Mineral Resources of the Upper West 

Little Owyhee Wilderness Study Area, 

Malheur County, Oregon

U.S. GEOLOGICAL SURVEY BULLETIN 1719-H
AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY

Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications 

that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and 

Availability List" are no longer available.

Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated monthly, which is for sale in microfiche from the U.S. Geological Survey, Books and Open-File Reports Section, Federal Center, Box 

25425, Denver, CO 80225. Reports released through the NTIS may be obtained by writing to the National Technical Information 

Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry.

Order U.S. Geological Survey publications by mail or over the counter from the offices given below.

BY MAIL 

Books

Professional Papers, Bulletins, Water-Supply Papers, Techniques 

of Water-Resources Investigations, Circulars, publications of general interest (such as leaflets, pamphlets, booklets), single copies of Earthquakes 

& Volcanoes, Preliminary Determination of Epicenters, and some miscellaneous reports, including some of the foregoing series that have gone 

out of print at the Superintendent of Documents, are obtainable by mail 

from

U.S. Geological Survey, Books and Open-File Reports

Federal Center, Box 25425

Denver, CO 80225

Subscriptions to periodicals (Earthquakes & Volcanoes and 

Preliminary Determination of Epicenters) can be obtained ONLY from 

the

Superintendent of Documents

Government Printing Office

Washington, D.C. 20402

(Check or money order must be payable to Superintendent of Documents.)

Maps

For maps, address mail orders to

U.S. Geological Survey, Map Distribution

Federal Center, Box 25286

Denver, CO 80225

Residents of Alaska may order maps from

Alaska Distribution Section, U.S. Geological Survey,

New Federal Building - Box 12 

101 Twelfth Ave., Fairbanks, AK 99701

OVER THE COUNTER 

Books

Books of the U.S. Geological Survey are available over the 

counter at the following Geological Survey Public Inquiries Offices, all 

of which are authorized agents of the Superintendent of Documents:

WASHINGTON, D.C.-Main Interior Bldg., 2600 corridor, 

18th and CSts.,NW.

DENVER, Colorado-Federal Bldg., Rm. 169, 1961 Stout St. 

LOS ANGELES, California-Federal Bldg.. Rm. 7638, 300 N. 

Los Angeles St.

MENLO PARK, California-Bldg. 3 (Stop 533), Rm. 3128, 

345 Middlefield Rd.

RESTON, Virginia-503 National Center, Rm. 1C402,12201 

Sunrise Valley Dr.

SALT LAKE CITY, Utah-Federal Bldg., Rm. 8105,125 

South State St.

SAN FRANCISCO, California-Customhouse, Rm. 504, 555 

Battery St.

SPOKANE, Washington-U.S. Courthouse, Rm. 678, West 

920 Riverside Ave..

ANCHORAGE, Alaska-Rm. 101,4230 University Dr. 

ANCHORAGE, Alaska-Federal Bldg, Rm. E-146, 701 C St.

Maps

Maps may be purchased over the counter at the U.S. Geological Survey offices where books are sold (all addresses in above list) and 

at the following Geological Survey offices:

 ROLLA, Missouri-1400 Independence Rd.

 DENVER, Colorado-Map Distribution, Bldg. 810, Federal 

Center

 FAIRBANKS, Alaska-New Federal Bldg., 101 Twelfth Ave.
Chapter H

Mineral Resources of the Upper West 

Little Owyhee Wilderness Study Area, 

Malheur County, Oregon

By JAMES G. EVANS, ROBERT L. TURNER, DONALD PLOUFF, 

and DON L. SAWATZKY 

U.S. Geological Survey

J. MITCHELL LINNE 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1 719

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

OWYHEE RIVER REGION, IDAHO AND NEVADA
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade names and trademarks 

in this publication is for descriptive 

purposes only and does not constitute 

endorsement by the U.S. Geological Survey

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center, Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Mineral resources of the Upper West Little Owyhee 

Wilderness Study Area, Maiheur County, Oregon

(U.S. Geological Survey Bulletin ; 1719-H)

Bibliography: p.

Supt. of Docs. no. : I 19.3:1719-H

1. Mines and mineral resources Oregon Upper West 

Little Owyhee Wilderness. 2. Upper West Little Owyhee 

Wilderness (Or.) I. Evans, James George, 1938- 

II. Series

QE75.B9 no. 1719-H 557.3 s 88-600061 

[TN24.07] [553'.095'97]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Area

The Federal Land Policy and Management Act (Public Law 94-579, October 21,1976) requires the U.S. 

Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine the 

mineral values, if any, that may be present. Results must be made available to the public and be submitted to 

the President and the Congress. This report presents the results of a mineral survey of the Upper West Little 

Owyhee Wilderness Study Area (OR-003-173), Malheur County, Oregon.

CONTENTS

Summary HI

Abstract 1

Character and setting 1

Identified mineral resources 1

Mineral resource potential 1 

Introduction 1

Area description 2

Previous and present investigations 3 

Appraisal of mineral resources 3

Mining history 3

Mineral resources 3 

Assessment of mineral resource potential 3

Geology 3

Geochemical studies 6

Geophysical studies 7

Mineral and energy resource potential 8 

References 8 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment 13

Resource/reserve classification 14

Geologic time chart 15

FIGURES

1. Index map showing location of Upper West Little Owyhee Wilderness Study Area, 

Malheur County, Oregon H2

2. Map showing mineral resource potential and generalized geology of the Upper West 

Little Owyhee Wilderness Study Area, Malheur County, Oregon 4

Contents V

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

OWYHEE RIVER REGION, IDAHO AND NEVADA

Mineral Resources of the Upper West 

Little Owyhee Wilderness Study Area, 

Malheur County, Oregon

By James G. Evans, Robert L. Turner, Donald Plouff, and Don L. Sawatzky 

U.S. Geological Survey

J. Mitchell Linne 

U.S. Bureau of Mines

SUMMARY

Abstract

At the request of the Bureau of Land Management, the Upper 

West Little Owyhee Wilderness Study Area and adjacent areas, 

totaling approximately 62,500 acres, were evaluated for mineral 

resources and mineral resource potential. Throughout this 

report, "wilderness study area" and "study area" refer to the 

62,500 acres for which mineral surveys were requested. The 

U.S. Geological Survey and the U.S. Bureau of Mines conducted 

geological, geophysical, and geochemical surveys to assess the 

identified mineral resources (known) and mineral resource 

potential (undiscovered) of the study area. Field work for this 

report was carried out in 1984 and 1985. No mines, significant 

prospects, or mining claims are located inside the study area, and 

no mineral resources were identified. The western part of the 

study area has low potential for mercury and the central part has 

low potential for mercury and silver. The entire study area has 

low potential for oil and gas. The study area has no potential for 

geothermal resources.

