U.S. Department of the Interior

U.S. Geological Survey

Circular 1305

Prepared in cooperation with the U.S. Department of Agriculture (USDA) Forest Service

Earth Science Studies in Support of Public Policy Development 

and Land Stewardship—Headwaters Province, 

Idaho and Montana
Earth Science Studies in Support of 

Public Policy Development and Land 

Stewardship—Headwaters Province, 

Idaho and Montana

By U.S. Geological Survey Headwaters Province Project Team

Prepared in cooperation with the U.S. Department of Agriculture (USDA) Forest Service

Circular 1305

U.S. Department of the Interior

U.S. Geological Survey

Karen Lund, Scientific Editor

USGS Contributors USDA Forest Service Contributors

John N. Aleinikoff G.L. Jackson

Robert R. Carlson D.W. Peters

Robert G. Eppinger Betsy Rieffenberger

Karl V. Evans

Gregory N. Green

Jane M. Hammarstrom

Terry L. Klein

Michael J. Kunk

Gregory K. Lee

Karen Lund

J. Michael O’Neill

P.K. Sims

Cliff D. Taylor

Russell G. Tysdal

Daniel M. Unruh

Bradley S. Van Gosen

Jeffrey A. Winick
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

U.S. Geological Survey Headwaters Province Project Team (Karen Lund, scientific ed.), 2007, Earth science studies 

in support of public policy development and land stewardship—Headwaters province, Idaho and Montana: 

U.S. Geological Survey Circular 1305, 92 p.

Cover photographs. Front upper: Color Creek falls, tributary to Middle Fork Salmon River. Flowing across 

Mesoproterozoic muscovite-biotite schist. (R.G. Eppinger, 2001.) Front lower: Stoddard packbridge, main Salmon 

River. Prominent north-dipping metamorphic layering in Mesoproterozoic biotite metasandstone on skyline. (K. Lund, 

2005.) Back: Rattlesnake Camp, Middle Fork Salmon River. Outcrops of Mesoproterozoic biotite metasandstone are 

prominent. Boat in mid-foreground is part of USGS–USDA Forest Service baseline geochemical characterization study 

of the river basin. (K. Lund, 2001.)
iii

Contents

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

Digital GIS-Based Geoscience Databases................................................................................................1

Preparation of the Digital Geologic Map for the Headwaters Province Project, by

 Gregory N. Green .........................................................................................................1

Planning ...........................................................................................................................1

Database Design ............................................................................................................2

Conclusions.....................................................................................................................7

Compilation and Interpretation for New Geologic Maps, by Karl V. Evans and 

 Gary L. Jackson ............................................................................................................7

Background.....................................................................................................................7

Use of Geologic Map Data Set in Producing a National Forest Soils Map ..........7

Statistical Integration and Geochemical Surface Modeling of the NURE and 

 USGS Geochemical Databases, by Robert R. Carlson and Gregory K. Lee......10

Methods of Study .........................................................................................................10

Analysis.................................................................................................................10

Surface Modeling and Geographic Information Systems (GIS)..................10

Results............................................................................................................................10

Integrative Geologic Framework of the Headwaters Province ...........................................................15

Architecture of the Geologic Basement, by J. Michael O’Neill, P.K. Sims, and 

 Karen Lund...................................................................................................................15

Metallogeny in the Context of the Great Falls Tectonic Zone ..............................................................17

Control of Epigenetic Metal Deposits by Paleoproterozoic Basement 

 Architecture, by Terry L. Klein and P.K. Sims..........................................................17

Geochronology and Geochemistry of the Idaho-Montana Porphyry Belt, by 

 Cliff D. Taylor, Jeffrey A. Winick, Daniel M. Unruh, and Michael J. Kunk.........26

Field Work and Classification of Occurrences by Deposit Type ..........................28

40Ar/39Ar Geochronology ..............................................................................................28

Whole-Rock Geochemistry and Radiogenic Isotopic Studies..............................33

Conclusions...................................................................................................................39

SHRIMP U-Pb and 40Ar/39Ar Age Constraints for Relating Plutonism and 

 Mineralization in the Boulder Batholith Region, Montana, by Karen Lund,

 John N. Aleinikoff, Michael J. Kunk, and Daniel M. Unruh.................................39

Geochronologic Results..............................................................................................39

Interpretations ..............................................................................................................46

Use of Multiple Techniques ........................................................................................46

Impacts ..........................................................................................................................46
iv

Stratigraphy and Structure of Proterozoic Strata of Central Idaho ....................................................46

Mesoproterozoic Strata of East-Central Idaho, by Karl V. Evans, Russell G. Tysdal,

 and Karen Lund...........................................................................................................48

Blackbird Gold-Bearing Cobalt-Copper Deposits, East-Central Idaho—

 Reevaluation of Stratigraphic and Structural Setting, by Karen Lund, 

 Russell G. Tysdal, Karl V. Evans, and Michael J. Kunk.........................................50

Stratigraphy...................................................................................................................50

Metamorphism and Deformation...............................................................................50

Deposits .........................................................................................................................50

Conclusions...................................................................................................................51

Implications...................................................................................................................51

Identification of Neoproterozoic Windermere Supergroup, Central Idaho,

 using Geologic Mapping and SHRIMP U-Pb Geochronology—Implications 

 for Neoproterozoic Rifting and Glaciation, by Karen Lund, John N. Aleinikoff, 

 and Karl V. Evans ........................................................................................................55

Stratigraphy...................................................................................................................55

Geochronology .............................................................................................................55

Results............................................................................................................................55

Implications for Models of Snowball Earth and Rifting of Rodinia ......................57

Mineral Resources in Relation to Potential Regional Environmental Effects....................................57

Baseline Geochemistry of a Part of the Salmon River Drainage—Two 

 Examples, by Robert G. Eppinger, Paul H. Briggs, and Betsy Rieffenberger....62

Methods.........................................................................................................................62

Example 1. Geochemical Contrasts Between Two Adjacent Basins .................64

Example 2. Assessing Effects of Wildfire on Stream Sediment and Water 

Geochemistry................................................................................................................67

Geochemical Signatures of Diverse Mineral Deposit Types in the Upper Salmon

 River Watershed, Central Idaho, by Bradley S. Van Gosen, Robert G. 

 Eppinger, Jane M. Hammarstrom, Paul H. Briggs, and D.W. Peters .................71

Reconnaissance Geochemical Study.......................................................................71

Study Methods..............................................................................................................73

Water Samples ....................................................................................................73

Solid Samples ......................................................................................................73

Results............................................................................................................................73

Highlights.......................................................................................................................76

Acid-Rock Drainage............................................................................................76

Lithologic Controls on Water Quality ...............................................................76

Arsenic..................................................................................................................76

Environmentally Significant Metals in Mine Wastes, Mill Tailings, and 

Stream Sediments...............................................................................................79

Conclusions...................................................................................................................79

Applications of the Study............................................................................................81

Summary........................................................................................................................................................81

References Cited..........................................................................................................................................81
v

Figures

1. Map showing sources of data used to compile digital geologic map database for 

Headwaters Province project study area...................................................................................3

2. Reduced view of geologic map of Salmon National Forest and vicinity ...............................8

 3–10. Maps showing:

 3. Geochemical distribution of cadmium in stream sediments (original (nonnormalized) NURE data) ...................................................................................................... 11

 4. Geochemical distribution of cadmium in stream sediments, standardized 

concentrations (normalized NURE data).......................................................................... 12

 5. Generalized Precambrian basement geology of part of northwestern 

United States......................................................................................................................... 16

 6. Basement geology of west-central Montana and east-central Idaho, showing 

location of Great Falls tectonic zone and crosscutting northwest-trending faults .. 18

 7. Location of studied epigenetic mineral deposits and outline of area for 

which mineral deposit data were compiled .................................................................... 20

 8. Location of epigenetic mineral deposits relative to basement geology...................... 21

 9. Location and quantity of metals produced from deposits with greater than 

100 tons ore production and prospects with identified resources .............................. 22

 10. Porphyry molybdenum and copper-molybdenum deposits of Idaho-Montana 

porphyry belt ......................................................................................................................... 27

11. Diagram showing new ages for porphyry deposits as determined by 40Ar/39Ar geochronology versus approximate distance from pre-Cretaceous continental margin.......32

12–14. Graphs showing:

 12. New whole-rock geochemical data for intrusive porphyry bodies at mineral 

deposits of Idaho-Montana porphyry belt ........................................................................34

 13. Chondrite-normalized rare earth element plots for Cretaceous porphyry intrusions 

and Cretaceous batholithic rocks of Idaho-Montana porphyry belt............................35

 14. Chondrite-normalized rare earth element plots of Eocene porphyry intrusions and

Cretaceous batholithic rocks ..............................................................................................36

15. Diagram showing strontium-neodymium (initial) isotopic values for porphyry 

intrusions and Cretaceous batholithic rocks from Idaho-Montana porphyry belt ............38

16. Generalized geologic map of Boulder batholith area, southwestern Montana, 

showing sample localities ...........................................................................................................40

17. Tera-Wasserburg concordia plots and weighted averages plots of SHRIMP U-Pb 

isotopic data for plutonic rocks of Boulder batholith and vicinity........................................42

18. Diagrams showing 40Ar/39Ar age spectra for mineralized and altered samples .................44

19. Photomicrograph image pairs showing representative zircons dated as part of the 

Headwaters Province project ..................................................................................................47

20. Regional geologic map showing cobalt-copper deposits in exposed belt of banded 

siltite of the Apple Creek Formation...........................................................................................52

21. Block diagram showing structures of Blackbird district........................................................54

22. Map showing Windermere Supergroup rocks of central Idaho and surrounding area ...56

23. Composite correlation chart of Neoproterozoic and lower Paleozoic rocks, central 

Idaho and other sections in the Cordillera ...............................................................................58

24. Photomicrographs of zircon crystals from metavolcanic rocks of the Edwardsburg 

Formation........................................................................................................................................60
vi

25. Tera-Wasserburg concordia plots and weighted averages plots of SHRIMP U-Pb 

isotopic data for metavolcanic rocks of the Edwardsburg Formation ................................61

26–28. Maps showing:

26. Stream-sediment and surface-water sample localities collected from Panther

 Creek, Middle Fork Salmon River, and Salmon River.........................................................63

27. Concentration of cobalt in stream-sediment samples ......................................................65

28. Sum of rare earth elements in stream-sediment samples................................................66

29. Diagram showing elements in stream sediments, showing statistically significant 

 differences between pre-wildfire and post-wildfire sampling periods...............................68

30. Photographs of Clear Creek 10 and 11 months after wildfire in 2000...................................69

31. Plot of arsenic in stream sediment, 1996 versus 2001 samples.............................................70

32. Map of upper Salmon River watershed and vicinity, showing sample sites, mineral

 deposit types, and generalized geology ...................................................................................72

33. Schematic cross section showing general geologic setting of mineral deposits in 

 upper Salmon River watershed..................................................................................................75

34. Ficklin diagram showing sum of dissolved base-metal concentrations in mine 

 water and river water as a function of pH................................................................................77

35. Diagram showing acidity and alkalinity measured in 37 mine water samples from 

 upper Salmon River watershed..................................................................................................78

36. Plot showing dissolved arsenic concentrations versus pH in natural waters 

 collected in upper Salmon River watershed............................................................................80
vii

Tables

1. Geologic map data sets used to construct Headwaters Province geologic map database .... 4

2. Inventory for the Headwaters Province project showing number of NURE samples 

analyzed for the indicated elements by each laboratory and analytical method used.......... 13

3. Characteristics of selected molybdenum deposits and mineralized areas in the IdahoMontana porphyry belt ...................................................................................................................... 29

4. New 40Ar/39Ar data for mineralized rocks, genetically related plutons, and country rocks 

of the Idaho-Montana porphyry belt ............................................................................................... 31

5. Summary of mineral deposit characteristics for Boulder and Butte mining districts ............. 41

6. Summary of isotopic data for Boulder and Butte mining districts.............................................. 45

7. Correlation diagram for Mesoproterozoic rocks of east-central Idaho..................................... 49

8. Types of mineral deposits sampled by this study within the upper Salmon River 

watershed............................................................................................................................................ 74
viii

Conversions, Abbreviations, and Acronyms

[Both metric and non-metric units were used in these studies, and some 

studies report older data using non-metric units; those data are not converted 

to metric herein]

To convert To Multiply by

2,000 lb tons Metric tons (t) 0.91

Ounces (oz) Grams (g) 28.35

Miles (mi) Kilometers (km) 1.60

Square miles (mi2

) Square kilometers (km2) 2.60

Feet (ft) Meters (m) 0.3048

Kilograms (kg) Pounds (lb) 2.21

Grams (g) Ounces (oz) 0.035

Metric tons (t) 2,000 lb tons 1.10

FLMA Federal Land Management Agencies

MRDS Mineral Resources Data System

MAS Mineral Availability System

CUSMAP Conterminous United States Mineral Assessment Program

NURE National Uranium Resource Evaluation

HSSR Hydrogeochemical and Stream Sediment Reconnaissance

MILS Minerals Industry Location System

RASS Rock Analysis Storage System
Introduction

The development and institution of sound Public Land 

policy and stewardship practices for a region require the 

accumulation and integration of earth science and biologic 

data. The U.S. Geological Survey Headwaters Province project 

covering western Montana and northern and central Idaho 

was designed to provide geoscience data and interpretations 

to Federal Land Management Agencies (FLMA). Managers in 

USDA Forest Service Regions 1 and 4 made national priority 

requests for the U.S. Geological Survey Mineral Resources 

Program (1) to provide interim products that help them meet 

their planning cycles and (2) to provide topical studies to meet 

longer range goals of integrating geoscience data into decision 

making. Toward this end, the Headwaters Province project 

team have emphasized development of digital geoscience data, 

GIS analyses, topical studies, and critical new geologic interpretation to ensure that geoscience data are available for GISbased science integration and land-use planning. The interrelated products of the project are at complementary scales.

A major goal of the project was to provide consistent 

background and baseline geoscience information for the Headwaters Province. Studies were designed to more completely 

map lithologic units and determine controls of deformation, 

magmatism, and mineralizing processes. These studies were 

initiated at localities determined to have the most application 

to regional issues. Topical studies addressed several aspects 

of geologic basement control on these processes within the 

region. These include studies of

1. Regional metallogenic patterns and their relationship 

to the composition and architecture of underlying, unexposed 

basement. A study of the Idaho-Montana porphyry belt was 

designed to determine whether igneous processes in the upper 

crust or basement metals endowment was critical to formation 

of these deposits.

2. Timing of igneous and hydrothermal systems, to identify regionally important metallogenic magmatism. Study of 

the Boulder batholith and associated mineral deposits at Butte, 

Mont., revealed much about an important set of systems.

3. The geologic setting of Proterozoic strata, to better 

understand how their sedimentary basins developed and to 

define the origin of sediment-hosted mineral deposits. This 

work includes proxy studies of the structural setting of the 

Blackbird mining district and identification of sedimentary 

successions that bear on Snowball Earth models.

Digital GIS-Based Geoscience 

Databases

The project developed internally consistent digital geoscience map databases using previously published 

sources, augmented by new studies at scales of 1:100,000 

and 1:250,000. Derivative and interpretive digital products 

developed from these base data were used in all aspects of the 

project. Digital data utilization was emphasized (1) to enhance 

FLMA’s ability to integrate geoscience data and (2) to provide 

geoscience data in a flexible format that enhanced their applicability to a large and evolving variety of uses. As a result, 

geoscience information will more likely be used in FLMA 

decision-making processes.

Preparation of the Digital Geologic 

Map for the Headwaters Province 

Project

By Gregory N. Green

Planning

For most earth science-based evaluations, a geologic 

map is required. At the start of this project, digital geologic 

Earth Science Studies in Support of Public Policy 

Development and Land Stewardship—Headwaters 

Province, Idaho and Montana

By U.S. Geological Survey Headwaters Province Project Team
2 Earth Science Studies—Headwaters Province, Idaho and Montana

maps at the appropriate scale and detail were available for 

only selected parts of the Headwaters Province study area. The 

quickest and least expensive way to create a comprehensive 

geologic database required that various published maps or 

maps-in-progress be mosaiced. Available geologic maps were 

evaluated for scale, areal extent, quality, and original purpose. 

Unfortunately, some gaps in coverage exist where mapping 

at the appropriate scale or detail was not available or where 

available maps did not contain sufficient detail.

Forty-five maps were finally selected for mosaicing 

(fig. 1; table 1). These maps varied in scale from 1:100,000 to 

1:250,000, covering areas from 122 square miles (3.15×108 

m2) to 9,537 square miles (2.47×1,010 m2). As noted, some 

available maps were not sufficiently detailed and were not 

used. Conversely, the content of some detailed or topical maps 

was not applicable to the mineral resource survey.

Existing digital formats varied from nonexistent to various fully attributed Arc/Info formats. Geologic data sets were 

simultaneously assembled at the Montana Bureau of Mines 

and Geology, at the Idaho Geological Survey, and at the U.S. 

Geological Survey (USGS) offices in Denver, Colo., Spokane, 

Wash., and Sioux Falls, S. Dak. After initial data collection, 

data conversion work was completed in USGS offices in Denver and Spokane.

In order to mosaic the maps using Arc/Info, digital versions of the 45 maps needed consistent internal formatting; each 

data set needed to contain the same items in the same sequence. 

Geologic features had to be consistently coded and stored in the 

same manner before joining. Digital data sources had slightly 

different standard format interpretations and required final revision before assembly was completed in Spokane.

Several map overlap problems had to be solved. Detailed 

but irregularly shaped geologic maps of national forests 

overlapped regular-shaped quadrangle maps. Project geologists decided which maps were the most accurate and current. 

A standard sequence of clipping, erasing, and joining of map 

data sets was used to create both geologic graphic decorations 

and geologic formation polygons. The sequence was used to 

create seamless geologic and graphic layers, both of which 

were required to create the digital geologic map.

Database Design

Arc/Info was chosen as the vector-based spatial database 

system. Raster-based or illustrator-style systems do not work 

as well as Arc/Info with geologic maps made of points, lines, 

and polygons (formations). All maps were converted to the 

same Albers Equal Area projection, and original map scale for 

each was preserved. Original data sets were archived at the 

U.S. Geological Survey, Denver.

To ensure consistent coding, a common data dictionary 

was created for line layers, whether contacts, folds, or faults. 

The dictionary contains a line description and specifies a 

standard color and width and whether dashes and (or) dots 

are needed. Each line type, in conjunction with the definition 

table, when used to plot a map yields graphical output that 

includes the standard linear components of a geologic map.

Polygon layers for formations, overprints, or graphical 

layers are specified in another common data dictionary. The 

dictionary contains polygon labels, age, description, color, and 

patterns as appropriate. Each type of polygon, in conjunction 

with this translation table, produces graphical output that looks 

like the polygonal components of a geologic map.

On geologic maps, contacts depict the boundary between 

two types or ages of rocks, so contacts denote the color boundaries between formations. Thus, in the database, the lines that 

define polygon perimeters are contacts. In this database, shorelines and map edges are included with the contacts because 

they are color boundaries as well. Because contacts define the 

spatial limits of formations, they are stored as an integral part 

of the formation layer. Each formation is also identified by a 

text label, and the database includes an attribute for the associated text label.

Faults can be contacts and thus may be color boundaries. 

In some data sets, faults are stored in the formation part of the 

database and so are part of the contact data. However, in many 

geologic data sets, the fault data are stored in a way similar 

to that for folds, as a separate layer. In most cases, this results 

from how the data were captured. Scanners can be set to 

recognize faults because they are graphically portrayed using 

thicker lines, and consequently these features can be saved in 

a separate database layer. Data subsets are easily created but 

much harder to integrate. Consequently, in this study the faults 

were stored in a separate database layer.

A separate graphic decoration layer was created for each 

map. For geologic mineral resource assessment work, the 

surface area of each formation must be accurate. In traditional 

single-layer geologic databases, graphic symbols disrupt areal 

geologic formation definitions. By keeping graphic symbols 

in a separate layer, the symbols did not impact these formation 

definitions.

Folds or warps in formations are represented on a geologic map by a line that traces the fold axis. Because almost 

no folds are color boundaries, graphical representations for 

folds are usually stored as a separate database layer. Regional 

zones, such as metamorphic grade, shear zones, or extent of 

glaciation, are similar in that few or none are coincident with 

geologic formation polygons; rather, they are depicted by 

some sort of pattern. These zones are considered overlays and 

are stored in separate graphical layers.

The graphical representation of faults often includes 

special symbols to indicate fault orientation and movement. 

These include teeth on thrust faults, bar-and-ball symbols on 

normal faults, and other markings. These asymmetrical lines 

can be generated in a variety of ways in Arc/Info. As all lines 

must have the same internal format in order to seamlessly join, 

lines for these faults were converted to a standard style. Issues 

arise when one data set decorates faults on their left whereas 

an adjacent data set decorates lines on the right; this requires 

line data to be converted, as well. One distinct disadvantage to 

using database-generated asymmetrical linesets is that finished 
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Figure 1. Sources of data (gray shade) used to compile digital geologic map database for Headwaters Province 

project study area. References for sources are in table 1.

Digital GIS-Based Geoscience Databases 3
4 Earth Science Studies—Headwaters Province, Idaho and Montana

Table 1. Geologic map data sets used to construct Headwaters Province geologic map database.

_______________________________________________________________________________________________________

 1. Berg, R.B., and Lonn, J.D., 1996, Preliminary geologic map of the Nez Perce Pass 30- by 60-minute quadrangle, Montana: 

Montana Bureau of Mines and Geology Open-File Report MBMG 339, 7 p., 1 plate, scale 1:100,000.

 2. Berg, R.B., Lonn, J.D., and Locke, W.W., 1999, Geologic map of the Gardiner 30’×60’ quadrangle, south-central Montana: 

Montana Bureau of Mines and Geology Open-File Report MBMG 387, 2 plates, scale 1:100,000.

 3. Berg, R.B., Lopez, D.A., and Lonn, J.D., 2000, Geologic map of the Livingston 30’×60’ quadrangle, south-central Montana: 

Montana Bureau of Mines and Geology Open-File Report MBMG 406, scale 1:100,000.

 4. Derkey, P.D., Johnson, B.R., Lackaff, B.B., and Derkey, R.E., 1998, Digital geologic map of the Rosalia 1:100,000 quadrangle, Washington and Idaho; a digital database for the 1990 S.Z. Waggoner map: U.S. Geological Survey Open-File Report 

98-357, 27 p., scale 1:100,000.

 5. Evans, K.V., and Green, G.N., compilers, 2003, Geologic map of Salmon National Forest and vicinity, east-central Idaho: 

U.S. Geological Survey Geologic Investigations Series Map I–2765, scale 1:100,000. 

 6. Fisher, F.S., McIntyre, D.H., and Johnson, K.M., 1992, Geologic map of the Challis 1°×2° quadrangle, Idaho: U.S. Geological Survey Miscellaneous Investigations Series Map I–1819, scale 1:250,000, 39 p. pamphlet. 

 7. Green, G.N., and Tysdal, R.G., 1996, Digital maps and figures on CD-ROM for mineral and energy resource assessment of 

the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-B, CD-ROM, scale 

1:126,720.

 8. Harrison, J.E., Cressman, E.R., and Whipple, J.W., 1992, Geologic and structure maps of the Kalispell 1°×2° quadrangle, 

Montana, and Alberta and British Columbia: U.S. Geological Survey Miscellaneous Investigations Map I–2267, scale 

1:250,000.

 9. Harrison, J.E., Griggs, A.B., Wells, J.D., Kelley, W.N., Derkey, P.D., and EROS Data Center, 2000, Geologic and structure 

maps of the Wallace 1°×2° quadrangle, Montana and Idaho—A digital database: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–1509–A, version 1.0, 21 p., scale 1:250,000.

10. Harrison, J.E., Whipple, J.W., and Lidke, D.J., 1998, Geologic map of the western part of the Cut Bank 1°×2° quadrangle, 

Montana: U.S. Geological Survey Geologic Investigations Series Map I–2593, 1 sheet, scale 1:250,000.

11. Idaho Geological Survey, 1996, Digital geology of the Riggins 1:100,000-scale quadrangle, Idaho, in Digital geologic map 

compilation for the Nez Perce and Clearwater National Forests: Idaho Geological Survey CD-ROM, produced under contract to USDA Forest Service [unpublished], scale 1:100,000.

12. Idaho Geological Survey, 1996, Digital geology of the Grangeville 1:100,000-scale quadrangle, Idaho, in Digital geologic 

map compilation for the Nez Perce and Clearwater National Forests: Idaho Geological Survey CD-ROM, produced under 

contract to USDA Forest Service [unpublished], scale 1:100,000.

13. Idaho Geological Survey, 1996, Digital geology of the Headquarters 1:100,000-scale quadrangle, Idaho, in Digital geologic 

map compilation for the Nez Perce and Clearwater National Forests: Idaho Geological Survey CD-ROM, produced under 

contract to USDA Forest Service [unpublished], scale 1:100,000.

14. Johnson, B.R., and Derkey, P.D., 1998, Digital geologic map of the Spokane 1:100,000 quadrangle, Washington and Idaho; a 

digital database for the 1990 N.L. Joseph map: U.S. Geological Survey Open-File Report 98-115, 13 p. and 1 digital plate, 

scale 1:100,000.

15. Kayser, H.Z., 2001, Digital geologic map of the east half of the Pullman 1°×2° quadrangle, Idaho; a digital database for the 

1979 Rember and Bennett map: U.S. Geological Survey Open-File Report 01-262, 29 p., 1 sheet, scale 1:250,000.

16. Kellogg, K.S., and Williams, V.S., 2000, Geologic map of the Ennis 30’×60’ quadrangle, Madison and Gallatin Counties, 

Montana, and Park County, Wyoming: U.S. Geological Survey Geologic Investigations Series I–2690, scale 1:100,000.

17. Kiilsgaard, T.H., Stanford, L.R., and Lewis, R.S., 2001, Geologic map of the Idaho City 30×60 minute quadrangle, Idaho: 

Idaho Geological Survey Geologic Map Series 29, scale 1:100,000.
Table 1. Geologic map data sets used to construct Headwaters Province geologic map database.—Continued

_______________________________________________________________________________________________________

18. Lewis, R.S., 1998, Geologic map of the Butte 1°×2° quadrangle, Montana: Montana Bureau of Mines and Geology OpenFile Report MBMG 363, 16 p., 1 plate, scale 1:250,000.

19. Lewis, R.S., 1998, Geologic map of the Montana part of the Missoula West 30- by 60-minute quadrangle: Montana Bureau 

of Mines and Geology Open-File Report MBMG 373, 20 p., 2 plates, scale 1:100,000.

20. Lewis, R.S., Burmester, R.F., Kauffman, J.D., and Frost, T.P., 2000, Geologic map of the St. Maries 30×60 minute quadrangle, Idaho: Idaho Geological Survey Digital Geologic Map DGM–1, scale 1:100,000.

21. Lewis, R.S., Burmester, R.F., McFadden, M.D., Derkey, P.D., and Oblad, J.R., 1999, Digital geologic map of the Wallace 

quadrangle, Idaho: U.S. Geological Survey Open-File Report 99-390, 46 p., scale 1:100,000.

22. Lewis, R.S., and Derkey, P.D., 1999, Digital geologic map of part of the Thompson Falls 1:100,000 quadrangle, Idaho: U.S. 

Geological Survey Open-File Report 99-438, 32 p., 1 digital plate.

23. Lewis, R.S., and Stanford, L.R., 2002, Digital geologic map of the Elk City 30×60 minute quadrangle, Idaho: Idaho Geological Survey Digital Geologic Map Series DGM–05, 1 CD-ROM, scale 1:100,000.

24. Lewis, R.S., and Stanford, L.R., 2002, Digital geologic map of the Kooskia 30×60 minute quadrangle, Idaho: Idaho Geological Survey Digital Geologic Map Series DGM–06, 1 CD-ROM, scale 1:100,000.

25. Lewis, R.S., and Stanford, L.R., 2002, Digital geologic map of the Hamilton 30×60 minute quadrangle, Idaho: Idaho Geological Survey Digital Geologic Map Series DGM–03, 1 CD-ROM, scale 1:100,000.

26. Lewis, R.S., and Stanford, L.R., 2002, Digital geologic map of the Missoula West 30×60 minute quadrangle, Idaho: Idaho 

Geological Survey Digital Geologic Map Series DGM–02, 1 CD-ROM, scale 1:100,000.

27. Lewis, R.S., and Stanford, L.R., 2002, Digital geologic map of the Nez Perce Pass 30×60 minute quadrangle, Idaho: Idaho 

Geological Survey Digital Geologic Map Series DGM–04, 1 CD-ROM, scale 1:100,000.

28. Link, P.K., Mahoney, J.B., Bruner, D.J., Batatian, L.D., Wilson, Eric, and Williams, F.J.C., 1995, Geologic map of outcrop 

areas of sedimentary units in the eastern part of the Hailey 1°×2° quadrangle and the southern part of the Challis 1°×2° 

quadrangle, south-central Idaho: U.S. Geological Survey Bulletin 2064–C, plate 1, scale 1:100,000.

29. Lonn, J.D., and Berg, R.B., 1996, Preliminary geologic map of the Hamilton 30- by 60-minute quadrangle, Montana: Montana Bureau of Mines and Geology Open-File Report MBMG 340, 9 p., 1 plate, scale 1:100,000.

30. Lonn, J.D., and McFaddan, M.D., 1999, Geologic map of the Montana part of the Wallace 30- by 60-minute quadrangle: 

Montana Bureau of Mines and Geology Open-File Report MBMG 388, 15 p., 2 plates, scale 1:100,000.

31. Lonn, J.D., Skipp, Betty, Ruppel, E.T., Janecke, S.U., Perry, W.J., Jr., Sears, J.W., Bartholomew, M.J., Stickney, M.C., Fritz, 

W.J., Hurlow, H.A., and Thomas, R.C., 2000, Geologic map of the Lima quadrangle, southwest Montana: Montana 

Bureau of Mines and Geology Open-File Report MBMG 408, 3 sheets, parts A, B, and C, scale 1:100,000.

32. Lopez, D.A., 2000, Geologic map of the Big Timber 30’×60’ quadrangle, south-central Montana: Montana Bureau of Mines 

and Geology Open-File Report MBMG 405, scale 1:100,000.

33. Lopez, D.A., 2001, Preliminary geologic map of the Red Lodge 30’×60’ quadrangle, south-central Montana: Montana 

Bureau of Mines and Geology Open-File Report MBMG 423, 1 plate, scale 1:100,000.

34. Lund, Karen, Derkey, P.D., Brandt, T.R., and Oblad, Jon, 1999, Digital geologic map database of the Payette National Forest 

and vicinity, Idaho: U.S. Geological Survey Open-File Report 98-219–B, 45 p., scale 1:100,000.

35. Miller, F.K., Burmester, R.F., Miller, D.M., Powell, R.E., and Derkey, P.D., 1998, Digital geologic map of the Sandpoint 

1°×2° quadrangle, Washington, Idaho, and Montana: U.S. Geological Survey Open-File Report 99-144, 72 p., 1 digital 

plate, scale 1:250,000.

36. Mudge, M.R., Earhart, R.L., Whipple, J.W., and Harrison, J.E., 1982, Geologic and structure map of the Choteau 1°×2° 

quadrangle, western Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I–1300, 2 sheets, scale 

1:250,000.

Digital GIS-Based Geoscience Databases 5
6 Earth Science Studies—Headwaters Province, Idaho and Montana

Table 1. Geologic map data sets used to construct Headwaters Province geologic map database.—Continued

_______________________________________________________________________________________________________

37. Munts, S.R., 2000, Digital geologic map of the Coeur d’Alene 1:100,000 quadrangle, Idaho and Montana: U.S. Geological 

Survey Open-File Report 00-135, version 1.0, 30 p., 1 digital plate, scale 1:100,000.

38. O’Neill, J.M., and Christiansen, R.L., 2002, Geologic map of the Hebgen Lake quadrangle, Beaverhead, Madison, and Gallatin Counties, Montana, Park and Teton Counties, Wyoming, and Clark and Fremont Counties, Idaho: Montana Bureau of 

Mines and Geology Open-File Report MBMG 464, 1 plate, scale 1:100,000.

39. Ruppel, E.T., 1998, Geologic map of the eastern part of the Leadore 30’×60’ quadrangle, Montana and Idaho: Montana 

Bureau of Mines and Geology Open-File Report MBMG 372, scale 1:100,000.

40. Ruppel, E.T., O’Neill, J.M., and Lopez, D.A., 1993, Geologic map of the Dillon 1°×2° quadrangle, Idaho and Montana: U.S. 

Geological Survey Miscellaneous Investigations Series Map I–1803–H, scale 1:250,000.

41. Van Gosen, B.S., Wilson, A.B., Hammarstrom, J.M., and Kulik, D.M., 1996, Mineral resource assessment of the Custer 

National Forest in the Pryor Mountains, Carbon County, south-central Montana: U.S. Geological Survey Open-File 

Report 96-256, scale 1:126,720.

42. Vuke, S.M., Berg, R.B., Lonn, J.D., and Kellogg, K.S., 1995, Geologic map of the Bozeman 30’×60’ quadrangle, Montana: 

Montana Bureau of Mines and Geology Open-File Report MBMG 334, scale 1:100,000.

43. Wilson, A.B., and Elliott, J.E., 1997, Geologic maps of western and northern parts of Gallatin National Forest, south-central 

Montana: U.S. Geological Survey Geologic Investigation Series I–2584, scale 1:126,720.

44. 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 Series Map I–2395, scale 1:250,000.

45. Worl, R.G., and Johnson, K.M., 1995, Map showing geologic terranes of the Hailey 1°×2° quadrangle and the western part of 

the Idaho Falls 1°×2° quadrangle, south-central Idaho: U.S. Geological Survey Bulletin 2064–A, plate 1, scale 1:250,000.

______________________________________________________________________________________
products seldom look like the originals. Authors generally 

place one bar-and-ball symbol near the center of the fault, or at 

some place that clearly shows known fault movement, whereas 

automatic asymmetrical decorations, placed by software, are 

added every inch or so. Inconsistency in identifying the start 

and end of a digital fault can cause associated decorations to 

switch sides along multi-segmented faults.

Manual and automatic placement of graphic teeth, ticks, 

boxes, bar-and-ball symbols, strike-slip symbols, and fold 

symbols, along with correction and simplification of symbols, was required to create digital geologic data sets. The 

decoration symbols for each feature were drawn in Arc/Info 

for Adobe Illustrator and then converted back to Arc/Info 

using the Adobe plug-in, Avenza MAPublisher. Consequently, 

symbols and decorations became isolated in a separate Arc/

Info layer that was no longer dependent upon associated line 

orientation. Regardless of how the original geologic symbol 

was depicted, the final separate graphic decoration layer was 

consistent. Geologic symbols were easily corrected or deleted 

without altering the areal geologic formation database.

Stroked or crosshatched graphic symbols were converted 

to filled-polygon symbols. Filled polygons draw faster, and 

associated graphic files are more compact. Paper versions of 

original maps were used to assure accurate symbol placement.

Conclusions

A new seamless spatial database was created for the 

Headwaters Province project area. The database is available 

for USGS resource assessments, for many needs of the FLMA, 

and is a critical resource for future geologic investigations; this 

single geologic database is available for local to regional studies and can be queried to create derivative maps.

Compilation and Interpretation for New 

Geologic Maps

By Karl V. Evans and Gary L. Jackson1

Background

A key goal of the Headwaters Province project was 

completion of new geologic maps of areas where existing 

maps were incomplete or inadequate. A number of new maps 

at intermediate regional scale were completed or updated as 

part of this project. An example is the new map of the Salmon 

National Forest and vicinity (Evans and Green, compilers, 

2003) at 1:100,000 scale—a scale useful for making land-use 

decisions, especially by FLMA.

Geologic investigations in the Salmon National Forest 

and vicinity have a long history, extending as far back as the 

Lewis and Clark expedition, but they began in earnest with 

studies at the turn of the 19th–20th century. (See, for example, 

Lindgren, 1904; Umpleby, 1913.) Through the years, much of 

this interest was prompted by the search for mineral resources 

such as gold, copper, cobalt, lead, and thorium (Umpleby, 

1913; Ross, 1925; Anderson, 1947; Vhay, 1948; Sharp and 

Cavender, 1962; Cater and others, 1973; Lund and others, 

1983; Ruppel and Lopez, 1988; Nash and Hahn, 1989; Moye, 

1990). Nevertheless, compared to many parts of the western 

United States, this area remained poorly studied, probably 

because of the inaccessibility of large parts of it. Considerable areas of the Salmon National Forest and of the adjacent 

Payette National Forest now are incorporated in the Frank 

Church–River of No Return Wilderness.

The new geologic map compilation of the Salmon 

National Forest (fig. 2) utilizes more than 50 sources of data. 

Because recent work resulted in significant revisions concerning regional structure and stratigraphy, older maps were 

directly incorporated only in areas for which no other coverage was available, or where these maps could be reinterpreted 

in light of more recent work. The scale of new mapping varied 

from reconnaissance at 1:100,000 to local studies done at 

1:24,000; however, even the reconnaissance work incorporates 

insights gained by topical mapping at larger scales.

