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ERRATA SHEET 

Bulletin 1741-G 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness 

Study Area, Malheur County, Oregon 

A line of text is missing from the bottom right column of page G9: 

... extension of the DeLamar-Duck Valley structural trend and ... 

Chapter G 

Mineral Resources of the Blue Canyon 

and Owyhee Breaks Wilderness Study Areas, 

Malheur County, Oregon 

By DEAN B. VANDER MEULEN, VINCENT E. BARLOCK, 

PATRICK S. PLUMLEY, JAMES G. FRISKEN, and 

ANDREW GRISCOM 

U.S. Geological Survey 

j. DOUGLAS CAUSEY 

U.S. Bureau of Mines 

U.S. GEOLOGICAL SURVEY BULLETIN 1741 

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

EAST-CENTRAL OREGON 
U.S. 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 : 1990 

For sale by the f 

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 Blue Canyon and Owyhee Breaks wilderness study 

areas, Malheur County, Oregon I by Dean B. Vander Meulen ... [et al.] 

p. em. - (Mineral resources of wilderness study areas-eastcentral Oregon; ch. G) (U.S. Geological Survey bulletin; 1741-G) 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3:1741-G 

1. Mines and mineral resources-Oregon-Blue Canyon Wilderness. 

2. Mines and mineral resources-Oregon-Owyhee Breaks Wilderness. 

3. Blue Canyon Wilderness (Or.) 4. Owyhee Breaks Wilderness (Or.) 

I. Vander Meulen, Dean B. II. Series. Ill. Series: U.S. Geological Survey 

bulletin : 17 41-G. 

QE75.B9 no. 1741-G 557.3 s-dc20 90-3902 

[TN24.07] [553 1.09795197] 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 repon presents the results of a mineral survey of the Blue 

Canyon (OR-003-073) and Owyhee Breaks (OR-003-059) Wilderness Study Areas 

Malheur County, Oregon. 

CONTENTS 

Summary G1 

Abstract G1 

Character and setting G 1 

Identified resources G3 

Mineral resource potential of the Blue Canyon Wilderness Study Area G3 

Mineral resource potential of the Owyhee Breaks Wilderness Study Area G4 

Introduction G4 

Area description G4 

Previous and present investigations GS 

Appraisal of identified resources GS 

History and production GS 

Mines, prospects, claims, and mineralized areas G8 

Acknowledgments G8 

Identified resources of the Blue Canyon Wilderness Study Area G8 

Identified resources of the Owyhee Breaks Wilderness Study Area G8 

Assessment of mineral resource potential G9 

Geology G9 

Caldera and structural evolution G9 

Volcanic stratigraphy G 10 

Sedimentary stratigraphy G11 

Geochemical studies G 12 

Regional gold mines and prospects G16 

Results and interpretation G 17 

Geophysical studies G 18 

Aeromagnetic survey G 18 

Gravity and gamma ray surveys G 18 

Mineral and energy resource potential of the Blue Canyon Wilderness Study 

Area G19 

Mineral and energy resource potential of the Owyhee Breaks Wilderness Study 

Area G20 

References cited G21 

Appendixes G25 

Definition of levels of mineral resource potential and certainty of 

assessment G26 

Resource/reserve classification G27 

Geologic time chart G 28 

FIGURES 

1. Index map showing location of Blue Canyon and Owyhee Breaks Wilderness 

Study Areas, Malheur County, Oregon G2 

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

Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, 

Oregon G14 

3. Bouguer gravity anomaly map of part· of the Lake Owyhee volcanic field, 

eastern Oregon G 19 

Contents V 
VI Contents 

TABLES 

1. Mines, prospects and mineralized areas in the Blue Canyon and Owyhee Breaks 

Wilderness Study Areas, Malheur County, Oregon G6 

2. Geochemical summary for 46 nonmagnetic panned-concentrate samples from the 

Blue Canyon and Owyhee Breaks Wilderness Study Areas and adjacent areas, 

Oregon G13 

3. Geochemical summary for 47 minus-80-mesh stream-sediment samples from the 

Blue Canyon and Owyhee Breaks Wilderness Study Areas and adjacent areas, 

Oregon G13 

4. Geochemical summary for 82 rock samples from the Blue Canyon and Owyhee 

Breaks Wilderness Study Areas and adjacent areas, Oregon Gl3 
Mineral Resources of the Blue Canyon 

and Owyhee Breaks Wilderness Study Areas, 

Malheur County, Oregon 

By Dean B. Vander Meulen, Vincent E. Barlock, Patrick S. Plumley, 

James G. Frisken, and Andrew Griscom 

.u.s. Geological Survey 

J. Douglas Causey 

U.S. Bureau of Mines 

SUMMARY 

Abstract 

At the request of the U.S. Bureau of land Management, 

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

conducted field studies of 1 2',700 acres and 13,1 00 acres, 

respectively, in the contiguous Blue Canyon (OR-003-073) 

and Owyhee Breaks (OR-003-059) Wilderness Study Areas; 

the areas are adjacent to and include part of the Owyhee 

River in eastern Oregon. In this report, the a.reas studied for 

mineral resources are referred to, individually or collectively, 

as the 11Wilderness study area" or simply the "study area." 

Fieldwork was conducted by the U.S. Geological Survey during 

1985 and 1988 and by the U.S. Bureau of Mines during 1988 

to appraise the identified mineral resources (known) and assess 

the mineral resource potential (undiscovered) of the study 

area. 

The southern part of the Blue Canyon Wilderness Study 

Area contains identified resources of jasper and perlite and 

occurrences of bentonite. The Owyhee Breaks Wilderness 

Study Area contains occurrences of bentonite, jasper, and 

zeolite minerals. Both study areas have sand and gravel deposits that are far removed from transportation routes and 

existing markets. No energy resources were identified in either 

study area. In the northern part of the study area, an area 

underlain by silicified lithic tuff has high mineral resource 

potential for gold, silver, mercury, and molybdenum. Silicified and brecciated tuffs exposed along two north-trending 

fault zones in the east-central part of the study area have high 

mineral resource potential for gold, mercury, and molybdenum. Rocks exposed along the west side of the Owyhee 

River in the western part of the study area have high mineral 

resource potential for gold in volcanic- and sediment-hosted 

Manuscript approved for publication, June 11, 1990 

hot-spring deposits. The rest of the study area has moderate 

mineral resource potential for gold in volcanic- and sedimenthosted deposits. Tuffs associated with the Mahogany Mountain 

caldera have low potential for zinc resources. These tuffs are 

exposed locally throughout the study area. North-trending 

fault zones within and adjacent to the study area have moderate potential for geothermal energy resources. Sedimentary 

rocks that underlie the northern and western parts of both 

study areas have moderate mineral resource potential for bentonite and diatomite, low mineral resource potential for fluorite, 

and low potential for oil and gas energy resources. 

Character and Setting 

The Blue Canyon (OR~3-073) and Owyhee Breaks 

(OR-003--059) Wilderness Swdy Areas lie along the west 

margin of the Mahogany Mountain caldera approximately 

62 mi west of Boise, Idaho, and 25 mi northwest of Jordan 

Valley, Oreg. (fig. 1). The swdy area includes part of the 

caldera-collapse structure, the west topographic wall of the 

caldera, and parts of a high plateau southwest of the caldera. 

The principal drainage in the region is the Owyhee River, a 

tributary of the Snake River. The river flows from west to 

east, then north across the study area through a spectacular, 

deeply eroded canyon. In the western part of the study 

area, the river has cut through a thick sequence of poorly 

consolidated volcaniclastic sedimentary rocks that have 

slumped and eroded to form a broad 5-mi-wide basin known 

as The Hole in the Ground. In the central part of the study 

area, the river encounters older, resistant ash-flow tuffs and 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G1 
intrusive rocks that form steep, rugged parts of the canyon 

known as the Owyhee Breaks. North of the study area, the 

river empties into the 25-mi-long Lake Owyhee. 

The study area is underlain by a thick sequence of 

middle Miocene rhyolite flows and ash-flow tuffs and middle 

Miocene to Pliocene sedimentary rocks and basalt flows. 

Time spanned by the middle Miocene is herein considered 

to extend from approximately 11.2 to 16.6 million years 

before present, or Ma (see "Appendixes" for geologic time 

chart). The oldest rocks, rhyolite flows exposed in the east118°00' 

43°30' 

117°45' 

5699 

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WILDERNESS STUDY AREA 

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Figure 1. Index map showing location of Blue Canyon and Owyhee Breaks Wilderness Study-Areas, Malheur County, 

Oregon. Gold prospects shown by X. Heavy dotted lines indicate inferred margins of the Three Fingers (TF) and 

Mahogany Mountain (MM) calderas. Open-circle dotted line indicates approximate margin of a possible caldera based 

on geophysical data. 

G2 Mineral Resources of Wilderness Study Areas: East ..Central Oregon 
central part of the study area, erupted from a precaldera 

silicic magma chamber beneath Mahogany Mountain, 7 mi 

east of the study area. Continued silicic volcanism during 

the middle Miocene resulted in the eruption of ash-flow 

and air-fall tuffs and the formation of the Mahogany Mountain and Three Fingers calderas and a possible caldera west 

of the study area (fig. 1). The rhyolite tuffs probably underlie 

most the study area at depth. 

The area has undergone extensional tectonism, resulting in basin-and-range topography, and occupies a northplunging lacustrine basin of regional extent that is cut by 

north- and northwest-trending faults. During the Miocene 

and Pliocene, lacustrine and fluvial volcaniclastic sedimentation within the basin was accompanied by intermittent 

episodes of basaltic and andesitic volcanism. Rocks that 

were deposited during this time are exposed locally throughout the study area. Plateau-forming basalts cap these sedimentary rocks and are the youngest rocks in the study area. 

