Mineral Resources of the

Rough Hills Wilderness Study Area,

Elko County, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1725-D

Chapter D

Mineral Resources of the

Rough Hills Wilderness Study Area,

Elko County, Nevada

By ALAN R. WALLACE, ROBERT J. TURNER, 

V.J.S. GRAUCH, and JOSEPH L. PLESHA 

U.S. Geological Survey

STAFF

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1725

MINERAL RESOURCES OF WILDERNESS STUDY AREASNORTHEASTERN 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 Rough Hills Wilderness Study Area, Elko 

County, Nevada.

(Mineral resources of wilderness study areas northeastern Nevada ; 

ch. D) (U.S. Geological Survey bulletin ; 1725-D)

Bibliography: p.

Supt. of Docs. No.: I 19.3:1725-D

1. Mines and mineral resources Nevada Rough Hills Wilderness 

(Nev.) I. Wallace, Alan R. II. Series. III. Series: U.S. Geological 

Survey bulletin ; 1725-D.

QE75.B9 no. 1725-D 557.3s [553'.09793'16] 87-600324 

[TN24.N3]
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 Rough Hills Wilderness Study 

Area (NV-010-151), Elko County, Nevada.

CONTENTS

Summary Dl 

Introduction Dl

Investigations by the U.S. Bureau of Mines D3

Investigations by the U.S. Geological Survey D3 

Appraisal of identified resources D3

Mining and mineral exploration history D3

Identified resources D4 

Assessment of potential for undiscovered resources D5

Geology D5

Geochemistry D6

Geochemical results D6

Geophysics D7

Mineral resource potential D9 

References cited DIG 

Appendix Dll

FIGURES

1. Summary map showing mineral resource potential and generalized geology of the 

Rough Hills Wilderness Study Area D2

2. Index map showing the location of the Rough Hills Wilderness Study Area D4

3. Complete Bouguer gravity map of the Rough Hills Wilderness Study Area D7

4. Total-field aeromagnetic map of the Rough Hills Wilderness Study Area D8

TABLE

1. Descriptions and analytical results of placer samples D5

Contents V

MINERAL RESOURCES OF WILDERNESS STUDY AREASNORTHEASTERN NEVADA

Mineral Resources of the

Rough Hills Wilderness Study Area,

Elko County, Nevada

By Alan R. Wallace, Robert J. Turner, V.J.S. Grauch, and Joseph L. Plesha 

U.S. Geological Survey

Staff

U.S. Bureau of Mines

SUMMARY

The Rough Hills Wilderness Study Area (NV-010- 

151), hereafter referred to as the study area, comprises 

approximately 6,685 acres about 60 mi (miles) north of 

Elko in northern Elko County, Nev. Field work was conducted by the U.S. Geological Survey (USGS) and U.S. 

Bureau of Mines (USBM) to assess the mineral resource 

potential and the known mineral resources of the study 

area. The Charleston, Island Mountain, and Alder mining 

districts, are short distances to the east, west, and northwest, respectively. However, other than minor, unrecorded production of placer gold from the Prunty Prospect near the northeast corner (fig. 1), the study area 

has no history of mining. The wilderness study area has 

a low mineral resource potential for undiscovered 

metasomatic gold, silver, tungsten, molybdenum, and 

copper, disseminated gold and silver, placer gold, barite, 

tin, sand and gravel, uranium and thorium, and oil and 

gas.

Most of the Rough Hills Wilderness Study Area is 

underlain by the Jarbidge Rhyolite, a volcanic rock that 

was erupted approximately 15 m.y. ago (million years 

ago; see geologic time chart in appendix of this report). 

Mesozoic sedimentary rocks and older Tertiary volcanic 

rocks underlie the Jarbidge Rhyolite, and upper Tertiary 

sedimentary rocks overlie the rhyolite. All of the rocks 

in the area are faulted to some degree.

Despite scattered geochemical anomalies in the 

wilderness study area, the geologic, geochemical, and 

geophysical evidence indicate that the wilderness study 

area has low mineral resource potential for undiscovered 

gold, silver, tungsten, copper, and molybdenum. One 

small gold placer prospect (Prunty) is in the northeast 

corner of the study area. Slightly anomalous arsenic and 

mercury values were obtained from faulted sedimentary 

rocks at the southwest corner of the study area, but the

geologic and geochemical evidence indicates that the extent of mineralized rocks is extremely limited and that 

the resource potential for associated gold and silver is 

low. The resource potential for oil and gas, sand and 

gravel, uranium and thorium, barite, and tin is low.

