Mineral Resources of the

Hawk Mountain Wilderness Study Area,

Harney County, Oregon

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Chapter F

Mineral Resources of the

Hawk Mountain Wilderness Study Area,

Harney County, Oregon

By BRENT D. TURRIN, JAMES E. CONRAD, 

DONALD PLOUFF, and HARLEY D. KING 

U.S. Geological Survey

CARL C. SWISCHER 111 

Berkeley Geochronology Center

RONALD T. MAYERLE and RICHARD L. RAINS 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1740

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

STEENS MOUNTAIN-RINCON REGION, OREGON
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L Peck, Director

Any use of trade, product, or firm names in this publication 

is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1989

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 Hawk Mountain Wilderness Study Area, Hamey

County, Oregon / by Brent D. Turrin . .. [et al.]. 

p. cm. (U.S. Geological Survey bulletin ; 1740)

"Chapter F."

Includes bibliographical references.

Supt. of Docs, no.: I 19.3:1740-F

1. Mines and mineral resources Oregon Hawk Mountain Wilderness. 

2. Hawk Mountain Wilderness (Or.) I. Turrin, Brent D. II. Series. 

QE75.B9 no. 1740 557.3 s-dc20 89-600284 

[TN24.07] [553'.09795'95] CIP
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 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 

part of the Hawk Mountain (OR-001-146A) Wilderness Study Area, Harney County, 

Oregon.

CONTENTS

Summary Fl 

Abstract Fl 

Character and setting Fl 

Identified resources Fl 

Mineral resource potential F2 

Introduction F3

Location and physiography F3 

Previous and present investigations F3 

Appraisal of identified resources F4

Mining and mineral exploration history F4 

Identified resources F4 

Assessment of mineral resource potential F4 

Geology F4

Fossil vertebrates from sedimentary deposits F6 

Geochemical studies F6 

Geophysical studies F8

Aerial gamma-ray spectroscopy F8 

Aeromagnetic survey F8 

Gravity survey F8 

Mineral and energy resources of the Hawk Mountain Wilderness Study

Area F9

Mineral resources F9 

Energy resources F9 

References cited FLO 

Appendixes

Definition of levels of mineral resource potential and certainty of

assessment F14

Resource/reserve classification F15 

Geologic time chart F16

FIGURES

1. Index map showing location of Hawk Mountain Wilderness Study Area, Harney 

County, Oregon F2

2. Map showing mineral resource potential and generalized geology of Hawk 

Mountain Wilderness Study Area, Harney County, Oregon F5

3. Complete Bouguer gravity anomaly map of Hawk Mountain Wilderness Study 

Area, Harney County, Oregon F9

TABLE

1. Vertebrate fauna from the Thousand Creek beds F7

Contents

Mineral Resources of the

Hawk Mountain Wilderness Study Area

Harney County, Oregon

By Brent D. Turrin, James E. Conrad, Donald Plouff, and Harley D. King 

U.S. Geological Survey

Carl C. Swischer III

Berkeley Geochronology Center

Ronald T. Mayerle and Richard L Rains 

U.S. Bureau of Mines

SUMMARY 

Abstract

The Hawk Mountain Wilderness Study Area (OR001-146A) encompasses approximately 69,640 acres along 

the Oregon-Nevada State line. The study area lies in southwestern Harney County, Oreg., approximately 20 mi southeast of Fields, Oreg., and 12 mi west of Denio, Nev. In this 

report, "study area" or "wilderness study area" refers to that 

area for which the mineral survey was requested by the U.S. 

Bureau of Land Management. Geologic, geochemical, and 

geophysical surveys of the study area were conducted by the 

U.S. Geological Survey and U.S. Bureau of Mines to evaluate 

the identified (known) mineral resources and to assess the 

mineral resource potential (undiscovered). No resources 

were identified in the study area. No mines or claims were 

observed in the study area nor are there any records of 

production or oil, gas, or geothermal leases for the study 

area. The study area is underlain by Tertiary volcanic rocks 

that are locally hydrothermally altered and silicified. In this 

region, altered rocks may host deposits of mercury, silver, 

and gold and industrial minerals (clay and zeolite). In 

addition, the geologic setting of the study area is favorable for 

rhyolite-hosted tin deposits. No evidence of mercury, silver, 

or tin mineralization or of clay and zeolites was found in the 

study area. However, geochemical data indicate that the 

west half of the study area has low resource potential for gold 

in epithermal deposits. Low potential for uranium in localized, 

small-volume deposits is associated with the tuffaceous 

sedimentary rock exposed in the south-central and eastern 

parts of the study area. Secondary uranium minerals (carnotite and schroeckingerite?) are reportedly associated with 

opalized zones in tuffaceous lacustrine sedimentary rock

Manuscript approved for publication August 14, 1989.

exposed south of the study area. The entire study area has 

low potential for geothermal resources and low potential for 

oil and gas resources.

Character and Setting

The Hawk Mountain Wilderness Study Area (OR001-146A) is situated in the transition zone between the 

Basin and Range and Columbia Plateau physiographic 

provinces. The Basin and Range province in Oregon and 

adjacent parts of Nevada is an extensive semiarid to arid 

tract of subparallel, north-trending en echelon mountain 

ranges and intervening valleys. The Columbia Plateau 

province is a high dissected plateau consisting mostly of 

Tertiary volcanic rocks. The 69,640-acre study area is 

situated along the Oregon-Nevada State line approximately 20 mi southwest of Fields, Oreg., and approximately 12 mi west of Denio, Nev. (fig. 1). Elevations 

range from 5,000 ft at the valley bottoms to almost 7,000 

ft at the highest peaks. The study area is underlain by a 

sequence of Tertiary rhyolitic ash-flow tuffs and lava 

flows (see geologic time chart in "Appendixes" for age 

definitions). Two major sets of faults that trend northwest and northeast cut the rocks of the study area.

