 

the surface to the deepest workings below the 850-foot level 

in the Triumph mine and was much more extensive than the 

stratiform sulfide ore. Fissure ore is present as lenses and 

pods of sulfide-carbonate-quartz as much as 30 ft thick 

within gouge and crushed rock of the Fissure fault zone. 

Average metal grade of the fissure ore was elevated in gold 

relative to complex and siliceous ores; 46,500 tons of Triumph fissure ore averaged 3.3 percent zinc, 3.3 percent lead,
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E23

6.7 ounces of silver per ton, and 0.13 ounces of gold per ton, 

whereas 20,000 tons of fissure ore from the North Star mine 

averaged 9.3 percent zinc, 5.8 percent lead, 9.2 ounces of silver per ton, and 0.18 ounces of gold per ton (C.W. Merriam 

and C.N. Bozian, written commun., 1942).

C.W. Merriam and C.N. Bozian (written commun., 

1942) reported that fissure ore contains galena, sphalerite, 

arsenopyrite, tetrahedrite, boulangerite, and pyrrhotite in a 

gangue of siderite, ankerite, and quartz. Locally coarse 

grained galena and other sulfide minerals are commonly 

massive and granular due to shearing. The fissure ore is similar to tetrahedrite-galena-siderite veins elsewhere in the 

Wood River area but has a higher arsenopyrite to tetrahedrite 

ratio (Hall, Rye, and Doe, 1978).

DEVONIAN SETTING OF 

STRATIFORM SULFIDE ORES

DEPOSITIONAL SETTING OF REGIONAL 

MILLIGEN STRATA

The internal stratigraphy of the Milligen Formation in 

the central part of the Milligen belt reflects deposition in an 

anoxic basinal environment of Devonian age dominated by 

hemipelagic and pelagic sedimentation (lower argillite and 

Triumph argillite units) and punctuated by periods of turbidite influx. A Middle to Late Devonian turbidite event coincident with local syndepositional faulting and stratiform 

sulfide formation at the Triumph deposit was composed of 

two separate distributary systems: a carbonate depocenter to 

the west (Lucky Coin limestone facies) that interfingers with 

a quartz-sand depocenter to the east (Cait quartzite facies). A 

younger and more widespread Late Devonian turbidite system deposited mixed siliciclastic and carbonate detritus 

across the Milligen basin (Independence sandstone unit).

Beds of the Lucky Coin limestone are interpreted to 

have been deposited by turbidity flows in an anoxic basin at 

a depth below wave base on the basis of graded nature of 

beds, lack of sediment reworking or bioturbation, and association with carbonaceous, siliceous mudrock. Thick massive micrite beds were deposited as lime-mud debris flows 

within a channelized deposystem; evidence for this is based 

on the presence of coarse mudclasts probably derived from 

incised channel walls and on a high sedimentation rate as 

indicated by the amalgamated character of beds. The anomalous thickness and predominance of thick-bedded micritic 

limestone suggest that the exposures in Independence Canyon were deposited near the center of this channelized system. Rhythmically interbedded limestone and argillite 

sequences likely represent turbidite fan or apron deposits 

lateral to, or distal to, the channel system. Thin-bedded

amalgamated calcareous turbidite could reflect more active 

sedimentation in channel levee or interchannel areas.

The lack of significant coarse bioclastic material and 

paleocurrent indicators limits what can be deduced about the 

source area of the Lucky Coin limestone. The minor bioclastic component suggests that the source area was, at least in 

part, shallow water. A coeval Devonian carbonate platform, 

presently exposed several tens of miles to the east of the Triumph area in the Lost River and Lemhi Ranges, was a likely 

source area.

Diamictite is interpreted as resedimented Milligen 

derived from a nearby source. The close spatial association 

of diamictite with the Triumph stratiform sulfide body suggests association with a synsedimentary fault. Though not 

recognized, this fault is likely within the immediate area of 

the deposit because the diamictite does not extend far 

beyond the extent of the deposit. Similar relations have been 

recognized at other Devonian stratiform zinc-lead deposits 

in the Cordillera (Winn and Bailes, 1987; Turner, 1990).

The Cait quartzite reflects a sudden influx of a small 

volume of well-sorted quartz sand into the Milligen basin. 

Although the dispersal system was channelized, thin deposits of quartzite blanketed much of the Milligen basin. Sands 

deposited in the vicinity of the East Fork Wood River were 

transported in a channelized system subparallel with the axis 

of the present drainage. A likely source of these sands was 

Ordovician or Proterozoic shelf sandstone presently exposed 

in the Pioneer, Lost River, and Lemhi Ranges to the east.

The Independence sandstone represents progradation of 

a major turbidite fan complex into the Milligen basin, likely 

from the east. The upward-thickening sequence of upwardthinning cycles of sandstone beds in the lower part of the 

Independence sandstone suggests prograding channelized 

deposition of an inner fan environment. The finer grained 

nature of the Independence sandstone elsewhere in the Milligen Formation suggests deposition dominated by channellateral, middle fan, or outer fan environments.

Conglomerate lenses in the lowermost part of the 

Independence sandstone noted near the Cait property in the 

eastern part of the East Fork valley are well-sorted, clastsupported chert-pebble conglomerate. The well-sorted, 

clast-supported nature implies significant transport by traction or turbidity flow mechanism, perhaps from a subaerial 

source. The source for chert may have been the lower argillite or older Ordovician to Devonian chert presently 

exposed northeast of the Milligen belt (fig. 1). The chert 

conglomerate suggests uplift of an intrabasinal source. 

Because the conglomerate was deposited only slightly after 

the diamictite and stratiform sulfides, uplift was probably 

related to intrabasinal faulting within the Milligen basin. 

The coincidence of chert conglomerate deposition and the 

onset of siliciclastic turbidite deposition may suggest association with a common tectonic event.
E24 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

EXHALATIVE ORIGIN AND 

DEPOSITIONAL SETTING OF 

STRATIFORM SULFIDE BODY

Stratiform ore was inferred by early workers to be the 

result of the replacement of limestone beds adjacent to a 

mineralizing fissure, probably during Mesozoic time (C.W. 

Merriam and C.N. Bozian, written commun., 1942). We 

agree, however, with the interpretation of Smith (1977) and 

Hall (1985) that the stratiform sulfide ore is of syngenetic 

origin and formed during the Middle to Late Devonian. The 

finely bedded and laminated nature of the complex ore is 

suggestive of a sedimentary origin. The association of diamictite with stratiform ore can be explained as detritus derived 

from the scarp of a syndepositional fault that was also the 

structural conduit for metalliferous fluids discharging on the 

seafloor (Winn and Bailes, 1987; Turner, 1990). White and 

buff chert beds at the ore horizon can be traced for more than 

3 mi along strike arid are interpreted as an exhalative silica 

facies distal to the sulfide depocenter. Such an exhalative 

origin for the Triumph sulfide body places it within the family of Devonian to Mississippian shale-hosted exhalative 

zinc-lead deposits widespread in British Columbia, Yukon, 

and Alaska (Turner, 1988). These deposits share a similar 

mineral assemblage (chert, pyrite, sphalerite, and galena 

with or without barite and ferroan carbonate), mineral facies 

(massive or banded ferroan carbonate, laminated chertpyrite-sphalerite-galena-barite), and host lithology (carbonaceous mudrock, chert, turbidite).

The Triumph stratiform sulfide body is interbedded 

with carbonaceous mudrock, chert, and limestone that lack 

evidence for bioturbation or wave reworking. Thin tuff beds 

and mafic sills interbedded with Lucky Coin limestone strata 

near the Triumph deposit suggest that sulfide deposition 

coincided with minor volcanism and local emplacement of 

sills. Basin sedimentation during sulfide formation was dominated by hemipelagic and pelagic sediments interrupted by 

an influx of carbonate, mixed carbonate-siliciclastic, and 

quartzose sediments. Coincidence of the location of the sulfide body and a thick channel complex of limestone turbidite 

suggests that the sulfide body formed within a carbonate turbidite inner fan setting.

Diamictite deposits are at and near the stratigraphic 

level of the sulfide body; they are thickest near the sulfide 

body and thin to the north and south of the deposit. The 

similar composition of diamictite clasts and underlying 

strata and the poorly sorted character of the diamictite suggest local derivation.

EAST FORK GRABEN AND ASSOCIATED

STRATIFORM ZINC-LEAD

SULFIDE DEPOSITS

The trend formed by stratiform base-metal deposits at 

the Triumph mine, Cait prospect, and Mascot mine is almost

east-west (fig. 1). All of these deposits are associated with 

diamictite or conglomerate units interpreted as locally 

derived detritus from eroded Milligen strata. Stratiform sulfide deposits at both the Triumph mine and Cait prospect are 

within interfingering Lucky Coin limestone and Cait quartzite near the contact with the overlying Triumph argillite. The 

stratigraphic level of the Mascot zinc-lead mineralized rock 

is unclear due to structural complication but may be within 

the Cait quartzite as well. We interpret these three stratiform 

deposits to have formed adjacent to an east-trending Devonian fault or fault system. The presence of the west-trending 

channel system of Cait quartzite just to the south of this proposed Devonian structure suggests structural control of the 

Cait distributary system. We refer to this structurally controlled Devonian depocenter along the present drainage of 

the East Fork Wood River as the "East Fork graben." 

Whether there is a structural margin on the south side of this 

East Fork graben is unclear because Milligen strata younger 

than the stratiform sulfide horizons (Independence sandstone) cover much of this area.

PALEOTECTONIC SETTING OF 

THE MILLIGEN FORMATION

Strata of the Milligen Formation are part of a northtrending belt of Paleozoic fine-grained clastic rocks and 

chert in central Idaho that is referred to as the Central Idaho 

shale belt (Hall, 1985). Near Ketchum, such strata include 

black shale, chert, and siltstone of Ordovician to Devonian 

age (fig. 1). Together with the Milligen Formation, these 

Paleozoic shale-rich strata have been interpreted as an outer 

continental margin sequence (Sandberg and others, 1975). 

These strata correlate with similar shale- and chert-dominant 

strata along the western Cordillera of North America from 

Yukon to Nevada (Turner and others, 1989). Based on distinctive internal stratigraphy, Turner and others suggested a 

common tectonic, eustatic, and depositional history from 

Cambrian to Late Devonian time for these outer continental 

margin sequences.

The Triumph deposit is part of a family of Middle 

Devonian to Mississippian stratiform sediment-hosted zinclead and stratiform barite deposits that are present in outer 

continental margin strata from Alaska to Sonora, Mexico. 

This family of syngenetic deposits is everywhere interpreted as related to local block faulting (Maclntyre, 1983; 

Abbott and others, 1986; Winn and Bailes, 1987; Abbott 

and Turner, 1990) that likely reflects an extensional, 

transextensional, or transcurrent regime along the entire 

western margin of western North America during Middle 

Devonian to Mississippian time (Eisbacher, 1983; Turner, 

1988; Turner and others, 1989).
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E25

DEFORMATION AND

METAMORPHISM OF THE

TRIUMPH OREBODY

Three major deformational events are recorded in the 

Milligen strata (Turner and Otto, 1988). Dl structures include 

tight folds and axial-planar cleavage that may be correlated 

with the Antler orogeny based on soft-sediment-style of some 

Fl folds and the absence of similar structures in younger 

Pennsylvanian and Permian strata. Dl structures may also be 

of Mesozoic age. Map-scale north-trending, east-vergent 

folds (fig. 2) and variably developed axial-planar cleavage 

deform Dl structures and are inferred to be Mesozoic in age 

based on similarities to structures in younger Pennsylvanian 

and Permian strata. North west-trending, southwest-dipping 

thrust faults are likely associated with D2 folds of Mesozoic 

age. D3 low-angle west-dipping extensional faults having 

displacements to the northwest and high-angle normal faults 

offset strata as young as Eocene and are interpreted to be 

related to Eocene extension and formation of the nearby Pioneer Mountains core complex.

EARLY MISSISSIPPIAN ANTLER 

OROGENY (Dl)

Strata of the Milligen Formation and black shale, chert, 

and siltstone of Ordovician to Devonian age of the Roberts 

Mountains allochthon have been interpreted as continentalrise deposits thrust eastward onto the continental margin of 

North America during the Mississippian Antler orogeny 

(Roberts and Thomasson, 1964; Poole and Sandberg, 1977; 

Dover, 1980). Strata of the Roberts Mountains allochthon 

structurally overlie westerly derived flysch deposits of the 

Mississippian Copper Basin Formation and are interpreted 

as synorogenic sediments (Nilsen, 1977).

The strongest evidence for such a history is in the stratigraphic record of the Copper Basin Formation. Defining the 

structural fabric associated with this erogenic event has been 

more problematic. At issue is the age of deformational fabrics within the Milligen Formation. An Antler age for cleavage in the Milligen Formation was inferred by Sandberg and 

others (1975) and Skipp and Hall (1975); however, Dover 

(1980) pointed out that, because these studies lacked detailed 

fabric analysis or rigorous comparison of fabrics between the 

Milligen and younger post-Antler stratigraphic units, a 

Mesozoic age could not be ruled out. Davis (1984) documented cleaved chert and argillite clasts within the Mississippian Copper Basin Formation in the Pioneer Mountains 

(Davis, 1984), clasts presumably derived from the deformed 

Antler highlands to the west (Nilsen, 1977). Turner and Otto 

(1988) described Milligen strata at the Cait property in 

which early Dl penetrative cleavage axial to isoclinal folds

is refolded by upright folds that have weak axial cleavage. 

Based on the ductile style of these early folds, Turner and 

Otto inferred that this deformation took place prior to sediment lithification and suggested that the folds are of Antler 

age. It is uncertain whether the early foliation and folding in 

the Triumph mine area are related to the Antler deformation 

or instead are an intense development of D2 strain.

MESOZOIC FOLDING AND 

THRUSTING (D2)

East-vergent map-scale folds, locally developed cleavage, and a stack of older-over-younger thrust sheets in the 

Pioneer Mountains and areas to the east have been attributed 

to the Late Jurassic and Cretaceous Sevier orogeny (Skipp 

and Hall, 1975; Skipp and Hait, 1977; Dover, 1980). The 

westernmost such thrust, the Pioneer thrust fault, places Milligen Formation, as well as lower Paleozoic shale- and chertrich strata, over Mississippian Copper Basin Formation 

(Skipp and Hall, 1975; Skipp and Hait, 1977; Dover, 1981). 

Link and Mahoney (1989) noted the lack of major thrust 

faults and the predominance of east-vergent folds west of the 

Pioneer Mountains core complex.

We correlate the northwest-trending belt of thrust faults 

in the area of the Triumph mine with this Mesozoic deformation. East of this thrust belt, compressive deformation is 

expressed as map-scale east-vergent folds that suggest 

greater amounts of shortening in rocks on the west side of the 

Milligen belt. Dl folds and cleavage in the Triumph area 

may be related to an early phase of Mesozoic deformation.

SILVER-LEAD-ZINC VEIN

MINERALIZATION AND

CONTACT METAMORPHISM

Hall, Rye, and Doe (1978) interpreted silver-lead-zinc 

vein mineralization in the Wood River area to have been 

related to intrusion of the Cretaceous Idaho batholith. The 

small-displacement D2 thrusts in the Triumph area probably 

were permeable and possibly active structures during 

younger Cretaceous plutonism and the site of sulfide deposition (fissure ore) within a large-scale hydrothermal system 

(Hall, Rye, and Doe, 1978). Contact metamorphism in the 

Triumph area may have been coincident with this plutonism 

and mineralization. Reactivation of the mineralized faults 

during the Tertiary sheared and dismembered veins.

Contact metamorphism in the Triumph area has been 

interpreted to be related to a buried intrusion below the Triumph mine (Batchelder and Hall, 1978). Granite dikes 

associated with hornfelsed rock below the Triumph mine 

are more similar in composition to the Tertiary granitic 

suite of the Pioneer Mountains than to quartz diorite and 

granodiorite intrusive rocks of Cretaceous age. For this reason, and because silver-lead-zinc vein mineralization is
E26 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

related to Cretaceous plutonism, granite dike formation and 

contact metamorphism postdate fissure mineralization at 

the Triumph deposit.

TERTIARY EXTENSIONAL FAULTING (D3)

Paleogene crustal extension has affected much of eastcentral Idaho. In the Pioneer Mountains just east of the Triumph area, metasedimentary rocks and Cretaceous and 

Eocene intrusive rocks are separated by the Eocene Wildhorse detachment fault from an upper plate of Paleozoic and 

Tertiary sedimentary and volcanic rocks (Wust, 1986; 

O'Neill and Pavlis, 1988). Displacement on the Wildhorse 

detachment fault is estimated to be at least 10.5 mi in a topto-the-northwest direction (Wust, 1986). Widespread 

younger-over-older low-angle faults in the upper plate of the 

Wildhorse detachment throughout the Wood River area were 

originally interpreted as thrust faults (Hall, Batchelder, and 

Tschanz, 1978; Dover, 1981) but have been reinterpreted as 

low-angle normal faults (Link and others, 1988; Turner and 

Otto, 1988). Northeast-trending high-angle faults that are 

widespread throughout the Wood River area are parallel with 

the Trans-Challis fault system northwest of the Wood River 

area and may also have accommodated northwest-southeast 

extension (Link and others, 1988). Southwest-northeast 

Neogene extension resulted in the northwest-trending basin 

and range faults and the present topography.

In the Triumph area, Paleogene extension resulted in 

movement to the northwest along a series of shallowly dipping normal faults. These faults dismembered the Mesozoic 

thrust belt and displaced the updip part of the Triumph stratiform sulfide body. Reactivation and normal or oblique-slip 

movement on the Mesozoic thrust faults resulted in deformation and dismemberment of sulfide-carbonate-quartz veins 

and granite and andesite dikes within the fault zones.

REFERENCES CITED

Abbott, J.G., Gordey, S.P., and Tempelman-Kluit, D.J., 1986, Setting of sedex, sediment-hosted Pb-Zn deposits in Yukon and 

northeastern British Columbia, in Morin, J., ed., Mineral 

deposits of the northern Cordillera: Canadian Institute of Mining and Metallurgy Special Volume 37, p. 1-18.

Abbott, J.G., and Turner, R.J.W., 1990, Character and paleotectonic setting of Devonian stratiform sediment-hosted Zn-Pb-barite 

deposits, Macmillan Fold Belt, Yukon, in Abbott, J.G., and 

Turner, R.J.W., eds., Mineral deposits of the northern Canadian Cordillera, Yukon-British Columbia: International Association on the Genesis of Ore Deposits Symposium, 8th, Field 

Trip Guidebook, Field Trip 14, Geological Survey of Canada 

Open File 2169, p. 99-136.

Anderson, A.L., Kiilsgaard, T.H., and Fryklund, V.C., Jr., 1950, 

Detailed geology of certain areas in the Mineral Hill and Warm 

Springs mining districts, Blaine County, Idaho: Idaho Bureau 

of Mines and Geology Pamphlet 90, 73 p.

Batchelder, J.N., and Hall, W.E., 1978, Preliminary geologic map 

of the Hailey 7.5-minute quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 78-545, scale 1:24,000.

Bouma, A.H., 1962, Sedimentology of some flysch deposits: 

Amsterdam, Elsevier, 168 p.

Davis, S., 1984, A microstructural perspective of orogenesis in the 

Pioneer Mountains, central Idaho: Missoula, University of 

Montana, M.S. thesis, 55 p.

Dover, J.H., 1980, Status of Antler orogeny in central Idaho, clarification and constraints from the Pioneer Mountains, in Fouch, 

T.D. and Magathan, E.R., eds., Paleozoic paleogeography of 

the West-Central United States: Rocky Mountain Section, 

Society of Economic Paleontologists and Mineralogists, WestCentral United States Paleogeography Symposium 1, p. 

371-381.

 1981, Geology of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho, in Mineral resources 

of the Boulder-Pioneer Wilderness Study Area, Blaine and 

Custer Counties, Idaho: U.S. Geological Survey Bulletin 

1497-A, p. 15-75.

Eisbacher, G.H., 1983, Devonian-Mississippian sinistral transcurrent faulting along the cratonic margin of western North America A hypothesis: Geology, v. 11, p. 7-10.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hall, W.E., Batchelder, J.H., and Tschanz, C.M., 1978, Geologic 

map of the Sun Valley 7.5-minute quadrangle, Blaine County, 

Idaho: U.S. Geological Survey Open-File Report 78-1058, 

scale 1:24,000.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district Intrusion-related lead-silver deposits derived from 

country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Link, P.K., and Mahoney, J.B., 1989, Stratigraphic setting of sediment-hosted mineralization in the eastern Hailey I°x2° quadrangle, Blaine, Custer, and Camas Counties, south-central 

Idaho, in Winkler, G.R., Soulliere, S.J., Worl, R.G., and 

Johnson, K.M., eds., Geology and mineral deposits of the 

Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. 

Geological Survey Open-File Report 89-639, p. 53-69.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke, Susanne, and 

Burton, B.R., 1988, Structural and Stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knob, Pioneer, Boulder, and Smoky Mountains, in Link, 

P.K., and Hackett, W.R., eds., Guidebook to the geology of 

central and southern Idaho: Idaho Geological Survey Bulletin 

27, p. 5^2.

Maclntyre, D.G., 1983, Geology and sedex barite-sulfide deposits 

of the Gataga District, northeastern British Columbia, in Sangster, D.F., ed.. Sediment-hosted stratiform lead-zinc deposits: 

Mineralogical Association of Canada Short Course Handbook, 

v. 9, p. 85-120.

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds.. Paleozoic paleogeography of the Western United States: Pacific Section, Society of Economic
TRIUMPH STRATIFORM ZINC-LEAD-SILVER DEPOSIT E27

Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 275-299.

O'Neill, R.L., and Pavlis, T.L., 1988, Superposition of Cenozoic 

extension on Mesozoic compressional structures in the Pioneer 

Mountains metamorphic core complex, central Idaho: Geological Society of America Bulletin, v. 100, p. 1833-1845.

Otto, B.R., 1984, Internal company report: Missoula, Montana, 

Noranda Exploration.

Otto, B.R., and Turner, R.J.W., 1987, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho: Northwest 

Geology, v. 16, p. 95-103.

Poole, F.G., and Sandberg, C.A., 1977, Mississippian paleogeography and tectonics of the Western United States, in Stewart, 

J.H., Stevens, C.H., and Fritsche, A.E., eds., Paleozoic paleogeography of the Western United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific 

Coast Paleogeography Symposium 1, p. 67-85.

Roberts, R.J., and Thomasson, M.R., 1964, Comparison of late 

Paleozoic depositional history of northern Nevada and central 

Idaho: U.S. Geological Survey Professional Paper 475-D, p. 

D1-D6.

Sandberg, C.A., Hall, W.E., Batchelder, J.N., and Axelson, Claus, 

1975, Stratigraphy, conodont dating, and paleotectonic interpretation of the type Milligen Formation (Devonian), Wood 

River area, Idaho: U.S. Geological Survey Journal of Research, 

v. 3, no. 6, p. 707-720.

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River Plain, Idaho: Wyoming 

Geological Association Guidebook, Twenty-Ninth Annual 

Field Conference, p. 499-515.

Skipp, Betty, and Hall, W.E., 1975, Structure and Paleozoic stratigraphy of a complex of thrust plates in the Fish Creek Reservoir 

area, south-central Idaho: U.S. Geological Survey Journal of 

Research, v. 3, no. 6, p. 671-689.

Smith, C.L., 1977, Internal company report: Westley Mines Ltd.

Turner, R.J.W., 1985, Summary report for 1985 field work, Milligen Project, Blaine County, Idaho: Private company report, 

Mintek Resources Ltd., Vancouver, B.C.

 1988, Massive sulphide deposits of mid-Paleozoic age: 

Mining Review, v. 8, no. 6, p. 43-47.

 1990, Jason stratiform Zn-Pb-barite deposit, Selwyn Basin,

Yukon Geological setting, hydrothermal facies and genesis, 

in Abbott, J.G., and Turner, R.J.W., eds., Mineral deposits of 

the northern Canadian Cordillera, Yukon-British Columbia: 

International Association on the Genesis of Ore Deposits Symposium, 8th, Field Trip Guidebook, Field Trip 14; Geological 

Survey of Canada Open File 2169, p. 137-176.

Turner, R.J.W., Madrid, R., and Miller, E.L., 1989, Roberts Mountains allochthon Stratigraphic comparison with lower Paleozoic outer continental margin strata of the northern Canadian 

Cordillera: Geology, v. 17, p. 341-344.

Turner, R.J.W., and Michelson, C, 1984, The geological character 

and setting of the stratiform Ag-Zn-Pb mineralization, Triumph-Annie properties, Blaine County, Idaho: Private company report, Mintek Resources Ltd., Vancouver, B.C.

Turner, R.J.W., and Otto, B.R., 1988, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho, in Link, P.K., 

and Hackett, W.R., eds., Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

153-167.

Turner, R.J.W., Otto, B.R., and Smith, D., 1986, Summary report, 

Triumph-Annie properties, Blaine County, Idaho: Private company report, Mintek Resources Ltd., Vancouver, B.C.

Winn, R.D., Jr., and Bailes, R.J., 1987, Stratiform lead-zinc sulfides, mudflows, and turbidites Devonian sedimentation 

along a submarine fault scarp of extensional origin, Jason 

deposit, Yukon Territory, Canada: Geological Society of 

America Bulletin, v. 98, p. 528-539.

Wust, S.L., 1986, Extensional deformation with northwest vergence, Pioneer core complex, central Idaho: Geology, v. 14, p. 

712-714.

Structural Setting of Ore Deposits in the 

Lake Creek Mineralized Area, 

Blaine County, South-Central Idaho

By Bradford R. Burton and Paul Karl Link

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-F

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Fl

Introduction........................................................................................................................... 1

Geology of the Lake Creek Mineralized Area...................................................................... 3

Stratigraphy................................................................................................................... 3

Structural Geology........................................................................................................ 3

Dl Deformation.................................................................................................... 5

D2 Deformation.................................................................................................... 5

D3 Deformation.................................................................................................... 7

D4 Deformation.................................................................................................... 7

Reinterpretation of the Wood River Thrust Fault................................................. 7

Trail Creek Fault................................................................................................... 9

Lake Creek Fault................................................................................................... 9

Economic Geology............................................................................................................... 11

Host-Rock Characteristics............................................................................................ 11

Alteration...................................................................................................................... 11

Geologic Setting of Mineral Deposits .......................................................................... 11

Homestake Mine and Long Grade and High Grade Prospects..................................... 12

Deposits of the Lake Creek and Price Groups.............................................................. 12

Exploration Model................................................................................................................ 13

References Cited................................................................................................................... 13

	FIGURES

1. Map showing major structural features, Lake Creek mineralized area.......................................................................... F2

2. Map showing geology of Lake Creek mineralized area................................................................................................. 4

3. Stratigraphic section of the Wood River Formation....................................................................................................... 6

4. Plots of pole-to-bedding inMilligen and Wood River Formations................................................................................ 8

5. Photograph mosaic of ridge between Lake and Eagle Creeks....................................................................................... 10

6. Geologic cross section through Lake Creek mineralized area....................................................................................... 11
Structural Setting of Ore Deposits in the

Lake Creek Mineralized Area, 

Blaine County, South-Central Idaho

By Bradford R. Burton1 and Paul Karl Link2

ABSTRACT

The Lake Creek mineralized area is on the west slope of 

the Boulder Mountains, northwest of Ketchum, Blaine 

County, Idaho. In this area silver-lead-zinc mineral deposits 

are present in fine-grained calcareous rocks of the Middle 

Pennsylvanian to Lower Permian Wood River Formation. 

The source of the metals in the Lake Creek mineralized area 

is thought to be syngenetic ore deposits in the unconformably underlying Milligen Formation.

Large-scale northeast-vergent overturned folds in both 

the Wood River and Milligen Formations probably formed 

during the late Mesozoic Sevier orogeny. In Paleogene time 

Mesozoic folds were cut by gently west dipping dextral-normal faults that show N. 60° W. mean transport direction. The 

previously named Wood River thrust fault crops out within 

the Lake Creek mineralized area. We reinterpret the Wood 

River thrust fault to be one of several faults in a southwestdipping imbricate stack of Paleogene extensional faults in 

the area and rename it the Trail Creek fault. These extensional faults are interpreted to result from crustal thinning in 

the upper plate of the Pioneer Mountains metamorphic core 

complex.

Mineral deposits in the Lake Creek area are in two geologic settings. Higher grade ore concentrations are in veinfilled fissures and replacement deposits along shear zones in 

the hanging wall of the Lake Creek fault. Lower grade 

deposits are not related to the Lake Creek fault but are in 

bedding-parallel brecciated pods above the locally sheared 

unconformity between the Milligen and Wood River Formations. The dominant ore minerals are zinc and lead carbonate 

minerals, sphalerite, galena, and chalcopyrite. Gangue minerals include quartz, calcite, hematite, and pyrite. Hydrothermal activity associated with magmatism of the Eocene 

Challis Volcanic Group was probably responsible for the

'Department of Geology and Geophysics, University of Wyoming, 

Laramie, Wyoming 82071.

2U.S. Geological Survey and Department of Geology, Idaho State 

University, Pocatello, Idaho 83209.

remobilization and concentration of metals. A new exploration model, based on the recognition of mineralized rock in 

the hanging wall of low-angle faults, can be applied to an 

extensive area of the Boulder and Pioneer Mountains.

INTRODUCTION

The Lake Creek mineralized area is about 16 km northwest of Ketchum, Blaine County, Idaho, on the west flank of 

the Boulder Mountains (fig. 1). Five inactive or abandoned 

mines and numerous prospects are in the Lake Creek, Eagle 

Creek, and Trail Creek drainage basins. The most extensive 

workings are in the Lake Creek drainage and include the 

Homestake, Long Grade, High Grade, Lake Creek, and Price 

Group properties (figs. 1, 2). The area is accessible from 

gravel roads along Lake, Eagle, and Trail Creeks. Steep 

northeast-trending valleys and intervening tree-covered 

ridges characterize the topography; elevations range from 

2,182 to 2,961m.

Ore deposits of Lake Creek mineralized area were 

described by Umpleby and others (1930), Service and Kellum (1956), and Tuchek and Ridenour (1981). The geology 

was described in general by Dover (1981) and Link and others (1988) and in detail by Burton (1988). The stratigraphy 

of the Wood River Formation in the Lake Creek mineralized 

area was described by Hall and others (1974, 1978), Burton 

(1988), and Mahoney and others (1991). The Milligen Formation in neighboring areas was described by Sandberg and 

others (1975), Otto and Turner (1987), Turner and Otto 

(1988, this volume), and Ratchford (1989, this volume) but 

has not been studied in detail in the Lake Creek mineralized 

area. Detailed geologic mapping of the Lake Creek mineralized area was conducted by W.E. Hall (unpublished U.S. 

Geological Survey maps), C.M. Tschanz (unpublished U.S. 

Geological Survey map), and Burton (1988). Recently completed, unpublished geologic mapping (B.R. Burton, P.K. 

Link, D.W. Rodgers, and A.D. Huerta) and stratigraphic 

studies (Burton, 1988) enable us to improve on previously 

published descriptions of the occurrence, structural setting, 

and host-rock characteristics of these mineral deposits. We

Fl
F2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°00'

PIONEER MOUNTAINS 

CORE COMPLEX

WILDHORSE

DETACHMENT

FAULT

43°45 

10 KILOMETERS

EXPLANATION

Paleogene detachment fault Double hachures indicate hanging wall

Thrust fault Sawteeth on upper plate

High-angle normal fault Bar and ball on downthrown side

Figure 1. Map showing major structural features of the Lake Creek mineralized area, Blaine County, Idaho.

also present data that affect regional structural models (see 

Rodgers and others, this volume).

The Lake Creek mineralized area is between the Idaho 

batholith on the west and the Pioneer Mountains metamorphic core complex on the east (fig. 1). The Lake Creek 

mineralized area is in the western part of the Sevier orogenic belt; 8 km to the northeast the Pioneer thrust fault is 

mapped above a major frontal ramp (Rodgers and Janecke,

1992). The Pioneer thrust fault juxtaposes Silurian and 

Ordovician rocks over Mississippian rocks. Paleozoic rocks 

in the Lake Creek mineralized area were transported to the 

east above this major thrust fault during the Late Cretaceous Sevier orogeny.

Paleozoic rocks of the central Idaho black-shale mineral 

belt (Hall, 1985) are the principal formations exposed in the 

Lake Creek mineralized area. These include carbonaceous
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F3

argillite, siltite, and sandstone of the Milligen Formation 

(Devonian) and fine-grained mixed carbonate and siliciclastic strata of the Wood River Formation (Middle Pennsylvanian to Lower Permian). The Late Cretaceous Idaho 

batholith, to the west of the Lake Creek mineralized area, consists of numerous biotite and hornblende-biotite granitic plutons that have yielded radiometric ages of 95-70 Ma (Lewis 

and others, 1987; Kiilsgaard and others, in press; Lewis, in 

press). Hydrothermal activity that accompanied the Late Cretaceous magmatism is thought to have remobilized metals 

from Paleozoic syngenetic ores to produce most of the silverlead-zinc deposits of the Wood River valley and Smoky 

Mountains (Hall and others, 1978; Hall, 1985; Darling and 

others, this volume; Sanford and Wooden, this volume; Park, 

in press). Recent work (Worl and Johnson, this volume) suggests, however, that Eocene hydrothermal activity associated 

with the Challis volcanic episode is responsible for mineralization in the Lake Creek mineralized area and other areas.

The Pioneer Mountains core complex (Dover, 1983; 

Kirn, 1986; Wust, 1986; O'Neill and Pavlis, 1988; Wust and 

Link, 1988; Silverberg, 1990), east of the Lake Creek mineralized area, formed in response to Paleogene regional extension. In the core complex, a major fault (the Wildhorse 

detachment fault) separates high-grade, ductilely deformed 

rocks in the footwall from low-grade metamorphic and 

unmetamorphosed rocks in the hanging wall. Radiometric 

age determinations (Silverberg, 1990) suggest that the infrastructure (footwall) of the core complex was subject to rapid 

erosion or active tectonic unroofing at a rate of 1.5 km per 

million years from 48 to 45 Ma. Volcanic rocks of the 

Eocene Challis Volcanic Group, also related to Paleogene 

extension, crop out immediately south of and within 5 km to 

the north of the Lake Creek mineralized area. Ductile deformation along the Wildhorse detachment system persisted to 

Oligocene time (36-33 Ma) (Silverberg, 1990).

Acknowledgments. Research and mapping presented 

in this report was conducted for the U.S. Geological Survey 

Hailey I°x2° quadrangle CUSMAP (Conterminous United 

States Mineral Assessment Project) under the direction of 

R.G. Worl. Part of this study was conducted as a Master of 

Science thesis at Idaho State University by Burton under the 

direction of Link and D.W. Rodgers. This report was partially funded by Idaho State Board of Education Grant 89-56 

to P.K. Link. We acknowledge useful reviews by S. Soulliere, R. Tysdal, and D.W. Rodgers.

GEOLOGY OF THE LAKE CREEK 

MINERALIZED AREA

STRATIGRAPHY

Paleozoic rocks of the Milligen and Wood River Formations in the Lake Creek mineralized area are dominantly 

fine grained, carbonaceous sedimentary rocks that were

deposited in deep-water environments. The Milligen Formation consists of dark-gray to black subphyllitic carbonaceous 

argillite and argillitic chert and subordinate interbeds of finegrained quartzite and dolomitic siltstone. Due to structural 

complexity, the thickness of the Milligen Formation is not 

known but is estimated to be at least 1,200 m (Sandberg and 

others, 1975).

The Milligen Formation is overlain by the Wood River 

Formation of the Middle Pennsylvanian to Lower Permian 

Sun Valley Group (Mahoney and others, 1991). An angular 

unconformity crosscuts both bedding and a pre-existing 

structural fabric of the Milligen Formation and separates 

the Milligen from the Sun Valley Group (fig. 3). The 

unconformity is marked by a paleoregolith composed of 

angular clasts derived from the Milligen Formation, identified by petrographic comparison of lithology and microstructures of the Milligen Formation and clasts of the 

paleoregolith (Mahoney and others, 1991). In other areas of 

the Wood River valley this contact has been sheared and 

injected with quartz veins and was previously mapped as 

the Wood River thrust fault (Hall and others, 1974; Dover, 

1981, 1983; Hall, 1985).

Above the unconformity the Wood River Formation is 

composed of conglomerate, fossiliferous limestone, silty 

micrite, micritic sandstone, siliceous sandstone, and cherty 

micritic siltstone (fig. 3). The Wood River Formation is at 

least 2,200 m thick; the uppermost part of the formation is 

truncated by the present-day erosional surface.

The Milligen and Wood River Formations are cut by 

dikes and sills related to the Eocene Challis Volcanic Group 

(Stewart and others, in press). Contact metamorphism associated with this intrusive activity is limited. In scattered, isolated areas within several kilometers of the Lake Creek 

mineralized area, Paleozoic sedimentary rocks are unconformably overlain by boulder and cobble conglomerate that 

correlates with the conglomerate of Smiley Creek (Paull, 

1974), which contains Eocene palynomorphs (Burton and 

Blakley, 1988; E. Davies, Branta Biostratigraphic Ltd., Calgary, Alberta, written commun., 1989). The conglomerate of 

Smiley Creek grades upward into volcaniclastic conglomerate and volcanic rocks of the Challis Volcanic Group (51^0 

Ma) (Mclntyre and others, 1982; Ekren, 1985; Moye and 

others, in press). Quaternary alluvial sediments that include 

Pleistocene glacial deposits of the Boulder Creek and Prairie 

Creek advances (Pearce and others, 1988) are present in the 

valley floors and headwaters of the Trail, Lake, and Eagle 

Creek drainages. Late Quaternary landslide deposits and 

landslide-dammed lacustrine deposits are also present.

STRUCTURAL GEOLOGY

The Lake Creek mineralized area has undergone four 

episodes of deformation, including two episodes of compressional deformation (Dl and D2) and two episodes of 

extensional deformation (D3 and D4). Evidence for these 

multiple episodes of deformation is discussed following.
F4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°20' 114°17'30"

R18E
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F5

Qa

Td

Pww

Pwh

EXPLANATION

Alluvium (Quaternary) 

Dacitic dike (Paleogene)

Wilson Creek Member of the Wqod River Formation (Lower 

Permian)

Eagle Creek Member of the Wood River Formation (Lower 

Permian to Middle Pennsylvanian)

Hailey Member of the Wood River Formation (Middle 

Pennsylvanian)

Milligen Formation (Devonian)

Contact Dashed where approximately located; dotted where

concealed 

Paleogene detachment fault Showing trend and plunge of fault

striae. Double hachures show hanging wall. Dashed where

approximately located; dotted where concealed 

1 High-angle normal fault Ball and bar on downthrown side.

Dashed where approximately located; dotted where concealed 

Anticline Dashed where approximately located

 Overturned anticline Showing direction of dip of limbs. Dashed

where approximately located; dotted where concealed 

Syncline Dashed where approximately located

Overturned syncline Showing direction of dip of limbs. Dashed

where approximately located; dotted where concealed 

Strike and dip of bedding Showing amount of dip

Strike and dip of overturned bedding Showing amount of dip

Adit

Trench

Mine or prospect Shown by circled number on map

1. Homestake mine

2. Long Grade prospect

3. High Grade prospect

4. Deposits of the Lake Creek group

5. Deposits of the Price group

1/2 1 MILE

0.5 1 KILOMETER

Figure 2 (above and facing page). Map showing geology of the 

Lake Creek mineralized area, Blaine County, Idaho. Line of section 

A-A' (fig. 6) is also shown. Modified from Burton (1988). Base is 

U.S. Geological Survey Rock Roll Canyon 7.5-minute topographic 

quadrangle (1967).

The tilted and folded rocks of the Devonian Milligen 

Formation were beveled by pre-Middle Pennsylvanian erosion, marked by an unconformity below the Wood River 

Formation. In several locations, notably just below the 

Long Grade mines and at the outcrop of the Hailey Member 

of the Wood River Formation on the central western edge 

of the map area (SE14NW14 sec. 8, T. 5 N., R. 18 E.) (fig. 

2), the unconformity crosscuts S1 cleavage and small-scale 

Fl folds. No strata in the Wood River Formation exhibit 

slaty S1 cleavage nor does the Wood River Formation contain small-scale Fl folds. These relationships constrain Dl 

deformation to pre-Middle Pennsylvanian time. We infer 

that Dl deformation was produced by the Early Mississippian Antler orogeny (Roberts and others, 1958), which is 

the only large-scale compressive tectonic event known to 

have affected this area between Late Devonian and Middle 

Pennsylvanian time (Dover, 1980; Skipp and Hall, 1980; 

Turner and Otto, this volume).

Equal-area projections of poles-to-bedding in the Milligen Formation are shown in figure 4. These data were measured in Devonian strata preserved in the upright lower limb 

of a map-scale F2 fold in the Lake Creek mineralized area. 

Considerable scatter is evident in the data, the source of 

which may be that reliable facing-direction indicators are 

seldom present in the Milligen Formation and therefore 

some data from near the hinge of the F2 fold may be for overturned beds. The data show a point maximum 52°, N. 56° E. 

(labeled D on fig. 4D), which lies along a best-fit great circle 

oriented N. 24° E., 68° SE. To determine the orientation of 

bedding in the Milligen Formation subsequent to Dl deformation but prior to D2 deformation, the point maximum and 

Fl fold axis were rotated to restore bedding in the Wood 

River Formation to horizontal (fig. 4£). The plot shows that 

Dl deformation resulted in folding of the Milligen Formation about an axis 2°, N. 84° W., and northward tilting of 

Milligen Formation strata. Dl deformation is not coaxial 

with D2 deformation.

Dl DEFORMATION

The first phase of compressional deformation (Dl) is 

recognized only in the Milligen Formation. Dl features 

include (1) a penetrative slaty cleavage (SI) in pelitic rocks 

and a spaced cleavage in coarser grained rocks, (2) smallscale (10 cm to several meters amplitude) isoclinal folds 

(Fl), and (3) north-directed folding and tilting about a westnorthwest-oriented fold axis. These features are observed 

throughout the Milligen Formation in the Lake Creek mineralized area. In the surrounding region, similar features are 

observed in the Milligen Formation (Turner and Otto, 1988, 

this volume) but are not present in all areas. The regional distribution of Dl features in the Milligen Formation may be 

related to proximity to a thrust fault formed during the Early 

Mississippian Antler orogeny but is not well understood.

D2 DEFORMATION

The second deformational event (D2) produced mapscale (hundreds of meters to 1,000 m amplitude) east-vergent asymmetric folds (F2). D2 deformation affects both the 

Wood River and Milligen Formations and is recognized 

throughout the eastern part of the Hailey I°x2° quadrangle.

F2 folds have open, concentric synclines and tight, chevron or kink anticlines (figs. 2, 5, 6). Bedding dips steeply to 

the southwest in both limbs of these folds and is overturned 

in the lower limbs of anticlines and the upper limbs of synclines. Equal-area projection of poles-to-bedding in the Wood 

River Formation define a F2 fold axis of 10°, S. 47° E., 

implying that the shortening direction during F2 deformation 

was oriented approximately N. 43° E. (fig. 4).
F6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

THICKNESS, 

METERS IN 

2,400 -

2,200 -

2,000 - 

1,800 -

1,600 -

1,400 -

1,200 -

1,000 -

800 -

600 -

400 -

200 -

0 -

SYSTEM

PERMIAN

z

<

>

C/5

Z 

Z

LU

0_

DEVONIAN

FORMATION

0 

|

cc

0

>

cc 

Q 

0

0

MILLIGEN FORMATION

STAGE

<

<

z

0

LU

^

^

< 

O 

LL

_l

0

z 

<

o 

cc

>

z

cc

ID

O 

C/5

^

<

Z 

O

:>

C/)

LU

D

MEMBER

o 

n

E

Creek i/Vilson M(

CU 

.Q

E

0)

^

^L

o> 

a>

O

0) 

O) 

CD

LU

QJ .Q

1|

-Tfft

/A/--/

/*./ /

T7-/ / 

/ / -/

/ " / / 

_L-- I 1 1

] .. 1

1 I

'l-'-l '.-'-1

1 - 1

1 ] 1

1- 1 1

! 1

1 - I 1

; -": ' 

;'_L 

^ ^

. _L 

. -_L . 

- . .-'A

 \ ! ! ' 1 '

i i i !i i i J

i-4 i ! i ! i .'

r i i i i

i i

i i

i- i i i

'v'/.i 'v.'.-

i i

_Lr 1 1 1

0 ' -Ja.- U'i1

4X2^^

^^

STRATIGRAPHIC DESCRIPTION

__ Top eroded; total thickness and

^

Abundant authigenic chert after micrite

Thin-to medium-bedded silty micrite in 

fining- and thinning-upward cyclic

_L

T.

'_ Massive micritic sandstone; thinning- 

- ' upward cyclic packets; thick to medium

 :;: : Massive thick-bedded siliceous 

: : : : sandstone

_ . sandstone

^ Thin- to medium-bedded silty micrite and

r- coarse bases.

mudstone

/

/ Coarse bioclastic limestone and biostrome 

_ , / hinlithitfi

^D oS<c?' Pebble-boulder conglomerate

°"Oo ^^

Cleaved argillite, small-scale isoclinal folds

STRATIGRAPHIC 

LOCATION OF 

MINES AND 

PROSPECTS

*- HOMESTAKE 

< HIGH GRADE

< LONG GRADE

c LMIxt Unttlx

*- PRICE

Figure 3. Stratigraphy of the Wood River Formation. The stratigraphic locations of mines and prospects discussed in the text are also shown. Modified from Mahoney and others (1991).
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F7

The tight, overturned anticlines are interpreted to be 

fault propagation folds cored by small-displacement splay 

thrusts above a basal detachment (fig. 6). These faults are 

generally not exposed at the surface in the Lake Creek mineralized area, but at least one small-offset thrust fault was 

mapped along an anticlinal trace in Murdock Creek, 2 km 

north of the headwaters of Eagle Creek beyond the northwestern corner of the mineralized area.

Numerous faults were previously mapped as thrust 

faults by other workers in Lake Creek mineralized area 

(Dover, 1983; W.E. Hall, unpublished mapping), but we 

reinterpret these faults as oblique-slip normal faults associated with D3 deformation (see later discussion). We identified no major thrust faults in the Lake Creek mineralized 

area. Instead, shortening was here accommodated dominantly by folding. Depth-to-detachment calculations, using 

the line-length area-balance method of Woodward and others (1985), indicate that a basal detachment fault in the lower 

part of the Milligen Formation (about 625 m above sea level) 

is necessary to explain the amount of shortening observed in 

the megascopically folded Wood River Formation.

We infer that D2 deformation in the Lake Creek mineralized area was produced by the Sevier orogeny (Armstrong, 

1975) during Late Cretaceous time. We found no direct evidence for the age of D2 deformation in the Lake Creek mineralized area but inferred the age from evidence in adjacent 

areas. In the Smoky Mountains, on the eastern margin of the 

Idaho batholith, approximately 40 km southwest of the Lake 

Creek mineralized area, D2 deformation is broadly synchronous with intrusion of the Idaho batholith and metamorphism at 83.9±3.4 Ma (Whitman, 1990, this volume). In the 

Mahoney Butte quadrangle, 25 km southwest of the Lake 

Creek mineralized area (Skipp and others, 1994), the Deer 

Creek thrust fault was folded and then intruded by the Deer 

Creek stock about 90 Ma. Thus, regionally recognized D2 

deformation in the area of the Lake Creek mineralized area 

must have occurred prior to and partly synchronous with 

emplacement of the Idaho batholith 90-85 Ma.

D3 DEFORMATION

The third phase of deformation in the Lake Creek mineralized area (D3) consists of extensional deformation that 

produced gently dipping corrugated dextral-normal faults 

with top-to-the-northwest displacement. Smaller displacement, synthetic, steeply dipping normal faults in the hanging 

wall of the larger scale, gently dipping faults are interpreted 

to flatten into the underlying detachment faults. D3 deformation affects Paleozoic and Mesozoic rocks and crosscuts D2 

features (fig. 5).

Northwest-striking oblique-slip normal faults that 

have shallow (10°-30°) southwest dip crosscut the F2 

folds. These faults generally place younger rocks of the 

Eagle Creek and Wilson Creek Members of the Wood

River Formation on older strata of the Hailey Member and 

Milligen Formation, although, locally, older-on-younger 

relations are present (figs. 2, 6). Slip indicators on the faults 

include fault striae or slickenlines and chatter marks, and 

they show that last movement of the hanging wall was 

toward the northwest (fig. 2) (Huerta, 1992). The faults display corrugated or curviplanar geometry and thus vary 

locally from dip-slip normal faults to strike-slip faults. 

They are related to Paleogene extension in the upper plate 

of the Pioneer Mountains core complex (Wust, 1986; Wust 

and Link, 1988; Burton and others, 1989; Batatian, 1991; 

Huerta, 1992; Rodgers and others, this volume). These 

faults were mapped by previous workers (Umpleby and 

others, 1930; Dover, 1981, 1983) as thrust faults.

Within the hanging wall of the shallowly dipping D3 

detachment faults are northwest-striking, moderately to 

steeply southwest dipping normal faults. These faults 

accommodated only tens of meters of displacement and, 

because their separation can only be mapped in single 

detachment-fault plates, are interpreted to sole into the 

underlying detachment faults. We suggest that they formed 

during movement on the underlying detachment in response 

to dextral-normal displacement above the curviplanar 

detachment fault surface. These minor structures are important because they host several of the mineral deposits in the 

Lake Creek mineralized area. The Lake Creek fault (figs. 1, 

2) is a D3 structure that hosts the most significant mineral 

deposits of the Lake Creek mineralized area.

D4 DEFORMATION

The last deformational event recognized in the Lake 

Creek mineralized area (D4) is manifested by steeply dipping 

dip-slip normal faults that strike north to northeast and 

accommodated down-to-the-west displacement. These faults 

cut Paleozoic, Mesozoic, and Paleogene rocks and include 

the Sun Valley fault (fig. 1). Northerly striking, steeply west 

dipping dip-slip normal faults (D4) that accommodated tens 

to possibly hundreds of meters of down-to-the-west displacement have been mapped to the south of Lake Creek mineralized area (Hall and others, 1978; Burton, 1988). The 

northwest-striking D4 faults are a product of Neogene crustal 

extension of the Basin and Range structural province of the 

western United States (Link and others, 1988; Rodgers and 

others, this volume). D4 features are not associated with economic mineral deposits of the Lake Creek mineralized area.

REINTERPRETATION OF THE 

WOOD RIVER THRUST FAULT

In the area north and east of the Lake Creek mineralized 

area, in the Boulder and Pioneer Mountains, Dover (1983) 

mapped two major structures, the Wood River thrust fault
F8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES 

N N

B

F21
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F9

and the Pioneer thrust system. Subsequent work, summarized here and in Rodgers and others (this volume), reinterprets the Wood River thrust fault as a normal fault associated 

with Paleogene crustal extension and early stages of formation of the Pioneer Mountains core complex. Part of the Pioneer thrust system that lies south of lat 43°47'30" N. was 

similarly reinterpreted and was renamed the Wildhorse 

detachment (Wust, 1986). North of this latitude, the Pioneer 

thrust fault juxtaposed Ordovician rocks over Mississippian 

rocks and is recognized as a major thrust fault (Dover, 1981, 

1983; Worl and others, 1991; Rodgers and Janecke, 1992).

The Wood River thrust fault as defined by Dover (1981, 

1983) included all locations where Wood River Formation 

lies directly stratigraphically or structurally above the Milligen Formation. Dover, following Hall and others (1978), 

applied the term "Wood River thrust" to areas where the 

unconformable contact of the Milligen and Wood River Formations is sheared due to flexural slip associated with F2 

folding. This contact is exposed in many locations in the 

Boulder and Pioneer Mountains (Worl and others, 1991). 

The contact demonstrates several geologic relations: (1) 

paleoregolith of Milligen Formation below conglomerate of 

the Hailey Member with no evidence of shearing, (2) a shear 

zone filled with quartz veins below the Hailey Member, as in 

the High Grade and Lake Creek mines (fig. 2), and (3) 

sheared and attenuated Hailey and lower part of the Eagle 

Creek Members above the Milligen Formation. The contact 

does not contain evidence of structural thickening, repeated 

strata, or older-on-younger relationships associated with 

thrust faulting. Our work suggests that the contact is not a 

regional thrust fault but rather an unconformity that experienced varying amounts of flexural slip between rocks of different competence.

TRAIL CREEK FAULT

We interpret the Wood River thrust as mapped by 

Dover (1981, 1983) on the northeast side of the Lake Creek 

mineralized area to be the lowest exposed, shallowly dipping 

dextral-normal fault in the hanging wall of the Wildhorse 

detachment fault, and we rename it the Trail Creek fault 

(figs. 1, 6). Above the Trail Creek fault, we identify and 

name the Lake Creek fault and the Neal Canyon fault as 

other, structurally higher faults that are also associated with 

the Wildhorse detachment fault (fig. 1).

The recognition that the Trail Creek fault is a D3 

transtensional feature is based on the following criteria: (1) 

the Trail Creek fault juxtaposes younger rocks in the hanging wall against older rocks in the footwall, (2) displacement on the Trail Creek fault is not coaxial with D2 

shortening (F2 folds in both the hanging wall and footwall 

display a N. 43° E. vergence direction associated with 

Sevier erogenic compression, but striae on the Trail Creek 

fault surface trend N. 50°-65° W., indicating fault displacement toward the northwest), and (3) the Trail Creek fault 

cuts across earlier formed F2 folds and must be a product of 

younger tectonism.

The cross sections of Umpleby and others (1930) and 

Dover (1981,1983) also show that the Trail Creek fault truncates F2 folds, but the interpretation by Umpleby and others 

and by Dover of this relationship was that both the folds and 

the thrust fault were produced by Sevier orogenic compression. This interpretation would require that the Wood River 

thrust fault be a late stage, out-of-sequence fault that cut previously folded rocks. Kinematic data presented in this report 

and by Burton and others (1989) and Huerta (1992) favor the 

simpler interpretation that the Trail Creek fault is a younger 

transtensional feature.

Figure 4 (facing page). Equal-area, lower hemisphere projections of poles-to-bedding in the Milligen and Wood River Formations in the Lake Creek mineralized area, Blaine County, Idaho. A, 

Poles-to-bedding in the Wood River Formation (data are from the 

upright limb of an F2 fold). B, Contour plot of data shown in A, 

showing best-fit great circle N. 43° E., 80° NW., which describes a 

fold axis, F2, oriented 10°, S. 47° E. C, Poles-to-bedding in the Milligen Formation. D, Contour plot of data shown in C, showing bestfit great circle N. 24° E., 68° SE., which intersects the point maximum at 52°, N. 56° E., and describes a fold axis, Fl, oriented 22°, 

N. 66° W. E, Plot showing rotation of Fl fold axis to remove the effects of D2 deformation. Points shown are Wood River Formation 

(P) and Milligen Formation (D) poles-to-bedding point maxima and 

Fl and F2 fold axes. The F2 fold axis was rotated to horizontal (solid arrows) along with the Fl fold axis and point maxima to yield 

F2', Fl', P', D', then Wood River Formation bedding was restored 

to horizontal (dashed arrows). The resulting orientation of Fl" is 2°, 

N. 84° W., and of D" is 68°, S. 3° E.

LAKE CREEK FAULT

At the headwaters of Lake Creek (fig. 2), a northwest-striking fault, here named the Lake Creek fault, dips 

30° SW. and places F2 folded Eagle Creek and Wilson 

Creek Members of the Wood River Formation on F2 

folded rocks of the subjacent Milligen and Wood River 

Formations (fig. 6). In most places, this results in a 

younger-over-older relationship. Klippen of the Lake 

Creek fault are on the top of the ridge east of the Homestake mine and in several places on the southwest slope 

of the Boulder Mountains. In these excellent exposures of 

the fault surface, the Lake Creek fault has consistent 

N. 50°-65° W. kinematic indicators (fault striae or slickenlines on the highly polished fault surface) indicating 

last movement to the northwest. The fault has a curviplanar geometry including long-wavelength, low-amplitude
Q m 

o

5Q

z 

w

w

on On

w

on O

w rez; a

atn 

O

G21 Q

W 

on

Figure 5. Photomosaic of a view to the northwest of the ridge between Lake and Eagle Creeks, Lake Creek mineralized area, Blaine County, Idaho. The location of Paleogene extensional faults associated with mineralization of the area and the location of the Homestake mine (circled number 1), High Grade prospect (circled number 3), and the Lake Creek group of deposits (circled number 4) are shown on the photo-overlay. Stratigraphic units 

are the Wilson Creek Member of the Wood River Formation (Pww), the Eagle Creek Member of the Wood River formation (PPwe), the Hailey Member of the Wood River Formation (Pwh), and the Milligen Formation (Dm).
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA Fll

SOUTHWEST 

FEET A

IO.OOCH

9.000 -

8.000 -

7.000 -

6,000 -

5.000 -

4,000

PPwe

NORTHEAST 

A1

Tectonic assemblage of Wood River^ 

'^''''-'vJ^A^'Formation, Milligen Formation, '< 

'f^-^^^'^"'' anc' unnamed Ordovician^'^'^'^ 

"" ' "' through Devonian rocks <X^'''' '''

2 KILOMETERS

Figure 6. Cross section showing geology of the Lake Creek mineralized area, Blaine County, Idaho. Line of section is shown in figure 

2. The Homestake mine is in a shear zone of the Homestake fault, a high-angle normal fault synthetic to the Lake Creek fault. Relative 

movement on the Lake Creek fault was dextral-normal slip with hanging wall toward N. 60° W. The fault displays a curviplanar geometry 

with axes of corrugations parallel with the movement direction. Circled x indicates movement direction is into plane of cross section; circled period indicates movement direction is out of plane of cross section. Tight anticlines in the Devonian Milligen Formation and the 

Pennsylvanian to Lower Permian Wood River Formation are thought to be thrust fault propagation folds. Stratigraphic units are the Wilson 

Creek Member of the Wood River Formation (Pww), the Eagle Creek Member of the Wood River Formation (PPwe), the Hailey Member 

of the Wood River Formation (Pwh), and the Milligen Formation (Dm).

sinusoidal undulations. The axes of these corrugations are 

approximately parallel with the measured northwestdirected displacement on the fault. The fault cuts both upand down-section through F2 folds in both the hanging 

wall and footwall. The Lake Creek fault is shown on the 

cross sections of Dover (1981, 1983) as a folded 

thrust fault.

ECONOMIC GEOLOGY 

HOST-ROCK CHARACTERISTICS

Host rocks in the Homestake mine are carbonaceous 

silty micrite and calcareous mudstone of the Eagle Creek and 

Wilson Creek Members of the Wood River Formation (fig. 

3). The largest deposits replace micritic wallrock adjacent to 

structurally controlled fissure veins. Silty micritic limestone 

wallrock has been replaced by ferruginous, porous zones that 

host ore deposits within a quartz matrix. Noncalcareous 

sandstone and quartzite are generally not mineralized.

The host rocks in the Lake Creek and Price Group prospects are conglomerate and limestone of the Hailey Member 

of the Wood River Formation (fig. 3). Here, replacementtype mineral deposits are within a few tens of meters of the 

underlying Devonian Milligen Formation.

Lead-isotope data (Sanford and Wooden, this volume) 

show that galena collected from the Homestake mine contains Triumph-type lead, similar to syngenetic galena from 

the Devonian Milligen Formation at the Triumph mine 5 km 

south of the Lake Creek mineralized area. Tightly folded and 

cleaved gray argillite of the Milligen Formation in the footwall of the Lake Creek fault is suspected to be the major 

source of the ore metals in the Lake Creek mineralized area.

ALTERATION

Alteration of the host rock consists of (1) oxidation of 

iron phases to a brick-red gossan that is present in a thin zone, 

notably around the Lake Creek and Price Group deposits, (2) 

oxidation of primary galena to cerussite, and (3) oxidation of 

primary sphalerite to smithsonite and hemimorphite. Breccia 

and gouge in the mineralized fissures are bleached and have 

wispy, discontinuous hematite staining.

GEOLOGIC SETTING OF 

MINERAL DEPOSITS

Mineral deposits in the area are in at least two geologic 

settings: (1) steeply southwest dipping normal faults host 

vein-filled fissures or replacement deposits (Homestake
F12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

mine and Long Grade and High Grade prospects), and (2) the 

sheared unconformity between the Milligen Formation and 

overlying Hailey Member of the Wood River Formation 

hosts pods of mineralized rock (deposits of the Lake Creek 

and Price groups).

HOMESTAKE MINE AND LONG GRADE 

AND HIGH GRADE PROSPECTS

The Homestake mine is near the headwaters of the west 

fork of Lake Creek (figs. 2, 5). The mine is in sections 3, 4, 

and 5, T. 5 N., R. 18 E., and in sections 32 and 33, T. 6 N., 

R. 18 E., Warm Springs Creek mining district, Blaine 

County, Idaho. Carbonaceous argillite and silty micrite of 

the Wilson Creek Member of the Wood River Formation 

host mineral deposits along a major northwest-striking 

(N. 26° W.) shear zone (the Homestake fault, figs. 2, 6) that 

dips 45°-75° SW. (Tuchek and Ridenour, 1981, p. 223). The 

shear zone can be traced on the surface for approximately 1.6 

km and can be inferred from discontinuous exposure for 

more than 4.8 km. The shear zone accommodated S. 70° W. 

extension and is synthetic to the underlying Lake Creek 

fault, which forms a dip slope north of the mine in the northeast headwaters of Lake Creek (figs. 2, 6).

The ore minerals formed by oxidation of primary 

galena and sphalerite. Altered remnants of galena are in the 

wallrock. The dominant ore minerals in veins and replaced 

limestone are zinc and lead carbonates and silicates, mainly 

smithsonite, hemimorphite, and cerussite. Silver is present 

as trace amounts in primary galena and sphalerite. On the 

margins of mineralized veins, the sheared, altered, brecciated, and veined country rock contains quartz, calcite, and 

hematite. Ore shoots are from 7 cm to 2 m in thickness and 

from 3 to more than 30 m in length. Production records from 

1923 to 1961 indicate that the average ore grade from filledfissure and replacement deposits was 6.5 ounces per ton silver, 4.5 percent lead, and 9.5 percent zinc (Tuchek and Ridenour, 1981). The mine today is mainly caved and 

inaccessible.

At the Homestake mine, ore is preferentially in carbonaceous silty micrite and calcareous mudstone of the Eagle 

Creek and Wilson Creek Members of the Wood River Formation. Ore is not present where the shear zone cuts quartzite 

or siliceous mudstone of the formation. The Homestake 

workings were described by Tuchek and Ridenour (1981), 

who estimated that at least 730,000 tons of submarginal 

reserves of silver, lead, and zinc ore remain in unexplored 

parts of the shear zone.

The Long Grade prospect is east of Lake Creek, about 

1.9 km south of the Homestake workings (fig. 2). Five adits 

expose northwest-trending, breccia-filled mineralized shear 

zones that cut gray silty mudstone and tan calcareous sandstone of the Wilson Creek Member of the Wood River Formation (fig. 3). The shear zones occupy the hanging wall of

the Lake Creek fault and are directly analogous in geologic 

setting to the Homestake structure (Tuchek and Ridenour, 

1981). The shear zones strike N. 10°-30° W. and dip 

30°-50° SW. Ore minerals include lead and zinc carbonate 

minerals and minor amounts of galena, sphalerite, and pyrite 

in a gangue of calcite, hematite, and crushed limestone wallrock. Tuchek and Ridenour (1981) estimated that the Long 

Grade property has 32,500 tons of submarginal reserves of 

lead and zinc ore.

The High Grade prospect (figs. 2, 5) is near the ridge 

top between Lake and Eagle Creeks, along the northward 

extension of the Homestake shear zone (Tuchek and Ridenour, 1981). The controls on mineralization are the same as 

those for the Homestake mine.

Mineral deposits of the Homestake mine and the Long 

Grade and High Grade prospects are confined to shear zones 

that are synthetic to, and in the hanging wall of, the Lake 

Creek fault (D3). The mineral deposits are therefore probably Eocene or younger in age. The metals are interpreted to 

have been remobilized from the Milligen Formation by 

hydrothermal convection cells associated with dacite porphyry dikes that are present throughout the area. These intrusive rocks are part of the regionally extensive Eocene 

magmatic rock suite associated with the Challis Volcanic 

Group and subjacent intrusive rocks (Moye and others, in 

press; Stewart and others, in press). Coeval extensional faulting related to uplift of the Pioneer Mountains core complex 

provided pathways for migration of metals and for formation 

of veins. The metals were deposited in veins and as replacements of calcareous rocks of the Wood River Formation.

DEPOSITS OF THE LAKE CREEK 

AND PRICE GROUPS

Deposits of the Lake Creek group of prospects (figs. 

2, 5), described in detail by Tuchek and Ridenour (1981), 

are about 245 m northwest of lower Lake Creek Lake, 280 

m above the valley floor. The workings follow a zincbearing and calcite-filled shear zone 0.1-1.1 m thick 

within silty micrite of the lower part of the Eagle Creek 

Member of the Wood River Formation (fig. 3). The shear 

zone strikes N. 40° W. and dips from 80° SW. to vertical. 

The shear zone is parallel with the strike of beds in the 

country rock and probably represents bedding-parallel 

shear produced during Mesozoic folding.

Deposits of the Price group (fig. 2) are about 405 m 

southeast of lower Lake Creek Lake, 312-499 m above the 

valley floor. Veins are developed in calcite-filled shear 

zones as long as 312 m that strike N. 40° W. and dip from 

80° SW. to vertical. The host rock is conglomerate of the 

Hailey Member of the Wood River Formation. Umpleby and 

others (1930, p. 196) noted that mineral deposits are present 

as pods along irregular zones of brecciation and in joints and
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F13

discontinuous fractures. These silver-lead-zinc-rich pods 

formed along the angular unconformity between the Hailey 

Member of the Wood River Formation and the underlying 

Milligen Formation. The unconformity has accommodated 

interstratal slip in the upper limb of a concentric, northeastverging, overturned F2 fold. A shear zone produced by this 

interstratal slip hosts the mineral-rich pods.

Structures that host deposits of the Lake Creek and 

Price groups are F2 folds, and thus mineralization occurred 

either during Late Cretaceous plutonism or during Eocene 

magmatism (coincident with mineralization in the Homestake, Long Grade, and High Grade prospects). The small 

size and podlike nature of the F2-hosted mineral deposits 

limit their value for future mineral development.

EXPLORATION MODEL

Source of metals. A source of metals is available from 

metamorphosed pelitic rocks of the Devonian Milligen 

Formation.

Remobilization. Mesozoic plutonism and associated 

hydrothermal activity may have remobilized and concentrated some metals in Mesozoic compressional structures.

Structural conduits. Paleogene detachment faults in 

the upper plate of the Pioneer Mountains core complex and 

associated shear zones served as sites of formation of vein 

and replacement ore.

Remobilization and concentration. The presence of 

Eocene hypabyssal intrusive rocks suggests that remobilization and concentration of metals by hydrothermal convection 

cells occurred during Eocene magmatism. Deposition of ore 

minerals during the Cretaceous is rejected because there are 

no Cretaceous intrusive rocks within several tens of kilometers of the Lake Creek mineralized area and because the 

extensional host structures are demonstrably of Eocene age.

Host rock. Calcareous fine-grained sedimentary rocks 

of the Wood River Formation are available as hosts for 

mineralization.

The Homestake and Long Grade mineral deposits previously were thought to be associated with D2 Mesozoic 

compressional structures; however, the recognition of Paleogene extensional tectonism (D3) (Link and others, 1988; 

Burton and others, 1989) in the eastern Boulder Mountains 

suggests that a new structural model should be used for 

silver-lead-zinc exploration in the region.

The Lake Creek deposits are similar in tectonic setting 

to silver-lead-zinc deposits in the southern Trigo Mountains 

of Yuma County, Arizona (Garner and others, 1982) and to 

gold deposits at the Picacho mine, Imperial County, 

California (Liebler, 1988). In these areas, mineralized rock 

is in the hanging wall of extensional faults, just as it is in 

the Boulder Mountains of Idaho. An areally extensive network of vertically stacked extensional faults is around the 

south, west, and northwest sides of the Pioneer Mountains 

core complex, an area that makes up most of the Boulder 

and Pioneer Mountains.

REFERENCES CITED

Armstrong, R.L., 1975, Sevier orogenic belt in Nevada and Utah: 

Geological Society of America Bulletin, v. 79, p. 429-458.

Batatian, L.D., 1991, Paleozoic stratigraphy and Cenozoic structure, central Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University, M.S. 

thesis, 85 p.

Burton, B.R., 1988, Stratigraphy of the Wood River Formation in 

the eastern Boulder Mountains, Blaine and Custer Counties, 

south-central Idaho: Pocatello, Idaho State University,.M.S. 

thesis, 165 p.

Burton, B.R., and Blakley, J.D., 1988, The basal Challis conglomerate, Custer County, south-central Idaho Implications for 

the initiation of Challis volcanism: Geological Society of 

America Abstracts with Programs, v. 20, no. 6, p. 408-409.

Burton, B.R., Link, P.K., and Rodgers, D.W., 1989, Death of the 

Wood River thrust Structural relations in the Pioneer and 

Boulder Mountains, south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 21, no. 5, p. 62.

Dover, J.H., 1980, Status of the Antler orogeny in central Idaho, 

clarification and constraints from the Pioneer Mountains, in 

Fouch, T.D. and Magathan, E.R., eds., Paleozoic paleogeography of the West-Central United States: Rocky Mountain Section, Society of Economic Paleontologists and Mineralogists, 

West-Central United States Paleogeography Symposium 1, p. 

371-381.

 1981, Geology of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho, in Mineral resources 

of the Boulder-Pioneer Wilderness Study Area, Blaine and 

Custer Counties, Idaho: U.S. Geological Survey Bulletin 

1497-A, p. 1-75. 

-1983, Geologic map and sections of the central Pioneer

Mountains, Blaine and Custer Counties, central Idaho: U.S. 

Geological Survey Miscellaneous Investigations Series Map 

1-1319, scale 1:48,000.

Ekren, E.B., 1985, Eocene cauldron-related volcanic events in the 

Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the 

geology and mineral deposits of the Challis I°x2° quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-C, p. 43-58.

Garner, W.E., Frost, E.G., Tanges, S.E., and Germinario, M.P., 

1982, Mid-Tertiary detachment faulting and mineralization in 

the Trigo Mountains, Yuma County, Arizona, in Frost, E.G., 

and Martin, D.L., eds., Mesozoic-Cenozoic tectonic evolution 

of the Colorado River region, California, Arizona, and Nevada: 

San Diego, Calif., Cordilleran Publishers, p. 158-172.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hall, W.E., Batchelder, J.H., and Douglass, R.D., 1974, Stratigraphic section of the Wood River Formation, Blaine County, 

Idaho: U.S. Geological Survey Journal of Research, v. 6, no. 5, 

p. 579-592.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, p. 579-592.
F14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Huerta, A.D., 1992, Lake Creek fault Evidence of pre-Challis 

shear within south-central Idaho: Pocatello, Idaho State University, M.S. thesis, 57 p.

Kiilsgaard, T.K., Lewis, R.S., and Bennett, E.H., in press, Plutonic 

and hypabyssal rocks of the Hailey I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 2064-U.

Kim, A.Y.H., 1986, The kinematics of brittle polyphase deformation within the Pioneer metamorphic core complex, Pioneer 

Mountains, Idaho: Bethlehem, Pa., Lehigh University, M.S. 

thesis, 130 p.

Lewis, R.S., in press. Alteration and mineralization in the eastern 

part of the Soldier Mountains, Camas County, Idaho: U.S. 

Geological Survey Bulletin 2064-V.

Lewis, R.S., Kiilsgaard, T.H., Bennett, E.H., and Hall, W.E., 1987, 

Lithologic and geochemical characteristics of the central and 

southeastern part of the southern lobe of the Idaho batholith, in 

Vallier, T.L., ed., Geology of the Blue Mountains region of 

Oregon, Idaho, and Washington; the Idaho batholith and its 

border zone: U.S. Geological Survey Professional Paper 1436, 

p. 171-196.

Liebler, G.S., 1988, Geology and gold mineralization at the Picacho 

Mine, Imperial County, California, in Schafer, R.W., Cooper, 

J.J., and Vikre, P.G., eds., Bulk mineable precious metal 

deposits of the western United States: Geological Society of 

Nevada, p. 453-472.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke., Susanne, and 

Burton, B.R., 1988, Structural and stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knob, Pioneer, Boulder, and Smoky Mountains, in Link, P.K., 

and Hackett, W.R., eds., Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

5-42.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvanian and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J.D., and 

Stevens, C.H., eds.. Paleozoic paleogeography of the western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-580.

Mclntyre, D.H., Ekren, E.D., and Hardyman, R.F., 1982, Stratigraphic and structural framework of the Challis volcanics in 

the eastern half of the Challis I°x2° quadrangle, Idaho, in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology 

of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, p. 

3-22.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-FF.

O'Neill, R.L., and Pavlis, T.L., 1988, Superposition of Cenozoic 

extension on Mesozoic compressional structures in the Pioneer 

Mountains metamorphic core complex, central Idaho: Geological Society of America Bulletin, v. 100, p. 1833-1845.

Otto, B.R., and Turner, R.J.W., 1987, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho: Northwest 

Geology, v. 16, p. 95-103.

Park, W.A., in press. The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-DD.

Paull, R.A., 1974, Upper Cretaceous(?) to lower Eocene post-orogenic conglomerate, south-central Idaho: Geological Society 

of America Abstracts with Programs, v. 6, no. 5, p. 466.

Pearce, S., Schlieder, G., and Evenson, E.B., 1988, Glacial deposits 

of the Big Wood River Valley, in Link, P.K., and Hackett, 

W.R., eds., Guidebook to the geology of central and southern 

Idaho: Idaho Geological Survey Bulletin 27, p. 203-207.

Ratchford, M.E., 1989, Geology of the Boulder Basin, Blaine and 

Custer Counties, Idaho: Moscow, University of Idaho, M.S. 

thesis, 154 p.

 in press, Epigenetic lead-tin-silver-antimony-gold veins in 

Boulder Basin, Blaine and Custer Counties, Idaho Potential 

for economic tin mineralization: U.S. Geological Survey Bulletin 2064-JJ.

Roberts, R.J., Hotz, P.E., Gilluly, J., and Furgusan, H.G., 1958, 

Paleozoic rocks of north central Nevada: American Association of Petroleum Geologists Bulletin, v. 42, p. 2813-2857.

Rodgers, D.W., and Janecke, S.U., 1992, Tertiary paleogeologic 

maps of the western Idaho-Wyoming-Montana thrust belt, in 

Link, P.K., Rodgers, D.W., and Platt, L.B., eds.. Regional geology of eastern Idaho and western Wyoming: Geological Society of America Memoir 179, p. 83-94.

Sandberg, C.A., Hall, W.E., Batchelder, J.N., and Axelson, Claus, 

1975, Stratigraphy, conodont dating, and paleotectonic interpretation of the type Milligen Formation (Devonian), Wood 

River area, Idaho: U.S. Geological Survey Journal of Research, 

v. 3, p. 707-720.

Service, A.L., and Kellum, D.F., 1956, Final report, contract 

Idm-E18, Homestake Mine (unpublished): Spokane, Wash., 

Defense Minerals Exploration Administration, 12 p.

Silverberg, D.S., 1990, The tectonic evolution of the Pioneer metamorphic core complex, south-central Idaho: Cambridge, Massachusetts Institute of Technology, Ph.D. dissertation, 279 p.

Skipp, B., and Hall, W.E., 1980, Upper paleozoic paleotectonics 

and paleogeography of Idaho, in Fouch, T.D., and Magathan, 

E.R., eds., Paleozoic paleogeography of the West-Central 

United States: Rocky Mountain Section, Society of Economic 

Paleontologists and Mineralogists, West-Central United States 

Paleogeography Symposium 1, p. 387-422.

Skipp, B., Hall, W.E., and Link, P.K., 1994, Geologic map of the 

Mahoney Butte quadrangle, Blaine County, Idaho: U.S. Geological Survey Geologic Quadrangle Map GQ-1742, scale 

1:24,000.

Stewart, D.E., Schmidt, K.L., Moye, F.J., Mahoney, J.B., and Link, 

P.K., in press, Eocene intrusive complexes in the Smoky and 

Boulder Mountains, south-central Idaho: U.S. Geological Survey Bulletin 2064-11.

Tuchek, E.T., and Ridenour, James, 1981, Economic appraisal of 

the Boulder-Pioneer Wilderness Study Area, Blaine and Custer 

Counties, Idaho, in Mineral resources of the Boulder-Pioneer 

Wilderness Study Area, Blaine and Custer Counties, Idaho: 

U.S. Geological Survey Bulletin 1497, p. 181-292.

Turner, R.J.W., and Otto, B.R., 1988, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho, in Link, P.K., 

and Hackett, W.R., eds., Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

153-167.

Umpleby, J.B., Westgate, L.G., and Ross, C.P., 1930, Geology and 

ore deposits of the Wood River region, Idaho: U.S. Geological 

Survey Bulletin 814, 250 p.
STRUCTURAL SETTING OF ORE DEPOSITS, LAKE CREEK MINERALIZED AREA F15

Whitman, S.K., 1990, Metamorphic petrology and structural geology of the Pennsylvanian-Permian Dollarhide Formation, 

Blaine and Camas Counties, south-central Idaho: Pocatello, 

Idaho State University, M.S. thesis, 108 p.

Woodward, N.B., Boyer, S.E., and Suppe, John, 1985, An outline 

of balanced cross sections (2nd ed.): University of Tennessee 

Studies in Geology 11, 170 p.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991,

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Wust, S.L., 1986, Extensional deformation with northwest vergence, Pioneer core complex, central Idaho: Geology, v. 14, 

p. 712-714.

Wust, S.L., and Link, P.K., 1988, Field guide to the Pioneer Mountains core complex, south-central Idaho, in Link, P.K., and 

Hackett, W.R., eds., Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 43-54.

Geologic Setting of Mineral Deposits in the 

Washington Basin Area, Custer County, 

South-Central Idaho

By J. Brian Mahoney

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-G

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Gl

Introduction........................................................................................................................... 1

Historical Perspective........................................................................................................... 2

Geologic Setting................................................................................................................... 2

Stratigraphy................................................................................................................... 2

Salmon River Assemblage.................................................................................... 4

Grand Prize Formation ......................................................................................... 4

Wood River Formation......................................................................................... 6

Structure........................................................................................................................ 7

Igneous Intrusive Rocks ............................................................................................... 8

Mineral Deposits................................................................................................................... 9

Polymetallic Veins........................................................................................................ 9

Shear-Zone-Hosted Polymetallic Veins ....................................................................... 10

Massive Replacement Deposits.................................................................................... 10

Genesis and Ore Controls............................................................................................. 10

Mineral Potential.......................................................................................................... 11

References Cited................................................................................................................... 11

FIGURES

1. Map showing location of Washington Basin area ......................................................................................................... G2

2. Map showing geology of Washington Basin area ......................................................................................................... 3

3. Cross sections showing geology of Washington Basin area.......................................................................................... 5

4. Stratigraphic section of part of Grand Prize Formation, Washington Basin area.......................................................... 6

5. Map showing location of mines and major mineralized veins in Washington Basin area............................................ 8
Geologic Setting of Mineral Deposits in the

Washington Basin Area, Custer County,

South-Central Idaho

By J. Brian Mahoney ]

ABSTRACT

In the Washington Basin area of south-central Idaho, 

mineral deposits of lead, silver, and zinc are contained 

within folded and faulted Paleozoic strata that have been 

intruded by Cretaceous and Eocene stocks and dikes. 

Micritic sandstone, siltstone, sandy micrite, and polymict 

conglomerate of the Middle Pennsylvanian to Lower Permian Sun Valley Group unconformably overlie black argillite of the Paleozoic Salmon River assemblage. These strata 

are contained in a northeast-trending, south-plunging, eastvergent anticline that is the dominant structure in the area. 

Deformation associated with Mesozoic folding led to the 

development of fractures parallel with the direction of the 

fold hinge and the interstratal slip that created intense 

shearing along the unconformable contact. The anticline 

was intruded by Cretaceous granodiorite and biotite quartz 

diorite in its hinge region, and Eocene dacite porphyry 

dikes are localized in one area near the Cretaceous granodiorite-Paleozoic contact. Paleozoic strata near the intrusive 

rocks are metamorphosed to hornblende hornfels facies and 

commonly bleached white. Northeast-trending high-angle 

faults offset folded Paleozoic rocks and Eocene andesitic to 

dactitic flow rocks of the Challis Volcanic Group in the 

southeastern part of the area.

Mineral deposit types in the Washington Basin area 

include polymetallic veins, shear-zone-hosted polymetallic 

veins, and replacement deposits. Sulfide ores contain pyrrhotite, sphalerite, chalcopyrite, pyrite, and galena and minor 

amounts of jamesonite, arsenopyrite, and telluride minerals. 

These deposits reflect at least two distinct phases of mineralization. Polymetallic vein deposits near the Cretaceous granodiorite-Paleozoic contact and in fold-hinge parallel 

fractures are interpreted to be the result of late-stage hydrothermal fluid circulation associated with intrusion of Cretaceous granodiorite. Massive replacement deposits near Red 

Hill formed when Cretaceous(?) biotite quartz diorite

'U.S. Geological Survey and University of British Columbia, Vancouver, British Columbia V6T 2B4.

intruded the Cretaceous granodiorite and Middle Pennsylvanian to Lower Permian Grand Prize Formation. Polymetallic 

vein deposits in high- and low-angle shear zones on Bible 

Back Mountain are of uncertain affinity but may be associated with Late Cretaceous mineralization. Lead-isotope signatures and the spatial association of the Paleozoic Salmon 

River assemblage and mineral deposits suggest that the 

Salmon River assemblage may be the source of metals in the 

mineral deposits of the Washington Basin area.

INTRODUCTION

Washington Basin is at the southern end of the White 

Cloud Peaks in the southeastern corner of Custer County, 

Idaho. The basin is a spectacular glacial cirque that has a 

southeasterly aspect, and it is drained by Washington 

Creek, a tributary to Germania Creek (fig. 1). The terrain is 

rugged; elevations range from 3,187 m (10,519 ft) on 

Washington Peak to 2,545 m (8,400 ft) at the east end of 

the cirque. In this report, the term "Washington Basin area" 

refers to both Washington Basin itself and to Germania 

Basin, directly to the south (fig. 2). The area is bounded on 

the north by the headwaters of Fourth of July Creek, on the 

west by Champion Lakes Basin, on the east by Washington 

Lake Creek, and on the south by Germania Creek. The area 

is reached by following the Pole Creek road 22 km (13.2 

mi) from State Highway 75, then continuing 3.5 km (2.1 

mi) along a rough jeep trail into the basin itself. The Washington Basin area is within the Sawtooth National Recreation Area and is withdrawn from new mineral entries; 

current exploration is limited to existing claims. The White 

Cloud Peaks adjacent to Washington Basin are currently 

under review for inclusion in the proposed White 

Cloud-Boulder Wilderness Area.

The Washington Basin area is on the boundary between 

the Hailey and Challis I°x2° quadrangles. The geology of 

Washington Basin was briefly described in conjunction with 

regional geologic studies of the White Cloud Peaks by Ross 

(1963), Fisher and others (1983), Sengebush (1984), Hall 

(1985), Tschanz and others (1986), and Hall and Hobbs

Gl
G2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

(1987). The most recent geologic maps of the area include 

those by Fisher and others (1983), and Worl and others 

(1991). I previously (1989) described the structure and 

stratigraphy of the area, and this report is a modification and 

expansion of those ideas.

Mineral deposits of the Washington Basin area were 

described in detail by Van Noy and others (1986) of the U.S. 

Bureau of Mines, who included the Washington Basin area 

in the Germania Creek mining district. Teepen (1985) 

described the content and genesis of sulfide mineral veins in 

a part of the area. I incorporated the mineral deposit evaluations of Van Noy and others (1986) into a description of mineral deposit types of the area (Mahoney, 1989).

Acknowledgments. I thank Paul K. Link and David 

W. Rodgers of Idaho State University for their assistance in 

the field and for numerous thought-provoking discussions 

about the geology of the region. Jeff Jones of the Sawtooth 

National Recreation Area was a valuable source of information about the mining history and geology of the area. This 

manuscript benefited from reviews by Reed S. Lewis, Paul 

K. Link, and Ronald G. Worl.

HISTORICAL PERSPECTIVE

The Washington Basin area has been the site of intermittent exploration and mining activity since the late 1800's. 

The first mining claims were located in 1879, and the majority of mining activity was in the 1890's and early 1900's. 

Other periods of notable activity were the mid-1930's and 

the early 1970's. More than 329 mining claims have been 

located in the area, of which 10 are patented lode claims 

(Van Noy and others, 1986). Exploration in the area has been 

sporadic since the main period of activity in the early 1900's.

Although records of production are limited, the major 

producing mines in the area were apparently on the northwestern flank of Bible Back Mountain (the Idahoan and 

Old Bible Back mines) and at the southwestern end of 

Washington Basin (Black Rock mine). Quantitative estimates of ore removed are nonexistent, but monetary values 

(1915 prices) exceed $250,000 from Bible Back Mountain 

and $125,000 from the Black Rock mine (Umpleby, 1915). 

The production in the Washington Basin area has been primarily in lead-silver ores, although some gold values have 

been reported (Van Noy and others, 1986). Small amounts 

of copper and zinc may have also been produced. Other 

reported commodities include Cu, Zn, Sb, W, Bi, Te, and 

Se (Van Noy and others, 1986). The area has been the subject of recent gold exploration activity.

115°30'

10 KILOMETERS

I T_J

0 5 MILES

Figure 1. Map showing location of the Washington Basin area, 

Custer County, Idaho. Location of map area of figure 2 is also shown.

dikes. The mineral deposits in the area display a strong 

structural control, and at least two separate mineralization 

events are believed to have occurred. Recent mapping 

(Mahoney, 1989, this report, unpublished data) has resulted 

in significant revision of previously postulated stratigraphic 

and structural models.

STRATIGRAPHY

Washington Basin is underlain by three Paleozoic sedimentary units: the Paleozoic Salmon River assemblage and 

the Middle Pennsylvanian to Lower Permian Wood River 

and Grand Prize Formations of the Sun Valley Group 

(Mahoney and others, 1991) (fig. 2). Mineral deposits are 

hosted by each of these units in the Washington Basin area, 

but the most important host is the Grand Prize Formation, 

which underlies most of the basin.

Pennsylvanian and Permian sedimentary rocks in the 

area previously were assigned to variety of stratigraphic 

units including the rocks at Pole Creek (Fisher and others,

GEOLOGIC SETTING

The geology of the Washington Basin area consists of 

complexly folded and faulted Paleozoic strata that have been 

intruded by at least two different types of igneous stocks and

Figure 2 (facing page). Map showing geology of the Washington Basin area, Custer County, Idaho. Location of map area is 

shown in figure 1. Lines of section of figure 3 are also shown. Base 

from U.S. Geological Survey 7.5-minute topographic series maps, 

Washington Peak (1964) and Horton Peak (1970).
GEOLOGIC SETTING OF MINERAL DEPOSITS IN THE WASHINGTON BASIN AREA

1/2 

EXPLANATION

Quaternary colluvium

CHALLIS VOLCANIC GROUP (EOCENE) 

Dacite lava

Dacite porphyry

CRETACEOUS INTRUSIVE ROCKS 

Quartz diorite (Cretaceous?)

Biotite granodiorite

SUN VALLEY GROUP (LOWER PERMIAN TO 

MIDDLE PENNSYLVANIAN)

Grand Prize Formation 

Member 4 (Lower Permian)

Member 3 (Lower Permian)

Member 2 (Lower Permian to Middle 

Pennsylvanian)

Member 1 (Middle Pennsylvanian)

40i

75

1MILE

Wood River Formation

Eagle Creek Member (Lower Permian to 

Middle Pennsylvanian)

OLDER PALEOZOIC STRATA 

Salmon River assemblage (Paleozoic)

Contact Dashed where approximately located; 

dotted where concealed; queried where uncertain

High-angle fault Ball and bar on downthrown 

side; dashed where approximately located; 

queried where uncertain

Low-angle fault Sawteeth on upper plate 

Dike

Overturned anticline Dashed where approximately located

Strike and dip of bedding

Strike and dip of overturned bedding
G4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

1983), the Wood River Formation (Tschanz and others, 

1986), and the Grand Prize Formation (Hall, 1985; 

Mahoney and Sengebush, 1988; Mahoney and others, 

1991). Mahoney and others (1991) included the Wood 

River and Grand Prize Formations in the Middle Pennsylvanian to Lower Permian Sun Valley Group. The unit designations presented in this report clarify stratigraphic 

nomenclature in the Washington Basin area.

SALMON RIVER ASSEMBLAGE

The Salmon River assemblage in the Washington Basin 

area consists of dark carbonaceous argillite, limestone, siltstone, and minor sandstone exposed on the ridge north of 

Washington Basin proper (fig. 2). Rocks of the assemblage 

extend northward from Washington Basin, underlie all of the 

Phyllis Lake cirque and continue north across Fourth of July 

Creek (figs. 1, 2). The Salmon River assemblage forms the 

core of a south-plunging, east-vergent anticline that dominates the structural setting of the area. Its upper contact 

forms an arcuate map pattern with the overlying Grand Prize 

Formation in Washington Basin (figs. 2, 3). The lower contact of the Salmon River assemblage has not been identified 

(Hall and Hobbs, 1987).

The Salmon River assemblage in the Washington Basin 

area is primarily thin-bedded, dark-gray to black, carbonaceous argillite that is locally iron stained and commonly has 

a phyllitic sheen. The dark argillite is intercalated with 

medium-bedded blue-gray sandy limestone, thin-bedded 

parallel- to cross-laminated fine-grained sandstone, and thinbedded dark-gray siltstone. The unit is structurally deformed 

with mesoscopic tight to isoclinal folds, near-bedding parallel cleavage, quartz veining, and abundant fractures. Primary 

bedding is difficult to recognize in many exposures. The 

Salmon River assemblage is locally contact metamorphosed 

to calc-hornfels and is commonly silicified. Carbonaceous 

units within the assemblage locally host mineral deposits, 

and the assemblage contains numerous mines and prospects 

throughout the White Cloud Peaks (Van Noy and others, 

1986).

The age of the Salmon River assemblage is problematic; 

age determinations range from Late Cambrian to Late Mississippian, and the assemblage is currently simply designated 

as Paleozoic (Hall and Hobbs, 1987). The Salmon River 

assemblage in Washington Basin is, however, lithologically 

similar to the Devonian Milligen Formation to the south and 

occupies a similar structural position (Link and others, this 

volume). Both the Paleozoic Salmon River assemblage and 

the Devonian Milligen Formation contain thick sections of 

homogeneous black argillite, abundant thin-bedded finegrained turbidite sequences, and intercalated blue-gray, 

locally tremolitic, limestone. They also both contain welldeveloped near-bedding-parallel cleavage and mesoscopic 

tight to isoclinal folds and display a characteristic phyllitic

sheen. They both host inferred syngenetic sulfide deposits 

having identical lead-isotope signatures (Sanford and 

Wooden, this volume). The Salmon River assemblage in the 

White Cloud Peaks has yielded Middle to Late Devonian 

conodonts (Hobbs, 1985; Hall and Hobbs, 1987); the 

reported Cambrian and Mississippian dates are obtained 

from rocks exposed to the north of the main White Cloud 

Peaks that are interpreted as structural imbrications within 

the assemblage (Hall, 1985). I interpret the Salmon River 

assemblage exposed in the White Cloud Peaks as primarily 

Devonian in age and suggest that the Salmon River assemblage is the lateral equivalent of the Devonian Milligen Formation exposed to the south.

GRAND PRIZE FORMATION

The Pennsylvanian and Permian Grand Prize Formation 

unconformably overlies the Salmon River assemblage in the 

Washington Basin area. The Grand Prize Formation is at 

least 3,000 m (9,840 ft) thick and is subdivided into four 

informal members, all of which are exposed in the Washington Basin area. A partial stratigraphic section of the Grand 

Prize Formation, measured on the east flank of Washington 

Peak, is shown in figure 4. Complete stratigraphic descriptions of the formation are in Mahoney and Sengebush (1988) 

and Mahoney and others (1991).

The contact between the Grand Prize Formation and the 

Salmon River assemblage has been the subject of dispute 

among workers in the region (Hall, 1985; Hall and Hobbs, 

1987; Mahoney and Sengebush, 1988; Mahoney and others, 

1991). Hall (1985) described the contact as a thrust fault in 

which the Grand Prize Formation is thrust over the Salmon 

River assemblage along an intensely brecciated fault zone. 

Sengebush (1984) suggested that the contact is actually a 

sheared unconformity and that the brecciated zone is a tectonically deformed clast-supported conglomerate at the base 

of the Grand Prize Formation. Mahoney and Sengebush 

(1988) and Mahoney and others (1991) described regional 

relations that support a sheared erosional unconformity 

between the Grand Prize Formation and the underlying 

Salmon River assemblage. Examination of the contact on the 

ridge north of Washington Basin strongly supports the 

sheared unconformity hypothesis. At this location, the contact consists of matrix-supported (locally clast supported) 

conglomerate and intercalated fine- to coarse-grained quartzite overlying black argillite with a low-angle structural discordance. The conglomerate contains intercalated quartzite 

beds, sedimentary structures including graded bedding and 

weak clast imbrication, and subrounded black argillite clasts 

strikingly similar to the underlying Salmon River assemblage. These features support a sedimentary, not tectonic, origin for the lowest member of the Grand Prize Formation in 

this area and suggest that the contact with the underlying 

Salmon River assemblage is an erosional unconformity. The
GEOLOGIC SETTING OF MINERAL DEPOSITS IN THE WASHINGTON BASIN AREA G5

5000

4000

5000-J

4000'

No vertical exaggeration

Figure 3. Cross sections showing geology of the Washington Basin area, Custer County, Idaho. Lines of section are shown in figure 2. 

Stratigraphic units: Kgd, quartz diorite (Cretaceous?); Kbd, biotite granodiorite (Cretaceous?); Grand Prize Formation of the Sun Valley 

Group including Pg4, member 4 (Lower Permian); Pg3, member 3 (Lower Permian); PPg2, member 2 (Lower Permian to Middle Pennsylvanian); and Pg 1, member 1 (Middle Pennsylvanian); PPwe, Eagle Creek Member of the Wood River Formation (Lower Permian to Middle 

Pennsylvanian); Rzsr, Salmon River assemblage (Paleozoic).

conglomerate displays local brecciation, quartz veining, and 

a preferential alignment of elongate clasts, particularly near 

the base of the unit. This preferred clast orientation and brecciation is interpreted as the result of shearing due to interstratal slip along the unconformable contact during 

megascopic folding in the Mesozoic and is not the result of 

intense brecciation during thrust displacement.

In the Washington Basin area, the Grand Prize Formation is contained in both limbs of a south-plunging, east-vergent anticline (figs. 2, 3). In the western limb of the anticline, 

member 1 of the Grand Prize Formation consists of

approximately 175 m (574 ft) of matrix- to clast-supported 

conglomerate and minor intercalated coarse-grained quartzite overlain by 175 m (574 ft) of thin- to medium-bedded, 

locally parallel to wavy laminated, fine-to medium-grained 

quartzite (fig. 4). Overlying this quartzite is approximately 

75 m (246 ft) of clast-supported conglomerate that is overlain by about 25 m (82 ft) of blue-gray bioclastic (fossil hash) 

sandy limestone.

Member 2 of the Grand Prize Formation is in conformable contact with the underlying member and, in the 

Washington Basin area, consists of about 250 m (820 ft) of
G6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

THICKNESS

(METERS)

800

600-

400-

200-

Member 3

Member 2

Member 1

Paleozoic 

Salmon River 

assemblage

EXPLANATION

Conglomerate 

Micritic sandstone 

Banded siltstone 

Limestone

Figure 4. Stratigraphic section of part of the 

Middle Pennsylvania!! to Lower Permian Grand 

Prize Formation, Washington Basin area, Custer 

County, Idaho. Measured from east to west on 

the ridge on the north side of Washington Basin 

in steeply west dipping beds on the east flank of 

peak 10,519 ft, Washington Peak U.S. Geological Survey topographic map (scale 1:24,000). 

Section starts at 10,200 ft and goes along ridge 

to top of peak 10,519 ft. Base of section is at lat 

44°15'00"N., long 114°39'38" W.

thick-bedded to massive, fine-grained, calcareous sandstone 

intercalated with minor thin- to medium-bedded, parallel- to 

cross-laminated, fine-grained sandstone and dark-gray calcareous siltstone (figs. 2, 4). Member 2 has a gradational 

contact with overlying member 3 (figs. 2, 4).

Member 3 of the Grand Prize Formation consists of 

thin-bedded, fine-grained sandstone and dark siltstone forming distinctive banded couplets, 15^5 cm (5.9-18 in.) thick, 

that are well exposed in the cirque headwall south of Washington Peak (fig. 2). Intercalated with these banded couplets 

are thick-bedded to massive sandstone beds as thick as 25 m 

(82 ft). Regionally, member 3 has an estimated thickness of 

650-1,700 m (2,130-5,580 ft); however, the thickness of 

member 3 in the Washington Basin area is uncertain due to 

faulting in the Champion Lakes cirque and intrusion-related 

deformation in the Washington Basin area (Mahoney and

others, 1991) (fig. 2). The member underlies most of the 

Champion Lakes cirque; its gradational upper contact with 

member 4 is exposed below the ridge west of Champion 

Lakes (Mahoney, 1991). In the Champion Lakes cirque, 

member 3 contains a much higher percentage of sandstone 

and quartzite than previously reported in the Grand Prize 

Formation (Mahoney and Sengebush, 1988; Mahoney and 

others, 1991).

In the Washington Basin area, member 4 is exposed in 

the eastern limb of the anticline on the east side of Croesus 

Peak. Member 4 consists of thin- to medium-bedded carbonaceous limestone, siltstone, and mudstone and forms a 

distinctive dark-gray unit. The siltstone and limestone contain abundant sedimentary structures including graded bedding, cross laminae, parallel laminae, and soft-sediment 

deformation features.

The Grand Prize Formation is Middle Pennsylvanian to 

Early Permian (Desmoinesian to Leonardian) in age, based 

on conodonts collected from the type section approximately 

8 km (4.8 mi) southwest of Washington Basin (Hall, 1985) 

and on lithostratigraphic correlations with the well-dated 

Wood River and Dollarhide Formations of the Sun Valley 

Group (Mahoney and others, 1991).

In Washington Basin, the Grand Prize Formation is 

locally contact metamorphosed to calc-silicate hornfels and 

is commonly bleached and silicified, resulting in a brightwhite appearance in outcrop. It hosts mineral deposits in 

members 2, 3, and 4 both in Washington Basin and in Germania Basin to the south; mineral deposits are in polymetallic veins in fracture systems and in replacement deposits. 

Regionally, the Grand Prize Formation contains numerous 

mines and prospects.

WOOD RIVER FORMATION

The Wood River Formation consists of more than 

2,500 m (8,200 ft) of micritic sandstone, siltstone, and 

sandy micrite and is subdivided into three members 

(Mahoney and others, 1991). Only the Eagle Creek Member of the Wood River Formation is exposed in the study 

area, most notably on Bible Back Mountain, where it is 

host to polymetallic veins in shear zones. The formation is 

exposed in a series of fault blocks to the southeast of Washington Basin (fig. 2).

In the Washington Basin area, the Eagle Creek Member of the Wood River Formation consists primarily of 

thick-bedded to massive, fine-grained micritic sandstone 

intercalated with minor thin- to medium-bedded, blue-gray 

sandy micrite and micritic siltstone. Regionally, the unit 

has an average thickness of 880-1,300 m (2,887-4,265 ft), 

but in the Washington Basin area extensive brecciation prevents an accurate thickness determination.

The Eagle Creek Member of the Wood River Formation 

is well constrained as Middle Pennsylvanian to Early
GEOLOGIC SETTING OF MINERAL DEPOSITS IN THE WASHINGTON BASIN AREA G7

Permian (Desmoinesian to Wolfcampian) in age and is interpreted as a lateral equivalent of member 2 of the Grand Prize 

Formation (Mahoney and others, 1991; Link and others, this 

volume). South of Bible Back Mountain, the Eagle Creek 

Member of the Wood River Formation is gradationally overlain by member 2 of the Grand Prize Formation. South of 

Germania Basin, outside the study area, a thin sequence 

(-100 m, 328 ft) of the Wilson Creek Member of the Wood 

River Formation is gradationally overlain by member 4 of 

the Grand Prize Formation. These intertonguing relations 

indicate that the Grand Prize Formation passes laterally into 

the Wood River Formation to the south and that the Grand 

Prize Formation represents a northern, sandy facies of the 

Sun Valley Group (Mahoney and others, 1991; Link and others, this volume).

The Wood River Formation is in high-angle fault contact with the Grand Prize Formation in the saddle west of 

Bible Back Mountain (figs. 2,3). On top of Bible Back Mountain, the Wood River Formation is metamorphosed to a siliceous quartzite and is extensively brecciated and iron stained; 

the formation is cut by numerous north-trending shear zones 

that host polymetallic lead-silver veins. This iron-stained unit 

is in low-angle fault contact with underlying, essentially 

unfractured Grand Prize Formation; this relationship is well 

exposed on the north face of Bible Back Mountain (fig. 2).

STRUCTURE

The dominant structure in the Washington Basin area 

is a northeast-trending, south-plunging, east-vergent anticline within the Salmon River assemblage and the overlying Grand Prize Formation (figs. 2, 3). This anticline and 

its associated hinge-parallel fractures controlled the location of mineralization in the area and probably localized 

Cretaceous intrusions (figs. 2, 5). The Salmon River assemblage forms the core of the anticline, which plunges southsoutheast at a moderate angle (~50°-60°) (fig. 2), as indicated by stereonet fold solutions. The west limb of the anticline consists of steeply southwest dipping to near vertical 

Grand Prize Formation in unconformable contact with the 

underlying Salmon River assemblage. Competency differences between the two units at the unconformity have 

resulted in ductile deformation of the upper part of the 

Salmon River assemblage and brecciation and shearing in 

the more competent conglomeratic member 1 of the Grand 

Prize Formation. The eastern limb of the anticline consists 

of near vertical to overturned, steeply southwest dipping 

Grand Prize Formation. The eastern limb of the fold is difficult to recognize due to widespread igneous intrusive 

activity. The structural orientation of the eastern limb is 

easily recognized on the east side of Croesus Peak, where 

steeply west dipping, overturned members 3 and 4 of the 

Grand Prize Formation are exposed (fig. 3).

Several northeast-trending high-angle faults that have 

minor displacement (tens of meters) are exposed in the 

Washington Basin area. Two high-angle faults in the area are 

interpreted to have significant displacement (tens to hundreds of meters) (fig. 2). The fault in the saddle west of Bible 

Back Mountain is steeply dipping and juxtaposes Grand 

Prize Formation (members 3 and 4) to the west with Wood 

River Formation (Eagle Creek Member) to the east. This 

fault has been reported to be a large northeast-trending, westdipping reverse fault with numerous parallel shear zones 

(Van Noy and others, 1986). The map pattern of the fault 

indicates that it is a near vertical to steeply east dipping normal fault of significant displacement (hundreds of meters). 

