Mineral Resources of the Owyhee River 

Canyon and Deep Creek-Owyhee River 

Wilderness Study Areas, Owyhee 

County, Idaho

U.S. GEOLOGICAL SURVEY BULLETIN 1719-D

Chapter D

Mineral Resources of the Owyhee River 

Canyon and Deep Creek-Owyhee River 

Wilderness Study Areas, Owyhee County, Idaho

By MICHAEL G. SAWLIN, HARLEY D. KING, JAMES D. HOFFMAN, 

and DOLORES M. KULIK

U.S. Geological Survey

PETER N. GABBY, DONALD O. CAPSTICK, . 

and ALAN R. BUEHLER

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1719

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

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987

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 Owyhee River Canyon and the 

Deep Creek-Owyhee River Wilderness Study areas, 

Owyhee County, Idaho

U.S. Geological Survey Bulletin 1719-D

Bibliography included.

Supt. of Docs. No. I 19.3: 1719-D

1. Mines and mineral resources Idaho Owyhee River

Canyon Wilderness. 2. Geology Idaho Owyhee River

Canyon Wilderness. 3. Mines and mineral resources 

Idaho Deep Creek-Owyhee River Wilderness. 4.

Geology Idaho Deep Creek-Owyhee River Wilderness.

5. Owyhee River Canyon Wilderness (Idaho). 6. Deep

Creek-Owyhee River Wilderness (Idaho). I. Sawlan,

Michael G. II. Series.

QE75.B9 No. 1719-D 557.3 s 86-600393

[TN24.I2] [553'.09796'21]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

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 of 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 Congress. This report presents the results of a mineral survey of the Owyhee River 

Canyon Wilderness Study Area (ID-16-48B) and of the Deep Creek-Owyhee River 

Wilderness Study Area (ID-16-49A), Owyhee County, Idaho.

in

CONTENTS

Summary Dl

Abstract 1

Character and setting 1

Mineral resource potential of the Owyhee River Canyon Wilderness Study Area, 

Owyhee County, Idaho 1

Mineral resource potential of the Deep Creek-Owyhee River Wilderness Study Area,

Owyhee County Idaho 3 

Introduction 3

Area description 3

Previous and present investigations 3

Acknowledgments 4 

Appraisal of identified resources 4

Jasper and opal 4

Diatomite 4

Gold 4

Sand and gravel 4 

Assessment of mineral resource potential 4

Geology 4

Geochemical studies 5

Geophysical studies 8

Conclusions for the Owyhee River Canyon Wilderness Study Area 8 

Conclusions for the Deep Creek-Owyhee River Wilderness Study Area 9 

References cited 10

Appendix 1. Definition of levels of mineral resource potential and certainty of assessment 11 

Geologic time chart 12

FIGURES

1. Index map showing location of the Owyhee River Canyon and the Deep Creek-Owyhee River 

Wilderness Study Areas, Owyhee County, Idaho. D2

2. Map showing mineral resource potential and geology of the Owyhee River Canyon and 

the Deep Creek-Owyhee River Wilderness Study Areas, Owyhee County, Idaho. 6

3. Major elements of mineral resource potential/certainty classification. 11

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: OWYHEE RIVER REGION, IDAHO AND NEVADA

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, and Dolores M. Kulik 

U.S. Geological Survey

and Peter N. Gabby, Donald O. Capstick, and Alan R. Buehler 

U.S. Bureau of Mines

SUMMARY 

Abstract

The Owyhee River Canyon Wilderness Study Area 

(ID-16-48B) and the Deep Creek-Owyhee River 

Wilderness Study Area (ID-16-49A) are contiguous 

areas located in the southwest corner of Idaho. At the 

request of the Bureau of Land Management, 33,700 

acres of the Owyhee River Canyon Wilderness Study 

Area and 67,400 acres of the Deep Creek-Owyhee 

River Wilderness Study Area were studied. In this 

report, the areas studied are refered to as the 

"wilderness study areas," or simply "the study areas." 

The Owyhee River Canyon Wilderness Study Area 

extends along the Owyhee River and the South Fork 

Owyhee River canyons. The Deep Creek-Owyhee 

River Wilderness Study Area extends along the Owyhee 

River, and Deep and Dickshooter Creeks. Fieldwork 

for this report was conducted during 1984 and 1985. 

Two prospects for lapidary jasper, chalcedony, and 

common opal are located adjacent to the study areas, 

and one of these extends into both study areas. These 

prospects have yielded materials that are mainly of 

interest to hobbyists. There are no active mines 

located inside either study area and no mineral 

resources were identified. A small area in the 

southwest part of the Deep Creek-Owyhee River 

Wilderness Study Area has low resource potential for 

silver. There is no evidence of mineral resources 

within the Owyhee River Canyon Wilderness Study 

Area. A diatomite deposit is located within a mile of 

the northeast margin of the Deep Creek-Owyhee River 

Wilderness Study Area but has not been mined for over 

50 years. Oil and natural gas leases cover parts of 

both study areas, but no exploration has occurred. 

Geologic and geophysical evidence for hydrocarbon 

source beds or structural traps is lacking in both study 

areas.

Character and Setting

The Owyhee River Canyon Wilderness Study Area 

and the Deep Creek-Owyhee River Wilderness Study 

Area are both located in the Owyhee Plateau region in 

the extreme southwest corner of Idaho (fig. 1). The 

terrain consists of a flat to rolling plateau into which 

deep, narrow canyons have been cut by the Owyhee 

River and its tributaries, Deep Creek and Dickshooter 

Creek. Canyon depths range from 300 ft in upper 

Dickshooter Creek to more than 1,000 ft along the 

Owyhee River at the Oregon-Idaho border. The 

plateau is underlain by more than 1,000 ft of middle 

and late Miocene (9-14 million years before present 

(Ma); see geologic time chart, fig. 3) rhyolite 

rheoignimbrite (material originally deposited as an ash 

flow but which flowed in the manner of lava before 

coming to rest). These volcanic rocks are locally 

overlain by fluvio-lacustrine sedimentary rocks that 

may include minor intercalated basalt flows. Basalt 

flows that have a composite thickness of 20-100 ft 

form a discontinuous, thin, widespread veneer upon the 

rhyolites and sedimentary rocks south of the Owyhee 

River and in the Lambert Table area. Locally 

abundant, northwest to northeast-trending high-angle 

faults are most common in the Owyhee River Canyon 

Wilderness Study Area and the Deep Creek-Owyhee 

River Wilderness Study Area west of Lambert Table. 