Use of Geologic Map Data Set in Producing a 

National Forest Soils Map

As an example of derivative uses for the Headwaters 

Province geologic maps, the geologic map of the Salmon 

National Forest is being used as the basis for a forest soils map 

by USDA Forest Service personnel. Chemical, weathering, 

and other characteristics of geologic units can be used to infer 

soil characteristics known as Land Type Association (LTA) for 

large areas not covered by detailed soil studies (Soil Resource 

Inventories). In this process, all lithologic units are assigned 

to one of four broad categories determined by the type of soil 

they weather to produce: granitic, volcanic, quartzitic, and 

sedimentary (mostly calcareous). Once this information is 

converted to a spatial database, it becomes possible to conduct 

rapid evaluation of landscapes for forest planning and management in support of decisions regarding construction of roads 

or building sites associated with timber sales, mineral exploration, mining, grazing, or public recreation. In addition, if a forest fire occurs in the forest, this LTA information is especially 

useful for evaluating the erodability of denuded hillslopes 

associated with precipitation runoff or mass wastage processes (such as landslides). In either a hillwash or a landslide 

1

USDA Forest Service, Salmon-Challis National Forest, Rural Route 2, 

Box 600, Salmon, ID 83467.

Digital GIS-Based Geoscience Databases 7
8 Earth Science Studies—Headwaters Province, Idaho and Montana

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BIGHORN CRAGS PLUTON

C A S T O P L U T O N

C H A M B E R L A I N B A S I N P L U T O N

PAI NTED ROCKS PLUTON

I R O N

L A K E

F A U L T

P O I S O N

C R E E K

F A U L T

H O T S P R I N G S

F A U L T

P O I S O N

C R E E K

F A U L T ( ? )

F A U L T

CHIEF JOSEPH

PLUTONIC

COMPLEX

B R U S H Y G U L C H

I R O N

L A K E

F A U L T

114°00'

114°00'

115°00'

115°00'

45°30' 45°30'

45°00' 45°00'

114°30'

114°30'

Base from U.S. Geological Survey, Bighorn Crags, 

Challis, 1982, Nez Perce Pass, 1981, Wisdom, 1994.

Projection: Universal Transverse Mercator, 

zone 11 (Bighorn Crags, Challis, Nez Perce Pass), 

zone 12 (Wisdom).

1927 North American Datum

See "Index to sources of geologic mapping"

Editing and digital cartography by Alessandro J. Donatich,

Central Publications Group

Manuscript approved for publication July 1, 2002

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGIC INVESTIGATIONS SERIES

I–2765 (Sheet 1 of 2)

Pamphlet accompanies map

Printed on recycled paper

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

1-888-ASK-USGS

ArcInfo coverages and a PDF for this map are available at 

http://pubs.usgs.gov/imap/2003/i-2765/

1 0 1 2 43 5678 9 10 KILOMETERS

SCALE 1:100 000

CONTOUR INTERVAL 50 METERS

1 0 1 2 3 4 5 6 7 8 MILES

GEOLOGIC MAP OF THE SALMON NATIONAL FOREST AND VICINITY, EAST-CENTRAL IDAHO

Compiled by

Karl V. Evans and Gregory N. Green 2003

Geologic Map of the Western Part of the Salmon National Forest

By

R.G. Tysdal, K.I. Lund, and K.V. Evans

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SURFICIAL

DEPOSITS

SEDIMENTARY ROCKS VOLCANIC ROCKS INTRUSIVE ROCKS METAMORPHIC ROCKS

CORRELATION OF MAP UNITS

Holocene

and

Pleistocene

Lower

Triassic

Lower

Permian

Upper

Mississippian

Lower

Mississippian

Lower

Silurian

Upper

Ordovician

Middle

Ordovician

Lower

Ordovician

Lower Cambrian

Upper

Devonian

Pliocene

Miocene

Oligocene

Eocene

QUATERNARY

TERTIARY

CRETACEOUS

TRIASSIC

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

SILURIAN

ORDOVICIAN

CAMBRIAN

NEOPROTEROZOIC

MESOPROTEROZOIC

PALEOPROTEROZOIC

?

?

?

?

?

Thunder Mountain

cauldron complex

Castle

Rock

Camas Creek–

Black Mountain

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity Unconformity Relative age unknown Relative age unknown Relative age unknown Relative age very approximate

Lemhi Group

?

?

DESCRIPTION OF MAP UNITS

[Boxes colored only for units shown on this sheet]

SURFICIAL DEPOSITS

Alluvial, colluvial, landslide, and glacial deposits, undivided (Quaternary)

CENOZOIC SEDIMENTARY ROCKS

Gravel, limestone, sandstone, and volcaniclastic sediments (Holocene to Oligocene(?))

Tuff and tuffaceous conglomerate (Pliocene to Miocene)

Sedimentary rocks—basin fill (Miocene(?) to Eocene)

Older colluvium of Panther Creek (Eocene)

CENOZOIC VOLCANIC ROCKS

Challis Volcanic Group (Eocene)

Challis Volcanic Group, undivided

Tuffs and lavas of Thunder Mountain cauldron complex (southwestern part of 

Salmon National Forest)—See Fisher and others (1992)

Sunnyside tuff

Perlitic rhyolite

Lapilli tuff

Lower latite lava

Tuffs of Castle Rock segment of Van Horn Peak cauldron complex (southwestern part of 

Salmon National Forest)—See Ekren (1988)

Tuffs of Castle Rock

Tuffs of Camas Creek–Black Mountain and related rocks of Van Horn Peak cauldron complex 

(southwestern part of Salmon National Forest)—See Ekren (1988)

Tuffs of Camas Creek–Black Mountain

Intermediate and mafic lavas

Tuff of Eightmile Creek

Tuff of Ellis Creek

TERTIARY TO CRETACEOUS INTRUSIVE ROCKS

Mafic to felsic intrusions, undivided (Eocene)

Gray porphyry (Eocene)

Granite (Eocene)

Granite, granodiorite, and quartz monzodiorite (Eocene)

Intrusive rhyolite (Eocene)

Intrusions, mostly intermediate and felsic (Tertiary to Cretaceous)

Hornblende-biotite tonalite (Cretaceous)

Biotite-muscovite granite (Cretaceous)

Porphyritic granite and granodiorite (Cretaceous)

Biotite granodiorite (Cretaceous)

Foliated biotite granodiorite (Cretaceous)

MESOZOIC TO PROTEROZOIC SEDIMENTARY ROCKS

Dinwoody Formation (Lower Triassic)

Phosphoria Formation (Lower Permian)

Snaky Canyon (Lower Permian to Upper Mississippian) and Bluebird Mountain (Upper 

Mississippian) Formations, undivided

Surrett Canyon(?), South Creek(?), and Scott Peak Formations (Upper Mississippian) and 

Middle Canyon (Upper and Lower Mississippian) Formation, undivided

Surrett Canyon, South Creek, and Scott Peak Formations (Upper Mississippian) and Middle 

Canyon (Upper and Lower Mississippian) Formation, undivided

Railroad Canyon Formation (Upper Mississippian)

Scott Peak Formation (Upper Mississippian)

Middle Canyon Formation (Upper and Lower Mississippian)

McGowan Creek Formation (Lower Mississippian)

Three Forks and Jefferson Formations, undivided (Upper Devonian)

Laketown Dolomite (Silurian) and Saturday Mountain Formation (Lower Silurian to Middle 

Ordovician), undivided

Saturday Mountain Formation (Lower Silurian to Middle Ordovician)

Kinnikinic Quartzite (Middle Ordovician)

Summerhouse Formation (Lower Ordovician)

Kinnikinic Quartzite (Middle Ordovician) and Summerhouse Formation (Lower Ordovician), 

undivided

Wilbert Formation (Lower Cambrian to Neoproterozoic?)

PALEOZOIC TO PROTEROZOIC VOLCANIC ROCKS

Metavolcanic and metasedimentary strata (lower Paleozoic(?) to Neoproterozoic)

PALEOZOIC INTRUSIVE ROCKS

Mafic to predominantly felsic alkalic intrusions (Ordovician to Cambrian)

PALEOZOIC TO PROTEROZOIC METAMORPHIC ROCKS

Gray marble (lower Paleozoic(?) to Neoproterozoic)

PROTEROZOIC SEDIMENTARY ROCKS

Lawson Creek Formation (Mesoproterozoic)

Swauger Formation (Mesoproterozoic)

Gunsight Formation (Mesoproterozoic)

Apple Creek Formation, undivided (Mesoproterozoic)

Banded siltite unit

Coarse siltite unit

Diamictite unit

Fine siltite unit

Big Creek Formation (Mesoproterozoic)

Lawson Creek Formation, Swauger Formation, and (or) Lemhi Group, undivided 

(Mesoproterozoic)

Argillaceous quartzite, unnamed (Mesoproterozoic)

Hoodoo Quartzite (Mesoproterozoic)

Yellowjacket Formation (Mesoproterozoic)

Feldspathic metasandstone (Mesoproterozoic)

Missoula Group, undivided (Mesoproterozoic)

Helena and Empire Formations, undivided (Mesoproterozoic)

Spokane and Greyson Formations, undivided (Mesoproterozoic)

PROTEROZOIC INTRUSIVE ROCKS

Mafic intrusive rock (Neoproterozoic?)

Megacrystic granite and augen gneiss (Mesoproterozoic)

Amphibolite and magnetite-hornblende gneiss (Mesoproterozoic)

PROTEROZOIC METAMORPHIC ROCKS

Biotite gneiss (Mesoproterozoic)

Quartzite (Mesoproterozoic)

Calc-silicate quartzite (Mesoproterozoic)

Basement gneiss (Paleoproterozoic)

Contact—Dashed where approximately located; queried where uncertain. Scratch boundaries 

used where contacts omitted along lat 45° N.

Strike-slip fault—Dashed where approximately located; dotted where concealed. Opposed 

arrows show relative movement

Normal fault—Dashed where approximately located; dotted where concealed; queried where 

uncertain. Bar and ball on downthrown side

Thrust fault—Dashed where approximately located; dotted where concealed; queried where 

uncertain. Sawteeth on upper plate

Low-angle normal fault—Dashed where approximately located; dotted where concealed. Box on 

upper plate

Thrust fault with later normal movement—Dashed where approximately located; dotted where 

concealed. Sawteeth on upper plate; bar and ball on downthrown side

Thrust fault with younger-on-older relationship and multiple-stage development—Dashed 

where approximately located; dotted where concealed. Sawteeth on upper plate. Youngeron-older relationship may be caused by multiple phases of compressional deformation and (or) 

by decoupling in lower plate during thrust juxtaposition. Superposed brittle deformation by 

low-angle normal movement

Anticline—Dotted where concealed

Syncline

Overturned anticline—Dotted where concealed

Overturned syncline—Dotted where concealed

Caldera margin

Dikes of unknown age or chemistry

Strike and dip of bedding

Inclined

Overturned

Strike and dip of silicified breccia-zone and cataclasite surface east of Baker and Lemhi, 

and west of Tendoy, Idaho

Strike and dip of inclined foliation

Bearing and plunge of lineation—May be combined with foliation symbol

Drill hole

Area in which stratigraphic unit occurs at a higher-than-typical metamorphic grade

85

50

12

40

20

Qu

QT

Ttu

Ts

Toc

Tc

Tcs

Tcp

Tct

Tcll

Tcc

Tcb

Tcl

Tcem

Tce

Ti

Tgp

Tg

Tgd

Tir

TKi

Kt

Kg

Kpg

Kgd

Kgdf

d

Pp

PMs

Mu

Mss

Mr

Ms

Mm

Mg

Du

SOu

SOs

Ok

Os

Oks

Oi

Ylc

Ys

Yg

Ya

Yab

Yac

Yad

Yaf

Yb

Yu

Yaq

Yh

Yy

Yfm

Ym

Yhe

Ysg

Zm

Ymg

Yam

Ybgn

Yq

Ycsq

Xg

Zw

Zv

Zgm

INDEX MAP TO SALMON (PINK) AND PAYETTE (BLUE) INDEX TO STUDY AREA

NATIONAL FORESTS, IDAHO

INDEX TO PHYSIOGRAPHIC FEATURES IN MAP AREA

Shoup

North

Fork

Salmon

Leadore

CLEARWATER

MOUNTAINS

SALMON RIVER

MOUNTAINS

LEMHI

RANGE

BEAVERHEAD

MOUNTAINS

Middle Fork Sa ml on River

Salmon

River

Salmon

River

Lemhi

River

N Fork Sa ml on R

INDEX TO MAJOR GEOLOGIC STRUCTURES IN MAP AREA

EXPLANATION

Normal fault—Bar and ball on downthrown side

where movement known. HSF, Hot Springs fault

Thrust fault—Sawteeth on upper plate. CCF, 

Cow Creek fault; ILF, Iron Lake fault; PCF,

Poison Creek fault

Cretaceous-Tertiary intrusions

POISON CREEK

FAULT

PCF(?)

IRON LAKE FAULT

Castle Rock

cauldron

Thunder

Mtn.

caldera Panther

Creek

graben

BRUSHY GULCH FAULT

ILF

HSF

CCF

Area of

sheet 1

Area of

sheet 2

DIGITAL ELEVATION MODEL OF SALMON NATIONAL FOREST AND VICINITY

Salmon
d

d

d

d

Du

Du

Du

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Ms Ms

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Ms

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Ms Ms

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Ms

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Oi

Oi Oi

Oi

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Oks

Os Oks

Os

Os

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Ok

Ok

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Ok

Ok

Ok Ok Ok Ok

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Ok Ok

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Ok Ok

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Ok

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Ok Ok

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Ok Ok

Ok

Ok

Ok

Ok

Ok

Ok

Ok

Ok

Ok

PMs

PMs

PMs

PMs PMs PMs

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PMs

PMs

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PMs

PMs

PMs PMs

PMs

PMs PMs

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PMs

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PMs

PMs

PMs

Pp

Pp

Pp

Pp

Pp

Pp

Pp

Pp

Pp Pp Pp

Pp

Pp

Pp

Pp

Pp

Pp Pp

Pp

Pp

SOs

SOs

SOs SOs

SOs

SOs

SOs

SOs

SOs

SOs

SOs

SOu

SOu

SOu

SOu

SOu

SOu SOu

SOu

SOu SOu

SOu

SOu

SOu

SOu SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

SOu

TKi

TKi TKi

TKi

TKi

TKi

Tcb

Tcb

Tce

Tce

Tce

Tce

Tce

Tce

Tcl

Tcl

Tcl

Tcl Tcl

Tcl

Tcl

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Tcl

Tcl

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Tc Tc

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Tc

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Tc

Tc

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Tc Tc

Tc Tc

Tc

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Tc

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Tc

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Tg

Tg

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Tgd

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Tgd

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Tgd

Tgd

Tgd

Tgd

Tgd Tgd

Tgd

Tgd Tgd

Tgd

Tgd

Tgd

Tgd

Tgd

Tgd

Tgd

Tgd

Ti

Ti

Ti

Ti

Ti

Ti

Ti

Ti

Ti

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Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

Ts

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Ttu

Ttu

Ttu

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Ttu

Ttu

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Yg

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Yg Yg

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Yg

Yg Yg

Yg

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Yg Yg

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Yg

Yg

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Yg

Yg

Yg

Yg

Yg

Yg

Yg

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Ys

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Ys

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Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys

Ys Ys

Ys

Ys

Ys

Ys

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Ys Ys

Ys

Ys

Ys

Ys

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Ys

Ys

Ys

Ys

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Ys

Zm

Zm

Amoco Prod. Co.

#19-1 Milford Federal

Amoco Prod. Co.

#1 Idaho State

40

57

52

60

62

42

22

40

50

16 25

20

46

32

65

70

65

35

34

60

45

53 85

72

76

65

54

43 70

57 70

26

83

42 70

70

60

36

67

20

30

73

73 40

60

25

57

25

40 61 25

23 29

40

70

47

56

15

37

26

50

37

55

20

30

45

42

75

21 60

52

12

15

36

55

32

30

17

43

50

31

56

52

46

25

50

70

28

58

15 52

25

35

20

40

9 32

7

37

CARMEN

STOCK

BIG EIGHTMILE STOCK

P O I S O N

C R E E K

F A U L T

L E M

P E A K

FA U LT

S A L M O N

R I V E R

FA U LT

B R U S H Y G U L C H F A U L T

C O W

C R E E K

F A U L T

44°30' 44°30'

45°00' 45°00'

45°30' 45°30'

114°00'

114°00'

113°00'

113°00'

113°30'

113°30'

Base from U.S. Geological Survey, Borah Peak, 1989, 

Leadore, 1980, Salmon, 1981.

Projection: Universal Transverse Mercator, zone 12.

1927 North American Datum

See "Index to sources of geologic mapping"

Editing and digital cartography by Alessandro J. Donatich,

Central Publications Group

Manuscript approved for publication July 1, 2002

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGIC INVESTIGATIONS SERIES

I–2765 (Sheet 2 of 2)

Pamphlet accompanies map

Printed on recycled paper

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

1-888-ASK-USGS

ArcInfo coverages and a PDF for this map are available at 

http://pubs.usgs.gov/imap/2003/i-2765/

1 0 1 2 43 5 6 7 8 9 10 KILOMETERS

SCALE 1:100 000

CONTOUR INTERVAL 50 METERS (BORAH PEAK, SALMON), 40 METERS (LEADORE)

1 0 1 2 3 4 5 6 7 8 MILES

GEOLOGIC MAP OF THE SALMON NATIONAL FOREST

AND VICINITY, EAST-CENTRAL IDAHO

Compiled by

Karl V. Evans and Gregory N. Green 2003

Geologic Map of the Eastern Part of the Salmon National Forest

By

K.I. Lund, K.V. Evans, R.G. Tysdal, and G.R. Winkler

DESCRIPTION OF MAP UNITS

[Boxes colored only for units shown on this sheet]

SURFICIAL DEPOSITS

Alluvial, colluvial, landslide, and glacial deposits, undivided (Quaternary)

CENOZOIC SEDIMENTARY ROCKS

Gravel, limestone, sandstone, and volcaniclastic sediments (Holocene to Oligocene(?))

Tuff and tuffaceous conglomerate (Pliocene to Miocene)

Sedimentary rocks—basin fill (Miocene(?) to Eocene)

Older colluvium of Panther Creek (Eocene)

CENOZOIC VOLCANIC ROCKS

Challis Volcanic Group (Eocene)

Challis Volcanic Group, undivided

Tuffs and lavas of Thunder Mountain cauldron complex (southwestern part of 

Salmon National Forest)—See Fisher and others (1992)

Sunnyside tuff

Perlitic rhyolite

Lapilli tuff

Lower latite lava

Tuffs of Castle Rock segment of Van Horn Peak cauldron complex (southwestern part of 

Salmon National Forest)—See Ekren (1988)

Tuffs of Castle Rock

Tuffs of Camas Creek–Black Mountain and related rocks of Van Horn Peak cauldron complex 

(southwestern part of Salmon National Forest)—See Ekren (1988)

Tuffs of Camas Creek–Black Mountain

Intermediate and mafic lavas

Tuff of Eightmile Creek

Tuff of Ellis Creek

TERTIARY TO CRETACEOUS INTRUSIVE ROCKS

Mafic to felsic intrusions, undivided (Eocene)

Gray porphyry (Eocene)

Granite (Eocene)

Granite, granodiorite, and quartz monzodiorite (Eocene)

Intrusive rhyolite (Eocene)

Intrusions, mostly intermediate and felsic (Tertiary to Cretaceous)

Hornblende-biotite tonalite (Cretaceous)

Biotite-muscovite granite (Cretaceous)

Porphyritic granite and granodiorite (Cretaceous)

Biotite granodiorite (Cretaceous)

Foliated biotite granodiorite (Cretaceous)

MESOZOIC TO PROTEROZOIC SEDIMENTARY ROCKS

Dinwoody Formation (Lower Triassic)

Phosphoria Formation (Lower Permian)

Snaky Canyon (Lower Permian to Upper Mississippian) and Bluebird Mountain (Upper 

Mississippian) Formations, undivided

Surrett Canyon(?), South Creek(?), and Scott Peak Formations (Upper Mississippian) and 

Middle Canyon (Upper and Lower Mississippian) Formation, undivided

Surrett Canyon, South Creek, and Scott Peak Formations (Upper Mississippian) and Middle 

Canyon (Upper and Lower Mississippian) Formation, undivided

Railroad Canyon Formation (Upper Mississippian)

Scott Peak Formation (Upper Mississippian)

Middle Canyon Formation (Upper and Lower Mississippian)

McGowan Creek Formation (Lower Mississippian)

Three Forks and Jefferson Formations, undivided (Upper Devonian)

Laketown Dolomite (Silurian) and Saturday Mountain Formation (Lower Silurian to Middle 

Ordovician), undivided

Saturday Mountain Formation (Lower Silurian to Middle Ordovician)

Kinnikinic Quartzite (Middle Ordovician)

Summerhouse Formation (Lower Ordovician)

Kinnikinic Quartzite (Middle Ordovician) and Summerhouse Formation (Lower Ordovician), 

undivided

Wilbert Formation (Lower Cambrian to Neoproterozoic?)

PALEOZOIC TO PROTEROZOIC VOLCANIC ROCKS

Metavolcanic and metasedimentary strata (lower Paleozoic(?) to Neoproterozoic)

PALEOZOIC INTRUSIVE ROCKS

Mafic to predominantly felsic alkalic intrusions (Ordovician to Cambrian)

PALEOZOIC TO PROTEROZOIC METAMORPHIC ROCKS

Gray marble (lower Paleozoic(?) to Neoproterozoic)

PROTEROZOIC SEDIMENTARY ROCKS

Lawson Creek Formation (Mesoproterozoic)

Swauger Formation (Mesoproterozoic)

Gunsight Formation (Mesoproterozoic)

Apple Creek Formation, undivided (Mesoproterozoic)

Banded siltite unit

Coarse siltite unit

Diamictite unit

Fine siltite unit

Big Creek Formation (Mesoproterozoic)

Lawson Creek Formation, Swauger Formation, and (or) Lemhi Group, undivided 

(Mesoproterozoic)

Argillaceous quartzite, unnamed (Mesoproterozoic)

Hoodoo Quartzite (Mesoproterozoic)

Yellowjacket Formation (Mesoproterozoic)

Feldspathic metasandstone (Mesoproterozoic)

Missoula Group, undivided (Mesoproterozoic)

Helena and Empire Formations, undivided (Mesoproterozoic)

Spokane and Greyson Formations, undivided (Mesoproterozoic)

PROTEROZOIC INTRUSIVE ROCKS

Mafic intrusive rock (Neoproterozoic?)

Megacrystic granite and augen gneiss (Mesoproterozoic)

Amphibolite and magnetite-hornblende gneiss (Mesoproterozoic)

PROTEROZOIC METAMORPHIC ROCKS

Biotite gneiss (Mesoproterozoic)

Quartzite (Mesoproterozoic)

Calc-silicate quartzite (Mesoproterozoic)

Basement gneiss (Paleoproterozoic)

Contact—Dashed where approximately located; queried where uncertain. Scratch boundaries 

used where contacts omitted along lats 44°30' N. and 45° N.

Strike-slip fault—Dashed where approximately located; dotted where concealed. Opposed 

arrows show relative movement

Normal fault—Dashed where approximately located; dotted where concealed; queried where 

uncertain. Bar and ball on downthrown side

Thrust fault—Dashed where approximately located; dotted where concealed; queried where 

uncertain. Sawteeth on upper plate

Low-angle normal fault—Dashed where approximately located; dotted where concealed. Box on 

upper plate

Thrust fault with later normal movement—Dashed where approximately located; dotted where 

concealed. Sawteeth on upper plate; bar and ball on downthrown side

Thrust fault with younger-on-older relationship and multiple-stage development—Dashed 

where approximately located; dotted where concealed. Sawteeth on upper plate. Youngeron-older relationship may be caused by multiple phases of compressional deformation and (or) 

by decoupling in lower plate during thrust juxtaposition. Superposed brittle deformation by 

low-angle normal movement

Anticline—Dotted where concealed

Syncline

Overturned anticline—Dotted where concealed

Overturned syncline—Dotted where concealed

Caldera margin

Dikes of unknown age or chemistry

Strike and dip of bedding

Inclined

Overturned

Strike and dip of silicified breccia-zone and cataclasite surface east of Baker and Lemhi, 

and west of Tendoy, Idaho

Strike and dip of inclined foliation

Bearing and plunge of lineation—May be combined with foliation symbol

Drill hole

85

50

12

40

20

Qu

QT

Ttu

Ts

Toc

Tc

Tcs

Tcp

Tct

Tcll

Tcc

Tcb

Tcl

Tcem

Tce

Ti

Tgp

Tg

Tgd

Tir

TKi

Kt

Kg

Kpg

Kgd

Kgdf

d

Pp

PMs

Mu

Mss

Mr

Ms

Mm

Mg

Du

SOu

SOs

Ok

Os

Oks

Oi

Ylc

Ys

Yg

Ya

Yab

Yac

Yad

Yaf

Yb

Yu

Yaq

Yh

Yy

Yfm

Ym

Yhe

Ysg

Zm

Ymg

Yam

Ybgn

Yq

Ycsq

Xg

Zw

Zv

Zgm

Qu

QT

d

Pp

PMs

Mu

Mg

Du

SOu

Oks

Zw Zv

SOs

Ok

Os

Ylc

Ys

Yg

Ya

Yu

Yb

Yab Yh Yfm

Yaq

Yy

Yhe

Ym

Yac Ysg

Yad

Yaf

Mss

Mm

Ms

Mr

Ttu

Ts

Toc

Tc

Tcs

Tcc

Ti Tg

Tgd

Kg

Kpg

Kgd

Oi

Zm

Zgm

Ymg Yam

Ybgn Yq

Xg

Ycsq

Kt Kgdf

TKi

Tgp

Tir

Tcp

Tct Tcl

Tcem

Tce

Tcb

Tcll

SURFICIAL

DEPOSITS

SEDIMENTARY ROCKS VOLCANIC ROCKS INTRUSIVE ROCKS METAMORPHIC ROCKS

CORRELATION OF MAP UNITS

Holocene

and

Pleistocene

Lower

Triassic

Lower

Permian

Upper

Mississippian

Lower

Mississippian

Lower

Silurian

Upper

Ordovician

Middle

Ordovician

Lower

Ordovician

Lower Cambrian

Upper

Devonian

Pliocene

Miocene

Oligocene

Eocene

QUATERNARY

TERTIARY

CRETACEOUS

TRIASSIC

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

SILURIAN

ORDOVICIAN

CAMBRIAN

NEOPROTEROZOIC

MESOPROTEROZOIC

PALEOPROTEROZOIC

?

?

?

?

?

Thunder Mountain

cauldron complex

Castle

Rock

Camas Creek–

Black Mountain

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity Unconformity Relative age unknown Relative age unknown Relative age unknown Relative age very approximate

Lemhi Group

?

?

114°30' 114°00' 113°30'

45°30'

45°00'

44°30'

Anderson (1959)

Anderson (1961)

Bennett (1977)

Cater and others (1973)

Connor (1990)

Connor and Evans (1986)

Desmarais (1983)

Ekren (1988)

Evans (1981)

Evans and Connor (1993)

Hait (1965)

Hillesland (1981)

Kaiser (1956)

Lopez (1982a)

Lopez (1982b)

Lucchitta (1966)

Lund, Evans, and Esparza (1983)

Lund, Rehn, and Holloway (1983)

Lund and others (1992)

Maley (1974)

M’Gonigle (1994)

Rember and Bennett (1979)

Ruppel (1968)

Ruppel (1980)

Ruppel and Lopez (1981)

Ruppel and others (1993)

Schmidt and others (1994)

Shockey (1957)

Skipp and others (1984)

Spence (1984)

Staatz (1973)

Staatz (1979)

Tucker (1975)

Tysdal (1996a)

Tysdal (1996b)

Tysdal (1996c)

Tysdal (2000b, 2003)

Tysdal (2002)

Tysdal and Desborough (1997)

Tysdal and others (2000)

Tysdal and Moye (1996)

Unpublished mapping, K.V. Evans, USGS, 1995–97

Unpublished mapping, K.V. Evans, USGS, 1993–97

Unpublished mapping, K.V. Evans, F. Moye, and R.F. 

Hardyman, USGS, 1991–94

Unpublished mapping, K.I. Lund, USGS, 1995–2000

Unpublished mapping, G.R. Winkler, USGS, 1995–97, 

and R.G. Tysdal, USGS, 1999–2001

Unpublished mapping, G.R. Winkler, USGS, 1994–96

Unpublished mapping, K.I. Lund, USGS, 1997

Unpublished mapping, R.G. Tysdal, USGS, 1997–99

Unpublished mapping, R.G. Tysdal and K. Lund, 

USGS, 1997–99

Unpublished mapping, R.G. Tysdal, USGS, 1996–98

SOURCES OF GEOLOGIC MAPPING

INDEX TO SOURCES OF GEOLOGIC MAPPING

Salmon National Forest

EXPLANATION

1

2

3

4

5

6

7

8

9

10

11

12

30

31

32

33

34

35

36

40

41

42

43

44

45

46

47

28

48

38

49

50

51

39

37

52

53

13

14

15

16

17

18

19

21

20

22

23

24

25

26

27

29

19

4 27

18

17

3

12

13 30

15

42

1

14

7

26

22

43

10

40

8

5

39

9 33

46

41

44

34

47

37

51

52

32

45 2

38

50

49

24 23

25

11, 48

35

36

31 21

16

29

6, 28

53

20

Figure 2. Reduced 

view of geologic map 

of Salmon National 

Forest and vicinity. See 

U.S. Geological Survey 

Geologic Investigations 

Series Map I–2765; 

published on paper as 

well as posted online at 

URL http://pubs.usgs.

gov/imap/i-2765/.

Digital GIS-Based Geoscience Databases 9
10 Earth Science Studies—Headwaters Province, Idaho and Montana

situation, large influxes of clastic debris can adversely affect 

populations of anadromous fish (seagoing–fresh-waterbreeding species such as salmon, steelhead, bull trout) and 

other fish in rivers draining the burned region.

Statistical Integration and 

Geochemical Surface Modeling of 

the NURE and USGS Geochemical 

Databases 

By Robert R. Carlson and Gregory K. Lee

The geochemical data used in this report derive from 

chemical analyses performed on the 51,411 stream-sediment 

samples collected under the auspices of the National Uranium 

Resource Evaluation (NURE) Hydrogeochemical and Stream 

Sediment Reconnaissance (HSSR). Within the Headwaters 

Province project area, NURE data are available for the rectangle bounded by lat 42°–49°N., long 108°–118°W. (example 

(cadmium), figs. 3, 4). This area contains thirty-five 1°×2° 

quadrangles, of which thirty-one were fully sampled, two 

partially sampled, and two not sampled by the NURE program. The areas not sampled are the Pullman and Grangeville 

quadrangles and the west halves of the Driggs and Preston 

quadrangles. The number of the NURE analyses performed by 

the HSSR program varies by element and ranges from a low 

of 17,338 samples analyzed for selenium to a high of 50,251 

samples analyzed for uranium. In addition, various USGS 

investigations reanalyzed NURE samples relevant to specific 

study areas. In these cases also, the number of analyses varies 

by element and ranges from a low of 264 samples analyzed for 

tungsten to a high of 8,926 samples analyzed for arsenic.

Methods of Study

Analysis

The NURE samples were analyzed by a wide variety of 

analytical methods and in many laboratories (table 2). Four 

U.S. Department of Energy (DOE) laboratories were charged 

with analyzing NURE stream-sediment samples under the 

HSSR program: Lawrence Livermore Laboratory, Los Alamos 

Scientific Laboratory, Oak Ridge Gaseous Diffusion Plant, and 

Savannah River Laboratory. Each DOE laboratory developed 

its own sample collection, analytical, and data management 

methodologies and used contractors to do much of the work. 

NURE samples reexamined by the USGS were analyzed using 

USGS methods (table 2).

Each of the many analytical methods–laboratory combinations just mentioned has its own lower and upper determination limits and different levels of accuracy, precision, and 

analytical interferences. Sampling and analysis protocols for 

the NURE program were specific to individual 1°×2° quadrangles. Consequently, artificial anomalies are present along 

quadrangle boundaries (fig. 3), whether analytical results are 

plotted for the entire study area as original chemical values or 

as normalized values (derived from the entire data set). Normalizing analytical data on a quadrangle-by-quadrangle basis 

(to reduce or eliminate boundary anomalies) for all elementmethod combinations would produce more than 1,800 normalized data sets. Instead, all quadrangles for which the contained 

samples share common laboratory and analytical methods are 

treated as one data set for each element. This reduced the number of data sets to be normalized to 197. The NURE samples 

reanalyzed for the USGS were treated similarly, resulting in an 

additional 55 data sets to be normalized.

Surface Modeling and Geographic Information 

Systems (GIS)

Each of the elements was modeled using Dynamic 

Graphics, Inc., EarthVision software. Erdas, Inc., IMAGINE 

image-processing/GIS software was used to interpret the geochemical surface models and drape the surfaces over digital 

shaded-relief topography to provide geographic reference.

Results

Standardizing concentration values on an element-byelement, method-by-method, and laboratory-by-laboratory 

basis resulted in three categories. These categories are those 

with (1) relatively little difference between anomalies on the 

element-concentration and the standardized-values surfaces; 

(2) significant positive differences between the two surfaces; 

and (3) significant negative differences between the two 

surfaces. Positive differences are those that suppress areas of 

artificial anomalies or enhance areas of artificially suppressed 

anomalies (or both). The accompanying figures for cadmium 

(figs. 3, 4), as an example of significant positive differences, 

show the suppression of artificial, low-level anomalies and the 

resulting enhancement of suppressed real anomalies.

Normalization of data sets based on laboratory, analytical 

method, and element groupings appears to be a viable methodology and reduces the amount of work involved in equating 

disparate geochemical data in the Headwaters Province study 

area. Artificial geochemical anomalies that remain, or are 

created, after normalizing indicate areas that require further 

subsetting prior to standardization.
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Figure 3. Original (non-normalized) NURE data showing geochemical distribution of cadmium in stream sediments, for comparison to 

normalized data in figure 4. Shown as concentrations in parts per million.

Digital GIS-Based Geoscience Databases 11
12 Earth Science Studies—Headwaters Province, Idaho and Montana

EXPLANATON

0 

0 20 40 60 80 100 MILES 

100 KILOMETERS 

Figure 4. Normalized NURE data showing geochemical distribution of cadmium in stream sediments. Shown as standardized 

concentrations.

EXPLANATION
LA2 LA3 LA5 LL1 OR7 SR2 SR3A SR3B ICP10 ICP40a icp40b aa1 aa2 inaa

Ag 12,167 14,343 2,055 14,497 2,991 1,481 3,221 2,046

As 14,343 2,055 2,749

(SR3XX) 1,481 3,221 2,046 2,046 132

Au 26,834 5,946 1,479 3,221 2,004 43 3,193 264

Ba 26,867 2,055 14,497 3,221 2,045

Bi 12,167 14,343 1,481 3,221 2,046

Cd 12,167 14,343 1,481 3,221 2,046

Co 26,825 2,055 14,497 2,993 3,221 2,046

Cr 26,853 2,055 14,497 2,994 3,221 2,046

Cu 12,167 14,343 14,497 2,993 1,481 3,221 2,046

Li 20,303

(LA4) 14,497 2,982(SR3FE) 3,221 2,046

Mo 1,269 14,497 2,994 1,481 3,221 2,046

Ni 12,167 14,343 14,497 2,992 3,221 2,046

Pb 12,167 14,343 11,974 2,981 1,481 3,221 2,046

Sb 26,712 2,055 1,479 264

Se 14,343 2,995

(SR3XX) 2,046 132

Sn 12,167 14,343 2,980 3,221 2,046

Th 26,854 2,055 14,497 6,079 3,221 2,046

V 26,865 2,055 14,497 6,129 3,221 2,046

W 12,167 14,343 2,055 2,989

(SR3CA)

264

Zn 26,437 2,055 14,497 2,993 1,481 3,221 2,046

UDN-LA1

UDNLL1UDNOR2UDNSR1

UFL ICP40A ICP40B

U 30,966 2,058 8,569 6,149 2,509 3,221 2,046

NURE-HSSR program analytical methods:

LA2 - Los Alamos Energy dispersive X-ray fluorescence analysis of sediments for Ag, Bi, Cd, Cu, Nb, Ni, Pb, Sn, and W.

LA3 - Los Alamos Energy dispersive X-ray fluorescence analysis of sediments for Ag, As, Bi, Cd, Cu, Nb, Ni, Pb, Se, Sn, W, 

and Zr.

(Note: Some LA3 analyses may include Mo—noted only in Special Studies.)

LA4 - Los Alamos arc-source emission spectrography analysis of sediments for Be and Li.

LA5 - Los Alamos neutron activation analysis of sediments for Al, Au, Ba, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, 

Mg, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, Ti, V, Yb, and Zn.

LL1 - Lawrence Livermore neutron activation analysis of sediments for Ag, Al, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, Fe, 

Hf, Hg, K, La, Lu, Mg, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, Ti, U, V, W, Yb, and Zn.

OR7 - Oak Ridge emission spectrochemical analysis of sediments for Ag, Al, B, Ba, Be, Ca, Ce, Co, Cr, Cu, Fe, Hf, K, La, Li, 

Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Sc, Sr, Th, Ti, V, Y, Zn, and Zr.

SR2 - Savannah River neutron activation analysis of sediments for Al, Ce, Dy, Eu, Fe, Hf, La, Lu, Mn, Na, Sc, Sm, Th, Ti, V, and 

Yb.

(Note: Detectable Au values for samples analyzed by SR2 reported in GJBX-135(82).) 