The western side of this fault exposes medium-grained Cretaceous granodiorite and contact-metamorphosed, ductilely 

deformed Grand Prize Formation in the eastern limb of a 

south-plunging anticline. The eastern side of the fault 

exposes brittlely deformed, moderately dipping Eagle Creek 

Member of the Wood River Formation and overlying member 2 of the Grand Prize Formation, both of which are structurally overlain in low-angle fault contact by fractured, 

brecciated, and iron-stained quartzite of the Eagle Creek 

Member (figs. 2, 3). The difference in styles of structural 

deformation, intrusion, and metamorphism across the fault 

suggests that this fault is down to the east, an interpretation 

supported by three-point fault solutions indicating normal 

offset on a steeply east dipping fault. Several mineralized 

veins are parallel with this fault on the north side of Washington Basin, and Van Noy and others (1986) suggested that 

there may be mineralized zones along this fault.

The second fault of significant displacement in the 

Washington Basin area is in the southeastern corner of the 

map area, where a northeast-trending normal fault places the 

Eagle Creek Member of the Wood River Formation against 

andesitic to dacitic flow rocks of the Challis Volcanic Group 

(fig. 2). The lack of Paleozoic sedimentary units and the 

presence of more than 500 m (1,640 ft) of volcanic rocks to 

the east of this fault, together with the absence of volcanic 

rocks on the west side of the structure, suggest that the fault 

has a displacement of at least 500 m (1,640 ft).

A prominent low-angle structure is exposed on the north 

face of Bible Back Mountain, where massive quartzite and 

calc-silicate of the Eagle Creek Member of the Wood River 

Formation structurally overlie thin- to thick-bedded quartzite, siltite, and limestone of member 2 of the Grand Prize Formation and the Eagle Creek Member of the Wood River 

Formation. The structure strikes to the northeast and dips 

about 18° SE. (Van Noy and others, 1986). Rocks on both 

sides of the structure are heavily brecciated and fractured, but 

the upper plate rocks are much more silicified and iron 

stained than lower plate rocks. Van Noy and others (1986) 

described the low-angle structure as a thrust fault, although 

sense of movement indicators are lacking. This structure contains polymetallic shear-zone-hosted mineral deposits (Van 

Noy and others, 1986).
G8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°40' 114°37'30"

'<" "'

j^ ^f j. &^s^) -vv °Y;^. i i ^ .^''/^ff^^^^^y$f^^f\ ','f .^t^r'^

<V^^>-\- 'H' cx^C! f^^4:T^/^^^-^r^^$^',K\-*/ Cr''" '

i ) ^"' j h : ( f'M.'s \ '-' /.^ t--. Ti> \" '/S' ' - -/" ^ /% ^___ ^>-v\ ^.;'; ^- 'J; M ^>.X" U'i,^ 

'-/ -- ... . . ., j . ^ -^ -\ - s" "~T: ^V^\"Vv V xx x' ^ ^^

-/ , i' -^_ -^ Ab -Ax- x^._-^-^>" \^v< A ;\ --N

^ A T'./ (i:%^--^<W^ " ' \ V X. vY,..^V.St-i-^~*: >- -"'-- -_ I v" X . ?-. " '^.-?-^^_^C'.^ >'-^-"'"-

V" ^1 ^\'4o0S'VV'T^I,,('j, ; VLACKROCKMINE

"% sf ;' 'V v/-'/'^/' '/ "i .''V^'V-'XK^ l</ >-A\ . - ,, , ^ 

% j, V \> i, ,f ^o" W^^x,v%^k/ -%--~^ 'x> Washio.gton -- --. __^/Ba sin ,-__/ '/^~^--^f^

1'(°'f° }- V^'~''A;/V/^<''4flC7^^ ) / Av 'V 

i/// /X \ <x/ -^3>y GERMANIA / ' ^.^./T"' /'~^' ,.,,fi^. OLD BIBLE ""' '. $ '} 'V

r^-

0.5 2 KILOMETERS

1/2

I 

1MILE

Figure 5. Map showing mines and major mineralized veins in the Washington Basin area, Custer County, Idaho. Modified from E. Oberbilling (unpublished Defense Minerals Exploration Administration report, 1962). Base from U.S. Geological Survey 7.5-minute topographic 

series maps, Washington Peak (1964) and Horton Peak (1970).

IGNEOUS INTRUSIVE ROCKS

The Washington Basin area contains at least three separate igneous rock units. The most extensive unit is 

porphyritic biotite granodiorite that makes up several stocks 

within the Washington Basin area (fig. 2). The granodiorite 

also forms dikes on the north side of Croesus Peak and in the 

headwall of the Washington Basin cirque. The biotite granodiorite is medium to coarse grained, has a grussy weathered 

appearance, and locally contains phenocrysts of alkali feldspar 3-10 cm (1.2-3.9 in.) long. The porphyritic texture of

the granodiorite decreases with depth and is believed to be the 

result of potassium metasomatism near intrusive contacts. 

The granodiorite intrudes the Grand Prize Formation and the 

Salmon River assemblage and locally contains metasedimentary roof pendants. Randomly oriented aplite dikes and mafic 

xenoliths are common in the granodiorite. The granodiorite 

is locally iron stained near contact zones, particularly in 

exposures on the west side of peak 9776 ft (Red Hill) (fig. 2). 

Because of its proximity to the Cretaceous White Cloud stock 

and because it is cut by Eocene dacite porphyry dikes, the 

granodiorite is believed to be Cretaceous in age. The location
GEOLOGIC SETTING OF MINERAL DEPOSITS IN THE WASHINGTON BASIN AREA G9

of several of the Cretaceous stocks near the hinge region of 

the anticline suggests that stock emplacement may have been 

structurally controlled (figs. 2, 3).

A fine-grained, holocrystalline, biotite-rich quartz diorite dike intrudes the porphyritic granodiorite and the Grand 

Prize Formation on Red Hill (figs. 2, 3). The dike is 10-15 m 

(33-49 ft) wide on Red Hill and splits into three separate 

dikes on the north side of Red Hill. Fine-grained biotite 

makes up more than 50 percent of the unit. The dike is probably Cretaceous in age and is believed to be a late-stage 

intrusive feature associated with the porphyritic granodiorite; however, the biotite quartz diorite dike crosscuts the porphyritic granodiorite and may therefore be as young as 

Eocene in age. Chloritic alteration of biotite precludes a 

more accurate age determination. Quartzite of the Grand 

Prize Formation hosts replacement mineralization adjacent 

to the diorite dike. Similar dikes are adjacent to massive sulfide replacement deposits in quartzite of the Grand Prize 

Formation at the Pole prospect approximately 8 km (4.8 mi) 

to the southeast along Pole Creek.

Eocene dacite porphyry dikes intrude both the Grand 

Prize Formation and the Cretaceous granodiorite in the head 

of Germania Basin. Emplacement of the dikes was primarily 

along the contact between the granodiorite and the Paleozoic 

rocks. A mafic dike of uncertain age cuts the quartzite on the 

west end of Bible Back Mountain and is spatially related to 

mineralized rocks; similar lamprophyric dikes elsewhere in 

the White Clouds are interpreted as Cretaceous in age (R.G. 

Worl, oral commun., 1989).

MINERAL DEPOSITS

In the Washington Basin area, mineral deposits are 

hosted by members 2, 3, and 4 of the Grand Prize Formation, 

by the Eagle Creek Member of the Wood River Formation, 

and by the Cretaceous porphyritic granodiorite. Mineralization was primarily structurally controlled, as suggested by 

mineralized north-trending shear zones on Bible Back 

Mountain and by northeast-trending (fold-hinge parallel) 

mineralized veins in Washington Basin (fig. 5). Alteration 

of host rocks is pervasive and includes oxidation in both the 

igneous and sedimentary hosts and sericitic alteration in the 

igneous host. Alteration products include limonite, hematite, 

goethite, and sericite (Van Noy and others, 1986).

Teepen (1985) described the mineral deposits and 

paragenetic sequence of the Empire and Black Rock claims 

in Washington Basin (fig. 4). Van Noy and others (1986) 

provided a complete description of mines and prospects in 

the Washington Basin area. Information from these reports is 

included in the following descriptions.

Three types of mineral deposits are present in the 

Washington Basin area: (1) polymetallic veins and replacement deposits associated with the Cretaceous porphyritic 

granodiorite, (2) shear-zone-hosted polymetallic veins in 

sedimentary rocks, and (3) massive replacement deposits in 

quartzitic rocks.

POLYMETALLIC VEINS

Two types of polymetallic veins are present in Washington Basin: (1) northeast-trending veins localized along 

fold hinge-parallel fractures and (2) veins along the contact 

between the Cretaceous porphyritic granodiorite and calcsilicate rocks of the intruded Grand Prize Formation.

The most prominent mineralized structure in the Washington Basin area is a system of northeast-trending quartzpyrrhotite-pyrite veins on the floor of Washington Basin. 

These veins are contained in shear zones and fracture systems that are subparallel with the fold axial plane of the 

asymmetric anticline that dominates the structure of the area, 

and they are probably the result of tensional stresses in the 

axis of the fold (figs. 2, 5). The vein system includes the Last 

Resort, Empire, Reconstruction, and Yacomella veins and is 

easily recognized by heavily oxidized sulfide minerals at the 

surface (fig. 5). The veins consist primarily of quartz and 

pyrrhotite and lesser amounts of pyrite, chalcopyrite, 

sphalerite, and galena. Small amounts of scheelite, telluride 

minerals, and jamesonite have also been reported (Van Noy 

and others, 1986). Samples assayed from the Empire vein, in 

the center of Washington Basin, average less than 0.01 

ounces of gold per ton, 0.59 ounces of silver per ton, 0.28 

percent Pb, 0.40 percent As, and less than 0.01 percent WC«3 

(Van Noy and others, 1986). Minor amounts of gold have 

documented from all the veins (Van Noy and others, 1986), 

and disseminated gold has been reported from wallrock near 

the vein systems (J. Jones, oral commun., 1988).

Teepen (1985) conducted petrographic, geochemical, 

and geothermometry studies on sulfide minerals from the 

vein systems in the Empire and Black Rock claims and documented a paragenetic sequence of sulfide mineralization of 

pyrrhotite>pyrite>sphalerite>chalcopyrite. Teepen disagreed with the analytical results of Van Noy and others 

(1986) and was unable to detect bismuth-, lead-, arsenic-, or 

gold-bearing minerals in petrographic, X-ray, or geochemical studies of the Empire and Black Rock claims (fig. 4). 

This discrepancy is problematic, but the higher sampling 

density and broader sampling techniques of Van Noy and 

others (1986) lend credence to their observations.

The Grand Prize Formation and the porphyritic granodiorite are hydrothermally altered and mineralized with 

finely disseminated sulfide minerals along the vein system in 

Washington Basin, suggesting post-intrusion mineralization 

that is probably the result of late-stage circulation of metalbearing fluids associated with Cretaceous plutonic activity.

The second type of polymetallic veins in the Washington Basin area is along the contact between the Cretaceous 

porphyritic granodiorite and calc-silicate rocks of the 

intruded Grand Prize Formation. Intrusion of the granodiorite resulted in contact metamorphism of members 1, 2, and 

3 of the Grand Prize Formation and mineralization of both 

the Paleozoic sedimentary rocks and the granodiorite itself. 

Examples of this type of veins are in the Black Rock mine
G10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

in the southwestern part of Washington Basin and in prospects of the Germania group and Arctic group in the head 

of Germania Basin.

At the Black Rock mine, mineral deposits consist of a 

northwest-striking, southwest-dipping quartz-pyrite zone 

(Washington vein) that cuts both granodiorite and the Grand 

Prize Formation (Van Noy and others, 1986). The mineralized zone is subparallel with the intrusive contact. Sulfide 

minerals are contained in pods as much as 0.3 m (0.98 ft) in 

diameter and 0.6 m (2.0 ft) in length in the granodiorite and 

in tactile zones in the Paleozoic sedimentary rocks (Van Noy 

and others, 1986). In the granodiorite, the wallrock is sericitized and disseminated pyrite is common; Paleozoic rocks 

are contact metamorphosed to calc-silicate hornfels. The 

entire contact zone is heavily iron stained. Sulfide minerals 

include pyrrhotite, arsenopyrite, pyrite, and minor sphalerite. 

Assays of the vein material averaged 0.005 ounces of gold 

per ton, 1.3 ounces of silver per ton, 1.27 percent Pb, and 

0.32 percent Sb (Van Noy and others, 1986).

In Germania Basin, prospects of the Germania group 

and Arctic group contain mineralized veins that closely parallel the contact between the porphyritic granodiorite and 

members 2 and 3 of the Grand Prize Formation. The vein 

material is predominantly quartz and leached pyrite and is 

vuggy and iron stained. Reported sulfide minerals include 

pyrite, galena, sphalerite, pyrrhotite, and arsenopyrite (Van 

Noy and others, 1986). Assay values from the vein quartz 

contain an average of 0.06 ounces of gold per ton, 8.2 ounces 

of silver per ton, and 6.14 percent Pb (Van Noy and others, 

1986). Numerous Eocene dacite porphyry dikes cut the mineralized area; these dikes are iron stained, and the possibility 

of associated Eocene mineralization cannot be discounted.

SHEAR-ZONE-HOSTED 

POLYMETALLIC VEINS

Two types of shear-zone-hosted polymetallic veins are 

in the Washington Basin area: (1) a thick mineralized breccia 

zone associated with the low-angle structure on Bible Back 

Mountain and (2) north-trending veins on Bible Back Mountain containing finely disseminated, oxidized sulfide minerals (Van Noy and others, 1986). In addition, Van Noy and 

others (1986) reported polymetallic veins contained in minor 

shear zones associated with northeast-trending brittle structures throughout the area.

The most important shear-zone-hosted polymetallic 

veins in the Washington Basin area are within the low-angle 

structure exposed on the north face of Bible Back Mountain. 

The fault zone is extensively mineralized and has been 

responsible for much of the production from the Washington 

Basin area (Umpleby, 1915; Van Noy and others, 1986). The 

brecciated fault zone is 1-1.5 m (3.3-4.9 ft) thick, strikes to 

the northeast, and dips about 18° to the southeast (Van Noy 

and others, 1986). The fault zone is highly oxidized, and iron 

staining is common; visible sulfides are rare. Van Noy and

others (1986) reported small, irregular replacement-type ore 

shoots within the fault zone that consist of small amounts of 

pyrite, galena, and jamesonite in a quartz and calcite gangue. 

Samples from the mineralized zone collected by the U.S. 

Bureau of Mines (Van Noy and others, 1986) averaged 0.06 

ounces of gold per ton, 12.6 ounces of silver per ton, 4.27 

percent Pb, 1.02 percent Zn, 0.58 percent Cu, and 0.45 percent Sb. The U.S. Bureau of Mines estimated that approximately 8,600 tons of paramarginal resources are present 

within the old workings on Bible Back Mountain and that an 

additional 30,000 tons of paramarginal resources may be 

present in unexplored parts of the fault zone.

The second type of polymetallic vein system consists of 

north-trending shear zones that cut the brecciated Eagle 

Creek Member of the Wood River Formation on Bible Back 

Mountain. The Eagle Creek Member on Bible Back Mountain is pervasively sheared and brecciated and comprises the 

upper plate of the low-angle structure previously discussed. 

The shear zones are almost vertical and are generally 0.5-1.5 

m (1.6-4.9 ft) wide. Visible sulfide minerals are rarely 

observed, but the entire mountain is pervasively iron stained 

(limonite), and oxidized gouge is common in the shear 

zones. Both quartz and calcite stringers are present. Shear 

zone samples analyzed by Van Noy and others (1986) averaged 0.08 ounces of gold per ton, 13.7 ounces of silver per 

ton, 21.0 percent Pb, 0.4 percent Sb, and minor amounts of 

copper and zinc.

MASSIVE REPLACEMENT DEPOSITS

A small replacement-type deposit is exposed in a bulldozer cut on the north side of Red Hill (fig. 1). The deposit 

consists of almost complete replacement of massive quartzite, probably member 2 of the Grand Prize Formation, by 

massive sulfides. The ore zone is highly oxidized and iron 

stained, and the deposit has a distinct sulfurous odor to it. 

Within the ore zone, massive sulfide material, including 

galena and sphalerite, has completely replaced the calcareous cement between the fine to medium sand-sized quartz 

grains comprising the quartzite. Mineralized veins are 

absent, although small stringers of quartz are associated with 

the deposit. The replacement deposit apparently grades into 

unaltered sedimentary rock, although exposure in the area is 

poor. The bulldozer cut is exploratory, and no evidence of 

production exists. The replacement deposit is at the north 

end of a biotite quartz diorite dike associated with the main 

biotite quartz diorite on Red Hill and is probably genetically 

related to that intrusion.

GENESIS AND ORE CONTROLS

The most prominent mineral deposits in the Washington Basin area are in veins that occupy fractures along the 

axial trace of the asymmetric anticline. The anticline formed 

as a result of northwest- to southeast-directed compressive
GEOLOGIC SETTING OF MINERAL DEPOSITS IN THE WASHINGTON BASIN AREA Gil

stress related to the Cretaceous Sevier erogenic event; northeast-trending fractures formed parallel with the fold hinge. 

The anticline apparently controlled emplacement of the Cretaceous porphyritic granodiorite, and hydrothermal systems 

driven by this intrusion remobilized metals from the Paleozoic sedimentary rocks and deposited them within northeasttrending fractures. The intrusive event also resulted in polymetallic vein mineralization in the calcareous Paleozoic 

country rock. The most probable source of the metals is the 

Paleozoic Salmon River assemblage, which forms the core 

of the anticline and is spatially associated with each of the 

mineralized areas. Lead-isotope studies also suggest that the 

Salmon River assemblage was a probable source of metals 

(Sanford and Wooden, this volume).

Mineral deposits in the Washington Basin area formed 

during at least two separate mineralization events. The earlier event produced polymetallic vein deposits believed to 

have formed from late-stage hydrothermal fluid circulation 

associated with the intrusion of Cretaceous granodiorite. 

These polymetallic veins were emplaced in fold-hinge-parallel fractures or along the contact between the Grand Prize 

Formation and the Cretaceous granodiorite. A later mineralization event formed replacement deposits within quartzite 

of the Grand Prize Formation. This event is associated with 

intrusion of the biotite quartz diorite dike into Cretaceous 

granodiorite and the Grand Prize Formation on Red Hill. 

Crosscutting relations clearly show that the biotite quartz 

diorite dike is younger than the granodiorite, but the timing 

of the mineralization events is less clear. It is possible that 

intrusion of the biotite quartz diorite dike and both replacement and polymetallic vein mineralization are genetically 

related and therefore coeval; however, the presence of polymetallic veins along the granodiorite-Grand Prize Formation 

contact and pervasive alteration of both granodiorite and 

Grand Prize Formation throughout the area suggest that the 

polymetallic vein mineralization was associated with intrusion of the granodiorite. In addition, the lack of polymetallic 

veins associated with the biotite quartz diorite and the 

absence of biotite quartz diorite and replacement deposits 

elsewhere in the area also suggest that the replacement 

mineralization and dike intrusion postdate an earlier polymetallic vein mineralization event.

The timing of emplacement of the polymetallic shearzone-hosted veins on Bible Back Mountain is problematic. 

As stated previously, replacement mineralization on Red 

Hill is believed to postdate polymetallic vein mineralization 

associated with the Cretaceous intrusive activity. The temporal relationship between the shear-zone-hosted polymetallic 

veins on Bible Back Mountain and the other mineral deposit 

types is difficult to determine. The shear-zone-hosted veins 

may represent a higher structural level of mineralization 

associated with Cretaceous intrusive activity, or they may be 

the result of a younger event associated with younger 

(Eocene?) high- and low-angle fault displacement. More 

detailed structural analysis of Bible Back Mountain and dating of alteration minerals are needed to resolve the timing of 

mineralization in that area.

MINERAL POTENTIAL

The Washington Basin area has potential for minable 

lead-silver ores in and adjacent to the well-documented 

northeast-trending mineralized rocks and moderate potential 

for gold skarn deposits. The U.S. Bureau of Mines (Van Noy 

and others, 1986) reported that between 25,000 and 100,000 

tons of submarginal ore-grade material (1974 prices) may be 

present in the Washington Basin area and that there is potential for the discovery of minable ore shoots in the area.

Future exploration activities should concentrate on 

exploiting the prominent northeast-trending vein system in 

Washington Basin. The localization of veins along foldhinge fractures suggests that veins continue at deeper levels 

beneath Germania Basin to the south. Additional polymetallic vein deposits may be present along the contact 

between porphyritic granodiorite and Paleozoic sedimentary rocks, particularly in Germania Basin. The deposits on 

Bible Back Mountain are probably of too low grade to warrant further exploration.

REFERENCES CITED

Fisher, F.S., Mclntyre D.H., and Johnson, K.M., 1983, Geologic 

map of the Challis I°x2° quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 83-523, scale 1:250,000, 41 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hall, W.E., and Hobbs, S.W., 1987, Black shale terrane, in Fisher, 

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral resource potential and geology of the Challis I°x2° 

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87^80, p. 29^2.

Hobbs, S.W., 1985, Precambrian and Paleozoic sedimentary terranes in the Bayhorse area of the Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the geology and mineral 

deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-D, p. 59-68.

Mahoney, J.B., 1989, Geology and mineral deposits of the Washington Basin area, Custer County, Idaho, in Winkler, G.P., 

Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., Geology 

and mineral deposits of the Hailey and western Idaho Falls 

I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File 

Report 89-639, p. 95-110.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvanian and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J.D., and 

Stevens, C.H., eds.. Paleozoic paleogeography of the Western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-580.

Mahoney, J.B., and Sengebush, R.M., 1988, Stratigraphy of the 

Lower Permian Grand Prize Formation, south-central Idaho, in 

Link, P.K., and Hackett, W.R., eds., Guidebook to the geology
G12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 169-182.

Ross, C.P., 1963, Geology along U.S. Highway 93 in Idaho: Idaho 

Bureau of Mines and Geology Pamphlet 130, 98 p.

Sengebush, R.M., 1984, The geology and tectonic history of the 

Fourth of July Creek area, White Cloud Peaks, Custer Country, 

Idaho: Missoula, University of Montana, M.S. thesis, 79 p.

Teepen, K.L., 1985, Sulfide mineralization in Washington Basin, 

Idaho: Bowling Green, Ohio, Kent State University, M.S. thesis, 84 p.

Tschanz, C.M., Kiilsgaard, T.H., and Seeland, D.A., 1986, Geology 

of the eastern part of the Sawtooth National Recreation Area, 

Idaho, in Mineral resources of the eastern part of the Sawtooth

National Recreation Area, Custer and Blaine Counties, Idaho: 

U.S. Geological Survey Bulletin 1545-A, p. 17-43.

Umpleby, J.B., 1915, Ore deposits in the Sawtooth quadrangle, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 580-K, p. 221-249.

Van Noy, R.M., Ridenour, James, Zilka, N.T., Federspiel, F.E., 

Evans, R.K., Tuchek, E.T., and McMahan, A.B., 1986, Economic appraisal of the eastern part of the Sawtooth National 

Recreation Area, Idaho: U.S. Geological Survey Bulletin 

1545-E, p. 232^172.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.
Mineral Deposits at Leadbelt, 

Lava Creek Mining District, 

South-Central Idaho

By Sandra J. Soulliere, Anna B. Wilson, and Betty Skipp

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-H

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. HI

Introduction........................................................................................................................... 1

Exploration Perspective........................................................................................................ 1

Geologic Setting.................................................................;.................................................. 2

Mineral Deposits................................................................................................................... 5

Summary............................................................................................................................... 9

References Cited................................................................................................................... 9

FIGURES

1. Map showing location of Leadbelt area, Lava Creek mining district............................................................................ H2

2. Map showing location of Leadbelt and Butte-Antelope mines ..................................................................................... 3

3. Map showing geology of Leadbelt area, Lava Creek mining district............................................................................ 4

TABLES

1. Production data for deposits in the Leadbelt area, Lava Creek mining district............................................................. H2

2. List of elements and their limits of detection for panned-concentrate samples............................................................. 6

3. Results of geochemical analysis of rock samples from the Leadbelt area, Lava Creek mining district........................ 7

4. Results of geochemical analysis of panned-concentrate samples from the Leadbelt area, Lava Creek mining district 8

5. Summary of analytical results of panned-concentrate samples from the Leadbelt area, Lava Creek mining district... 8

6. Correlation coefficients for each pair of selected elements for panned-concentrate samples from the

	Leadbelt area, Lava Creek mining district..................................................................................................................... 9
Mineral Deposits at Leadbelt,

Lava Creek Mining District,

South-Central Idaho

By Sandra J. Soulliere, 1 Anna B. Wilson, 1 and Betty Skipp]

ABSTRACT

The Leadbelt mines of the Lava Creek mining district 

of south-central Idaho produced lead, silver, and zinc from 

polymetallic vein deposits in Mississippian terrigenous and 

carbonate rocks. Ore is present as discontinuous lenses and 

isolated clots within veins cutting carbonate rocks. Veins of 

this type have little or no surface expression in the area but 

are known to be associated with north-northwest-trending 

faults or with fractures related to folding.

INTRODUCTION

The Leadbelt mines of the Lava Creek mining district 

are about 12 mi west of Arco and 3 mi south of Grouse in 

Butte County, Idaho (fig. 1). The mines are on the southeastern flank of the Pioneer Mountains, south of Antelope Creek 

and near the heads of Leadbelt and Dry Fork Creeks (fig. 2). 

In this area, Mississippian terrigenous rocks of the 

McGowan Creek Formation and carbonate rocks of the Middle Canyon and Scott Peak Formations host polymetallic 

vein deposits containing lead, silver, and zinc.

The Leadbelt deposits and study area are within the 

Challis National Forest or on adjacent land administered by 

the Bureau of Land Management; the area is adjacent to privately owned land on its eastern, western, and southern 

sides. Access is by unimproved roads along Leadbelt Creek, 

south of the road along Antelope Creek. A four-wheel-drive 

road from the Leadbelt mine provides access to Cave Rock 

(fig. 2). Permission to use private roads on the eastern and 

southern boundaries of the study area was denied.

Topography of the area is characterized by broad 

ridges and steep valleys, and elevations range from 6,800 to 

9,178 ft. Tributaries of Dry Fork and Leadbelt Creeks drain 

the area.

'U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

Descriptions of the early mine workings and production 

estimates are given in Umpleby (1917) and Anderson 

(1929). Worl and others (1989) assessed the potential for 

undiscovered mineral resources of the Challis National Forest including the Leadbelt Creek area. Skipp and Hait 

(1977), Skipp and Hall (1980), and Link and others (1988) 

described the structure and stratigraphy of south-central 

Idaho. Recent geologic mapping of the Mackay 4 SE and 

Blizzard Mountain North 7.5-minute quadrangles by Skipp 

and others (1990) and Skipp and Bollman (1992), respectively, includes the Leadbelt area and was used to prepare 

figure 3 of this report.

EXPLORATION PERSPECTIVE

Although prospecting began in the area in 1890, significant lead and silver deposits at Leadbelt were not mined 

until 1905. Only two deposits, the Leadbelt and ButteAntelope, were extensively developed (Anderson, 1929). 

From 1905 to 1913, several shipments of lead-silver ore, 

having an estimated total value of $100,000 (1917 dollars), 

were hauled from the mines (Umpleby, 1917). Anderson 

(1929) reported that the Leadbelt mine produced 1,050 tons 

of ore in 1913. Production values for the deposits from 

1913 to 1941 are given in table 1 (R.G. Worl, written commun., 1991).

The portal of the Leadbelt mine is at the head of Leadbelt Creek at an elevation of about 7,200 ft (fig. 2). The stope 

is reportedly less than 40 ft along the north-trending strike of 

the vein, which apparently pinched with depth (Anderson, 

1929). Principal production from the mine was in 1913 when 

21 cars of 50 tons each were shipped; ore averaged 16 percent lead and 16 ounces of silver per ton (Umpleby, 1917). 

The Leadbelt mine is currently overgrown, although several 

open shafts were located, and no ore was found on the dump.

The portal of the Butte-Antelope mine is also at the 

head of Leadbelt Creek, about 0.5 mi southwest of the 

Leadbelt mine, at an elevation of about 7,250 ft (fig. 2). 

The old workings consist of open cuts, short tunnels and 

drifts scattered along the hillside. In 1928, a tunnel was cut

Hi
H2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

45' 

30'

43°15'

Mac/cay 

^Reservoir \ Area of

... } V map Mackay ( ^-*i

IDAHO

CHALLIS

NATIONAL

FOREST

V O/ /cv

_ APPROXIMATE / 1 

BOUNDARY OF THE

LAVA CREEK V 

MINING DISTRICT

CRATERS ( 

 I OF THE MOON 

j/ NATIONAL 

S. MONUMENT

0 SMILES

Figure 1. Map showing location of the Leadbelt area, Lava Creek 

mining district, south-central Idaho.

through the old workings and extended about 300 ft 

through black carbonaceous shale. Anderson (1929) 

reported assay values of 31 ounces of silver per ton from 

selected samples of galena at the mine. A visit to the site in 

1987 found the original Butte-Antelope mine workings virtually obliterated by recent excavations. All that remains is 

a steep cutbank with no sign of dumps or workings.

A number of old prospects and adits are also scattered 

along the hillside at the head of Dry Fork Creek; no production values are known for these.

At the time of this study in 1987-88, there was active 

exploration at an adit between the Leadbelt and Butte-Antelope mines. Rehabilitation of the adit and a nearby shaft 

indicated that a small-scale mining venture was operating 

in the area.

A mining operation with heap leach pads was underway 

in 1988 on privately owned land about 2 mi southwest of the 

Leadbelt mines. This mine is in argillite of the Copper Basin 

Formation, on the Copper Basin thrust plate (fig. 3), and was 

not studied by the authors. No other information was available for this site, and permission for access was denied.

Table 1. Production data for deposits in the Leadbelt area, Lava 

Creek mining district, south-central Idaho. 

[Data collected by R.G. Worl (U.S. Geological Survey) from U.S. 

Bureau of Mines files, Spokane Field Office. Crude ore is in dry tons; 

Au and Ag in ounces (troy); Cu and Pb in pounds. Zero (0) indicates no 

production; leaders (--) indicate no recorded production]

Year Ore Au Ag Cu Pb

Antelope Creek district

1935

1939

1940

Total

456

401

814

1,671

14.00

14.00

373

201

475

1,049

1

198

339

538

68

68

Unnamed mine, Antelope Creek

1924

Mine total

16

16

205

205

774

774

Butte (Antelope Creek) mine

1935

Mine total

40

40

1.00

1.00

519

519

24

24

1,763

1,763

Leadbelt mine

1913

1914

1915

1916

1917

1918

1919

1921

1922

1923

1924

1925-28

1929

1941

Mine total

34

353

205

83

557

416

276

0

39

0

24

0

57

13

2,057

6.00

4.00

2.00

22.00

6.00

3.00

0

1.00

0

-

0

3.00

47.00

514

5,619

1,902

1,162

4,788

5,369

3,742

0

1,242

0

348

0

511

121

25,318

~

136

-

~

736

2,030

995

0

65

0

~

0

34

3,996

8,409

123,810

43,615

23,522

130,074

111,038

93,619

0

23,767

0

6,935

0

12,031

2,217

579,037

District total 3,784 62.00 27,091 4,558 581,642 

Short tons 2.3 290.8

GEOLOGIC SETTING

Geologic units exposed in the Leadbelt area are mainly 

Mississippian sedimentary rocks unconformably overlain to 

the northwest by flows of the Eocene Challis Volcanic 

Group (fig. 3). Several north-northwest- and east-trending 

faults and folds transect the area.

In south-central Idaho, several major thrust plates separate distinct stratigraphic rock sequences (Skipp and Hait, 

1977; Skipp, 1987; Link and others, 1988). Paleozoic sedimentary rocks in the Leadbelt area are part of two such thrust 

plates, the Copper Basin plate to the west of the Copper 

Basin thrust fault and the Grouse plate to the east (fig. 3). 

Both plates were probably emplaced during east-westdirected compression in mid-Cretaceous time (Skipp, 1987). 

Most of the Paleozoic rocks in the Leadbelt area are on the 

Grouse thrust plate. The Copper Basin thrust fault, exposed 

along the western edge of the Leadbelt area (fig. 3), forms
43°37'30"

MINERAL DEPOSITS AT LEADBELT, LAVA CREEK MINING DISTRICT

113°40' 113037'30"

H3

35'

43°32'30"

^ , , ;;u*°oX';; ,

if--Ap{lro_kirna(e boundary <gT/_ 

* 5QhaJiis National Forest x /I

-4r-' - *''!

/, :--~-A n- & V-O/ViT < ?/

 ^'IV^^^-l^^^ai^K-^l' ' ^ ;;"'""vi> s^,-) -: ;.'<-*

M . ^---^X 1- \ ff¥ S '/^'- ri-^-~~ r/'-/,! S>] ' - 3 ' J ir-'ApRjQ>tirna(e bo 

^^ ^^''^ (O ^^'^'^^''^^^^} ^ f- Chkiiis Nationc

 ;ffi:?;"^^^^^\5^^^' %/^^^^ l^. v:^\ iK /F:- . z^^^tez^-,.j,tffc(^y%^;/. i--^> \i! ci/ » .I.

fc^^^llfSi|^i(^ ^.fevk' ^

^XX\N ;./i/,-,X. ^ '^" V N^C^AL« '^' ' %(^:^§%^^§^^r|<l (( ^'ff;:f\i r-

?'.. V_T ;OJ\ --' ~~ -vf! *~f ^^ "^ in'-fi''-. . ^IA-'^.<^=ST .^)i\\ ^'jV^.u \\ ! ri44?- / i'-'t^- ^ 

^^^IJ^*^^ /^'^i^y^Sl

^^^ii)\{('f'//L ';=&^r^'),ll' 5\ \feb:\v^w:

,\\ .... ; ' / .^ ; . //.:; /'/ ^ . ^ . _7:--?^-* ' . : ,\ \ * -\^-\\\-.\\:, \\ \\ . v \\ \ i

^^f^c^-;mi§ >. :^mjj^mi??»t , . H*P^^lfe-t fe|p^lte^il//1iv,. .^ fe^fttSll^^?: l?i^^i^|ip^ii^LJj2^

I'! I) i ' ' \'!J?5Sfl;--JiS'=^>]! I i ti^S^K?': ^sW'Si;*^^'"6"*]

D OO C D O/l C

:x>\

2&,

T3N

R 23 E R 24 E 

0

EXPLANATION

X Prospect

_( Adit

1MILE 

J

Figure 2. Map showing location of Leadbelt and Butte-Antelope mines, south-central Idaho. Topographic base U.S. Geological Survey Grouse 15-minute quadrangle; contour interval 80 ft.
H4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

43°37'30'

113°40'

.

113°37'30"

43°32'30'

UVN

 ^- ! '' --' '' ; :i6^co '"-

^-s\^^mm^Ks

^M^mWi.^

^M^7^^&

T3N

R 23 E R 24 E

0

I_____

1 MILE

J

Figure 3 (above and facing column). Map showing geology of the Leadbelt area. Sample localities are also shown. Modified from Skipp and others (1990) and Skipp and Bollmann (1992).
MINERAL DEPOSITS AT LEADBELT, LAVA CREEK MINING DISTRICT H5

EXPLANATION

Unconformity

\ QUATERNARY

Miocene

Unconformity

/Tr/

Tta

Unconformity

Eocene

TERTIARY

MISSISSIPPIAN

Alluvium (Quaternary) 

Landslide deposits (Quaternary)

IDAVADA VOLCANICS (MIOCENE) 

Tuffs of Little Chokecherry Canyon

CHALLIS VOLCANIC GROUP (EOCENE) 

Rhyolite dikes 

Rhyolite flows 

Rhyolite lava flows 

Rhyolite pipe 

Tuffs of Stoddard Gulch 

Tuffs of Antelope Creek

GROUSE THRUST PLATE (MISSISSIPPIAN) 

Surrett Canyon and Scott Peak Formations 

Middle Canyon Formation 

McGowan Creek Formation 

COPPER BASIN THRUST PLATE (MISSISSIPPIAN) 

Copper Basin Formation

- Contact

-J Fault Bar and ball on downthrown side, dotted where concealed

-* Thrust fault Sawteeth on upthrown side, dotted where concealed

-J Syncline

-3 Anticline 

) Adit 

B Shaft

X Prospect

LRfi 

 Sample locality and number

the western boundary of the Grouse plate and juxtaposes 

Lower Mississippian clastic rocks of the Little Copper Member of the Copper Basin Formation against the Lower Mississippian McGowan Creek Formation (Skipp and others, 

1990; Skipp and Bollmann, 1991, unpub. mapping).

In the Grouse plate, carbonate bank and forebank 

deposits of the Lower and Upper Mississippian Middle Canyon and Upper Mississippian Scott Peak Formations (Skipp 

and others, 1979) overlie turbidite of the Lower Mississippian McGowan Creek Formation. The McGowan Creek Formation was deposited in the eastern part of a foreland basin 

(Nilsen, 1977; Skipp and others, 1979). Sedimentary rocks 

of the McGowan Creek Formation generally dip to the northeast and locally are folded. The Middle Canyon and Scott 

Peak Formations constitute part of a prograding carbonatebank and forebank complex.

Late Cretaceous and (or) early Tertiary uplift, erosion, 

and deposition of conglomerate preceded Eocene Challis 

volcanism. Rocks of the Challis Volcanic Group are widespread north of the Leadbelt area, where they unconformably overlie Paleozoic sedimentary rocks. In the immediate 

area of the mines, all contacts between sedimentary rocks 

and volcanic rocks are faults. The volcanic rocks consist 

mainly of rhyolitic flows, pipes, and dikes and andesitic 

tuffs, breccias, and flows. Intrusion of hypabyssal stocks 

and dikes accompanied Eocene volcanism. Several rhyolite 

dikes are present in the Leadbelt area, and one dike crops 

out near the Leadbelt mine. A positive magnetic anomaly 

northeast of the mines may indicate an intrusive body at 

depth (Worl and others, 1989).

High-angle faults are widespread in the area and formed 

during three periods of Tertiary extension (Skipp and others, 

1990). Isotope data suggest that Late Cretaceous extension 

may also have been important in the region (Snee and Kunk, 

1989). East-trending faults represent a period of local northsouth extension that followed Mesozoic thrusting and preceded Challis volcanism. North-trending rhyolite dikes are 

considered to be the result of syn-Challis extension (Anderson, 1929; Skipp and others, 1990). Post-Challis extension is 

represented north of the mines where rocks of the Challis 

Volcanic Group are faulted against Paleozoic rocks (Skipp 

and others, 1990).

North- and northwest-trending anticlines and synclines 

are also widespread. These folds are locally fractured and 

steep and have limbs that dip 25°-45°. Several north-trending folds are displaced by east-trending faults.

MINERAL DEPOSITS

The deposits in the Leadbelt area are polymetallic veins 

in carbonate terrane. They are irregularly shaped orebodies 

of base- and precious-metals in veins along fractures and
H6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 2. List of elements and their limits of detection for 

panned-concentrate samples.

[All values in parts per million except gold, which is in parts per billion. 

Detection limits are computed for a standard size sample of nominal 

weight. If the actual weight of sample is greater than the nominal 

weight of standard, then the limit of detection may be lower; if the 

acutal weight is lower, then the limit of detection may be higher. 

Analyses by Geochemical Services, Inc., Sparks, Nevada]

Element

Silver (Ag)

Arsenic (As)

Gold (Au)

Bismuth (Bi)

Cadmium (Cd)

Copper (Cu)

Gallium (Ga)

Mercury (Hg)

Molybdenum (Mo)

Lead (Pb)

Antimony (Sb)

Selenium (Se)

Thallium (Tl)

Zinc (Zn)

Lower limit

0.015

1.0

0.5

0.25

0.25

0.025

0.50

0.10

0.10

0.25

0.25

1.0

0.5

1.0

Upper limit

12,500

25,000

6,250

12,500

12,500

50,000

12,500

6,250

12,500

25,000

12,500

100

12,500

50,000

faults in carbonate rocks. The sulfide minerals argentiferous galena, pyrite, tetrahedrite, and sphalerite are present 

as disseminations, clots, and discontinuous lenses in calcite 

veins 2-3 ft wide (Anderson, 1929). Gangue minerals in the 

veins include calcite, rhodochrosite, and, in places, quartz. 

Individual orebodies vary in size and were mostly worked in 

the oxide zones where iron and manganese oxide minerals, 

cerussite, and cerargyrite are common.

Mines and prospects of the Leadbelt area are in or near 

terrigenous rocks of the McGowan Creek Formation and carbonate rocks of the Middle Canyon and Scott Peak Formations (fig. 3). The McGowan Creek Formation (Lower 

Mississippian) consists of distal turbidite, calcareous siltstone, and minor silty limestone (Sandberg, 1 975). The Middle Canyon Formation (Lower and Upper Mississippian) 

overlies the McGowan Creek and consists of medium-gray, 

fine- to medium-grained, spiculitic, thin- to medium-bedded, 

silty limestone (Skipp and others, 1990). Thin, noncalcareous siltstone beds are present in the basal few feet. Mediumto dark-gray, thick-bedded, variably cherty, fossiliferous 

limestone of the Scott Peak Formation (Upper Mississippian) overlies the Middle Canyon Formation. Fossils in the 

Scott Peak are varied and abundant and include corals, brachiopods, mollusks, bryozoans, algae, calcareous foraminifers, trilobites, ostracodes, and shark teeth (Skipp and others, 

1979). Locally, all of these units are cut by dikes.

Host rocks generally are not visibly altered; a narrow 

zone of calcite, rhodochrosite, and calc-silicate minerals is 

present along some of the veins (Umpleby, 1917; Anderson, 

1929). Primary ore is locally oxidized. Because the underground workings are inaccessible and the mineralized zones

are not exposed, it was not possible to examine alteration at 

the mineralized zones. Rock samples were collected and 

examined at mine dumps and prospect pits.

Previous studies (Anderson, 1929; Worl and others, 

1989) suggest that the location of orebodies is controlled by 

fractures and faults in favorable carbonate host rocks. Orebearing veins at the Leadbelt and Butte-Antelope mines fill 

fractures that trend north and dip steeply west (Anderson, 

1929). These fractures may be related to folding of the 

nearby anticline (fig. 3). The Butte-Antelope mine adit follows an east-trending high-angle fault (fig. 3), and the intersection of northwest- and east-trending faults may also be an 

important control for deposition of ore minerals. Some 

deposits are along bedding-plane faults and fractures in 

folded carbonate rocks. The Leadbelt mine adit is on the 

western flank of a north-trending anticline (fig. 3).

Analyses of mineralized rocks provide useful geochemical information about the trace-element assemblages associated with a mineralizing solution. In 1987, four rock-chip 

samples of mineralized rock were collected from mine 

dumps and prospect pits in the Leadbelt area (fig. 3). At each 

site a 5-lb bag of rock chips and one or more hand samples 

were collected. The samples were analyzed for 34 elements 

using the semiquantitative emission spectrographic methods 

of Golightly and others (1987).

In 1988, 17 stream-sediment samples were collected in 

a reconnaissance-scale survey of tributary streams that drain 

the area (fig. 3). Permission to collect samples on private 

land south and east of the mines was denied. At each sample 

site a 10-lb bag of bulk stream sediment was collected. 

Stream sediment was then panned in the field to a more concentrated form and analyzed in the laboratory for 14 elements using inductively coupled emission spectrographic 

methods. Table 2 lists the elements and their detection limits. 

Analyses of stream-sediment samples are useful in identifying those drainage basins that contain concentrations of elements that may be derived from mineral deposits.

Zinc, copper, lead, arsenic, gold, silver, manganese, and 

barium are elements common to polymetallic vein deposits 

regardless of host rock type (Cox and Singer, 1986). Many 

of these elements were detected in rock-chip and pannedconcentrate samples from the Leadbelt area.

Table 3 presents the results of the analyses of rock samples collected from mine dumps and prospect pits. Rockchip sample LB6, collected from outcrop in a small prospect 

pit near Cave Rock (fig. 3), had the highest concentrations of 

Ag (1.95 ppm), Au (0.005 ppm), Cd (15.5 ppm), Mo (33.1 

ppm), Sb (31.8 ppm), Zn (334 ppm), Tl (7 ppm), and Se 

(97.4 ppm).

The suite of elements Ag, As, Cu, Hg, Mo, Pb, Sb, Zn, 

Cd, Ga, and Se was detected in a majority of the pannedconcentrate samples (table 4). Sample LB13, collected 

downstream from a northeast-trending fault in the Middle
MINERAL DEPOSITS AT LEADBELT, LAVA CREEK MINING DISTRICT H7

Table 3. Results of geochemical analyses of rock samples from the Leadbelt area, Lava Creek mining district, south-central Idaho. 

[Ca, Fe, Mg, Na, P, and Ti in percent; all other elements in parts per million. Lower limit of detection is shown in parentheses above element symbol. L 

indicates less than lower limit of detection; N indicates not detected; B indicates that the sample was not analyzed for this element. Sample LB6 was 

analyzed by Geochemical Services, Inc.; detection limits are given in table 2]

87M-120

87M-122

87M-123

LB6

87M-120

87M-122

87M-123

LB6

87M-120

87M-122

87M-123

LB6

(0.05) 

Ca

10

L

N

B

(20) 

Cd

N

N

N

15.5

(100) 

Sb

N

N

N

31.8

(0.05) 

Fe

2

1.5

0.5

B

(10) 

Co

N

N

N

B

(5) 

Sc

N

L

N

B

(0.02) 

Mg

0.7

0.5

0.3

B

(10) 

Cr

N

N

N

B

(10) 

Sn

N

N

N

B

(0.2)

Na

0.5

N

N

B

(5) 

Cu

10

70

20

35.0

(100) 

Sr

200

N

N

B

(0.002) 

Ti

0.03

0.2

0.15

B

(5) 

Ga

15

30

10

<4.71

(100) 

Th

N

N

N

B

(0.5) 

Ag

1.5

0.7

1

1.95

(10) 

Ge

L

5

5

B

(10) 

V

20

200

150

B

(200) 

As

1500

N

N

332

(50) 

La

N

N

N

B

(20) 

W

N

N

N

B

(10) 

Au

N

N

N

0.005

(10) 

Mn

300

N

15

B

(10) 

Y

N

N

N

B

(10) 

B

L

70

30

B

(5) 

Mo

N

N

N

33.1

(200) 

Zn

200

N

N

334

(20) 

Ba

200

2000

700

B

(20) 

Nb

N

N

L

B

(10) 

Zr

10

50

70

B

(1) 

Be

N

L

N

B

(5)

Ni

5

10

5

B

TI

B

B

B

7.00

(10) 

Bi

N

N

N

<2.35

(10) 

Pb

150

N

20

<2.35

Se

B

B

B

97.4

Canyon Formation, had the highest concentrations of As 

(123 ppm), Cu (32.1 ppm), Mo (28.7 ppm), Zn (494 ppm), 

and Se (5.98 ppm). Sample LB1 was collected downstream 

from the intersection of east-trending and northeast-trending faults in Middle Canyon Formation and has the highest 

Hg (1.73 ppm) and Pb (46.7 ppm) concentrations. The 

highest concentrations of Sb (18.80 ppm) and Cd (2.5 ppm) 

are from sample LB5, which was collected downstream 

from the intersection of east- and north-trending faults in 

Middle Canyon Formation. No significant concentrations 

of silver were detected in the panned-concentrate samples. 

The highest concentration of Ag (0.286 ppm) was from 

sample LB19, collected downstream from a mineralized 

prospect pit. Table 5 presents a summary of analytical 

results for panned-concentrate samples.

Correlation analysis of the panned-concentrate data 

shows Mo-As-Zn-Cu and Sb-Cd associations (correlation 

coefficient >0.90), a Cu-As-Mo-Zn-Sb-Cd-Ga association 

(correlation coefficient >0.85), and a Cu-As-Mo-Zn-SbCd-Ga-Pb-Hg association (correlation coefficient >0.75) 

(table 6).

No geophysical signatures specific to polymetallic 

replacement vein deposits have been identified in the Leadbelt area. Regional aeromagnetic surveys of the Hailey and 

Idaho Falls I°x2° quadrangles provide criteria for mapping 

buried intrusive complexes, delineating major fault and 

shear zones, and identifying areas that might be hydrothermally altered or mineralized (Kleinkopf and others, 1988a, 

b). A belt of high-intensity magnetic gradients, known as the 

Great Rift shear zone, trends northwest from about the

Craters of the Moon National Monument to Sun Valley 

(Kleinkopf and others, 1989). The Leadbelt area is in the 

center of this shear zone, and a magnetic high or positive 

anomaly is northeast of the mines (Worl and others, 1989). 

This magnetic high may indicate a buried intrusive body at 

depth that could represent a thermal source for a regional 

hydrothermal system. In addition, parallel magnetic contours 

east of the magnetic high indicate a north-northwest-trending fault and fold zone through the Leadbelt area.

In simplistic terms, ore deposition was from hydrothermal fluids probably associated with Eocene igneous 

intrusive activity. Three possible sources for the fluid are 

(1) hydrothermal water from magma at depth, (2) convecting meteoric water, or (3) connate water from the Paleozoic 

rocks. Fractures and faults formed by extensional tectonism provided conduits for mineralizing solutions. Calcite, silica, magnesium carbonate minerals, and lead-, zinc-, 

and silver-bearing sulfide minerals were deposited as veins 

in carbonate rocks.

The influence of local intrusive activity on the formation of the base-metal deposits is uncertain. Intrusive activity 

at depth may have been the source of a regional hydrothermal system that either supplied the metals or acted as a heat 

source for transport of metals from sedimentary rocks. Leadisotope data from vein deposits near Leadbelt (Sanford and 

others, 1989; Sanford and Wooden, this volume) suggest that 

either the Tertiary intrusive bodies or Precambrian basement 

rocks may be the source of the lead; however, until additional analyses are performed, the source of the metals at 

Leadbelt is uncertain.
H8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 4. Results of geochemical analysis of panned-concentrate samples from the Leadbelt area, Lava Creek mining district, southcentral Idaho.

[Samples were also analyzed for Tl, Bi, Pd, and Te, but all values were below the limits of detection. All values are in parts per million; L indicates a 

value less than the detection limit shown]

Sample 

number

LB1

LB2

LB3

LB4

LB5

LB8

LB9

LB10

LB11

LB12

LB13

LB14

LB15

LB16

LB17

LB18

LB19

Ag

0.109

0.049

0.074

0.160

0.098

0.047

0.064

0.107

0.084

0.140

0.084

0.071

0.113

0.126

0.087

0.146

0.286

As

71.9

26.1

21.6

30.2

98.6

35.0

46.0

66.3

74.0

86.0

123.0

44.7

53.9

102.0

47.6

34.2

16.1

Au

0.001

0.0005L

0.0007L

0.001

0.001

0.002

0.0007L

0.0005L

0.0006L

0.0007L

0.0007L

0.0005L

0.0004L

0.001

0.001

0.0006L

0.001

Cu

30.6

12.2

9.49

19.2

28.9

24.6

18.4

28.5

22.7

28.1

32.1

20.0

25.8

30.8

19.4

22.3

15.4

Hg

1.73

0.488

0.210

0.095L

0.426

0.319

0.138

0.314

0.430

0.230

0.322

0.325

0.859

0.537

0.549

0.119

0.097L

Mo

13.8

4.64

2.77

4.89

12.2

4.64

8.22

13.5

8.55

13.4

28.7

7.31

7.03

21.0

12.1

6.17

1.66

Pb

46.7

15.5

11.8

14.0

29.6

16.8

25.4

20.3

22.5

25.6

29.4

19.1

21.6

32.7

24.0

16.3

10.5

Sb

9.66

3.70

4.80

4.71

18.8

4.46

6.64

7.86

8.68

10.6

12.1

5.48

6.35

11.2

6.56

7.06

2.37

Zn

436

176

144

207

447

239

236

343

273

395

494

237

304

470

286

259

125

Cd

1.89

0.780

0.706

0.493

2.50

1.03

1.37

1.48

1.31

1.62

1.76

1.07

0.928

2.01

1.24

0.722

0.379

Ga

4.25

2.91

0.832

1.62

4.31

2.77

3.96

4.14

2.78

2.98

4.36

2.17

2.00

4.24

2.99

1.81

1.18

Se

1.34

0.967L

1.36L

2.59

5.40

2.60

1.98

2.05

1.41

5.58

5.98

2.28

2.45

2.60

2.68

4.34

2.06

Table 5. Summary of analytical results of panned-concentrate samples from the Leadbelt area, Lava Creek

mining district, south-central Idaho

[In parts per million. Samples were analyzed for Tl, Bi, Pd, and Te, but all values were below the limits of detection]

Ag

As

Au

Cu

Hg 

Mo

Pb

Sb

Zn

Cd

Ga

Se

Minimum 

value detected

0.047 

16.1

<0.0004

9.49

<0.095 

1.66

10.50

2.37

125.0

0.379

0.832

<0.967

Maximum 

value detected

0.29 

123.0

0.002

32.10

1.73 

28.70

46.70

18.80

494.0

2.50

4.360

5.980

Mean 

of values

0.11 

57.48

0.0008

22.85

0.423 

10.03

22.46

7.666

298.9

1.252

2.900

2.805

Deviation Number of samples 

of values having detectable values

0.056 

31.14

0.0004

6.7

0.39 

6.89

8.93

3.989

115.76

0.577

1.168

1.557

17 

17

10

17

15 

17

17

17

17

17

17

15
MINERAL DEPOSITS AT LEADBELT, LAVA CREEK MINING DISTRICT H9

Table 6. Correlation coefficients for each pair of selected elements for panned-concentrate samples from the Leadbelt area, Lava Creek 

mining district, south-central Idaho

[Data analyzed by using USGS STATPAC statistical computer package (Van Trump and Miesch, 1976) to determine element associations. These 

elements were selected because they were detected in more than 50 percent of the samples. Results of geochemical analysis and summary of results are 

given in tables 4 and 5]

Ag 

As 

Au 

Cu

Hg 

Mo

Pb

Sb

Zn

Cd

Ga

Se

1.00 

-0.17 

0.03 

-0.02

-0.18 

-0.16

-0.21

-0.14

-0.14

-0.30

-0.36

0.11

Ag

1.00 

0.03 

0.85

0.26 

0.91

0.72

0.87

0.95

0.88

0.78

0.60

As

1.00 

0.25

0.04 

0.03

0.06

0.05

0.10

0.05

0.07

0.13

Au

1.00

0.40 

0.77

0.73

0.73

0.92

0.76

0.72

0.55

Cu

1.00 

0.24

0.75

0.22

0.43

0.39

0.38

-0.26

Hg

1.00

0.68

0.68

0.89

0.74

0.77

0.54

Mo

1.00

0.67

0.83

0.83

0.79

0.19

Pb

1.00

0.86

0.92

0.71

0.66

Sb

1.00

0.89

0.81

0.58

Zn

1.00

0.87 1.00

0.44 0.28

Cd Ga

1.00

Se

SUMMARY

Silver, lead, and zinc production in the Lava Creek mining district of south-central Idaho was from small isolated 

clots and discontinuous lenses in veins cutting carbonate 

rocks. Veins of this type have little or no surface expression 

in the area but are known to be associated with north-northwest-trending faults or with fractures related to folding. 

Exploration for hidden orebodies should therefore concentrate on the structural fabric of the area and favorable host 

rocks. Further detailed geochemical and geophysical surveys 

would also be useful in locating hidden orebodies. Detailed 

electrical surveys would facilitate detection of individual 

orebodies containing conductive sulfide minerals. Isotope 

data for ore in the Leadbelt area would help determine the 

source of the metals in these deposits.

REFERENCES CITED

Anderson, A.L., 1929, Geology and ore deposits of the Lava 

Creek district, Idaho: Idaho Bureau of Mines and Geology 

Pamphlet 32, 70 p.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Golightly, D.W., Dorrzapf, A.F., Jr., Mays, R.E., Fries, T.L., and 

Conklin, N.M., 1987, Analysis of geologic materials by directcurrent arc emission spectrography and spectrometry, in Baedecker, P.A., ed., Methods for geochemical analysis: U.S. Geological Survey Bulletin 1770, p. A1-A13.

Kleinkopf, M.D., Bankey, Vicki, and McCafferty, A.E., 1988a, 

Aeromagnetic and gravity anomaly maps of the Hailey and 

part of the Idaho Falls two-degree quadrangles, Idaho: Geological Society of America Abstracts with Programs, v. 20, 

no. 6, p. 424-^25.

 1988b, The application of regional geophysical data in mineral resource assessments in the Hailey and Idaho Falls quadrangles, Idaho: Geological Society of America Abstracts with 

Programs, v. 20, no. 6, p. 425.

-1989, Gravity and magnetic anomaly patterns applied to

mineral resource exploration, Hailey I°x2° quadrangle, Idaho, 

in Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, 

K.M., eds., Geology and mineral deposits of the Hailey and 

Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey 

Open-File Report 89-639, p. 26-32.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke, Susanne, and 

Burton, B.R., 1988, Structural and stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knob, Pioneer, Boulder, and Smoky Mountains, in Link, 

P.K., and Hackett, W.R., eds., Guidebook to the geology of 

central and southern Idaho: Idaho Geological Survey Bulletin 

27, p. 5^12.

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds., Paleozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 275-299.

Sandberg, C.A., 1975, McGowan Creek Formation, new name for 

Lower Mississippian flysch sequence in east-central Idaho: 

U.S. Geological Survey Bulletin 1405-E, 11 p.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Skipp, Betty, 1987, Basement thrust sheets in the Clearwater orogenic zone, central Idaho and western Montana: Geology, v. 

15, p. 220-224.

Skipp, Betty, and Bollmann, D.D., 1992, Geologic map of Blizzard 

Mountain North quadrangle, Blaine and Butte Counties, Idaho:
H10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

U.S. Geological Survey Open-File Report 92-280, scale 

1:24,000.

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River Plain, Idaho: Wyoming 

Geological Association Guidebook, Twenty-Ninth Annual 

Field Conference, p. 499-515.

Skipp, Betty, and Hall, W.E., 1980, Upper Paleozoic paleotectonics 

and paleogeography of Idaho, in Fouch, T.D., and Magathan, 

E.R., eds., Paleozoic paleogeography of the West-Central 

United States: Rocky Mountain Section, Society of Economic 

Paleontologists and Mineralogists, West-Central United States 

Paleogeography Symposium 1, p. 387^22.

Skipp, Betty, Kuntz, M.A., and Morgan, L.A., 1990, Geologic map 

of Mackay 4 (Grouse) SE quadrangle, Butte County, Idaho: 

U.S. Geological Survey Open-File Report 89^31, scale 

1:24,000.

Skipp, Betty, Sando, W.J., and Hall, W.E., 1979, The Mississippian 

and Pennsylvanian (Carboniferous) Systems in the United

States-Idaho: U.S. Geological Survey Professional Paper 

1110-AA,p. AA1-AA42.

Snee, L.W., and Kunk, M.J., 1989, 40Ar/39Ar thermochronology of 

mineral deposits in the southern part of the Idaho batholith, in 

Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., 

eds., Geology and mineral deposits of the Hailey and western 

Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey 

Open-File Report 89-639, p. 37-38.

Umpleby, J.B., 1917, Geology and ore deposits of the Mackay 

region, Idaho: U.S. Geological Survey Professional Paper, 

scale 1:375,000, 129 p.

Van Trump, George, Jr., and Miesch, A.T., 1976, The U.S. Geological Survey RASS-STATPAC system for management and statistical reduction of geochemical data: Computers and 

Geosciences, v. 3, p. 475^88.

Worl, R.G., Wilson, A.B., Smith, C.L., Kleinkopf, M.D., and 

Sykes, R.C., 1989, Mineral resource potential and geology of 

the Challis National Forest, Idaho: U.S. Geological Survey 

Bulletin 1873, 101 p.
Mineral Deposits of the Mackay and

Copper Basin Mineralized Areas,

White Knob Mountains, South-Central Idaho

By Anna B. Wilson, Sandra J. Soulliere, and Betty Skipp

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-1

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. II

Introduction........................................................................................................................... 1

Previous Work.............................................................................................................. 1

Historical Perspective........................................................................................................... 6

Mackay Mineralized Area............................................................................................ 6

Copper Basin Mineralized Area ................................................................................... 6

Development................................................................................................................. 6

Mackay Mineralized Area.................................................................................... 6

Copper Basin Mineralized Area ........................................................................... 6

Production..................................................................................................................... 7

Mackay Mineralized Area.................................................................................... 7

Copper Basin Mineralized Area ........................................................................... 7

Exploration Activity..................................................................................................... 7

Geologic Setting................................................................................................................... 7

Description of Rock Units ............................................................................................ 8

McGowan Creek Formation................................................................................. 8

White Knob Limestone......................................................................................... 8

Mackay Stock....................................................................................................... 8

Challis Volcanic Group ........................................................................................ 9

Marble................................................................................................................... 9

Skarn..................................................................................................................... 9

Jasperoid............................................................................................................... 9

Structure........................................................................................................................ 9

Mineral Deposits................................................................................................................... 11

Copper Skarn Deposits ................................................................................................. 11

Inner Zone............................................................................................................. 11

Outer Zone............................................................................................................ 14

References Cited................................................................................................................... 15

FIGURES

1. Map showing boundaries of Copper Basin and Alder Creek mining districts, location of mines, and

prominent geographic features, White Knob Mountains............................................................................................... 12

2. Map showing simplified geology, structural elements, and location of mines, Mackay and Copper Basin

mineralized areas............................................................................................................................................................ 3

3. Map showing geology of the Mackay and Copper Basin mineralized areas................................................................. 10

TABLES

1. Production data for mines in the Mackay and Copper Basin mineralized areas, White Knob Mountains.................... 14

2. Summary of geochemical data for 34 rock samples from the Mackay and Copper Basin mineralized areas,

White Knob Mountains .................................................................................................................................................. 13
Mineral Deposits of the Mackay and

Copper Basin Mineralized Areas, 

White Knob Mountains, South-Central Idaho

By Anna B. Wilson, 1 Sandra J. Soulliere, 1 and Betty Skipp ]

ABSTRACT

Between 1879 and 1982 about 1 million tons of ore 

were produced from skarn deposits and associated replacement veins near Mackay and Copper Basin, Idaho. The 

deposits contain copper, lead, zinc, silver, and gold and 

formed during contact metamorphism and metasomatism of 

the Mississippian White Knob Limestone by intrusion of 

the Eocene Mackay stock and related rocks. Field observations and statistical analysis of geochemical data indicate 

that the deposits are typical of zoned copper skarns. 

Copper-gold-silver is the geochemical signature of the 

inner zone, grading outward to gold-silver, and then to 

lead-zinc-silver in the outer zone. Deposits of the inner 

zone typically are in metamorphosed and metasomatized 

limestone along the contacts of the Mackay Granite and 

leucogranite porphyry phases of the Mackay stock, and 

copper is the chief product. In the outer zone, the limestone 

is generally unaltered, contact metamorphism is limited, 

and lead, zinc, and silver are the commodities mined.

In 1988 the area was explored for sediment-hosted, jasperoid-associated, precious-metal deposits and for hotsprings-type, volcanic-hosted, disseminated gold deposits.

undiscovered, sediment-hosted, jasperoid-associated, precious-metal deposits near the Mackay stock is high.

The area described herein extends from the town of 

Mackay to Copper Basin (fig. 1) in a wedge-shaped northeast-trending block, approximately 13 mi long by 2l/2 mi 

wide at the northeast end and 8 mi wide at the southwest end 

(fig. 2). It contains the highest peaks in the central White 

Knob Mountains including Shelly (11,278 ft), Redbird 

(11,273 ft), Cabin (11,244 ft), and Lime (11,179 ft) Mountains, White Knob (10,529 ft), and Mackay Peak (10,273 ft). 

The lowest elevations in the area are 6,000 ft near Mackay 

and 7,700 ft near Copper Basin. Both the Alder Creek mining 

district and the eastern part of the Copper Basin mining district are in the study area (fig. 1).

The study area is within or immediately adjacent to the 

Challis National Forest. Access to the Alder Creek mining 

district is by graded roads from Mackay via Rio Grande Canyon and Alder Creek and by various four-wheel-drive roads 

near the mines. Access to the Copper Basin area is by graded 

Forest Service roads from Antelope Pass, Trail Creek Road, 

or Burma Road. Other than old four-wheel-drive roads to the 

Copper Basin mine, no roads access the western part of the 

study area east of the mine.

INTRODUCTION

Poly metallic skarn deposits are prevalent in the Mackay 

and Copper Basin mineralized areas, southwest of the town 

of Mackay, Idaho (fig. 1). These copper, lead, zinc, silver, 

and gold deposits of probable Paleogene age were formed by 

replacement of carbonate-bearing rocks during contact metamorphism and metasomatism. The Upper Mississippian 

White Knob Limestone adjacent to the Eocene Mackay stock 

(fig. 2) is the host rock. Total production for the Mackay and 

Copper Basin mineralized areas is estimated to have been 

about 1 million tons of ore (table 1). Potential for as yet

U.S. Geological Survey, Denver Federal Center, Denver, Colorado

80225.

PREVIOUS WORK

Nelson and Ross (1968, 1969a) prepared geologic 

maps of the Mackay and Copper Basin mineralized areas at 

1:24,000 and 1:125,000 scales. Skipp and Hait (1977), 

Skipp and Harding (1985), and Wilson and Skipp (1994) 

updated and reinterpreted the geology as previously presented but at a much smaller scale. Unpublished detailed 

maps of several mines by other authors included in the 

Anaconda Geological Documents Collection (International 

Archive of Economic Geology, American Heritage Center, 

University of Wyoming, Laramie) were useful.

Kemp and Gunther (1907) and Umpleby (1917) published the first comprehensive studies of the ore deposits in 

the Mackay region. Other studies include those of Ross 

(1930), Nelson and Ross (1968, 1969a, b), and Leland
12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

WHITEKNOB BLUEBIRD 

MINE^ MINE :

HORSESHOE MINE

_ " EMPIRE MINE 10:273 ciiff 9 GRANDPRIZEMINE

CHAMPION MINE

Approximate

boundary of the

Alder Creek mining

district

Lime Mtn 

11,179

Redbird Mtn 

11 '273

COPPER BASIN \ 

M/Wf

Area of figures 

2 and 3

Approximate

boundary of the

Copper Basin mining

district

43°45'

5 MILES

Figure 1. Map showing approximate boundaries of the Copper Basin and Alder Creek mining districts, location and elevation (in feet) of 

prominent mountains, access roads to the mines, and mines mentioned in the text, Mackay and Copper Basin mineralized areas, White Knob 

Mountains, Idaho.
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS

113°50' 45' 113°40'

13

EMPIRE MINE 

GRAND PRIZE MINE

R 22 E R 23 E

0 1

R 23 E R 24 E

4 MILES

TV

Mu

EXPLANATION

Quaternary deposits, undifferentiated 

Jasperoid 

Mackay stock intrusive rocks (Eocene)

Challis Volcanic Group (Eocene)

Sedimentary rocks, undifferentiated (Mississippian)

Contact

Fault Dashed where inferred, dotted where concealed, 

and queried where unknown

Thrust fault Dotted where concealed; sawteeth 

on upper plate

Mine

Figure 2. Map showing simplified geology, structural elements, and location of mines, Mackay and Copper Basin mineralized areas, 

White Knob Mountains, Idaho. Geology modified from Nelson and Ross (1968, 1969a) and Dover (1981).
14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 1. Production data for mines in the Mackay and Copper Basin mineralized areas, White Knob Mountains, Idaho. 

[Compiled from Ross (1930), Farwell and Full (1944), Leland (1957), and Nelson and Ross (1968). Asterisk (*) indicates summary of data 

collected by R.G. Worl and T.H. Kiilsgaard (U.S. Geological Survey) from U.S. Bureau of Mines files, Spokane Field Office. Values for the 

Champion mine were computed from assay data and tonnage reported by Leland (1957). Crude ore is in dry tons; Au and Ag in ounces (troy); 

Cu, Pb, and Zn in pounds. Leaders (--) indicate no value on record. Total for Alder Creek mining district does not include the Copper Basin 

mine]

Year Ore Au Ag Cu Pb Zn

Copper Basin mine

*1912

*1915-19

*1953

Total

60

5,685

429

6,174

0.60

88.96

13.00

102.56

163

16,064

1,758

17,985

13,654

682,406

27,344

723,404

2,662

2,662

--

Blue Bird mine

* 1924-28

* 1935-39

Total

571

365

936

8.89

7.55

16.44

5,472

4,525

9,997

574

90

664

135,038

143,931

278,969

3,111

~

3,111

Champion mine

*1908

1938

1943

1944

1947

1948

1949

1950

1951

1952

1953

1954

1955

Total

26

18

339

200

65

161

106

481

107

617

459

2,579

0.23

3.39

2.00

0.81

1.21

1.59

4.81

0.93

5.55

2.30

22.82

126

152

993

532

954

576

212

1,443

251

1,462

1,193

7,668

--

234

2,373

1,400

1,105

386

1,102

~

3,175

835

8,761

1,102

20,473

2,812

4,608

86,106

42,000

13,650

42,504

18,656

~

126,984

22,042

159,186

115,668

634,216

~

504

20,340

13,200

6,890

10,304

4,452

-

28,860

6,206

34,552

24,786

150,094

Horseshoe mine

1916

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

* 1936-51

*1954

* 1970-71

Total

196

1,462

1,087

1,128

2,319

116

651

660

79

75

865

182

49

1,691

31

3,271

13,862

0.88

6.99

8.64

4.76

5.96

2.25

7.61

6.98

4.33

1.50

11.72

1.52

0.43

20.32

36.00

119.89

1,468

17,293

11,440

12,011

21,165

1,811

9,297

5,014

1,012

1,776

10,236

2,275

123

21,366

233

13,210

129,726

3,093

2,997

1,522

2,333

2,021

376

902

1,603

287

348

3,198

495

1,159

6,211

100

12,100

38,745

55,587

678,074

446,628

361,937

386,352

55,902

246,659

169,872

36,538

59,310

332,597

58,256

791

837,355

11,200

280,700

4,017,758

~

-

~

~

--

-

-

-

-

18,942

18,163

2,366

79,822

~

330,420

449,713
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 15

Table 1. Production data for mines in the Mackay and Copper Basin mineralized areas, White Knob Mountains, Idaho 

Continued.

[Compiled from Ross (1930), Farwell and Full (1944), Leland (1957), and Nelson and Ross (1968). Asterisk (*) indicates summary of data

collected by R.G. Worl and T.H. Kiilsgaard (U.S. Geological Survey) from U.S. Bureau of Mines files, Spokane Field Office. Values for the

Champion mine were computed from assay data and tonnage reported by Leland (1957). Crude ore is in dry tons; Au and Ag in ounces (troy);

Cu, Pb, and Zn in pounds. Leaders (--) indicate no value on record. Total for Alder Creek mining district does not include the Copper Basin

mine]

Year Ore Au As Cu Pb Zn

Empire mine

1902

1903

1904

1905

1906

1907

1908

1909

1910

1911

1912

1913

1914

1915

1916

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

1930

1935

1936

1937

1939

1940

1941

1942

* 1943^9

* 1954-65

* 1970-71

* 1974-75

*1982

Total

1,721

15,681

67,850

13,000

40,838

37,141

382

1,436

7,206

11,057

26,227

35,950

17,801

54,295

69,907

66,808

53,211

12,904

15,755

9,992

16,717

15,791

11,775

24,753

3,635

13,627

11,532

66,573

26,214

190

173

22

996

4,484

3,169

1,274

15,404

85,486

26,443

11,651

446

899,517

14.00

241.00

85.00

385.00

1,842.00

1,823.00

16.00

28.00

265.00

663.00

1,766.00

1,892.00

971.00

3,155.00

2,875.00

2,530.00

2,476.00

673.00

1,369.00

1,236.00

2,019.00

1,458.00

1,245.00

2,096.00

234.00

761.00

495.00

2,282.00

755.00

10.00

9.00

1.00

207.00

526.00

381.00

141.00

1,009.00

2,549.00

563.00

113.00

41,159.00

607

12,658

3,500

22,065

71,854

70,222

673

2,236

28,754

40,900

69,942

106,463

59,243

125,134

123,453

74,645

56,014

31,833

29,888

23,354

33,988

25,908

18,808

35,439

6,453

9,734

9,776

60,883

22,925

1,510

639

306

2,465

11,300

7,013

1,874

16,223

62,431

9,579

1,615

901

1,293,208

14,966

441,286

2,700,000

684,134

2,807,926

2,895,881

38,698

90,347

919,492

1,415,314

2,854,281

3,962,125

2,106,441

4,702,119

5,006,291

4,208,401

3,404,161

1,300,518

1,480,678

1,088,148

1,843,200

1,449,838

1,137,771

2,352,306

239,785

684,154

514,697

2,824,032 1,000

1,121,586

26,518

18,897

3,876

175,940

632,217

380,469

104,000

822,272

4,245,260 4,200

710,800

51,271 18,642

29,537

61,460,098 53,379

-

-

--

--

--

~

~

-

-

-

-

--

-

--

--

--

--

--

--

--

--

--

-

--

-

-

~

--

--

--

41,247

--

870,768

912,015

Alder Creek district

Total 916,894 41,318.15 1,440,825

Short tons

61,519,978 4,984,322

30,760 2,492

1,514,933

757
16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

(1957) on the Alder Creek district and that of Farwell and 

Full (1944) on the Empire mine. Except for Ross (1930), 

detailed information on the Copper Basin mine is proprietary 

and is not available for public use. A study of the mineral 

resource potential and general geology of the Challis 

National Forest (Worl and others, 1989) and recent studies 

on jasperoid deposits (Soulliere and others, 1988; Wilson 

and others, 1988) provide a summary of current (as of 1988) 

activity and geologic interpretations. A mining history of the 

area (Wells, 1983) makes for enjoyable reading.

In 1990 geologists from Idaho State University were 

conducting detailed mapping and studies of the ore deposits 

in the volcanic rocks of the Challis Volcanic Group in the 

Mackay and Copper Basin mineralized areas.

HISTORICAL PERSPECTIVE 

MACKAY MINERALIZED AREA

Prospectors first discovered copper in Alder Creek in 

1879, but it was not until the 1884 discovery of ore at what 

is now known as the Empire mine that the Alder Creek mining district was established. Mining camps were settled at 

Houston and Cliff City (fig. 1) in 1884 (Wells, 1983, p. 124), 

and a small copper smelter constructed at Cliff City operated 

intermittently for several years with varying success 

(Umpleby, 1917, p. 93).

A railroad was built from Blackfoot to service the 

Empire mine in 1901, and the new mining center at its terminus, Mackay, lured settlers from the mining camps. A 

smelter built at Mackay operated from 1902 to 1907 but was 

not successful. After 1907 ore was shipped to Bingham, 

Utah (T.H. Kiilsgaard, written commun., January 1991) or 

Salt Lake (Umpleby, 1917, p. 93) for smelting.

Early mining operations at the Empire mine had problems (Umpleby, 1917, p. 13-14, 93; Wells, 1983, p. 125), 

but Umpleby (1917, p. 14, 93) noted that conditions at the 

mine improved when, in 1907, the property was acquired 

by the Empire Copper Company, and a leasing system was 

established that allowed individual miners to be paid for the 

ore they produced. About this time, improvements were 

made to the Empire mine, including replacement of the 12- 

mile-long "expensive electric railway with a Shay steam 

locomotive" (Wells, 1983, p. 125) that was 73/4 mi long 

(Umpleby, 1917, p. 100). The steam locomotive was 

replaced in 1918 by an overhead tram (Wells, 1983, p. 

126), whose towers were still visible in Rio Grande Canyon 

(fig. 1) in 1990. In 1924, a flotation mill was constructed to 

handle the ore from the Empire mine (Farwell and Full, 

1944, p. 4; Wells, 1983, p. 126). Mining operations continued more or less steadily until 1930 and resumed on a 

smaller scale in the mid-1930's after one of the largest orebodies in the mine was discovered (T.H. Kiilsgaard, written 

commun., January 1991).

The entire 1,100-foot level of the Empire mine was 

driven in the 1960's, and ore was mined from it (T.H. Kiilsgaard, written commun., 1991). A large reworked open-pit 

mine on the southern edge of the Empire mine property is 

evidence of a mining revival in the early 1970's. All that 

remains of the operation are skeletons of heavy machinery, 

deteriorating platforms, and empty tanks indicative of a heap 

leach operation. Records for this operation could not be 

located. Production records (table 1) indicate production 

from the Empire mine as recently as 1982.

COPPER BASIN MINERALIZED AREA

In 1888, copper ore containing lesser amounts of lead 

and silver was discovered in Copper Basin. Until a smelter 

was completed at the mine site in 1901, the ore was hauled 

to Ketchum for shipment (Wells, 1983, p. 124). The Copper 

Basin smelter was not a success; it proved cheaper to haul the 

ore to the railroad at Mackay (Umpleby, 1917, p. 103) for 

shipment. Mining at the Copper Basin mine has been intermittent since its discovery, and only some of its ore is 

accounted for in official records (table 1).

DEVELOPMENT 

MACKAY MINERALIZED AREA

None of the underground workings at any of the mines 

was examined by the authors of this paper. Previous reports 

on the Empire mine (Farwell and Full, 1944; Nelson and 

Ross, 1968) indicate that there were more than 60,000 ft of 

underground workings driven on grade and numerous stopes 

in an area that extends two-thirds of a mile and is as wide as 

400 ft. The lowest level of the mine is the Cossack Tunnel 

(the 1,600-foot level) at 7,010 ft elevation from which no ore 

has been mined. The lowest level that produced ore was the 

1,100-foot level (about 7,500 ft elevation). The highest level 

is at about 8,500 ft, and the main workings are at about 7,700 

ft elevation. Surface mining extends as high as 8,880 ft.

Workings at the Horseshoe mine on six levels covered a vertical distance of 350 ft (Nelson and Ross, 1968). 

Both the major developments and the ore zones trend 

about N. 30° W. (Ross, 1930). The Champion mine was 

developed on four levels and had almost 2,100 ft of workings. Most of the ore was mined from the No. 2 level, and 

the lower levels were never productive (T.H. Kiilsgaard, 

written commun., April 23, 1952, U.S. Geological Survey 

(USGS) files, Spokane Field Office).

COPPER BASIN MINERALIZED AREA

The mine at Copper Basin was considerably smaller 

than the Empire mine. As of 1917, it had five adits, a 265- 

foot-long shaft, and more than 3,000 ft of workings
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 17

(Umpleby, 1917). A map from 1968 (USGS files, Spokane 

Field Office) shows a glory hole and more than 1,600 ft of 

workings in only four adits.

PRODUCTION 

MACKAY MINERALIZED AREA

Detailed production records for the mines in the Alder 

Creek mining district are summarized in table 1. Some of the 

early figures can be verified in Ross (1930, p. 8, 9), Farwell 

and Full (1944, p. 5, 6), Leland (1957, p. 17-19), and Nelson 

and Ross (1968, p. A28-A30). Additional data are summarized from files at the U.S. Bureau of Mines Western Field 

Office, Spokane. The district produced at least 916,000 tons 

of crude ore that yielded more than 41,159 ounces of gold, 

1.44 million ounces of silver, 30,760 tons of copper, 2,490 

tons of lead, and 750 tons of zinc.

Oxidized copper ore in skarn was produced from the 

Empire mine, the main producer in the Alder Creek mining 

district. From 1902 through 1982, the Empire mine produced 

at least 30,730 tons of copper, 41,159 ounces of gold, and 

1,293,208 ounces of silver from 899,517 tons of crude ore 

(table 1). Most of the oxidized copper ore averaged 4-5 percent Cu, whereas the sulfide ore contained half that amount 

of copper (Ross, 1930, p. 15).

Oxidized lead-zinc bearing veins containing lesser 

amounts of copper, silver, and gold have also been exploited 

from deposits near the Empire mine, notably the Blue Bird, 

Champion, Horseshoe, and White Knob mines (fig. 1).

From 1916 through 1971, the Horseshoe mine produced 

almost 14,000 tons of ore (table 1). From this, almost 120 

ounces of gold, 130,000 ounces of silver, 19 tons of copper, 

2,000 tons of lead, and 225 tons of zinc were recovered (table 

1). Approximately 4,500 tons of ore is reported to have come 

from the Champion mine prior to 1960 (Nelson and Ross, 

1968, p. A28), although Leland (1957) reports only 2,579 

tons (table 1) and records from the U.S. Bureau of Mines 

show only 2,000 tons. The 936 tons of ore produced from the 

Blue Bird mine yielded 139 tons of lead (table 1). The only 

production figure found for the White Knob mine is 2,100 

tons of 17-percent zinc ore in 1941-42 (Farwell and Full, 

1944, p. 6). T.H. Kiilsgaard (written commun., January 

1991) recalled that the White Knob was producing 

smithsonite zinc ore in 1946. No production records for the 

other mines are available.

COPPER BASIN MINERALIZED AREA

Estimates for the value of ore produced at Copper Basin 

vary widely and cover different time periods. Umpleby 

(1917, p. 103) estimated $40,000 by 1914, whereas Ross 

(1930, p. 10) estimated $230,000 by the late 1920's. Other

estimates of production are proprietary but are within this 

range (USGS files, Spokane Field Office). Only scanty production data are preserved in U.S. Bureau of Mines files: 

almost 6,200 tons of ore yielded 102 ounces of gold, 18,000 

ounces of silver, 360 tons of copper, and 1.3 tons of zinc 

from 1912 to 1919 and in 1953 (table 1).

EXPLORATION ACTIVITY

Exploration interest in 1989-90 focused on jasperoidassociated, low-grade, large-tonnage, precious-metal deposits and gold skarns in the sedimentary terrane of the region. 

Claims were staked on and surrounding silicified outcrops, 

and assessment work was kept current on many old claims. 

Numerous small jasperoid outcrops were staked between 

Mackay and the Empire mine. Newly located claims were 

staked in the Copper Basin mine area. Representatives from 

large and small mining companies were active in the area, 

but no extensive rehabilitation of the old workings was 

undertaken nor were any of the jasperoid deposits developed.

Concurrently, there was exploration for hot-springstype, volcanic-hosted, disseminated gold deposits in the volcanic rocks adjacent to the area. New prospects and exploration targets were identified, but none was developed. Interest 

was focused on newly mapped intersections of northeastand northwest-trending structures (L.G. Snider, Idaho State 

University, oral commun., May 1990). Volcanic-hosted ore 

deposits are discussed by Moye and others (in press).

GEOLOGIC SETTING

The Mackay and Copper Basin mineralized areas are 

east of the Idaho batholith and north of the Snake River 

Plain. They are in the Cordilleran thrust belt, at the edge of 

the Basin and Range structural province. Thrust plates composed predominantly of Paleozoic quartzite, carbonate, and 

shale were emplaced from west to east during Mesozoic 

time. The thrust plates are offset by northeast-striking normal faults of probable Eocene age, which in turn truncate 

less well developed, northwest-striking Eocene faults 

(Southworth, 1988). The northeast-striking faults are truncated by younger, northwest-striking basin and range faults 

(Skipp and Harding, 1985).

A pair of the northeast-striking Eocene faults forms the 

margins of the White Knob horst, which includes the 

Mackay and Copper Basin mineralized areas (Skipp and 

Harding, 1985). Exposed on the horst are Mississippian sedimentary rocks, a middle Eocene pluton (the Mackay stock), 

and, locally, volcanic rocks. Adjacent to the horst, volcanic 

rocks predominate (fig. 2).
18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

DESCRIPTION OF ROCK UNITS

Rocks exposed in the Mackay and Copper Basin mineralized areas are primarily carbonate rocks and minor clastic 

units, granitic intrusive rocks, and skarn. In addition, jasperoid is present locally. For more complete descriptions refer 

to the cited publications and references contained therein.

McGOWAN CREEK FORMATION

The Lower Mississippian McGowan Creek Formation 

(mapped as the Copper Basin Formation of Nelson and 

Ross (1968, 1969a) in this area) is the oldest rock unit 

exposed on the White Knob horst (fig. 3). It is an argillite 

sequence more than 4,000 ft thick composed of distal thinbedded turbidite and interlayered mudstone, siltstone, and 

limestone deposited as flysch in a foreland basin (Nilsen, 

1977; Skipp and others, 1979).

WHITE KNOB LIMESTONE

The Upper Mississippian White Knob Limestone conformably overlies the McGowan Creek Formation (fig. 3). It 

consists of more than 5,500 ft of folded and faulted, variably 

fossiliferous, blue-gray to black, chiefly thick bedded, 

locally dolomitic limestone that contains abundant nodules 

and lenses of chert in some beds. The upper 3,000 ft contains 

conglomerate, sandstone, and mudstone interbeds. The formation was deposited in a gradually shoaling marine environment ranging from deep slope at the base (exposed 

immediately west of Mackay) to shallow turbulent shelf 

margin in the upper part (exposed at the Copper Basin mine) 

(Skipp and others, 1979; Neely and Isaacson, 1982). The 

White Knob Limestone, locally altered to marble and (or) 

skarn (described following), is the primary host rock for ore. 

The quartzite and quartzite conglomerate described near the 

Copper Basin mine, and mineralized locally, are probably in 

the upper part of the formation. The formation has not been 

mapped in sufficient detail to determine which layers are 

likely to host ore.

MACKAY STOCK

The Eocene Mackay stock intrudes the Mississippian 

formations (fig. 2). It includes the Mackay Granite, quartz 

monzonite, leucogranite porphyry, and dikes of quartz 

latite, rhyolite, and porphyritic rhyolite (Nelson and Ross, 

1968). None of the intrusive phases is mineralized. The 

descriptions that follow are based on the work of Nelson 

and Ross (1968) and supplemented with our reconnaissance-scale observations. Nelson and Ross (1968) reported 

that all of the intrusive rocks, and possibly some of the 

extrusive rocks, were derived from a single parent magma. 

Detailed studies of the intrusive rocks and their genetic 

relationships are described by Doyle (1989).

The Mackay Granite (fig. 3), technically a granite porphyry, is the most prominent of the intrusive phases and is 

exposed in an area of more than HVz mi2. Although most 

outcrops are weathered to a rusty pink, fresh surfaces and 

fine-grained chill margins are greenish gray. Phenocrysts of 

pinkish, subhedral to euhedral orthoclase as long as 1 cm and 

medium-gray, rounded quartz (as long as 0.5 cm) make up 

25-35 percent and 5-15 percent of the granite, respectively. 

The groundmass is composed of quartz, orthoclase, and plagioclase and lesser biotite, hornblende, chlorite, magnetite, 

apatite, zircon, and rutile (Nelson and Ross, 1968). Recent 

argon data bracket the age of the granite between 49 and 47 

Ma (L.W. Snee, oral commun., May 1990).

Quartz monzonite as described by Nelson and Ross 

(1968) is exposed in three places at the northern end of the 

stock (fig. 3) and is reported in several places in the underground workings. The quartz monzonite is light to medium 

gray and is generally darker and finer grained than the 

Mackay Granite. Phenocrysts of oligoclase as long as 0.15 

cm make up almost 25 percent of the rock. Locally, tiny, 

rounded phenocrysts of quartz are present. The groundmass consists of fine- to medium-grained orthoclase, 

quartz, oligoclase, diopside, hornblende, and biotite. Apatite, sphene, magnetite, and chlorite are common (Nelson 

and Ross, 1968).

Leucogranite porphyry (equivalent to quartz porphyry 

of Kemp and Gunther, 1908) crops out at the northeastern 

end of the main intrusive complex (fig. 3). Euhedral to subhedral phenocrysts of orthoclase as long as 2 cm, oligoclase 

as long as 0.4 cm, and rounded and embayed quartz as long 

as 0.8 cm are conspicuous. The very pale gray groundmass 

is composed of very fine grained quartz and feldspar (primarily orthoclase). Diopside, calcite, and sphene are accessory minerals. Based on crosscutting relations, the 

porphyry is assumed to be younger than the Mackay Granite (Nelson and Ross, 1968).

Quartz latite dikes (mapped as unit Tmr, fig. 3) are 

light to dark greenish gray. In hand sample, the quartz latite 

contains small phenocrysts of altered oligoclase, patches of 

chlorite (with calcite, magnetite, limonite, and quartz), and, 

locally, pyroxene, amphibole, or biotite. Quartz grains are 

not visible. The groundmass is orthoclase, oligoclase, and 

quartz (Nelson and Ross, 1968).

Abundant rhyolite dikes trend northeast across the 

length of the stock and extend into the sedimentary country 

rocks (fig. 3). Approximately 25 percent of the dike rock is 

composed of euhedral to subhedral phenocrysts as long as 

0.5 cm of clear and smoky quartz, oligoclase, and orthoclase. 

The groundmass is very fine grained and yellowish to greenish, light to medium gray. The rhyolite may be contemporaneous with the leucogranite porphyry because these units 

tend to grade into each other at the northeastern end of the 

stock (Nelson and Ross, 1968). Preliminary age data indicate 

that the rhyolite dikes are approximately 48-47 Ma (L.W. 

Snee, oral commun., May 1990).
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 19

Porphyritic rhyolite dikes contain conspicuous euhedral 

phenocrysts (1 cm) of white oligoclase and fewer phenocrysts (1.5-2.5 cm) of orthoclase, rounded and embayed 

quartz (1 cm), and minor secondary chlorite after biotite, epidote, and calcite (Nelson and Ross, 1968). These dikes have 

also been described as porphyritic granodiorite and trachyte 

porphyry (Farwell and Full, 1944). Commonly, the margins 

of the porphyritic rhyolite dikes are bordered by dark finegrained dikes whose composition and relationship were not 

studied. Some porphyritic rhyolite dikes were emplaced after 

mineralization (Farwell and Full, 1944, p. 14).

Dikes of several other compositions such as granite, 

aplite, and andesite porphyry mentioned in the literature and 

on unpublished maps are not shown in figure 3.

CHALLIS VOLCANIC GROUP

Rocks of the Challis Volcanic Group are not widely 

exposed on the White Knob horst. Most exposures (figs. 2, 

3) on the horst are thin remnants of flows, indurated and 

welded tuff, and tuff breccia (Nelson and Ross, 1968). Rhyolite, quartz latite, porphyritic obsidian, andesite, and dacite 

are distinctive shades of reddish and purplish brown, greenish gray to gray, and light tan. The volcanic rocks were 

extruded 51-44 Ma (Moye and others, 1988).

Geologic mapping by Nelson and Ross (1968, 1969a) 

does not differentiate volcanic rock types. Detailed mapping 

of volcanic rocks on either side of the White Knob horst was 

in progress by geologists, primarily from Idaho State University, in 1990. The new mapping (Moye and others, in 

press) correlates volcanic units across the horst, locates eruptive centers, and identifies many more structures, especially 

northwest-striking fault zones, than were previously known.

surrounded by the leucogranite porphyry. Early reports 

noted that the skarn is in the intrusive rocks (Umpleby, 

1917), but later studies (Nelson and Ross, 1968) and our 

observations show that these skarns are totally altered 

xenoliths, septa, and roof pendants of limestone within the 

intrusive rock. Endoskarn is scarce.

As much as 75 percent of the skarn consists of andradite 

and grossularite garnet; diopside, hedenbergite, magnetite, 

hematite, actinolite, tremolite, scapolite, wollastonite, epidote, vesuvianite, fluorite, calcite, chlorite, gypsum, and 

quartz are also present. Locally the skarn is almost entirely 

composed of magnetite and hematite. The texture of the 

skarn is crystalline and granular, but in places relict bedding 

is preserved. Exposures of skarn are sporadic at the surface; 

without access to underground exposures we could not determine if zoning is present within the skarn bodies.

JASPEROID

Jasperoid crops out along the southern fault boundary 

of the horst block and also locally is present as scattered 

lenses throughout the White Knob Limestone peripheral to 

skarn (fig. 3). The jasperoid is commonly gray to brown, 

very fine grained, brecciated, and ferruginous. Hematite and 

limonite stain exterior weathered surfaces. The degree of 

silicification varies from patchy and diffuse to massive and 

dense. Textures commonly indicate more than one episode 

of brecciation and silicification. Veins of quartz and calcite 

are common, and barite, fluorite, jarosite, and stibiconite are 

less prevalent. Petrographic studies show no grains of identifiable minerals nor any fluid inclusions large enough for 

analysis. Detailed descriptions and geochemistry of jasperoid samples from the Mackay area are given in Wilson and 

others (1988) and Soulliere and others (1988).

MARBLE

At the margins of the intrusive rocks, the White Knob 

Limestone is metamorphosed locally to a very pure, white, 

coarsely crystalline marble bordered by a zone of tremolite 

adjacent to unbleached limestone. The marble is finer 

grained closer to the unmetamorphosed limestone. The limestone probably was metamorphosed to marble in Eocene 

time during intrusion of the plutonic rocks.

SKARN

Skarn, considered Eocene in age, developed locally 

along the margins of the Mackay stock (fig. 3) where the 

stock is in contact with the White Knob Limestone or carbonate-bearing beds of the McGowan Creek Formation. 

The skarn may be tens of feet thick adjacent to the leucogranite porphyry, especially where engulfed or partly

STRUCTURE

In south-central Idaho, several Cretaceous thrust plates 

separate distinct stratigraphic rock sequences (Skipp and 

Hait, 1977; Skipp, 1987; Link and others, 1988). The 

Mackay and Copper Basin mineralized areas are on the 

White Knob thrust plate. The Copper Basin thrust fault, 

exposed on the hillside immediately below, and southwest 

of, the Copper Basin mine, forms the western margin of the 

thrust plate (fig. 2). The eastern margin of the White Knob 

thrust plate, the Lost River thrust fault, is not exposed in the 

study area but is postulated to be buried under alluvium in 

the Lost River Valley east of Mackay (Skipp and Harding, 

1985). Thrust faults are probably Cretaceous in age and have 

been used to explain abrupt facies changes in Mississippian 

rocks (Skipp and Hait, 1977; Skipp and Harding, 1985).

Paleozoic rock units in the area are folded as a result of 

the Cretaceous thrusting. Locally the folding varies, but in
110 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

113°50' 45' 113°40'

Figure 3 (above and facing column). Map showing geology of the Mackay and Copper Basin mineralized areas, White Knob Mountains, 

Idaho. Geology modified from Nelson and Ross (1968, 1969a) and Dover (1981).
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 111

TV

Td

Tm

Tmr

Tq

Mw

Mmg

Mcu

EXPLANATION

Quaternary deposits, undifferentiated

Jasperoid

Skarn

Challis Volcanic Group (Eocene)

Dikes, undifferentiated (Eocene)

Leucogranite porphyry (Eocene)

Mackay Granite (Eocene)

Zone of rhyolite dikes in the Mackay Granite (Eocene)

Quartz monzonite (Eocene)

White Knob Limestone (Mississippian)

McGowan Creek Formation (Mississippian)

Copper Basin Formation (Mississippian)

Contact

Fault Dashed where inferred; dotted where concealed; queried 

where unknown

Thrust fault Dotted where concealed; sawteeth on upper plate

Small dikes and intrusive bodies

Min

general the anticlines and synclines trend north-northwest. 

The limbs have moderate to steep dips to the northeast and 

southwest. Locally, due to intense folding, the strikes and 

dips vary (Nelson and Ross, 1969a).

Within the White Knob thrust plate is the northeasttrending White Knob horst, which is composed of Mississippian sedimentary rocks cored by exposed middle Eocene 

plutonic rocks (Skipp and Hait, 1977; Skipp and Harding, 

1985). The horst is bounded on the southeast by a high-angle 

fault that cuts rocks of the Eocene Challis Volcanic Group 

and on the northwest by a fault that has been mapped as buried by the same volcanic rocks (Nelson and Ross, 1968) (fig. 

2). The latter fault may dip to the northwest at about 40° 

(L.G. Snider, Idaho State University, oral commun., May 

1990). Uplift of the horst has been considered to be coincident with emplacement of the intrusion (Nelson and Ross, 

1968; Skipp and Harding, 1985); however, recent studies of 

the volcanic rocks show that uplift may postdate intrusion 

(L.G. Snider, oral commun., May 1990).

Regional aeromagnetic data (Worl and others, 1989) 

indicate that the main body of the Mackay stock continues 

southwest of the exposed outcrop. The stock is elongate and 

dips under the Copper Basin mine area to the southwest.

Prevalent northeast-striking Eocene structures, including the horst, faults, intrusions, and dike swarms, reflect the 

influence of regional northwest-southeast extension. The 

same trend is noted in the Trans-Challis fault system to the 

northwest and in the Hailey gold belt to the west (Kiilsgaard 

and others, 1986; Worl and Johnson, this volume).

Numerous northwest-striking faults of probable 

Eocene age are present in rocks of the Challis Volcanic 

Group on either side of the White Knob horst. Geologists 

from Idaho State University have identified a major fault 

zone in the Challis Volcanic Group that appears to cross the 

horst at the northeastern end of the main pluton (L.G. 

Snider, oral commun., May 1990). The quartz monzonite 

and leucogranite porphyry, as well as most of the major ore 

deposits near Mackay, are confined to this zone. After discussions with L.G. Snider, we agree that these intrusions 

followed a well-defined fault zone and that the ore may be 

preferentially located at the intersections of northeast- and 

northwest-trending structures.

MINERAL DEPOSITS 

COPPER SKARN DEPOSITS

Known mineral deposits in the Mackay and Copper 

Basin mineralized areas can be classified as copper skarn 

deposits. The Empire mine is typical of the inner zone of 

copper skarns, and the Blue Bird, Champion, Horseshoe, and 

White Knob mines represent the outer zone. There is, of 

course, some overlap between zones and their boundaries are 

gradational, but for the purpose of this paper the zones are 

discussed separately. The Copper Basin mine displays characteristics of both the inner and outer zones.

INNER ZONE

Description. The most prominent and prolific ore 

producers in the Mackay and Copper Basin mineralized 

areas are copper skarn deposits. The deposits are along the 

contacts of the Mackay Granite and leucogranite porphyry 

with the surrounding White Knob Limestone. The skarn, a 

product of metamorphism and metasomatism, is the ore 

host. It is developed primarily in limestone (exoskarn) 

blocks that are included in the intrusive rocks and along 

parts of the leucogranite porphyry-limestone contact. The 

ore is massive to disseminated within the skarn. Locally, 

abundant iron minerals are suggestive of iron skarn, but 

iron minerals also are found in copper skarns (Einaudi and 

Burt, 1982). Copper, lead, zinc, silver, gold, and minor 

tungsten have also been produced. Gold-bearing skarns 

were the exploration targets in 1990.

Type example. Empire mine, Alder Creek district

Other example. Copper Basin mine, Copper Basin 

district

Orebodies. Deposits are present where reactive carbonate strata were replaced by calcium-iron-magnesiummanganese silicate minerals and ore minerals within, or close 

to, the Mackay Granite and the leucogranite porphyry. Contacts between the intrusive and carbonate rocks, local bedding
112 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

planes, faults, joints, and breccia zones control location of the 

orebodies. Most orebodies are pipelike, chimney or pod 

shaped, irregular, and small. Orebodies are at the contact 

between skarn and limestone, entirely within the skarn, and 

at the contact of skarn with intrusive rocks (Nelson and Ross, 

1968, p. A25). Several orebodies are cut, and possibly were 

displaced, by rhyolite porphyry dikes that were emplaced 

after mineralization (Farwell and Full, 1944, p. 14).

Most of the deposits are confined to a northwest-trending, narrow, arcuate band, approximately 4 mi long, at the 

northeast end of the Mackay stock (fig. 2), and the largest 

skarn deposits are adjacent to the leucogranite porphyry. 

Concentrated near the middle of this zone are orebodies of 

the Empire mine. Individual orebodies are commonly 

15-200 ft long by 5-55 ft wide, and the largest extend vertically for about 600 ft.

Texture. In the skarn, ore minerals are interstitial to 

gangue. Copper ore minerals may be massive to disseminated, but other ore minerals are disseminated in widely 

varying concentrations throughout the skarn. Magnetite and 

hematite ore minerals are commonly, but not exclusively, 

massive. Farwell and Full (1944, p. 11) described the oxidized ore as calc-silicate minerals "carrying disseminations 

and spongelike aggregates of metallic minerals."

Calc-silicate skarn rocks range from fine to very coarse 

grained and granular. The ore-bearing skarn is coarser 

grained and contains more calcite than barren skarn. Pure 

white marble beds have a sugary texture. Blue-gray limestone is moderately crystalline and, locally, is interlayered 

with bands of the white marble.

Mineralogy. At the Empire mine, the principal ore 

minerals are chrysocolla (copper silicate), malachite, and 

azurite (copper carbonates), tenorite (copper oxide), and 

sparse copper sulfate minerals. Locally, the deposits are 

almost entirely composed of magnetite and hematite, and 

siderite is abundant peripheral to these zones (such as at the 

Grand Prize mine, fig. 2). Sulfide minerals are rare, although 

chalcopyrite, pyrite, pyrrhotite, molybdenite, sphalerite, and, 

infrequently, bornite are present with associated calcite, 

quartz, magnetite, fluorite, scheelite, and specularite.

Similarly, most ore at Copper Basin is oxidized except 

where it is in black shaly limestone. Oxidized copper minerals are malachite, azurite, chrysocolla, cuprite, and tenorite. 

Magnetite and siderite are abundant. Sulfide minerals are 

rare, although bornite, chalcopyrite, chalcocite, and pyrite 

have been found, especially in the shaly layers.

Much of the material on the mine dumps consists of 

iron hydroxide in siliceous material with secondary hematite, magnetite, quartz, garnet, and diopside and stains of 

copper oxides. Well-developed extensively oxidized gossan 

is present in brecciated quartzite (probably part of the White 

Knob Limestone) at the Copper Basin mine.

Geochemical signature. The geochemical signature 

commonly associated with copper skarns is copper-gold-silver in the proximal (inner) zone grading outward to gold-silver to lead-zinc-silver in the distal (outer) zone. Some copper

skarns are anomalous in copper, arsenic, antimony, and bismuth (Cox and Theodore, 1986, p. 86). For comparison, 

lead-zinc skarn deposits are anomalous in Zn, Pb, Mn, Cu, 

Co, Au, Ag, As, W, Sn, F, and Be (Cox, 1986a, p. 90), and 

iron skarns tend to be anomalous in Fe, Cu, Co, Au, and Sn 

(Cox, 1986b, p. 94).

Thirty-four rock and two stream-sediment samples 

from the Mackay and Copper Basin mineralized areas were 

semiquantitatively analyzed for 35 elements by a directcurrent arc emission spectrographic method (Bullock and 

others, 1990). Table 2 gives the lower limit of detection, 

minimum and maximum values, mean, standard deviation, 

and number of unqualified values for each element for the 

34 rock samples. Of the 35 elements analyzed, Ca, Fe, Mg, 

Ti, Ag, Ba, Cr, Cu, Ga, Mn, Ni, Pb, V, Zn, and Zr were 

detected in at least half the samples. P, Au, Ge, Nb, Sc, and 

Th had insufficient detectable values to compute mean and 

standard deviation. The complete data set is given in Bullock and others (1990).

Statistical analysis of the geochemical data shows correlations of arsenic-cobalt-bismuth, silver-lead-zinc, and 

beryllium-tungsten. The first two associations are typical of 

copper skarns, but alone they are not conclusive evidence 

that the system near Mackay is exclusively a copper skarn. 

The same elements, beryllium, and tungsten, are present, for 

instance, in lead-zinc skarns. The same associations resulted 

when the data were reevaluated excluding the samples specifically collected from the copper skarn at the Empire mine. 

The data set was too small to make statistically valid correlations between specific rock types, ores, and alteration.