INTRODUCTION

The Rough Hills Wilderness Study Area covers approximately 6,685 acres in northern Elko County, Nevada 

(fig. 2). It is approximately 12 mi east of Wild Horse 

and 60 mi north of Elko, Nev. The area is accessible 

on the west and south sides and, in part, on the east 

side by dirt roads. Its appellation is appropriate, as the 

terrain is rugged and ranges in elevation from approximately 6,000 ft (feet) along the Bruneau River to 7,923 

ft along the ridgecrest on the west side of the study area. 

Scattered juniper trees and abundant sagebrush cover the 

hillsides, and willows and aspen grow along the small 

streams.

This report presents an evaluation of the mineral 

endowment (identified resources and mineral resource potential) of the study area and is the product of several 

separate studies by the USBM (U.S. Bureau of Mines) 

and the USGS (U.S. Geological Survey). Identified resources are classified according to the system of the 

USBM and USGS (1980) which is shown in the appendix 

of this report. Mineral resource potential, the likelihood 

of occurrence of undiscovered metals and nonmetals, industrial rocks and minerals, and of energy sources (coal, 

oil, gas, oil shale, and geothermal sources), is classified 

according to the system of Goudarzi (1984), shown in 

the appendix of the report.

Rough Hills Wilderness Study Area D1
115°35'

41°40'

APPROXIMATE BOUNDARY 

OF THE ROUGH HILLS 

WILDERNESS STUDY 

AREA(NV-010-151)

7

Figure 1 (above and facing page). Summary map showing mineral resource potential and generalized 

geology of the Rough Hills Wilderness Study Area.

D2 Mineral Resources of Wilderness Study Areas Northeastern Nevada
EXPLANATION

L/C Geologic terrane having low mineral resource 

potential for disseminated gold and silver, placer 

gold; contact metasomatic gold, silver, copper, 

tungsten, and molybdenum; barite; tin; sand and 

gravel; uranium and thorium, and oil and gas 

Applies to entire study area

CORRELATION OF MAP UNITS

j QUATERNARY

Unconformity

TERTIARY

TRIASSIC, 

PERMIAN, 

PENNSYLVANIAN, 

Mississippian MISSISSIPPIAN

Qal Qc Qls

Un 

Un

Ts

Tjr

/ Miocene

conformity

TV

conforrr

 &MS

ity Lower 

*\ Triassic to ^ 

J Upper J

locations of patented and unpatented mining claims, mineral leases, and oil and gas leases in and near the study 

area. Field studies concentrated on the examination of 

known and unrecorded mines, prospects, and mineralized 

areas inside or near the study area. Eighteen placer samples were collected from the Prunty placer prospect and 

from sand and gravel deposits along Copper Creek and 

the Bruneau River. Detailed information is available from 

the U.S. Bureau of Mines, Western Field Operations Center, E. 360 Third Avenue, Spokane, WA 99202.

Investigations by the U.S. Geological Survey

Geologic mapping and sampling of the study area 

were done by the USGS. Mapping was carried out during 

one week in the summer of 1986, during which time the 

field work was supported by helicopter access to the area. 

Mapping was done on 1:24,000 topographic maps and 

aerial photographs, and rock samples were collected at 

the same time for chemical analysis. Stream-sediment 

sampling was done during the summer of 1985 under the 

supervision of R.J. Turner. Geophysical data were compiled by V.J S. Grauch and J.L. Plesha.

Qal 

Qc 

Qls 

Ts 

Tjr 

TV

LIST OF MAP UNITS 

Alluvium (Quaternary) 

Colluvium (Quaternary) 

Landslide deposits (Quaternary) 

Sedimentary rocks, undivided (Tertiary) 

Jarbidge Rhyolite (Miocene) 

Volcanic rocks, undivided (Tertiary)

Sedimentary rocks, undivided (Lower Triassic 

through Mississippian)

Contact Queried where uncertain 

Fault, approximately located 

USBM sample locality

Investigations by the U.S. Bureau of Mines

The USBM examined U.S. Bureau of Land Management, USBM, state, county, and other records for the

APPRAISAL OF IDENTIFIED RESOURCES

By Staff

U.S. Bureau of Mines

Mining and Mineral Exploration History

The study area has no history of mining other than 

minor, unrecorded production of placer gold from the 

Prunty prospect at the confluence of Copper Creek and 

the Bruneau River (fig. 1). Local residents reportedly recovered about 2 oz (troy ounces) of gold during the 

depression years of the 1930's, and in 1981 other local 

residents did exploration work at the prospect (Frank 

Prunty, 1985, personal commun.). Although no records 

were found to indicate that the deposit has ever been 

claimed, there are nine pits and trenches, and an area 

of about 5,000 ft2 has been sluiced to bedrock.