SR3A - Savannah River (supplemental analysis by contract laboratory) Atomic Absorption Spectroscopy Analysis of sediments 

for Ag, Ba, Be, Co, Cr, Cu, Mg, Mo, Ni, Pb, Sn, Sr, Y, and Zn.

Table 2. Inventory for the Headwaters Province project showing number of NURE samples analyzed for the indicated elements by each 

laboratory and analytical method used.

[NURE data subsetted for this report]

Digital GIS-Based Geoscience Databases 13
14 Earth Science Studies—Headwaters Province, Idaho and Montana

SR3B:

 SR3CA - Savannah River (supplemental analysis by unnamed contract laboratory) colorimetric analysis of sediments for Nb, 

P, and W.

 SR3FE - Savannah River (supplemental analysis by unnamed contract laboratory) flame emission analysis of sediments for K, 

and Li.

 SR3XX - Savannah River (supplemental analysis by unnamed contract laboratory) analysis (analytical method not recorded) 

of sediments for As, Se, and Ca.

UDN-LA1 - Los Alamos delayed-neutron counting analysis of sediments for U.

UDN-LL1 - Lawrence Livermore neutron activation analysis of sediments for Ag, Al, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, 

Fe, Hf, Hg, K, La, Lu, Mg, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, Ti, U, V, W, Yb, and Zn.

UDN-OR2 - Oak Ridge neutron activation analysis—neutron counting of sediments for U.

UDN-SR1 - Savannah River neutron activation analysis—neutron counting of sediments for U.

UFL - Oak Ridge fluorescence spectroscopy analysis of sediments for U.

UNA-LL1 - Lawrence Livermore neutron activation analysis of sediments for Ag, Al, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, 

Fe, Hf, Hg, K, La, Lu, Mg, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, Ti, U, V, W, Yb, and Zn.

UNA-OR2 - Oak Ridge neutron activation analysis—neutron counting of sediments for U.

UXX-SR3 - Savannah River (supplemental analysis by unnamed contract laboratory) analysis (analytical method not recorded) 

of sediments for extractable U.

USGS analytical methods:

ICP10 - ICP-AES (inductively coupled plasma–atomic emission spectroscopy) performed in USGS laboratories using a method 

described by Motooka (1988).

ICP40A - ICP-AES performed in USGS laboratories using a method described by Crock and others (1983).

ICP40B - ICP-AES performed in USGS-contracted laboratories using a method described by Briggs (1990).

AA1 - (Au) - GF-AA (graphite furnace atomic absorption) performed in USGS-contracted laboratories using a method 

described by O’Leary and Meier (1986).

 - (As, & Se) - Hydride generation atomic absorption spectrophotometry performed in USGS-contracted laboratories using 

a method described by Welsch and others (1990).

AA2 - (Au) - GF-AA (graphite furnace atomic absorption) performed in USGS laboratories using a method described by 

O’Leary and Meier (1986).

 - (As & Se) - Hydride generation atomic absorption spectrophotometry performed in USGS laboratories using a method 

described by Welsch and others (1990).

INAA - (Au, Sb & W) neutron activation analysis in private sector laboratory.

Table 2. Inventory for the Headwaters Province project showing number of NURE samples analyzed for the indicated elements by 

each laboratory and analytical method used.—Continued.
Integrative Geologic 

Framework of the Headwaters 

Province

Ancient Laurentian (pre-Mesozoic continental core 

of North America) basement rocks underlie thick younger 

Proterozoic and Paleozoic sedimentary rocks and Proterozoic to Tertiary magmatic rocks in the eastern, central, and 

northern Headwaters Province but are only locally exposed at 

the surface. In western Idaho, oceanic rocks were accreted to 

the Laurentian continental core during Cretaceous time. The 

fabrics of the continental basement and of the western accretionary belt control many of the younger geologic features, 

depositional basins, composition and chemistry of magmatic 

rocks, location and type of epithermal mineral deposits, and 

multiple-times-reactivated structures. Study and better understanding of this architecture knits together the studies in the 

Headwaters Province.

Architecture of the Geologic Basement

By J. Michael O’Neill, P.K. Sims, and Karen Lund

The age and configuration of Precambrian crystalline 

(pre-Belt Supergroup) basement rocks in northwestern United 

States have been problematical because of sparse, widely 

dispersed exposures, a generally thick cover of Mesoproterozoic and younger sedimentary rocks, and the complexity 

of younger superposed tectonism and magmatism. Because 

direct observations of basement rocks are scarce, except in 

the mountains of southwestern Montana, knowledge of these 

rocks is strongly dependent on geophysical data and geochemical heritage gained from isotopic studies of younger igneous 

rocks.

Recent compilations of Precambrian basement maps of 

the States of Idaho (Sims and others, 2005), Montana (Sims 

and others, 2004), and Wyoming (Sims, Finn, and Rystrom, 

2001) utilized updated aeromagnetic data (NAMAG, 2002) 

and available geologic and geochemical data (Rhodes and 

Hyndman, 1988; Mueller and others, 1995; O’Neill, 1999; 

Doughty and others, 1998; Mueller and others, 2002). These 

data provide a means to decipher the basement terranes and 

integrate them with the Precambrian geology of the western 

margin of Laurentia in adjacent Canada (Cook, 1995; Ross, 

2002; Gorman and others, 2002).

Our study confirms and extends the postulate of O’Neill 

(1999), which has been further substantiated by new age data 

(Mueller and others, 2002), that the Archean Medicine Hat 

block was attached to the northwest margin of the Archean 

Wyoming province (fig. 5) by convergent deformation in 

Paleoproterozoic time. The long, broad disturbed zone in the 

basement was first delineated by reactivation features in overlying Phanerozoic rocks and named the Great Falls tectonic 

zone (O’Neill and Lopez, 1985; this report, see figs. 5, 6), and 

subsequently, the features of the underlying Paleoproterozoic 

suture were defined (O’Neill, 1999).

Conclusions reached during study of the geologic architecture and tectonic framework of the Precambrian basement 

of the Headwaters Province and adjacent regions are as follows. The Precambrian crystalline basement of the northern 

Rocky Mountains consists of the Archean Wyoming province 

in the southeastern part and an accreted composite terrane, 

the Trans-Montana orogen, composed of the Paleoproterozoic 

Wallace ocean-arc terrane and two accompanying minicontinents(?), the Pend Oreille domain and the Medicine Hat block 

in the northwestern part (fig. 5). The amalgamated terranes of 

the Trans-Montana orogen were accreted to the northern margin of the Wyoming province at about 1.9–1.8 Ga as a result 

of late Paleoproterozoic convergence (O’Neill, 1999; Brady 

and others, 2004). The accretionary events produced a zone 

of juvenile crust and a metamorphic-plutonic belt between the 

Great Falls and Dillon shear zones (fig. 5). Southeast of the 

Dillon shear zone is a 125-km-wide fold-and-thrust belt along 

the convergent margin of the Wyoming province, characterized by imbricate juxtaposition of thrust wedges composed 

of Archean and Paleoproterozoic rocks. Farther southeast, 

this Paleoproterozoic orogenic belt is interpreted to include 

a north-facing passive continental assemblage overlying the 

Archean Wyoming basement province, which is overstepped 

southward by a synorogenic foredeep succession (O’Neill, 

1999).

Suturing of the Precambrian terranes and their incorporation into what was to become the Laurentian continent were 

followed at about 1.5 Ga (only about 200 m.y. after) by a 

major, continent-wide episode of strike-slip shearing. These 

Mesoproterozoic shear zones are generally oriented northwestward and segmented the crust into fault-bounded blocks of 

varying dimensions (fig. 5).

All of these basement structural features influenced and 

provided centers for subsequent deformation, sedimentation, 

magmatism, and mineral deposits in the Great Falls tectonic 

zone. Northeast-trending ductile shears within the Great Falls 

tectonic zone controlled the emplacement of major late 

Mesozoic-Eocene magmatic systems and the formation of 

related mineral deposits, extending from central Idaho to 

north-central Montana. Reactivation of the northwest-trending 

Mesoproterozoic strike-slip fault system provided depocenters for the Belt Supergroup (U.S.) and equivalent Purcell 

Supergroup (Canada). Reactivation of the northwest-trending 

structures in the late Mesozoic influenced tectonic activity 

along the western margin of the continent possibly by controlling orientation of the Sevier thrust faults.

Integrative Geologic Framework of the Headwaters Province 15
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Figure 5. Generalized Precambrian basement map of part of northwestern United States, showing major geologic terranes assembled in the Paleopnorthwest-trending strike-slip shear zones recurrently active since the Mesoproterozoic are superimposed on the basement map. The faults are confcontinental rocks. Barbs indicate relative horizontal displacement, where known. Compiled from Sims, Bankey, and Finn (2001); Sims, Finn, and Rystro(2004); Sims and others (2005). CB, Cheyenne belt suture; CF, Cedar Creek fault; CZ, Clearwater zone; DSZ, Dillon shear (suture) zone; GFSZ, Great Falls Clark fault zone; SF, Snake River fault zone; SR, Snake River Plain volcanic field; SRS, Salmon River suture.
Metallogeny in the Context of 

the Great Falls Tectonic Zone

Major mineral deposit trends in the Headwaters Province 

include the northwest-trending Coeur d’Alene, a less well 

defined northwest-trending zone of cobalt-copper deposits, 

and the northeast-trending Idaho-Montana porphyry belt. (See 

the report by Taylor and others, p. 26.) The Idaho-Montana 

porphyry belt was originally named for elongated Eocene 

porphyry intrusions and dike swarms that are coincident with 

lode deposits in the Boise Basin (Ross, 1934a) and Casto 

(Ross, 1934b) areas. The belt was later identified across the 

entire province (Armstrong and others, 1978; Rostad, 1978) 

after many along-trend porphyry molybdenum deposits had 

been identified. The Montana-Idaho porphyry belt was one of 

the features originally used to define the Great Falls tectonic 

zone (O’Neill and Lopez, 1985). The basement architecture 

framework and particularly our understanding of its significant 

impact on subsequent regional mineralization trends were 

significantly improved as a consequence of geologic map 

compilations and metallogenic tectonic syntheses produced by 

the Headwaters Province project. (See the report by Klein and 

Sims, this page.)

Additionally, at the more local scale, determination of 

the magmatic systems responsible for particular hydrothermal 

mineralization events is considered crucial for development of 

mineral exploration models that include age, source, geochemical, tectonic, and emplacement characteristics of deposit 

types of interest. Assessment of mineral resource potential and 

potential geoenvironmental impacts of mineralizing systems 

requires similar data and models. Comparing and contrasting different mineralizing systems hosted by a single pluton 

can provide important constraints for predictive models. The 

Boulder batholith (Lund, Aleinikoff, Kunk, and Unruh, p. 39) 

lies at a critical junction between the basement structures that 

influenced mineralization in the Coeur d’Alene district and the 

Great Falls tectonic zone that controlled the Montana-Idaho 

porphyry belt and other types of epigenetic deposits. Topical studies in the Boulder batholith and its mineral deposits 

provide detailed data on timing, source, and emplacement 

characteristics for one of the regionally most important deposit 

systems.

As part of the Headwaters Province study, information 

on epigenetic mineral deposits was acquired by three studies 

at different scales within the Idaho-Montana porphyry belt. 

The results determine that the Great Falls tectonic zone is the 

fundamental structural and possibly geochemical control for 

mineral accumulations across the Headwaters Province. Future 

mineral resource and geoenvironmental assessments as well 

as future minerals exploration programs will be significantly 

enhanced by the results of these studies.

Control of Epigenetic Metal Deposits 

by Paleoproterozoic Basement 

Architecture

By Terry L. Klein and P.K. Sims

Large quantities of metals (gold, silver, copper, molybdenum, lead, and zinc) have been produced from mineral 

deposits in central and western Montana and central Idaho 

from the early 1860s to the present. The majority of these 

deposits are epigenetic and are associated with granitoid rocks 

of the Late Cretaceous Idaho and Boulder batholiths as well as 

felsic volcanic rocks of the Eocene Challis Volcanic Group and 

related subvolcanic intrusions in central and western Montana 

and central Idaho. Most of the deposits are in a 200-km-wide 

northeast-trending belt that extends from southwestern Idaho 

to the Little Rocky Mountains of north-central Montana, a 

distance of more than 1,000 km (figs. 5, 6). This belt contains 

the world-class copper deposits of the Butte district and more 

than 80 deposits designated as economically significant (Long 

and others, 1998; Spanski, 2004). 

The deposits chiefly coincide with the northeast-trending Great Falls tectonic zone (O’Neill and Lopez, 1985), the 

multiple-times-reactivated and poorly exposed northeasttrending Paleoproterozoic suture complex in the basement 

between previously amalgamated Paleoproterozoic and 

Archean terranes of the Trans-Montana orogen (to the northwest) and the Archean Wyoming province to the southeast 

(Sims and others, 2004; Sims and others, 2005). A Paleoproterozoic magmatic arc, which extends between the Great Falls 

and Dillon shear zones, formed at 1.9–1.8 Ga (Mueller and 

others, 2002) during collision and continued convergence of 

the amalgamated Paleoproterozoic and Archean terranes of the 

Trans-Montana orogen with the Archean Wyoming province. 

A Paleoproterozoic fold-and-thrust belt affects Paleoproterozoic marginal basin sediments, as well as the edge of the 

Wyoming province, and extends from the Dillon shear zone 

southeastward to the Madison mylonite zone (fig. 6). This belt 

predominantly consists of Archean gneisses but includes thrust 

slices of early Paleoproterozoic quartzite and metadolomite 

(O’Neill, 1999).

The location and the economic significance of the Cretaceous and Eocene mineralized belt are associated with two 

fundamental aspects of the Precambrian geology. The northeast-striking shear zones (thrust faults) that formed during collision along the Paleoproterozoic Dillon shear zone provided 

the primary structural control for intrusion of the metal-bearing Cretaceous and Eocene magmas. The Paleoproterozoic 

magmatic arc that developed within the suture complex likely 

was a major source of metals. Reactivation of the preexisting 

Metallogeny in the Context of the Great Falls Tectonic Zone 17
18 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 6. Basement map of west-central Montana and east-central Idaho, showing location of Great Falls tectonic zone and 

crosscutting northwest-trending faults.
fractures in the suture zone by recurrent regional tectonism 

in the Late Cretaceous and Tertiary provided openings for 

magma emplacement and conduits for ore-bearing fluids; it 

also facilitated concentration of the metals by convection in 

hydrothermal systems. A secondary but important control in 

localizing epigenetic metal deposits is the northwesttrending Mesoproterozoic fault system that traverses the 

region and overlaps with the northeast-striking shears formed 

during earlier suturing.

Updated aeromagnetic data (McCafferty and others, 

1998) were critical to identification of Precambrian basement 

geology and the ore-controlling structures (Sims and others, 2004; Sims and others, 2005). Mineral deposit data were 

compiled and classified from information in the U.S. Geological Survey MRDS and MAS mineral occurrences databases. 

Information from U.S. Geological Survey CUSMAP and 

national forest studies and published reports from the Idaho 

Geological Survey and the Montana Bureau of Mines and 

Geology were used to supplement information gleaned from 

the databases and to upgrade location and production data 

(Klein, 2004).

Epigenetic metal deposits of probable Cretaceous 

age within this northeast-trending mineralized belt include 

(1) polymetallic veins (gold, silver, copper, lead, antimony, 

and zinc), (2) polymetallic carbonate replacement deposits, (3) epithermal gold veins, (4) distal disseminated gold 

deposits, (5) base- and precious-metal and tungsten skarn and 

contact metamorphic deposits, (6) disseminated, stockwork 

and breccia-hosted porphyry copper and molybdenum deposits, (7) Butte district silver veins, (8) high-sulfidation copper 

veins (Butte district copper vein deposits), and (9) tungsten 

veins (figs. 7, 8). Deposits related to Eocene magmatism 

include (1) epithermal vein, disseminated, and breccia-pipe 

controlled precious-metal deposits, (2) porphyry copper and 

molybdenum deposits, (3) polymetallic veins, and (4) alkaline 

intrusion-related precious-metal deposits. Alkaline intrusionrelated deposits are concentrated in the northeastern part of 

the mineralized belt and are associated with Eocene intrusions 

that make up the Montana alkalic province (Larsen, 1940). 

Both temporal groups of deposits are spatially related to a 

pronounced gravity low (shown in fig. 8) that encompasses 

the Late Cretaceous Idaho and Boulder batholiths and also the 

Eocene Challis volcanic and subvolcanic intrusive rocks.

Many mineral districts and individual deposits are 

located at fault intersections between a northwest-trending, 

Mesoproterozoic set and a northeast-trending, Paleoproterozoic set that were both reactivated during the Late Cretaceous 

Sevier orogeny and Neogene extensional deformation. The 

northwest-striking Lewis and Clark zone (fig. 6), in particular, 

controlled the location of many deposits in the northern part of 

the study area. Perhaps significantly, this zone marks the transition from calc-alkaline magmatism in the southwestern part 

of the mineralized belt to alkaline magmatism to the northeast. 

Detailed structural studies have shown that the Boulder and 

adjacent Pioneer batholiths were localized by reactivation of 

preexisting Proterozoic structures during the Sevier orogeny 

(Kalakey and others, 2001). These intrusions lie in the northeasternmost part of the area of calc-alkaline magmatism.

Most of the large porphyry copper, porphyry molybdenum, and epithermal gold deposits are confined to the Paleoproterozoic juvenile magmatic arc and metamorphic-plutonic 

belt in the Paleoproterozoic suture complex directly northwest 

of the Dillon shear zone (fig. 6). These deposits lie within the 

–180 mGal (milligal) Bouguer anomaly of the central Idaho 

gravity low (Bankey and Kleinkopf, 1988; this report, fig. 8), 

or in the directly adjacent low-density area in the Medicine 

Hat block. Most of the large polymetallic vein and carbonate replacement deposits are confined to the belt of juvenile 

magmatic arc rocks in the Paleoproterozoic suture complex 

but extend southward into the foreland fold-and-thrust belt 

(figs. 5, 6). These epithermal deposits are coincident with a 

major zone of Eocene magmatism, as is depicted by mapped 

exposures and inferred from aeromagnetic data (fig. 8). 

Gold production and resources, primarily from epithermal and gold-rich polymetallic vein deposits, are overwhelmingly concentrated in the part of the Great Falls tectonic zone 

underlain by juvenile magmatic arc rocks of the Paleoproterozoic suture zone and directly adjacent areas underlain by basement rocks of the Archean Medicine Hat block and Paleoproterozoic Wallace terrane. The most productive deposits, for all 

deposit types, in the Great Falls tectonic zone overlie the area 

thought to be composed of Paleoproterozoic juvenile crust 

(fig. 9A). The distribution of silver deposits is similar to that 

of gold (fig. 9B). The areal distribution of significant copper 

production and resources also is similar to that of gold; note 

that significant copper production is coincident spatially with 

the area underlain by the Boulder batholith (fig. 9C). Deposits with the greatest lead (fig. 9D) resources are more widely 

distributed areally than deposits containing gold and copper; 

these lead-rich deposits are present in all basement sectors 

of the Great Falls tectonic zone and are most abundant in the 

southern part of the Idaho batholith and the northern part of 

the Boulder batholith. The metal distribution of zinc is similar 

to that of lead. 

An estimate of production from lode deposits (current to 

1999) is based on available USGS MRDS and MAS databases 

and data from the CUSMAP (Butte, Dillon, Challis, Hailey–

Idaho Falls) and national forest mineral resource assessments 

(Helena, Salmon, Payette), significant deposits databases 

(Long and others, 1998), and recent data compiled by Spanski 

(2004) and Klein (2004). These data indicate that epigenetic 

deposits in this area have produced more than 21 million troy 

ounces of gold, nearly 1 billion troy ounces of silver, 11 million tons of copper, nearly 0.5 million tons of molybdenum, 

1 million tons of lead, and more than 2.5 million tons of zinc 

(all 2,000-pound tons). This amount of metal production is 

similar to that for the Colorado mineral belt of central and 

southwestern Colorado. The Colorado mineral belt and the 

Idaho-Montana porphyry belt are geologically similar. In 

particular, the Colorado mineral belt includes Cretaceous and 

Metallogeny in the Context of the Great Falls Tectonic Zone 19
20 Earth Science Studies—Headwaters Province, Idaho and Montana

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VEINDEPOSIT

Figure 7. Location of studied epigenetic mineral deposits and outline of area for which mineral deposit data were compiled 

(Klein, 2004).
0 60 120 180 240 KILOMETERS 

0 50 100 MILES 

Study area boundary 

Area with less than -180 mGal 

 total Bouguer anomaly 

Strong positive magnetic features 

 (probable Eocene plutons) 

116° 114° 112° 110° 106° 

44° 

46° 

48° Polymetallic vein 

Antimony hot spring 

 and vein 

Alkaline epithermal 

 precious metal 

Tungsten vein 

Distal disseminated gold 

Polymetallic carbonate 

 replacement 

Tertiary polymetallic vein 

Skarn/contact 

Epithermal/hotspring gold 

Porphyry copper and 

 molybdenum 

Butte silver vein 

Butte copper vein 

Mercury hot spring 

EXPLANATION 

Area not studied or not in 

 Great Falls tectonic zone 

Approximate extent of

 Eocene volcanic rocks

ID MT 

Figure 8. Location of epigenetic mineral deposits, shown by deposit type, relative to basement geology. Principal areas of 

Tertiary volcanism and intrusions and a regional negative Bouguer gravity anomaly (related to Late Cretaceous and Tertiary 

granitic intrusions) shown. Basement units and structure are same as in figure 6. 

Metallogeny in the Context of the Great Falls Tectonic Zone 21
22 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 9 (above and following three pages). Location and quantity of metals produced from deposits with greater than 100 tons 

ore production and prospects with identified resources. Basement units and structure are same as in figure 6. A, gold; B, silver; 

C, copper; D, lead.
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Metallogeny in the Context of the Great Falls Tectonic Zone 23
24 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 9—Continued. Location and quantity of metals produced from deposits with greater than 100 tons ore production and 

prospects with identified resources. C, copper; D, lead.
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Metallogeny in the Context of the Great Falls Tectonic Zone 25
26 Earth Science Studies—Headwaters Province, Idaho and Montana

Tertiary epigenetic mineral deposits that are contained within 

Mesoproterozoic host rocks and which were inferred by Tweto 

and Sims (1963) to be localized by Proterozoic-age basement 

structures. Data for metal production from lode deposits in the 

Idaho-Montana porphyry belt and the Colorado mineral belt 

(compiled from Vanderwilt, 1947; Del Rio, 1960; and U.S. 

Bureau of Mines Mineral Yearbooks from 1959–1990) show 

that each area has produced similar amounts of gold, silver, 

and zinc. Molybdenum production is two times greater and 

lead production three times greater in the Colorado mineral 

belt than in the Idaho-Montana porphyry belt, whereas copper 

production is five times greater in the Idaho-Montana porphyry belt than in the Colorado mineral belt. 

The tectonic history and composition of the Archean 

and Paleoproterozoic basement are interpreted to have greatly 

influenced the location, metal ratios, and size of epigenetic 

deposits in the Headwaters Province study area. We propose 

that the coincidence of the epigenetic deposits to juvenile 

magmatic rocks in the underlying basement resulted in melting of those fertile rocks during subsequent orogenic pulses 

and remobilization of metals. This permits first-order definition of permissive mineral resource assessment tracts for 

many deposit types. Refinement of the location and history 

of basement structures through more detailed studies will aid 

in further defining areas with higher economic potential. The 

close relationship between epigenetic metal deposits and basement rock compositions and preexisting structures in Archean 

and Paleoproterozoic terranes is not unique to the IdahoMontana porphyry belt (see Sims and others, 2002), and it 

offers additional options in defining permissive tracts for 

national- and global-scale mineral resource assessments.

Geochronology and Geochemistry of 

the Idaho-Montana Porphyry Belt

By Cliff D. Taylor, Jeffrey A. Winick, Daniel M. Unruh, 

and Michael J. Kunk

The vast majority of the known molybdenum and copper 

resources in the Headwaters Province are contained in the 

northeast-trending Idaho-Montana porphyry belt (Rostad, 

1978), a zone of porphyry-related deposits that extends from 

the Boise Basin in central Idaho, through southwestern Montana, to the Little Belt Mountains, and possibly as far east as 

the Hawkeye prospect (fig. 10) in the Zortman Landusky district of north-central Montana. The porphyry belt is truncated 

on the west by the Salmon River suture (fig. 10). 

Two periods of silicic magmatism resulted in (1) 

voluminous Late Cretaceous tonalite to granite of the Idaho, 

Pioneer, and Boulder batholiths (related to convergent 

tectonism, subduction, and construction of an Andean-style 

cordillera along the Pacific margin) and (2) smaller Eocene 

plutons and associated dikes of more evolved monzogranite to granite-rhyolite composition (thought to have been 

emplaced during a period of crustal relaxation and rifting 

that followed subduction-related magmatism; Rehn and 

Lund, 1981). Regionally, these plutonic rocks were emplaced 

into the Archean Wyoming province, the Medicine Hat block, 

and the Paleoproterozoic Wallace terrane. Significantly, the 

northeast-trending porphyry belt is coincident with the Great 

Falls tectonic zone, the structurally complex underlying 

Paleoproterozoic orogenic zone originally produced by collision of the Wyoming province with Trans-Montana orogen 

rocks to the northwest during assembly of the Paleoproterozoic continent (fig. 5). This crystalline basement is obscured 

by younger sedimentary, volcanic, and plutonic rocks, 

including the Mesoproterozoic metasedimentary rocks of the 

Belt Basin, Paleozoic sedimentary rocks, Eocene volcanic 

rocks, and both major periods of magmatism. 

Although most of the porphyry copper-molybdenum 

occurrences within this 750-km-long belt are economically 

insignificant, potentially important deposits exist at CUMO, 

Cannivan Gulch, and Heddleston; and major deposits at Thompson Creek and Butte have been mined. These deposits highlight 

the economic importance and undiscovered resource potential of 

the Idaho-Montana porphyry belt. Despite recognition between 

the 1930s and 1970s (Ross, 1934; Rostad, 1978) that deposits 

were aligned, very little information concerning age or geologic 

and geochemical characteristics is available in the literature. 

Thus, any attempt to discuss deposits in this belt has created 

controversy regarding whether deposits share similar origins, 

whether discrete episodes of porphyry deposit formation exist, 

or whether mineralization was associated with the two major 

periods of silicic magmatism.

Previous age data, mostly K-Ar analyses on minerals 

from both the host intrusions and mineral deposit-related alteration, span a range of ≈87 to 29 Ma (Armstrong and others, 

1978; Rostad, 1978). Clearly, when compared with the normal 

lifespan of most mineral deposits, measured in hundreds of 

thousands to several million years (Stein and Cathles, 1997), 

the nearly 60 million years of igneous intrusive activity and 

mineralization cannot be related to a single magmatic episode 

or tectonic event. (1) How many periods of porphyry mineralization are present? (2) Is there a periodicity, or is deposit 

formation within the belt distributed evenly through time? 

(3) Is there a relationship between the age of formation and the 

geographic position of deposits within the belt? (4) What is 

the fundamental control resulting in the linearity of the belt in 

the first place? (5) What effect does the source region of the 

porphyries have on the size and characteristics of the deposits? 

(6) Do all these deposits share similar genetic origins regardless of age and nature of their source rocks?

In light of these questions, some of the important goals 

of the Headwaters Province project include (1) to more fully 

describe the characteristics of porphyry mineral deposits and 

occurrences, (2) to conduct a geochronological study of the 
Ima 

CUMO 

April 

Walton 

Hawkeye 

Big Ben 

Monaghan 

Heddleston 

Bald Butte 

White Cloud 

Peach Creek 

Cold Spring 

Spring Creek 

Little Falls 

Granite Peak 

Bobcat Gulch 

Turnley Ridge 

Donald pluton 

Emigrant Gulch 

Blue Jay-Big Eightmile 

Lower Seymour Lake 

116° 

116° 

115° 

115° 

114° 

114° 113° 

113° 

112° 

112° 

111° 

111° 

110° 

110° 

109° 

109° 

108° 

108° 

44° 

44° 

45° 

45° 

46° 

46° 

47° 

47° 

48° 

48° 

43° 

0 50 100 200 KILOMETERS 

EXPLANATION 

Porphyry deposits sampled in this study 

Idaho-Montana porphyry deposits 

Cretaceous intrusions 

Tertiary-Cretaceous intrusions 

Tertiary intrusions 

Paleoproterozoic-Archean Medicine Hat block 

Archean Wyoming province 

Paleoproterozoic Wallace terrane 

Great Falls tectonic zone 

Butte 

McCartney Mtn

Cannivan Gulch 

Thompson Creek 

IDAHO MONTANA 

Figure 10. Location of porphyry molybdenum and copper-molybdenum deposits of Idaho-Montana porphyry belt. Pale gray shade, 

area not studied or not in Great Falls tectonic zone or Trans-Montana orogen. Dashed red line, Salmon River suture.

Metallogeny in the Context of the Great Falls Tectonic Zone 27
28 Earth Science Studies—Headwaters Province, Idaho and Montana

deposits within the belt using the high-precision 40Ar/39Ar 

method, and (3) to characterize and evaluate the genetic 

origins of the host plutons using modern geochemical and 

radiogenic isotopic analytical methods.

Field Work and Classification of Occurrences by 

Deposit Type 

Sixty-three molybdenum and molybdenum-copper deposits 

and occurrences (fig. 10) are listed in the MRDS and MAS/MILS 

USGS mineral databases (McFaul and others, 2000); thirty of these 

were visited. We collected rock samples primarily to obtain new 

40Ar/39Ar data (1) to determine cooling ages of the igneous host 

rocks (using hornblende, biotite, muscovite, or potassium feldspar 

mineral separates) that host deposits, and (2) to establish deposit 

ages for alteration minerals (using sericite mineral separates). 

The least altered igneous rocks were collected for whole-rock 

geochemical and radiogenic isotopic characterization. A subset of 

these samples includes Cretaceous batholith rocks and Proterozoic 

gneiss, collected and analyzed in order to better constrain the age 

and geochemistry of local country rocks.

At each site, we analyzed the mineralogical composition 

and texture of the host igneous rock and the form of intrusion 

(pluton, sill, or dike), as well as associated mineral deposit 

mineralogy, type and extent of alteration, and deposit style 

and morphology. These data were used to assign deposits to 

a stockwork, vein, or disseminated porphyry deposit class. 

Because intrusions related to porphyry molybdenumcopper deposits are generally associated with subductionrelated continental arcs, molybdenum-only deposits were 

divided into low-fluorine, granodiorite-hosted deposits (generally associated with subduction-related Andean style continental arcs) or high-fluorine monzogranite-hosted to high-silicarhyolite-hosted Climax-type deposits (generally related to 

intracontinental rift environments).

One set of deposits was difficult to characterize due to 

their small size and poor exposure relative to standard porphyry deposit models. Further characterization of age relationships and geochemistry (following) helped in characterization. 

A second group of deposits within the linear trend exhibited 

commonly accepted characteristics of porphyry deposits. The 

best known and well-studied deposits in the Idaho-Montana 

porphyry belt, the molybdenum-only Thompson Creek mine 

and the copper-molybdenum mine at Butte, are somewhat 

atypical examples of molybdenum and copper-molybdenum 

porphyry deposits. All three groups are shown in table 3.

40Ar/39Ar Geochronology

In order to constrain the age relationships between Cretaceous 

and Tertiary igneous rocks and their associated mineral deposits 

within the Idaho-Montana porphyry belt, we obtained 54 highprecision 40Ar/39Ar analyses at 17 sites (table 4). Minerals analyzed 

include hornblende, biotite, potassium feldspar, and muscovite 

separated from the host igneous rocks, and sericite from ore-related 

alteration assemblages. Due to the wide and variable range (400°–

250°C) of argon closure temperatures for the minerals analyzed, 

the 40Ar/39Ar technique provides a minimum age of the last thermal 

event to affect the rock. Yellow highlighted samples on table 4 represent cooling of sericite in alteration assemblages to below 250°C 

and, thus, represent minimum mineralization ages. Gray highlighted samples represent minimum cooling ages for igneous country rocks spatially associated with the porphyry deposits but only 

indirectly related to mineralizing events. For example, the analyses 

of potassium feldspar and biotite from the Mesoproterozoic augen 

gneiss at Spring Creek (Doughty and Chamberlain, 1996) probably 

reflect metamorphism of that unit during emplacement of the Idaho 

batholith. Similarly, Eocene ages for three mineral separates from 

the quartz monzonite of the Idaho batholith collected at Rattlesnake 

Gulch, about 20 km east of the Little Falls deposit, probably reflect 

resetting and cooling of batholith rocks near Eocene dikes related 

to the deposits at Little Falls and CUMO. The remainder of the 

samples in table 4 represent cooling ages of rock-forming minerals 

in intrusive rocks that are directly related to hydrothermal mineralization events.

The age of intrusion and mineralization as a function of 

distance from the continental margin is summarized in figure 

11. Two major features are apparent. First, samples of Cretaceous age exhibit a poorly defined but consistent younging 

trend with increasing distance northeast of the Salmon River 

suture. The oldest deposits related to the Idaho batholith have 

a maximum age of 85.2 Ma (biotite) for the Little Boulder 

Creek stock (White Cloud deposit, figs. 10, 11). The youngest of the Cretaceous batholith-related deposits is located 

in the easternmost Tobacco Root batholith at Granite Peak, 

where mineralized dikes cutting the batholith have a minimum age of 69.6 Ma (potassium feldspar). Cooling ages for 

additional samples of batholithic country rocks, not directly 

related to mineralization, such as at Peach Creek and the 

Donald pluton, support the general eastward younging trend. 

Second, samples of Tertiary age show a more tightly constrained age distribution that appears to be largely independent of position relative to the continental margin. The range 

in age for Eocene intrusive host rocks spans an interval from 

38.8 Ma (CUMO) to 51.3 Ma (Bluejay-Big Eightmile). In 

comparison, if ages of batholithic plutonic country rocks 

that host the deposits are included, the Cretaceous samples 

indicate a ≈34 m.y. range.

Examination of the cooling histories at six Cretaceous 

and six Tertiary locations for which age data for multiple mineral separates are available suggests fundamental differences 

between Cretaceous and Tertiary deposits. Normal age progressions of hornblende>biotite>sericite>potassium feldspar 

are observed at five of the six Tertiary deposits and generally 

indicate cooling histories of less than ≈4 m.y. The longest age 

span is 6.6 m.y. at the Walton deposit. Normal age progressions are also observed at four of the six Cretaceous deposits, 

although the age span is greater than for the Tertiary deposits. 

Three of six span a range of about 8 to 11 m.y., and share 

the characteristic of being hosted by the Idaho and Tobacco 

Root batholiths. The two deposits that exhibit relatively short 
Table 3. Characteristics of selected molybdenum deposits and mineralized areas in the Idaho-Montana porphyry belt.1

________________________________________________________________________________________________

Deposit name(s) Host rock Form Diagnostic minerals Alteration

________________________________________________________________________________________________

 Deposits difficult to characterize relative to standard porphyry deposit models

________________________________________________________________________________________________

Peach Creek, Genetically unrelated Sparse fracture coatings Molybdenum or Unknown.

 McCartney Moun- country rock. and disseminations molybdenum-copper 

 tain, April Claim, associated with large minerals.

 Thrift Stamp. veins or pods of quartz.

Walton-------- Felsic dikes peripheral Large, discontinuous Unknown Unknown.

 to the Little Fall quartz-sericite veins.

 Creek pluton.

Pear Lake-Anchor Granodiorite country Widely dispersed Pyrite and molybdenite Unknown.

 Lake-Monaghan. rock. coated fractures.

Spring Creek-- Proterozoic gneiss Highly mineralized massive Molybdenite Unknown.

 that may be gen- quartz-sericite vein.

 etically associated

 with the minor occur-

 rence of felsic dikes

 noted in drill core.

Granite Peak, Large felsic dikes Unknown Disseminated pyrite Unknown.

 Emigrant Gulch. and molybdenite.

Bald Butte--- Unexposed quartz Molybdenum geochem- Molybdenum Unknown.

 diorite intrusion ical anomaly in soils.

 at depth from drill

 core (Rostad, 1978).

Turnley Ridge Large and continuous Sparse mineralized Unknown Potassium feldspar-

 aplite dike cutting rock. sericite flooded.

 quartz-potassium

 feldspar porphyry.

Bluejay-Big Big Eightmile stock Disseminated mineraliza- Pyrite, chalcopyrite, and rare Unknown.

 Eightmile. tion in greisen developed molybdenite with malachite

 at the top of the stock. and azurite.

________________________________________________________________________________________________

 Porphyry-related deposits

________________________________________________________________________________________________

Little Falls-- Extensive set of Quartz vein stockworks Molybdenite-pyrite coated Weak pyritic altera-

 Eocene porphyritic associated with rhyolite fractures and molybdenite- tion halo.

 calc-alkaline dikes porphyry dikes and altera- rich quartz vein stockworks.

 that intrude the tion halo extending a short

 Idaho batholith. distance into the surround-

 ing Idaho batholith.

CUMO Extensive set of Idaho batholith country Significant disseminated Central zone of

 Eocene porphyritic rocks. molybdenum-copper intensely silicified

 calc-alkaline dikes mineralization. host rock surround-

 that intrude the ed by extensive

 Idaho batholith. argillic halo. 

 Extensive pyrite-

 sericite alteration in

 country rocks.