Geophysical signature. Aeromagnetic data outline 

the Mackay stock and suggest that the stock is more extensive to the west in the subsurface than in surface exposure 

(Worl and others, 1989). The Mackay Granite probably 

underlies the Copper Basin mine area. No geophysical signatures specific to skarn are indicated in the Mackay and Copper Basin mineralized areas. Detailed electrical and 

magnetic surveys might reveal additional smaller sulfidebearing orebodies, depending on the mineralogy and composition of the host rock.

Genesis and ore controls. Mineralized rock is at the 

intersection of the northeast-trending intrusive rocks and the 

White Knob Limestone. Ore is in a narrow, north-trending 

arcuate zone in contact with metamorphosed limestone or in 

xenoliths or roof pendants in granitic rock and related porphyry close to the limestone. This zone is the only one in the 

horst that has prominent northwest-trending structures.

Ore slopes are along crosscuts that are radial to the 

northeast-trending haulageways (Nelson and Ross, 1968, p. 

A24). The crosscuts follow zones of shearing in both the 

igneous rock and altered limestone (Ross, 1930, p. 15; Nelson and Ross, 1968, p. A24). The shear zones are ore guides. 

Irregular porphyry dikes that cut both granite and limestone 

are approximately parallel with these shear zones. Ore is also 

present along bedding in the limestone.
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 113

Table 2. Summary of geochemical data for 34 rock samples from the Mackay and Copper Basin mineralized areas, White Knob 

Mountains, Idaho.

[Complete data set is given in Bullock and others (1990). Ca, Fe, Mg, Na, P, and Ti in percent; all other values in parts per million. Limit is the 

detection or determination limit. Mean and standard deviation were computed using the lower detection limit for all N and L values and the

unqualified values or the highest value was the same as the lower detection limit. Valid indicates number of samples without qualified values 

(N, L, or G): N indicates not detected; L indicates detected but below limit of determination; G indicates greater than the uppermost detection 

limit]

Element

Ca

Fe

Mg

Na

P

Ti

Ag

As

Au

B

Ba

Be

Bi

Cd

Co

Cr

Cu

Ga

Ge

La

Mn

Mo

Nb

Ni

Pb

Sb

Sc

Sn

Sr

Th

V

w

Y

Zn

Zr

Limit

0.05

0.05

0.02

0.2

0.2

0.002

0.5

200

10

10

20

1

10

20

10

10

5

5

10

50

10

5

20

5

10

100

5

10

100

100

10

20

10

200

10

Minimum 

value detected

N

L

0.02

N

N

N

N

N

N

N

N

N

N

N

N

N

L

N

N

N

L

N

N

N

N

N

N

N

N

N

N

N

N

N

N

Maximum 

value detected

20

20

5

3

L

.3

200

10,OOOG

L

100

5,000

7

200

500

700

100

20.000G

50

N

150

5,OOOG

300

20

100

20,OOOG

200

5

500

500

N

100

1,000

20

10,OOOG

150

Mean

4.73

7.16

1.03

0.685

0.067

40.6

629

-

12.8

592

1.40

27.7

39.7

41.6

23.2

284

19.1

54.1

1,297

22.4

16.9

497

103

45.2

140

28.2

60.6

10.4

2,844

33.1

Standard 

Deviation

5.83

7.15

1.20

0.866

0.082

59.5

1,732

-

15.4

1,111

1.09

43.4

8.45

120

24.0

5,209

13.4

17.6

1,820

52.8

19.5

8,053

17.2

~

92.5

87.7

25.1

169

1.89

3,804

37.0

Valid

33

33

34

10

0

33

19

6

0

7

26

12

9

4

11

17

30

26

0

5

32

15

1

26

28

1

3

12

11

0

27

10

4

18

19

The Mackay stock and its related intrusions probably 

provided the heat and fluids that caused metasomatism and 

the formation of skarn. Presence of jasperoid and alteration 

of the intrusive and carbonate rocks are indications of hydrothermal activity.

Deposits at the Empire mine are representative of the 

skarn-forming process. The White Knob Limestone, with 

its calcic and dolomitic variations, was invaded by the 

intrusive rocks of the Eocene Mackay stock. Contact metamorphism caused the marbleization of the limestone beds, 

and minor skarn may have developed as hornfels in the

more clastic layers. Metasomatism and continued skarn formation took place only where porosity and permeability 

permitted fluids to enter; thus, the ore-forming solutions 

penetrated the skarn rocks chiefly along preexisting fractures (Ross, 1930, p. 16; Worl and others, 1989, p. 60). 

These fractures probably formed coincident with the 

leucogranite porphyry, as did most of the larger skarn bodies. It should be emphasized that the ore formed by replacement, not by filling of open cavities.

Exploration guides. Additional, undiscovered copper 

skarn deposits are likely to be found near the Empire and
114 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Copper Basin mines. Elsewhere near the margins of the 

Mackay stock, potential for additional discoveries of skarn 

with economic value is moderate.

The orebodies are scattered along the intrusive rocklimestone contact in skarn, and exploration should obviously 

concentrate on this zone; however, fully engulfed blocks of 

skarn in the intrusive bodies and contacts not exposed at the 

surface or in underground workings also are potential sites 

for ore. In addition, further research should focus on locating 

the intersections of major northeast- and northwest-trending 

structures. It is likely that the entire Empire mine area may 

be at such an intersection.

Geochemical studies on the composition of the border 

phases of the intrusive rock bodies could help delineate locations where thicker skarn bodies might be present because 

most of the larger deposits are related to intrusions of leucogranite porphyry. Detailed studies of the spatial relationships 

of oxide and sulfide ores could be used to restrict the areas of 

search to those having the greatest potential. Most of the 

Empire ore was relatively shallow and, therefore, oxidized. 

Perhaps this zone is underlain by sulfide-bearing ore. 

Finally, there is not a clear understanding of the compositional variation in the White Knob Limestone, especially the 

calcite-dolomite distribution. Such an understanding might 

lead to delineation of calcium-rich areas more susceptible to 

sulfide deposition and magnesium-rich areas containing 

iron-oxide-rich skarn.

Future studies should include detailed geochemical 

sampling and analysis for gold and silver, both of which 

commonly are present in anomalous quantities in the inner 

and outer zones of typical copper skarns (Cox and Theodore, 

1986, p. 86). Areas of the skarn that are enriched in precious 

metals could possibly be exploited in the future.

OUTER ZONE

Description. Ore deposits of lead, zinc, and silver and 

accompanying copper and gold, such as at the Blue Bird, 

Champion, Horseshoe and White Knob mines, are in veins in 

the Paleozoic sedimentary rocks. Because a close spatial and 

genetic relationship exists between these deposits and the 

skarn deposits of the inner zone, discussed previously, the 

geologic characteristics are similar.

Host rock is the White Knob Limestone and intercalated quartzite and, locally, adjacent intrusive rocks, particularly dikes. Unlike the inner zone, the limestone is generally 

unaltered, and contact metamorphism is limited to a narrow 

zone of marble and some calc-silicate minerals such as wollastonite, scapolite, diopside, grossularite, and tremolite 

(Nelson and Ross, 1968, p. A20). Veins tend to parallel highangle, northeast-striking faults and northwest-trending shear 

zones. Ore may be concentrated at the intersections of these 

northeast- and northwest-trending structures.

Lead, zinc, and silver are the main commodities mined 

from small deposits of the outer zone near the Mackay stock. 

These deposits are privately owned, and very little detailed 

information regarding them is published. Although these 

deposits contributed to the economic development of the 

region, they were insignificant from a commercial standpoint. Most of the ore in the Mackay area came from copper 

deposits in the inner zone.

Examples. Blue Bird, Champion, Horseshoe, and 

White Knob mines in the Alder Creek district; Copper Basin 

mine in Copper Basin district (fig. 1)

Orebodies. Deposits of lead, zinc, and silver are 

mainly replacements along fractures and bedding planes in 

the White Knob Limestone. Most are intimately associated 

with, and overlap, the inner zone skarn deposits that are so 

prominent in the region.

Individual orebodies are generally tabular and vary 

greatly in size. Exact dimensions are unknown, but these are 

considered to be small mines. The orebodies were probably 

several hundreds of feet by several tens of feet and not more 

than 30 ft thick.

At the Copper Basin mine, the principal orebodies were 

near aplite and porphyry dikes in the "limonite zone" of the 

quartzite conglomerate (H.H. Doelling and K.C. Thompson, 

written commun., 1960, USGS files, Spokane Field Office), 

in northeast- and northwest-trending fissures, and in crushed 

ground at the intersections of these fissures (E.R. Zalinsky, 

written commun., 1917, USGS files, Spokane Field Office). 

Replacement ore, generally striking N. 20° E. and dipping 

gently to the southeast, was also bedded in the limestone and 

quartzite units in the upper part of the White Knob Limestone. These replacement bodies were 6 in.-6 ft thick in the 

quartzite (Ross, 1930, p. 16), 6-20 ft thick in limestone 

(Anonymous, (probably C.P. Heiner) written commun. to 

OME Field Officer, April 18, 1969, USGS files, Spokane 

Field Office), and as much as 30 ft thick in shale (E.R. Zalinsky, written commun., 1917, p. 7, USGS files, Spokane 

Field Office).

Also at the Copper Basin mine, dikes of granite, andesite porphyry, and aplite are mineralized locally (Ross, 1930, 

p. 16). This local mineralized rock is always associated with 

introduced vein quartz or silicification (E.A. Baxter, written 

commun., November 1966, p. 4, USGS files, Spokane Field 

Office). A mineralized breccia zone containing remnants of 

leached chrysocolla in vuggy limonite was reported at depth 

(Anonymous (probably C.P. Heiner), April 18, 1969, USGS 

files, Spokane Field Office).

The ore zones and main workings at the Horseshoe 

mine trend N. 30° W. in marbleized limestone (Ross, 1930, 

p. 16; Nelson and Ross, 1968, p. A27). At least several of the 

ore zones in the Horseshoe are along limestone-intrusive 

rock contacts (G.M. Fowler, written commun., 1926; F.W. 

Anderson, written commun., 1941; both from the Anaconda 

Geological Documents Collection).
MINERAL DEPOSITS OF MACKAY AND COPPER BASIN MINERALIZED AREAS 115

Most ore at the Champion mine is in brecciated and 

sheared limestone, and the ore shoots are generally parallel 

to each other. The main orebody strikes north and dips 

60°-70° W.; it is 1,400 ft long and 15-30 ft wide and extends 

250 ft downdip (T.H. Kiilsgaard, written commun., April 23, 

1952, p. 3, USGS files, Spokane Field Office).

Ore shoots at the Blue Bird mine are small pipes that dip 

steeply to the northeast. Their locations probably are controlled by north-striking fissures (D.C. Gilbert, written commun., 1935, Anaconda Geological Documents Collection).

Mineralogy and texture. The deposits in the outer 

zone were mined primarily for lead and silver; trace to 

byproduct amounts of zinc, copper, and gold contributed to 

their economic value.

The ore minerals are primarily cerussite, argentiferous 

galena, pyrite, chalcopyrite, and sphalerite. Lesser quantities 

of cerargyrite, smithsonite, and oxide minerals of zinc, manganese, and iron are common and are present as disseminations, clots, and lenses. Gangue is not abundant and is mostly 

quartz and lesser calcite, except at the Grand Prize mine 

where siderite dominates the dumps.

Cerussite is the primary ore mined at the Champion, 

Horseshoe, and White Knob mines and probably at the 

Blue Bird as well (Ross, 1930, p. 15; Farwell and Full, 

1944, p. 12; T.H. Kiilsgaard written commun., April 23, 

1952, p. 4, USGS files, Spokane Field Office). At the 

Champion mine it is present with complex secondary lead, 

silver, and zinc minerals, remnant fragments of galena 

(T.H. Kiilsgaard, written commun., April 1952, USGS 

files, Spokane Field Office), and rare chalcopyrite (Farwell 

and Full, 1944, p. 12). At the Horseshoe mine the ore, 

which is principally cerussite, also contains gold, silver, 

and copper. There are also coexisting bodies of sulfides, 

including pyrite, iron-rich sphalerite (marmatite), galena, 

chalcopyrite, (Ross, 1930, p. 15), and pyrrhotite (Farwell 

and Full, 1944, p. 12). At the Blue Bird mine the oxidized 

lead ore had high iron content (D.C. Gilbert, written commun., 1935, Anaconda Geological Documents Collection).

Ore in veins at the Grand Prize mine is argentiferous 

galena in siderite. Coarse-grained siderite is abundant on the 

surface at the mine site. Umpleby (1917, p. 101) described 

the ore as "sand carbonate in limonite gangue," probably 

referring to cerussite as sand carbonate, a popular miner's 

term (T.H. Kiilsgaard, written commun., January 1991).

Geochemical signature. The geochemistry of the 

outer zone is discussed in the section on the inner zone. The 

Copper Basin, Blue Bird, Champion, Horseshoe, and White 

Knob deposits are classified as the outer zone of the copper 

skarn, even though most contain little copper, based on the 

element associations arsenic-cobalt-bismuth and silver-leadzinc. Previous summaries of local ore deposits (Worl and 

Johnson, 1989; Worl and others, 1989) did not include 

detailed geochemistry, statistical analysis of the data, or a 

broader, more regional perspective and therefore classified 

these mines as polymetallic replacement veins. Such deposits

would be expected to have anomalous concentrations of Cu, 

Pb, Ag, Zn, Mn, Au, As, Sb, Bi, and Ba (Morris, 1986, p. 99). 

In rocks of the outer zone most of these elements are present 

but not necessarily in anomalous quantities.

Geophysical signature. Detailed electrical survey 

methods may detect sulfide-bearing veins that are typical of 

outer zone skarn deposits, but no such data are available for 

this area.

Genesis and ore controls. Hydrothermal systems 

active during the late stages of intrusion and dike emplacement probably formed the deposits in this area. These 

replacement deposits in the outer zone tend to follow the 

northeast- and northwest-trending dike swarms or are at their 

intersections peripheral to main skarn bodies.

At the Copper Basin mine, ore deposits in the outer 

skarn zone have a wide variety of controls. The principal 

orebodies are near dikes, in crushed ground at the intersection of almost vertical northeast- and northwest-trending 

fissures (E.R. Zalinsky, written commun., August 1917, 

USGS files, Spokane Field Office; H.H. Doelling and K.C. 

Thompson, written commun., September 1960, USGS 

files, Spokane Field Office). Replacement ore is also bedded in the sedimentary units, generally striking N. 20° E. 

and dipping gently to the southeast (Anonymous (probably 

C.P. Heiner), written commun., April 1969, USGS files, 

Spokane Field Office).

Exploration guides. Much of the lead and zinc production in the Alder Creek district was from relatively small 

replacement veins in limestone. Hidden orebodies of this 

type are difficult to detect; however, deposits similar to those 

at the Empire and Copper Basin mines may exist in the 

Mackay and Copper Basin mineralized areas. Exploration 

efforts should concentrate on the northwest-trending shear 

zones that cross the horst block, particularly at intersections 

with northeast-trending faults. Jasperoid may be an indicator 

of these deposits; it is present near most of the known mines 

in this region.

REFERENCES CITED

Bullock, J.H., Jr., Wilson, A.B., and Soulliere, S.J., 1990, Analytical results and sample locality maps of rock samples from the 

northwestern Idaho Falls and the northeastern Hailey I°x2° 

quadrangles, Idaho: U.S. Geological Survey Open-File Report 

90-645, 20 p.

Cox, D.P., 1986a, Descriptive model of Zn-Pb skarn deposits, in 

Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 90.

 1986b, Descriptive model of Fe skarn deposits, in Cox, 

D.P., and Singer, D.A., eds., Mineral deposit models: U.S. 

Geological Survey Bulletin 1693, p. 94.

Cox, D.P., and Theodore, T.G., 1986, Descriptive model of Cu 

skarn deposits, in Cox, D.P., and Singer, D.A., eds., Mineral 

deposit models: U.S. Geological Survey Bulletin 1693, p. 86.
116 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Dover, J.H., 1981, Geology of the Boulder-Pioneer Wilderness 

Study Area, Blaine and Custer Counties, Idaho, in Mineral 

resources of the Boulder-Pioneer Wilderness Study Area, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 1497-A, p. 15-75.

Doyle, M.A., 1989, Geology, petrology, and geochemistry of the 

Eocene intrusive suite of the Mackay Peak area, south-central 

Idaho, in Winkler, G.R., Soulliere, S.J., Worl, R.G., and 

Johnson, K.M., eds., Geology and mineral deposits of the 

Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. 

Geological Survey Open-File Report 89-639, p. 86-90.

Einaudi, M.T., and Burl, D.M., 1982, Introduction Terminology, 

classification, and composition of skarn deposits: Economic 

Geology, v. 77, p. 745-754.

Farwell, F.W., and Full, R.P., 1944, Geology of the Empire Copper 

Mine near Mackay, Idaho: U.S. Geological Survey Open-File 

Report 370, 22 p.

Kemp, J.F., and Gunther, C.G., 1907, The White Knob copper 

deposits, Mackay, Idaho: Transactions of the American Institute of Mining Engineers, v. 38, p. 269-296.

Kiilsgaard, T.H., Fisher, F.S., and Bennett, E.H., 1986, The transChallis fault system and associated precious metal deposits: 

Economic Geology, v. 81, p. 721-724.

Leland, G.R., 1957, General geology and mineralization of the 

Mackay Stock area: Moscow, University of Idaho, M.S. thesis, 

71 p.

Link, P.K., Skipp, Betty, Hait, M.H., Janecke, Susanne, and Burton, 

B.R., 1988, Structural and stratigraphic transect of south-central Idaho A field guide to the Lost River, White Knob, Pioneer, Boulder, and Smoky Mountains, in Link, P.K., and 

Hackett, W.R., eds., Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 

87-98.

Morris, H.T., Descriptive model of polymetallic replacement 

deposits, in Cox, D.P., and Singer, D.A., eds., 1986, Mineral 

deposit models: U.S. Geological Survey Bulletin 1693, p. 99.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-EE.

Moye, F.J., Hackett, W.R., Blakley, J.D., and Snider, L.G., 1988, 

Regional geologic setting and volcanic stratigraphy of the 

Challis volcanic field, central Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 87-98.

Neely, K.W., and Isaacson, P.E., 1982, Stratigraphy and depositional paleoenvironments of the White Knob Formation (late 

Mississippian), south-central Idaho: Geological Society of 

America Abstracts with Programs, v. 14, no. 6, p. 343.

Nelson, W.H., and Ross, C.P., 1968, Geology of part of the Alder 

Creek mining district, Custer County, Idaho: U.S. Geological 

Survey Bulletin 1252-A, 30 p.

 1969a, Geologic map of the Mackay quadrangle, south-central Idaho: U.S. Geological Survey Miscellaneous Geologic 

Investigations Series Map 1-580, scale 1:125,000.

-1969b, Geology of the Mackay 30-minute quadrangle, Idaho: U.S. Geological Survey Open-File Report 70-242, 161 p. 

Nilsen, T.H., 1977, Paleogeography of Mississippian turbidites in 

south-central Idaho, in Stewart, J.H., Stevens, C.H., and 

Fritsche, A.E., eds., Paleozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 275-299.

Ross, C.P., 1930, Geology and ore deposits of the Seafoam, Alder 

Creek, Little Smoky Creek, and Willow Creek mining districts, 

Custer and Camas Counties, Idaho: Idaho Bureau of Mines and 

Geology Pamphlet 33, p. 7-18.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls 1 °x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Skipp, Betty, 1987, Basement thrust sheets in the Clearwater orogenic zone, central Idaho and western Montana: Geology, v. 

15, p. 220-224.

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River Plain, Idaho: Wyoming 

Geological Association Annual Field Conference, 29th, Guidebook, p. 499-515.

Skipp, Betty, and Harding, S.T., 1985, Preliminary report on geology of Borah Peak area, Idaho, including interpretation of seismic and gravity data, in Stein, R.S., and Bucknam, R.C., eds., 

Proceedings of Workshop 28 on the Borah Peak, Idaho, earthquake: U.S. Geological Survey Open-File Report 85-290-A, 

p. 657-671.

Skipp, Betty, Sando, W.J., and Hall, W.E., 1979, The Mississippian 

and Pennsylvanian (Carboniferous) Systems in the United 

States-Idaho: U.S. Geological Survey Professional Paper 

1110-AA,p.AAl-AA42.

Soulliere, S.J., Wilson, A.B., Moye, F.J., and Rhea, K.P., 1988, 

Analytical results and sample locality map of jasperoid samples from Mackay Idaho: U.S. Geological Survey Open-File 

Report 88-589, 28 p.

Southworth, C.S., 1988, Preliminary lineament map of the Hailey, 

Idaho, and west half of the Idaho Falls, Idaho, I°x2° quadrangles, with inset of regional image mosaic and geologic structures: U.S. Geological Survey Open-File Report 88-640, scale 

1:250,000.

Umpleby, J.B., 1917, Geology and ore deposits of the Mackay 

region, Idaho: U.S. Geological Survey Professional Paper 97, 

scale 1:375,000, 129 p.

Wells, M.W., 1983, Gold camps and silver cities (2nd ed.): Idaho 

Bureau of Mines and Geology Bulletin 22, 165 p.

Wilson, A.B., and Skipp, Betty, 1994, Geologic map of the eastern 

part of the Challis National Forest and vicinity, Idaho: U.S. 

Geological Survey Miscellaneous Investigations Map 1-2395, 

scale 1:250,000.

Wilson, A.B., Soulliere, S.J., Skipp, Betty, Worl, R.G., and Rhea, 

K.P., 1988, Geology and geochemistry of jasperoid near Mackay, Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook 

to the geology of central and southern Idaho: Idaho Geological 

Survey Bulletin 27, p. 183-192.

Worl, R.G., and Johnson, K.M., 1989, Geologic terranes and mineral deposit types in the Hailey and western Idaho Falls 1 °x2° 

quadrangles, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds., Geology and mineral deposits 

of the Hailey and western Idaho Falls 1 °x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, p. 3-16.

Worl, R.G., Wilson, A.B., Smith, C.L., Kleinkopf, M.D., and 

Sykes, R.C., 1989, Mineral resource potential and geology of 

the Challis National Forest, Idaho: U.S. Geological Survey 

Bulletin 1873, 101 p.
Jasperoid-Associated Precious-Metal Deposits 

in the Northwestern Part of the 

Idaho Falls I°x2° Quadrangle, 

South-Central Idaho

By Sandra J. Soulliere, Anna B. Wilson, and Betty Skipp

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-J

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Jl

Introduction........................................................................................................................... 1

Geologic Setting................................................................................................................... 1

Jasperoid............................................................................................................................... 1

Recent Exploration............................................................................................................... 4

References Cited................................................................................................................... 5

FIGURES

1. Map showing location of mines in the study area, northwestern part of the Idaho Falls quadrangle............................ J2

2. Map showing geology of the study area ....................................................................................................................... 3

TABLE

1. Summary of analytical results of samples from jasperoid outcrops in the northwestern part of the

Idaho Falls I°x2° quadrangle........................................................................................................................................ J4
Jasperoid-Associated Precious-Metal Deposits in the 

Northwestern Part of the Idaho Falls I°x2° Quadrangle,

South-Central Idaho

By Sandra J. Soulliere, 1 Anna B. Wilson, 1 and Betty Skipp 1

ABSTRACT

Jasperoid bodies in the northwestern part of the Idaho 

Falls I°x2° quadrangle in south-central Idaho have geologic 

and geochemical characteristics similar to those associated 

with known sedimentary-rock-hosted, disseminated precious-metal deposits elsewhere in the western United States. 

The Jasperoid bodies are mainly replacements of limestone, 

commonly along high-angle fault systems, and many outcrops show evidence of more than one period of brecciation 

and silicification. Geochemical analyses of 117 Jasperoid 

samples show that the suite of elements Ag, Au, As, Hg, Sb, 

and Tl is consistently present, commonly in anomalous 

amounts. The results of the study were used to assess the 

potential for undiscovered precious-metal deposits associated with Jasperoid in this region.

INTRODUCTION

Recent exploration interest in precious-metal deposits 

associated with Jasperoid prompted a reconnaissance study 

of Jasperoid bodies in the northwestern part of the Idaho 

Falls I°x2° quadrangle in south-central Idaho. This study 

was undertaken in order to assess the potential for the occurrence of this type of deposit within the quadrangle (Worl and 

Johnson, 1989). The study area is near the town of Mackay, 

west of U.S. Highway 93 and north of the Pioneer Mountains 

(fig. 1). Jasperoid, as used in this paper, refers to "an epigenetic siliceous replacement of a previously lithified host 

rock" (Lovering, 1972).

Jasperoid bodies in this area have geologic and 

geochemical characteristics similar to Jasperoid associated 

with known sedimentary-rock-hosted, disseminated precious-metal deposits elsewhere in the Western United States 

(Wilson and others, 1988a). No gold deposits of this type 

have been discovered as yet near Mackay; however, claims

'U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

have been staked around most of the Jasperoid outcrops. 

Recent exploration activity has consisted mainly of detailed 

mapping, geochemical sampling, and some local drilling 

near Jasperoid bodies.

Jasperoid bodies were located using recent geologic 

mapping by Skipp (1988, 1989), Skipp and others (1990), 

Skipp and Bollman (1992), earlier mapping by Nelson and 

Ross (1969a, b), and data supplied by Keith Rhea of Ampro 

Resources, Missoula, Montana. One hundred and seventeen 

Jasperoid samples were collected for geochemical and petrographic analyses. The results are briefly summarized here; 

details are given in Soulliere and others (1988), Wilson and 

others (1988a, b), and Soulliere (1992).

GEOLOGIC SETTING

In the northwestern part of the Idaho Falls I°x2° quadrangle, Paleozoic sedimentary rocks were intruded by Tertiary granitic stocks and hypabyssal bodies and covered by 

rocks of the Eocene Challis Volcanic Group (fig. 2). Northeast- and northwest-striking high-angle faults cut all rock 

types in the area. Extensive areas of Jasperoid are along 

these faults.

Paleozoic sedimentary rocks that crop out in the area 

are Early Mississippian to Early Permian in age and consist 

of, in approximate ascending order, the Copper Basin and 

McGowan Creek Formations, White Knob Limestone, and 

Middle Canyon, Scott Peak, South Creek, Surrett Canyon, 

Bluebird Mountain, and Snaky Canyon Formations (fig. 2).

JASPEROID

Jasperoid bodies in the region are principally in Paleozoic limestone near high-angle faults or volcanic rocks; a few 

are in sandstone, mudstone, or conglomerate, or in volcanic 

rocks of the Challis Volcanic Group. Jasperoid outcrops 

range from massive, gray-pink, dense cryptocrystalline

Jl
J2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 1. Map showing location of the study area in the northwestern part of the Idaho Falls I°x2° quadrangle, Idaho. Dashed 

lines outline mining districts: 1, Alder Creek; 2, Copper Basin; 3, 

Lava Creek.

quartz bodies in which original host-rock textures are preserved to very brecciated, quartz-healed, gossan-stained siliceous bodies showing no sign of relict lithology (Wilson and 

others, 1988a). Some variations in grain size and texture are 

evident in thin section. Microtextures range from characteristic jigsaw-puzzle patterns (Levering, 1972) that have 

sutured grain boundaries to granular textures. Petrographic 

analyses reveal a complex history of replacement followed 

by multiple periods of brecciation and cementation, oxidation, and weathering. Quartz and calcite veins are common, 

and veinlets of barite, fluorite, stibiconite, and jarosite are 

present locally.

One hundred and seventeen rock-chip samples were 

collected from jasperoid outcrops and analyzed by atomic 

absorption and inductively coupled plasma emission spectrographic methods. Ag, As, Au, Cu, Hg, Mo, Pb, Sb, and 

Zn were detected in more than 85 percent of the samples 

and Tl in almost half of the samples. A summary of the 

data set is shown in table 1. The highest gold value in this 

reconnaissance sampling was 0.16 ppm, from an outcrop 

sample near Bartlett Point (fig. 1) (Soulliere and others, 

1988). The highest gold values reported from recent drilling in the Bartlett Point area are 0.4 ppm and 0.23 ppm in 

adjacent 5-foot intervals in pervasively silicified limestone 

and 0.3 ppm in partially silicified limestone (Keith Rhea, 

written commun., 1990).

Several theories have been put forth regarding the origin of the jasperoid bodies in the region. Nelson and Ross 

(1968) suggested that some jasperoid formed from fluids 

migrating downward from the Challis Volcanic Group into 

underlying limestone. Skipp suggested that some of the jasperoid may have been formed by meteoric water in karst 

zones, as well as in fault zones (Wilson and others, 1988a). 

Recent geochemical and petrographic studies by us indicate 

that the formation of some of the jasperoid is consistent 

with deposition from hydrothermal fluids (Wilson and 

others, 1988a).

Geochemical analyses of jasperoid show that the suite 

of elements Ag, Au, As, Hg, Sb, and Tl is consistently 

present, commonly in anomalous amounts (Soulliere and 

others, 1988; Wilson and others, 1988a). These elements are 

present in hot-springs-type mineral deposits (Berger and Silberman, 1985), geothermal systems (Silberman and Berger, 

1985), and sedimentary-rock-hosted disseminated preciousmetal deposits (Bagby and Berger, 1985). The presence of 

these elements in jasperoid samples from the Mackay area 

suggests that some, if not most, jasperoid formed by the 

replacement of sedimentary rocks with silica and associated 

elements that were carried in hydrothermal solutions 

(Wilson and others, 1988a).

Moye and others (1989) identified hot-springs deposits 

in volcanic rocks near Bartlett Point and Lehman Butte and 

at the Champagne Creek mine near Timbered Dome (fig. 1). 

Jasperoid bodies in sedimentary rocks at these locations may 

be related to these hot-springs systems. Fluids rising along 

structurally controlled breccia zones formed siliceous sinter 

in the volcanic rocks (Moye and others, 1989) and replaced 

sedimentary rocks with jasperoid at the surface. If the jasperoid was deposited in a shallow hot-springs environment, it is 

likely that fluid movement within the system was episodic.

Figure 2 (facing page). Map showing geology of the study area 

in the northwestern part of the Idaho Falls I°x2° quadrangle, 

Idaho. Modified from Wilson and others (1988a) and Wilson and 

Skipp (1994).
JASPEROID-ASSOCIATED PRECIOUS-METAL DEPOSITS, IDAHO FALLS QUADRANGLE J3

EXPLANATION

Alluvium (Quaternary) 

Basalt (Quaternary) 

Jasperoid

Extrusive rocks (Tertiary) 

Predominantly Eocene 

Challis Volcanic Group

Intrusive rocks (Tertiary)

113°30'

Carbonate rocks (Permian 

to Mississippian) Includes 

Snaky Canyon, Bluebird 

Mountain, Surrett Canyon, 

South Creek, Scott Peak, 

and Middle Canyon Formations, White Knob Limestone, 

and unnamed Permian and 

Devonian carbonate rocks, 

undifferentiated

Flysch (Mississippian) 

Includes Copper Basin 

and McGowan Creek 

Formations, undifferentiated

Contact

Thrust fault Dotted where 

concealed. Sawteeth on 

upper plate

Fault Dotted where 

concealed
J4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 1. Summary of analytical results of samples from jasperoid outcrops in the northwestern part of the

Idaho Falls I°x2° quadrangle, Idaho.

[In parts per million. 117 samples were analyzed for Ag, As, Au, Hg, and Sb; 104 samples were analyzed for Cu, Mo, Pb,

Ag

As

Au

Cu

Hg

Mo

Pb

Sb

Tl

Zn

Bi

Cd

Ga

Pd

Pt

Se

Sn

Te

Minimum 

value detected

0.013

2.17

<0.0005

1.24

0.04

0.34

0.62

<0.25

<0.44

<0.89

<0.22

<0.22

<0.44

<0.09

<0.22

<0.87

<0.44

<0.44

Maximum 

value detected

22.70

2,064

0.16

127.00

20.60

121.00

5,708

470.0

17.70

582.00

18.60

3.68

3.52

0.25

0.50

15.90

4.14

7.70

Mean

0.60

151.1

0.01

11.36

1.33

11.46

74.47

15.86

1.36

32.82

0.54

0.39

0.86

0.11

0.27

1.86

0.67

0.58

Number of samples 

Deviation having detectable values

2.63

255.18

0.02

16.38

2.17

17.74

560.38

45.73

2.22

66.89

1.83

0.43

0.69

0.05

0.08

1.91

0.59

0.72

112

117

106

104

102

104

104

111

64

100

22

32

49

1

9

28

22

7

Modern hot springs associated with mineral deposition tend 

to deposit metallic sulfides in irregular episodic pulses 

(Dickson and Tunnell, 1968). Assuming that ancient hot 

springs acted similarly, this could account for the slight 

regional variations in the concentrations of elements in 

Mackay jasperoids. Distance from the source, pressure-temperature evolution of the fluids, lithology and chemistry of 

the host rocks, and structural setting also effect the geochemical associations in each area.

Oxygen-isotope studies by Snyder and Moye (1989) 

indicate that the hydrothermal alteration in the Lehman 

Basin area is related to large-scale convective movement of 

meteoric waters that were most likely heated by shallow 

intrusions or to high heat flow related to extensional tectonism. Some of the metals may have been remobilized by 

circulating meteoric fluids from Paleozoic sedimentary 

country rocks. Jasperoid bodies that are not proximal to hot 

springs may have formed as a result of mixing of heated and 

cold meteoric fluids. Research by Hofstra and others (1991) 

on the sedimentary-rock-hosted disseminated gold deposit at 

Jerritt Canyon, Nevada, indicates that heated, highly 

evolved meteoric fluids were responsible for mineral deposition. When these fluids reacted with the host rocks, the fluids were cooled, diluted, and oxidized, and gold and other 

metals precipitated. It is possible that some of the jasperoid 

in the study area formed in the same manner as jasperoid at 

Jerritt Canyon. Variation in the concentrations and diversity 

of elements at each geographic location may be the result of 

regional and local variations in temperature, fluid

composition, host-rock composition, extent of fluid mixing, 

and extent of wallrock reaction. Detailed studies of the 

geochemistry, alteration, lithology, structure, and isotopic 

composition of the jasperoid and country rocks are needed to 

determine the origin of each jasperoid body.

RECENT EXPLORATION

Claims have been staked around most of the jasperoid 

outcrops in the Mackay area. Recent exploration activity 

consists mainly of detailed mapping, geochemical sampling, 

and some local drilling near jasperoid bodies. In 1986 and 

1987, Homestake Mining Company collected samples from 

2,695 ft of reverse-circulation drilling in eight holes near jasperoid outcrops at Bartlett Point (Keith Rhea, written commun., 1990).

Ore deposits at the Champagne mine near the jasperoid 

bodies at Timbered Dome are shallow-epithermal or hotsprings deposits in volcanic rocks localized in north-trending 

structures as siliceous veins and breccia zones (Moye and 

others, 1989). In 1988, Bema Gold Corporation of Canada 

began a pilot heap-leach test at the Champagne Creek mine 

and reported that an oxide orebody containing 2.4 million 

tons of minable reserves at 0.038 of gold per short ton equivalent had been defined. Production of gold and silver at the 

mine began in June 1989, and further exploration is continuing (Engineering and Mining Journal, 1989).
JASPEROID-ASSOCIATED PRECIOUS-METAL DEPOSITS, IDAHO FALLS QUADRANGLE J5

A heap-leach operation has been set up (as of 1989) 

about 5 mi southwest of the Champagne Creek mine along 

Dry Fork Creek. Jasperoid may be present at the site but 

could not be verified because permission to examine the 

property was denied.

REFERENCES CITED

Bagby, W.C., and Berger, B.R., 1985, Geologic characteristics of 

sediment-hosted, disseminated precious-metal deposits in the 

Western United States, in Berger, B.R., and Bethke, P.M., eds., 

Geology and geochemistry of epithermal systems: Society of 

Economic Geologists Reviews in Economic Geology, v. 2, p. 

169-202.

Berger, B.R., and Silberman, M.L., 1985, Relationships of traceelement patterns to geology in hot-spring-type precious-metal 

deposits, in Berger, B.R., and Bethke, P.M., eds., Geology and 

geochemistry of epithermal systems: Society of Economic 

Geologists Reviews in Economic Geology, v. 2, p. 233-247.

Dickson, F.W., and Tunnell, G., 1968, Mercury and antimony 

deposits associated with active hot springs in the western United States, in Ridge, J.D., ed., Ore deposits of the United States, 

1933-1967 (Graton-Sales volume): American Institute of Mining, Metallurgical, and Petroleum Engineers, p. 1673-1701.

Engineering and Mining Journal, 1989, A toast to the Champagne 

mine: Volume 190, no. 8, p. 15.

Hofstra, A.H., Leventhal, J.S., Northrup, H.R., Landis, G.P., Rye, 

R.O., Birak, D.J., and Dahl, A.R., 1991, Genesis of sedimenthosted disseminated-gold deposits by fluid mixing and sulfidization Chemical-reaction-path modeling of ore-depositional processes documented in the Jerritt Canyon district. 

Nevada: Geology, v. 19, p. 36^t-0.

Lovering, T.G., 1972, Jasperoid in the United States Its characteristics, origin, and economic significance: U.S. Geological Survey Professional Paper 710, 164 p.

Moye, F.J., Sanford, R.F., Erdman, J.A., and Johnson, K.M., 1989, 

Volcanic-hosted and intrusion-related mineral deposits in the 

Hailey and western Idaho Falls quadrangles, Idaho, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds.. 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 70-71.

Nelson, W.H., and Ross, C.P., 1968, Geology of part of the Alder 

Creek mining district, Custer County, Idaho: U.S. Geological 

Survey Bulletin 1252-A, 130 p.

 1969a, Geology of the Mackay 30-minute quadrangle, 

Idaho: U.S. Geological Survey Open-File Report 70-242, 

161 p. 

-1969b, Geologic map of the Mackay quadrangle south-central Idaho: U.S. Geological Survey Miscellaneous Geologic 

Investigations Series Map 1-580, scale 1:125,000. 

Silberman, M.L., and Berger, B.R., 1985, Relationship of trace-element patterns to alteration and morphology in epithermal

precious-metal deposits, in Berger, B.R., and Bethke, P.M., 

eds.. Geology and geochemistry of epithermal systems: Society of Economic Geologists Reviews in Economic Geology, v. 

2, p. 203-232.

Skipp, Betty, 1988, Geologic map of Mackay 4 (Grouse) NE quadrangle, Butte and Custer Counties, Idaho: U.S. Geological Survey Open-File Report 88-423, scale 1:24,000.

 1989, Geologic map of Mackay 4 (Grouse) NW quadrangle, 

Butte and Custer Counties, Idaho: U.S. Geological Survey 

Open-File Report 89-142, scale 1:24,000.

Skipp, Betty, and Bollmann, D.D., 1992, Geologic map of Blizzard 

Mountain North quadrangle, Blaine and Butte Counties, Idaho: 

U.S. Geological Survey Open-File Report 92-280, scale 

1:24,000.

Skipp, Betty, Kuntz, M.A., and Morgan, L.A., 1990, Geologic map 

of Mackay 4 (Grouse) SE quadrangle, Butte Custer County, 

Idaho: U.S. Geological Survey Open-File Report 89-431, scale 

1:24,000.

Snyder, L.G., and Moye, F.J., 1989, Regional stratigraphy, physical 

volcanology, and geochemistry of the southeastern Challis volcanic field, in Winkler, G.R., Soulliere, S.J., Worl, R.G., and 

Johnson, K.M., eds., Geology and mineral deposits of the 

Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. 

Geological Survey Open-File Report 89-639, p. 122-127.

Soulliere, S.J., 1992, Geochemistry and description of Jasperoid 

near Grouse, south-central Idaho: Golden, Colorado School of 

Mines, M.S. thesis, 103 p.

Soulliere, S.J., Wilson, A.B., Moye, F.J., and Rhea, K.P., 1988, 

Analytical results and sample locality map of Jasperoid samples from Mackay, Idaho: U.S. Geological Survey Open-File 

Report 88-589, 28 p.

Wilson, A.B., and Skipp, Betty, 1994, Geologic map of the eastern 

part of the Challis National Forest, Idaho: U.S. Geological Survey Miscellaneous Investigations Series Map 1-2395, scale 

1:250,000.

Wilson, A.B., Soulliere, S.J., Skipp, Betty, Worl, R.G., and Rhea, 

K.P., 1988a, Geology and geochemistry of Jasperoid near 

Mackay, Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 183-192.

 1988b, Geology and geochemistry of Jasperoid from Mackay, Idaho: Geological Society of America Abstracts with Programs, v. 20, no. 6, p. 474.

Worl, R.G., and Johnson, K.M., 1989, Geologic terranes and mineral deposit types in the Hailey and western Idaho Falls 1 °x2° 

quadrangles, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds., Geology and mineral deposits 

of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, p. 

3-16.

Tertiary Sedimentary Rocks of the Payette Formation 

(Miocene) and the Lower Part (Miocene and Pliocene) 

of the Idaho Group, Hailey I°x2° Quadrangle and 

Vicinity, West-Central Idaho

By Anthony B. Gibbons

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-K

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Kl

Introduction........................................................................................................................... 1

Geology of the Payette Formation and Idaho Group............................................................ 1

Petrology of the Payette Formation...................................................................................... 3

Petrography................................................................................................................... 3

Chemistry...................................................................................................................... 4

Placer Gold................................................................................................................... 6

Potential for Gold Resources of the Payette Formation and Idaho Group........................... 8

Suggestions for Further Study.............................................................................................. 8

References Cited................................................................................................................... 9

FIGURES

1. Map showing sample localities, Hailey quadrangle and vicinity................................................................................... K2

2. Generalized stratigraphic sections on the south and west sides of the Idaho batholith................................................. 4

TABLES

1. Sample information for study......................................................................................................................................... K3

2. Approximate abundance of mineral species in density fractions of nonmagnetic sand-size material from 

samples of the Payette Formation and from representative stream sediment derived from a granitic area, 

Hailey I°x2° quadrangle and vicinity............................................................................................................................ 5

3. Results of instrumental neutron activation analysis of coal from the Payette Formation, Hailey I°x2°

quadrangle and vicinity.................................................................................................................................................. 6

4. Results of semiquantitative emission spectrographic analysis of heavy-mineral concentrates of sandstones

of the Payette Formation and of modern stream sediment, Hailey I°x2° quadrangle and vicinity............................... 7

5. Results of inductively coupled plasma-atomic emission spectrographic analysis of sandstones of the

Payette Formation and modern stream sediment, Hailey I°x2° quadrangle and vicinity............................................. 8
Tertiary Sedimentary Rocks of the Payette Formation

(Miocene) and the Lower Part (Miocene and Pliocene) of the

Idaho Group, Hailey I°x2° Quadrangle and Vicinity,

West-Central Idaho

By Anthony B. Gibbons 1

ABSTRACT

Tertiary sedimentary rocks of the Hailey I°x2° quadrangle and vicinity (west-central Idaho) consist of several 

thousands of feet of continental strata belonging to the Payette Formation (Miocene) and the lower part (Miocene and 

Pliocene) of the Idaho Group (Miocene to Pleistocene). Both 

the Payette Formation and the Idaho Group include conglomerate, sandstone, shale, and diatomite and are generally 

unmineralized; in addition, the Payette contains low-grade 

coal. A very few hydrothermal mineral deposits are present 

in rocks of the Payette Formation, and apparently at least one 

deposit is in sedimentary rocks of the Idaho Group.

Sandstone of the Payette Formation is highly arkosic 

and has heavy-mineral suites consistent with derivation from 

granitic rocks of the Idaho batholith. Three of eight panned 

concentrates of Payette sandstone analyzed contained 

unusual amounts of gold. The possibility of a paleoplacer 

gold resource in sandstone of the Payette Formation or in 

similar sandstone of the Idaho Group should be investigated 

by further sampling and chemical analysis.

(Miocene-Pleistocene) in the southwestern part of the quadrangle (Worl and others, 1991). Of the two units, the Payette is of more interest with respect to mineral resources 

because it is present in the mineralized part of the Hailey 

I°x2° quadrangle and directly overlies mineralized terranes 

(mainly gold mineralized) of the Idaho batholith. For this 

reason, a reconnaissance field study was made of the Payette Formation during three weeks in the summer of 1988 

to supplement information from published sources. Published information on the chemistry of the Payette Formation is almost nonexistent, and therefore a main emphasis 

of the field study was sampling of the Payette at widely 

separated points both within and outside the Hailey I°x2° 

quadrangle area (fig. 1, table 1) for chemical analysis, particularly for gold.

Acknowledgments. Thanks are due to C.L. Smith, 

W.H. Raymond, T.H. Kiilsgaard, R.W. Leinz, S.K. McDanal, and G.A. Desborough for making their expertise available to the author at various stages of this study and to O.K. 

Allerton and D.E. Wilson for preparation of heavy-mineral 

concentrates of rock and sediment samples.

INTRODUCTION

Tertiary sedimentary rocks in the Hailey I°x2° quadrangle of west-central Idaho crop out in only small areas and 

are not known to contain significant mineral deposits. Information on these rocks, mostly from the literature, was compiled as part of the Hailey I°x2° U.S. Geological Survey 

Conterminous United States Mineral Assessment Program 

(CUSMAP), mainly to insure that the possibility of undiscovered mineral resources in them was considered.

Tertiary sedimentary rocks in the Hailey I°x2° quadrangle consist of the Payette Formation (Miocene) in the 

northwestern part of the quadrangle and the Idaho Group

'U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

GEOLOGY OF THE PAYETTE 

FORMATION AND IDAHO GROUP

The study area is in west-central Idaho on the north side 

of the Snake River Plain and on the east side of the Columbia 

Plateau (fig. 1). The area of the Hailey quadrangle itself is 

largely mountainous country, much of it underlain by granitic rocks of the Idaho batholith.

Tertiary sedimentary rocks, generally interbedded with 

flows of basalt, crop out locally on the south and west sides 

of the Idaho batholith. Similar rocks may also be present in 

the subsurface in that part of Hailey I°x2° quadrangle that is 

in the Snake River Plain (fig. 1). To the west, major areas of 

Tertiary crop out well beyond the quadrangle border, but 

small areas of Tertiary rock are present within the quadrangle near Idaho City and Atlanta. Tertiary sedimentary rocks

Kl
K2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

117° 116° 115°

Middle Fork 

Payette River

V£ COLUMBIA 

/^ PLATEAU 

jgPayette

XBOUNDARY OF HAILEY 

1°x 2° QUADRANGLE

^-~O BLACK , 

Emmett CANYON 

DAM

Sun

Valley

Ketchum

Comas Creek 

MOUNT BENNETT HILLS

43° -

EXPLANATION

^ ^ ^ Generalized boundary of Idaho batholith 

Flat side of line toward batholith

G88-1 x Sample locality and number

^ Inactive mine in rocks of Payette or younger age

Figure 1. Map showing sample localities, Hailey I°x2° quadrangle and vicinity, Idaho. Sample information is given in table 1. TransChallis mineralized area is from Kiilsgaard and others (1989).

of the study area belong to the mid-Miocene Payette Formation and to the lower part (Miocene and Pliocene) of the 

Idaho Group of Miocene to Pleistocene age (fig. 2).

Tertiary sedimentary rocks belonging to the lower part 

of the Idaho Group crop out on the south side of the Mount 

Bennett Hills in the southwestern part of Hailey quadrangle. 

These rocks comprise several hundred feet of mostly brownish sandstone and pebble gravel in lenticular channel deposits and light-colored silt, clay, and diatomite in lake deposits 

(Malde and others, 1963). They form a generally medial unit 

in the Banbury Formation (fig. 2), which consists mostly of 

basalt. Southward into the Snake River Plain, the Tertiary 

rocks, including the Banbury Formation sedimentary strata, 

dip beneath Quaternary deposits associated with later stages 

of the filling of the Snake River downwarp.

To the west of the Hailey I°x2° quadrangle, sedimentary rocks of the Idaho Group form a sequence at least 1,800 

ft thick (Kirkham, 1931) that rests with angular unconformity on a Miocene section that includes sedimentary rocks 

of the Payette Formation. The Payette, at least 1,180 ft thick, 

consists of sedimentary strata contemporaneous, and commonly interbedded, with the lavas of the Columbia River 

Basalt Group.

In general, the Payette Formation is lithologically 

similar to the sedimentary rocks of the Idaho Group as 

described above. Outcrops of Payette Formation along the 

Middle Fork of the Payette River near Crouch (fig. 1) include 

arkosic sandstone, conglomerate, thin-bedded dark-gray to 

black shale, diatomite, and tuff (Fisher and others, 1983). 

Thin, lenticular beds of carbonaceous shale and low-rank
TERTIARY SEDIMENTARY ROCKS, PAYETTE FORMATION AND IDAHO GROUP K3

Table 1. Sample information for the study. 

[Sample localities are shown in figure 1]

Locality 

no.

G88-1

G88-2

G88-3

G88-4

G88-5

G88-6

G88-7

G88-8

G88-9

G88-10

Latitude 

(north)

44°23'51"

43°55' 49"

43°52'46"

43°54'42"

43°58'22"

43°49'05"

44°09'04"

44° 11 '39"

44°13'02"

44°16'03"

Longitude 

(west)

116°35'33"

116°26'35"

115°23'00"

115 024'41"

115°33'36"

115°48'32"

115°57'52"

115°56'20"

115°55'50"

115°52'44"

Topographic quadrangle 

(scale 1:24,000)

Hog Creek Butte, 1986

Northeast Emmett, 1985

Bear River, 1972

Bear River, 1972

Big Owl Creek, 1972

Idaho City, 1976

Pyle Creek, 1988

Pyle Creek, 1988

Pyle Creek, 1988

Sixmile Point, 1988

Lithology 

sampled

Sandstone

Sandstone

Sandstone

Gravelly sand

Gravelly sand

Sandstone

Sandstone

Coal, sandstone

Sandstone

Gravelly sand

Formation 

sampled

Payette Formation

Payette Formation

Payette Formation

Stream sediment

Stream sediment

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Stream sediment

Stratigraphic 

assignment

Fitzgerald (1982)

Fitzgerald (1982)

Kiilsgaard1

Lindgren(1898)

Fisher and others (1983)

Fisher and others (1983)

Fisher and others (1983)

^.S. Geological Survey, oral commun., March 2,1988.

coal are also present; these are characteristic of the Payette 

Formation but not of younger sedimentary sequences, and 

thus the coaly layers constitute a lithologic marker for the 

Payette. Moreover, because such layers commonly contain 

well-preserved plant fossils, they help to date the Payette 

Formation, as well as the time-equivalent Columbia River 

Basalt Group (Knowlton, 1898; Lindgren, 1898; Smiley and 

others, 1975).

Despite their lithologic similarities, the Payette Formation and the Idaho Group probably represent different environments of deposition. According to Kirkham (1931), the 

Payette was deposited in a series of separate north-trending 

intramontane basins prior to development of the east-trending Snake River downwarp, whereas the Idaho Group represents deposition in one or more large lakes that formed in the 

downwarp concurrently with its development. Malde and 

Powers (1962), Kimmel (1982), and Swirydczuk and others 

(1982) related the stratigraphy of the Idaho Group to stages 

in the development of the Snake River downwarp.

Prior to and contemporaneous with downwarping of the 

Snake River Plain, high-angle faulting along north-south and 

northwest lines occurred in the tectonically positive area to 

the north (Malde and Powers, 1962). The faults, which have 

displacements of as much as several thousand feet, mostly 

determine the present outcrop pattern of the Tertiary rocks. 

Sizable outliers of Payette Formation in generally granitic 

terranes at Crouch and Idaho City (fig. 1) are preserved on 

blocks dropped down along late Cenozoic faults (Jones, 

1917; Fisher and others, 1983).

Late Cenozoic faulting is commonly associated with 

hot-springs activity but not with hydrothermal mineralization, and the Payette Formation and Idaho Group are, with 

only a few local exceptions, unmineralized. Mercury deposits on an economic scale are present in the Payette Formation 

east of Weiser (fig. 1). Ross (1956) reported that between 

1939 and 1942 deposits in this area produced almost 4,000 

flasks of quicksilver from almost 53,000 tons of ore. About 

10 mi north of Weiser, the Monroe Creek (Weiser) gold district consists of subeconomic occurrences of gold and

mercury in and adjacent to small mafic bodies intrusive into 

Tertiary sedimentary rock (Varley and others, 1919; Ross, 

1956). Available geologic mapping (Fitzgerald, 1982), suggests that rocks of both the Payette Formation and Idaho 

Group are mineralized.

Other commodities in the Tertiary sedimentary rocks of 

southwestern Idaho include diatomite deposits in both the 

Payette Formation and the Idaho Group (Powers, 1947).

PETROLOGY OF THE 

PAYETTE FORMATION

PETROGRAPHY

Estimated abundances of mineral species in bulk 

(unpanned) material for 10 disaggregated Payette rock samples and 1 stream-sediment sample are given in table 2. The 

grain-size fraction 35-170 mesh (0.5-0.088 mm), representing medium to very fine sand, of these samples was studied 

in a medium of refractive index n= 1.5402, which facilitates 

recognition of alkali feldspar grains. Prior to study, successive heavy-liquid separations were made in bromoform (specific gravity about 2.85) and methylene iodide (specific 

gravity about 3.32), and strongly magnetic grains were 

removed using a hand magnet. The resulting nonmagnetic 

grain-density fractions less than 2.85, between 2.85 and 

3.32, and greater than 3.32 were examined separately. 

Mineral species abundances in each density fraction (table 2) 

were assigned according to the following scale.

Numerical 

designation

1

2

3

4

5

Semiquantitative 

characterization

Rare

Not common

Common

Abundant

Dominant

Approximate 

grain percent

<1

2-5

5-19

20^9

>50
K4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

West side of 

Idaho batholith

South side of 

Idaho batholith

QUATERNARY

TERTIARY

Holocene Snake River 

Group

Pleistocene

Pliocene

Idaho 

Group

Black Mesa Gravel

Bruneau Formation

Tuana Gravel

Glenns Ferry Formation

Chalk Hills Formation

Banbury Formation

Poison Creek Formation

Idavada Volcanics

Miocene Columbia River 

Basalt Group

Payette 

Formation

Oligocene

Eocene

Paleocene

Challis Volcanic Group

CRETACEOUS

Granite of the 

Idaho batholith

Granite of the 

Idaho batholith

Figure 2. Generalized stratigraphy on the south and west sides of the Idaho batholith, Idaho. Subdivision of Idaho Group is from Malde 

and Powers (1962) and Malde and others (1963).

In the light-mineral fraction, the most striking feature is 

the great abundance of feldspar, particularly plagioclase, in 

the sandstone and sand samples (table 2). A petrographic 

study of the Payette Formation in the Weiser area (Nakai, 

1979) indicates only a small proportion of feldspar in the 

sandstone. In material examined for the present study, most 

of the plagioclase is probably in the calcic oligoclase range. 

Alkali feldspar has large 2V and is mostly without grid twinning. Both plagioclase and alkali feldspar show much sericitic alteration in most samples.

In the moderately heavy mineral fraction, biotite is 

generally the most abundant mineral, then muscovite (table 

2). Hornblende, of the common green variety, is negligible 

in most samples, but it is abundant or even dominant in 

some samples.

In the heaviest mineral fraction, opaque grains are very 

abundant, and garnet and epidote a grain category here 

including some zoisite and clinozoisite are abundant 

among the translucent, nonaggregate grains (table 2).

Aside from the great abundance of feldspar noted 

above, sand from the Payette Formation is characterized by 

angular to subangular grain shapes and, on average, a large 

proportion of heavy-mineral grains, about 0.6 weight percent 

of total rock. Recognizable volcanic constituents included 

only a few grains of probable augite and one grain of basaltic 

hornblende, a remarkably small amount considering the 

close association in space and time between the Payette Formation and the Columbia River Basalt Group. Basalt flows 

form part of the areal stratal succession at localities G88-1, 

G88-2, and G88-6 (fig. 1).

CHEMISTRY

Chemical analysis was carried out on all 10 samples 8 

sandstone and 2 coal from the Payette Formation and on 3 

samples of modern stream-sediment alluvium from the area 

in which the Payette is present. Panning, followed by heavyliquid and magnetic separation, was used on a portion of the
Table 2. Approximate abundance of mineral species in density fractions of nonmagnetic sand-size material from samples of the Payette Formation and f

sediment derived from a granitic area, Hailey I°x2° quadrangle and vicinity, Idaho.

[Sample information is given in table 1. Approximate mineral abundance: 1, rare; 2, not common; 3, common; 4, abundant; 5, dominant; see text for discussion]

Light mineral grains; density less than 2.85

Field no.

G88-1-1

G88-2-1

G88-3-1

G88-3-2

G88-6-1

G88-7-1

G88-8-3

G88-9-1

G88-8-1

G88-8-2

G88-10-1

Sedimentary unit

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Stream sediment

Lithology

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Coal

Coal

Sand

Quartz

4

3

4

3

4

4

4

4

3

3

4

Alkali

Plagioclase feldspar

3 2

4 4

4 3

4 4

4 4

4 2

4 3

3 3

3 2

3 2

4 3

Biotite

3

2

2

3

2

4

4

3

3

2

2

Moderately heavy mineral grains;

Field no.

G88-1-1

G88-2-1

G88-3-1

G88-3-2

G88-6-1

G88-7-1

G88-8-3

G88-9-1

G88-8-1

G88-8-2

G88-10-1

Sedimentary unit

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Stream sediment

Lithology

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Coal

Coal

Sand

Biotite

4

5

5

4

5

4

5

4

2

2

4

MuscoviteHornblende

1 5

3

4

4 2

3

2 4

4

4

5

5

4

Quartz

2

2

3

2

3

Muscovite Opaques

3

3

2

3

2

3

3

3 3

3 4

2

2

Aggregates

4

3

2

2

4

2

3

2

3

5

2

Gypsum

3

Other

2

2

1

2

1

2

density between 2.85 and 3.32

Alkali

Plagioclase feldspar

2 2

2 2

3 2

Apatite

2

2

Opaques

4

4

2

Aggregates

3

2

3

3

2

Other

2

2

2

2

2

2

1

2

2

3

Heaviest mineral grains; density greater than 3.32

Field no.

G88-1-1

G88-2-1

G88-3-1

G88-3-2

G88-6-1

G88-7-1

G88-8-3

G88-9-1

G88-8-1

G88-8-2

G88-10-1

Sedimentary unit

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Payette Formation

Stream sediment

Lithology

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Sandstone

Coal

Coal

Sand

Opaques,

black

4

3

5

4

4

3

5

4

4

3

Opaques,

nonblack Aggregates

3

4

4

4

4

4

2

4

4

Garnet

3

3

2

3

3

3

3

3

4

Pale

isotropics Zircon

2

2 2

2 1

4

2

4 2

5

3

2

Sphene

3

3

3

3

3

2

3

2

2

Epidote

4

4

4

4

4

2

4

Biotite

1

3

1

1

2

Chlorite 

1 

2

4
K6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 3. Results of instrumental neutron activation analysis of 

coal from the Payette Formation, Hailey I°x2° quadrangle, and 

vicinity, Idaho.

[Analyst: J.S. Mee. In parts per million unless otherwise indicated. 

Error limits (in percent) are one standard deviation based on counting 

statistics alone. Sample information is given in table 1]

Laboratory number 

Field number

Na (percent) 

K (percent) 

Fe (percent) 

Sc

Cr

Co

Ni

Zn

As

Se

Br

Rb

Sr

Sb

Cs

Ba

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

Hf

Ta

W

Au

Th

U

D-323476 

G88-8-1

0.488±3 

1.07±8 

1.34±3 

9.07±2

22.1+6

13.3±3

<40

58±23

4.1±8

<2

3.1±12

<140

370±11

2.14±5

3.63±4

<500

39.4+3

53.7±3

<60

4.94±3

1.22+4

0.620±5

2.96±5

0.37±36

4.65+4

2.54±5

<1

<0.019

13.6±3

6.9±9

D-323477 

G88-8-2

0.140±3 

0.189+14 

0.736±3 

7.32+3

5.6±15

14.8±3

<40

57±6

3.44±8

<2

4.2±8

<80

390+13

1.65+5

0.62±11

700±18

18.1±4

28.8±6

<50

2.70±3

0.68±5

0.387±6

1.98±6

0.33±27

2.78+4

0.54±7

<2

<0.012

4.36+4

7.1±9

sandstone and alluvium samples to provide nonmagnetic 

heavy-mineral concentrates for analysis. (These panned concentrates were not duplicates of any of the grain-density 

fractions of unpanned material prepared for petrographic 

study.) All of the concentrates were analyzed for 37 elements 

by direct current-arc emission spectrography (Myers and 

others, 1961; Grimes and Marranzino, 1968). Four bulk 

sandstone and alluvium samples whose concentrates had 

high values for gold were analyzed for 10 elements by inductively coupled plasma-atomic emission spectrometry 

(ICP-AES) following acid digestion and solvent extraction 

(Motooka, 1988). All of the concentrates, as well as the four 

bulk samples selected for ICP-AES analysis, were also analyzed for gold by flameless atomic absorption spectrophotometry (Meier, 1980). The two coals were analyzed for 30 

elements by instrumental neutron activation analysis 

(INAA) (Baedecker and McKown, 1987).

The chemical data are presented in tables 3,4, and 5. In 

the discussion that follows, the significance of the analytical 

values for the bulk sandstone and alluvium samples and the 

coal samples is evaluated mainly by comparing these values 

with published values for average abundances of the 

elements (Mason, 1958;HawkesandWebb, 1962;Levinson, 

1974). The significance of the data for the concentrates can 

be similarly evaluated if one considers that concentrations for 

some elements may be enhanced by as much as three orders 

of magnitude relative to bulk sample data.

If viewed as the product of a granitic source area, the 

Payette Formation has few apparent chemical peculiarities. 

The two samples of Payette coal (table 3) are substantially 

enriched in arsenic and antimony with respect to crustal 

abundances, though not with respect to average shale, and 

are moderately enriched in uranium with respect to both 

standards. As a class, the sandstone samples from the Payette 

(tables 4, 5) are not enriched in any of the chalcophile elements. An exception is arsenic in samples G88-2-1 and 

G88-6-1 (table 5), which is at levels moderately above 

crustal abundance. With reference to the crustal standard, the 

Payette sandstones as a group are enriched to some degree in 

manganese, barium, and niobium, in the rare earth elements 

lanthanum and scandium, and, most significantly, in gold.

PLACER GOLD

The analyses obtained for the present study indicate that 

there is gold in the Payette Formation but do not indicate 

how much. Unusually large amounts of gold in the panned 

concentrates of three of the eight samples of Payette sandstone were indicated by flameless atomic absorption analysis 

(table 4, second column of gold values); however, bulk 

material from the same samples (table 5) showed no gold, 

either by flameless atomic absorption analysis or by solvent 

extraction ICP-AES. Taken together, the high gold values 

for concentrates and the low gold values for bulk material 

suggest that gold is present in rare particles separated by 

large volumes of barren material. Because this kind of distribution produces mostly nonrepresentative individual samples (Clifton and others, 1969), gold values obtained for the 

present study do not give a good idea of the overall gold content of even the Payette sandstone beds that were sampled.

The exact form in which gold is present in the Payette 

sandstones is not known. It probably is fairly coarse, as suggested by its ability to impart high gold values to the particular samples or sample splits in which it is present. It must 

also be dense because it can be concentrated by panning. No 

free gold was identified in any of the samples at any stage of 

processing. Lack of chemical or other evidence for hydrothermal mineralization in the sampled parts of the Payette 

implies that the gold values represent placer deposition.
TERTIARY SEDIMENTARY ROCKS, PAYETTE FORMATION AND IDAHO GROUP K7

Table 4. Results of semiquantitative emission spectrographic analysis of heavy-mineral concentrates of sandstones of the Payette 

Formation and of modern stream sediments, Hailey I°x2° quadrangle and vicinity, Idaho.

[Sample location information in table 1. In parts per million unless otherwise indicated. Six-step semiquantitative spectrographic analysis by D.E. 

Detra and M. Malcolm. Results are reported to the nearest number in the series 1,0.7, 0.5, 0.3, 0.2, 0.15, 0.1, and so on, which represent approximate 

midpoints of grouped data on a geometric scale. N indicates not detected at limit of detection or at value shown; < indicates detected but below limit of 

determination or below value shown. Second value reported for gold is by flameless atomic absorption; analysts, R.M. O'Leary and P. Roushey. 

Asterisk (*) is before field number of stream-sediment sample]

Lab no. Field no.

D-323478 G88-1-1

D-323479 G88-2-1

D-323480 G88-3-1

D-323481 G88-3-2

D-323484 G88-6-1

D-323485 G88-7-1

D-323486 G88-8-3

D-323487 G88-9-1

D-323482 *G88-4-l

D-323483 *G88-5-l

D-323488 *G88-10-1

Lab no. Field no.

D-323478 G88-1-1

D-323479 G88-2-1

D-323480 G88-3-1

D-323481 G88-3-2

D-323484 G88-6-1

D-323485 G88-7-1

D-323486 G88-8-3

D-323487 G88-9-1

D-323482 *G88^-1

D-323483 *G88-5-l

D-323488 *G88-10-1

Lab no. Field no.

D-323478 G88-1-1

D-323479 G88-2-1

D-323480 G88-3-1

D-323481 G88-3-2

D-323484 G88-6-1

D-323485 G88-7-1

D-323486 G88-8-3

D-323487 G88-9-1

D-323482 *G88-4-l

D-323483 *G88-5-l

D-323488 *G88-10-1

Lab no. Field no.

D-323478 G88-1-1

D-323479 G88-2-1

D-323480 G88-3-1

D-323481 G88-3-2

D-323484 G88-6-1

D-323485 G88-7-1

D-323486 G88-8-3

D-323487 G88-9-1

D-323482 *G88-4-l

D-323483 *G88-5-l

D-323488 *G88-10-1

Ca(%)

7

10

1.5

5

0.2

20

1.5

0.5

20

20

15

B

30

N20

<20

<20

N20

N20

N20

N20

N20

N20

N20

La

1,500

1,500

>2,000

>2,000

>2,000

500

>2,000

>2,000

2,000

1,500

>2,000

Th

200

200

3,000

3,000

3,000

N200

700

1,000

700

500

>5,000

Fe(%)

1

1

5

5

2

0.5

2

5

1.5

0.7

2

Ba

300

200

500

500

1,000

70

1,500

>10,000

300

150

300

Mn

1,000

2,000

7,000

7,000

5,000

1,000

5,000

5,000

2,000

1,500

7,000

V

500

700

300

300

150

300

150

150

150

150

70

Mg(%)

0.2

<0.05

0.2

0.3

0.2

0.07

0.15

0.15

0.3

0.3

0.5

Be

N2

N2

3

5

N2

N2

3

3

2

3

N2

Mo

<10

20

N10

<10

N10

<10

N10

15

<10

N10

N10

W

N50

N50

N50

N50

N50

N50

N50

N50

200

100

N50

Na(%)

<0.5

<0.5

0.5

0.5

<0.5

<0.5

<0.5

0.5

0.5

<0.5

0.5

Bi

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

Nb

100

500

1,500

1,500

200

200

300

500

700

500

300

Y

500

700

1,500

1,500

1,000

500

700

700

1,000

700

3,000

P(%)

2

3

2

3

1.5

10

7

1.5

7

10

10

Cd

N50

N50

N50

N50

N50

N50

N50

N50

N50

N50

N50

Ni

N10

<10

<10

<10

10

<10

N10

N10

<10

<10

<10

Zn

N500

N500

N500

N500

N500

N500

N500

N500

N500

N500

N500

Ti(%)

>2

>2

>2

>2

>2

>2

>2

>2

>2

>2

2

Co

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

Pb

<20

20

150

100

30

N20

100

100

15,000

1,000

100

Zr

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

>2,000

Ag

Nl

20

Nl

Nl

Nl

Nl

Nl

Nl

Nl

Nl

70

Cr

150

150

100

70

1,500

30

<20

<20

100

200

70

Sb

N200

N200

N200

N200

N200

N200

N200

N200

1,000

N200

N200

Pd

N5

N5

N5

N5

N5

N5

N5

N5

N5

N5

N5

As

N500

N500

N500

N500

N500

N500

N500

N500

N500

N500

N500

Cu

<10

<10

<10

10

<10

<10

<10

70

100

<10

<10

Sc

70

70

' 200

200

150

20

150

150

100

70

200

Pt

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

Au

N20

300

N20

N20

N20

N20

N20

N20

N20

N20

1,000

Ga

20

<10

30

30

<10

N10

10

15

10

<10

20

Sn

100

100

1,000

70

30

100

20

1,500

700

70

N20

Au

351

135

N1.66

N1.176

264

N0.005

NO. 161

N0.869

NO. 104

72.6

0.869

Ge

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

N20

Sr

200

200

700

1,000

N200

200

200

300

500

300

300
K8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 5. Results of inductively coupled plasma-atomic emission spectrographic (ICP-AES) analysis of sandstones of the Payette 

Formation and modern stream sediments, Hailey I°x2° quadrangle, and vicinity, Idaho.

[Sample location information in table 2. In parts per million. Samples analyzed by inductively coupled plasma-atomic emission spectrography using 

diisobutyl ketone extraction by P.H. Briggs and J.M. Motooka. N indicates not detected at limit of detection or at value shown. Second value shown 

for gold is by flameless atomic absorption (analysts, R.M. O'Leary and P. Roushey). Asterisk (*) is before field number of stream-sediment sample]

Lab no. Field no.

D-341248 G88-1-1 

D-341249 G88-2-1 

D-341250 G88-6-1 

D-341251 *G88-10-1

Ag

0.075 

0.045 

0.057 

N0.045

As

N0.60 

9.3 

10 

N0.60

Au

NO. 15 

NO. 15 

NO. 15 

NO. 15

Au

N0.002 

N0.002 

N0.002 

N0.002

Bi

N0.60 

N0.60 

N0.60 

N0.60

Cd

0.030 

N0.030 

N0.030 

N0.030

Cu

4.5 

1.0 

4.0 

0.51

Mo

N0.090 

0.28 

1.7 

N0.090

Pb

5.0 

2.4 

6.7 

1.4

Sb

N0.60 

N0.60 

N0.60 

N0.60

Zn

22 

7.7 

13 

11

POTENTIAL FOR GOLD RESOURCES

OF THE PAYETTE FORMATION

AND IDAHO GROUP

The chemical data resulting from reconnaissance sampling of the Payette Formation indicate the possibility of a 

gold rs ource in the Payette. The three sandstone samples 

that have high gold values in the concentrates are from 

widely separated locations (fig. 1, localities G88-1, G88-2, 

and G88-6). In addition, the samples are from widely separated levels above granitic or other pre-Payette, pre-Columbia River basement terranes. Inferred vertical distance to 

basement is on the order of 3,500 and 1,500 ft, respectively, 

for samples G88-1-1 and G88-2-1, on the basis of data in 

Fitzgerald (1982), and on the order of 600 ft for sample 

G88-6-1, on the basis of data in Jones (1917).

In the analytical data for the Payette Formation, high 

gold values have a high incidence. This is true if incidence is 

taken at the level of three occurrences of high values out of 

eight concentrates, on the basis of atomic absorption analysis, or even at the level of one such occurrence out of eight 

samples, on the basis of spectrographic analysis.

A comparison with the Payette data is furnished by the 

incidence of detectable gold in the semiquantitative spectrographic analyses of a select group of 74 concentrates of 

modern stream-sediment samples. The sediment samples 

were collected from that part of the drainage basin of the 

South Fork of the Payette River within the Trans-Challis 

mineralized area of Kiilsgaard and others (1989) (fig. 1). 

Of these alluvium samples, taken from streams draining 

terrain marked by many mines and prospects for gold, lead, 

and silver, only one contained detectable gold (McDanal 

and others, 1984).

The analyses of the alluvial concentrate samples cited 

above and the analyses of the Payette concentrate samples 

collected for this study are directly comparable in most 

respects. The two groups of samples were analyzed in the 

same laboratory and received exactly the same laboratory 

processing; however, field panning was by different

operators, and the Payette samples were panned to a volume of perhaps a fifth of what is usual. Thus, a possible 

concentration of gold in samples of the Payette Formation 

relative to the alluvial samples must be taken into account. 

The relative enhancement of gold values in the Payette 

would probably be somewhat more than fivefold. Even so, 

these values seem very significant, and the incidence of 

high gold values in sandstone of the Payette Formation 

compares more than favorably with the incidence of high 

gold values in alluvium selected to be gold rich.

Overall, the results of chemical analysis of the Payette 

Formation are distinctly positive for gold. Unusually high 

gold values are indicated to be present in the Payette. 

Moreover, they apparently are widely distributed and of 

common occurrence.

SUGGESTIONS FOR 

FURTHER STUDY

The possibility of significant placer gold in the Payette 

was considered by Lindgren (1898, p. 668-669). Although 

Lindgren felt that there might be placer gold in the very basal 

part of the Payette Formation at some locations, his evaluation was essentially negative. His evaluation reflects a want 

of essential information, the presence of gold in nonbasal 

parts of the Payette, as shown by the present study. His evaluation also reflects the presence of competing resources. The 

gold lode mines and Quaternary placers of southwest-central 

Idaho were readily amenable to the exploration and extraction technology of Lindgren's day and were then still rich. In 

the very different economic and technical context of today, 

re-examination of the placer gold potential of the Payette 

may be in order. Sedimentary rocks of the Idaho Group are 

similar in lithology and apparent provenance to those of the 

Payette Formation and should be included in any program of 

further sampling for placer gold in the Tertiary sedimentary 

rocks of the Hailey I°x2° quadrangle and vicinity.
TERTIARY SEDIMENTARY ROCKS, PAYETTE FORMATION AND IDAHO GROUP K9

REFERENCES CITED

Baedecker, P.A., and McKown, D.M., 1987, Instrumental neutron 

activation analysis of geochemical samples, in Baedecker, 

P.A., ed., Methods for geochemical analysis: U.S. Geological 

Survey Bulletin 1770, p. H1-H14.

Clifton, H.E., Hunter, R.E., Swanson, F.J., and Phillips, R.L., 1969, 

Sample size and meaningful gold analysis: U.S. Geological 

Survey Professional Paper 625-C, p. C1-C17.

Fisher, F.S., Mclntyre, D.H., and Johnson, K.M., 1983, Geologic 

map of the Challis I°x2° quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 83-523, scale 1:250,000, 41 p.

Fitzgerald, J.F., 1982, Geology and basalt stratigraphy of the Weiser embayment, west-central Idaho, in Bonnichsen, Bill, and 

Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho 

Bureau of Mines and Geology Bulletin 26, p. 103-128.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc and 

alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials: 

U.S. Geological Survey Circular 591, 6 p.

Hawkes, H.E., and Webb, J.S., 1962, Geochemistry in mineral 

exploration: New York, Harper and Row, 415 p.

Jones, E.L., Jr., 1917, Lode mining in the Quartzburg and Grimes 

Pass porphyry belt, Boise Basin, Idaho: U.S. Geological Survey Bulletin 640-E, p. 83-111.

Kiilsgaard, T.H., Fisher, F.S., and Bennett, E.H., 1989, Gold-silver 

deposits associated with the trans-Challis fault system, Idaho, 

in Shawe, D.R., and Ashley, R.P., eds., United States gold terranes Part I: U.S. Geological Survey Bulletin 1857-B, p. 

B22-B44.

Kimmel, P.O., 1982, Stratigraphy, age, and tectonic setting of the 

Miocene-Pliocene lacustrine sediments of the western Snake 

River Plain, Oregon and Idaho, in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho Bureau 

of Mines and Geology Bulletin 26, p. 559-578.

Kirkham, V.R.D., 1931, Revision of the Payette and Idaho Formations: Journal of Geology, p. 39, no. 3, p. 193-239.

Knowlton, F.H., 1898, The fossil plants of the Payette Formation: 

U.S. Geological Survey 18th Annual Report, pt. 3, p. 721-744.

Levinson, A.A., 1974, Introduction to exploration geochemistry: 

Calgary, Canada, Applied Publishing, 612 p.

Lindgren, W., 1898, The mining districts of the Idaho Basin and the 

Boise Ridge, Idaho: U.S. Geological Survey 18th Annual 

Report, pt. 3, p. 625-719.

Malde, H.E., and Powers, H.A., 1962, Upper Cenozoic stratigraphy 

of the western Snake River Plain, Idaho: Geological Society of 

America Bulletin, v. 73, p. 1197-1220.

Malde, H.E., Powers, H.A., and Marshall, C.H., 1963, Reconnaissance geologic map of west-central Snake River Plain, Idaho: 

U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-373, scale 1:125,000.

Mason, Brian, 1958, Principles of geochemistry: New York, John 

Wiley and Sons, 310 p.

McDanal, S.K., Cooley, E.F., and Callahan, J.E., 1984, Analytical 

results of stream-sediment and non-magnetic heavy-mineralconcentrate samples with locality map from portions of the 

Challis I°x2° quadrangle, Idaho: U.S. Geological Survey 

Open-File Report 84-634, 287 p.

Meier, A.L., 1980, Flameless atomic absorption determination of 

gold in geological materials: Journal of Geochemical Exploration, v. 13, p. 77-85.

Motooka, J.M., 1988, An exploration geochemical technique for 

the determination of preconcentrated organometallic halides 

by ICP-AES: Applied Spectroscopy, 42, p. 1293-1296.

Myers, A.T., Havens, R.G., and Dunton, P.J., 1961, A spectrochemical method for the semiquantitative analysis of rocks, 

minerals, and ores: U.S. Geological Survey Bulletin 1084-1, p. 

11-1229.

Nakai, T.S., 1979, Stratigraphy of the Payette Formation, Washington County, Idaho: Moscow, University of Idaho, M.S. 

thesis, 187 p.

Powers, H.A., 1947, Diatomite deposits of southwestern Idaho: Idaho Mineral Resources Report 4, 27 p.

Ross, C.P., 1956, Quicksilver deposits near Weiser, Washington 

County, Idaho: U.S. Geological Survey Bulletin 1042-D, p. 

79-104.

Smiley, C.J., Shah, S.M., and Jones, R.W., 1975, Later Tertiary 

stratigraphy and paleobotany of the Weiser area, Idaho: Idaho 

Bureau of Mines and Geology Information Circular 28, 12 p.

Swirydczuk, K., Larson, G.P., and Smith, G.R., 1982, Volcanic ash 

beds as stratigraphic markers in the Glenns Ferry and Chalk 

Hills Formations from Adrian, Oregon, to Bruneau, Idaho, in 

Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic 

geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 

26, p. 543-558.

Varley, Thomas, Wright, C.A., Soper, E.K., and Livingston, D.C., 

1919, A preliminary report on the mining districts of Idaho: 

U.S. Bureau of Mines Bulletin 166, p. 1-89.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Interpretation of the Regional Geochemistry of the 

Hailey I°x2° Quadrangle, South-Central Idaho

By Cole L. Smith

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-L

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995

CONTENTS

Abstract................................................................................................................................. LI

Introduction.......................................................................................................................... 1

Methods of Study.................................................................................................................. 2

Sampling and Chemical Analysis................................................................................. 2

Data Processing............................................................................................................ 3

Geologic Setting................................................................................................................... 7

Geochemistry........................................................................................................................ 8

Introduction.................................................................................................................. 8

Geochemical Suites...................................................................................................... 9

Polymetallic Areas................................................................................................ 9

Outer Zone Suite................................................................................................... 10

Outer Middle Zone Suite...................................................................................... 10

Inner Middle Zone Suite....................................................................................... 12

Inner Zone Suite................................................................................................... 12

Evolved-Rock Suite.............................................................................................. 13

Pegmatite Suite..................................................................................................... 13

Discussion............................................................................................................................. 14

Known Mineralized Areas............................................................................................ 15

Polymetallic Mineralization ................................................................................. 15

Outer Zone Mineralized Areas............................................................................. 16

Middle Zone Mineralized Areas........................................................................... 17

Inner Zone Mineralized Areas.............................................................................. 18

Mineralized Areas Having Weak Geochemical Signatures ................................. 19

Speculative Targets Based on Geochemistry............................................................... 20

References Cited................................................................................................................... 20

FIGURES

1. Index map showing location of Hailey quadrangle................................................................................................. L2

2. Box plots of sample-site scores within area and outside area of Paleozoic rock outcrops, Hailey quadrangle...... 6

3. Box plots of sample-site scores of different sample media, Hailey quadrangle...................................................... 7

4. Diagram showing summed sample-site scores of geochemical suites in mineralized areas, Hailey quadrangle ... 10

5. Map showing dominant geochemical signatures of mineralized areas, Hailey quadrangle.................................... 12

6-13. Maps showing sample sites, Hailey quadrangle, having anomalous:

6. Outer zone scores........................................................................................................................................... 13

7. Outer middle zone scores............................................................................................................................... 14

8. Inner middle zone scores ............................................................................................................................... 15

9. Inner zone scores ........................................................................................................................................... 16

10. Evolved-rock scores....................................................................................................................................... 17

11. Pegmatite scores............................................................................................................................................ 18

12. Evolved-rock and outer zone scores, northwest quadrant of quadrangle...................................................... 19

13. Outer and inner middle zone scores, southeast quadrant of quadrangle........................................................ 20
CONTENTS

TABLES

1. Previous geochemical studies in the Hailey I°x2° quadrangle, south-central Idaho..................................................... L3

2. NURE and USGS sampling programs in the Hailey I°x2° quadrangle, south-central Idaho........................................ 3

3. Limits of detection for USGS and NURE methods of analyses..................................................................................... 4

4. Rank sum example ......................................................................................................................................................... 5

5. Element suites used for interpretation of regional geochemistry of the Hailey 1 °x2° quadrangle,

	south-central Idaho........................................................................................................................................................ 9

6. Classification of mineralized areas in the Hailey I°x2° quadrangle, south-central Idaho............................................. 11
Interpretation of the Regional Geochemistry of the 

Hailey I°x2° Quadrangle, South-Central Idaho

By Cole L. Smith1

ABSTRACT

Results of 1,914 analyses of sediment samples were 

used to interpret the regional geochemistry of the Hailey 

I°x2° quadrangle, south-central Idaho. Many of the samples, 

1,240, were originally collected for the National Uranium 

Resource Evaluation (NURE) program. The low sampling 

density in this geochemical study makes it difficult to recognize individual mineral deposits. Only large geochemical 

features can be reliably distinguished by their characteristic 

suites of elements in this survey. The geochemistry was 

interpreted by using suites of elements rather than individual 

elements. The suites were chosen because they characterize 

either rocks associated with some types of mineral deposits 

or primary alteration halos associated with some types of 

mineral deposits.

Two geochemical suites, Li+Be and Li+Be+Nb+Th+Y, 

are associated with evolved rocks. The geochemical suite 

Li+Be+Nb+Th+Y is associated with outcrops of Eocene 

granite and with outcrops of some Miocene to Pliocene rhyolites. The element suite Li+Be tends to be associated with 

pegmatites and veins that formed near the margins of the 

Eocene granite.

Four element suites, Sb+As+Au, Ag+Pb, Zn+Cu, and 

Bi+Mo, are used to recognize primary geochemical halos 

formed by mineralizing events. The element suite Bi+Mo is 

commonly associated with plutonic margins, and the element suite Sb+As+Au is commonly distal from plutonic 

margins. The element suites Zn+Cu and Ag+Pb are commonly between the other two element suites. Zoning patterns 

effectively outline most known mineral deposits and prospects in the Hailey I°x2° quadrangle. Some of the element 

suites are anomalous at sites not associated with significant 

known mining activity. If supported by geologic information, this geochemical information can be useful for both 

exploration and resource assessment.

U.S. Geological Survey, W. 904 Riverside Avenue, Spokane, Washington 99201.

INTRODUCTION

This report is a description and interpretation of the 

regional geochemistry of the Hailey I°x2° quadrangle, 

south-central Idaho (fig. 1). The Hailey quadrangle, which 

covers an area of about 6,800 mi2, was sampled at a density 

of about one sample per 4.2 mi2. Work was performed as part 

of the U.S. Geological Survey Conterminous United States 

Mineral Assessment Program (CUSMAP) study of the 

Hailey quadrangle, which was started in the fall of 1986; 

fieldwork was completed in the summer of 1989.

Previously published reports (table 1) that incorporate 

geochemistry discuss only small parts of the Hailey quadrangle. The only geochemical data set that covers the entire 

Hailey quadrangle with widely spaced sample sites is from 

the National Uranium Resource Evaluation (NURE) program. In order to limit the expense of sample collection, the 

U.S. Geological Survey (USGS) reanalyzed NURE samples 

collected by Savannah River Laboratories and analyzed by 

Oak Ridge Gaseous Diffusion Plant (ORDGP). Samples 

were collected for this study to fill gaps in NURE coverage. 

Personnel from the USGS, mostly volunteers, collected samples during the summer of 1987. Three areas of special interest were more densely sampled by the USGS in the summers 

of 1988 and 1989.

A major goal of this study was to provide an interpretation of how mineralized areas in the Hailey quadrangle fit 

into a regional geochemical framework. Another goal was to 

use multielement analytical methods to provide geochemical 

information about a wide range of mineral deposit types and 

their associated alteration halos. The emphasis of the study 

was on those mineral deposit types whose occurrence is 

plausible within the Hailey quadrangle (Worl and Johnson, 

this volume). Many deposit types described in Cox and 

Singer (1986) cannot be distinguished by their chemical 

characteristics alone. Nash (1988, p. 6), after studying the 

chemical analyses of more than 2,000 mineralized rock samples from the Tonopah I°x2° quadrangle in Nevada, stated 

"that there are no simple chemical distinctions between the 

many ore types because element concentrations usually have 

overlapping ranges." Geological characteristics must be

Ll
L2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 1. Index map showing location of the Hailey I°x2° quadrangle, south-central Idaho.

considered to separate one deposit type from another; however, for many common metalliferous deposits, the vertical 

zoning sequence of primary geochemical halos is somewhat 

independent of geologic environment (Ovchinnikov and 

Grigoryan, 1971).

Acknowledgments. Many people, both within and 

outside the USGS, contributed to this geochemical study. 

Samples were collected by many volunteers including 

Craig Fanshier, Craig Bogdon, Brian Nelson, and Keegan 

Schmidt from outside the USGS. Janice Nadeau, an 

employee of the USGS, collected samples for this study 

during her vacation. Jack Antweiler, a retired employee of 

the USGS, also collected samples. Employees of the 

USGS, those from other projects, who collected samples 

were Betty Bailey, Helen Whitney, Janet Jones, and Jerry 

Gaccetta. Chris McDougal both controlled sample flow of 

USGS samples and helped to locate and recover samples 

collected for the NURE program. Paul Briggs, Mollie 

Malcolm, and Rich O'Leary provided analyses of samples

collected for the USGS. Jerry Motooka analyzed USGS 

samples and reanalyzed samples collected for the NURE 

program. Gary Seiner and Dick Taylor designed and wrote 

a computer program to digitize sample locality information, 

as well as a program to display geochemical information. 

Joe Christie and Larry Jackson wrote computer programs to 

automate sample submittal for this project. Jim Hoffman 

and Wendy Speckman helped retrieve existing geochemical 

data from the NURE program. Ron Worl, Reed Lewis, Earl 

Bennett, Thor Kiilsgaard, and Kate Johnson provided helpful advice on geology. Thor Kiilsgaard and Ken Watts thoroughly reviewed the manuscript. I thank these and other 

people for their contributions to this project.

METHODS OF STUDY 

SAMPLING AND CHEMICAL ANALYSIS

Samples of soil and samples of stream sediment from 

the channels of dry streams were collected during the NURE 

program; details of sampling procedures are given in Ferguson and others (1977). In 1987, the USGS collected and analyzed 337 samples of stream sediment from channels of both 

dry and flowing streams; details of sampling procedures are 

given in Malcolm and Smith (1992). In order to integrate 

NURE geochemical data with that of the USGS and to save 

sample collecting costs, the USGS reanalyzed 1,240 samples 

that Savannah River Laboratories had collected for the 

NURE program. Analytical methods for both groups of samples are summarized in table 2. Limits of determination for 

the methods of analysis are given in table 3. Analytical 

results for both the samples collected and analyzed by the 

USGS (337 samples) and the samples reanalyzed by the 

USGS (1,240 samples) were used to interpret the regional 

geochemistry of the Hailey quadrangle.

Because of the cost and time required to analyze 1,577 

samples, only a limited number of analytical techniques 

could be used. Multielement analytical techniques were 

chosen because they determine the concentrations of a wide 

range of elements that are characteristic of many types of 

mineral deposits. An alternative to using multielement techniques would have been to select a few single-element analytical methods that have limits of detection at or near 

crustal abundance for the analyzed element; however, this 

would not have provided information about many types of 

deposits that are likely to be present in the Hailey quadrangle. Even using multielement analytical procedures, the 

geochemical sampling and analysis program was not 

designed to evaluate the Hailey quadrangle for the occurrence of industrial minerals.

In the summers of 1988 and 1989, USGS volunteers 

collected 106 samples in three areas of special interest. Both 

stream-sediment samples and their heavy-mineral fractions 

were analyzed. Sediment samples collected from the special 

study areas were analyzed by the USGS methods previously
INTERPRETATION OF REGIONAL GEOCHEMISTRY 

Table 1. Previous geochemical studies in the Hailey I°x2° quadrangle, south-central Idaho.

L3

Study name

Boulder-Pioneer Wilderness

White Cloud-Boulder Wilderness

Eastern part of the Sawtooth National 

Recreation Area

Sawtooth Primitive Area

Ten Mile Roadless Area

King Hill Creek Wilderness

National Uranium Resource Evaluation 

(NURE) of the Hailey quadrangle

Size 

(mi2)

450

78.6

820

314

134

43.2

6,937

Sample type

Stream sediment 

Soil 

Rock

Stream sediment 

Heavy-mineral concentrate 

Rock

Stream sediment 

Heavy-mineral concentrate 

Rock

Stream sediment 

Soil 

Heavy-mineral concentrate 

Rock

Stream sediment 

Rock

Stream sediment 

Heavy-mineral concentrate 

Rock

Stream sediment 

Soil

Number of 

samples

1,151 

161 

783

101 

73 

172

2,875 

255 

1,506

820 

15 

78 

359

313 

271

43 

28 

70

610 

638

Reference

Simons (1981)

Fisher and May (1983).

Tschanz and Kiilsgaard (1986).

Kiilsgaard and others (1970).

Kiilsgaard (1982).

Toth and others (1987).

Grimes (1982a).

Table 2. NURE and USGS sampling programs in the Hailey I°x2° quadrangle, south-central Idaho.

NURE USGS

Sample media Sediments from dry stream beds

Number of samples 608

Soils

638

Sediments from the beds of 

flowing streams

337

Method of analysis Plasma source emission spectrometry, Plasma source emission spectrometry, Plasma source emission spectromneutron activation (Grimes, 1982b) neutron activation (Grimes, 1982b) etry (Crock and others, 1983)

Plasma source emission spectrometry Plasma source emission spectrometry

after partial extraction (Motooka, 1988) after partial extraction (Motooka, 1988)

Results reported Grimes (1982a) 

Malcolm and Smith (1992)

Grimes (1982a) 

Malcolm and Smith (1992) Malcolm and Smith (1992)

described. The nonmagnetic heavy-mineral fractions of the 

stream-sediment samples were analyzed for 36 elements by 

a semiquantitative emission spectrographic method. Results 

of the analyses and a description of the analytical method is 

given in Malcolm and Smith (1992).

DATA PROCESSING

A microcomputer and a combination of commercial 

computer programs and computer programs written by 

employees of the USGS were used to aid interpretation of the

data generated by the Hailey CUSMAP project. Much of the 

data manipulation was done using commercial spreadsheet 

programs. The commercial computer programs SYSTAT 

and SYGRAPH (by SYSTAT Inc.) were used for statistical 

and some graphical applications. Illustrations were originally produced using a combination of USGS programs 

(GSPOST and GSMAP) and a commercial program 

(MASS11DRAW, by Microsystems Engineering Corp.).

The regional geochemistry of the Hailey quadrangle 

was interpreted using groups of elements (geochemical 

suites) that were chosen to reflect the vertical zonation 

(Tauson and others, 1971) of primary geochemical halos.
L4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 3. Limits of detection for USGS and NURE methods of analysis

[In parts per million unless otherwise indicated. ICP indicates inductively coupled plasma; partial indicates partial

extraction. Leaders (--) indicates element not analyzed for. Crustal abundances from Rose and others (1979, p. 30)]

Element

Ag

Al (percent)

As

Au

B

Ba

Be

Bi

Ca (percent)

Cd

Ce

Co

Cr

Cu

Eu

Fe (percent)

Ga

Hf

Ho

K (percent)

La

Li

Mg (percent)

Mn

Mo

Na (percent)

Nb

Nd

Ni

P (percent)

Pb

Sb

Sc

Sn

Sr

Ta

Th

Ti (percent)

U

V

Y

Yb

Zn

Zr

NURE 

ICP

2

0.05

10

2

1

0.05

10

4

1

2

-

0.05

15

0.05

2

1

0.05

4

4

0.05

4

2

0.0005

10

1

~

1

_

2

0.001

2

1

2

2

USGS 

ICP

2

0.05

10

8

--

1

1

10

0.05

2

4

1

1

1

2

0.05

4

_.

4

0.05

2

2

0.005

4

2

0.005

4

4

2

0.005

4

__

2

10

2

40

4

0.005

100

2

2

1

2

--

USGS ICP 

partial

0.05

1.0

0.3

--

_.

1.0

-

0.075

0.1

-

_

--

_

~

0.25

_

--

1.5

1.5

..

--

_

~

-

 _

0.1

--

Neutron Crustal 

activation abundance

0.05

8.1

2

0.003

8

580

2

0.1

3.3

0.1

81

25

100

50

1.1

4.65

26

3

0.78

2.5

25

30

1.7

1,000

1.5

2.5

20

16

75

0.09

10

0.1

13

2

300

2

10

0.44

0.02 2.5

150

20

2.2

80

150
INTERPRETATION OF REGIONAL GEOCHEMISTRY L5

Table 4. Rank sum example. 

[Concentrations are in parts per million]

Concentration

Sample site

AA01

AA02

AA03

AA04

AA05

AA06

AA07

AA08

AA09

AA10

AA11

AA12

AA13

AA14

AA15

AA16

AA17

AA18

AA19

AA20

Ag

43.0

0.51

0.91

1.20

0.72

0.81

0.09

0.31

0.42

0.53

0.67

0.22

0.49

0.08

0.32

0.85

0.92

1.07

0.17

0.23

Pb

21

37

42

75

45

57

32

44

34

37

48

28

41

29

32

46

59

63

21

27

Rank Rank Sum

Ag

20

10

16

19

13

14

2

6

8

11

12

4

9

1

7

15

17

18

3

5

Pb

1.5

9.5

12

20

14

17

6.5

13

8

9.5

16

4

11

5

6.5

15

18

19

1.5

3

Ag+Pb

21.5

19.5

28

39

27

31

8.5

19

16

20.5

28

8

20

6

13.5

30

35

37

4.5

8

Anomaly threshold

Ordered sample sites

AA04

AA18

AA17

AA06

AA16

AA03

AA11

AA05

AA01

AA10

AA13

AA02

AA08

AA09

AA15

AA07

AA12

AA20

AA14

AA19

39

37

35

31

30

28

28

27

21.5

20.5

20

19.5

19

16

13.5

8.5

8

8

6

4.5

Percentile

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

A nonparametric statistical method (Goldfarb and others, 

1983) that combines information about chemical components having widely different concentration ranges was 

chosen to manipulate the geochemical data. This method 

was used to assign scores to each sample site for each of 

the groups of elements that were used to characterize primary geochemical halos. An unpublished computer program called "RANKS" was used to organize, in 

descending order, the concentrations of chemical components in the geochemical database and to replace concentration with rank. For equal concentrations the ranks were 

averaged, and concentrations below the limit of determination were assigned a rank of 0.

Table 4 gives an example of how geochemical suites 

were used to define anomaly thresholds for this study. In this 

example, the geochemical suite (Ag+Pb) is discussed. Data 

are shown for 20 samples sites. Silver concentrations range 

from 0.08 to 43 ppm and lead concentrations from 21 to 75 

ppm. Anomaly thresholds were chosen at the 95th and 90th 

percentile. If a sample-site score is at the 95th percentile, it 

means that 95 percent of all sample-site scores are below that 

score and 5 percent of all sample-site scores are above that 

score. For 20 samples, only one sample site is anomalous at 

the 95th percentile, site AA04, with a rank sum of 39. 

Another sample site is anomalous at the 90th percentile, site 

AA18, with a rank sum of 37. Because a suite of elements, 

rather than a single element, is used to define anomaly

thresholds, a sample site having a highly anomalous concentration of a single element of the suite might not have an 

anomalous rank sum value. For example, sample site AA01 

has a very anomalous silver concentration of 43 ppm; all 

other silver concentrations are less than or equal to 1.2 ppm. 

Sample site AA01 is anomalous, however, only at the 55th 

percentile. By using suites of elements rather than single elements to interpret the regional geochemistry of the Hailey 

quadrangle, spurious analytical results involving single elements tend to be filtered out.

Concentrations of silver, copper, lead, molybdenum, 

and zinc were determined using more than one analytical 

method. Because of its lower limits of detection (table 3), the 

analytical results of the USGS partial-extraction ICP method 

(Motooka, 1988) were used to rank Ag, As, Au, Bi, Cu, Pb, 

Mo, Sb, and Zn.

Parts of the geochemical data set were affected by the 

following factors: (1) concentrations of some elements 

were determined by more than one method of analysis; (2) 

unmineralized samples of some rock types, such as black 

shale, have high background concentrations of some elements relative to other unmineralized rocks; and (3) three 

different sample media were collected and used to interpret 

the Hailey geochemistry. Not all elements and element 

suites were affected to the same degree by these factors. 

Where necessary, the Hailey geochemical data set was
L6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

PALEO

NO PALEO

PALEO

NO PALEO

1234 

RANK SUM Ag+Pb(x10-3 )

1234 

RANK SUM Bi+Mo (x10-3)

PALEO

NO PALEO

PALEO

NO PALEO

1234 

RANK SUM Sb+As+Au (xlO'3)

1 2 3 

RANK SUM Zn+Cu(x10-3)

Figure 2. Box plots of sample-site scores within area of Paleozoic rock outcrops (PALEO) and outside of area of Paleozoic 

outcrops (NO PALEO), Hailey I°x2° quadrangle, south-central Idaho. See text for discussion.

separated into subsets, and sample-site scores were calculated separately for each subset.

Concentrations of the elements beryllium, lithium, 

niobium, thorium, and yttrium were determined by different analytical methods at the USGS and ORDGP laboratories. For geochemical suites containing these elements, 

sample-site scores for samples analyzed by the USGS laboratory were calculated separately from those for samples 

analyzed by ORDGP.

Samples of black shale of Paleozoic age in the Hailey 

quadrangle have high background concentrations (Simons, 

1981) of elements that are used in some of the geochemical 

suites. The southern and western extent of the Paleozoic 

rocks, including black shale, is known; however, the distribution of black shale within the area of Paleozoic rocks is not 

as well known. Because of this, subsets of the Hailey 

geochemical data were formed of sample sites associated

with Paleozoic rocks and sample sites not associated with 

Paleozoic rocks. For geochemical suites containing Ag, As, 

Au, Bi, Cu, Mo, Pb, Sb, or Zn, sample-site scores of samples 

collected from the area where sample sites might be associated with Paleozoic black shale were calculated separately 

from sample-site scores of samples collected elsewhere.

Box plots graphically summarize data distribution 

(Chambers and others, 1983). The box plots in figure 2 

show that median sample-site scores within the area where 

sample sites might be associated with Paleozoic black shale 

are higher than median sample-site scores outside this area. 

For several reasons not all sample sites within this area are 

associated with high background values: (1) rocks other 

than those of Paleozoic age crop out within the area of 

Paleozoic rock outcrop; (2) not all Paleozoic rocks are 

metal-rich black shale; and (3) no detailed studies have 

been made of metal distribution in all black-shale units, and
INTERPRETATION OF REGIONAL GEOCHEMISTRY L7

USGS-SS

NURE-SS

NURE-SO

USGS-SS

NURE-SS

NURE-SO

1 2 3 

RANK SUM Ag+Pb(x10 3)

1 2 3 

RANK SUM Bi+Mo(x10-3)

USGS-SS

NURE-SS

NURE-SO

USGS-SS

NURE-SS

NURE-SO

1234 

RANK SUM Sb+As+Au (x10 3 )

1 2 3 

RANK SUM Zn+Cu(x10 3 )

Figure 3. Box plots of sample-site scores of different sample media, Hailey I°x2° quadrangle, south-central Idaho. 

USGS-SS indicates samples from beds of flowing streams; NURE-SS indicates samples from dry stream beds; NURE-SO 

indicates soil samples.

it is not certain that all Paleozoic black shale units in the 

Hailey quadrangle are metal rich.

Despite being analyzed by the same method, different 

sample media can produce significantly different ranges of 

sample-site scores. The Hailey geochemical data show, however, that different sample media have a significant overlap 

in the ranges of sample-site scores for the same geochemical 

suites (fig. 3). Because of this overlap, it was decided not to 

form sample-media subsets.

GEOLOGIC SETTING

Rocks in the Hailey quadrangle are Precambrian to 

Holocene in age. Thrust-faulted Paleozoic sedimentary and 

metasedimentary rocks crop out in the northeastern part of

the quadrangle. These rocks are flanked by granitic rocks of 

the Idaho batholith on the west and locally overlain by 

volcanic rocks of the Challis Volcanic Group. The southern 

part of the Hailey quadrangle is covered by volcanic rocks of 

the Snake River Plain.

The oldest rocks in the Hailey quadrangle are in the 

northeastern part of the quadrangle. Precambrian granitic 

gneiss forms a part of the northwest-trending core of the Pioneer Mountains. Paleozoic sedimentary and metasedimentary rocks also are present in this part of the quadrangle and 

are commonly cut by major thrust faults. The Phi Kappa Formation is mainly black, locally silicified argillite and shale of 

Early Ordovician to Middle Silurian age, and the Trail Creek 

Formation is siliceous metasiltstone and very fine grained 

quartzite of Middle Silurian age (Dover and others, 1980). 

The Devonian Milligen Formation contains carbonaceous
L8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

argillite, quartzite, and limestone. The Mississippian Copper 

Basin Formation contains limestone, sandstone, argillite, 

siltstone, and conglomerate. The Middle Pennsylvanian to 

Early Permian Wood River Formation is dominantly calcareous sandstone and calcarenite that contain layers of conglomerate, quartzite, limestone, and argillite.

Rocks of the Atlanta lobe of the Idaho batholith of 

Cretaceous age crop out in much of the northwestern and 

central parts of the Hailey quadrangle. The Idaho batholith 

is composed of plutonic rocks that range in composition 

from tonalite to granite; granodiorite is dominant. Parts of 

the batholith were intruded by Eocene plutons that range in 

composition from diorite to evolved granite. The granite 

has geochemical affinities with evolved (A-type) granite 

(Lewis and Kiilsgaard, 1991). Evolved granite is enriched 

in incompatible elements and depleted in compatible elements. Some of the Paleozoic sedimentary rocks in the 

northeastern part of the quadrangle also were intruded by 

Eocene quartz monzonite stocks that postdate metamorphism and regional thrust faulting. Eocene volcanic rocks 

of the Challis volcanic field are mainly andesitic in composition and are coeval with quartz monzonite stocks in the 

northeastern part of the quadrangle.