These faults displace rhyolite and overlying 

sedimentary rocks but, in most instances, do not 

displace the mesa-forming basalts.

Mineral Resource Potential of the Owyhee River 

Canyon Wilderness Study Area

The Owyhee River Canyon Wilderness Study Area 

exhibits no evidence of the existence of metallic or 

nonmetallic mineral resources. Available geologic and 

geophysical data do not suggest the occurrence of 

hydrocarbon source rocks or structural traps within the

Dl
42°30'

117°00' 116°45' 116°30'

42° 15' -

42°00'

, To Jordan Valley.OR To Grandview 50 mi. 1 ,'

\ 42 mi. '

4 Juniper Mountain

WILDERNESS STUDY AREA 

(ID 016-49A)

Squaw Meadows

OWYHEE RIVER CANYON

WILDERNESS STUDY AREA

(ID 016-48B)

To Owyhee, 

s-sJlV14mi.

HUMBOLDT CO

Figure 1. Index map showing location of Owyhee River Canyon and Deep Creek-Owyhee River 

Wilderness Study Areas, Owyhee County, Idaho.

D2
study area. Geochemical analyses of stream sediments 

indicate widespread anomalous concentrations of tin 

and local anomalous concentrations of bismuth for 

areas underlain by rhyolite, but geologic field study 

does not indicate the presence of favorable structures, 

such as caldera ring fractures or vent systems within 

the study area. Widespread anomalies of tin and 

associated elements in stream sediment samples are 

attributed to generally higher tin concentrations in the 

rhyolites and do not indicate regional tin 

mineralization. These anomalies are best regarded as 

high background levels. Construction-grade sand and 

gravel occurrences are small and scattered. Available 

geologic and geophysical data give no indication of the 

occurrence of favorable source rocks or structural 

traps for oil and gas. There are no producing oil or gas 

wells in Idaho, and exploratory drilling in geologically 

more favorable areas 50 mi to the north and south has 

yielded only dry holes. Hence, this area is considered 

to have no resource potential for oil and gas.

Mineral Resource Potential of the Deep Creek-Owyhee 

River Wilderness Study Area

The Deep Creek-Owyhee River Study Area has 

low mineral resource potential for epithermal silver 

that may be associated with faults in the western part 

of the study area. Geochemical analyses indicate 

anomalous concentrations of tin, and slightly 

anomalous concentrations of cadmium and zinc in 

areas underlain by rhyolite. Favorable structures for 

mineralization of tin and associated elements are 

lacking, however, and the anomalous values most likely 

reflect the generally higher concentrations of these 

elements in the rhyolite. Although a diatomite deposit 

occurs adjacent to the study area, diatomite 

occurrences within the study area are small and 

impure; hence, this study area is considered to have no 

potential for diatomite. Construction-grade sand and 

gravel occurrences are small, scattered, and poorly 

accessible. Available geologic and geophysical data 

give no indication of the occurrence of favorable 

source rocks or structural traps for oil and gas. There 

are no producing oil or gas wells in Idaho, and drilling 

in geologically more favorable areas 50 mi to the north 

and south has yielded only dry holes. Hence, this area 

is considered to have no resource potential for oil and 

gas.

INTRODUCTION 

Area Description

The Owyhee River Canyon Wilderness Study Area 

(ID-16-48B) includes 33,700 acres, and the Deep 

Creek-Owyhee River Wilderness Study Area (ID-16- 

49 A) includes 67,400 acres. Both study areas are in 

the flat to gently rolling Owyhee Plateau of 

southwestern Idaho and have average elevations of 

about 5,000 ft. In the study areas, spectacular canyons 

as much as 1,000 ft deep have been cut into the 

plateau by the Owyhee River and its tributaries, Deep 

Creek and Dickshooter Creek. The climate is arid to

semiarid; vegetation is sparse and consists 

predominantly of sagebrush and grasses.

The study areas are located at least 40 mi from 

the nearest paved roads. Areas north of the Owyhee 

River can be reached by gravel and dirt roads either 

southeast from Jordan Valley, Oregon, or southwest 

from Grandview, Idaho (fig. 1). Access to areas 

located south of the Owyhee River is provided by 

gravel and dirt roads that lead west from Idaho State 

Highway 51 through the Duck Valley Indian 

Reservation. Jeep trails provide limited vehicle 

access after entering the Owyhee region via the main 

dirt roads shown in figure 1.

Previous and Present Investigations

Previous geologic studies related to the 

wilderness study areas have focused on the regional 

stratigraphy (Ekren and others, 1984) and the 

emplacement mechanism of the rhyolites (Ekren and 

others, 1982). The geologic map of western Owyhee 

County (Ekren and others, 1981; 1:125,000 scale) 

includes both study areas. Geologic mapping for the 

present study was done at 1:24,000 scale and compiled 

at 1:62,500 scale. Lithologic units were based on unit 

assignments made by Ekren and others (1981).

Regional evaluations of uranium resource 

potential in parts of the study areas and (or) adjacent 

areas were prepared by Geodata International, Inc. 

(1980), Berry and others (1982), and the Union Carbide 

Corporation (1982) as part of the National Uranium 

Resource Evaluation (NURE) program administered by 

the U.S. Department of Energy. Previous nonspecific 

mineral-resource or exploration geochemical studies in 

or adjacent to the study areas include those of 

Matthews and Blackburn (1983), R. W. Morris (1976, 

unpub. report; available at U.S. Bureau of Mines, 

Western Field Operations Center, Spokane, Wash.), and 

Gloria Derby (1981, unpub. report; available at U.S. 