Identified Resources 

No energy resources have been identified within or 

adjacent to the study area Several prospects, claims, and 

two mines contain identified resources of jasper. The deposits are commonly restricted to brecciated, silicified, and 

pyritized welded tuff along fault and fracture zones .. The 

southern part of the Blue Canyon Wilderness Study Area 

has an estimated 4.8 million short tons (st) of jasper-bearing 

welded tuff. Less than 0.1 percent of the rock contains 

usable jasper, and less than 0.001 percent contains highvalue jasper. 

The southern part of that study area also has an estimated 5.8 million st of identified perlite resources, and the 

western and northern parts have occurrences of bentonite. 

The Owyhee Breaks Wilderness Study Area has occurrences of bentonite, jasper, and zeolite minerals. 

An estimated 5 million yd3 of sand and gravel deposits are exposed in the Owyhee River, on small isolated 

benches near the river, and in the Blue Canyon and other 

drainages within both study areas. Because they are remote 

and inaccessible, none of the river gravels are expected to 

be quarried. 

Welded tuff exposed within the study area is suitable 

for construction; however, because similar tuff elsewhere is 

more accessible and closer to existing markets, this tuff 

does not constitute a resource. 

Mineral Resource Potential of the Blue Canyon 

Wilderness Study Area 

Three samples of a silicified lithic-rich tuff collected 

in the northern part of the Blue Canyon Wilderness Study 

Area contain anomalous concentrations of gold, silver, mercury, and molybdenum. The silicified tuff caps a sequence 

of sedimentary rocks and is exposed along a north-trending 

normal fault Silicified parts of the tuff have high potential 

for gold, silver, mercury, and molybdenum resources. 

Five samples of silicified and brecciated tuff collected 

along two north-trending fault zones in the central part of 

the study area contain anomalous concentrations of gold, 

mercury, and molybdenum. Silicified and brecciated rocks 

exposed along these fault zon~ have high potential for gold, 

mercury, and molybdenum resources. 

Geochemical associapons favorable for gold in epithermal hot-spring deposits have been identified in the study 

area. The volcanic and sedimentary stratigraphy and structure of known gold prospects in the region can be traced 

into the study area Therefore the entire study area, except 

those parts having high resource potential for gold, has 

moderate potential for gold resources in volcanic- and sediment-hosted deposits. 

In the central part of the Mahogany Mountain caldera, 

4 mi east of the study area, anomalous concentrations of 

zinc were detected in 43 samples of caldera-forming rhyolite 

tuff and in 10 samples of rhyolite vent breccia Therefore, 

parts of the study area underlain by this tuff have low resource potential for zinc in volcanogenic disseminated deposits. 

Approximately one-third of the stream-sediment and 

nonmagnetic-panned-concentrate samples collected for this 

investigation contain anomalous fluorine. The fluorine 

anomalies are probably associated with either lacustrine 

sedimentary rocks or epithermal hot-springs mineralization. 

Sedimentary rocks that underlie the north and central parts 

of the study area have low potential for fluorite resources. 

In the same parts of the study area, beds of bentonite 

and diatomite are intercalated with the lacustrine sedimentary rocks. The bentonite units typically form low subdued 

hills and have estimated maximum thicknesses of 50 ft. A 

sample of bentonitic clay collected in the northern part of 

the study area contains the swelling clays smectite and illite. Beds of diatomite exposed along the northern tip of 

the study area have maximum thicknesses of 5 ft, are very 

clean, and may be of industrial quality. The sedimentary 

rocks have moderate potential for bentonite and diatomite 

resources. 

Approximately 1.5 mi west of the study area, athermal spring issues from a north-trending fault zone (fig. 2). 

Another thermal spring issues from a north-trending fault 

zone approximately 2.5 mi east of the study area near Lake 

Owyhee. Although no thermal springs were identified in 

the study area, geothermal waters may exist at depth along 

north-trending fault zones. Areas along these fault zones 

have moderate potential for geothermal energy resources. 

A 650-ft-thick sequence of interbedded carbonaceous 

claystone and siltstone that underlies the northern part of 

the study area could serve as source rocks for oil and gas 

resources. North of the study area, similar rocks are folded 

to form three south-plunging anticlines. Such folded rocks 

could serve as trap structures for oil and gas reservoirs. 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G3 
Therefore, sedimentary rocks exposed in the northern part 

of the study area have low potential for oil and gas energy 

resources. 

Mineral Resource Potential of the Owyhee Breaks 

Wilderness Study Area 

Five samples of silicified tuff, conglomerate, and black 

chert (siliceous sinter) collected in the central part of the 

study area contain anomalous concentrations of gold. Sedimentary rocks and tuffs that underlie this area are cut by 

north- and northwest-trending fault zones. Gold resources 

have been discovered in similar rocks in a similar geologic 

setting at the Red Butte gold prospect, 8 mi north-northeast 

of the study area. Therefore, this area is considered to have 

high resource potential for gold in volcanic- and sedimenthosted hot-spring deposits. 

Geochemical associations favorable for gold in epithermal hot-spring deposits have been identified in the study 

area. The volcanic and sedimentary stratigraphy and structure of known gold prospects in the region can be traced 

into the study area. Therefore, the remaining study area has 

moderate potential for gold resources in volcanic- and sediment-hosted deposits. 

In the central part of the Mahogany Mountain caldera, 

10 mi east of the study area, anomalous concentrations of 

zinc were detected in 43 samples of caldera-forming rhyolite tuff and in 10 samples of rhyolite vent breccia. Therefore, parts of the study area underlain by this tuff have low 

potential for zinc resources in volcanogenic disseminated 

deposits. 

Approximately one-third of the stream-sediment and 

nonmagnetic-panned-concentrate samples collected for this 

investigation contain anomalous fluorine. The fluorine 

anomalies are probably associated with lacustrine sedimentary rocks or epithermal hot-springs mineralization. Sedimentary rocl,cs that underlie the northwestern part of the 

study area have low potential for fluorite resources. 

In the same part of the study area, beds of bentonite 

and diatomite are intercalated with the lacustrine sedimentary rocks. A sample of bentonitic clay collected near the 

northwest boundary of the study area is 80 to 95 percent 

smectite, a clay mineral that has swelling properties. Thin 

beds of diatomaceous earth are also exposed in the northern 

and northwestern parts of the study area. The sedimentary 

rocks have moderate potential for bentonite and diatomite 

resources. 

Near the central part of the study area, a thermal 

spring (fig. 2) issues from a north-trending fault zone. Another thermal spring issues from a north-trending normal 

fault approximately 6.5 mi northeast of the study area near 

Lake Owyhee. Similar fault zones that cut the study area 

may be associated with geothermal waters at depth. Therefore, north-trending fault zones within and adjacent to the 

study area have moderate potential for geothermal energy 

resources. 

A 1,000-ft-thick sequence of lacustrine and fluvial 

sedimentary rocks that underlie the northwestern part of the 

study area could serve as source rocks for oil and gas resources. These rocks have low potential for oil and gas 

energy resources. 

INTRODUCfiON 

These mineral surveys were requested by the U.S. 

Bureau of Land Management and are the result of a cooperative effort by the U.S. Geological Survey and 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 the U.S. Bureau of Mines and U.S. Geological Survey 

(1980). Studies by the U.S. Geological Survey 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 

minernl 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 definition of levels of mineral resource potential and 

certainty of assessment and for the resource/reserve classification. 

Area Description 

The contiguous Blue Canyon (OR-003--073) and 

Owyhee Breaks (OR-003--059) Wilderness Study Areas 

encompass 25,800 acres along the Owyhee River in eastern 

Oregon. The study area is approximately 24 mi north of 

Rome, Oreg., and 9 mi west of Mahogany Mountain (fig. 

1). The area is accessible from U.S. Highway 95 via the 

Cow Lakes and Jordan Craters improved gravel roads that 

approach the study area from the east. Maximum elevation 

in the study area is approximately 4,750 ft above sea level 

along the plateau rim east of the Owyhee River; minimum 

elevation is about 2,680 ft along the river. The area is 

drained by several small creeks that flow north or south 

into the Owyhee River. The climate is semiarid, and the 

average annual precipitation is 10 in. or less. Vegetation is 

sparse and includes sagebrush and grasses at all elevations. 

G4 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
Juniper, aspen, and cottonwood trees grow along creek bottoms and in protected gulches. 

Previous and Present Investigations 

Previous geologic investigations that include the study 

area are a reconnaissance geologic map of the Owyhee region by Kittleman and others (1967) and an aeromagnetic 

survey by Boler (1979). An airborne radiometric and aeromagnetic survey of the study area was conducted by geoMetries, Inc. (1979) during the U.S. Department of Energy's 

National Uranium Resource Evaluation (NURE) program. 

A preliminary evaluation of the mineral resources of the 

Owyhee Breaks Wilderness Study Area was made by the 

Oregon Department of Geology and Mineral Industries 

(DOGAMI) (Gray and others, 1983). Other energy and 

mineral resource studies that include the study area were 

conducted by Bukofski and others (1984) and Robinson 

and others (1985). 