The northern edge of the Snake River Plain extends 

across the southern part of the Hailey quadrangle. Rocks of 

the Snake River Plain include the Idavada Volcanics of 

Miocene age and fluvial and lacustrine sediments and interbedded basalt flows that were deposited in the subsiding 

basin. The silicic Idavada Volcanics lie unconformably on 

granite and compose much of the Mount Bennett Hills. They 

were extruded during the formation of the Snake River Plain. 

The youngest rhyolite domes of the Magic Mountain eruptive center are of Pliocene age. Fluvial and lacustrine sediments and interbedded basalt were deposited on the Snake 

River Plain from Miocene to Pleistocene time and include 

the Banbury Basalt, the Glenns Ferry Formation, and the 

Bruneau Formation.

Just north of the northern edge of the Snake River Plain, 

in the south-central part of the Hailey quadrangle, is the 

Camas prairie, a downwarped block filled with Eocene and 

younger volcanic rocks and sediments.

Mineral deposits in the Hailey quadrangle include 

tungsten stockworks, Tertiary molybdenum stockworks, 

Tertiary poly metallic veins, epithermal precious-metal 

veins, Tertiary polymetallic replacements, copper skarns, 

Cretaceous molybdenum stockworks, polymetallic quartz 

veins and lodes, Cretaceous polymetallic veins, and Cretaceous polymetallic replacements (Johnson and Worl, 1989, 

in press; Worl and Johnson, 1989, this volume). Gold and 

radioactive black-sand placers, hot-springs deposits, antimony veins, gold-bearing skarns, sedimentary stratabound 

lead-zinc deposits, and stratabound barite are also present.

GEOCHEMISTRY 

INTRODUCTION

One objective of this study was to develop methods 

with which to present regional geochemical data in a way 

that aids resource assessment. The low sampling density of 

many regional surveys hinders reliable detection of individual mineral deposit targets; however, two types of large 

geochemical features believed to be present in the Hailey 

quadrangle are appropriate targets for more detailed studies: 

(1) the zoned primary geochemical halos described by 

Ovchinnikov and Grigoryan (1971) and (2) evolved rocks, 

both Eocene granite and Miocene to Pliocene rhyolite.

Mineralizing events that form many types of sulfidebearing mineral deposits also form zoned primary 

geochemical halos (Ovchinnikov and Grigoryan, 1971). 

These primary geochemical halos can affect areas large 

enough to be detected using the low-sampling density used 

in regional surveys. Tauson and others (1971) summarized 

the vertical zoning sequence of primary geochemical halos 

as follows, from top to bottom: Hg, Sb, As, Ba, Ag, Pb, 

Zn, Cu, Bi, W, Mo, Sn, Co, Ni, and Be. Tschanz and Kiilsgaard (1986) indicated that geochemical halos could have 

been used in their interpretation of the geochemistry of 

Sawtooth National Recreation Area. Primary halos suggested by the regional geochemical data are discussed in 

following sections of this report.

Lewis and Kiilsgaard (1991) described Eocene granite 

in south-central Idaho as having some geochemical characteristics of A-type (evolved) granitoids, and Bennett's 

(1980) description of the characteristics of the Eocene granite in the Idaho batholith matches some of the characteristics 

of evolved granite. Based on this and on geochemical evidence from this study, Eocene granite in the Hailey quadrangle is considered evolved granite. Relative to other types of 

granite and rhyolite, evolved rocks tend to be enriched in 

incompatible elements and depleted in compatible elements. 

Evolved rocks, both granite and rhyolite, are characterized 

by high concentrations of elements such as Be, Cs, F, K, Li, 

Nb, Rb, Sn, Th, U, and Y and low concentrations of elements 

such as Ba, Ca, Mg, and Sr. Evolved granite commonly comprises epizonal multiphase plutons that crop out over broad 

areas. Because of these characteristics, evolved rocks are 

good targets in regional geochemical surveys. This was demonstrated by Howarth and others (1981), who used NURE 

geochemical data to identify uranium-rich (evolved) granite 

in Colorado. Outside of Idaho, evolved rocks are associated 

with mineralized areas that are important sources of elements such as beryllium, lithium, uranium, and tin; however, 

in the Hailey quadrangle, evolved rocks have produced only 

minor amounts of beryl.

Regional geochemical studies can suggest areas where 

some types of mineral deposits might be present; however, 

with any geochemical survey a possibility of error exists in
INTERPRETATION OF REGIONAL GEOCHEMISTRY L9 

Table 5. Element suites used for interpretation of regional geochemistry of the Hailey I°x2° quadrangle, south-central Idaho.

Name Characteristic elements Comments

Outer zone

Inner zone

Pegmatite 

Evolved rock

Sb+As+Au

Outer middle zone Ag+Pb

Inner middle zone Zn+Cu

Bi+Mo

Li+Be

Li+Be+ Nb+Th+Y

Elements tend to be present in near-surface environments. Some of these 

elements may be volatile. Deposits may be precious metal enriched.

Deposits associated with this part of the primary geochemical halo may be 

precious metal enriched.

Deposits associated with this part of the primary geochemical halo tend to be 

base metal enriched.

This part of the primary geochemical halo suggests nearby plutonic margins. 

Gold may also be associated with these elements.

Element suite is associated with margins of evolved plutons. 

Elements is associated with outcrops of evolved rocks.

sample collecting, handling, and analysis. For this reason, 

not much importance is attached to an anomalous sample site 

that is isolated from other anomalous sample sites. More 

attention is given to an anomaly that is represented by a cluster of sample sites.

The multielement analytical methods used in this 

regional survey provide information about the concentrations of a variety of elements in stream-sediment and soil 

samples. This information can lead to identification of primary geochemical halos of the types that are associated with 

a wide range of sulfide-bearing mineral deposits (Ovchinnikov and Grigoryan, 1971). Single-element analytical methods having low detection limits are better for providing 

information about an element, such as gold, that is associated 

with specific deposit types, particularly deposit types having 

low anomaly-to-background contrasts and poorly developed 

primary geochemical halos.

GEOCHEMICAL SUITES

Geochemical suites were used to interpret the regional 

geochemistry of the Hailey quadrangle. Sample sites are 

defined as anomalous on the basis of scores that are the sums 

of the ranks of geochemical suites of elements rather than 

single elements. The distribution of geochemical anomalies 

defined by these suites is consistent with the distribution of 

prospects, alteration, and mining activity. Some of the mineralized areas defined by Worl and Johnson (this volume) 

are characterized by anomalous sample-site scores for more 

than one geochemical suite.

In this study, six element suites are used to discuss the 

regional geochemistry of the Hailey quadrangle (table 5). 

The first four element suites are related to the vertical zoning 

sequence of primary geochemical halos described by Tauson 

and others (1971). The first three elements in the top of the

vertical zoning suite summarized by Tauson are mercury, 

antimony, and arsenic. Because samples in this study were 

not analyzed for mercury and in order to emphasize epithermal gold deposits, the outer zone geochemical suite in this 

study was defined as Sb+As+Au. Names given to the first 

four element suites are based on their vertical position in primary geochemical halos; those for the last two element 

suites reflect the geochemical signature associated with 

evolved rocks. The term "polymetallic" is used to describe 

mineralized areas in which no one or two suites of the first 

four geochemical suites of elements dominate.

Unless otherwise indicated, the mineralized areas 

referred to in this report are those delineated by Worl and 

Johnson (this volume). The boundaries of the mineralized 

areas delineated by Worl and Johnson are not necessarily the 

same as those that would be delineated by geochemistry. 

Most of these mineralized areas are characterized by or dominated by one or more of the element suites Sb+As+Au, 

Ag+Pb, Zn+Cu, and Bi+Mo (fig. 4).

A point system was used to characterize geochemical 

suites in each of the mineralized areas. The classification of 

the mineralized areas and a description of the point system 

used to classify the areas are given in table 6. The geochemistry of two mineralized areas, Neal (7) and Elk Creek (23), 

is not well characterized by the sample media and analytical 

methods used in this study, and these two areas are unclassified. Samples were not collected in the Bunker Hill (23) or 

Washington Basin (31) mineralized areas, and the areas are 

not discussed herein.

POLYMETALLIC AREAS

Most of the mineralized areas containing polymetallic 

deposits are wholly or partly within the area where Paleozoic 

rocks crop out (fig. 5). In these mineralized areas none of the 

geochemical suites are dominant. Polymetallic deposits
L10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

1. Quartzburg

2. Idaho City

3. Swanholm

4. Black Warrior

5. Atlanta

6. Rocky Bar

8. Pine

9. Volcano

10. Marshall Peak

11. Vienna

12. Rooks Creek stock

13. Deer Creek stock

14. Croesus stock

15. Hailey gold belt

16. Soldier

17. Middle Fork Boise River

18. Corral Creek

19. Sawtooth

20. Smoky Mountains

21. Carrietown

22. Bullion

24. Minnie Moore

25. Bellevue

26. Wood River

EXPLANATION 

Primary geochemical zones

Inner

Bi+Mo

Inner

middle

Zn+Cu

Outer

middle

Ag+Pb

Outer

Au+

Sb+As |

27. Triumph

28. East Fork Wood River

29. Lake Creek

30. Galena

32. Baker Creek

33. Boulder Basin

34. East Fork Salmon River

35. Summit

44. Pioneer

45. Magic

B. Geochemistry

E. Geochemistry

Highest score 

Medium-high score 

Medium score 

Low score

 ZED

Figure 4. Summed sample-site scores of geochemical suites in mineralized areas of Worl and Johnson (this volume), Hailey 1 °x2° 

quadrangle, south-central Idaho. P indicates area is polymetallic; w indicates weak geochemical signature. Mineralized areas are 

shown in figure 5.

characterize the following areas: Boulder Basin (33), Summit (35), East Fork Wood River (28), Triumph (27), Rooks 

Creek stock (12), Deer Creek stock (13), Bullion (22), Bellevue (25), Minnie Moore (24), Magic (45), Carrietown (21), 

and Hailey gold belt (15). The polymetallic areas at Pine (8), 

Volcano (9), and Magic (45) are outside of the area of Paleozoic rock outcrop.

OUTER ZONE SUITE

Figure 6 shows sample sites that contain anomalous 

amounts of elements that characterize the outer zone of the 

primary geochemical halo described by Tauson and others 

(1971). The elements antimony, arsenic, and gold define this 

suite. Samples were not collected and analyzed specifically 

for gold at levels near crustal abundance (about 3 ppb), and 

only 1 percent of the samples contained detectable amounts 

of gold. In this study the elements arsenic and antimony are 

the main pathfinder elements for precious-metal mineralization that might be associated with the outer zone halo. Most 

anomalous samples of the outer zone that are not in polymetallic-mineralized areas are in the northern third and western 

two-thirds of the quadrangle (fig. 6). The outer zone suite is 

the dominant geochemical signature in the Idaho City (2), 

Swanholm (3), Black Warrior (4), Atlanta (5), Vienna (11), 

and Rocky Bar (6) mineralized areas (fig. 5). With the

exception of Swanholm, precious metals were produced 

from mines in these areas. The main commodity produced at 

Swanholm was antimony. The outer zone suite also is dominant in area E in the southeastern corner of the Hailey quadrangle (fig. 5), which was delineated on the basis of the 

regional geochemistry.

A few scattered samples in the southern part of the 

quadrangle contain anomalous amounts of the outer zone 

suite of elements. The anomalous samples in this area are 

single-sample anomalies associated with the Idavada Volcanics. Epithermal, low-sulfide, precious-metal deposits associated with volcanic terrane can have weak geochemical 

signatures (Nash, 1988), and the occurrence of hot-springstype precious-metal deposits may be underestimated in the 

southern part of the Hailey quadrangle.

OUTER MIDDLE ZONE SUITE

Figure 7 shows sample sites that have anomalous 

scores for the outer middle zone suite of elements (Ag+Pb) 

(Tauson and others, 1971). This geochemical signature is 

the dominant suite in the Marshall Peak (10) and Sawtooth 

(19) mineralized areas (fig. 5). The Sawtooth mineralized 

area is associated with rocks of a Tertiary granite batholith, 

and the Marshall Peak area is just to the south in an area of 

regional shear zones in rocks of the Idaho batholith.
INTERPRETATION OF REGIONAL GEOCHEMISTRY Lll

Table 6. Classification of mineralized areas in the Hailey I°x2° quadrangle, south-central Idaho.

[Mineralized areas are defined in Worl and Johnson (this volume), and the location of the areas is shown in figure 5. No. is number of sample sites 

whose drainages are within boundary of mineralized area. Sample sites having a percentile ranking between the first and second number are given a 

score of 1; those having a ranking of greater than the second number are given a score of 2. I is the inner zone (Bi+Mo) score; I-M is the inner middle 

zone (Zn+Cu) score; O-M is the outer middle zone (Ag+Pb) score; and O is the outer zone (Sb+As+Au) score. The geochemical suite having the 

highest sample site score is shown in uppercase letters; geochemical suite(s) having score(s) greater than or equal to half of the dominant sample site 

score is shown in lowercase letters. If the dominant suite at the 90th and 95th percentiles has less than 15 percent of the maximum possible points for 

the mineralized area, then the suites were evaluated at the 75th and 90th percentiles. Geochemical suites chosen at the 75th and 90th percentiles are 

described by the adjective "weak." Polymetallic suites either have at least three of four zones whose scores area separated by three or less points or 

have at least three of four zones whose scores are greater than or equal to one-half that of the zone having the highest score. If a mineralized area has a 

total score of less than four for all zones when evaluated at the 75th and 90th percentiles, then the area was not classified]

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

44

45

46

B

E

Mineralized area

Quartzburg

Idaho City

Swanholm

Black Warrior

Atlanta

Rocky Bar

Neal

Pine

Volcano

Marshall Peak

Vienna

Rooks Creek stock

Deer Creek stock

Croesus stock

Hailey gold belt

Soldier

Middle Fork Boise River

Corral Creek

Sawtooth

Smoky Mountains

Carrietown

Bullion

Bunker Hill

Minnie Moore

Bellevue

Wood River

Triumph

East Fork Wood River

Lake Creek

Galena

White Clouds

Baker Creek

Boulder Basin

East Fork Salmon River

Summit

Pioneer

Magic

Elk Creek

Defined by geochemistry

Defined by geochemistry

No.

21

35

4

12

12

15

12

37

9

16

8

6

3

4

12

9

45

21

17

17

14

5

0

3

8

24

4

7

16

7

0

5

1

14

18

11

2

3

17

22

Percentile

90-95

90-95

90-95

90-95

90-95

90-95

75-90

90-95

90-95

90-95

90-95

90-95

90-95

90-95

90-95

90-95

90-95

75-90

90-95

75-90

90-95

90-95

90-95

90-95

75-90

90-95

90-95

75-90

75-90

75-90

90-95

75-90

90-95

90-95

90-95

75-90

90-95

90-95

I

12

6

0

0

2

0

1

12

12

5

2

0

1

2

7

1

26

4

10

7

3

0

2

0

0

3

4

9

1

2

0

5

11

10

2

0

6

0

I-M

2

5

0

0

0

0

0

12

9

3

2

2

2

2

6

6

5

7

2

10

4

2

3

2

4

3

7

10

1

1

2

2

13

1

2

2

18

11

O-M

7

8

1

2

3

5

2

10

9

21

7

3

2

4

6

1

23

4

13

15

4

3

3

3

9

6

5

9

3

2

2

4

8

2

3

0

1

6

0

5

19

6

6

16

6

0

6

4

19

13

3

2

1

4

1

5

0

2

14

0

3

4

1

15

4

6

11

0

1

2

6

13

2

0

0

0

22

Classification

INNER with outer middle zones

OUTER zone

OUTER zone

OUTER zone

OUTER zone

OUTER with outer middle zones

Not classified

POLYMETALLIC

POLYMETALLIC

OUTER MIDDLE with outer zone

OUTER with outer middle zone

POLYMETALLIC

POLYMETALLIC

Weak polymetallic

POLYMETALLIC

INNER MIDDLE zone

INNER with outer middle zone

Weak polymetallic

OUTER MIDDLE with inner zone

Weak polymetallic

POLYMETALLIC

POLYMETALLIC

No samples

POLYMETALLIC

POLYMETALLIC

Weak outer with outer middle zone

POLYMETALLIC

POLYMETALLIC

Weak polymetallic

Weak polymetallic

No samples

Weak polymetallic

POLYMETALLIC

Weak polymetallic

POLYMETALLIC

INNER zone

POLYMETALLIC

Not classified

INNER MIDDLE zone

OUTER with inner middle zone
L12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

116° 115° 114°

EXPLANATION

Outer zone ^^^^H Polymetallic

Outer middle zone f j Weak

Inner middle zone No samples or not classified

Inner zone (. ^ Boundary of Paleozoic rock outcrop

Figure 5. Dominant geochemical signatures of mineralized areas, Hailey I°x2° quadrangle, south-central Idaho. Numbers of mineralized areas are from Worl and Johnson (this volume) and table 6 (this report).

INNER MIDDLE ZONE SUITE

Figure 8 shows sample sites that have high scores for 

the inner middle zone suite of elements (Zn+Cu) (Tauson 

and others, 1971). Most of these samples sites are associated 

with Paleozoic rocks in mineralized areas that have a 

polymetallic character; only two mineralized areas that are 

not associated with Paleozoic rocks have inner middle zone 

signatures as the dominant signature. One of the areas, Soldier (16), is a mineralized area defined by Worl and Johnson 

(this volume). The other area, area B (fig. 5), was delineated 

by the regional geochemistry.

INNER ZONE SUITE

The elements bismuth and molybdenum define the 

inner zone signature (Tauson and others, 1971). Only 4.1

percent of the sediment samples contain amounts of bismuth greater than 1.5 ppm, the limit of determination for 

bismuth in this study. Authors such as Nash (1988) found 

bismuth to be a good indicator of pluton margins and used 

it, together with tungsten, as a diagnostic element for skarn 

deposits. The inner zone suite of elements is the dominant 

element suite in the Quartzburg (1), Middle Fork Boise 

River (17), and Pioneer (44) mineralized areas (fig. 5). 

With the exception of Quartzburg, mineralized areas having 

inner zone signatures are associated with Eocene granite 

(fig. 9). The inner zone signature associated with the Middle Fork Boise River (17) mineralized area extends beyond 

the mineralized area delineated by Worl and Johnson (this 

volume). A weak inner zone signature is associated with 

rhyolite of the Idavada Volcanics in the southern part of the 

quadrangle. The inner zone signature in this area is
116°

44°

INTERPRETATION OF REGIONAL GEOCHEMISTRY

115°

L13

114°

O o

o 

O O

° o°.

o

O oo

O

O

©o

o < 

P

O 

o

o O 

O

o 

o °O O O

O O

O

RB 6> 0Oo

°

°

O

O

O

O

o o

o o

o o

o

ex

o

o

43°

25 MILES

EXPLANATION

O O Outer zone suite (Sb+As+Au) Small circle

indicates 90 percent anomaly threshold, large circle 

indicates 95 percent anomaly threshold

C. "^ Boundary of Paleozoic rock outcrop 

X Mine

Figure 6. Sample sites having anomalous outer zone scores, Hailey 1 °x2° quadrangle, south-central Idaho. Mineralized areas: 1C, Idaho 

City; RB, Rocky Bar; S, Sawtooth; V, Vienna; A, Atlanta.

probably the result of high background concentrations of 

molybdenum in the Idavada rhyolites.

EVOLVED-ROCK SUITE

The elements beryllium, lithium, niobium, thorium, and 

yttrium characterize the evolved-rock geochemical suite in 

the Hailey quadrangle. The evolved-rock element suite is 

usually associated with either Eocene granite or Miocene to 

Pliocene rhyolite (fig. 10). Some Miocene to Pliocene rhyolite has been recognized as evolved rock. In the Cannonball 

Mountain area, Lewis (1990) found an evolved peralkaline 

rhyolite, a comendite, of Miocene age (about 10.2 Ma) and 

proposed that this unit be named "tuff of Cannonball Mountain." A single anomalous sample is associated wth rhyolite 

at Wedge Butte (fig. 10), where a 3-million-year-old rhyolite

was described by Leeman (1982) as "evolved" as compared 

with most Snake River Plain rhyolites. Some scattered sample sites having high scores for the evolved-rock element 

suite do not have close associations with either Eocene granite or Miocene to Pliocene rhyolite (fig. 10); these sites are 

north and northwest of the Eocene granite around Sheep 

Mountain, within the Pine (8) mineralized area, and southsoutheast of the Sawtooth batholith.

PEGMATITE SUITE

Pegmatite associated with evolved granite can be 

enriched in both beryllium and lithium, and pegmatite fields 

commonly emanate from the cupolas of parental granite 

(see, for example, London, 1990). Compared to the evolvedrock element suite, the pegmatite suite has fewer anomalous
L 14

116 44°

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

115° 114°

43°

A 

A A

A

A

A A

AA

A

A A

A

A A

A

RB A

A 

V

A .

A

A

A A

A

A A ^-,

A

A A A

A

A

A

A AA

A

A A

A

25 MILES

EXPLANATION

A A Outer middle zone suite (Ag+Pb) Small solid triangle 

indicates 90 percent anomaly threshold, large open 

triangle indicates 95 percent anomaly threshold

C^ ^l Boundary of Paleozoic rock outcrop 

^ Mine

Figure 7. Sample sites having anomalous outer middle zone scores, Hailey I°x2° quadrangle, south-central Idaho. Mineralized areas: 

1C, Idaho City; RB, Rocky Bar; S, Sawtooth; V, Vienna; A, Atlanta.

sample sites within the area where Eocene granite crops out. 

Also, unlike the evolved-rock element suite, the pegmatite 

suite is not strongly associated with Miocene rhyolite (fig. 

1 1). Because of these contrasts with the evolved-rock suite, 

Li+Be was chosen as a separate element suite. Despite the 

name "pegmatite suite" given to this suite of elements, mineralized veins can be the source of anomalous amounts of 

beryllium in sediment samples. As much as 150 ppm Be is in 

mineralized veins near Mattingly Creek and La Moyne and 

Leggitt Creeks (fig. 12) (Kiilsgaard and others, 1970). These 

veins also contain anomalous amounts of-other elements, 

including silver and gold.

Clusters of sample sites containing anomalous amounts 

of the pegmatite suite of elements are in the following areas 

(fig. 11): south of the Sawtooth batholith, in the Pioneer (44)

mineralized area, east of the Soldier Mountains, in a northeast-trending corridor indicated by outcrops of Eocene granite including those in the Soldier and Smoky Mountains, and 

within the outcrop area and north of the Eocene granite at 

Sheep Mountain. Many of the sediment samples containing 

anomalous amounts of the pegmatite suite of elements were 

not derived from areas where Eocene granite crops out.

DISCUSSION

Several authors have estimated the age or ages of mineralization in the Idaho batholith. For example, Bennett 

(1980) emphasized the close spatial relationship between 

Eocene epizonal granite and mineralized rock in the Idaho
116°

44°

INTERPRETATION OF REGIONAL GEOCHEMISTRY

115°

L15

114°

43°

D

n

D

D 

D D

n

n

n

n

n a

n

n

n

n

n nn

n n D

n

n '^

D D n 'x

D

n

n

D tflin n n

P D

n n

n

D an

n n 

DD n

D a

nD 

a

n

n

n

n

n

n Da

D

D

25 MILES

EXPLANATION

Inner middle zone suite (Zn+Cu) Small square 

indicates 90 percent anomaly threshold, large square 

indicates 95 percent anomaly threshold

^ Boundary of Paleozoic rock outcrop

Figure 8. Sample sites having anomalous inner middle zone scores, Hailey I°x2° quadrangle, south-central Idaho.

batholith. Anderson (1951) believed that all mineralization 

in the southern batholith is Tertiary in age. Ross (1931) 

believed that mineralization is both Cretaceous and Tertiary 

in age. Snee (1989), using 40Ar/39Ar thermochronology, 

found that some mineralization in the southern part of the 

Idaho batholith occurred between 78 and 57 Ma.

Results of regional geochemical surveys do not 

directly indicate age of mineralization. Most geochemical 

suites cannot be tied to geologic events that occurred in a 

particular time period; however, geochemical sediment 

samples containing large amounts of the elements that 

define two geochemical suites, the evolved-rock and pegmatite suites, are related to source rocks that are of Eocene 

age or younger. Source rocks of the sediment samples 

enriched in these suites of elements are probably the result

of polyphase plutonism that caused incompatible elements 

to be enriched in Eocene granite and younger rhyolite.

KNOWN MINERALIZED AREAS 

POLYMETALLIC MINERALIZATION

Most mineralized areas characterized by polymetallic 

mineralization are related to the area in which Paleozoic 

rocks crop out (fig. 5). Black shale usually is enriched in a 

range of elements (Vine and Tourtelot, 1970). Although 

Paleozoic black shale of the Hailey quadrangle is not 

enriched relative to other black shale (Simons, 1981), the 

unmineralized parts of the black shale units in the Hailey
L16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

MIDDLE FORK 

BOISE RIVER

EXPLANATION

Inner zone suite (Bi+Mo) Small triangle ($) 

indicates 90 percent anomaly threshold, large triangle (4) 

indicates 95 percent anomaly threshold

Tertiary granite 

Miocene-Pliocene rhyolite 

Mineralized area

Figure 9. Sample sites having anomalous inner zone scores, Hailey I°x2° quadrangle, south-central Idaho.

quadrangle are enriched in a range of elements relative to 

other unmineralized rocks in the quadrangle.

Black shale could be the source of the metals in at least 

some of the mineral deposits within the area where Paleozoic 

rocks crop out. Simons (1981) concluded that black shale 

could be the source of some of his geochemically anomalous 

stream-sediment samples. Hall and others (1978) proposed 

that metals in vein deposits were leached from Paleozoic 

black shale and deposited in favorable structures related to 

the Wood River thrust fault.

In areas containing black shale, mineral deposits may 

be telescoped. Epizonal intrusions could have provided heat 

to drive shallowly circulating hydrothermal cells that 

extracted metals from a nearby source, the black shale. As a

result of rapidly changing pressure and temperature conditions between the shallow intrusion and the surface, the metals could have been precipitated in a relatively narrow zone 

to form the deposits. Telescoping of deposits is consistent 

with the polymetallic character of many mineralized areas 

associated with Paleozoic rock outcrops, and it is consistent 

with the suggestion of Sanford and others (1989) that at least 

the lead in some deposits could have been remobilized from 

syngenetic deposits in black shale.

OUTER ZONE MINERALIZED AREAS

As previously indicated, Bennett (1980) found a spatial 

relationship between Eocene granite and mineralization,
INTERPRETATION OF REGIONAL GEOCHEMISTRY

115°

L17

TUFF OF

CANNONBALL

MOUNTAIN

114°

x X

EXPLANATION

Evolved-rock suite (Li+Be+Th+Nb+Y) Small x 

indicates 90 percent anomaly threshold, large X 

indicates 95 percent anomaly threshold

Tertiary granite 

Miocene-Pliocene rhyolite 

Mineralized area

Figure 10. Sample sites having anomalous evolved-rock scores, Hailey I°x2° quadrangle, south-central Idaho. Solid triangle shows 

the location of Sheep Mountain.

including epithermal mineralization. Eocene igneous activity is suggested by anomalous amounts of elements that 

characterize both the evolved-rock and pegmatite geochemical suites. The area containing mines at Atlanta, Sawtooth, 

Mattingly Creek, and La Moyne and Leggitt Creeks has a 

combined pegmatite and outer zone geochemical suite signature (fig. 12). The pegmatite signature in this area, and the 

veins found by Kiilsgaard and others (1970) that contain 

both beryllium and precious metals, suggests that near-surface, but unexposed, Eocene granite might have affected 

both mineralization associated with outer zone primary 

geochemical halos and the distribution of the pegmatite suite 

of elements. The implication that Eocene igneous activity 

played a role in some of the mineralization at Atlanta is

difficult to reconcile with Snee's findings that the youngest 

mineralizing event at Atlanta is 57 Ma.

The outer zone suite of elements is enriched farther to 

the south and southeast of the Sawtooth batholith than is the 

pegmatite suite of elements (fig. 12). The mines at Vienna and 

Rocky Bar are characterized only by the outer zone suite of 

elements. The outer zone suite of elements is enriched between 

the Rocky Bar and Atlanta mineralized areas. This linear zone 

of enrichment could reflect a structure that controlled mineralization between these known mineralized areas.

MIDDLE ZONE MINERALIZED AREAS

Two mineralized areas are dominated solely by the 

outer middle zone geochemical signature: Marshall Peak
L18

116C

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

44°

43°

114°

- + SAWTOOTH 

+ ++ BATHOLITH

SHEEP + 

+ MOUNTAIN

+ + + + + + + +

+ ^ ++ /

CORRAL CREEK

«r

-VOLCANO

25 MILES

EXPLANATION

Pegmatite suite (Li+Be) Small plus (+) 

indicates 90 percent anomaly threshold, large plus (+) 

indicates 95 percent anomaly threshold

Tertiary granite 

Miocene-Pliocene rhyolite 

Mineralized area

Figure 11. Samples sites having anomalous pegmatite scores, Hailey I°x2° quadrangle, south-central Idaho. Solid triangle shows the 

location of Sheep Mountain.

(10) and Sawtooth (19). The Middle Fork Boise River (17) 

mineralized area also has a significant outer middle zone signature. In all three areas the outer middle zone signature is 

associated with the inner zone signature (fig. 4). It is not 

known why these areas do not have a stronger inner middle 

zone signature.

Soldier (16) is the only known mineralized area that is 

characterized solely by an inner middle zone signature. Mineralization in the Soldier area is hosted by rocks of the Idaho 

batholith (Worl and Johnson, this volume), west of an 

evolved peralkaline rhyolite (fig. 13), a comendite, of 

Miocene age (Lewis, 1990). The chemistry of this rhyolite is 

unique in the Hailey quadrangle and unusual for Snake River 

Plain rhyolite (Lewis, 1990). Evolved rocks can have high

concentrations of halogens such as fluorine and chlorine. 

Both fluorine and chlorine can be important in the transport 

of gangue and ore minerals from granitic magmas during the 

final stages of crystallization (see, for example, Burnham 

and Ohmoto, 1980); however, it is not certain if the emplacement of the comendite played a role in forming the deposits 

of the Soldier mineralized area.

INNER ZONE MINERALIZED AREAS

Mineralized areas characterized by an inner zone signature commonly are associated with Eocene granite outcrops 

or with geologic or geochemical indications of near-surface
INTERPRETATION OF REGIONAL GEOCHEMISTRY

45' 30' 15' 115°00'

L19

114° 45'

43°30' L

EXPLANATION

+ + Evolved-rock suite-Small plus (+) indicates 90 percent anomaly threshold, 

large plus (+) indicates 95 percent anomaly threshold

O O Outer zone suite-Small circle (O) indicates 90 percent anomaly threshold, 

large circle (O) indicates 95 percent anomaly threshold

Mine

Tertiary granite

Figure 12. Sample sites in the northwest quadrant of the Hailey I°x2° quadrangle, south-central Idaho, having anomalous 

evolved-rock and outer zone scores. Mineralized areas: 1C, Idaho City; RB, Rocky Bar; S, Sawtooth; V, Vienna; A, Atlanta; 

LL, La Moyne Creek-Leggit Creek; MC, Mattingly Creek.

Eocene granite. Both the Pioneer (44) and the Middle Fork 

Boise River (17) mineralized areas are near exposures of 

Eocene granite (fig. 9). The Corral Creek (18), Pine (8), and 

Volcano (9) mineralized areas have polymetallic signatures 

and a significant inner zone component and are within a 

northeast-trending belt that is indicated both by outcrops of 

Eocene granite, such as in the Soldier and Smoky Mountains, and by a pegmatite geochemical signature (fig. 11). 

The Quartzburg (1) mineralized area (fig. 9) contains Tertiary dike swarms. Rhyolite dikes in this swarm are compositionally equivalent to evolved Eocene granite (Kiilsgaard 

and Hingley, 1989; Kiilsgaard and others, in press). In the 

Quartzburg area sample sites that are anomalous with 

respect to the evolved-rock signataure are not contiguous. 

The scattered character of the evolved-rock signature in the 

Quartzburg area is consistent with dike source rocks (fig. 

10). Bennett (1980) suggested that Tertiary dike swarms in 

the Boise Basin are apophyses of Eocene granite plutons. 

The relationship between the inner zone signature and 

Eocene granite is important. Not only does this signature

indicate a potential for tungsten and molybdenum mineralization, it also is associated with gold-mineralized rock in 

the Quartzburg, Volcano, Corral Creek, and Pioneer 

mineralized areas.

MINERALIZED AREAS HAVING WEAK 

GEOCHEMICAL SIGNATURES

Except for the Corral Creek (18) mineralized area, mineralized areas having weak geochemical signatures (table 6, 

fig. 5) are wholly or partly within the area where Paleozoic 

rocks might crop out. Anomaly thresholds for the area where 

Paleozoic rocks might crop out were calculated separately 

from the rest of the Hailey quadrangle. The area where Paleozoic rocks might crop out contains black shale as well as 

other rock types. Commonly, mineralized areas that are 

within the area of Paleozoic outcrop and that have weak 

geochemical signatures may not be closely associated with 

black shale. For example, most mines in the Galena (30)
L20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

115°00'

EXPLANATION

o O Outer zone suite Small circle (o) indicates 90 

percent anomaly threshold, large circle (O) 

indicates 95 percent anomaly threshold

D d Inner middle zone Small squares (a) indicates 

90 percent anomaly threshold, large square (D) 

indicates 95 percent anomaly threshold

) Proposed caldera boundary (Leeman, 1982) 

Miocene and Pliocene rhyolite 

Outline of mineralized area 

Boundary of Paleozoic rock outcrop

Figure 13. Sample sites in the southeast quadrant of the Hailey 

I°x2° quadrangle, south-central Idaho, having anomalous outer and 

inner middle zone scores.

rhyolite in the area is the dome at Wedge Butte. Area E is 

associated with Quaternary basalt. The recent igneous activity in both areas B and E suggests the possibility of associated recent hydrothermal activity; however, the source or 

sources of the anomalous elements in these areas is not 

known. Further sediment and rock sampling is suggested for 

these two areas. Samples from area E should be analyzed for 

gold using an analytical technique that has a limit of detection close to the crustal abundance of gold, about 2 ppb.

Three areas (fig. 14) in the northwestern part of the 

Hailey quadrangle were sampled in more detail than the 

regional geochemical survey. Both stream-sediment samples 

and the heavy-mineral-fraction of stream sediments (concentrates) were collected in these areas, and the results of that 

sampling are reported in Kiilsgaard and Smith (in press).

In China and Canada, some black shale beds are characterized by enrichments in platinum-group elements, gold, 

arsenic, and zinc and molybdenum- and nickel-sulfide minerals (Coveney and Nansheng, 1991; Grauch and others, 

1991). Grauch indicated that the mineralization is in a single 

stratiform, metal-rich sulfide layer. The sulfide layer is thin, 

from 2 to about 15 cm in thickness, and commonly overlies 

a phosphorite layer that is as thick as a meter. Some sediment 

samples associated with Paleozoic rocks in the Hailey quadrangle are enriched in molybdenum, nickel, arsenic, zinc, 

and phosphorus (Malcolm and Smith, 1992), and black shale 

in the Hailey quadrangle should be investigated for the 

occurrence of molybdenum-nickel sulfide minerals.

mineralized area are hosted in quartzite (Van Noy and others, 1986) of the upper part of the Wood River Formation 

(Worl and Johnson, this volume). Mineralized areas containing black shale commonly have high background concentrations of elements that define some of the element suites. 

Because of the high background produced by black shale, the 

occurrence of mineral deposits that are not closely associated 

with black shale might be underestimated in the area where 

Paleozoic rocks crop out.

SPECULATIVE TARGETS BASED ON 

GEOCHEMISTRY

Some areas in the Hailey quadrangle have strong 

geochemical signature but are not associated with known 

mining districts. Two areas in the southeastern part of the 

Hailey quadrangle, areas B and E (fig. 13), have strong 

geochemical signatures. Area B has an inner middle zone 

signature; area E has an outer zone signature. Area B is spatially associated with the buried caldera proposed by Leeman 

(1982) (fig. 13), who estimated that the main eruptive activity occurred 5-10 million years ago. The youngest (3 Ma)

REFERENCES CITED

Anderson, A.L., 1951, Metallogenic epochs in Idaho: Economic 

Geology, v. 46, p. 592-607.

Bennett, E.H., 1980, Granitic rocks of Tertiary age in the Idaho 

batholith and their relation to mineralization: Economic Geology, v. 75, p. 278-288.

Burnham, C.W., and Ohmoto, H., 1980, Late-stage processes of felsic magmatism: Mining Geology Special Issue, v. 8, p. 1-11.

Chambers, J.M., Cleveland, W.S., Kleiner, B., and Tukey, P.A., 

1983, Graphical methods for data analysis: Boston, Duxbury 

Press, 395 p.

Coveney, R.M., and Nansheng, C, 1991, Ni-Mo-PGE-Au-rich ores 

in Chinese black shales and speculations on possible analogues 

in the United States: Mineralium Deposita, v. 26, no. 2, p. 

83-88.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Crock, J.G., Lichte, F.E., and Briggs, P.H., 1983, Determination of 

elements in National Bureau of Standards geological reference 

materials SRM 278 obsidian and SRM 688 basalt by inductively coupled argon plasma-atomic emission spectrometry: Geostandards Newsletter, v. 7, p. 334-340.

Dover, J.H., Berry, W.B.N., and Ross, R.L, Jr., 1980, Ordovician 

and Silurian Phi Kappa and Trail Creek Formations, Pioneer 

Mountains, central Idaho Stratigraphic and structural
INTERPRETATION OF REGIONAL GEOCHEMISTRY L21

revisions, and new data on graptolite faunas: U.S. Geological 

Survey Professional Paper 1090, 54 p.

Ferguson, R.B., Price, V., and Baucom, E.I., 1976, Field manual for 

stream sediment reconnaissance: U.S. Department of Energy 

Open-File Report GJBX-30(77), 55 p.

Fisher, F.S., and May, G.D., 1983, Geochemical characteristics of 

metalliferous Salmon River sequence, central Idaho: U.S. Geological Survey Open-File Report 83-670, 28 p.

Goldfarb, R.J., Leach, D.L., and Speckman, W.S., 1983, An application of rank-order statistics to exploration geochemistry 

[abs.]: Helsinki, Finland, Association of Exploration 

Geochemists, p. 30.

Grauch, R.I., Coveney, R.M., Jr., Murowchick, J.B., and Chen Nansheng, 1991, Black shales as hosts for unconventional platinum-group-element resources? Examples from southern China 

and the Yukon, Canada, and implications for U.S. resources, in 

Good, E., Slack, J., and Kotra, R., eds., USGS Research on 

Mineral Resources 1991, Program and Abstracts, Seventh 

Annual V.E. McKelvey Forum on Mineral and Energy 

Resources: U.S. Geological Survey Circular 1062, p. 33.

Grimes, J.G., 1982a, Hydrogeochemical and stream sediment 

reconnaissance basic data for Hailey and Challis quadrangles, 

Idaho: U.S. Department of Energy Open-File Report 

GJBX-55(82), 121 p.

 1982b, Supplement to hydrogeochemical and stream sediment reconnaissance basic data reports K/UR-405 and K/ 

UR-408 through K/UR^43 [GJBX-52(82) through 

GJBX-88(82)]: U.S. Department of Energy Open-File Report 

GJBX-51(82), 25 p.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, p. 579-592.

Howarth, R.J., Koch, G.S., Plant, J.A., and Lowry, R.K., 1981, 

Identification of uraniferous granitoids in the USA using 

stream sediment geochemical data: Mineralogical Magazine, 

v. 44, p. 455^70.

Johnson, K.M., and Worl, R.G., 1989, Preliminary assessment of 

mineral resources of the Hailey and western Idaho Falls I°x2° 

quadrangles, Idaho: U.S. Geological Survey Open-File Report 

89-639, p. 17-22.

 in press, Assessment of the potential for undiscovered mineral resources in the Hailey I°x2° quadrangle and the western 

part of the Idaho Falls I°x2° quadrangle, Idaho: U.S. Geologial 

Survey Bulletin 2064-S.

Kiilsgaard, T.H., 1982, Analytical determinations from samples 

taken in the Ten Mile West Roadless Area, Boise and Elmore 

Counties, Idaho: U.S. Geological Survey Open-File Report 

82-1099, 32 p.

Kiilsgaard, T.H., Freeman, V.L., and Coffman, J.S., 1970, Mineral 

resources of the Sawtooth Primitive Area, Idaho: U.S. Geological Survey Bulletin 1319-D, p. D1-D174.

Kiilsgaard, T.H., and Hingley, Frank, 1989, Regional geology of 

the northwestern part of the Hailey I°x2° quadrangle and ore 

deposits of the Atlanta district, Idaho, in Winkler, G.R., SoulHere, S.J., Worl, R.G., and Johnson, K.M., eds., Geology and 

mineral deposits of the Hailey and western Idaho Falls I°x2° 

quadrangle quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 35-36.

Kiilsgaard, T.H., Lewis, P.S., and Bennett, E.H., in press, Plutonic 

and hypabyssal rocks of the Hailey I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 2064-U.

Kiilsgaard, T.H., and Smith, C.L., in press, Geology, geochemistry, 

and mineral resources of the lower part of the Middle Fork 

Boise River drainage basin, Boise and Elmore Counties, Idaho: 

U.S. Geological Survey Bulletin 2064-AA.

Leeman, W.P., 1982, Geology of the Magic Reservoir area, Snake 

River Plain, Idaho, in Bonnichsen, Bill, and Breckenridge, 

R.M., eds., Cenozoic geology of Idaho: Idaho Bureau of Mines 

and Geology Bulletin 26, p. 369-376.

Lewis, R.S., 1990, Geology, geochemistry and mineral potential of 

Cretaceous and Tertiary plutons in the eastern part of the Soldier Mountains, Idaho: Corvallis, Oregon State University, 

Ph.D. dissertation, 214 p.

Lewis, R.S., and Kiilsgaard, T.H., 1991, Eocene plutonic rocks in 

south central Idaho: Journal of Geophysical Research, v. 96, 

no. B8,p. 13295-13311.

London, D., 1990, Internal differentiation of rare-earth pegmatites A synthesis of recent research, in Stein, H.J., and Hannah, J.L., eds., Ore-bearing granite systems Petrogenesis and 

mineralizing processes: Geological Society of America Special 

Paper 246, p. 35-50.

Malcolm, M.J., and Smith, C.L., 1992, Analytical results and sample locality maps of USGS and NURE samples from the Hailey 

I°x2° quadrangle, Idaho: U.S. Geological Survey Open-File 

Report 92-24, 267 p.

Motooka, J.M., 1988, An exploration geochemical technique for 

the determination of preconcentrated organometallic halides 

by ICP-AES: Applied Spectroscopy, v. 42, p. 1293-1296.

Nash, J.T., 1988, Interpretation of the regional geochemistry of 

the Tonopah I°x2° quadrangle, Nevada, based on analytical 

results from stream-sediment and nonmagnetic heavy-mineral-concentrate samples: U.S. Geological Survey Bulletin 

1849, 28 p.

Ovchinnikov, L.N., and Grigoryan, S.V., 1971, Primary halos and 

prospecting for sulfide deposits, in Geochemical exploration: 

International Geochemical Exploration Symposium, 3rd, Toronto, Canada, April 16-18,1970; Canadian Institute of Mining 

and Metallurgy Special Volume 11, p. 375-380.

Rose, A.W., Hawkes, H.E., and Webb, J. S., 1979, Geochemistry 

in mineral exploration (2nd ed.): New York, Academic Press, 

657 p.

Ross, C.P., 1931, A classification of the lode deposits of south-central Idaho: Economic Geology, v. 26, p. 169-185.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Simons, F.S., 1981, A geological and geochemical evaluation of the 

mineral resources of the Boulder-Pioneer Wilderness Study 

Area, Blaine and Custer Counties, Idaho: U.S. Geological Survey Bulletin 1497-C, p. 85-180.

Snee, L.W., 1989, 40Ar/39Ar thermochronology of mineral deposits 

in the southern part of the Idaho batholith [abs.]: U.S. Geological Survey Open-File Report 89-639, p. 37-38.
L22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Tauson, L.V., Ovchinnikov, L.N., Polikarpochkin, V.V., and Grigoryan, S.V., 1971, The use and development of geochemical 

prospecting methods for ore deposits in the U.S.S.R., in 

Geochemical exploration: International Geochemical Exploration Symposium, 3rd, Toronto, Canada, April 16-18, 1970; 

Canadian Institute of Mining and Metallurgy Special Volume 

2, p. 42-43.

Toth, M.I., King, H.D., Kulik, D.M., and Leszcykowski, A.M., 

1987, Mineral resources of the King Hill Creek Wilderness 

Study Area, Elmore County, Idaho: U.S. Geological Survey 

Bulletin 1721-B, 8 p.

Tschanz, C.M., and Kiilsgaard, T.H., 1986, Geologic appraisal of 

mineral resources in the eastern part of the Sawtooth National 

Recreation Area, Idaho, in Mineral resources of the eastern part 

of the Sawtooth National Recreation Area, Custer and Blaine

Counties, Idaho: U.S. Geological Survey Bulletin 1545-C, p. 

54-210.

Van Noy, R.M., Ridenour, James, Zilka, N.T., Federspiel, F.E., 

Evans, R.K., Tuchek, E. T., and McMahan, A.B., 1986, Economic appraisal of the eastern part of the Sawtooth National 

Recreation Area, Idaho: U.S. Geological Survey Bulletin 

1545-E, p. 232^72.

Vine, J.D., and Tourtelot, E.B., 1970, Geochemistry of black shale 

deposits A summary report: Economic Geology, v. 65, p. 

253-272.

Worl, R.G., and Johnson, K.M., 1989, Geologic terranes and mineral deposit types in the Hailey and western Idaho Falls 1 °x2° 

quadrangles, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds., Geology and mineral deposits 

of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, p. 3-16.
Lead-Isotope Characteristics of Ore Systems 

in Central Idaho

By Bruce R. Doe and Richard F. Sanford

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-M

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Ml

Introduction.......................................................................................................................... 2

The Theory................................................................................................................... 4

The Model..................................................................................................................... 5

Sulfur Isotopes.............................................................................................................. 5

Geology........................................................................................................................ 6

Analytical Techniques.......................................................................................................... 8

Data....................................................................................................................................... 9

Lead Isotopes................................................................................................................ 9

Sulfur Isotopes.............................................................................................................. 15

Discussion............................................................................................................................. 15

Nature of Basement Source Lead................................................................................. 15

Consideration of Other Lead Sources........................................................................... 19

Model for Lead Derivation........................................................................................... 20

Comparison with Major Tin-Producing Areas............................................................. 21

Origin of Granite.......................................................................................................... 23

References Cited................................................................................................................... 26

FIGURES

1, 2. Maps showing sample localities:

1. Chain's quadrangle ......................................................................................................................................... M2

2. Hailey quadrangle.......................................................................................................................................... 3

3, 4. Diagrams showing:

3. Isotopic relationships between uranium, thorium, and lead in the Earth's crust........................................... 4

4. Sulfur-isotope data for some magmatothermal ore deposits.......................................................................... 6

5-6. Graphs showing ore minerals and igneous rocks of the Challis and Hailey quadrangles:

5. 207Pb/204Pb versus 206Pb/204Pb .................................................................................................................... 18

6. 208Pb/204Pb versus ^Pb/^Pb....................................^ 19

7. Graph showing lead-isotope areas of Zartman (1974)............................................................................................ 21

8. Map showing lead-isotope data and simplified Bouguer gravity anomalies, Challis quadrangle........................... 22

9-11. Graphs showing 208Pb/204Pb versus 206Pb/204Pb:

9. Ore minerals and sedimentary rocks.............................................................................................................. 23

10. Ore minerals of Challis and Hailey quadrangles and Mesozoic and Cenozoic ore minerals

of the Belt Supergroup................................................................................................................................... 24

11. Ore minerals of Challis and Hailey quadrangles and ore minerals from largest

tin-producing countries, Malaysia and Bolivia.............................................................................................. 25

TABLES

1. Maximum 206Pb/204Pb for Mesozoic and Cenozoic magmatothermal ore deposits in various dollar-value

production groups.......................................................................................................................................................... M5

2. Hypothesis for lead and sulfur isotopes in mineral prospect evaluation........................................................................ 7

3. Sample information, Challis and Hailey I°x2° quadrangles, Idaho.............................................................................. 10

4. Lead and sulfur isotopic compositions, Challis and Hailey I°x2° quadrangles, Idaho................................................. 16

5. U, Th, and Pb concentrations and calculated initial lead ratios for igneous and sedimentary rocks,

Challis and Hailey I°x2° quadrangles, Idaho................................................................................................................ 18
Lead-Isotope Characteristics of Ore Systems

in Central Idaho

By Bruce R. Doe 1 and Richard F. Sanford2

ABSTRACT

More than 60 new lead-isotope analyses on ore minerals, igneous rocks, and shale were used to test the use of lead 

isotopes in mineral prospect evaluation of Cretaceous and 

Tertiary magmatothermal deposits of central Idaho in the 

Challis and Hailey I°x2° quadrangles. The lead-isotope pattern is complex but separable into two groups: group A has 

many values of 206Pb/204Pb of 18.0 or less but with a continuum of values that exceed 21, whereas group B always has 

values of 2o6Pb/204Pb of 18.5 or more and most values are 

between 19 and 20. Although samples of groups A and B 

have similar values of 206Pb/204Pb, values of 208Pb/204Pb are 

always greater for group A than for group B. Data for group 

A are similar to those for Early Proterozoic crystalline-rock 

terranes of the Rocky Mountains, whereas data for group B 

are similar to those for deposits in the Phanerozoic sedimentary rock terrane of the Great Basin. Large fluorine-poor 

molybdenum-porphyry deposits generally have lower values 

of 206Pb/204Pb (most notably Thompson Creek), although 

values are in both isotopic groups (for example, group A, 

Thompson Creek; group B, White Cloud). The Clayton Silver mine the largest silver deposit in Idaho outside the 

Coeur d'Alene district is in group A but has a value of 

206Pb/204Pb between 18 and 19. Tin granites can also be in 

either group A or B and cannot be distinguished from molybdenum deposits by lead isotopes.

The area of interest is mostly within the central Idaho 

gravity low, which may represent extensions of the Idaho 

batholith in the subsurface. Although some exposures of 

Early to Middle Proterozoic sedimentary rocks equivalent to 

the Belt Supergroup are present around the margins of the 

area of interest, Precambrian crystalline rocks are present 

only in the eastern part of the Challis quadrangle. Two major 

areas containing group A lead isotopes in the Challis quadrangle are in areas of Bouguer gravity highs within the 

regional low and possibly indicate the presence of structural

'U.S. Geological Survey, National Center, Reston, Virginia 22092. 

2U.S. Geological Survey, Federal Center, Denver, Colorado 80225.

highs in the crystalline Precambrian basement. Thus, the 

group A lead isotopes may reflect a buried terrane of geographically restricted surface exposure. Two major areas in 

the Challis quadrangle containing group B lead isotopes 

have magnetic anomalies but not Bouguer gravity anomalies. Both of these areas are within a Basin and Range terrane 

south of the Trans-Challis fault system that trends southwest-northeast across the Challis I°x2° quadrangle. Lead 

isotopes do not reflect a Rocky Mountain style of Proterozoic metamorphosed crystalline rocks at depth. Precambrian 

basement, if present, is deeper than the horizon at which isotopic signatures were acquired by magmas and ore fluids.

Central Idaho differs from the normal situation in which 

834S is -5>834S<+3 in the best magmatothermal deposits 

because 834S tends to be high in the best deposits (for example, Thompson Creek >+8). Consideration thus should be 

given to prospects having nonradiogenic lead isotopes and 

heavy sulfur isotopes. Further confirmation of this unusual 

hypothesis is needed.

Both lead-isotope signatures and sulfur-isotope data of 

igneous rocks and ores are representative of crustal rocks 

and do not indicate mantle influences. Molybdenum and tin 

also are enriched in the crust. The granites therefore are most 

likely crustal melts or, if mantle melts, were extensively 

modified by reactions within the crust. Eocene tin granite has 

the same lead-isotope signature as Cretaceous and Eocene 

molybdenum granites, whether the lead-isotope signature is 

in group A or B. This similarity is surprising because molybdenum granites are classified as I-type (igneous rock parent) 

and tin granites as S-type (sedimentary rock parent). The 

Eocene tin granites could have formed, however, by remelting sulfide-mineralized Cretaceous granite or by extensively 

reacting tin granite melts with mineralized Cretaceous granite. The lead-isotope signatures would then be inherited from 

the Cretaceous granite; the inherited sulfur would keep the 

tin granite melts reduced, and the observed stannite mineralization would result rather than cassiterite mineralization. If 

the reduced tin granite magmas were produced from reactions with carbon-rich material, the material must have had a

Ml
M2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

116° 115° 114°

45'

Camas Creek 

Sn

Singheiser 

 Mo

K.G. D

Mountain 

King Lost Packer Parker Mountain 

» 

Mo

Deadwood

*> 

BPM

Seafoam Lake

Sunrise

Mo

Sunbeam

GROUPA

£ Sn

Warm Springs

Red Mountain Mt Q reylock

Thompson Creek M 

Mo

Ramshorn Pacific

H Q Mountain

To0,

,0 )01 n u

0 Sn 

Stanley Lake

X I n Clayton 

Silver

O

Hoodoo

O

O

CUMO

44°

Mo Little Falls

0°

GROUPB 

Sn ^ear R |ver' North

O White Cloud 

TimberlineO ^ Q 

Q Mo

25 MILES

J

Figure 1. Map showing sample localities, Challis I°x2° quadrangle, Idaho. Names are included for selected localities including all granite and rhyolite and all mineral deposits having 206Pb/204Pb of less than 18.0. The dashed line separates lead-isotope compositions of group 

A and group B. Symbols: open circle, ore having 206Pb/204Pb greater than 19.1; open square, ore having 206Pb/204Pb 18.1-19.1; solid 

square, ore having 206Pb/204Pb less than 18.0; solid circle, granite- or rhyolite-type (Sn, tin; Mo, molybdenum; BPM, base- and preciousmetals); X, shale.

low lead content, such as petroleum, natural gas, or perhaps 

coal. Eocene molybdenum granite and rhyolite then could 

have evolved without extensive reaction with mineralized 

Cretaceous intrusive rocks.

INTRODUCTION

New lead-isotope analyses for 38 samples of ore minerals, 9 whole-rock and potassium feldspar samples from 

molybdenum porphyry units, 7 whole-rock samples of tin 

granite, and 2 samples of shale from the Challis and Hailey 

I°x2° quadrangles, together with 12 previously published 

analyses (Hall and others, 1978; Davis, 1978), were used to 

test the use of lead isotopes in mineral prospect evaluation 

of Cretaceous and Tertiary magmatothermal deposits (figs. 

1, 2). The northwestern part of the Challis quadrangle and

the southwestern part of the Hailey quadrangle were not 

sampled. This study documents the conclusions of Doe and 

Delevaux (1985) that the lead-isotope ratios form two 

groups: group A, similar to lead-isotope ratios in the Rocky 

Mountain provinces, and group B, similar to those in the 

Basin and Range provinces. These data, data by Small 

(1968), and 59 additional analyses were used to further subdivide the major isotopic groupings into six subgroups by 

Sanford and others (1989) and Sanford and Wooden (this 

volume). The geology of the Challis quadrangle is 

described by Fisher and others (1983), Mclntyre (1985), 

and Fisher and Johnson (1987b) and the geology of the 

Hailey quadrangle by Worl and others (1991).

Molybdenum granite and tin granite are thought to form 

by quite different processes; notably, tin granite differentiates under more highly reduced conditions than molybdenum 

granite (Ishihara, 1977). The molybdenum porphyry granite
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS

116°

M3

114°

44

Wolf Mountain Sn 

West

Sn

Big Silver Creek Mississippian Shale X 

O GROUPB

Webfoot O 

O

D

Carrie Leonard

Horn Silver O DoMarhide\

\ X

\

O

Milligen Formation

\

GROUP A

O

__ Minnie Moore

O

BPM

McCoy

43°

25 MILES

Figure 2. Map showing sample localities, Hailey I°x2° quadrangle, Idaho. Names are included for selected localities including all granite 

and rhyolite and all mineral deposits having 206Pb/204Pb of less than 18.0. The dashed line separates lead-isotope compositions of group A 

and group B. Symbols: open circle, ore having 206Pb/204Pb greater than 19.1; open square, ore having 206p^/204p^ 18.1-19.1; solid square, 

ore having 206Pb/204Pb less than 18.0; solid circle, granite- or rhyolite-type (Sn, tin; BPM, base- and precious-metals).

of central Idaho is included in a belt of subduction-related, Itype, molybdenum-enriched plutons that extends from eastcentral California to Northwest Territories (Westra and 

Keith, 1981; Hall and others, 1984). Molybdenum porphyry 

granite of central Idaho is low in fluorine (model 21b, Theodore, 1986), generally O.OX percent, is believed to be free 

of tin minerals (Westra and Keith, 1981), and differs from 

molybdenum porphyry granite of the more famous Climaxtype fluorine-rich ores (as much as 2-3 percent F) in Colorado and northern New Mexico (model 16, Ludington, 1986), 

which can contain tin minerals (Westra and Keith, 1981). 

Lead-isotope compositions of Climax-type molybdenum 

porphyry granite are given by Stein (1985); Church and others (1986) give lead-isotope data for a low-fluorine porphyry 

granite in Washington. Tin has almost no production in the 

United States, and, because tin-mineralized rocks (tin as stannite) and bodies of S-type granite, tin granite, are known in 

central Idaho, tin was selected as a second commodity for

emphasis. Because the main tin mineralization is stannite in 

polymetallic veins in black shale, no mineral deposit model 

completely fits the Idaho setting; however, the mineralization 

was said to be of the Bolivian type by Hall (1985), and perhaps the porphyry tin (model 20a, Reed, 1986) and tin-polymetallic veins (model 20b, Togashi, 1986) models may be of 

interest. A variety of samples from silver-producing mines 

were also analyzed including a sample from the Clayton Silver mine, the largest producer of silver in Idaho outside the 

Coeur d'Alene district.

The goals of the study are to (1) determine the use of 

lead isotopes in central Idaho for mineral prospect evaluation 

using the methods outlined by Doe and Stacey (1974) and 

Doe (1979); (2) ascertain if coupling of sulfur isotopes and 

lead isotopes might refine this evaluation, as was done by 

Doe and others (1986) for west-central Montana; (3) examine if there is any information in the lead isotopes to show 

why molybdenum and tin are so common in central Idaho
M4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

(for example, different or unique source rocks); and (4) 

refine the plumbotectonic classification of Zartman (1974) 

for central Idaho. Gravity (Bankey and Kleinkopf, 1988) and 

magnetic (Mabey and Webring, 1985; Webring and Mabey, 

1987) geophysical data are utilized to strengthen the interpretations based on isotopic data.

Acknowledgments. Most of the lead-isotope analyses 

of ore minerals were made under the supervision of M.H. 

Delevaux by Stephen Kish (now at Florida State University), 

Ake Johansson (now at Geologiska Institutionen, Stockholm, Sweden), Anne LeHuray (now at Lamont-Doherty 

Geological Observatory), and Holly Stein (now at the U.S. 

Geological Survey). Discussions with D. Mabey, M. 

Webring, and W. Hanna of the U.S. Geological Survey on 

geophysical measurements and their possible meaning were 

very helpful. Samples were provided by and we benefitted 

greatly from discussion with our colleagues, the late Wayne 

Hall, Frederick S. Fisher, Charles M. Tschanz, Thor Kiilsgaard, and S. Warren Hobbs. This paper was originally to be 

written by Wayne Hall, but he died before he was able to do 

so; we here recognize his enormous contributions to the 

study of Idaho geology.

THE THEORY

The theory of lead isotopes has been discussed by a 

number of authors. In order that this report may be self contained, we excerpt the following from a readily accessible 

source (Doe and Stacey, 1974, p. 758-759).

The variations in lead isotopic composition are the result of radioactive 

decay of 238U and 235U to the radiogenic isotopes 206Pb and 207Pb (uranogenic leads) respectively and 232Th to the radiogenic isotope 208Pb (thorogenic lead). The fourth stable lead isotope, 204Pb, has no long-lived 

radioactive parent. The physicochemical effects that are so all important on 

the stable light isotopes are very minor in the case of heavy elements such 

as lead; variations of 238U/235U in nature are only 0.07 percent (an empirical justification for this statement is given in Doe [and others, 1966]). The 

generalized relationships of primordial and radioactivity produced (i.e., 

radiogenic) stable lead isotopes are shown in [fig. 3 of this report]. Because 

it is reasonable to believe that the earth began with some primeval lead 

(primordial lead) just as it began with some silver and other elements, the 

primeval lead isotope values are adopted from the least radiogenic leads 

ever found, i.e., the values in the troilite phase of meteorites * * * [fig. 3 of 

this report] shows that the abundance of 206Pb has about doubled since the 

earth formed, 207Pb has increased by about one-half, and 208Pb by about 

one-third. Unlike U-Th-Pb dating where the emphasis is placed on the lead 

produced by radioactive decay of uranium and thorium present in a phase, 

in common lead studies emphasis is placed on interpreting the significance 

of the initial lead isotopic composition of a phase, i.e., the lead that cannot 

be accounted for by the in situ decay of uranium and thorium in the phase 

being analyzed.

The most popular way of representing lead isotopic compositions is 

through ratios of a radiogenic isotope to the nonradiogenic isotope whose 

abundance does not change with time 206Pb/204Pb, 207Pb/204Pb, and 

208pb/204pj.) because such representation are subject to the simplest mathematical interpretation. A present-day lead isotope ratio evolves from an 

initial lead isotope ratio plus radiogenic additions by radioactive decay 

involving the product of a time term with the ratio of the radioactive parent 

isotope to the nonradiogenic isotope of the daughter element (238U/204Pb,

235U/204Pb, and 208Pb/204Pb which are always normalized to the present 

day to cancel variable effects of radioactive decay) * * * Although the lead 

isotope ratios are not subject to physicochemical fractionation, the ratios of 

the parent radioactive isotope to the nonradiogenic isotope of the daughter 

element are. Changes in these ratios eventually result in differences in lead 

isotope ratios. For example, the present-day value of 206Pb/204Pb in a Precambrian mineral such as zircon or monazite will be very large (perhaps 

several thousand) because 238U/204Pb is very large (perhaps tens of thousands). In contrast, the present-day values of 206Pb/204Pb in a Precambrian 

mineral such as galena or feldspar will be relatively small (perhaps less 

than 20) because 238U/204Pb is near zero. Variations in the values of parent/ 

daughter for rocks are more subtle for example, a subalkaline basalt may 

have a value of 238U/204Pb of about 6, whereas a silicic volcanic might be 

more like 20 but usable variations in lead isotope ratios still result. Customarily lead isotopes have evolved through a sequence of stages which 

will be discussed below. A number of ores and igneous rocks have leads 

that evolved under conditions that closely approach single-stage conditions, that is, where the only changes in the value of the parent/daughter 

ratio are due to the radioactive decay of the parent. These are the model 

leads and the model lead ages approach the time of formation of the deposit 

or igneous rocks. Many ores and igneous rocks have leads that clearly did 

not form under such simple conditions and are anomalous. A number of 

these anomalous leads approximate two-stage conditions, that is, the values 

of the parent/daughter ratio were altered sometime after the earth was 

formed, usually to a variety of values, so that the present-day lead isotope 

ratio evolved under two stages of parent/daughter values. Leads that underwent two-stage evolution are called anomalous because model-lead "formation" ages calculated from them have a demonstrated tendency to be 

grossly incorrect. Secondary Pb-Pb isochron ages may often be calculated, 

making use of the near-constant value of 238U/235U, for either the formation-age or the age of the source material from which the lead was derived 

(source-ages), if one of the ages can be independently determined. Because 

the earth has had a complex history, often three-stage systems must be 

involved in the evolution of lead in many ores and igneous rocks. Threestages systems are difficult to interpret, but several special cases that have 

some characteristics of two-stage systems [can be solved].

NO

PARENT 

KNOWN

238 235

_ U

204 206 207 

Pb

tAK

H

EXPLANATION

Amount remaining 

Amount decayed

Initial amount 

Amount formed

Figure 3. Isotopic relationships between uranium, thorium, and 

lead in the Earth's crust. Modified from Cannon and others (1961, 

fig. 1). Reproduced with permission, as modified, from Economic 

Geology Publishing Company.
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M5

Table 1. Maximum 206Pb/204Pb for Mesozoic and Cenozoic magmatothermal ore deposits in various dollar-value production groups. 

[Dollar amounts not adjusted for inflation. Modified from Doe (1979)]

Maximum observed

Production (dollars) Largest districts or deposits in production group

>$ 1,500,000,000

$ 150,000,000-$ 1,500,000,000

$ 15,000,000-$ 150,000,000

$1,500,000-$ 15,000,000 

^$1,500,000

18.0 Butte, Montana; Bingham, Utah; Climax and Urad-Henderson, Colorado; GlobeMiami, Arizona; Santa Rita-Hanover and Tyrone, New Mexico.

19.1 Tintic and Park City, Utah; pene- and post-caldera ores, San Juan Mountains and 

Leadville-Gilman, Colorado; Bisbee, Arizona.

22 Selected deposits include Wood River, Idaho; Ophir and Milford, Utah; Alma and 

Central City-Silver Plume, Colorado.

20 Selected deposits include Star and Big Cotton Wood, Utah; Hilltop, Colorado.

25 Santaquin (Mt. Nebo), Utah; Yarmony and precaldera ores (Embargo district), San 

Juan Mountains, Colorado.

THE MODEL

The model is well illustrated in table 1, modified from 

Doe (1979). In the 15 years since the table was first published, there has been little change in dividing isotopic compositions between the economic groupings. Some supergiant 

deposits have been found that have associated galenas with 

values of 206Pb/204Pb of 18 or more, and a bounding value of 

18.1 might work a little better than the value of 18.0 given in 

table 1; however, some grayness in the dividing isotope-ratio 

values is to be expected. Doe (1979, p. 229) pointed out that, 

although all medium-sized to supergiant magmatothermal 

deposits known at the time had values of 206Pb/204Pb of 19.1 

or less and ratios similar to plutonic leads, not all prospects 

having the appropriate lead-isotope ratios may be expected 

to be of medium to supergiant in size.

Of course, the lead isotope data are only pointing to trends of economic 

potential, and many valueless prospects are to be expected with 206Pb/204Pb 

values less than 19.1. Conversely, not all districts currently inactive have 

been mined out, and much more may remain to be found. A case in point is 

the Leadville/Gilman grouping which, according to Ogden Tweto (oral 

commun., 1977) might move into the supergiant category and be a leadzinc skarn-type deposit to rival porphyry coppers, if the excessively thick 

cover did not hamper prospecting.

This cautionary note should not be ignored, and the 

study of the Hailey and Challis quadrangles forms an interesting test of the statement.

We still know of no operating Cretaceous or Tertiary 

magmatothermal deposit that has a value of 206Pb/204Pb of 

20 or more. The observation that the more radiogenic the 

lead isotopes, the less likely one is to find an economic ore 

deposit is probably a reliable indicator. If exceptions are 

found, they are likely to involve the precious metals gold, 

silver, and platinum that respond to monetary factors as 

well as to utilitarian values. Lateral-secretion deposits can 

have more radiogenic values, such as those in southeast Missouri with values of 206Pb/204Pb of 20.0-22.5, and a judgment must be made as to just what class of ore deposit to

which the prospect belongs. This judgment is also not always 

easy. Other kinds of ore deposits may also be involved in a 

regional study, such as bedded ores in black shale of 

essentially syngenetic origin. These usually have model lead 

ages in approximate agreement with the sedimentary or 

submarine volcanic host rocks by both the 206Pb/204Pb and 

208pb/204 Pb models of Stacey and Kramers (1975). In 

the Cretaceous-Tertiary magmatogenic ore deposits, 208Pb/ 

204Pb provides little information of value in plumbic 

prospecting but commonly helps to distinguish the 

Cretaceous-Tertiary deposits because agreement between 

the 206Pb/204Pb age and the 208Pb/204Pb age is poor.

SULFUR ISOTOPES

Doe and others (1986) presented a first attempt to combine sulfur isotopes and lead isotopes to refine the plumbic 

prospecting evaluation, and Rye and others (1980) used sulfur isotopes to classify ore deposit types. We expand on both 

studies herein.

Unlike lead-isotope ratios, which are controlled by 

radioactive decay and mixing, sulfur-isotopic variations are 

a consequence of physico-chemical effects and, perhaps, 

mixing. Data are usually expressed relative to a standard,

.32,

8 =

>V &)sample 1 

_(. S/ ^standard _

x 1,000

with the values reported in per mil. Although sulfur-isotope 

ratios are difficult to utilize by themselves in mineral-prospect evaluation, especially on single samples, they help us 

refine the lead-isotope results.

Figure 4 shows values of 834S for a variety of hydrothermal ore deposits. Magmatothermal deposits such as porphyry copper deposits generally have values of 534S for 

pyrite of between -3 and +1 (Ohmoto and Rye, 1979). 

Because we are analyzing galena, and because sulfur
M6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Galore Creek, B.C. 

Valley Copper, B.C. 

Craigmont, B.C. 

Butte, Montana 

Bingham, Utah 

Tintic, Utah 

Marysvale, Utah 

Chino, New Mexico 

Ajo, Arizona 

Sierrita, Arizona 

Twin Butte, Arizona 

Morococha, Peru

El Salvador, Chile 

______I

i i

-20

834 S, IN PER MIL

20

Providencia 

Casapalca 

Pasto Bueno 

Panasqueira 

Darwin 

Mogul i 

Bluebell 

Black Hills 

Cortez 

Kuroko 

Pine Point 

Echo Bay 

Greece 

Park City

-30 -20 -10 0 10 

B 83" S, IN PER MIL

20 30

Figure 4. Sulfur-isotope data for some magmatothermal ore deposits. Solid line or area indicates sulfide mineral; open line or 

area indicates sulfate mineral; dashed line indicates late-stage 

mineral. A, Porphyry copper deposits. Modified from Ohmoto and 

Rye (1979, fig. 10.12). Reproduced with permission from John 

Wiley and Sons. B, Various hydrothermal deposits. Modified 

from Rye and Ohmoto (1974, fig. 1). Reproduced with permission, as modified, from Economic Geology Publishing Company.

isotopes in galena are usually somewhat isotopically lighter 

than sulfur isotopes in pyrite, we use a range for igneous 

rocks of -5 to +3. There are a few exceptions; values for 

Galore Creek are around -10 and values for scattered samples from some other deposits are close to -10 (Craigmont 

and Tintic). No subaerial magmatothermal deposits are 

known to have values of 534S greater than +6 (the extreme 

value for the Henderson molybdenum porphyry of Colorado; 

Stein, 1985). Normally, however, heavy sulfur-isotope values are indicative of an interaction with evaporites, as for

Mississippi Valley deposits (such as Pine Point), and some 

light sulfur-isotopic values are in ores associated with 

organic material (such as Mogul) or where sulfur in the ore 

fluids is mainly in the form of sulfates (anhydrite, barite, 

alunite, and so on). Echo Bay is an unusual Precambrian uranium-nickel-silver-copper deposit.

Although we emphasize subaerial magmatothermal 

deposits in this study, a number of other kinds of ore deposits 

must be taken into account. Sulfur-isotope values for submarine volcanogenic massive-sulfide deposits (such as kurokotype deposits) can range widely, and the sulfur isotopes can 

be heavy as a result of the role of seawater in the ore fluid. 

As seen in figure 4, however, the more values of 534S for 

galena are lighter than -5, the less likely that one is dealing 

with a major magmatothermal ore deposit. In fact, few major 

ore deposits of any origin contain such light sulfur isotopes, 

although some notable exceptions are known among shalehosted ores, such as the Kupferschiefer in Germany and 

Udokan in the Soviet Union. The same predictive statement 

could be said for values greater than +3 for magmatothermal 

ores; however, a number of important ore deposits of other 

origins especially of lateral-secretion (Mississippi Valley) 

and sedimentary exhalative (SEDEX) origin exist and 

must be considered in the present study.

By combining lead and sulfur isotopes, the plumbicprospecting evaluation can be refined (table 2). In many 

cases, whether one is looking at a magmatothermal deposit 

can be determined just from looking at the lead and sulfur 

isotopes; however, incorporation of as much other geologic 

information as possible improves the isotopic assessment. 

For example, volcanogenic and shale-hosted deposits 

should be of an age similar to the host rocks, lateral-secretion deposits normally form at temperatures lower than economic magmatothermal deposits, a crosscutting ore is not 

stratiform, and so forth.

GEOLOGY

The stratigraphy, structure, and geologic history of the 

study area have been extensively described as a result of the 

Conterminous United States Mineral Assessment Program 

(CUSMAP) of the U.S. Geological Survey and associated 

research groups (Mclntyre, 1985; Fisher and Johnson, 

1987a; Link and Hackett, 1988; Winkler and others, 1989; 

this volume). We briefly review the geology of the parts of 

the Challis and Hailey quadrangles that were sampled for 

lead isotopes.

Although Middle Proterozoic metasedimentary rocks 

of the Belt Supergroup are widely exposed north of the study 

area, the only Precambrian rocks exposed in the study area 

are in the structural core of the Pioneer Mountains (Dover, 

1981). Highly deformed Middle Proterozoic or older gneiss 

is overlain by less deformed, medium- to high-grade, 

younger Proterozoic to Ordovician metasedimentary rocks 

(Dover, 1981). Preexisting and (or) underlying Archean
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M7

Table 2. Hypothesis for lead and sulfur isotopes in mineral prospect evaluation. 

[Modified from Doe and others (1986). For examples of magmatothermal ore deposits, see table 1]

Ore type and largest deposits 206pb/204pb 8*8

Lateral secretion: southeast Missouri, Tri-State, east and central Tennesee 1 '2 .................

Magmatothermal, very small.............................................................................................

Magmatothermal, very small, oxidized .............................................................................

Lateral secretion: Pine Point ............................................................................................

Magmatothermal, large3 ....................................................................................................

Submarine-volcanogenic or shale hosted: Bathhurst, Canada; Rammelsberg,

West Germany (Paleozoic)3 .........................................................................................

Shale hosted: Kupferschiefer, West Germany (Paleozoic) ...............................................

Magmatothermal, medium, oxidized: Pasto Bueno, Peru.................................................

Magmatothermal, supergiant, rejuvenated cratons (Cretaceous-Tertiary)3 .......................

Submarine-volcanogenic or shale hosted: Mt. Isa, Australia (Proterozoic) ......................

Submarine-volcanogenic: Kidd Creek, Canada (Archean)...............................................

............. >19.1 >0

............. >19.1 -3 to +3

............. >19.1 <-3

>18.1-<19.1 >0

............. >18.1-<19.1 -3to+3

>18 1-<19 1 >0

>18 1-<19 1 <-5

............. >18.1-<19.1 <-3

............. <18.1 -3 to +3

............. <18.1 >0

............. <18.1 ~0

lateral-secretion deposits usually plot on or below the evolution curve of Stacey and Kramers (1975) for ^Pb/^Pb versus 206Pb/204Pb.

2Unusual samples from Mississippi Valley deposits have 834S <+3. The most notable exception is the Tri-State district where 834S is 0 to -10.

3Magmatothermal ores usually plot above the curve of Stacey and Kramers (1975) for 208Pb/204PbPb versus 206Pb/w4Pb in rejuvenated cratons; 

however, Creede, Colorado, does not. Submarine volcanogenic ores usually plot on or below the 208Pb/204Pb versus 206Pb/204Pb curve, but the Kuroko 

ores of Japan plot above it. Some molybdenum porphyry deposits in the Challis I°x2° quadrangle have values of 834S >+3 (Howe and Hall, 1985; this 

paper). Because these deposits may be of supergiant size (such as Thompson Creek), an additional refinement would be to survey the sulfur isotopes in 

a region to establish the possibility of an anomalous character.

crust to the south is indicated by xenoliths in lavas of the 

Snake River Plain that suggest Archean crust was present 

prior to major thermal events dated at about 3.4-3.1 Ga and 

2.8 Ga (Leeman and others, 1985).

Paleozoic sedimentary rocks underlie much of the study 

area and are host to numerous ore deposits, many of which 

are represented in this study. These rocks span all time periods from Cambrian to Permian. A continental shelf environment during the Paleozoic in the eastern part of the study area 

is characterized by predominantly shallow water carbonate 

rocks, whereas continental slope and basin environments in 

the western part are characterized by fine-grained, commonly 

carbonaceous, argillaceous rocks of the "black shale belt" 

(Skipp and Hall, 1975; Skipp and Sandberg, 1975; Poole and 

others, 1977; Skipp and Hait, 1977; Hall and others, 1978; 

Hobbs, 1987; McFaddan and others, 1988).

Rocks representing the carbonate shelf include the Cambrian or Ordovician Bay horse Dolomite, Ordovician Ella 

Dolomite, Ordovician Saturday Mountain Formation, Devonian Jefferson Formation, and undifferentiated Proterozoic 

and Paleozoic limestone in roof pendants of the Idaho 

batholith. Ore in these carbonate rocks typically formed by 

replacement, although vein- and breccia-filling are locally 

important (Hobbs, 1987; Hobbs and others, 1987). The Bayhorse Dolomite hosts ore deposits of lead, zinc, silver, and 

fluorite at the Pacific mine and lead, silver, and zinc at the 

Riverview mine (Davis, 1978; Hobbs, 1987). The Ella Dolomite hosts lead, silver, and zinc deposits of the Clayton Silver 

mine (Hobbs, 1987). The Saturday Mountain Formation 

hosts vein and replacement deposits of lead, copper, and zinc 

in the Dryden mine (Mitchell and others, 1986; Hobbs, 1987).

The Jefferson Formation hosts deposits of lead, silver, zinc, 

and gold at the Hilltop mine (Mitchell and others, 1981). A 

total of $24.6 million (values unconnected for inflation) of ore 

has been produced from carbonate-hosted deposits in the 

Challis quadrangle. Mineralization probably took place in the 

Late Cretaceous (Hobbs and others, 1987).

The black shale belt of the slope-basin environment 

includes the Ordovician Ramshorn Slate, Devonian Milligen 

Formation, Paleozoic Salmon River assemblage, Mississippian Copper Basin Formation, and Pennsylvanian and Permian Wood River and Dollarhide Formations (Paull and 

others, 1972; Hall and others, 1974; Sandberg and others, 

1975; Hall, 1985; Wavra and others, 1986; Hall and Hobbs, 

1987; Turner and Otto, 1988). Black-shale-hosted deposits 

are predominantly in veins that yielded mainly lead, silver, 

zinc, antimony, and tin (Hall, 1987a). The veins are typically 

beneath major thrust faults or near regional unconformities 

and are typically associated with Late Cretaceous or Eocene 

intrusive rocks (Hall, 1987a). Some of these deposits (Livingston, Hoodoo, and Triumph mines) have textures suggesting at least partial syngenetic deposition of ore and 

sediments. Deposits of interest for their tin concentrations 

include the sulfide-bearing quartz and siliceous vein deposits 

of the Timberline and Patti Flynn mines, among others, in 

the Fourth of July, Galena, and Boulder Basin mineralized 

areas (Tschanz and others, 1986; Tschanz and Kiilsgaard, 

1986; Hall, 1987a).

Late Cretaceous and Tertiary igneous rocks of the Idaho 

batholith and Challis Volcanic Group underlie the largest 

part of the study area (Mclntyre and others, 1982; Bennett 

and Knowles, 1985; Ekren, 1985; Kiilsgaard and Lewis,
M8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

1985; Fisher and Johnson, 1987a; Johnson and others, 1988; 

Moye and others, 1988). Igneous rocks include Cretaceous 

intrusive rocks, Tertiary intrusive rocks, and Tertiary extrusive rocks (Challis Volcanic Group). Biotite granodiorite is 

the most widespread of the Cretaceous intrusive rocks; hornblende-biotite granodiorite, porphyritic granodiorite, 

tonalite, quartz diorite, muscovite-biotite granite, and leucocratic granite are also present (Johnson and others, 1988; 

Lewis, 1989). The granodiorite and granite further belong to 

distinct potassic and sodic suites (Lewis, 1989). Tertiary 

intrusive rocks are compositionally bimodal, including both 

granite and quartz monzodiorite (Johnson and others, 1988). 

Tertiary extrusive rocks of the Challis Volcanic Group 

include basaltic, intermediate, and rhyolitic types (Mclntyre 

and others, 1982). Numerous dikes and hypabyssal rocks 

were feeders for the extrusive rocks, and these are compositionally and textually transitional between intrusive and 

extrusive varieties. Virtually all of the Tertiary rocks were 

emplaced during the Eocene between 51 and 40 Ma.

Cretaceous and Tertiary igneous rocks are associated 

with characteristic types of ore deposits (Hardyman, 1985; 

Hardyman and Fisher, 1985; Kiilsgaard and Bennett, 1985, 

1987a, b; Mclntyre and Johnson, 1985; Kiilsgaard and Hingley, 1989; Lewis, 1989; Moye and others, 1989). Stockwork molybdenum deposits and mixed precious- and basemetal veins are thought to be genetically related to Cretaceous intrusions. Stockwork molybdenum deposits of probable Cretaceous age include the Little Boulder Creek deposit 

(White Cloud) (>100 million tons averaging 0.15 percent 

MoS2 and 0.02 percent WO3) and the productive silver-bearing Thompson Creek open-pit mine (200 million tons averaging 0.18 percent MoS2) (Hall, 1987b). Mineralized rock at 

the Thompson Creek mine is in the stock but near the contact 

with the Salmon River assemblage; mineralized rock at the 

White Cloud deposit is in the Wood River Formation, but the 

ore grade is greatest near the stock. The molybdenum-bearing copper-silver veins of the Lost Packer mine and the zinclead-silver veins of the Deadwood, Greyhound, K.G., 

Seafoam, Mountain King, Sunrise, and Comeback mines 

also are thought to be related to Cretaceous intrusions (Kiilsgaard and Bennett, 1987c).

Deposits of probable Tertiary age include vein stockwork and disseminated molybdenum deposits, preciousmetal veins, and high-level precious-metal veins (Fisher and 

others, 1987; Johnson and Fisher, 1987; Kiilsgaard and Bennett, 1987b, d). Significant Tertiary molybdenum mineralization is in the CUMO (1,000 million tons at an estimated 

0.1 percent MoS2) and Little Falls (a multimillion ton 

deposit at 0.05 percent MoS2) deposits and other smaller 

deposits such as that at Red Mountain (Kiilsgaard and Bennett, 1987d). Molybdenum typically is in subparallel quartz 

veins that are in or near intensely altered host rocks that are 

cut by Eocene rhyolite dikes. Precious-metal veins include 

the Comeback, Singheiser, and Parker mines (Fisher and 

others, 1987a). Gold and silver are the main commodities,

but copper, lead, and zinc are present in variable amounts. 

The veins are epithermal and are in altered host rocks typically cut by Eocene rhyolite dikes. Rhyolite-hosted preciousmetal deposits include the Sunbeam, Parker Mountain, and 

Singheiser mines (Johnson and Fisher, 1987). Ore is present 

as irregular stockwork quartz veins and disseminations in 

hydrothermally altered host rocks, typically rhyolite.

The three types of Tertiary deposits discussed here may 

be genetically related. At many locations elsewhere, stockwork molybdenum deposits pass upward and outward into 

precious-metal vein deposits, which in turn grade into stockwork and disseminated precious-metal deposits. In the study 

area, all three deposit types are associated with hydrothermally altered hypabyssal rhyolitic rocks and are concentrated along the Trans-Challis fault system. Precious-metal 

veins and high-level precious-metal deposits in the study 

area are commonly enriched in molybdenum. Thus, for this 

study, samples from these molybdenum-enriched deposits 

and their associated intrusive rocks are classified with 

molybdenum systems.

Although minable tin deposits are absent, much Tertiary granite in the study area has geochemical characteristics of tin-bearing granite elsewhere. Most Tertiary intrusive 

rocks in the area are evolved or anorogenic (A-type), highpotassium, slightly peraluminous, probably alkali-calcic to 

calc-alkaline granite (Bennett and Knowles, 1985). They 

typically have high tin, tungsten, uranium, thorium, molybdenum, niobium, zirconium, certain rare earth elements, lithium, beryllium, and fluorine contents and low strontium and 

barium contents (Bennett and Knowles, 1985; Cole Smith, 

written commun., 1990). Thus, their major- and trace-element abundances are similar to those of tin granites worldwide (for example, Tischendorf, 1977).

ANALYTICAL TECHNIQUES

Lead separated from whole-rock samples and from 

mineral samples was analyzed by the surface-emission (silica gel) ionization technique of solid-source mass spectrometry. The mass-analysis methods for all samples and 

lead-separation techniques used for silicate minerals are 

those of Doe and Delevaux (1980). For lead-rich samples 

such as galena, jamesonite, and boulangerite, an HC1 dissolution was substituted for the HF-HCLj. decomposition step 

on silicate samples, followed by anodic electrodeposition. 

The rest of the procedures were the same except if great 

bismuth or thallium signals were observed. Although isotopes of these elements do not directly interfere with lead 

isotopes, they are at adjacent masses and add to uncertainties in the background. These samples were reprocessed on 

chloride-anion resin columns eluted with water to separate 

the bismuth and thallium from lead.
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M9

Lead, uranium, and thorium concentrations were determined by stable-isotope dilution as described in Doe and 

Delevaux (1980).

Sulfur-isotope compositions were determined by the 

U.S. Geological Survey laboratories in Menlo Park, Calif., 

or by Geochron Laboratories Division of Kruger Enterprises, 

Inc. Analyses from Geochron Laboratories have a standard 

error of the mean of 0.3 per mil for 834S. Although this laboratory uses Trenton City troilite as a reference sample on 

which they reported values of 0.18 and 0.20 per mil, their 

data are systematically 0.4 per mil greater than those 

obtained on a common sample that was analyzed several 

times in both Geochron Laboratories and the U.S. Geological Survey laboratories in Denver. In order to facilitate direct 

comparison of data from Geochron Laboratories with that 

from the U.S. Geological Survey, 0.4 per mil arbitrarily has 

been subtracted from analyses done by Geochron Laboratory. The difference, however, is not considered to be significant compared to the isotopic differences between samples.

DATA 

LEAD ISOTOPES

The lead-isotope data (tables 3-5) form a complex pattern (figs. 5, 6) that is easily separable into two groups on a

plot Of 208pb/204pb yersus 206pb/204pb (Doe and Delevaux,

1985). The two groups were originally defined on the basis 

of ore leads. Group A forms a diffuse cluster having relatively high 208Pb/204Pb for its 206Pb/204Pb, whereas group 

B forms a fairly tight cluster having relatively low 208Pb/ 

204Pb for its 206Pb/204Pb. Igneous rocks of group A lie 

close to group A ore leads, and igneous rocks of group B 

lie close to group B ore leads. Ore samples of group A lie 

on or above the regression line for igneous rocks of group 

A in figure 6. Many samples in group A have values of 

206Pb/204Pb of 18.0 or less, but some values are as high as 

21.0 or more. In contrast, all samples of group B have values of 206Pb/204Pb of 18.5 or more, and most values are 

between 19.0 and 20.0. Where 206Pb/204Pb values overlap, 

group A shows a trend of 208Pb/204Pb values greater than 

group B. The isotopic distinction is so clear that there is 

confusion in classification of only one ore mineral in a 

group of more than 50 ore minerals and (or) igneous rocks. 

Groups A and B can be further subdivided (Sanford and 

others, 1989; and Sanford and Wooden, this volume), but 

these subdivisions are not discussed here.

Data for group A are similar to those from the Rocky 

Mountains or from area I in the classification of Zartman 

(1974) (see fig. 7), although there is some tendency for 

208Pb/204Pb values in central Idaho to be greater for given 

values of 206Pb/204Pb. For example, the average values of 

the two samples from the Thompson Creek mine in central 

Idaho for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb are

17.597, 15.588, 40.945, respectively, whereas the Climaxtype (fluorine-rich) molybdenum deposit having the highest 

values of 208Pb/204Pb in the Front Range of the Rocky 

Mountains of Colorado is the Henderson mine (342 million 

metric tons, averaging 0.297 percent Mo; David Singer, 

oral commun., July 11, 1991), which has ratios of 17.696, 

15.508, and 39.375, respectively (Stein, 1985). The Henderson mine also has the highest 534S, as much as +6 

(Stein, 1985), for a molybdenum porphyry, aside from that 

for Thompson Creek. For two samples from the low-fluorine Cannivan Gulch molybdenum porphyry deposit of 

Montana (203 million metric tons of 0.096 percent Mo; 

David Singer, oral commun., July 11, 1991), the leadisotope ratios are 17.602, 15.552, and 38.378, respectively 

(Doe and others, 1986). The similarity of 206Pb/204Pb and 

207Pb/204Pb for all three deposits is remarkable, close to 

analytical uncertainties.

In contrast, group B values in central Idaho are similar 

to those in the Great Basin or area II in Zartman's classification (see fig. 7). For example, a feldspar and a galena from 

the White Cloud molybdenum porphyry system have average values of 19.304, 15.705, and 39.310 for 206Pb/204Pb, 

207Pb/204pb? and 208Pb/204Pb? respectively, whereas these

ratios for the low-fluorine Mt. Tolman molybdenum porphyry deposit (1,180 million metric tons of 0.055 percent 

Mo; Donald Singer, oral commun., July 11, 1991) in the 

Zartman area II of Washington are 19.377, 15.672, and 

39.191 (Church and others, 1986). Again, the differences in 

isotope ratios between these two deposits are close to analytical uncertainties.

Large deposits of molybdenum porphyry generally 

have lower values of 206Pb/204Pb but are in either isotopic 

grouping (for example, group A, Thompson Creek; group B, 

White Cloud and CUMO). The data for the largest and most 

productive deposit in group A (Thompson Creek) follow the 

apparent rule observed by Doe (1979) of 206Pb/204Pb values 

of 18 or less for supergiant and many giant magmatothermal 

ore deposits of area I of Zartman.

Previously (Doe, 1979), consideration was given only 

to deposits in area Ib of Zartman (oldest rocks are Proterozoic basement to the south) with the exception of Butte in 

area la of Zartman (oldest rocks are Archean in the north). 

Data for Thompson Creek add additional evidence that the 

same lead-isotope rule of 206Pb/204Pb less than 18 for supergiant deposits can be applied to area la as well as to area Ib. 

The lead in potassium feldspar from the stock at Thompson 

Creek is highly radiogenic (206Pb/204Pb >20), however, and, 

because the data were the last obtained, we were unable to 

determine whether this radiogenic nature is a primary feature 

of the stock or is the result of additions of radiogenic lead to 

the feldspar subsequent to crystallization of the stock.

Mineral-deposit evaluation through use of lead isotopes 

has not yet been assessed for the Great Basin area or area II 

of Zartman. Galenas from both the White Cloud and CUMO 

molybdenum porphyry bodies are toward the less radiogenic
Table 3. Sample information, Challis and Hailey I°x2° quadrangles, Idaho.

[Two-letter designation following sample number indicates sample type: GN, galena; BO, boulangerite; BA, barite; JA, jamesonite; KF, potassium feldspar; OR, ore; WR, w

degrees, minutes, and seconds north, longitude in degrees, minutes, and seconds west]

Sample 

Group number Name or location Age and host rock type

Relative 

age Deposit type Commodities District Cou

Ore samples

A

A

B

B

A

A

A

B

B

B

B

A

B

A

A

A

Buckskin? GN

S76-895 GN

T 49M GN

Fl 12 GN

T 68M GN

SWH 78-65 GN

80WH-1 GN

79T565M GN

F107 GN

T597M GN

79T 5MGN

584-13 GN

KR880 GN

76T 23M GN

SWH154-76a GN

SWH154-76b GN

Thompson CreekBuckskin Drill Road

Thompson CreekBuckskin Drill Road?

Bulldozer cut/dump

Carlson GulchGrimes Creek

Carrie Leonard

Clayton Silver

Clayton Silver

Combination? New

vein

Comeback

Crest Lake?-Trail

Creek?

Crown Point

CUMO

Deadwood

Dollarhide

Dryden

Dryden

Cretaceous Idaho batholith

Cretaceous Idaho batholith

Pennsylvanian-Permian

Wood River Formation?

Cretaceous Idaho batholith

Lower Permian upper

member of the Dollarhide

Formation

Ordovician Ella Dolomite

Ordovician Ella Dolomite

Pennsylvanian-Permian

Wood River Formation, limy

sandstone

Cretaceous Idaho batholith

Devonian Milligen

Formation(?)?

Pennsylvanian-Permian

Wood River Formation, limy

sandstone

Tertiary Idaho batholith

Cretaceous Idaho batholith

Pennsylvanian Dollarhide

Formation

Ordovician Saturday Mount

Formation

Ordovician Saturday Mount

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Epithermal

Vein

Porphyry

Vein

Veinreplacement

Veinreplacement

Vein

Vein

Porphyry

Vein

Vein

Vein

Vein

Pb, precious Bayhorse

metals?

Mo Bayhorse

Boyle

Mountain

Grimes Pass

Carrietown

Pb, Ag, Zn Bayhorse

Pb, Ag, Zn Bayhorse

Galena

Precious metals Grimes Pass

Warm Spring

Boulder Basin

Mo Pioneerville

Base- and precious- Dixie

metals

Carrietown

Pb, Ag, Zn, Sb, Sn Bayhorse

Pb, Ag, Zn, Sb, Sn Bayhorse

Cust

Cust

Blain

Bois

Cam

Cust

Cust

Blain

Bois

Blai

Blai

Bois

Elm

Cam

Cust

Cust

Formation
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS Mil

U u u a a PQ

O PQ

J

PQ

PQ

<i

u 

co

Cfl

§

U

OH

T3

01 £3cd ^

PQ £5

Gilmore (Texas)

3

8 'a' G ^

g c§ T3 J<! § "-< [__, s g O gl««i o b PQ u

c

cod"

N

DO

^

f^

CU

s

Boulder Creek-Si

c

co

CO

J

N

00

<!

<&CU

s

Carrieto

co 

oo

fi"

Jg

>

Epithermal

Pennsylvanian-Permian 

River limy Wood Formation, 

sandstone

6

1

Z

76T 32MG

PQ

Epithermal

Paleozoic SalmonRiver assemblage, carbonaceous 

argillite

I

ORR-366 

PQ

Epithermal

Lower Permian upper 

of theDollarhide member

Formation

1

Z

O

WH70-13B

PQ

Epithermal

Tertiary Idaho batholith

>-,

1>

o

co

bp 'PQ

PH (D <c a o u

o

m

fe r-

<C

Epithermal

Pennsylvanian-Permian 

Wood River Formation, limy 

sandstone

o

5

1 

§

z

79T580M G

PQ

c '8

>

Epithermal

batholith Cretaceous Idaho

|

0

!

s

g

<

Epithermal

Devonian Jefferson 

Formation

1

2

c^-

z

o

ioo

<

Epithermal

Jefferson Devonian 

Formation

1

c^-

O

ioo

<

 8

PQ

Syngeneticepithermal

Paleozoic SalmonRiver argillite assemblage, and 

limestone

Hoodoo

0

VO

co

PQ

'8

 o

u

PQ

Syngenetic

Paleozoic SalmonRiver 

assemblage, argillite

Hoodoo

< 

PQ 

en

&

PQ

Epithermal

Dollarhide Pennsylvanian 

Formation

&

Horn Si

GNT 81M

<

Epithermal

Idaho batholith Cretaceous 

O

X

! </ >

e<

<

Epithermal

Pennsylvanian Dollarhide 

Formation

1

GNA176 

PQ

'S

PQ

Syngenetic remobilized

Paleozoic SalmonRiver assemblage, carbonaceous 

argillite

Q

1

>

J

5CN

fe 

OO

PQ

C '8

 6

PQ

Syngenetic remobilized

Paleozoic SalmonRiver assemblage, carbonaceous 

limestone

0

00

a

<< > § 

1

PQ

and ase-necious-mf

PQ a

Epithermal

limestone Paleozoic Idahoin 

batholith

CO

c

1 1

R-154GN

<
M12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

U

O

PH

e

u

c

q

u

T

£

C

^

|

C

t

T

.5*

Q

c' C

S

£

|

6

£

Deposit t>

Cohtinued 

<*>

TEL (D rt 

> C

 ,S (D «

e3 tu «i 

"B rt «

* 0

g.

1

o

T3 

cj 

U

M

|SCd 

O

o

s

u

2

t 6 rt 3 

00 d

O.

3

t§

o) rs 5 WO Tt

00 rt

^H o

VO ON 

en en

-* m

(D f*

d 5

S ffi

5 rt ^

OH C JH

o g u

s 5 s

M > s

1 S I d

§ 3 'S 

i _O >

PQ OH ffl

^

£3 'o S

lH d C

1 iM

ij C/D (D

O

 s

s

s

d d

2

U 

<» .2?

S 3 o

is N 3 iid a 

oo o a

U J3 > g

ll ll

bO

S

S C/5

1 ^

2 2

z

6

2 PQ

0 ^

^H ^

a i

< PQ

rn en

0) 0)

ON ON

2 2i

T 1 T 1

^f ^f

cs o)

^f ^f

(D aj

tfl Cfl

a a

(D (D

2 >2

0 0

J3 _e

S > CO TO

PQ PQ

UH

bb

<I

N

fi

^

u

§

i

u

OS

H H

C &

Hi (L>

<S -3

a a

(D (D

CA CA

0 0

"1 f

PQ PQ

§ u .2 <u .G .| .G .|

J5 0 00

a "3 "S "3 

0 Q 0 Q

d d

'3 '3

d c

3 3

0 0

S S

O O

*G 'G

PH OH

0

PQ ^. >o

2 57N s 3 s £

S

o 2

<c <

m0)

2

2

,-H

^f

S

^f

Tf

a

u

2

o

f

PQ

UH

bb

<! N"

£

'd

Replaceme

g

ti -a(S1

u

g

f

PQ

Ordovician Dolomite

d

ad

§

o

OH

§

KD74-P9-5B

<

m

ON

s

,-H

^f

s

^-JQ 

U

(Dcfl 

H

O

f

PQ

UH

bb

<!

4

£

*&

Replaceme

gH

1

fi1

u

01

8

f

PQ

Ordovician Dolomite

d"

3 u

d O

§ .g

'G o

o.-i

5

KD72-9-124

<

cn en

ON ON

S S

,-H ^H

^f ^f

S S

^fc ^

3 3

U U

<D Hi

2 £3

0 0

E? ^

PQ PQ

UH PL,

bb bb

^C "^

g S

7? PH &PH

<-> *-i

(D (D

S S Hi Hi

o o

& u"

f nH

u S3

& &

u u

rt rt1

pa pa

|.| || 

O Q O Q

_d" _d"

 4 * J »

d c

3 3

O O

o o

1 1 |-i

PH T3 PH S

0 O

00 ON 

^O VD

<c <

tq

ON

2

, ,

^f

S

^^

3

U

u

* o

^

PQ

UH

bb

<!

4

fi

S

Replaceme

HH

S3

^

u

o

f

PQ

Ordovician Dolomite

o'*""' d"

'3

c

3

O

? 1

£ S

2

4 

cA

<

en

ON

2

^H

^f

^

^-

a

£3

o

f]

ci

m

UH

bb

<!

4

£

^

Replaceme

6S-l

&

U

1

PQ

Ordovician Dolomite

<-.

1

£

§

<C

^" rs m 

o <* w-i

O ^H ON 

 <* 0) -H

2 S 2i

o) \o o

rs m 10

-* -* o 

o cs o)

^^ ^^ ^^

333

U U U

I I

O CA CA

-3 _o o

o & &

PL, PQ PQ

-1

Hi ^

'C '^

3 «

° -S

cd 4)

u "ii

o§

c 'S

> a

G S S

U-, IH 1-H

D O O

P^ ^ ^

«

i- oo .& u e u

|t | |

*e3 PS PQ

|| I ||

S § ^ ^ ,2 

SIS 0 Q

««l

u

s

1

ffi

I e 1 r-" ° £

£ OS PsS

^ 2

6 o £

H r- oo

PQ < PQ

0) 

0)

oo

2;

VOl/*t

n

 ^

Cfl

a

lH

O

JS

m

d

N

bb

£

s

Replaceme

a

G

 1

|H

U

O

f

PQ

Ordovician Dolomite

u

1

OS

<^«

1885AgGN'

<c

ts ts

oo

**

vOi/"}

Js

 ^f

a

8

S*

O

f

PQ

d

Sl

bb

£

<_,

Replaceme

§

 3 a

u

1

PQ

Ordovician Dolomite

1

1

<S

s

<c

o) wo ts o

oo wo

-H 0)

S S

vo vo

ts ^

^^ ^

I/I Cfl

3 3 

O O

U U

o S

JS JS

m PQ

ooP'

oo

d d"

N N

bb bb

£ £

s

Replaceme 

Vein

S C

5 C

 s J

OH a

.S

<D O

1 § >, C3

PQ PJ

'G . " 'G

'> S '>

 81 1

0 Q O

 s ^

1 1

OS OS

§

GN? 

SWH120-79

<> 
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M13

§

en 

«

oo oo 0 0

v> >o

o c-~

en ^H

O <N

en m

Ul Ul

a 

en 

Cj

u u

00 00

 a 13

Q S

(U 0) s -s

'On 'p|

w w

 5 5

i^3 *^

o o

H I

^3 .0

0 0 

^y ^3

I/I I/I

Cretaceou Cretaceou

to

S(if

Seafoam Lk< 

Silver Bell

§ § -i *^ ^ v>

V> rn

E c<

< <

VO

£

2

oo*o

en

u

1 

CQ

ffi

Mineral

130

u

'Sn

w

c

'is*o

fl

£

c

u

bO i 

s

Devonian

1

Silver Qi Star 

Z

O

VO

3

£5X

£

CQ

oo <! 

en

S

* '

en

Q 

U

 a

Yankee £!

 g 

i

 o v i 3

1 .2

03 BH

 a

c

u

'On

 S

yg^ 

,0

O

I/I

Cretaceou

.8

3 

00

O

,_H

«

00

<

2

o\ 

en

2

^CN

en O

^

en 

U

^

3

o

00

j£

00

c

N

%>

-

£

c

1

c

p

13

S

,§

'Bn

ST

en s § ! s

05 c

11

1 °.

OO <U

Paleozoic assemblag 

argillite

Timberline

S

Scs

E

'CQ

^

o

5

VO

cs

oo

5

t-4

u

a

l

CQ

13

fi

1

OH

U

sa3

> §

£ §

c o

ll 1 °.

oo u

Paleozoic assemblag 

shale

Twin Apex

§hM

00

CQ

O 

en

O

2

eni *

oo 

en

u

5

cti 

1

13

C

1'p l w

.g^

o 

1

^3

1

T3

in

Cretaceou

Webfoot

O

rsl

S?H

<

o

cs

en

2

o^f

cs

o

1

U

3

,1 £ °

1 CQ

1*cd O

W i 1

c

00

^*

N

bb

<

fio"

s

c

1

£"E

o

OH

13

G

 S'On

U

>">

.S* H

.1 g

g i

C E 

cu c

i^

'S i5

Pennsylva Wood Riv

sandstone

i

White Cloud-

§<cs

en 

^

CQ

1'S

c

u

T3

3

3

&

1 

u

0

'1

3

i/i

=3

o

o

U

8

'«

ga

 ao

 8

i/i i/i ^

^

^ 

^

i/i 

5

T3i

&<

|

o

loNamer 

00 C

o

3

<§

U

"S

t

 fcj

§

*p^

0

ON

cs

cs

*Tl

V)

8

1

^

For] East 

 |

Ul

_d

'E?