Bureau of Land Management, Boise District Office, 

Boise, Idaho).

The U.S. Geological Survey conducted field 

investigations in the study areas in 1984 and 1985. The 

work included field checking of existing geologic maps, 

new mapping where necessary, and geochemical 

sampling. Analytical data were obtained for 45 

stream-sediment samples and 39 nonmagnetic, heavymineral panned concentrates from the Owyhee River 

Canyon area, and 70 stream-sediment samples and 59 

nonmagnetic, heavy-mineral, panned concentrates 

from the Deep Creek-Owyhee River area.

The U.S. Bureau of Mines conducted a library 

search for information on mines and prospects within 

the wilderness study areas. These data were 

supplemented by information from Owyhee County and 

U.S. Bureau of Land Management mining and minerallease records and by U.S. Bureau of Mines and State 

production records. Field studies were conducted in 

1984 for both the Owyhee Canyon Wilderness Study 

Area (Gabby, 1985) and the Deep Creek-Owyhee River 

Wilderness Study Area (Capstick and Buehler, 1985). 

Prospects and claims near the study areas were studied 

to determine if mineralized zones extend into the 

study areas and to establish guides to mineral deposits 

in the region. Reconnaissance panned-concentrate

D3
sampling was done along the Owyhee River and along 

Deep and Dickshooter Creeks to test for gold and 

other heavy minerals. Areas of obvious rock alteration 

were examined for evidence of prospecting activity 

that may not have been recorded.

Twenty-one rock and 11 placer samples were 

collected at prospects and mineralized sites in or near 

the Owyhee River Canyon Wilderness Study Area. 

Sixty rock and 19 placer samples, and 10 samples of 

possible diatomaceous material were collected in or 

near the Deep Creek-Owyhee River Wilderness Study 

Area. Samples were analyzed by fire-assay, atomic 

absorption, and semiquantitative methods, examined 

under a petrographic microscope, scanned with a 

binocular microscope to characterize the heavymineral content, and checked for radioactivity and 

fluorescence. Complete analyses are on file at the 

U.S. Bureau of Mines, Western Field Operations 

Center, Spokane, Wash.

Acknowledgments

The staff of the Boise area office of the U.S. 

Bureau of Land Management provided logistical 

support, information, maps, and the use of the U.S. 

Bureau of Land Management camp at Mud Flat, Idaho.

APPRAISAL OF IDENTIFIED RESOURCES

By Peter N. Gabby, Donald 0. Capstick, and Alan R. 

Buehler U.S. Bureau of Mines

The two study areas contain no known mines, 

mining claims, or prospects and do not lie in or 

adjacent to an established mining district. Lode 

claims for lapidary jasper, chalcedony and common 

opal straddle the study area boundaries at the White 

Point prospect (fig. 2). Oil and gas leases or lease 

applications cover the approximately 25 percent of the 

Deep Creek-Owyhee River Wilderness Study Area in 

its northeast part, and approximately 7 percent of the 

Owyhee River Canyon Wilderness Study Area in its 

southeast part, east of the South Fork of the Owyhee 

River. There are no identified mineral or oil and gas 

resources within either of the study areas.

Jasper and Opal

Jasper, chalcedony, and common opal occur 

within silicified rhyolite throughout the study areas; 

most occurrences are small, scattered, and poor in 

quality. In some localities, these materials form 

colorful massive specimens or hollow spheroidal 

masses (commonly known as geoids or "thundereggs"). 

Lapidary specimens have been intermittently 

extracted from the White Point and Lu Lew prospects 

(fig. 2), but the informal production at these sites has 

not been recorded. Most production apparently has 

been from the White Point prospect. The larger 

occurrences of jasper, chalcedony, and common opal 

(which are various forms of silica), as at the two 

prospects cited here, have formed as replacements of 

rhyolite and porous tuffaceous rocks along faults. The

White Point prospect includes about 10 acres of 

silicified rock, but lapidary material is found only 

locally; part of this prospect extends into both study 

areas along a common boundary. The Lu Lew prospect 

consists of small, isolated occurrences of jasper and 

associated silicified rock. These commodities are 

mainly of interest to hobbyists.

Diatomite

The diatomite located north of the northeast tip 

of the Deep Creek-Owyhee River Wilderness Study 

Area is one of Idaho's largest diatomite deposits 

(Staley, 1964), but apparently there has not been any 

production since the 1930's when a "few" tons were 

extracted (Powers, 1947). The diatomaceous earth, 

also reported as fuller's earth or clay deposit (Derby, 

1981, unpub. report; available at U.S. Bureau of Land 

Management, Boise District Office, Boise, Idaho), 

occurs in a basin cut in the Little Jacks Rhyolite and is 

overlain by 10-20 ft of basalt. This deposit covers an 

area of about 0.07 mi , approximately 1,000 ft northsouth by 2,000 ft east-west, and has a maximum 

thickness of 150 ft. It contains an estimated 4.2 

million tons of material (Staley, 1964) and has been 

regarded as Idaho's best "reserve" because of its purity 

and grain size appropriate for industrial use (Powers, 

1947). Production from this deposit has apparently 

been used as cement admixture, polishing agent, 

insulation, and filter media (Powers, 1947; Elevatorski, 

1975). Minor amounts of diatomite were found within 

the wilderness study areas but the diatomite here is 

impure and volumetrically insignificant in terms of 

consideration as a resource.

Gold

Trace amounts of gold were detected in heavymineral panned concentrates of stream sediments from 

both study areas, but the gold concentrations in all 

samples are neither anomalous nor economic. These 

stream sediments contain gold valued at less than 

$0.02/yd3 (calculated at a gold value of $400 per troy 

ounce) whereas $0.10-0.15/yd<i is considered 

anomalous, and $8-10/yd is marginally economic.