The Charleston mining district is adjacent to the 

eastern boundary of the study area (Quade and Tingley, 

1984). Two other mining districts, the Island Mountain 

to the west and the Alder to the northwest, extend to 

within approximately 1 mi and 5 mi, respectively, of the 

study area. The first discoveries were made in the districts 

in the 1860's and 1870's. Since then, each district has

Rough Hills Wilderness Study Area D3
116°00' 115°00'

42°00'

41°00'

APPROXIMATE BOUNDARY OF 

\ THE ROUGH HILLS WILDERNESS 

STUDY AREA (NV-010-151)

20 MILES 

i

Figure 2. Index map showing location of the Rough Hills Wilderness Study Area in Elko County, 

Nevada. Dashed lines are dirt roads. A, Alder mining district; IM, Island Mountain mining district.

produced gold from placer deposits; gold, silver, copper, 

lead, antimony, tungsten, and minor zinc from quartz 

veins within pre-Tertiary sedimentary rocks cut by intrusives; and tungsten from tactile deposits (Smith, 1976). 

Some of the vein deposits contain fairly high gold and 

silver values, but none of the deposits are large. Bismuth, 

uranium, and molybdenum minerals also occur in some 

of the deposits; however, there was no production of these 

metals reported.

In recent years, there has been continued or renewed mining interest in the region. Several small mines 

in the three districts are producing or being explored for 

gold and silver in vein deposits, and some barite has been 

produced from a stratiform deposit in the Charleston district (unpub. data, Bureau of Land Management). Exploration for disseminated gold deposits has occurred in the 

districts and at the isolated Golden Empire prospect, 1.5 

mi southwest of the study area.

Identified Resources

No identified resources were delineated within the 

study area. Sand and gravel at the Prunty prospect and 

along Copper Creek and the Bruneau River were 

examined for placer gold and other heavy minerals (fig. 

1). Sample locations are on figure 1 and sample data are 

presented in table 1.

The Prunty placer prospect contains a perched deposit of gold-bearing gravel that covers about an acre and

D4 Mineral Resources of Wilderness Study Areas Northeastern Nevada
Table 1 . Descriptions and analytical results of placer samples.

Sample

loc. Name or

(fig. 1) location Sample type Workings and production Sample data

1 Copper Creek Sand from plant roots None

2 Copper Creek Pebbly gravel on bed- None 

rock.

3 Copper Creek Sandy gravel on bedrock.

4 Copper Creek Sandy gravel on bedrock.

5 Bruneau River Gravel on bedrock.

Prunty 

Prospect

Bruneau 

River

Stream gravel a few 

inches to about 8 ft 

thick, covering 

about an acre, is 

perched 5-25 ft above 

the present stream 

level. The gravel 

is derived primarily 

from quartzite and 

rhyolitic volcanic 

rocks. Fine placer 

gold is concentrated 

just above or in 

fractures in the rhyolitic bedrock. 

Scattered stream 

gravel, 0 to about 

2 ft thick extends 

upslope for about 

125 ft above the 

workings.

Slope wash and river 

gravel.

None.

None,

None.

In the northeastern portion 

of the prospect, there are 

four pits as much as 15 ft 

across and 6 ft deep. In 

the southwestern portion, 

there are three pits and 

two trenches as much as 

40 ft long and 5 ft deep. 

The trenches connect with 

an area about 100 ft long 

and 50 ft wide that has 

been sluiced to bedrock. 

It is estimated that about o

450 yd j of gravel was 

processed from the 

workings. Local residents 

reported that about 2 oz 

of gold was recovered 

from the prospect 

during the 1930's.

None.

One pan sample; no gold.

One pan sample; $0.02 gold/yd 3

One pan sample; 

$0.10 gold/yd 3 .

One pan sample; no gold.

One pan sample; no gold.