Identified Resources

The Hawk Mountain Wilderness Study Area does 

not contain any identified mineral resources. In addition, 

no mines, claims, prospects, or mineralized zones were 

identified in the study area. However, four mining districts are located near the study area. They are (1) the 

Steens-Pueblo mining district, a 40-mi-long belt of epithermal gold, copper, and mercury deposits that lies

Mineral Resources of the Hawk Mountain Wilderness Study Area, Oregon F1
along the east edge of the Steens and Pueblo Mountains, 

approximately 30 and 10 mi northeast and east of the 

study area, respectively, (2) the Warm Springs gold and 

tungsten mining district that is approximately 20 mi east 

of the study area, (3) the Virgin Valley opal mining 

district that is approximately 10 mi south of the study 

area, and (4) the Lone Pine gold-mercury mining district 

that is approximately 30 mi southwest of the study area.

Mineral Resource Potential

The Hawk Mountain Wilderness Study Area is 

part of a region characterized by extensive exposures of 

Tertiary volcanic rocks that are locally hydrothermally 

altered and silicified. Outside the study area, these 

altered rocks host deposits of base and precious metals 

(mercury, silver, and gold) and industrial minerals (zeolites and clays). Of these commodities, gold is the only 

one found in the study area. The western part of the study 

area has low resource potential for gold in epithermal 

deposits (fig. 2).

The entire study area has low favorability for the 

occurrence of oil and gas resources. No drilling or other 

exploration for oil and gas has been done inside the study 

area. Because of the extensive Miocene magmatism and 

associated high heat flow in this part of the Basin and 

Range province, the region is generally too thermally 

mature to have developed hydrocarbon reserves. Therefore, the entire study area has low potential for oil and 

gas resources.

On the basis of the aerial gamma-ray spectroscopy 

data, there is low potential for uranium in localized, 

small-volume deposits in tuffaceous sedimentary rock. 

This unit is widespread in the eastern and southern parts 

of the study area. Secondary uranium minerals (carnotite

118°45'

APPROXIMATE BOUNDARY

OF

HAWK MOUNTAIN

WILDERNESS STUDY AREA

6750 A (OR-001-146A)

Hawks Mountain

HARNEY CO _____j ___ 

HUMBOLDTCO

"OREGON ^ 

NEVADA

| 6547 A Big Spring Butte

Black Mountain 

J A 5918

<( \Big Spring Reservoi og Hot Springs Baltazor Hot Spring

and Reservoir

Figure 1. Index map showing location of Hawk Mountain Wilderness Study Area, Harney County, Oregon. 

F2 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
and schroeckingerite?) are reportedly associated with 

opalized zones in the tuffaceous lacustrine sedimentary 

rock of the Virgin Valley Formation south of the study 

area.

No hot springs were found in the study area nor are 

there any geothermal production leases for land in the 

study area. However, the presence of young volcanic rock 

(less than 2 Ma) and the occurrence of hot springs within 

10 mi of the study area suggest that the entire study area 

has low potential for geothermal resources.

INTRODUCTION

This mineral survey was requested by the U.S. 

Bureau of Land Management and is the result of a 

cooperative effort by the U.S. Geological Survey and the 

U.S. Bureau of Mines. An introduction to the wilderness 

review process, mineral survey methods, and agency 

responsibilities was provided by Beikman and others 

(1983). The U.S. Bureau of Mines 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 a system that is a modification 

of that described by McKelvey (1972) and U.S. Bureau of 

Mines and U.S. Geological Survey (1980). U.S. Geological Survey studies 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 ore-deposit models. Goudarzi (1984) discussed mineral assessment methodology and terminology 

as they apply to these surveys. See "Appendixes" for the 

definition of levels of mineral resource potential and 

certainty of assessment and for the resource/reserve 

classification.

Location and Physiography

The Hawk Mountain Wilderness Study Area comprises approximately 69,640 acres along the OregonNevada State line in eastern Harney County, Oreg., 

approximately 20 mi southwest of Fields, Oreg., and 

approximately 12 mi west of Denio, Nev. (fig. 1). Most 

parts of the study area are accessible via unimproved 

roads from Nevada Highway 140 and Oregon Highway 

140. The study area also can be accessed from the north 

on a partly improved gravel road leading from the 

Fields-Frenchglen road, which is northeast of the area 

shown in figure 1. Unimproved roads parallel the north, 

northeast, and northwest borders of the study area. 

These roads, however, are periodically washed out and in

places may only be passable to high-clearance fourwheel-drive vehicles.

The climate in the study area, typical of a middlelatitude desert, is semiarid to arid; it is dominated by 

continental tropical air masses in summer and continental polar air masses in winter (Sthraler, 1969; Houghton 

and others, 1975). Annual temperatures range from less 

than -4 °F in winter to more than 100 °F during the 

summer. Daily summer temperature changes frequently 

exceed 90 °F. Precipitation, mostly as snow and winter 

rain, ranges from 5 to 15 in. annually. During summer, 

relative humidity averages about 20 percent but may fall 

to 10 percent.

Several varieties of sagebrush and grass flourish in 

most of the study area. Willow, cottonwood, and aspen 

occur along drainages. Wildlife in the area includes 

pronghorn antelope, deer, coyote, bobcat, mountain lion, 

and a variety of smaller mammals. Feral horses and 

burros are also abundant. The avian population varies 

seasonally in number and species.

Previous and Present Investigations

A reconnaissance geologic map of the Adel quadrangle, Lake, Harney and Malheur Counties, Oregon, by 

Walker and Repenning (1965) at a scale of 1:250,000 

includes the study area. In addition, radiometric data, 

compiled by Geodata International, Inc. (1980) for the 

National Uranium Resource Evaluation (NURE) program of the Department of Energy and regional aeromagnetic surveys (U.S. Geological Survey, 1972a, b) by 

the U.S. Geological Survey cover the area. In 1980 the 

U.S. Bureau of Land Management conducted a reconnaissance geochemical survey in the Hawk Mountain 

Wilderness Study Area (Rimal, 1980). The adjoining 

Charles Sheldon Wilderness Study Area, south of the 

study area in Nevada, was examined for mineral resource 

potential by the U.S. Geological Survey and the U.S. 

Bureau of Mines (Greene, 1984; Plouff, 1984; Cathrall 

and others, 1984; and Tuchek and others, 1984).