Character and Setting

The Upper West Little Owyhee Wilderness Study Area is 

located on the Owyhee Plateau, 12 mi northeast of McDermitt, 

Nevada (fig. 1). The area has a total relief of 1,450 ft and consists of broad flat areas and rolling hills cut by canyons incised 

to depths of 400 ft. The area is underlain by flat-lying volcanic, pyroclastic, and sedimentary rocks of middle Miocene

Publication authorized by the Director, U.S. Geological Survey, March 15,1988.

through Holocene age (fig. 2) (see appendixes for geologic 

time chart). The S wisher Mountain Tuff is the oldest and most 

abundant rock unit in the study area. Basalt overlies the 

S wisher Mountain Tuff and forms low, rounded buttes that are 

probably remnants of shield volcanoes. One steep, arcuate 

fault offsets basalt against Swisher Mountain Tuff in the 

northern part of the study area.

Identified Mineral Resources

No identified mineral resources were classified in the study 

area. Although zeolite of the heulandite group was found in a 

tuff bed, the volume of the tuff is too small for the occurrence 

to constitute an identified resource.

Mineral Resource Potential

The western part of the Upper West Little Owyhee Wilderness Study Area has low mineral resource potential for mercury (fig. 2). The central part of the study area has a low 

potential for silver and mercury resources. These metals are 

associated with zones of possible weak epithermal alteration 

on the west flank of the Horse Hill basalt vent and the east 

flank of the Summit 6518 basalt vent. The entire study area 

has low potential for oil and gas resources. The study area has 

no potential for geothermal resources.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau of 

Land Management and is a joint effort by the U.S. Geological

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H1
Survey and U.S. Bureau of Mines. An introduction to the 

wilderness review process, mineral survey methods, and agency responsibilities is provided by Beikman and others (1983). 

The U.S. Bureau of Mines (USBM) evaluates identified 

resources at individual mines and known mineralized areas by 

collecting data on current and past mining activities and 

through field examination of mines, prospects, claims, and 

mineralized areas. Identified resources are classified according to the system described by U.S. Bureau of Mines and U.S. 

Geological Survey (1980). Studies by the U.S. Geological Survey (USGS) are designed to provide a reasonable scientific 

basis for assessing the potential for undiscovered mineral 

resources by determining geologic units and structures, possible environments of mineral deposition, presence of 

geochemical and geophysical anomalies, and applicable oredeposit models. Mineral assessment methods and terminology as they apply to these surveys are discussed by Goudarzi 

(1984). See appendixes for definition of levels of mineral 

resource potential, certainty of assessment, and classification 

of identified resources.

Area Description

The Upper West Little Owyhee Wilderness Study Area 

(OR-003-173) covers approximately 62,500 acres along the 

West Little Owyhee River and Big Antelope Creek and adjacent parts of the Owyhee Plateau northeast of McDermitt, 

Nev. (fig. 1). Terrain in the study area is generally flat to gently rolling, rising gradually from approximately 5,600 ft in the 

north to more than 6,400 ft in the southwest corner and at 

Horse Hill, near the center of the study area. Canyons cut by

117°45' 117°30'

42° 15'

APPROXIMATE BOUNDARY

OF

UPPER WEST LITTLE OWYHEE 

WILDERNESS STUDY AREA

(OR-003-173) -N

APPROXIMATE^-, 

,\ey BOUNDARY

OWYHEECANYON / 

WILDERNESS 

STUDY AREA

'(6R~063-195/ > y I 

^ < 

I i Black Butte

Anderson Crossing

A avel road

Indian / Reservation

42°00' 

Figure 1. Index map showing location of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon. 

H2 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
the West Little Owyhee River and Big Antelope Creek are as 

much as 400 ft deep. The arid climate supports sagebrush, rabbit brush, and sparse native grasses. Stands of cottonwood, 

aspen, and willow occur below the canyon rims. The area is 

used for cattle grazing and also supports mule deer, pronghom 

antelope, and numerous species of birds, small mammals, and 

reptiles.

The study area is most easily accessible from Antelope Rat 

Road, which joins U.S. Highway 9515 mi north of McDermitt, 

Nev. (fig. 1). A branch of this road forms the north boundary 

of the study area and crosses the West Little Owyhee River at 

Anderson Crossing. Several jeep trails branch from this road 

to provide access to points in the study area. The southwestern 

part of the study area can also be reached by very rough jeep 

trails from McDermitt through the Fort McDermitt Indian 

Reservation.

Previous and Present Investigations

Reconnaissance geologic maps that include the study area 

were published by Walker and Repenning (1966) and by 

Walker (1977). Hart (1982), Hart and Aronson (1983), Hart 

and Mertzman (1983), Gray and others (1983), and Hart and 

others (1984) studied the stratigraphy and chemistry of volcanic rocks in southeastern Oregon and adjacent regions, including the Upper West Little Owyhee Wilderness Study 

Area.

The U.S. Geological Survey carried out field investigations 

in the study area during 1985. This work included geologic 

mapping at the scale of 1:24,000 and geochemical sampling. 

Rock samples were collected for petrographic analysis. 

Geochemical data were obtained from 66 stream sediment 

samples, 66 heavy-mineral concentrate samples, and 11 rock 

samples (R.L. Turner, unpub. data, 1987).

The U.S. Bureau of Mines examined Malheur County 

records and Bureau of Land Management master title plats and 

records for mining claims in the study area. Additional information was obtained from U.S. Bureau of Mines' library 

materials and production records. A field search was conducted in July 1986 for prospects or mineralized zones in or 

near the study area. Three alluvial samples, 7 rock samples, 

and 7 stream-sediment samples were collected and analyzed. 

The alluvial samples were scanned for heavy minerals. Six of 

the rock samples were analyzed for gold and silver by fire 

assay-atomic absorption spectroscopy, and 5 were analyzed 

for 23 elements by inductively coupled plasma spectroscopy 

(ICP). One rock sample was analyzed for 26 elements by 

neutron activation. One rock sample was analyzed for zeolites 

by X-ray diffraction. Stream-sediment samples were analyzed for 30 elements by ICP and for gold by fire assay-atomic 

absorption spectroscopy. All samples were checked for radioactivity and fluorescence. Sample analyses are on file at the 

U.S. Bureau of Mines, Western Field Operations Center, E. 

360 Third Ave., Spokane, WA 99202.

APPRAISAL OF MINERAL RESOURCES

By\. Mitchell Linne 

U.S. Bureau of Mines

Mining History

No history of mining or prospecting is known within or near 

the study area. The closest mining activity is at the McDermitt 

caldera complex, 25 mi southwest of the study area.