?3

1

Tertiary gi

o

>

oa

VO

*o

g

CQ

oo

o\

vi

enO

in

'S8

CQ

3

Gambrir

 |

bb

.S

'e'

ss

1

1

10

s

H

^r

i

CQ

m vi

0 * 

m en

 >* v>

C^ i '

O OO

v> cs

g

§ « 

J W

1

1 '§

o 3

3

O

1

T3

?

00

03

 |

bb c

C3 *(jj

p >

^

_ £ c ^

Q N

5

rt

.s 1

Tertiary gi

Cretaceou

Creek Camas 

Deadwood

u ^

en en

~? ^&

g §

< CQ

VO

^

(?

^

5 5 5 5

CQ U

a 3 -° .2

^

<

3 C

< N

u

Parker 

Mountain

i/i

1

(A

§

1OH

O

s

^

Yankee Foi

1

S

en

§

1

d.

O

S

U

bo

Gravel Ran

i/> H

1en

§

1OH

O

s

I

bO 

3

a o, ad,

II 11

O 1

a »

CQ CQ
M14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

 3

1

<?

 9

3

«8 '5b

1

o 

(S 

X

o

iu*

EG"S

g

LO i 

ag"

 £o

CO

St-l

!s

H

00

^

^ j

cs 

H

u

T3

3

c

,3

3

3

>,

c

o 

U

«

en

Q

t/>

O

 3

1

I

U

&

.&

.S

I

_o

 J2

1

<D

£

i

host Age and r

c

 3o

o

_o"i

u

g

Z

.S S3 o,Jo

00 C

Q.

i

(U

"o 

|i*

 e

a

(U

0

00 O 1-1 O O ID O O ^H v) en i i

^O ^d" ^f c^« vi c^ O -<3- cs »-c en en

V) rf V) V) Tj- t^-

fS 01 ^t O O O V) 1-1 i-i en O O

en \O ON oo en o\ 

 <t fS V) ^H o 1-1 

^^ ^J" en ^J" ^J" ^" ^^ ^j~ ^j~ ^j~ ^~ ^j~

U, l_ l_ U.

in en .« .52 to M 

33 O O fl 3

U U 03 03 U U

|

is p- "^ <>. *a g

d> _H ^* FT O

cd S W) s J2 SlT*

oo >i n oo W 03

_, o o o

w S S S

(U (U O

'§ CH* '9 'S &* &*

bO -g^ bb bO §* -^

 So .2 .2 S o

H OH H H OH OH

S"

bO

^ <,

^"A "c1 'c' o o 

w ^ w w S S

0 ^

1 B1

> a a

W) CJ _c bb bfi D D

 ^3 "* o o

E-. H O H H U U

i^ 4)

53 r~\ <& £A

U .2 CO ^ P

0 3 £P T3 (5

^ 3 - S O C 

l-J C O CH - O

O ID J* g O g 1 11 5 ^ s 5

oo oo > ^ > H

£ o ^ ^

f-H ^ H H S 3

"^ vi o\ en ** 

o JH CN o oo o

OO pq V) OO OO (S

^ on ^H ^H t^ ^

< < 03 < 03 <

3 

2

&CQ

I

w

o c- o

 <t eN <* fS en ^H

222

 <t en r^

o vi ^o

Tf ^H V)

en TJ m 

"^f "M" ^"

(U U, UH

3 1 i

03 U U

c

U 0 

00 «

C Q

k^^ i f. CO ^-«2

^ 03 <

1

0-

>»

1OH

C C

N N

£ £

bO bO

< < P

 §

rt

S «

§^ U '^|l G P-~I Isrt *^H

.£?£ § '5b u 3 s bo S ff^ ;. oo " H -a 3 S b ^H CQ w ^ eg CQ

|| || ||

"o "3 S So

Q tin OH C« S BH

to

J2 ^

O i^

"3 "i

6 8

z! u

^ S 0

g S o

^"32

- DH J ^

^ 

^ ^ ^

1 s i

> H- H

PQ 03 03

end of the assemblage and are similar in lead-isotopic composition to the potassium feldspar from the White Cloud 

stock. The observation of Stacey and others (1968), Doe and 

Stacey (1974), and Doe (1979) that the largest magmatothermal deposits are most similar to igneous rocks in lead-isotopic composition may also apply to the Great Basin 

environment.

Ores from the largest Cretaceous and Tertiary magmatothermal gold and silver deposits in the Rocky Mountain 

region have values of 206Pb/204Pb of 19.1 or less (Doe, 

1979). The largest production for these kinds of deposits is 

from the Sunnyside gold mine (206Pb/204Pb 18.2 -18.6) and 

the Creede silver mine (206Pb/204Pb 18.8-19.1) of the San 

Juan Mountains of Colorado (Doe and others, 1979) and 

the Clayton Silver mine of central Idaho (206Pb/204Pb 

18.9-19.0) (table 4). There is some indication (Doe, 1979), 

however, that these deposits have more radiogenic values 

of 206Pb/204Pb than ores from the largest Cretaceous and 

Tertiary magmatothermal base-metal deposits, such as 

Butte, Montana, Bingham Canyon, Utah, and Climax, Colorado, which have values of 206pb/204pb of less than 18 j 

(table 2). Although at one time the Sunnyside mine was the 

second largest gold producer in the United States (after the 

Precambrian deposit of the Homestake mine, South 

Dakota) and the Clayton Silver mine was the largest silver 

producer in Idaho (after the Precambrian deposit of the 

Coeur d'Alene mine), the dollar production of both the 

Sunnyside mine and the Clayton Silver mine is modest in 

comparison to the largest base-metal mines and gold or silver mines. Although the new data from the Clayton Silver 

mine validates the previous suggestion that Cretaceous and 

Tertiary magmatothermal gold and silver deposits tend to 

have more radiogenic values of 206Pb/204Pb than the largest 

Cretaceous and Tertiary magmatothermal base-metal 

deposits, data from gold and silver deposits of equivalent 

production to the largest base-metal deposits are not available for comparison. Therefore, the suggestion remains 

tentative that, among Cretaceous and Tertiary magmatothermal deposits in the Rocky Mountain area, gold and silver deposits will have somewhat more radiogenic values of 

206Pb/204Pb than the largest base-metal deposits.

Tin is currently classified as a strategic mineral but has 

little production in the United States. Finding a good tin 

deposit is complicated by the requirement that the tin be in 

the form of cassiterite because of smelting considerations. 

Although some cassiterite has been found in the study area, 

stannite is more abundant (Hall, 1985, 1987a). The best 

occurrence of tin is at the Timberline prospect, but stannite 

also is present at the Patti Flynn prospect and elsewhere. 

Both Timberline (206Pb/204Pb of 20.10) and Patti Flynn 

(206pb/204pb of 19 33)^ which are vein deposits in black 

shale, are in group B. The Rob Roy mine has the greatest 

value of 206Pb/204Pb but is of uncertain isotopic classification. In contrast, samples of tin granite (all but one having 

values of 206Pb/204Pb less than 19.0) are in either isotopic
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M15

group and are isotopically indistinguishable from molybdenum porphyry. No granite has the lead-isotope composition 

of the lead in the tin veins. The lead in the tin veins most 

likely was derived from a Precambrian source at depth and a 

lower Paleozoic source in the upper crust (Sanford and 

Wooden, this volume). Thus, the relationship between tin 

granite and tin-bearing veins is not simple.

SULFUR ISOTOPES

No economic subaerial magmatothermal deposit previously was known that has 534S values greater than +6 per mil 

(the extreme value for the Henderson molybdenum porphyry 

of Colorado; Stein, 1985). The "normal" igneous range is -5 

to +3 per mil, as discussed above. Central Idaho, however, is 

an astounding exception to this previous observation (table 

4) (see also Howe and Hall, 1985). Of 25 samples from different mines, 17 have 534S greater than +3 per mil. Indeed, 

the very biggest mineral deposits of Thompson Creek and 

White Cloud have exceptionally heavy sulfur isotopes (+8 

per mil or more and +4 per mil or more, respectively). Some 

deposits have galenas of the appropriate 534S values for the 

igneous range, but they are not among the best producers. 

Among prospects having values of 206Pb/204Pb of 18.0 or 

less, only Webfoot (534S of+3.6) is near the normal igneous 

range for sulfur isotopes. For 206Pb/204Pb values between 

18.0 and 19.1, galenas from the Carrie Leonard mine, GAP 

prospect, Horn Silver mine, and perhaps the Dryden and 

Comeback mines are in or near the igneous range for 834S. 

Among radiogenic group B deposits, only the mine at Crest 

Lake-Travel Creek is in the normal igneous range for 834S.

Unlike all other areas for which data are available, the 

sulfur isotope rule in the Challis and Hailey quadrangles 

may be that the biggest deposits contain heavy sulfur isotopes. If this is true, then the areas near the prospect at 

Seafoam Lake (206Pb/204Pb=17.75, 534S=+7.0) and near 

the Ramshorn mine (206Pb/204Pb=17.75, 534S=+10.3) 

would have exceptional potential.

DISCUSSION 

NATURE OF BASEMENT SOURCE LEAD

Deposits of group A such as the Ramshorn mine have 

lead-isotope signatures representative of metamorphosed 

Proterozoic crystalline rocks from the Rocky Mountains. 

Such an isotopic signature is derived either directly from 

Precambrian crystalline rocks at depth or indirectly from 

Mesozoic or Cenozoic igneous intrusions that derived their 

lead from such a source. Deposits of group A are associated 

with structural highs in Precambrian basement or with Cretaceous intrusive complexes. The two main examples are the 

Bayhorse anticline and the Casto structure. The Ramshorn,

Pacific, Riverview, Rattlesnake Creek, Rob Roy, Clay ton 

Silver, Dryden, Thompson Creek, and Twin Apex mines are 

associated with the Bayhorse anticline. The Seafoam Lake, 

KG, Silver Bell, Mountain King, Sunrise, Deadwood, Sunbeam, Parker Mountain, Greyhound, Lost Packer, and Singheiser mines are associated with the Casto structure.

The Ramshorn mine is in the Bayhorse anticline and is 

within 1 km of the exposed Cretaceous granodiorite and 

quartz monzonite of Juliette Creek (Hobbs and others, 1975; 

Mclntyre and others, 1976; Hobbs, 1985) to the south. 

Although the exposures are less than 2.5 km2 in areal extent, 

they are within the Bayhorse gravity high and adjacent to a 

magnetic anomaly that has closure at 2,000 gammas (relative). Closure at 1,800 gammas (relative) is shaped rather 

like an Idaho potato (fig. 8), about 16 km long and 7.25 km 

wide. Webring and Mabey (1987, p. 78) (also see Mabey and 

Webring, 1985) said of this feature:

The gravity high may reflect a topographic high on the Precambrian crystalline basement or an underlying intrusive basement *** The rocks in the 

Bayhorse anticline may be an autochthon or an allochthon overlying a 

basement high. The other possibility, that a large intrusive complex may 

underlie the Bayhorse high, is suggested by the extensive magnetic high 

apparently at least in part produced by the 98 m.y. Juliette stock. Mclntyre 

and others (1976) consider this stock to be a satellite of the Idaho batholith, 

but the large mass of rock underlying the Bayhorse high is both more dense 

and more strongly magnetized than the main mass of the Idaho batholith. 

The gabbro dikes and sills [that occur in the Bayhorse high] suggest that a 

mafic intrusive may underlie the area.

The intrusion may be a thin, batholith-sized body, and 

the Ramshorn mine may be within 1.5 km of the cupola. A 

number of other deposits may overlie deeper parts of the 

igneous mass or be adjacent to it. These include deposits of 

the Pacific and Riverview mines to the east, Rattlesnake 

Creek mine in the center, and Rob Roy, Clayton Silver, and 

Dryden mines to the southwest.

The Bayhorse gravity anomaly has a lobe that extends 

considerably to the west of the Bayhorse magnetic anomaly 

and includes the area of the Thompson Creek molybdenum 

porphyry and Twin Apex mine. The area of the gravity 

anomaly, which possibly represents elevated basement, is 

one of the areas containing nonradiogenic group A lead and 

heavy sulfur isotopes. Although some deposits in this area 

are in group A, the rest have values of 206Pb/204Pb greater 

than 18.0. Deposits in group A include the Dryden mine, 

Clayton Silver mine, Rattlesnake River prospect, and Pacific 

Mountain mine. Potassium feldspar from the Thompson 

Creek stock is also in this radiogenic assemblage. Some 

deposits, however, are in group B, including the Riverview 

and Twin Apex mines. The Rob Roy mine may be a mixture 

of group A and group B leads.

The Casto structure, as used here, includes the Casto 

pluton and associated gravity and magnetic highs. In the area 

of the Casto structure, all deposits except the Deadwood mine 

are in group A (Seafoam Lake prospect, K.G. prospect, Silver 

Bell prospect, Mountain King mine, Sunrise prospect). Also 

in group A are, from southwest to northeast, the Eocene tin
M16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 4. Lead and sulfur isotopic compositions, Challis and Hailey I°x2° quadrangles, Idaho.

[Sample information is given in table 3. Two-letter designation following sample number indicates sample type: GN, galena; BO, boulangerite; BA, 

barite; JA, jamesonite; KF, potassium feldspar; OR, ore; WR, whole rock. Analysts: 1, M.H. Delevaux; 2, A. Johansson; 3, S.A. Kish; 4, A.P. 

LeHuray; 5, H.J. Stein; 6, K.E. Davis; 7, Geochron Laboratory; 8, S.S. Howe]

Sample no. Mine or location 206pb/204pb 207pb/204pb 208pb/204pb Analyst 534S Analyst

Ore samples

Buck? GN

S76-895 GN

T49MGN

F112GN

T68MGN

SWH 78-65 GN

80WH-1 GN

79T565M GN

F107 GN

T597M GN

79T 5M GN

584-13 GN

KR880 GN

76T 23M GN

SWH154-76aGN

SWH154-76b GN

76T 32M GN

R-366 OR

WH70-13B GN

76T31GN

79T580M GN

GHM-1 GN

80R-1 GN?

80R-1 GN?

S-16 GN

R-13 BA

T81MGN

R-151 GN

A176GN

80T-2 GN

80T-1 GN, JA

R-154GN

K52-1 GN

WH74-2B GN

D6S3 GN?

KD74-P9-5B GN

KD74-P9-5B GN

KD72-9-124GN

KD68GN

KD69 GN

KD73-4-161 GN

T576M BO, A

79T 23M GN

SWH 52-67 GN

1885AgGN?

Thompson Creek-Buckskin Drill Road

Thompson Creek-Buckskin Drill Road?

Bulldozer cut

Carlson Gulch

Carrie Leonard

Clayton Silver

Clayton Silver

Combination?-new

Comeback

Crest Lake?

Crown Point

CUMO

Deadwood

Dollarhide

Dryden

Dryden

Emporium

Empire

Eureka

GAP, Big Smokey Creek

Golden Glow

Greyhound

Hilltop

Hilltop

Hoodoo

Hoodoo

Horn Silver

K.G.

Liberty

Livingston

Livingston

Mountain King

Mountain King

North Star

Pacific

Pacific Mountain

Pacific Mountain

Pacific Mountain above

Pacific Mountain, dump

Pacific Mountain, main

Pacific Mountain, top

Patti Flynn

Ramshorn

Rattlesnake Peak

Riverview

17.577

17.617

19.692

19.144

18.094

18.965

18.944

19.735

19.097

19.952

19.624

19.039

19.341

18.081

18.586

18.584

19.785

19.831

20.220

18.311

19.767

18.110

18.376

18.407

19.502

19.810

18.441

17.990

20.013

19.779

20.030

17.943

17.810

19.688

21.452

21.355

21.375

21.323

21.332

21.431

21.347

19.333

17.776

20.479

21.073

15.583

15.594

15.808

15.672

15.591

15.718

15.709

15.800

15.678

15.797

15.800

15.656

15.754

15.572

15.706

15.690

15.788

15.673

15.910

15.622

15.844

15.646

15.573

15.606

15.859

15.795

15.652

15.578

15.917

15.786

15.833

15.606

15.593

15.906

15.840

15.777

15.807

15.765

15.771

15.767

15.801

15.809

15.578

15.784

15.804

40.875

41.014

39.383

39.087

39.975

39.948

39.990

39.367

39.083

39.619

39.274

38.965

39.527

39.918

40.608

40.549

39.311

39.111

40.904

39.883

39.677

40.565

38.955

39.039

39.177

39.192

39.735

39.286

40.619

39.499

39.673

40.299

40.290

39.438

41.145

40.897

41.004

40.796

40.948

40.899

40.966

39.026

39.861

40.874

40.808

3

3

3

2

3

2

4

3

2

3

2

5

1

2

2

2

2

3

1

2

3

5

1

4

3

3

2

1

1

2

3

1

5

1

1

6

6

6

6

6

6

3

3

2

1

8.7

8.7

5.0

7.1,7.1

-0.1

_

-

7.6, 7.9

0.8, 0.8

0.8

4.5

-

-

-0.4

4.6

5.4

-

-

6.3

0.2

6.8

-

-

-

-

_

1.2

-

2.2

11.1

-

-

-

7.2

10.1

_

-

-

-

_

-

10.1, 10.1

4.2

-

8

8

7

7

7

_

-

7

7,8

7

7

-

-

7

-

-

7

7

7

-

-

-

-

_

7

-

8

-

-

-

8

_

-

-

-

-

-

7,8

7

-
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M17

Table 4. Lead and sulfur isotopic compositions, Challis and Hailey I°x2° quadrangles, Idaho Continued.

[Sample information is given in table 3. Two-letter designation following sample number indicates sample type: GN, galena; BO, boulangerite; BA, 

barite; JA, jamesonite; KF, potassium feldspar; OR, ore; WR, whole rock. Analysts: 1, M.H. Delevaux; 2, A. Johansson; 3, S.A. Kish; 4, A.P. 

LeHuray; 5, H.J. Stein; 6, K.E. Davis; 7, Geochron Laboratory; 8, S.S. Howe]

Sample no. Mine or location 206pb/204pb 207pb/204pb 208pb/204pb Analyst 534S Analyst

Ore samples Continued

KD-7 GN

SWH 120-79 GN

F154 GN

R-155 GN

WH70-16

SR-1 GN

T572M JA

SWHGN

T302M GN

W312AGN

Riverview

Rob Roy

Seafoam Lake, West

Silver Bell

Silver Star Queen

Sunrise

Timberline

Twin Apex

Webfoot

White Cloud, East

19.704

20.474

17.747

17.596

20.421

17.473

20.099

19.357

17.785

19.404

15.806

15.870

15.604

15.574

15.962

15.562

15.772

15.753

15.587

15.732

39.281

40.143

39.765

39.785

41.301

40.348

39.460

39.341

39.895

39.358

6

2 6.6

2 7.0

1

1 10.7

5

3

2

3 4.2

1 4.0

-

8

7

-

_

-

-

7

Granite and rhyolite

KR56TWR

KR842TWR

KR493C WR

KR743 WR

LF-1 WR

LP-1 WR

A230KF

Grey-1 WR

GM-31 WR

RH-122 WR

GM-365 WR

KR804TWR

SB215120WR

KR529TWR

KR803TWR

W188KF

W320KF

Bear River, North

Big Silver Creek

Camas Creek

Deadwood

Little Falls

Lost Packer

McCoy (Croesus stock)

Mt. Greylock

Parker Mountain

Red Mountain Dome

Singheiser

Stanley Lake Creek

Sunbeam

Wolf Mountain

Warm Springs Creek

White Cloud, West

Thompson Creek

18.842

18.826

18.762

19.488

19.149

19.768

19.572

17.536

17.869

17.493

18.885

17.551

17.803

18.637

17.580

19.204

20.508

15.637

15.632

15.645

15.716

15.653

15.742

15.762

15.525

15.526

15.522

15.645

15.549

15.529

15.612

15.552

15.694

15.811

39.094

39.108

39.755

39.320

39.186

40.078

39.309

39.272

39.634

39.459

39.818

39.330

39.497

39.055

39.219

39.262

40.329

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

-

-

-

-

-

_

-

-

-

-

_

-

-

-

-

_

-

Sedimentary rocks

WH2112WR

T-270 WR

T-602WR

"Sawmill Gulch"

Holman Creek, West

Urexco

19.308

24.073

29.384

15.673

15.954

16.238

39.526

39.145

38.881

1

1

1

-

-

-

granites of Stanley Lake Creek and Warm Springs Creek, the 

molybdenum prospects in rhyolitic intrusive rocks of volcanic 

assemblages of Red Mountain dome, Mt. Greylock barren 

dome, and Sunbeam mine, and the Eocene rhyolite of the 

Parker Mountain mine. Samples in group A that have values 

of 206Pb/204Pb of 18.0 or more are galena from the Greyhound 

mine, igneous rocks from the granite of the Lost Packer mine, 

which have a base-metal ore association, tin granite of Camas 

Creek in the Casto pluton geophysical anomaly of both magnetic and gravity highs, and Singheiser mine molyrhyolite 

(table 3), to the east of which Precambrian rock crops out. The 

Casto structure contains major geologic and structural complexities that defy simple synthesis, although the western part 

of the area is one generally of positive residual gravity anomaly (Mabey and Webring, 1985) that may reflect Precambrian

crystalline rocks at some depth. D.R. Mabey (written commun., February 1980) said about the northeastern part of this 

region, "A large area of relative high magnetic intensity and 

high Bouguer gravity values lies between the Thunder Mountain Caldera and the Twin Peaks area. The gravity high may 

reflect a general high in the Precambrian basement. The magnetic anomalies appear to reflect a combination of basement, 

intrusive, and volcanic rocks."

Alternatively, Webring and Mabey (1987) interpreted 

the Casto structure as being underlain by units of the Casto 

pluton that are more dense than the Idaho batholith because 

Precambrian rocks are not known at the surface. In this case, 

the higher density indicates a more mafic composition. Thus, 

as with the Bayhorse geophysical anomaly, the Casto 

anomaly is permissive of some combination of more mafic
M18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

16.0

EXPLANATION D Ore

Igneous rocks today

X Igneous rocks 90 Ma 

Potassium feldspar

15.4

17 19 20 

206 pb/204 pb

Figure 5. 207Pb/204Pb versus 206Pb/204Pb for ore minerals and igneous rocks of the Challis and Hailey Fx2° quadrangles, Idaho. 

Symbol sizes are approximately two standard deviations. Solid and dashed sloping lines are regressions as labeled.

intrusive rocks and a general high in the Precambrian crystalline basement. Areas of gravity lows can be attributed to 

near-surface, less dense volcanic rocks (for example, the 

Twin Peaks caldera) or granitic intrusive rocks (for example, 

the Soldier Lakes magnetic high) that can make positive 

gravity anomalies at depth.

Thus, the two areas of samples of group A, the Bayhorse anticline and Casto structures, include major geophysically defined areas of positive gravity anomalies that 

possibly indicate structural highs in the crystalline Precambrian basement. Almost no samples of group B are in the 

area of the Casto structure.

Although the igneous-rock and ore samples have, in 

general, similar values of 206Pb/204Pb, the ore samples generally have values of 208Pb/204Pb greater than the igneous 

rocks (except for the K.G. deposit). Corrections to 206Pb/ 

204Pb and 208Pb/204Pb in the igneous rocks for in situ decay 

of uranium and thorium since the igneous rocks formed 

90-45 Ma, though small, will only increase the differences 

in 208Pb/204Pb between ore and igneous rock. Thus, derivation of some ore lead from outside the stocks is likely. The 

geographic distribution of ore and igneous rocks sampled is 

similar; however, the sampling scheme did not involve possibly related igneous rock-ore pairs in group A (except

perhaps for Thompson Creek, the pair that has a major difference in isotopic composition). It may be, therefore, that 

stocks exist that have values of 208Pb/204Pb greater for a 

given value of 206Pb/204Pb than we found during this study. 

Perhaps more likely is the existence at depth of high-rank 

metamorphic Precambrian basement. High values of Th/U 

are common in granulite facies metamorphic rocks (Doe and 

Zartman, 1979).

The two major areas studied for which samples are 

exclusively in group B are along the southern boundary of 

the Challis I°x2° quadrangle and are associated with magnetic anomalies without gravity anomalies (D.R. Mabey, 

written commun., February 1980; also see Mabey and 

Webring, 1987). The White Cloud Peaks-Little Boulder 

Creek area includes the White Cloud Peaks magnetic high 

(granite) and Little Boulder Creek magnetic low (volcanic 

rocks), the White Cloud stockwork molybdenum prospect, 

the Patti Flynn and Timberline prospects, the Empire vein, 

and the Livingston and Hoodoo mines and adjacent magnetic 

anomalies to the north. The Grimes area includes the magnetic anomaly of Grimes, the area of the CUMO and Comeback deposits, Carlson Gulch adit, and the prospect of the 

Little Falls intrusion. The magnetic anomaly may represent
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M19

40.9

40.5

40.1

39.7

39.3

38.9

38.5

EXPLANATION D Ore

f ) Igneous rocks today

X Igneous rocks 90 Ma

* Potassium feldspar

17 18 19 20 

206pb/204pb

21 22

Figure 6. 208Pb/204Pb versus 206Pb/204Pb for ore minerals and igneous rocks of the Challis and Hailey I°x2° quadrangles, Idaho. 

Symbol sizes are approximately two standard deviations. Solid line is regression as labeled.

a large diorite stock underlying the area, with some surface 

exposure. The Deadwood ore-igneous rock pair is the most 

northerly location of group B. Because it is associated with 

gravity and magnetic anomalies and a large Eocene diorite 

stock, it may be related to the Grimes deposits, which are 

associated with a magnetic anomaly and an Eocene dike 

swarm. The intrusion of Bear River on the southern boundary of the Challis quadrangle is also on a slight magnetic 

anomaly within the Sawtooth magnetic anomaly without a 

gravity anomaly and includes the tin granites of Wolf Mountain and Big Silver Creek just south of the boundary with the 

Hailey I°x2° quadrangle.

The lack of gravity anomalies associated with these 

group B deposits suggests that Precambrian crystalline basement, if present at all, is deeper than in group A areas such 

that the isotopic signatures of the group B magmas were 

imprinted on both igneous rocks and veins above any Precambrian basement.

Although we do not have equivalent geophysical information for the Hailey quadrangle, one might speculate that 

the isotopic signatures from the area including the Webfoot

mine to the Carrie Leonard mine are from Precambrian crystalline basement at unknown depth. Deposits to the east of 

these deposits again have group B isotopic signatures of 

Basin and Range rocks. Precambrian crystalline basement, if 

present at all, must be deeper than the horizon where the isotopic signatures were acquired.

The two areas of group B deposits and rocks along the 

boundary between the Challis and Hailey I°x2° quadrangles 

suggest that a strip of Great Basin (group B) lead in igneous 

rocks and ores is present along the length of the boundary. 

More data are needed to fill in the gaps.

CONSIDERATION OF OTHER 

LEAD SOURCES

No rock has been analyzed from the study area that has 

208Pb/204Pb values as high as those for the ore minerals of 

group A. Mineral deposits in the black shale belt of central 

Idaho are discussed at length by Sanford and others (1989) 

and Sanford and Wooden (this volume), who conclude that
M20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 5. U, Th, and Pb concentrations and calculated initial lead ratios for igneous and sedimentary rocks, Challis and Hailey I°x2°

quadrangles, Idaho.

[Sample information is given in table 3. U, Th, Pb concentrations are in parts per million]

Group Name U Th Pb Age (Ma) 206pb/204pb 207pb/204pb 208pb/204pb

GRANITE AND RHYOLITE

Molybdenum stockwork

A

A

A 

A

A 

B 

B

B

A

Sunbeam

Red Mountain dome

Mt. Greylock 

Parker Mountain

Singheiser 

Little Falls 

White Cloud-West1

Lost Packer 

Thompson Creek1

6.63

4.45

5.46 

4.23

3.14 

5.12

1.27

24.2

24.2

27.9 

24.4

16.3 

16.3

3.11

8.55

10.7

31.5 

13.0

9.06 

8.14

4.61

90

90

90 

90

90 

90 

90

90 

90

17.11

17.12

17.38 

17.58

18.57 

18.58 

19.20

19.51 

20.51

15.50

15.50

15.52 

15.51

15.63 

15.63 

15.69

15.73 

15.81

38.66

38.79

39.01 

39.08

39.28 

38.59 

39.26

39.87 

40.33

Base- and precious-metal veins

B 

B

Deadwood1 

McCoy1

- - - 90 

90

19.49 

19.57

15.72 

15.76

39.32 

39.31

Tin granite

A 

A 

B

B

A

B

Stanley Lake Creek 

Warm Springs Creek 

Wolf Mountain

Big Silver Creek 

Camas Creek

Bear River, North

2.28 

2.43 

2.32

3.83 

1.60

3.44

24.9 

17.3 

14.4

14.7 

12.1

12.7

18.0 

16.7 

29.4

18.4 

13.6

20.3

90 

90 

90

90 

90

90

17.44 

17.45 

18.57

18.64 

18.65

18.69

15.54 

15.55 

15.61

15.62 

15.64

15.63

38.93 

38.92 

38.91

38.87 

39.49

38.91

SEDIMENTARY ROCKS

"Sawmill Gulch"

Holman Creek-West

Urexco

1.05

91.10

13.80

4.41

10.90

2.99

4.12

42.10

15.00

90

500

500

19.06

11.98

23.98

15.66

15.26

15.92

39.20

38.68

28.50

Potassium feldspar.

few, if any, of the vein leads in either group A or B were 

derived solely from the shale in the section. One might ask 

whether mineralized samples in either group A or B might 

contain significant components (for example, lead in detritus) of either Paleozoic sedimentary rocks or rocks of the 

Belt Supergroup. Three samples of Paleozoic shale or argillite from central Idaho that were analyzed in this study 

(tables 2, 4) are plotted in figure 9, along with four samples 

of limestone from the Dillon, Montana, I°x2° quadrangle 

(Doe and others, 1986) and one sample of limestone from 

north-central Nevada (Rye and others, 1974). Although the 

samples of Paleozoic limestone are not from central Idaho, 

little difference in isotopic ratios is seen between them and 

the local shaly rocks. We have no reason to suspect that the 

lead-isotope data are not reasonably representative of a very 

large area. The significant point is that, although the overall 

trend in 208pb/204pb versus 206pb/204pb for the Paieozoic

sedimentary rocks is much flatter than that for ore minerals, 

one sample of shale and two of limestone have lead-isotopic 

compositions similar to ore lead of group B. Thus a component of lead from sediments in the group B assemblage cannot be ruled out.

Rocks of the Belt Supergroup are exposed in the 

extreme northern part of the Challis I°x2° quadrangle. Data 

for ore minerals of group B are shown in figure 10 together 

with data for ore minerals from Cretaceous and Tertiary 

veins in the Wallace I°x2° quadrangle to the north in the 

Belt Supergroup. Although there is some overlap in the 

lead-isotopic compositions for the two groups of ore minerals, samples from the Belt Supergroup have a tendency to 

be less radiogenic than samples from the Challis and Hailey 

quadrangles. Any rocks of the Belt Supergroup underlying 

the Paleozoic section seem to be excluded as possible 

source rocks.

MODEL FOR LEAD DERIVATION

In the Challis and Hailey I°x2° quadrangles, there are 

two large areas of group A lead-isotope assemblages one 

in the central and northern parts of the Challis quadrangle 

and one in the central part of the Hailey quadrangle. These 

areas are separated by a strip of group B lead-isotope assemblages along the length of the boundary between the two
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M21

41

40 -

39

38

37

36

16.0

15.8

.15.6

15.4

15.2

III

16 17 18 

206pb/204pb

19 20

Figure 7. Lead-isotope areas of Zartman (1974). Area I is the area 

of rejuvenated cratons: la (+) includes Archean basement rocks and 

is the area north of the Colorado-Wyoming State line; Ib (X) includes only Proterozoic basement rocks. Area II (open boxes) is the 

Basin and Range miogeosynclinal area mostly in Nevada. Area III 

(solid circles) is the eugeosynclinal continental margin mostly in 

California, Oregon, and Washington.

quadrangles that perhaps widens to the east. Because the 

geophysical anomalies tend to have north-south trends, our 

sampling leaves the possibility of patches of group A and 

group B leads.

Group A lead is deduced to come from areas where 

magmas and ore fluids were generated in or interacted with 

Precambrian crystalline rocks metamorphosed to high rank 

during the Precambrian. Because exposures of Precambrian 

crystalline rocks are sparse on the surface and restricted to 

the far eastern parts of the Challis and Hailey quadrangles,

the source of these igneous rocks and ore minerals must be 

deeper than rocks now observed on the surface. These crystalline source rocks must have high and variable values of 

Th/U as reflected by high values of 208Pb/204Pb relative to 

the values of 206Pb/204Pb in our samples. Because some of 

the ore minerals have values of 208Pb/204Pb greater than any 

of the igneous rocks, we conclude that the lead of these ore 

minerals represents a larger component of partially extracted 

lead from phases having very high values of Th/U (such as 

monazite) in the Precambrian crystalline basement, whereas 

lead of the igneous rocks probably more closely represents 

whole-rock extraction. That is, lead of the mineral deposits 

may have components derived either from Cretaceous or 

Tertiary igneous rocks and from partially extracted lead from 

Precambrian crystalline wallrocks. The possibility remains 

that appropriate igneous rocks were not sampled.

There is little distinction between lead-isotope ratios 

of igneous rocks of group B and mineral deposits of group 

B, although many ore minerals of group B have values of 

207Pb/204Pb greater than any of the igneous rocks. Some 

Paleozoic sedimentary rocks at the surface have lead-isotope ratios similar to those for ore and igneous rock samples of group B. Thus, igneous rocks and ores of group B 

may be derived, at least in part, from sources such as now 

at the surface. Mineral deposits of group B may be adjacent 

to igneous rocks of group A, but no mineral deposits of 

group A are known to be adjacent to igneous rocks of 

group B, except for the Wood River district (for example, 

Minnie Moore). These relationships lead us to propose a 

conceptual model whereby (1) the deep crust is composed 

of Precambrian crystalline rocks, at least in part, (2) units 

of the Great Basin are present in patches, particularly along 

the boundary between the Hailey and Challis quadrangles, 

to establish the observed lead-isotope signatures in some 

igneous rocks and ores, either through their generation or 

through interactions during transport or emplacement, and 

(3) lead isotopes are mainly derived from beneath the 

exposed section through interactions of magmas and attendant ore fluids with country rocks.

COMPARISON WITH MAJOR 

TIN-PRODUCING AREAS

In addition to tin granite in the Hailey and Challis I°x2° 

quadrangles, ore deposits in the black shale belt commonly 

contain stannite and may contain minor cassiterite (Hall, 

1985,1987a). Samples of mineralized rock in the black shale 

belt can contain more than 1 percent tin3 (in the Boulder 

Basin at lat 43°50' N., long 114°3r W.) (Hall, 1987a) in a

3Earlier analyses by quantitative X-ray fluorescence in Tschanz and 

others (1974) and Tschanz and Kiilsgaard (1986) gave much higher values 

for tin, as much as 6 percent. These high values may be due to loss of sulfur 

and other volatiles in the fusion step used to form a bead for X-ray fluores-
M22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

25 MILES 

J

Figure 8. Map showing lead-isotope data and simplified Bouguer gravity anomalies, Challis I°x2° quadrangle, Idaho. Contour interval 

10 gammas; H, gravity high; L, gravity low. Heavy solid lines delineate aeromagnetic high at 1,800 gammas (relative) closure in the Bayhorse anticline area and magnetic low west of the Trans-Challis fault complex. Dashed line separates group A and group B isotopic areas. 

Straight heavy dashed lines trending northeast-southwest indicate margins of Trans-Challis fault complex. Symbols: open circle, ore having 206Pb/204Pb greater than 19.1; open square, ore having 206Pb/204Pb 18.1-19.1; solid square, ore having 206Pb/204Pb less than 18.0; 

solid circle, granite- or rhyolite-type. Geophysical data from D.R. Mabey (written commun., February 1980).

mineralogical and chemical assemblage similar to Bolivian 

tin deposits (Hall, 1985; Tschanz and Kiilsgaard, 1986). 

Although they are half a world apart, the two major tin mining areas of the world, Malaysia and Bolivia, both have 

unusual but similar lead-isotope ratios for ore deposits, typical of upper crust (Doe, 1992). Though the sample size is 

small, the values of 208Pb/204Pb and, especially, 207Pb/204Pb 

are unusually great for galenas in both tin-producing areas.

Lead-isotopic compositions for galena and tin granite 

from the Challis and Hailey quadrangles are shown in figure 

11, along with data from the tin provinces of Malaysia (Doe, 

1992) and Bolivia (Tilton and others, 1981). A few galenas 

of group A from the Challis and Hailey quadrangles have values of 207Pb/204Pb that are similarly as high as those from the 

tin provinces, but their 208Pb/204Pb values are even higher. 

Galenas of group B from the Grimes Pass district (and

Gilmore district) compare more favorably with data from the 

tin-producing areas, and an especially good fit is for tin granite along the boundary between the Challis and Hailey quadrangles. Perhaps surprisingly, data from the best stannitebearing areas of the Challis (Timberline and Patti Flynn prospects) and the Hailey (Golden Glow and Crown point deposits in Boulder Basin and Combination deposit in Galena 

Basin) quadrangles show values of 206Pb/204Pb higher than 

the tin producers; however, all the tin-bearing deposits have 

high values of 207Pb/204Pb and 208Pb/204Pb, typical of the 

upper crust. Although not too much weight should be placed 

on this "fingerprinting" involving such widely spaced localities, further interest in the Challis and Hailey I°x2° quadrangles for tin resources is warranted, especially in those 

areas of the Boulder Basin that are also silver rich such that 

tin might be produced as a byproduct (Hall, 1987a).
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M23

40.9

40.1

39.3

38.5

EXPLANATION 

Ore

 f Group A 

Q] GroupB

Sedimentary rocks 

L Calcareous, today 

S Shaly, today 

X Rock, 90 Ma

17 19 21 23 25 

206pb/204pb

27 29

Figure 9. 208Pb/204Pb versus 206Pb/204Pb for ore minerals and sedimentary rocks (ore minerals and shaly rocks are from central Idaho, 

limestone is from Montana). Solid line is regression for group A igneous rocks (fig. 6).

ORIGIN OF GRANITE

There were three significant surprises in this study. The 

first is the discovery of two lead-isotope terranes: one terrane 

similar to Proterozoic and Precambrian crystalline-rock terranes of the Rocky Mountains, in which rock units have nonradiogenic uranogenic leads that have high values of 232Th/ 

238U, and the other terrane similar to the Basin and Range, in 

which normal to moderately radiogenic lead is present. The 

second surprise is that stockwork molybdenum porphyry and 

tin granite are present in both terranes. The third surprise is 

that the stockwork molybdenum and tin granite within each 

isotopic terrane have similar lead-isotopic compositions 

(table 5).

All of the lead-isotope data in central Idaho have crustal 

signatures, and there is no evidence of an oceanic mantle 

component. In fact, the values of 207Pb/204Pb tend to be high 

for their values of 206Pb/204Pb, a characteristic of the upper 

crust (Doe and Zartman, 1979). Norman and Leeman (1989) 

presented lead-isotope data for four samples of Idaho 

batholith (Cretaceous) and five samples of Challis Volcanic 

Group (Eocene) from central and southwestern Idaho, as 

well as data for younger igneous rocks. They also presented 

data on strontium and neodymium isotopes and a number of 

trace elements. Although they do not use the group A and B 

classification of Doe and Delevaux (1985) or the areas of 

Zartman (1974), their lead-isotope data for the Cretaceous

Idaho batholith fit in group B and their data for the Eocene 

Challis Volcanic Group fit in group A. Utilizing trace element and other isotopic data, they interpreted the group B 

leads as being mixtures of subduction-related magmas 

(asthenospheric mantle, oceanic lithosphere, and continental 

lithospheric mantle), as represented by basalts of the Cascade Range (included in area III of Zartman) and Precambrian continental crust. They interpreted group A leads as 

coming from continental lithospheric sources (subcontinental lithospheric mantle, unradiogenic lower crust, and more 

radiogenic upper crust) but said there is a strong case for 

intracrustal melting.

Norman and Leeman (1989) related the isotopic differences between leads of group A and group B to the change 

in tectonic environments, probably from compression during 

the Cretaceous to strike-slip movement during the Eocene. 

We find, however, that leads of group A and group B are 

present in either the Cretaceous or Tertiary igneous rocks, 

and, thus, the isotopic groupings probably are not time 

related. We are in substantial agreement with Norman and 

Leeman as to the sources of group A leads, but their interpretation of the sources of group B leads is an alternative interpretation to ours and that of Church and others (1986) for the 

Mt. Tolman molybdenum porphyry in eastern Washington; 

that is, derivation from a Basin and Range geologic section 

or area II of Zartman. Unfortunately, neodymium and strontium isotope data are not available for our samples in order
M24 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

40

39

38

37

36

0

EXPLANATION

Ore sample, Challis and Hailey quadrangles 

[ ] Ore sample, Belt Supergroup, Idaho 

M Ore sample, Belt Supergroup, Montana

16 17 18

206r

19 20 21

Figure 10. 208Pb/204Pb versus 206Pb/204Pb for ore minerals of the Challis and Hailey I°x2° quadrangles, Idaho, and Mesozoic 

and Cenozoic ore minerals of the Belt Supergroup in Idaho and Montana. Data for Belt Supergroup from Zartman and Stacey 

(1971), Marvin and others (1983), and Marvin and Zartman (1984).

that we might further evaluate these possibilities. The important point, however, is that consideration of expanded 

geochemical data indicates derivation of the igneous rocks 

from two quite different source environments. Both molybdenum porphyry and tin granite formed, however, in both 

source environments.

Although the molybdenum porphyries of central Idaho 

are classed as low-fluorine porphyries, samples from the 

Thompson Creek mine, a group A isotopic deposit, have 

nonradiogenic values of 206Pb/204Pb and high values of 

208Pb/204Pb (table 4), as do samples from the Henderson

Climax-type of molybdenum porphyry in the Colorado Front 

Range (Stein, 1985); such values indicate derivation from 

high-rank metamorphic rocks (Doe and Zartman, 1979). The 

sulfur-isotope data are also characteristic of crustal sources, 

particularly sedimentary sources (Howe and Hall, 1985). 

Although their 834S values are not as heavy as those for the 

stockwork molybdenum deposit of Thompson Creek in 

Idaho, molybdenum porphyries of the Climax type in the 

Rocky Mountain provinces tend to have high values of 834S 

relative to the mantle. Stein (1985) gave values of 834S for 

molybdenum porphyries at Henderson and Mount Emmons,
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M25

42

41

40

39

38

\

M 

B M

M

M

B B

EXPLANATION

ORE SAMPLES, IDAHO 

T Group A 

PI Group B

TIN-PRODUCING COUNTRIES 

B Bolivia 

M Malaysia

17 18 19 20 21

Figure 11. 208Pb/204Pb versus 2o6Pb/204Pb for ore minerals of the Challis and Hailey I°x2° quadrangles, Idaho, and ore minerals from the 

largest tin-producing countries, Malaysia and Bolivia (Tilton and others, 1981; Doe, 1992).

Colorado, of about +4 to +6 and at Climax, Colorado, of 

about +2 to +4, whereas 634S values at Questa, New Mexico, 

are close to mantle values of zero.

The mantle is generally highly depleted in molybdenum 

and moderately depleted in tin, as compared to the bulk crust 

(primitive mantle is depleted in molybdenum by more than a 

factor of 10 and in tin by a factor of 2; Lehman, 1990), and 

is a poor source for these metals. In fact, Lehman (1990) 

concluded that the Eastern tin belt of Malaysia is less tin rich 

than the Main tin belt because the magmas of the Eastern belt 

may have included a mantle component, as deduced from 

strontium and neodymium isotope data. Molybdenum and 

tin are enriched in the upper crust as compared to primitive 

mantle (molybdenum by more than a factor of 20 and tin by

a factor of 5), whereas copper is present in about equal 

amounts (Lehman, 1990). It therefore is likely that the 

molybdenum and tin granites of Idaho were derived from 

within the crust or at least from differentiating mantle magmas that reacted extensively with intruded crust.

Tin granite is expected to have a lead-isotope signature different from that of stockwork molybdenum granite 

because tin enrichment by differentiation requires that the 

magma be highly reduced, whereas molybdenum-enriched 

magma is more oxidizing (Ishihara and others, 1979; Candela and Holland, 1986; Lehman, 1990). This reduced 

nature is commonly presumed to arise through reaction of 

magma with carbon-rich rocks such as pelitic schist or 

black shale; however, sulfur-rich sources also may reduce a
M26 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

magma (Lehman, 1990). Reduction by sulfur generally has 

less appeal than reduction by carbon because the tin mineral of interest is the tin oxide cassiterite. If tin granite magmas have interacted more with carbonaceous sediments 

than have molybdenum granite, a difference in lead-isotope 

signatures might be expected because shaly rocks have lead 

contents similar to those of the granites analyzed, and old 

shale generally has more radiogenic lead by Eocene time 

(fig. 9) than does the granite, especially more than the granite of group A. But such an isotopic difference between 

molybdenum and tin granites is not the case.

A model is needed whereby the molybdenum and tin 

granite magmas are derived from the same sources and follow the same reaction paths with wallrocks of normal lead 

contents (which would give similar lead-isotope signatures) 

but follow different differentiation trends. In one possible 

model, tin granite magmas reacted with lead-poor, carbonrich material such as petroleum, natural gas, or perhaps coal, 

whereas molybdenum granite magmas did not. Because the 

major stockwork molybdenum-bearing granites in the study 

area are about 45 m.y. older than the tin granites, the carbonrich material could have been absent during the Cretaceous 

but present during the Eocene as a result of thrusting and 

fluid migration. Eocene molybdenum-enriched magmas 

then would not have intersected the carbonaceous lead-poor 

material. In a second, and perhaps more likely, model, tin 

granite magmas reacted with older sulfide-mineralized Cretaceous igneous rocks and mineralized country rocks. Some 

radiogenic lead would have formed in the Cretaceous 

igneous rocks between the time of their origin about 90 Ma 

and the time of formation of the tin granite about 45 Ma. 

Because Cretaceous granites were not isotopically uniform 

when they formed, the radiogenic lead evolution may be lost 

in the noise of the isotopic signatures. Also, we have corrected all whole-rock samples back to a common time of 90 

Ma (table 5) to remove any isotopic effects associated with 

the age difference.

In the second model, the tin granite magmas were 

reduced by sulfur associated with the Cretaceous intrusive 

rocks. That the predominant tin mineral is stannite, a copper-iron-tin sulfide, rather than cassiterite, a tin oxide, supports this hypothesis. The Cretaceous intrusive rocks may 

also be a source of tin, even though the low-fluorine molybdenum granites do not contain tin minerals, because the tin 

may be in minerals such as sphene, magnetite, ilmenite, epidote, and hornblende. Eocene molybdenum granites and 

rhyolites then would have evolved without extensive reactions with Cretaceous mineralized intrusive rocks.

REFERENCES CITED

Bankey, Viki, and Kleinkopf, M.D., 1988, Bouguer gravity anomaly map and four derivative maps of Idaho: U.S. Geological 

Survey Geophysical Investigations Map GP-978, 3 sheets.

Bennett, E.H., and Knowles, C.R., 1985, Tertiary plutons and related rocks in central Idaho, in Mclntyre, D.H., ed., Symposium

on the geology and mineral deposits of the Challis 1 °X2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-F, p. 

81-95.

Candela, P.A., and Holland, H.H., 1986, A mass transfer model for 

copper and molybdenum in magmatic hydrothermal systems The origin of porphyry-type ore deposits: Economic 

Geology, v. 81, p. 1-17.

Cannon, R.S., Pierce, A.P., Antweiler, J.C., and Buck, K.L., 1961, 

The data of lead isotope geology related to problems of ore 

genesis: Economic Geology, v. 56, p. 1-38.

Church, S.E., LeHuray, A.P., Grant, A.R., Delevaux, M.H., and 

Gray, I.E., 1986, Lead-isotopic data from sulfide minerals 

from the Cascade Range, Oregon and Washington: Geochimica et Cosmochimica Acta, v. 50, p. 317-328.

Davis, K.E., 1978, Lead isotope ratios of galena from the Bayhorse 

mining district, Custer County, Idaho: Isochron/West, no. 22, 

p. 15-16.

Doe, B.R., 1979, The application of lead isotopes to mineral prospect evaluation of Cretaceous-Tertiary magmatothermal ore 

deposits in the Western United States, in Watterson, J.R., and 

Theobald, P.K., eds., Geochemical exploration 1978: International Geochemical Exploration Symposium, 7th, Golden, 

Colorado, Proceedings; Association of Exploration Geochemists, p. 227-232.

 1992, Lead isotopic composition of galena from Malaysia, 

an S-type granite terrane, in Informal notes of the workshop on 

the application of isotope systems to geological problems: U.S. 

Geological Survey Open-File Report 92-525, p. 28-62.

Doe, B.R., Berger, B.R., and Elliott, I.E., 1986, Lead-isotope evaluation of selected ores and mineral prospects in the Butte and 

Dillon I°x2° quadrangles, Montana: U.S. Geological Survey 

Open-File Report 86-111, 40 p.

Doe, B.R., and Delevaux, M.H., 1973, Variations in lead isotopic 

compositions in Mesozoic granitic rocks of California A preliminary investigation: Geological Society of America Bulletin, v. 84, p. 3513-3526.

 1980, Lead isotope investigations in the Minnesota River 

valley I, Late- and post-tectonic granites: Geological Society 

of America Special Paper 182, p. 105-112.

-1985, Lead-isotope characteristics of ore systems in central

Idaho, in Mclntyre, D.H., ed., Symposium on the geology and 

mineral deposits of the Challis I°x2° quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658-O, p. 181.

Doe, B.R., Hedge, C.E., and White, D.E., 1966, Preliminary investigation of the source of lead and strontium in deep geothermal 

brines underlying the Salton Sea geothermal area: Economic 

Geology, v. 61, p. 462-483.

Doe, B.R., and Stacey, J.S., 1974, The application of lead isotopes 

to the problems of ore genesis and ore prospect evaluation A 

review: Economic Geology, v. 69, p. 757-776.

Doe, B.R., Steven, T.A., Delevaux, M.H., Stacey, J.S., Lipman, 

P.W., and Fisher, F.S., 1979, Genesis of ore deposits in the San 

Juan volcanic field, southwestern Colorado Lead isotope evidence: Economic Geology, v. 74, p. 1-26.

Doe, B.R., and Zartman, R.E., 1979, Plumbotectonics, The Phanerozoic, in Barnes, H., ed., Geochemistry of hydrothermal ore 

deposits: New York, Wiley Interscience Publications, p. 

22-70.

Dover, J.H., 1981, Geology of the Boulder-Pioneer Wilderness 

Study Area, Blaine and Custer Counties, Idaho, in Mineral
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M27

resources of the Boulder-Pioneer Wilderness Study Area, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 1497-A, p. 15-75.

Ekren, E.B., 1985, Eocene cauldron-related volcanic events in the 

Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the 

geology and mineral deposits of the Challis 1 °x2° quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-C, p. 43-58.

Fisher, F.S., and Johnson, K.M., eds., 1987a, Preliminary manuscript for "Mineral-resource potential and geology of the Challis I°x2° quadrangle, Idaho": U.S. Geological Survey OpenFile Report 87^80, 251 p.

 1987b, Challis rock terrane, in Fisher, F.S., and Johnson, 

K.M., eds., Preliminary manuscript for "Mineral-resource 

potential and geology of the Challis I°x2° quadrangle, Idaho": 

U.S. Geological Survey Open-File Report 87-480, p. 51-54.

Fisher, F.S., Kiilsgaard, T.H., Johnson, K.M., and Bennett, E.H., 

1987, Precious-metal veins, in Fisher, F.S., and Johnson, K.M., 

eds., Preliminary manuscript for "Mineral-resource potential 

and geology of the Challis I°x2° quadrangle, Idaho": U.S. 

Geological Survey Open-File Report 87-480, p. 117-126.

Fisher, F.S., Mclntyre, D.H., and Johnson, K.M., 1983, Geologic 

map of the Challis I°x2° quadrangle, Idaho: U.S. Geological 

Survey Open-File Report 83-523, 1:250,000 scale, 41 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

 1987a, Lead-silver-zinc-antimony-tin vein deposits, in 

Fisher, F.S., and Johnson, K.M., eds., Preliminary manuscript 

for "Mineral-resource potential and geology of the Challis 

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87-480, p. 133-140.

-1987b, Cretaceous molybdenum stockworks, in Fisher,

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral-resource potential and geology of the Challis I°x2° 

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87^80, p. 152-158.

Hall, W.E., Batchelder, J.N., and Douglass, R.D., 1974, Stratigraphic section of the Wood River Formation, Blaine County, 

Idaho: U.S. Geological Survey Journal of Research, v. 2, no. 1, 

p. 89-95.

Hall, W.E., and Hobbs, S.W., 1987, Black shale terrane, in Fisher, 

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral-resource potential and geology of the Challis I°x2° 

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87^80, p. 29-42.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, p. 579-592.

Hall, W.E., Schmidt, E.A., Howe, S.S., and Broch, M.J., 1984, The 

Thompson Creek, Idaho, porphyry molybdenum deposit An 

example of a fluorine deficient molybdenum granodiorite system: Proceedings of the Sixth Quadrennial IAGOD Symposium, v. 6, p. 349-357.

Hardyman, R.F., 1985, The Twin peaks caldera and associated ore 

deposits, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis 1 °x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-G, p. 97-105.

Hardyman, R.F., and Fisher, F.S., 1985, Rhyolite intrusions and 

associated mineral deposits in the Challis volcanic field, Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis I°x2° quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-N, p. 167-179.

Hobbs, S.W., 1985, Structural and stratigraphic controls of ore 

deposits in the Bayhorse area, Idaho, in Mclntyre, D.H., ed., 

Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-K, p. 133-140.

 1987, Carbonate rock terrane, in Fisher, F.S., and Johnson, 

K.M., eds., Preliminary manuscript for "Mineral-resource 

potential and geology of the Challis I°x2° quadrangle, Idaho": 

U.S. Geological Survey Open-File Report 87-480, p. 20-29.

Hobbs, S.W., Fisher, F.S., and Johnson, K.M., 1987, Irregular 

replacement deposits of base and precious metals, in Fisher, 

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral-resource potential and geology of the Challis I°x2° 

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87^80, p. 175-179.

Hobbs, S.W., Hays, W.H., and Mclntyre, D.H., 1975, Geologic 

map of the Clayton quadrangle, Custer County, Idaho: U.S. 

Geological Survey Open-File Report 75-76, scale 1:62,500, 

23 p.

Howe, S.S., and Hall, W.E., 1985, Light-stable-isotope characteristics of ore systems in central Idaho, in Mclntyre, D.H., ed., 

Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-P,p. 183-192.

Ishihara, S., 1977, The magnetite-series and ilmenite-series granitic 

rocks: Mining Geology (Japan), v. 27, p. 293-305.

Ishihara, S., Sawata, H., Arpornsuwan, S., Busaracome, P., and 

Bungbrakearti, N., 1979, The magnetite-series and ilmeniteseries granitoids and their bearing on tin mineralization, particularly of the Malay Peninsula region: Geological Society of 

Malaysia Bulletin, v. 11, p. 103-110.

Johnson, K.M., and Fisher, F.S., 1987, High-level rhyolite-hosted 

precious-metal deposits, in Fisher, F.S., and Johnson, K.M., 

eds., Preliminary manuscript for "Mineral-resource potential 

and geology of the Challis I°x2° quadrangle, Idaho": U.S. 

Geological Survey Open-File Report 87-480, p. 163-166.

Johnson, K.M., Lewis, R.S., Bennett, E.H., and Kiilsgaard, T.H., 

1988, Cretaceous and Tertiary intrusive rocks of south-central 

Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the 

geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 55-86.

Kiilsgaard, T.H., and Bennett, E.H., 1985, Mineral deposits in the 

southern part of the Atlanta lobe of the Idaho batholith and 

their genetic relation to Tertiary intrusive rocks and to faults, in 

Mclntyre, D.H., ed., Symposium on the geology and mineral 

deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-M, p. 153-165.

 1987a, Idaho batholith terrane, in Fisher, F.S., and Johnson, 

K.M., eds., Preliminary manuscript for "Mineral-resource 

potential and geology of the Challis I°x2° quadrangle, Idaho": 

U.S. Geological Survey Open-File Report 87-480, p. 43-51.

 1987b, Eocene plutonic rock terrane, in Fisher, F.S., and 

Johnson, K.M., eds., Preliminary manuscript for "Mineralresource potential and geology of the Challis I°x2°
M28 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87-480, p. 54-60.

 1987c, Mixed base- and precious-metal veins, in Fisher, 

F.S., and Johnson, K.M., eds., Preliminary manuscript for 

"Mineral-resource potential and geology of the Challis 1 °x2° 

quadrangle, Idaho": U.S. Geological Survey Open-File Report 

87-480, p. 126-133.

 1987d, Tertiary molybdenum stockworks, in Fisher, F.S.,

and Johnson, K.M., eds., Preliminary manuscript for "Mineralresource potential and geology of the Challis I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File Report 87-480, 

p. 158-162.

Kiilsgaard, T.H., and Hingley, Frank, 1989, Regional geology of 

the northwestern part of the Hailey I°x2° quadrangle and ore 

deposits of the Atlanta district, Idaho, in Winkler, G.R., SoulHere, S.J., Worl, R.G., and Johnson, K.M., eds., Geology and 

mineral deposits of the Hailey and western Idaho Falls 1 °x2° 

quadrangle quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 35-36.

Kiilsgaard, T.H., and Lewis, R.S., 1985, Plutonic rocks of Cretaceous age and faults in the Atlanta lobe of the Idaho batholith, 

Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the 

geology and mineral deposits of the Challis 1 °x2° quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-B, p. 29-44.

Leeman, W.P., Menzies, M.A., Matty, D.J., and Embree, G.F., 

1985, Strontium, neodymium and lead isotopic compositions 

of deep crustal xenoliths from the Snake River Plain Evidence for Archean basement: Earth and Planetary Science Letters, v. 75, p. 354-368.

Lehman, Bernd, 1990, Metallogeny of tin, in Bhattacharji, S., and 

others, eds., Lecture notes in earth sciences: New York, 

Springer Verlag, v. 32, 211 p.

Lewis, R.S., 1989, Plutonic rocks in the southeastern part of the Idaho batholith and their relation to mineralization, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles: U.S. Geological Survey Open-File 

Report 89-639, p. 33-34.

Link, P.K., and Hackett, W.R., eds., 1988, Guidebook to the geology of central and southern Idaho: Idaho Geological Survey 

Bulletin 27, 319 p.

Ludington, S.D., 1986, Descriptive model of Climax Mo deposits, 

in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 73.

Mabey, D.R., and Webring, M.W., 1985, Regional geophysical 

studies in the Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-E,p. 69-79.

Marvin, R.F., and Zartman, R.E., 1984, A tabulation of lead isotopic ratios for lead minerals from mines and prospects in the 

Belt-Purcell Basin in the United States and Canada: U.S. Geological Survey Open-File Report 84-210, 15 p.

Marvin, R.F., Zartman, R.E., Obradovich, J.D., and Harrison, J.E., 

1983, Geochronometric and lead isotope data on samples from 

the Wallace I°x2° quadrangle, Montana and Idaho: U.S. Geological Survey Miscellaneous Field Studies Map MF-1354-G.

McFadden, M.D., Measures, E.A., and Isaacson, P.E., 1988, Early 

Paleozoic continental margin development, central Idaho, in 

Link, P.K., and Hackett, W.R., eds., Guidebook to the geology

of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 129-152.

Mclntyre, D.H., ed., 1985, Symposium on the geology and mineral 

deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658, 227 p.

Mclntyre, D.H., Ekren, E.B., and Hardyman, R.F., 1982, Stratigraphic and structural framework of the Challis volcanics in 

the eastern half of the Challis I°x2° quadrangle, Idaho, in 

Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic 

geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, p. 3-22.

Mclntyre, D.H., Hobbs, S.W., Marvin, R.F., and Mehnert, H.H., 

1976, Late Cretaceous and Eocene ages for hydrothermal alteration and mineralization, Bayhorse District and vicinity, Custer 

County, Idaho: Isochron/West, no. 16, p. 11.

Mclntyre, D.H., and Johnson, K.M., 1985, Epitherrnal gold-silver 

mineralization related to volcanic subsidence in the Custer graben, Custer County, Idaho, in Mclntyre, D.H., ed., Symposium 

on the geology and mineral deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-1, p. 

109-115.

Mitchell, V.E., Strowd, W.B., Hustedde, G.S., and Bennett, E.H., 

1981, Mines and prospects of the Dubois quadrangle, Idaho: 

Idaho Bureau of Mines and Geology, Mines and Prospects 

Map Series, scale 1:250,000, 22 p.

 1986, Mines and prospects of the Challis quadrangle, Idaho 

(2nd ed.): Idaho Bureau of Mines and Geology, Mines and 

Prospects Map Series, scale 1:250,000, 56 p.

Moye, F.J., Hackett, W.R., Blakley, J.D., and Snider, L.G., 1988, 

Regional geologic setting and volcanic stratigraphy of the 

Challis volcanic field, central Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 87-97.

Moye, F.J., Sanford, R.F., Erdman, J.A., and Johnson, K.M., 1989, 

Volcanic-hosted and intrusion-related mineral deposits in the 

Hailey and western Idaho Falls quadrangles, Idaho, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 70-72.

Norman, M.D., and Leeman, W.P., 1989, Geochemical evolution of 

Cenozoic-Cretaceous magmatism and its relation to tectonic 

setting, southwestern Idaho, U.S.A.: Earth and Planetary Science Letters, v. 94, p. 78-96.

Ohmoto, Hiroshi, and Rye, R.O., 1979, Isotopes of sulfur and carbon, in Barnes, H.L., ed., Geochemistry of hydrothermal ore 

deposits (2nd ed.): New York, Wiley-Interscience, p. 509-567.

Paull, R.A., Wolbrink, M.A., Volkmann, R.G., and Grover, R.L., 

1972, Stratigraphy of the Copper Basin Group, Pioneer Mountains, south-central Idaho: American Association of Petroleum 

Geologists Bulletin, v. 56, p. 1370-1401.

Poole, F.G., Sandberg, C.A., and Boucot, A.J., 1977, Silurian and 

Devonian paleogeography of the western United States, in 

Stewart, J.H., Stevens, C.H., and Fritsche, A.E., eds., Paleozoic 

paleogeography of the Western United States: Pacific Section, 

Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 1, p. 39-65.

Reed, B.L., 1986, Descriptive model of porphyry Sn, in Cox, D.P., 

and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 108.
LEAD-ISOTOPE CHARACTERISTICS OF ORE SYSTEMS M29

Rye, R.O., Doe, B.R., and Wells, J.D., 1974, Stable isotope and lead 

isotope study of the Cortez, Nevada, gold deposit and surrounding area: U.S. Geological Survey Journal of Research, v. 

2, p. 13-23.

Rye, R.O., and Ohmoto, Hiroshi, 1974, Sulfur and carbon isotopes 

and ore genesis A review: Economic Geology, v. 69, p. 

826-842.

Rye, R.O., Roberts, R.J., Whelan, J.F., and Mawad, M.M., 1980, 

Reconnaissance sulfur isotope investigations of mineral deposits in the Precambrian shield, Kingdom of Saudi Arabia: U.S. 

Geological Survey Saudi Arabian Mission Technical Record 7 

(Interagency Report 346), 77 p.

Sandberg, C.A., Hall, W.E., Batchelder, J.N., and Axelson, Claus, 

1975, Stratigraphy, conodont dating, and paleotectonic interpretation of the type Milligen Formation (Devonian), Wood 

River area, Idaho: U.S. Geological Survey Journal of Research, 

v. 3, p. 707-720.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River Plain, Idaho: Wyoming 

Geological Association Guidebook, Twenty-Ninth Annual 

Field Conference, p. 499-515.

Skipp, Betty, and Hall, W.E., 1975, Structure and Paleozoic stratigraphy of a complex of thrust plates in the Fish Creek Reservoir 

area, south-central Idaho: U.S. Geological Survey Journal of 

Research, v. 3, p. 671-689.

Skipp, Betty, and Sandberg, C.A., 1975, Silurian and Devonian 

miogeosynclinal and transitional rocks of the Fish Creek Reservoir window, central Idaho: U.S. Geological Survey Journal 

of Research, v. 3, p. 691-706.

Small, W.D., 1968, Cordilleran geochronology deduced from 

hydrothermal leads: Vancouver, University of British Columbia, Ph.D. thesis, 96 p.

Stacey, J.S., and Kramers, J.D., 1975, Approximation of terrestrial 

lead isotope evolution by a two-stage model: Earth and Planetary Science Letters, v. 26, p. 207-221.

Stacey, J.S., Zartman, R.E., and NKomo, I.T., 1968, A lead isotope 

study of galenas and selected feldspars from mining districts in 

Utah: Economic Geology, v. 63, p. 796-814.

Stein, H.J., 1985, A lead, strontium, and sulfur isotope study of 

Laramide-Tertiary intrusions and mineralization in the Colorado mineral belt with emphasis on Climax type porphyry 

molybdenum systems plus a summary of other newly acquired 

isotopic and rare earth element data: Chapel Hill, University of 

North Carolina, Ph.D. thesis, 500 p.

Theodore, T.G., 1986, Descriptive model of porphyry Mo, low-F, 

in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 120.

Tilton, G.R., Pollak, R.J., Clark, A.H., and Robertson, R.C.R., 

1981, Isotopic composition of Pb in central Andean ore deposits: Geological Society of America Memoir 154, p. 791-816.

Tischendorf, G., 1977, Geochemical and petrographic characteristics of silicic magmatic rocks associated with rare-element 

mineralization, in Stemprok, M., and others, eds.,

Metallization associated with acid magmatism: Czechoslovakia Geological Survey, v. 2, p. 41-96.

Togashi, Y., 1986, Descriptive model of Sn-polymetallic veins, in 

Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 109.

Tschanz, C.M., and Kiilsgaard, T.H., 1986, Geologic appraisal of 

mineral resources of the eastern part of the Sawtooth National 

Recreation Area, Idaho, in Mineral resources of the eastern part 

of the Sawtooth National Recreation Area, Custer and Blame 

Counties, Idaho: U.S. Geological Survey Bulletin 1545-C, p. 

54-210.

Tschanz, C.M., Kiilsgaard, T.H., and Seeland, D.A., 1986, Geology 

of the eastern part of the Sawtooth National Recreation Area, 

Idaho, in Mineral resources of the eastern part of the Sawtooth 

National Recreation Area, Custer and Blaine Counties, Idaho: 

U.S. Geological Survey Bulletin 1545-A, p. 17-43.

Tschanz, C.M., Kiilsgaard, T.H., Seeland, D.A., Van Noy, R.M., 

Ridenour, James, Zilka, N.T., Federspiel, F.E., Evans, R.K., 

Tuchek, E.T., and McMahan, A.B., 1974, Mineral resources 

of the eastern part of the Sawtooth National Recreation Area, 

Custer and Blaine Counties, Idaho, with sections on 

Aeromagnetic survey and tentative interpretation, by D.R. 

Mabey and C.M. Tschanz, and Electromagnetic surveys, by 

F.C. Frischknecht: U.S. Geological Survey Open-File Report 

74-1100, 2 v., 648 p.

Turner, R.J.W., and Otto, B.R., 1988, Stratigraphy and structure of 

the Milligen Formation, Sun Valley area, Idaho, in Link, P.K., 

and Hackett, W.R., eds., Guidebook to the geology of central 

and southern Idaho: Idaho Geological Survey Bulletin 27, p. 

153-167.

Wavra, C.S., Isaacson, P.E., and Hall, W.E., 1986, Studies of the 

Idaho black shale belt Stratigraphy, depositional environment, and economic geology of the Permian Dollarhide Formation: Geological Society of America Bulletin, v. 97, p.

1504-1511.

Webring, M.W., and Mabey, D.R., 1987, Geophysical anomalies in 

the Challis quadrangle, in Fisher, F.S., and Johnson, K.M., 

eds., Preliminary manuscript for "Mineral-resource potential 

and geology of the Challis I°x2° quadrangle, Idaho": U.S. 

Geological Survey Open-File Report 87-480, p. 66-80.

Westra, G., and Keith, S.B., 1981, Classification and genesis of 

stock work molybdenum deposits: Economic Geology, v. 76, p.

844-873.

Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

1989, Geology and mineral deposits of the Hailey and western 

Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey 

Open-File Report 89-639, 140 p.

Worl, R.G., Kiilsgaard, T.K., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Zartman, R.E., 1974, Lead isotopic provinces in the Cordillera of 

the Western United States and their geologic significance: Economic Geology, v. 69, p. 792-805.

Zartman, R.E., and Stacey, J.S., 1971, Lead isotopes and mineralization ages in Belt Supergroup rocks, northwestern Montana 

and northern Idaho: Economic Geology, v. 66, p. 849-860.

Sources of Lead in Ore Deposits of Central Idaho

By Richard F. Sanford and Joseph L. Wooden

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-N

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Nl

Introduction........................................................................................................................... 2

Methods................................................................................................................................. 5

208pb/204pb.206pb/204pbResults .......................................................................................... 6

Precambrian and Lower Paleozoic Quartzite and Carbonate Rocks............................. 6

Devonian Argillitic Rocks............................................................................................. 7

Mississippian Rocks...................................................................................................... 13

Pennsylvanian and Permian Rocks ............................................................................... 14

Cretaceous Intrusive Rocks........................................................................................... 15

Eocene Intrusive and Extrusive Rocks.......................................................................... 15

Summary....................................................................................................................... 16

207Pb/204Pb-206Pb/204Pb Results.......................................................................................... 17

Discussion............................................................................................................................. 18

Western Crustal Zone Carrietown Type .................................................................... 19

Central Crustal Zone Triumph- and Black Shale-Types............................................ 19

Central Crustal Zone Minnie Moore- and Pacific-Types........................................... 22

Eastern Crustal Zone Lava Creek Type..................................................................... 22

References Cited................................................................................................................... 23

FIGURES

1. Map showing geologic terranes of central Idaho....................................................................................................... N3

2. Map showing locations cited in text, mining districts, and selected mines............................................................... 4

3-8. Graphs showing lead-isotope ratios for samples of:

3. Galena in veins hosted by Precambrian and lower Paleozoic quartzite and carbonate rocks............................ 6

4. Whole rock and galena from Devonian Milligen Formation argillite................................................................ 7

5. Vein and syngenetic galena for argillite from the Devonian part of the Paleozoic Salmon River

assemblage and from the Mississippian Copper Basin Formation..................................................................... 7

6. Vein and conformable epigenetic galena and whole rocks from Pennsylvanian and Permian argillite............. 14

7. Vein galena, whole rock, and potassium feldspar from Cretaceous intrusive rocks........................................... 15

8. Vein galena and whole rock from Eocene intrusive and volcanic rocks ............................................................ 15

9. Graph showing lead-isotope ratios for group A......................................................................................................... 18

10. Graph showing lead-isotope ratios for group B......................................................................................................... 18

11. Graphs summarizing lead-isotope types.................................................................................................................... 20

12. Map showing distribution of lead-isotope types for galena and other sulfide minerals............................................ 21

TABLES

1. Summary of relationships among lead-isotope types, crustal zones, geologic terranes, and lithostratigraphic

units in central Idaho................................................................................................................................................. N5

2. Lead-isotope data for central Idaho........................................................................................................................... 8

3. Summary of lead-isotope types of sampled rocks and ore deposits in central Idaho................................................ 16
Sources of Lead in Ore Deposits of Central Idaho

By Richard F. Sanford1 and Joseph L. Wooden2

ABSTRACT

Ore and rock samples in central Idaho are divided into 

six types on the basis of distinctive lead-isotope signatures. 

Lead previously identified as group A lead is subdivided 

into the Carrietown-, Minnie Moore-, Pacific-, and Lava 

Creek-types, which are characterized by discrete ranges in 

uranogenic (206Pb/204Pb and 207Pb/204Pb) and thorogenic 

(208Pb/204Pb) lead ratios. Carrietown-type lead, which is 

low in uranogenic lead and high in thorogenic lead, is probably derived from Precambrian upper crustal rocks beneath 

the Cretaceous Idaho batholith. Minnie Moore- and 

Pacific-type leads, which are high in both uranogenic and 

thorogenic lead, have no obvious source, but recycled Precambrian upper crustal rocks are likely candidates. Lava 

Creek-type lead, which is low in both uranogenic and 

thorogenic lead, is probably derived from Precambrian 

upper crustal rocks having lower 208Pb/204Pb than rocks 

beneath the Idaho batholith.

Lead previously identified as group B lead is subdivided into the Triumph- and black shale-types, both of which 

are high in uranogenic lead and low in thorogenic lead. Triumph-type lead has higher 207Pb/204Pb than black shale-type 

lead. Black shale-type lead probably was derived from recycled Proterozoic upper crustal rocks eroded from the craton 

to the east and northeast, whereas Triumph-type lead probably was derived from recycled Archean and Proterozoic 

rocks in the middle or lower crust. The variety of lead-isotope types that originated in Precambrian basement suggests 

that the Precambrian basement is quite heterogeneous.

The six types of lead suggest three crustal zones: a 

western crustal zone characterized by Carrietown-type lead 

(low uranogenic lead ratios and high thorogenic lead ratio); 

a central zone having four lead-isotope types, Minnie 

Moore, Pacific, black shale and Triumph, all of which are 

high in 207Pb/204Pb; and an eastern zone characterized by 

Lava Creek-type lead, which is low in both uranogenic and

U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025.

thorogenic lead. These crustal zones correspond closely to 

five of eight geologic terranes previously recognized in the 

central Idaho area. The broad western crustal zone corresponds to the Cretaceous intrusive rock terrane and small 

parts of the black shale terrane; the narrow arcuate central 

zone corresponds to almost all of the black shale terrane; 

and the broad eastern zone corresponds to the flysch, shelf 

carbonate, and Precambrian terranes.

Ore deposit types typically have characteristic leadisotope signatures. Carrietown-type lead is in veins hosted 

by the Idaho batholith and adjacent, locally metamorphosed 

sedimentary rocks. The association of intrusive rocks, 

metamorphic rocks, and veins suggests a common and contemporaneous plumbing system that extends down to the 

Precambrian basement. The Cretaceous intrusions probably provided the heat for hydrothermal circulation, but the 

metals apparently came from the underlying basement, not 

from the intrusions.

Triumph-type lead is typical of the lead in syngenetic, 

massive sulfide, "black smoker" deposits that formed in a 

syndepositional rift basin. This lead probably came from a 

Precambrian source at depth and was transported upward by 

hydrothermal fluids and deposited at submarine vents. During transport, this lead may have mixed with a component of 

lead from argillite, but argillite could not have been the sole 

source of lead in these deposits. Triumph-type lead in epigenetic veins represents either the contemporaneous feeder 

system for the syngenetic deposits or syngenetic sulfides 

from which lead was later remobilized. Most likely, veins in 

Devonian argillite having Triumph-type lead were part of the 

feeder system for contemporaneous syngenetic deposits, 

whereas those in Pennsylvanian-Permian argillite consist of 

remobilized Devonian syngenetic sulfides.

Black shale-type lead is typical of argillite as well as 

Cretaceous intrusive rocks. Very few vein deposits have a 

black shale-type lead signature similar to that of the host 

argillite. Therefore, these ore deposits probably did not form 

by lateral secretion. Most argillite-hosted veins probably 

derived their lead ultimately from Precambrian basement, 

either directly or by remobilization of syngenetic lead, but 

not from the detrital component of the argillite.

Nl
N2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Epigenetic sulfides in central Idaho thus have lead-isotope types that differ with crustal zone. Epigenetic sulfides 

in the western crustal zone have mostly Carrietown-type lead, 

those in the central crustal zone have Minnie Moore-, Pacific- 

, black shale-, and Triumph-type lead, and those in the eastern 

crustal zone have mainly Lava Creek-type lead. Lava Creektype lead probably is unique to, and characteristic of, Eocene 

veins. Syngenetic sulfides are present only in the black shale 

terrane and have only Triumph-type lead.

INTRODUCTION

The black shale terrane of central Idaho (figs. 1, 2) has 

been a significant area of silver-lead-zinc production since 

the late 1800's and is the subject of several modern oredeposit studies (Hall and others, 1978; Hall, 1985). Lead isotopes in galena from the Minnie Moore mine in the Big 

Wood River valley, central Idaho, were noted as unusually 

radiogenic for deposits of this size in the Western United 

States (Doe, 1978), and metals for the Minnie Moore mine 

were thought to be derived from the enclosing host rocks by 

lateral secretion (Hall and others, 1978). Regression of

207pb/204pb_206pb/204pb data yidds isochron ages of 2,5QO

and 1,600-1,400 Ma for the primary source material (Small, 

1968; Doe and Delevaux, 1985). Sulfur isotope data suggest 

that sulfur was derived from crustal sources such as syngenetic sulfide minerals in sedimentary rocks (Howe and Hall, 

1985). Hydrogen- and oxygen-isotope studies suggest that 

the hydrothermal fluid that transported the metals was meteoric water driven by heat from igneous intrusions (Criss and 

others, 1984, 1985; Howe and Hall, 1985). Although these 

studies suggest some of the mineralizing processes involved, 

they fail to account for the complexity of different ore 

deposit types and ages that have been identified by recent 

mineral deposit studies. For example, a classification of 

deposit types in the Challis quadrangle includes 23 types of 

known hydrothermal deposits (Fisher and Johnson, 1987). 

Further, dating of hydrothermal minerals shows at least five 

periods of mineralization in Late Cretaceous to Eocene time 

alone (Snee and Kunk, 1989). This complexity requires that 

present and future studies focus in detail on the major types 

of deposits and geologic settings.

The goal of the present study is to extend earlier isotopic studies to include much of central Idaho and to investigate in more detail the sources of lead as a function of 

mineral deposit type, host-rock lithology, and geologic terrane. We present new analyses for 59 samples of vein 

material, much of which contains galena, and metalliferous 

argillitic whole rock and discuss the implications of these 

data in combination with previously reported results of Doe

and Delevaux (1985), Small (1968), Davis (1978), Hall and 

others (1978), Sanford and others (1989), and Doe and Sanford (this volume). These data show that lead-isotope 

groups A and B of Doe and Delevaux (1985) and Doe and 

Sanford (this volume) can be divided into six subgroups 

that are related to distinct source-rock terranes and oredeposit types. (Group B has no relation to the B type of 

early workers (Holmes, 1946; Houtermans, 1946; Russell 

and Farquhar, I960)). Further, the lateral-secretion model 

for shale-hosted ore deposits (Hall and others, 1978) is 

revised in light of the new data.

The geology and ore deposits of the study area are 

described elsewhere in this volume, but a brief review is 

given here. The study area is underlain by eight discrete geologic terranes (fig. 1), all of which, except the Miocene volcanic rock terrane, contain significant mineral deposits 

(Fisher and Johnson, 1987; Worl and Johnson, 1989, this 

volume). The Paleozoic and Mesozoic terranes generally 

have parallel northwest trends. Precambrian and Paleozoic 

shelf carbonate terranes are dominant in the northeast. The 

next terrane to the southwest is the Mississippian flysch terrane representing foreland-basin deposits. The next terrane 

to the southwest, the Paleozoic black shale terrane, represents deeper water basinal deposits. The western third of the 

study area is underlain by the Cretaceous intrusive rock terrane of the Idaho batholith. Tertiary igneous rock terranes 

are distributed throughout the area. The Eocene extrusive 

rock terrane forms an irregular north-trending belt in the center of the area, and most, but not all, of the Eocene intrusive 

rock terrane is west of this belt. The Miocene volcanic rock 

terrane is restricted to the southwestern part of the study area.

The ore deposit types studied here are mainly epigenetic polymetallic veins in various rock types, replacement 

polymetallic sulfide deposits in carbonate rocks, and syngenetic massive sulfide deposits in black shale and argillite. 

As we will show, the relationships between ore deposit 

types and lead isotopes are complex but systematic. Initially, field criteria were used to group samples, but the 

lead-isotope results indicated further refinements in classification. For example, vein sulfides originally were distinguished from bedded, possibly syngenetic, sulfides based 

on macroscopic textural features. Later, we found that the 

vein sulfides required further subdivision based on systematic isotopic variations according to geographic area and 

geologic terrane. Similarly, we found that bedded sulfides 

include both epigenetic and syngenetic material. Our final 

classification of six lead-isotope types reflects both field 

criteria and isotopic characteristics.

Table 1 provides a summary of the results and a guide 

through the subsequent presentation of data, particularly the 

relationships among lead-isotope types, lithostratigraphic 

units, and geologic terranes. Divisions based on lead-isotope
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N3

EXPLANATION

Quaternary and Recent deposits 

Miocene volcanic rock terrane 

Eocene volcanic rock terrane 

Eocene intrusive rock terrane 

Cretaceous intrusive rock terrane

Paleozoic black shale terrane (includes 

calcareous clastic rocks)

Paleozoic flysch terrane 

Paleozoic shelf-carbonate terrane 

Precambrian terrane

Figure 1. Map showing geologic terranes in the area of the Hailey and Challis 1 °x2° quadrangles and the western parts of the Dubois and 

Idaho Falls I°x2° quadrangles, central Idaho. Heavy solid and dashed lines delineate western, central, and eastern crustal zones. Modified 

from Rember and Bennett (1979); Worl and Johnson (1989); A.B. Wilson (unpublished compilation, 1991).
N4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

. 116

45

115 114 113

Challis

ChaJlis

o

 Pacific

 Riverview

Stanley

o

i Hoodoo 

1 Livingston

44

Dubote

Leadore

o

Idaho City

o

... . VIENNA Atlanta

. BIGSMOKEY 

FEATHERVILLE

ALTO

 !

., PhijKappa

Ketchum

o Carrietown area Triumph

PINE SOLDIER

VOLCANO

Mackay

o

LAyAOKEEK Aroo

i "Minnie Moore-Silver Star Queen 

Westlajce North

CAMAS

Mountain Home

o

43 Halley

MINERAL HILL

CroyCkarea

(e.g., Eureka,

liberty,

JayGould,

Idahoan)

20 Ml

20 KM

Idaho Falls

Figure 2. Map showing locations cited in text, central Idaho. Mining districts are shown by dotted lines; names are in capital letters, 

lected mines (solid squares) are shown.

Seratios are shown across the top, and divisions based on geology are shown down the left side. Group A and B leads are 

divided into six types. Group A lead is divided into Carrietown-, Minnie Moore-, Pacific-, and Lava Creek-types, and 

Group B lead is divided into black shale- and Triumph-types. 

Except for the black shale type, the names correspond to 

important mines or districts that exhibit the particular type of 

lead in sulfides. The black shale type is named for the argillitic rocks, which generally exhibit a characteristic lead-isotope signature.

Table 1 shows the isotopic characteristics of rocks 

(whole rock and potassium feldspar), epigenetic vein and

bedded sulfides, and possibly syngenetic sulfides. Sulfides 

are listed according to the enclosing host rock. Almost all 

rocks (Paleozoic argillite and Cretaceous intrusive rocks) 

have black shale-type lead, except for Eocene rocks, which 

exhibit a range of lead-isotope types. Epigenetic sulfides 

have lead-isotope types that differ with crustal zone. Epigenetic sulfides in the western crustal zone have mostly Carrietown-type lead, those in the central crustal zone have 

Minnie Moore-, Pacific-, black shale-, and Triumph-types of 

lead, and those in the eastern crustal zone have mainly Lava 

Creek-type lead. Syngenetic sulfides are present only in the 

black shale terrane and have only Triumph-type lead.
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N5

Table 1. Summary of relationships among lead-isotope types, crustal zones, geologic terranes, and lithostratigraphic units in central

Idaho.

[Abbreviations: R, r, whole rock and potassium feldspar; E, e, epigenetic vein and bedded sulfide; S, syngenetic sulfide. Capital letter indicates that

interpretation is based on a larger number of samples]

Lead-isotope type

Group A Group B Group A

Carrie- Minnie Black Lava 

town Moore Pacific Triumph shale Creek

Western crustal zone

Eocene volcanic rock terrane: Eocene volcanic rock, central Idaho batholith 

Eocene intrusive rock terrane 

Eocene granite, central Idaho batholith 

Eocene granite, southeast Idaho batholith 

Cretaceous intrusive rock terrane 

Cretaceous intrusive rocks, central Idaho batholith 

Cretaceous intrusive rocks, Vienna district, Idaho batholith 

Cretaceous intrusive rocks, southeast Idaho batholith 

Cretaceous intrusive rocks, south-central Idaho batholith 

Paleozoic carbonate roof pendants in Idaho batholith 

Black shale terrane 

Pennsylvanian-Permian argillite, Dollarhide Formation, 

Carrietown-Westlake area 

Ordovician carbonate rocks, Ella Dolostone group

R r

R,e R

r

E r e R E, r 

E 

E re 

E 

E

E R

E e

Central crustal zone

Black shale terrane 

Pennsylvanian-Permian argillite, Dollarhide Formation, 

Croy Creek area 

Pennsylvanian-Permian argillite, Grand Prize Formation 

Pennsylvanian-Permian argillite, Wood River Formation 

Devonian argillite, part of Paleozoic Salmon River assemblage 

Devonian argillite, Milligen Formation, (except Triumph block) 

Devonian argillite, Milligen Formation, Triumph block 

Cambrian Ordovician carbonate rocks and phyllite, Bayhorse 

Dolostone group

E R

e 

E e 

E, S E, r 

E E, S R, e 

e E, S r

e E e

Eastern crustal zone

Eocene extrusive rock terrane: Eocene volcanic rock, Lava Creek district 

Flysch terrane: Mississippian argillite, Copper Basin Formation 

Shelf carbonate terrane: Devonian carbonate rocks, Jefferson Dolostone 

Precambrian terrane: Middle Proterozoic Swauger Formation

E 

r E 

E 

E

The five pre-Tertiary terranes closely correspond to 

the lead-isotope types identified here (table 1, fig. 1). The 

broad western crustal zone consists of the Cretaceous 

intrusive rock terrane and a small part of the black shale 

terrane. The narrow central crustal zone corresponds to 

almost all of the black shale terrane. The broad eastern 

crustal zone corresponds to the flysch, shelf carbonate, and 

Precambrian terranes. The three Tertiary rock terranes are 

either unmineralized or exhibit several lead-isotope types 

in sulfides. Isotopically, the Tertiary terranes are in crustal 

zones, and apparently the major control on lead-isotope 

types was the preexisting, pre-Tertiary crust beneath the 

Tertiary volcanic cover.

Acknowledgments. We thank Reed Lewis, Paul Link, 

Falma Moye, Sandy Soulliere, Craig Wavra, and Anna Wilson for collecting some of the samples analyzed in this study. 

Constructive comments by Brian Mahoney, Betty Skipp,

Gary Winkler, and Ron Worl improved the manuscript. 

Anna Wilson's compilations were invaluable for constructing figure 1. Larry Dee, U.S. Bureau of Land Management, 

provided much assistance in the field. Stan Church, Anna 

Wilson, and Paul Link gave particularly thoughtful reviews 

of the manuscript.

METHODS

Sample material includes galena from epigenetic 

crosscutting and bedding-conformable veins, one sample 

each of siderite vein and copper sulfide vein without visible galena, and several whole-rock samples of pyrite-rich 

argillite. Sulfide samples were prepared by handpicking a 

few milligrams of sulfide material and dissolving it in 1-2 

mL of concentrated HNC»3. After 12 hours, this solution
N6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

was diluted to about 15 mL total volume with distilled 

water and heated at 50°-80°C for another 12 hours. 

Approximately 10 uL of this final solution was loaded 

directly on a bed of silica gel-H3PO4 that had been partly 

dried on a single rhenium filament. Whole-rock shale samples were treated with concentrated HNO3 to dissolve sulfides and then given a normal HF dissolution treatment for 

the silicate residue. The total sample was centrifuged to 

remove graphite, and then lead was separated by anion 

exchange using HBr as the medium. Loading of all the 

samples for mass spectrometry followed the silica gelH3?O4 procedure described above. All samples were analyzed for lead-isotope composition by simultaneous collection of all four isotopes (204Pb, 206Pb, 207Pb, and 208Pb) on 

multicollector Finnigan-MAT mass spectrometers. Isotopic ratios were corrected for thermal fractionation by 0.11 

percent per mass unit based on average values of numerous 

analyses of the standards, NBS-981 and -982, determined 

at the same operating conditions as samples. Precision at 

the 95 percent confidence level is approximately 0.04 percent per mass unit difference (that is, 0.08 percent for 

206Pb/204Pb, 0.12 percent for 207Pb/204Pb, and 0.16 percent 

for 208Pb/204Pb), and the correlation of errors is about 

0.97. Regressions were performed according to the method 

of York (1969) using the program ISOPLOT (Ludwig, 

1990). Our new data, as well as previously published data, 

corrected for different standards where necessary, are listed 

in table 2.

Results are presented by age of lithostratigraphic unit 

starting with the Precambrian (table 2, figs. 3-8). Veins are 

discussed according to the host rock in which they are 

found. The clustering of lead-isotope ratios into recurring 

characteristic types will become apparent during this analysis. The data presentation concludes with a summary of the 

six lead-isotope types. In the discussion, the lead-isotope 

types are related to geologic terranes, the three crustal 

zones are identified, and the lead-isotope types are related 

to ore deposit types.

The variation in 208Pb/204Pb is moderately independent of 206Pb/204Pb in sulfide and whole-rock samples and 

has been successfully used to discriminate between source 

terranes (see, for example, Zartman, 1974). The 207Pb/ 

204Pb ratio better correlates with 206Pb/204Pb than with 

208Pb/204Pb, but it can also be used to discriminate between 

source terranes. Because the 208Pb/204Pb-206Pb/204Pb diagrams provide more resolution in discriminating between 

lead-isotope type than the 207Pb/204Pb-206Pb/204Pb diagrams, the data are first presented on a series of 208Pb/ 

204pb_206Pb/204pb diagrams (figs. 3-8). Further subdivision of types is accomplished using 207Pb/204Pb-206Pb/ 

204Pb diagrams (figs. 9, 10). (The terms "low," "high," 

"intermediate," and other similar terms for isotopic ratios in 

this paper are used to describe relative values within the 

range of ratios observed in this data set.)

39.6

39.2

38.8

38.4

Pacific type

Carrietown type

f Error ellipse

19

206 Pb/^Pb

EXPLANATION

A Middle Proterozoic Swauger Formation quartzite 

host rock, sulfide sample

B Paleozoic carbonate roof pendants in Idaho 

batholith, sulfide samples

c Cambrian or Ordovician carbonate host rock, 

Bayhorse Dolostone group, sulfide samples

D Ordovician carbonate and phyllite host rock, Ella 

Dolostone group, sulfide samples

E Devonian carbonate host rock, Jefferson 

Dolostone, sulfide samples

Figure 3. Lead-isotope ratios for samples of galena in veins hosted by Precambrian and lower Paleozoic quartzite and carbonate 

rocks, central Idaho. Average shale growth curve of Godwin and 

Sinclair (1982) is also shown.

208pb/204pb_206pb/204pb RESULTS

PRECAMBRIAN AND LOWER PALEOZOIC 

QUARTZITE AND CARBONATE ROCKS

Lead-isotope ratios for galena in an epithermal vein in 

Precambrian quartzite and in several replacement deposits in 

lower Paleozoic carbonate rocks show three main clusters that 

belong to Lava Creek-, Carrietown-, and Pacific-types (fig. 3).

Lead-isotope ratios for galena in a vein in the Middle 

Proterozoic Swauger Formation (A) and in replacement 

deposits in the Upper Devonian Jefferson Dolostone (E) 

form a cluster that has 206Pb/204Pb=17.9-18.4 and 208Pb/ 

204Pb=38.7-39.1. This cluster partly defines the Lava Creek 

type (fig. 3). It has 206Pb/204Pb ratios similar to Carrietowntype lead but lower 208pb/204pb ratios.

Replacement and vein galena in Paleozoic carbonate 

roof pendants in the Idaho batholith (B) and in the Ella dolostone group (D), which we define to include the Ordovician 

Ramshorn slate, Middle Ordovician Ella Dolostone, and 

Middle Ordovician to Lower Silurian Saturday Mountain 

Formation, forms a cluster of low 206Pb/204Pb and high

208pb/204pb ratios 206pb/204pb=17 g_ 19 o and 208Pb/

204Pb=39.9^0.6, and belongs to the Carrietown type.

Galena from replacement deposits in the Upper Cambrian or Ordovician Bayhorse Dolostone (C) that is, from
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N7

41.6

41.2

40.8

40.4

40

39.6

39.2

38.8

38.4

Minnie Moore type

Triumph type

Group B

EXPLANATION

Devonian argillite host rock, Milligen Formation, 

Minnie Moore mine group, sulfide samples

Devonian argillite host rock, Milligen Formation, 

Triumph block, epigenetic sulfide samples

Devonian argillite host rock, Milligen Formation, 

Triumph block, syngenetic sulfide samples

Devonian argillite, Milligen Formation, Triumph 

block, whole-rock samples

Devonian argillite host rock, Milligen Formation, 

epigenetic sulfide samples

Devonian argillite host rock, Milligen Formation, 

syngenetic sulfide samples

Devonian argillite, Milligen Formation, whole-rock 

samples

Figure 4. Lead-isotope ratios for samples of whole rock and galena from Devonian Milligen Formation argillite, central Idaho. Average shale growth curve of Godwin and Sinclair (1982) is also 

shown. Arrow indicates possible initial ratios for argillite host rocks 

assuming average shale concentrations of uranium and thorium.

the Pacific and Riverview mining areas (Davis, 1978) has 

radiogenic lead, 206Pb/204Pb=20.5-21.5 and 208Pb/ 

204Pb=40.8-41.1, that we designate Pacific type (fig. 3). 

Together with a sample from the Wilbert mine, these samples are from what we call the Bayhorse dolostone group.

DEVONIAN ARGILLITIC ROCKS

Samples of Devonian argillite are from the Milligen 

Formation (fig. 4) and from the Devonian part of the Paleozoic Salmon River assemblage (Link and others, this volume) (fig. 5). The argillite of the Milligen in the Triumph 

block is plotted separately, as discussed following. Samples 

from the Milligen Formation include (1) sulfides from epigenetic veins in the Silver Star Queen mine (Minnie Moore 

group of mines) (F), Triumph block (G), and other localities 

in the black shale terrane (H); (2) galena from conformable, 

possibly syngenetic sulfides of the Triumph (open squares) 

and Snoose mines (open diamonds); and (3) pyrite-rich argillite whole-rock samples from the Triumph block (filled

41.6

41.2

40.8

40.4

40.0

39.6

39.2

38.8

38.4

Lava Creek type

Group B

Triumph type

| Enor ellipse

*" PW "~Pb

EXPLANATION

I Devonian argillite host rock, part of Salmon River 

assemblage, epigenetic sulfide samples

a Devonian argillite host rock, part of Salmon River 

assemblage, syngenetic sulfide samples

J Mississippian argillite host rock, Alto-MuldoonLava Creek area, crosscutting vein sulfide 

samples

o Mississippian argillite host rock, Phi Kappa mine, 

bedded sulfide sample

Figure 5. Lead-isotope ratios for samples of vein and syngenetic 

galena from argillite from the Devonian part of the Paleozoic Salmon River assemblage and from the Mississippian Copper Basin Formation, central Idaho. Average shale growth curve of Godwin and 

Sinclair (1982) is also shown.

square) and other parts of the black shale terrane (filled diamonds) (fig. 4). Samples from the Devonian part of the 

Salmon River assemblage include galena from epigenetic 

veins (I) and from conformable, possibly syngenetic sulfide 

ore (open squares) (fig. 5). Some of the ore (the "complex 

ores") from the Triumph mine is probably syngenetic (Thor 

Kiilsgaard, oral commun., 1988; Turner and Otto, this volume). Similar deposits, namely the Livingston, Hoodoo, and 

Snoose deposits, may also contain syngenetic sulfides, but 

the evidence is less definitive (Hall, 1985; Link and others, 

this volume). For the purposes of this paper, these four 

deposits are referred to as syngenetic. A previously reported 

analysis of whole-rock argillite from the Devonian part of 

the Salmon River assemblage (Holman Creek sample 

T-270) is anomalously radiogenic due to uranium enrichment and plots off the diagram (fig. 5) to the right.

Lead isotopes in sulfides and in whole rocks from Milligen and Salmon River argillites form two discrete clusters 

belonging to group A (Minnie Moore type) and group B 

(Triumph- and black shale-types) (figs. 4, 5). Minnie 

Moore-type lead includes the cluster having 206Pb/ 

204Pb=20.2-20.6 and 208Pb/204Pb=40.8^U.4, and Triumph- and black shale-type leads include the cluster having 

206Pb/204pb=19 2-20.2 and 208Pb/204Pb=39.2-^0.0. Lead 

isotopes for epithermal vein galena (F, fig. 4) in the Minnie
Table 2. Lead-isotope data for central Idaho.

[Letter or other symbol in parentheses following sample description indicates plotting symbol (figs. 3-8). Lead-isotope types ("Type"): BS, black shale, CT, Carrietown; L

Moore; PA, Pacific; TR, Triumph. Host-rock types ("Host"): Dj, Devonian Jefferson Dolostone; Dm, Devonian Milligen Formation; Dmt, Milligen Formation in the Trium

aplite porphyry; Kgd, Cretaceous granodiorite; Kgdh, Cretaceous hornblende granodiorite; Kgp, Cretaceous granite porphyry, Kqd, Cretaceous quartz diorite; Me, Mississi

Mm, Mississippian McGowan Creek Formation; Ob, Cambrian or Ordovician Bayhorse Dolostone; Oe, Ordovician Ella Dolostone; Ok, Ordovician Kinnikinic Quartzite; O

SOsm, Ordovician and Silurian Saturday Mountain Formation; PPd, Pennsylvanian-Permian Dollarhide Formation, undivided; Pdu, Permian upper Dollarhide; Pdm, Permi

Pennsylvanian-Permian lower Dollarhide; PPw, Pennsylvanian-Permian Wood River Formation; Pzl, Paleozoic carbonate roof pendants in Idaho batholith, undivided; Pzsr, 

assemblage; Tc, Eocene Challis Volcanic Group; Tcr, Eocene Challis Volcanic Group, rhyolite; Tg, Eocene granite; Ys, Middle Proterozoic Swauger Formation. Column la

whether sulfide minerals are epigenetic (Epi), possibly syngenetic (Syn), or remobilized syngenetic (Syn-rmbl) based on textural relations or, in the case of whole-rock samp

associated with the host rock. Abbreviations for ore-deposit types: combinations of Au-Ag-Pb-Zn-Cu-(Mo), precious- and base-metal veins possibly associated with molyb

inferred tin granite based on chemistry and mineralogy of granite; Mo, molybdenum porphyry; U, uranium. Analytical methods: Gel, silica gel; Mth, tetramethyl lead; 3Fil

(1) Small, 1968; (2) Doe and Rohrbough, 1977; (3) Davis, 1978; (4) Hall and others, 1978; (5) Doe and Sanford, this volume); (6) Sanford and others, 1989, and this work

been corrected by multiplying the original 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios by 0.99324,0.99067, and 0.98910, respectively; other data are as published]

Sample no. Mine or location

206pb/ 

204pb

207pb/ 208pb/ 

204pb 204pb Type Material Host Association Mining district 

Middle Proterozoic Swauger quartzite host rock, sulfide (A) (fig. 3)

591 Blue Lead 18.304 15.643 39.125 LC Galena Ys Epi Junction 

Paleozoic carbonate roof pendants in Idaho batholith, sulfide (B) (fig. 3)

K52-1

R-154

Mountain King

Mountain King

17.810

17.943

15.593 40.290

15.606 40.299

CT

CT

Galena

Galena

Pzl

Pzl

Epi

Epi

Sheep MountainVienna

Sheep MountainVienna

Ordovician carbonate host rock, Bayhorse Dolostone group, sulfide (C) (fig. 3)

D6S3

KD68

KD69

KD72-9-124

KD73-4-161

KD74-P9-5B

KD74-P9-5B

SWH 52-67

1885Ag

KD-7

607

Pacific

Pacific Mountain-dump

Pacific Mountain-main ore body

Pacific Mountain-above main ore

body

Pacific Mountain-top, main ore

body

Pacific Mountain

Pacific Mountain

Rattlesnake prosp.

Riverview

Riverview

Wilbert

21.452

21.332

21.431

21.323

21.347

21.375

21.355

20.479

21.073

19.704

20.692

15.840 41.145

15.771 40.948

15.767 40.899

15.765 40.796

15.801 40.966

15.807 41.004

15.777 40.897

15.784 40.874

15.804 40.808

15.806 39.281

15.957 40.914

PA

PA

PA

PA

PA

PA

PA

PA

PA

TR

MM

Galena?

Galena

Galena

Galena

Galena

Galena

Galena

Galena

Galena?

Galena

Galena

OCb

OCb

OCb

OCb

OCb

OCb

OCb

OCb

OCb

OCb

OkSOsm

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Dome

Ordovician carbonate and phyllite host rock, Ella Dolostone group, sulfide (D) (fig. 3)

79T 23M

572

80WH-1

SWH 78-65

SWH120-79

SWH154-76a

SWH154-76b

Ramshorn

Clayton Silver

Clayton Silver

Clayton Silver

Rob Roy

Dryden

Dryden

17.776

18.895

18.944

18.965

20.474

18.586

18.584

15.578 39.861

15.736 39.982

15.709 39.990

15.718 39.948

15.870 40.143

15.706 40.608

15.690 40.549

CT

CT

CT

CT

MM

CT

CT

Galena

Galena

Galena

Galena

Galena

Galena

Galena

Or

Oe

Oe

Oe

Oe

SOsm

SOsm

Epi

Epi

Epi

Epi

Epi

Epi

Epi

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse

Bayhorse
Devonian carbonate host rock, Jefferson Dolostone, sulfide (E) (fig. 3)

590 

80R-1 

80R-1

Gilmore 

Hilltop 

Hilltop

17.947 15.556 38.746 LC Galena Dj Epi Gilmore-Texas 

18.376 15.573 38.955 LC Galena? Dj Epi Gilmore-Texas 

18.407 15.606 39.039 LC Galena? Dj Epi Gilmore-Texas

Devonian argillite host rock, Milligen Formation, Minnie Moore mine group, sulfide (F) (fig. 4)

578 

579 

580 

581 

581 

581 

WH70-16

Silver Star Queen 

Silver Star Queen 

Silver Star Queen 

Silver Star Queen 

Silver Star Queen 

Silver Star Queen 

Silver Star Queen

20.622 16.021 41.320 MM Galena Dm Epi Mineral Hill 

20.378 15.978 41.275 MM Galena Dm Epi Mineral Hill 

20.597 16.018 41.387 MM Galena Dm Epi Mineral Hill 

20.275 15.937 41.199 MM Galena Dm Epi Mineral Hill 

20.298 15.957 41.229 MM Galena Dm Epi Mineral Hill 

20.267 15.946 41.215 MM Galena Dm Epi Mineral Hill 

20.421 15.962 41.301 MM Galena Dm Epi Mineral Hill

Devonian argillite host rock, Milligen Formation, Triumph block, epigenetic sulfide (G) (fig. 4)

8H91A 

8H92C 

WH74-2B

575

Courier 

Independence 

North Star 

Triumph

19.910 15.863 39.493 TR Galena Dmt Epi Warm Spring 

19.789 15.820 39.450 TR Galena Dmt Epi Warm Spring 

19.688 15.906 39.438 TR Galena Dmt Epi Mineral Hill 

20.515 16.086 40.886 MM Galena Dmt Epi Warm Spring

Devonian argillite host rock, Milligen Formation, Triumph block, syngenetic sulfide (open square) (fig. 4)

8H112A 

8H112B 

8H112C1

Triumph 

Triumph 

Triumph

19.730 15.886 39.729 TR Galena Dmt Syn Warm Spring 

19.454 15.847 39.145 TR Galena Dmt Syn Warm Spring 

19.493 15.852 39.370 TR Galena-sphalerite Dmt Syn Warm Spring

Devonian argillite, Milligen Formation, Triumph block, whole rock (filled square) (fig. 4)

8H98 Ida Harlan 20.118 15.835 39.431 BS Whole rock, pyrite in Dmt Ag-Pb- Warm Spring 

argillite Zn

Devonian argillite host rock, Milligen Formation, epigenetic sulfide (H) (fig. 4)

T597M 

8H170 

8H31

Crest Lake?-Trail Creek? 