During the summers of 1985 and 1988, the U.S. Geological Survey mapped the geology of the study area at a 

scale of 1:24,000. The Diamond Butte 7.5-minute quadrangle, which includes the Red Butte gold prospect and the 

northern part of the study area, was mapped by Vercoutere 

and others (1987). The Jordan Craters North 7.5-minute 

quadrangle, which includes the southeastern part of the study 

area, was mapped by V.E. Barlock and Vander Meulen 

(unpub. data) as part of the present wilderness study. The 

geology of The Hole in the Ground 7 .5-minute quadrangle, 

which includes the western part of the study area, was 

mapped by Plumley (1986). A caldera collapse structure, 

referred to as the Mahogany Mountain caldera, which underlies the eastern part of the study area (fig. 1), was fll'St 

recognized by Rytuba and others (1985). 

The U.S. Bureau of Mines investigation consisted of 

prefield and field studies (Causey, 1989a, b). During the 

prefield study, current and past mining-related and claimlocation data were examined. These data were gathered 

from the libraries and records of the U.S. Bureau of Mines 

and the U.S. Bureau of Land Management, from State, 

County, and other government agencies, and from the 

Mineral Industry Location System file. Field studies 

included a ground reconnaissance to search for evidence of 

possible mineralized areas and unrecorded mining activity. 

Additional information is available from the U.S. Bureau of 

Mines, Western Field Operations Center, E. 360 Third 

Avenue, Spokane, W A 99202. 

The U.S. Geological Survey conducted a combined 

geologic, geochemical, and geophysical survey of the 

wilderness study areas during 1988. Field investigations 

focused on correlating geochemical and geophysical 

anomalies with rock units and geologic structures. Rock, 

stream-sediment, and nonmagnetic heavy-mineralconcentrate samples were analyzed for 35 elements by 

semiquantitative emission spectrography and argon plasmaatomic emission spectrography. Atomic absorption was used 

to analyze for gold and mercury; an ion-selective electrode 

method was used to detect fluorine; and the presence of 

uranium was determined by ultraviolet fluorescence. 

APPRAISAL OF IDENTIFIED RESOURCES 

By J. Douglas Causey 

U.S. Bureau of Mines 

History and Production 

Most of the precious metal exploration activity in the 

region is north of the Blue Canyon and Owyhee Breaks 

Wilderness Study Areas. Some of the recently discovered 

gold prospects include Red Butte, Quartz Mountain, and 

Grassy Mountain, 4, 8, and 23 mi north of the study area, 

respectively (fig. 1; Wheeler, 1988). These discoveries 

produced a claim-staking rush in 1988-89 that includes most 

of the study area. Near Rome, Oreg., 25 mi south of the 

study area (fig. 1), sedimentary rocks known as the "Rome 

beds" have been extensively explored and evaluated for 

fluorite and zeolite minerals. These rocks contain as much 

as 16 percent fluorite and 90 percent zeolite minerals 

(Sheppard, 1976; Santini and LeBaron, 1982; Mumpton, 

1983). Jasper has been mined in and around the Honeycombs Wilderness Study Area (Scott, 1986) 8 mi northeast 

of the study area and in the southern part of the Blue Canyon 

Wilderness Study Area. 

In 1964, the Big Hole jasper claim was staked by 

Arnold H. Peterson and Emmett Morris, and the Sheep Head 

Ridge and associated jasper claims were staked by John 

Turner and Emmett Morris in the area now covered by the 

Meadowlark mine (fig. 2). Since the 1970's, several jasper 

claims have been located in this area known as the Sheep 

Head mining district. Jasper produced from this area is 

called Morrison Ranch jasper or Morrisonite. In 1976, three 

jasper claims (North Birch, Middle Birch, and South Birch) 

were located by Dale Huell along Birch Creek at the boundary of the Blue Canyon and Owyhee Breaks Wilderness 

Study Areas (site 7, fig. 2, table 1). Bulldozer cuts are 

apparent, but no mining occurred at these prospects. 

Flower jasper was mined from the Rocky Rim claim 

(site 4, fig. 2, table 1), which was established in 1986. It 

operated for a few months before it was closed by the U.S. 

Bureau of Land Management for not having filed a plan of 

operation. The mine area, which is less than 2 mi from the 

Morrison Ranch area, was completely reclaimed and no 

outcrop of flower jasper is exposed. 

Jasper is exposed in numerous small pits throughout 

the Morrison Ranch area (fig. 2). The total amount of 

jasper recovered from these pits is unknown. Value of the 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon CS 
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Table 1 . Mines, prospects, mineralized areas, and occurrence in the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon 

("Occurrence" indicates commodity is too low grade, too market dependent, or too small to classify at this time] 

Site Name Summary Workings and production Resource and sample data 

(fig. 2) 

1 Jasper prospect ............ Tuffs and tuffaceous sedimentary rocks, Seven small prospect pits, most of which- No resources delineated. Two samples 

fractured and filled with silica. Silica do not have exposed bedrock. Less than analyzed for 18 elements, none contain 

(jasper) is commonly tan with some 100 lb of jasper have been removed. anoma lous concentrations of metals. 

blue-gray zones. Result is a picturetype jasper as thick as 6 in. 

2,3 Morrison Ranch: Jasper occurs as fracture fillings in Three mine areas and several smaller Mines have a calculated reserve of 4. 7 

Meadowlark and highly brecciated welded tuff. Jasper prospects. Largest mine area had an million short tons of jasper-bearing 

Christine Marie crops out in linear pattern indicating a estimated 25,000 to 30,000 short tons of rock. Of31 samples analyzed for 18 

mines (jasper, possible correlation with east-trending jasper-bearing rock removed from an elements, none contain anomalous 

morrisonite ). faults. open pit. Total jasper production not concentrations of metals. 

known. 

Perlite exposures ......... Perlite occurs as irregular-shaped bodies No workings or production ......................... An estimated 5.8 million short tons of 

within welded tuff near Meadowlark subeconomic perlite resources. One 

jasper mine. Perlite bodies are not sample analyzed for 18 elements 

large enough to be mined individually does not contain anomalous 

and possibly are in landslide blocks. concentrations of metals. 

4 Rocky Rim claim Host rock is tuff and tuffaceous Three pits, all of which were back-filled No jasper resources delineated because mine 

(flower sedimentary rocks. Jasper is seen with soil. Production estimated to have was reclaimed. Of 5 samples analyzed for 

jasper). only as float; none crops out been less than 3 short tons of jasper. 18 elements, 1 contains 27 ppb gold 

because workings have been 

reclaimed. 

5 Jasper prospect ............ Brecciated welded tuff of Birch Creek. Four distinct prospect pits. Some Prospect has a calculated reserve of 

Breccia fragments are supported in mining probably occurred, but no 125,000 short tons of jasper-bearing 

matrix of jasper, clay, and calcite. record of production was found. rock. Of 3 samples of jasper and 1 

sample of tuff analyzed for 18 elements, 

none contain anomalous concentrations 

of metals. 
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Stewart claims............... Tuffs and tuffaceous sedimentary rocks 

North Birch, Middle 

Birch, and South Birch 

claims (jasper and 

zeolite). 

Clay occurrence ............. . 

Jasper prospect .............. . 

contain small am01mts of jasper and 

silicified wood. Wood is locally 

opalized and highly fractured. 

Volcaniclastic sedimentary rocks host 

greenish-gray to tan jasper. No 

distinctive or unusual patterns were 

observed in jaspeT deposits examined. 

Tuffs altered to gray and greenish-gray 

clay. 

Frac~ bleached, and red iron-oxidestained welded tuff with jasper cement. 

JaspeT is multicolored, fractured, and 

commonly fills fractures less than 1 in. 

thick. 

No workings, no known production.............. No resources delineated. Quantity and 

Bulldozer scrapings along ridge that parallels 

Birch Creek. No record of production, but 

a few tons of jasper may have been 

removed. 

No workings or production ........................ . 

No workings or production ........................ . 

quality of jasper or silicified wood are 

not sufficient to be commercially 

minable. 

No jasper resources delineated. Deposit 

classified as zeolite occurrence. Two 

samples analyzed for 34 elements. Jasper 

is generally of uniform color without 

distinctive patterns. This jasper deposit is 

of interest to lapidary enthusiasts but of 

minimal commercial value. X-ray 

analysis of one sample indicates it is 

about 65 percent quartz, 20 percent 

sanidine, and 15 percent heulandite 

(zeolite). 

Deposit classified as an occurrence that 

contains less than 40,000 short tons of 

bentonitic clay. X-ray analysis of one 

sample indicates it is 85 to 90 percent 

smectite (bentonitic clay) and 10 to 15 

percent quartz. 

Deposit has no commercial value. Two 

samples collected; neither contains 

anomalous concentrations of metals. 

Jasper is fractured, is in narrow seams, 

and is not exposed over a large area. 
jasper varies; most of the material averages at least $2.50/lb 

($5,000/st). Operators of the Meadowlark and Christine 

Marie mines in the ranch area estimate that more than 3 

short tons (st) of jasper were recovered between 1986 and 

1988. An estimated 25,000 to 30,000 st of rock have been 

mined from the main workings on the Meadowlark mine 

(table 1). The rest of the workings on this and surrounding 

claims probably had less rock removed. Probably less than 

100 st of rock was mined from the largest pit at the Christine 

Marie mine. 

Mines, Prospects, Claims, and Mineralized Areas 

Jasper, tuffs, perlite, alluvial deposits, and basalt flows 

were sampled for this investigation. Two placer samples, 

one clay sample, and 95 rock samples were collected. 

Sample descriptions and analytical results are reported in 

Causey (1989a, b). The Meadowlark, Christine Marie, and 

associated claims (sites 2, 3, fig. 2, table 1) have an estimated 4.7 million st of rock containing 1 to 5 percent jasper. 