A total of 12 placer samples were taken: On the 

slope above workings, one pan and three channel 

samples of scattered stream gravels from at or 

bedrock showed no significant gold. At or near 

the northeastern workings, two channel samples 

from a pit (not to bedrock) and two pan samples 

from bedrock showed nil to $0.05 gold/yd 3 . At 

the southwest workings, a pan sample from a 

fracture in bedrock in the sluiced area showed 

$12.88 gold/yd 3 . In an adjoining trench, a 

channel sample from the surface to 2.25 ft 

showed $0.57 gold/yd 3 , another from 2.25 to 

2.50 ft (to bedrock) showed $3.06 gold/yd 3 , 

and a pan sample from a fracture in bedrock 

showed $0.54 gold/yd 3 . The average grade of 

the three samples from the trench is about 

$0.85 gold/yd3

One pan sample; $0.09 gold/yd 3 .

J7Assuming gold values at $425/oz.

averages about 4 ft thick. This implies about 6,500 yd3 

(cubic yards) of gravel; however significant values (greater than $0.10 gold/yd3 , at a gold price of $425/oz) were 

found only in samples taken in the southwestern portion 

of the occurrence. There the gravel averages less than 

$1.00 gold/yd3 , and only about 3,000 yd3 are present. 

This grade and volume of gravel is insufficient to be minable by large-volume commercial methods. These mining 

methods require gold values of several dollars per cubic 

yard and volumes of several thousand cubic yards of 

gravel treated per day. However, the occurrence may have 

value for recreational mining by hobbyists.

The source of the placer gold at the Prunty prospect 

is uncertain because placer gold was found in trace 

amounts along both Copper Creek and the Bruneau River. 

It is suspected, however, that most of the gold at the 

prospect was transported there via Copper Creek from the 

Charleston mining district. Apparently, the physical conditions necessary to significantly concentrate the gold occurred only at the confluence of the creek with the 

Bruneau River.

Other than placer gold, no mineral deposits similar 

to those that occur in the three nearby mining districts,

or at the Golden Empire prospect, are known within the 

study area.

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Alan R. Wallace, Robert L. Turner, 

V.J.S. Grauch, and Joseph L. Plesha 

U.S. Geological Survey

Geology

The geology of northeastern Nevada, in which the 

study area is located, is dominated by complexly deformed pre-Tertiary sedimentary rocks that are unconformably overlain by Tertiary sedimentary, volcanic, and 

volcaniclastic rocks. Regionally, these units are cut by 

steep normal faults, creating a series of northerly trending 

horsts and grabens.

Upper Mississippian through Lower Triassic sedimentary rocks (unit"fi Ms, fig. 1) are exposed in the extreme southwestern corner of the study area, as well as

Rough Hills Wilderness Study Area D5
to the south and west of the area. The sedimentary units 

are likely equivalents to the Lower Triassic Thaynes Formation (Hope and Coats, 1976) and to the Lower Permian 

to Upper Mississippian limestone, which includes Poorman Peak and Hammond Canyon Formations of Coash 

(1967). The lithologies included in this map unit are 

bluish-black orthoquartzite, blue-gray fossiliferous limestone, tan phyllite, conglomerate and sandstone containing 

subrounded clasts of black to white quartzite, and gray 

phyllitic chert.

Volcanic rocks of inferred Oligocene age (Hope and 

Coats, 1976) are exposed in the southwestern and western 

parts of the area. The rocks include yellowish tuffaceous 

sedimentary rocks, air-fall tuffs, and ash-flow tuffs. The 

latter contain abundant small plagioclase and pyroxene 

phenocrysts in a fine-grained, purplish-gray groundmass. 

The tuffs contain locally abundant pumice fragments and 

xenoliths of andesite and latite. The Tertiary volcanic 

rocks (unit TV, fig. 1) dip steeply to the northwest and 

overlie the pre-Tertiary sedimentary rocks in the southern 

part of the area.

Most of the study area is underlain by the Jarbidge 

Rhyolite (unit Tjr, fig. 1), which was erupted approximately 15.4 m.y. ago (Coats and others, 1977). This unit 

includes complexly intercalated rhyolitic domes, ash flow 

tuffs, flows, and volcaniclastic sedimentary rocks. The 

rhyolite is massive to convoluted; flow units dip both to 

the east and west, and they overlap and are cut by domes. 

The rock typically contains large (0.3 inch) phenocrysts 

of quartz and potassium feldspar in a fine-grained reddish 

to light-pink groundmass. The phenocrysts are subhedral 

to ovoid or rounded, and they comprise approximately 

5-40 percent of the rocks. Small pyroxene phenocrysts 

are rare. The volcanic rocks are generally unaltered, although vapor-phase alteration is present in the upper parts 

of many flows.