The U.S. Geological Survey conducted field investigations of the Hawk Mountain Wilderness Study Area 

in the spring of 1986. This work included geologic 

mapping at scales of 1:62,500 and 1:24,000, geochemical 

sampling, and examining outcrops for evidence of mineralization. The geochemical survey utilized rock and 

stream-sediment (including a fine fraction and heavymineral concentrate) samples that were analyzed for 33 

elements by semiquantitative emission spectrography. 

Gold, arsenic, antimony, cadmium, mercury, zinc, and 

bismuth were detected using atomic-absorption methods, and uranium and thorium were detected using 

delayed-neutron count. Earlier geophysical data, which 

consisted of regional gravity and magnetic surveys, were 

compiled and analyzed for this study. Further details on

Mineral Resources of the Hawk Mountain Wilderness Study Area, Oregon F3
analytical procedures used for this resource assessment 

are given in the appropriate sections that follow.

The U.S. Bureau of Mines gathered data on mines, 

claims, prospects, and mineralized areas from U.S. 

Bureau of Land Management records, published literature, U.S. Bureau of Mines files and production records, 

and county mining records. Fieldwork was conducted 

during the summer of 1986.

APPRAISAL OF IDENTIFIED RESOURCES

By Ronald T. Mayerle and Richard L. Rains, 

U.S. Bureau of Mines

Mining and Mineral Exploration History

The U.S. Bureau of Mines found no record of 

mining activities for the study area. The nearest mining 

district, the Virgin Valley, is about 10 mi south of the 

study area in the Charles Sheldon National Antelope 

Range. Precious opal is currently being produced in the 

district and building stone was previously produced in the 

district (Tuchek and others, 1984). Uranium occurs in 

the district and the adjacent region.

The only reported mineral exploration in the study 

area is a reconnaissance geochemical survey of the Hawk 

Mountain area and the adjoining Lone Mountain area 

conducted by the U.S. Bureau of Land Management 

(Rimal and others, 1980). The results of this study are 

discussed in the "Geochemical Studies" section.

Identified Resources

No mineral resources were identified within the 

Hawk Mountain Wilderness Study Area (Mayerle and 

Rains, 1988). During the U.S. Bureau of Mines field 

study, special attention was given to three drainages in 

the northern part of the study area west of Hawks 

Mountain (fig. 1). These drainages were considered by 

the U.S. Bureau of Land Management on the basis of 

anomalous gold found during their geochemical study as 

suitable for "further scrutiny" (Rimal and others, 1980) 

that might reveal evidence of possible mineral deposits. 

Of the 12 alluvium (placer) samples taken by the U.S. 

Bureau of Mines, 7 were collected from dry streambeds 

in the three drainages; 1 alluvium sample from each of 

the three drainages was taken as close to the U.S. Bureau 

of Land Management stream-sediment sample locality as 

possible. The other five alluvium samples were taken 

from drainages adjacent to the three drainages, at localities that were not sampled by the U.S. Bureau of Land 

Management.

No gold or other heavy minerals were found in any 

of the 12 alluvium samples collected, and no mineralized 

or significantly altered rock was found in outcrops or as

float1 in the drainages. The anomalous concentrations of 

gold found in the stream-sediment samples taken by the 

U.S. Bureau of Land Management, however, show that 

small amounts of gold are present in the study area. The 

U.S. Bureau of Mines and U.S. Bureau of Land Management studies indicate that the distribution of gold in 

the study area is irregular and is probably not related to 

gold deposits in the drainages sampled.2

Common opal and fossil mammalian bones of 

Hemphillian age (late Miocene) are contained in ash 

beds east and southeast of the study area. Although these 

fossils do not constitute a mineral resource, they are 

deemed valuable by some collectors and paleontologists. 

Precious opal and building stone resources, and uranium 

occurrences similar to those found in the Virgin Valley 

mining district to the south are not known in the wilderness study area.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Brent D. Turrin, James E. Conrad, Donald Plouff, and

Harley D. King

U.S. Geological Survey

Carl C. Swischer III

Berkeley Geochronology Center

Geology

The Hawk Mountain Wilderness Study Area is 

underlain by a sequence of late Tertiary volcanic flows, 

volcaniclastic, and continental sedimentary rocks and 

Quaternary alluvium and playa deposits. Although the 

basal contact of the Tertiary section is not exposed, local 

relief indicates that the volcanic section is more than 

1,500 ft thick. Major fault trends within the study area, 

northwest and northeast, are typical of this part of the 

Basin and Range province.

The oldest geologic unit, exposed just south of the 

study area, is the Idaho Canyon Tuff of Noble and others 

(1970); it is 200 to 400 ft thick and consists mostly of 

densely welded, devitrified tuff that is medium gray to 

light brown and weakly porphyritic. Phenocrysts in the 

Idaho Canyon Tuff are predominantly alkali feldspar and

1Float-pieces of rock lying on the surface and which may have 

been transported some distance from their origin, generally by water or 

gravity.

2The stream-sediment samples taken by the BLM were assayed 

for a variety of elements by laser-induced fluorescence, atomic absorption, chemical, and other analytical methods. In comparison, alluvium 

(placer) sampling analyses are relatively unsophisticated; however, 

alluvium sampling has been used for centuries to detect heavy metals 

or minerals that are commonly associated with a variety of mineral 

deposits and, coupled with a ground reconnaissance, can provide much 

valuable data.

F4 Mineral Resources of Wilderness Study Areas: Steens Mountaln-Rincon Region, Oregon
119° 15' 119° 00'

Tic 

L/B Geo

L/D O,G

(entire study area)

APPROXIMATE BOl'NDAR\

OF

HAWK MOl NTAIN 

-WILDERNESS STUDY AREA 

(OR-001-146A) lT/r T

4 MILES

o (Oo

EXPLANATION

Geologic map units 

Qal Alluvium (Quaternary) Qpl Playa deposits (Quaternary) 

Qb Basalt of Railroad Point of Greene (1984) (Quaternary) Olivine

basalt 

Tb Basalt of Catnip Creek of Greene (1984) (Tertiary) Discontinuous

outcrops unconformably overlying and interbedded with tuffaceous sedimentary rock of Tst 

Tst Tuffaceous sedimentary rock (Tertiary) Consists of Virgin Valley

and Thousand Creek Formations of Merriam (1910, 1911),

undivided 

Trf Canon Rhyolite of Merriam (1910) (Tertiary)--Rhyolite flows,

domes, and pyroclastic deposits 

Tic Idaho Canyon Tuff of Noble and others (1970) (Tertiary) Densely

welded, devitrified ash-flow tuff 

Contact 

 j_ _ _ ... Normal fault Dashed where approximate; dotted where concealed.