Sand and Gravel

Construction-grade sand and gravel occur in the 

study area in small bars in the narrow canyons but are 

not considered to be significant resources because 

deposits are small and scattered.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By Michael G. Sawlan, Harley King, James D. 

Hoffman, and Dolores M. Kulik 

U.S. Geological Survey

Geology

The Owyhee River Canyon and Deep Creek-
Owyhee River Wilderness Study Areas are underlain by 

laterally extensive, flat-lying, middle Miocene rhyolite 

rheoignimbrites. These are locally overlain by fluviolacustrine sedimentary strata deposited in shallow 

north-trending grabens. Upper Miocene and (or) 

Pliocene basalt locally form thin caps of low-lying 

mesas. Pre-Miocene basement rocks are not exposed 

within the study areas, but may include Cretaceous 

granitoid rocks and associated metamorphic country 

rock of the Idaho batholith, and perhaps Eocene and 

(or) Oligocene volcanic rocks. These pre-Miocene 

rocks are exposed in the Owyhee Mountains 25 to 30 

mi north of the study areas and may extend beneath 

the volcanic rocks of the study areas.

The rhyolitic rocks in the study areas are 

rheoignimbrites: that is, they were emplaced as ash 

flows that continued to flow in the manner of lava 

after collapse of the dense ash cloud. Ekren and 

others (1984) applied the descriptive term "tuff" in 

naming each of these rock-units on the basis of their 

inferred emplacement mechanism. However, in most 

localities within the study areas, the rhyolite forms 

flow-banded devitrified lava. Vitroclastic textures are 

recognizable in parts of some outcrops, most 

commonly at the tops and bottoms of flow units, but 

these have been largely destroyed by annealing and 

shear deformation of glass shards during flow. 

Sigmoidal flow foliations, folds, and diapiric structures 

are common in the lava-like parts of the flows. The 

amplitude (A) of these structures ranges from a few 

centimeters to more than 100 m. Partially welded tuff 

occurs in parts of the rhyolite of upper Juniper 

Mountain. At transitions between lava and partially 

welded tuff in this unit, the tuff is strongly folded (A = 

50-150 m) and strata are inclined as much as 55°.

Five rhyolite units were distinguished within the 

study areas on the basis of the stratigraphy of Ekren 

and others (1984). The stratigraphically lowest four 

rhyolite units range in age from about 14 to 12 Ma 

(Neill, 1975; Armstrong and others, 1980). In 

ascending stratigraphic order, these are the Swisher 

Mountain Rhyolite (= the Swisher Mountain Tuff of 

Ekren and others, 1984), the lower rhyolite of Juniper 

Mountain (= the lower-lobes unit of Ekren and others, 

1984), the upper rhyolite of Juniper Mountain (= the 

upper-lobes unit of Ekren and others, 1984), and the 

rhyolite of The Badlands (= the tuff of The Badlands of 

Ekren and others, 1984). These rhyolite units are 

overlain by the Little Jacks Rhyolite (= the Little 

Jacks Tuff of Ekren and others, 1984), which is about 

9-10 Ma in age (Neill, 1975; Armstrong and others, 

1980).

The name "Swisher Mountain Tuff" is herein 

redefined only in its outcrop area south of Juniper 

Mountain (located in southwestern Idaho) as the 

Swisher Mountain Rhyolite to more adequately reflect 

its lithlogic character. In this area, the Swisher 

Mountain Rhyolite is a dense, flow-foliated rhyolite 

lava having a maximum thickness in excess of 200 m. 

It comprises a single cooling unit in which the 

uppermost 10-15 m consist of brecciated vitrophyre 

set within an ash matrix. The lava part of this unit 

characteristically forms the nearly vertical canyon 

walls along the Owyhee River; the upper breccia part 

of this unit forms gently sloping recesses in the 

canyons. The basal part of this unit was not observed,

but is presumed to be a vitrophyre and ash breccia 

similar to the upper 10-15 m of this unit. Upper and 

lower vitrophyres and vitrophyre and ash breccias are 

characteristic of all lava-like rhyolitic units in the 

study areas. Local silicification has produced small 

pockets of jasper, chalcedony, and common opal in the 

porous upper and lower breccias of these rhyolite 

units; more pervasive silicification, as at the White 

Point and Lu Lew prospects (fig. 2), is associated with 

faults. Trace-element concentrations of rock samples 

suggest that the Swisher Mountain Rhyolite has a 

peralkaline chemistry (J.J. Rytuba, oral commun., 

1985).

In the study areas, the rhyolite units may 

comprise a single cooling unit (for example, the lower 

rhyolite of Juniper Mountain, the rhyolite of The 

Badlands, and the Swisher Mountain Rhyolite) or 

multiple cooling units (the upper rhyolite of Juniper 

Mountain and the Little Jacks Rhyolite). These 

rhyolites contain 10 to 25 percent phenocrysts, which 

are mainly plagioclase and (or) sanidine feldspar. 

Quartz phenocrysts are abundant in the lower and 

upper rhyolites of Juniper Mountain but absent or rare 

in the Swisher Mountain and Little Jacks Rhyolites. A 

deep green, iron-rich(?) pigeonite is ubiquitous but 

relatively minor in abundance. Zircon and allanite(?) 

may be present in trace amounts.

Upper Miocene sedimentary rocks consist of 

poorly lithified mudstone, sandstone, and pebble and 

cobble conglomerate. Clasts are most commonly 

rhyolitic rock fragments, and the finer grained 

sedimentary deposits are locally diatomaceous or 

tuffaceous and rarely contain pumice lapilli. Sediment 

deposition occurred in a fluvio-lacustrine environment, 

most likely within shallow grabens. These rocks 

generally underlie basalt, although sedimentary rocks 

and basalt are locally intercalated.

Upper Miocene and (or) Pliocene basalt locally 

forms from one to four flows of intergranular to 

subophitic, sparsely and finely porphyritic, olivine- or 

olivine and plagioclase-phyric lava. Chromian spinel is 

commonly included within the olivine phenocrysts. 