Lost Dump 

Memorial prospect

19.952 15.797 39.619 BS Galena Dm Epi Warm Spring 

19.545 15.826 39.408 TR Galena Dm Epi Warm Spring 

19.817 15.829 39.512 TR Galena Dm Epi Mineral Hill

Devonian argillite host rock, Milligen Formation, syngenetic sulfide (open diamond) (fig. 4)

8H76C 

8H76D 

8H76I

Snoose 

Snoose 

Snoose

20.117 15.852 39.900 TR Galena Dm Syn? Mineral Hill 

20.090 15.835 39.828 TR Galena Dm Syn? Mineral Hill 

20.092 15.836 39.840 TR Galena Dm Syn? Mineral Hill

Devonian argillite, Milligen Formation, whole rock (filled diamond) (fig. 4)

8H29 

8H28A 

8L625 

WH2112

Roadside 

Slaughterhouse Creek 

Slaughterhouse Creek 

"Sawmill Gulch"

19.887 15.753 39.420 BS Whole rock, pyrite in Dm Ag-Pb- Mineral Hill 

phyllite Zn 

19.857 15.789 39.500 BS Whole rock, quartz and Dm Ag-Pb- Mineral Hill 

pyrite in phyllite Zn 

19.903 15.784 39.363 BS Whole rock, pyrite in Dm Ag-Pb- Mineral Hill 

argillite Zn 

19.308 15.673 39.526 BS Whole rock, argillite Dm Ag-Pb- Warm Springs 

Zn

Devonian argillite host rock, part of Salmon River assemblage, epigenetic sulfide (I) (fig. 5)

R-366 

T576M

T572M 

SWH

Empire 

Patti Flynn

Timberline 

Twin Apex

19.831 15.673 39.111 BS Pyrrhotite, sphalerite, Pzsr Epi Washington Basin 

and scheelite 

19.333 15.809 39.026 TR Boulangerite and Pzsr Epi Fourth of July 

jamesonite 

20.099 15.772 39.460 BS Jamesonite Pzsr Epi Fourth of July 

19.357 15.753 39.341 TR Galena Pzsr Epi Bayhorse
N10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

-2

_c

o

u

1H-l

1a

8

V-,

.2

CO

1

10

oCO

3

r4

JU

2

P^

1

 a

c

|

c

3

0

U

t]

T

 5

b

'c

_C

3

1

^

c

ffi

 a g

rt

1

^

||

II

° <N

^X>

r

3

^

C

_o

5

S

.i

S

u*E

CO

eb

S

li?

ca

9

I?

g. o

0) e

i

?G 

o>

^^in

«T 

j?

assemb er 

>

§

"CB

1

a

v^

1O

1cs

o

cu

o

in m in

m

3333

IH IH bH IH

CO CO CO V.

3 3 33 

U U U U

, ,

"io* "u

tH !_ tH !_ l_ U, D C ) oj r_) o u

»-H D i flj »2 S 

§3 §3 § §

PQ co PQ co 03 PQ

S3

c c c a

CO CO CO CO

IH U, |_l l-l

S S S S 

fX, (X PH CL,

1

y

fi *O

a c c c ' d " u u

PQ O O O

B B ee

r>) r- m ON ON r- r- ON

ON ON ON ON m m mm

in ON m *o ON in m oo 

r- oo oo rin vn in in

O <N O ON i o m i-»

oo m o rON ON o ON

rt rt (S) ^H

II 

% % II

o o '? '?

m \o 7? 2

 ' T-H E 1 f-H

', ^ O 0

« CO 00 OO

2

M

.3

^3

fc

A

i

|

0) "3

1

1

assembl T 

V

Ri mon 

cs

S

a

«T

1

cs

.1So

(U

O

m

3

IH

CO

U

u

|

PQ

£

t>0 e

< N

IH

£

s3

j£

Whole roc

CO

PQ

S

<%

ON

in

m

o *'

CN

B

^u 

9>

Holman Q

o

S)

i 1

C?

eb 

S

f=j

 S

i

c

1

1

i

§

2

*

cs

cs 

cs

|O

i0

1

1h

 4->

SA

M

1c

cs 'S,

1

i

VO VO VO VO VO VO VO

33333 33

U IH In IH U l_

*5 +S Q Q C « 5;

<3 u u u S u CE

.s .s

J^ 'S T3 'co L>

o ca o ca -^ S PQ o 03 g

<: < < 6 3 2 u j

0,0,0,0,0, O, Q

PQ W M PQ W PQ PQ

o o o o o o S

S SSSS SS

S C C fi C o C 

u 53 53 u fry u

O O O O O U O

u u u u u u u

ON vo oo in 04 -rj- <* 

O4 m i ON O4 O *£>

ON ON oo ON ON ON ON

vo 04 i CM r>) o oo *o ^ o o i oo oo 

r- oo ^o r- oo vo t~-

 n in vn m in m in

t-» ON in m in oo <* i < i i i ^- m m oo

ON ON oo OO ON oo oo

*-

B 3 § ! ^ sb 9 3

Hi! 8-1 ° "S . c 8 ° TS

^

?; § S 8 ^ S 5^

oo K oo S ri ri oo ac risoo

^

eb 

S

^*

^

 3

c

1

1

 8

 e

1

mine, ippa 

1

I

|h 

1

t>

*J

S3

t

&

1

.2

.as

^

u

_c'5 

S

a

^

'S

o

u-3 

O

^

in

ON

oo

O

in

 n

oo

C^J

oo

Phi Kappa

c in

I

&>

'O

Sw

o

t

J

0) "o

2

"

ca 

U

1H

>- 'M

o

JS

a

 3

M)

c

cs 'a 

,a

Lc

^

m

6

u

i

CO

a

_o

^

D

o

S

3 a

u

1

co 

PQ

oo 

oo

oo

oo

VO

sm

ON

i

1

H

<e

ei)

B

£?(jj,

0) e

i

1"cs

o

tM

I

 8

1

 g

g

1

JS

Si

ys

t

c 

.S*g

1

a

i

a

inminminvovovo vom

33333333 33

UUUWUUUflJ flJ*-»

^N^NfHiUr^r^r^r^ KK(M^KKG(M r^U K,£S

SpQfflUSpQpSS PQU

 2 .S

3 .2 e§ -S 60 (50 60 60 "(^

S 3 'ScoSSCGC co M-I ca c <" ..H .[H ..H *c t *-<

o WrtPQarao, &,^O

illlliii ifl

MO«OPQ£££ ^woa

0,0,0,0,0,0,0,0, 0,0,

iiiiniiiii

cccccccc c c 

OOOOOOOO OO

^Hf-Hf-HpQpf-Hf-Hf-H E"HQQ

Sgg^gg8| §g

ONONONONONONONON ONON

oooooor- OOOOOOON oorinin«ninininin«n <nin

gsasssss *or vot^t~-r~t^ON asoo^jONONONONONONONON ONON

_g'u

& ^ to 5 y u to

TD i ^

3 C -g ? & ? "O

O'^c'CCCCco hn

ll | &^^2 | .o| 

pQUUwOOODC O^

^ ^! S ** -ff

|S^^§Si8^ |^

^"ONONVOONffiSffi ffi2 Hr-r-r-r-oooooo ool>

-

eb

S

0) e

(S

1

cf

cs

0)

cs 

1

I

.2

^

cs

c

£

O

ta

0) e

1"3

a

2

1

JS

0)

3

fe

tCB

1

cs

1

f

£

u-, m !S m ^ !-T vo vo

33l3il33

COWJyWJcncOWJWJ

23c3r-p3p

UUMUUUUU

£t ^t £A £A

1 li iJJJJ

. H J 1 .| 1 o I o 

S S.S Si33i3i3

uu'Su^^^^

0,0,0,0,0,0,0,0,

lllgllgg

Qj G

 a

CCCCCC'CC

OOOOOO'coO

GB&BCGbt:

jHmoog^ooujinON

?i?i^mm?i?i?i

^§S^^mS§

ininminmininin

*-H »-H oo ^~ ON oo co »~H 

oo O^T ^~ in ON T^ co oo 0*1 iOinoot-t~-

OOOOONOOOOOOOOOO

 a

Ui C

U U O _ _ _ _

 a > 30,0,0,0,

 ^ r3 J 3 3 3 3 

"COS i33 33

QScoOPQPQPQPQ

"5

S S | ^ §

HoO^VO^g^Jjjg

r Hint iin<noooo
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO Nil

»«

S3

1 3

u S

J2 i ^'^

il

as

§§

OH PH

cd cd 1 s

cd "cd 

O O

H H

U U

o ^o

Os Os 

VO CX)

Os Os

en en

Os ^h

<n vi

^H en

oo' os

^

IBu Z

Hidden TiWestlake

en V)

V) 00

00 00

^

ec

S

L*

ca

af i

s

^

U

S

 "o

f

ef

£CQ

^

Ul

^^

C

I

_o

is

o

i

2

"o

Q 

sT

s

ca

.2

s

£

«

ca^ ^

8

e

S

« «

3 3

W W

1 1

u u

1) flj i) S

C u

o o

a a

PH PH

60 c 60 C

 0 T3 

PH PH

.s .s

1 1

o* o*

 8 # 0 0

tD tD

"2 3 "° f3 

^ >

1/3 on

PQ PQ

^H 00

vO O 

O CN

Os Os

en en

£ 2

^O C^

V) vj

04 Tfr

oo r~-

Os Os

£

1

T3

U

1 * cd 35

Buttercup Willow Q

t~- o

VD vo

OO OO

Co"

s

i

"O

i

'S

I

1

s« 25o i* 

u 

-fCQ

o>

ca

O

^

O

c

0

fe

!S

2

Q

0

1

.-s

!§)

ca

CQ

1

frl

ji

'S

ca

1

£

 =* <* 

_C _C _C _C _C .C _C .C .G

PQPQPQPQPQPQPQPQPQ

uu 2 U 2 U 2 U 2

ccccccccc § s § § § § s § i

[T~| [T~| pTl [T~| fT~) [T~| ^T~) [T~| ^T~)

 a"O"OT3S 3 3 3 3 

PHPHPHPH-aT3T3T3i3

CCCCCCCCC 

cd cd cd cd cd cd cd cd cd

OOOOOOOOO

sssssssss

sssssssss

Sg§8§SS§§ ddddddddd

sgggsssgg

v-iv-iiov-ivi>o<nin>o

§I§S§s§§S OOOOOsOsOOO <N<N<N<N "H "H<N<N<N

to

U

_ 1

| 6 t ^ 3 ^ ! 1 1

PQen

. < < <! 2 u ^

ss<sss^ss

Co"

ec

S

"u

'3

e

a 

3

g "3

% 

 o

a> O 

"O

a>

Xi

ef ?*^

a

K<C

cu

o

s*

o

Formation,

S

J5

2

Q

u

£

to

O

.tn

ca 

ca

g

&H

(3 '3

ca

^

w"

c

S

«

3

'J3

PQ

s

3"§

u

§

cc

1/3

 S

PH

cd 

1

O

s

s

Os 

Os

d

en 

enOs

vt

oo 

en 

<N

O

cs

Idahoan

uOs rac

00

Co

oi)

X

a

1

ca 3

 o

S

1^4

o> "3

1

tf

u

ca

cy

o

!

"H

g

1

1

ia

a

1

aT

!B

a

e 

.2

£UH

i

5

a

Ul

e

e

ftj

« «

S S

u u

_c _c

5 5

DS S

u u 

.S .S

s is

-p .p

PH PH

60 c 60 C

2 2

2

 S § g

1) DO

 c c 2

?*»* ?*«* *"^

^ ^ .s

2 o 2|

ja g Jj| -§!-§!

PQ PQ

^H en

00 1-H

en TJOs Os 

en en

vo c»

 i 00

oo c^

>n \r>

vo rCS 00

en c^

O Os

04 ^H

O O

 c, -§

2 2

< PJ

Os Os

r- rffi ac

00 00

Co

ec

S

g

 o

% 

go

"ea

g

«

 2£

i

ca 

O

^4

O

 W

t

ca

.2*p

£

ca

U)

e

£

«

3 

S3

U

J4

1

'a

&

cd

1

06

H

en

CS

Os 

en

0)

00

>n

en

Os

*

S

Grand Pri:

en

Soo

P

2£

O

 S

"3

.a"

"S

"ea 

Xi

o

ca o

;h-central I

1

1

1

.£: "w

"S

Ul

1u

es 1s

o

«««

|||

53 u w

o l

8 ||

S> 1

o< ex a PJ PJ PJ

cd 60 60

cd cd cd

o o 6

H H H

U U U

o cs vo 

en en ^O ^H Os O

d od os rf en en

 1 Tfr OS 

(^ Tt VO

vo 10 TJVS >0 VI

O4 ^- ^O

en o rOO V) O

r~ r~ r~

^

u &

Franklin Blackston Marsh Cn

00 OS rf

en ^H T}-

S3 ffi S3 

oo oo oo

ei

S

§

 S

"3 

%fH

.t; "o

^

ca Xi

o

A

ca o

NH

district, na 

a

£

 g

1

A

.££

.3

2u

ca

O

«.« 

S33S

u u u u

_c _c _c _c

PQ PQ PQ PQ

cd cd cd cd 

C C C C

c c c c u u u u

> > > >

o, o, o, a 

pq PJ PJ PJ

T3 T3 -a T3 

60 60 60 M

W W W W

c c c c

D D O D

cd cd cd cd

O O O O

H H H H

U U U U

en TJ- en vi

Tj- OS OO OS 

OO f- V) OO

Os Os OS Os 

en en en en

o r- r-- roo o 04 oo

V) V) V) V)

en O CN vi

V) 00 OS (X)

en os en c^

c» c^ oo c^

>

£

S -1-1

8 8 «l 

,3 ^2 S -8 ^^>^

< < ** O ^^ oo 2

,-H ^H O 04

i i i ii " O

aS 35 3n f^ 

00 (X) 00 H

^^

Sf

§

o> "O 

!«

1

fT

~5 

5

ca

o

a

mtheast Id;

g

 S

s

1

J£

1

§

8ca

2 

u

»,»,»»,», »

i)i)Di)4>i)a>cL>fl> y

ooooc5ooc5o o

111111133 3

UUUUUUUfflffl PQ

u

o c

SwawawwaUu'SS S

0,0,0,0,0,0,0,0,0, o.

J2 .g .fi -g

w> w°ww> w> w> w> ww> w< wr<

ccccccccc c 

OOOOOOOOO O

UHUHHHHHH E-1

JUp-JOUUUUU U

§s5§sSsl§ §

enenenen-rj-enenen-rj- en

^vO§2^S§S? S

V)V)V)V)V)V1V1V1V1 V)

§3S§§§SiS §

Osooooooosoooooooo oo

c c

° ° M

c (2 2 |

s 1 fi u <a 3

>. _ ^ ^ j3 >

Ijaljjjjl 1

»S|S|<uS| g

oooooooooooooo^ooo oo
Table 2. Lead-isotope data for central Idaho Continued.

Sample no. Mine or location

206pb/ 

204pb

207pb/ 

204pb

208pb/ 

204pb Type Material Host Association Mining district 

Cretaceous intrusive rock, southeast Idaho batholith, potassium feldspar (filled square) (fig. 7)

A230 McCoy mine stock 19.572 15.762 39.309 BS Potassium feldspar Kqd Au-AgPb-Zn

Mineral Hill 

Cretaceous intrusive host rock, central Idaho batholith, sulfide (R) (fig. 7)

Buck 

S76-895

F112 

F107 

KR880 

GHM-1 

R-151

F154 

R-155

Buckskin Drill Road-Thompson 

Creek 

Buckskin Drill Road?-Thompson 

Creek 

Carlson Gulch-Grimes Creek 

Comeback 

Deadwood 

Greyhound 

K.G.

Seafoam Lake-west 

Silver Bell

17.577 

17.617

19.144 

19.097 

19.341 

18.110 

17.990

17.747 

17.596

15.583 

15.594

15.672 

15.678 

15.754 

15.646 

15.578

15.604 

15.574

40.875 

41.014

39.087 

39.083 

39.527 

40.565 

39.286

39.765 

39.785

CT 

CT

LC 

LC 

TR 

CT 

CT

CT 

CT

Galena Kgd 

Galena Kgd

Galena Kgd 

Galena Kgd 

Galena Kgd 

Galena Kgd 

Galena Kgd

Galena Kgd 

Galena Kgd

Epi 

Epi

Epi 

Epi 

Epi 

Epi 

Epi

Epi 

Epi

Bayhorse 

Bayhorse

Grimes Pass 

Grimes Pass 

Dixie 

Seafoam 

SeafoamDeadwood 

Seafoam 

Seafoam

Cretaceous intrusive rocks, central Idaho batholith, whole rock and potassium feldspar (filled diamond) (fig. 7)

KR743Kf 

LP-1

W320 

W188

Deadwood 

Lost Packer

Thompson Creek 

White Cloud-west

19.488 

19.768

20.508 

19.204

15.716 

15.742

15.811 

15.694

39.320 

40.078

40.329 

39.262

BS 

PA

BS 

LC

Potassium feldspar Kgd 

Whole rock Kgd

Potassium feldspar Kgd 

Potassium feldspar Kgp

Zn-PbAg 

Cu-Ag- 

(Mo) 

Mo 

Mo

Dixie 

Loon Creek

Bayhorse 

East Fork

Eocene Challis Volcanic Group host rock, Lava Creek district, sulfide (S) (fig. 8)

638 

634 

640 

639 

8H161A

"Dry Fork Creek" 

Ella 

Hanni2-SilverBell? 

Hub 

St. Louis

17.909 

19.166 

17.290 

17.868 

19.030

15.628 

15.819 

15.579 

15.636 

15.761

38.696 

39.638 

38.508 

38.673 

39.334

LC 

LC 

LC 

LC 

LC

Galena Tc 

Galena Tc 

Galena Tc 

Galena Tc 

Galena Tc

Epi 

Epi 

Epi 

Epi 

Epi

Lava Creek 

Lava Creek 

Lava Creek 

Lava Creek 

Lava Creek

Eocene granite host rock, southeast Idaho batholith, sulfide (T) (fig. 8)

76T31 GAP, Big Smokey Creek 18.311 15.622 39.883 CT Galena Tg Epi Vienna 

Eocene Challis Volcanic Group, central Idaho batholith, whole rock (filled diamond) (fig. 8)

LF-1 

Grey-1

GM-31 

RH-122 

GM-365 

SB215120

Little Falls 

Mt. Greylock

Parker Mountain 

Red Mountain Dome 

Singheiser 

Sunbeam

19.149 

17.536

17.869 

17.493 

18.885 

17.803

15.653 

15.525

15.526 

15.522 

15.645 

15.529

39.186 

39.272

39.634 

39.459 

39.818 

39.497

LC 

CT

CT 

CT 

CT 

CT

Whole rock Tcr 

Whole rock Tcr

Whole rock Tcr 

Whole rock Tcr 

Whole rock Tcr 

Whole rock Tcr

Mo 

Au-Ag- 

(Mo) 

Au-Ag- 

(Mo) 

Au-Ag- 

(Mo) 

Ag-Au- 

(Mo) 

Au-Ag- 

(Mo)

Bear Creek 

Yankee Fork

Parker Mountain 

Yankee Fork 

Gravel Range 

Yankee Fork
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N13

O 3

PQ U

 a -a 

o o

PQ

3 O O

U PQ PQ

O O on

c c c c c c

H H H H H

HJ UJ (U UJ UJ

(X) VI O CT\ «O O «/"! en ^H V) ^H t-~ en CN O

en en en en en en

CT\ 04 04 

V) V~i O

O4 ^O 04 1-1 O t^~ TJ- cs ^o v> oo en

ao oo F~ u~i ir> \o

H O H H H (S en ^ en CT\ * CT\ (5 o r4

(X) Tj- 00 00 </1

Moore group of mines (mainly the Silver Star Queen mine) 

and for an epithermal vein galena (G, fig. 4) from the Old 

Triumph mine (sample number 575) plot in a cluster, which 

we designate Minnie Moore type, that has high 208Pb/204Pb 

and 206Pb/204Pb (fig. 4). The other cluster, group B lead, 

comprises whole rocks, possibly syngenetic sulfides, and 

other epithermal veins (figs. 4, 5). Group B lead consists of 

two types, Triumph (open squares, figs. 4, 5) and black 

shale (solid squares and diamonds, fig. 4), based on different 207Pb/204Pb ratios. Triumph-type lead characterizes the 

ore in the possibly syngenetic massive sulfide deposits at 

Triumph, Hoodoo, and Livingston. Lead in the Snoose 

deposit is Triumph type but is very close to the dividing 

line between the types.

Uranium and thorium in the whole-rock samples has 

contributed to the radiogenic lead (206Pb, 207Pb, and 208Pb) 

since the original sediments were deposited. In order to 

minimize these contributions, samples that were metal rich 

and contained visible pyrite, sphalerite, or other sulfides 

were selected for analysis. Thus the initial lead concentration should be high relative to uranium and thorium concentrations, and the contribution from radiogenic lead 

produced since sediment deposition should be relatively 

small. The fact that the lead-isotope ratios for whole-rock 

argillite (filled squares and diamonds, fig. 4) cluster in a 

tight group is evidence that this assumption is correct. If 

the initial lead had been low compared to uranium, the 

present-day lead-isotope ratios probably would plot as an 

extended linear array rather than a tight cluster. If there 

had been significant production of radiogenic lead, the initial 206Pb/204Pb and 208Pb/204Pb values would have been 

lower than the present-day values and might plot in the 

field shown by the arrow and dotted outline in figure 4, 

assuming lead and thorium concentrations for average shale 

in the Canadian Cordillera (Godwin and Sinclair, 1982). 

The adjustment of lead-isotope ratios shows that, if significant radiogenic lead has been produced, then the initial 

whole-rock lead would have been distinctly less radiogenic 

than lead in galena from veins and syngenetic deposits.

MISSISSIPPIAN ROCKS

Samples from Mississippian rocks include sulfides 

from veins in the Copper Basin and McGowan Creek Formations (J) and galena from conformable-bedded replacement sulfide ore of the Phi Kappa mine in the Copper 

Basin Formation (open circle) (fig. 5). One previously 

reported analysis of whole-rock argillite from the Copper 

Basin Formation (Urexco sample T-602) is anomalously 

radiogenic due to uranium enrichment and plots off the 

diagram (fig. 5) to the right.

The vein and bedded-replacement sulfides hosted by 

the Copper Basin Formation form a distinct group, the Lava 

Creek type, that has 206Pb/204Pb=l8.2-19.4 and 208Pb/ 

204Pb=38.7-39.6 and overlaps only slightly with the group B 

sulfide samples from the Milligen Formation and Salmon 

River assemblage.
N14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

200 Pb/ -^Pb

EXPLANATION

K Pennsylvanian-Permian argillite host rock, Wood 

River Formation, sulfide samples

L Pennsylvanian-Permian argillite host rock, 

Dollarhide Formation, Carrietown-Westlake area, 

sulfide samples

 Pennsylvanian-Permian argillite, Dollarhide 

Formation, Carrietown-Westlake area, wholerock samples

M Pennsylvanian-Permian argillite host rock, 

Dollarhide Formation, Croy Creek area, 

crosscutting vein sulfide samples

0 Pennsylvanian-Permian argillite host rock, 

Dollarhide Formation, Croy Creek area, bedded 

sulfide sample

* Pennsylvanian-Permian argillite, Dollarhide 

Formation, Croy Creek area, whole-rock 

samples

N Pennsylvanian-Permian argillite host rock, Grand 

Prize Formation, sulfide sample

Figure 6. Lead-isotope ratios for samples of vein and conformable 

epigenetic galena and whole rock from Pennsylvanian and Permian 

argillite, central Idaho. Average shale growth curve of Godwin and 

Sinclair (1982) is also shown. Arrow indicates correction for radiogenic lead.

PENNSYLVANIAN AND PERMIAN ROCKS

Samples from Pennsylvanian and Permian rocks 

include sulfides from epigenetic veins in the Wood River 

(K), Dollarhide (L, M), and Grand Prize Formations (N) 

(Sun Valley Group of Mahoney and others, 1991); galena 

from bedding-conformable concentrations in the Dollarhide 

Formation (open circle); and pyrite-rich argillite from the 

Dollarhide Formation (solid diamonds and squares, fig. 6).

Lead-isotope ratios define three types of samples, Carrietown and Minnie Moore (group A) and black shale 

(group B). Carrietown-type material, which has 206Pb/ 

204Pb= 18.0-19.2 and 208Pb/204Pb=39.5^K).0, includes 

some of the vein and bedding-conformable galena hosted 

by the Dollarhide Formation. Samples in this group are 

from the Buttercup mine, the Westlake North mine, and all 

the sampled deposits in the Carrietown mining district. The

rest of the vein and bedding-conformable sulfides hosted by 

the Dollarhide Formation form the radiogenic Minnie 

Moore type, having 206Pb/204Pb= 19.9-20.4 and 208Pb/ 

204Pb=40.5^1.1. This type includes samples from the 

Eureka, Liberty, Jay Gould, and Idahoan mines, for example, all in the Croy Creek area. The isotope ratios in the 

Croy Creek area are slightly but significantly different from 

those of the Minnie Moore mine group, indicating a different source, but are probably similar enough to justify 

grouping them into a single type. Group B, which has 

206Pb/204Pb= 19.2-20.4 and 208Pb/204Pb=39.0-40.0, 

includes four samples of whole rock from the Dollarhide 

Formation, one vein galena from the Grand Prize Formation, and all of the vein galena samples from the Wood 

River Formation. Within group B, the whole-rock samples 

define the black shale type. The Wood River vein galenas 

have slightly higher 208Pb/204Pb ratios on the average than 

the other samples in this group. Initial lead-isotope ratios 

were calculated assuming average shale concentrations of 

uranium and thorium, as described above for Devonian 

rocks. The displacement of the isotope ratios to lower values indicates that, if the assumption is valid, initial wholerock lead was distinctly different from the vein and syngenetic lead hosted by those rocks.

The isotopic ratios of the bedding-conformable concentration of galena in the Dollarhide Formation (bedded sulfide, open circle, fig. 6; sample 8H79E, table 2) show that 

isotopic characteristics can be used to discriminate between 

syngenetic and epigenetic sulfides. This sample has textural 

features suggestive of syngenetic material; however, isotopically it clearly resembles epithermal vein sulfides also 

hosted by the Dollarhide and is distinct from both the host 

argillite and all known syngenetic sulfides in the area.

The samples from the Triumph block were plotted separately from others of the Milligen Formation (fig. 4) in 

order to investigate whether the argillite of the Triumph 

block correlates with the Middle Pennsylvanian to Lower 

Permian Dollarhide Formation (Wavra, 1988; Wavra and 

Hall, 1989) or with the Milligen Formation (Mahoney and 

others, this volume; Turner and Otto, this volume). Leadisotope ratios for whole-rock samples cannot resolve this 

stratigraphic correlation problem; however, lead-isotope 

ratios from ore deposits support the assignment of the argillite of the Triumph block to the Milligen Formation. Ore 

deposits in the Triumph block have a lead-isotope signature 

(Triumph type) almost identical to that of deposits hosted by 

the Milligen Formation and by the Devonian part of the 

Salmon River assemblage elsewhere in the black shale terrane. In contrast, the lead-isotope signature of Dollarhidehosted veins (Carrietown- and Minnie Moore-types) is distinctly different from the lead-isotope signature of deposits 

in the Triumph block. This evidence supports the correlation 

of the Triumph argillite with the Milligen Formation.
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N15

Ore, central batholith

Ore, south-central batholith 

Ore, Vienna district 

Ore, southeastjiatholith

' Pb/ ""Pb 

EXPLANATION

o Cretaceous intrusive host rock, south-central 

Idaho batholith, sulfide samples

P Cretaceous intrusive host rock, Vienna district, 

east-central Idaho batholith, sulfide samples

Q Cretaceous intrusive host rock, southeast Idaho 

batholith, sulfide samples

* Cretaceous intrusive rock, southeast Idaho 

batholith, potassium feldspar sample

R Cretaceous intrusive host rock, central Idaho 

batholith, sulfide samples

* Cretaceous intrusive rock, central Idaho batholith, 

whole-rock and potassium feldspar samples

Figure 7. Lead-isotope ratios for samples of vein galena, whole 

rock, and potassium feldspar from Cretaceous intrusive rocks, central Idaho. Average shale growth curve of Godwin and Sinclair 

(1982) is also shown.

EXPLANATION

s Eocene Challis Volcanic Group host rock, Lava 

Creek district, sulfide samples

T Eocene granite host rock, southeast Idaho 

batholith, sulfide sample

* Eocene Challis Volcanic Group, central Idaho 

batholith, whole-rock samples

v Eocene granite host rock, central Idaho batholith, 

sulfide samples

 Eocene granite, central Idaho batholith, wholerock samples

Figure 8. Lead-isotope ratios for samples of vein galena and 

whole rock from Eocene intrusive and volcanic rocks, central Idaho. Average shale growth curve of Godwin and Sinclair (1982) is 

also shown.

CRETACEOUS INTRUSIVE ROCKS

Lead isotopes from four epigenetic vein galena samples 

(O, P, Q, and R), three feldspar samples (filled diamonds), 

and one whole-rock sample (filled square) from Cretaceous 

intrusive rocks include a wide range of 206Pb/204Pb and

208pb/204pb ratios (flg ?) An of the vein galena ha§ 206pb/

204Pb less than 19.7. The vein material from the Challis 

quadrangle (central Idaho batholith, R) has a wider isotopic 

range than that from the Hailey quadrangle (southern Idaho 

batholith, O, P, and Q). Vein material from the Hailey quadrangle can be divided into three moderately overlapping 

groups corresponding to geographic areas within the Idaho 

batholith. One group (O), having 206Pb/204Pb=17.0-18.0, 

includes three samples from the south-central part of the 

Idaho batholith, encompassing the Featherville, Pine, and 

Volcano mining districts. A second group (P), having 206Pb/ 

204Pb=17.8-18.4, comprises all the samples in the east-central part of the Idaho batholith from the Vienna district. A 

third group (Q), having 206Pb/204Pb=18.0-19.2, comprises 

veins in the southeast part of the Idaho batholith, composed 

of the Big Smoky, Camas, Mineral Hill, Skeleton Creek, and 

Soldier mining districts.

Lead from a whole-rock sample and four potassium 

feldspar samples from intrusive rocks of the Cretaceous 

Idaho batholith is group B, according to our definition. 

These samples have the same lead-isotope composition as 

the samples of Devonian and Pennsylvanian-Permian argillite. Lead-isotope ratios of Cretaceous whole-rock and 

potassium feldspar samples are clearly distinct from those of 

veins hosted by Cretaceous intrusive rocks. On the basis of 

our sampling of Cretaceous rocks, it appears that Cretaceous 

intrusive rocks were not the source for the lead in the Cretaceous-hosted veins.

EOCENE INTRUSIVE AND 

EXTRUSIVE ROCKS

Samples from Eocene rocks and Eocene-hosted veins 

include whole rocks from Eocene volcanic and intrusive 

rocks in the Challis quadrangle and vein galena hosted by 

intrusive and extrusive rocks from various parts of the study 

area (fig. 8). Vein galena (S) in the Lava Creek mining district in the Idaho Falls quadrangle is hosted by the Challis 

Volcanic Group and defines the Lava Creek type, 206Pb/ 

204Pb=17.3-19.2 and 208Pb/204Pb=38.5-39.6. These veins
N16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Table 3. Summary of lead-isotope types of sampled rocks and ore deposits in central Idaho.

GROUP A LEAD ISOTOPES

_______________________________Carrietown type___________________________ 

Whole-rock samples

Some Eocene granite whole-rock samples, central Idaho batholith.

Most Eocene volcanic whole-rock samples, central Idaho batholith. 

Sulfide samples

All replacement deposits in Paleozoic carbonate roof pendants in Idaho batholith.

Most replacement deposits in Ordovician carbonate and phyllite host rock, Ella Dolostone group.

All veins in Pennsylvanian-Permian Dollarhide Formation argillite host rock, Carrietown-Westlake area.

Most veins in Cretaceous intrusive host rock, central Idaho batholith.

All veins in Cretaceous intrusive host rock, Vienna district, Idaho batholith.

Most veins in Cretaceous intrusive host rock, southeast Idaho batholith.

All veins in Cretaceous intrusive host rock, south-central Idaho batholith.

Vein in Eocene granite host rock, southeast Idaho batholith. 

______Vein in Eocene granite host rock, central Idaho batholith.__________________________

______________________________Lava Creek type_____________________________

Whole-rock and potassium feldspar samples

Potassium feldspar in Cretaceous intrusive rocks, central Idaho batholith.

Some Eocene granite whole-rock samples, central Idaho batholith. 

Sulfide samples

Vein in Middle Proterozoic Swauger Formation host rock.

All replacement deposits in Devonian carbonate host rock, Jefferson Dolostone group.

All veins in Mississippian argillite host rock, Alto-Muldoon-Lava Creek area.

Bedded replacement deposit in Mississippian argillite host rock, Phi Kappa mine.

Some veins in Cretaceous intrusive host rock, central Idaho batholith.

All veins in Eocene Challis Volcanic Group host rock, Lava Creek district. 

_____Vein in Eocene granite host rock, central Idaho batholith.__________________________

______________________________Minnie Moore type______________________________

Sulfide samples

All veins in Devonian Milligen Formation argillite host rock, Minnie Moore mine group.

All veins in Pennsylvanian-Permian Dollarhide Formation argillite host rock, Croy Creek area. 

_____Bedded sulfide in Pennsylvanian-Permian Dollarhide Formation argillite host rock, Croy Creek area. 

________________________________Pacific type_____________________________ 

Whole-rock sample

Cretaceous intrusive whole-rock sample, central Idaho batholith. 

Sulfide sample 

____ Most replacement deposits in Ordovician carbonate host rock, Bayhorse Dolostone. ________

have a similar range in 206Pb/204Pb as veins from the Idaho 

batholith (Carrietown type); however, the 208Pb/204Pb ratios 

of the Lava Creek type are generally lower for a given 206Pb/ 

204Pb. Vein galena (T and V) hosted by Eocene granite 

defines a cluster, having 206Pb/204Pb=17.5-18.3 and 208Pb/ 

204Pb=39.9-41.0, that we include in the Carrietown type. 

Lead in Eocene whole-rock samples forms a broad but welldefined group, having 206Pb/204Pb= 17.5-20.5 and 208Pb/ 

204Pb=39.1-40.1, that overlaps many of the types defined 

above, specifically, Carrietown-, Lava Creek-, Pacific-, and 

black shale-types.

SUMMARY

The characteristic 208Pb/204Pb and 206Pb/204Pb ratios 

for sulfide minerals and whole rocks reveal distinct lead 

isotope signatures or types (see summary, table 3). The first

four types are in group A and the fifth is in group B. (1) 

Carrietown type, which is low in uranogenic lead and high 

in thorogenic lead, is defined by isotopic ratios in replacement deposits in carbonate roof pendants in the Idaho 

batholith, replacement deposits in the Middle Ordovician 

Ella Dolostone (fig. 3), veins hosted by the Middle 

Pennsylvanian to Lower Permian Dollarhide Formation in 

the Carrietown and Westlake mining areas (fig. 6), veins in 

the Cretaceous Idaho batholith of the Hailey quadrangle 

(fig. 7), and veins hosted by Eocene granite in the Challis 

quadrangle (fig. 8). (2) Pacific type, which is high in both 

uranogenic and thorogenic lead, is defined by isotopic 

ratios in replacement galena in the Upper Cambrian or 

Lower Ordovician Bayhorse Dolostone (fig. 3). (3) Minnie 

Moore type, which is high in both uranogenic and thorogenic lead, is defined by isotopic ratios in veins in the Minnie Moore group of mines in the Devonian Milligen
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N17

Table 3. Summary of lead-isotope types of sampled rocks and ore deposits in central Idaho Continued.

___________________________GROUP B LEAD ISOTOPES__________________________ 

_______________________________Triumph type______________________________

Syngenetic sulfide samples

All syngenetic sulfides Devonian Milligen Formation argillite host rock including Triumph block.

All syngenetic sulfides in Devonian part of Paleozoic Salmon River assemblage argillite host rock. 

Epigenetic sulfide samples

Most epigenetic veins in Devonian argillite host rock, Triumph block.

Some veins in rest of Devonian argillite host rock.

Some veins in Devonian part of Paleozoic Salmon River assemblage argillite host rock.

Most veins in Pennsylvanian-Permian Wood River Formation argillite host rock.

_____Vein in Pennsylvanian-Permian Grand Prize Formation argillite host rock.__________________ 

_______________________________Black shale type_____________________________ 

Whole-rock and potassium feldspar samples

Devonian Milligen Formation argillite whole-rock sample, Triumph block.

All other Devonian argillite whole-rock samples.

Mississippian Copper Basin Formation argillite whole-rock sample.

Devonian part of Paleozoic Salmon River assemblage argillite whole-rock sample.

Both Pennsylvanian-Permian Dollarhide Formation argillite whole-rock samples, Carrietown-Westlake area.

All Pennsylvanian-Permian Dollarhide Formation argillite whole-rock samples, Croy Creek area.

Some potassium feldspar in Cretaceous intrusive rocks, central Idaho batholith.

One potassium feldspar in Cretaceous intrusive rock, southeast Idaho batholith. 

Sulfide samples

Some veins in Devonian part of Paleozoic Salmon River assemblage argillite host rock.

Some veins in Pennsylvanian-Permian Wood River Formation argillite host rock.______________

Formation (fig. 4), one sample from the Old Triumph mine 

in the Triumph block (fig. 4), and veins in the Middle 

Pennsylvanian to Lower Permian Dollarhide Formation 

excluding the Carrietown district (fig. 6). (4) Lava Creek 

type, which is low in both uranogenic and thorogenic lead, 

is defined by isotopic ratios in a vein in Precambrian 

quartzite (fig. 3), replacement deposits in the Upper Devonian Jefferson Dolostone (fig. 3), veins and replacements in 

Mississippian argillite of the Copper Basin Formation (fig. 

5), and Eocene Challis Volcanic Group volcanic-hosted 

veins in the Idaho Falls quadrangle (fig. 8). (5) Group B 

(consisting of black shale- and Triumph-types, which are 

not distinguishable using 208Pb/204Pb and 206Pb/204Pb), 

which is high in uranogenic lead and low in thorogenic 

lead, is defined by isotopic ratios in all the whole-rock 

argillite (figs. 4, 6), all syngenetic deposits (figs. 4, 5), most 

veins in the Devonian Milligen Formation including argillite of the Triumph block (fig. 4), some veins in the Devonian part of the Salmon River assemblage (fig. 5), and most 

veins in the Middle Pennsylvanian and Lower Permian 

Wood River and Grand Prize Formations (fig. 6).

The Carrietown-, Minnie Moore-, and Pacific-types 

together correspond to group A of Doe (Doe and Delevaux, 

1985; Doe and Sanford, this volume) and to area la of Zartman (Zartman, 1974). The Triumph- and black shale-types 

correspond to group B of Doe and to area II of Zartman. The 

Lava Creek type, which has affinities to both groups A and 

B, is here included in group A because it is more similar to

area la of Zartman than to area II, as discussed below. Thus, 

some of the samples classified as group B in Doe and Sanford (this volume) are here classified as group A.

207Pb/204Pb.206pb/204pb RESULTS

The 207Pb/204Pb data are presented separately for 

groups A and B (figs. 9, 10). Carrietown-, Lava Creek-, and 

Minnie Moore-types display a fairly linear trend that yields 

a calculated model age of 2,400±100 Ma using the model 2 

least-squares regression of York (1969). Eocene igneous 

whole rocks of group A also exhibit a linear trend yielding a 

calculated model age of 1,450±300 Ma. These model ages 

agree well with previously calculated model ages (Small, 

1968; Doe and Delevaux, 1985) and probably indicate times 

of major erogenic reworking of crustal source rocks. Pacifictype lead does not show a trend by itself but is consistent 

with a model age of -1,450 Ma for the source rock.

207Pb/204Pb data for group B samples suggest two 

slightly overlapping groups (fig. 10). Triumph-type lead in 

syngenetic galena from the Triumph, Hoodoo, and Livingston mines in general has higher 207Pb/204Pb than black 

shale-type lead from whole rocks of the Milligen and Dollarhide Formations. Triumph-type lead is defined by isotopic 

ratios of syngenetic sulfides in Devonian argillic host rock 

(figs. 4, 5, 10). Black shale-type lead is defined by isotopic 

ratios of Devonian, Pennsylvanian, and Permian argillite
N18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Carrietown and 

Lava Creek types

Pacific type 

Eocene whole-rock samples

I Error ellipse

19

206 Pb/ 204Pb

EXPLANATION

A Undifferentiated Paleozoic carbonate, Devonian 

argillite and carbonate host rock, sulfide 

samples

B Ordovician carbonate host rock, sulfide samples

c Mississippian, Pennsylvanian, and Permian host 

rocks, sulfide samples

D Cretaceous and Eocene igneous host rock, central 

batholith, sulfide samples

E Cretaceous and Eocene host rock, southern 

batholith, sulfide samples

 Eocene rhyolite and granite, whole-rock samples

Figure 9. Lead-isotope ratios for samples in group A, central Idaho. Symbol A includes Milligen Formation (including Triumph 

block argillite), Ramshorn slate, Saturday Mountain Formation, Jefferson Dolostone, and Paleozoic carbonate roof pendants within the 

Idaho batholith. Average shale growth curve of Godwin and Sinclair 

(1982) is also shown. Model age is calculated from vein lead samples excluding those from Bayhorse and Ella carbonate rocks.

whole rocks (figs. 4, 6, 10) and Cretaceous igneous whole 

rocks and potassium feldspar (figs. 7, 10). Even if age corrections assuming decay of uranium and thorium are applied, 

the Triumph- and black shale-types are distinct. Leastsquares regression of 207Pb/204Pb-206Pb/204Pb data for argillite whole-rock samples yields a model age of 2,300±600 

Ma. Although the error is large, the model age agrees with 

that from group A lead (Carrietown-, Lava Creek-, and Minnie Moore-types) (fig. 9), which suggests a similar age for 

the source rock. Galena samples from sediment-hosted 

veins have 207Pb/204Pb values that span the range of Triumph and black shale lead-isotope ratios, but most correlate 

isotopically with the Triumph-type syngenetic galena rather 

than with the black shale-type whole-rock argillite. The distinction between Triumph- and black shale-type lead is not 

apparent on the 208Pb/204pb_206Pb/204pb diagram, unless the 

whole-rock lead is corrected for radiogenic growth since 

sediment deposition. Our classification scheme for central 

Idaho lead isotopes is summarized in figure 11.

For classifying lead-isotope ratios from other sources, 

straight lines are shown that closely correspond to

'Pb/ ""Pb

EXPLANATION

 Paleozoic argillite and Cretaceous intrusive rocks, 

whole-rock and potassium feldspar samples

n Paleozoic sedimentary host rock, syngenetic 

sulfide samples

s Paleozoic sedimentary host rock, epigenetic

sulfide samples 

O Igneous host rock, sulfide sample

Figure 10. Lead-isotope ratios for group B, central Idaho. 

Dashed curve shows isotopic ratios of black shale type assuming decay since the Devonian using data for average shale from 

Godwin and Sinclair (1982). Model age is calculated from 

whole-rock argillite samples only. Arrow indicates correction 

for radiogenic lead.

boundaries between the defined types (heavy lines in fig. 

11). Only relatively few samples having lead isotope ratios 

in the areas of overlap might be misclassified using these 

fields. Equations for the field boundaries are as follows. 

Boundary between Carrietown-Minnie Moore and 

Lava Creek-Triumph-black shale types:

208pb/204pb=0>516x206ph/204pbf 29.778

Boundary between Carrietown- and Minnie Mooretypes:

206pb/204pb=19 6

Boundary between Lava Creek and Triumph-black

shale types:

206pb/204pb=19 27

Boundary between Triumph- and black shale-types and 

between Minnie Moore- and Pacific-types: 

207pb/204Pb=0 .i49x206Pb/204Pb+12.855

DISCUSSION

The isotopic evidence reveals three major crustal 

zones (table 1, also compare figs. 12 and 1): a broad western zone that corresponds to the Cretaceous intrusive rock 

terrane and small parts of the black shale terrane and is 

characterized isotopically by low 206Pb/204Pb and high 

208pb/204pb (Carrietown type); a narrow arcuate central
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N19

zone corresponding to black shale terrane and characterized 

by high 206Pb/204Pb (Minnie Moore-, Pacific-, Triumph-, 

and black shale-types); and a broad eastern zone that corresponds to flysch, shelf carbonate and Precambrian terranes 

and is characterized by low 206Pb/204Pb and low 208Pb/ 

204Pb (Lava Creek type).

We determined the sources of lead in the ore deposits 

for each crustal zone and terrane by a process of elimination. 

If the isotopic ratios of lead in a potential source rock do not 

match those of the veins, then that source rock is eliminated 

as a possibility. Other factors, such as the relative ages of 

rocks and veins, can further eliminate source-rock candidates; for example, the source rock had to exist at the time 

the veins formed. The effect of radiogenic lead-isotope production in the source rock with time is considered when testing for any match. Summaries of the sulfide and rock 

samples in each lead-isotope type are given by crustal zone 

and terrane in table 1 and by isotope type in table 3.

WESTERN CRUSTAL ZONE 

CARRIETOWN TYPE

Most veins in the western crustal zone (Cretaceous 

intrusive rock terrane) probably derived their lead (Carrietown type) from a Precambrian source beneath the exposed 

Idaho batholith. The three samples from widely separated 

Cretaceous intrusions have black shale-type lead (fig. 7). 

Unless further sampling of Cretaceous rocks discloses a 

larger range of isotopic ratios specifically, lower 206Pb/ 

204Pb and higher 207Pb/204Pb and 208Pb/204Pb the Cretaceous igneous rocks cannot be the source for the lead in Cretaceous-hosted veins. Similarly, the vein lead could not have 

come from Paleozoic argillite. The limited areal distribution 

of argillite probably also rules argillite out as a direct source 

of lead in the Idaho batholith-hosted veins. The only known 

rocks having the appropriate isotopic ratios are some of the 

Eocene intrusive and volcanic rocks (figs. 8, 11); however, 

most of the veins are Cretaceous in age (Snee and Kunk, 

1989; Darling and others, this volume; Link and others, this 

volume; Whitman, this volume; Park, in press), which makes 

an Eocene source rock impossible. Further, Eocene rocks are 

mostly too low in 208Pb/204Pb to account for the entire range 

in Cretaceous-hosted veins. This virtually eliminates every 

conceivable source except the unexposed Precambrian basement.

The high 207Pb/204Pb of Carrietown-type lead (fig. 9) 

suggests that the Precambrian source for the intrusive-rockhosted veins contained a significant component of Archean 

as well as Proterozoic material. The absence of this Archean 

signature in Eocene intrusive rocks suggests that the veins 

and the intrusive rocks had different sources.

Carrietown-type lead in sedimentary rocks of the Middle Pennsylvanian to Lower Permian Dollarhide in the Carrietown and Westlake areas, in Paleozoic carbonate roof 

pendants within the Idaho batholith, and in Eocene granite 

host rock (table 3) strongly suggests that veins and

replacements in these sedimentary and intrusive rocks had 

the same type of source as veins in the Cretaceous intrusive 

rocks themselves. The proximity of all of these rocks to the 

Cretaceous intrusive rock terrane is consistent with a common "plumbing system" in the batholith and adjacent sedimentary rocks. This interpretation is consistent with the 

conclusions of other workers that Cretaceous intrusive 

activity, adjacent metamorphism of the Dollarhide Formation, and vein mineralization are all closely associated 

(Darling and others, this volume; Whitman, this volume; 

Park, in press). Although the Cretaceous intrusions probably provided the heat for hydrothermal circulation, the metals apparently came from the underlying basement and not 

from the intrusions themselves. For the Eocene intrusionhosted veins, the plumbing system would have had to 

develop later in the Eocene rocks but nevertheless appears 

to have tapped a similar source, one that may also have 

been enriched in Archean material. What is certain is that 

the vein lead in these sedimentary and igneous rocks did 

not come from the host rocks themselves.

Significantly, Dollarhide-hosted, bedding-conformable 

galena having Carrietown-type lead must also have had a 

source external to the host rock. Thus, the conformable sulfide in the Dollarhide Formation is simply vein filling that 

happened to be deposited parallel with bedding, and textural 

evidence is not a completely reliable guide to syngenetic 

material.

The recognition of Lava Creek-type lead suggests the 

reclassification of some samples that were classified as 

group B in earlier studies (Sanford and others, 1989; Doe and 

Sanford, this volume). The most important change is that the 

samples of galena and whole rock from the area northeast of 

Idaho City (left side of fig. 12 near lat 44°) are group A rather 

than group B. The occurrence of group B lead in the midst of 

the Idaho batholith had been puzzling; however, classifying 

this lead as group A is now consistent with the interpretation 

that Lava Creek-type lead is a low-208Pb/204Pb variety of 

group A lead that has a Precambrian source and is associated 

with Tertiary intrusive rocks (see discussion of eastern 

crustal zone below).

CENTRAL CRUSTAL ZONETRIUMPH- AND BLACK SHALE-TYPES

The narrow, arcuate black shale terrane contains four of 

the six lead-isotope types, all of which have relatively high 

206Pb/204Pb. The most widespread types in this terrane are 

Triumph- and black shale-types, which together define 

group B lead. The association of group B lead and argillitic 

sedimentary rocks is striking (table 1 and compare figs. 1 and 

12) and would appear to support the lateral-secretion theory 

whereby lead is leached from the black shale and then deposited nearby as ore (Hall and others, 1978). However, the 

difference in 207Pb/204Pb between Triumph- and black
N20 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

; Syngenetic galena, 

vein galena, and 

whole-rock samples

Triumph and 

black shale types

Whole-rock samples 

black shale type

Pb

Figure 11. Summary of lead-isotope types, central Idaho. Outlined areas indicate isotopic range of lead-isotope types described 

in text. Heavy lines are the straight boundaries that best approximate the observed boundaries and are to be used for samples 

whose association is unknown. Equations for these lines are given 

in text.

shale-types indicates that the ore was not derived exclusively 

from the sedimentary rocks but that some or all of it was 

derived from a different source, probably the underlying Precambrian basement.

Black shale-type lead probably represents the average 

isotopic composition of upper crustal rocks east and northeast of the black shale terrane. This type of lead characterizes all of the argillite of Devonian and PennsylvanianPermian age in the black shale terrane. Sedimentologic and 

paleogeographic studies suggest that this detrital material 

was eroded from highlands to the east and northeast 

(Mahoney and others, this volume; Turner and Otto, this volume). The low 207Pb/204Pb values indicate that the eroded 

crust consisted of Proterozoic rocks having no detectable 

component of Archean material.

Triumph-type lead in the syngenetic deposits probably 

consists mostly or entirely of hydrothermally derived lead 

having an Archean component. A second component of sediment-derived black shale-type lead is possible but not

required by the data. The Triumph-type lead in these deposits has significantly higher 207Pb/204Pb than the black shaletype lead in the argillite host rock (fig. 10). Although some 

of the lead in the syngenetic deposits having Triumph-type 

lead may have come from the enclosing sediments, there is 

clearly a high 207Pb/204Pb component that suggests a contribution of Archean material in the source. On the basis of 

similarity with the Triumph deposit (Turner and Otto, this 

volume), these possibly syngenetic deposits probably 

formed from "black smokers" in a submarine rift basin. Our 

data are consistent with such a model. The ore-forming 

hydrothermal fluid appears to have tapped a deep source of 

continental crustal lead having an Archean component 

while, contemporaneously, lead contained in detrital material was being eroded from a Proterozoic craton having no 

recognizable Archean component. The Triumph-type leadisotope ratios thus clearly indicate a component of hydrothermally derived lead from depth. An additional component from the black shale is consistent with the data but not 

required. A modern example of such a mixing process has 

been documented for active mid-ocean ridge hydrothermal 

vents (LeHuray and others, 1988).

Epigenetic veins hosted by the Devonian Milligen and 

Salmon River argillite were probably either part of the same 

hydrothermal system that produced the syngenetic Triumphtype deposits, and thus obtained their lead directly from the 

same underlying basement, or they formed later by remobilization of syngenetic sulfides from a Triumph-like source. 

As with the syngenetic deposits, the epigenetic veins could 

not have obtained their lead exclusively from the detrital 

argillite host rock. Comparison of all central Idaho veins 

having group B lead with syngenetic deposits and wholerock argillite shows that lead in almost all these veins isotopically resembles lead in syngenetic deposits and does not 

match lead in argillitic whole rocks (fig. 10), despite the 

close spatial association of veins and argillite.

If epigenetic veins in Devonian argillite constituted the 

feeder system for Triumph-like syngenetic deposits, this 

would explain the similar isotopic signatures. Examples of 

such epigenetic feeder veins and contemporaneous syngenetic exhalative deposits are in Alaska, Australia, Canada, 

and Ireland (Church and others, 1987). The contemporaneous formation of both bedded and crosscutting ore helps 

explain the commonly contradictory textural evidence that 

has prevented geologists from concluding definitively 

whether the deposits are syngenetic or epigenetic.

On the other hand, the presence of Tertiary-mineralized 

rock in the study area (Burton and Link, this volume) suggests that some or all veins in the Devonian argillite postdate 

the syngenetic deposits and that vein sulfide deposits represent remobilized syngenetic sulfides.

Vein deposits in the Wood River Formation probably 

reflect a remobilized Triumph-like sulfide component. 

Because they are in Pennsylvanian-Permian host rocks, 

which are not host to any syngenetic massive sulfide
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N2 1

11 

45°

44°

43°

6° 115° 114° 113°

Challis

Dominantiy Carrietown type 

in Cretaceous Idaho batholith

, %

Carrietown type / / i^\\ 

in Ella Dolostone group^ +/+ L I./J

/^^Sf,/ Pacific 

/+ / type

V / '

^ i 

x ^ XB \

V I '

\- \

\ * ^ \xx x

x \ Vxr^^

X -''il''- \* \

* \

/ \

Carrietown type Minnie Moore 

in Dollarhide Formation ^P6

Hailey

Dubois

x

x

X

Dominantiy 

Lava Creek

type

c

X

^^^- Belt of black shale

~^^~^^ and Triumph types

v x x >x

\ v \ fi \ x

\

0 20 Ml i i i i i

0 20 KM

Idaho Fails

EXPLANATION

+ Carrietown type (group A)

D Minnie Moore type (group A)

A Pacific type (group A)

X Lava Creek type (group A)

* Triumph type (group B)

 Black shale type (group B)

Figure 12. Map showing distribution of lead-isotope types for galena and other sulfide minerals, central Idaho.

deposits, they probably were not part of a feeder system for 

syngenetic deposits. As above, the Triumph-type lead in 

these veins indicates that the source was not exclusively 

argillite such as the Milligen Formation or Salmon River 

assemblage. Because of the isotopic similarity to lead in

syngenetic deposits such as the Triumph, the source for vein 

lead in the Wood River Formation may have been Triumphlike deposits, isotopically similar disseminated syngenetic 

sulfides within the argillite, or an isotopically similar source 

at depth. Although more work is needed, the most likely
N22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

interpretation at present is that veins in Devonian argillite 

that have Triumph-type lead were part of the feeder system 

for contemporaneous syngenetic deposits, whereas those in 

Pennsylvanian-Permian argillite consist of remobilized 

Devonian syngenetic sulfides. Because of the independent 

evidence for remobilization of older sulfides (Burton and 

Link, this volume), this is the most likely explanation.

The following model is consistent with the data and is 

preferred to the lateral-secretion model. Lead in the syngenetic sulfides came from Precambrian rocks at depth, was 

transported upward by hydrothermal fluids, and was deposited at submarine vents. During transport, this lead may 

have mixed with a second component of lead from detrital 

material in the host argillite, but this mixing is not required. 

Some argillite-hosted vein deposits probably formed contemporaneously with syngenetic exhalative deposits, 

whereas others probably formed by later remobilization of 

this syngenetic lead. Crosscutting veins in Devonian argillite were probably contemporaneous with syngenetic 

deposits, whereas those in Pennsylvanian-Permian argillite 

probably formed by remobilization.

Lead-isotope data can help resolve stratigraphic correlation problems. All whole-rock argillite samples in this 

study have black shale-type lead (except for two anomalously radiogenic uranium enriched samples). We therefore 

cannot use the lead isotopes in whole rocks to resolve stratigraphic problems. Lead-isotope signatures of ore deposits 

can help, however, in correlating units and, in the present 

case, confirm the assignment of the Triumph argillite to the 

Milligen Formation.

The anomalously radiogenic samples suggest a Permian-Triassic age for uranium enrichment. A least-squares 

regression line for 207Pb/204Pb-206Pb/204Pb data from 

whole-rock argillite is defined by a cluster of values having 

intermediate lead-isotope ratios and by the two most radiogenic samples (Urexco and Holman Creek), which plot off 

the diagrams to the right (table 2). Based on the model 2 

regression of York (1969), uranium enrichment in argillite 

probably occurred about 250-210 Ma; that is, Permian to 

Triassic. This age is only an estimate and should be used 

with caution. Permian and Triassic ages for uranium enrichment correspond to uranium enrichment events in the Colorado Plateau (Granger and Finch, 1988).

CENTRAL CRUSTAL ZONEMINNIE MOORE- AND PACIFIC-TYPES

Clusters of deposits having Minnie Moore-type lead and 

Pacific-type lead are at the south and north ends of the black 

shale terrane, respectively. The isotopic characteristics of 

these lead types rule out as possible sources all rocks analyzed so far within the study area because none are sufficiently radiogenic. The problem of source for this highly 

radiogenic vein lead has been discussed previously (for 

example, Doe and others, 1979).

The most likely source of the radiogenic lead is recycled upper crustal Precambrian material having an Archean 

component that had high initial 238U/204Pb (|j) and Th/U. 

Archean model ages in the range 2,700-2,300 Ma suggest 

that this time was a period of widespread crustal disturbance 

that created variations in |u. Zartman (1992) argued that variation in [i in Archean source rocks has produced some high 

values of 207Pb/204Pb. By extension, an Archean crustal 

component having even higher values of p, as well as higher 

initial Th/U, would explain the radiogenic Minnie Mooreand Pacific- types of lead. Recycling in Proterozoic time 

would further accentuate these variations. Later selective 

leaching of the radiogenic lead component might also have 

contributed to the radiogenic lead in the Pacific- and Minnie 

Moore-types. Further, the Pacific-type lead discussed here 

has some affinities with lead in some of the classic Mississippi Valley-type deposits, which these deposits resemble. 

An explanation for the source of lead in Mississippi Valleytype deposits might help explain the source of the central 

Idaho carbonate-hosted lead.

EASTERN CRUSTAL ZONELAVA CREEK TYPE

The eastern crustal zone is dominated by Lava Creektype lead in veins and replacements in flysch, shelf-carbonate, and Precambrian terranes. The most likely source for 

Lava Creek-type lead is Precambrian basement. The lead in 

Paleozoic argillite and Cretaceous intrusive rocks is too 

radiogenic for these rocks to be sources. Some Eocene 

whole rocks have lead-isotope ratios similar to those in the 

veins, and Eocene rocks could have been the source. Close 

spatial proximity of ore deposits and known Eocene intrusive rocks supports this supposition. Precambrian basement 

is the probable source for most of the lead in the western and 

central crustal zones, as discussed above, and therefore it 

could also be a source in the eastern crustal zone. Compared 

to the other crustal zones, the eastern crustal zone has the 

thinnest sedimentary cover over the basement, which makes 

a Precambrian source more likely.

Lava Creek-type lead seems to characterize Eocene-age 

veins. All of the veins in the eastern crustal zone are 

Eocene, as are many veins in the Trans-Challis fault zone 

northeast of Idaho City (Ronald G. Worl, oral commun., 

1992). All of these veins yield Lava Creek-type lead. Thus, 

the Lava Creek-type lead appears to be unique to and characteristic of Eocene veins.

The fact that Carrietown- and Lava Creek-types completely overlap when plotted on a 207Pb/204Pb-206Pb/204Pb 

diagram (fig. 9) indicates that there is no detectable difference in the age of the underlying crust in the western and 

eastern parts of central Idaho. Both sets of data are consistent with ~2,400-Ma crust that has a similar history; however, the consistently higher proportion of thorogenic lead in
SOURCES OF LEAD IN ORE DEPOSITS OF CENTRAL IDAHO N23

the Carrietown type suggests a major, long-lasting, compositional difference in the crust between these two zones.

In summary, lead isotopes reveal whether the galena in 

central Idaho ore deposits is syngenetic or epigenetic and 

indicate the type of source rock, whether Paleozoic argillaceous sedimentary rocks, remobilized syngenetic sulfides, 

Cretaceous-Eocene intrusive rocks, or a fourth, as yet unidentified, upper crustal rock type. The variety of lead-isotope types that originated in Precambrian basement suggests 

that the Precambrian basement is quite heterogeneous. 

Incorporation of data from other isotopes such as sulfur 

should help to identify better the source rocks.

REFERENCES CITED

Church, S.E., Gray, I.E., Delevaux, M.H., and LeHuray, A.P., 

1987, Pb-isotope signatures of Devonian-Mississippian massive sulfide deposits in Alaska and their significance to mineral 

exploration, in Elliott, I.L., and Smee, B.W., eds., GEOEXPO/ 

86, Exploration in the North American Cordillera: Association 

of Exploration Geochemists, Rexdale, p. 132-141.

Criss, R.E., Champion, D.E., and Mclntyre, D.H., 1985, Oxygen 

isotope, aeromagnetic, and gravity anomalies associated with 

hydrothermally altered zones in the Yankee Fork mining district, Custer County, Idaho: Economic Geology, v. 80, p. 

1277-1296.

Criss, R.E., Ekren, E.B., and Hardyman, R.F., 1984, Casto ring 

zone A 4,500-km2 fossil hydrothermal system in the Challis 

volcanic field, central Idaho: Geology, v. 12, p. 331-334.

Davis, K.E., 1978, Lead isotope ratios of galena from the Bayhorse 

mining district, Custer County, Idaho: Isochron/West, no. 22, 

p. 15-16.

Doe, B.R., 1978, The application of lead isotopes to mineral prospect evaluation of Cretaceous-Tertiary magmatothermal ore 

deposits in the western United States, in Watterson, J.R., and 

Theobald, P.K., eds., Geochemical exploration 1978: International Geochemical Exploration Symposium, 7th, Proceedings; Association of Exploration Geochemists, p. 227-232.

Doe, B.R., and Delevaux, M.H., 1985, Lead-isotope characteristics 

of ore systems in central Idaho, in Mclntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis I°x2° 

quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-O, 

p. 181.

Doe, B.R., and Rohrbough, Randall, 1977, Lead isotope data 

bank 3,458 samples and analyses cited: U.S. Geological Survey Open-File Report 77^18, 137 p.

Doe, B.R., Steven, T.A., Delevaux, M.H., Stacey, J.S., Lipman, 

P.W., and Fisher, F.S., 1979, Genesis of ore deposits in the San 

Juan volcanic field, southwestern Colorado Lead isotope evidence: Economic Geology, v. 74, p. 1-26.

Fisher, F.S., and Johnson, K.M., eds., 1987, Preliminary manuscript 

for "Mineral-resource potential and geology of the Challis 

I°x2° quadrangle, Idaho": U.S. Geological Survey Open-File 

Report 87^80, 251 p.

Godwin, C.I., and Sinclair, A.J, 1982, Average lead isotope growth 

curves for shale-hosted zinc-lead deposits, Canadian Cordillera: Economic Geology, v. 77, p. 675-690.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits derived 

from country rock source: U.S. Geological Survey Journal of 

Research, v. 6, p. 579-592.

Holmes, A., 1946, An estimate of the age of the earth: Nature, v. 

159, p. 127.

Houtermans, F.G., 1946, The isotopic ratios in natural lead and the 

age of uranium: Naturwissenschaften, v. 33, p. 185-186.

Howe, S.S., and Hall, W.E., 1985, Light-stable-isotope characteristics of ore systems in central Idaho, in Mclntyre, D.H., ed., 

Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-P, p. 183-192.

LeHuray, A.P., Church, S.E., Koski, R.A., and Bouse, R.M., 1988, 

Pb isotopes in sulfides from mid-ocean ridge hydrothermal 

sites: Geology, v. 16, p. 362-365.

Ludwig, K.R., 1990, ISOPLOT A plotting and regression program for radiogenic-isotope data, for IBM-PC compatible 

computers, version 2.11: U.S. Geological Survey Open-File 

Report 88-557, 32 p.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

1991, Pennsylvanian and Permian Sun Valley Group, Wood 

River basin, south-central Idaho, in Cooper, J.D., and Stevens, 

C.H., eds., Paleozoic paleogeography of the Western United 

States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-580.

Park, W.A., in press, The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-CC.

Rember, W.C., and Bennett, E.H., 1979, Geologic map of the Idaho 

Falls quadrangle, Idaho: Idaho Bureau of Mines and Geology, 

Geologic Map Series.

Russell, R.D., and Farquhar, R.M., 1960, Lead isotopes in geology: 

New York, Interscience, 141 p.

Sanford, R.F., Wooden, J.L., Doe, B.R., and Worl, R.G., 1989, Origin of ore deposits in the central Idaho black shale belt Implications from lead isotopes, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 39-52.

Small, W.D., 1968, Cordilleran geochronology deduced from 

hydrothermal leads: Vancouver, University of British Columbia, Ph.D. thesis, 96 p.

Snee, L.W., and Kunk, M.J., 1989, ^Ar/^Ar thermochronology of 

mineral deposits in the southern part of the Idaho batholith, in 

Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., 

eds., Geology and mineral deposits of the Hailey and western 

Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey 

Open-File Report 89-639, p. 37-38.

Wavra, C.S., 1988, Shale-hosted massive sulfide potential of the 

upper member/Permian Dollarhide Formation, south-central 

Idaho: Geological Society of America Abstracts with Programs, v. 20, p. 473^74.
N24 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Wavra C.S., and Hall, W.E., 1989, Potential for shale-hosted massive sulfides in the Permian Dollarhide Formation, south-central 

Idaho: U.S. Geological Survey Open-File Report 88-376, 9 p.

Worl, R.G., and Johnson, K.M., 1989, Geologic terranes and mineral deposit types in the Hailey and western Idaho Falls 1 °x2° 

quadrangles, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds., Geology and mineral deposits 

of the Hailey and Idaho Falls I°x2° quadrangles, Idaho: U.S. 

Geological Survey Open-File Report 89-639, p. 3-16.

York, D., 1969, Least-squares fitting of a straight line with correlated errors: Earth and Planetary Science Letters, v. 5, p. 320-324.

Zartman, R.E., 1974, Lead isotope provinces in the Cordillera of the 

western United States and their geologic significance: Economic Geology, v. 69, p. 792-805.

 1992, Archean crustal lead in the Helena embayment of the 

Belt basin, Montana, in Bartholomew, M.J., Hyndman, D.W., 

Mogk, D.W., and Mason, R., eds., Basement tectonics 

8 Characterization and comparison of Ancient and Mesozoic 

continental margins: International Conference on Basement 

Tectonics, 8th, Butte, Montana, Proceedings; Dordrecht, The 

Netherlands, Kluwer Academic Publishers, p. 699-709.
Geochemical Evidence for Epithermal Metallization 

in Mississippian Turbidites of the

McGowan Creek Formation, Lava Creek Mining District, 

South-Central Idaho

By James A. Erdman, Falma J. Moye, Betty Skipp, and Paul K. Theobald

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-O

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995

CONTENTS

Abstract................................................................................................................................. Ol

Introduction.......................................................................................................................... 1

Rationale for the Study......................................................................................................... 2

Geologic Setting................................................................................................................... 4

Mineral Deposits................................................................................................................... 5

Field Methods....................................................................................................................... 5

Reconnaissance-Scale and Followup Surveys.............................................................. 5

Sample Media and Collection....................................................................................... 5

Heavy-Mineral Concentrates................................................................................ 5

Stream Sediments and Soils ................................................................................. 7

Sagebrush.............................................................................................................. 8

Sample Preparation and Analysis......................................................................................... 8

Heavy-Mineral Concentrates........................................................................................ 8

Stream Sediments and Soils ......................................................................................... 8

Sagebrush...................................................................................................................... 8

Results and Discussion......................................................................................................... 9

Reconnaissance-Scale Survey...................................................................................... 9

Heavy-Mineral Concentrates................................................................................ 9

Sagebrush.............................................................................................................. 11

Followup Survey........................................................................................................... 11

Stream Sediments and Soils................................................................................. 12

Sagebrush.............................................................................................................. 15

Heavy-Mineral Concentrates................................................................................ 15

Conclusions.......................................................................................................................... 15

References Cited................................................................................................................... 17

FIGURES

1-5. Maps of the Lava Creek mining district showing:

1. Location of area............................................................................................................................................ O2

2. Generalized geology..................................................................................................................................... 3

3. Sample localities, reconnaissance-scale survey........................................................................................... 6

4. Sample localities, followup survey.............................................................................................................. 7

5. Distribution of selected ore minerals in heavy-mineral concentrates, reconnaissance-scale survey........... 10

6. Diagram showing factor compositions for sagebrush from reconnaissance-scale survey.................................... 12

7. Map showing location of sagebrush samples having high scores for the antimony-gold/bromine factor,

reconnaissance-scale survey.................................................................................................................................. 13

8. Photograph showing mineralized target area in the McGowan Creek Formation ................................................ 14

9, 10. Maps showing location of stream-sediment and soil samples, followup survey, containing anomalous 

amounts of:

9. Mercury........................................................................................................................................................ 16

10. Silver ................................................. 18

11. Photograph showing indicator plant Eriogonum ovalifolium in argentiferous soil near mineralized fault........... 19

12. Diagram showing factor compositions for sagebrush from followup survey....................................................... 20

13, 14. Maps showing location of big sagebrush samples, followup survey, containing anomalous amounts of:

13. Arsenic......................................................................................................................................................... 21

14. Tungsten....................................................................................................................................................... 23
CONTENTS

TABLES

1-4. Summary of selected data, Lava Creek mining district for:

1. Heavy-mineral concentrate samples from reconnaissance-scale geochemical survey........................................ O9

2. Sagebrush samples from reconnaissance-scale geochemical survey.................................................................. 9

3. Stream-sediment and soil samples from followup geochemical survey ............................................................. 12

4. Sagebrush samples from followup geochemical survey ..................................................................................... 14
Geochemical Evidence for Epithermal Metallization in

Mississippian Turbidites of the McGowan Creek Formation,

Lava Creek Mining District, South-Central Idaho

By James A. Erdman, 1 Falma J. Moye,2 Betty Skipp, 1 and Paul K. Theobald1

ABSTRACT

Geochemical and biogeochemical exploration techniques were used in the Lava Creek mining district, Butte 

County, Idaho, north of Craters of the Moon National Monument, to assess the potential for new metallic mineral 

occurrences. Heavy-mineral concentrates, stream sediments 

and soils, and big sagebrush (Artemisia tridentatd) were collected in two drainage-basin surveys: an initial reconnaissance-scale survey in 1987 and a followup survey in 1988. 

Samples of sagebrush were analyzed to investigate this species' ability to selectively remove hydromorphically bound, 

ore-related elements from the weathering environment. The 

plant results were compared with those from the more conventional sample media.

The Lava Creek district was selected because of its 

historical importance as a producer of silver and byproduct 

gold and because it is the only area of major mineralized 

rock in the southeastern Challis volcanic field. Much of this 

district is underlain by rocks of the Eocene Challis Volcanic Group that have been so hydrothermally altered that 

outcrop is limited. Thus, metal-bearing rocks are poorly 

exposed. Biogeochemical methods are especially effective 

under such conditions.

Anomalous concentrations of the element suite antimony, gold, and bromine in sagebrush collected in the 

reconnaissance-scale survey are characteristic of epithermal precious-metal deposits. These anomalies include two 

areas in the Lava Creek district where a possible host is 

Jurbidite of the Lower Mississippian McGowan Creek Formation. Exposures of this formation are peripheral to the 

formerly active mines and the new Champagne (gold) 

mine. The anomaly threshold for gold in sagebrush is 0.4

'U.S. Geological Survey, Denver Federal Center, Denver, Colorado 

80225.

Department of Geology, Idaho State University, Pocatello, Idaho 

83209.

ppb (dry-weight basis); the highest concentration, 1.0 ppb, 

was in a sample from the Champagne mine.

Followup sampling of sagebrush, stream sediments, 

and soils from these two areas led to the discovery in one of 

the areas of a north-northeast-trending, silicified fault breccia near a poorly exposed dacite porphyry intrusive body. 

This fault may be the focal point of a hydrothermal system 

that contains anomalous concentrations of silver, mercury, 

and arsenic. Gold, antimony, bromine, and tungsten anomalies are less widespread. Cinnabar was identified in several 

samples of heavy-mineral concentrates from the fault area.

Based on the results of the followup geochemical survey, we conclude that this fault breccia is a prospective target. Detailed studies should be conducted to identify the 

mineral deposit type(s) that might be present.

INTRODUCTION

The Lava Creek mining district (fig. 1), a major silver 

producer in Idaho in the 1880's, is in Butte County in the 

almost treeless foothills of the Pioneer Mountains where the 

dominant vegetation is big sagebrush (Artemisia tridentata 

Nutt.). A rock geochemical survey (Hillier and others, 1983) 

in rocks of the Eocene Challis Volcanic Group, host for the 

former and present mining, shows extremely high values for 

not only Ag, but also As, Sb, Hg, Mn, Bi, Pb, Cu, Zn, Cd, and 

some Au. Species of the genus Artemisia have been used in 

gold prospecting in arid regions of the former Soviet Union 

since the 1960's, and big sagebrush currently is being sampled extensively, especially in Nevada, in the search for disseminated, bulk-minable gold deposits.

The arid environment supports a vegetation type characterized by sagebrush but commonly containing less conspicuous shrubs such as antelope bitterbrush (Purshia 

tridentata [Pursh] DC.) and rabbitbrush (Chrysothamnus 

sp.). Small stands of mainly Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) commonly dominate slopes at higher 

elevations, primarily north exposures. Some of the smaller

Ol
02 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

113°30'

43°30' -

Approximate area of the 

Lava Creek District

CRATERS OF THE MOON 

NATIONAL MONUMENT

Figure 1. Index map showing area of the Lava Creek mining 

district, central Idaho. The center of the Lava Creek mining district 

is about 14 mi (22 km) southwest of Arco, Idaho. The elevation 

ranges from about 5,600 ft (1,700 m) at the mouth of Lava Creek in 

the southern part of the district to 8,356 ft (2,550 m) at Timbered 

Dome, the predominant geographic feature in the study area.

Qal

Qb

Th

EXPLANATION

Alluvium, gravel, and other unconsolidated sediments 

(Quaternary)

Basalt (Quaternary) 

Jasperoid (Tertiary) 

Volcanics at Heise (Tertiary)

Extrusive rocks (Tertiary) Including the Challis Volcanic 

Group (Eocene)

Intrusive rocks (Tertiary) Including subvolcanic rocks of the 

Challis Volcanic Group (Eocene) and prophyritic rocks not 

know to be Challis

Primarily carbonate rocks Including the Snaky Canyon 

Formation (Lower Permian to Upper Mississippian), Bluebird 

Mountain Formation (Upper Mississippian), Lower 

Mississippian rocks in the Beaverhead Mountains, Lemhi 

County, and Arco Hills Formation (Upper Mississippian)

Carbonate units Including the Surrett Canyon (Upper 

Mississippian), South Creek (Upper Mississippian), Scott 

Peak (Upper Mississippian), and Middle Canyon (Upper and 

Lower Mississippian) Formations

Copper Basin Formation (Upper and Lower Mississippian) 

McGowan Creek Formation (Lower Mississippian)

Undifferentiated rocks Including the Carey Dolomite (Middle 

and Lower Devonian:), Fish Haven Dolomite (?)(Upper 

Ordovician), Kinnikinic Quartzite (?)(Middle Ordovician), and 

Summerhouse Formation (Lower Ordovician). The latter 

three units may all be Summerhouse Formation

Contact Dashed where uncertain 

Fault Dashed where uncertain

valleys harbor stands of alder (Alnus sp.), aspen (Populus 

tremuloides Michx.), and poplar (Populus sp.) along the 

banks of perennial streams. The abundance of perennial 

grasses makes the district good pasturage for cattle and 

sheep (Anderson, 1929).

The dominance of sagebrush in the district and the poor 

outcrop prompted us to use biogeochemistry as a tool, along 

with conventional heavy-mineral concentrates, to assess the 

precious-metal potential of the area. The biogeochemical 

method uses the element concentrations of plants to outline 

secondary dispersion halos in soils and overburden (Boyle, 

1984, p. 10). Sampling of stream sediments and, to a limited 

extent, soils was included in the followup survey.

This paper describes the geochemical results from a 

reconnaissance-scale drainage-basin survey of the district 

conducted in 1987 and a detailed followup survey in 1988 of 

two selected areas underlain by Mississippian sedimentary 

rocks. To our knowledge, this is the first study in the Western 

United States to describe the use of sagebrush in a drainagebasin type of geochemical survey. Erdman designed the

study and conducted the geochemical surveys. Skipp 

mapped the geology, and Moye assessed the mineral potential using the geological and structural information. 

Theobald identified the heavy minerals.

RATIONALE FOR THE STUDY

The Lava Creek mining district is considered one of the 

most promising areas in the Hailey I°x2° quadrangle and the 

western part of the Idaho Falls I°x2° quadrangle for the 

occurrence of disseminated gold, based in large measure on 

the rock geochemical study by Hillier and others (1983). 

Other lines of evidence support this conclusion. Jasperoid 

(fig. 2), "a distinctive alteration type formed by intense silicification of marine sediments" (Nelson, 1990), is present as 

extensive outcrops in parts of the district. These outcrops 

were studied recently by Wilson and others (1988) and Soulliere and others (1988). The marine sedimentary rocks, turbidites of the Lower Mississippian McGowan Creek
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES O3

113°37'30" 113°30'

43°37'30" =

43° 30'

R 23 E R 24 E R24E R25E 

4 KILOMETERS

2 MILES

Figure 2 (above and facing column). Map showing generalized geology of the Lava Creek district, central Idaho. Mines in rocks of the 

Eocene Challis Volcanic Group are shown. Modified from Soulliere and others (1988). Base from U.S. Geological Survey Arco (scale 

1:100,000) quadrangle (1988).
O4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Formation, are one of the major sedimentary units exposed in 

the area and underlie much of the Eocene Challis Volcanic 

Group, which dominates the district. Carbonate facies of the 

McGowan Creek might have been physically reactive with 

hydrothermal fluids and, therefore, are potentially ideal sites 

for precipitation of metals. Recent papers on gold deposits in 

turbidite or black shale sequences (Boyle, 1986; Korobeynikov, 1986) are especially relevant to this study.

Acknowledgments. This study was supported in part 

by a grant to Falma Moye from the Idaho State Board of 

Education. The plant samples were sent to the laboratory of 

Minerals Exploration and Environmental Geochemistry, 

Reno, Nevada, for preparation, and were analyzed by US 

Mineral Laboratories, Inc. (formerly Geochemical Services, 

Inc.), North Highlands, California, and Nuclear Activation 

Services, Ltd., Ann Arbor, Michigan. The heavy-mineral 

concentrates, stream sediments, and soils were analyzed in 

the laboratories of U.S. Geological Survey, Denver, Colorado; analysts: John Bullock (emission spectrography of 

sediments and soils), Betty Adrian and Mollie Malcolm 

(emission spectrography of heavy-mineral concentrates), 

Karen Slaughter (inductively coupled plasma analysis of 

sediments and soils), Phil Hageman (mercury analysis of 

stream sediments and soils by cold-vapor atomic absorption 

spectroscopy), and Rich O'Leary (gold analysis of sediments and soils by flameless atomic absorption spectroscopy). We thank Idaho Gold Corp. (Arco, Idaho), a 

subsidiary of Bema Gold, Inc. (Vancouver, Canada), for 

permission to sample at the Champagne mine.

GEOLOGIC SETTING

The geology of the Lava Creek mining district (Skipp 

and others, 1990) consists of Paleozoic sedimentary rocks 

overlain by rocks of the Eocene Challis Volcanic Group and 

intruded by cogenetic Eocene dikes, plutons and domes. 

Locally, these units are capped by Miocene basalt and rhyolite that are related to volcanism of the Snake River Plain.

Paleozoic strata in the area that range in age from 

Ordovician through Pennsylvanian are allochthonous and 

make up part of the Grouse thrust plate (Skipp, 1987; Link 

and others, 1988). Mississippian rocks include the McGowan 

Creek Formation at the base overlain by the Middle Canyon, 

Scott Peak, South Creek, Surrett Canyon, and Bluebird 

Mountain Formations. The Lower Mississippian McGowan 

Creek Formation is part of a westward-thickening wedge of 

flysch sediments deposited on the east side of the Antler foreland basin. It is about 2,000 ft (610 m) thick and is divided 

into three parts on the eastern flank of Timbered Dome 

(Skipp and others, 1990). The lower 350 ft (107 m) consists 

of interbedded siltstone, sandstone, and granite- to pebbleconglomerate; the middle 1,300 ft (396 m) consists of mudstone, siltstone, very fine grained sandstone, and minor limestone; and the uppermost 370 ft (113 m) consists mostly of

gray laminated mudstone. West of the Champagne Creek 

thrust fault, however, the middle and upper parts of the 

McGowan Creek Formation contain minor gravel- to pebbleconglomerate and siltstone. The overlying Middle Canyon 

Formation, 508 ft (155 m) thick, comprises thin- to mediumbedded silty spiculitic limestone deposited in a foredeep in 

front of a prograding Late Mississippian carbonate bank. The 

remainder of the Mississippian formations are chiefly thick 

bedded, variably cherty, pure fossiliferous limestone of the 

Late Mississippian carbonate bank.

The Eocene Challis Volcanic Group is the main rock 

unit in the area and rests unconformably on the Paleozoic 

strata. The Challis Volcanic Group in the Lava Creek area 

includes a great variety of rock compositions. Radiometric 

ages (K/Ar and 40Ar/39Ar) define a time span for the unit 

from 49 to 44 Ma (Moye, unpublished data); however, field 

relations suggest that the most voluminous activity was 

between 49 and 47 Ma. The basal Challis unit comprises a 

pre-volcanic conglomerate that grades from an orthoconglomerate lacking volcanic debris to a tuffaceous paraconglomerate that signifies the onset of volcanism. The earliest 

volcanism recorded in the area is dominantly andesite lava 

and tuff breccia. These rocks are 0-1,148 ft (350 m) thick and 

fill local paleotopography. They comprise a great number of 

individual flows that erupted from scattered vents throughout 

the region. Flows are generally porphyritic and contain plagioclase, pyroxene, and hornblende phenocrysts. This dominantly andesite volcanism was followed by a period of 

voluminous intermediate volcanism, including dacite to 

quartz latite lava flow rocks and ash-flow tuff and interbedded tuffaceous sedimentary rocks. The intermediate volcanic 

rocks are as much as 2,625 ft (800 m) thick, and a number of 

individual flow units were erupted from different sources. 

Dacite lava flow rocks are strongly porphyritic and contain as 

much as 40 percent phenocrysts of plagioclase, biotite, hornblende, and pyroxene in varied proportions. The flows generally are of small aerial extent and most likely were ponded in 

paleotopographic depressions. Dacite ash-flow tuff is poorly 

to densely welded, crystal-lithic tuff, and lithic content and 

size vary with distance from source. Sources for older dacite 

ash-flow tuff have been recognized to the north of the Lava 

Creek district near Lehman Basin. The final pulse of magmatic activity was small-volume explosive silicic activity 

and emplacement of rhyolite and dacite domes, dikes, and 

shallow granitic intrusions.

Evidence for both Mesozoic and Cenozoic tectonism is 

present in the structurally complex Lava Creek district. Paleozoic strata were thrust faulted and folded during middle to 

late Mesozoic compressional tectonism. Early Tertiary structures characteristically are northeast- and north-northwesttrending high-angle faults that show evidence of pre- and 

post-volcanic displacement. North-northeast-trending faults 

parallel with the margins of the Snake River Plain have only 

post-Eocene displacement.
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES

MINERAL DEPOSITS FIELD METHODS

O5

Historically, the Lava Creek district is primarily known 

for its silver deposits because during the main period of 

activity in the late 1 800' s most of the ore recovered was from 

oxidized bonanza silver ore. Recently, however, the new 

Champagne mine is an oxidized low-grade gold mine (The 

Mining Record, 1989).

Anderson (1929, 1947) provided the most detailed 

descriptions of ore deposits in the Lava Creek district. Ore 

deposits in the district are associated with the youngest 

silicic intrusive phase of the Challis Volcanic Group and are 

typically breccia or fissure deposits. The breccia deposits are 

generally considered to be hydrothermal explosion breccias 

that are localized along north-northwest-trending structures 

or at the intersection of northeast- and northwest-trending 

structures. Breccia zones show evidence of multiple periods 

of brecciation and silicification. Open-space textures are 

present but not common. Deposits are primarily in rocks of 

the Challis Volcanic Group or in cogenetic intrusive rocks, 

although there are some fissure deposits in limestone. In 

highly silicified hydrothermal breccia zones, original rock 

textures are partly to completely replaced by silica. Locally, 

tuffaceous sedimentary beds in the Challis Volcanic Group 

are pyritized and silicified but are not considered ore grade.

Ore of the Lava Creek mining district shows much mineralogical variation but can generally be classified as epithermal precious-metal deposits. These deposits also contain 

lead and zinc, as well as bismuth, tungsten, and antimony 

(Anderson, 1929). Silver was recovered from argentiferous 

galena, aikinite (a comparatively rare copper-lead-bismuth 

sulfide mineral that locally has high silver values), or surficial oxidized ore.

One of the most striking features about the Lava Creek 

district is the widespread hydrothermal alteration (Skipp, 

1988; Skipp and others, 1990). Sericitization is the predominant alteration type; near vein margins rock textures are 

completely obliterated by sericite and quartz, and farther 

from veins more selective replacement of feldspar has 

occurred. In the Champagne Creek area, mineralized zones 

are characterized by complete silicification to chalcedonic 

quartz and by intense clay alteration to halloysite forming a 

dense white chertlike rock (Anderson, 1929).

Anderson (1929) suggested that deposits in the southwestern part of the district, in the Lava Creek area, formed at 

higher temperature than those in the Champagne Creek area. 

This is consistent with his observations, and our own, that the 

deposits to the southwest are associated with deeper granitic 

intrusive rocks and those in the Champagne Creek area are 

associated with shallow epizonal intrusions where hydrothermal systems may have vented to the surface as hot springs.

RECONNAISSANCE-SCALE AND 

FOLLOWUP SURVEYS

A reconnaissance-scale survey of the district was conducted July 8-17, 1987, using the U.S. Geological Survey 

Grouse l:62,500-scale topographic quadrangle as a base 

map. Two types of samples heavy-mineral concentrates 

from stream sediments and current growth of big sagebrush were collected at the mouths of 30 drainage basins of 

mostly first- and second-order streams (fig. 3). These sample 

localities were chosen to reflect areas of mineralized rock in 

the Lava Creek and Champagne Creek watersheds and to 

assess the possibility of mineralized rock in adjoining areas. 

The Timbered Dome area was included because of extensive 

outcrops of jasperoid. The sample localities include most of 

the critical parts of the district, except for the far western 

edge. Inclement weather forced an end to the field effort, and 

access to private holdings in the southwest part of the district 

was denied by the owner.

Based on the interpretation of analytical results from 

the reconnaissance survey, two areas were selected for a 

more detailed study May 19-25, 1988: Hammond Spring 

Creek on the east and Sawmill Canyon to the west (fig. 4). 

Samples of stream sediments (or, much less commonly, 

soils) and sagebrush were collected from 62 localities in 

these two areas, using advance sheets of the U.S. Geological 

Survey Mackay 4 Southeast and Southwest l:24,000-scale 

topographic maps. Soil and sagebrush samples were also 

collected near four drillholes in exposed or thinly covered 

oxidized ore that is hosted by Challis Volcanic Group at the 

new Champagne mine (The Mining Record, 1989). Heavymineral concentrates were collected from three localities.

Analytical results for the area around Hammond Spring 

Creek were clearly more promising than those for Sawmill 

Canyon, and therefore we report only the former here.

SAMPLE MEDIA AND COLLECTION 

HEAVY-MINERAL CONCENTRATES

The nonmagnetic fraction of a heavy-mineral concentrate sample is useful in detecting mineralized areas 

because primary and secondary ore minerals are commonly 

in this fraction. This is particularly true for uncommon minerals such as gold and cinnabar (mercury sulfide). The concentration of ore and ore-related minerals in these samples 

facilitates determination of elements that are not easily 

detected in bulk stream-sediment samples. The contrast in 

metal content between geochemical anomalies and normal 

background is greatly expanded such that anomalies which 

are fairly subtle in stream sediments may be strong and 

easily recognized.
06 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

113°35'

43°35'

T3N

T2N

T4N

R23E

1 2 KILOMETERS

____I

1MILE
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES O7

43° 

35'

113°35'

H^'f ^ iV«l

* . OV*""

iS|^*4Z»43r ' 1"

v4J$?' ?^\"W : '^.^:

/'.//,//' '-^v/i'$>a«=-'-; iix, X. JA»" ''' 'p r ^~ ..^V'-'^'r' Charnpagi -^^ f«^!-^- '' -1'- '>^; - '*-^>;':\ f->^'f' V' ^ '.' J '- ci-:> ' lx^f.'S?g!1^-'

eg- : ip9^^r'7^'y:> '|!^ ^^i^^S^f/^f' ,.^- r . ^ "-'v_Ji>-

; ?-' ,48 £- -«"^-"^* -: VT ^\ -^r^-x; 'A7*

^3'i,'"' ^- ~-~

 5-i *'31 ? -^ ' 

Od...^! co

R 23 E R 24 E

2 KILOMETERS

1 MILE

Figure 4. Map showing sample localities, followup geochemical survey, Lava Creek mining district, central Idaho. Base from U.S. 

Geological Survey Grouse (scale 1:62,500) quadrangle.

Heavy-mineral concentrates were separated from 

stream-sediment samples collected from sites favorable for 

the accumulation of heavy minerals in the active channels. 

The concentrate samples represent weathered surface-rock 

material mechanically transported to the sample locality. 

Each sample consisted of two 6- by 10-in. cloth bags filled 

with the sediments that passed a 10-mesh screen (2-mm 

opening). The < 10-mesh fraction of the bulk sediment 

samples was panned in the field until most of the quartz, feldspar, clay, and organic matter was removed. This panned 

concentrate was then placed in paper bags for further processing in the laboratory.

Figure 3 (facing page). Map showing sample localities, reconnaissance-scale geochemical survey, Lava Creek mining district, 

central Idaho. Base from U.S. Geological Survey Grouse (scale 

1:62,500), Inferno Cone (scale 1:24,000), and Blizzard Mountain 

South (scale 1:24,000) quadrangles.

STREAM SEDIMENTS AND SOILS

Stream-sediment samples represent the rock material 

eroded from the drainage basin upstream from each locality. 

Such information is useful in identifying those basins that 

contain concentrations of elements that may be related to 

mineral deposits. The stream-sediment samples consist of 

active alluvium collected, with few exceptions, from the 

bases of small ephemeral drainages.

In the followup survey, 54 stream-sediment samples 

and 2 soil samples were collected from 56 of the 62 localities 

shown on figure 4. Four additional soil samples were collected from the Champagne mine. Of the six localities where 

stream sediments were not collected, five (localities 1, 22, 

58, 61, and 62) are springs and the sixth (locality 27) is the 

dump at a prospect pit. The sediment and soil samples were 

sieved to <10 mesh and placed in small HUBCO bags for 

further processing and analysis.
O8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

SAGEBRUSH

Plant samples provide information on soluble metals 

that are transported, under the conditions of this study, down 

the drainage basin and that are available at depth, although 

the roots of sagebrush are not known to extend downward 

more than several meters (Weaver and Clements, 1938, p. 

320). Sturges (1977) reported that big sagebrush has both a 

fibrous root system that can feed near the surface and a taproot that can draw moisture and nutrients from deep in the 

soil profile. Quantitative data on the depth and lateral spread 

of the root systems of big sagebrush are given in Tabler 

(1964), Sturges (1977), and Sturges and Trlica (1978).

Despite the relatively shallow rooting depths of sagebrush, Kovalevskii (1979) reported that Artemisia responds 

to geochemical features at depths of 40-60 m. He stated that 

plants may respond to orebodies 100 m or more below the 

surface where the roots tap hydrogeochemical haloes.

In the reconnaissance survey, each of the 30 big sagebrush samples was a composite of new growth (stems and 

leaves combined) from several shrubs that grew at the edge 

of the active channel of small streams or in the dry washes; 

sagebrush is usually not present in the channel proper 

where the flow is fairly constant. The samples were composites of clippings from several shrubs within about 5 m 

of one another; each sample of about 50 g was placed in a 

small cloth bag.

For the followup survey, leaves were stripped from the 

new growth and, to some extent, the previous year's growth. 

Sagebrush samples were collected from 58 of the 62 localities shown in figure 4, and four additional samples were collected from localities at the Champagne mine. No sagebrush 

grew at four of the sample localities (34, 35, 39, and 40), in 

the upper reaches of Sawmill Canyon.

SAMPLE PREPARATION AND 

ANALYSIS

HEAVY-MINERAL CONCENTRATES

The panned concentrates were air dried and sieved to 

less than 0.425 mm (<35 mesh); the light minerals remaining 

in the <35-mesh fraction were removed by heavy-liquid flotation (bromoform, specific gravity 2.85). The heavy-mineral concentrate samples were then separated into magnetic, 

weakly (para-) magnetic, and nonmagnetic fractions by placing the sample in contact with the face of a large electromagnet (in this case a modified Frantz Isodynamic Separator). 

The most magnetic material (removed at a setting of 0.25 

ampere), primarily magnetite, was not analyzed. The second 

fraction (removed at a setting of 1.75 ampere), mostly ferromagnesian silicate minerals and iron and manganese oxide 

minerals, was archived; this paramagnetic fraction may

contain limonite and manganese oxide minerals, which may 

contain high trace-metal values related to mineral deposits. 

The third fraction (the nonmagnetic material, which may 

include the nonmagnetic ore minerals zircon, sphene, and so 

on) was split using a Jones splitter.

One split of the nonmagnetic fraction was ground and 

chemically analyzed for 35 elements by direct-current arc 

emission spectrography (Grimes and Marranzino, 1968). 

The second split was used for mineralogical studies of individual grains with a conventional binocular microscope at 

low magnification (10 x-30 x).

STREAM SEDIMENTS AND SOILS

The stream-sediment and soil samples were air dried, 

then sieved using a 35-mesh stainless-steel sieve. The part of 

sample passing through the sieve was saved for analysis. 

Gold was determined by flameless atomic absorption spectroscopy using a graphite furnace (O'Leary and Meier, 

1986). Antimony, arsenic, bismuth, cadmium, and zinc were 

determined by inductively coupled argon plasma-atomic 

emission spectroscopy after a hydrochloric acid-hydrogen 

peroxide digestion (Crock and others, 1987). Mercury was 

determined by continuous-flow, cold-vapor atomic absorption spectroscopy (Crock and others, 1987). A 35-element 

suite was determined by direct-current arc emission spectrography (Grimes and Marranzino, 1968).

SAGEBRUSH

The sagebrush samples were sent to Minerals Exploration and Environmental Geochemistry, Reno, Nevada, for 

preparation before analysis. After washing, they were air 

dried for a day with a finish drying by microwave for 15 minutes. The dried samples were then macerated and homogenized through a 2-mm sieve in a Wiley mill.

Splits of the 30 reconnaissance samples were further 

processed as follows. A 30-gram split of dry plant material 

was ashed at 480°C for 36 hours, and the remaining ash was 

sent to Geochemical Services Inc. (GSi), Rocklin, California, for analysis. At the GSi labs, the ash was digested in a 

strong oxidizing acid mixture, heated to 80°C, and cooled. 

Metals were extracted from the ash into an organic solution 

and the solution analyzed by inductively coupled plasma 

emission spectroscopy for 13 trace elements and by graphite 

furnace atomic absorption for ultra-trace-amounts of gold. 

The suite of elements used from the GSi results include Ag, 

Cd, Cu, Ga, Mo, and Pb. An 8-gram split of dry material was 

pelletized to a 40-mm-diameter wafer for analysis of 17 elements, including mercury, by direct instrumental neutron 

activation analysis by Nuclear Activation Services, Ann 

Arbor, Michigan. The suite of elements from the neutron
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES O9

activation analysis includes As, Au, Ba, Br, Co, Cr, Fe, Hg, 

Sb, U, W, and Zn.

The 62 sagebrush samples from the followup survey 

were prepared by Minerals Exploration and Environmental 

Geochemistry and the pelletized wafers sent to Nuclear 

Activation Services for analysis by direct instrumental neutron activation analysis. Analytical splits of six of the samples were submitted as a check on laboratory analytical 

precision, which was satisfactory except for antimony. The 

accuracy of the activation analysis method was checked by 

several internal plant standards that Minerals Exploration 

Geochemistry included in the sample suite; correspondence 

of the concentrations determined in these standards with 

established values was excellent.

RESULTS AND DISCUSSION

Geochemical anomalies were delineated using several 

criteria: published norms, frequency distributions in histograms, cumulative probability plots, and multivariate Rmode factor analysis (sagebrush only).

All of the analytical results are given in Adrian and 

others (1990).

RECONNAISSANCE-SCALE SURVEY 

HEAVY-MINERAL CONCENTRATES

The heavy-mineral concentrates include a variety of 

accessory minerals from the country rocks and a few ore minerals. Three minerals barite, apatite, and zircon constitute

Table 1. Summary of selected data for 30 heavy-mineral 

concentrate samples from the reconnaissance-scale geochemical 

survey, Lava Creek mining district, Idaho. 

[In parts per million except where noted. All elements by emission 

spectrography; see text for details. Ratio is the number of samples in 

which the element was detected to number of samples analyzed]

Element

Fe (percent)

Ag

As

Au

B

Ba

Bi

Cu

Pb

Sb

Sn

W

Zn

Minimum

<0.1

<1

<500

<20

<20

1,500

<20

<10

<20

<200

<20

<50

<500

Maximum

7

500

>20,000

150

200

>10,000

150

2,000

10,000

300

>1,000

100

>20,000

Median

0.5

<1

<500

<20

20

>10,000

<20

<10

30

<200

<20

<50

<500

Ratio

29:30

6:30

1:30

2:30

24:30

30:30

2:30

14:30

27:30

2:30

10:30

1:30

2:30

the greater part of the concentrates, either singly or in combination. Most of the barite-rich samples are from drainage 

basins underlain by the Chain's Volcanic Group and presumably reflect barite-bearing veins that cut these rocks. Apatite, 

with or without barite or zircon, is the most abundant mineral 

throughout the area. Zircon, although invariably present in 

the concentrates, is most abundant in the northern part of the 

area, around and to the north of Champagne Creek. Corundum is fairly common in concentrates from the northern part 

of the district. It has a mottled or zoned blue color and is in 

flat hexagonal plates in most of the samples. In samples from 

some of the northern localities it is more blocky, favoring a 

dipyramidal form, and has a purple tint that resembles fluorite, which was not identified in any of the samples.

Pyrite is present in most concentrate samples, even those 

from drainages underlain by Paleozoic sedimentary rocks in 

the Timbered Dome area. No pyrite was identified in the sample from locality 25 at Sawmill Canyon or in samples from 

localities 11 and 12 in the Hammond Spring Creek drainage 

where the sagebrush samples were anomalous (fig. 5).

Ore minerals in the concentrate samples include cinnabar, sphalerite, cuprite, arsenopyrite, cerussite, lead, and 

native gold. Cinnabar, gold, cuprite, and, in some places, 

arsenopyrite are present in samples from a tight cluster of 

localities around Lava Creek (fig. 5). Sphalerite, cerussite, 

and galena in concentrates close to Champagne Creek

Table 2. Summary of data for 30 sagebrush samples from the 

reconnaissance-scale geochemical survey, Lava Creek mining 

district, Idaho

[In parts per million unless otherwise noted. Concentrations on a dryweight basis; see text for details. Ratio is the number of samples in 

which the element was detected to number of samples analyzed]

Element Minimum Maximum Median Ratio

Neutron activation analysis

As

Au (ppb) 

Ba

Br

Co

Cr

Fe (percent) 

Hg (ppb) 

Sb

Se

U

W

Zn

<0.01

<0.2 

<20

1.2

<0.3

<0.3

0.006 

<50 

0.04

<0.5

<0.02

<~0.04

23

0.13

1.0 

50

17

0.6

1.0

0.023 

60 

0.36

1.8

0.05

0.10

65

0.04

0.3 

20

3.7

<0.3

<0.3

0.011 

<50 

0.06

<0.5

<0.02

<~0.04

30

29:30

20:30 

14:30

30:30

12:30

15:30

30:30 

2:30 

30:30

3:30

10:30

6:30

30:30

Inductively coupled plasma emission spectrometry

Ag (ppb) 

Cd (ppb) 

Cu

Ga (ppb) 

Mo (ppb) 

Pb (ppb)

1.1 

19

3.3

<28 

64 

140

31 

300 

21

48 

66< 

2,400

4.5 

45 

11

<28 

240 

210

30:30 

30:30 

30:30

5:30 

30:30 

30:30
O10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

113°35'

43°35

f" -"" - X-**as* ..»«{«'*: ^g:

^ ..J /-,,>. \ r..ij-*1 ;-^ .,w .» i

T4N

1MILE
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES Oil

presumably reflect contamination from the mining activity 

in that area. Cinnabar and gold are peripheral to the area of 

mining at Champagne Creek and extend northward along 

the east side of Dry Fork Creek.

A single grain of weilerite was identified in the concentrate from locality 12 (fig. 5). Weilerite is a barium aluminum 

arsenate that can form in a hydrothermal environment (Botinelly, 1976). Although its singular presence is scant evidence for such an environment, it supports other more 

convincing data described below. Interestingly, no barite was 

identified in the concentrate sample containing weilerite.

The minerals incorporated in the heavy-mineral concentrates must be derived from surface material. Thus, the 

ore minerals in the concentrates neatly define the areas of 

exposed mineralization, mainly in rocks of the Challis Volcanic Group. Except for cinnabar at localities 14 and 21 in 

the Mississippian sedimentary rocks (fig. 5), these concentrates correlate with known mines and prospects.