Of this rock, less than 0.1 percent is estimated to be recoverable for lapidary purposes, and less than 0.001 percent is 

high-value jasper. An estimated 125,000 st of jasper-bearing rock are calculated for an unnamed prospect (site 5, fig. 

2, table 1) west of the Rocky Rim claim; less than 0.1 

percent is considered recoverable for lapidary purposes. On 

the basis, of previous mining activity, additional resources 

of flower jasper are very likely on the Rocky Rim claim 

(site 4, fig. 2, table 1), even though the area has been reclaimed. Other jasper prospects in the study area may contain additional resources, but defining them without further 

exploration is not possible. 

Perlite resources are exposed near the Meadowlark 

mine (fig. 2). There are an estimated 5.8 million st of 

perlite having an expanded density of less than 14 lb/ft3• 

These resources are far from existing markets, contain as 

much as 15 percent red jasper, and would be competing in 

an industry that is self-supporting at present in the United 

States. 

An estimated 10 million yd3 of sand and gravel are 

present in the Blue Canyon drainage, and approximately 

half of this resource is within the study area. However, 

adequate and more accessible deposits of sand and gravel 

outside of the study area are closer to existing markets. 

A small amount of gold was found in gravels in the 

Blue Canyon drainage. No known deposits of placer gold 

occur in the study area. 

No lode gold was found in the study area. There is 

no indication that any other precious or base metals occur 

in the study area. 

Zeolite resources have been identified southwest of 

the study area in the adjoining Lower Owyhee Canyon Wilderness Study Area (Causey, 1989c; Evans and others, 1990). 

The Blue Canyon Wilderness Study Area has small isolated 

.. 

exposures of tuff and sedimentary rock that contain lowgrade zeolite minerals (heulandite and (or) clinoptilolite), 

but they are not considered to be resources. Rhyolite tuffs 

that underlie most of the Owyhee Breaks Wilderness Study 

Area are not highly altered to zeolite minerals. There is no 

record of zeolite claims in either study area. 

In the northern and western parts of the study area, 

tuffaceous sedimentary rocks include beds that have been 

altered to bentonitic clays. A sample of bentonite collected 

in the northern part of the Owyhee Breaks Wilderness Study 

Area contains 80 to 95 percent smectite, a clay mineral that 

has swelling properties. However, these beds are far from 

existing markets, and no prospects or resources for them 

were identified in the study area. 

Acknowledgments 

The author would like to thank Eugene Mueller and 

Darrell Jacobitz, claimants, for tours of their claims and 

samples of jasper. 

Identified Resources of the Blue Canyon 

Wilderness Study Area 

The Blue Canyon Wilderness Study Area contains 

marginally economic inferred resources of jasper, subeconomic inferred resources of perlite, and occurrences of sand 

and gravel. Detailed information on these resources is found 

in Causey (1989a). Other mineral commodities found in 

the study area are not of sufficient grade or volume to be 

resources, or they are covered by excessive amounts of 

overburden. 

Identified Resources of the Owyhee Breaks 

Wilderness Study Area 

The Owyhee Breaks Wilderness Study Area contains 

occurrences of bentonite jasper, zeolite minerals, and sand 

and gravel. Detailed information about these commodities is 

found in Causey (1989b). The northern part of the study area 

has an estimated 40,000 st of bentonite clay. Sand and gravel 

deposits are exposed along the Owyhee River and on small 

isolated benches near the river. Because these deposits are 

small and inaccessible, no mining is expected. Sand and 

gravel deposits exposed along the Owyhee River north of 

Rome, Oreg. (fig. 1 ), and in the southern part of the study area 

along Birch Creek contain trace amounts of gold. No economic placer gold deposits are known in the region. No other 

energy or mineral resources were identified in the Owyhee 

Breaks Wilderness Study Area . 

G8 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL 

By Dean B. VanderMeulen, Vincent E. Barlock, 

Patrick S. Plumley, James G. Frisken, and 

Andrew Griscom 

U.S. Geological Survey 

Geology 

Caldera and Structural Evolution 

The Blue Canyon and Owyhee Breaks Wilderness 

Study Areas lie within the north-central part of the Basin and 

Range physiographic province, a region characterized by 

east-west extensional tectonism. The eastern part of the study 

area includes the west margin of the Mahogany Mountain 

caldera (fig. 1), a collapse structure that resulted from the 

eruption of voluminous ash-flow and air-fall tuffs. The 

caldera, and its associated tuffs, is one of five calderas that 

make up the Lake Owyhee volcanic field in eastern Oregon 

(Rytuba and others, 1990a). The volcanic field extends 

westward from the Idaho border (fig. 1) to about longitude 

118°30' and northward from Jordan Valley, Oreg. (fig. 1), to 

about latitude 44 °15 '. 

The Mahogany Mountain caldera is expressed 

topographically as an 8- by 12-mi elliptical depression that 

has been deeply eroded by the Owyhee River. The caldera 

margin (fig. 1) parallels the base of the topographic wall 

that is well exposed along the north escarpment of Mahogany 

Mountain. The topographic margin of the Mahogany 

Mountain caldera is controlled in part by north-trending 

nonnal faults, which suggests that caldera collapse may 

have occurred along these preexisting faults. The volcanic 

and structural evolution of the caldera generally parallels 

the stages of caldera evolution proposed by Smith and Bailey 

(1968). Three episodes of silicic volcanism are associated 

with the fonnation of this caldera: (1) an extensive precaldera 

rhyolite dome and flow complex at Mahogany Mountain, 

(2) rhyolite ash-flow and air-fall tuffs that erupted 

concurrently with the collapse of the caldera, and (3) 

postcaldera rhyolite dikes and plugs that intrude calderafanning tuffs. Although mineralization in the study area is 

associated with a later post-caldera episode of silicic and 

intennediate volcanism, it was probably localized along the 

caldera ring faults. 

In the east-central part of the study area, precaldera 

rhyolite flows fonn the southwest wall of the caldera and 

are the oldest rocks exposed in the study area (fig. 2). Rhyolite ash-flow and air-fall tuffs that erupted concurrently 

with the collapse of the caldera filled the resulting depression with an estimated 2,600 vertical ft of intracaldera tuff 

(VanderMeulen, 1989). These intracaldera tuffs represent 

the second stage of silicic volcanism and are part of the 

Leslie Gulch Ash-Flow Tuff Member of the Sucker Creek 

Fonnation of Kittleman and others (1965) (also see Kittleman, 1973). A potassium-argon age obtained from the tuff 

is 15.5±0.5 Ma (VanderMeulen and others, 1987b). All 

ages reported in this investigation were obtained from sanidine mineral separates. Major- and trace-element analyses 

indicate that the tuff is chemically zoned, ranging from 

high-silica, weakly peralkaline comendite to intennediatesilica comendite trachyte (Vander Meulen, 1989). 

Silicic volcanism associated with the Mahogany 

Mountain caldera concluded with rhyolite intrusions. R~yolite plugs that intrude the south-central part of the study 

area may be related to this episode of volcanism. A potassium-argon age obtained from a northwest-striking_ rhyolite 

dike, 6 mi east of the study area, is 14.9±0.4 Ma (Vander 

Meulen and others, 1987b). The rhyolite intrusions are 

locally brecciated, silicified, and cut by quartz veins. 

The west half of the study area lies within a 15- by 

30-mi gravity low (fig. 3) that may reflect a concealed 

caldera filled with low-density tuff and sedimentary rocks. 

The unit mapped as the tuff of Birch Creek, first described 

by Plumley (1986), may have erupted from this possible 

caldera. 

North-trending nonnal faults that cut the map area 

(fig. 2) defme a horst that is flanked by two grabens in the 

north-central part of the study area. The north-trending 

fault traces are generally discontinuous and poorly defined, 

although one fault in the north-central part of the study area 

can be traced for approximately 5 mi. Faults that divide the 

horst from the eastern graben are superimposed on, and 

parallel to, the west margin of the Mahogany Mountain 

caldera. Within this graben, most of the caldera margin is 

buried by postcaldera basalt flows, sedimentary rocks, and 

debris slides; this sequence suggests that subsidence along 

the graben-fonning faults continued after caldera collapse. 

Subsidence within the western graben displaced a thick sequence of partly consolidated tuffaceous and lacustrine 

sedimentary rocks and diverted the east-flowing Owyhee 

River northward along its strike. 

A second and younger set of faults, striking N. 35° 

W. toN. 55° W., offsets the north-trending faults. Tl)ese 

younger faults are best exposed in the northern part of the 

study area. They are discontinuous; segments are a mile or 

less in length and may have been reactivated several times 

during the late Miocene to Pliocene. The northwest-trending faults parallel three major shear zones that cut the northem part of the Basin and Range, including the Brothers and 

Vale fault zones (Lawrence, 1976), and the DeLamar-Duck 

Valley structural trend (Rytuba, 1989). The Brothers fault 

zone, located approximately 60 mi southwest of the study 

area, extends northwest 160 mi across central Oregon from 

Steens Mountain to the Cascade Range. At the surface, the 

15-mi-wide fault zone is delineated by a series of en echelon faults and fractures striking N. 55° W. (Walker 1977; 

Lawrence, 1976). The Vale fault zone is part of the northern 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G9 
is subparallel to the Brothers fault zone. The surface expression of this major 15-mi-wide fault zone is delineated 

by a series of northwest-striking faults (Walker, 1977; Ekren 

and others, 1981; Ferns, 1989a, b, c; Ferns and Ramp, 1989) 

that extend 120 mi from north-central Nevada into eastern 

Oregon. The study area is 14 mi southwest of the main 

fault zone. In this part of the Lake Owyhee volcanic field, 

most of the known sediment-hosted hot-spring gold deposits 

are localized where northwest-trending faults intersect older 

north-trending normal faults and younger north-northeasttrending normal faults. 