Bar and ball on downthrown side

Figure 2. Mineral resource potential and generalized geology (from Walker, 1965) of Hawk Mountain Wilderness Study Area, Harney County, Oregon.

oXx- Area having low mineral resource potential (L)

g Levels of certainty of assessment 3 B Data only suggest level of assessment 5' C Data give good indication of assessment

^ D Data clearly define level of assessment a g Commodities % Au Gold 

w Geo Geothermal 

| O,G Oil and Gas 

"5 U Uranium

Sample locality See text for discussion HM078H
quartz but include trace amounts of fayalite and magnetite.

Overlying the Idaho Canyon Tuff is the middle 

Miocene Canon Rhyolite of Merriam (1910,1911). This 

unit is composed of rhyolite flows, domes, and subordinate intercalated pyroclastic deposits. A potassium-argon 

(K-Ar) age of 15 Ma for the unit is reported in Noble and 

others (1970) and Harvey and others (1986). The unit 

mostly consists of light-purplish-gray to reddish-brown, 

microcrystalline to fine-grained silicic lava flows containing fractured phenocrysts of alkali feldspar, quartz, and 

minor amounts of euhedral to subhedral biotite and 

alkali amphibole. Flow banding, flow foliations, and ramp 

structures are common features of the Canon Rhyolite. 

Rocks of the unit are peralkaline, as are most rhyolitic 

tuffs and lava flows of middle Miocene age in the region 

(Noble and others, 1968; Noble and others, 1970; Korringa, 1973; Bonham, 1969; and Harvey and others, 

1986).

Interbedded with and unconformably overlying the 

Canon Rhyolite and Idaho Canyon Tuff is a sequence of 

tuffaceous sedimentary rock. Common opal and fossil 

mammalian bones are contained within this unit. This 

sequence was divided into two units by Merriam (1910, 

1911); they are the Virgin Valley Formation, which 

contains Barstovian (approximately 14 to 17 Ma) fauna 

and the Thousand Creek Formation, which contains 

Hemphillian (approximately 4 to 8 Ma) fauna. The 

tuffaceous sedimentary rock unit is mostly white to 

light-gray claystone and tuffaceous siltstone, sandstone, 

and waterworked air-fall tuff. However, there is no clear 

lithologic break between the Virgin Valley Formation 

and the Thousand Creek Formation, so they are shown as 

one unit in figure 2.

Unconformably overlying and interbedded with the 

tuffaceous sedimentary unit is the Basalt of Catnip Creek 

of Greene (1984). This basalt forms a distinct mesacapping unit in the southeastern part of the study area. 

Two K-Ar ages of 8.84±0.1 Ma and 9.87±1.2 Ma are 

reported for this unit (Greene, 1984).

The youngest volcanic unit in the study area is the 

Basalt of Railroad Point of Greene (1984), a canyonfilling flow. Subsequent erosion has inverted the topography and produced an elongated basalt-capped ridge. 

K-Ar ages reported for the unit are 1.2 ±0.1 Ma (McKee 

and Marvin, 1974) and 1.58±0.2 Ma (Greene, 1984).

The youngest units in the study area are Quaternary playa and alluvium deposits; the playa unit consists 

of clay, silt, sand, and some evaporites, and the alluvium 

consists of unconsolidated fluvatile gravel, sand, and silt.

Fossil Vertebrates from Sedimentary Deposits

No fossil vertebrate remains have been recorded 

from the Hawk Mountain Wilderness Study Area. However, late Miocene sedimentary rock contiguous with

those exposed in the study area occur to the east and 

southeast along the Black Rocks Table escarpment and 

along the northern end of Railroad Point (fig. 1) near the 

Nevada-Oregon State line. Fossil vertebrates from these 

rocks known collectively as the Thousand Creek Fauna 

indicate an early Hemphillian age (late Miocene, approximately 9-7 Ma). No formal geologic name has been 

given to these deposits, but they have been informally 

referred to as the Thousand Creek beds. Farther southwest, the underlying Virgin Valley Formation contains 

older vertebrate fauna of Barstovian or middle Miocene 

age (approximately 15 Ma). However, faunas of this age 

have not been found in the vicinity of Black Rocks Table 

or near the Hawk Mountain Wilderness Study Area. In 

addition, no intermediate faunas of Clarendonian age 

(approximately 12-9 Ma) have been reported from this 

region.

The most recent review of the Thousand Creek 

Fauna is that of MacDonald and Pelletier (1956). Merriam (1907, 1909, 1910, 1911, 1915, and 1917) first 

mapped the geology and described the vertebrate fauna 

of these fossil-bearing deposits. Later, fossil collections 

were made by C. Stock at the Carnegie Institute of 

Technology in the 1930's (collection now stored in the 

Los Angeles County Museum), by A. Shotwell at the 

University of Oregon in the 1960's, by C. Falkenbach 

from the American Museum of Natural History in New 

York in the late 1950's and early 1960's, and by C. 

Repenning at the U.S. Geological Survey. Various field 

parties from the University of California at Berkeley 

Museum of Paleontology have also made fossil collections of the Thousand Creek Fauna. The vertebrate 

collections housed at the aforementioned institutions are 

the most complete collections of these fauna. A general 

list of the Thousand Creek Fauna from MacDonald and 

Pelletier (1956) is given in table 1.

Geochemical Studies

The reconnaissance geochemical study of the 

Hawk Mountain Wilderness Study Area included the 

collection and analysis of 93 stream-sediment samples, 

90 nonmagnetic heavy-mineral-concentrate samples of 

stream sediment, and 14 rock samples. The streamsediment samples are representative of the rock eroded 

from drainage basins upstream from sample sites. Chemical analyses of stream sediment are useful in identifying 

those basins containing concentrations of elements that 

may be related to mineralization. Nonmagnetic heavymineral-concentrate samples provide information about 

the chemical composition of a limited number of minerals in rock eroded from the drainage basin upstream 

from each sample site. Minerals in heavy-mineral concentrates are commonly ore related. Analyses of the 

concentrates permit detection of some elements that are 

not easily detected in bulk stream-sediment samples.