The distribution of concentrates that have anomalous 

element concentrations generally mirrors the distribution of 

the ore-related minerals described above. Further discussion 

of the results therefore is unwarranted; however, data for 

selected elements are summarized in table 1.

SAGEBRUSH

Analytical data for the 30 sagebrush samples are summarized in table 2. Because of excessive censoring (>50 

percent), gallium, mercury, selenium, uranium, and tungsten are not included in the multivariate interpretation 

described following. Cobalt and chromium are not 

included, both because of censoring and because of their 

limited importance.

The gold concentrations, dry-weight basis, of sagebrush range from less than 0.2 to 1.0 ppb, and the median is 

0.3 ppb. We tested the possibility that the skewed distribution represents two populations by using a statistic proposed by Miesch (1981). The statistic is a standardized gap, 

which, if significant, can be taken as the separation 

between two geochemical populations. The results indicate 

a significant gap at 0.35 ppb (confidence level, -90 percent); 10 of the 30 samples contain gold at anomalous levels of 0.4 ppb or greater.

A varimax solution of R-mode factor analysis, widely 

used in exploration geochemistry, reduced a log-transformed 

data base of 11 elements to help define interrelated element 

assemblages. (The censored data were first replaced with 

values 0.7 of the lower limits of determination because the

Figure 5 (facing page). Map showing distribution of selected ore 

minerals in heavy-mineral concentrates, reconnaissance-scale 

geochemical survey, Lava Creek mining district, central Idaho.

procedure will not accept qualified data. This modified data 

set was then transformed to a log base 10 because of the tendency of geochemical data to be positively skewed.) Molybdenum was eliminated from the data set because it 

constituted a single-element factor when a five-factor solution was selected. A four-factor model proved to be the most 

interpretable. Correlations between the factor scores and the 

concentrations of each dominant element (correlation coefficients >0.3) for each factor are given in figure 6. Approximately 70 percent of the standardized data are accounted for 

in this four-factor model.

We consider factor three, in the third column, most 

important because the key elements antimony, gold, and, to 

a lesser extent, bromine reflect an epithermal precious-metal 

suite. Colin Dunn (Geological Survey of Canada, oral commun., 1990) has also found a weak positive correlation 

between bromine and gold in his biogeochemical studies in 

the boreal forests of Canada. In his work in northern 

Saskatchewan, for example, he noted "that Br levels in ashed 

alder twigs are commonly elevated near gold mineralization" (Dunn and Hoffman, 1986, p. 378). This association of 

bromine and gold in plant tissue is probably widespread. 

Leslie Thompson (Gold Fields Mining Corp., Denver, oral 

commun., April 1990) found that bromine is associated with 

gold, arsenic, and antimony in samples of mesquite (Prosopis sp.) and creosote-bush (Larrea tridentata [DC.] Coville) 

from the deserts of southern California.

Factor scores represent a measure of the effect of a 

factor on each sample. The locations of those sagebrush 

samples having higher scores for the antimony-gold-bromine factor (fig. 7) point not only to the Lava Creek and 

Champagne Creek subdistricts, especially where cinnabar 

is present in the concentrates, but also to Sawmill Canyon 

and Hammond Spring Creek in terrain characterized by turbidite of the McGowan Creek Formation (Erdman and others, 1988). Sagebrush samples from these latter two areas 

contained the only detectable mercury and selenium, but 

cinnabar was identified in the associated concentrates only 

at locality 14.

Although chemical anomalies were identified in concentrates from drainage basins in and adjacent to mines in 

rocks of the Challis Volcanic Group of the Lava Creek district, none were associated with anomalies in sagebrush 

that grew in sediments derived from the McGowan Creek 

Formation. The source of the Sawmill Canyon and Hammond Spring Creek biogeochemical anomalies appeared 

to be hidden.

FOLLOWUP SURVEY

Results from the 10 localities sampled in Sawmill Canyon (fig. 4) indicate no prospective target, whereas results 

from the Hammond Spring Creek area, which is almost 

entirely underlain by the McGowan Creek Formation, led us
012 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

1.0

0.9

IZ 0.8

LLJ

O

LL

§0.7

o

z

0

P 0.6

LLJ

§0.5

o

0.4

0.3

Factor

1

Cd

Ag

_

Cu

-

Zn

Pb

2

As

Fe

Pb

Ag

3

Sb

Au

Br

4

Ba

Zn

28.8 16.9 14.3 10.8 

PERCENT VARIANCE ACCOUNTED FOR BY EACH FACTOR

Figure 6. Factor compositions for sagebrush from reconnaissance-scale survey, Lava Creek mining district, central Idaho. Elements are arranged in descending order of correlation 

coefficient, which indicates importance of element.

Table 3. Summary of selected data for 60 stream-sediment and 

soil samples from the followup geochemical survey, Lava Creek 

mining district, Idaho

[All values in parts per million except where noted; see text for details. 

Ratio is the number of samples in which the element was detected to 

number of samples analyzed]

Element Minimum Maximum Median Ratio

Graphite-furnace atomic absorption spectrometry

Au (ppb) <2 70 <2 8:60

Emission spectrography

Ag 

B 

Pb 

V

<0.5 

<10 

<10 

70

5 

300 

150 

700

<0.5 

50 

10 

150

23:60 

59:60 

51:60 

60:60

Inductively coupled plasma spectrometry

As 

Bi 

Cd 

Sb 

Zn

<5 

<2 

0.1 

<2 

21

48 

6 

3.1 

9 

490

20 

<2 

0.7 

2 

94

57:60 

2:60 

60:60 

32:60 

60:60

Cold- vapor atomic absorption spectrometry

Hg <0.02 1.2 0.08 56:60

to a prospective target at the head of a small unnamed tributary (Erdman and others, 1989). For this reason, we report 

only the latter results here.

From casual observation, this unnamed tributary (fig. 8) 

lacks any clear evidence of mineralized rocks; however, a 

well-exposed fault breccia is present at the very head of the 

tributary valley. Slickensides were seen on float at several of 

the sample localities near the head of the tributary. A small, 

propylitically altered dacite porphyry intrusive body is near 

the north-northeast-trending fault breccia. The altered dacite 

porphyry and explosive hydrothermal breccia may constitute 

the upper part of a breccia pipe. The geochemical results for 

both sediments and sagebrush, and the occurrence of cinnabar in concentrates, may indicate leakage of hydrothermal 

solutions from depth.

STREAM SEDIMENTS AND SOILS

Data for selected elements from the 60 sediment and 

soil samples are summarized in table 3. Few of the samples 

contain detectable gold; of the eight samples in which gold 

was detected, the three highest concentrations, 10, 40, and 

70 ppb, are in samples from the Champagne mine. The five 

remaining samples contain only 2 ppb gold and are from 

widely scattered localities. Bismuth concentrations also are 

above the detection limit only in soils from the Champagne 

mine; the two samples in which it was detected (4 and 6 

ppm) are from the mine. Lead concentrations are also

anomalous only in soils from the mine; three of the four 

samples from the mine contain from 70 to 150 ppm Pb, as 

compared to samples elsewhere that contain from less than 

10 to 30 ppm Pb.

Soils associated with oxidized gold ore at the Champagne mine are characterized by a unique gold-bismuth-lead 

suite; sediments derived from the turbidite are characterized 

by a unique suite of boron, cadmium, vanadium, and zinc. 

Boron concentrations of 100-300 ppm are associated with 

mineralized rock in the McGowan Creek Formation, as compared to background amounts of from less than 10 to 70 ppm. 

Threshold values (and background ranges) of the other 

remaining three elements are cadmium, >1 ppm (0.1-0.8); 

vanadium, >500 ppm (70-200); and zinc, >150 ppm 

(21-100).

In general, soils from the Champagne mine and sediments from the fault-breccia area yielded above-median concentrations of silver, arsenic, and mercury. Because of its 

volatility, mercury is used as a pathfinder for buried metallic 

orebodies (Maciolek and Jones, 1987). As shown in figure 9,

Figure 7 (facing page). Map showing location of sagebrush samples having high scores for the antimony-gold/bromine factor, reconaissance-scale geochemical survey, Lava Creek mining district, 

central Idaho. Large asterisk indicates greater than 90th percentile; 

small asterisk indicates 80th-90th percentile.
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES O13

43° 35'

1MILE
O14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Fault

Figure 8. Mineralized target area, a silicified and brecciated, north-northeast-trending fault in the McGowan Creek Formation, Lava Creek 

mining district, central Idaho.

the mercury content delineates a broad halo over the faultbreccia area. Anomalous mercury concentrations in sediments from a tributary of Champagne Creek west of the 

divide from the Hammond Spring Creek drainage system 

suggest that the mineralized area associated with the fault 

might be more extensive.

In contrast to the distribution pattern of anomalous mercury in sediments, anomalous concentrations of silver delineate a more restricted target that coincides with the fault (fig. 

10). Samples from localities peripheral to this target contain 

silver at or below the 0.5-ppm limit of determination.

In the course of sampling, Erdman observed that Eriogonum ovalifolium Nutt., one of many species of wild 

buckwheat, dominated parts of a slope that lay on strike with 

the mineralized fault (fig. 11). A century ago Lidgey (1897) 

reported, "In Montana experienced miners look for silver 

wherever the 'Eriogonum ovalifolium' flourishes. This plant 

grows in low dense bunches; its small leaves coated with 

thick white down." A soil sample from the locality where 

this plant is abundant contains 3 ppm Ag, second only to a

Table 4. Summary of data for 62 sagebrush samples from the 

followup geochemical survey, Lava Creek mining district, Idaho 

[Asterisk (*) indicates element was used in factor analysis. 

Concentrations on a dry-weight basis. In parts per million unless 

otherwise noted. All elements by neutron activation analysis; see text 

for details. Ratio is the number of samples in which the element was 

detected to number of samples analyzed]

Element

*As

*Au (ppb)

*Ba

*Br

Co

Cr

*Fe (percent)

Hg

*Mo

*Sb

*Se

U

*w

*Zn

Minimum

<0.01

<0.1

<20

0.69

<0.3

<0.3

<0.005

<50

0.18

0.03

<0.5

<0.2

0.09

31

Maximum

0.12

1.0

130

14

0.5

0.9

0.017

50

1.4

0.15

6.1

0.07

2.0

100

Median

0.03

0.14

30

1.6

<0.3

0.5

0.008

<50

0.50

0.045

<0.5

<0.2

0.46

50

Ratio

59:62

29:62

59:62

62:62

6:62

50:62

58:62

4:62

62:62

62:62

27:62

7:62

62:62

62:62
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES 015

soil sample from the Champagne mine that contains 5 ppm 

Ag. Species of the genus Eriogonum are commonly associated with copper and molybdenum occurrences in the Western United States (U.S. Geological Survey, unpublished 

data), but this is the first case where Eriogonum seems to be 

so strongly controlled by a silver-rich substrate.

SAGEBRUSH

Data for selected elements from the 62 sagebrush samples are summarized in table 4. R-mode factor analysis was 

used with 10 of the elements listed in the table. The optimum 

model derived from this analysis was again four factors, as 

shown in figure 12. This data set represents sagebrush growing on country rock dominated by black marine shale of the 

McGowan Creek Formation. Factor one is characterized by 

the element suite, in descending order of importance, 

arsenic, antimony, iron, bromine, and gold.

The geochemical signature of sagebrush associated 

with both the Champagne mine and the fault consists of the 

element assemblage gold, antimony, arsenic, bromine, and 

barium. The highest gold values, 1.00 and 0.80 ppb, are in 

two samples of sagebrush collected above the oxidized orebody at the Champagne mine; gold concentrations in the 

other two samples of sagebrush collected at the Champagne 

mine are only slightly anomalous at 0.4 ppb. Overall, the 

gold results for sagebrush are more useful than those for the 

sediments, but we do not recommend reliance on gold biogeochemical data alone.

Concentrations of selenium and zinc are anomalous in 

samples of sagebrush from suspected mineralized localities 

in the McGowan Creek Formation but not from the Champagne mine. Evidence from our data, as well as from data 

from similar marine sedimentary rocks north of the Lava 

Creek district (Sandra Soulliere, U.S. Geological Survey, 

unpublished data), suggests that marine black shale (turbidite) of the McGowan Creek Formation is enriched in selenium and zinc and that this enrichment is reflected in the 

sagebrush growing in soils derived from this shale. Where 

these elements have been remobilized through hydrothermal 

processes, the selenium content of sagebrush from altered 

areas is well above the normal maximum concentration of 

1.1 ppm in sagebrush in the Western United States (Gough 

andErdman, 1983).

Because arsenic dominates the element suite that characterizes factor one, the distribution of anomalous arsenic in 

sagebrush mirrors the distribution of high scores for this factor. Arsenic is a well-known pathfinder element in gold 

exploration and is more easily interpreted than multielement 

factors. The pattern of high arsenic in sagebrush (fig. 13) is 

remarkably similar to the pattern of high mercury in sediments (fig. 9) and reflects the mobility of arsenic as an anion 

in arid environments.

The distribution of anomalous tungsten in sagebrush 

(fig. 14) centers on the single drainage just to the southwest 

of the zone of silver-rich sediments and the fault breccia. By 

itself tungsten might not warrant further notice, but the associated mercury anomalies in the sediments and the presence 

of cinnabar in the concentrate from the reconnaissance survey raise the possibility of an epithermal precious-metal 

occurrence. In his biogeochemical studies of gold occurrences in turbidite of Nova Scotia, Dunn (1989) found zones 

of weak tungsten enrichment near some gold deposits.

HEAVY-MINERAL CONCENTRATES

A microscopic inspection of a heavy-mineral concentrate sample taken immediately downstream from the breccia zone (fig. 8) shows that barite is dominant m the mineral 

assemblage and that sparse, small fragments of probably 

sedimentary pyrite and, most importantly, a single grain of 

cinnabar are also present. The cinnabar provides evidence of 

low-temperature mineralization associated with the breccia 

exposure upstream and supports the strong mercury anomalies in the sediments.

Analysis of the powdered split of this concentrate produced a 5-ppm Ag anomaly and an unexplained 2,000-ppm 

La anomaly but no base-metal anomalies. The silver anomaly is consistent with the 3-ppm Ag anomaly in the soil sample on a nearby slope that supported the indicator plant, 

Eriogonum ovalifolium.

CONCLUSIONS

We now have evidence, initially obtained using plant 

chemistry, of epithermal precious-metal mineralization in 

the Hammond Spring Creek drainage of the Lava Creek 

mining district, Idaho, east of the outcrop area of the 

Eocene Challis Volcanic Group, in an area where the country rock is predominantly turbidite of the Lower Mississippian McGowan Creek Formation. The key elements that 

drew us to this conclusion are gold, antimony, and bromine 

and, to a lesser extent, arsenic, mercury, and selenium. On 

the basis of analytical results in samples of big sagebrush 

and heavy-mineral concentrates from a reconnaissancescale survey, the source was considered blind.

A followup survey of two selected areas in the turbidite terrain, during which sagebrush and stream sediments 

were sampled, reveals that the most prospective area for 

metallization is on the east edge of the Lava Creek district: 

an explosive hydrothermal breccia and weakly exposed, 

propylitically altered dacite porphyry intrusive body subjacent to a clearly defined north-northeast-trending fault. 

The geochemical results and the presence of cinnabar in 

concentrates from the anomalous area may indicate
016 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

43° 113°32'30" 113°30'

1/2

R 24 E R 25 E

1MILE

2 KILOMETERS 

I
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES on

Qa

Qc

Qac

Qf

Trl

Tqm

Tta

Tc

Mba

Msu

Msc

Ms

Mm

Dp

EXPLANATION

Alluvium (Holocene)

Colluvium (Holocene and Pleistocene)

Alluvium and colluvium, undifferentiated (Holocene and 

Pleistocene)

Alluvial fan deposits (Holocene and Pleistocene) 

Landslide deposits (Holocene and Pleistocene) 

Older alluvial deposits (Holocene and Pleistocene)

LAVA FLOWS AND RELATED DEPOSITS OF THE SNAKE 

RIVER GROUP

Pahoehoe basalt flows and shield volcano (Pleistocene)

ROCKS OF THE HEISE VOLCANIC FIELD 

Tuffs of Blue Creek and Blacktail, undivided (Miocene)

IDAVADA VOLCANICS 

Tuffs of Little Chokecherry Canyon (Miocene)

SILICIFIED ROCK 

Jasperoid (Eocene or younger)

CHALLIS VOLCANIC GROUP 

Dikes

Rhyodacite breccia 

Rhyodacite lava flows 

Quartz monzonite porphyry

Tuffs of Antelope Creek and granite porphyry of Anderson 

(1947)

Basal conglomerate, breccia, and sandstone

SEDIMENTARY ROCKS

Bluebird Mountain and Arco Hills formation, undivided 

(Upper Mississippian)

Surrett Canyon Formation (Upper Mississippian)

South Creek Formation (Upper Mississippian)

Scott Peak Formation (Upper Mississippian)

Middle Canyon Formation (Upper and Lower Mississippian)

McGowan Creek Formation (Lower Mississippian)

Picabo(?) Formaition (Upper Devonian)

Contact Dashed where approximately located

Fault Dashed where approximately located; dotted where concealed. Bar and ball on downthrown side. Single arrow indicates apparent relative lateral movement. Arrow and number (in degrees) indicate dip of fault plane

Thrust fault Sciwteeth on upper plate. Dashed where approximately located; dotted where concealed

Photo lineament Probable fault or fracture having undetermined offset

Anticline Showing trace of axial plane. Dashed where 

approximately located; dotted where concealed

Syncline Showing trace of axial plane. Dashed where 

approximately located; dotted where concealed

Argillic alteration 

Tectonic breccia 

Flow direction in basalt 

Outline of basalt vent crater

leakage of hydrothermal solutions from depth. The source 

of the anomaly in the area on the west side of the district 

was not identified.

The unique response of sagebrush to fairly subtle metallization in the Lava Creek district led to the discovery of a 

silver- and mercury-rich brecciated zone in the Mississippian 

turbidite and underscores the value of biogeochemical methods in an initial mineral assessment. The followup survey of 

selected areas to locate the sources of the geochemical anomalies shows, however, that either sediments or sagebrush 

would have provided equally satisfactory results.

REFERENCES CITED

Adrian, Betty, Erdman, J.A., Bullock, J.H., and Hageman, P.L., 

1990, Analytical results and locality map of heavy-mineralconcentrate, stream-sediment, soil, and big sagebrush samples 

from the Lava Creek mining district, within the Idaho Falls 

I°x2° quadrangle, Butte, County, Idaho: U.S. Geological Survey Open-File Report 90-545.

Anderson, A.L., 1929, Geology and ore deposits of the Lava Creek 

district, Idaho: Idaho Bureau of Mines and Geology Pamphlet 

32, 70 p.

 1947, Epithermal mineralization at the Last Chance and 

Hornsilver Mines, Lava Creek district, Butte County, Idaho: 

Geological Society of America Bulletin, v. 58, p. 451-482.

Botinelly, T., 1976, A review of the minerals of the alunite-jarosite, 

beudantite, and plumbogummite groups: U.S. Geological Survey Journal of Research, v. 4, p. 213-216.

Boyle, R.W., 1984, The prospect for geochemical exploration Predictable advances and new approaches: Journal of 

Geochemical Exploration, v. 21, p. 1-18.

 1986, Gold deposits in turbidite sequences Their geology, 

geochemistry and history of the theories of their origin, in Keppie, J.D., Boyle, R.W., and Haynes, S.J., eds., Turbidite-hosted 

gold deposits: Geological Association of Canada Special Paper 

32, p. 1-13.

Crock, J.G., Briggs, P.H., Jackson, L.L., and Lichte, F.E., 1987, 

Analytical methods for the analysis of stream sediments and 

rocks from Wilderness Study Areas: U.S. Geological Survey 

Open-File Report 87-84, 35 p.

Figure 9 (left and facing page). Map showing location of streamsediment and soil samples that contain anomalous amounts of mercury (>0.10 ppm)(solid red circles), followup survey, Lava Creek 

mining district, central Idaho. Open red circles indicate samples containing less than 0.10 ppm Hg; observed range of values O.02-1.2 

ppm Hg. Geology modified from Skipp and others (1990).
018 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

43° 113°321 30" 113°30'

R 24 E R 25 E

2 KILOMETERS

1 I 

1/2

1

1 MILE
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES O19

Figure 11. Indicator plant Eriogonum ovalifolium (foreground) in 

argentiferous soil near mineralized fault, Lava Creek mining district, central Idaho.

Figure 10 (facing page). Map showing location of stream-sediment and soil samples that contain anomalous amounts of silver 

(>1.0 ppm)(solid red circles), followup survey, Lava Creek mining 

district, central Idaho. Open red circles indicate samples containing 

less than 1.0 ppm Ag; observed range of values <0.5-5.0 ppm Ag. 

Geology modified from Skipp and others (1990); see figure 9 for 

explanation.

Dunn, C.E., 1989, A multi-element and multi-media approach to 

geochemical exploration for gold in eastern Nova Scotia, Canada: International Geochemical Exploration Symposium, 13th, 

Rio de Janeiro, Brazil, October 1989, Abstracts, p. 5-6.

Dunn, C.E., and Hoffman, Eric, 1986, Multi-element study of vegetation from a zone of rare-earth rich allanite and apatite in 

northern Saskatchewan, Canada: Applied Geochemistry, v. 1, 

p. 375-381.

Erdman, J.A., Moye, Falma, and Theobald, P.K., 1989, Geochemical expression of poorly exposed metallization in the southeastern Challis volcanic field, Idaho Emphasis on 

biogeochemical methods, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls 1 °x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 91.

Erdman, J.A., Skipp, Betty, Theobald, P.K., and Moye, Falma, 

1988, Drainage-basin geochemical survey of Lava Creek district in central Idaho using sagebrush and heavy-mineral concentrates Preliminary evidence for sediment-hosted gold in 

McGowan Creek Formation: Geological Society of America 

Abstracts with Programs, v. 20, no. 6, p. 414.

Gough, L.P., and Erdman, J.A., 1983, Baseline elemental concentrations for big sagebrush from Western U.S.A." Journal of 

Range Management, v. 36, p. 718-722.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc and 

alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials: 

U.S. Geological Survey Circular 591, 6 p,

Hillier, B.M., Grimes, D.J., Vaughn, R., Arbogast, B., and McDougal, C., 1983, Analyses of samples from the Lava Creek mining 

district, Blaine and Butte Counties, Idaho: U.S. Geological 

Survey Open-File Report 83-705, 11 p.

Korobeynikov, A.F., 1986, Gold distributions in black shale associations: Geochemistry International, v. 23, p. 114-124.

Kovalevskii, A.L., 1979, Biogeochemical exploration for mineral 

deposits: Faridabad, India. Oxonian Press Pvt. Ltd., 136 p. 

Available from U.S. Department of Commerce, National Technical Information Service, 5285 Port Royal Road, Springfield, 

Va. 22161.

Lidgey, E., 1897, Some indications of ore deposits: Transactions, 

Australasian Institute of Mining Engineers, v. 4, p. 110-122.

Link, P.K., Skipp, Betty, Hait, M.H., Jr., Janecke, Susanne, and 

Burton, B.R., 1988, Structural and stratigraphic transect of 

south-central Idaho A field guide to the Lost River, White 

Knobe, Pioneer, Boulder, and Smoky Mountains, in Link, 

P.K., and Hackett, W.R., eds., Guidebook to the geology of 

central and southern Idaho: Idaho Geological Survey Bulletin 

27, p. 5^2.

Maciolek, J.B., and Jones, V.T., 1987, Mobile mercury application 

in the search for gold: Explore, no. 61, p. 6-7.

Miesch, A.T., 1981, Estimation of the geochemical threshold and 

its statistical significance: Journal of Geochemical Exploration, v. 16, p. 49-76.

Nelson, C.E., 1990, Comparative geochemistry of jasperoids from 

Carlin-type gold deposits of the western United States: Journal 

of Geochemical Exploration, v. 36, p. 171-195.

O'Leary, R.M., and Meier, A.L., 1986, Analytical methods used in 

geochemical exploration: U.S. Geological Survey Circular 

948,48 p.
020 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

1.0

0.9

1-

ON COEFFIC

o ^

CORRELAT p o in 05

0.4

n -3

Factor

1

As

~~ Sb 

Fe

__ Br

-

Au

2

Zn

Se

3

Ba

W

4

Mo

W

22.0 18.6 13.4 11.2 

PERCENT VARIANCE ACCOUNTED FOR BY EACH FACTOR

Figure 12. Factor compositions for sagebrush from followup survey, Lava Creek mining district, central Idaho. Elements are arranged in descending order of correlation coefficient, which 

indicates importance of the element.

Skipp, Betty, 1987, Basement thrust sheets in the Clearwater orogenic zone, central Idaho and western Montana: Geology, v. 

15, p. 220-224.

 1988, Geologic map of Mackay 4 (Grouse) SE Quadrangle, 

Butte County, Idaho: U.S. Geological Open-File Report 

88-423, scale 1:24,000.

Skipp, Betty, Kuntz, M.A., and Morgan, L.A., 1990, Geologic map 

of Mackay 4 (Grouse) SE Quadrangle, Butte County, Idaho: 

U.S. Geological Open-File Report 89-431, scale 1:24,000.

Soulliere, S.J., Wilson, A.B., Moye, F.J., and Rhea. K.P., 1988, 

Analytical results and sample locality map of jasperoid samples from Mackay, Idaho: U.S. Geological Survey Open-File 

Report 88-589, 28 p.

Sturges, D.L., 1977, Soil water withdrawal and rooting characteristics of individual big sagebrush plants: American Midland Naturalist, v. 98, p. 257-274.

Sturges, D.L., and Trlica, M.J., 1978, Root weights and carbohydrate reserves of big sagebrush: Ecology, v. 59, p. 1282-1285.

Tabler, R.D., 1964, The root system of Artemisia tridentata at 

9,500 feet in Wyoming: Ecology, v. 45, p. 633-636.

The Mining Record, 1989, Bema Gold's Champagne Mine in production: February 8, v. 100, p. 25.

Weaver, I.E., and Clements, F.E., 1938, Plant ecology: McGrawHill, New York, 601 p.

Wilson, A.B., Soulliere, S.J., Worl, R.G., Skipp, Betty, and Rhea, 

K.P., 1988, Geology and geochemistry of jasperoid near Mackay, Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to 

the geology of central and southern Idaho: Idaho Geological 

Survey Bulletin 27, p. 183-192.

Figure 13 (facing page). Map showing location of big sagebrush 

samples that contain anomalous amounts of arsenic (>0.05 

ppm)(solid red circles), followup survey, Lava Creek mining district, central Idaho. Open red circles indicate samples containing 

less than 0.05 ppm As; observed range of values O.01-0.12 ppm 

As. Geology modified from Skipp and others (1990); see figure 9 

for explanation.
EPITHERMAL METALLIZATION IN MISSISSIPPIAN TURBIDITES

113°32'30"

1/2

R 24 E R 25 E

1 MILE

2 KILOMETERS 

I
O22 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Figure 14 (facing page). Map showing location of big sagebrush 

samples that contain anomalous amounts of tungsten (>0.77 

ppm)(solid red circles), followup survey, Lava Creek mining district, central Idaho. Open red circles indicate samples containing 

less than 0.77 ppm W; observed range of values O.09-2.0 ppm W. 

Geology modified from Skipp and others (1990); see figure 9 for 

explanation.
43C 

37' 

30

EPITHERMAL METALLIZATION IN

113°32'30"

MISSISSIPPIAN TURBIDITES O23

113°30'

1/2

R 24 E R 25 E

1MILE

2 KILOMETERS 

I

Petrogenesis of Silver-Lead-Zinc Veins on the 

Eastern Margin of the Idaho Batholith in the 

Carrietown Mineralized Area, 

Blaine and Camas Counties, 

South-Central Idaho

By Robert S. Darling, Harry W. Campbell, and Paul Karl Link

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-P

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. PI

Introduction.......................................................................................................................... 1

Geologic Setting................................................................................................................... 2

Dollarhide Formation................................................................................................... 2

Cretaceous Intrusive Rocks.......................................................................................... 5

Metamorphism.............................................................................................................. 5

Eocene Extrusive and Intrusive Rocks......................................................................... 7

History and Production......................................................................................................... 7

Silver-Lead-Zinc Deposits.................................................................................................... 7

Ore Petrography.................................................................................................................... 7

Petrogenesis of Silver-Lead-Zinc Ores................................................................................. 11

Lithologic Controls....................................................................................................... 11

Structural Controls........................................................................................................ 13

Thermal Conditions of Mineralization......................................................................... 14

Sulfur-Isotope Geothermometry........................................................................... 14

Cubanite Exsolution Geothermometry................................................................. 14

Arsenopyrite Geothermometry............................................................................. 14

Oxygen and Sulfur Fugacities of Ore Fluids................................................................ 14

Source of Sulfur and Lead............................................................................................ 14

Age of Mineralization................................................................................................... 15

Proposed Pressure-Temperature-Time Path................................................................. 16

General Model and Comparison to Other Silver-Lead-Zinc Deposits in the

Black Shale Belt of Idaho............................................................................................. 16

References Cited................................................................................................................... 17

FIGURES

1, 2. Maps of the Dollarhide Mountain quadrangle and the western half of Buttercup Mountain quadrangle showing:

1. Location.............................................................................................................................................................. P2

2. Simplified geology ............................................................................................................................................. 3

3-6. Maps showing geology and topography of:

3. Carrietown area................................................................................................................................................... 4

4. Warm Springs and Little Smoky Creek areas..................................................................................................... 6

5. Cabin Gulch-Willow Creek area........................................................................................................................ 8

6. Buttercup Mountain area.................................................................................................................................... 9

7. Ternary diagram showing modal mineralogy of Cretaceous intrusive rocks in study area....................................... 10

8. Schmidt equal-area lower hemisphere plot of poles to veins listed in table 2........................................................... 10

9. Diagram showing general paragenetic sequence for hypogene minerals in the Carrietown mineralized area.......... 10

10. Log/O2-log/S2 diagram illustrating volatile fugacity of ore-forming fluids between banded quartzite and

carbonaceous marble of the Dollarhide Formation.................................................................................................... 15

11. Graph showing proposed pressure-temperature-time path for rocks in the Carrietown mineralized area................ 17

TABLES

1. Recorded production from the Carrietown, northern Willow Creek, and eastern Little Smoky Creek

mining districts .............................................................................................................................................................. Pll

2. Summary of geological information on mines and prospects in the Carrietown mineralized area............................... 12

3. Summary of available thermal data from mines in the Carrietown mineralized area.................................................... 15
Petrogenesis of Silver-Lead-Zinc Veins on the

Eastern Margin of the Idaho Batholith in the

Carrietown Mineralized Area, Blaine and Camas Counties,

South-Central Idaho

By Robert S. Darling, 1 Harry W. Campbell,2 and Paul Karl Link3

ABSTRACT

The Carrietown mineralized area, approximately 30 km 

southwest of Ketchum and 25 km northwest of Fairfield, 

Idaho, includes the Carrietown mining district, the eastern part 

of the Little Smoky Creek mining district, and the northern 

part of the Willow Creek mining district in the Dollarhide 

Mountain and Buttercup Mountain 7.5-minute quadrangles. 

The mineralized area covers approximately 75 km2 in the 

southwestern part of the central Idaho black shale mineral belt.

Silver-lead-zinc deposits in the Carrietown area have 

similarities in ore mineralogy, deposit type, geologic setting, 

and petrogenesis. All of the deposits are epigenetic vein-type 

bodies containing galena, sphalerite, tetrahedrite, pyrite, 

arsenopyrite, pyrrhotite, and chalcopyrite. Galena and tetrahedrite are the principal silver-bearing phases. Distribution 

of deposits is controlled by both structure and lithology; silver-lead-zinc deposits are best developed in northeast-trending fault zones in rocks of the metamorphosed Middle 

Pennsylvanian to Lower Permian Dollarhide Formation and 

the Cretaceous Idaho batholith. These mineralized fault 

zones are (1) near contacts between carbonaceous marble 

and banded quartzite of the lower member of the Dollarhide 

Formation (previously known as the Carrietown sequence); 

(2) near contacts between banded quartzite of the Dollarhide 

Formation and Cretaceous intrusive rocks; and (3) in shear 

zones within the intrusive rocks. Lead-isotopic data suggest 

that lead was derived from Precambrian basement, whereas 

sulfur-isotopic data suggest a mixed igneous and sedimentary sulfur source. Stability of iron-bearing phases in ore 

assemblages indicates that conditions were reducing (low 

/C>2) in the Dollarhide Formation and that sulfur fugacities 

were lower in banded quartzite than in carbonaceous marble.

'Department of Geology, State University of New York College at 

Cortland, P.O. Box 2000, Cortland, New York 13045.

2Western Field Operations Center, U.S. Bureau of Mines, E. 360 3rd 

Ave., Spokane, Washington 99202.

3Department of Geology, Idaho State University, Pocatello, Idaho 

83209.

Temperatures of ore formation estimated from several independent geothermometers suggest mesothermal to hypothermal (250°C-^50°C) mineralization. Field, thermal, 

mineralogical, and available radiometric data indicate that 

mineralization was related to Cretaceous igneous activity.

INTRODUCTION

Silver-lead-zinc deposits in the Carrietown mineralized 

area of Idaho are in the northern half of the Dollarhide 

Mountain 7.5-minute topographic quadrangle and western 

half of the Buttercup Mountain 7.5-minute topographic 

quadrangle. The quadrangles are in the central Smoky 

Mountains, a north-trending range that extends from Galena 

Summit on the north to the northern margin of the Snake 

River Plain near the town of Fairfield. The principal divide 

of the range forms the boundary between Blaine and Camas 

Counties (fig. 1).

The old village of Carrietown is in the northern part of 

the Dollarhide Mountain quadrangle and was the principal 

settlement when mining operations flourished in all three 

districts in the late 1800's and early 1900's. Today, however, 

the village is abandoned and only a few buildings remain. 

Carrietown can be reached by light-duty roads from the 

towns of Ketchum, 30 km to the east, and Fairfield, 25 km to 

the south (fig. 1).

Umpleby (1915) called the entire area the Rosetta district. He believed that the Carrietown ores were epigenetic 

and related to Cretaceous igneous activity, a conclusion 

with which we substantially agree. Ross (1930) distinguished the Little Smoky Creek and Willow Creek districts. Gehlen (1983) examined mines in the eastern part of 

the Little Smoky Creek district. Hall (1985) defined only 

the Carrietown district, as did Darling (1987, 1988). Federspiel and others (1987, 1992) described parts of the Little 

Smoky and Rosetta districts. We use the term "Carrietown 

mineralized area" to include the Carrietown mining district, the eastern part of the Little Smoky Creek mining

PI
P2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

TO STANLEY 1 14°45'

43° 

30'

_ / Carrietown

Area shown in 

figure 2

50 KILOMETERS

EXPLANATION

Dollarhide Mountain quadrangle

West half Buttercup Mountain quadrangle

Figure 1. Map showing location of the Dollarhide Mountain 7.5- 

minute topographic quadrangle and the western half of the Buttercup Mountain 7.5-minute topographic quadrangle, Blaine and Camas Counties, Idaho.

district, and the northern part of the Willow Creek mining 

district. Silver-lead-zinc deposits in these areas share a 

genetic mineral deposit type, that of shear-zone-hosted 

veins, and have similar ore mineral assemblages and pressure-temperature-chemical conditions of ore formation. 

These mineral deposits are all near the contact between the 

Idaho batholith and the Middle Pennsylvanian to Lower 

Permian Dollarhide Formation.

Recognition in the 1800's of syngenetic lead-zinc mineral deposits in Paleozoic rocks of central Idaho (Hall, 1985; 

Turner and Otto, this volume) has led to renewed interest in 

the sediment-hosted deposits along the eastern margin of the 

Idaho batholith. The principal objectives of our research 

were to characterize the geology of silver-lead-zinc deposits 

in the Carrietown area and to determine their petrogenesis.

Acknowledgments. This research was supported by 

an Idaho State University graduate student research grant 

and by the U.S. Geological Survey. The paper presented 

here is an extension of the senior author's M.S. thesis 

research completed at Idaho State University. Research by 

Campbell was conducted under the Idaho Land Assessment 

Program of the U.S. Bureau of Mines. Earlier versions of 

the manuscript benefited greatly from reviews by M.L. 

Sorensen and D. Frishman.

GEOLOGIC SETTING

The Carrietown area is on the southwestern margin of 

the central Idaho black shale mineral belt of Hall (1985), at 

the junction between folded Paleozoic strata and Cretaceous 

intrusive rocks of the Atlanta lobe of the Idaho batholith 

(Link and others, this volume; Lewis, in press). In the Dollarhide Mountain and Buttercup Mountain quadrangles, 

folded rocks of the Pennsylvanian and Permian Dollarhide 

Formation are intruded by three phases of the Late Cretaceous Idaho batholith. The Dollarhide Formation is preserved as a large, almost completely isolated roof pendant 

between the Atlanta lobe to the west and the Deer Creek 

stock to the east (fig. 2). In both quadrangles, the Cretaceous 

intrusive rocks and the Dollarhide Formation are unconformably overlain by rocks of the Eocene Challis Volcanic 

Group and intruded by Eocene dacite porphyry dikes and 

small stocks (fig. 2). Figures 3-6 are geologic-topographic 

maps of the mines investigated in this report.

DOLLARHIDE FORMATION

The Middle Pennsylvanian to Lower Permian Dollarhide Formation is named for exposures on Dollarhide Summit in the northern part of the Dollarhide Mountain 7.5- 

minute quadrangle. The unit was first defined by Hall (1985) 

and has been described by various workers including Wavra 

(1985), Wavra and others (1986), Geslin (1986), Link and 

others, (1988), Whitman (1990, this volume), O'Brien 

(1991), Mahoney and others (1991), and Link and others 

(this volume). The unit is divided into three informal members: (1) a lower member (800 m) consisting of rhythmically 

interbedded, very fine grained, light-gray to light-brown 

micritic sandstone and dark-gray carbonaceous silty micrite 

and subordinate medium- to thick-bedded light-brown 

micritic sandstone and light-gray lenticular conglomerate 

containing both extra- and intra-basinal clasts; (2) a middle 

member (300 m) consisting of fine-grained light-brown 

micritic sandstone and light-gray sandy micrite and subordinate dark-gray to black carbonaceous siltstone and lenticular 

conglomerate; (3) an upper member (900 m) consisting of 

thin-bedded to laminated dark-gray carbonaceous siltstone 

and light-gray silty micrite and minor light-brown micritic 

sandstone and conglomerate (Mahoney and others, 1991).

The lower and middle members of the Dollarhide Formation are widely exposed in the Dollarhide Mountain quadrangle, whereas the upper member is more abundant in the 

Buttercup Mountain quadrangle (fig. 2). The lowest exposed 

part of the lower member contains dark-brown banded 

quartzite, biotite phyllite, and minor calc-silicate hornfels. 

These metasedimentary rocks were informally named the 

"Carrietown sequence" by Skipp and Hall (1980) and 

mapped and described in detail by Geslin (1986) and Darling 

(1987, 1988, 1989). Following the interpretation of W.E.
PETROGENESIS OF SILVER-LEAD-ZINC VEINS

114° 45' 15"

P3

; Tcv

Pdu

\ Pdm\

EXPLANATION

Intrusive dacite porphyry (Eocene)

Challis Volcanic Group (Eocene)

Intrusive rocks (Cretaceous)

Upper member of the Dollarhide Formation (Permian)

Middle member of the Dollarhide Formation (Permian)

Lower member of the Dollarhide Formation 

(Permian-Pennsylvanian)

Foliated rocks of the Dollarhide Formation 

(Permian-Pennsylvanian)

Contact 

High-angle fault

Figure 2. Map showing simplified geology of the Dollarhide Mountain 7.5-minute topographic quadrangle and the western half of the Buttercup Mountain 7.5-minute topographic quadrangle, Blaine and Camas Counties, Idaho. Detailed geology of selected areas is shown in figures 3-6. Mines and prospects in the Carrietown mineralized area (location shown in figure 1) are shown by number: 1, Carrie Leonard mine; 

2, Margaret mine; 3, Dollarhide mine; 4, Isabella mine; 5, Last Chance mine; 6, Jane Lee mine; 7, Silver Star mine; 8, Silver Crown mine; 

9, Horn Silver mine; 10, Fletcher mine; 11, King of the West mine; 12, Stormy Galore mine; 13, Tyrannis mine; 14, Alma mine; 15; Red 

Star prospect; 16, Taft prospect; 17, Hidden Treasure mine; 18, Smoky Bullion prospect; 19, Main Moly prospect; 20, Pine Creek mine; 21, 

unnamed mine; 22, Buttercup mine. A summary of geological information on these mines and prospects is given in table 2. Compiled from 

Gehlen (1983), Geslin (1986), Darling (1987, 1989, unpub. mapping), Whitman (1990), and O'Brien (1991).
P4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

11 4° 42' 30"

--r- V

:lX^-::::H:::V^V::x: MINE ^::

KING OF THE WEST MINE :ffcSTORMY GALORE MINE it ^; 8525

CONTOUR INTERVAL 200 FEET 

EXPLANATION

Intrusive dacite porphyry (Eocene) 

Tcv | Challis Volcanic Group (Eocene)

Intrusive rocks (Cretaceous)-Includes leucocratic granite 

(unit Klgr), aplite and pegmatite (unit Ka), biotite 

granodiorite (unit Kbg), and homblende-biotite 

granodiorite (unit Khbg)

Lower member of the DoIIarhide Formation 

(Permian-Pennsylvanian)

Foliated rocks of the DoIIarhide Formation 

(Permian-Pennsylvanian)-Includes banded 

quartzite and biotite phylite

Contact

.70

 Normal fault-Bar and ball on downthrown side;

dashed where approximately located 

Strike and dip of beds 

Adit
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P5

Hall (unpublished mapping, 1980-1984), these workers also 

inferred that the contact between the Dollarhide Formation 

and the Carrietown sequence is a thrust fault for reasons discussed in Darling (1987, p. 59). Subsequent studies by Whitman (1990, this volume) revealed, however, that the 

boundary between the two units is lithologic and that no evidence exists to support a structural contact. Following Whitman (1990, this volume), the term Carrietown sequence is 

abandoned, and the rocks are now interpreted as foliated and 

light-colored parts of the lower and middle members of the 

Dollarhide Formation.

CRETACEOUS INTRUSIVE ROCKS

The Dollarhide Formation is intruded by three separate phases of the Idaho batholith, from oldest to youngest, 

(1) hornblende-biotite granodiorite, (2) biotite granodiorite, 

and (3) leucocratic granite (figs. 3-6). The hornblendebiotite granodiorite forms a small stock in the western part 

of the Dollarhide Mountain quadrangle (fig. 3) and the 

northern part of the Willow Creek area (fig. 6). This pluton 

has been intruded by biotite granodiorite that is volumetrically the most abundant Cretaceous intrusive phase in both 

quadrangles. Both granodiorite bodies are host to numerous 

aplite and simple pegmatite dikes and pods. Leucocratic 

granite is the youngest phase and forms small stocks or 

dikes in both granodiorite bodies but is especially common 

near contacts between granodiorite and surrounding country rocks (figs. 3-5).

The modal mineralogy of Cretaceous intrusive rocks in 

the Carrietown district is illustrated in figure 7. This plot is 

based on results of point counting 20 stained slabs of rocks 

(1,000 points) using a transparent grid overlay (Darling, 

1987). Similar plots for Cretaceous intrusive rocks in the Little Smoky Creek and Willow Creek districts are in Gehlen 

(1983) and Geslin (1986), respectively. Hornblende-biotite 

granodiorite is dominated by medium- to coarse-grained 

normally zoned plagioclase, medium- to coarse-grained 

quartz, and fine- to medium-grained, interstitial, poikilitic, 

perthitic microcline. Biotite (-9 percent) forms medium- to 

coarse-grained anhedral books, and hornblende (-5-6 percent) forms medium- to coarse-grained, dark-brown to 

black, locally twinned prisms. Some rocks are so alkali feldspar deficient that they are more properly named tonalite 

(fig. 7). Biotite granodiorite contains medium- to coarsegrained normally zoned plagioclase, medium- to coarsegrained quartz, and fine- to medium-grained, interstitial and 

separate crystals of perthitic microcline. Biotite is less abundant than in the older phase (-4-5 percent) and is present as

Figure 3 (facing page). Map showing geology and topography of 

the Carrietown area, Idaho. Location of map area is shown in figure 

2. Geology modified from Darling (1987, 1989). Base from U.S. 

Geological Survey Dollarhide Mountain 7.5-minute quadrangle.

fine-grained disseminated flakes and books. Both types of 

granodiorite have abundant myrmekitic intergrowths and 

apatite, magnetite, titanite, and zircon accessory phases. 

Leucocratic granite is dominated by subequal amounts of 

fine- to medium-grained plagioclase, quartz, and microcline. 

The granite has abundant micrographic and myrmekitic 

intergrowths and garnet and allanite accessory phases.

The Cretaceous intrusive rocks in the study area have 

not been radiometrically dated; however, biotite granodiorite 

of the Rooks Creek stock, 18 km to the northeast, has been 

dated at 92.2±2.2 Ma by K-Ar methods on biotite (Marvin 

and Dobson, 1979). A minimum age of 77.4±2.6 Ma is indicated for leucocratic granite in the Dollarhide Mountain 

quadrangle based on a K-Ar age for hydrothermal muscovite 

(M. Tschanz, 1982, unpublished report; cited in Gehlen, 

1983) (see discussion on age of mineralization). The above 

field and radiometric dates are consistent with data collected 

on Cretaceous intrusive rocks in the Challis 1 °x2° quadrangle (Kiilsgaard and Lewis, 1985) and elsewhere in the Hailey 

I°x2° quadrangle (Lewis, in press).

METAMORPHISM

In the Dollarhide Mountain and Buttercup Mountain 

quadrangles, the lower member of the Dollarhide Formation 

has been metamorphosed proximal to intrusive rocks of the 

Idaho batholith. Metamorphosed Dollarhide Formation contains sillimanite, andalusite, staurolite, tremolite, and wollastonite, an assemblage that indicates metamorphic 

temperatures of 500°C-600°C and pressures of 2.5-3.5 kb 

(Whitman, 1990, this volume). The metamorphism is dated 

at 83.9±3.4 Ma by whole-rock K-Ar methods (R.L. Armstrong, written commun., 1990), and this age, combined with 

the estimated contact metamorphic pressure, indicates an 

emplacement depth of 8-11 km for the Idaho batholith 

(Whitman, 1990, this volume).

Whitman (1990, this volume) divided the lower member of the Dollarhide Formation into three informal textural 

units. Unit 1 consists of purplish-brown phyllite, local fineto medium-grained black to brown schist, and purplishbrown fine-grained phyllitic quartzite; unit 2 consists of purple-brown phyllite and phyllitic quartzite, centimeter-scale 

banded quartzite containing locally stratiform sulfide minerals (pyrrhotite and chalcopyrite), and gray to white calcareous to siliceous, massive to finely laminated marble and 

calc-silicate hornfels; and unit 3 consists of black carbonaceous marble, gray to white calc-silicate hornfels, and very 

fine grained argillite. Units 1 and 2 have strong metamorphic 

fabric, and marble of unit 3 displays less fabric. Units 1 and 

2 are shown as foliated Dollarhide Formation (unit PPdf) in 

figures 2-6.
P6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°40'

43°35'

CONTOUR INTERVAL 200 FEET

Figure 4 (above and facing column). Map showing geology and topography of the Warm Springs (top part of map 

area) and Little Smoky Creek areas (bottom part of map area), Idaho. Location of map area is shown in figure 2. 

Geology modified from Darling (1987, 1989) and Gehlen (1983). Base from U.S. Geological Survey Dollarhide 

Mountain 7.5-minute quadrangle.
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P7

70

EXPLANATION 

Intrusive dacite porphyry (Eocene) 

Challis Volcanic Group (Eocene)

Intrusive rocks (Cretaceous) Includes leucocratic granite 

(unit Klgr) and biotite granodiorite (unit Kbg)

Middle member of the Dollarhide Formation (Permian)

Lower member of the Dollarhide Formation (PermianPennsylvanian)

Foliated rocks of the Dollarhide Formation (PermianPennsylvanian) Includes banded quartzite and biotite 

phyllite

Contact

Normal fault-Bar and ball on downthrown side; dashed where 

approximately located

Strike and dip of beds

Anticline-Showing direction of plunge

Adit

Prospect

of the century (Umpleby, 1915; Ross, 1930). Since then, the 

districts have been inactive except for small-scale mining 

and annual assessment work. In the early 1980's, however, 

when silver prices soared, both local and major mining companies explored the Dollarhide Formation for undiscovered 

silver-lead-zinc deposits. This exploration abated with 

depressed silver prices in the late 1980's.

Recorded metal production from the Carrietown area is 

listed in table 1. The districts in the area produced $6.6 million in silver, $915,770 in lead, and $273,000 in zinc 

(expressed in 1990 dollars). Small quantities of gold and 

copper were locally recovered as well (table 1). Refer to 

Ross (1930), Federspiel and others (1992), and unpublished 

U.S. Bureau of Mines files (Spokane, Washington) for specific dates of mine operation. The average ore grade was 

15-400 ounces of silver per ton (Umpleby, 1915), but local 

miners working in the area reported grades as high as 1,000 

ounces of silver per ton.

EOCENE EXTRUSIVE AND 

INTRUSIVE ROCKS

In the Dollarhide Mountain and Buttercup Mountain 

quadrangles, both the Dollarhide Formation and the Cretaceous intrusive rocks are unconformably overlain by rocks 

of the Eocene Challis Volcanic Group, which formed during 

widespread magmatism between 51 and 40 Ma (Mclntyre 

and others, 1982; Moye and others, 1988; Moye and others, 

in press). Volcanic rocks in the Carrietown area consist of 

andesite, dacite, and rhyolite porphyry tuff, lava flow rocks, 

tuff breccia, and volcaniclastic sedimentary rocks. Detailed 

descriptions and petrologic interpretations of these rocks are 

given in Gehlen (1983). The volcanic rocks are intruded by 

numerous Eocene hypabyssal dacite porphyry dikes and 

small stocks. These dikes are present throughout the study 

area but are especially abundant in the northern Dollarhide 

Mountain quadrangle near Shaw Mountain (fig. 4). The 

intrusive rocks are coeval, subvolcanic equivalents of the 

Challis Volcanic Group (Stewart and others, in press). One 

dike 0.7 km west of Carrietown has been dated at 47.2±0.9 

Ma by K-Ar methods on biotite (W.E. Hall, unpublished 

report, 1978) (fig. 3).

HISTORY AND PRODUCTION

Mining in the Carrietown area began in the early 

1880's, but production from many mines decreased substantially by 1890, and almost all operations ceased by the turn

SILVER-LEAD-ZINC DEPOSITS

Silver-lead-zinc deposits in the Carrietown area are 

tabular, vein-type bodies that generally occupy northeasttrending fault zones in the Dollarhide Formation and its 

metamorphosed equivalents. The mineralized shear zones 

dip moderately to steeply southeast and northwest (fig. 8) 

and locally are parallel with bedding in the host rocks. Significant geologic information for mines in all three districts 

is summarized in table 2. Veins are generally (1) at or near 

the contact between banded quartzite (unit 2, PPdf) and 

carbonaceous marble (unit 3, PPdl) of the Dollarhide Formation, (2) near contacts between the banded quartzite and 

Cretaceous granodiorite, and (3) in minor shear zones in the 

Cretaceous intrusive rocks (figs. 3-6). Veins have an average width of 1-2 m and extend into the country rock for 

several tens of meters. Within the veins, ore minerals are 

present in a series of irregular, lenslike pods that are parallel with the vein walls.

ORE PETROGRAPHY

Ore minerals from mines in the Carrietown area 

include galena, sphalerite, tetrahedrite, pyrite, arsenopyrite, 

pyrrhotite, chalcopyrite, and cubanite. Tennantite, boulangerite, and molybdenite are present in minor amounts. 

Quartz and siderite are the principal gangue minerals where 

the ore is hosted by the banded quartzite (unit 2) of the Dollarhide Formation, but ore hosted by carbonaceous marble 

or limestone has a quartz-calcite gangue (see table 2). A
P8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114° 4Q'

43°35'

CONTOUR INTERVAL 200 FEET 

EXPLANATION

Tcv

Pdu

LxPdm\

:PPdl::

Challis Volcanic Group (Eocene)

Intrusive rocks (Cretaceous) Includes leucocratic granite 

(unit Klgr), and homblende-biotite granodiorite (unit Khbg)

Upper member of the Dollarhide Formation (Permian) 

Middle member of the Dollarhide Formation (Permian)

Lower member of the Dollarhide Formation 

(Permian-Pennsylvanian)

70

Foliated rocks of the Dollarhide Formation (Permian 

Pennsylvanian) Includes banded quartzite and biotite 

phyllite

Contact

1 Normal fault Bar and ball on downthrown side 

Strike and dip of beds 

Adit

Figure 5. Map showing geology and topography in the Cabin Gulch-Willow Creek area, Idaho. Location of map area is shown 

in figure 2. Geology modified from O'Brien (1991, plate 1). Base from U.S. Geological Survey Buttercup Mountain 7.5-minute 

quadrangle.
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P9

114° 35'

43°3V

KILOMETER

CONTOUR INTERVAL 200 FEET 

EXPLANATION

Tcv

Khbg

Pdu

NPdrrv

PPdf

Challis Volcanic Group (Eocene) 

Hornblende-biotite granodiorite (Cretaceoous)

Upper member of the Dollarhide Formation 

(Permian)

Middle member of the Dollarhide Formation 

(Permian)

Foliated rocks of the Dollarhide Formation

(Permian-Pennsylvanian)-Includes banded 

quartzite and biotite phylite

70

Contact

Normal fault Bar and ball on downthrown 

side

Strike and dip of beds 

Adit

Figure 6. Map showing geology and topography of the Buttercup Mountain area, Idaho. Location of map area 

is shown in figure 2. Geology modified from Geslin (1986), Whitman (1990), and O'Brien (1991). Base from 

U.S. Geological Survey Buttercup Mountain 7.5-minute quadrangle.
P10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Quartz

Potassium feldspar Plagioclase

EXPLANATION

n Leucocratic granite 

 Biotite granodiorite 

0 Hornblende-biotite granodiorite

Figure 7. Modal mineralogy of Cretaceous intrusive rocks in the 

study area. Specified fields according to Streckeisen (1976).

Quartz

Siderite

Calcite

Molybdenite

Arsenopyrite

Pyrite

Pyrrhotite

Sphalerite

Chalcopyrite

Tennantite

Tetrahedrite

Cubanite

Galena

Boulangerite

Figure 9. General paragenetic sequence for hypogene minerals in 

the Carrietown mineralized area, Idaho. Lines represent periods of 

deposition; time progressing to the right.

Figure 8. Schmidt equal-area lower hemisphere plot of poles to 

veins listed in table 2. Note average northeast trend of veins.

general paragenetic sequence for mineralization is illustrated in figure 9. This sequence is based on field observations and petrographic studies of 74 polished sections from 

deposits in the Carrietown area (Darling, 1987). Figure 9 

shows an early phase of iron and arsenic±molybdenum(?) 

metallization (pyrite, pyrrhotite, arsenopyrite, and molybdenite), followed by a middle phase of zinc and copper 

metallization (sphalerite and chalcopyrite) that overlapped 

with, and was superseded by, a late stage of copper, antimony, lead, and silver metallization (tetrahedrite, tennantite, galena, and boulangerite).

Many of the minerals listed in figure 9 are very coarse 

grained (1-2 cm) and are easily recognized in hand sample; 

however, cubanite, boulangerite, and tennantite are microscopic. Mineralogical and textural identifications of sulfide 

minerals in polished section were made according to Craig 

and Vaughan (1981), Picot and Johan (1982), and Ramdohr 

(1980). Common ore microtextures include (1) chalcopyrite 

blebs in sphalerite, (2) cubanite exsolution lamellae in chalcopyrite, (3) pyrite and arsenopyrite intergrowths, (4) combstructured quartz and siderite, (5) crustiform siderite, (6) 

deformed galena, (7) tetrahedrite inclusions in galena, and 

(8) spindle-shaped deformation twins in chalcopyrite.

Umpleby (1915) reported that galena and tetrahedrite 

are the principal silver-bearing phases in the Carrietown 

district. Tennantite and boulangerite, although volumetrically insignificant, could also be silver-bearing phases. The 

manner in which silver is present in galena is not known, 

but microscopic tetrahedrite inclusions are a probable 

source. Regardless of the source, the silver-bearing phases 

were deposited relatively late in the mineralization 

sequence (fig. 9).
PETROGENESIS OF SILVER-LEAD-ZINC VEINS Pll

Table 1. Recorded production from the Carrietown, northern Willow Creek, and eastern Little Smoky Creek 

mining districts, Idaho.

[Compiled from Ross (1930), Federspiel and others (1992), and unpublished files of the U.S. Bureau of Mines, Spokane, 

Washington. Ounces are troy ounces; NR indicates no record. Commodity prices used in calculations (Mineral Commodity 

Summaries, U.S. Bureau of Mines, 1990): gold, $385 per ounce; silver, $5.55 per ounce; copper, $1.32 per pound; lead, $0.40 

per pound; zinc, $0.83 per pound]

Gold (ounces) Silver (ounces) Copper (ounces) Lead (pounds) Zinc (pounds)

Carrietown mining district

Carrie Leonard

Margaret

Dollarhide

Isabella

Last Chance

Jane Lee

Silver Star

Silver Crown

Horn Silver

Fletcher

King of the West

Stormy Galore

Tyrannis

Alma

23

NR

0.28

10.4

NR

NR

118.92

0.62

21.92

NR

95.02

16.87

1.96

NR

869,000

NR

3,420

19,000

NR

NR

42,511

767.3

7,187

NR

108,263

55,450

32,486.1

NR

645

NR

0

600

NR

NR

600

0

984

NR

1,897

234

0

NR

989,000

NR

18,928

61,500

NR

NR

287,850

8,430

11,601

NR

364,048

51,995

472,456

NR

171,000

NR

0

31,000

NR

NR

12,587

0

5,721

NR

99,637

3,277

6,191

NR

Eastern Little Smoky Creek mining district

Red Star

Taft

Hidden Treasure

Smoky Bullion

Main Moly

Pine Creek

NR

0

1.2

8.15

NR

NR

NR

20

30

828

NR

NR

NR

0

7

148

NR

NR

NR

341

1,038

22,238

NR

NR

NR

0

0

0

NR

NR

Northern Willow Creek mining district

Buttercup

Unnamed mine

Total production

Dollar value

14.11

NR

312.45

$120,293

Total dollar value all commodities

57,731.1

NR

1,196,694

$6,641,652

$7,958,540

500

NR

5,615

$7,412

1,000,674

NR

2,289,425

$915,770

73,613

NR

329,413

$273,413

PETROGENESIS OF 

SILVER-LEAD-ZINC ORES

In recent years, much attention has been focused on 

stratiform, syngenetic ore deposits in Paleozoic rocks of the 

black shale belt of Idaho. Ore deposits of inferred syngenetic origin have been described in the Triumph mine (Triumph-Parker mineral belt, 40 km to the east) and in the 

Hoodoo and Livingston mines (Slate Creek district, 70 km 

to the north) (Hall, 1985; Turner and Otto, this volume). In 

the Carrietown mineralized area, however, the orebodies 

are interpreted to have an epigenetic origin. This interpretation is supported by the strong structural control of the 

deposits and the ubiquitous open-space-filling textures 

(crustiform and comb-structured quartz and siderite). Minor 

stratiform pyrrhotite and chalcopyrite in banded quartzite 

(unit 2) of the lower member of the Dollarhide Formation is 

the only syngenetic sulfide mineralization inferred.

LITHOLOGIC CONTROLS

The abundance of silver-lead-zinc sulfide minerals in 

veins is strongly controlled by lithology because the most 

productive veins are hosted by Paleozoic metasedimentary 

rocks rather than Cretaceous intrusive rocks. This lithologic 

control is best illustrated by quartz veins that can be traced 

from granodiorite into banded quartzite, where, after they 

enter the quartzite, the abundance of vein sulfide minerals 

increases (for example, Silver Crown and Last Chance 

mines). It is inferred that rocks of the Dollarhide Formation, 

which contain syngenetic pyrrhotite and carbonaceous material, provided a reducing environment for the deposition of 

metal-sulfide minerals, an environment not normally 

expected in the more oxidized (magnetite-bearing) Cretaceous intrusive rocks.

Gangue mineralogy is also strongly controlled by 

host-rock lithology. Deposits hosted by quartzite in the
Table 2. Summary of geological information on mines and prospects in the Carrietown mineralized area, Idaho. 

[Mines are shown by number in fig. 2. Minerals are listed in order of decreasing abundance]

Mine or prospect

1. Carrie Leonard

2. Margaret

3. Dollarhide

4. Isabella

5. Last Chance

6. Jane Lee

7. Silver Star

8. Silver Crown

Host rock

Lower member, Dollarhide Formation

Lower member, Dollarhide Formation

Lower member, Dollarhide Formation

Dollarhide Formation (foliated, banded

quartzite±phyllite)

Dollarhide Formation (foliated, banded

quartzite+phyllite)

Dollarhide Formation (foliated, banded

quartzite±phyllite)

Lower member, Dollarhide Formation;

Dollarhide Formation (foliated, banded

quartzite±phyllite)

Dollarhide Formation (foliated, banded

quartzite±phyllite); Cretaceous biotite

granodiorite

T-> 1.-A -C <- tt r A K A A

Vein attitudes

N. 40° E., 40° S.;

N. 55° E., 58° S.

Not available

N. 55° W., 60° S.;

N. 55° W., 70° N.

Not available

N. 85° E., 20° S.;

N. 75° E., 64° N.

Not available

N. 65° E., 43° S.;

N. 65° E., 80° S.

N.20°E., 81° S.

Ore minerals

Sphalerite, galena, pyrite

Pyrite, galena, sphalerite,

Sphalerite, galena, pyrite

Pyrite, sphalerite, pyrrhotite

Pyrite, chalcopyrite, arsenopyrite,

pyrrhotite, sphalerite, galena

Pyrite, chalcopyrite, arsenopyrite,

pyrrhotite, sphalerite, galena

Pyrite, sphalerite, galena, pyrrhotite,

chalcopyrite, arsenopyrite

Pyrite, sphalerite, galena, arsenopyrite,

molybdenite

. . .

Gangue minerals

Calcite, quartz

Quartz, calcite

Calcite, quartz

Quartz, siderite

Siderite, quartz

Siderite, quartz

Quartz, calcite, siderite

Quartz

Darl

Darl

Darl

Darl

Darl

Cam

Darl

Darl

10. Fletcher

11. King of the West

12. Stormy Galore

13. Tyrannis

14. Alma

15. Red Star

16. Taft

quartzite+phyllite); lower member, 

Dollarhide Formation

Dollarhide Formation (foliated, banded 

quartzite±phyllite)

Lower member, Dollarhide Formation

Dollarhide Formation (foliated, banded 

quartzite±phyllite)

Dollarhide Formation (foliated, banded 

quartzite±phyllite)

Dollarhide Formation (foliated, banded 

quartzite±phyllite)

Dollarhide Formation (foliated, banded 

quartzite+phyllite)

Dollarhide Formation (foliated, banded 

quartzite±phyllite)

N. 5° W., 42° E.; 

N. 10° E., 53° S.; 

N. 60° E., 79° S.; 

N. 55° E., 69° S.

N. 75° E., 84° S.; 

N. 85° W., 72° N.

N. 7° E., 60° S.

N. 60° E., 37° N. 

Not available 

Not available 

N. 75° E., 45° S.

arsenopyrite, chalcopyrite

Galena, sphalerite, pyrite, chalcopyrite, Quartz, siderite 

tetrahedrite, pyrrhotite

Sphalerite, galena, pyrite, tetrahedrite Quartz, calcite 

Tetrahedrite, galena, pyrite Quartz, siderite

Galena, pyrite, chalcopyrite, pyrrhotite, Quartz, siderite 

arsenopyrite

Galena, sphalerite, pyrite, pyrrhotite, Siderite, quartz 

tetrahedrite, arsenopyrite

Galena, sphalerite, pyrite, chalcopyrite, Quartz 

pyrrhotite

Galena, chalcopyrite, pyrite, Quartz 

chalcopyrite, pyrrhotite

Darl

Dar

Dar

Dar

Dar

Geh

Geh
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P13

S" 

g

O

«

/ N

cn

00

ON

^ 

fH

1

u

'J^

 s

3

o

a

1o u

0

3

I

3

1

*fl

§1 

^t

o &;

u*2

Ca

'"3

S"o

Z

T3

^ o

X) o"

S03

1

c

o

 3 ^

e^ qj i 3

£! 

|!

i!

i

Hidden Trea

t>

/ ^ CO

00

ON

^ ^

B

U

I

 g3

 S3

N

i

3

o

a

*

8

1

1 

f

§ a

T3 'S

|1

0)

^3

CO 1c^

o

Z

T3

1

1)

T3

.2

2

1 g ^^

P JJ3 £ 1

If

11

O

Smoky Bulli prospect

00

"

^*^

en

00

ON

^ ^

C

1

a

o

o

1

(J

a3

a

S"

'o 

"o

w"

alena, pyri

60

 a3

u

1! ^ § "5 2

« o

b

ON

QJ MJ

0

<o

Z

.a

§

60

.y

fc! 

O

0

1

CA

I

S

1

Mainoly i

o\

?*o

xi

3

C3

3

1

U

1

 s

fj 'i

^

a

es

1 

00

3

1 g.

EA

s

u

1

1"o

Z

 a

u

T3

 a" n

.2

1

c

o ^ ^

p '^1

p° ]§

If

11

Pine Creek

o

(N

e3

T3

r*\

aB

3

1

W

 ^H

0

1

N"

1

a

i

60

3

1

f

3

u*y^

rt

^

^

rt

 g

z

c

o

1

1<a

103

2r.

X>

1

I

C

mi Unnamed 

i_j

fN

B

ON

1

^V/ S

ON

^^

.S

1

a

1[a'S 

u"

'0

-3 

u

N"

i

3

a

3

1

J3

3

rf

160

1

 a a

CA

S

u*^

c^

^^.

03

3

T3

u

T3

J

1

.2

1

C

t o

03 (U

S ;rj

O >t

p

1!

Buttercup

(^

(N

Dollarhide Formation have a quartz-siderite gangue, 

whereas those hosted by carbonaceous marble have a 

quartz-calcite assemblage. The factor controlling gangue 

mineralogy is interpreted to be the Fe2+/Ca2+ ratio of oreforming fluids in equilibrium with their host rock. This 

control is explained by the reaction

FeC0 + Ca2 CaCO + Fe2 + 

(aq) (1)

where high Fe2+/Ca2+ favors formation of siderite and low 

Fe2+/Ca2+ favors formation of calcite. Because siderite is the 

principal carbonate phase in ores hosted by banded quartzite, 

ore-forming fluids had relatively high Fe2+/Ca2+ ratios, 

whereas fluids precipitating calcite-rich veins in the carbonaceous marbles had relatively low Fe2+/Ca2+ ratios. Ferrousiron-bearing phases (pyrite, sphalerite) are common in veins 

from both types of host rocks; however, calcium-bearing 

phases are absent in veins hosted by banded quartzite. Therefore, the Fe2+ content of ore-forming fluids could have 

remained constant while the Ca2+ content varied as fluids 

interacted with host rocks containing different amounts of 

calcium (high Ca2+ marble versus low Ca2+ quartzite).

STRUCTURAL CONTROLS

The average northeast trend of the veins (fig. 8) suggests 

that the veins formed in regional northeast-striking shear 

zones in central Idaho. The age of these structures has been 

a matter of debate. Although many Eocene shear zones 

related to the Trans-Challis fault system strike northeast 

(Bennett, 1986; Kiilsgaard and others, 1986), northeast-striking Cretaceous shear zones have been documented regionally. Lund and others (1986, p. 995) indicated that northeaststriking fractures in the Buffalo Hump district, 50 km east of 

Riggins, Idaho, host Cretaceous lode deposits in the Idaho 

batholith and were formed during a regional extension event 

about 71 Ma. Gammons and others (1985) documented similar Cretaceous structures in the Big Creek district, 80 km 

southeast of Riggins, Idaho. In both the Big Creek and Buffalo Hump districts, as in the Carrietown area, mineral deposits are concentrated in roof pendants in the batholith.

A regional network of Cretaceous northeast-striking 

faults and shear zones are in the Smoky Mountains (Park, 

in press), some of which are manifest in bedding-parallel 

faults in the Dollarhide Formation. At least some silverlead-zinc deposits in the Carrietown area (for example, Silver Star and Fletcher mines) are interpreted to have formed 

in bedding-parallel faults because the veins are parallel 

with the bedding of their host rocks. In the Last Chance 

mine (fig. 3), the orebody formed where the fault plane was 

locally flattened from an otherwise uniform steep dip. The 

Carrie Leonard orebody (fig. 3) formed at the intersection 

of two northeast-striking faults.
P14 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

In previous work, Darling (1987, 1988) suggested that 

the abundance of mineral deposits along the contact between 

banded quartzite and carbonaceous marble was caused by 

ore fluids migrating along the thrust fault that separated the 

two units. Although the concept of a regional thrust fault has 

been disproven, differences in rheological behavior between 

quartzite and marble during Mesozoic folding may have 

caused development of open fissures for the movement of 

ore fluids, as suggested by Whitman (1990, this volume).

THERMAL CONDITIONS OF 

MINERALIZATION

SULFUR-ISOTOPE GEOTHERMOMETRY

Howe and Hall (1985), in an isotopic study of the blackshale belt, performed nine sulfur-isotope analyses in the Carrietown area, four of which were used to calculate temperatures of ore formation by sulfur-isotope fractionation 

methods (Ohmoto and Rye, 1979). The analyses yielded 

temperatures of 269±45°C on a sphalerite-galena pair from 

the Carrie Leonard mine and 375±45°C on a pyrite-galena 

pair from an unnamed dump (Howe and Hall, 1985, p. 192). 

In polished section, both sulfide pairs commonly exhibit 

mutual grain boundaries, suggesting that isotopic equilibrium was obtained and that the calculated temperatures are 

reliable; however, because galena is paragenetically later 

than pyrite and sphalerite (fig. 9), the temperatures may only 

reflect isotopic equilibrium during deposition of galena.

CUBANITE EXSOLUTION GEOTHERMOMETRY

A minimum temperature of ore formation of 

250°C-300°C is indicated by cubanite exsolution lamellae in 

chalcopyrite (Ramdohr, 1980, p. 639). Cubanite exsolution 

lamellae are almost ubiquitous in chalcopyrite from mines 

near Carrietown, but, because they can only be observed 

under the microscope, their presence was not established in 

chalcopyrite from mines along Little Smoky Creek and from 

the Buttercup mine.

outlined in Kretschmer and Scott (1976). Arsenopyrite 

from the Alma and Tyrannis mines contain 31.55±0.45 and 

32.68±0.45 mole percent arsenic, amounts yielding temperatures of ore formation of 394°C±25°C, and 465°C±30°C, 

respectively. The temperatures were estimated by the intersection of the pyrite-pyrrhotite univariant and the atomic 

percent arsenic isopleths in figure 7 of Kretschmer and 

Scott (1976). Both ore samples from the Alma and Tyrannis mines contained the necessary 82 buffering assemblage 

of pyrite-pyrrhotite required for use of the arsenopyrite 

geothermometer (Kretschmer and Scott, 1976).

A summary of all available thermal information from 

the Carrietown mineralized area is listed in table 3. Thermal 

constraints imposed by fixed-point geothermometers agree 

well with temperatures calculated from sulfur isotopes and 

arsenopyrite and are consistent with a mesothermal to hypothermal (250°C^50°C) environment. Thermal data collected from ore deposits in the Carrietown mineralized area 

are generally consistent with those for similar deposits in the 

Wood River district, 30 km to the east (Hall and Czamanske, 

1972; Hall and others, 1978).

OXYGEN AND SULFUR FUGACITIES 

OF ORE FLUIDS

Estimation of C>2 and 82 fugacity in ore-forming fluids 

of the Carrietown area is illustrated in figure 10. Stability 

fields for pyrite, pyrrhotite, magnetite, and hematite were 

calculated at 350°C (average ore-forming temperature) by 

use of thermodynamic data of Robie and others (1978) and 

methods outlined in Garrels and Christ (1965) and Nordstrom and Munoz (1985). Because ores hosted by banded 

quartzite commonly contain pyrite and pyrrhotite, ore-forming fluids have sulfur fugacities in the lO^-lO"9 bar range 

at 350°C, whereas ore hosted by carbonaceous marble 

(pyrite, without pyrrhotite) has higher sulfur fugacities 

(about lO^-lO"4 bars). The lack of iron oxide minerals 

(magnetite, hematite) in samples from any mine in the area 

indicates low oxygen fugacities (about 10~35 bars), reflective 

of strongly reducing conditions.

ARSENOPYRITE GEOTHERMOMETRY

Clark (1960) showed that the equilibrium assemblage 

of pyrite and arsenopyrite melts to form pyrrhotite and liquid from 491°C±12°C (at 1 bar) to as much as 528°C±10°C 

(at 2,070 bars). Thus, the pyrite-arsenopyrite intergrowths 

at many of the mines establish a thermal maximum at 

491 °C-528°C (if PT < 2,070 bars). Furthermore, two arsenopyrite separates from the Alma and Tyrannis Mines were 

X-rayed to determine their atomic percent arsenic content 

by measurement of the ^-spacing of the (131) plane. The 

samples were prepared and analyzed according to methods

SOURCE OF SULFUR AND LEAD

In their isotopic study of the black shale belt, Howe and 

Hall (1985) performed nine sulfur-isotope analyses from 

four mines in the Carrietown district. The mines and sulfides 

analyzed from them include (1) the Carrie Leonard mine, 

galena and sphalerite; (2) the Horn Silver mine, galena and 

pyrite; (3) the Upper prospect, galena, molybdenite and 

sphalerite; and (4) an unnamed dump, galena and pyrite. As 

previously discussed, analyses from the Carrie Leonard mine 

and the unnamed dump were used to calculate sulfur-isotope 

fractionation temperatures. The location of the unnamed
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P15

dump is not known, but the Upper prospect described by 

Howe and Hall (1985) is most likely the Silver Crown mine 

because it is the only location in the Carrietown district that 

has a sphalerite+galena+molybdenite sulfide assemblage. 

834S values for the analyzed sulfides range from -0.1 to +6.2 

per mil (Howe and Hall, 1985, p. 192). These isotope values 

are depleted in 34S with respect to Pennsylvanian-Permian 

seawater (that is, Dollarhide Formation) and indicate a more 

depleted source of sulfur for ore deposits in the Carrietown 

district. Howe and Hall (1985) indicated that ore deposits 

having this isotopic signature suggest isotopic mixing 

between enriched sedimentary sulfur and strongly depleted 

magmatic sulfur.

Sanford and Wooden (this volume), as part of an isotopic study of the black shale belt, performed lead-isotope 

analyses on 10 samples from various mines in the 

Carrietown area (specific mines unknown). The samples 

included galena from both vein-type and bedding-conformable deposits in the Dollarhide Formation. The galena separates yielded 206Pb/204Pb ratios of 18.0-19.2 and 208Pb/ 

204Pb ratios of 39.5^0.0. These Pb/Pb ratios are not consistent with a Paleozoic argillite source and, if combined with 

other lead-isotopic data from similar silver-lead-zinc deposits in central Idaho (Carrietown, Lava Creek, and Minnie 

Moore lead types), yield a calculated model age of 

2,400±100 Ma. These data indicate that the source of lead in 

ore deposits from the above mines is not the Dollarhide Formation but rather upper crustal Precambrian basement rocks 

(Sanford and Wooden, this volume). Furthermore, because 

epigenetic and bedding-conformable galena have almost 

identical isotopic ratios, Sanford and Wooden (this volume) 

also infer that bedding-conformable galena has an epigenetic 

rather than syngenetic origin.

The sulfur- and lead-isotope data suggest that magmas 

were generated in the lower crust and, as they ascended, 

transported their inherited (Precambrian) lead and depleted 

magmatic sulfur. The magma crystallized, differentiated, 

and may have generated late-stage magmatic (metal-bearing) hydrothermal fluids that circulated through the Dollarhide Formation scavenging enriched sedimentary sulfur. The

-20

-40

-20 -15 -10

LOG f S2

EXPLANATION 

Banded quartzite 

Carbonaceous marble

Figure 10. Log ./O2-log f§2 diagram illustrating volatile 

fugacity of ore-forming fluids between banded quartzite and 

carbonaceous marble of the Dollarhide Formation, Carrietown mineralized area, Idaho.

resulting hydrothermal fluid precipitated sulfide phases having Precambrian lead-isotopic and mixed (igneous+sedimentary) sulfur-isotopic signatures.

AGE OF MINERALIZATION

Because the ore deposits of the Carrietown mineralized area have an epigenetic origin and are partly hosted by 

granodiorite at the Silver Crown mine (Darling, 1987) and 

granite at the Main Moly prospect (Gehlen, 1983), the 

deposits are not older than Late Cretaceous. Furthermore,

Table 3. Summary of available thermal data from mines in the Carrietown mineralized area, Idaho.

Mine name

Mines near Carrietown

Carrie Leonard mine

Unnamed dump

Alma mine

Tyrannis mine

Mines near Carrietown

Method

Cubanite exsolution thermometer

Sulfur-isotope thermometer

Sulfur-isotope thermometer

Arsenopyrite thermometer

Arsenopyrite thermometer

Pyrite-arsenopyrite thermometer

Notes

Thermal minimum

Sphalerite-galena pair

Pyrite-galena pair

rf-spacing of FeAsS (131) plane

rf-spacing of FeAsS (131) plane

Thermal maximum

Estimated 

temperature

250°C-300°C

269°C±45°C

375°C±45°C

394°C±25°C

465°C±30°C

491°C-528°C

Source

Darling (1987, 1988).

Howe and Hall (1985).

Howe and Hall (1985).

This report.

This report.

Darling (1987, 1988).
P16 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

the principal mineralized structure in the Dollarhide mine is 

cut by a dacite porphyry dike (Umpleby, 1915; Darling, 

1987), indicating the deposits are no younger than Eocene 

(47.2 Ma). Because the ore deposits formed at elevated 

temperatures (250°C-450°C), mineralization is interpreted 

to be temporally related to either Cretaceous or Eocene 

intrusive activity.

The thermal data and field relations previously discussed suggest a Cretaceous age of mineralization. Ore 

deposits in the Dollarhide, Silver Star, Stormy Galore, King 

of the West, and Buttercup mines are less than 150 m vertically below the unconformable contact between the hosting 

Dollarhide Formation and overlying Eocene Challis Volcanic Group (figs. 2-4, 6). The ore-forming event is inferred to 

be prevolcanic because the volcanic rocks (which are highly 

susceptible to alteration) lack hydrothermal alteration 

(Gehlen, 1983) and do not host sulfide mineral deposits. An 

Eocene, prevolcanic ore-forming event would, therefore, 

require a very shallow depth, an environment that conflicts 

with observed mesothermal to hypothermal mineral assemblages and the thermal minimum of 250°C-300°C.

Silver-lead-zinc deposits hosted by the Dollarhide Formation lack extensive hydrothermal alteration and therefore 

are without suitable material for radiometric dating by K-Ar 

or Ar-Ar methods. The lack of alteration in the Dollarhide 

Formation is probably a result of its composition. The 

banded quartzite and marble contain few, if any, feldspar or 

iron-magnesium silicate minerals, phases typically susceptible to hydrothermal alteration. Similar silver-lead-zinc 

deposits hosted by granodiorite at the Ontario mine in the 

Rooks Creek mineralized area, 18 km to the northeast, have 

been dated, however, at 91.09±0.25 Ma by Ar-Ar methods 

on hydrothermal muscovite (Park, 1990, in press).

At the Main Moly prospect in the Little Smoky Creek 

district (fig. 4), muscovite in Cretaceous leucocratic granite 

is dated at 77.4±2.6 Ma (M. Tschanz, 1982, unpublished 

report; cited in Gehlen, 1983). This date was cited by Darling (1987) as the age of the leucocratic granite; however, 

we now infer that muscovite in this rock is hydrothermal in 

origin because (1) it is present as patchy masses spatially 

associated with quartz-molybdenite veins, (2) it lacks the 

primary igneous texture (books and laminated flakes) typical of two-mica granite in the core of the Idaho batholith 

(Kiilsgaard and Lewis, 1985), and (3) an igneous origin 

requires a minimum magmatic pressure of 3.7±0.2 kb, a 

pressure higher than the 2.5-3.5-kb range inferred from 

metamorphic mineral assemblages (Whitman, 1990, this 

volume). The 3.7±0.2-kb minimum is derived from the 

intersection of the upper stability curve of muscovite+quartz (Chatterjee and Johannes, 1974) and the minimum granite (Ab+Or+Qtz+H2O) melting temperature 

(Tuttle and Bowen, 1958). For these textural and petrologic 

reasons, the K-Ar date of 77.4±2.6 Ma is inferred to reflect 

the age of quartz-molybdenite mineralization in the Dollarhide Mountain quadrangle. This date and the 91.09-Ma date

for hydrothermal muscovite in the Rooks Creek district 

indicate that active ore-forming fluids were present during 

the Late Cretaceous but suggest that silver-lead-zinc mineralization is temporally related to the older granodiorite 

phases of the Idaho batholith, and molybdenum mineralization is related to the younger leucocratic granite.

PROPOSED PRESSURETEMPERATURE-TIME PATH

A proposed pressure-temperature-time path from the 

Late Cretaceous to the Eocene is illustrated in figure 11. 

Rocks in the Carrietown mineralized area underwent 

regional heating from intrusion of Cretaceous plutons and 

contact metamorphism (-84 Ma) at 500°C-600°C and 

2.5-3.5 kb (Whitman, 1990, this volume). Ore deposits are 

interpreted to have formed soon after metamorphism 

(-75-80 Ma) and probably with little change in crustal level 

(inferred isobaric cooling). Subsequent uplift and erosion 

resulting in exposure of the Dollarhide Formation and Cretaceous intrusive rocks at the surface during Eocene tune (-47 

Ma) is indicated by the unconformable contact between the 

Challis Volcanic Group and both these units. The convexupward pressure-temperature-time path illustrated in figure 

11 is typical for magmatic-hydrothermal ore deposits.

GENERAL MODEL AND COMPARISON

TO OTHER SILVER-LEAD-ZINC

DEPOSITS IN THE BLACK SHALE

BELT OF IDAHO

Our work suggests that the important controls on formation of mineral deposits in the Carrietown area are (1) 

presence of Fe2+- and carbon-bearing roof pendants to 

change fluid chemistry from relatively oxidizing to reducing; (2) proximity to the top of the batholith, perhaps on a 

cupola containing metal-enriched fluids from the last stages 

of magmatic crystallization; and (3) open structures for fluid 

migration and ore deposition.

Geologic conditions thought to be common to all silverlead-zinc vein deposits in the central Idaho black shale mineral belt were discussed by Hall (1985, p. 127). These conditions, as we now understand them, are discussed as they 

relate to ore deposits in the Carrietown area.

Host rocks. Host rocks for mineral deposits in the 

Smoky Mountains were generally described as "blackshales" by Hall (1985). The term black shale is a misnomer 

in the Carrietown area because banded quartzite, carbonaceous marble, and phyllite of the lower member of the Dollarhide Formation are the principal host rocks. Only the 

phyllite could have originated as a black shale. More than half 

the deposits are hosted by banded quartzite, which clearly 

lacks compositional or textural similarities to black shale.
PETROGENESIS OF SILVER-LEAD-ZINC VEINS P17

5 

4 

Ore-forming 

conditions 

-75-80 Ma)

Inferred 

isobaric 

cooling

o 3 -

Peak M2 

metamorphism 

(-84 Ma)

2 

100 200 300 400 500 600 

TEMPERATURE, IN °C

700 800

Figure 11. Proposed pressure-temperature-time path for rocks in 

the Carrietown mineralized area, Idaho. Vertical solid heavy lines 

are arsenopyrite temperatures; vertical dashed heavy lines are sulfur-isotope temperatures; vertical thin line is cubanite thermal minimum; inclined solid-dashed line is pyrite-arsenopyrite thermal 

maximum. Square box indicates metamorphic conditions (Whitman, 

this volume); rectangular box indicates inferred ore-forming conditions. Very heavy line represents inferred pressure-temperature time 

path from plutonism, metamorphism, and sulfide mineralization 

during the Late Cretaceous to volcanism of the Challis Volcanic 

Group and associated hypabyssal plutons during the middle Eocene.

Relationship of mineralization to regional thrust 

faults. Hall and others (1978) and Hall (1985) developed a 

model in which mineralized veins are under but close to 

regional thrust faults, citing the Triumph mine southeast of 

Ketchum as an example. As discussed earlier in this paper, 

the interpretation of a regionally extensive thrust fault separating the Dollarhide Formation from the "Carrietown 

sequence" has been abandoned and with it the inference that 

the thrust fault acted as a principal pathway for hypogene ore 

fluids (Darling, 1987, 1988). Furthermore, Hall's mapping 

of a regional Wood River thrust fault in the area of the Triumph Mine, south of Ketchum, has been reinterpreted (Link 

and others, this volume; Turner and Otto, this volume). The 

permeability barrier in the Triumph area is the sheared 

unconformity between the Devonian Milligen Formation 

and the overlying Middle Pennsylvanian and Lower Permian 

Wood River Formation.

Relationship of mineralization to granitic intrusive 

rocks. The general model of Hall (1985) states that mineralized veins are close to contacts of granitic intrusive rocks, 

predominantly of Cretaceous age but also of Eocene age. 

Our findings in the Carrietown area suggest that only the 

Cretaceous intrusive rocks directly influenced formation of 

mineral deposits. Eocene mineralization is unlikely.

Characteristics of gangue minerals. The general 

model of Hall (1985) states that the most productive deposits 

have siderite-quartz gangue rather than calcite-quartz 

gangue. This is true in the Carrietown mineralized area. In all

three districts of the area, ore grades of deposits having 

quartz-calcite gangue are generally lower than those of 

deposits having quartz-siderite gangue. For example, ore in 

the Carrie Leonard and King of the West mines (quartz-calcite gangue) averaged 150 and 120 ounces of silver per ton, 

respectively, whereas ore in the Stormy Galore and Isabella 

mines averaged 400 ounces of silver per ton (Umpleby, 

1915). Furthermore, geochemical studies of both host rocks 

(Darling, 1987) indicate that banded quartzite (veins with 

siderite-quartz gangue) has higher overall trace-metal contents than does calcareous marble (veins with calcite-quartz 

gangue), and future exploration in the district should 'focus 

on locating deposits in banded quartzite.

REFERENCES CITED

Bennett, E.H., 1986, Relationship of the trans-Challis fault system 

in central Idaho to Eocene and Basin and Range extensions: 

Geology, v. 14, p. 481^84.

Chatterjee, N.D., and Johannes, W., 1974, Thermal stability and 

standard thermodynamic properties of synthetic 2Mi-muscovite, KAl2[AlSi3Oio(OH)2]: Contributions to Mineralogy and 

Petrology, v. 48, p. 89-114.

Clark, L.A., 1960, The Fe-As-S system Phase relations and applications: Economic Geology, v. 55, p. 1345-1381,1631-1652.

Craig, J.R., and Vaughan, D.J., 1981, Ore microscopy and ore 

petrography: New York, John Wiley and Sons, 406 p.

Darling, R.S., 1987, The geology and ore deposits of the Carrietown silver-lead-zinc district, Blaine and Camas Counties, 

Idaho: Pocatello, Idaho State University, M.S. thesis, 168 p.

 1988, Ore deposits of the Carrietown silver-lead-zinc district, Blaine and Camas Counties, Idaho, in Link, P.K., and 

Hackett, W.R., eds., Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 

193-198.

 1989, Geologic map and cross-sections of the northern half

of the Dollarhide Mountain quadrangle: Idaho Geological Survey Technical Report 89-1,1 plate.

Federspiel, F.E., Gabby, P.N., Neumann, T.N., and Leszcykowski, 

A.M., 1987, Mineral resources of the South Boise Yuba Study 

Area and additions, Blaine, Camas, and Elmore Counties, Idaho: U.S. Bureau of Mines Open-File Report MLA 64-87,117 p.

Federspiel, F.E., Horn, M.E., Campbell, H.W., and Peters, T.J., 

1992, Mineral resource investigation of the Smokies Study 

Area, Blaine, Camas, and Elmore Counties, Idaho: U.S. 

Bureau of Mines Open-File Report MLA 4-92, 244 p.

Gammons, C.H., Rose, A.W., Snee, L.W., and Lund, K., 1985, 

Paragenesis, fluid inclusions, and Ar-dating of the Big Creek 

mining district, Valley County, central Idaho: Geological Society of America Abstracts with Programs, v. 17, p. 588.

Garrels, R.M., and Christ, C.L., 1965, Solutions, minerals and equilibria: New York, Harper and Row, 380 p.

Gehlen, W.T., 1983, The geology and mineralization of the eastern 

part of the Little Smoky Creek mining district, Camas County, 

Idaho: Moscow, University of Idaho, M.S. thesis, 116 p.

Geslin, J.K., 1986, The Permian Dollarhide Formation and Paleozoic Carrietown sequence in the SWV4 of the Buttercup
P18 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Mountain quadrangle, Blaine and Camas Counties, Idaho: 

Pocatello, Idaho State University, M.S. thesis, 1 16 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis I°x2° quadrangle, Idaho: 

U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hall, W.E., and Czamanske, O.K., 1972, Mineralogy and trace element content of the Wood River lead-silver deposits, Blaine 

County, Idaho: Economic Geology, v. 67, p. 350-361.

Hall, W.E., Rye, R.O., and Doe, B.R., 1978, Wood River mining 

district, Idaho Intrusion-related lead-silver deposits from a 

country rock source: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 579-592.

Howe, S.S., and Hall, W.E., 1985, Light-stable isotope characteristics of ore-systems in central Idaho, in Mclntyre, D.H., ed., 

Symposium on the geology and mineral deposits of the Challis 

I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 

1658-P, p. 183-192.

Kiilsgaard, T.H., Fisher, F.S., and Bennett, E.H., 1986, The transChallis fault system and associated precious metal deposits, 

Idaho: Economic Geology, v. 81, p. 721-724.

Kiilsgaard, T.H., and Lewis, R.S., 1985, Plutonic rocks of Cretaceous age and faults in the Atlanta lobe of the Idaho batholith, 

Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the 

geology and mineral deposits of the Challis 1 °x2° quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-B, p. 29^2.

Kretschmer, U., and Scott, S.D., 1976, Phase relations involving 

arsenopyrite in the system Fe-As-S and their application: 

Canadian Mineralogist, v. 14, p. 364-386.

Lewis, R.S., in press, Alteration and mineralization in the eastern 

part of the Soldier Mountains, Camas County, Idaho: U.S. 

Geological Survey Bulletin 2064-V.

Link, P.K., Skipp, Betty, Hait, M.H.Jr., Janecke, Susanne, and Burton, B.R., 1988, Structural and stratigraphic transect of southcentral Idaho A field guide to the Lost River, White Knob, 

Pioneer, Boulder and Smoky Mountains, in Link, P.K., and 

Hackett, W.R., eds., Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 5-42.

Lund, K., Snee, L.W., and Evans, K.V., 1986, Age and genesis of 

precious metals deposits, Buffalo Hump district, central Idaho Implications for depth of emplacement of quartz veins: 

Economic Geology, v. 81, p. 990-996.

Mahoney, J.B., Link, P.K., Burton, B. R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvanian and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J., and 

Stevens, C., eds., Paleozoic paleogeography of the Western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-580.

Marvin, R.F., and Dobson, S.W., 1979, Radiometric ages Compilation B, U.S. Geological Survey: Isochron West, no. 26, p. 17.

Mclntyre, D.H., Ekren, E.B., and Hardyman, R.F., 1982, Stratigraphic and structural relations of the Challis volcanics in the 

eastern half of the Challis 1 °x2° quadrangle, in Bonnichsen, 

Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: 

Idaho Bureau of Mines and Geology Bulletin 26, p. 3-22.

Moye, F.J., Hackett, W.R., Blakely, J.D., Snider, L.G., 1988, 

Regional geologic setting and volcanic stratigraphy of the 

Challis volcanic field, central Idaho, in Link, P.K., and Hackett, W.R., eds., Guidebook to the geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 87-98.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-EE.

Nordstrom, D.K., and Munoz, J.L., 1985, Geochemical thermodynamics: Menlo Park, Calif., Benjamin/Cummings, 477 p.

O'Brien, J.P., 1991, Stratigraphy of the Pennsylvanian-Permian 

Dollarhide Formation in the Buttercup Mountain quadrangle, 

Blaine and Camas Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 163 p.

Ohmoto, Hiroshi, and Rye, R.O., 1979, Isotopes of sulfur and carbon, in Barnes, H.L., ed., Geochemistry of hydrothermal ore 

deposits (2nd ed.): New York, Wiley-Interscience, p. 509-567.

Park, W.A., 1990, The geology and ore deposits of the Rooks Creek 

stock, Blaine County, Idaho: Pocatello, Idaho State University, 

M.S. thesis, 135 p.

Park, W.A., in press, The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-CC.

Picot, P., and Johan, Z., 1982, Atlas of ore minerals: Amsterdam, 

Netherlands, Elsevier, 458 p.

Ramdohr, P., 1980, The ore minerals and their intergrowths (2nd 

ed.): Oxford, England, Pergamon, 1,207 p.

Robie, R.A., Hemingway, B.R., and Fisher, J.R., 1978, Thermodynamic properties of minerals and related substances at 298.15 

K and 1 bar (105 pascals) pressure and at higher temperatures: 

U.S. Geological Survey Bulletin 1452, 456 p.

Ross, C.P., 1930, Geology and ore deposits of the Seafoam, Alder 

Creek, Little Smoky Creek, and Willow Creek mining districts, 

Custer and Camas Counties, Idaho: Idaho Bureau of Mines and 

Geology Pamphlet 33, p. 7-18.

Skipp, B., and Hall, W.E., 1980, Upper Paleozoic paleotectonics 

and paleogeography of Idaho, in Fouch, T.D., and Magathan, 

E.R., eds., Paleogeography of the West-Central United States: 

Rocky Mountain Section, Society of Economic Geologists 

and Mineralogists, West-Central Paleogeography Symposium 

1, p. 387-422.

Stewart, D.E., Schmidt, K.L, Moye, F.J., Mahoney, J.B., and Link, 

P.K., in press, Eocene intrusive complexes in the Smoky and 

Boulder Mountains, south-central Idaho: U.S. Geological Survey Bulletin 2064-HH.

Streckeisen, A., 1976, To each plutonic rock its proper name: Earth 

Science Reviews, v. 12. p. 1-33.

Turtle, O.F., and Bowen, N.L., 1958, Origin of granite in the light 

of experimental studies in the system NaAlSi3Og-KAlSi3OgSiO2~H2O: Geological Society of America Memoir 74, 153 p.

U.S. Bureau of Mines, 1990, Mineral commodity summaries: 201 p.

Umpleby, J.B., 1915, Ore deposits in the Sawtooth quadrangle, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 580-K, p. 221-249.

Wavra, C.S., 1985, Structural geology and petrology of the SWVi of 

the Mahoney Butte quadrangle, Blaine County, Idaho: Moscow, University of Idaho, M.S. thesis, 103 p.

Wavra, C.S., Issacson, P.E., and Hall, W.E., 1986, Studies of the 

Idaho black shale belt Stratigraphy, depositional environment and economic geology of the Permian Dollarhide Formation: Geological Society of America Bulletin, v. 97, p. 

1504-1511.

Whitman, S.K., 1990, Metamorphic petrology and structural geology of the Pennsylvanian-Permian Dollarhide Formation, 

Blaine and Camas Counties, south-central Idaho: Pocatello, 

Idaho State University, M.S. thesis, 108 p.
Metamorphism and Deformation on the Eastern Margin 

of the Idaho Batholith, Blaine and Camas Counties, 

South-Central Idaho

By Shelly K. Whitman

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-Q

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Ql

Introduction........................................................................................................................... 1

Regional Setting.................................................................................................................... 3

Pennsylvanian and Permian Strata of the Dollarhide Formation.................................. 3

Cretaceous Idaho Batholith and Metamorphic Aureole................................................ 3

Eocene Volcanic Rocks................................................................................................. 4

Metamorphic Petrology......................................................................................................... 4

Metamorphic Conditions............................................................................................... 4

Description of Metamorphic Features........................................................................... 6

Structural Geology of the Dollarhide Formation Adjacent to the Idaho Batholith............... 7

Timing of Metamorphism and Deformation......................................................................... 8

Regional Implications............................................................................................................ 10

Mesozoic Deformation.................................................................................................. 10

Relation to Mineralization............................................................................................. 10

Summary............................................................................................................................... 11

References Cited.................................................................................................................... 11

FIGURES

1. Map showing geology of eastern margin of Idaho batholith and adjacent Dollarhide Formation,

Buttercup Mountain and Dollarhide Mountain quadrangles ......................................................................................... Q2

2. Pressure-temperature-partial pressure (CO2) diagram for metamorphic aureole of Dollarhide Formation.................. 4

3. Diagram showing mineral assemblage and structural elements in protoliths of pelite and limestone.......................... 6

4. Equal-area Pi diagrams for various domains in study area............................................................................................ 9

5. Diagram showing increase in strain for Dollarhide Formation during metamorphism................................................. 10

TABLE

1. Temperature and pressure of M2 metamorphism in the Dollarhide Formation............................................................. Q5
Metamorphism and Deformation on the

Eastern Margin of the Idaho Batholith,

Blaine and Camas Counties, South-Central Idaho

By Shelly K. Whitman1

ABSTRACT

Rocks of the Middle Pennsylvanian to Lower Permian 

Dollarhide Formation that crop out on the southeastern edge 

of the Cretaceous Idaho batholith, south-central Idaho, have 

undergone two Late Cretaceous pulses of heating and strain 

related to intrusion of the batholith. During the first metamorphic event (Mj), andalusite, tremolite, diopside, and 

staurolite porphyroblasts formed pre- or syn-kinematically 

in the Dollarhide Formation along with a poorly developed 

biotite foliation (Si). Retrogression after MI resulted in formation of elliptical mica spots and poikiloblastic porphyroblasts and pseudomorphs of quartz and potassium feldspar 

after andalusite and staurolite.

Features of a second metamorphic event (M2) overprint the earlier MI prograde and retrograde features. During the M2 event, porphyroblasts of sillimanite, staurolite, 

andalusite, tremolite, diopside, and wollastonite formed 

pre- or syn-kinematically along with a well-developed penetrative biotite foliation (82). These parageneses constrain 

the temperature of M2 metamorphism to 525CC-600°C, the 

pressure to 2.5-3.5 kb, and the fluid composition to 

PcO2<0-18. Whole-rock K-Ar analysis of schist containing 

well-preserved M2 minerals yields an age of 83.9±3.4 Ma 

(R.L. Armstrong, written commun., 1990), interpreted to be 

the minimum age of the M2 metamorphic event. This age, 

and the synkinematic nature of the porphyroblasts, indicates that both metamorphism and deformation are Late 

Cretaceous in age.

Emplacement of the batholith caused strain in the surrounding Dollarhide Formation. Deformation manifested by 

map-scale folds began before peak metamorphism (M2) and 

continued after late-stage Cretaceous leucocratic dike 

emplacement, although most folding probably occurred during development of 82 foliation. Fold hinges and mineral, 

boudin, and intersection lineations are all parallel and have 

an average orientation of 45°, N. 70° E., perpendicular to the 

south-southeast trend of fold hinges measured throughout

'Matney Frantz Engineering, Bozeman, Montana 59771.

south-central Idaho. The unusual orientation of fold axes in 

the study area is thought to be due to high shear strain in 

rocks along the margin of the batholith. Prolonged strain in 

the margin area could have caused the rotation of fold axes 

to their present east-northeast direction.

A previously mapped regionally extensive thrust fault 

separating the Paleozoic so-called Carrietown sequence from 

the overlying Pennsylvanian and Permian Dollarhide Formation has been reinterpreted as a stratigraphic contact between 

phyllitic quartzite and siliceous marble. Both rock types are 

now included in the Dollarhide Formation; the name Carrietown sequence was previously abandoned. Mineralized 

shear zones along the contact most likely formed due to rheologic differences between quartzite and marble during deformation and are not the result of regional thrusting.

INTRODUCTION

The study area discussed herein is in the Smoky Mountains along the southeastern edge of the Atlanta lobe of the 

Idaho batholith in Blaine and Camas Counties, south-central 

Idaho (fig. 1). The Middle Pennsylvanian to Lower Permian 

Dollarhide Formation in this area is part of the central Idaho 

black shale mineral belt, a northwest-trending belt 145 km 

long and 15^5 km wide composed of black shale, argillite, 

and carbonate rocks that crop out on the eastern side of the 

Idaho batholith from the Salmon River in the south-central 

Challis I cx2° quadrangle south to Bellevue in the Hailey 

I°x2° quadrangle (Hall, 1985) (fig. 1). Mineral deposits 

hosted by sedimentary rocks in the black shale belt include 

syngenetic and epigenetic silver-lead-zinc deposits, as well 

as tungsten skarn deposits (Hall, 1985; Darling and others, 

this volume; Link and others, this volume; Park, in press).

Umpleby (1915) and Ross (1930) were the first to map 

and study the mineral deposits of the Smoky Mountains. The 

contact between Cretaceous batholith and Paleozoic sedimentary rocks in the Buttercup Mountain and Dollarhide 

Mountain 7.5-minute quadrangles was mapped in detail by 

Hall (1985), who delineated and named the Dollarhide Formation, which had previously been included in the Wood

Ql
Q2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

114°45' 114°37'30"

43°15'

INDEX TO 7.5-MINUTE QUADRANGLES CONTOUR INTERVAL 40 METERS

EXPLANATION

Pdu-

-PPdlChallis Volcanic Group (Eocene) Mainly dacite and 

andesite flow rocks

Dacite porphyry (Eocene) Hypabyssal intrusive rock 

Dacite porphyry dike (Eocene)

Biotite granodiorite (Cretaceous) Includes 

leucogranite and quartz diorite

Hornblende-biotite granodiorite (Cretaceous)

Upper member of the Dollarhide Formation (Lower 

Permian)

Middle member of the Dollarhide Formation (Lower 

Permian)

Lower member of the Dollarhide Formation (Lower 

Permian to Middle Pennsylvanian)

Contact

Area of strong metamorphic overprint

Strike and dip

Strike and dip where top of bed is known

Overturned bedding and dip

Vertical bedding

Normal fault Bar and ball on downthrown side; dashed 

where approximately located; dotted where concealed

Anticline Showing direction of plunge 

Overturned anticline Showing direction of plunge 

Syncline Showing direction of plunge 

Overturned syncline Showing direction of plunge

Figure 1. Map showing geology of the eastern margin of the Idaho batholith and adjacent Dollarhide Formation in the Buttercup Mountain and Dollarhide Mountain 7.5-minute quadrangles, Blaine and Camas Counties, south-central Idaho. Modified from Worl and others 

(1991) and P.K. Link (unpublished mapping).
METAMORPHISM AND DEFORMATION, EASTERN MARGIN OF IDAHO BATHOLITH Q3

River Formation (Middle Pennsylvania!! to Lower Permian), 

and mapped the Carrietown sequence-Dollarhide Formation 

contact as a thrust fault.