Mineral Resources

No metallic mineral resources were identified in the study 

area. One stream-sediment sample and four basalt samples 

contained 0.2 ppm (parts per million) silver. No other geochemical anomalies were found. One sample of air-fall tuff 

contained 50 to 75 percent zeolite of the heulandite group. This 

sample was from a thin tuff layer exposed between basalt 

flows near the north boundary of the study area. Due to its 

small volume it is not classified as a mineral resource (Linne, 

1987). Basalt can be used for several commercial purposes, 

but it is not considered to have resource potential in the study 

area because it is common throughout the region and other 

sources occur closer to the sites of probable use.

In its draft Environmental Impact Statement on Oregon 

Wilderness, the U.S. Bureau of Land Management (1985) 

identified an area with medium potential (very low confidence 

level) for manganese on the south flank of Horse Hill. Because 

the area was designated as having potential, stream-sediment 

and rock samples from the area were collected and analyzed. 

No samples contained more than 1,500 ppm manganese, a concentration that is typical for basalt and does not indicate significant mineralization.

Sand and gravel deposits in the West Little Owyhee River, 

Jack Creek and Big Antelope Creek are not considered a 

resource because larger sand and gravel deposits in the region 

are more accessible.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By James G. Evans, Robert L. Turner, Donald Plouff, and

Don L. Sawatzky

U.S. Geological Survey

Geology

The Upper West Little Owyhee Wilderness Study Area is 

underlain chiefly by flat-lying Tertiary welded rhyolite tuff 

and basalt flows (fig. 2). The oldest rock unit in the study area 

is the S wisher Mountain Tuff (Ekren and others, 1984). In the 

study area, the S wisher Mountain Tuff is composed of black 

to dark-gray and purple, massive to laminated, vitrophyre

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H3
breccia containing fragments as much as 1 ft across, and 

devitrified welded tuff. These rocks are continuous with the 

welded ash-flow tuff unit described by Evans and others 

(1987) in the Owyhee Canyon Wilderness Study Area just 

north of Anderson Crossing (fig. 1) that is also considered to

be Swisher Mountain Tuff. In the study area, the Swisher 

Mountain Tuff contains as much as 55 percent angular to 

rounded phenocrysts and lithic fragments. Lithic fragments 

include vitrophyre, vitrophyre breccia, laminated welded tuff, 

and metabasalt and are as much as 0.3 in. across. Phenocrysts

117°30' 117°22f 30"

APPROXIMATE BOUNDARY

OF

IUPPER WEST LITTLE OWYHEE

WILDERNESS STUDY AREA

(OR-003-173)

L/B O,G (entire study area)

Summit 6518

Twin 

A Buttes

Figure 2. Mineral resource potential and generalized geology of the Upper West Little Owyhee Wilderness Study Area, Malheur 

County, Oregon.

H4 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
consist mostly of plagioclase (andesine), but also include 

lesser amounts of quartz, potassium feldspar (sanidine, perthite), clinopyroxene and orthopyroxene, magnetite, hematite, 

hornblende, and olivine that is partly altered to bowlingite. 

Phenocrysts and lithic fragments show features related to 

strain, including fractures, brecciation, and, in quartz 

phenocrysts, extinction shadows and deformation lamellae. 

Magnetite and hematite are minor constituents; the hematite 

is locally disseminated along lamellae and forms rims on magnetite and pyroxene grains. Devitrification has resulted in 

crystallization of quartz and feldspar in the matrix; microspherulites and perlitic cracks are abundant. Zeolites, chalcedony, epidote, chlorite, and carbonate are present in some 

of the rocks.

Minimum thickness of the Swisher Mountain Tuff in the 

study area is estimated at 400 ft; the maximum thickness is exposed in canyon walls along the Upper West Little Owyhee 

River. However, the base is not exposed and approximately 

1,000 ft of the formation is exposed north of the study area in 

the Owyhee Canyon Wilderness Study Area (Evans and 

others, 1987). Geophysical evidence in the region suggests 

that the Swisher Mountain Tuff was deposited as a result of 

caldera-forming eruptions in southwest Idaho.

Potassium-argon ages on samples of the Swisher Mountain 

Tuff are Middle Miocene, ranging from 12.5 to 14.6 Ma (million years before present) (Hart and Aronson, 1983; Neill, 

1975). A sample of the vitrophyre at Anderson Crossing gives 

a potassium-argon age of 13.58 ± 0.63 (whole rock) and 13.07 

± 0.59 Ma (glass) (Hart and Aronson, 1983).

EXPLANATION

Area of low mineral resource potential-See appendix for 

definition of levels of mineral resource potential (L) 

and certainty of assessment (B,C)

Commodities

Ag Silver

Hg Mercury

O,G Oil and gas

[1 ] Epithermal alteration

Geologic map units

Qal Alluvium (Quaternary)

QTs Tuffaceous sandstone (Quaternary or Tertiary)

Ts Siltstone (Pliocene or Miocene)

Tb Basalt (Pliocene or Miocene)

Tsm Swisher Mountain Tuff (middle Miocene)

 Contact

 Fault-Dotted where concealed

Figure 2. Continued.

Black to dark-gray basalt flows, showing crude columnar 

joints and platy fractures, unconformably overlie the Swisher 

Mountain Tuff. These flows are as much as 100 ft thick near 

Horse Hill and Summit 6518, west of the study area. Basalt 

flows in the study area are also described by Walker and 

Repenning (1966), Hart (1982), Hart and Mertzman (1982, 

1983), and Hart and others (1984). In the study area the basalt 

flows are generally massive, but locally exhibit flow brecciation and flow layering defined by arrays of phenocrysts. The 

flows are commonly diktytaxitic and contain as much as 15 

percent vesicles as much as 0.8 in. across that are partly to 

completely filled with white zeolites and calcite. The rock is 

aphyric to porphyritic with as much as 20 percent phenocrysts 

of plagioclase and olivine as much as 0.15 in. long. Some of 

the rock is glomeroporphyritic with clumps of plagioclase and 

olivine 0.4 in. across. Major constituents are plagioclase 

(labradorite, 40-55 percent), olivine (1-25 percent), and 

clinopyroxene (20-40 percent). Clinopyroxene is commonly 

ophitic. Ilmenite, magnetite, and hematite are minor constituents. Olivine is slightly altered to bowlingite and iddingsite along grain margins.