Volcanic Stratigraphy 

The stratigraphically lowest rocks exposed in the study 

area are the precaldera rhyolite flows of Mahogany Mountain (unit Trf, fig. 2), formerly called the Jump Creek Rhyolite by Kittleman (1973). In the east-central part of the 

study area, these flows form the southwest topographic wall 

of the Mahogany Mountain caldera. The northern part of 

this rhyolite complex subsided with the formation of the 

caldera and is no longer exposed. 

Three mappable ash-flow tuff units are exposed in 

the study area: units Tlg, Tsc, and Tbc (fig. 2). The tuffs 

were originally mapped as the Leslie Gulch Ash-Aow Tuff 

of the Sucker Creek Formation (Kittleman and others, 1965) 

but are here divided into three separate, informally designated units. From oldest to youngest they are the tuff of 

Leslie Gulch (VanderMeulen and others, 1987b), the tuff 

of Spring Creek (VanderMeulen and others, 1987b), and 

the tuff of Birch Creek (Plumley, 1986). 

In the study area, the tuff of Leslie Gulch consists of 

an interbedded sequence of partly welded to nonwelded 

rhyolite ash-flow tuff and several smaller air-fall and surge 

deposits, all of which cooled as single unit. Throughout the 

study area, this composite tuff sheet dips between 10° and 

20° west and has a minimum thickness of 900 ft. The unit is 

exposed west and south of the caldera margin and is interpreted as an outflow ash-flow tuff that erupted from the 

caldera. In the north-central part of the study area, near the 

projected caldera margin, the tuff locally consists of matrixsupported orange-brown angular pumice blocks as large as 

10 in. across. This near-vent pumiceous tuff indicates that at 

least part of the outflow unit was erupted from a caldera ring 

vent. The unit is generally massive and unsorted, showing 

only crude layering, although parts of the tuff grade up into 

well-bedded air-fall tuff. The tuff is typically crystal poor 

with 1 to 5 percent quartz and sanidine phenocrysts. The unit 

is exposed locally throughout most of the study area and 

probably underlies the entire study area at depth. The tuff 

erodes to irregular spires and steep slopes that are honeycombed with pockets from wind erosion. Internal stratigraphy of the outflow tuff is relatively consistent. 

Following the collapse of the Mahogany Mountain 

caldera, two post-caldera rhyolite ash-flow tuffs unrelated 

to the Mahogany Mountain caldera erupted from nearby 

centers and ponded in the caldera moat. The tuff of Spring 

Creek (unit Tsc, fig. 2) was the frrst ash-flow tuff to pond 

in the caldera and unconformably overlies the tuff of Leslie 

Gulch. It is a composite ash-flow tuff that erupted from the 

Three Fingers caldera (Vander Meulen and others, 1989) 

20 mi northeast of the study area (fig. 1). The tuff consists 

of multiple ash-flow sheets that cooled as a single unit. In 

the south-central part of the study area the tuff of Spring 

Creek has a maximum thickness of 600 ft. 

The tuff of Birch Creek (unit Tbc, fig. 2) is the 

younger of the two postcaldera ash-flow tuffs. Gravity data 

and stratigraphic relations indicate that the vent for the tuff 

is within or west of the study area.' Chemically, the tuff of 

Birch Creek is calc-alkaline rhyolite (Plumley, 1986). The 

tuff ranges from approximately 200 ft thick in the central 

part of the study area, where it forms an angular unconformably with the underlying tuff of Leslie Gulch, to an 

estimated 500 ft thick in the southern part of the study area 

near the Owyhee River. Thicker parts of the tuff are welded 

to densely welded and contain irregular-shaped pods and 

stringers of dark-colored vitrophyre. Repetition of vitrophyric zones and welding zonation within the ash-flow sequence indicate that the tuff is composed of two cooling 

units. Locally, the tuff displays rheomorphic features such 

as recumbent folds and ramp structures and has well-developed eutaxitic foliation. It contains plagioclase, hornblende, 

and biotite phenocrysts. 

In the central and southern parts of the study area, 

rhyolite and dacite plugs and dikes (units Trp and Tdi, fig. 2) 

cut the entire sequence of caldera-forming and postcaldera 

tuffs. The intrusions crop out as discontinuous irregular 

bodies, as thick as 60 ft, that typically pinch and swell 

along strike. They are highly resistant to erosion and form 

steep spired ridges that typically rise hundreds of feet above 

the surrounding topography. Most of these intrusions contain phenocrysts of alkali feldspar and plagioclase and are 

chemically classified as high-potassium dacite (Plumley, 

1986). Hydrothermal silicification and calcification is common in the intrusions and adjoining country rock. 

In the southern part of the study area along the 

Owyhee River, two large intermediate-silica plugs (unit Tai, 

fig. 2) intrude the tuff of Leslie Gulch. Composition ranges 

from basaltic andesite to high-potassium andesite. The intrusions have a maximum exposed thickness of approximately 700ft. Chemically and petrographically these rocks 

are similar to, and probably comagmatic with, porphyritic 

andesite flows intercalated with the lower part of the sedimentary sequence (discussed below). 

In the northern part of the study area, a large 0.5- by 1-

mi mafic to intermediate plug (unit Tbi, fig. 2) intrudes a 

thick sequence of sedimentary rocks. The west margin of 

this basaltic intrusion is in fault contact with the tuff of 

Leslie Gulch. 

Gl 0 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
Several vitric and crystal-vitric air-fall tuffs and one 

lithic-rich ash-flow tuff are intercalated with the sedimentary rocks and are mapped as part of the sedimentary rocks 

(unit Ts, fig. 2). The lithic-rich tuff crops out across the 

northern part of the study area, has a maximum thickness of 

approximately 80ft, and forms a resistant cap rock near the 

upper part of the sedimentary sequence. The tuff is commonly silicified and locally contains anomalous concentrations of gold, silver, mercury, and molybdenum. 

The youngest volcanic rocks in the study area are 

plateau-forming olivine tholeiitic-basalt flows (unit Tb, fig. 

2) that unconformably overlie the sedimentary rocks and 

rhyolite flows of Mahogany Mountain. The lava flows cap 

plateaus, mostly in the southern part of the study area, and 

yield whole-rock potassium-argon ages ranging from 3.8 to 

0.2 Ma (Hart and Mertzman, 1983). Along the plateau rim, 

the basalt flows are as thick as 100 ft; at two locations in 

the southern part of the study area, flows cascaded over the 

rim and ponded in a north-trending paleovalley where they 

are as thick as 330 ft. Remnants of these ponded basalt flows 

cap intercanyon buttes and are exposed as discontinuous 

ledge$ along the river canyon. One vent area for the basalt 

flows is a small shield volcano centered at Deer Butte (fig. 

1), 2 mi southwest of the study area. 

Sedimentary Stratigraphy 

Several sediment-hosted hot-spring gold prospects 

recently have been discovered north and east of the study 

area; as a result, the sedimentology of the study area has 

been extensively investigated. In the northern and western 

parts of the study area, an estimated 1,000-ft-thick sequence 

of sedimentary rocks (unit Ts, fig. 2) unconformably overlies the caldera-forming and postcaldera tuffs. The general 

lithology from the base up consists of tuffaceous sandstone, 

interbedded palagonite tuff and basaltic-andesite flows, 

evaporite deposits and diatomaceous earth interbedded with 

thick sequences of claystone and siltstone, and arkosic 

sandstone and conglomerate units. This general sequence 

indicates the evolution of a lake from initial basin filling to 

the point of total inundation, subaerial exposure, followed 

by subsidence and resumption of deep-water deposition. 

This sedimentary cycle was not'interrupted until basin-andrange tectonism extended the region and voluminous basalt 

flows covered the sedimentary rocks (fig. 2). 

Locally in the northern part of the study area, excellent exposures of tuffaceous sedimentary rocks with largescale crossbeds form the basal part of the section. The 

dominant lithology is pebble- and sand-size tuffaceous detritus with minor basaltic and rhyolitic fragments. Detritus 

is upward fining, well sorted, and moderately rounded. The 

entire unit has an estimated thickness of 70 ft. Contact 

between the large composite sets (crossbeds) and the underlying fine-grained sedimentary rocks is sharp. The composite sets contain both stratified and cross-stratified units 

of similar or gradational lithology. Forsets dip at angles 

between 11° and 17° to the west and are approximately 120 

ft in length. McKee and Weir (1953) have described similar sedimentary structures in lacustrine deltas. These largescale crossbedded volcaniclastic sandstone horizons most 

likely formed by the progradation of a steep deltaic lobe 

adjacent to a topographic high. 

At the extreme northeast edge of the study area and 

near the Owyhee River in the western part of the study 

area, palagonite tuffs (unit Tpt, fig. 2) stratigraphically 

overlie the tuffaceous sedimentary rocks. The unit has a 

total estimated thickness of 120 ft and contains basaltic 

blocks, lithic and pumice fragments, and ash. Stratified 

parts of the palagonite tuff contain parallel beds, parallel 

crossbeds, lithic trains, and inverse grading of tephra. Features exposed near the base include cut-and-fill structures, 

dunes, explosion breccia, and sag ·structures. The breccia 

contains conspicuous biotite- and hornblende-bearing blocks 

of the welded tuff of Birch Creek. Flow features near the 

base are those created during the formation of basaltic tuff 

cones, specifically the stage dominated by base surge 

(Wohletz and Sheridan, 1983). Similar tuff cone deposits 

are described by Cummings and Growney (1988) in a detailed study of basaltic hydrovolcanic deposits, 14 mi north 

of the study area. In the northern and western parts of the 

study area, the palagonite tuffs are exposed along northstriking fault zones, as are basaltic dikes and plugs that 

intrude delta deposits. Palagonite tuffs that locally overlie 

fine-grained claystone and are near a preserved delta suggest 

that these basaltic eruptions occurred in relatively deep water. The spatial association of palagonite tuffs with northtrending normal faults is also apparent north of the study 

area, near the Red Butte gold prospect (fig. 2). Several of 

the known sediment-hosted hot-spring gold prospects in the 

region, including Red Butte, Quartz Mountain, and Mahogany (fig. 1), are floored by thick sequences of palagonite 

tuff or basalt flows. 