In the Smoky Mountains, the eastern edge of the 

Atlanta lobe of the Idaho batholith intrudes phyllite, quartzite, marble, and argillite of the Dollarhide Formation (Hall, 

1985; Wavra, 1985; Geslin, 1986; Wavra and others, 1986; 

Darling, 1987; Whitman, 1990; Mahoney and others, 1991; 

O'Brien, 1991). The lower part of the Dollarhide Formation 

was divided into three stratigraphic units by Whitman 

(1990). Rocks of unit 1 primarily consist of phyllite, phyllitic 

quartzite dominates unit 2, and unit 3 is composed of marble 

and argillite. The contact between units 2 and 3 was formerly 

interpreted as a thrust fault (Hall, 1985; Geslin, 1986; Darling, 1987). As described later, structural and metamorphic 

similarities between units 2 and 3 instead indicate a continuous stratigraphic section.

The present study concerns the metamorphic and deformational history of the eastern edge of the Atlanta lobe of the 

Idaho batholith in the Smoky Mountains west of Ketchum, 

Idaho, and is built on several theses (Wavra, 1985; Geslin, 

1986; Darling, 1987; Whitman, 1990; O'Brien, 1991), as 

well as published and unpublished mapping by R.S. Lewis 

and P.K. Link. Six structural and metamorphic domains 

were studied in detail (Whitman, 1990): Tyrannis Creek, 

Blackhorse Canyon, Little Smoky Creek, West Fork of Willow Creek, Willow Creek, and Buttercup mine (fig. 1). The 

bulk chemistry of the sedimentary protolith has contributed 

to the useful and diagnostic metamorphic parageneses 

observed and helps to tightly constrain the pressure, temperature, and fluid composition at the time of metamorphism. 

Regional interpretation of the style and timing of metamorphism can be made from comparison of the petrographic elements and pressure-temperature-PcO2 conditions between 

different areas within the study area.

Acknowledgments. I would like to thank the many 

people involved in this project who shared their thoughts and 

time including Paul Link, David Rodgers, J.P. O'Brien, and 

Robert Darling, among others. This study was supported by 

the U.S. Geological Survey U.S. Geological Survey Conterminous United States Mineral Assessment Program (CUSMAP Program), Idaho State Board of Education Grant 

89-56 to P.K. Link, and an Idaho State University Student 

Research Committee grant. The manuscript was reviewed by 

P.K. Link, D.W. Rodgers, R.G. Worl, and R. Darling.

PENNSYLVANIAN AND PERMIAN STRATA 

OF THE DOLLARHIDE FORMATION

Pennsylvanian and Permian strata of the Dollarhide 

Formation consist of phyllite, phyllitic quartzite, banded 

quartzite, calc-silicate hornfels, marble, and argillite derived 

from calcareous pelitic and psammitic protoliths. Rocks of 

the Dollarhide Formation have been divided into three members and comprise the southwestern carbonaceous basinal 

facies of the Middle Pennsylvanian to Lower Permian Sun 

Valley Group (Mahoney and others, 1991; Link and others, 

this volume). Contrary to earlier reports (Hall, 1985; Link 

and others, 1988), the Dollarhide Formation is now known to 

contain Pennsylvanian as well as Lower Permian rocks (Link 

and others, this volume; Betty Skipp, oral commun., 1991).

The lower member of the Dollarhide Formation has 

been divided into three stratigraphic units (Whitman, 1990). 

The stratigraphic units of the lower part of the Dollarhide 

Formation can be delineated in the field but, due to the scale 

of figure 1, are not shown in that figure. Unit 1 consists of 

brownish-purple phyllite having a golden phyllitic sheen, 

local black to brown fine- to medium-grained schist, and 

purple-brown fine-grained phyllitic quartzite. Unit 2 is characterized by purple-brown phyllite and phyllitic quartzite, 

centimeter-scale banded quartzite, gray to white, calcareous 

to siliceous, massive to finely laminated marble and calc-silicate hornfels, and moderately thin bedded intervals (<10 m) 

of black carbonaceous marble. The boundary between units 

1 and 2 is defined by the lowest occurrence of pink to white 

centimeter-scale pods or layers within phyllite or quartzite. 

Unit 3 consists of black carbonaceous marble, gray to white 

calc-silicate hornfels, and very fine grained black argillite. 

The boundary between units 2 and 3 is placed at the lowest 

occurrence of thick (>10 m) beds of black carbonaceous 

marble or argillite. Rocks of unit 3 rarely exhibit a foliation 

in outcrop, but under microscopic examination they exhibit 

a strong foliation defined by the parallel elongation of 

recrystallized calcite and quartz. Rocks of unit 3 contain 

tremolite, diopside, wollastonite and sillimanite, as do rocks 

of the appropriate bulk composition in units 1 and 2.

The contact between units 2 and 3 was previously 

mapped as a thrust fault (Hall, 1985; Geslin, 1986; Darling, 

1987), but structural and metamorphic similarities of units 2 

and 3 instead support the interpretation of a stratigraphically 

continuous section.

REGIONAL SETTING

Rocks of the Middle Pennsylvanian to Lower Permian 

Dollarhide Formation, Cretaceous intrusive rocks of the 

Idaho batholith, and Eocene dacitic volcanic and intrusive 

complexes of the Challis Volcanic Group crop out in the 

study area (fig. 1).

CRETACEOUS IDAHO BATHOLITH AND 

METAMORPHIC AUREOLE

The Cretaceous Idaho batholith in the southern Smoky 

Mountains contains hornblende-biotite granodiorite, biotite 

granodiorite, and leucocratic granite that have yielded radiometric dates of 93-77 Ma (Darling, 1987; Lewis, in press).
Q4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

c/) 

cc

g 

S

? 4

CC.

Is

LLJ 

CC 

0_

500 600 700 

TEMPERATURE, IN °C

800

Figure 2. Pressure (P)-temperature (T)-partial pressure (Pccfe) diagram for the metamorphic aureole of the Dollarhide Formation. 

The experimental curves are discussed in the text. The shaded area 

represents the P-T-PcO2 field for the Dollarhide Formation adjacent 

to the Idaho batholith in the southern Smoky Mountains study area; 

data from Whitman (1990). Minerals: And, andalusite; Chl, chlorite; Cord, cordierite; Di, diopside; Fo, forsterite; Gt, garnet; Ky, kyanite; Sill, sillimanite; Stt, staurolite; Tr, tremolite; Wo, 

wollastonite.

Satellite plutons east of the main batholith yield Late Cretaceous ages (L.W. Snee, U.S. Geological Survey, unpublished data, 1992; Park, in press).

A broad metamorphic aureole several kilometers wide 

has developed next to the eastern edge of the batholith, 

where it appears to be confined to the rocks of the Dollarhide 

Formation. The exact extent of the aureole is not known at 

most locations because metamorphic grade cannot always be 

determined in the field and thin section sampling is sparse. 

The presence of sillimanite in Dollarhide rocks 2 km from 

the nearest exposed igneous contact in the Buttercup Mountain quadrangle may suggest, however, that the aureole has 

affected a large area or that the batholith is extensive in the 

shallow subsurface.

EOCENE VOLCANIC ROCKS

Tertiary intrusive rocks intruded between 51 and 44 Ma 

thought to be subvolcanic equivalents of the Challis Volcanic Group (Bennett and Knowles, 1985; Lewis and Kiilsgaard, 1991; Stewart and others, in press) are widespread in 

the Smoky Mountains.

Eocene (51-40 Ma) volcanic rocks of the Challis Volcanic Group (Johnson and others, 1988; Moye and others, in

press) overlie many of the older rocks in central Idaho. Tertiary hypabyssal plutons intrude rocks of the Cretaceous 

batholith and Tertiary extrusive rocks. Extensive hydrothermal systems having circulation halos 25-50 km wide and 

5-7 km deep formed adjacent to some of these plutons (Criss 

and Taylor, 1983). Tertiary hydrothermal halos were not 

observed in rocks of the Dollarhide Formation in the study 

area (Whitman, 1990; Darling and others, this volume).

METAMORPHIC PETROLOGY 

METAMORPHIC CONDITIONS

The mixed siliceous and calcareous protolith bulk compositions of the Dollarhide Formation allowed for the development and coexistence of a variety of metamorphic 

minerals including diopside, tremolite, andalusite, sillimanite, staurolite, and wollastonite. By plotting the stability 

fields of the coexisting phases on a pressure-temperature diagram with respect to fluid composition, the temperature, 

pressure, and fluid composition at the time of M2 metamorphism has been tightly constrained.

Pressures and temperatures of M2 metamorphism 

(shaded area, fig. 2) were deduced from the stability fields of 

the many coexisting minerals using mineral stability curves 

derived from experimental data. The curves shown in figure 

2 are univariant mineral reaction curves shown in pressuretemperature space. For any curve, phases to the left of the 

curve react during prograde metamorphism to form those 

minerals indicated to the right. During prograde metamorphism, the unstable phases are "out," and the stable phases 

are "in." These reactions also occur in reverse during retrograde metamorphism, assuming a closed system.

The A^SiOs curves used in this study were proposed 

by Holdaway (1971). These curves best predict mineral 

assemblages observed in the field and are further verified by 

independent determinations of pressure and temperature of 

phases other than the aluminosilicates. For these reasons the 

Holdaway curves are the most widely used and are most 

appropriate for this study.

The staurolite-in curve used in this study is from Richardson (1968). This curve assumes pure iron-end member 

staurolite. If the staurolite has magnesium substituting for 

iron, the effect is to shift the curve slightly to the left, to 

lower temperatures; however, the composition of staurolite 

varies only within narrow limits and there is no significant 

variation in the replacement of Fe+2 by magnesium (Deer 

and others, 1966, p. 49). The abundance of iron-titanium 

oxide minerals in rocks in the study area indicates excess 

iron at the time of metamorphism. In addition, no predominantly magnesium bearing assemblages such as brucite, periclase, or forsterite are present even though temperature and 

pressure conditions were such that these minerals could have 

formed. It must follow that magnesium was not a major
METAMORPHISM AND DEFORMATION, EASTERN MARGIN OF IDAHO B ATHOLITH Q5

constituent of the original bulk composition of these rocks. 

Geochemical data (O'Brien, 1991) indicate equal amounts of 

Fe2O3 and MgO for rocks of the lower part of the Dollarhide 

Formation collected in the Willow Creek area. Any available 

magnesium was probably consumed by the formation of 

tremolite and diopside, with no excess left to form other 

magnesium-bearing minerals. Staurolite in the study area is 

most likely close to the iron-end member, and the staurolitein curve is therefore fixed as shown in figure 2.

The wollastonite reaction curves are from Winkler 

(1979, p. 130). The wollastonite-in curves are sensitive to 

fluid composition as shown in figure 2.

The tremolite-in, diopside-in, and forsterite-in curves 

are from Turner (1980, p. 167-68). These curves assume 

^CO2 between 0.4 and 1.0. If Pco2 values are less than 0.25, 

the tremolite-in, diopside-in, and forsterite-in curves shift to 

slightly lower temperatures. The exact amount of the shift is 

unknown but is less than 200°C (Turner, 1980). Metamorphic conditions in the study area probably are constrained by 

the kyanite-andalusite reaction curve and the andalusite-sillimanite reaction curve as suggested by the absence ofkyanite and the apparent equilibrium of sillimanite and 

andalusite. The tremolite-in, diopside-in, and forsterite-in 

curves cannot have shifted left of the kyanite-out/andalusitein reaction line or else kyanite would be the stable aluminosilicate. The absence of kyanite restricts the metamorphic 

conditions to the right of the kyanite-out/andalusite-in reaction curve. Any leftward shift of the tremolite-in, diopsidein, and forsterite-in curves therefore can not exceed approximately 25°C, a value that does not significantly alter the 

pressure-temperature values reported here. The tremolite-in, 

diopside-in, and forsterite-in curves are indicated in figure 2.

Rocks in the study area commonly exhibit the assemblage diopside, tremolite, and either andalusite or sillimanite. A sampling traverse along the ridge near the Buttercup 

mine yielded an M2 andalusite-bearing rock approximately 210 m from the intrusive contact and a M2 sillimanite-bearing rock a few meters farther from the 

batholith. Therefore it is thought that metamorphic conditions lie very near the andalusite-out/sillimanite-in univariant equilibrium curve. The absence of kyanite indicates 

that the staurolite-in, tremolite-in, and diopside-in curves 

all are to the right of the kyanite-andalusite reaction curve. 

Therefore, pressure-temperature conditions are controlled 

by the kyanite-andalusite and the sillimanite-andalusite 

univariant reaction curves.

Rocks in this area also contain tremolite, diopside, and 

staurolite. The tremolite-in curve intersects the andalusiteout/sillimanite-in curve at 3.25 kb and 525°C. The staurolitein curve also intersects the tremolite-in curve at approximately 3.25 kb and 525°C. If the tremolite-in curve shifts left 

(if /Jco2<0-25), then the upper pressure value would be 

approximately 3.5 kb. Any greater increase in pressure would 

be too far from the sillimanite-in/andalusite-out curve and 

andalusite would not be observed in the rocks. At 3.5 kb, the 

temperature must remain above 525°C or chlorite+kyanite

would be the stable assemblage rather than staurolite. Therefore, 525°C is the minimum temperature of M2 metamorphism. The maximum temperature at which staurolite can 

exist near the andalusite-sillimanite equilibrium is approximately 600°C. At 600°C, staurolite-andalusite-sillimanite 

can only coexist in a narrow pressure range near 2.5 kb.

The assemblages diopside-tremolite-andalusite/sillimanite-staurolite define the pressure and temperature of M2 

metamorphism to be approximately 2.5-3.5 kb and 

525°C-600°C. Metamorphic conditions were similar 

throughout the study area as shown by table 1.

These temperatures and pressures correspond to conditions of medium-high grade dynamothermal metamorphism, 

and, if fluid pressure is equal to total pressure, then they indicate a depth of metamorphism and therefore a depth of 

emplacement of 8.5-12.5 km for the Idaho batholith in the 

southern Smoky Mountains.

Composition of the fluid phase with respect to CC«2 during M2 metamorphism can be determined by examining the 

stability of wollastonite with respect to diopside and to the 

conspicuous lack of forsterite. The assemblage tremolite, 

diopside, sillimanite, and wollastonite without forsterite has 

been observed in the Willow Creek, West Fork of Willow 

Creek, and Tyrannis Creek areas. As the pressure-temperature diagram (fig. 2) indicates, wollastonite is quite sensitive 

to fluid composition and the temperature at which it forms is 

lowered considerably with a lowering of Pco2- ^ 

Q.25<Pco2<QAQ, then forsterite is the stable phase at the 

expense of tremolite at 2.5-3.5 kb and 525°C-600°C. Forsterite was not observed in any of the rocks in the study area. 

Therefore, in order for the observed assemblage diopsidetremolite-wollastonite-sillimanite to have formed, Pco2 

must have been less than 0.25. If the lower metamorphic 

pressure limit is 2.5 kb, as indicated by the coexistence of 

staurolite-andalusite±sillimanite, and cordierite is absent, 

then wollastonite is stable atPco2<Q.l8 (fig. 2). The wollastonite-in curve at Pco2=Q.18 also corresponds to a temperature maximum of 600°C.

During metamorphism of marble, the CC«2 component 

of the fluid phase usually is from 0.4 to 1.0 Pco2 (Turner, 

1980), and the unusually low CC«2 content of the fluid 

phase of the Dollarhide marbles may be related to dilution 

by high amounts of water coming from the cooling wet granodiorite or to removal of CC«2 from the system by an unidentified process or processes.

Table 1. Temperature and pressure of M2 metamorphism in the 

Dollarhide Formation, south-central Idaho. 

[Data from Whitman, 1990]

Temperature (°C) Pressure (kilobars)

Buttercup mine 

Willow Creek

West Fork of Willow Creek

Tyrannis Creek

525-600 

545-630

500-600

500-600

2.5-3.5 

2.25^.5

2.5-3.5

2.5-3.5
Q6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

DESCRIPTION OF METAMORPHIC 

FEATURES

Numerous metamorphic features have been observed 

in rocks in the study area including two sets of porphyroblasts, two foliations, mineral, boudin, and intersection lineations, hornfelsic micaceous spots, and pseudomorphs 

(fig. 3). The types of features and their crosscutting relationships define the chronology of two metamorphic and 

deformational episodes.

The lower part of the Dollarhide Formation contains 

two sets of crosscutting porphyroblasts, two sets of crosscutting foliations, hornfelsic micaceous spots, and pseudomorphs. The nature of these features and their relationships to 

each other indicate that two prograde metamorphic events 

have occurred (Mi and M2) and that MI was followed by a 

period of retrograde thermal alteration (Ri). Each prograde 

event was accompanied by strain that formed a foliation 

within the rocks (Si and 82). Only one event (M2) was 

accompanied by folding. Field relationships and a wholerock K-Ar age of 83.9±3.4 Ma constrain both events to the 

Late Cretaceous.

Large, well-preserved porphyroblasts of tremolite, 

diopside, sillimanite, andalusite, staurolite, wollastonite, 

biotite, muscovite, potassium feldspar, plagioclase, and 

epidote are present throughout the lower part of the Dollarhide Formation in the study area. The original bulk composition of the protolith controls the metamorphic 

assemblages: in pelitic beds andalusite or sillimanite 

formed, in calcareous beds tremolite, diopside, and wollastonite formed, and in quartz-rich beds biotite and recrystallized quartz formed (fig. 3).

The porphyroblasts vary in size from about 0.25 to 1-3 

mm and are the same size in any one thin section, except for 

some samples that have two distinctly different sizes of porphyroblasts. Porphyroblasts are typically euhedral to subhedral and are surrounded by quartz-biotite or quartz-calcite 

matrices. Sillimanite, tremolite, plagioclase, and biotite were 

observed in mutual grain-boundary contact, as were diopside, tremolite, and epidote. Wollastonite and scapolite were 

identified in rocks of the West Fork of Willow Creek and 

Tyrannis Creek areas. Idocrase was identified in samples 

from the Tyrannis Creek area near the Stormy Galore mine.

Rocks in the study area exhibit three foliations. Primary bedding (So) is defined by compositional and grainsize variations. A poorly developed foliation (Si) is 

defined by the parallel alignment of fine-grained biotite and 

muscovite in the pelitic rocks of units 1 and 2. A welldeveloped penetrative foliation (82) is defined by the parallel alignment of coarse-grained biotite and muscovite in the 

pelitic rocks and by the parallel alignment of calcite and 

quartz in the calcareous rocks. The 82 foliation crosscuts 

the finer grained Sj foliation in rocks from the Buttercup 

mine area. The 82 foliation is present throughout the lower 

part of the Dollarhide Formation in the study area, although

Protolith

Pelite

Limestone

M,

Porphyroblasts 

Micaceous spots

Si

Porphyroblasts 

Micaceous spots

Si

Ri

Pseudomorphs 

Retrograded 

porphyroblasts

Pseudomorphs 

Retrograded 

porphyroblasts

M2

Quartz-biotite-muscovitepotassium feldsparandalusite-sillimanite-calcitediopside-tremolite-staurolite

S2< L2xO' LOx2< Lm- Lb

Calcite-quartz-tremolitediopside-wollastonitescapolite-idocraseplagioclase-epidote

S2- L2xO< LOx2' Lm< Lb

Figure 3. Mineral assemblages and structural elements formed in 

protoliths of pelite and limestone of the study area during first prograde metamorphism (Mi), first retrograde metamorphism (R2), and 

second prograde metamorphism (M2). Abbreviations: Si, first foliation; 82, second foliation; Lox2» intersection lineation of 82 and 

bedding measured on bedding surface; L2Xo, intersection lineation 

of bedding and 82 measured on the 82 surface; Lm, mineral lineation; Lb, boudin lineation defined by aggregates of mineral grains.

it is not clearly visible in the calcareous rocks in outcrop. 

Two mineral lineations were observed in some rocks. Both 

LI and L2 are defined by elongated biotite grains in the pelitic rocks and by elongated calcite and quartz grains in the 

calcareous rocks. The lineations are contained within their 

respective foliations, Si and 82-

Most rocks in the study area exhibit a spotted or hornfelsic texture in hand sample and in thin section. In hand 

sample, the spots are white to pink, millimeter- to centimeter-scale pods or bands and are present in phyllitic quartzite 

and black marble and argillite. Microscopic examination 

reveals that the spots have an ellipsoidal shape and vary in 

size from about 0.45 mm by 0.2 mm to 0.75 mm by 0.4 mm. 

The spots are composed of muscovite, biotite, chlorite, and 

minor quartz. Although the micas are fine grained in some 

hornfelsic spots, most have a coarser texture than the surrounding matrix. Most of the hornfelsic spots are oriented 

with their long axis parallel with the strong biotite foliation 

(82) of the rock; however, some spots have their long axis 

oblique to the foliation by as much as 20°. In the Buttercup 

mine area, approximately 200-565 m from the intrusive contact, hornfelsic spots contain a finer grained biotite foliation 

(Si) that is subparallel with the coarser grained matrix foliation. Most of the spots in this rock are overprinted by micas 

of the matrix foliation (82).

Throughout the study area rocks of the lower part of the 

Dollarhide Formation contain pseudomorphs. Tetrahedral 

pseudomorphs are larger than the ellipsoidal hornfelsic spots 

and average approximately 1.0 mm long on a side. They are 

composed of fine-grained polycrystalline quartz and minor 

potassium feldspar and micas. Because their size and shape 

is identical to andalusite porphyroblasts observed elsewhere 

in rocks in the study area, they are interpreted as pseudomorphs after andalusite. Other pseudomorphs in the study area 

resemble staurolite porphyroblasts and are interpreted to be 

pseudomorphs after staurolite.
METAMORPHISM AND DEFORMATION, EASTERN MARGIN OF IDAHO BATHOLITH Q7

A chronology of the timing of metamorphism and 

deformation can be determined by examining the nature of, 

and relationships between, the various petrographic elements observed in the rocks.

Two sets of porphyroblasts were identified in samples 

from the Tyrannis Creek, Willow Creek, and Buttercup mine 

areas. The two sets of diopside, tremolite, and andalusite 

porphyroblasts have two distinctly different sizes and two 

different degrees of alteration. A sample from the Tyrannis 

Creek domain near the Stormy Galore mine (fig. 1) exhibits 

very large (3.2 mm by 1.4 mm), highly retrograded diopside 

porphyroblasts overgrown by smaller (1.6 mm by 0.52 mm), 

much fresher diopside porphyroblasts. Numerous samples 

from the Buttercup mine and Willow Creek areas contain 

two sets of diopside and andalusite porphyroblasts; one set is 

thermally altered and shows signs of retrogression, the other 

set is unaltered and fresh looking. This suggests that two 

metamorphic events (Mi and M2) of similar temperature and 

pressure have affected these rocks. The events were separated by a period of retrograde metamorphism (Ri) that 

caused the alteration of the first set of porphyroblasts. The 

presence of pseudomorphs of quartz after andalusite and 

staurolite in samples containing fresh andalusite, tremolite, 

and diopside porphyroblasts also indicates two metamorphic 

events: andalusite and staurolite growth during MI and subsequent replacement of the andalusite and staurolite porphyroblasts with quartz and growth of more andalusite and other 

minerals during M2-

Two foliations (Si and 82) were observed in the rocks. 

The Si foliation is finer grained and oriented at an angle of 

approximately 20° to the second foliation (82). This relationship suggests that two deformational events have occurred 

and that the orientation of the rocks with respect to the principal strain axes accompanying the second event was slightly 

different from that during the first event.

The ages of the foliation can be tied to the ages of metamorphism through observations of the relationship between 

the foliations, the MI and M2 porphyroblasts, the MI 

pseudomorphs, and the MI and M2 hornfelsic mica spots. In 

most rocks in the study area, the strong 82 foliation wraps 

around porphyroblasts, and no porphyroblasts were 

observed cutting this foliation. This relationship indicates 

that the porphyroblasts grew before or during deformation 

and foliation development. Clearly, if deformation did not 

precede contact metamorphism, evidence of porphyroblasts 

overgrowing and crosscutting the foliation would be 

observed. Two generations of hornfelsic spots were 

observed: fine-grained biotite-muscovite spots and coarsegrained spots. In samples from the Buttercup mine area, 

fine-grained spots are aligned with their long axes 20° to the 

well-developed 82 foliation. The 82 foliation cuts some of 

the fine-grained spots.

A sample of micaceous calc-silicate from the head of 

Cabin Gulch (fig. 1) was dated using the whole-rock K-Ar 

method. An age of 83.9±3.4 Ma was obtained (R.L.

Armstrong, written commun., 1990). Based on the metamorphic textures and compositions described above, this age is 

interpreted as the minimum age of M2 metamorphism. 

Therefore, the foliation observed in rocks of the lower part 

of the Dollarhide Formation on the margin of the Idaho 

batholith is no older than Late Cretaceous. This Late Cretaceous age is substantiated by other field evidence for Late 

Cretaceous metamorphism in the study area and by Late Cretaceous ages for satellite plutons east of the main batholith 

(L.W. Snee, U.S. Geological Survey, unpublished data, 

1992; Park, in press).

STRUCTURAL GEOLOGY OF THE

DOLLARHIDE FORMATION

ADJACENT TO THE IDAHO

BATHOLITH

Rocks along the eastern edge of the Idaho batholith in 

the Smoky Mountains have undergone intense deformation 

as evidenced by plentiful map- and microscopic-scale geologic structures including northeast- and northwest-striking 

faults, Si and 82 foliations, open to isoclinal folds, and 

intersection, mineral, and boudin lineations (L2Xo, Lm, and 

Lb, respectively).

Regionally extensive northeast- and northwest-striking 

faults (Bennett, 1986; Kiilsgaard and others, 1986) having 

no more than several kilometers of offset are present in the 

study area (Darling, 1987; Worl and others, 1991; Darling 

and others, this volume; Lewis, in press) (fig. 1). Many outcrop-scale faults having less than 10 m displacement were 

observed in the field but were not mapped.

The regionally extensive metamorphic foliation (82) 

cuts an older, poorly developed foliation (Si). The 82 foliation is present in all members of the Dollarhide Formation in 

the Buttercup Mountain quadrangle and has not been subsequently folded, except at one location on the ridge immediately west of the Buttercup mine ridge where the foliation 

has been folded with a small, late-stage leucocratic dike; 82 

is axial planar to the folds.

Folds are present throughout the study area and range 

in wavelength from several kilometers, such as those in the 

Tyrannis Creek area, to microscopic, such as in samples 

collected from the West Fork of Willow Creek. The folds 

are gently to moderately plunging and moderately inclined 

to recumbent, and they exhibit open to isoclinal apical 

angles and rounded to kinked hinges. They are present in 

phyllitic quartzite as well as siliceous and calcareous marble. All fold hinges trend east-northeast (fig. 4). Differences in fold morphology are likely due to rheologic 

differences between rock types and to differences in distance from the batholith margin rather than being indications of two folding events. Apparent parallel laminations 

in hand samples of marble are actually highly attenuated 

limbs of recumbent isoclinal folds.
Q8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Mineral lineations, intersection lineations, and boudins 

are also present in the study area. Mineral lineations (Lm) 

are defined by 2-3 millimeter-long black euhedral mica 

pseudomorphs after amphibole in phyllitic quartzite. Intersection lineations (L2Xo, LoX2) were formed by the intersection of 82 cleavage and bedding (So), measured on the 82 

and SQ surfaces, respectively. Boudins of quartz or feldspar 

crystals are present but are not as widespread as the other 

structural features.

Lower hemisphere equal-area projections of structural 

data from the vicinity of Buttercup mine (fig. 4A), West Fork 

of Willow Creek (fig. 4B) and Blackhorse Canyon (fig. 4C) 

were constructed. Composite data from the Blackhorse Canyon, West Fork of Willow Creek, Willow Creek, and Buttercup mine areas are shown in figure 4D.

The clustering of poles to bedding (So) in the southwest 

quadrant indicates a regional northeast dip of bedding. 

Although numerous folds are present throughout the area, 

the poles to bedding do not define a great-circle distribution 

because of sampling bias; extreme attenuation of most folds 

in the study area precluded measurement of bedding in the 

axial regions of folds.

Poles to 82 also cluster in the southwest quadrant 

around an average 82 orientation of N. 20° W., 40° E. In 

most places SQ and 82 are almost parallel. Fold hinges, as 

well as intersection, boudin, and mineral lineations, have 

wide scatter but in general cluster in the northeast quadrant 

around an average orientation of 45°, N. 70° E., for the fold 

axes. The lineations also cluster in the northeast quadrant. 

The 45°, N. 70° E., orientation was derived from the best-fit 

great-circle distribution of poles to SQ and 82 obtained from 

data in the vicinity of Blackhorse Canyon. If folding is cylindrical, or almost so, the fold axis lies 90° from the great circle containing the poles to 82- The 45°, N. 70° E., orientation 

of the fold axis lies 90° from the best-fit great circle containing the poles to S2 (figs. 45,4Q. This derived value (45°, N. 

70° E.) corresponds well with actual field measurements of 

fold hinges (figs. 4B-D) throughout the study area.

All folds in the study area trend east-northeast and 

plunge moderately away from the batholith. Mapping east 

of the batholith indicates that regionally folds trend southsoutheast and plunge gently (Rodgers and others, this volume). It is herein proposed that anomalous orientations of 

the fold hinges in this area are due to high shear strain. In 

areas of high shear stain, the X- and Z- axes of finite strain 

rotate about the Y axis of finite strain. The XF-plane is parallel with the axial plane of the folds, and it rotates from a 

normal orientation (45°) with respect to the shear zone 

boundary (batholith margin) in low shear strain environments to a parallel position with respect to the shear zone 

boundary in areas of high shear strain (figs. 5A-D). Features 

such as fold hinges and mineral and boudin lineations generally form parallel with the direction of the intermediate

strain axis (Y). In areas of high shear strain, where the magnitude of X is much greater than that of Y, these features can 

be passively rotated to a position that is parallel with the 

original direction of least extension (Z). This process, originally explained by Hansen (1971), could account for the 

anomalous orientation of fold axes and mineral lineations in 

the study area. To confirm this hypothesis, more fold orientation data are needed from the area between the Buttercup 

Mountain and Griffin Butte quadrangles, where the transition from south-southeast-trending folds to east-northeasttrending folds should be present.

In the northwestern part of the study area, not all mapscale folds (fig. 1) trend east-northeast; this variation in trend 

may represent broad warping of the foliation. Folding of a 

late-stage leucocratic dike may also indicate continued 

deformation after peak metamorphism. Evidence of a second 

major folding event was not observed in thin section or in the 

structural analysis. More structural data are needed in order 

to define the extent and character of structures in this part of 

the study area.

TIMING OF METAMORPHISM 

AND DEFORMATION

Petrographic and field evidence suggest that two episodes of metamorphism and deformation occurred during 

Late Cretaceous time in the study area. The early S\ foliation 

is poorly developed and not generally visible in outcrop. MI 

features such as porphyroblasts, hornfelsic texture, and 

pseudomorphs have been preserved. These features are 

crosscut by a stronger penetrative foliation (82) that wraps 

around M2 porphyroblasts. Evidence of postdeformational 

porphyroblast growth was not observed in any sample. 

Deformation must have occurred simultaneously with M2 

metamorphism. The minimum age of M2 metamorphism has 

been dated by whole-rock K-Ar to be 83.9±3.4 Ma (R.L. 

Armstrong, written commun., 1990), the time at which the 

temperature cooled from the peak metamorphic temperature 

of 525°C-600°C to the blocking temperature of the analyzed 

micas at approximately 300°C. The age of peak metamorphism is unknown.

Figure 3 summarizes the structural and metamorphic 

elements produced during each phase of metamorphism 

and deformation. Field observations, thin sections, and 

structural analysis (fig. 4) show that fold hinges lie within 

the plane of the 82 foliation such that the 82 foliation is 

axial planar to the folds. Because of the axial planar nature 

of the 82 foliation, folding was synchronous with development of 82 foliation. Because the 82 foliation formed during M2 metamorphism, which was coeval with 

emplacement of the batholith, folds in the study area are 

Late Cretaceous in age. There is no evidence of an earlier
METAMORPHISM AND DEFORMATION, EASTERN MARGIN OF IDAHO BATHOLITH

N N

Q9

Average fold axis 

45°, N.71°E.

EXPLANATION

D L2xo A Lm 

O Fold axis, open A M-, 

® Fold axis, kinked X S2 

O Fold axis, isoclinal \ SQ

Figure 4. Equal-area Pi diagrams for (A) Buttercup mine, (5) West Fork of Willow Creek, (Q Blackhorse Canyon, and (£>) composite of Blackhorse Canyon, West Fork of Willow Creek, Willow Creek, and Buttercup mine domains. The Pi diagrams contain plots of 

poles to SQ (PiSo), poles to 82 (PiS2), intersection lineation measured on the 82 surface (L2Xo), mineral lineations (Lm), boudin axes 

(Lb), and fold axes. Data from Whitman (1990).
Q10 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

EAST

Low strain Y//Lm; Y//FA; Zi S2, AP; X-Y

B F.A.

Intermediate strain Y//Lm; Y//FA; Zi S2, AP; X>Y

F.A.

Intermediate strain Y//Lm; Y=FA; Zi S2, AP; X»Y

D

F.A.

High strain Y//Lm ; Zi S2, AP; X>»Y

Figure 5. Diagram showing progressive increase in strain for the 

Dollarhide Formation during Mj and M2 metamorphism. Original 

east-west compression causes rotation of fold axes to 45°, N. 70° E. 

orientation; mineral lineations and fold axes become parallel. X is 

direction of most extension; Z is direction of least extension; Y is direction of intermediate extension. L^ is mineral lineation; FA is fold 

axis; AP is axial plane; S2 is foliation formed during M2. Modified 

from Whitman (1990, fig. 21). A, Possible configuration after MI 

and early in M2. B, Possible configuration during intermediate stages of M2. C, Possible configuration during late stages of M2; the 

present configuration at distances greater than 2 km from the 

batholith. D, Present configuration near the batholith.

(pre-Cretaceous) deformational event. On the ridge immediately west of the Buttercup mine ridge, a small leucocratic dike has been folded with the 82 foliation into a small 

S-fold. The dike is certainly related to late-stage differentiation of the Idaho batholith, and therefore folding occurred 

on a local scale after peak metamorphism.

The Si foliation formed simultaneously with MI metamorphism. The Si foliation is poorly developed, and structural data were not collected for the MI event. Pressure and 

temperature of metamorphism were such that diopside and 

andalusite porphyroblasts, as well as hornfelsic texture, 

developed in the rocks. Although the Si foliation and MI 

petrographic features are preserved, there is no evidence of 

folding related to the MI event. The MI event probably represents the initial stages of batholith emplacement, whereas 

the M2 event represents peak metamorphism and high strain 

in the margin area.

REGIONAL IMPLICATIONS 

MESOZOIC DEFORMATION

The presence of an Antler-age fabric in phyllitic quartzite near Carrietown (fig. 1) was suggested by Geslin (1986) 

and Darling (1987); however, the present structural and petrographic study reveals no evidence for deformation of the 

Dollarhide Formation prior to intrusion of the Idaho 

batholith in the Late Cretaceous. Rotation of fold hinges in 

regions of high shear strain near the batholith throughout the 

study area could account for the parallelism between fold 

axes and mineral and boudin lineations. High shear strain 

and rotation also account for the disparity between foldhinge orientations in the Dollarhide Mountain and Buttercup 

Mountain quadrangles and fold-hinge orientations in surrounding areas. A single generation of folds is documented 

in the study area. The coeval nature of foliation and fold 

development with M2 porphyroblast development prior to 

the minimum age of metamorphism at 83.9±3.4 Ma indicates 

that large- and small-scale folds within the study are not 

much older than Late Cretaceous.

RELATION TO MINERALIZATION

Metasomatic mineral assemblages (idocrase-scapolitecalcite) were observed in the western part of the study area 

in the vicinity of Tyrannis Creek and the West Fork of Willow Creek (fig. 3). Tungsten minerals are present in phyllite 

in the West Fork of Willow Creek. Idocrase and scapolite are 

absent from calcareous rocks in the eastern part of the study 

area. This pattern may indicate that skarn processes were 

better developed in the western part of the study area.

Cretaceous mineralization in the study area and in 

nearby areas is well documented (Darling, 1987; Darling and 

others, this volume; Park, in press). Silver-lead-zinc mineral 

deposits in the study area are in northeast-trending shear 

zones along the lithologic change from quartzite and phyllite 

to carbonaceous marble and granodiorite and country rocks 

(Darling and others, this volume). The contact between phyllite of unit 2 and marble of unit 3 previously had been 

thought to be the thrust fault contact between the Carrietown 

sequence and the Dollarhide Formation, but the mineral 

deposits are not localized along one thoroughgoing structure. 

Almost half of the mines in the study area are from more than 

100 m below to several hundreds of meters above this contact (Darling, 1987; Darling and others, this volume). Rather 

than being structurally controlled by a thrust fault, the mineralized shear zones most likely formed during Cretaceous 

compressional deformation as a result of differential stresses 

along the lithologic and rheologic contact between competent quartzite and less competent marble.
METAMORPHISM AND DEFORMATION, EASTERN MARGIN OF IDAHO BATHOLITH Qll

SUMMARY

Rocks of the Pennsylvania!! to Permian Dollarhide Formation of south-central Idaho underwent moderate- to highgrade dynamothermal metamorphism during the Late Cretaceous, reaching temperatures of 525°C-600°C and pressures 

of 2.5-3.5 kb. Metamorphic fluids were dominated by H2O 

CPcO2<0.18) despite the calcareous rock types involved. 

Depth of emplacement of the southeastern edge of the 

Atlanta lobe of the Idaho batholith is estimated at 8.5-12.5 

km. Although two pulses of heat and strain were documented 

in the study area, only one generation of folds was observed. 

Foliation axial planar to the folds indicates that folding was 

contemporaneous with development of foliation. Fold 

hinges and mineral, boudin, and intersection lineations are 

anomalously oriented 45°, N. 70° E., in the study area in contrast to south-southeast-trending folds in areas further from 

the batholith. It is herein proposed that high shear strain on 

the margin of the batholith rotated fold hinges and mineral, 

boudin, and intersection lineations into their present anomalous orientations. Silver-lead-zinc mineralized rock is concentrated in Cretaceous-age northeast-trending shear zones 

and is related to Cretaceous intrusive activity. Cretaceous 

mineralization, deformation, and metamorphism were 

broadly contemporaneous in this area. M2 metamorphism 

has been dated by the K-Ar method at 83.9±3.4 Ma, which 

represents the minimum age of metamorphism. A pre-Cretaceous deformational event is not documented along the eastern edge of the Idaho batholith.

REFERENCES CITED

Bennett, E.H., 1986, Relationship of the trans-Challis fault system 

in central Idaho to Eocene and Basin and Range extensions: 

Geology, v. 14, p. 481^84.

Bennett, E.H., and Knowles, C.R., 1985, Tertiary plutons and related rocks in central Idaho, in Mclntyre, D.H., ed., Symposium 

on the geology and mineral deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-F, p. 

81-96.

Criss, R.E., and Taylor, H.P., 1983, An 18O/16O and D/H study of 

Tertiary hydrothermal systems in the southern half of the Idaho 

batholith: Geological Society of America Bulletin, v. 94, p. 

640-663.

Darling, R.S., 1987, The geology and ore deposits of the Carrietown silver-lead-zinc district, Blaine and Camas Counties, 

Idaho: Pocatello, Idaho State University, M.S. thesis, 168 p.

Deer, W.A., Howie, R.A., and Zussman, J., 1966, An introduction 

to the rock forming minerals: Essex, England, Longman Group 

Limited, 528 p.

Geslin, J.K., 1986, The Permian Dollarhide Formation and Paleozoic Carrietown sequence in the SW1/^ of the Buttercup Mountain quadrangle, Blaine and Camas Counties, Idaho: Pocatello, 

Idaho State University, M.S. thesis, 116 p.

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle 

and upper Paleozoic rocks of the black-shale mineral belt,

central Idaho, in Mclntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis I°x2° quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-J, p. 117-132.

Hansen, Edward, 1971, Strain facies: New York, Springer-Verlag, 

207 p.

Holdaway, M.J., 1971, Stability of andalusite and the aluminum silicate phase diagram: American Journal of Science, v. 271, p. 

97-131.

Johnson, K.M., Lewis, R.S., Bennett, E.H., and Kiilsgaard, T.H., 

1988, Cretaceous and Tertiary intrusive rocks of south-central 

Idaho, in Link. P.K., and Hackett, W.R., eds., Guidebook to the 

geology of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 55-86.

Kiilsgaard, T.H., Fisher, F.S., and Bennett, E.H., 1986, The transChallis fault system and associated precious metal deposits, 

Idaho: Economic Geology, v. 81, p. 721-724.

Lewis, R.S., in press, Alteration and mineralization in the eastern 

part of the Soldier Mountains, Camas County, Idaho: U.S. 

Geological Survey Bulletin 2064-V.

Lewis, R.S., and Kiilsgaard, T.H., 1991, Eocene plutonic rocks in 

south central Idaho: Journal of Geophysical Research, v. 96, 

no. B8,p. 13295-13311.

Link, P.K., Skipp, Betty, Hait, M.H., Janecke, Susanne, and Burton, 

B.R., 1988, Structural and stratigraphic transect of south-central Idaho A field guide to the Lost River, White Knob, Pioneer, Boulder, and Smoky Mountains, in Link, P.K., and 

Hackett, W.R., eds.. Guidebook to the geology of central and 

southern Idaho: Idaho Geological Survey Bulletin 27, p. 5^2.

Mahoney, J.B., Link, P.K., Burton, B.R., Geslin, J.K., and O'Brien, 

J.P., 1991, Pennsylvania and Permian Sun Valley Group, 

Wood River Basin, south-central Idaho, in Cooper, J.D., and 

Stevens, C.H., eds., Paleozoic paleogeography of the Western 

United States-II: Pacific Section, Society of Economic Paleontologists and Mineralogists, Publication 67, v. 2, p. 551-579.

Moye, F.J., Hackett, W.R., Snider, L.G., and Mertzman, S.A., in 

press, Stratigraphy, chronology, and petrology of the southeastern Challis volcanic field, central Idaho: U.S. Geological 

Survey Bulletin 2064-EE.

O'Brien, J.P., 1991, Stratigraphy of the Pennsylvanian-Permian 

Dollarhide Formationin the Buttercup Mountain quadrangle, 

Blaine and Camas Counties, Idaho: Pocatello, Idaho State University, M.S. thesis, 163 p.

Park, W.A., in press, The geology and ore deposits of the Rooks 

Creek stock, Blaine County, Idaho: U.S. Geological Survey 

Bulletin 2064-CC.

Richardson, S.W., 1968, Staurolite stability in a part of the system 

Fe-Al-Si-O-H: Journal of Petrology, v. 9, pt. 3, p. 467^88.

Ross, C.P., 1930, The Little Smoky and Willow Creek mining districts, Camas County: Idaho Bureau of Mines Pamphlet 33, p. 

19-26.

Stewart, D.E., Schmidt, K.L., Moye, F.J., Mahoney, J.B., and Link, 

P.K., in press, Eocene intrusive complexes in the Smoky and 

Boulder Mountains, south-central Idaho: U.S. Geological Survey Bulletin 2064-HH.

Turner, Francis, 1980, Metamorphic petrology Mineralogical, 

field and tectonic aspects (2nd ed.): New York, Hemisphere, 

524 p.

Umpleby, J.B., 1915, Ore deposits in the Sawtooth quadrangle, 

Blaine and Custer Counties, Idaho: U.S. Geological Survey 

Bulletin 580-K, p. 221-249.
Q12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Wavra, C.S., 1985, Structural geology and petrology of the SWV4 of 

the Mahoney Butte quadrangle, Blaine County, Idaho: Moscow, University of Idaho, M.S. thesis, 103 p.

Wavra, C.S., Isaacson, P.E., and Hall, W.E., 1986, Studies of the 

Idaho black shale belt Stratigraphy, depositional environment, and economic geology of the Permian Dollarhide Formation: Geological Society of America Bulletin, v. 97, p. 

1504-1511.

Whitman, S.K., 1990, Metamorphic petrology and structural

geology of the Pennsylvanian-Permian Dollarhide Formation, 

Blaine and Camas Counties, south-central Idaho: Pocatello, 

Idaho State University, M.S. thesis, 108 p.

Winkler, H.G.F., 1979, Petrogenesis of metamorphic rocks (5th 

ed.): New York, Springer-Verlag, 348 p.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.
Regional Geophysical Studies Applied to 

Mineral Resource Assessment of the 

Hailey l°x2°Quadrangle and the Western Part 

of the Idaho Falls I°x2° Quadrangle, 

South-Central Idaho

By M. Dean Kleinkopf, Anne E. McCafferty, and Gerda A. Abrams

GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND 

IDAHO FALLS QUADRANGLES

U.S. GEOLOGICAL SURVEY BULLETIN 2064-R

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1995
CONTENTS

Abstract................................................................................................................................. Rl

Introduction........................................................................................................................... 2

Magnetic Anomaly Data....................................................................................................... 4

Gravity Anomaly Data.......................................................................................................... 4

Physical Properties of the Rocks .......................................................................................... 5

Crustal Provinces.................................................................................................................. 5

Mineral Resources................................................................................................................ 7

Conclusions........................................................................................................................... 8

References Cited................................................................................................................... 9

PLATE

[Plate is in pocket]

1. Residual total-intensity aeromagnetic anomaly map, complete Bouguer gravity anomaly map, and residual Bouguer 

gravity anomaly map of the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, 

south-central Idaho.

FIGURES

1. Index map showing location of the Hailey I°x2° quadrangle and the western part of the Idaho Falls

I°x2° quadrangle........................................................................................................................................................ R2

2, 3. Maps of the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle showing:

2. Geologic terranes and major faults...................................................................................................................... 3

3. Distribution of precious-metal and polymetallic deposits................................................................................... 8
Regional Geophysical Studies Applied to

Mineral Resource Assessment of the Hailey I°x2° Quadrangle

and the Western Part of the Idaho Falls I°x2° Quadrangle,

South-Central Idaho

By M. Dean Kleinkopf, 1 Anne E. McCafferty, 1 and Gerda A. Abrams 1

ABSTRACT

Interpretations of aeromagnetic and gravity anomaly 

data for the Hailey I°x2° quadrangle and the western part of 

the Idaho Falls I°x2° quadrangle in south-central Idaho were 

used to delineate buried intrusive complexes, major geologic 

structures, and areas of possible volcanic subsidence that 

may relate to hydrothermally altered and mineralized areas.

Three crustal provinces were identified from the aeromagnetic and gravity signatures. The northwest province is 

composed of Cretaceous granitic terranes of the Idaho 

batholith that are weakly magnetic and have slowly varying, 

highly negative Bouguer anomaly values. The northeast 

province exhibits a variety of weak to strong aeromagnetic 

anomalies in the Pioneer and White Knob Mountains, which 

are made up of assorted terranes of thrust- and block-faulted 

sedimentary rocks, Precambrian metamorphic rocks, Tertiary granitic intrusive rocks, and Eocene and Miocene volcanic rocks. This assemblage has an overall negative mass 

effect on the gravity field similar to that of the Idaho 

batholith. The Snake River Plain province consists predominantly of Cenozoic basalt that exhibits complex patterns of 

high-frequency positive and negative aeromagnetic anomalies that result from high magnetic susceptibility contrasts 

and reversed magnetizations of the basalt.

The highest aeromagnetic values outside the Snake 

River Plain province correlate spatially with Tertiary epizonal plutons such as granitic intrusive rocks of the Sawtooth 

batholith north of Atlanta, the stock at Steel Mountain just 

north of Rocky Bar, and the Sheep Creek batholith about 24 

km west of Rocky Bar. The magnetic anomaly data indicate 

that each of these granitic masses is a composite intrusive 

complex of variable composition or state of alteration and is 

commonly more extensive in the subsurface than in outcrop. 

Most granitic rocks of the Cretaceous Idaho batholith are 

biotite granodiorite and two-mica granite. The batholithic

!U.S. Geological Survey, Denver, Colorado 80225.

terrane exhibits exceptional uniformly low magnetization 

and low density, except for some diorite and minor border 

facies of tonalite, both of which are more strongly magnetized and denser than the main mass of the batholith.

The Bouguer gravity anomaly map is dominated by the 

southern part of a regional negative anomaly of 50-80 mGal 

in south-central Idaho that shows a strong inverse correlation 

with regional topography resulting from thickened crust 

beneath the Idaho batholith. Superimposed on the regional 

negative gravity anomaly are local positive and negative 

anomalies that result from mass anomalies in the upper crust. 

The negative anomalies may be associated with low-density 

granite stocks or with accumulations of low-density alluvial 

material in intermontane basins and valleys.

Two buried shear zones that may have influenced the 

distribution of mineral deposits are interpreted from the 

aeromagnetic and gravity anomaly patterns. The Atlanta 

shear zone is defined by a northeast-trending belt of high 

magnetic gradient that passes through Atlanta. Intrusive 

rocks of the Sawtooth, Steel Mountain, and Sheep Creek 

batholiths are along the northwest side of this belt of steep 

magnetic gradients. The Bouguer gravity anomaly data 

along the belt show some corroborative evidence for the aeromagnetic interpretation of a buried shear zone. The second 

proposed shear zone, the Great Rift shear zone, is interpreted 

from northwesterly trending aeromagnetic and gravity patterns that are projected from similar trends associated with 

the Great Rift near Craters of the Moon National Monument.

The distribution of mineral deposits commonly correlates with known geologic features or with geologic features 

postulated from geophysical information. A number of gold 

deposits are present northeast of Atlanta along the belt of 

high magnetic gradient. The belt extends to the northeast and 

to the southwest and may help delineate other areas of undiscovered mineral resources. Four volcanic features defined 

from geologic mapping in the study area show varying 

expression in the aeromagnetic and gravity anomaly data.

Rl
R2 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

43°

HAILEY IDAHO 

FALLS

IDAHO

_______ _________

Figure 1. Index map showing the location of the Hailey I°x2c 

quadrangle and the western part of the Idaho Falls I°x2° quadrangle, south-central Idaho.

These are the caldron west of Ketchum, the Magic Reservoir 

eruptive center east of Fairfield, the Lehman Basin caldron 

complex west of Mackay, and the Alder Creek eruptive center south of Mackay. The aeromagnetic anomaly data indicate three other possible volcanic features in areas where 

some mineralized rock is present. Along the postulated Great 

Rift shear zone, just southeast of the Pioneer Mountains core 

complex, complex magnetic anomaly patterns suggest a possible volcanic center. Two other possible volcanic features 

are along the proposed Atlanta shear zone northeast of 

Atlanta where complex negative magnetic anomaly patterns 

suggest local fracturing in the granitic rocks and possible 

volcanic subsidence features.

Interpretation of the aeromagnetic and gravity anomaly 

data suggests a number of areas for followup studies to identify possible new mineral deposits. These include (1) areas 

interpreted to be underlain by igneous intrusive rocks, (2) 

northeast-trending belts of high magnetic gradient reflecting

possible faulting parallel with the Trans-Challis fault system, 

(3) areas of crossfaulting along the proposed Atlanta and 

Great Rift shear zones, and (4) aeromagnetic and gravity 

anomalies that correlate with geochemical anomalies.

INTRODUCTION

Analyses of aeromagnetic and gravity anomaly data 

were made as part of a multidisciplinary effort, the U.S. Geological Survey Conterminous United States Mineral Assessment Program (CUSMAP), to assess the mineral resource 

potential of the Hailey I°x2° quadrangle and the western 

part of the Idaho Falls I°x2° quadrangle in south-central 

Idaho (fig. 1). The objectives were (1) to compile and display 

available aeromagnetic and gravity anomaly data for the area 

and (2) to interpret the geologic significance of the anomaly 

fields and evaluate their application to mineral resource studies. Herein we provide results of geophysical interpretations 

that we previously have presented both orally and as poster 

papers at conferences and public meetings during the course 

of the CUSMAP investigations (Kleinkopf and others, 

1988a, b, 1989; Kleinkopf, 1989). Total-intensity magnetic 

and complete Bouguer gravity anomaly maps of the study 

area have been published at a scale of 1:250,000 (Abrams, 

1991; McCafferty and Abrams, 1991). These are companion 

maps to geological (Worl and others, 1991), geochemical, 

and radioelement maps prepared at the same scale by other 

members of the Hailey CUSMAP team.

Radioelement data were compiled for the study area by 

M.G. Medberry (written commun., 1989) from aerial 

gamma-ray spectrometer surveys flown as part of the 

National Uranium Resource Evaluation (NURE) program of 

the U.S. Department of Energy (Geometries, Inc., 1979a, b). 

Radioelement maps were prepared that show surface concentration values for potassium, thorium, and uranium.

Interpretation of aeromagnetic and gravity anomaly 

data was an integral part of the mineral assessment of the 

study area. The anomaly data were used in conjunction with 

geological and geochemical investigations to predict locations of buried intrusive complexes, to delineate major fault 

and shear zones, and to identify locations that might be 

hydrothermally altered or mineralized. The aeromagnetic 

anomaly data were more useful in the direct detection of 

mineralized features, whereas the gravity anomaly data 

helped to define regional structure and discriminate lowdensity intrusive bodies in terranes of high-density rocks.

A map of generalized geologic terranes and major 

structures of the study area is shown in figure 2 (Worl and 

Johnson, 1989, this volume). A geologic terrane is defined 

herein as an area in which one or more assemblages of rock 

types are present in surface outcrops. Comparison of the 

aeromagnetic and gravity anomaly data with the geology 

illustrates signatures that correlate with major structures and 

lithology, as well as other signatures that correlate with similar structures and lithology projected in the subsurface.
SAWTOOTH 

BATHOLITH

. >* , II! ' I

. Xvl'A PIONEER : £: : .': MOUNTAINS^:, : : J: :x: :CORE COMPLEX

I SHEEP '/A 

-, MOUNTAIN, J

X Camas Prairie

0 10 20 30 KILOMETERS 

I I I

15'

43°00

EXPLANATION

Quaternary terrane X Tertiary volcanic rock terranes 

Miocene-Pliocene terrane

Eocene terrane

Tertiary intrusive rock terrane 

Cretaceous intrusive rock terrane

Paleozoic sedimentary rock terranes 

Black shale terrane

Flysch terrane Carbonate terrane

Middle Proterozoic

metamorphic rock terrane

Contact 

Major fault

Figure 2. Map showing geologic terranes and major faults of the Hailey I°x2° quadrangle and the western part of the Idaho Falls I°x2° quadrangle, south-central Idaho. Modified 

from Worl and Johnson (1989, this volume).

O

1

> 

Os3

H<onn

>

on 

Hm

on

1

cn O H Ocn

cnon on
R4 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

Mines and prospects containing precious metals are 

widely scattered in the study area. Many deposits are associated spatially with granitic intrusive rocks and known or 

inferred fault zones, particularly the northeast-trending 

Trans-Challis fault system and subparallel systems (Bennett 

and Lewis, 1989). Geophysical studies of the Trans-Challis 

fault system by Mabey and Webring (1985) during mineral 

resource assessment of the adjacent Challis I°x2° quadrangle provide information applicable to the study area. The 

northeast-trending Hailey mineral belt is of particular interest in the mineral resource studies because of its parallelism 

and proximity to northeast-trending mineralized faults of the 

Trans-Challis fault system in the northwestern part of the 

Hailey quadrangle.

In this part of Idaho, numerous magnetic and gravity 

surveys and regional compilations for mineral resource 

exploration and regional framework studies have been conducted during the past 30 years. Published reconnaissance 

magnetic and gravity anomaly maps are particularly useful 

for describing the general geophysical setting of the region 

(Bonini, 1963; Mabey and others, 1974; Eaton and others, 

1978; Mabey and others, 1978; Zietz and others, 1978; Geometries, Inc., 1979a, b; Hildenbrand and others, 1982; Bankey and others, 1985; Jachens and others, 1985; Hill, 1986; 

Bankey and Kleinkopf, 1988; Cady and others, 1991; Bankey, 1992; McCafferty, 1992). Various workers have made 

geophysical studies applied to mineral resource assessment 

and to interpretation of structural framework of the southern 

Idaho batholith and the Snake River Plain (Hill and others, 

1961; La Fehr and Pakiser, 1962; Hill, 1963; Hill and 

Pakiser, 1966; Mabey, 1966, 1976, 1978, 1981, 1982a, b, 

1986; Kleinkopf, 1970, 1989; Zohdy and Stanley, 1973; 

Zoback and Thompson, 1978; Bhattacharyya and Mabey, 

1980; Pankratz and Ackermann, 1982; Kuntz and others, 

1983; Criss and Champion, 1984; Mabey and Webring, 

1985; Mabey and Tschanz, 1986; Whitehead, 1986; Cluer, 

1987; Toth and others, 1987; Webring and Mabey, 1987; 

Cluer and others, 1988; Kleinkopf and others, 1988a, b, 

1989; Sanford and others, 1989; Wilson and others, 1990; 

Abrams, 1991; McCafferty and Abrams, 1991).

Acknowledgments. Viki Bankey and Robert Kucks 

assisted in computer processing of the data. Robert Kucks 

also helped with the fieldwork.

MAGNETIC ANOMALY DATA

The residual total-intensity aeromagnetic map was 

compiled using data from nine surveys flown at different 

line spacings and altitudes (pi. 1A). Through a series of 

standard analytical techniques, the data were reduced to a 

common surface of 1,000 ft (305 m) above ground (pi. 1A). 

The description of the computational procedures and the

contoured aeromagnetic anomaly map at a scale of 

1:250,000 have been published previously (McCafferty and 

Abrams, 1991). Because of the large variation of flightline 

spacings, from 0.5 to 3 mi (0.8^.8 km), an index of the 

magnetic surveys used in the compilation is included on 

plate 1 to aid the reader in evaluating the data in specific 

areas. The aeromagnetic data for this study are included in a 

previous compilation done for a regional mineral resource 

assessment of the Idaho batholith and adjacent areas 

(McCafferty, 1992). The data are in digital form (McCafferty and others, 1990) and can be obtained through the 

Earth Resources Observation Systems (EROS) Data Center, 

U.S. Geological Survey, Sioux Falls, South Dakota 57198, 

or the National Geophysical Data Center (NGDC), National 

Oceanic and Atmospheric Administration (NOAA), 

Boulder, Colorado 80303.

Other reconaissance aeromagnetic maps of the Hailey 

and Idaho Falls I°x2° quadrangles, from surveys flown as 

part of the National Uranium Resource Evaluation (NURE) 

program of the Department of Energy, are available from 

the U.S. Geological Survey (Geometries, Inc., 1979a, b; 

Hill, 1986).

GRAVITY ANOMALY DATA

The complete Bouguer gravity anomaly map (pi. IB) is 

controlled by more than 2,500 unevenly spaced gravity stations. Most of this control is from a data set compiled for the 

recently published Bouguer gravity anomaly map of Idaho 

(Bankey and others, 1985). These data are from surveys conducted by the U.S. Geological Survey, U.S. Department of 

Defense, and various universities. Other data compiled for 

the map are from almost 300 observations made by B.L. 

Cluer collected as part of a Master of Science thesis study of 

Camas Prairie in the area around Fairfield (Cluer, 1987). 

Additional data are from 120 new stations collected by the 

U.S. Geological Survey during 1989 and 1990. The Bouguer 

gravity anomaly values for the map are estimated to be accurate to 1 milligal (mGal).

Description of the computational procedures and an 

earlier version of contoured gravity anomaly map at a scale 

of 1:250,000 were published previously (Abrams, 1991). 

The data are for this study are included in an earlier compilation done for a regional mineral resource assessment of the 

Idaho batholith and adjacent areas (Bankey, 1992). The data 

in digital form (McCafferty and others, 1990) may be 

obtained from the Earth Resources Observation Systems 

(EROS) Data Center, Sioux Falls, South Dakota 57198, or 

the National Geophysical Data Center (NGDC), National 

Oceanic and Atmospheric Administration (NOAA), 

Boulder, Colorado 80303.
REGIONAL GEOPHYSICAL STUDIES APPLIED TO MINERAL RESOURCE ASSESSMENT R5

PHYSICAL PROPERTIES OF 

THE ROCKS

Only qualitative generalizations are made herein about 

values of density and magnetic susceptibility because of the 

wide variety of rock types in the study area and the variable 

lithology within rock unit. Estimates judged to be approximately representative of the major lithologic units were made 

from a consensus of three sources: (1) laboratory and field 

measurements, (2) values obtained by Mabey and Webring 

(1985) from their studies of the adjacent Challis quadrangle, 

and (3) values obtained by Criss and Champion (1984), who 

made analyses of more than 600 samples of granitic rocks 

from the southern part of the Idaho batholith to study effects 

of hydrothermal alteration on magnetic properties. Cretaceous granodiorite and two-mica granite that make up the 

main part of the Idaho batholith have an average density of 

less than 2.6 g/cm3, and diorite intrusive rocks have an average density of about 2.7 g/cm3 . Densities of Cenozoic sedimentary and Tertiary volcanic rocks are less than 2.5 g/cm3 ; 

however, the volcanic rocks show large variations in density 

and magnetization. Tertiary granite has an average density 

of about 2.56 g/cm3, less than that of Cretaceous granite. 

Paleozoic sedimentary rocks comprising the allochtons in the 

eastern part of the study area have an average density of about 

2.6 g/cm3 . The low density of granitic rocks of the Cretaceous Idaho batholith and Tertiary batholiths and stocks is 

possibly related to extensive hydrothermal alteration. Criss 

and Champion (1984) concluded that pervasive hydrothermal alteration may cause minor lowering of density, on the 

order of 0.02-0.04 g/cm3 , of most rock types.

Granitic rocks of the Tertiary batholiths and stocks are 

considerably more magnetic than granitic rocks of the Cretaceous Idaho batholith. In general, granitic rocks of the 

Idaho batholith, excluding the border facies, are granodiorite and two-mica granite that are weakly magnetic and 

exhibit few positive anomalies. Exceptions are dioritic 

intrusive rocks, which give positive magnetic anomalies 

similiar to expressions of the Tertiary intrusive rocks. Tertiary volcanic rocks, in particular extrusive rocks of the 

Snake River Plain, are moderately to strongly magnetic. 

The extrusive volcanic rocks commonly exhibit remanent 

magnetization greater than induced magnetization, by several orders of magnitude. Criss and Champion (1984) found 

that induced magnetization is predominant in Cretaceous 

and Tertiary intrusive rocks and concluded that effects of 

remanent magnetization are unimportant to the interpretation of magnetic maps of these intrusive rock terranes. The 

Paleozoic allochthons composed of Devonian to Permian 

sedimentary rocks are nonmagnetic, except for areas of 

local alteration or areas of magnetite enrichment around 

Tertiary intrusions; such differences could be important to 

the small-scale prospector who might wish to conduct 

detailed ground magnetometer traverses.

CRUSTAL PROVINCES

Three crustal provinces were distinguished in the 

study area on the basis of contrasting aeromagnetic and 

gravity signatures (pis. IA, B). These crustal provinces can 

be used to provide a framework for the application of geophysical interpretations to mineral resource evaluation. (1) 

The northwest province, composed of Cretaceous granitic 

terranes of the Idaho batholith, is weakly magnetic and has 

slowly varying, highly negative Bouguer anomaly values. 

(2) The northeast province in the area of the Pioneer and 

White Knob Mountains comprises assorted terranes of 

thrust and block-faulted Paleozoic sedimentary rocks, Precambrian metamorphic rocks of the Pioneer Mountains 

core complex, Tertiary granitic intrusive rocks, and Eocene 

and Miocene volcanic rocks that exhibit a variety of weak 

to strong magnetic anomalies and give an overall negative 

mass effect on the gravity field similar to that of the Idaho 

batholith (Bankey and Kleinkopf, 1988). (3) The Snake 

River Plain province of predominantly Cenozoic basalt 

exhibits complex patterns of high-frequency positive and 

negative magnetic anomalies that reflect high magnetic susceptibilities and reversed magnetizations.

Most of the granitic rocks of the Cretaceous Idaho 

batholith (northwest province) are biotite granodiorite and 

two-mica granite (Kiilsgaard and Lewis, 1985; Lewis and 

Kiilsgaard, 1991). The batholithic terrane exhibits exceptional uniformly low magnetization and low density, except 

for a few diorite intrusive bodies and minor border facies of 

tonalite, which are more strongly magnetized and denser 

than the main mass of the batholith. The highest magnetic 

values in the study area, except for volcanic rocks of the 

Snake River Plain province, correlate spatially with Tertiary 

epizonal plutons such as granitic intrusive rocks of the Sawtooth batholith north of Atlanta, the stock at Steel Mountain 

just north of Rocky Bar, and the Sheep Creek batholith about 

24 km west of Rocky Bar. The magnetic anomaly data indicate that each of these granitic masses is a composite intrusive complex of variable composition or state of alteration 

and is more extensive in the subsurface than in outcrop.

The series of prominent gradients on the Bouguer gravity anomaly map (pi. IB) that decrease from the Snake River 

Plain province to the negative values in the north-central part 

of the study area are part of a regional negative mass anomaly in central Idaho, 50-80 mGals in amplitude, resulting 

from a thickened crust beneath the Idaho batholith. This 

large negative anomaly shows a strong inverse correlation 

with regional topography. Bonini (1963) calculated the isostatic anomalies to be near zero; thus the region is in approximate isostatic equilibrium (Jachens and others, 1985; 

Mabey and Webring, 1985). Superimposed on the regional 

negative gravity anomaly are local positive and negative 

anomalies, in the form of nosings or closures in the contours, 

that result from mass anomalies in the upper crust. The negative anomalies may be associated with low-density granite
R6 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

stocks or with accumulations of low-density alluvial material in intermontane basins and valleys such as Sawtooth valley and southeast and northwest of Mackay (Wilson and 

others, 1990).

In order to remove the broad negative anomaly of 

50-80 mGal that dominates the Bouguer gravity anomaly 

map (pi. IB), a residual map (pi. 1C) was prepared. The 

residual map also enhances local gravity anomalies assumed 

to be associated with shallow sources of interest. To prepare 

the residual map the Bouguer gravity anomaly data was 

transformed to the frequency domain, then the data were filtered (Hildenbrand, 1983) to remove long-wavelength 

anomalies greater than 50 km, in particular, the regional negative anomaly. The resulting residual map is composed 

mainly of short-wavelength anomalies; this procedure 

assumes that the cut-off wavelength of the filter and the maximum depth of source are related (Hildenbrand and others,

1982). On the basis of empirical relationships (Hildenbrand,

1983), the resulting residual gravity anomalies consisting of 

wavelengths of 50 km and less likely are related to sources 

above depths of 4-8 km.

The southern part of the Idaho batholith comprises a 

series of rhombic blocks that are bounded by a combination 

of northeast-oriented faults, parallel with the Trans-Challis 

fault system, related to Eocene extension and northwestoriented faults related to Miocene basin and range extension (Bennett and Lewis, 1989). Segments of these faults 

can be inferred in the geophysical data. In particular, belts 

of steep magnetic gradient correlate with faults or postulated shear zones.

The northeast-trending belt of high magnetic gradient 

near Atlanta (pi. 1A) is interpreted to reflect a buried shear 

zone (Kleinkopf, 1993). The proposed shear zone, here 

called the Atlanta shear zone, may be related to the northeast-trending Trans-Challis fault system. Intrusive rocks of 

the Sawtooth, Steel Mountain, and Sheep Creek batholiths 

are along the northwest side of this belt. The Bouguer gravity 

anomaly data along the belt show some corroborative evidence for the interpretation of a buried shear zone. To 

illustate this, the trace of the Atlanta shear zone, as interpreted from the magnetic anomaly data, was plotted on the 

gravity anomaly maps (pis. IB, C). The dominantly northwesterly grain of the gravity anomaly data is interrupted 

intermittently along the trace of the proposed shear zone by 

northeasterly contour deflections and alignments of lowamplitude negative and positive residual gravity anomalies, 

expressed in the form of subtle nosings in the contours. 

Regional basin and range faults, such as the Deer Park and 

Montezuma faults, and correlative magnetic and gravity 

trends show subtle changes of strike from south-southeast 

north of the proposed shear zone to southeast south of the 

shear zone (pi. 1).

Across the southern boundary of the Idaho batholith, 

irregular changes in the magnetic and gravity anomaly patterns reflect the complex lithology of the transition zone 

between the Idaho batholith and young basalts of the Snake

River Plain (pis. 1A, B). Some of these signatures reflect 

blocks of granitic rocks of the Idaho batholith intermixed 

with rocks of the volcanic terrane along the edge of the 

Snake River Plain province. Residual anomalies in the form 

of nosings of the contours may be the expression of irregular 

edges of Tertiary intrusive rocks along the transition zone. 

The magnetic anomaly map shows that the rather elongate 

low-amplitude anomalies of the batholith change laterally to 

smaller, high-amplitude, somewhat equidimensional anomalies characteristic of younger basalts of the Snake River 

Plain province.

The Bouguer gravity anomaly data in the Camas Prairie 

area show an east-trending gravity trough (pis. IB, C) of 

5-10 mGal amplitude near the southern boundary of the 

Idaho batholith. On the basis of gravity modeling, Cluer and 

others (1988) interpreted Camas Prairie as an intermontane 

basin containing some 2.5-3 km of alluvium and basalt and 

bounded by high-angle normal faults. They described the 

basin as "structurally within the transition zone between the 

late Cretaceous-early Tertiary granitic batholith and the 

Miocene-Recent Snake River Plain volcanogenic province." 

The magnetic anomaly data exhibit negative anomalies 

along a corresponding east-west axis at Camas Prairie (pi. 

1A). The Bouguer gravity anomaly contours trend east, then 

curve north along outcrops of Eocene extrusive rocks and 

Paleozoic sedimentary rocks at the edge of the Snake River 

Plain (fig. 2. pi. IB). Several distinctive negative gravity 

anomalies are present along the plain, especially near Craters 

of the Moon National Monument and the town of Arco. To 

the west of Camas Prairie, east trends in the gravity and magnetic anomaly data changing to northwest trends are punctuated by positive and negative anomalies that reflect mixing 

of lithologies of the Idaho batholith (northwest province) and 

the Snake River Plain province.

The eastern boundary of the Idaho batholith, which is 

generally considered to be near the eastern limit of outcrops 

of Cretaceous granitic rocks (fig. 2), is indistinct in the geophysical data. The Idaho batholith may extend in the subsurface of the northeast province to the east, possibly as far as 

Mackay, beneath allochthons of Paleozoic black shale and 

clastic rocks and younger Eocene volcanic cover. Just to the 

north, in the Challis quadrangle, in the same structural setting, Mabey (1982b) concluded that allochthonous Paleozoic 

sedimentary rocks (Hall, 1985) may be underlain by a magnetized basement.

A possible structural boundary, herein called the Great 

Rift shear zone, is suggested by the geophysical data. In the 

southeastern part of the study area, in the Snake River Plain 

province, a northwest-trending zone, named the Great Rift by 

Stearns (1928), is described by Kuntz and others (1983) as 

consisting of a volcanic rift, volcanic vents, and fissures. On 

the basis of alignments of gravity and magnetic anomalies (pi. 

1), we interpret the Great Rift shear zone as a deep-seated 

shear zone that projects northwest past the Pioneer Mountains 

core complex as far as the north-central part of the study area
REGIONAL GEOPHYSICAL STUDIES APPLIED TO MINERAL RESOURCE ASSESSMENT R7

where it is terminated by northeast trends of the proposed 

Atlanta shear zone, believed to be part of the Trans-Challis 

fault system. Bennett (1984) noted that the intersection of the 

Trans-Challis fault system and basin and range structures 

marks the change from northwest extension during the 

Eocene (?) to northeast extension during the Oligocene (?).

MINERAL RESOURCES

The aeromagnetic anomaly data provide definitive 

information for identifying and mapping plutons and mineralized fault zones, whereas the gravity anomaly data provide 

general constraints on mapping lithology of granitic units, 

commonly within batholithic complexes, and information 

for detecting and projecting major structural features in the 

subsurface. The aeromagnetic and gravity anomaly data are 

complementary because the two types of data are measures 

of different physical properties of the rocks. For example, 

low-density, high-magnetic-susceptibility felsic granitic 

intrusive rocks of Tertiary age can be distinguished from 

higher density, low-magnetic-susceptibility granodioritic 

intrusive rocks of the Cretaceous Idaho batholith.

The distribution of control for the aeromagnetic and 

gravity data is also different due to different systems of measurements. The magnetic control consists of almost continuous data collected along flightlines that are usually regularly 

spaced for a given survey at an interval of 1 mi (1.6 km) or 

more for regional studies, such as this study (pi. 1A). Sampling rates are typically several milliseconds, which translate 

into recording measurement of magnetic field intensity 

every few hundred feet. The gravity data, on the other hand, 

consist of isolated and unevenly distributed data points collected on the ground. The observation points, or stations, 

normally are spaced from 1 to 3 mi (1.6-4.8 km) or more 

apart, depending on the accessibility of the terrain, field time 

available, and the method of transport. In detailed studies 

that might be considered in the future for the study area, 

closely spaced data could be collected to map segments of 

faults or granitic intrusive rocks that have been intensely 

hydrothermally altered or shattered to the extent that contrasts in magnetic susceptibility and density are perceptibly 

decreased relative to adjacent unaltered or undisturbed rock.

In order to study spatial relationships between geophysical anomalies and the location of precious-metal and polymetallic deposits, a generalized summary plot (Worl and 

Johnson, 1989) was prepared that combines distribution of 

precious-metal and polymetallic vein, stockwork, and skarn 

deposits for the study area (fig. 3). The deposit types shown 

correspond to mineral deposit models, or modifications of 

models, described in Cox and Singer (1986).

In general, the distribution of these particular deposit 

types correlates with known geologic features or those postulated from the geophysical data. Northeast of Atlanta, 

gold deposits are clustered along the belt of high magnetic 

gradient (fig. 3, pi. 1A), which is extensive to the northeast

and to the southwest and has been interpreted as a major 

northeast-trending shear zone (Atlanta shear zone) in the 

Idaho batholith that is probably related to the Trans-Challis 

fault system. If the trend is part of the Trans-Challis fault 

system, it may have been the focus of extensive epithermal 

gold mineralization characteristic of the Trans-Challis fault 

system (Bennett, 1984; Kiilsgaard and Bennett, 1985).

In view of the association of mineral deposits with volcanic centers and graben structure observed in the neighboring Chain's quadrangle (Fisher, 1985; Hardyman, 1985; 

Mclntyre and Johnson, 1985), four volcanic features defined 

from geologic mapping in the study area are shown on the 

magnetic and gravity anomaly maps (pi. 1). These are the caldron west of Ketchum (Hall and Mclntyre, 1986), the Magic 

Reservoir eruptive center east of Fairfield (Leeman, 1982; 

Bonnichsen and others, 1989), the Lehman Basin caldron 

complex west of Mackay (Moye and others, 1989), and the 

Alder Creek eruptive center south of Mackay (Moye and others, 1989). Just west of Ketchum, Hall and Mclntyre (1986) 

described an area of downdropped rocks bounded by arcuate 

faults on three sides as a volcanic caldron. Propyllitic alteration and extensive pyritization are present. High-frequency 

magnetic anomalies on the east, west, and north sides of the 

area are suggestive of possible ring structure around the volcanic feature (labeled "caldron" on pi. 1A). The Lucky Boy 

and the Ontario mines are within the caldera and reportedly 

produced silver, lead, zinc, and copper (Hustedde and others, 

1981; Park, 1989). Southeast of Fairfield, a postulated volcanic eruptive and subsidence center at Magic Reservoir (Leeman, 1982; Bonnichsen and others, 1989) exhibits a complex 

magnetic pattern consisting of a deep low surrounded on 

three sides by high-frequency positive anomalies (pi. 1A). 

Gold production reportedly has exceeded more than 100,000 

ounces (2,830 kg) in the neighboring Camas mining district 

(Hustedde and others, 1981; Bennett and Lewis, 1989), 

although no direct relationship between the mineral deposits 

and the Magic Reservoir eruptive center is inferred.

In the Mackay area, the Lehman basin caldron complex 

and the Alder creek eruptive center (pi. 1) were mapped and 

interpeted during the geologic studies (Moye and others, 

1989). These were sites of eruptions of intermediate lavas 

and ash-flow tuffs and intrusions of silicic plutonic rocks. In 

the Lehman basin and the Alder Creek mining district, baseand precious-metals were deposited in porphyry systems and 

veins controlled by north- to northwest-trending structures 

(Strowd and others, 1981; Moye and others, 1989; Snider and 

Moye, 1989; Worl and Johnson, 1989). The magnetic anomaly data exhibit mainly negative values associated with the 

volcanic centers (pi. 1), but the 3-mi (4.8 km) spacing of the 

flightlines in this area provides data of insufficient detail to 

define boundaries of the centers. The reconnaissance-scale 

gravity control in this area is not sufficient to define the volcanic features; however, the anomaly data show north- to 

northwest- and northeast-trends (pis. IB, Q that are consistent with regional structural trends (Southworth, 1988; 

Soulliere and others, 1989).
R8 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

116° 115° 114°

44°

Idaho City

Mackay

Ketchum

Hailey

Fairfield

20 30 KILOMETERS

\ 

20 MILES

43°

Figure 3. Map showing distribution of precious-metal and polymetallic deposits (shaded areas) in the Hailey 1 °x2° quadrangle and the 

western part of the Idaho Falls I°x2° quadrangle, south-central Idaho. Deposits include complex precious-metal veins, shear-zone-hosted 

precious-metal veins, shear-zone-hosted polymetallic veins, stockwork deposits containing significant gold, massive gold veins, and massive silver veins. Modified from Worl and Johnson (1989); deposit types following Cox and Singer (1986).

Three volcanic or subsidence features that have not 

been mapped geologically are suggested by the aeromagnetic anomaly data. One feature is along the postulated Great 

Rift shear zone just southeast of the Pioneer Mountains core 

complex, where complicated magnetic anomaly patterns and 

variable gravity anomaly trends suggest the possibility of a 

volcanic-intrusive center (pi. 1). The Lake Creek stock is in 

the eastern part of the feature. The pattern of high-frequency 

positive and negative anomalies arranged in an annular pattern around the edges of the feature gives a sense of possible 

ring structure. Base- and precious-metal deposits (fig. 3) that 

are part of the Little Wood River and Copper Basin mining 

districts are in the central part of the proposed center (Strowd 

and others, 1981; Worl and Johnson, 1989).

Two other possible volcanic features (pi. 1A) are along 

the proposed Atlanta shear zone northeast of Atlanta. These 

are local areas of complex negative magnetic anomaly patterns that may indicate local fracturing in the granitic rocks 

and possible volcanic subsidence (pi. 1A). Other anomalies 

are in areas that are mineralized, such as the Yuba district 

near Atlanta (fig. 3), which has produced more than 

100,000 ounces (2,830 kg) of gold (Bennett and Lewis, 

1985). Additional areas of possible undiscovered mineral

resources may extend southwest of Atlanta along the proposed Atlanta shear zone. The Red Warrior mining district, 

another district in Idaho that exceeded 100,000 ounces 

(2,830 kg) of gold production, is along this proposed shear 

zone southwest of Atlanta.

An arbitrarily defined belt, referred to as the Hailey mineral belt, is shown on plate 1. The belt contains variably mineralized rock including precious- and base-metal deposits 

(fig. 3). It extends northeasterly in a discontinuous fashion for 

almost 160 km from near Mountain Home, across the southeastern part of the Idaho batholith, past the White Knob and 

Pioneer Mountains, to as far northeast as Mackay (Johnson 

and Worl, 1989). Some of the northeast-trending geophysical 

features within the belt suggest geologic structure approximately parallel with the Trans-Challis fault system.

CONCLUSIONS

Magnetic and gravity anomaly data for the Hailey 

I°x2° quadrangle and the western part of the Idaho Falls 

I°x2° quadrangle suggest a number of areas that may be 

favorable for followup studies to identify new occurrences of
REGIONAL GEOPHYSICAL STUDIES APPLIED TO MINERAL RESOURCE ASSESSMENT R9

mineral resources. Detailed studies and collection of additional control can be prioritized on the basis of favorable 

geological and geochemical areas. The following areas for 

possible undiscovered mineral resources are suggested from 

interpretation of the aeromagnetic and gravity anomaly data.

1. Areas interpreted to be underlain by igneous intrusive rocks along the postulated Atlanta and Great Rift shear 

zones.

2. Areas of interpreted crossfaulting along the Atlanta 

and Great Rift shear zones including intersections of basin 

and range faults such as the Montezuma and Deer Park faults.

3. Belts of steep magnetic gradient that may indicate 

covered border zones and subcrop contacts around Tertiary 

intrusions such as the Sawtooth, Steele Mountain, Sheep 

Creek, and Soldier Mountains igneous complexes.

4. Areas of magnetic and gravity anomalies whose 

sources may be buried intrusions in regions of geochemical 

anomalies. For example, Smith (1989) reported, from analysis of the nonmagnetic fraction of heavy-mineral concentrates, the possibility of tin granite in the Sheep Creek area of 

the Twin Springs pluton. The variable magnetic patterns 

suggest that there probably were multiple intrusions in the 

Twin Springs area.

5. Southern border zones of the Idaho batholith where 

magnetic patterns suggest the presence of shallow Tertiary 

intrusive rocks that may be masked by young basalt of the 

Snake River Plain.

6. Areas of black shale and calcareous clastic rock 

terrane marked by positive magnetic anomalies suggestive 

of granitic intrusive rocks in sedimentary rocks, for example 

in the Pioneer and White Knob Mountains.

7. Aeromagnetic and gravity signatures that may indicate the presence of mineralized structure or hydrothermal 

alteration in areas of the mapped and postulated volcanic 

features discussed in preceding sections (pi. 1). The magnetic and gravity anomaly control are sufficient, in most 

cases, to corroborate the presence but not the details of the 

volcanic features, particularly in areas of 3-mile-spaced 

flightlines (pi. 1A). The data indicate, however, that detailed 

surveys should provide additional subsurface information 

for a better understanding of the geology and alteration patterns of these volcanic features.

REFERENCES CITED

Abrams, Gerda, 1991, Bouguer gravity anomaly map of the Hailey 

and western part of the Idaho Falls I°x2° quadrangles, Idaho: 

U.S. Geological Survey Miscellaneous Field Studies Map 

MF-2160-B, scale 1:250,000.

Bankey, Viki, 1992, Complete Bouguer gravity, isostatic residual 

gravity, and related geophysical maps centered on the Idaho 

batholith and Challis volcanic field, lat 42°^7°N., long 

110°-118° W.: U.S. Geological Survey Geophysical Investigations Map GP-995, scale 1:1,000,000.

Bankey, Viki, and Kleinkopf, M.D., 1988, Bouguer gravity anomaly map and four derivatives: U.S. Geological Survey Geophysical Investigations Map GP-978, scale 1:1,000,000.

Bankey, Viki, Webring, M.W., Mabey, D.R., Kleinkopf, M.D., and 

Bennett, E.H., 1985, Complete Bouguer anomaly map of Idaho: U.S. Geological Survey Miscellaneous Field Investigations 

Map MF-1773, scale 1:500,000.

Bennett, E.H., 1984, The trans-Challis fault zone A major crustal 

discontinuity in central Idaho: Geological Society of America 

Abstracts with Programs, v. 16, no. 6, p. 442.

Bennett, E.H., and Lewis, R. S., 1989, The geology and ore deposits 

of the Idaho batholith in the Hailey I°x2° quadrangle, Idaho, in 

Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., 

eds., Geology and mineral deposits of the Hailey and western 

Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey 

Open-File Report 89-639, p. 26-32.

Bhattacharyya, B.K., and Mabey, D.R., 1980, Interpretation of 

magnetic anomalies over southern Idaho using generalized 

multibody models: U.S. Geological Survey Open-File Report 

80-475, 48 p.

Bonini, W.E., 1963, Gravity anomalies in Idaho: Idaho Bureau of 

Mines and Geology Pamphlet 132, 10 p.

Bonnichsen, Bill, Leeman, W.P., Jenks, M.D., and Honjo, Norio, 

1989, Geologic field guide to the central and western Snake 

River Plain, Idaho, emphasizing the siliceous volcanic rocks, in 

Link, P.K., and Hackett, W.R., eds., Guidebook to the geology 

of central and southern Idaho: Idaho Geological Survey Bulletin 27, p. 183-192.

Cady, J.W., Bankey, Vicki, Lee, Keenan, McCafferty, A.E., Pitkin, 

J.A., and Stanley, W.R., 1991, Synthesis of geophysical and 

geological data centered on the Idaho batholith and the Challis 

volcanic field, Idaho, in Good, E.E., Slack, J.F., and Kotra, 

R.K., eds., USGS Research on Mineral Resources-1991, Program and Abstracts, Seventh Annual V.E. McKelvey Forum 

on Mineral and Energy Resources: U.S. Geological Survey 

Circular 1062, p. 6-7.

Cluer, B.L., 1987, A gravity model of basement geometry and 

resulting hydrogeologic implications of the Camas Prairie, 

south-central Idaho: Flagstaff, Northern Arizona University, 

M.S. thesis, 99 p.

Cluer, B.L., Best, D.M., and Agenbroad, L.D., 1988, A hydrogeological interpretation of the Camas Prairie, south-central Idaho, 

based on gravity anomaly modeling: Geological Society of 

America Abstracts with Programs, v. 20, no. 6, p. 410.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Criss, R.E., and Champion, D.E., 1984, Magnetic properties of granitic rocks from the southern half of the Idaho 

batholith Influences of hydrothernal alteration and implications for aeromagentic interpretation: Journal of Geophysical 

Research, v. 89, no. B8, p. 7061-7076.

Eaton, G.P., Wahl, R.R., Prostka, H.J., Mabey, D.R., and Kleinkopf, M.D., 1978, Regional gravity and tectonic patterns, their 

relation to late Cenozoic epeirogeny and lateral spreading in 

the western Cordillera in Cenozoic tectonics and regional geophysics of the western Cordillera: Geological Society of America Memoir 152, p. 51-91.

Fisher, F.S., 1985, Summary of the geology, mineral deposits, and 

resource potential for selected commodities in the Challis 

quadrangle, in Mclntyre, D.H., ed., Symposium on the geology
RIO GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

and mineral deposits of the Challis quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658-A, p 1-27.

Geometries, Inc., 1979a, National Uranium Resource Evaluation 

aerial gamma-ray and magnetic survey, Idaho Falls quadrangle, Idaho Final report: U.S. Department of Energy, Grand 

Junction Office, Open-File Report GJM-310, scale 1:250,000.

 1979b, National Uranium Resource Evaluation aerial gamma-ray and magnetic survey, Hailey quadrangle, Idaho Final 

report: U.S. Department of Energy, Grand Junction Office, 

Open-File Report GJM-338, scale 1:250,000.

Hall, W.E., 1985, Stratigraphy and mineral deposits in middle and 

upper Paleozoic rocks of black-shale mineral belt, central Idaho, in Mclntyre, D.H., ed., Symposium on the geology and 

mineral deposits of the Challis quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-J, p. 117-131.

Hall, W.E., and Mclntyre, D.H., 1986, Eocene cauldron, batholith, 

and hydrothermal alteration west of Ketchum, Idaho: U.S. 

Geological Survey Open-File Report 86-0122, 5 p.

Hardyman, R.F., 1985, The Twin Peaks cauldera and associated ore 

deposits, in Mclntyre, D.H., ed., Symposium on the geology 

and mineral deposits of the Challis quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658-G, p. 97-105.

Hildenbrand, T.G., 1983, FFTFIL A filtering program based on 

two-dimensional fourier analysis of geophysical data: U.S. 

Geological Survey Open-File Report 83-237, 60 p.

Hildenbrand, T.G., Simpson, R.W., Godson, R.H., and Kane, M.F., 

1982, Digital colored residual and regional Bouguer gravity 

maps of the conterminous United States with cut-off wavelengths of 250 km and 1000 km: U.S. Geological Survey Geophysical Investigations Map GP-953-A, scale 1:7,500,000.

Hill, D.P., 1963, Gravity, volcanism and crustal deformation of the 

eastern Snake River Plain, Idaho: Journal of Geophysical 

Research, v. 68, no. 20, p. 5897-5819.

Hill, D.P., Baldwin, H.L. Jr, and Pakiser, L.C., 1961, Gravity, volcanism and crustal deformation of the eastern Snake River 

Plain, Idaho, in Short papers in the geologic and hydrologic 

sciences: U.S. Geological Survey Professional Paper 424-B, p. 

B248-B250.

Hill, D.P., and Pakiser, L.C., 1966, Crustal structure between the 

Nevada test site and Boise Idaho, from seismic-refraction measurements, in Steinhard, J.S., and Smith, T.J., eds., The earth 

beneath the continents: American Geophysical Union, Geophysical Monograph 10, p. 391-419.

Hill, P.L., 1986, Lists and location maps of aeromagnetic and aeroradiometric publications from the Department of Energy 

NURE program: U.S. Geological Survey Open-File Report 

86-525-G, 22 p.

Hustedde, G.S., Copeland, J.A., Strowd, W.B., Mitchell, V.E., and 

Bennett, E.H., 1981, Mines and prospects of the Hailey quadrangle, Idaho: Idaho Bureau of Mines and Geology Mines and 

Prospects Map Series, 41 p., 1 map, scale, 1:250,000.

Jachens, R.C., Simpson, R.W., Saltus, R.W., and Blakely, R.J., 

1985, Isosatic residual gravity anomaly map of the United 

States (exclusive of Alaska and Hawaii): National Oceanic and 

Atmospheric Administration Geophysical Data Center Map, 

scale 1:2,500,000.

Johnson, K.M., and Worl, R.G., 1989, Preliminary assessment of 

the mineral resources of the Hailey and western part of the Idaho Falls I°x2° quadrangles, Idaho, in Winkler, G.R., Soulliere, 

S.J., Worl, R.G., and Johnson, K.M., eds., Geology and

mineral deposits of the Hailey and western Idaho Falls 1 °x2° 

quadrangles, Idaho: U.S. Geological Survey Open-File Report 

89-639, p. 17-22.

Kiilsgaard, T.H., and Bennett, E.H., 1985, Mineral deposits in the 

southern part of the Atlanta lobe of the Idaho batholith and 

their genetic relation to Tertiary intrusive rocks and to faults, in 

Mclntyre, D.H., ed., Symposium on the geology and mineral 

deposits of the Challis quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-M, p. 153-165.

Kiilsgaard, T.H., Freeman, V.L., and Coffman, J.S., 1970, Mineral 

resources of the Sawtooth Primitive Area, Idaho: U.S. Geological Survey Bulletin 1319-D, 174 p.

Kiilsgaard, T.H., and Lewis, R.S., 1985, Plutonic rocks of Cretaceous age and faults of the Atlanta lobe of the Idaho batholith, 

in Mclntyre, D.H., ed., Symposium on the geology and mineral 

deposits of the Challis quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-B, p. 29^2.

Kleinkopf, M.D., 1970, Aeromagnetic survey and interpretation, in 

Kiilsgaard, T.H., Freeman, V.L., and Coffman, J.S., Mineral 

resources of the Sawtooth Primitive Area, Idaho: U.S. Geological Survey Bulletin 1319-D, p. D26-D27.

 1989, Gravity and magnetic anomaly patterns in mineral 

resource exploration, Hailey CUSMAP, Idaho, in Schlindler, 

K.S., ed., USGS Research on Mineral Resources 1989 Program and abstracts: U.S. Geological Survey Circular 1035 p. 40.

 1993, Magnetic interpretation of a mineralized shear in the

southern part of the Idaho batholith, in Scott, R.W., Detra, P.S., 

and Berger, B.R., eds., Advances related to United States and 

international mineral resources Developing framework and 

exploration technologies: U.S. Geological Survey Bulletin 

2039, p. 31-33.

Kleinkopf, M.D., Bankey, Viki, and McCafferty, A.E., 1988a, 

Aeromagnetic and gravity anomaly maps of the Hailey and 

part of the Idaho Falls two-degree quadrangles, Idaho: Geological Society of America Abstracts with Programs, v. 20, 

no. 6, p. 424-425.

 1988b, The application of regional geophysical data in mineral resource assessments in the Hailey and Idaho Falls quadrangles, Idaho: Geological Society of America Abstracts with 

Programs, v. 20, no. 6, p. 425.

 1989, Gravity and magnetic anomaly patterns applied to

mineral resource exploration, Hailey I°x2° quadrangle, Idaho, 

in Winkler, G.R., Soulliere, S.J., Worl, R.G., and Johnson, 

K.M., eds., Geology and mineral deposits of the Hailey and 

western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological 

Survey Open-File Report 89-639, p. 26-32.

Kuntz, M.A., Mabey, D.R., Champion, D.E., Stanley, D.W., Lefebvre, R.H., Spiker, B.C., McBroome, L.A., and Covington, 

H.R., 1983, Geologic and geophysical maps of the Great Rift 

Instant Study Area, Blaine, Butte, Minidoka, and Power counties, Idaho: U.S. Geological Survey Miscellaneous Field Studies Map MF-1462-A, scale 1:125,000.

La Fehr, T.R., and Pakiser, L.C., 1962, Gravity, volcanism and 

crustal deformation of the eastern Snake River Plain, in Short 

papers in the geologic and hydrologic sciences: U.S. Geological Survey Professional Paper 450-D, p. D76-D78.

Leeman, W.P., 1982, Geology of the Magic Reservoir area, Snake 

River Plain, Idaho, in Bonnichsen, Bill, and Breckenridge, 

R.M., eds., Cenozoic geology of Idaho: Idaho Bureau of Mines 

and Geology Bulletin 26, p. 369-376.
REGIONAL GEOPHYSICAL STUDIES APPLIED TO MINERAL RESOURCE ASSESSMENT Rll

Lewis, R.S., and Kiilsgaard, T.H., 1991, Eocene plutonic rocks in 

south-central Idaho: Journal of Geophysical Research, v. 96, 

no. B8, p. 13,295-13,311.

Mabey, D.R., 1966, Relation between Bouguer gravity anomalies 

and regional topography in Nevada and the eastern Snake 

River Plain, Idaho: U.S. Geological Survey Professional Paper 

550-B, p. B108-B110.

 1976, Interpretation of a gravity profile across the western 

Snake River Plain, Idaho: Geology, v. 4, p. 53-55.

 1978, Regional gravity and magnetic anomalies in the eastern Snake River Plain, Idaho: U.S. Geological Survey Journal 

of Research, v. 6, no. 5, p. 553-562.

 1981, Aeromagnetic studies of the Boulder-Pioneer Wilderness Study Area, Blaine and Custer Counties, Idaho: U.S. Geological Survey Bulletin 1497-B, p. 81-83.

 1982a, Geophysics and tectonics of the Snake River Plain, 

Idaho, in Bill Bonnichsen and R.M. Breckenridge, eds., Cenozoic geology of Idaho: Idaho Bureau of Mines and Geology 

Bulletin 26, p. 139-153.

 1982b, Gravity and magnetic features along the eastern margin of the Idaho batholith in central Idaho: Geological Society 

of America Abstracts with Programs, v. 14, no. 6, p. 320.

 1986, Gravity and magnetic anomaly maps of the Ten Mile

West Roadless Area, Boise and Elmore Counties, Idaho: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1500-D, scale 1:62,500.

Mabey, D.R., Peterson, D.L., and Wilson, C.W., 1974, Preliminary 

gravity map of southern Idaho: U.S. Geological Survey OpenFile Report 74-78, scale 1:500,000.

Mabey, D.R., and Tschanz, C.M., 1986, Aeromagnetic survey and 

tentative interpretation, eastern part of the Sawtooth National 

Recreation Area, Idaho, in Mineral resources of the eastern part 

of the Sawtooth National Recreation Area, Custer and Blaine 

Counties, Idaho: U.S. Geological Survey Bulletin 1545-B, p. 

45-52.

Mabey, D.R., and Webring, M.W., 1985, Regional geophysical 

studies in the Challis quadrangle, in Mclntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis 

quadrangle, Idaho: U.S. Geological Survey Bulletin 1658-E, p. 

69-79.

Mabey, D.R., Zietz, Isidore, Eaton, G.P., and Kleinkopf, M.D., 

1978, Regional magnetic patterns in part of the Cordillera in 

the western United States, in Smith, R.B.and Eaton, G.P., eds., 

Cenozoic tectonics and regional geophysics of the western 

Cordillera: Geological Society of America Memoir 152, p. 

93-106.

McCafferty, A.E., 1992, Magnetic maps and terrace magnetization 

map for the Idaho Mineral Initiative Study, Idaho and vicinity: 

U.S. Geological Survey Geophysical Investigations Map 

GP-994, scale 1:1,000,000.

McCafferty, A.E., and Abrarns, G.A., 1991, Aeromagnetic anomaly map of the Hailey and western part of the Idaho Falls I°x2° 

quadrangles, Idaho: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-2160-A, scale 1:250,000.

McCafferty, A.E., Bankey, V.L., and Cady, J.W., 1990, Digital 

aeromagnetic, terrace-magnetization, Bouguer gravity, isostatic gravity, terrace-density, and topographic grids for data 

centered on the Idaho batholith: U.S. Geological Survey data 

release through EROS data center, Sioux Falls, S.D., 1 9- 

track magnetic tape.

Mclntyre, D.H., and Johnson, K.M., 1985, Epithermal gold-silver 

mineralization related to volcanic sugsidence in the Custer graben, Custer County, Idaho, in Mclntyre, D.H., ed., Symposium 

on the geology and mineral deposits of the Challis quadrangle, 

Idaho: U.S. Geological Survey Bulletin 1658-1, p. 109-131.

Moye, F. J., Sanford, R.F., Erdman, J.A., and Johnson, K.M., 1989, 

Volcanic-hosted and intrusion-related mineral deposits in the 

Hailey and western Idaho Falls quadrangles, Idaho, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 70-72.

Pankratz, L.W., and Ackermann, H.D., 1982, Structure along the 

northwest edge of the Snake River Plain interpreted from seismic refraction: Journal of Geophysical Research, v. 87, no. B4, 

p. 2676.

Park, W.A., 1989, Geology and ore deposits of the Rook's Creek 

stock, Blaine County, Idaho, in Winkler, G.R., Soulliere, S.J., 

Worl, R.G., and Johnson, K.M., eds., Geology and mineral 

deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, 

p. 118-120.

Sanford, R.F., Whitney, H.A., McCafferty, A.E., and Gese, D.D., 

1989, Mineral resources of the Little Wood River Wilderness 

study area, Blaine County, Idaho: U.S. Geological Survey Bulletin 1721-D, 15 p.

Smith, C.L., 1989, Geochemical characterization of some mineral 

terranes in the Hailey I°x2° quadrangles, Idaho, in Winkler, 

G.R., Soulliere, S.J., Worl, R.G., and Johnson, K.M., eds., 

Geology and mineral deposits of the Hailey and western Idaho 

Falls I°x2° quadrangles, Idaho: U.S. Geological Survey OpenFile Report 89-639, p. 23-25.

Snider, L.G., and Moye, F.J., 1989, Regional stratigraphy, physical 

volcanology and geochemistry of the southeastern Challis volcanic field, in Winkler, G.R., Soulliere, S.J., Worl, R.G., and 

Johnson, K.M., eds., Geology and mineral deposits of the 

Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. 

Geological Survey Open-File Report 89-639, p. 122-127.

Soulliere, S.J., Wilson, A.B., and Skipp, Betty, 1989, Geologic controls for mineralization in sedimentrary rocks, western Idaho 

Falls I°x2° quadrangle, Idaho, in Winkler, G.R., Soulliere, 

S.J., Worl, R.G., and Johnson, K.M., eds., Geology and mineral deposits of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 

89-639, p. 128-135.

Southworth, C.S., 1988, Preliminary lineament map of the Hailey, 

Idaho and west half of the Idaho Falls, Idaho I°x2° quadrangles, with inset of regional image mosaic and geologic structures: U.S. Geological Survey Open-File Report 88-640, scale 

1:250,000.

Stearns, H.T., 1928, Craters of the Moon National Monument, Idaho: Idaho Bureau of Mines and Geology Bulletin 13, 57p.

Strowd, W.B., Mitchell, V.E., Hustedde, G.S., and Bennett, E.H., 

1981, Mines and prospects of the Idaho Falls quadrangle, Idaho: Idaho Bureau of Mines and Geology Mines and Prospects 

Map Series, 10 p.

Toth, M.I., King, H.D., Kulik, D.M., and Leszcoykowski, A.M., 

1987, Mineral resources of the King Hill Creek Wilderness 

Study Area, Elmore County, Idaho: U.S. Geological Survey 

Bulletin 1721-8,88 p.
R12 GEOLOGY AND MINERAL RESOURCES OF THE HAILEY AND IDAHO FALLS QUADRANGLES

U.S. Department of Defense, 1974, World relative gravity reference network, part 2, North America (vol. 2): Defense Mapping Agency Aerospace Center Reference Publication 25, with 

supplement updating gravity values to the International Gravity Standardization Net (IGSN-71), 1,635 p.

U.S. Geological Survey, 1974, Residual magnetic intensity 

map Bruneau, Idaho: U.S. Geological Survey Open-File 

Report 74-149, scale 1:62,500.

 1979a, Aeromagnetic map of the Pioneer area, Idaho: U.S. 

Geological Survey Open-File Report 79-1450, scale 1:62,500.

 1979b, Aeromagnetic map of the Arco area, Idaho: U.S.

Geological Survey Open-File Report 79-1445, scale 

1:250,000.

Webring, M.W., and Mabey D.R., 1987, Geophysical anomalies in 

the Challis quadrangle, in Fisher, F.S., and Johnson, K.M., 

eds., Preliminary manuscript for "Mineral-resource potential 

and geology of the Challis I°x2° quadangle, Idaho": U.S. Geological Survey Open-File Report 87^80, p. 66-80.

Whitehead, R.L., 1986, Compilation of selected geophysical references for the Snake River Plain, Idaho and eastern Oregon: 

U.S. Geological Survey Geophysical Investigations Map 

GP-969.

Wilson, A.A., Janecke, S.U., Skipp, Betty, Kleinkopf, M.D., 

McCafferty, A.E., Barton, H.N., and Miller, M.S., 1990, 

Mineral resources of the Borah Peak Wilderness Study Area,

Custer County, Idaho: U.S. Geological Survey Bulletin 1718, 

p. E15.

Worl, R.G. and Johnson, K.M., 1989, Geologic terranes and mineral deposit types in the Hailey and western Idaho Falls I°x2° 

quadrangles, Idaho, in Winkler, G.R., Soulliere, S.J., Worl, 

R.G., and Johnson, K.M., eds., Geology and mineral deposits 

of the Hailey and western Idaho Falls I°x2° quadrangles, Idaho: U.S. Geological Survey Open-File Report 89-639, p. 3-16.

Worl, R.G., Kiilsgaard, T.H., Bennett, E.H., Link, P.K., Lewis, 

R.S., Mitchell, V.E., Johnson, K.M., and Snyder, L.D., 1991, 

Geologic map of the Hailey I°x2° quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 91-340, scale 1:250,000.

Zietz, Isidore, Gilbert, P.P., and Kirby, J.R., 1978, Aeromagnetic 

map of Idaho Color coded intensities: U.S. Geological Survey Geophysical Investigations Map GP-920, scale 

1:1,000,000.

Zoback, M.L., and Thompson, G.A., 1978, Basin and range rifting 

in northern Nevada Clues from a mid-Miocene rift and its 

subsequent offsets: Geology, v. 6, p. 111-116.

Zohdy, A.A.R., and Stanley, W.D., 1973, Preliminary interpretation of electrical sounding curves obtained across the Snake 

River Plain from Blackfoot to Arco, Idaho: U.S. Geological 

Survey Open-File Report 73-370, 5 p.

ir