Regionally, basalt was extruded during three main pulses: 

7 to 10 Ma, 3.5 to 6 Ma, and 0 to 2.5 Ma (Hart, 1982; Hart and 

others, 1984). However, it is not clear which of the pulses 

created the Horse Hill and Summit 6518 basalt flows. North 

of the study area, basalt flows in the Owyhee Canyon Wilderness Study Area give ages ranging from 11.5 to 1.5 Ma (Hart, 

1982; Hart and Mertzman, 1983). A basalt flow at Anderson 

Crossing that was extruded from Black Butte, 4 mi northeast 

of the study area, was dated at 5.04 ± 0.81 Ma (Hart, 1982). 

The lack of well-preserved volcanic landforms in the study 

area suggests that the basalt flows are Pliocene or older. In 

this report the basalt of the study area is tentatively assigned a 

Miocene and (or) Pliocene age.

Light-brown, moderately well-lithified, conglomeratic 

siltstone, 50 ft thick or less, is interbedded with basalt at the 

north end of the study area. Siltstone, as thick as 100 ft, underlies the basalt at the south end of the study area. The siltstone 

contains 50 percent small (less than 0.12 in. diameter), angular 

to rounded clasts of massive and laminated densely welded 

tuff, basalt, metachert, and vitrophyre. Grains, as much as 

0.02 in. long, include tourmaline, magnetite that is partly altered to hematite, plagioclase, biotite that is partly altered to 

chlorite, clinopyroxene, and hornblende. Clear and brown 

glass shards are common.

A well-cemented conglomeratic tuffaceous sandstone is 

deposited over a fault that offsets basalt against Swisher 

Mountain Tuff at the north end of the study area. The 

sandstone contains conspicuous angular black basalt pebbles 

as much as 0.4 in. across in a matrix of sand, silt, and clay with 

silica cement. The matrix contains small clasts of basalt, 

siltstone containing diatom frustules, perlitic brown glass, 

clear glass shards, and devitrified welded tuff that are no more 

than 0.04 in. across. Some of the welded tuff clasts are altered

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H5
to zeolites on the margins. Grain fragments include quartz, 

olivine that is partly altered to bowlingite, plagioclase, 

zeolites, pyroxene, and hornblende. Total pyroclastic fraction 

of the sandstone is 45 percent. Age of the tuffaceous 

sandstone is clearly younger than the basalt and is therefore 

between late Miocene and Quaternary.

The metachert clasts in the siltstone suggest that, between 

episodes of basalt volcanism in the study area, the area was 

connected by through-going drainages to sources of 

metasedimentary rock outside of the Owyhee Plateau. Chert 

and quartzite clasts are common in stream gravels in the 

Owyhee River 22 mi northeast of the study area; sources of 

these clasts are most likely upstream in Idaho and Nevada. 

These sources may also have supplied sediments to the ancestral Owyhee River drainage during Miocene and (or) 

Pliocene time.

Holocene deposits include alluvium along parts of Big Antelope Creek, Jack Creek, and West Little Owyhee River and 

playa deposits on the basalt flows around Horse Hill.

An arcuate fault separates basalt flows and the Swisher 

Mountain Tuff at the north end of the study area. Stratigraphic 

separation could be as much as 140 ft at the north end of the 

fault, but probably is less than that because the base of the 

basalt flows slopes up eastward toward the Swisher Mountain 

Tuff. Walker and Repenning (1966) mapped several steep 

northeast-striking faults and one northwest-striking fault in the 

western part of the study area. These faults were not found by 

Evans (unpub. data, 1985).

Geochemical Studies

A reconnaissance geochemical survey was conducted in 

the Upper West Little Owyhee River Wilderness Study Area 

in the summer of 1986. Minus-80-mesh stream-sediment 

samples, nonmagnetic heavy-mineral concentrates derived 

from stream sediments, and rocks were selected as the sample 

media in this study. Samples of stream sediments and heavymineral concentrates were collected at 66 sites and 11 rock 

samples were collected at additional sites.

Stream-sediment samples were collected from active alluvium in stream channels. Each sample was collected from 

several localities along a channel length of approximately 50 

ft. Stream sediments represent a composite sample of the rock 

and soil exposed upstream from the sample site. The heavymineral concentrate represents a concentration of any oreforming and ore-related minerals present that permits 

determination of some elements that are not easily detected in 

bulk stream sediments.

Rocks were taken from mineralized and unmineralized outcrop and stream float. Samples that appeared fresh and unaltered were collected to provide information on geochemical 

background values. Altered or mineralized samples were collected to determine the suite of elements associated with the 

observed alteration or mineralization.

The heavy-mineral concentrates, stream sediments, and 

rocks were analyzed for 31 elements by direct-current arc, 

semiquantitative, emission spectrographic analysis (Grimes 

and Marranzino, 1968). Other elements were analyzed by 

atomic-absorption methods (antimony, arsenic, bismuth, cadmium, zinc) by the method described by O'Leary and Viets 

(1986), gold by the method described by Thompson and others 

(1968), and mercury by the method described by Koirtyohann 

and Khalil (1976). These analyses were used to identify 

drainages with anomalous concentrations of minor elements. 

Anomalous concentrations in stream sediment and rock 

samples were determined by comparing the analytical data 

with the average abundance for rock types in the drainages. 

Abundance data are from Rose and others (1979). Concentrations of at least twice the average abundance are defined as 

anomalous.

The heavy-mineral concentrates contained concentrations 

greater than 2,000 ppm (parts per million) of tin, the upper 

limit of detection. Greater than 2,000 ppm is considered 

anomalous in this study. The tin is most likely derived from 

the Swisher Mountain Tuff. Tin at this concentration in this 

sample medium is most likely contained in the mineral cassiterite, but cassiterite was not visually identified in the 

samples. Tin was not detected in the -80-mesh stream-sediment samples. Tin in heavy-mineral concentrates occurs in 

amounts that are large relative to the crustal abundance of tin 

(Sainsbury and Reed, 1973), but not unusual for concentrations from ordinary silicic volcanic rock sources. Anomalous 

concentrations of tin were found in scattered drainages, some 

of which are underlain exclusively by the Swisher Mountain 

Tuff, a likely source rock. Tin anomalies in drainages underlain mostly by basalt may result from eolian material blown in 

from the broad expanses of the Swisher Mountain Tuff that 

surround the basalt, or the anomalous tin could have been 

transported from the vitrophyre into the basalt by hydrothermal activity.

The stream-sediment samples delineate a zone of somewhat anomalous mercury concentrations (0.08 to 0.34 ppm) 

and arsenic concentrations (10 to 20 ppm) on the west side of 

the study area (fig. 2). The zone encompasses the west flank 

of the Horse Hill basalt vent and may have undergone weak 

epithermal alteration related to basalt volcanism at Horse Hill. 