F6 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
Table 1. Vertebrate fauna from the Thousand Creek beds 

(from MacDonald and Pelletier, 1959)

PISCES

Indeterminate fragments. 

REPTILIA

SQUAMATA

OPHIDIA gen. indet. 

AVES

ANSERIFORMES

Brcnita sp. 

MAMMALIA

INSECTIVORA

Scapcuius sp. 

LAGOMORPHA

Hypolagus vetus (Kellogg) (type locality). 

RODENTIA

Liodontia furlongi Gazin (type locality).

Mylagaulus cf. M. monodon.

Mannota ne\>adensis (Kellogg) (type locality).

Mannota minor (Kellogg) (type locality).

Dipoides sp.

Diprionomys parvus (Kellogg) (type locality).

Diprionomys minimus (Kellogg) (type locality).

Cupidinimus magnus (Kellogg) (type locality).

Citellus sp.

Peromyscus antiquus (Kellogg) (type locality). 

PROBOSCIDEA

Mammut (Pliomastodon) nevadanus (Stock) (type locality). 

CARNIVORA

Canis sp. or Vulpes sp.

Tatidea nevadensis Butterworth (type locality).

Pliogale furlongi (Merriam) (type locality). 

PERISSODACTYLA

Neohipparion leptode Merriam (type locality).

Pliohippus sp.

Teleoceras sp. 

ARTIODACTYLA

Prosthennops sp.

Paracamelus? sp.

Sphenophalos nevadanus Merriam (type locality).

Illingoceros alexandrae Merriam (type locality).

Illingoceros schizoceros Merriam (type locality).

All samples were analyzed semiquantitatively for 

31 elements using a direct-current arc emission spectregraphic method (Grimes and Marranzino, 1968). For 

detecting certain ore-related elements or those that have 

high limits of detection by emission spectrography, inductively coupled argon plasma-atomic emission spectroscopy (ICP-AES) was used to analyze for antimony, 

arsenic, bismuth, cadmium, and zinc. Atomic-absorption 

methods (described in Crock and others, 1987) were 

used to analyze for gold and mercury.

A reconnaissance geochemical study was conducted by the U.S. Bureau of Land Management in the 

Hawk Mountain Wilderness Study Area (Rimal and 

others, 1980). In that study, stream-sediment samples 

were collected at 45 sites within and along the boundary 

of the study area and were analyzed for 15 elements. In 

the study by Rimal and others (1980), gold was analyzed

by an atomic-absorption method with a lower limit of 

detection of 0.001 ppm (parts per million). The atomicabsorption method used by the U.S. Geological Survey 

for detecting gold and mercury in this study has a lower 

limit of determination of 0.05 ppm for gold.

Rimal and others (1980) reported anomalous values of gold in three stream-sediment samples. Gold 

values of 0.030 and 0.040 ppm were found in two samples 

from sites just west of Hawk Mountain and a gold value 

of 0.170 ppm was reported from a sample collected from 

a site along the west boundary of the study area. This site 

is about 2 mi north of a U.S. Geological Survey sample 

site where a particle of gold less than 0.02 in. in diameter 

was found in a nonmagnetic heavy-mineral-concentrate 

sample (HM078H, fig. 2). Analyses of U.S. Geological 

Survey samples from the same drainages where the U.S. 

Bureau of Land Management sediment samples containing these anomalous gold values were obtained did not 

detect any gold. (All of the above noted gold values are 

detectable with the atomic-absorption method used by 

the U.S. Geological Survey but the values of 0.030 or 

0.040 ppm would be reported as less than 0.05 ppm, the 

lower limit of determination for the method used in this 

study).

The sample containing the gold grain also contains 

several grains of pyrite and one grain of scheelite. Additional sampling near site HM078H, as part of a follow-up 

study, did not show any additional gold.

These results indicate that gold in the study area is 

apparently very sporadically distributed as microscopic 

particles in the alluvium of a few drainages. The small 

amounts of gold found suggest that bedrock sources also 

have sporadically distributed gold. All samples anomalous in gold were obtained from drainages that are cut by 

faults. Sporadic gold may occur in these faults, which 

could have served as pathways for ascending hydrothermal and ore-forming fluids. Whether greater amounts of 

gold occur at depth in the study area could not be 

determined on the basis of the results of these investigations.

Bismuth at values ranging from less than 20 ppm to 

greater than 2,000 ppm was detected in heavy-mineral 

concentrates from 20 sites in the west half of the study 

area. A yellowish earthy grain, bismite(?), a secondary 

bismuth mineral formed by the oxidation of native bismuth or other bismuth minerals, was observed in one of 

the concentrates with an anomalous concentration of 

bismuth. However, no other bismuth minerals were 

definitely identified in samples having high bismuth concentrations.

The area of the anomalous bismuth concentrations 

is chiefly underlain by welded rhyolitic tuff. Bismuth was 

not detected in any steam-sediment or rock samples. The 

bismuth in the heavy-mineral concentrates may have 

been eroded from faults or other fractures in the drainage areas.

Mineral Resources of the Hawk Mountain Wilderness Study Area, Oregon F7
Bismuth occurs in a number of deposit types and 

often indicates various types of mineral deposits (Boyle, 

1974, p. 29). It is largely a by-product from ores of other 

metals (Hasler and others, 1973). The amounts of bismuth contained in the heavy-mineral-concentrate samples, together with the absence of detected bismuth in 

stream-sediment and rock samples, is evidence that bismuth occurs only in trace amounts in the alluvium or 

bedrock. The geochemical data and the geologic setting 

of the area suggest that the bismuth anomaly could be 

related to tin or gold mineralization, although the bismuth shows little or no correlation with gold found in the 

area. Whether or not the bismuth anomaly suggests gold 

at depth in the study area cannot be determined with 

available data.