Stratigraphically above the palagonite tuffs is a sequence of claystone and siltstone that typically exceeds 50 

ft in thickness and is locally as thick as 650 ft. These rocks 

contain carbonaceous material, leaf fragments, small twigs, 

and possibly fish vertebrae. Thick sequences, greater than 

50 ft, of finely laminated claystone are intercalated with 

lenticular horizons of organic-rich detritus. Within these 

thick carbonaceous sequences, dark basal layers of carbonaceous claystone or siltstone typically grade up into more 

mottled, bioturbated, lighter colored strata. The top of each 

gradational layer contains root casts, calcium carbonate 

nodules, and intermittent undulatory horizons of caliche. In 

several locations the bedding was destroyed by bioturbation. 

Dark organic-rich clays that contain scattered silt lenses, 

evidence of bioturbation, and fluid-escape structures are 

characteristic of lake-bottom depositional environments associated with delta-fill processes (Coleman, 1976). 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G11 
Interbedded with the claystone and siltstone are beds 

of diatomaceous earth and thin evaporite deposits, primarily of gypsum. Large extensive sheets of gypsum were not 

seen, although exposed strata are planar and as much as 2 

in. thick. The diatomaceous earth is exposed in the northem part of the study area. Individual beds of diatomite, 

which are very clean and possibly of industrial quality, are 

typically 2 to 4 in. thick and range up to 5 ft thick. Locally, 

the diatomaceous earth is well bedded to finely laminated, 

consolidated to punky, and contaminated in part with calcium carbonate and volcanic ash. Thicker beds are massive 

and very clean; however, the massive beds are poorly exposed and crop out only where slopes are oversteepened. 

Nonalkaline conditions are necessary for the preservation 

of diatomite because the solubility of silica increases abruptly 

at a pH greater than 9 (Krauskopf, 1959). To preserve 

large amounts of diatomite, immediate coverage is necessary, such as deposition in a stable basin or preservation by 

a cover of volcanic tuffs and flows. 

In the study area, arkosic sandstone and gravel beds 

range from 10 to 40 ft thick and overlie the fine-grained 

claystone and siltstone beds. The prefiX "arkosic" has bee~ 

used for sandstone units that contain more than 25 percent 

feldspar. The remaining detritus in the sandstone is mostly 

quartz, minor biotite, and fragments of basalt and rhyolite. 

The arkosic sandstone and gravel beds are locally well indurated and silicified and contain medium-scale planar 

crossbeds that grade laterally into zones of planar-bedded 

fme-grained sedimentary rocks. These beds are regionally 

extensive and syndepositional with hot-spring sinter deposits at the Red Butte and Katie gold prospects. Arkosic 

sandstone and conglomerate beds within the study area are 

interpreted as stratigraphically equivalent to the silicified 

and mineralized sedimentary rocks exposed at the Red Butte 

gold prospect, 2.5 mi north of the study area. 

Landslide deposits (unit Qls, fig. 2) cover approximately 3 mil in the western part of the study area and approximately 7 mil northeast of the study area. The deposits 

consist of rotated blocks and debris slides that have developed in poorly consolidated tuffaceous sedimentary rocks 

along the plateau rims. Rotated basalt blocks displaced 

along transverse cracks form broad arcuate headwall scarps 

along the plateau rims. These slides commonly terminate 

in canyon bottoms as bulbous toes covered with pressure 

ridges. From head to toe, some of the slides are 3 mi long. 

Other surficial deposits consist of talus, colluvium, and alluvium .. The thickest alluvial deposits are restricted to the 

Owyhee River and main stream drainages. 

Geochemical Studies 

In 1988, the U.S. Geological Survey conducted a·reconnaissance geochemical study of the Blue Canyon and 

Owyhee Breaks Wilderness Study Areas. Stream sediments 

and heavy-mineml concentrates from stream sediments were 

selected as the primary sample media on the basis of their 

ability to reveal elemental anomalies. During this study, 47 

stream-sediment samples and 46 nonmagnetic heavy-mineml-concentrate samples were collected in and near the study 

area and were analyzed. Stream-sediment and concentrate 

samples were collected from fJCSt- and second-order, primarily dry stream beds. In addition, 82 rock samples, predominantly silicified and (or) brecciated volcanic and 

sedimentary rock from outcrops or stream cobbles, were 

collected to determine the suite of elements associated with 

the observed alteration. 

Stream-sediment and nonmagnetic heavy-mineralconcentrate samples represent composites of eroded bedrock 

exposed upstream from sample sites. Stream-sediments 

reflect bedrock geochemistry useful in identifying basins 

that contain concentrations of elements possibly related to 

mineralized rock. Nonmagnetic heavy-mineral-concentrate 

samples provide information about the chemistry of a limited 

number of minemls which may be ore forming or ore related. 

Such selective concentration of minerals permits 

determination of some elements that are not easily detected 

in bulk stream-sediment samples. 

All samples were analyzed for 35 elements (antimony, 

arsenic, barium, beryllium, bismuth, boron, cadmium, calcium, chromium, cobalt, copper, gallium, germanium, gold, 

iron, lanthanum, lead, magnesium, manganese, molybdenum, nickel, niobium, phosphorus, scandium, silver, sodium, strontium, thorium, tin, titanium, tungsten, vanadium, 

yttrium, zinc, and zirconium) by using a six-step semiquantitative emission-spectrographic method described by Crock 

and others (1987). In addition, the nonmagnetic concentrates were also analyzed spectrographically for platinum 

and palladium. Rock and stream-sediment-samples were 

analyzed for gold, mercury, arsenic, antimony, cadmium, 

bismuth, and zinc nonspectrographically to provide data on 

elements not determined spectrographically or to provide 

data at low levels of detection. The mercury analyses were 

done by atomic absorption and the arsenic, antimony, cadmium, bismuth, and zinc analyses were done by inductively 

coupled argon plasma-atomic emission spectrography 

(Crock and others, 1987). Gold analyses were done by 

graphite-furnace atomic absorption (Meier, 1980), whi~h 

has a lower level of detection of 2 parts per billion (ppb ). 

This method. does not break down silicate minerals; therefore, detected values represent detrital gold. 

All of the stream-sediment samples and 15 of the rock 

samples were analyzed for uranium by Centanni ultraviolet 

fluorescence (O'Leary and Viets, 1986). All of the streamsediment samples, 13 concentrate samples, and 2 rock 

samples were analyzed for fluorine by an ion-selective electrode method (O'Leary and Viets, 1986). Detailed analytical data on which the following account is based have not 

been published (MJ. Malcolm and others, unpub. data, 1990). 

Summaries of the analyses are presented in tables 2-4. One 

C12 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
Table 2. Geochemical summary for 46 U.S. Geological Table 4. Geochemical summary for 82 U.S. Geological SurSurvey nonmagnetic panned-concentrate samples from the vey rock samples from the Blue Canyon and Owyhee Breaks 

Blue Canyon and Owyhee Breaks Wilderness Study Areas Wilderness Study Areas and adjacent areas, Oregon 

and adjacent areas, Oregon 

[All values are expressed in parts per million. Pint-column values are 

[All values expressed in parts per rniJ.lion. Pint-column values are lower lower levels of determination for emission spectrometry (S), atomic ablevels of determination for emission spectrometry (S) and ion-selective sorption (AA), inductively coupled plasma-atomic emission spectroscopy 

electrode (ISE) analytical methods. L represents detection below the limit (ICP), and ion-selective electrode (ISE) analytical methods. L represents 

of analytical determination, > represents detection above it] detection below the limit of analytical determination] 

Anomalous Threshold Range of No. of anomalous Anomalous Threshold Range of No. of anomalous 

elements values anomalous values sample sites elements values anomalous values sample sites 

Ag (S 1) 1 1.5-70 3 Ag (S 0.5) 1..(0.5) 1..(0.5)-3 19 

As (S 20) 1..(20) 30-700 2 As (S 200) 1..(200) 1..(200) 3 

Ba (S 50) 10,000 1 0,000-> 10,000 22 As (ICP 1) 3 3.4-309 51 

F (ISE 100) 3,000 3,100-380,000 12 Au (AA 0.002) 0.0021 0.002-0.04 17 

La (S 50) 500 500-1,000 6 B (S 10) 20 20-70 7 

Mo (S 10) 15 15 1 Ba (S 20) 1,000 1,000-3,000 20 

Nb (S 50) 150 150-200 6 Be (S 1) 5 5-7 7 

Pb (S 20) 150 150-15,000 7 Cd (ICP 0.05) 0.3 0.4 3 

Sb (S 200) 1..(200) 1..(200)-500 2 Co (S 5) 70 70 1 

Sn (S 20) 100 100-2,000 10 F (ISE 100) 1,000 90,000 1 

Sr (S 200) 3,000 7,000 1 Ga (S 5) 50 50 6 

y (S 20) 700 700-1,000 20 Ge (S 10) 5 1..(10)-100 5 

Hg (AA 0.02) 0.1 0.1-2.2 20 

La (S 20) 50 50-150 14 

Mn (S 10) 3,000 3,000 1 

Mo (S 5) 1..(5) 1..(5)-150 37 

Table 3. Geochemical summary for 47 U.S. Geological Sur- Nb (S 20) 30 30 7 

vey minus-80-mesh stream-sediment samples from the Blue Pb (S 10) 30 50-70 2 

Canyon and Owyhee Breaks Wilderness Study Areas and Sb (S 100) 1..(100) 1..(100) 1 

adjacent areas, Oregon Sb (ICP 1) 1 1-14 33 

Sn (S 10) 5 20 1 

[All values are expressed in parts per million. Pint-column values are Sr (S 100) 1,000 1,000-1,500 3 

lower levels of determination for emission spectrometry (S), atomic ab- v (S 10) 500 500 1 

sorption (AA), inductively coupled plasma-atomic emission spectroscopy y (S 10) 70 70-150 19 