The southwestern part of the anomaly may be due to weak 

epithermal alteration associated with the basalt vent at Summit 6518. Some rock samples from the western part of the 

study area contain relatively high and somewhat anomalous 

amounts of arsenic (to 10 ppm), cadmium (1.6 to 2.3 ppm), 

antimony (3 to 5 ppm), and mercury (to 0.09 pm).

An area of anomalous bismuth (2 to 4 ppm in stream sediment, 30 ppm in panned concentrate) is located in the southeastern part of the study area. Drainages in and near the area 

have anomalous concentrations of arsenic (13-18 ppm) and

H6 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
molybdenum (5 ppm). This area is underlain largely, but not 

exclusively, by the Swisher Mountain Tuff. The area may be 

a product of weak epithermal alteration associated with the 

Twin Butte basalt vent 1 mi southeast of the study area.

Low concentrations of silver (0.2 ppm) were found in basalt 

in a small area on the south flank of Horse Hill by the U.S. 

Bureau of Mines (Linne, 1987). This concentration of silver 

is twice the average abundance in basalt (Vinogradov, 1962) 

and is considered anomalous in this report. Analysis of the 

USGS stream-sediment sample of the area did not detect silver because the lower limit of detection is 0.5 ppm.

The concentrations of arsenic, bismuth, cadmium, antimony, mercury, molybdenum, and silver cited above are 

anomalous for the Swisher Mountain Tuff and basalt flows, 

but are not much higher than crustal abundances for these elements (antimony, Miller, 1973; arsenic, Gualtieri, 1973; bismuth, Hasler and others, 1973; cadmium, Wedow, 1973; 

mercury, Bailey and others, 1973; molybdenum, King and 

others, 1973; silver, Vinogradov, 1962).

The arsenic-mercury-antimony-silver element suite found 

in the western part of the study area suggests the occurrence 

of weak epithermal alteration processes, although broad zones 

of epithermally altered rocks were not found during this study. 

Devitrification and perlitification, common in many ash-flow 

tuffs, is widespread in the Swisher Mountain Tuff. These 

processes and vapor-phase recry stallization may have released 

minor elements for redistribution by weak hydrothermal systems that could have resulted from cooling of the welded tuff 

or from basalt volcanism at Horse Hill, Summit 6518, and 

Twin Buttes.

The anomalies reported by Gray and others (1983) and by 

Bukofski and others (1984) were not confirmed by this study 

at current U.S. Geological Survey levels of detection. The 

concentrations they report as anomalous for beryllium, copper, gold, manganese, nickel, silver, tungsten, uranium, and 

zinc are low and generally approximate crustal abundance. 

Their data suggest that most of the rocks of the study area have 

lower than average concentrations of these elements for the 

rock types present. If their data are indeed anomalous, they 

are largely consistent with a model of weak alteration associated with the basalt vents of the study area and vicinity.

Geophysical Studies

Gravity, aeromagnetic, aerial gamma-ray, and remote sensing studies were undertaken as part of the mineral resource 

evaluation of the study area. The geophysical data provide information on subsurface distribution of rock masses and the 

structural framework.

Aerial gamma-ray data were compiled by Geodata International, Inc. (1980) for the National Uranium Resource Evaluation (NURE) program of the Department of Energy. The 

coverage consists of five east-west flightlines at 3-mi intervals

and one north-south flightline. The flightlines total about 43 

mi in length. Flight altitudes ranged from 250 to 600 ft above 

the ground. Recordings were made of gamma-ray flux from 

radioactive isotopes of uranium, thorium, and potassium. 

Count rates show a strong correlation with the geology 

mapped by Walker and Repenning (1966). Count rates for all 

three isotopes were low over basalt flows and moderately high 

over rocks mapped as welded tuff, rhyolite flows, and dacite 

flows, with abrupt changes where the basalt is in contact with 

the other rock units. No site within the study area had count 

rates above the regional background level. Although no lines 

were flown over the basalt vent at Horse Hill, count rates for 

the vent area are expected to be low because basalt elsewhere 

in the area showed low counts.

A regional aeromagnetic survey was flown over the study 

area at a constant barometric elevation of 9,000 ft above sea 

level and a flightline spacing of 2 mi (U.S. Geological Survey, 

1972). The low intensities of magnetic anomalies reflect a 

combination of low rock magnetization in the study area and 

high flight altitudes, averaging about 3,000 ft above the 

ground. The most conspicuous magnetic anomaly is a northwest-trending magnetic ridge along a line between Horse Hill 

and Twin Butte, 1 mi southeast of the study area. A local high 

is centered at the mafic vent at Twin Butte. A crest along the 

magnetic ridge is centered about 4 mi northwest of the vent at 

Horse Hill. Another magnetic ridge extends northeastward 

from Horse Hill. The complex magnetic highs may reflect 

apices of concealed Cenozoic intrusions. A northwest-trending magnetic trough includes local lows centered near the 

southwest and southeast corners of the study area. The magnetic lows may reflect underlying rocks with reversed magnetization, or rocks of low magnetization between rocks of 

higher magnetization.

The U.S. Geological Survey established 34 gravity stations 

within 3 mi of the border of the study area in 1986 (Plouff, 

1987). These data were supplemented by data at three stations 

obtained from the National Geophysical Data Center (1984). 

Only two stations are located in the study area, and no stations 

are located along the west edge of the study area. A preliminary gravity map prepared from these widely spaced stations 

shows east-trending gravity contours that decrease southward 

about 13 milligals in 8 mi across the southern half of the study 

area and a small gravity high centered about 2 mi east and 4 

mi south of the northern tip of the study area. A poorly defined 

gravity low near the southwest corner of the study area may 

coincide with the source of a magnetic low.

Linear features in Landsat multispectral scanner (MS S) images at the scale of 1:800,000 were mapped by photogeologic 

means for southeastern Oregon, and trend-concentration maps 

were made. Linear features are the topographic and spectral 

expression of rock fracture patterns and other structural and 

lithologic lineaments. This expression can be enhanced or 

subdued by scanner resolution, sun orientation, atmospheric 

phenomena, and vegetation. Analyses of linear features in

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H7
conjunction with geologic and geophysical maps may reveal 

relations such as fracture control of mineralized areas.

Linear features of many orientations are generally well expressed on the surface in southeastern Oregon in terrains not 

underlain by volcanic rocks. Some areas have joint systems 

that are locally related to faults. Trend-concentration maps indicate that no concentration of linear features is expressed at 

the surface of the study area because the area is underlain by 

volcanic rocks. Two major concentrations lie to the northwest 

and southeast of the study area and consist of north-northeasttrending linear features with azimuths in the range N. 5 e-35e 

E.