White Cloud, Granodiorite to mon- Well-developed quartz- Abundant molybdenite Concentrically zoned

 Cannivan Gulch, zogranite porphyry potassium feldspar- phyllic and argillic

 Black Lion intrusions. (White sericite-pyrite- alteration haloes sur-

 Cloud, Idaho batho- molybdenite vein rounding silicic and

 lith; Cannivan Gulch stockworks. potassically altered

 and Black Lion, cores.

 Pioneer batholith).

Metallogeny in the Context of the Great Falls Tectonic Zone 29
30 Earth Science Studies—Headwaters Province, Idaho and Montana

Big Ben----- Intrusive high-silica Unknown “Climax-type” molybdenum Unknown.

 porphyritic rhyolite. deposit.

Pipestone Pass Granitic Homestake Disseminated mineraliz- Minor concentrations of Unknown.

 occurrences. and granodioritic ation. disseminated molybdenite.

 Donald plutons of the

 Boulder batholith.

Heddleston, Granodioritic Disseminated and stock- Pyrite, chalcopyrite, and Pervasive and con-

 Bobcat Gulch. intrusions. work veins in standard molybdenum. Protore and centrically zoned

 porphyry copper- supergene enriched bodies alteration.

 molybdenum deposit. of chalcocite.

Cold Spring- Sanidine-rich dacite Unknown Unknown Heavily altered.

 Grasshopper. plug.

________________________________________________________________________________________________

 Somewhat atypical examples of molybdenum and copper-molybdenum porphyry deposits

________________________________________________________________________________________________

Thompson Creek Outer equigranular, Little to no disseminated Molybdenite associated with Pervasive weak 

 medium-grained, molybdenite in deposit. minor pyrite. Metals aggre- argillic alteration. 

 biotite granodiorite, Tenor of orebody defined gate within the intrusive Potassic and phyllic

 with an inner weakly by size and density of bodies primarily as selvages alteration of the host

 porphyritic biotite stockwork quartz-molyb- to coarse-grained, quartz- intrusions confined 

 granite. denite veining, Deposit potassium feldspar- to within a few cent-

 scale: veins constitute a muscovite-biotite veins. imeters of the veins.

 stockwork. Outcrop

 scale: widely spaced dis-

 crete veins are centimeters

 to a meter wide. Grade

 controlled by high con-

 centrations of coarsely 

 crystalline molybdenite in

 selvages of large veins.

Butte Butte granite pluton Concentrically arranged Stockwork of randomly Chalcopyrite-

 massive to disseminated oriented and discontinuous molybdenite veinlets

 shells of ore. Bulk of chalcopyrite-molybdenite enclosed within

 the metal (Main Stage) veinlets with superimposed sericite-biotite

 contained by swarm of rich copper veins. potassium feldspar

 large, subparallel poly- alteration envelopes.

 metallic veins and coeval

 quartz porphyry dikes.

 Earlier, pre-Main Stage

 porphyry mineralization

 present at depth.

____________________________________________________________________________________________________________ 1

See figure 10 for locations of studied sites.

Table 3. Characteristics of selected molybdenum deposits and mineralized areas in the Idaho-Montana porphyry 

belt—Continued.

________________________________________________________________________________________________

Deposit name(s) Host rock Form Diagnostic minerals Alteration

________________________________________________________________________________________________

 Porphyry-related deposits—Continued

________________________________________________________________________________________________
Field No. Prospect Rock type Mineral Age (Ma) ±1s Type 

K-01-7-19A Walton altered quartz monzonite adjacent to vein Sericite 44.49 4.86 Isochron 

K-01-7-19B Walton biotite quartz monzonite-Little Fall Creek pluton Biotite 47.80 0.25 Total fusion 

K-01-7-19B Walton biotite quartz monzonite-Little Fall Creek pluton Biotite 47.23 0.55 Isochron 

K-01-7-19B Walton biotite quartz monzonite-Little Fall Creek pluton K-spar 41.20 4.94 Isochron 

K-01-7-21C CUMO silicified, MoS 2 -bearing quartz monzonite K-spar 38.80 0.30 Isochron 

K-01-7-21D CUMO altered, brecciated lamprophyre Biotite 45.62 0.23 Total fusion 

K-01-7-21D CUMO altered, brecciated lamprophyre Biotite 45.71 0.25 Plateau 

K-01-7-21F CUMO hornblende gabbro Hornblende 39.01 0.21 Plateau 

01HW-69 quartz monzonite-Rattlesnake Gulch K-spar 44.32 0.24 Plateau 

01HW-69 quartz monzonite-Rattlesnake Gulch Biotite 47.61 0.24 Total fusion 

01HW-69 quartz monzonite-Rattlesnake Gulch Biotite 45.02 1.28 Isochron 

K-01-7-23A White Cloud quartz-MoS 2 vein cutting Little Boulder Creek stock Sericite 84.98 0.35 Plateau 

K-01-7-23A White Cloud quartz-MoS 2 vein cutting Little Boulder Creek stock Sericite 84.53 0.35 Plateau 

K-01-7-23A White Cloud quartz-MoS 2 vein cutting Little Boulder Creek stock Sericite 84.40 0.30 Isochron 

K-01-7-23B White Cloud biotite quartz monzonite-Little Boulder Creek stock K-spar 78.09 1.53 Isochron 

K-01-7-23B White Cloud biotite quartz monzonite-Little Boulder Creek stock Biotite 85.19 0.30 Total fusion 

K-01-7-23B White Cloud biotite quartz monzonite-Little Boulder Creek stock Biotite 84.67 0.22 Total fusion 

K-01-7-23C White Cloud hornfelsed Wood River Fm.-quartz-MoS 2 vein selvage Sericite 85.10 0.30 Plateau 

01HW-73 White Cloud quartz monzonite-White Cloud stock Biotite 86.33 0.27 Total fusion 

JW-6-17-02D Big Ben altered Snow Creek quartz porphyry Sericite 49.40 1.30 Isochron 

JW-6-17-02E Big Ben Snow Creek quartz porphyry-drill core K-spar 47.90 0.20 Plateau 

JW-6-17-02F Big Ben Snow Creek quartz porphyry-drill core Biotite 47.38 0.07 Total fusion 

02DU-08 Big Ben Carpenter Creek biotite granite porphyry-drill core Biotite 47.53 0.09 Total fusion 

02DU-08 Big Ben Carpenter Creek biotite granite porphyry-drill core K-spar 45.95 0.26 Isochron 

JW-6-18-02A Bald Butte diorite-Belmont dike Biotite 42.96 0.12 Total fusion 

JW-6-18-02A Bald Butte diorite-Belmont dike Biotite 43.05 0.24 Total fusion 

JW-6-18-02A Bald Butte diorite-Belmont dike K-spar 57.45 0.17 Total gas 

JW-6-19-02A Heddleston altered quartz monzonite porphyry Sericite 43.83 0.18 Plateau 

JW-6-19-02D Heddleston altered quartz monzonite porphyry Sericite 46.50 0.60 Isochron 

JW-6-21-02A granodiorite-Boulder batholith Biotite 72.81 0.25 Total fusion 

JW-6-21-02A granodiorite-Boulder batholith K-spar 81.00 0.20 Plateau 

JW-6-21-02A granodiorite-Boulder batholith Hornblende 102.31 3.34 Isochron 

JW-6-22-02B Pipestone Pass leucocratic granite-Donald pluton K-spar 69.10 0.30 Isochron 

JW-6-22-02B Pipestone Pass leucocratic granite-Donald pluton K-spar 70.07 0.62 Isochron 

JW-6-23-02B April Claim-Crystal Butte altered quartz monzonite Sericite 73.71 0.20 Plateau 

JW-6-23-02D April Claim-Crystal Butte diorite Biotite 74.78 0.26 Total fusion 

JW-7-17-02A Emigrant Gulch rhyolite porphyry Sericite 48.10 0.27 Plateau 

JW-7-17-02C Emigrant Gulch rhyolite porphyry Biotite 49.57 0.21 Total fusion 

JW-7-17-02C Emigrant Gulch rhyolite porphyry K-spar 47.90 0.50 Isochron 

JW-7-18-02C Granite Peak quartz monzonite dike K-spar 69.60 0.40 Isochron 

JW-7-18-02D Granite Peak biotite granite K-spar 68.60 0.40 Isochron 

JW-7-18-02D Granite Peak biotite granite Hornblende 79.41 0.47 Isochron 

JW-7-19-02C McCartney Mtn biotite granodiorite stock Biotite 75.13 0.26 Total fusion 

JW-7-19-02C McCartney Mtn biotite granodiorite stock K-spar 72.80 0.30 Isochron 

JW-7-20-02A Cold Spring-Grasshopper dacite plug Sanidine 72.50 0.20 Weighted mean 

JW-7-21-02A Black Lion Clifford Creek granodiorite Sericite 63.36 0.34 Plateau 

JW-7-23-02A Lower Seymore Lake altered white mica-bearing leucomonzogranite White mica(?) 75.40 0.26 Plateau 

JW-7-23-02B Lower Seymore Lake leucomonzogranite Sericite 44.75 0.13 Plateau 

JW-7-25-02B Spring Creek quartz-pyrite-sericite-molybdenite vein Sericite 46.53 0.55 Isochron 

JW-7-25-02D Spring Creek biotite-hornblende augen gneiss K-spar 89.88 0.49 Plateau 

JW-7-25-02D Spring Creek biotite-hornblende augen gneiss Biotite 79.91 0.49 Total fusion 

JW-7-25-02E Ima quartz vein cutting Precambrian quartzite Sericite 44.50 0.13 Plateau 

JW-7-26-02A Bluejay-Big Eightmile biotite monzogranite-Big Eightmile stock Biotite 49.52 0.14 Total fusion 

JW-7-26-02A Bluejay-Big Eightmile biotite monzogranite-Big Eightmile stock Biotite 47.40 2.77 Total fusion 

JW-7-26-02A Bluejay-Big Eightmile biotite monzogranite-Big Eightmile stock K-spar 48.00 0.30 Isochron 

JW-7-26-02B Bluejay-Big Eightmile basaltic andesite dike cutting Big Eightmile stock Biotite 50.60 0.22 Total fusion 

JW-7-26-02C Bluejay-Big Eightmile quartz-sericite vein cutting altered monzogranite Sericite 51.10 0.40 Plateau 

JW-7-26-02C Bluejay-Big Eightmile quartz-sericite vein cutting altered monzogranite Sericite 50.48 1.06 Isochron 

JW-7-26-02D Bluejay-Big Eightmile heavily altered malachite-rich greisen at Bluejay Sericite 51.30 0.40 Isochron 

JW-7-27-02B Peach Creek quartz monzonite-Idaho batholith K-spar 79.50 0.40 Isochron 

02DU-11 Hawkeye k-spar flooded rhyolite porphyry K-spar 62.80 0.34 Plateau 

O2HW-06B Hawkeye rhyolite porphyry-drill core K-spar 64.71 0.35 Plateau 

Table 4. New 40Ar/39Ar data for mineralized rocks (gold color), genetically related plutons, and country rocks (gray) of the Idaho-Montana 

porphyry belt.

Metallogeny in the Context of the Great Falls Tectonic Zone 31
AGE (Ma) 

30 40 50 60 70 80 90 100 

DISTANCE FROM CONTINENTAL MARGIN (KM) 

0 

100 200 300 400 500 600 700 800 

K-feldspar Biotite Sericite Hornblende CUMO 

Rattlesnake Gulch-Idaho batholith 

Walton 

Ima 

Bluejay-Big Eightmile 

Lower Seymour Lake McCartney Mountain 

April Claim-Crystal Butte 

White Cloud 

White Cloud 

stock 

Peach Creek-Idaho batholith 

Spring Creek Proterozoic augen gneis

Donald pluton

Granite Peak Granite Peak Emigrant Gulch 

Bald Butte Belmont diorite 

N. Elkhorn Mountains Boulder batholith 

Big Ben 

Heddleston 

Spring Creek 

Cold Spring-Grasshopper 

Black Lion 

Hawkeye Hawkeye 

Figure 11. New ages for porphyry deposits as determined by 40Ar/39Ar geochronology versus approximate distance from pre-Cretaceous continenta

margin. Blue type indicates the age of igneous rock that hosts a porphyry deposit. Black type indicates the age of the porphyry intrusions or alteration related to one of the porphyry deposits.
cooling histories of 1.1 and 2.3 m.y. are in close proximity 

to each other and are outside known boundaries of the major 

batholiths. Mineral separates from rocks that host the Boulder batholith in the northern Elkhorn Mountains indicate an 

anomalously long cooling history of 29.5 m.y.

Whole-Rock Geochemistry and Radiogenic 

Isotopic Studies

Describing the host plutons helps to explain the origin of 

the metals as it reflects the character of the crystalline basement underlying the Idaho-Montana porphyry belt. To this 

end, detailed geochemical analyses were obtained on 62 samples at 29 sites of least altered Cretaceous and Tertiary igneous 

rocks and country rocks at and near many of the deposits. 

Although major-element and some minor-element data are 

published for the major batholiths and to a lesser extent for 

the Tertiary plutons, very little trace-element and REE (rare 

earth element) geochemistry has been reported. Similarly, 

radiogenic isotope abundances of strontium, neodymium, and 

lead were determined for a suite of selected samples. Together, 

these new geochemical data provide a refined perspective on 

the character of the Cretaceous and Tertiary plutons related 

to the porphyry deposits and will enhance understanding 

concerning the nature and origin of the porphyry belt (Taylor 

and others, 2004; C.D. Taylor and D.M. Unruh, unpub. data, 

2003).

Whole-rock major-element variation (Harker) diagrams 

based on data recalculated to anhydrous compositions are displayed in figure 12. In general, most of the plots display coherent trends, suggesting that both the Cretaceous and Tertiary 

rocks have evolved by similar fractionation and (or) assimilation 

processes. The range in SiO2, from ≈53 to 76 percent SiO2, indicates that rock samples range from gabbro to granite-rhyolite 

composition. Above 68 percent SiO2, Cretaceous rock compositions cluster from about 68 to 73 percent SiO2

, reflecting their 

predominantly tonalitic to granodioritic compositions. Samples 

with higher SiO2

 values are mostly Tertiary and reflect their 

more evolved compositions. Differences in the relative enrichments and depletions of major elements between the Cretaceous 

and Tertiary rocks are distinctive. Cretaceous rocks are enriched 

in Al2O3, CaO, and MnO, and depleted in K2O and TiO2 compared to Tertiary rocks. FeTO3

, MgO, and P2O5 abundances in 

the Cretaceous and Tertiary rocks are indistinguishable. Na2O 

and Zr abundances show no consistent variation relative to SiO2

variation. Loss on ignition (LOI) provides a useful proxy for 

the alteration intensity of a rock; data points >2 percent LOI 

indicate samples that are from within the alteration haloes of 

the porphyry deposits. The higher LOI values of Tertiary rocks 

suggest that those rocks are more likely to be altered, or alternatively that they intrinsically have a higher magmatic volatile 

content. The smooth decrease in abundance of Al2O3, FeTO3, 

MgO, CaO, TiO2, P2O5, and MnO, as well as the increase in 

K2O with increasing SiO2 for both Cretaceous and Tertiary 

rocks, is characteristic of normal calc-alkaline fractionation 

processes.

Plots of chondrite-normalized REE data for Cretaceous 

batholiths and plutons related to the porphyry deposits are 

in figure 13. REE data for Tertiary plutons and dikes in the 

southwestern and central parts of the porphyry belt are shown 

in figure 14A, and those in the northeastern part in figure 14B. 

REE patterns of basic and intermediate rocks are not considered here. The shape of REE patterns of the Cretaceous plutons is significantly different from that of most of the Tertiary 

intrusions. In general, the Cretaceous rocks exhibit moderately negative sloping light REE (LREE) profiles (starting at 

abundances 60–250 times chondrites), they include minor to 

no negative Eu anomalies, and they have gently negatively 

sloping heavy REE (HREE) abundances (2–20 times chondrites). In contrast, REE profiles of Tertiary igneous rocks 

in the southwestern and central portions of the porphyry 

belt (fig. 14A) display weak to moderately well developed 

negative Eu anomalies. Light REE abundances are 50–200 

times chondrite, whereas HREE abundances are 2–20 times 

chondrite. With the exception of the negative Eu anomalies 

characteristic of the Tertiary samples, the overall shapes of the 

REE patterns are very similar, as are their REE abundances. 

A possible interpretation is that both the Cretaceous and the 

Tertiary samples are derived from the same source material 

but are melting under slightly different conditions. Negative Eu anomalies may indicate plagioclase retention in the 

source prior to extraction of the Tertiary melts or plagioclase 

fractionation during solidification. The comparatively flat and 

somewhat elevated HREE profiles (with respect to chondrites) 

suggest that both Cretaceous and Tertiary melts experienced 

no HREE fractionation resulting from either retention of 

HREE-bearing phases in the source region or removal by 

crystal settling during solidification. 

Tertiary plutons and dikes in the northeastern part of the 

porphyry belt (fig. 14B) have REE patterns slightly different 

from those for plutons in the southwestern part of the belt. 

Most noticeably, the northeastern plutons have moderately 

negative slopes, with slight or no Eu anomalies, like the 

Cretaceous rocks. Reasons for the differences exhibited by 

these Tertiary rocks, specifically those from the Heddleston, 

Emigrant Gulch, and Big Ben deposits, are unclear. However, 

these patterns may reflect melting of fundamentally different 

Archean and Paleoproterozoic basement rocks that underlie these deposits outside the boundaries of the Great Falls 

tectonic zone (fig. 10). Possible differences in the basement 

blocks include basic geochemical differences in the disparate 

crustal blocks, melting of source rocks at shallower levels in 

the crust where garnet remains in the residuum, and (or) melting of rocks that did not undergo metasomatic changes resulting from the Paleoproterozoic compression and orogenesis.

Sr-Nd-Pb radiogenic isotopic data from a subset of the 

samples from the Headwaters Province project area (fig. 

15) provide a powerful tool to evaluate plutonic evolution. 

Radiogenic isotopes serve as tracers of the original material 

Metallogeny in the Context of the Great Falls Tectonic Zone 33
34 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 12. New whole-rock geochemical data for intrusive porphyry bodies at mineral deposits of Idaho-Montana porphyry 

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Figure 13. Chondrite-normalized rare earth element plots for Cretaceous porphyry intrusions and Cretaceous batholithic rocks of Idaho-M

porphyry belt. Numbers are field numbers. K, Cretaceous; bqm, biotite quartz monzonite; qm, quartz monzonite; g, granite; t, tonalite; bgd, biogranodiorite; gd, granodiorite; d, diorite; m, leucomonzonite; bm, biotite leucomonzonite.
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A

Figure 14. Chondrite-normalized rare earth element plots of Eocene porphyry intrusions and Cretaceous batholithic rocks. 

A, Intrusions in so

and central part of Idaho-Montana porphyry belt. Numbers are field numbers. T, Tertiary; rp, rhyolite porphyry; bqlp, biotite quartz latite porphr, rhyolite; qm, quartz monzonite; g, granite; bqm, biotite quartz monzonite; qm, quartz monzonite; bmg, biotite monzogranite; bql, biotite quartz lgd, granodiorite.
Figure 14—Continued. Chondrite-normalized rare earth element plots of Eocene porphyry intrusions and Cretaceous batholithic rocks. B, Intrusi

Idaho-Montana porphyry belt. Numbers are field numbers. T, Tertiary; qmp1, quartz monzonite porphyry #1; rp, rhyolite porphyry; g, granite; bqm, bgranite porphyry; qp, quartz porphyry.

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Boulder batholithIdaho batholithWhite Cloud/Little BouldTertiary-Walton prospecTertiary-Little Falls prosTertiary-CUMO depositPioneer batholithWhite Cloud metasedimTertiary-Belmont diorite Tertiary-HeddlestonTertiary-Emigrant GulchCretaceous plutons

Atlanta lobe

Idaho batholith

Boulder batholith

Pioneer

batholith

SW MobasemMesoz

Big Belt Mtns

Salmon Riversuture zoneplutons

W. Idaho/E. Oregon island arc plutons

Tobacco Rootbatholith April Claim diorite

Anaconda-Pintlarbatholith

Figure 15. Plot of strontium-neodymium (initial) isotopic values for porphyry intrusions and Cretaceous batholithic rocks from Idaho-Montana Sr-Nd analyses are shown as discrete points relative to a larger database (colored fields) of published and unpublished analyses (Big Belt Mouand D.M. Unruh, unpub. data, 2004; Idaho batholith, island arc plutons, and suture zone plutons: M.A. Kuntz, D.M. Unruh, and Karen Lund, unpubLund and D.M. Unruh, unpub. data, 2002; Boulder batholith: Karen Lund, J.M. O’Neill, and D.M. Unruh, unpub. data, 1999; southwest Montana: Gubatholith: Zen and others (1975); Arth and others (1986); Hammarstrom and others (1993, and unpub. data, 1992).
from which crustal rocks are derived. They provide insights 

into magma genesis and the nature and degree of subsequent 

magma contamination by assimilation of preexisting crustal 

rocks. Our data are limited, but they include isotopic abundances for the Idaho batholith in the vicinity of the Little 

Falls and CUMO deposits; Tertiary intrusions from Little 

Falls, CUMO, and Walton; and the White Cloud stock and the 

Paleozoic metasedimentary rocks it intruded (fig. 15). These 

data, compared with a larger database of published and unpublished analyses, provide the opportunity to evaluate basement 

compositions within the Idaho-Montana porphyry belt and to 

compare those trends to the isotopic character of the basement 

elsewhere in the project area.

A general and expected evolutionary trend of both neodymium and strontium towards more radiogenic or evolved 

from west to east reflects compositions that form a transition 

from oceanic to continental interior. Thus, the most unradiogenic (primitive) rocks (fig. 15) are from allochthonous island 

arc terranes west of the Salmon River suture where melting of 

oceanic crust produced magmas with relatively unradiogenic 

isotopic composition. Compared to rocks derived from the 

allochthonous terranes, all of the remaining analyses exhibit 

more radiogenic compositions typical of continental granitic 

rocks (Faure, 1986). Therefore, rocks of the Idaho and Boulder 

batholiths and those of the Big Belt Mountains, which are 

thought to be derived primarily by relatively deep melting of 

old, radiogenic cratonic crust (Armstrong and others, 1977), 

have more evolved compositions (fig. 15).

Another, lesser trend (fig. 15) may enhance our understanding of the genesis of the Cretaceous and Tertiary rocks. 

Isotopic data for rocks from the Idaho and Boulder batholiths 

and the Big Belt Mountains define discrete clusters that suggest distinct source region differences. These data depict a 

weakly defined trend of progressively less radiogenic strontium and to a lesser extent progressively more radiogenic neodymium with distance from the continental margin. Previous 

strontium isotope studies (Armstrong and others, 1977) noted 

that the Idaho batholith is more radiogenic than the Boulder 

batholith and credited a possibly higher proportion of melting and mixing of Mesoproterozoic sediments into the Idaho 

batholith parent magmas. Alternatively, the Boulder batholith 

and Big Belt Mountains plutons may reflect less radiogenic 

Archean sources in the Medicine Hat and Wyoming Archean 

crustal blocks compared to the source chemistry of the Paleoproterozoic Wallace terrane, which probably was a source for 

the Idaho batholith magmas.

Conclusions

New mineralization ages, whole-rock geochemical data, 

and radiogenic isotopic data represent the most extensive 

collection of constraints available with which to evaluate the 

timing of emplacement, cooling history, and mineralization 

associated with the Idaho-Montana porphyry belt. These new 

data suggest that the location and type of mineral deposits 

in the Headwaters Province are less controlled by the composition, age, or emplacement depth (cooling conditions) of 

magmatic systems than by the composition and (or) structural 

character of the underlying basement.

SHRIMP U-Pb and 40Ar/39Ar Age 

Constraints for Relating Plutonism and 

Mineralization in the Boulder Batholith 

Region, Montana

By Karen Lund, John N. Aleinikoff, Michael J. Kunk, 

and Daniel M. Unruh

The composite Boulder batholith, Montana, hosts a 

variety of mineral deposit types including important silverrich polymetallic quartz vein districts in the northern part of 

the batholith and the giant Butte deposit (porphyry coppermolybdenum pre-Main Stage system and crosscutting 

copper-rich Main Stage vein system) in the southern part 

of the batholith (Smedes and others, 1973; fig. 16; table 

5). Limited dating studies previously identified ambiguous 

relationships among igneous and mineralizing events (see 

discussion in Lund and others, 2002). Mineralizing hydrothermal fluids for these types of deposits and magma for 

quartz porphyry dikes at Butte have all been considered to be 

late-stage differentiates of the Boulder batholith. 

Geochronologic Results

To resolve ages of magmatism and mineralization, single 

age domains within zircon crystals from plutonic rock samples 

were dated using the Sensitive High Resolution Ion Microprobe (SHRIMP), and 40Ar/39Ar geochronology was used to 

date white mica, biotite, and potassium feldspar from mineralized samples (table 6; figs. 17, 18).

Outlying 74.4 Ma silver-rich polymetallic quartz veins 

(samples 98BL010, 98BL011, 98BL016, fig. 18) of the Basin 

and Boulder mining districts probably are directly related to 

the 74.5 Ma Butte Granite (sample 98BL004, fig. 17), having 

formed less than a million years after crystallization age of the 

hosting pluton. At Butte, east-west-trending quartz porphyry 

dikes (named Steward-type) cut the Butte Granite and crystallized from 66 to 65 Ma (samples 98BL006 and 98BL013, fig. 

17); and the copper-molybdenum porphyry system formed 

at about 63.6 Ma (sample 98BL014B, fig. 18). Thus, quartz 

porphyry dikes and Butte pre-Main Stage deposits are parts 

of a 66–64 Ma magmatic/mineralization system unrelated to 

emplacement of the Boulder batholith (table 6). The age of the 

crosscutting Main Stage veins may be about 61 Ma as originally 

Metallogeny in the Context of the Great Falls Tectonic Zone 39
40 Earth Science Studies—Headwaters Province, Idaho and Montana

013 

006 

004 

010 

011 

016 

005 

002 

014 

Pulpit Rock gr 

007 

26B2 

46 ̊

30 ́ 

112 ̊ 30 ́ 112 ̊ 00 ́

46 ̊ 

00 ́ 

Elkhorn Mountains Volcanics

Prevolcanic rocks

Satellite plutons Post-batholith rocks

of Cenozoic age

Silicic facies of Butte Granite

Butte Granite

Granodiorite

Mafic rocks

Leucocratic plutons

Mineral deposits 

Plutonic rocks 

Samples 

0 5 10

10

MILES

0 KILOMETERS

Unionville gd 

quartz porphyry 

 Continental fault 

} 

Marysville gd 

Butte gr 

008 

Idaho batholith 

Idaho 

batholith 

Marysville 

Boulder Baldy Flint 

 Creek 

Pioneer 

Tobacco 

 Root 

 Judith 

Mountains 

Moccasin 

 Mountains 

Little Rocky 

 Mountains 

Bears Paw 

Mountains 

Madison 

Range 

Blacktail 

 Range 

 Boulder 

batholith 

WYOMING 

IDAHO 

MONTANA 

EXPLANATION 

HELENA 

Butte 

Boulder 

Normal fault—Bar and ball 

 on downthrown side 

Boulder batholith

014 

002 

UNITED STATES 

CANADA 

Rader Creek gd 

Figure 16. Generalized geologic 

map of Boulder batholith area, 

southwestern Montana, showing 

sample localities (from Lund and 

others, 2002). Sample locality 010 

(98BL010) is in the Boulder mining 

district. Sample localities 011 

(98BL011), 016 (98BL016), and 26B2 

are in the Basin mining district. 

Sample locality 006 (98BL006) is 

from an exposure along Interstate 

highway 15 on east side of 

Continental deposit, in the Butte 

district. Sample localities 013 and 

014 (98BL013 and 98BL014) are 

in Continental pit, Butte district; 

gd, granodiorite. Marysville 

gd, granodiorite at Marysville; 

Unionville gd, Unionville 

Granodiorite; Pulpit Rock gr, 

granite at Pulpit Rock; Rader Creek 

gd, Rader Creek Granodiorite.
Table 5. Summary of mineral deposit characteristics for Boulder and Butte mining districts.

Deposit type Commodities Vein type Sulfide 

mineralogy Alteration zones

Basin and 

Boulder mining 

districts

Silver-rich 

quartz veins

Ag, Pb, Zn, 

Cu

1 cm anastomosing 

quartz veinlets to 

15 m quartz veins. 

Overall tabular 

geometry with 

E.-W. trend. Rare 

open-space textures. 

Several episodes 

of brecciation and 

sealing with vein 

material.

Pink carbonate 

veinlets are late 

stage and crosscutting.

Ubiquitous pyrite 

+ chalcopyrite, 

galena, 

arsenopyrite, 

sphalerite, and 

tetrahedrite. 

Reported 

stibnite, bornite, 

cosalite, enargite, 

chalcocite, 

ruby silver, 

boulangerite, 

bournonite, and 

albandite.1

Sericite 

zone nearest 

vein several 

centimeters 

wide. Argillic 

zones as much 

as several meters 

wide. Propylitic 

zones as much 

as several 

decimeters wide.

Butte

Pre-Main 

Stage: Porphyry 

copper and 

molybdenum 

porphyry 

systems

Cu, Mo Biotite breccia 

dikes: biotite and 

potassium feldspar 

matrix with breccia 

fragments.2

“Early dark mica” 

veinlets:1- to 5-

mm- wide veinlets 

of quartz, potassium 

feldspar, muscovite, 

and biotite.3

Quartz-molybdenite 

veinlets: form main 

part of deposit.4

“Early dark 

mica” veinlets: 

chalcopyrite, 

pyrite, and 

magnetite.

Quartzmolybdenite 

veinlets: 

molybdenite.

Porphyry 

copper: complex 

overlapping 

potassiumsilicate alteration 

systems.5

Porphyry 

molybdenum: 

biotitic 

alteration 

dome above 

molybdenum 

mineralization.2,3

Main Stage:

Copper-rich 

veins in center 

of district 

gradational to 

silver-rich veins 

in periphery

Cu, Zn, Pb, 

Ag, Mn, Au

2- to 10-m-wide 

veins; some are as 

wide as 30 m.4

Central deposits: 

Pyrite+ chalcocite, 

digenite, covellite, 

and enargite. 

Chalcocite 

and enargite 

with bornite at 

higher levels. 

Chalcopyrite more 

common in outer 

and deeper parts.4 

Peripheral 

deposits:

silver-rich zinc 

mineralization, 

sphalerite, galena, 

tennantite, 

tetrahedrite.

Central deposits: 

overlapping 

acid-sulfate 

alteration zones.5

Peripheral 

deposits: 

sericitic zones 

close to veins 

and outer 

intense argillic 

assemblages 

with manganese 

carbonate 

gangue.4

 

1

Becraft and others (1963) and Ruppel (1963). 4Meyer and others (1968). 

2

Miller (1973). 5Sales and Meyer (1948); Brimhall (1973); Roberts (1973);

3

Brimhall (1973); Brimhall and others (1984). and Brimhall and others (1984).

Metallogeny in the Context of the Great Falls Tectonic Zone 41
42 Earth Science Studies—Headwaters Province, Idaho and Montana

200 120 280 

0.04 

0.08 

0.12 

0.16 

0.20 

10 30 50 70 90 110 

238U/206Pb 

207Pb/206Pb 

mantles 

100 

300 

500 

0.04 

0.06 

0.08 

0.10 

0.12 

0 20 40 60 80 100 

70 

75 

80 

85 

90 

Age = 78.2 ± 0.8 Ma 

(MSWD = 0.99) 

206Pb/238U age (Ma) 

238U/206Pb 

207Pb/206Pb 

98BL002 

Rader Creek 

Granodiorite 

cores 

207Pb/206Pb ages 

2.42 - 3.36 Ga 

60 

70 

80 

90 

100 

Age = 80.4 p 1.2 Ma 

(MSWD = 0.95) 

206Pb/238U age (Ma) 

98BL005 

Unionville 

Granodiorite 

100 

300 

500 

0.04 

0.06 

0.08 

0.10 

0.12 

0 20 40 60 80 100 

69 

72 

75 

78 

81 

Age = 74.5 ± 0.9 Ma 

(MSWD = 0.74) 

206Pb/238U age (Ma) 

238U/206Pb 

207Pb/206Pb 

98BL004 

Butte Granite 

100 

300 

500 

0.04 

0.06 

0.08 

0.10 

0.12 

0 20 40 60 80 100 

65 

70 

75 

80 

85 

Age = 76.5 ± 0.8 Ma 

(MSWD = 0.99) 

206Pb/238U age (Ma) 

238U/206Pb 

207Pb/206Pb 

98BL007 

granite at 

Pulpit Rock 

238U/206Pb 

207Pb/206Pb 

100 

300 

500 

0.02 

0.04 

0.06 

0.08 

0.10 

0.12 

70 

75 

80 

85 

90 

Age = 78.8 ± 1.6 Ma 

(MSWD = 2.1) 

206Pb/238U age (Ma) 

00KL008 

granodiorite 

at Marysville 

0 20 40 60 80 100

Figure 17 (above and facing page). Tera-Wasserburg concordia 

plots and weighted averages plots of SHRIMP U-Pb isotopic data 

for plutonic rocks of Boulder batholith and vicinity. 98BL002, etc., 

are sample numbers. Open dots on curves represent ages, as 

shown, in Ma. Data are shown as 1-sigma error ellipses; error 

bars are ± 2 sigma. Unshaded bars and ellipses are excluded from 

age calculations. MSWD, mean standard weighted deviation.
100

300

500

0.04

0.06

0.08

0.10

0.12

0 20 40 60 80 100 120

54

62

70

78

86

Age = 66.5 ± 1.0 Ma

(MSWD = 1.38)

206Pb/238U age (Ma)

98BL006

quartz 

porphyry

(roadcut)

100

300

500

0.04

0.06

0.08

0.10

0.12

0 20 40 60 80 100 120

54

62

70

78

Age = 65.7 ± 0.9 Ma

(MSWD = 1.22)

206Pb/238U age (Ma)

238U/206Pb

207Pb/206Pb

98BL013

quartz 

porphyry

(pit)

100

300

500

0.04

0.06

0.08

0.10

0.12

0 20 40 60 80 100 120

60

64

68

72

Age = 66.2 ± 0.9 Ma

(MSWD = 1.02)

206Pb/238U age (Ma)

238U/206Pb

207Pb/206Pb

238U/206Pb

207Pb/206Pb

202944

quartz 

monzodiorite

of Boulder Baldy, 

Big Belt Mtns

Metallogeny in the Context of the Great Falls Tectonic Zone 43
44 Earth Science Studies—Headwaters Province, Idaho and Montana

98BL011

Muscovite

Eva May mine

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

98BL011

Sericite

Eva May mine

74.46 ± 0.26 Ma

74.44 ± 0.26 Ma 

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

98BL010

Muscovite

Hope-Bullion

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

98BL014B

Potassium 

feldspar

EDM vein

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

98BL014B

Muscovite

EDM vein

63.58 ± 0.22 Ma

80

70

60

50

APPARENT AGE (Ma)

39ArK RELEASED, IN PERCENT

0 100

98BL016

Muscovite

Bullion mine

Figure 18. 40Ar/39Ar age spectra for mineralized and altered samples. Rectangles in age spectra depict ± 2 sigma uncertainties.
Table 6. Summary of isotopic data for Boulder and Butte mining districts. 

[Error estimates for U-Pb data are ±2 sigma, those for 40Ar/39Ar data are ±1 sigma]

________________________________________________________________________________

Sample Unit or mine Mineral1 Dating Age (Ma)

 No. method2

 

 U-Pb data

________________________________________________________________________________

Boulder batholith:

98BL002 Rader Creek Granodiorite zrn SHRIMP 80.4 ± 1.2

98BL005 Unionville Granodiorite zrn SHRIMP 78.2 ± 0.8

00KL008 Granodiorite at Marysville zrn SHRIMP 78.8 ± 1.6

98BL007 Granite at Pulpit Rock zrn SHRIMP 76.5 ± 0.8

 TIMS 74.7 ± 1.2

26B2 Granophyric phase of zrn TIMS 74.5 ± 0.7

 Butte Granite.

98BL004 Butte Granite zrn SHRIMP 74.5 ± 0.9

Quartz porphyry dikes at Butte:

98BL006 Steward-type zrn SHRIMP 66.5 ± 1.0

 quartz porphyry dike TIMS (1 grain) 71.2 ± 0.3

 (I-15 roadcut).

98BL013 Steward-type zrn SHRIMP 65.7 ± 0.9

 quartz porphyry dike TIMS (1 grain) 65.9 ± 0.8

 (Continental pit).

Regional magmatic event related to quartz porphyry dikes:

202994 Quartz monzodiorite zrn SHRIMP 66.2 ± 0.9

 of Boulder Baldy.

________________________________________________________________________________

 40Ar/39Ar data

________________________________________________________________________________

Mineralization in Boulder and Basin mining districts:

98BL016 Bullion mine mu Minimum 77.0 ± 0.4

98BL010 Hope-Bullion mine mu Isochron 74.4 ± 1.2

98BL011 Eva May mine mu Isochron 73.9 ± 0.7

98BL011 Eva May mine ser Plateau 74.4 ± 0.3

 Isochron 74.6 ± 0.3

Copper-molybdenum porphyry mineralization in Butte mining district:

98BL014A Biotite breccia dike bt Total fusion 63.6 ± 0.2

98BL014B “Early dark mica” vein mu Plateau 63.6 ± 0.2

 bt Total fusion 63.6 ± 0.2

98BL014B “Early dark mica” vein ks Maximum 63.3 ± 0.2

 Minimum 59.4 ±0.2

_________________________________________________________________________________

 1Mineral abbreviations: zrn, zircon; mu, muscovite; ser, sericite; bt, biotite; ks, potassium feldspar.