Individual flows are thin (10-40 ft) and their composite 

thickness is typically less than 100 ft. These lavas 

erupted locally from low-profile shield volcanoes, such 

as Spring Butte and Lambert Table (fig. 1).

Northwest- to northeast-trending high-angle 

normal faults displace the rhyolite and overlying 

sedimentary strata from 20-80 ft, to as much as 150 ft 

in the study areas south of Juniper Mountain (fig. 1). 

Most faults are located in the Owyhee River Canyon 

Wilderness Study Area and the western part of the 

Deep Creek-Owyhee River Wilderness Study Area. 

Most capping basalts post-date faulting in this area, 

but shallow grabens (10-50 ft deep) have formed in the 

basalt mesas along Battle Creek, 5-15 mi east of the 

Deep Creek-Owyhee River Wilderness Study Area.

Geochemical Studies

A reconnaissance geochemical study included 

analysis and evaluation of stream sediments and 

nonmagnetic, heavy-mineral panned concentrates 

(hereafter referred to as panned concentrates). These

D5
117°00' 

T

116°52'30" 

I

116°45'

T

116°37'30"

42°22'30"

42°15'

APPROXIMATE BOUNDARY 

OF

OWYHEE RIVER CANYON

WILDERNESS STUDY AREA

(ID 016-48B)

Tb

Ts

Diatomite 

deposit APPROXIMATE BOUNDARY 

OF

DEEP CREEK-OWYHEE RIVER 

WILDERNESS STUDY AREA (ID016-49A)

Silver

White 

Point 

prospect

Lu Lew prospect

Figure 2. Map showing mineral resource potential and geology of the Owyhee River Canyon 

and the Deep Creek-Owyhee River Wilderness Study Areas, Owyhee County, Idaho.
EXPLANATION

AREA WITH LOW RESOURCE POTENTIAL-Certainty level C (commodity indicated). See appendix 1 and 

figure 3 for definition of mineral resource potential and certainty of assessment

CORRELATION OF MAP UNITS 

~|_ Pliocene andJ (or) Miocene

- Miocene

h TERTIARY - CENOZOIC

GEOLOGIC MAP UNITS

Tb BASALT (PLIOCENE AND (OR) MIOCENE)

Ts SEDIMENTARY ROCKS (PLIOCENE AND (OR) MIOCENE)

Tlj LITTLE JACKS RHYOLITE (MIOCENE)Trb RHYOLITE OF THE BADLANDS (MIOCENE)

Tju UPPER RHYOLITE OF JUNIPER MOUNTAIN (MIOCENE)

TJ1 LOWER RHYOLITE OF JUNIPER MOUNTAIN (MIOCENE)

Tsm SWISHER MOUNTAIN RHYOLITE (MIOCENE)

MAP SYMBOLS

CONTACT

- - - FAULT-Dashed where uncertain

Figure 2. Continued
samples contain materials derived from rock units of 

tributary drainage basins. All samples were analyzed 

for 31 elements by semiquantitative emission 

spectrography. Analyses of stream-sediment samples 

were by the method of Myers and others (1961); the 

panned concentrates were analyzed by the method of 

Grimes and Marranzino (1968). Samples from the Deep 

Creek-Owyhee River wilderness Study Area were 

analyzed for an additional five elements by inductively 

coupled argon plasma atomic-emission spectroscopy. 

In the Owyhee River Canyon Wilderness Study Area, 45 

stream- sediment samples and 39 panned-concentrate 

samples were analyzed. In the Deep Creek-Owyhee 

River Canyon Wilderness Study Area, 70 streamsediment samples and 59 panned-concentrate samples 

were analyzed.

Tin concentrations are generally high in pannedconcentrate geochemical samples collected from 

rhyolite provenances within the study areas. The 

distribution and concentration of tin within the 

rhyolite units are nonsystematic, however. Analyses 

of the panned-concentrate samples in this study 

commonly exceed 1,000 parts per million (ppm) tin, a 

value suggested by Cox and Singer (1986) as a general 

exploration guide with this type of sample. However, 

the tin values obtained from the panned-concentrate 

samples in this study are not due to significantly 

mineralized rock. Mildly anomalous concentrations of 

zinc and cadmium were also observed in geochemical 

samples collected from rhyolitic provenances. The 

high levels of tin and associated elements most likely 

result from generally higher abundances in these 

particular rhyolites.

Although tin mineralization may occur in 

rhyolite, the geologic setting of the study areas is not 

favorable for significant localization of tin. Rhyolitehosted tin deposits are characteristically located 

within or near vent deposits. For example, in the 

Mexican tin deposits tin ore is found in domes, flows, 

stocks, and breccias (Huspeni and others, 1984). 

However, rhyolites in the study areas formed as 

outflow-facies ash flows and are not located within a 

vent system. Berry and others (1982) reached a similar 

conclusion regarding "near-anomalous" concentrations 

of uranium in areas of the Owyhee plateau underlain 

by rhyolite. The lack of vents and associated 

structures favorable for uranium mineralization also 

applies to tin. Furthermore, rhyolite-hosted tin 

deposits are characteristically of low grade and 

tonnage (Cox and Singer, 1986).

Lead anomalies (100-3,000 ppm versus 20 ppm 

background) in panned-concentrate samples from the 

vicinity of the 45 Ranch (fig. 1) and small lead 

anomalies (50-200 ppm) in the southeast part of the 

Deep Creek-Owyhee River Wilderness Study Area are 

most likely due to man-made materials such as bullets, 

birdshot, and tin cans. Both localities are near roads 

easily accessible to hunters. A single heavy-mineral 

panned-concentrate sample containing an anomalous 

concentration of antimony also was found in the 

southeastern part of the Deep Creek-Owyhee River 

Wilderness Study Area.