Upper Tertiary tuffaceous sedimentary rocks (unit 

Ts, fig. 1) cover the Jarbidge Rhyolite along the eastern 

margin of the study area. These poorly exposed units are 

composed primarily of tan to yellowish tuffaceous sedimentary rocks with thin lenses of conglomerate.

Colluvial deposits containing poorly sorted fragments of the Jarbidge Rhyolite cover the steep slopes on 

the western and southern edges of the study area. Hummocky landslide deposits cover slopes south of the study 

area. Small alluvial deposits are present along some of 

the streams in the study area; larger deposits are found 

along the floodplain of the Bruneau River east of the area 

and along Annie Creek just south of the study area (fig.

1).

Only a few minor faults were identified in the massive to convoluted Jarbidge Rhyolite, which underlies the 

majority of the study area. North- and east-trending, 

steeply dipping joints are locally abundant, and weathering along the closely spaced joint surfaces has created 

an erratic surface texture in the rhyolite.

The pre-Tertiary sedimentary rocks were moderately 

folded and weakly metamorphosed, probably during Jurassic and Cretaceous deformation (Stewart, 1980). Slaty 

cleavage is visible in the phyllites. Several faults, defined 

by zones of breccia and secondary iron oxides, cut the 

sedimentary rocks; they cut the Oligocene volcanic rocks 

as well, but their possible extension into the Jarbidge 

Rhyolite is concealed by colluvium.

Geochemistry

Twenty-nine stream sediment, twenty-five heavy 

mineral concentrate, and five rock samples were collected 

for this study. Five additional rock samples were collected 

for chemical analysis during geologic mapping.

Minus-80-mesh stream sediment and heavy mineral 

concentrate samples were selected as the primary sample 

media as they represent a composite of the rock and soil 

exposed upstream from the sample sites. The samples 

were collected from the active alluvium in the stream 

channels. Each sample was composited from several 

localities over a channel length of no greater than 50 ft. 

Analytical data and a description of the sampling and 

analytical techniques are given in a future publication.

Geochemical Results

Analytical data from the minus-80-mesh stream sediment samples show weakly anomalous but low-level values for zinc, arsenic, and silver at scattered sites throughout the study area. Six samples from drainages on the 

east side of the study area contained from 120 to 190 

ppm (parts per million) zinc; no other element was consistently associated with the zinc. Ten ppm arsenic was detected in two samples at the southwestern corner of the 

area, and in two samples in the northern half of the area. 

Two samples at the northwestern and southeastern corners 

of the wilderness study area contained 0.5 ppm silver.

The analytical data for the nonmagnetic fraction of 

the heavy mineral concentrate samples have anomalous 

values for barium (> 10,000 ppm), as well as slightly 

anomalous values for tin (100-200 ppm), molybdenum 

(one sample; 20 ppm), and silver (two samples; 20 and 

100 ppm). Two of the samples with more than 10,000 

ppm barium are from streams that drain areas underlain 

only by the Jarbidge Rhyolite. The other samples with 

highly anomalous barium are from streams that drain both 

the rhyolite and older rocks, or streams that drain only 

pre-Tertiary sedimentary rocks southwest of the study 

area. The other samples containing slightly anomalous silver, molybdenum, and tin are scattered throughout and 

near the study area.

Analytical data for rock samples showed one sample 

with slightly anomalous mercury (0.12 ppm) and arsenic

D6 Mineral Resources of Wilderness Study Areas Northeastern Nevada
115°45' 115°30

41°45' 

41°30' -

APPROXIMATE 

BOUNDARY OF 

THE ROUGH HILLS 

WILDERNESS 

STUDY AREA

10 MILES

Figure 3. Complete Bouguer anomaly map. Reduction density=2.67 g/cm3 . Study area is outlined by the heavy solid 

line; density boundaries inferred from the horizontal gradient method by heavy dashed lines. Gravity stations are 

indicated by triangles. Hachures indicate areas of gravity lows. Contour interval is 5 milligals.

(70 ppm) and a second sample with slightly anomalous 

lead (50 ppm). The sample with arsenic and mercury was 

collected from pre-Tertiary sedimentary rocks in the 

southwest corner of the study area, an area from which 

two stream-sediment samples contained slightly anomalous arsenic. A rock sample collected from an altered fault 

zone in the pre-Tertiary rocks contained 14 ppm arsenic 

but no other anomalous elements. Although mercury and 

arsenic are typically associated with epithermal gold deposits, the values encountered here are relatively low.