Mineral and Energy Resource Potential

Geologic and geochemical data indicate that the Upper 

West Little Owyhee Wilderness Study Area has low resource 

potential for mercury and silver-mercury deposits with a C certainty level. The resource potential for petroleum and natural 

gas is low with a B certainty level.

The investigations by the U.S. Geological Survey indicate 

that there is low mineral resource potential for mercury in the 

western part of the study area (fig. 2). This potential is indicated by somewhat anomalous concentrations of mercury, arsenic, cadmium, and antimony. A certainty level of C is 

assigned because the highest concentrations of mercury in 

stream-sediment and rock samples are not much greater than 

occur in ordinary volcanic rocks (Bailey, 1973), and no zones 

of altered rock were found in the well-exposed formations in 

the study area.

A low mineral resource potential for silver and mercury occurs in a small area in the central part of the study area on the 

south flank of Horse Hill. The low potential is indicated by the 

previously mentioned geochemical anomalies and by the 

slightly anomalous silver concentrations reported by Gray and 

others (1983) and Bukofski and others (1984). A certainty 

level of C is assigned because the highest concentrations of 

both metals are only slightly above their crustal abundances, 

the area of the anomaly is small (1.5 mi ), and no zones of 

visibly altered rock were found.

Slightly anomalous concentrations of antimony, arsenic, 

bismuth, cadmium, and molybdenum in stream-sediment and 

rock samples may indicate weak epithermal alteration and 

possible mineralization. These elements can be indicative of 

gold, silver, and other metal deposits, but by themselves do 

not constitute potential resources.

Anomalous concentrations of tin (greater than 2,000 ppm) 

in panned concentrates occur in a few scattered drainages in 

amounts typical of silicic volcanic rocks such as the Swisher 

Mountain Tuff. Some of the tin is from drainages underlain 

by the Swisher Mountain Tuff. Tin also occurs in drainages 

largely underlain by basalt. In these areas the tin may have 

been hydrothermally redistributed from the Swisher Mountain 

Tuff or brought into the drainages in eolian deposits. The

study area is judged to contain no potential for tin resources, 

certainty level D.

Wells were drilled for oil and gas 95 mi northeast of the 

study area in the western Snake River basin of Oregon and 

Idaho. Study of these wells and the regional geology led Newton and Corcoran (1963) to conclude that the depositional environments of the Snake River basin resemble other 

nonmarine basins that produce oil and gas and that hydrocarbons formed there during the late Miocene and early Pliocene. 

Late Miocene and early Pliocene time in the study area, 

however, was characterized by volcanism. Warner (1980) 

suggested that southeastern Oregon is underlain by Mesozoic 

and Tertiary rocks that contain potential source material for 

petroleum. However, pre-Tertiary rocks exposed in the region 

at South Mountain in Idaho and the Pueblo Mountains in 

Nevada and Oregon are metasedimentary and metavolcanic 

rocks that would not be good potential petroleum sources. 

During this study no surficial evidence was found that indicates the presence of hydrocarbons at depth. Any potential 

hydrocarbon reservoirs that might be present beneath the 

Swisher Mountain Tuff probably would have to be located by 

seismic surveys. Although it is likely that heat from volcanism 

in the area would have driven off any hydrocarbons, hydrocarbon concentrations below the Swisher Mountain Tuff cannot 

be ruled out. Fouch (1983) estimated the oil and gas potential 

of the study area to be low. Available geological and geophysical information indicates that the likelihood for occurrence of oil and gas within the study area is remote; for the 

purpose of this study the resource potential for oil and gas is 

considered low, certainty level B, for the entire study area.

No geothermal resources were found in or adjacent to the 

study area. The study area lies between areas of warm springs 

in the Owyhee Canyon near Three Forks, 26 mi northeast 

(Evans and others, 1987), and near McDermitt, 12 mi to the 

southwest (Muffler, 1978). Although the study area is in a 

region characterized by young silicic volcanic rocks, some 

parts of which offer likely geologic settings for magmatic heat 

reservoirs (MacLeod and others, 1976), the magma source of 

the Swisher Mountain Tuff is possibly in Idaho 35 mi northeast of the study area (Evans and others, 1987). The Swisher 

Mountain Tuff is of middle Miocene age and has probably 

cooled to ambient temperatures. The warm springs near Three 

Forks may be a result of young basalt volcanism. The study 

area, however, lacks extensive late Tertiary to Quaternary volcanism. The small basalt vents in and adjacent to the study 

area (Horse Hill, Summit 6518, Twin Buttes) have most likely cooled to ambient temperatures since Late Miocene to Early 

Pliocene. Therefore, there is no potential for geothermal 

resources in the study area with a certainty of D.

REFERENCES CITED

Bailey, E.H., Clark, A.L., and Smith, R.M., 1973, Mercury, fnBrobst, 

D.A., and Pratt, W.P., eds., United States mineral resources: 

U.S. Geological Survey Professional Paper 820, p. 401-414.

H8 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
Beikman, H.M., Hinkel, M.E., Frieders, Twila, Marcus, S.M., and 

Edward, J.R., 1983, Mineral surveys by the Geological Survey 

and Bureau of Mines of Bureau of Land Management wilderness study areas: U.S. Geological Survey Circular 901, 28 p.

Bukofski, J.F., Lovell, J.S., and Meyer, W.I., 1984, Mineral resource 

assessment through geochemical studies of heavy mineral concentrates from wilderness study areas in the Burns, Prineville, 

and Vale districts, southeastern Oregon: Barringer Resources, 

Inc., prepared for U.S. Department of the Interior, Bureau of 

Land Management, Oregon State Office, Portland, 94 p.

Eckren, E.B., Mclntyre, D.H., and Bennett, E.H., 1984, Hightemperature, large-volume, lav alike ash-flow tuffs without 

calderas in southwestern Idaho: U.S. Geological Survey Professional Paper 1272,76 p.

Evans, J.G., 1987, Geologic map of the Owyhee Canyon Wilderness 

Study Area: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1926, scale 1:62,500.

Evans, J.G., Hoffman, J.D., and Kulik, D.M., 1987, Mineral resources of the Owyhee Canyon Wilderness Study Area, Malheur 

County, Oregon: U.S. Geological Survey Bulletin 1719-E, 11

PFouch, T.D., 1983, Petroleum potential of wilderness lands in 

Oregon: U.S. Geological Survey Circular 902-J, 5 p.

Geodata International, Inc., 1980, Aerial radiometric and magnetic 

survey, National Topographic Map, Jordan Valley, Oregon, 

Idaho: U.S. Department of Energy Open-File Report GJBX95(80), v. 2, 205 p.

Goudarzi, G.H., 1984, Guide to preparation of mineral reports on 

public lands: U.S. Geological Survey Open-File Report 84- 

787, 51 p.