In the northwestern part of the Owyhee River 

Canyon Wilderness Study Area south of Bald Mountain 

(fig. 2), panned-concentrate samples exhibit anomalous 

concentrations of bismuth (100-1,000 ppm versus 20

ppm background), lead (50-150 ppm), and beryllium (20 

ppm versus 5 ppm background). These elements 

characteristically accompany tin (Cox and Singer, 

1986). A strong gradient in bismuth anomalies, from 

100 ppm at the Owyhee River to 1,000 ppm 2 mi south 

of Bald Mountain, may indicate minor concentrations 

of bismuth associated with tin. Tin and associated 

elements may have been concentrated in a vapor phase 

and deposited as these rhyolites cooled, but this 

hypothesis is speculative.

In the southwest part of the Deep Creek-Owyhee 

River Wilderness Study Area along the Owyhee River, 

anomalous high concentrations of silver (20 ppm versus 

1 ppm background) and copper (200 ppm versus 30 

ppm) were detected in one heavy-mineral pannedconcentrate sample. The presence of these anomalies 

in a region cut by numerous faults may be due to local 

epithermal mineralization from fluid circulation along 

faults. These geochemical anomalies are not 

associated with silicification in tuffaceous layers in 

the rhyolite units. Analyses of silicified tuff from the 

White Point prospect by the U.S. Bureau of Mines show 

no geochemical anomalies.

Geophysical Studies

Geophysical data are consistent with the 

geological mapping that shows the study areas are 

underlain by extensive horizontal strata. Gravity data 

were obtained from files maintained by the 

Department of Defense and were supplemented by 

additional data collected in 1985. Bouguer gravityanomaly values show only a gentle gradient of less 

than 10 mGal across both study areas. A broad gravity 

low, 40-50 mi in diameter, is approximately centered 

on the study areas. This gravity low generally 

corresponds to the distribution of the Little Jacks 

Rhyolite; there are no geologic indications of the 

presence of a caldera in this region. Aeromagnetic 

contours exhibit no gradient across the Owyhee River 

Canyon Wilderness Study Area and only about a 100- 

nanotesla gradient across the Deep Creek-Owyhee 

River Wilderness Study Area (U.S. Geological Survey, 

1972, 1978). These geophysical data do not provide 

additional constraints on the geology, mineral resource 

potential, or oil and gas potential over and above those 

obtained from geologic mapping and geochemical 

studies.

Conclusions for the Owyhee River Canyon Wilderness 

Study Area

The absence of geologic and geochemical 

evidence of mineral-forming processes in the Owyhee 

River Canyon Wilderness Study Area indicates that 

there is no potential for any metallic-mineral 

resources in this wilderness study area. Constructiongrade sand and gravel are found in the study areas, but 

these deposits are small and scattered and are not 

considered to be resources. Diatomite has been 

detected within the study area, but it is impure and 

present in quantities and too small to constitute a 

resource.

Available geologic and geophysical data give no

D8
indication of the presence of oil and gas resources. In 

Sandberg's (1983) statewide assessment of oil and gas 

resources, this study area and the adjacent Owyhee 

canyonlands were rated as having low potential for oil 

and gas, based largely on Warner's (1980) suggestion 

that hydrocarbon source rocks are present among the 

Cenozoic lacustrine strata. In the study area, 

however, there is no evidence for hydrocarbon source 

beds or structural traps; no surficial tar or oil seeps 

are present. The exposed Tertiary strata in the study 

area, consisting mainly of volcanic and tuffaceous 

sedimentary rocks, are not sources of hydrocarbons. It 

is conjectural whether carbonaceous source rocks are 

present beneath the volcanic strata in the study area. 

The nearest exposures of potential source rocks are 

carbonaceous shales of the Sucker Creek Formation of 

Miocene age located 40 mi to the north and northwest 

(Ekren and others, 1981, 1984). The structure and 

lithology of the subvolcanic basement is poorly known 

but may include plutonic and (or) metamorphic rocks 

associated with the Idaho batholith, and possibly 

Tertiary volcanic, volcaniclastic, and lacustrine 

sedimentary rocks.

At present, there are no producing oil or gas 

wells in Idaho or adjacent northernmost Nevada within 

50 mi of the study area. In the Anschutz Federal No. 1 

drill hole, located 45 mi north in the southern Snake 

River Plain, no oil or gas shows were reported and the 

hole bottomed-out in granite (Mclntyre, 1979). Three 

drill holes in northern Nevada, located about 40-55 mi 

from the study area, have been "dry." These include 

an 800' hole drilled by the Bull Run Oil and Gas 

Company in 1922, and a 3386-ft well drilled by the 

Richfield Corporation in 1956; these were located 

within 2 mi of each other. A more recent exploration 

attempt by Exxon Corporation in 1985 in a locality 22 

mi west of these drill holes resulted in a 14,464-ft dry 

hole through a stratigraphic section composed 

completely of rhyolitic tuff.

The thick cover of volcanic rocks, which may be 

as much as 1 km in thickness in the study area (Ekren 

and others, 1984), has undoubtedly discouraged oil and 

gas exploration, and petroleum industry interest in 

southwest Idaho appears to be declining. Atlantic 

Richfield Corporation, which presently holds the only 

leases in the study area, apparently plans to drop the 

lease without further exploration. In consideration of 

the absence of positive indications for source rocks 

and structural traps, and a history documenting a lack 

of oil and gas production in the state of Idaho and 

areas 50 mi south into Nevada, we conclude that there 

is no potential for oil and gas in the study area.

Conclusions for the Deep Creek-Owyhee River 

Wilderness Study Area

Geologic and geochemical studies indicate that 

part of the Deep Creek-Owhyee River Wilderness 

Study Area has low mineral resource potential for 

silver, certainty level C (fig. 2). The presence of 

silver is indicated in only a single geochemical sample, 

and no widespread, strongly altered, or oxidized zones

were observed in this area. Hence, the source of the 

silver is thought to be small and local, possibly forming 

small hydrothermal veins along faults in the vicinity of 

the anomalous geochemical sample. Some high-quality 

diatomite appropriate for industrial use occurs in a 

deposit located outside the wilderness study area. 