(ICP), ion-selective electrode (ISE), and fluorimetric (F) analytical meth- Zn (S 200) 1..(200) 1..(200)-200 7 

ods. L represents detection below the limit of analytical detenninatioo] Zn (ICP 0.05) 150 150 1 

Anomalous Threshold Range of No. of anomalous 1 Analytical method used does not break down the silicate 

elements values anomalous values sample sites minerals, so detected gold is detrital. 

As (ICP 1) 3 3-30 36 

Au (AA 0.002) 0.0021 0.002-{).007 3 water sample from a thermal spring north of the Owyhee B (S 10) 20 20 3 

Ba (S 20) 1,000 1,000-2,000 26 River, in the western part of the study area (fig. 2), contains 

Be (S 1) 5 5 1 no gold or uranium at a detection limit of 0.1 ppb. 

Cd (ICP 0.05) 0.3 0.3-{).6 6 Most of the rock units exposed in the study area are 

Co (S 5) 70 70 1 silicic pyroclastic deposits or basalt flows. Too few 

Cr (S 10) 300 300 7 unmineralized rocks were collected to provide a sufficient F (ISE 100) 600 620-3,200. 15 

Ga (S 5) 50 50 1 data base for a statistical approach to calculating geochemical 

Hg (AA 0.02) 0.10 0.10-0.18 4 threshold values. Therefore, the threshold values Oowest 

La (S 20) 50 50-70 32 anomalous values) chosen for rock and stream-sediment 

Mo (S 5) 1..(5) 1..(5)-7 5 samples were calculated at two to three times the Nb (S 20) 30 30 1 concentrations for bulk continental crust (see Taylor and Pb (S 10) 30 30. 2 

Sb (ICP 1) 1 1-3 3 McLennan, 1985, p. 62, 67). Whenever threshold values 

Sr (S 100) 1,000 1,000 7 for elements were below their lower levels of detection, the 

u (F 0.4) 4 8.7 1 quantitative values were considered anomalous. Threshold 

v (S 10) 500 500-700 4 values for the nonmagnetic concentrate samples were based y (S 10) 70 70 1 

on the experience with other geochemical surveys in the 

1 Analytical method used does not break down the silicate region. Data presented in tables 2-4 indicate the calculated 

minerals, so detected gold is detrital. threshold values, the range of anomalous values, and the 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon C13 
C"l 

... 

• 

EXPLANATION 

• Area having high mineral resource potential (H) 

Area having modemte (M) or low (L) mineral resource potential for commodities as 

listed 

m Area having low mineral resource potential (L) for zinc 

2 Mine having identified resources -Number refers to list below and to table 1 

X 5 Prospect or claim having identified resources-Number refers to list below and to 

table 1 

~ Area including identified resources of jasper and (or) perlite 

Level of certainty of assessment 

B Data only suggest level of potential 

C Data give good indication of level of potential 

Commodities 

Ag Silver Mo Molybdenum 

Au Gold Zn Zinc 

F Fluorite Ben Bentonite 

Geo Geothermal Dia Diatomite 

Hg Mercury 0/G Oil and gas 

Deposit types 

[1] Fault-controlled volcanic- and sediment-hosted epithermal deposits 

[2] Volcanic- and sediment-hosted epithermal deposits 

[3] Volcanogenic disseminated deposits 

[4] Sedimentary lake deposits 

[5] Sediment-hosted deposits 

Qal 

Qc 

Ot 

Qls 

Tb 

Ts 

Tpt 

Tbi 

Tai 

Tdi 

Trp 

Tbc 

Tsc 

Tlg 

Trf 

Geologic map units 

Alluvium (Quaternary) 

Colluvium (Quaternary) 

Talus (Quaternary) 

Landslide deposits (Quaternary) 

Basalt flows (Tertiary) 

Sedimentary rocks (Tertiary) 

Palagonite tuff (Tertiary) 

Basalt intrusions (Tertiary) 

Andesite intrusions (Tertiary) 

Dacite intrusions (Tertiary) 

Rhyolite porphyry (Tertiary) 

Tuff of Birch Creek (Tertiary) 

Tuff of Spring Creek (Tertiary) 

Tuff of Leslie Gulch (Tertiary) 

Rhyolite flows (Tertiary) 

~ Area of silicified sandstone and conglomerate 

Contact-Dashed where approximately located 

......... --··· Fault-Dashed where inferred; dotted ~here conc~.Ued; ball and bar on 

downthrown side 

_ b Anticline-Showing crestline and direction of plunge. Dashed where approximate 

@) Thermal spring 

X 7 Prospect or claim-Number refers to list below and table I .8 43° ~ ... ·., 15' ..•. . . . . 

117°30' 

.:; 1 

iJ< 

.:.., /)' 

.'::.. .... -

Au. Ag, Hg.'Mo llJ -'~._,~ 

r l!!('~ 

\ 

(' 

~ v 

: [ ~< '! \ o..', l•r • 

~..,....<:"""" ~r ..l,;l:-"7~-..._ L ~ ~"*/( 1 • 

-~ ../ \..o- ..... _I 

\ 

\ 

Mines, prospects, claims, and deposit 

[Numbers refer to table l] 

Jasper prospect 

Morrison Ranch: 

Meadowlark mine 

Christine Marie mine 

Rocky Rim claim 

Jasper prospect 

Stewart claims 

117"22'30" 

-.-

North Birch, Middle Birch, and South Birch claims 

Clay deposit 

APPRO~TEBOUNDARY 

OF 

OWYHEE BREAKS 

WILDERNESS STUDY AREA 

Jasper prospect ;--:J 

I\. / 

APPRO~TEBOUNDARY 

OF 

BLUE CANYON 

·: · __ ·_._·,·,;··_·.·· ___ ._•· .· ,,_._·· .. 't'_:JE~ •. ~. ._-_ ..- -:Lh Q WILDERNESS STUDY AREA 1 ~· .;- · ... ~:. , , ~'. ·.· · , . '" ,1 -": [> oa. (OR-003-073) 

"-~"· :. } ... . -- .· . ... ~ 

0 2 MILES 

(OR-003-059) 43° . . - . • ' . ' . ' . - . 

10' Base from U.S. Geological Survey 1:24,000: Geology modified from Vercoutere and 

Diamond Butte, 1967; Jordan Craters North, others (1987), Plumley (1986), and V.E. 

1969; Mud Flat, 1972; and The Hole in the Barlock and D.B. VanderMeulen (unpub. 

Ground, 1972 data, 1990) 

. I 

F1gure 2. Mineral resource potential and generalized geology of Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon. 

C"l 

... 

\11 
number of sample sites containing anomalous concentrations 

of metals (elements) in the map area, for each sample 

medium. 

Regional Gold Mines and Prospects 

Ferns and Huber (1984) reported several epithermal 

gold deposits in southeastern Oregon which they described 

as fossil geothermal systems that formed near the surface in 

hot-spring systems. The systems are commonly associated 

with Tertiary fault zones, rhyolitic volcanic centers, and 

tuffaceous sedimentary rocks. Systems favorable for gold 

generally cover several square miles, contain anomalous 

concentrations of mercury and antimony, and have extensive caps of siliceous sinter (opalite) and large woes of 

clay alteration. 

Several deposits of this type are near the study area 

(Wheeler, 1988). They are pervasively silicified and 

brecciated and are hosted by fluvial and lacustrine sandstone and conglomerate that have been faulted. The highest 

gold concentrations are usually in sandstone adjacent to 

conglomerate beds or brecciated rocks. Most of the deposits 

have associated clay alteration, silicification, and disseminated pyrite. The geochemistry of these deposits is characterized by anomalous concentrations of mercury and arsenic. 

Gold is, for the most part, micron size. 

Quartz veins, clay alteration, hydrofractured rock, and 

pervasive silicification of host rocks was present at all the 

disseminated gold prospects examined. In addition, northwest-trending structures intersect north-trending basin-andrange faults at these prospects. Siliceous sinter is exposed 

at the Grassy Mountain, Red Butte, Quartz Mountain, Katie, 

and Mahogany prospects (fig. 1). Of rock samples collected 

from the Quartz Mountain prospect, 10 have anomalous 

values that range from 10 to 850 ppb gold, 0.2 to 5.5 parts 

per million (ppm) silver, 7 to 90 ppm arsenic, 6 to 77 ppm 

antimony, 120 to more than 5,000 ppb mercury, and 30 to 

700 ppm fluorine. At the Red Butte prospect, 18 rock 

samples have values that range from 5 to 1,120 ppb gold, 

11 to 1,000 ppm arsenic, and 25 to 700 ppb mercury. 