Gray, J.J., Peterson, N.N., Clayton, Janine, and Baxter, Gary, 1983, 

Geology and mineral resources of 18 BLM wilderness study 

areas, Harney and Malheur Counties, Oregon: Oregon Department of Geology and Mineral Resources Open-File Report 0- 

83-2,106 p.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc and alternating current spark emission spectrographic field methods 

for the semiquantitative analysis of geologic materials: U.S. 

Geological Survey Circular 591, 6 p.

Gualtieri, J.L., 1973, Arsenic, in Brobst, D.A., and Pratt, W.P., eds., 

United States mineral resources: U.S. Geological Survey 

Professional Paper 820, p. 51-61.

Hart, W.K., 1982, Chemical, geochronologic, and isotopic significance of low-K, high-alumina olivine tholeiite in the northwestern Great Basin, U.S.A.: Cleveland, Ohio, Case Western 

Reserve University Ph.D. dissertation, 410 p.

Hart, W.K. and Aronson, J.L., 1983, K-Ar ages of rhyolites from the 

western Snake River Plain area, Oregon, Idaho, and Nevada: 

Isochron/West, no. 36, p. 17-19.

Hart, W.K., Aronson, J.L., and Mertzman, S.A., 1984, Areal distribution and age of low-K, high alumina olivine tholeiite magmatism 

in the northwestern Great Basin: Geological Society of America 

Bulletin, v. 95, no. 2, p. 186-195.

Hart, W.K. and Mertzman, S.A., 1982, K-Ar ages of basalts from 

south-central and southeastern Oregon: Isochron/West, no. 33, 

p. 23-26.

 1983, Late Cenozoic volcanic stratigraphy of the Jordan Valley area, southeastern Oregon: Oregon Geology, v. 45, no. 2, p. 

15-19.

Hasler, J.W., Miller, M.H., and Chapman, R.M., 1973, Bismuth, in

Brobst, D.A., and Pratt, W.P., eds., United States mineral resources: U.S. Geological Survey Professional Paper 820, p. 581- 

603.

King, R.U., Shawe, D.R., and MacKevett, E.M., Jr., 1973, Molybdenum, in Brobst, D.A., and Pratt, W.P., eds., United States 

mineral resources: U.S. Geological Survey Professional Paper 

820, p. 425^35.

Koirtyohann, S.R., andKhalil, Moheb, 1976, Variables in determination of mercury by cold vapor atomic absorption: Analytical 

Chemistry, 48, p. 136-139.

Linne, J.M., 1987, Mineral resources of the Upper West Little 

Owyhee Wilderness Study Area, Malheur County, Oregon: 

U.S. Bureau of Mines Open-File Report MLA-^0-87, 10 p.

MacLeod, N.S., Walker, G.O., and McKee, E.H., 1976, Geothermal 

significance of eastward increase in age of Upper Cenozoic 

rhyolitic domes in southwestern Oregon, in Proceedings Second 

United Nations Symposium on the development and use of 

geothermal resources, v. 1: Washington, U.S. Government 

Printing Office, p. 465^76.

Miller, M.H., 1973, Antimony, in Brobst, D.A., and Pratt, W.P., eds., 

United States mineral resources: U.S. Geological Survey 

Professional Paper 820, p. 45-50.

Muffler, L. J.P., ed., 1978, Assessment of geothermal resources of the 

United States 1978: U.S. Geological Survey Circular 790, 

163 p.

National Geophysical Data Center, 1984, DMA gravity file of the 

U.S.: National Oceanic and Atmospheric Administration, 

Boulder, Colo., 2 magnetic tapes.

Neill, W.M., 1975, Geology of the Southeastern Owyhee Mountains 

and environs, Owyhee County, Idaho: Stanford, Calif. Stanford 

University, M.S. thesis, 59 p.

Newton, V.C., and Corcoran, R.E., 1963, Petroleum geology of the 

western Snake River B asin, Oregon-Idaho: Oregon Department 

of Geology and Mineral Industries Oil and Gas Investigations, 

no. 1, 67 p.

O'Leary, R.M., and Viets, J.G., 1986, Determination of antimony, arsenic, bismuth, cadmium, copper, lead, molybdenum, silver, and 

zinc in geologic materials by atomic absorption spectrometry 

using a hydrochloric acid-hydrogen peroxide digestion: Atomic 

Spectroscopy, 7, p. 4-8.

Plouff, Donald, 1987, Gravity observations by the U.S. Geological 

Survey in northwest Nevada, southeast Oregon, and northeast 

California, 1984-1986: U.S. Geological Survey Open-File 

Report 87-639,33 p.

Rose, A.R., Hawkes, H.E., and Webb, J.S., 1979, Geochemistry in 

mineral exploration: New York, Academy Press, 657 p.

Sainsbury, C.L., and Reed, B .L., 1973, Tin, mBrobst, D.A., and Pratt, 

W.P., eds., United States mineral resources: U.S. Geological 

Survey Professional Paper 820, p. 637-651.

Thompson, C.E., Nakagawa, H.M., and Van Sickle, G.H., 1968, 

Rapid analysis for gold in geologic materials, in Geological Survey Research 1968: U.S. Geological Survey Professional Paper 

600B,p.B130-B132.

U.S. Bureau of Land Management, 1985, Oregon wilderness draft 

environmental impact statement, v. 4, 360 p.

U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles 

of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, 5 p.

U.S. Geological Survey, 1972, Aeromagnetic map of the Adel and 

parts of theBurns, Boise, and Jordan Valley 1° x 2° quadrangles,

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H9
Oregon: U.S. Geological Survey Open-File Report 72-390, 

scale 1:250,000.

Vinogradov, A.P., 1962, Average contents of chemical elements in 

the principal types of igneous rocks of the Earth's crust: 

Geochemistry, no. 7, p. 641-664.

Walker, G.W., 1977, Geologic map of Oregon east of the 121st 

meridian: U.S. Geological Survey Miscellaneous Investigations Series Map 1-902, scale 1:500,000.

Walker, G.W., and Repenning, C.A., 1966, Reconnaissance geologic map of the west half of the Jordan Valley quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous

Investigations Series Map 1-457, scale 1:250,000. 

Warner, M.M., 1980, Southern Idaho, northern Nevada, southeastern

Oregon a prime regional target for petroleum exploration:

Wyoming Geological Association Earth Science Bulletin, v. 13,

no. 1, p. 19^0. 

Wedow, Helmuth, Jr., 1973, Cadmium, in Brobst, D.A., and Pratt,

W.P., eds., United States mineral resources: U.S. Geological

Survey Professional Paper 820, p. 103-109.