Bismuth shows some correlation with tin values. 

Heavy-mineral concentrates with tin values ranging from 

less than 20 ppm to 1,000 ppm were measured, but only 

a few of the samples are considered anomalous with 

respect to tin. Anomalous concentrations of tin are 

values that exceed 500 ppm. The two highest tin values, 

700 and 1,000 ppm, were found in the western part of the 

study area in samples from a small drainage on the east 

slope of Acty Mountain. The bedrock in this drainage is 

cut by a northeast-trending fault, which suggests that this 

fault is weakly mineralized.

The geologic setting is permissible for rhyolitehosted tin deposits (Reed and others, 1986, p. 168). 

However, the evidence does not support the existence of 

such a deposit in the study area. Furthermore, such a 

deposit is not suggested in exposed bedrock of the study 

area.

Geophysical Studies

Aerial Gamma-Ray Spectroscopy

Radiometric 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 three east-west flightlines spaced 3 mi apart and totaling about 32 mi in length 

and two north-south flightlines spaced 13 mi apart and 

totaling 8 mi in length. Flight altitudes ranged from 200 

ft to an unacceptable 800 ft above the ground. Recordings were made of gamma-ray flux from radioactive 

isotopes of uranium, thorium, and potassium. Radioactivity count rates exceed the mean background level for 

uranium and thorium in most of the study area and for 

potassium in the eastern third of the study area. High 

count rates for uranium and thorium reflect the chemical 

composition of the exposed Tertiary rhyolite and tuffaceous sedimentary rock. No localities were identified 

where the concentration of either element is high enough 

to constitute a mineral resource.

Aeromagnetic Survey

Regional aeromagnetic surveys were flown at constant barometric elevations of 9,000 ft above sea level and 

east-west flightline spacings of 2 mi (U.S. Geological 

Survey, 1972a, b). A 6- by 9-mi, 800-nanotesla magnetic 

high centered 1 mi south of Hawk Mountain dominates 

the aeromagnetic map (Plouff, 1984, p. 40). The magnetic high mostly reflects the shape of a mass of volcanic 

rock concealed beneath the surface because the anomaly 

is neither congruent with topography nor with the extent 

of exposed rhyolitic rock, and the flanks of the anomaly 

span a circle about 7 mi in diameter. The weak magnetic 

low in the westernmost 5 mi of the study area may 

represent low elevation and low or possibly reversed 

remanent magnetization of underlying volcanic rock.

Gravity Survey

The U.S. Geological Survey established 31 gravity 

stations in and within 5 mi of the study area in 1986 

(Plouff, 1987). These data were supplemented by data 

from 37 gravity stations that were part of the gravity 

survey of the Charles Sheldon Wilderness Study Area 

(Plouff, 1977,1984). The most conspicuous anomaly on 

a preliminary gravity map prepared from these data is an 

east-trending 7- by 16-mi gravity low with an amplitude 

of 8 milligals, which is centered about 2 mi south of the 

study area (Donald Plouff, unpub. data). An extension of 

the gravity low projects into the southern part of the 

study area (fig. 3).

The gravity low is the northeasternmost of a series 

of gravity lows extending almost 50 mi northwest from 

the study area (Plouff, 1984, pi. 2; Ach and others, 1987, 

fig. 3; and Turrin and others, 1988, fig. 3). The number 

and intensity of gravity lows in this part of Oregon 

suggest the possible occurrence of a series of nested 

underlying calderas (Greene and Plouff, 1981; Plouff, 

1984, p. 46; Ach and others, 1987; and Turrin and others, 

1988). Presumably, the gravity low is present because of 

the accumulation of fairly low density tuffaceous sedimentary rock within the caldera depression. Caldera 

subsidence is likely the result of large volumes of silicic 

magma being erupted from shallow magma chambers. 

Thus, each gravity low may represent a bowl-shaped 

basin filled with tuffaceous sediment that is surrounded 

by denser wallrock. The study area contains tuffaceous 

sedimentary rock, rhyolite, and numerous normal faults, 

which suggest an underlying caldera. However, the presence of a caldera is speculative because the amplitude of 

this gravity low is small compared to other gravity lows of 

the region.

A 4-mi-diameter gravity high is centered in Hawk 

Valley about 2 mi north of Hawk Mountain. The gravity 

high may represent the center of a mass of intrusive rocks 

that formed a conduit for extrusive volcanic rocks

F8 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
exposed at the surface. The nose of the large magnetic 

high extends about 1 mi east of the gravity high. The 

intensity of this part of the large magnetic high is low 

near the gravity high because the ground surface is 1,000 

ft below the level of observation at Hawk Mountain. The 

weakened north wall of this area of subsidence is a likely 

place for a conduit from a renewed magma system.

Mineral and Energy Resources of the 

Hawk Mountain Wilderness Study Area

Mineral Resources

The Hawk Mountain Wilderness Study Area is 

part of a region characterized by extensive exposures of

Tertiary volcanic rock that are locally hydrothermalty 

altered and silicified. In this region hydrothermally 

altered rocks may host deposits of mercury, silver, and 

gold, and industrial minerals (clay and zeolite). No 

evidence of mercury or silver mineralization or of clay 

and zeolites was observed in the study area. However, 

geochemical data and the geologic setting of the area 

suggest that the west half of the study area has low 

resource potential for gold in epithermal deposits, certainty level B (fig. 2).

Energy Resources

The entire study area has a low favorability for the 

occurrence of oil and gas (Fouch, 1983a, b). No drilling

1 45'

5 MILES

Figure 3. Complete Bouguer gravity anomaly map of region near Hawk Mountain Wilderness Study Area, Harney County, 

Oregon. Approximate boundary of study area shown in gray. Contour interval 2 milligals; hachured in direction of gravity low. 

Small squares denote gravity stations. South boundary of study area lies along Oregon-Nevada State line.

Mineral Resources of the Hawk Mountain Wilderness Study Area, Oregon F9
or other exploration has been done in the study area. 

Because of extensive Miocene volcanic activity in this 

part of the Basin and Range province, the area is too 

thermally mature to have formed any hydrocarbon 

reserves (Sandberg, 1983). Moreover, the area lacks 

suitable source rocks for hydrocarbon generation. Therefore, the entire study area has low potential for oil and 

gas resources, certainty level D.