 2SHRIMP, Super high resolution ion microprobe. TIMS, Thermal ionization mass spectrometry.

Metallogeny in the Context of the Great Falls Tectonic Zone 45
46 Earth Science Studies—Headwaters Province, Idaho and Montana

reported (Woakes, 1960), but the veins are only known to be 

older than the ≈50 Ma intrusions of the Eocene Lowland Creek 

Volcanics.

Interpretations

Resolution of the age and probable magmatic source of 

the Butte pre-Main Stage porphyry copper-molybdenum system and of the silver-rich polymetallic quartz vein systems in 

the northern part of the Boulder batholith indicates that these 

deposits formed from two discrete periods of hydrothermal 

mineralization related to two discrete magmatic events. The 

approximately 64 Ma porphyry copper-molybdenum systems 

at Butte and porphyry gold mineralization at Miller Mountain 

(Lang and others, 2000) are indicative of regionally important, 

≈66 million year old, small plutonic and associated hydrothermal mineralizing systems that may be common in the Boulder 

batholith region, especially to the northeast (du Bray, 1995; 

Lund and others, 2002). Deposits at Butte and in the Boulder 

batholith overlie an important basement juncture between the 

Paleoproterozoic suture zone of the Great Falls tectonic zone 

and a multiple-times-reactivated Mesoproterozoic northwesttrending fracture system along the Lewis and Clark line, 

probably indicating metal-enriched basement and reactivated 

basement structural flaws. 

Use Of Multiple Techniques

U-Pb zircon dating of plutonic rocks results in magma 

crystallization ages. This technique avoids problems resulting 

from slow cooling of plutonic systems that are inherent in the 

original K-Ar dates for both the Boulder batholith plutons and 

the quartz porphyry dikes. Our study documents the degree of 

inheritance of older zircon cores (fig. 19); inheritance probably caused conventional thermal ionization mass spectrometry 

U-Pb geochronologic methods to produce the inconclusive 

results identified by Martin and others (1999). Those results 

illustrate the importance of using single-grain SHRIMP U-Pb 

techniques, by which the complex genetic history of each 

grain can be carefully documented.

Alteration minerals were dated by 40Ar/39Ar geochronology for corroborating evidence of the age of mineralization relative to intrusion of the Boulder batholith and the 

Steward-type quartz porphyry dikes. Samples of silver-rich 

polymetallic quartz vein deposits in mining districts northwest of Boulder (fig. 16) were also analyzed by 40Ar/39Ar 

methods, for the first time, to determine their age relative 

to the age of emplacement of the Boulder batholith and of 

mineralization at Butte. 

Impacts

Determination of ages for mineralization and magmatic 

systems demonstrated that porphyry copper-molybdenum and 

copper-vein deposits at Butte resulted from a different magmatic 

source than silver-vein deposits in the northern part of the batholith. The silver-rich polymetallic vein systems are related to fluid 

accumulations in cooling fractures at the roof of Late Cretaceous 

Butte Granite. The huge mineralizing systems at Butte are related 

to latest Cretaceous-Paleocene, shallowly emplaced, quartzporphyry systems that can now be related on a regional basis to 

other magmatic systems of this age. This clarification of models 

for the two deposit systems allows exploration and topical studies 

of these deposits to be considerably more meaningful. The new 

temporal framework also more clearly defines the scale of the 

two deposit types. Specifically, the silver-rich polymetallic vein 

systems are relatively older and not genetically related to the magmatic source associated with younger porphyry copper-molybdenum systems at Butte. These conceptual breakthroughs yield 

better predictive models for (1) mineral resource exploration; (2) 

regional mineral resource potential, which is of interest to FLMA; 

(3) scale of natural environmental degradation, potentially associated with these deposits; and (4) the areal extent of metal contamination potentially resulting from metallic resource development 

as a function of mining techniques and deposit types.

Stratigraphy and Structure of 

Proterozoic Strata of 

Central Idaho

Much of the Headwaters Province is underlain by 

Proterozoic strata. In northern Idaho and western Montana, 

these units are the thick succession of the Mesoproterozoic 

Belt Supergroup. The south-central part of the Headwaters 

Province, east-central Idaho, is underlain by Mesoproterozoic 

strata whose internal stratigraphy is poorly understood. Their 

age and their stratigraphic relationships to the better known, 

nearby Belt Supergroup are likewise unknown. Additionally, 

vast areas of western and central Idaho (west-central Headwaters Province) are underlain by metamorphosed rocks about 

which little information on age, composition, or origin is available. Geologic mapping of west-central Idaho is complicated 

by difficulty of access and by the metamorphic grade of the 

area’s stratified rocks. In the absence of age data, correlations 

are unreliable, and workers have universally accepted ages of 

Archean or Mesoproterozoic for rocks that underlie the area; 

Neoproterozoic strata, present along the rest of the Cordillera, 

were assumed to be absent (Stewart, 1991). Because so many 

regional questions exist about these rocks whose ages could 

range from about 2.5 to 0.5 Ga, the possible geologic settings 

in which the rocks formed and the possible predictions for 

associated mineral deposit types, scale of probable alteration 

systems, and regional buffering characteristics are very poorly 

defined. Many questions remain about much of this terrain.
98BL006 (roadcut)

xenocryst

77p2 Ma

igneous

67p2 Ma

98BL013 (pit) 

xenocryst

2053p14 Ma

igneous

65p1 Ma

Figure 19. Transmitted light (left) and 

cathodoluminescence (right) image pairs for 

representative zircons from samples of granitic 

rocks dated as part of the Headwaters Province 

project. A, 98BL002 (Rader Creek Granodiorite), 

98BL005 (Unionville Granodiorite), 98BL007 

(granite at Pulpit Rock), 98BL004 (Butte Granite), 

98BL006 and 98BL013 (Steward-type quartz 

porphyry). White circles show locations of 

ion microprobe analyses, in all cases about 

25 micrometers in diameter. Ages are shown 

as ± 1 sigma uncertainties. Note rounded 

cores with incomplete oscillatory zoning that 

yield very old ages in samples 98BL002 and 

98BL006. B, Xenocrystic zircon grains, which 

were incorporated into Steward-type quartz 

porphyry dikes (samples 98BL006 and 98BL013), 

illustrate the problem of zircon inheritance for 

conventional U-Pb dating. Zircon from sample 

98BL006 is a Late Cretaceous xenocryst related 

to the Boulder batholith and is remarkably 

similar to the zircon shown in A from the granite 

at Pulpit Rock. Zircon from sample 98BL013 is an 

inherited grain of Proterozoic age.

A

B

Stratigraphy and Structure of Proterozoic Strata of Central Idaho 47
48 Earth Science Studies—Headwaters Province, Idaho and Montana

Topical studies of Proterozoic rocks in the Headwaters 

Province study area focused on specific areas and topics 

regarding Proterozoic rocks of western and central Idaho. 

Geologic mapping combined with detailed stratigraphic and 

structural studies in east-central Idaho resulted in unraveling 

the stratigraphy and structural geometry of Mesoproterozoic strata there. (See Evans, Tysdal, and Lund, this page.) 

Advances in the understanding of regional stratigraphic and 

structural setting set the framework for a detailed topical study 

of the structural setting of the Blackbird gold-cobalt-copper 

deposit, east-central Idaho. This study resulted in limiting 

the strata that host Blackbird-type deposits and in documenting origin of metamorphic and transpositional features of the 

deposits. (See Lund, Tysdal, Evans, and Kunk, p. 50.) Stratigraphic, structural, and dating studies resulted in recognition 

of an important belt of Neoproterozoic rocks crossing the area 

(Lund, Aleinikoff, and Evans, p. 55). With respect to Neoproterozoic rocks worldwide, recent studies led some to suggest 

that, at least twice, the entire surface of the Earth was frozen 

(Snowball Earth), thus producing simultaneous worldwide 

glacial deposits (Hoffman and others, 1998). Lund, Aleinikoff, 

and others (2003) firmly dated one of those two events using 

rocks from central Idaho, but also questioned whether the 

glaciation was truly synchronous on a global scale.

Mesoproterozoic Strata of 

East-Central Idaho

By Karl V. Evans, Russell G. Tysdal, and Karen Lund

During the past decade, our understanding and ability to 

correlate Proterozoic rocks across central Idaho have increased 

considerably (fig. 2, the reduced version of USGS Map 

I–2765). Deciphering unknown structure and unknown stratigraphy is always an iterative process, as these two aspects are 

interdependent. Detailed studies, especially by Tysdal (2000a, 

2002; compare Ruppel and Lopez, 1988) in the well-exposed 

Lemhi Range have both built on and revised previous mapping 

of Mesoproterozoic strata and provided a speculative template 

for evaluation of the less accessible areas of central Idaho. In 

addition, Lund, Tysdal, and others (2003) have firmly established the presence of Neoproterozoic glacial and volcanic 

rocks across a large part of the Frank Church–River of No 

Return Wilderness (Evans and Green, 2003; Lund, 2004).

Unlike the results of most previous studies which 

assumed little or no tectonic transport of rocks in the area 

(Armstrong, 1975; Ruppel, 1978), the Headwaters Province 

study indicates that the structural geology of central Idaho 

is characterized by several major northwest-striking Mesozoic thrust faults. These faults juxtapose blocks of differing 

stratigraphy and (in places) metamorphic grade. Further work 

remains to establish the full continuity of these thrust faults, 

especially in the least accessible areas, but the thrust faults are 

now adequately documented and form an integral connecting 

link between the well-known parts of the Cordilleran thrust 

belt in northern Idaho and those in southeastern Idaho, as was 

conceptually hypothesized by Skipp (1987) based on much 

less information. Complicating the interpretation of structure, 

there is evidence that, prior to the dominant Mesozoic folding 

and thrusting, Mesoproterozoic deformation, metamorphism, 

and probably migmatization took place at least locally. 

Furthermore, Cenozoic faulting has superimposed largemagnitude extension on the previously contractional orogen 

(Janecke and others, 1998).

The metasedimentary Proterozoic rocks of central Idaho 

have long been considered to be temporal correlates of the 

Mesoproterozoic Belt Supergroup of Montana and northern 

Idaho. Determination of the time span necessary for deposition of the Belt strata was for many years a persistent problem; 

early isotopic dating, for instance, suggested a span of about 

600 m.y. (Obradovich and Peterman, 1968). Fortunately, 

improved isotopic techniques combined with recognition 

of volcanic units within the Belt have greatly improved our 

understanding of Mesoproterozoic geochronology in Idaho 

and Montana. Evans and others (2000) used SHRIMP U-Pb 

techniques to analyze zircons from several stratigraphic levels 

throughout the Belt sequence. Their results, combined with 

recent studies in Canada (for example, Anderson and Davis, 

1995), have established that nearly all of the Belt Supergroup 

was deposited in about 70 m.y. (1,470 to 1,400 Ma).

Within the Headwaters Province project area, considerable new mapping indicates that some previous stratigraphic 

assignments and correlations of Mesoproterozoic strata 

required revision. Table 7 summarizes the historical development of Mesoproterozoic stratigraphic terminology in central 

Idaho, and presents the results compiled and used in the present study. Perhaps most significantly, the formerly widespread 

“Yellowjacket Formation” is restricted to its original definition 

(Ross, 1934). Other units to which the name Yellowjacket 

had been extended (Ruppel, 1975; Ruppel and Lopez, 1988; 

Evans, 1998) are now considered to be parts of the Lemhi 

Group (Tysdal, 2000b). In this light, the Yellowjacket strata are 

now everywhere separated from the Lemhi Group by faults, 

thereby leaving correlations between the two stratigraphic 

packages unresolved. Furthermore, the stratigraphically controlled gold-bearing cobalt-copper deposits of the Blackbird 

mine and Idaho cobalt belt (Nash and Hahn, 1989) are now 

known to occur mostly within the banded siltite member of 

the Apple Creek Formation. This member pinches out in the 

Lemhi Range to the southeast of Blackbird, making it unlikely 

that undiscovered cobalt deposits are present in that area. 

Additional work is ongoing in an attempt to establish regional 

correlations with the classic Belt basin deposits (for example, 

Link and others, 2003; R.G. Tysdal, unpub. data); new findings 

could greatly enhance understanding of Mesoproterozoic basin 

development and distribution of associated stratigraphically 

controlled mineral deposits.
Table 1. Correlation diagram for Middle Proterozoic rocks of east-central Idaho. [Diagram is separated into upper and lower parts. Some workers interpreted the Yellowjacket Formation to underlie the Lemhi Group and superjacent strata; other wo

typeYellowjacket (of Ross, 1934) (leftmost column) to be separated by a fault from other rocks. I interpret the type Yellowjacket, Hoodoo, and unnamed overlying uni

block juxtaposed against the Lemhi Group and superjacent rocks. Upper part of diagram shows lateral correlation of rock units. Lower part of diagram shows lateral co

units of Ross (1934); the other units of the lower part are a mix of units of Ross (1934) and units of the Lemhi Group and superjacent strata, as explained in the text. DYellowjacket Formation as defined and mapped by Ross (1934) and rock units of subsequent workers that I interpret to be the same formation. Light shading indicates as defined and mapped by Anderson (1961) and rock units of subsequent workers that I interpret to be the same formation. Interpretation is necessary because maps of au

include rocks that I believe are of formations other than those to which they were assigned due to unrecognized faults, contacts, misinterpretation of contrasting deposnames introduced subsequent to an author's mapping. No thickness of formations is implied. “Height” of boxes is greater for some units to accommodate different nomdivisions of formations] Ross (1947), upper column. Ross (1934), lower column. Ruppel (1975) Lopez (1981) Ruppel and Lopez (1988) Bennett (1977) Connor and Evans (1986); Connor (1990A); Evans and Connor (1993); Evans (1999) Ekren (1988) Winston and Link 1993) Tysdal and Moye (1996), Tysdal (1996a, b, 2000) and THIS REPORT Tietbohl 

1986) 

mF keerC noswaL mF keerC noswaLmF keerC noswaL Swauger Fm Swauger Fm Swauger Fm Swauger Fm mF reguawS mF reguawS 

mF thgisnuG mF thgisnuG wolleY mF thgisnuGE meM - 

Apple Apple Mem B, C, D Apple c. siltite Apple Cr

Lemhi Creek Creek jacket Creek diamictite diamictit

Fm Fm Fm Fm f. siltite Big Big Big Big Creek mF keerC mF keerC etiztrauQ oodooH mF keerC mFmF keerC giB mF kroF tseW mF kroF tseW mF kroF tseW mF kroF tseW mF keerC oynI mF keerC oynI mF keerC oynImF keerC oynI FAULT Unnamed unit tinu demannU tinu demannU Hoodoo Quartzite THRUST FAULT FAULT THRUST FAULT etiztrauQ oodooH etiztrauQ oodooH Yellowjacket Fm Yellow- Yellow- Mem E Yellow- Mem E Yellowjacket Yellow- U Yellowjacket Fm Yellowjacket Fm

Mem D Mem D Fm Phylite L M

jacket jacket Mem C jacket Mem C jacket L

Mem B B meM L

Fm Fm Mem A Fm Mem A Fm L

Quartzite

Yellow- Yellow

HoodooQuartzite

Table 7. Correlation diagram for Mesoproterozoic rocks of east-central Idaho.[From Tysdal, 2000b]
50 Earth Science Studies—Headwaters Province, Idaho and Montana

Blackbird Gold-Bearing CobaltCopper Deposits, East-Central Idaho—

Reevaluation of Stratigraphic and 

Structural Setting

By Karen Lund, Russell G. Tysdal, Karl V. Evans, and 

Michael J. Kunk

The Blackbird gold-bearing cobalt-copper deposit is the 

most important of a unique type of sediment-hosted cobaltiferous massive sulfide deposits and is located within a 50-kmlong northwest-trending zone in east-central Idaho (Hughes, 

1983; Hahn and Hughes, 1984; Nold, 1990; fig. 20). The 

Blackbird deposit is hosted in a thick Mesoproterozoic siltitemetasandstone sequence, first placed in the Mesoproterozoic 

Yellowjacket Formation (Vhay, 1948; Nash and Hahn, 1989). 

Early work suggested that the gold-cobalt-copper deposits in 

the Blackbird district may have been epigenetic hydrothermal 

deposits (Anderson, 1947) or hydrothermal replacement along 

shear zones (Vhay, 1948). More recently they were interpreted 

as synsedimentary exhalative and diagenetic brineremobilization deposits that formed in a Mesoproterozoic rift 

basin (Hahn and Hughes, 1984; Nash and Hahn, 1989); postdiagenetic processes were deemphasized.

Reconciling new broader scale understanding with previous local information caused the stratigraphic and structural 

setting of the Blackbird deposits to be refined such that the 

original setting of individual prospects can be geometrically 

related. Thus, the origin, diagenetic character, and amount of 

remobilization can be reconsidered.

Stratigraphy

Revision of the formations, definition of environment 

of deposition for the strata, and new delineation of their 

areal distribution require that the stratigraphic setting of the 

host rocks for Blackbird deposits be significantly revised. 

Although long thought to be hosted in the Mesoproterozoic 

Yellowjacket Formation, which was mapped as the dominant 

formation throughout central Idaho, deposits of the Blackbird 

mineral deposit type throughout this region are now known to 

be hosted by strata in the upper Apple Creek Formation and 

strata transitional to the basal Gunsight Formation (fig. 20). 

The Yellowjacket Formation is now limited to fault-bounded 

exposures west of the district and does not contain sedimenthosted deposits. These reevaluations resolve the conflict 

between the interpretation that Blackbird type deposits formed 

in a deep-water rift environment and the interpretation that the 

Yellowjacket Formation, as originally described, formed in 

relatively shallow water. Placement of the Blackbird deposit in 

the Apple Creek Formation and strata transitional to the basal 

Gunsight Formation limits the distribution of the formation 

that hosts the cobalt-copper-gold deposits in a way that is critical to future exploration for such deposits. The conclusion also 

limits the distribution of exposures of strata that formed in this 

deep basinal (rift) setting to a northwest-trending belt. 

Metamorphism and Deformation

Regional understanding of the metamorphism and the 

location and style of Cretaceous compressional deformation 

in the Headwaters Province is changed by recent regional 

subdivision of the Mesoproterozoic stratigraphic units and discrimination of structures (Tysdal, 2000a, 2000b; Lund, Tysdal, 

and others, 2003; Tysdal and others, 2003; K. Lund, unpub. 

mapping, 2001–2002). Metamorphic grade, which increases 

northwest and northward across the district (Vhay, 1948; 

Cater and others, 1975; Lund and others, 1983), and the garnet 

isograd, which loops across part of the Blackbird mine area 

(Vhay, 1948), were attributed to contact metamorphism during 

emplacement of granitic rocks (which were first interpreted 

as Cretaceous but later as Mesoproterozoic; Cater and others, 

1975; Nash and Hahn, 1989). The Blackbird district lies in the 

complexly deformed upper footwall to the northwest-trending Iron Lake fault (figs. 20, 21). Deposits in the district are 

located at the northeast-trending hinge zone of a down-to-thenorth lateral ramp in the Iron Lake thrust fault (fig. 21). This 

structural setting resulted in folds of all scales from megascopic to microscopic, in axial-planar and shear zone schistosity in lower grade rocks, and in widespread transposition of 

features in the most deformed rocks. The most deformed zone 

is at the top of the footwall to the Iron Lake, herein called the 

Indian Creek subplate (figs. 20, 21); these rocks are essentially 

part of the thrust fault zone and contain the rocks above the 

garnet isograd. 40Ar/39Ar dating of white mica below the Iron 

Lake fault indicates that the white mica formed during thrust 

faulting, at about 84 Ma. Most of the previously explored 

deposits lie in the Blackbird subplate, at intermediate structural levels (figs. 20, 21). A few deposits lie in the structurally 

lowest Haynes-Stellite subplate that is in the gradational zone 

between Apple Creek and Gunsight Formations (figs. 20, 21).

The area of the Blackbird deposit was modified by postmineralization normal faults (figs. 20, 21). The north-trending 

White Ledge shear zone marks the west edge of mineralized 

rock, and the Slippery Creek fault marks the east edge (Vhay, 

1948; Bennett, 1977). Most of the thrust faults were reactivated by normal faults (figs. 20, 21).

Deposits

Recent stratigraphic studies (Sobel, 1982; Tysdal, 2000a, 

b) corroborate conclusions of Nash and Connor (1993) that 

the Blackbird deposits formed in a deep-water environment. 

However, observations of metamorphic or structural disruption 

and remobilization of the deposits, described by early studies 

(Anderson, 1947; Vhay, 1948), were not reconciled with more 
recent sediment-hosted deposit models (for example, Nash and 

Hahn, 1989). Studies conducted during the Headwaters Province project demonstrated that mineral deposits in the Blackbird district formed in three related sedimentary environments 

that underwent different degrees of dynamothermal overprinting and that were structurally stacked in an inverted sequence 

(Lund and Tysdal, 2007).

1. Tourmalinite diatreme deposits, now at the structurally 

lowest levels in the Haynes-Stellite subplate, formed during 

diagenesis and by remobilization during later tectonism in the 

upper banded siltite member of the Apple Creek Formation 

and where it is transitional to fine-grained sandstone strata of 

the basal Gunsight Formation. These deposits formed relatively higher in the stratigraphic succession as the deep host 

basin began to fill with sediment and water level shallowed. 

Thus, they are not feeder pipes for the stratigraphically layered 

synsedimentary deposits in the main deposits of the Blackbird 

district to the west as suggested by earlier work (Hahn and 

Hughes, 1984; Nash and Hahn, 1989). 

2. Silica-facies iron-formation tourmalinite and biotitite 

(“mafic”) layers and their diagenetically disrupted equivalents 

(which host cobaltite deposits in the central structural levels 

of the Blackbird subplate; fig. 21) underwent deformation and 

mild localized metamorphism; metals as well as the tourmaline biotite-silica synsedimentary exhalative layered system 

were remobilized to some degree. Tectonic remobilization 

resulted in veins and veinlets of quartz-biotite-tourmaline and 

in a more sulfide-rich metal suite. 

3. Tourmalinite-biotitite zones, which host gold-cobaltcopper deposits in the Indian Creek (higher structural level) 

subplate (fig. 21), are strongly metamorphosed, transposed, 

and deformed. Chloritoid-garnet-feldspar-quartz-biotite schist 

that hosts the deposits formed by regional dynamothermal 

metamorphism during thrust faulting; deposits in these rocks 

are chemically and mineralogically different from those 

of the Blackbird subplate. The schists are in structural, not 

stratigraphic, contact with underlying strata. Deposits of the 

Indian Creek subplate contain lower sulfide but higher silica, 

arsenic, and gold abundances than deposits in other subplates. 

Whether these were original characteristics or whether they 

developed as a result of dynamothermal and related hydrothermal processes during deformation is indeterminate at present. 

Subsequent normal faulting juxtaposed different structural 

levels and reduced the amount of apparent thrust fault separation. Deformation may have been localized near the deposits 

because of physical properties of metal-rich zones and, as a 

corollary, deposits may have been enriched by remobilization 

processes related to the local nature of deformation.

Conclusions

Deposits in the Blackbird district are related to ancient 

basement structures (northwest-trending fracture system) that 

may have controlled the orientation of depositional basins that 

crossed central Idaho parallel to the present structural fabric. 

Blackbird-type deposits have many synsedimentary and diagenetic characteristics similar to those observed in the less structurally disturbed Mesoproterozoic Sullivan-type deposits in 

British Columbia, but these two deposit types probably formed 

in separate or subsidiary depositional basins. Thus, although 

the Blackbird- and Sullivan-type deposits are remarkably similar with respect to chemistry and associated iron-formations, 

differences in age, tectonic setting, basement, and chemistry of 

underlying rocks probably contributed to metallogenic features 

that are unique to the Blackbird cobalt-copper deposits.

Poorly understood stratigraphic relations, metamorphism, 

and deformation all contributed to the uncertainty about the 

geometry of Blackbird deposits. Heterogeneous deformation in the Blackbird district is now known to be confined to 

distinct structural domains that controlled metal paragenetic 

variation in the district.

Implications

A wide array of information previously gathered from 

this mining district fits well in the newly developed, more 

comprehensive framework concerning the depositional setting 

and subsequent dynamothermal processes that contributed to 

the genesis of these deposits. Ultimately, establishing a better 

understanding of the origin and tectonic history of the unique 

Blackbird sediment-hosted massive sulfide deposits will 

improve genetic models for massive sulfide deposits in the 

Mesoproterozoic of North America and elsewhere. Information concerning the Blackbird district provides a useful point 

of comparison with other more dismembered massive sulfide 

deposits, such as the Broken Hill type, because the array of 

Blackbird-type deposits ranges from being largely undisturbed 

by dynamothermal processes to nearly completely transposed 

during upper greenschist facies metamorphism and deformation. Characterization and consideration of the basinal setting 

for distal deposits hosted in the Apple Creek Formation may 

result in better understanding of the similarities and differences among sediment-hosted massive sulfide deposit types, 

such as Sullivan, Broken Hill, and possibly Olympic Dam 

types that are presently considered to be distinct deposit types.

The Headwaters Province study has contributed to a more 

complete understanding of the stratigraphic and structural 

setting that prevails near the Blackbird mining district, and 

with this knowledge, the genesis of known Blackbird goldcobalt-copper deposits can be reconstructed. These insights 

contribute to (1) development of better exploration models and 

more effective geoenvironmental assessment of Blackbird-type 

deposits; (2) more precise reconstruction of the sedimentary 

basin(s) in which these deposits formed; and (3) better understanding of how Blackbird-type deposits are related in time, 

space, and tectonic setting to deposits, such as Sullivan, which 

formed in part of the same or a related basin.

Stratigraphy and Structure of Proterozoic Strata of Central Idaho 51
52 Earth Science Studies—Headwaters Province, Idaho and Montana

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Formation. Compiled from Tysdal and others (2003), Vhay (1948); Karen Lund, unpub. mapping, 2001–2002. Rocks above garnet isograd 

are patterned. B, Blackbird mine; EC, Elkhorn Creek prospect; HS, Haynes-Stellite deposit; SR, Sweet Repose mine.

Stratigraphy and Structure of Proterozoic Strata of Central Idaho 53
54 Earth Science Studies—Headwaters Province, Idaho and Montana

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fault; red dots, location of major deposits in Blackbird district.
Identification of Neoproterozoic 

Windermere Supergroup, Central 

Idaho, using Geologic Mapping and 

SHRIMP U-Pb Geochronology—

Implications for Neoproterozoic Rifting 

and Glaciation

By Karen Lund, John N. Aleinikoff, and Karl V. Evans

Vast areas of central Idaho are underlain by poorly known 

metamorphic rocks isolated within voluminous Mesoproterozoic to Eocene magmatic rocks. New mapping identified 

metamorphosed sedimentary and volcanic rocks that form a 

discontinuous northwest-southeast belt across central Idaho. 

New Sensitive High Resolution Ion Microprobe (SHRIMP) 

U-Pb age determinations on zircon in the volcanic rocks 

show that these rocks are part of the Neoproterozoic glacial 

and continental margin sediments of the western margin of 

Laurentia (pre-Cretaceous North America). The ages and location of these previously unrecognized strata require revision 

of mineral resource potential estimates across the Headwaters 

Province and reevaluation for models of Proterozoic supercontinent development and disintegration as well as models of 

global climate change.

Stratigraphy

As part of the Headwaters Province project, geologic 

mapping in central Idaho (fig. 22) and subsequent geochronologic studies determined that roof pendants in the northern 

Atlanta lobe of the Idaho batholith include strata correlative 

with (1) Mesoproterozoic strata of east-central Idaho, (2) the 

Neoproterozoic Windermere Supergroup, and possibly (3) the 

lower Paleozoic miogeocline (Lund, Aleinikoff, and others, 

2003; Lund, 2004). The presence of Neoproterozoic Windermere Supergroup and related rocks in central Idaho provides 

a link between strata extending from the Alaska-Yukon region 

to California (fig. 22; Crittenden and others, 1972; Gabrielse, 

1972; Stewart, 1972, 1991; Ross and others, 1989; Link and 

others, 1993; Dehler and others, 2001). Consequently, much of 

the Neoproterozoic western margin of Laurentia is preserved 

in central Idaho and was not removed by Mesozoic rifting 

or transcurrent faulting. As a result, the geometries of the 

Neoproterozoic rift belt and subsequent Mesozoic accretionary 

tectonics require redefinition.

In the northwestern part of the Headwaters Province, a 

succession of nine newly named Neoproterozoic formations 

of the Gospel Peaks succession A–D (fig. 23) record middle 

Neoproterozoic preglacial, rift-glacial, and postglacial events 

as well as late Neoproterozoic glacial and rift events (Lund, 

Aleinikoff, and others, 2003; Lund, 2004). Gospel Peaks succession A includes three newly named formations composed 

of schist, quartzite, and calc-silicate gneiss or marble—

Plummer Point, Square Mountain, and Anchor Meadow Formations—that may correlate with Neoproterozoic strata found 

below glaciogenic rocks elsewhere in the Cordillera. Gospel 

Peaks succession B includes three new formations (bottom to 

top): (1) the Edwardsburg Formation (which is divided into 

four members composed of interfingered bimodal rift-related 

volcanic and glaciogenic diamictite strata), (2) the Moores 

Station Formation, and (3) the Goldman Cut Formation. The 

latter two are postglacial deeper water successions. Gospel 

Peaks succession C includes two newly established formations, the coarse siliciclastic Moores Lake Formation and the 

laminated siltite-carbonate Missouri Ridge Formation, which 

represent younger glacial and postglacial events. Gospel Peaks 

succession D is dominantly quartzite of the Umbrella Butte 

Formation, which contains evidence of continental extension.

The strata of the Edwardsburg Formation are particularly 

important, as dating of the interlayered volcanic and diamictite 

rocks provides ages for regional to global rifting and glacial 

events. From bottom to top, the rift-glaciogenic succession in 

the Edwardsburg Formation (shown in fig. 23) is (1) the Wind 

River Meadows Member, metamorphosed very coarse grained 

glacial sediments (diamictite) interlayered with rhyodacite 

flows and volcanogenic rocks; (2) the Golden Cup Member, 

mafic volcanic flows; (3) the Placer Creek Member, volcanogenic rocks, volcanic-clast conglomerate, and heterogeneous 

clast-supported diamictite; and (4) the Hogback Rhyolite 

Member, a local rhyolite flow. 

Geochronology

Zircon crystals were separated from intermediatecomposition volcanic rocks in the upper and lower members 

of the Edwardsburg Formation. Zircon from the Wind River 

Meadows Member is tan, clear, and blocky to prismatic 

(length to width ratios of 2–6); most grains contain longitudinal cracks and (or) partially filled fluid inclusion tubes 

(fig. 24A). These imperfections rendered isotopic analysis difficult. In contrast, zircon from the Hogback Rhyolite Member 

is relatively pristine; crystals are tan, clear, blocky (length to 

width ratios of about 1–3), and contain few cracks or inclusions (fig. 24B). These zircons were dated using a Sensitive 

High Resolution Ion Microprobe (SHRIMP). The rhyodacite 

of the Wind River Meadows Member yielded a weighted average of 687±10 Ma whereas the Hogback Rhyolite Member 

yielded a weighted average of 687±7 Ma (fig. 25). 

Results

Geologic mapping was used to identify distinct stratigraphic packages in roof pendants of the Idaho batholith. Our 

subsequent geochronologic studies document the existence 

of Neoproterozoic strata in these pendants. Identification of 

Stratigraphy and Structure of Proterozoic Strata of Central Idaho 55
56 Earth Science Studies—Headwaters Province, Idaho and Montana

116° 

115°30' 115°

45°30' 

45° 

0 10 

0 10 

20 MILES 

20 KILOMETERS 

CHAMBERLAIN BASIN PLUTON 

Savage Point 

 pluton 

CASTO PLUTON 

THUNDER MOUNTAIN CALDERA 

Alluvium and glacial deposits (Quaternary) 

Challis Volcanic Group (Eocene) 

Eocene magmatic complex 

Rhyolite to dacite dikes (Eocene) 

Hypabyssal intrusive rocks (Eocene) 

Granite and granodiorite (Late Cretaceous) 

Foliated granodiorite and tonalite (Late Cretaceous) 

Idaho batholith 

Syenite-diorite pluton (Neoproterozoic) 

Windermere Supergroup (Neoproterozoic) 

Mesoproterozoic metasedimentary rocks 

Contact 

Normal fault—Bar and ball on down-dropped side 

Thrust fault—Sawteeth on upper plate 

IDAHO 

BATHOLITH 

Marshall Mountain 

roof pendant 

Stibnite 

roof pendant 

Gospel Peaks 

roof pendant 

Anticline 

Syncline 

Fault, movement unknown 

EXPLANATION 

49°N 

30°N 

60°N 

110°W 

120°W 

65°N 

CAN 

U.S.A. 

U.S.A. 

this figure 

MEXICO 

Big Creek 

roof 

pendant 

Salmon 

Salmon River River 

Figure 22. Windermere Supergroup rocks of central Idaho and surrounding area. Index map shows Windermere and equivalent rocks 

of the North American Cordillera. Canadian Cordillera from Ross and others (1989); southern U.S. Cordillera from Stewart (1991), Link and 

others (1993), and Dehler and others (2001); and central Idaho from Lund, Aleinikoff, and others (2003).
previously unrecognized Neoproterozoic strata in the belt 

across central Idaho poses many new questions. Of particular 

importance to local or global mineral resource assessments is 

that the potential for rift-related mineral deposits, which could 

be present in Neoproterozoic rift environments, has never been 

considered for this region. Possible deposits include sedimenthosted deposits of several types associated with silicate-facies 

iron-formation, carbonate-hosted deposit types, and conglomerate-related deposit types peculiar to the atmospheric/

climatic/tectonic conditions of the developing Neoproterozoic 

Earth. 

The presence of carbonate-bearing units in the Neoproterozoic section is important relative to the ability of country 

rocks to buffer acid drainage emanating from undisturbed as 

well as mined Cretaceous and Eocene sulfide-bearing mineral 

deposits across central Idaho. The presence of buffering capacity in newly defined geologic formations interspersed through 

several kilometers of stratigraphic section is an important new 

observation for FLMA relative to potential future mineral 

resource development and associated environmental issues.

Implications for Models of Snowball Earth and 

Rifting of Rodinia

Correlation of central Idaho metamorphic rocks to strata 

of the Neoproterozoic Windermere Supergroup (fig. 23) 

provided the first direct age determinations for the Windermere strata in the Cordillera. The consequence of identifying 

western Laurentian events at 687 Ma is that it alters models for 

Neoproterozoic Rodinia1 paleogeography and resultant paleolatitude of Neoproterozoic glaciations. In that time frame, 

several Snowball Earth events may have enveloped the planet 

in glaciers due to unique climatic factors while the supercontinent Rodinia broke apart (Hoffman, 1999). However, our 

new dates and correlations particularly impact the number, 

synchroneity, and paleolatitude of possible Snowball Earth 

events. In particular, our study indicates that the time of rifting 

and glaciation was as much as 65 million years younger than 

previously thought.

Middle Neoproterozoic Rapitan glaciation of western 

Laurentia is often included as part of a worldwide glacial 

period, internationally called “Sturtian,” hypothesized to have 

plunged the Earth into a global ice age that included glaciers 

even in equatorial regions (Hambrey and Harland, 1985; Hoffman and others, 1998). A reevaluation of this glacial record 

indicates that (1) two associated glacial intervals at about 

687 Ma in the Edwardsburg Formation correlate with the Rapitan glaciation; (2) the Sturtian Snowball Earth event must be 

reevaluated based on revision of the age of Rapitan glaciation 

from 750–700 Ma to about 687 Ma, and (3) several different, 

older glaciations are known on other continents. Consequently, 

either there were more Snowball Earth events than previously 

inferred or the glaciations identified as “Sturtian” were not 

globally synchronous. The new, relatively young age for the 

Rapitan glacial event raises questions: (1) was this glaciation 

unique to western Laurentia rather than contemporaneous 

with (less well dated) Sturtian deposits worldwide and, thus, 

(2) was the Earth indeed a planetary snowball during the Sturtian glacial?

Our dates for interlayered volcanic and sedimentary 

rocks indicate that they formed about 687 Ma, as a result of 

rifting along the length of Laurentia during breakup of the 

Rodinian supercontinent (Stewart, 1972; Bond and Kominz, 

1984; Young, 1995). This age clarifies a step-wise history of 

rifting that ultimately culminated in breakup of Rodinia about 

570 million years ago (Bond and Kominz, 1984); however, 

this brings into question the timing of specific continental 

reconstructions and separations. Reevaluation of geochronology and correlations indicates that middle Neoproterozoic 

rifting (1) may have been protracted between 780 and 687 

Ma; (2) may have been diachronous along the Cordillera; or 

(3) may have proceeded step-wise, including a Cordilleranwide event at about 687 Ma that initiated onset and geometry 

of the Cordilleran miogeocline.

Mineral Resources in 

Relation to Potential Regional 

Environmental Effects

Federal Land Management Agencies (FLMA) are responsible for the stewardship of nearly one-third of the land in 

the United States. These agencies are faced with a variety of 

issues related to mineral resources, ranging from the permitting of new mines and the regulation of active mines to prioritizing inactive and abandoned mines for cleanup. Increasingly, 

FLMA incorporate principles of ecosystem management in 

planning and management processes.