Geophysics

Gravity and aeromagnetic data were interpreted for 

the study area. The gravity data were compiled using data 

available from the Department of Defense data bank 

(NOAA National Geophysical Data Center) and Erwin 

(1980). The complete Bouguer gravity anomaly map (fig. 

3) generally represents deviations in rock density from 

2.67 g/cm3 (grams per cubic centimeter). The aeromagnetic data were obtained from a survey flown east-west with

Rough Hills Wilderness Study Area D7
115°45' 115°30'

41°45'

41°30'

OF THE ROUGH HILLS 

WILDERNESS STUDY AREA

10 MILES

Figure 4. Total-field aeromagnetic map from a survey flown east-west with 1-mi spacing at 9,000-ft elevation. Letters 

are referred to in text. Hachures indicate areas of aeromagnetic lows. Contour interval is 20 nanoteslas.

1 mi spacing at 9,000 ft above sea level (U.S. Geological 

Survey, 1968a and b). The total-field aeromagnetic anomaly map (fig. 4) represents changes in the magnetic field 

caused by differences in the magnetic properties of rocks 

and variations in height of the magnetic sensor above the 

rocks. The lack of detailed gravity and aeromagnetic data 

make only regional interpretations possible.

Within the Basin and Range province, mountain 

ranges typically are associated with gravity highs and adjacent valleys are associated with gravity lows, as a result 

of the contrast between relatively high-density rocks (bedrock) of the mountains and lower-density rocks (alluvial 

fill) of the valleys. The study area is at the northern end 

of a large gravity low (fig. 3) that generally correlates 

with a valley. Density boundaries producing the low were 

inferred (fig. 3) by applying the horizontal gradient 

method to the gravity data (Cordell, 1979). These boundaries cut across topography and match faults exposed just 

east of the study area (Stewart and Carlson, 1978), 

suggesting that the low is produced by a structurally controlled graben. The graben terminates just north of the 

wilderness study area.

The wilderness study area is on a large aeromagnetic low (marked A on fig. 4), corresponding to exposures 

of Jarbidge Rhyolite, which is surrounded by essentially 

nonmagnetic sedimentary rocks. This implies that the Jarbidge Rhyolite has a large, reversely polarized remanent 

magnetization (greater than the induced component). This 

conclusion is further supported by the association of a 

large aeromagnetic low (B) with exposures of the Jarbidge 

Rhyolite southeast of the study area.

Aerial gamma-ray spectroscopy data were compiled 

and processed at a scale of 1:1,000,000. The resulting 

map indicates that the wilderness study area has no uraD8 Mineral Resources of Wilderness Study Areas Northeastern Nevada
nium or thorium anomalies (J. Duval, USGS, written 

commun., 1985).

In summary, the reconnaissance scale of the 

geophysical data identifies regional geologic features but 

does not identify features that might indicate specific mineral resources.

Mineral Resource Potential

Mineral deposits known to occur in the vicinity of 

the study area include contact metasomatic deposits of 

gold, silver, tungsten, copper, and molybdenum; vein deposits of gold and silver; bedded barite deposits; placer 

deposits of gold; and sand and gravel deposits. In addition, disseminated deposits of gold and silver in preTertiary sedimentary rocks constitute a major source of 

gold and silver in northern Nevada.

The contact metasomatic deposits, as well as some 

of the vein deposits northwest of the study area, are genetically related to a Cretaceous granodiorite that was 

emplaced in Paleozoic sedimentary rocks, especially limestone (Granger and others, 1957; Lowe and others, 1985). 

Contact metasomatism converted the limestone to a 

garnet-magnetite hornfels with gold, silver, tungsten, copper, and molybdenum minerals. Although limestone is exposed in the southwestern part of the study area, it is 

not altered nor does it contain anomalous amounts of metals. In addition, no intrusive rock is present nor do the 

geophysical data indicate a buried pluton. Therefore, the 

potential for resources of gold, silver, tungsten, molybdenum, and copper in deposits related to contact 

metasomatism is low, with certainty level C. The absence 

of veins and a pluton also make the potential for goldsilver resources in intrusive-related vein deposits low, at 

certainty level C. The potential for these types of resources beneath the thick cover of Tertiary volcanic and 

sedimentary rocks is unknown due to the lack of exposure 

and reconnaissance nature of the geophysical data.