Within the wilderness study area, occurrences of 

diatomite are poor in quality and small in volume. The 

study area has no resource potential for diatomite.

Available geologic and geophysical data give no 

indication of the presence of oil and gas resources. In 

Sandberg's (1983) statewide assessment of oil and gas 

resources, this study area and adjacent Owyhee 

canyonlands were rated as having low potential for oil 

and gas, based largely on Warner's (1980) suggestion 

that hydrocarbon source rocks are present among the 

Cenozoic lacustrine strata. In the study area, 

however, there is no evidence for hydrocarbon source 

beds or structural traps; no surficial tar or oil seeps 

are present. The exposed Tertiary strata in the study 

area, consisting mainly of volcanic and tuffaceous 

sedimentary rocks, are not sources of hydrocarbons. It 

is conjectural whether carbonaceous source rocks are 

present beneath the volcanic strata in the study area. 

The nearest exposures of potential source rocks are 

carbonaceous shales of the Sucker Creek Formation of 

Miocene age located 40 mi north and northwest (Ekren 

and others, 1981, 1984). The structure and lithology of 

the subvolcanic basement is poorly known but may 

include plutonic and (or) metamorphic rocks associated 

with the Idaho batholith, and possibly Tertiary 

volcanic, volcaniclastic, and lacustrine sedimentary 

rocks.

At present, there are no producing oil or gas 

wells in Idaho or adjacent northernmost Nevada within 

50 mi of the study area. In the Anschutz Federal No. 1 

drill hole, located 45 mi north in the southern Snake 

River Plain, no oil or gas shows were reported and the 

hole bottomed-out in granite (Mclntyre, 1979). Three 

drill holes in northern Nevada, located about 40-55 mi 

from the study area, have not produced oil or gas. 

These include an 800' hole drilled by the Bull Run Oil 

and Gas Company in 1922, and a 3386-ft well drilled by 

the Richfield Corporation in 1956; these were located 

within 2 mi of each other. A more recent exploration 

attempt by Exxon Corporation in 1985 in a locality 22 

mi west of these drill holes resulted in a 14,464-ft 

dry hole through a stratigraphic section composed 

completely of rhyolitic tuff.

The thick cover of volcanic rocks, which may be 

about 1 km in thickness in the study area (Ekren and 

others, 1984), has undoubtedly discouraged oil and gas 

exploration and petroleum industry interest in 

southwest Idaho appears to be declining. Atlantic 

Richfield Corporation, one of two oil and gas leasees 

in the study area, apparently plans on dropping the 

lease without further exploration. In consideration of 

the absence of positive indications for source rocks 

and structural traps, and a history documenting a lack 

of oil and gas production in the state of Idaho and 

areas 50 mi south into Nevada, we conclude that there 

is no potential for oil and gas in the study area.

D9
REFERENCES CITED

Armstrong, R.L., Harakal, J.E., and Neill, W.M., 1980, 

K-Ar dating of Snake River Plain (Idaho) volcanic 

rocks new results: Isochron/West, no. 27, p. 5-10.

Armstrong, R.L., Leeman, W.P., and Malde, H.E., 

1975, K-Ar dating, Quaternary and Neogene 

volcanic rocks of the Snake River Plain, Idaho: 

American Journal of Science, v. 275, p. 225-251.

Berry, M.R., Castor, S.B., and Robins, J.W. (Bendix 

Field Engineering Corporation), 1982, National 

uranium resource evaluation, Jordan Valley 

quadrangle, Oregon and Idaho (contract no. DEAC07-76GJ01664): U.S. Department of Energy 

Open-File Report PGJ/F-132(82), 33 p.

Capstick, D.O., and Buehler, A.R., 1985, Mineral 

Resources of the Deep .Creek-Owyhee River 

Wilderness Study Area, Owyhee County, Idaho: 

U.S. Bureau of Mines Open-File Report MLA 54-85, 

14 p.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral 

deposit models: U.S. Geological Survey Bulletin 

1693, 379 p.

Derby, Gloria, 1981, Owyhee Resource Area (Garat 

and '45'): unpublished Bureau of Land Management 

wilderness management situation supplemental, 

Boise District Office, Boise, Idaho, 7 p.

Ekren, E.B., Mclntyre, D.H., and Bennett, E.H., 1984, 

High-temperature, large-volume, lavalike ash-flow 

tuffs without calderas in southwestern Idaho: U.S. 

Geological Survey Professional Paper 1272, 76 p.

Ekren, E.B., Mclntyre, D.H., Bennett, E.H., and Malde, 

H.E., 1981, Geologic map of Owyhee County, Idaho, 

west of 116° West Longitude: U.S. Geological 

Survey Miscellaneous Geologic Investigations Map 

1-1256, scale 1:125,000.

Ekren, E.B., Mclntyre, D.H., Bennett, E.H., and 

Marvin, R.F., 1982, Cenozoic stratigraphy of 

western Owyhee County, Idaho, in Bonnischen, Bill 

and Breckenridge, R. M., eds., Cenozoic geology of 

Idaho: Idaho Bureau of Mines and Geology Bulletin 

26, p. 215-235.

Evelatorski, E.A., 1975, Idaho Industrial Minerals: 

MINOBRAS, 55p.

Gabby, P.N., 1985, Mineral resources of the Owyhee 

River Canyon Wilderness Study Area, Owyhee 

County, Idaho: U.S. Bureau of Mines Open-File 

Report MLA 68-85, 15 p.

Geodata International, Inc., 1980, Aerial radiometric 

and magnetic survey, national topographic map, 

Jordan Valley, Oregon/Idaho: prepared under 

Bendix Field Engineering Corp. subcontract no. 79-

336-S, U.S. Department of Energy Open-File 

Report GJBX-95(80), 201 p.

Grimes, D.J., and Marranzino, A.P., 1968, Directcurrent arc and alternating-current spark 

emmission spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

U.S. Geological Survey Circular 591, 6 p.