Several radioactive prospects are located within the 

Virgin Valley Formation south of the study area in 

northwestern Humboldt County, Nevada. Secondary 

uranium minerals (carnotite and schroeckingerite?) are 

reportedly associated with opalized zones within the 

tuffaceous lacustrine sedimentary rock (Garside, 1973). 

Although no localities were identified where the uranium 

concentrations were high enough to be considered a 

mineral resource, the aerial gamma-ray spectroscopy 

data and the large amount of tuffaceous sedimentary 

rock suggest that the eastern and southern parts of the 

study area have low potential for uranium in localized, 

small-volume deposits, certainty level C.

No hot springs are present in the study area, nor 

are there any geothermal production leases for the study 

area. However, the occurrence of young volcanic rock 

and of hot springs within 10 mi of the study area indicates 

that the entire study area has low potential for geothermal resources, certainty level B.

REFERENCES CITED

Ach, JA., Plouff, Donald, Turner, R.L., and Schmauch, S.W., 

1987, Mineral resources of the East Fork High Rock 

Canyon Wilderness Study Area, Washoe and Humboldt 

Counties, Nevada: U.S. Geological Survey Bulletin 1707- 

B,14p.

Bonham, H.F., 1969, Geology and mineral deposits of Washoe 

and Storey Counties, Nevada, with a section on industrial 

minerals by K.G. Papke: Nevada Bureau of Mines and 

Geology Bulletin 70, 140 p.

Boyle, R.W., 1974, Elemental associations in mineral deposits 

and indicator elements of interest in geochemical prospecting (revised): Geological Survey of Canada Paper 

74-45, 40 p.

Cathrall, J.B., Siems, D.F., Crenshaw, G.L., and Cooley, E.F., 

1984, Geochemical evaluation of the mineral and geothermal resources of the Charles Sheldon Wilderness 

Study Area, Nevada and Oregon: U.S. Geological Survey 

Bulletin 1538-C, p. 51-87.

Crock, J.G., Briggs, P.H., Jackson, L.L., and Lichte, F.E., 1987, 

Analytical methods for the analysis of stream sediments 

and rocks from wilderness study areas: U.S. Geological 

Survey Open-File Report 87-84, 35 p.

Fouch, T.D., 1983a, Petroleum potential of wilderness lands, 

Oregon: U.S. Geological Survey Miscellaneous Investigations Series Map 1-1544, scale 1:1,000,000.

 1983b, Petroleum potential of wilderness lands in Oregon: U.S. Geological Survey Circular 902-J, 5 p.

Garside, L.J., 1973, Radioactive mineral occurrences in 

Nevada: Nevada Bureau of Mines and Geology Bulletin 

81, 121 p.

Geodata International, Inc., 1980, Aerial radiometric and magnetic survey, National Topographic Map, Adel, Oregon: 

U.S. Department of Energy Open-File Report GJBX104 (80), v. 2, 145 p.

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

mineral survey reports on public lands: U.S. Geological 

Survey Open-File Report 84-787, 51 p.

Greene, R., 1984, Geologic appraisal of the Charles Sheldon 

Wilderness Study Area, Nevada and Oregon: U.S. Geological Survey Bulletin 1538-A, p. 13-34.

Greene, R., and Plouff, Donald, 1981, Location of a caldera 

source for the Soldier Meadow Tuff, northwestern 

Nevada, indicated by gravity and aeromagnetic data: 

Geological Society of America Bulletin, v. 92, pt. 1, p. 

4-6 and pt. 2, p. 39-56.

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.

Harvey, S.D., Noble, D., and McKee, E.H., 1986, Hog Ranch 

gold property, northwestern Nevada: age and genetic 

relation of hydrothermal mineralization to coeval peralkaline silicic and associated basaltic magmatism: Isochron/West, no. 47, p. 9-11.

Hasler, J.W., Miller, M.H., and Chapman, R.M., 1973, Bismuth, in Brobst, DA., and Pratt, W.P., eds., 1973, 

United States Mineral Resources: U.S. Geological Survey Professional Paper 820, p. 95-98.

Houghton, J.G., Sakamoto, C.M., and Gifford, R.O., 1975, 

Nevada's weather and climate: Nevada Bureau of Mines 

and Geology Special Publication 2, 78 p.

Korringa, M.K., 1973, Linear vent area of the Soldier Meadow 

Tuff, an ash-flow sheet in northwestern Nevada: Geological Society of America Bulletin, v. 84, p. 3849-3866.

MacDonald, J.R. and Pelletier, W.J. 1956. The Pliocene mammalian faunas of Nevada, U.SA: 20th International 

Geol. Congress (Mexico), Sec. 8, Paleontology, Taxonomy, and Evolution, p. 365-388.

McKee, E.H. and Marvin, R.F., 1974, Summary of radiometric 

ages of Tertiary volcanic rocks in Nevada; Part IVNorthwestern Nevada: Isochron/West, no. 10. p. 1-6.

McKelvey, V.E., 1972, Mineral resource estimates and public 

policy: American Scientist, v. 60, p. 32-40.

Mayerle, R.T., and Rains, R.L., 1988, Mineral resources of the 

Hawk Mountain Wilderness Study Area, Harney County, 

Oregon: U.S. Bureau of Mines Open-File Report MLA 

21-88, 12 p.

Merriam, J., 1907, The occurrence of middle Tertiary mammalbearing beds in northwestern Nevada: Science, v. 26, p. 

380-382.

 1909, The occurrence of strepsicerine antelopes in the 

Tertiary of northwestern Nevada: University of California, Berkeley, Department of Geology Bulletin, v. 5, no. 

22, p. 319-330.

 1910, Tertiary mammal beds of Virgin Valley and 

Thousand Creek in northwestern Nevada; Part 1, Geologic history: University of California, Berkeley, Department of Geology Bulletin, v. 6, no. 2, p. 21-53.

F10 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
-1911, Tertiary mammal beds of Virgin Valley and 

Thousand Creek in northwestern Nevada; Part 2, Geologic history: University of California, Berkeley, Department of Geology Bulletin, v. 6, no. 11, p. 21-53.