The Paleozoic and Mesozoic sedimentary rocks in 

the southwestern corner of the study area are faulted and 

weakly altered, but discrete veins are not evident. One 

sample of brecciated and altered rock contained slightly 

anomalous amounts of arsenic (70 ppm) and mercury 

(0.12 ppm), and two stream-sediment samples contained 

anomalous arsenic (15 and 25 ppm). Gold and silver were 

not detected due to their high analytical detection limits; 

the slightly anomalous arsenic and mercury, which commonly occur with gold and silver in epithermal mineral 

deposits, suggest that gold and (or) silver may be present. 

However, the extremely limited extent of the faults and 

related breccia and altered rocks indicates that the area 

influenced by hydrothermal activity was very small. 

Therefore, the pre-Tertiary sedimentary rocks in the southwestern part of the area have a low potential, at certainty 

level C, for deposits of gold and silver.

Heavy-mineral concentrates from streams that drain 

the Jarbidge Rhyolite contain detectable amounts of tin, 

which may be present in small grains of cassiterite. The 

sample-preparation procedure for heavy-mineral concentrates increases the relative concentration of tin-bearing 

minerals in the fraction to be analyzed, and tin concentrations below 500 ppm are not considered to be anomalous 

in rhyolitic terranes (du Bray and others, 1982). Rock 

and stream-sediment samples do not contain anomalous 

amounts of tin. The Jarbidge Rhyolite typically contains 

trace amounts of tin and other metals (Coats and others, 

1977), but they are not present in significant amounts in 

the study area. Therefore, the study area has a low potential, at certainty level C, for tin.

Sedimentary barite deposits are present in Ordovician sedimentary rocks 6 mi west and 2 mi east of the 

study area. Similar deposits are common in northern 

Nevada, and they are typically associated with Ordovician 

and Devonian eugeosynclinal sedimentary rocks, especially bedded cherts (Papke, 1984). The pre-Tertiary sedimentary rocks exposed in the southwestern corner of the 

study area are of Triassic age and do not contain rocks 

typical of a eugeosynclinal depositional environment. Furthermore, barite was not observed in these rocks, nor did 

stream-sediment or rock samples from this area contain 

anomalous barium. Rocks exposed in the two drainages 

in the Jarbidge Rhyolite, from which heavy-mineral concentrate samples with anomalous barium were collected, 

did not contain visible barite or evidence of mineralization. The anomalous barium values may reflect local surficial formation of barite. Therefore, the study area has a 

low potential, at certainty level C, for barite resources.

Gold was mined from placer deposits 5 mi to the 

northwest and 2 mi to the east from Quaternary and Tertiary alluvial deposits. In addition, a small amount of 

placer gold was mined from the Prunty prospect within 

the study area, and alluvium in both the Bruneau River 

and Copper Creek contain traces of placer gold. The gold 

was probably derived from the nearby Charleston mining 

district. However, only small amounts of alluvium are 

present at these sites and elsewhere in the study area. 

Stream-sediment and heavy-mineral samples from other 

streams in the study area do not indicate the presence 

of gold in alluvial deposits. Although a small amount of 

placer gold was mined within the study area, the mineral 

resource potential for undiscovered placer gold resources 

is low at certainty level C.

Only small amounts of sand and gravel are present 

in alluvial deposits along the Bruneau River and Annie 

Creek. Therefore, the study area has a low potential, at 

certainty level C, for undiscovered sand and gravel 

resources.

The study area lacks the host rocks and structures 

favorable for the occurrence of oil and gas. Sandberg 

(1983) rated the potential for oil and gas resources in the

Rough Hills Wilderness Study Area D9
study area as low. The mineral resource potential for oil 

and gas is low, with certainty level C. The aerialradiometric studies showed no anomalies for uranium or thorium. 

The mineral resource potential for uranium or thorium resources is also low, at confidence level C.

REFERENCES CITED

Coash, J.R., 1967, Geology of the Mount Velma quadrangle, 

Elko County, Nevada: Nevada Bureau of Mines Bulletin 

68, 21 p.

Coats, R.R., Greene, R.C., Cress, L.D., and Marks, L.Y., 

1977, Mineral resources of the Jarbidge Wilderness and adjacent areas, Elko County, Nevada, with a section on interpretation of aeromagnetic data by W.E. Davis: U.S. 

Geological Survey Bulletin 1439, 79 p.