Huspeni, J.R., Kesler, S.E., Ruiz, Joaquin, Tuta, Zane, 

Sutter, J.F., and Jones, L.M., 1984, Petrology and 

geochemistry of rhyolites associated with tin 

mineralization in northern Mexico: Economic 

Geology, v. 79, p. 87-105.

Mathews, G.W., and Blackburn, W.H., 1983, 

Assessment of geology, energy, and mineral (GEM) 

resources, Owyhee River GEM Resource Area (ID010-11), Owyhee County, Idaho: prepared under 

U.S. Bureau of Land Management contract: YA553-CT2-1042, TERRADATA, Lakewood, Colorado, 

37 p.

Mclntyre, 1979, Preliminary description of Anschutz 

Federal no. 1 drill hole, Owyhee County, Idaho: 

U.S. Geological Survey Open-File Report 79-651, 

15 p.

Myers, A.T., Haven, R.G., and Dunton, P.J., 1961, A 

spectrochemical method for the semiquantitative 

analysis of rocks, minerals, and ores: U.S. 

Geological Survey Bulletin 1084-1, p. 207-229.

Neill, W.M., 1975, Geology of the southeastern Owyhee 

Mountains and environs, Owyhee County, Idaho: 

Stanford, Calif., Stanford University, M.S. thesis, 

59 p.

Powers, H.A., 1947, Diatomite deposits of 

southwestern Idaho: Idaho Bureau of Mines and 

Geology Mineral Resources Report 4, 27 p.

Sandberg, C. A., 1983, Petroleum potential of 

wilderness lands in Idaho: U.S. Geological Survey 

Circular 902-F, 6 p.

Staley, W.W., 1964, Diatomite, in Mineral and water 

resources of Idaho: Idaho Bureau of Mines and 

Geology Special Report 1, p. 74-79.

Union Carbide Corp., 1982, Hydrogeochemical and 

stream sediment reconnaissance basic data for 

Adel, Jordan Valley, and Twin Falls, Oregon and 

Idaho (contract W-7405 eng 26): U.S. Geological 

Survey Open-File Report GJBX-170(82), 70 p.

U.S. Geological Survey, 1978, Aeromagnetic map of 

Idaho: U.S. Geological Survey Geophysical 

Investigations Map GP-919, scale 1:500,000, 1 

sheet.

Warner, M.M., 1980, S. Idaho, N. Nevada, southeastern 

Oregon- prime exploration target: Oil and Gas 

Journal, p.325/341 (not inclusive).

D10
APPENDIX 1. Definition of levels of mineral resource 

potential and certainty of assessment

Mineral resource potential is defined as the 

likelihood of the presence of mineral resources in a 

defined area; it is not a measure of the amount of 

resources or their profitability.

Mineral resources are concentrations of naturally 

occurring solid, liquid, or gaseous materials in such 

form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible.

Low mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment where 

the existence of resources is unlikely. This level of 

potential embraces areas of dispersed mineralized rock 

as well as areas having few or no indications of 

mineralization. Assignment of low potential requires 

specific positive knowledge; it is not used as a catchall 

for areas where adequate data are lacking.

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 a reasonable chance for resource 

accumulation, and where an application of genetic and 

(or) occurrence models indicates favorable ground.

High mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment 

favorable for resources, where interpretations of data 

indicate a high likelihood for resource accumulation, 

where data support occurrence and (or) genetic models 

indicating presence of resources, and where evidence 

indicates that mineral concentration has taken place. 

Assignment of high resource potential requires positive 

knowledge that resource-forming processes have been 

active in at least part of the area; it does not require 

that occurrences or deposits be identified.

Unknown mineral resource potential is assigned 

to areas where the level of knowledge is so inadequate 

that classification of the area as high, moderate, or

low would be misleading. The phrase "no mineral 

resource potential" applies only to a specific resource 

type in a well-defined area. This phrase is not used if 

there is the slightest possibility of resource 

occurrence; it is not appropriate as the summary 

rating for any area.

Expression of the certainty of the mineral 

resource assessment incorporates a consideration of (1) 

the adequacy of the geologic, geochemical, geophysical, and resource data base available at the time of 

the assessment, (2) the adequacy of the occurrence or 

the genetic model used as the basis for a specific 

evaluation, and (3) an evaluation of the likelihood that 

the expected mineral endowment of the area is, or 

could be, economically extractable.

Levels of certainty of assessment are denoted oy 

letters, A-D (fig. 3).

A. The available data are not adequate to 

determine the level of mineral resource potential. 

Level A is used with an assignment of unknown mineral 

resource potential.

B. The available data are adequate to suggest 

the geologic environment and the level of mineral 

resource potential, but either evidence is insufficient 

to establish precisely the likelihood of resource occurrence, or occurrence and (or) genetic models are not 

known well enough for predictive resource assessment.

C. The available data give a good indication of 

the geologic environment and the level of mineral 

resource potential, but additional evidence is needed 

to establish precisely the likelihood of resource occurrence, the activity of resource-forming processes, or 

available occurrence and (or) genetic models are 

minimal for predictive applications.

D. The available data clearly define the geologic 

environment and the level of mineral resource 

potential, and indicate the activity of resourceforming processes. Key evidence to interpret the 

presence or absence of specified types of resources is 

available, and occurrence and (or) genetic models are 

adequate for predictive resource assessment.

M D

MODERATF POTENTIAL

LEVEL OF CERTAINTY

Figure 3. Major elements of mineral resource potential/certainty classification.

Dll
GEOLOGIC TIME CHART 

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

EON

Phanerozoic

Proterozoic

Archean

pre- Arc

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

hean 2

PERIOD

Quaternary

Tertiary

Neogene 

Subpenod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 -(3800?)- -

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

- -

AGE ESTIMATES 

OF BOUNDARIES 

(in Ma)

- 0.010

- 1.7

- 5

_ IB

- 55

_ fiC

- 96 

-no

one

- 410

- 500

_ ion/1

OUwU

O*fW

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

'Informal time term without specific rank.

D12

GPO 785-048/48031