-1915, New species of the Hipparion group from the 

Pacific Coast and Great Basin provinces of North America: University of California, Berkeley, Department of 

Geology Bulletin, v. 9, p. 1-8.

-1917, Relationships of Pliocene mammalian faunas from

the Pacific Coast and Great Basin provinces of North 

America: University of California, Berkeley, Department 

of Geology Bulletin, v. 10, p. 421-443.

Noble, D., Chipman, D.W., and Giles, D.L., 1968, Peralkaline 

silicic volcanic rocks in northwestern Nevada: Science, v. 

160, p. 1337-1338.

Noble, D., McKee, E.H., Smith, J.R., and Korringa, M.K., 1970, 

Stratigraphy and geochronology of Miocene volcanic 

rocks in northwestern Nevada, in: U.S. Geological Survey Research 1970: U.S. Geological Survey Professional 

Paper 700-D, p. D23-D32.

Plouff, Donald, 1977, List of principal facts and gravity anomalies for an area between Orovada, Nevada and Adel, 

Oregon: U.S. Geological Survey Open-File Report 

77-683, 40 p.

 1984, Interpretation of aeromagnetic and gravity data, 

Charles Sheldon Wilderness Study Area, Nevada and 

Oregon: U.S. Geological Survey Bulletin 1538-B, p. 

35-50, plate 2, scale 1:125,000. 

-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.

Reed, B.L., Duffield, Wendell, Ludington, S.D., Maxwell, C.H., 

and Richter, D.H., 1986, Descriptive model of rhyolitehosted Sn, in Cox, D.P., and Singer, D.A., eds., Mineral

deposit models: U.S. Geological Survey Bulletin 1693, 

379 p.

Rimal, Durga, Simontacchi, Dennis, and Brown, George, 1980, 

Reconnaissance geochemical stream sediment survey of 

the Hawk Mountain and the Lone Mountain Areas, 

Harney County, Oregon: U.S. Bureau of Land Management, Oregon, 26 p.

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

in Nevada: U.S. Geological Survey Circular 902-H, lip.

Sthraler, A., 1969, Physical geography: New York, John Wiley 

and Sons, Inc., p. 219-238.

Tuchek, E.T., Johnson, F.J., and Conyac, M.D., 1978, Economic appraisal of the Charles Sheldon Wilderness 

Study Area, Nevada and Oregon: U.S. Geological Survey 

Bulletin 1538-D, p. 89-139.

Turrin, B.D., Bergquist, J.R., Turner, R.L., Plouff, Donald, 

Ponader, C.W., Scott, D.F., 1988, Mineral resources of 

the High Rock Canyon Wilderness Study Area, Washoe 

County, Nevada: U.S. Geological Survey Bulletin 1707- 

D, 14 p.

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

and parts of the Burns, Boise, and Jordan Valley 1° by 2° 

quadrangles, Oregon: U.S. Geological Survey open-file 

report, scale 1:250,000.

 1972b, Aeromagnetic map of the Vya and part of the 

McDermitt 1° by 2° quadrangle, Nevada: U.S. Geological 

Survey open-file report, scale 1:250,000.

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.

Walker, G.W., and Repenning, C.A., 1965, Reconnaissance 

geologic map of the Adel quadrangle, Lake, Harney, and 

Malheur Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-446, scale 

1:250,000.

Mineral Resources of the Hawk Mountain Wilderness Study Area, Oregon F11

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.

Z

LU

A

U/A

UNKNOWN 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.

F14 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

jrves

Marginal 

Reserves

Demonstrated 

Subeconomic 

Resources

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

I

1

l 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 the Hawk Mountain Wilderness Study Area, Oregon F15
GEOLOGIC TIME CHART

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

EON

Phanerozoic

Proterozoic

Archean

pre-Archean*

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Neogene

Subperiod

r a 1 trUK En C

Subperiod

l*rClai.c\JU9

Jurassic

Triassic

Permian

Pennsylvania!! 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

f3or\r\7\

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

ACE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (Ma)

 0.010

 1.7

5

* » M

:>Q

 55

 66

96

1 10

 205

_..,,,. ~9/in

 290 

 -330

 360

 410

 435

 500 

 1-570

 900

 1600

 2500

 3000

 3400

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

Informal time term without specific rank.

F16 Mineral Resources of Wilderness Study Areas: Steens Mountain-Rincon Region, Oregon
Mineral Resources of 

Wilderness Study Areas: 

Steens Mountain-Rincon Region, 

Oregon

This volume was published as separate chapters A-F

U.S. GEOLOGICAL SURVEY BULLETIN 1740
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L Peck, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the High Steens and Little Blitzen Gorge Wilderness 

Study Area, Harney County, Oregon, by Scott A. Minor, Donald Plouff, 

Leon E. Esparza, and Thomas J. Peters.

(B) Mineral Resources of the Pueblo Mountains Wilderness Study Area, Harney 

County, Oregon, and Humboldt County, Nevada, by Robert C. Roback, 

Dean B. Vander Meulen, Harley D. King, Donald Plouff, Steven R. Munts, 

and Spencee L. Willett.

(C) Mineral Resources of the Home Creek Wilderness Study Area, Harney

County, Oregon, by Dean B. Vander Meulen, Andrew Griscom, Harley D. King, 

Thomas L. Vercoutere, and Phillip R. Moyle.

(D) Mineral Resources of the Blitzen River Wilderness Study Area, Harney

County, Oregon, by Dean B. Vander Meulen, Andrew Griscom,

Harley D. King, and Phillip R. Moyle. 

(E) Mineral Resources of the Rincon Wilderness Study Area, Harney County,

Oregon, by Dean B. Vander Meulen, Donald Plouff, Harley D. King,

Ronald T. Mayerle, and Richard L. Rains. 

(F) Mineral Resources of the Hawk Mountain Wilderness Study Area, Harney

County, Oregon, by Brent D. Turrin, James E. Conrad, Donald Plouff,

Harley D. King, Carl C. Swischer III, Ronald T. Mayerle, and

Richard L. Rains.



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 arc 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 71/2-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.
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