Cordell, Lindrith, 1979, Gravimetric expression of graben faulting in Santa Fe Country and the Espanola Basin, New 

Mexico: New Mexico Geological Society Guidebook, 30th 

Field Conference, Santa Fe Country, p. 59-64.

du Bray, E.A., Elliott, J.E., and Stoeser, D.B., 1982, 

Geochemical evaluation of felsic plutonic rocks in the eastern and southeastern Arabian Shield, Kingdom of Saudi 

Arabia: U.S. Geological Survey Saudi Arabian Mission 

Technical Report TR-02-2, 53 p.

Erwin, J.W., 1980, Bouguer gravity map of Nevada, Wells 

Sheet, Nevada: Nevada Bureau of Mines and Geology, Map 

65, 4 p., scale 1:250,000.

Goudarzi, G.H., compiler, 1984, Guide to the preparation of 

mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-787, 42 p.

Granger, A.E., Bell, M.M., Simmons, G.C., and Lee, Florence, 1957, Geology and mineral resources of Elko County, 

Nevada: Nevada Bureau of Mines Bulletin 54, 190 p.

Hope, R.A., and Coats, R.R., 1976, Preliminary geologic map 

of Elko County, Nevada: U.S. Geological Survey Open-file 

Report 76-779, scale 1:100,000.

Lowe, N.T., Raney, R.G., and Norberg, J.R., 1985, Principal 

deposits of strategic and critical minerals in Nevada: U.S. 

Bureau of Mines Information Circular 9035, 202 p.

Papke, K.G., 1984, Barite in Nevada: Nevada Bureau of Mines 

and Geology Bulletin 98, 125 p.

Quade, Jack, and Tingley, J.V., 1984, Reconnaissance 

geochemical assessment of mineral resources in Rough Hills 

Wilderness Study Area (NV-010-151), Elko County, 

Nevada: U.S. Bureau of Land Management contract YA553-CT1-1058, Nevada Bureau of Mines and Geology, 

Reno, 15 p.

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

Nevada: U.S. Geological Survey Miscellaneous Investigations Map 1-1542, scale 1:1,000,000.

Smith, R.M., 1976, Mineral resources of Elko County, Nevada: 

U.S. Geological Survey Open-File Report 76-56, 194 p.

Stewart, J.H., 1980, Geology of Nevada: Nevada Bureau of 

Mines and Geology Special Publication 4, 136 p.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U.S. Geological Survey Map, scale 1:500,000.

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, 1968a, Aeromagnetic map of part of 

the Jarbidge Quadrangle, Elko County, Nevada: U.S. 

Geological Survey Open-File Report 68-286, scale 

1:62,500.

 1968b, Aeromagnetic map of Wild Horse, Mt. Velma, 

Mountain City, Elko County, Nevada: U.S. Geological Survey Open-File Report 68-293, scale 1:62,500.

O10 Mineral Resources of Wilderness Study Areas Northeastern Nevada
APPENDIX
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

Definitions of Mineral Resource Potential

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 unlikely. This broad 

category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few 

or no indications of having been mineralized.

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 likelihood of resource accumulation, and (or) where an application of 

mineral-deposit models indicates favorable ground for the specified type(s) of deposits.

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.

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

moderate, or high levels of resource potential.

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

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

I

o

Q_

o

OC 

O

LLJ 

QC

U.

O

B C 

LEVEL OF CERTAINTY

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

B. Available information 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.

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.
RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

Inferred

UNDISCOVERED RESOURCES

Probability Range

 (or) 

Hypothetical i Speculative

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

Reserves Inferred Reserves

Marginal Reserves

Demonstrated 

Subeconomic Resources

Inferred 

Marginal Reserves

Inferred

Subeconomic

Resources

+

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from 

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.
GEOLOGIC TIME CHART 

Terms and boundary ages used 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 

Subperiod

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

 -

BOUNDARY AGE 

IN 

MILLION YEARS

- 0.010

- 1.7

_ 5

OQ

- 55

cc

- 96

1 OO

one

-~ 240

- 290 

-~ 330

_ ocri

- 410

- 500 

- ~ 570'

- 900 

- 1600

- 2500

- 3000 

- 3400

4RRO

1 Rocks older than 570 m.y. also called Precambrian, a time term without specific rank.

2 Informal time term without specific rank.

*U.S. GOVERNMENT PRINTING OFFICE: 1987-0-773-047/66003

* x.:-&;,' 'W' ^Viv.-fc.'.lm. s'.'.-S