Mineral deposits are natural concentrations of minerals 

formed by geologic processes. Materials from mineral deposits, whether mined or undisturbed by humans, disperse into 

the environment through natural and anthropogenic processes. 

Natural processes include physical and chemical weathering and erosion by wind and water, landslides, and wildfire. 

Anthropogenic (human) activities, such as mining and milling 

of ores, smelting, agriculture, logging, and road construction, 

also disperse mineral deposits and their components. (See Kesler, 1994, for an overview of mineral environmental issues.) 

A mineral deposit represents a potential resource, but it can 

also represent an existing or potential threat to ecosystems or 

human health. As FLMA seek the best available science for 

1

Rodinia was a Neoproterozoic-age supercontinent that formed by collisional events at about 1 Ga and broke apart into eight separate continents 

starting at about 750 Ma. The name is from Russian, meaning “motherland.”

Mineral Resources in Relation to Potential Regional Environmental Effects 57
58 Earth Science Studies—Headwaters Province, Idaho and Montana

Figure 23. Composite correlation chart of Neoproterozoic and lower Paleozoic rocks, central Idaho and other 

sections in the Cordillera (see Lund, Aleinikoff, and others, 2003 for references), showing isotopic ages. Note that 

although an attempt has been made to tie rock units to geologic time in constructing this diagram, the lack of 

dates throughout the Cordillera results in much interpretation in intervals indicated for units as well as in individual 

correlations. Letters in Central Idaho column are designations for Gospel Peaks succession A–D. CN, Canada. SG, 

Supergroup; Gp, Group; Fm, Formation; M, Member; Cgl, Conglomerate; Dol, Dolomite; Ls, Limestone; Qzt, quartzite; 

Volc, Volcanic; Cn, Canyon, Cr, Creek; Lk, Lake; Mdw(s), Meadow(s); Rdg, Ridge; Rv, River.

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60 Earth Science Studies—Headwaters Province, Idaho and Montana

! "

Figure 24. Photomicrographs of zircon crystals from metavolcanic rocks of the Edwardsburg Formation. 

Upper images in cathodoluminescence; lower images in transmitted light. A, Zircons from rhyodacite of 

Wind River Meadows Member of the Edwardsburg Formation. B, Zircons from Hogback Rhyolite Member of 

the Edwardsburg Formation.
500 

600 

800 

900 

1000 

1100 

0.056 

0.060 

0.064 

0.068 

0.072 

0.076 

0.080 

4 6 8 10 12 

500 

600 

700 

800 

900 

207Pb/206Pb age (Ma) 

Age = 687 ± 7 Ma 

(MSWD = 0.47) 

207Pb/206Pb 

238U/206Pb 

97KE074 

rhyolite, 

Placer Creek Member 

2S error ellipses 

500 

700 

800 

900 

1000 

1100 

0.056 

0.060 

0.064 

0.068 

0.072 

0.076 

0.080 

4 6 8 10 12 

500 

600 

700 

800 

206Pb/238U age (Ma) 

Age = 687 ± 10 Ma 

(MSWD = 2.7) 

207Pb/206Pb 

238U/206Pb 

00KL040 

rhyodacite, 

Wind River Meadows 

Member 

2S error ellipses 

Figure 25. Tera-Wasserburg concordia plots and weighted averages plots of SHRIMP U-Pb isotopic data 

for metavolcanic rocks of the Edwardsburg Formation. Open dots on curves represent ages, as shown, in Ma. 

Data are shown as 2 sigma error ellipses; error bars are ± 2 sigma. Unshaded bars and ellipses are excluded 

from age calculations. MSWD, mean standard weighted deviation.

Mineral Resources in Relation to Potential Regional Environmental Effects 61
62 Earth Science Studies—Headwaters Province, Idaho and Montana

land-use planning, data on environmental signatures of mineral deposits and on unmineralized country rocks are needed 

in addition to data on location and economic aspect of known 

or potential mineral resources. Different types of mineral 

deposits have different environmental signatures, depending 

largely on the nature of the ore minerals and the host rock. In 

addition, climate variation can cause a single deposit type to 

have significantly different environmental contributions. A 

single watershed can contain a large variety of mineral deposit 

and host rock types. 

Baseline Geochemistry of a Part of 

the Salmon River Drainage—Two 

Examples

By Robert G. Eppinger, Paul H. Briggs, and Betsy 

Rieffenberger1

A baseline geochemical study was undertaken in the 

Salmon River drainage basin to provide a geochemical “snapshot” of the area for the Salmon-Challis National Forest. A 

stream-sediment and stream-water baseline study covered tributaries of the Middle Fork Salmon River, Panther Creek, and 

the Salmon River from Dump Creek to Corn Creek (fig. 26). 

The drainage basins chosen for study are underlain by similar 

geologic units but represent a pristine, largely unmined basin, 

an adjacent basin heavily impacted by past mining activity, 

and a stretch of river connecting these two basins. Described 

here are two ways these baseline geochemical data can be 

used. The first contrasts geochemical differences between the 

pristine, unmined basin and the adjacent, heavily mined basin. 

The second describes how these data were used in assessing 

the effects of wildfires that swept through the region in the 

summer of 2000. The area is underlain predominantly by Cretaceous Idaho batholith granitoids, Proterozoic to lower Paleozoic metasedimentary rocks, and Eocene granitic plutons.

The Middle Fork Salmon River, hereafter called the Middle Fork, drains a large (2,830 mi2

, 7,330 km2) basin largely 

within the Frank Church–River of No Return Wilderness. The 

Middle Fork basin is pristine, mostly unimpacted by resource 

extraction activities (such as logging, mining, roads, grazing) 

since the early part of the 20th century; any early extraction 

activities were generally minor. In the last few decades, however, the Middle Fork has become internationally recognized 

as a whitewater river rafting and fishing destination. Currently 

between 10,000 and 11,000 people visit the river yearly on 

self-guided or commercially guided multi-day raft trips.

In contrast, Panther Creek, adjacent to and partly within 

the Frank Church–River of No Return Wilderness, has had a 

long, rich logging and mining history and contains numerous 

inactive mines and some areas in which exploration activity is ongoing. The Panther Creek basin is about 532 mi2

(1,378 km2) in size. It is roughly parallel to, and lies east of the 

Middle Fork (fig. 26). Most of the mines in the Panther Creek 

basin were small base- and precious-metal mines that operated 

into the early 20th century. However, the two largest mines, 

Blackbird and Beartrack, were active in the latter decades of 

the 20th century and are presently undergoing remediation and 

reclamation activities.

The Blackbird mine exploited sediment-hosted cobaltcopper deposits through the 1960s. The metal-rich belt of 

Mesoproterozoic metamorphosed sedimentary rocks is within 

the Apple Creek Formation and extends well beyond the 

limits of the Blackbird mine. Deposits hosted by the Apple 

Creek Formation contain the Nation’s largest cobalt resources. 

Exploration within this belt continues to the present day (see 

Formation Capital Corporation website http://www.formcap.

com), although no cobalt-copper mines are currently active in 

the area. The Blackbird mine produced at least 5.7 million t 

(metric tons) of ore, grading 1.4 percent copper, 0.74 percent 

cobalt, and 0.015 ounces gold/t (Nash and Hahn, 1986, 1989). 

A descriptive model of Blackbird-type deposits is found in 

Earhart (1986). Mine site remediation work is well underway 

at the Blackbird mine and presently involves work to meet 

mandatory water-quality objectives, including removal of 

contaminated sediments and installation of ground-water wells 

to capture and remove contaminated ground water.

The Beartrack mine, Idaho’s largest gold producer, was a 

recent open-pit, heap leach gold mine, along Napias Creek, a 

tributary to Panther Creek. The deposit is classified as a distaldisseminated gold deposit (Klein, 2004; Cox, 1992). The Beartrack mine operated from 1995 through 2000, when reserves 

were exhausted. Through 2001, the mine produced about 44 

million t of ore, with gold grades of 0.85 g/t (Klein, 2004). 

Residual gold was being produced from the remaining leach 

pads through 2003. Mine site reclamation is ongoing as of 2004.

The Salmon River is one of the larger rivers of the Snake 

River system. The part of the Salmon included in this study 

is about 61 km long and extends from about 32 km upstream 

of the confluence with Panther Creek to about 11 km downstream of the confluence with the Middle Fork (fig. 26), and 

lies within Salmon-Challis National Forest. Tributaries of 

the Salmon River along this stretch contain numerous small 

mineral deposits that were historically mined for precious and 

base metals.

Methods

Bedload stream-sediment and water samples were collected from main river channels and major tributaries at 82 

sites during a 3-week period in July 1996, and sampling was 

repeated in June 2001. For water samples, time constraints 

1

USDA Forest Service, Salmon-Challis National Forest, Rural Route 2, 

Box 600, Salmon, ID 83467.
 

FIRE 

CLEAR 

 

LITTLE PISTOL 

FIRE 

SHELLROCK 

DIAMOND 

FIRE 

FLOSSIE 

FIRE 

Shoup 

F o r k 

S a l m o n 

R i v e r 

R i v e r 

r e h t n a P

k e e r C

M i d 

d l e 

R i v e r 

S a l m 

o n 

M a i n 

M 

a 

i n 

S 

a l 

m o n 

 s a m a C 

g i B 

Soldier Cr 

Gr eyhound Cr 

l o t s i P 

n a i d n I 

e l b r a M 

r C 

Cr eek 

r C 

e k e C r 

C r e e k 

Elkhor n Cr 

R a p i d 

R i v e r 

Little 

Soldier Cr Little Loon Cr 

White Cr 

r C n o t r o N 

Gr ouse Cr 

L o o 

n 

C r e e k 

B r u s h C r 

S h e e p C r 

W i l s o n 

C r 

W ater fall Cr 

Ship 

Island Cr 

Papoose Cr 

G o a t C 

Stoddar d Cr r 

Parr ot Cr 

Color Cr 

B o u n d a r y 

C r 

S u l p h u r C r 

r C e g a S 

East 

Boulder Cr 

Moose 

Cr 

Dump 

Cr 

Spring Cr 

P i n e C r Big Sheepeater 

Cr 

O w l C r 

G a r d e n C r 

C o l s o n C r Lake Cr 

Butts Cr 

D e e p C r 

N a p i a s C r 

Big Jur eano Cr 

M o y e r C r 

B i g D e e r C r 

M u s g r o v e 

C r 

P o r p h y r y C r 

B l a c k b i r d C r 

T rail Cr 

B e a v e r C r 

Fourth of 

July Cr 

Kitchen Cr 

North Fork 

Salmon River 

Boulder Cr 

C l e a r C r 

o C r C r n 

r C 

W r C 

r e p p o C 

k c i t d o o 

115° 114° 30' 114° 

45° 

44° 30' 

45° 30' 

BLACKBIRD MINE 

BEARTRACK MINE 

EXPLANA TION 

Main river or creek sample site 

Side creek sample site 

Squaw

Cr

CREEK 

 FIRE

CREEK 

 FIRE

0 10 20 KILOMETERS 

0 10 20 MILES 

Figure 26. Location map for stream-sediment and surface-water samples collected from Panther Creek, Middle Fork 

Salmon River, and Salmon River. Wildfire perimeters and names for year 2000 wildfires shown in orange. Base from U.S. 

Geological Survey EROS Data Center digital elevation map data.

Mineral Resources in Relation to Potential Regional Environmental Effects 63
64 Earth Science Studies—Headwaters Province, Idaho and Montana

and access precluded strict adherence to USGS ppb-protocol 

water sampling procedures, but clean procedures were used 

throughout. On-site measurements included pH, conductivity, 

alkalinity, dissolved oxygen, water temperature, ferrous iron, 

turbidity, and a flow estimate.

Mixed water samples were filtered at 0.45 μm (micrometer), collected in acid-rinsed polypropylene bottles, and 

acidified with ultra-pure nitric acid. Water samples for 

mercury analysis were filtered as just noted, collected in 

acid-rinsed glass bottles with Teflon lids, and preserved with 

potassium dichromate/nitric acid. Unacidified water samples 

were refrigerated prior to analysis.

Bedload stream sediments were composited 1 kg (kilogram) samples from active alluvium. A minimum of 30 

increments were collected at each site. Samples were air dried, 

sieved to minus-80 mesh (0.177 mm), and pulverized for 

chemical analysis. Clean quartz sand was pulverized between 

samples to reduce risk of contamination.

Samples were analyzed by a variety of methods including inductively coupled plasma–atomic emission spectroscopy 

(ICP-AES), ICP mass spectrometry, ion chromatography, and 

various atomic absorption methods. Quality assurance and 

quality control concerns were addressed through the use of site 

duplicates, analytical duplicates, and standards, which made 

up approximately 15 percent of the samples analyzed. Further details on methodology are found in Eppinger and others 

(2001) and Eppinger, Briggs, Rieffenberger, Van Dorn, and 

others (2003).

Example 1. Geochemical Contrasts Between 

Two Adjacent Basins

The Middle Fork and adjacent Panther Creek basins show 

strong geochemical contrasts in stream-sediment samples. 

These contrasts are largely due to differences in the geologic 

substrates of the basins. The Middle Fork basin is underlain 

largely by granodiorites and lesser granite of the Cretaceous 

Idaho batholith in its upper reaches and by quartz-rich Proterozoic biotite gneisses in its lower reaches. These rocks are 

intruded throughout much of the length of the Middle Fork 

basin by Eocene granitic plutons (Evans and Green, 2003; 

Lund, 2004; Fisher and others, 1992). In contrast, the Panther 

Creek basin is underlain in its upper reaches by Mesoproterozoic sedimentary rocks, including the Hoodoo Quartzite and 

the Yellowjacket, Gunsight, and Apple Creek Formations; 

and by Mesoproterozoic granite and augen gneiss in its lower 

reach (Evans and Green, 2003). The rich legacy of mining in 

the Panther Creek basin compared to the relative lack of mineral deposits exploited in the Middle Fork basin is a function 

of the differing geologic settings in the two basins.

The geochemical differences between the two basins are 

well illustrated by a plot of two variables, cobalt and the combined rare earth elements (REE), from stream-sediment samples. 

For simplicity, the variables are plotted in terms of average crustal 

abundance values. The average crustal abundance value for cobalt 

used here is 29 ppm (parts per million; Fortescue, 1992), which 

agrees closely with the new recommended average continental 

crust value of 26.6 ppm (Rudnick and Gao, 2004). For the combined REE (cerium, europium, holmium, lanthanum, neodymium, and ytterbium), the average crustal abundance value used 

here is 147 ppm (Fortescue, 1992), which is high compared with 

the new recommended average continental crust value of 88 ppm 

(Rudnick and Gao, 2004). The higher value was used here 

because of the generally felsic nature of the rocks in the region; 

felsic rocks tend to have higher REE contents than mafic rocks.

Cobalt in the Middle Fork basin is uniformly well below 

average crustal abundance (fig. 27). These low abundances are 

commensurate with the granitic to intermediate character of 

most rocks in the basin. Granitic rocks have low cobalt abundances, around 1 ppm on average, whereas intermediatecomposition igneous rocks contain around 10 ppm Co (Rose 

and others, 1979; Levinson, 1980). The average cobalt content 

in stream sediments from 42 sites within the Middle Fork 

basin is 5 ppm. In contrast, considerably higher concentrations of cobalt are found in stream sediments from the Panther 

Creek basin (1.5 to greater than 3.5 times crustal abundance; 

fig. 27). In the Panther Creek basin, cobalt was mined from 

sediment-hosted deposits in several areas within the Apple 

Creek Formation, most notably at the Blackbird mine. The 

highest concentrations of cobalt in stream sediment (>250 ppm 

Co; nearly nine times crustal abundance) were from Blackbird 

Creek and Big Deer Creek, which both drain and are proximal 

to the Blackbird mine area. Cobalt concentrations in excess of 

2.5 times crustal abundance are common around Blackbird and 

downstream along Panther Creek. Elevated cobalt abundances 

in stream sediments and upstream outcrops of the Apple Creek 

Formation are closely associated (fig. 27). This association is a 

predictable consequence of the sediment-hosted nature of the 

cobalt deposits. In fact, outcrops of the Apple Creek Formation closely define the limits of the Idaho cobalt belt (Evans 

and Connor, 1993; Tysdal, 2000b). Similar to cobalt, concentrations of arsenic and copper are high in stream sediments 

from the Panther Creek basin (hundreds and thousands of parts 

per million, respectively) but are negligible in the Middle Fork 

basin (generally <10 ppm for both elements). Arsenic and copper are closely associated with cobalt in Blackbird-type cobalt 

deposits (Nash and Hahn, 1989).

The sum of the REE cerium, europium, holmium, lanthanum, neodymium, and ytterbium provides another geochemical contrast between the Middle Fork and Panther Creek 

basins (fig. 28). Concentrations of these elements are clearly 

elevated in Middle Fork basin; most stream-sediment samples 

have REE concentrations in excess of 2.5 times crustal abundance. In fact, stream sediments from 22 of the 42 sites within 

the Middle Fork have REE concentrations more than 3.5 

times crustal abundance (515 ppm, fig. 28). A strong spatial 

correlation exists between stream sediments with high REE 

concentrations and bodies of Eocene granite (fig. 28). Eocene 

granites in the region contain elevated concentrations of REE, 

radiogenic elements, and other lithophile elements (Kiilsgaard 

and Bennett, 1995; Rehn, 1983). Rare earth element-bearing 
	
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Figure 27. Cobalt in stream-sediment samples. Green polygons, outcrops of Proterozoic Apple 

Creek Formation; geology from Evans and Green (2003) and Lund (2004); crustal abundance value 

is from Fortescue (1992); see figure 26 for stream and river names.

Mineral Resources in Relation to Potential Regional Environmental Effects 65
66 Earth Science Studies—Headwaters Province, Idaho and Montana

	
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Figure 28. Sum of rare earth elements in stream-sediment samples. Pink polygons, outcrops of 

Eocene intrusive igneous rocks; geology from Evans and Green (2003) and Lund (2004); crustal 

abundance value is from Fortescue (1992); see figure 26 for stream and river names.
minerals sphene, allanite, monazite, zircon, and apatite are 

common accessory minerals in the Eocene granites (Kiilsgaard 

and Bennett, 1995). These heavy, resistate minerals are concentrated in alluvial sands. The rare-earth phosphate monazite, 

and the rare-earth oxide euxenite, were placer mined along 

Bear Valley Creek, in the headwaters of the Middle Fork, 

and their bedrock source is believed to be Eocene intrusive 

rocks (Kiilsgaard and Hall, 1995). Collectively, these features 

indicate that high REE concentrations in stream sediments are 

derived from the surrounding Eocene granite. Other elements 

that follow the overall pattern of enrichment in stream sediments from sites proximal to Eocene granite include barium, 

phosphorus, and, to a lesser degree, beryllium, lead, thorium, 

and yttrium. In contrast, REE concentrations are generally much lower in sediments from the Panther Creek basin, 

where, not coincidentally, only a minor volume of Eocene 

granitic rocks is present (fig. 28). Throughout the majority of 

the Panther Creek basin, stream sediments from 21 sites have 

REE concentrations that are about 1.6 times crustal abundance 

(240 ppm). Two exceptions to this are at the uppermost and 

lowermost ends of the Panther Creek basin, where high REE 

concentrations exceeding 3.5 times crustal abundance are 

present. High REE concentrations in upper Panther Creek are 

likely related to isolated outcrops of Eocene intrusive rhyolite. 

At the mouth of Panther Creek and along the Salmon River 

to the east, high REE concentrations are probably related to 

surrounding Mesoproterozoic megacrystic granites (Evans and 

Green, 2003), which locally contain accessory sphene, monazite, apatite, and zircon (Evans and Zartman, 1990).

Example 2. Assessing Effects of Wildfire on 

Stream Sediment and Water Geochemistry

The baseline geochemical study conducted in 1996 was 

principally undertaken to address issues of inactive or abandoned mines in the region. However, resulting data assumed 

a new significance when, in the summer of 2000, much of 

the previously sampled area was burned by the Clear Creek 

(>206,000 acres; >83,300 hectares) and Wilderness Complex 

(>182,000 acres; >73,600 hectares) wildfires. Ten months 

after the fires, in a jointly funded USGS–USDA Forest Service 

study, the area was revisited, in June 2001. The 82 sites initially sampled during the baseline study were resampled over 

a 3-week period, in order to determine whether the wildfires 

caused stream-sediment and water geochemistry to change. 

Samples were analyzed for the same suite of elements as in 

the initial study. Analytical results for this wildfire study were 

compiled by Eppinger and others (2001) and Eppinger, Briggs, 

Rieffenberger, Van Dorn, and others (2003). Interpretive 

results are presented by Eppinger (2002), Eppinger and others 

(2002), Eppinger, Briggs, Rieffenberger, and Van Dorn (2003), 

and Eppinger (2003).

Two statistical tests, called Wilcoxon matched pair and 

sign tests (Helsel and Hirsch, 2002), were used to determine 

whether pre- and post-wildfire data sets include statistically 

significant differences (fig. 29). The sign test simply computes the number of times that the value of the first chemical 

element (such as Mg (magnesium) in 2001 samples) is larger 

than that of the second element (Mg in 1996 samples). The 

Wilcoxon matched pair test also considers the magnitude of 

the difference between the two and is thus a more rigorous 

test. In figure 29, data for elements in the blue box are statistically significant (all have p-values <0.05) for both the sign and 

Wilcoxon matched pair tests relative to the pre- and post-fire 

sample sets. Elements plotting progressively closer to the 

origin at the lower left corner of the box depict differences that 

are progressively more statistically significant.

In stream-sediment samples, no statistically significant 

differences were found for Bi, Ca, CO3

2-, Ce, Fe, Ho, K, La, 

Nb, Nd, Sb, Te, Th, or Ti (all are abundances beyond the blue 

box of fig. 29). However, post-wildfire sediment samples 

are more enriched in the major elements Al, organic C, total 

C, and Mg, and the trace elements Ba, Co, Cu, Li, Mn, Ni, 

Sc, V, and Zn. In contrast, post-wildfire stream-sediment 

samples are slightly depleted in As. Higher total and organic 

C in post-wildfire stream sediments probably results from 

the abundant charcoal and ash observed in sediments at most 

sites downstream of burned areas. In post-wildfire sediments, 

higher concentrations of the rock-forming elements, such as 

Al, Ba, Li, Mg, Mn, Ni, Sc, V, and Zn, are likely the result of 

addition of fine, immature, unwinnowed sediment from debris 

flows and landslides derived from granitoids and black slates 

(fig. 30). In the Panther Creek basin, Co and Cu enrichments 

in post-fire sediment samples may be due to new entrainment 

of metalliferous soils into debris flows and landslides, from 

areas of metal-rich rocks (Apple Creek Formation) containing sediment-hosted cobalt-copper deposits. Most of the area 

that contains these sediment-hosted deposits was extensively 

burned by the wildfire.

For stream-water samples, no statistically significant differences (p-levels >0.05) for the major ions Ca, F–

, K, Mg, Na, 

and Si in pre- and post-wildfire samples were identified. Water 

samples collected in 1996 had variably elevated temperature, 

conductivity, alkalinity, and concentrations of Ba, Cl–, Co, 

Cu, Mn, Ni, SO4

2–, U, V, and Zn (all p-levels <0.05). These 

effects are probably seasonal and reflect the fact that waters 

collected in early June of 2001 were dilute compared to those 

collected in mid-July of 1996. Except for pH changes (pH 

slightly higher in the 2001 post-wildfire samples), differences 

in stream-water samples collected following the wildfires were 

not discernible from the pre-wildfire samples.

Of particular interest in the pre-and post-fire analyses is the 

observation that the seven stream-sediment samples with the highest arsenic concentrations were all from the vicinity of or downstream from the Blackbird cobalt-copper mine (fig. 31). However, 

arsenic concentrations were lower in post-fire sediment samples 

than in pre-fire samples from the same sites. For these seven 

samples, the difference in arsenic concentrations between the two 

sampling periods was greater than that expected from combined 

analytical and sample site variation. In the most extreme cases, 

nearest the mine, arsenic concentrations decreased by more than 

Mineral Resources in Relation to Potential Regional Environmental Effects 67
68 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 30. Photographs of Clear Creek. A, June 8, 2001, 10 months after the wildfire, 

prior to significant thunderstorm activity. B, July 7, 2001, same site as A, following 

thunderstorm. Note increase in fine, ash-laden, immature, unwinnowed sediment 

deposited by storm water.

Mineral Resources in Relation to Potential Regional Environmental Effects 69
70 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 31. Arsenic in stream sediment, 1996 versus 2001 samples. Red dashed lines enclose ± 14 

percent analytical error limits; ppm, parts per million; DL, analytical detection limit. 1, Blackbird Creek; 

2, South Fork of Big Deer Creek; 3, Big Deer Creek at mouth; 4, Panther Creek upstream of Deep Creek; 

5, Panther Creek upstream of Big Deer Creek; 6, Panther Creek upstream of Beaver Creek; 7, Panther 

Creek at mouth.
40 percent. For example, at the mouth of Big Deer Creek, the 1996 

arsenic concentration was 140 ppm, while the 2001 arsenic concentration was only 26 ppm, an 80 percent reduction. The Blackbird 

mine area is being remediated, and a water treatment plant to divert 

and treat mine drainage was installed between the 1996 and 2001 

sampling periods. Lower arsenic concentrations in 2001 sediments 

appear to reflect the success of this treatment plant in reducing 

precipitation of arsenic-bearing iron oxyhydroxide precipitates in 

affected drainages.

Geochemical Signatures of Diverse 

Mineral Deposit Types in the Upper 

Salmon River Watershed, Central Idaho

By Bradley S. Van Gosen, Robert G. Eppinger, Jane 

M. Hammarstrom, Paul H. Briggs, and D.W. Peters1

The upper part of the Salmon River watershed, in Custer 

County, central Idaho (fig. 32), was selected for a pilot study 

concerning the geochemistry of ore, mine waste, host rock, 

altered rock, stream sediment, and water. This huge watershed 

provides a cross section of the geology and mineral deposits 

that characterize the central part of the Headwaters Province. 

This topical area extends from near Stanley on the west to 

Challis on the east and includes mainly public but also some 

private lands that lie north and south of the Salmon River 

(fig. 32). 

The purpose of this investigation is to support studies 

of ecosystem structure and function by providing appropriate information about the geologic framework within which 

the ecosystem operates. Lithologic/lithochemical units and 

mineral deposit types, as influences on biological processes, 

can be linked with local water properties to forecast environmental conditions. Thus, physical and chemical analysis of the 

region’s various rock types produces information that impacts 

(1) assessment of forest health and salmon habitat, (2) assessment of local water characteristics in terms of quality and 

natural element content, and (3) development of management 

decisions and practices.

Reconnaissance Geochemical Study

Fifty-six sites were sampled, including mines, mill and 

smelter sites, and prospects located along tributaries to the 

Salmon River. Sites away from known mineralized areas were 

also sampled. The selected area is ideally suited to serve as 

a pilot project concerning geoenvironmental signatures of mineral deposits because: 

1. The upper Salmon River watershed contains a number 

of distinct mineral deposit types, hosted by a wide variety of rock types and geologic settings, within a relatively 

small region.

The geologic framework and mineral-resource potential of the watershed are well documented (Worl and others, 

1989; Fisher and Johnson, 1995). The Stanley to Challis 

region includes more than 200 inactive mines and prospects as 

well as a few active and recently reclaimed mines, mill sites, 

and smelter sites (Mitchell and others, 1986). Eleven types 

of mineral deposit types are represented. The area includes 

both mined and unmined deposits that are hosted by a variety 

of different lithologies (table 8). Many of the deposit types 

contain pyrite and other metal-sulfide minerals that can create 

acid drainage. Host rocks include carbonates that can provide 

natural acid neutralization, as well as granites, argillites, sandstones, black shale, and silicic volcanic rocks that have little 

or no acid-neutralizing capacity. The types of mineral deposits 

and host lithologies in the upper Salmon River watershed are 

also present in many other parts of the Headwaters Province.

2. Tributaries of the upper Salmon River contain spawning 

grounds of the threatened chinook salmon and endangered 

sockeye salmon, as well as habitats of threatened steelhead 

(migratory rainbow trout) and bull trout. 

Efforts are being made to protect and restore habitat for 

these fish species throughout the Salmon River. Data collected 

in this area address the following questions:

•	 Are the waters and sediments in the upper Salmon 

River watershed affected by past mining and (or) 

by natural erosion of mineral deposits (for example, 

elevated metal concentrations, acidity)? 

•	 Do the metal concentrations exceed regulatory standards or habitat conditions that would impede the 

reintroduction of these fish? 

•	 Do stream sediments contain elevated concentrations 

of elements that may affect the health of benthic 

organisms?

3. The upper Salmon watershed includes Federal lands 

that are used for a variety of purposes.

The Salmon River is a designated National Wild and 

Scenic River. The topical area borders the Salmon River in the 

Salmon-Challis and Sawtooth National Forests. Lands administered by the Bureau of Land Management (BLM) also occur 

within the watershed. The area is used for numerous recreational 

purposes, including hiking, camping, rafting, and fishing. To 

address human health or ecosystem issues, a number of mines in 

the study area have already been reclaimed by the FLMA working cooperatively with the State and the U.S. Environmental 

Protection Agency (EPA). 

1

Salmon-Challis National Forest

 HC63, Box 1669

 Challis, ID 83226.

Mineral Resources in Relation to Potential Regional Environmental Effects 71
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Figure 32. Upper Salmon River watershed and vicinity, showing sample sites, mineral deposit types, and generalized geology. See table 8 fonumerical identities.
Study Methods

Representative examples of different types of mineral 

deposits were sampled throughout the watershed during the 

summers of 1999 through 2002 (table 8; fig. 32), including 

inactive mines and prospects, mineral occurrences, drainages, 

and unmineralized areas. Host rocks include granitoid igneous 

and volcanic rocks, metamorphosed rocks, and sedimentary 

rocks of several different ages and facies belts (Fisher and 

Johnson, 1995). A variety of different mineral deposit types, 

including those rich in precious metals (gold and silver), 

base metals (lead, copper, zinc), tungsten and molybdenum, 

uranium, or fluorite, or some combination of these elements 

(table 8; figs. 32, 33), were sampled at multiple sites. 

At each site, samples of mineralized rock, altered rock, 

host rock, secondary minerals, mine waste, tailings (if present), and any available mine or seep discharges were collected 

(Van Gosen and others, 2000; Hammarstrom and others, 

2002). A number of “background” sites, including active hot 

springs, streams upgradient from past and present mining 

activity, and representative outcrops of particular lithologies 

(not listed in table 8), were sampled to characterize natural 

conditions away from known mineralized areas. True “background” conditions are difficult to establish in developed 

areas; our data are actually “baseline” data because they represent the geochemistry at a particular time. 

Previous studies demonstrate a number of geologic 

controls on the composition of natural water and mine water 

that drain mineral deposits in other geologic settings (Plumlee 

and others, 1999). By collecting geochemical data for multiple 

sample media, multiple mineral deposit types, and multiple 

examples of each deposit type in the same watershed and 

same climatic setting, we have been able to evaluate geologic 

controls of diverse types of mineral deposits and host rock 

on the water in the upper Salmon River watershed. Chemical 

composition of solid samples (mineralized rock, altered rock, 

host rock, secondary minerals, mine waste, tailings) provides a 

link to the interpretation of water samples collected at or near 

the same sites. For example, the presence of elevated cadmium 

and lead concentrations in water downstream from a mine 

may be explained by conditions originating at the mine site. 

If these metals are absent in solid samples of ore and mine or 

mill waste, then elevated cadmium and lead abundances may 

be related to some other source, such as discarded batteries or 

equipment. Water concentration may exceed standards because 

of elevated natural background concentrations or because of 

contamination from mining or other human activities. Similarly, both natural and disturbed streambed sediment may be 

inhospitable to benthic organisms, thereby having an adverse 

impact on the food supply for fish and other species. 

Water Samples

Water was sampled at adit drainages, streams, ponds, 

springs, and seeps. Water directly related to mined deposits 

was collected, as well as background water samples. All 

water sampling was conducted in August, when stream and 

river discharges approach low-flow conditions following peak 

discharge in June. At each sample site, a filtered (0.45 μm 

disposable filter), acidified (HNO3

) sample and an unfiltered 

(raw), acidified (HNO3) sample were collected and analyzed 

for comparison of dissolved versus suspended chemical constituents. Water parameters measured in the field at each site 

included pH, conductivity, field alkalinity, turbidity, dissolved 

oxygen, acidity, flow (estimate), color, and odor. Cations were 

determined by inductively coupled plasma–atomic emission 

spectrometry (ICP-AES) and inductively coupled plasma–

mass spectrometry (ICP-MS); anions were measured by ion 

chromatography (Taggart, 2002).

Solid Samples

The solid media collected in this study included

1. Composite samples of fine (<2 mm diameter) material 

from the upper 5 cm of mine-waste, mill-tailings, and 

flotation-tailings piles

2. Stream sediments upstream and downstream of mined 

deposits and occurrences 

3. Ore- to sub-ore-grade rocks from mine dumps, ore 

piles, and adits 

4. Wallrocks found adjacent to the ore zones, containing 

the alteration minerals that border the ore bodies

5. Unaltered examples of the rock types that host the 

mineral deposits

6. Soils in mineralized and unmineralized (background) 

settings in mined areas, and

7. Secondary minerals, coatings, and crusts.

Solid samples were analyzed for 40 major, minor, and 

trace elements by ICP-AES. In addition, arsenic, antimony, 

selenium, tellurium, thallium, gold, mercury, total carbon, 

carbonate carbon, and total sulfur were analyzed by elementspecific techniques. Composite mine-waste materials were 

subjected to a passive leach procedure (Hageman and Briggs, 

2000; Hageman, 2000) to simulate the potential chemical 

composition of initial rainwater runoff from the surfaces of 

mine-waste and mill-tailings piles.

Results

All of the analytical data and site observations from this 

study were compiled in a digital database, which can be used 

to create customized views of the geochemical landscape at a 

variety of scales. The database provides a tool for land managers, ecologists, biologists, geoscientists, and consultants to 

evaluate relationships between the geochemical signature of 

the topical area and other spatial parameters.

The following site-specific reports were prepared for 

areas of particular interest to the USDA Forest Service and 

BLM:

Mineral Resources in Relation to Potential Regional Environmental Effects 73
Table 8. Types of mineral deposits sampled by this study within the upper Salmon River watershed. No. in fig. 331 Deposit type Mineral deposit description Host-rock type Examples sampled in the project area2 1 Polymetallic veins Pb-Cu-Zn-Ag-Au quartz veins within granitic rocks Bronco mine (1A), Aztec mine (1B). shear zones. 2 Precious-metal veins Au-Ag-bearing quartz veins granitic rocks Prospect along Rankin Creek (2A). 3 Epithermal Au Au-bearing rhyolite porphyry dike granitic rocks Iron Crown mine (3A). 4 Hot spring Active hot springs variable Sunbeam (4A), Elkhorn (4B), Basin Creek (4C

 (4D) hot springs. 5 Fluorite veins F-quartz veins filling fault zones granitic rocks Hideout group (5A). 6 Vein U U concentrations in fracture zones granitic rocks Baker claims (6A), Lightning No. 2 mine (6B)

 7 Sandstone-hosted U U minerals in fluvial rocks arkosic conglomerate, Shorty Pit (7A), East Basin No. 1 (7B), Coal C

 arkosic sandstone, No. 1 (7C), and Deer Strike mines (7D); Littl siltstone. Joe prospects (7E). 3 Epithermal Au Au-Ag-base-metal (Cu-Pb-Zn)- volcanic rocks Charles Dickens (3B), General Custer (3C), Lu

 bearing veins. (3D), Montana (3E), McFadden (3F), Golden 

 (3G), and Tonto (3H) mines. 3 Epithermal Au Thin veins with low Au values rhyolitic volcanics Hindman and Jumbo claims (3I); several prosp Red Mountain area (3J). 3 Epithermal Au Disseminated and vein Au-Ag volcanic and vol- Grouse Creek mine (3K). deposits. caniclastic rocks. 8 W-Mo skarn and W-Mo deposits contact-metamorphosed Peach Creek W claims (8A), Thompson Creek 

 stockwork. argillite and quartzite. Baker Lake molybdenum prospect (8C). 9 Polymetallic Zn-Pb-Cd-Ag deposits argillite-limestone- Hoodoo mine (9A). replacement. quartzite-marble- hornfels breccia.

 1 Polymetallic veins Pb-Zn-W-Ag in quartz veins granitic rock Reconstruction vein (1C).

 within shear zones.

10 Polymetallic skarn Zn-Pb-Ag (±W±Au) deposits contact-metamorph- Confidence property (10A), Deer Trail mine (1

 osed argillite and mine (10C), Meadow View property (10D), sheared argillite. Empire Vein (10E).

 9 Polymetallic replacement Zn-Pb-Ag-Cu deposits along sheared argillite Livingston mine (9B), Cal-Ida mine (9C), Silve

 faults. Hermit mine (9E).

 9 Polymetallic replacement Pb-Zn-Ag deposits calcareous argillite Redbird mine (9F). 9 Polymetallic replacement Ag-Pb-Zn deposits dolomite and quartzite Clayton mine (9G), South Butte mine (9H), un11 Polymetallic-fluorite Fluorite-rich Ag-Cu-Pb-Zn- slate Skylark mine (11A).

 replacement. veins in fault zones.