H10 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
APPENDIXES
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

LEVELS OF RESOURCE POTENTIAL

H HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data 

indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit models 

indicating presence of resources, and where evidence indicates that mineral concentration has taken place. 

Assignment of high resource potential to an area requires some positive knowledge that mineral-forming processes 

have been active in at least part of the area.

M MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data 

indicate reasonable likelihood for resource accumulation, and (or) where an application of mineral-deposit models 

indicates favorable ground for the specified type(s) of deposits.

L LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics 

define a geologic environment in which the existence of resources is permissive. This broad category embraces 

areas with dispersed but insignificantly mineralized rock, as well as areas with little or no indication of having 

been mineralized.

N NO mineral resource potential is a category reserved for a specific type of resource in a well-defined area.

U UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign a low, 

moderate, or high level of resource potential.

LEVELS OF CERTAINTY

A Available information is not adequate for determination of the level of mineral resource potential.

B Available information only suggests the level of mineral resource potential.

C Available information gives a good indication of the level of mineral resource potential.

D Available information clearly defines the level of mineral resource potential.

IZ

LJJ

oQ_ 

LLJ 

U

ex. 

D 

OCO

LJJ 

CX.

§

A

U/A

UN KNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

L/C

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

Taylor, R.B., and Steven, T.A., 1983, Definition of mineral resource potential: Economic Geology, v. 78, no. 6, p. 1268-1270.

Taylor, R.B., Stoneman, R.J., and Marsh, S.P., 1984, An assessment of the mineral resource potential of the San Isabel National Forest, south-central Colorado: U.S.

Geological Survey Bulletin 1638, p. 40-42. 

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-0787, p. 7, 8.

H12 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

;rves

I 

Marginal 

Reserves

I

i 

Demonstrated

Subeconomic

Resources

i

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

I

I

I

I

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from McKelvey, V.E., 1972, Mineral 

resource estimates and public policy: American Scientist, v. 60, p. 32-40; and U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles 

of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, p. 5.

Mineral Resources of Upper West Little Owyhee Wilderness Study Area, Malheur County, Oregon H13
GEOLOGIC TIME CHART

Terms and boundary ages used by the U.S. Geological Survey in this report

EON

Phanerozoic

Proterozoic

Archean

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

 

PERIOD

Quaternary

Neogene 

Subperiod

Tertiary . 

Paleogene

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

/3flnn?t

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

pre-Archean2

ACE ESTIMATES OF 

BOUNDARIES (in Ma)

0.010

 1.7

5

1 A

T Q

55

 66

1 1O

205

^-940

 290

-,'}'}(}

ifr\

 410

A 1 C*

_Jv/w

 1600

 3400

'Rocks older than 570 Ma also called Precambrian, a time term without specific rank, 

informal time term without specific rank.

H14 Mineral Resources of Wilderness Study Areas: Owyhee River Region, Idaho and Nevada
Mineral Resources of

Wilderness Study Areas: 

Owyhee River Region, 

Idaho and Nevada

This volume was published as chapters A H

U.S. GEOLOGICAL SURVEY BULLETIN 1719
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the North Fork Owyhee River Wilderness Study Area, 

Owyhee County, Idaho, by Scott A. Minor, Don L. Sawatzky, and Andrew M. 

Leszcykowski.

(B) Mineral Resources of the Battle Creek, Yatahoney Creek, and Juniper Creek

Wilderness Study Areas, Owyhee County, Idaho, by Carolyn A. Goeldner, Michael 

G. Sawlan, Harley D. King, Richard A. Winters, Andrew M. Leszcykowski, and 

Donald E. Graham.

(C) Mineral Resources of the Little Owyhee River Wilderness Study Area, Owyhee 

County, Idaho, by Jay A. Ach, Harley D. King, Alan R. Buehler, and Donald O. 

Capstick.

(D) Mineral Resources of the Owyhee River Canyon and Deep Creek-Owyhee River 

Wilderness Study Areas, Owyhee County, Idaho, by Michael G. Sawlan, Harley D. 

King, James D. Hoffman, Dolores M. Kulik, Peter N. Gabby, Donald O. Capstick, 

and Alan R. Buehler.

(E) Mineral Resources of the Owyhee Canyon Wilderness Study Area, Malheur County, 

Oregon, by James G. Evans, James D. Hoffman, Dolores M. Kulik, and J. Mitchell 

Linne.

(F) Mineral Resources of the Owyhee Canyon and South Fork Owyhee River

Wilderness Study Areas, Elko County, Nevada, and Owyhee County, Idaho, by 

Eugene E. Foord, Michael J. Luessen, Dirk S. Hovorka, Joseph L. Plesha, V J.S. 

Grauch, Harlan Barton, Harley D. King, Donald O. Capstick, Ronald T. Mayerle, 

Alan R. Buehler, and Peter N. Gabby.

(G) Mineral Resources of the Upper Deep Creek Wilderness Study Area, Owyhee 

County, Idaho, by Scott A. Minor, Harley D. King, Dolores M. Kulik, Donald L. 

Sawatzky, and Donald O. Capstick.

(H) Mineral Resources of the Upper West Little Owyhee Wilderness Study Area,

Malheur County, Oregon, by James G. Evans, Robert L. Turner, Donald Plouff, Don 

L. Sawatzky, and J. Mitchell Linne.
GPO 585-045/78053
SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports of 

wide and lasting interest and importance to professional scientists and engineers. Included are reports on the results of resource studies and of 

topographic, hydrologic, and geologic investigations. They also include 

collections of related papers addressing different aspects of a single scientific topic.

Bulletins contain significant data and interpretations that are of lasting scientific interest but are generally more limited in scope or 

geographic coverage than Professional Papers. They include the results 

of resource studies and of geologic and topographic investigations; as well 

as collections of short papers related to a specific topic.

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrogeology, 

availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific 

information of wide popular interest in a format designed for distribution 

at no cost to the public. Information is usually of short-term interest.

Water-Resources Investigations Reports are papers of an interpretive nature made available to the public outside the formal USGS publications series. Copies are reproduced on request unlike formal USGS 

publications, and they are also available for public inspection at 

depositories indicated in USGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at 

depositories. They are a nonpermanent form of publication that may be 

cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 71/2- or 15-minute quadrangle formats (scales mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric 

bases at various scales; they show results of surveys using geophysical 

techniques, such as gravity, magnetic, seismic, or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 7 1/2-minute quadrangle photogeologic maps on planimetric bases 

which show geology as interpreted from aerial photographs. Series also 

includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information 

for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; principal scale 

is 1:24,000 and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche.

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982,1983,1984,1985,1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only.

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only.

Selected copies of a monthly catalog "New Publications of the U.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.