11 Polymetallic-fluorite Massive fluorite and quartz dolomite breccia in a Chalspar No. 1 claim (11B).

 replacement. paleokarst horizon.

11 Polymetallic-fluorite Fluorite-rich Ag-Pb-Zn-Cu deposits dolomite Pacific mine (11C).

 replacement. along fault zones. 

11 Polymetallic-fluorite Fluorite-rich Cu-Ag-Pb-Zn deposits dolomite breccia in a Keystone mine (11D).

 replacement. paleokarst horizon.

1Numbers refer to areas labeled in figure 33 (west to east). 2Number-letter combinations refer to sample sites in figure 32.
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Figure 33. Schematic cross section displaying general geologic setting of mineral deposits in upper Salmon River watershed of central Idaho. Circledeposit types listed in table 8. Diagram is not to scale and is designed for descriptive purposes only; precise relationships between mineral deposits, sshould not be inferred from the diagram. Rock unit descriptions are provided in Fisher and others (1992), Hobbs and others (1991), and Hobbs (1985).
76 Earth Science Studies—Headwaters Province, Idaho and Montana

1. Results for the Thompson Creek tungsten mine 

(fig. 32, site 8B), a tungsten-molybdenum skarn deposit, are 

summarized in Van Gosen and others (2000).

2. Hammarstrom and others (2002) described the prereclamation environmental composition of waters and stream 

sediments at the Clayton silver mine (fig. 32, site 9G), a 

polymetallic replacement deposit.

3. Chemical and mineralogical data for massive slag from 

the Clayton Smelter (fig. 32), which processed ore from many 

of the deposits in the watershed, are included in Piatak and 

others (2003). 

Highlights

Acid-Rock Drainage

Acid-rock drainage is the water-quality hazard produced 

by the oxidation of pyrite in an aqueous environment. Acid 

water that drains waste rock, tailings, open pits, and adits typically has low pH values (2–4) and elevated concentrations of 

potentially toxic metals (Nordstrom and Alpers, 1999). Minerelated acid-rock drainage is referred to as acid mine drainage. 

Mine-related water in the watershed topical area falls into two 

groups: (1) acidic water with pH in the range from 3 to 4 and 

dissolved base-metal concentrations >100 ppb (parts per billion, equal to μg/L, micrograms per liter); and (2) near-neutral 

water (pH 5.5–8.5) with highly variable dissolved base-metal 

concentrations (fig. 34). Group 1 water samples are associated 

with epithermal gold deposits, such as the Grouse Creek mine. 

These deposits are pyrite rich and are hosted by silica-rich 

volcanic rocks that have little to no acid-neutralizing capacity. 

Group 2 water samples include those draining carbonate-hosted 

deposits (polymetallic skarn and replacement deposits). Zinc is 

the principal dissolved base metal. Fourteen mine-related water 

samples and 1 stream sample (collected 0.8 km downstream 

from a mine site) contained dissolved zinc concentrations that 

exceed the EPA’s recommendation for the maximum concentration for zinc in surface water that is safe for aquatic life, 

which they established as 120 μg/L of zinc (U.S. Environmental 

Protection Agency, 2002, p. 13). An aquatic community exposed 

to these high concentrations of zinc (>120 μg/L), even briefly, is 

expected to result in an “unacceptable effect” on the aquatic life. 

Background stream waters sampled upstream of mines in the 

topical area are all near-neutral and contain <3 μg/L dissolved 

zinc. The natural hot springs sampled had elevated pH (8.8–9.5) 

and very low dissolved base metals. Natural cold-water springs 

in unmineralized or weakly mineralized areas have near-neutral 

pH and dissolved base-metal contents of <50 μg/L. One spring 

flowing from beneath a talus pile in an area of altered volcanic 

rock had a pH of 4.2. Although pyrite was present in many of 

the mineral deposits in the watershed, this study shows that 

significant acid mine drainage was not present at most of the 

mine sites. However, natural acid-rock drainage is associated 

with hydrothermally altered rocks of the Challis volcanic terrain 

in the western part of the study area.

Lithologic Controls on Water Quality

Acidity and alkalinity are useful parameters for comparison of water from diverse sources. Acidity of a water sample 

is its quantitative capacity to neutralize a strong base. Acidity 

is calculated by measuring the volume of strong base that must 

be added to the water sample in order to reach a designated pH 

(pH of 8.3 for total acidity). Alkalinity is similarly calculated, 

and is the capacity of water to neutralize a strong acid to a 

pH of 4.5 (Ficklin and Mosier, 1999). Acidity and alkalinity reflect the pH and buffering capacity of the water being 

studied. Mine drainage associated with the mineral deposits 

in the topical area that are hosted by rhyolitic (quartz-rich) 

volcanic rocks has high acidity (fig. 35; table 8). The streams 

sampled across the pilot area had alkalinity ranging from 22 to 

110 ppm CaCO3

, indicating that the streams have at least some 

acid-neutralizing capacity.

Arsenic 

Elevated arsenic abundances are common to a variety of 

mineral deposit types within the upper Salmon River watershed. Consequently, arsenic abundances are elevated in a 

variety of sample media collected from a variety of different 

types of deposits in the watershed. For example, uranium ore 

in the Stanley area contains up to 8,600 ppm (parts per million) arsenic (fig. 32, sites 7A–7E). Ore from many polymetallic skarn, vein, and replacement deposits, as well as ore 

from epithermal gold deposits, contains more than 1,000 ppm 

arsenic. Approximately 40 percent of the mine-waste piles and 

mill tailings sampled contain arsenic in soil-size material in 

excess of the EPA preliminary remediation goal for arsenic in 

industrial soils (260 ppm As). About 30 percent of our streamsediment samples exceeded the consensus-based probable 

effects concentration (PEC) guideline for arsenic (>33 ppm 

As) in sediments associated with fresh-water aquatic ecosystems. PEC is defined as the concentration above which adverse 

toxic effects are likely to occur (MacDonald and others, 2000). 

These data provide a screening tool to define areas where sitespecific toxicity studies may be warranted.

The enforceable Maximum Contaminant Level (MCL) 

for arsenic allowed in drinking water was previously 50 ppb 

(equal to 0.05 mg/L), as set by the EPA. On January 23, 

2006, the MCL for arsenic in drinking water was lowered to 

10 ppb (U.S. Environmental Protection Agency, 2001). All 

the background water samples collected in the upper Salmon 

River watershed contained <10 ppb dissolved arsenic (fig. 36). 

However, some mine-related water contains dissolved 

arsenic concentrations in excess of the previous and the 

revised drinking water standards. A natural spring discharging 

from mineralized bedrock near the General Custer mine 
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Figure 34. Ficklin diagram showing sum of dissolved base-metal concentrations in mine water (adit drainage, springs or 

seeps in mined areas, and open pit water) and river water as a function of pH. Mine-related water in the watershed falls into 

two broad groups: (1) Group 1 water is acidic (pH 3 to 4) with dissolved base-metal concentrations >100 ppb, and (2) Group 2 

water is near-neutral (pH 5.5 to 8.5) with variable dissolved base-metal concentrations. Boundaries and names of fields are 

from Plumlee and others (1999). Parts per billion (ppb) and micrograms per liter (μg/L) are equivalent concentration units.

Mineral Resources in Relation to Potential Regional Environmental Effects 77
78 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 35. Graphical display of acidity and alkalinity measured in 37 mine water samples from upper 

Salmon River watershed. These samples, also plotted in figure 34, include adit drainage and pond, spring, 

and seep water from within mined areas. Labels indicate primary host rock type at each mineral deposit. 

Acidity and alkalinity defined by Ficklin and Mosier (1999). 
(fig. 32, site 3C) contained 110 ppb dissolved arsenic. Some 

adit water and water in a pond that fills an open pit contained 

dissolved arsenic concentrations in excess of current (2003) 

EPA fresh-water chronic and acute contaminant criteria (150 

and 340 ppb, respectively).

Wildlife such as deer and elk are known to drink 

arsenic-rich mine water in the area, which may affect their 

health. However, relationships between mine-water chemistry 

and wildlife health have not been studied in this region. New 

domestic water wells are likely to be developed in the watershed as more homes are built. Further, water supplies in public 

campgrounds may be unsuitable for drinking as indicated by 

new water-quality standards. Thus, in central Idaho, management issues of natural and anthropogenically modified water 

and (or) sediment include an evaluation of concerns related to 

arsenic abundances when plans are prepared or modified.

Environmentally Significant Metals in Mine 

Wastes, Mill Tailings, and Stream Sediments 

Many metals, including arsenic, cadmium, chromium, 

mercury, nickel, lead, zinc, and a number of others (Kelly, 

1999; Goyer and Clarkson, 2001; Sullivan and Krieger, 2001), 

can act as toxins to humans and biota. Several metals that 

potentially pose significant environmental risk are concentrated in mine-waste piles and mill tailings that are scattered 

throughout the pilot area and the greater watershed area. 

The metals occur in a variety of concentrations and mineral 

forms, each of which can react at different rates via an array of 

dynamic processes throughout the ecosystem.

High metal concentrations do not necessarily indicate an 

environmental hazard. Many factors influence metal hazard 

potential, including solubility, physical and chemical mobility, exposure setting, and biologic availability of the metal 

(Krieger and others, 1999). Analyses of solid media, considered relative to water-quality data, are useful in evaluating the 

chemical characteristics of (1) specific sites of interest and (2) 

groups of deposits sharing similar attributes (deposit types).

Analyses of fine (<2 mm diameter) material on the 

surfaces of mine-waste and mill-tailings piles show that most 

polymetallic skarn, polymetallic replacement, and polymetallic-fluorite replacement deposits in the watershed (table 

8) contain the highest concentrations of metals; especially 

enriched are antimony, lead, and zinc. For example, surfaces 

of about three-fourths of the waste piles associated with 

polymetallic deposits have lead concentrations that exceed the 

EPA’s preliminary goal for lead in industrial soils (1,200 ppm 

Pb). About one-fourth of the same mine and mill piles contain 

antimony in excess of the EPA remediation goal of 410 ppm 

Sb. High zinc concentrations are common in mine and mill 

piles associated with polymetallic deposits—more than threefourths of the surficial samples from polymetallic dumps 

contain at least 0.1 weight percent Zn. Additionally, as noted 

previously, a majority of the deposit types and their waste piles 

contain arsenic concentrations that exceed the EPA’s preliminary goal for industrial soils (260 ppm As).

Many of the stream-sediment samples that were collected downstream from former mining operations reveal 

metal concentrations that exceed PEC guidelines (MacDonald 

and others, 2000) for sediment in fresh-water aquatic ecosystems. Many stream-sediment samples collected downstream 

of polymetallic skarn deposits exceed the PEC guidelines for 

arsenic, cadmium, chromium, nickel, and zinc. Concentrations of these metals, plus lead, typically exceed the PEC in 

sediment downstream of developed polymetallic replacement 

deposits. Chromium and nickel concentrations exceed the PEC 

in sediment collected downstream from tungsten-molybdenum 

skarn and stockwork deposits.

Metal abundances in stream sediment downstream from 

mined deposits should be compared to background sediment collected from the same or similar geologic setting. For 

example, some background sediment samples were collected 

upstream from mines and mill sites, yet contain abundances of 

cadmium and chromium that exceed the PEC guideline values. 

Cadmium and chromium enrichments of this sort were most 

common where the stream segments crossed dark, carbonaceous, fissile sedimentary rocks (argillite or black shale or 

slate). Thus, surrounding host rocks can naturally contribute metals to the streambed through erosion; as examples, 

cadmium and chromium are dispersed from black shale and 

arsenic from volcanic rocks in this fashion.

Conclusions

Mine-related water in the upper region of the Salmon 

River watershed is an expression of varied mineral deposit 

types and their host geologic environments. Water samples 

were collected during periods (in August of three successive 

years) when stream and river discharges were approaching 

base flow. Results suggest that acid mine drainage is not a 

widespread problem in the area. However, natural acid-rock 

drainage occurs locally in mineralized areas of the volcanic 

terrain. Additionally, mineral deposit types and geologic terrains not associated with volcanic rocks (fig. 32) typically 

yield neutral to alkaline natural water that exhibits a variety of 

different metal concentrations (fig. 34).

A number of potentially toxic metals are concentrated 

in abandoned mine waste piles and mill tailings in the upper 

Salmon River watershed. Polymetallic skarn, polymetallic 

replacement, and polymetallic-fluorite replacement deposits 

contain the highest concentrations of metals; these deposit 

types are especially enriched in antimony, lead, and zinc. Most 

deposits in the watershed contain elevated concentrations of 

arsenic.

To fully evaluate the significance of the metal anomalies 

requires comparison to background values obtained from the 

same drainage or similar geologic environment. Metal hazard 

analyses also consider the solubility, physical and chemical 

Mineral Resources in Relation to Potential Regional Environmental Effects 79
80 Earth Science Studies—Headwaters Province, Idaho and Montana

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Figure 36. Dissolved arsenic concentrations versus pH in natural waters collected in the upper Salmon 

River watershed. Samples include: mine water, which includes adit drainage and ponds, seeps, and springs 

in mined areas; and background water, such as creeks, ponds, and springs that lie upgradient of mined areas. 

Dashed lines, prior and current (January 23, 2006) Maximum Contaminant Level (MCL) standard for arsenic 

in drinking water, as set by the EPA (U.S. Environmental Protection Agency, 2001). Deposit type is shown for 

water samples with arsenic above the MCL.
mobility, exposure setting, and biologic availability of potentially toxic metals.

Applications of the Study

Geochemical data for different sample media provide a 

snapshot of prevailing conditions in the upper region of the 

Salmon River watershed and can be used to

•	 Prioritize inactive and abandoned mine site cleanup and 

develop cost-effective remediation strategies

•	 Anticipate environmental effects of future mine development for similar deposit types

•	 Identify the geochemical signature of solid materials 

and water that may affect biota

•	 Extrapolate to geologically similar settings elsewhere 

in the Headwaters Province to predict the likelihood of 

adverse environmental effects of mining

•	 Increase our understanding of the geoenvironmental 

signature for a number of mineral deposit types within 

a relatively dry ecoregion: the Middle Rocky Mountain 

Steppe–Coniferous Forest–Alpine Meadow Province 

ecoregion (Bailey, 1995).

Summary

The quantity and quality of geologic data and of geologic 

understanding of the Headwaters Province, part of the geologically least well known area in the continental United States, 

are significantly enhanced through the research activities of 

this project. Improved geologic mapping, newly acquired digital geologic map data sets, and standardization of digital data 

sets enhance future availability and use of geoscience data at a 

variety of scales for assessments of mineral resource potential, 

interpretation of geology, and interpretation of geophysical 

and geochemical data sets. Geochemical data, initially available for the project area from the NURE and RASS databases, 

were compromised by the presence of artificial anomalies 

along quadrangle and project boundaries that resulted from 

variable determination limits and levels of accuracy and precision. Normalization of these data using standardized concentrations fostered creation of geochemical surface models that 

can be combined with diverse data sets in future evaluations. 

As a consequence of data synthesis and conversion activities conducted by the Headwaters Province project, complete 

province-wide digital data sets are now more easily accessible, 

scalable, available in standardized formats, and adaptable for 

local and regional uses; they are consequently readily applicable to land-use planning decisions.

New interpretations of aeromagnetic maps for the Headwaters Province were combined with limited new geologic 

observations of mostly covered basement to develop a comprehensive basement framework; the resulting synthesis integrates 

topical and regional studies that are applicable to local as well 

as global mineral resource assessments. Although the Great 

Falls tectonic zone was previously identified as a zone of concentrated mineralization, the overwhelming influence on metal 

endowment exerted by the Paleoproterozoic suture in the center of the zone is now demonstrated in findings of the Headwaters Province project. Results of the project identify the 

fundamental impact of endowed basement composition and of 

deep-seated structural flaws related to basement architecture as 

the features critical to localizing much younger hydrothermal 

mineralization across the Headwaters Province. Development 

of these concepts has resulted from accumulation and evaluation of region-wide deposit data sets, study of the composition, 

age, and origin of the many plutonic systems that host mineral 

deposits, and investigation (in four dimensions) of magmatism 

and hydrothermal mineralization associated with the Boulder 

batholith.

Reevaluation of basement tectonics in the context of the 

stratigraphic and structural setting of Mesoproterozoic strata is 

applied in formulating region-wide models that document how 

tectonic setting and basin evolution influenced the location 

of sediment-hosted mineral deposits. Crosscutting northwesttrending Mesoproterozoic structures are now seen to have 

clearly exerted fundamental controls on development of Proterozoic sedimentary basins (the Belt, east-central Idaho, and 

Windermere). These structures were also probably important 

in localizing sediment-hosted deposits and later in channeling basement metal endowments through associated fractures, 

resulting in crustal metal recycling during later orogenesis and 

resulting mineralization episodes. The geochemical signature 

of these structurally controlled facies belts in the upper region 

of the Salmon River watershed is now well established, as a 

consequence of baseline multi-media sampling and analysis 

completed as part of the Headwaters Province project. Hostrock and mineral deposit compositional characteristics are 

available for extrapolation to assessments of the impacts of 

geologic factors on endangered habitats, province-wide. The 

Headwaters Province project has significantly enhanced the 

potential efficacy of future regional, national, and global mineral resource and geoenvironmental assessments by providing 

comprehensive data, readily accessible to future use by all 

interested parties. 

References Cited

Anderson, A.L., 1947, Cobalt mineralization in the Blackbird 

district, Lemhi County, Idaho: Economic Geology, v. 42, p. 

22–46.

Summary 81
82 Earth Science Studies—Headwaters Province, Idaho and Montana

Anderson, A.L., 1961, Geology and mineral resources of the 

Lemhi quadrangle, Lemhi County, Idaho: Idaho Bureau of 

Mines and Geology Pamphlet 124, 111 p.

Anderson, H.E., and Davis, D.W., 1995, U-Pb geochronology 

of the Moyie sills, Purcell Supergroup, southeastern British 

Columbia—Implications for the Mesoproterozoic geological history of the Purcell (Belt) basin: Canadian Journal of 

Earth Sciences, v. 32, p. 1180–1193.

Armstrong, R.L., 1975, Precambrian (1,500 m.y. old) rocks 

of central Idaho—The Salmon River Arch and its role in 

Cordilleran sedimentation and tectonics: American Journal 

of Science, v. 275–A, p. 437–467.

Armstrong, R.L., Hollister, V.F., and Harakel, J., 1978, K-Ar 

dates for mineralization in the White Cloud–Cannivan porphyry molybdenum belt of Idaho and Montana: Economic 

Geology, v. 73, p. 94–108.

Armstrong, R.L., Taubeneck, W.H., and Hales, P.L., 1977, Rb/

Sr and K/Ar geochronometry of Mesozoic granitic rocks and 

their Sr isotopic composition, Oregon, Washington, and Idaho: 

Geological Society of America Bulletin, v. 88, p. 397–411.

Arth, J.G., Zen, E-an, Sellers, G., and Hammarstrom, J.M., 

1986, High initial Sr isotopic ratios and evidence for magma 

mixing in the Pioneer batholith of southwest Montana: 

Journal of Geology, v. 94, p. 419–430.

Bailey, R.G., 1995, Descriptions of the ecoregions of the 

United States: U.S. Department of Agriculture Forest Service Miscellaneous Publication 1391, 108 p.

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, 

scale 1:1,000,000.

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral resources of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: 

U.S. Geological Survey Professional Paper 428, 101 p.

Bennett, E.H., 1977, Reconnaissance geology and geochemistry of the Blackbird Mountain–Panther Creek region, 

Lemhi County, Idaho: Idaho Bureau of Mines and Geology 

Pamphlet 167, 108 p.

Berg, R.B., and Lonn, J.D., 1996, Preliminary geologic map of 

the Nez Perce Pass 30- by 60-minute quadrangle, Montana: 

Montana Bureau of Mines and Geology Open-File Report 

MBMG 339, 7 p., 1 plate, scale 1:100,000.

Berg, R.B., Lonn, J.D., and Locke, W.W., 1999, Geologic map 

of the Gardiner 30’×60’ quadrangle, south-central Montana: 

Montana Bureau of Mines and Geology Open-File Report 

MBMG 387, 2 plates, scale 1:100,000.

Berg, R.B., Lopez, D.A., and Lonn, J.D., 2000, Geologic map 

of the Livingston 30’×60’ quadrangle, south-central Montana: Montana Bureau of Mines and Geology Open-File 

Report MBMG 406, scale 1:100,000.

Bond, G.C., and Kominz, M.A., 1984, Construction of tectonic 

subsidence curves for the early Paleozoic miogeocline, 

southern Canadian Rocky Mountains—Implications for subsidence mechanisms, age of break up and crustal thinning: 

Geological Society of America Bulletin, v. 95, p. 155–173.

Brady, J.B., Burger, H.R., Cheney, J.T., and Harms, T.A., eds., 

2004, Precambrian geology of the Tobacco Root Mountains, 

Montana: Geological Society of America Special Paper 

377, 256 p.

Briggs, P.H., 1990, Elemental analysis of geologic materials 

by inductively coupled plasma–atomic emission spectrometry, in Arbogast, B.F., Quality assurance manual for the 

Branch of Geochemistry: U.S. Geological Survey OpenFile Report 90-668, p. 83–91.

Brimhall, G.H., Jr., 1973, Mineralogy, texture, and chemistry 

of early wall rock alteration in the deep underground mines 

and Continental area, Butte district, Montana, in Miller, 

R.N., ed., Guidebook for the Butte field meeting of Society 

of Economic Geologists, 1973: Butte, Mont., Society of 

Economic Geologists, p. H1–H5.

Brimhall, G.H., Jr., Cunningham, A.B., and Stoffregen, R., 

1984, Zoning in precious metal distribution within base 

metal sulfides—A new lithologic approach using generalized 

inverse methods: Economic Geology, v. 79, p. 209–226.

Cater, F.W., Pinckney, D.M., Hamilton, W.B., Parker, R.L., 

Weldin, R.D., Close, T.J., and Zilka, N.T., 1973, Mineral 

resources of the Idaho Primitive Area and vicinity, Idaho, 

with a section on The Thunder Mountain district, by B.F. 

Leonard, and a section on Aeromagnetic interpretation, by 

W.E. Davis: U.S. Geological Survey Bulletin 1304, 431 p., 

plates in pocket.

Cater, F.W., Pinckney, D.M., and Stotelmeyer, R.B., 1975, 

Mineral resources of the Clear Creek–Upper Big Deer 

Creek Study Area, contiguous to the Idaho Primitive Area, 

Lemhi County, Idaho: U.S. Geological Survey Bulletin 

1391–C, 41 p.

Christie-Blick, N., and Levy, M., 1989, Concepts of sequence 

stratigraphy, with examples from strata of Late Proterozoic 

and Cambrian age in the western United States, in Christie-Blick, N., and Levy, M., eds., Late Proterozoic and 

Cambrian tectonics, sedimentation, and record of metazoan 

radiation in the Western United States: Washington, D.C., 

American Geophysical Union, 28th International Geological 

Congress, Field Trip Guidebook T331, p. 23–38.
Colpron, M., Logan, J.M., and Mortensen, J.K., 2002, U-Pb 

zircon age constraint for late Neoproterozoic rifting and 

initiation of the lower Paleozoic passive margin of western Laurentia: Canadian Journal of Earth Sciences, v. 39, 

p. 133–143.

Connor, J.J., 1990, Geochemical stratigraphy of the Yellowjacket Formation (Middle Proterozoic) in the area of the 

Idaho cobalt belt, Lemhi County, Idaho, Part A, Discussion; 

Part B, Geochemical data: U.S. Geological Survey OpenFile Report 90-0234, 30 p.

Connor, J.J., and Evans, K.V., 1986, Geologic map of the 

Leesburg quadrangle, Idaho: U.S. Geological Survey Miscellaneous Field Studies Map MF–1880, scale 1:62,500.

Cook, F.A., 1995, Lithospheric processes and products in the 

southern Canadian Cordillera, a Lithoprobe perspective: 

Canadian Journal of Earth Sciences, v. 32, p. 1803–1824.

Cox, D.P., 1992, Descriptive model of distal disseminated AgAu, in Bliss, J.D., Developments in mineral deposit modeling: U.S. Geological Survey Bulletin 2004, p. 19–20. 

Crittenden, M.D., Jr., Stewart, J.H., and Wallace, C.A., 1972, 

Regional correlation of Upper Precambrian strata in western 

North America: 24th International Geological Congress, 

1972, Section 1, p. 334–341.

Crittenden, M.D., Jr., and Wallace, C.A., 1973, Possible 

equivalent of the Belt Supergroup in Utah, in Belt Symposium 1973, Volume 1: Moscow, Idaho, Idaho Bureau of 

Mines and Geology, p. 116–138.

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, no. 2, p. 335–340.

Dehler, C.M., Elrick, M., Karlstrom, K.E., Smith, G.A., 

Crossey, L.J., and Timmons, J.M., 2001, Neoproterozoic 

Chuar Group (≈800–742 Ma), Grand Canyon—A record of 

cyclic marine deposition during global cooling and supercontinent rifting: Sedimentary Geology, v. 141–142, p. 465–499.

Del Rio, S.M., 1960, Mineral resources of Colorado First 

Sequel: Denver, Colo., State of Colorado Mineral Resources 

Board, 764 p. 

Derkey, P.D., Johnson, B.R., Lackaff, B.B., and Derkey, R.E., 

1998, Digital geologic map of the Rosalia 1:100,000 quadrangle, Washington and Idaho; a digital database for the 

1990 S.Z. Waggoner map: U.S. Geological Survey OpenFile Report 98-357, 27 p., scale 1:100,000.

Doughty, P.T., and Chamberlain, K.R., 1996, Salmon River 

Arch revisited—New evidence for 1370 Ma rifting near

 the end of deposition in the Middle Proterozoic Belt basin:

 Canadian Journal of Earth Science, v. 33, p. 1037–1052.

Doughty, P.T., Price, R.A., and Parrish, R.R., 1998, Geology and U-Pb geochronology of Archean basement 

and Proterozoic cover in the Priest River complex, 

northwestern United States, and their implications for 

Cordilleran structure and Precambrian continent constructions: Canadian Journal of Earth Sciences, v. 33, 

p. 1037–1052.

du Bray, E.A., 1995, Geologic map showing distribution of 

Cretaceous intrusive rocks in the central Big Belt Mountains, Broadwater and Meagher Counties, Montana: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF–2291, scale 1:50,000.

Earhart, R.L., 1986, Descriptive model of Blackbird Co-Cu, in

Cox, D.P., and Singer, D.A., Mineral deposit models: U.S. 

Geological Survey Bulletin 1693, p. 142.

Ekren, E.B., 1988, Stratigraphic and structural relations of the 

Hoodoo Quartzite and Yellowjacket Formation of Middle 

Proterozoic age from Hoodoo Creek eastward to Mount 

Taylor, central Idaho: U.S. Geological Survey Bulletin 

1570, 17 p.

Eppinger, R.G., 2002, Pre-fire baseline stream-sediment and 

stream-water geochemical data from a recently burned 

area in central Idaho, and suggestions for application of 

geochemical data to wildfire science [abs], in Coffelt, L.L., 

and Livingston, R.K., Second U.S. Geological Survey 

wildland fire science workshop, Los Alamos, New Mexico, 

Oct. 31–Nov. 3, 2000: U.S. Geological Survey Open-File 

Report 02-11, p. 51. Accessed 1/24/2007 at URL 

http://pubs.er.usgs.gov/usgspubs/ofr/ofr0211/. 

Eppinger, R.G., 2003, Geochemical comparison of pre- and 

post-wildfire stream sediment and water samples from 

drainages impacted by large wildfires of 2000, central 

Idaho, U.S.A. [abs.]: Geological Society of America special meeting, Wildland fire impacts on watersheds; understanding, planning, and response, October 21–23, 2003, 

Denver, Colo., Program and Proceedings, Poster Abstracts 

section, p. 3.

Eppinger, R.G., Briggs, P.H., Brown, Zoe Ann, Crock, 

J.G., Meier, Allen, Theodorakos, P.M., and Wilson, 

S.A., 2001, Baseline geochemical data for stream sediment and surface water samples from Panther Creek, 

the Middle Fork of the Salmon River, and the Salmon 

River from North Fork to Corn Creek, collected prior 

to the severe wildfires of 2000 in central Idaho: U.S. 

Geological Survey Open-File Report 01-0161. Accessed 

1/24/2007 at URL http://pubs.usgs.gov/of/2001/ofr-01-

0161/. 

References Cited 83
84 Earth Science Studies—Headwaters Province, Idaho and Montana

Eppinger, R.G., Briggs, P.H., Rieffenberger, Betsy, and Van 

Dorn, Carol, 2004, Comparing pre- and post-wildfire stream 

sediment and water geochemistry from drainages impacted 

by the Clear Creek and Wilderness Complex wildfires of 

2000, central Idaho [abs], in Livingston, R.K., Third U.S. 

Geological Survey wildland fire-science workshop, Denver, 

Colorado, Nov. 12–15, 2002: U.S. Geological Survey Scientific Investigations Report 2004-5005, p. 23, CD-ROM. 

Accessed 1/24/2007 at URL http://pubs.er.usgs.gov/usgspubs/sir/sir20045005/. 

Eppinger, R.G., Briggs, P.H., Rieffenberger, Betsy, and Van 

Dorn, Carol, 2003, Comparing pre- and post-wildfire stream 

sediment and water geochemistry from drainages impacted 

by large wildfires of 2000, Central Idaho, U.S.A.: Sixth 

International Symposium on Environmental Geochemistry, 

Sept. 7–11, 2003, final programme and book of abstracts, 

University of Edinburgh, p. 201.

Eppinger, R.G., Briggs, P.H., Rieffenberger, Betsy, Van Dorn, 

Carol, Brown, Zoe Ann, Crock, J.G., Hageman, P.L., Meier, 

Allen, Sutley, S.J., Theodorakos, P.M., and Wilson, S.A., 

2003, Geochemical data for stream sediment and surface 

water samples from Panther Creek, the Middle Fork of the 

Salmon River, and the Salmon River, collected before and 

after the Clear Creek, Little Pistol, and Shellrock wildfires 

of 2000 in central Idaho: U.S. Geological Survey Open-File 

Report 03-152. Available on CD-ROM; accessed 2/13/2006 

at URL http://pubs.usgs.gov/of/2003/152/.

Evans, K.V., 1998, The Yellowjacket Formation of east-central 

Idaho, in Berg, R.B., ed., Belt Symposium III: Montana 

Bureau of Mines and Geology Special Publication 112, 

p. 17–30.

Evans, K.V., Aleinikoff, J.N., Obradovich, J.D., and Fanning, 

C.M., 2000, SHRIMP U-Pb geochronology of volcanic 

rocks, Belt Supergroup, western Montana—Evidence for 

rapid deposition of sedimentary strata: Canadian Journal of 

Earth Sciences, v. 37, p. 1287–1300.

Evans, K.V., and Connor, J.J., 1993, Geologic map of the 

Blackbird Mountain 15-minute quadrangle, Lemhi County, 

Idaho: U.S. Geological Survey Miscellaneous Field Studies 

Map MF–2234, scale 1:62,500.

Evans, K.V., and Green, G.N., compilers, 2003, Geologic map 

of Salmon National Forest and vicinity, east-central Idaho: 

U.S. Geological Survey Geologic Investigations Series Map 

I–2765, scale 1:100,000. Accessed 5/18/2004 at URL http://

pubs.usgs.gov/imap/i-2765/.

Evans, K.V., and Zartman, R.E., 1990, U-Th-Pb and Rb-Sr 

geochronology of middle Proterozoic granite and augen 

gneiss, Salmon River Mountains, east-central Idaho: Geological Society of America Bulletin, v. 102, p. 63–73.

Faure, G., 1986, Principles of isotope geology: New York, 

John Wiley, 589 p.

Ferri, R., Rees, C., Nelson, J., and Legun, A., 1999, Geology and mineral deposits of the northern Kechika Trough 

between Gataga River and the 60th parallel: British Columbia Ministry of Energy and Mines Bulletin 107, 122 p.

Ficklin, W.H., and Mosier, E.L., 1999, Field methods for sampling and analysis of environmental samples for unstable 

and selected stable constituents, Chapter 12 in Plumlee, 

G.S., and Logsdon, M.J., eds., The environmental geochemistry of mineral deposits—Part A, Processes, techniques, 

and health issues: Society of Economic Geologists, Inc., 

Reviews in Economic Geology, v. 6A, p. 249–264.

Fisher, F.S., and Johnson, K.M., eds., 1995, Geology and mineral resource assessment of the Challis 1°×2° quadrangle, 

Idaho: U.S. Geological Survey Professional Paper 1525, 

204 p. plus appendixes, 23 plates.

Fisher, F.S., McIntyre, D.H., and Johnson, K.M., 1992, Geologic map of the Challis 1°×2° quadrangle, Idaho: U.S. 

Geological Survey Miscellaneous Investigations Series 

Map I–1819, scale 1:250,000, 39 p. pamphlet. Accessed 

5/18/2004 at URL http://pubs.usgs.gov/imap/i-1819/. 

Fortescue, J.A.C., 1992, Landscape geochemistry; retrospect 

and prospect—1990: Applied Geochemistry, v. 7, p. 1–54.

Gabrielse, H., 1972, Younger Precambrian of the Canadian Cordillera: American Journal of Science, v. 272, p. 521–536.

Gorman, A.R., and 12 others, 2002, Deep Probe—Imaging the 

roots of western North America: Canadian Journal of Earth 

Sciences, v. 39, p. 375–398.

Goyer, R.A., and Clarkson, T.W., 2001, Toxic effects of metals, Chapter 23 in Klaassen, C.D., ed., Casarett and Doull’s 

toxicology—The basic science of poisons: New York, 

McGraw-Hill, p. 811–867. 

Green, G.N., and Tysdal, R.G., 1996, Digital maps and figures 

on CD-ROM for mineral and energy resource assessment 

of the Helena National Forest, west-central Montana: U.S. 

Geological Survey Open-File Report 96-683-B, CD-ROM, 

scale 1:126,720.

Gunn, S.H., 1991, Isotopic constraints on the crustal evolution 

of southwest Montana: Santa Cruz, Calif., University of 

California at Santa Cruz Ph. D. dissertation, 190 p.

Hageman, P.L., 2000, A simple field leach test for rapid 

screening and qualitative characterization of mine waste 

dump material on abandoned mine lands: U.S. Geological 

Survey Open-File Report 00-015, 13 p.

Hageman, P.L., and Briggs, P.H., 2000, A simple field leach 

test for rapid screening and qualitative characterization of 

mine waste dump material on abandoned mine lands, in

ICARD 2000, Proceedings of the Fifth International Conference on Acid Rock Drainage, Volume 2: Society for Mining, 

Metallurgy, and Exploration, Inc., p. 1463–1475.
Hahn, G.A., and Hughes, G.J., Jr., 1984, Sedimentation, 

tectonism, and associated magmatism of the Yellowjacket 

Formation in the Idaho Cobalt Belt, Lemhi County, Idaho, 

in Hobbs, S.W., ed., The Belt: Montana Bureau of Mines 

and Geology Special Publication 90, p. 65–67.

Hambrey, M.J., and Harland, W.B., 1985, The Late Proterozoic glacial era: Palaeogeography, Palaeoclimatology, 

Palaeoecology, v. 51, p. 255–272.

Hammarstrom, J.M., Eppinger, R.G., Van Gosen, B.S., Briggs, 

P.H., and Meier, A.L., 2002, Case study of the environmental signature of a recently abandoned, carbonate-hosted 

replacement deposit—The Clayton mine, Idaho: U.S. 

Geological Survey Open-File Report 02-10, 44 p. Available 

at URL http://pubs.usgs.gov/of/of02-010/.

Hammarstrom, J.M., Tomascak, P., and Krogstad, E.J., 1993, 

Old crustal Nd signature for the Pioneer Batholith: American Geophysical Union 1993 Spring Meeting abstracts, Eos 

Supplement, April 20, 1993, p. 335.

Harrison, J.E., Cressman, E.R., and Whipple, J.W., 1992, Geologic and structure maps of the Kalispell 1°×2° quadrangle, 

Montana, and Alberta and British Columbia: U.S. Geological Survey Miscellaneous Investigations Map I–2267, scale 

1:250,000.

Harrison, J.E., Griggs, A.B., Wells, J.D., Kelley, W.N., Derkey, 

P.D., and EROS Data Center, 2000, Geologic and structure maps of the Wallace 1°×2° quadrangle, Montana and 

Idaho—A digital database: U.S. Geological Survey Miscellaneous Investigations Series Map I–1509–A, version 1.0, 

21 p., scale 1:250,000.

Harrison, J.E., Whipple, J.W., and Lidke, D.J., 1998, Geologic 

map of the western part of the Cut Bank 1°×2° quadrangle, 

Montana: U.S. Geological Survey Geologic Investigations 

Series Map I–2593, 1 sheet, scale 1:250,000.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques of 

Water Resources Investigations, Book 4, Chapter A3, 510 

p. Only available online at URL http://water.usgs.gov/pubs/

twri/twri/twri4a3/.

Hobbs, S.W., 1985, Structural and stratigraphic controls of 

ore deposits in the Bayhorse area, Idaho, Chapter K in

McIntyre, D.H., ed., Symposium on the geology and mineral deposits of the Challis 1°×2° quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658–A–S, p. 133–140.

Hobbs, S.W., Hays, W.H., and McIntyre, D.H., 1991, Geologic 

map of the Bayhorse area, central Custer County, Idaho: 

U.S. Geological Survey Miscellaneous Investigations Series 

Map I–1882, scale 1:62,500, 14 p. pamphlet.

Hoffman, P.F., 1999, The break-up of Rodinia, birth of Gondwana, true polar wander and the snowball Earth: Journal of 

African Earth Sciences, v. 28, p. 17–33.

Hoffman, P.F., Kaufman, A.J., Halverson, G.P., and Schrag, 

D.P., 1998, A Neoproterozoic snowball earth: Science, 

v. 281, p. 1342–1346.

Hughes, G.J., Jr., 1983, Basinal setting of the Idaho Cobalt 

Belt, Blackbird mining district, Lemhi County, Idaho, in

The genesis of Rocky Mountain ore deposits—Changes 

with time and tectonics: Denver Region Exploration Geologists Society, p. 21–27.

Idaho Geological Survey, 1996a, Digital geology of the Riggins 1:100,000-scale quadrangle, Idaho, in Digital geologic 

map compilation for the Nez Perce and Clearwater National 

Forests: Idaho Geological Survey CD-ROM, produced 

under contract to USDA Forest Service [unpublished], scale 

1:100,000.

Idaho Geological Survey, 1996b, Digital geology of the 

Grangeville 1:100,000-scale quadrangle, Idaho, in Digital 

geologic map compilation for the Nez Perce and Clearwater National Forests: Idaho Geological Survey CD-ROM, 

produced under contract to USDA Forest Service [unpublished], scale 1:100,000.

Idaho Geological Survey, 1996c, Digital geology of the 

Headquarters 1:100,000-scale quadrangle, Idaho, in Digital 

geologic map compilation for the Nez Perce and Clearwater National Forests: Idaho Geological Survey CD-ROM, 

produced under contract to USDA Forest Service [unpublished], scale 1:100,000.

Janecke, S.U., Vandenburg, C.J., and Blankenau, J.J., 1998, 

Geometry, mechanisms and significance of extensional 

folds from examples in the Rocky Mountain Basin and 

Range province, U.S.A.: Journal of Structural Geology, 

v. 20, p. 841–856.

Jefferson, C.W., and Parrish, R.R., 1989, Late Proterozoic 

stratigraphy, U-Pb zircon ages, and rift tectonics, Mackenzie Mountains, northwestern Canada: Canadian Journal of 

Earth Sciences, v. 26, p. 1784–1801.

Johnson, B.R., and Derkey, P.D., 1998, Digital geologic map 

of the Spokane 1:100,000 quadrangle, Washington and 

Idaho; a digital database for the 1990 N.L. Joseph map: 

U.S. Geological Survey Open-File Report 98-115, 13 p. and 

1 digital plate, scale 1:100,000.

Kalakey, T.J., John, B.E., and Lageson, D.R., 2001, Fault-controlled emplacement in the Sevier fold-and-thrust belt of 

southwest Montana, U.S.A.: Journal of Structural Geology, 

v. 23, p. 1151–1165.

References Cited 85
86 Earth Science Studies—Headwaters Province, Idaho and Montana

Karlstrom, K.E., Bowring, S.A., Dehler, C.M., Knoll, A.H., 

Porter, S.M., Des Marais, D.J., Weil, A.B., Sharp, Z.D., 

Geissman, J.W., Elrick, M.B., Timmons, J.M., Crossey, 

L.J., and Davidek, K.L., 2000, Chuar Group of the Grand 

Canyon—Record of breakup of Rodinia, associated change 

in the global carbon cycle, and ecosystem expansion by 

740 Ma: Geology, v. 28, p. 619–622.

Kayser, H.Z., 2001, Digital geologic map of the east half of 

the Pullman 1°×2° quadrangle, Idaho; a digital database for 

the 1979 Rember and Bennett map: U.S. Geological Survey 

Open-File Report 01-262, 29 p., 1 sheet, scale 1:250,000.

Kellogg, K.S., and Williams, V.S., 2000, Geologic map of the 

Ennis 30’×60’ quadrangle, Madison and Gallatin Counties, Montana, and Park County, Wyoming: U.S. Geological Survey Geologic Investigations Series I–2690, scale 

1:100,000.

Kelly, M.G., 1999, Effects of heavy metals on the aquatic 

biota, Chapter 18 in Plumlee, G.S., and Logsdon, M.J., eds., 

The environmental geochemistry of mineral deposits—Part 

A, Processes, techniques, and health issues: Society of 

Economic Geologists, Inc., Reviews in Economic Geology, 

v. 6A, p. 363–371.

Kesler, S.E., 1994, Mineral resources, economics and the 

environment: New York, Macmillan College Publishing 

Company, Inc., 391 p.

Kiilsgaard, T.H., and Bennett, E.H., 1995, Eocene plutonic 

terrane, in Fisher, F.S., and Johnson, K.M., Geology and 

mineral resource assessment of the Challis 1°×2° quadrangle, Idaho: U.S. Geological Survey Professional Paper 

1525, p. 44–47.

Kiilsgaard, T.H., and Hall, W.E., 1995, Radioactive black-sand 

placer deposits, in Fisher, F.S., and Johnson, K.M., Geology 

and mineral resource assessment of the Challis 1°×2° quadrangle, Idaho: U.S. Geological Survey Professional Paper 

1525, p. 183–189.

Kiilsgaard, T.H., Stanford, L.R., and Lewis, R.S., 2001, 

Geologic map of the Idaho City 30×60 minute quadrangle, 

Idaho: Idaho Geological Survey Geologic Map Series 29, 

scale 1:100,000.

Klein, T.L., 2004, Mineral deposit data for epigenetic baseand precious-metal and uranium-thorium deposits in southcentral and southwestern Montana and southern and central 

Idaho: U.S. Geological Survey Open-File Report 2004-

1005, 16 p. Accessed 5/18/2004 at URL http://pubs.usgs.

gov/of/2004/1005/. 

Krieger, G.R., Hattemer-Frey, H.A., and Kester, J.E., 1999, 

Bioavailability of metals in the environment—Implications 

for health risk assessment, Chapter 17 in Plumlee, G.S., and 

Logsdon, M.J., eds., The environmental geochemistry of 

mineral deposits—Part A, Processes, techniques, and health 

issues: Society of Economic Geologists, Inc., Reviews in 

Economic Geology, v. 6A, p. 357–361.

Lang, J.R., Baker, T., Hart, C.J.R., and Mortensen, J.K., 2000, 

An exploration model for intrusion-related gold systems: 

Society of Economic Geologists Newsletter 40, p. 1–15.

Larsen, E.S., Jr., 1940, Petrographic province of central 

Montana: Geological Society of America Bulletin, v. 51, 

p. 887–948. 

Levinson, A.A., 1980, Introduction to exploration geochemistry, 

Second Edition: Wilmette, Ill., Applied Publishing, 924 p.

Lewis, R.S., 1998a, Geologic map of the Butte 1°×2° quadrangle, Montana: Montana Bureau of Mines and Geology Open-File Report MBMG 363, 16 p., 1 plate, scale 

1:250,000.

Lewis, R.S., 1998b, Geologic map of the Montana part of the 

Missoula West 30- by 60-minute quadrangle: Montana 

Bureau of Mines and Geology Open-File Report MBMG 

373, 20 p., 2 plates, scale 1:100,000.

Lewis, R.S., Burmester, R.F., Kauffman, J.D., and Frost, T.P., 

2000, Geologic map of the St. Maries 30×60 minute quadrangle, Idaho: Idaho Geological Survey Digital Geologic 

Map DGM–1, scale 1:100,000.

Lewis, R.S., Burmester, R.F., McFadden, M.D., Derkey, P.D., 

and Oblad, J.R., 1999, Digital geologic map of the Wallace quadrangle, Idaho: U.S. Geological Survey Open-File 

Report 99-390, 46 p., scale 1:100,000.

Lewis, R.S., and Derkey, P.D., 1999, Digital geologic map of 

part of the Thompson Falls 1:100,000 quadrangle, Idaho: 

U.S. Geological Survey Open-File Report 99-438, 32 p., 1 

digital plate.

Lewis, R.S., and Stanford, L.R., 2002a, Digital geologic map 

of the Elk City 30×60 minute quadrangle, Idaho: Idaho 

Geological Survey Digital Geologic Map Series DGM–05, 

1 CD-ROM, scale 1:100,000.

Lewis, R.S., and Stanford, L.R., 2002b, Digital geologic map 

of the Kooskia 30×60 minute quadrangle, Idaho: Idaho 

Geological Survey Digital Geologic Map Series DGM–06, 

1 CD-ROM, scale 1:100,000.
Lewis, R.S., and Stanford, L.R., 2002c, Digital geologic map 

of the Hamilton 30×60 minute quadrangle, Idaho: Idaho 

Geological Survey Digital Geologic Map Series DGM–03, 

1 CD-ROM, scale 1:100,000.

Lewis, R.S., and Stanford, L.R., 2002d, Digital geologic map 

of the Missoula West 30×60 minute quadrangle, Idaho: 

Idaho Geological Survey Digital Geologic Map Series 

DGM–02, 1 CD-ROM, scale 1:100,000.

Lewis, R.S., and Stanford, L.R., 2002e, Digital geologic map 

of the Nez Perce Pass 30×60 minute quadrangle, Idaho: 

Idaho Geological Survey Digital Geologic Map Series 

DGM–04, 1 CD-ROM, scale 1:100,000.

Lindgren, Waldemar, 1904, A geological reconnaissance 

across the Bitterroot Range and Clearwater Mountains in 

Montana and Idaho: U.S. Geological Survey Professional 

Paper 27, 123 p.

Link, P.K., Christie-Blick, N., Devlin, W.J., Elston, D.P., 

Horodyski, R.J., Levy, M., Miller, J.M.G., Pearson, R.C., 

Prave, A., Stewart, J.H., Winston, D., Wright, L.A., and 

Wrucke, C.T., 1993, Middle and Late Proterozoic stratified rocks of the western U.S. Cordillera, Colorado Plateau, 

and Basin and Range province, in Reed, J.C., Jr., Bickford, 

M.E., Houston, R.S., Link, P.K., Rankin, D.W., Sims, P.K., 

and Van Schmus, W.R., eds., Decade of North American 

Geology, Precambrian—Conterminous U.S.: Geological 

Society of America, The Geology of North America, v. C–2, 

p. 463–595.

Link, P.K., Mahoney, J.B., Bruner, D.J., Batatian, L.D., 

Wilson, Eric, and Williams, F.J.C., 1995, Geologic map of 

outcrop areas of sedimentary units in the eastern part of the 

Hailey 1°×2° quadrangle and the southern part of the Challis 1°×2° quadrangle, south-central Idaho: U.S. Geological 

Survey Bulletin 2064–C, plate 1, scale 1:100,000.

Link, P.K., Winston, D., and Boyack, D., 2003, Stratigraphy 

of the Mesoproterozoic Belt Supergroup, Salmon River 

Mountains, Lemhi County, Idaho: Northwest Geology, 

v. 32, p. 107–123.

Long, K.R., DeYoung, J.H., and Ludington, S.D., 1998, 

Database of significant deposits of gold, silver, copper, lead, 

and zinc in the United States—Part B, Digital data: U.S. 

Geological Survey Open-File Report 98-206–B.

Lonn, J.D., and Berg, R.B., 1996, Preliminary geologic map 

of the Hamilton 30- by 60-minute quadrangle, Montana: 

Montana Bureau of Mines and Geology Open-File Report 

MBMG 340, 9 p., 1 plate, scale 1:100,000.

Lonn, J.D., and McFaddan, M.D., 1999, Geologic map of the 

Montana part of the Wallace 30- by 60-minute quadrangle: 

Montana Bureau of Mines and Geology Open-File Report 

MBMG 388, 15 p., 2 plates, scale 1:100,000.

Lonn, J.D., Skipp, Betty, Ruppel, E.T., Janecke, S.U., Perry, 

W.J., Jr., Sears, J.W., Bartholomew, M.J., Stickney, M.C., 

Fritz, W.J., Hurlow, H.A., and Thomas, R.C., 2000, Geologic map of the Lima quadrangle, southwest Montana: 

Montana Bureau of Mines and Geology Open-File Report 

MBMG 408, 3 sheets, parts A, B, and C, scale 1:100,000.

Lopez, D.A., 1981, Stratigraphy of the Yellowjacket Formation 

of east-central Idaho: U.S. Geological Survey Open-File 

Report 81-1088, 218 p.

Lopez, D.A., 2000, Geologic map of the Big Timber 30’×60’

quadrangle, south-central Montana: Montana Bureau of 

Mines and Geology Open-File Report MBMG 405, scale 

1:100,000.

Lopez, D.A., 2001, Preliminary geologic map of the Red 

Lodge 30’×60’ quadrangle, south-central Montana: Montana Bureau of Mines and Geology Open-File Report 

MBMG 423, 1 plate, scale 1:100,000.

Lund, Karen, 2004, Geology of the Payette National Forest, 

Valley, Idaho, Washington, and Adams Counties, westcentral Idaho: U.S. Geological Survey Professional Paper 

1666, 86 p., 2 plates.

Lund, Karen, Aleinikoff, J.N., Evans, K.V., and Fanning, 

C.M., 2003, SHRIMP U-Pb geochronology of Neoproterozoic Windermere Supergroup, central Idaho—Implications 

for rifting of western Laurentia and synchroneity of Sturtian 

glacial deposits: Geological Society of America Bulletin, 

v. 115, p. 349–372.

Lund, Karen, Aleinikoff, J.N., Kunk, M.J., Unruh, D.M., Zeihen, G.D., Hodges, W.C., du Bray, E.A., and O’Neill, J.M., 

2002, SHRIMP U-Pb and 40Ar/39Ar age constraints for 

relating plutonism and mineralization in the Boulder batholith region, Montana: Economic Geology, v. 97, p. 241–267.

Lund, Karen, Derkey, P.D., Brandt, T.R., and Oblad, Jon, 

1999, Digital geologic map database of the Payette National 

Forest and vicinity, Idaho: U.S. Geological Survey OpenFile Report 98-219–B, 45 p., scale 1:100,000.

Lund, Karen, Evans, K.V., and Esparza, L.E., 1983, Mineral 

resource potential map of the Special Mining Management 

Zone—Clear Creek, Idaho: U.S. Geological Survey Miscellaneous Field Studies MF–1576–A.

References Cited 87
88 Earth Science Studies—Headwaters Province, Idaho and Montana

Lund, Karen, Tysdal, R.G., Evans, K.V., and Winkler, G.R., 

2003, Geologic map of the west half of the Salmon National 

Forest, in Evans, K.V., and Green, G.N., compilers, Geologic map of the Salmon National Forest and vicinity, 

east-central Idaho: U.S. Geological Survey Miscellaneous 

Investigations Map I–2765.

Lund, K.I., and Tysdal, R.G., 2007, Stratigraphic and structural setting of the sediment-hosted Blackbird cobalt-copper deposits, east-central Idaho, U.S.A., in Link, P.K., and 

Lewis, R.S. eds., Proterozoic geology of western North 

America and Siberia: Society for Sedimentary Geology 

Special Publication 86, p. 129–147.

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives 

of Environmental Contamination and Toxicology, v. 39, 

p. 20–31.

Martin, M.W., Dilles, J.H., and Proffett, J.M., 1999, U-Pb 

geochronologic constraints for the Butte porphyry system: 

Geological Society of America Abstracts with Programs, 

v. 31, p. 380.

McCafferty, A.E., Bankey, Viki, and Brenner, K.C., 1998, 

Montana aeromagnetic and gravity maps and data: U.S. 

Geological Survey Open-File Report 98-333.

McFaul, E.J., Mason, G.T., Ferguson, W.B., and Lipin, B.R., 

2000, U.S. Geological Survey Mineral Databases—MRDS 

and MAS/MILS: U.S. Geological Survey Digital Data 

Series DDS-52, CD-ROM.

Meyer, C., Shea, E.P., Goddard, C.C., Jr., Zeihen, L.G., Guilbert, J.M., Miller, R.N., McAleer, J.F., Brox, G.B., Ingersoll, R.G., Jr., Burns, G.J., and Wigal, T., 1968, Ore deposits 

at Butte, Montana, in Ridge, J.D., ed., Ore deposits of the 

United States, 1933–1967, The Graton-Sales Volume II: 

American Institute of Mining and Metallurgical Engineers, 

p. 1373–1416.

Miller, F.K., Burmester, R.F., Miller, D.M., Powell, R.E., and 

Derkey, P.D., 1998, Digital geologic map of the Sandpoint 

1°×2° quadrangle, Washington, Idaho, and Montana: U.S. 

Geological Survey Open-File Report 99-144, 72 p., 1 digital 

plate, scale 1:250,000.

Miller, F.K., McKee, E.H., and Yates, R.G., 1973, Age and 

correlation of the Windermere Group in northeastern 

Washington: Geological Society of America Bulletin, v. 84, 

p. 3723–3730.

Miller, R.N., 1973, Production history of the Butte district and 

geological function, past and present, in Miller, R.N., ed., 

Guidebook for the Butte field meeting of Society of Economic Geologists, 1973: Butte, Mont., Society of Economic 

Geologists, p. F1–F10.

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

E.H., 1986, Mines and prospects of the Challis quadrangle, 

Idaho, Second Edition: Idaho Geological Survey Mines and 

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

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.

Moye, F.J., ed., 1990, Geology and ore deposits of the TransChallis fault system/Great Falls tectonic zone: Tobacco 

Root Geological Society, Fifteenth Annual Field Conference 

Guidebook, 121 p.

Mudge, M.R., Earhart, R.L., Whipple, J.W., and Harrison, J.E., 

1982, Geologic and structure map of the Choteau 1°×2° 

quadrangle, western Montana: U.S. Geological Survey 

Miscellaneous Investigations Series Map I–1300, 2 sheets, 

scale 1:250,000.

Mueller, P., Shuster, R., D’Arcy, K., Heatherington, A., Hutman, 

A., and Williams, I., 1995, Source of the northeastern Idaho 

batholith—Evidence for a Paleoproterozoic terrane in the 

northwestern U.S.: Journal of Geology, v. 103, p. 63–72.

Mueller, P.A., Heatherington, A.L., Kelly, D.M., Wooden, J.A., 

and Mogk, D.W., 2002, Paleoproterozoic crust within the 

Great Falls tectonic zone—Implications for the assembly of 

southern Laurentia: Geology, v. 30, p. 127–130.

Munts, S.R., 2000, Digital geologic map of the Coeur d’Alene 

1:100,000 quadrangle, Idaho and Montana: U.S. Geological Survey Open-File Report 00-135, version 1.0, 30 p., 1 

digital plate, scale 1:100,000.

NAMAG, 2002, Magnetic anomaly map of North America: 

Compiled by North America Magnetic Anomaly Group 

(available from U.S. Geological Survey).

Nash, J.T., and Connor, J.J., 1993, Iron and chlorine as guides 

to stratiform Cu-Co-Au deposits, Idaho cobalt belt, U.S.A.: 

Mineralium Deposita, v. 28, p. 99–106.

Nash, J.T., and Hahn, G.A., 1986, Volcanogenic character of 

sediment-hosted Co-Cu deposits in the Blackbird mining 

district, Lemhi County, Idaho; an interim report: U.S. Geological Survey Open-File Report, 29 p.

Nash, J.T., and Hahn, G.A., 1989, Stratabound Co-Cu deposits and mafic volcaniclastic rocks in the Blackbird mining 

district, Lemhi County, Idaho, in Boyle, R.W., Brown, A.C., 

Jefferson, C.W., Jowett, E.C., and Kirkham, R.V., eds., 

Sediment-hosted stratiform copper deposits: Geological 

Association of Canada Special Paper 36, p. 339–356.

Nold, J.L., 1990, The Idaho cobalt belt, northwestern United 

States—A metamorphosed Proterozoic exhalative ore district: Mineralium Deposita, v. 25, p. 163–168.
Nordstrom, D.K., and Alpers, C.N., 1999, Geochemistry of 

acid mine waters, in Plumlee, G.S., and Logsdon, M.J., eds., 

The environmental geochemistry of mineral deposits—Part 

A, Processes, techniques, and health issues: Society of 

Economic Geologists, Inc., Reviews in Economic Geology, 

v. 6A, p. 133–160.

Obradovich, J.D., and Peterman, Z.E., 1968, Geochronology 

of the Belt Series, Montana: Canadian Journal of Earth Sciences, v. 5, p. 737–747.

O’Leary, R.M., and Meier, A.L., 1986, Analytical methods 

used in geochemical exploration, 1984: U.S. Geological 

Survey Circular 948, 48 p.

O’Neill, J.M., 1999, An Early Proterozoic collisional orogen 

beneath and south of the Belt Basin, in Berg, R.B., ed., Belt 

Symposium III: Montana Bureau of Mines and Geology 

Special Publication 111, p. 227–234.

O’Neill, J.M., and Christiansen, R.L., 2002, Geologic map of 

the Hebgen Lake quadrangle, Beaverhead, Madison, and 

Gallatin Counties, Montana, Park and Teton Counties, Wyoming, and Clark and Fremont Counties, Idaho: Montana 

Bureau of Mines and Geology Open-File Report MBMG 

464, 1 plate, scale 1:100,000.

O’Neill, J.M., and Lopez, D.A., 1985, The Great Falls tectonic 

zone—Its character and regional significance: American Association of Petroleum Geologists Bulletin, v. 69, 

p. 437–447.

Piatak, N.M., Seal, R.R., II, Hammarstrom, J.M., Meier, 

A.L., and Briggs, P.H., 2003, Geochemical characterization of slags, other mine waste, and their leachate from the 

Elizabeth and Ely mines (Vermont), the Ducktown mining 

district (Tennessee), and the Clayton smelter site (Idaho): 

U.S. Geological Survey Open-File Report 03-260, 53 p. 

Available at URL http://pubs.usgs.gov/of/2003/of03-260/.

Plumlee, G.S., Smith, K.S., Montour, M.R., Ficklin, W.H., and 

Mosier, E.L., 1999, Geologic controls on the composition 

of natural waters and mine waters draining diverse mineraldeposit types, Chapter 19 in Filipek, L.H., and Plumlee, 

G.S., eds., The environmental geochemistry of mineral 

deposits—Part B, Case studies and research topics: Society 

of Economic Geologists, Inc., Reviews in Economic Geology, v. 6B, p. 373–432.

Prave, A.R., 1999, Two diamictites, two cap carbonates, two 

D13C excursions, two rifts; The Neoproterozoic Kingston 

Peak Formation, Death Valley, California: Geology, v. 27, 

p. 339–342.

Rehn, W.M., 1983, Petrology and geochemistry of the Blue 

Joint area, southwestern Montana: Golden, Colo., Colorado 

School of Mines M.S. thesis, 203 p.

Rehn, W.M., and Lund, Karen, 1981, Eocene extensional plutonism in the Idaho batholith region: Geological Society of 

America Abstracts with Programs, v. 13, no. 7, p. 536.

Rhodes, B.P., and Hyndman, D.W., 1988, Regional metamorphism, structure, and tectonics of northeastern Washington 

and northern Idaho, in Ernst, W.G., ed., Metamorphism and 

crustal evolution of the western United States (Rubey volume 7): Englewood Cliffs, N.J., Prentice-Hall, p. 272–295.

Roberts, S.A., 1973, Pervasive early alteration in the Butte 

district, Montana, in Miller, R.N., ed., Guidebook for the 

Butte field meeting of Society of Economic Geologists, 

1973: Butte, Mont., Society of Economic Geologists, 

p. HH1–HH8.

Roots, C.F., and Parrish, R.R., 1988, Age of the Mount Harper 

volcanic complex, southern Ogilvie Mountains, Yukon, in

Radiogenic age and isotopic studies, Report 2: Geological 

Survey of Canada Paper 88-2, p. 29–35.

Rose, A.W., Hawkes, H.E., and Webb, J.S., 1979, Geochemistry in mineral exploration, Second Edition: London, 

Academic Press, 657 p.

Ross, C.P., 1925, The copper deposits near Salmon, Idaho: 

U.S. Geological Survey Bulletin 774, 44 p.

Ross, C.P., 1934a, Some lode deposits in the northwestern part 

of the Boise Basin, Idaho: U.S. Geological Survey Bulletin 

846–D, p. 279–285.

Ross, C.P., 1934b, Geology and ore deposits of the Casto 

quadrangle, Idaho: U.S. Geological Survey Bulletin 854, 

135 p.

Ross, C.P., 1947, Geology of the Borah Peak quadrangle, 

Idaho: Geological Society of America Bulletin, v. 58, 

p. 1085–1160.

Ross, G.M., McMechan, M.E., and Hein, F.J., 1989, Proterozoic history—The birth of the miogeocline, in Ricketts, 

B.D., ed., Western Canada sedimentary basin; A case history: Calgary, Alta., Canadian Society of Petroleum Geologists, p. 79–104.

Ross, G.M., ed., 2002, The lithoprobe Alberta basement transect: Canadian Journal of Earth Sciences, v. 39, no. 3, 437 p.

Rostad, O.H., 1978, K-Ar dates for mineralization in the 

White Cloud–Cannivan porphyry molybdenum belt of Idaho 

and Montana—A discussion: Economic Geology, v. 73, 

p. 1366–1368.

Rudnick, R.L., and Gao, S., 2004, Composition of the continental crust, in Rudnick, R.L., ed., The crust; Holland, H.D., 

and Turekian, K.K., executive eds., Treatise on geochemistry, Volume 3: Amsterdam, Elsevier, p. 1–64.

References Cited 89
90 Earth Science Studies—Headwaters Province, Idaho and Montana

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: U.S. 

Geological Survey Bulletin 1151, 121 p.

Ruppel, E.T., 1975, Precambrian Y sedimentary rocks in eastcentral Idaho: U.S. Geological Survey Professional Paper 

889–A, 23 p.

Ruppel, E.T., 1978, Medicine Lodge thrust system, east-central Idaho and southwest Montana: U.S. Geological Survey 

Professional Paper 1031, 23 p.

Ruppel, E.T., 1998, Geologic map of the eastern part of the 

Leadore 30’×60’ quadrangle, Montana and Idaho: Montana 

Bureau of Mines and Geology Open-File Report MBMG 

372, scale 1:100,000.

Ruppel, E.T., and Lopez, D.A., 1988, Regional geology and 

mineral deposits in and near the central part of the Lemhi 

Range, Lemhi County, Idaho: U.S. Geological Survey Professional Paper 1480, 122 p.

Ruppel, E.T., O’Neill, J.M., and Lopez, D.A., 1993, Geologic 

map of the Dillon 1°×2° quadrangle, Idaho and Montana: 

U.S. Geological Survey Miscellaneous Investigations Series 

Map I–1803–H, scale 1:250,000.

Sales, R.H., and Meyer, C., 1948, Wall-rock alteration, Butte, 

Montana: Transactions of the American Institute of Mining 

Engineers, v. 178, p. 9–35.

Sharp, B.J., and Cavender, W.S., 1962, Geology and thoriumbearing deposits of the Lemhi Pass area, Lemhi County, 

Idaho, and Beaverhead County, Montana: U.S. Geological 

Survey Bulletin 1126, 76 p.

Sims, P.K., Bankey, Viki, and Finn, C.A., 2001, Preliminary 

Precambrian basement map of Colorado—A geologic interpretation of an aeromagnetic anomaly map: U.S. Geological Survey Open-File Report 01-0364, scale 1:1,000,000.

Sims, P.K., Finn, C.A., and Rystrom, V.L., 2001, Preliminary 

Precambrian basement map showing geologic-geophysical 

domains, Wyoming: U.S. Geological Survey Open-File 

Report 01-199, scale 1:1,000,000.

Sims, P.K., Lund, Karen, and Anderson, E.M., 2005, Precambrian crystalline basement map of Idaho—An interpretation 

of aeromagnetic anomalies: U.S. Geological Survey Scientific Investigations Map 2884, scale 1:1,000,000.

Sims, P.K., O’Neill, J.M., Bankey, Viki, and Anderson, E.M., 

2004, Precambrian basement geologic map of Montana—An interpretation of aeromagnetic anomalies: U.S. 

Geological Survey Scientific Investigations Map 2829, scale 

1:1,000,000. 

Sims, P.K., Stein, H.J., and Finn, C.A., 2002, New Mexico 

structural zone—An analogue of the Colorado Mineral Belt: 

Ore Geology Reviews, v. 21, p. 211–225.

Skipp, Betty, 1987, Basement thrust sheets in the Clearwater 

orogenic zone, central Idaho and western Montana: Geology, v. 15, p. 220–224.

Smedes, H.W., Klepper, M.R., and Tilling, R.I., 1973, The 

Boulder batholith, Montana (A summary), in Miller, R.N., 

ed., Guidebook for the Butte Field Meeting of the Society 

of Economic Geologists: Butte, Mont., The Anaconda 

Company, p. E1–E3.

Sobel, L.S., 1982, Sedimentology of the Blackbird mining 

district, Lemhi County, Idaho: Cincinnati, Ohio, University 

of Cincinnati M.S. thesis, 235 p.

Spanski, G.T., 2004, Inventory of significant deposit occurrences in the Headwaters area in western Montana, Idaho, 

and extreme eastern Oregon and Washington: U.S. Geological Survey Open-File Report 2004-1038.

Stein, H.J., and Cathles, L.M., 1997, The timing and duration of 

hydrothermal events: Economic Geology, v. 92, p. 763–765.

Stewart, J.H., 1972, Initial deposits in the Cordilleran geosyncline; evidence of a Late Precambrian (<850 m.y.) continental separation: Geological Society of America Bulletin, 

v. 83, p. 1345–1360.

Stewart, J.H., 1991, Latest Proterozoic and Cambrian rocks of 

the western United States—An overview, 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, v. 1, p. 13–38.

Sullivan, J.B., Jr., and Krieger, G.R., eds., 2001, Clinical 

environmental health and toxic exposures, Third Edition: 

Philadelphia, Pa., Lippincott Williams and Wilkins, 1,323 p.

Taggart, J.E., Jr., ed., 2002, Analytical methods for chemical 

analysis of geologic and other materials, U.S. Geological 

Survey: U.S. Geological Survey Open-File Report 02-223. 

Available at URL http://pubs.usgs.gov/of/ofr-02-0223/.

Taylor, C.D., Winick, J.A., Unruh, D.M., and Kunk, M.J., 

2004, Geochronology and geochemistry of the IdahoMontana porphyry belt: Geological Society of America 

Abstracts with Programs, v. 36, no. 4, p. 4.

Tietbohl, D.R., 1981, Structure and stratigraphy of the Hayden 

Creek area, Lemhi Range, east-central Idaho: University 

Park, Pa., The Pennsylvania State University M.S. thesis, 

121 p.

Tietbohl, D.R., 1986, Proterozoic diamictite beds in the Lemhi 

Range, east-central Idaho, in Roberts, S.M., ed., Belt Supergroup: Montana Bureau of Mines and Geology Special 

Publication 94, p. 197–207.

Tweto, Ogden, and Sims, P.K., 1963, Precambrian ancestry of 

the Colorado mineral belt: Geological Society of America 

Bulletin, v. 74, p. 991–1014.
Tysdal, R.G., 1996a, Geologic map of adjacent parts of the 

Hayden Creek and Mogg Mountain quadrangles, Lemhi 

County, Idaho: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–2563, scale 1:24,000.

Tysdal, R.G., 1996b, Geologic map of the Lem Peak quadrangle, Lemhi County, Idaho: U.S. Geological Survey 

Geologic Quadrangle Map GQ–1777, scale 1:24,000.

Tysdal, R.G., 2000a, Stratigraphy and sedimentology of 

Middle Proterozoic rocks in northern part of Lemhi Range, 

Lemhi County, Idaho: U.S. Geological Survey Professional 

Paper 1600, 40 p.

Tysdal, R.G., 2000b, Revision of Middle Proterozoic Yellowjacket Formation, central Idaho: U.S. Geological Survey 

Professional Paper 1601–A, 13 p.

Tysdal, R.G., 2002, Structural geology of western part of 

Lemhi Range, east-central Idaho: U.S. Geological Survey 

Professional Paper 1659, 33 p.

Tysdal, R.G., and Desborough, G.A., 1997, Scapolitic metaevaporite and carbonate rocks of Proterozoic Yellowjacket 

Formation, Moyer Creek, Salmon River Mountains, central 

Idaho: U.S. Geological Survey Open-File Report 97-268, 

26 p.

Tysdal, R.G., and Moye, Falma, 1996, Geologic map of the 

Allison Creek quadrangle, Lemhi County, Idaho: U.S. Geological Survey Geologic Quadrangle Map GQ–1778, scale 

1:24,000.

Tysdal, R.G., Lund, Karen, and Evans, K.V., 2003, Geologic 

map of the west half of the Salmon National Forest, in

Evans, K.V., and Green, G.N., compilers, Geologic map of 

the Salmon National Forest and vicinity, east central Idaho: 

U.S. Geological Survey Miscellaneous Investigations Map 

I–2765.

Umpleby, J.B., 1913, Geology and ore deposits of Lemhi 

County, Idaho: U.S. Geological Survey Bulletin 528, 182 p.

U.S. Environmental Protection Agency, 2001, 40 CFR Parts 9, 

141 and 142—National primary drinking water regulations; 

Arsenic and clarifications to compliance and new source 

contaminants monitoring: Federal Register, v. 66, no. 14 

[Monday, January 22, 2001], p. 6976–7066.

U.S. Environmental Protection Agency, 2002, National recommended water quality criteria—2002: U.S. Environmental 

Protection Agency Report EPA-822-R-02-047, 33 p.

Vanderwilt, J.W., 1947, Mineral resources of Colorado: Mineral Resource Board, Colorado Geological Survey, 547 p.

Van Gosen, B.S., Eppinger, R.G., Hammarstrom, J.M., Briggs, 

P.H., Crock, J.G., Gent, Carol, Meier, A.L., Sutley, S.J., and 

Theodorakos, P.M., 2000, Analytical data for reconnaissance geochemical samples from mine dumps, stream sediments, and waters at the Thompson Creek tungsten mine, 

Custer County, Montana: U.S. Geological Survey OpenFile Report 00-0239, 28 p. of text, 5 data files. Available at 

URL http://pubs.usgs.gov/of/2000/ofr-00-0239/. 

Van Gosen, B.S., Wilson, A.B., Hammarstrom, J.M., and 

Kulik, D.M., 1996, Mineral resource assessment of the 

Custer National Forest in the Pryor Mountains, Carbon 

County, south-central Montana: U.S. Geological Survey 

Open-File Report 96-256, scale 1:126,720.

Vhay, J.S., 1948, Cobalt-copper deposits of the Blackbird 

district, Lemhi County, Idaho: U.S. Geological Survey 

Strategic Minerals Investigation Preliminary Report 3-219, 

26 p.

Vuke, S.M., Berg, R.B., Lonn, J.D., and Kellogg, K.S., 1995, 

Geologic map of the Bozeman 30’×60’ quadrangle, Montana: Montana Bureau of Mines and Geology Open-File 

Report MBMG 334, scale 1:100,000.

Welsch, E.P., Crock, J.G., and Sanzolone, Richard, 1990, 

Trace-level determination of arsenic and selenium using 

continuous-flow hydride generation atomic absorption spectrophotometry, in Arbogast, B.F., Quality assurance manual 

for the Branch of Geochemistry: U.S. Geological Survey 

Open-File Report 90-668, p. 38–45.

Wilson, A.B., and Elliott, J.E., 1997, Geologic maps of 

western and northern parts of Gallatin National Forest, 

south-central Montana: U.S. Geological Survey Geologic 

Investigation Series I–2584, scale 1:126,720.

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 Series Map I–2395, scale 1:250,000.

Winston, D., and Link, P.K., 1993, Middle Proterozoic rocks 

of Montana, Idaho, and eastern Washington—The Belt 

Supergroup, in Reed, J.C., Jr., Bickford, M.E., Houston, R.S., Link, P.K., Rankin, D.W., Sims, P.K., and Van 

Schmus, W.R., eds., Decade of North American geology, 

Precambrian—Conterminous U.S.: Geological Society 

of America, The Geology of North America, v. C–2, p. 

487–517.

Woakes, M., 1960, Potassium-argon dates on the mineralization at Butte, Montana: Berkeley, Calif., University of 

California M.S. thesis, 42 p.

References Cited 91
92 Earth Science Studies—Headwaters Province, Idaho and Montana

Worl, R.G., and Johnson, K.M., 1995, Map showing geologic 

terranes of the Hailey 1°×2° quadrangle and the western part 

of the Idaho Falls 1°×2° quadrangle, south-central Idaho: U.S. 

Geological Survey Bulletin 2064–A, plate 1, scale 1:250,000.

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

1989, Mineral resource potential and geology of the Challis 

National Forest, Idaho: U.S. Geological Survey Bulletin 

1873, 101 p., 4 plates.

Young, G.M., 1995, Are Neoproterozoic glacial deposits preserved on the margins of Laurentia related to the fragmentation of two supercontinents?: Geology, v. 23, p. 153–156.

Zen, E-an, Marvin, R.F., and Mehnert, H.H., 1975, Preliminary petrographic, chemical, and age data, on some intrusive and associated contact metamorphic rocks, Pioneer 

Mountains, southwestern Montana: Geological Society of 

America Bulletin, v. 86, p. 367–370.
Lund, ed.—Earth Science Studies—Headwaters Province, Idaho and Montana—U.S. Geological Survey Circular 1305