In 1988, more than 40 companies were exploring for 

gold in the northe~ Basin and Range province of southeast 

Oregon, where approximately 5,000 new claims were filed. 

The main area of interest is an epithermal-gold province in 

the northeastern part of Malheur County, Oreg. (Ferns, 

1989d), which includes the study area, and adjacent Owyhee 

County, Idaho, where a total of at least 28 prospects are 

being evaluated. The Grassy Mountain prospect (fig. 1 ), 

has reserves of more than 1 million ounces at a grade of 

0.065 oz/short ton gold (Ferns and Ramp, 1989). The deposit 

is a hot-spring-type epithermal system hosted by arkosic 

sandstones. The age of mineralization for the Red Butte, 

Quartz Mountain, and Katie prospects (fig. 1) is probably 

middle Miocene. At the Mahogany gold prospect, veins of 

quartz and adularia cut the host rocks; a K-Ar age on adularia 

from one of these veins dates the mineralization at 12.6 Ma 

(Rytuba and others, 1990b). Gold mineralization at prospects 

north of this area, such as Grassy Mountain, is associated 

with younger intermediate and silicic intrusions (Cummings, 

1989; Ferns and Ramp, 1989). 

The DeLamar silver mine, 35 mi east-southeast of 

the study area in Owyhee County, Idaho, and several nearby 

prospects are similar Miocene hot-spring-type epithermal 

deposits. The DeLamar mine produced more than 17 million 

oz of silver and 230 oz of gold by bulk mining methods 

between 1977 and late 1987 and an estimated 42 million 

ounces of silver and 600,000 oz of gold by underground 

lode-vein mining between 1863 and 1914. Production is 

predominantly from silver selenide minerals and native gold 

in quartz veins hosted by a rhyolite ring-dome complex 

(Halsor and others, 1984, 1988; Barrett, 1985; Ekren, 1985). 

Mineralization is controlled by north-trending faults that 

intersect younger northwest-trending faults. Principal gangue 

minerals in the veins are quartz and adularia, with lesser 

amounts of calcite, barite, pyrite, fluorite, and siderite. 

Alteration woes are dominated by clays associated with 

pyrite and quartz. 

The Red Butte prospect is an epithermal hot-springtype gold deposit characterized by silicified lacustrine and 

fluvial volcaniclastic sedimentary rocks, quartz veins, and 

hydrothermal explosion breccia (Evans and Cummings, 

1986). They report that anomalous concentrations of gold, 

mercury, arsenic, and antimony are present in banded quartz, 

quartz-adularia veins, silicified sandstone, and rarely in calcite-quartz veins in basalt Silicification is both structurally 

and stratigraphically controlled; silicified mudstones are 

generally barren. Part of a hydrothermal explosion crater 

and vent exposed on the southeast side of Red Butte lies at 

the intersection of north and northwest-trending faults. The 

Red Butte minernlizing system developed as silica-saturated 

hot-spring fluids issued into cooler lake waters. Silica flocculation near the vent formed massive beds of siliceous 

sinter. Gold and pyrite were also deposited at the vent. 

During this study, samples collected from the siliceous sinter, silicified mudstones and sandstones, and the veins and 

breccia yielded anomalous values as high as 0.040 ppm 

gold, 220 ppm arsenic, 51 ppm antimony, and 1.03 ppm 

mercury. Correlation coefficients comparing gold to arsenic, antimony, and mercury show no linear correlations, but 

samples high in gold are usually enriched in arsenic and 

antimony. A sample of silicified breccia collected by the 

U.S. Geological Survey from the hydrothermal explosion 

crnter along the southeast side of Red Butte contains 0.04 

ppm gold, 2.2 ppm mercury, 310 ppm arsenic, 17 ppm 

antimony, 3 ppm silver, 20 ppm molybdenum, and more 

than 10,000 ppm barium. A nonmagnetic concentrate sample 

collected at the site contains 80 percent fluorite and some 

pyrite. 

C16 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
The Mahogany prospect (fig. 1) is hosted by tuffs, 

tuffaceous sedimentary rocks, and volcaniclastic sandstones 

(Gilbert, 1988). The prospect lies along a north-trending 

fault zone that localized hydrothennal solutions of a hotspring system. The dominant alteration is described as silicification and argillation with abundant quartz, calcite, and 

quartz-adularia veins. Chalcedony is the predominant type 

of silica. Arsenic, antimony, mercury, and silver anomalies 

accompany the gold mineralization. Anomalous concentrations of gold, as much as 7.4 ppm, are typically confmed to 

quartz-calcite stockwork zones, banded quartz-calcite veins, 

and breccia dikes within a lithic tuff. Gold mineralization 

is spatially associated with silicified hydrothennal explosion breccia and fossilized siliceous hot-spring sinter deposits. 

Results and Interpretation 

The volcanic and sedimentary stratigraphy and the 

structure of the study area are similar to those features in 

nearby areas that have been prospected for epithermal gold 

deposits. In the southern and western parts of the study 

area, Plumley (1986) indicated that hydrothermally altered 

and silicified rocks typical of hot-spring systems are restricted to volcaniclastic sedimentary rocks of the Sucker 

Creek Formation (Kittleman and others, 1965), tuff of Birch 

Creek, and tuff of Leslie Gulch. In the north-central part of 

the study area, altered and mineralized rocks are locally 

associated with northwest-trending faults and the west margin of the Mahogany Mountain caldera (VanderMeulen, 

1989). 

Rocks at most sample sites show evidence of silicification and (or) brecciation. Quartz, opal, chalcedony, or 

silicified sedimentary rocks are present in outcrop or as 

cobbles in streams at 25 of 45 sites. In the Owyhee Breaks 

Wilderness Study Area, a horizontal layer of green silicified tuff 6 to 8 ft thick crops out approximately 3.2 mi 

downstream from the thermal spring (fig. 2). Brecciated 

limonitic rocks are common. Pyrite is present in 14 nonmagnetic concentrate samples. 

Barite and fluorite are also commonly found in the 

concentrate samples and may be associated with epithermal 

mineralization; barium and fluorine are anomalous in all 

samples of all media (tables 2-4). The fluorite and barite 

may have been deposited by chemical precipitation along 

with lake sediments distal to hot-spring vent areas. Fluorite 

constitutes as much as 16 percent of some lacustrine beds 

near Rome, Oreg. (fig. 1; Brobst and Pratt, 1973, p. 223). 

The fluorite-rich beds at Rome lack associated epithermal 

gold mineralization, but similar occurrences, if more concentrated in fluorite, could constitute a fluorite resource. In 

the study area, individual beds of sedimentary rock would 

have to be sampled to locate potential deposits. The highest concentrations of fluorine in stream-sediment and concentrate samples are from a site at Red Butte. Plumley 

(1986) reported that barium values average 1,200 ppm for 

the tuff of Birch Creek; 1,100 ppm for andesite intrusions; 

and 800 ppm for the tuff of Leslie Gulch. These values are 

above normal for silicic tuffs and intermediate intrusions 

and may have contributed to the barium anomalies in the 

stream-sediment and concentrate samples from the study 

area. 

Reconnaissance geochemical studies and initial mineral resource appraisals for the study area were conducted 

the Oregon Department of Geology and Mineral Industries 

(Gray and others, 1983), Barringer Resources, Inc. (Bukofski 

and others, 1984), and Robinson and others (1985). Although their samples were analyzed for fewer elements, 

and threshold values varied, anomalies similar to those in 

the present study were detected in their stream-sediment 

samples. 

During the present study, anomalous gold was detected in two stream-sediment samples (0.002 and 0.004 

ppm) and in two nonmagnetic concentrate samples (30 and 

700 ppm). One of the nonmagnetic concentrate samples 

was collected near river level at the base of a waterfall in 

the south-central part of the study area, and the other came 

from the northwestern part of the study area below perched 

alluvial gravels presumably deposited by the Owyhee River. 

Gold and silver anomalies in the concentrate samples may 

be due to placer gold flakes derived from Owyhee River 

sediments. Ten rock samples collected in the study area 

have gold values ranging from 0.002 to 0.024 ppm. They 

were collected from silicified tuffs and sedimentary rocks 

in the western part of the study area west of the Owyhee 

River and in the north-central part of the study area west of 

Blue Canyon. 

Three concentrate samples from the western part of 

the study area contain 1.5 to 70 ppm silver. In two of these 

samples, the silver is associated with the 30- to 700-ppm 

gold values discussed above. Silver is anomalous in 12 

rock samples (0.5-3 ppm), but none was detected in the 

stream-sediment samples. 

Two stream-sediment samples and 15 rock samples 

collected in the central part of the study area have anomalous mercury (0.10-0.16 ppm and 0.10-0.72 ppm, respectively). Thirty-four stream-sediment samples contain 3 to 

27 ppm arsenic, and 32 rock samples contain 3 to 250 ppm 

arsenic. Anomalous antimony was detected in two streamsediment samples (1 and 2 ppm), and two concentrate 

samples contain 500 ppm antimony; 23 rock samples contain 

1 l9 7 ppm antimony. Anomalous concentrations of antimony and lead detected in the stream-sediment and concentrate samples may represent contamination from lead shot. 

All samples collected for this investigation are 

anomalous in at least one element; 26 samples are anomalous in the combination of gold, silver, arsenic, mercury, 

antimony, and molybdenum. These elements probably best 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G17 
characterize and delineate areas for epithennal hot-spring 

gold deposits. Other low-level anomalies that may also be 

associated with epithennal hot-spring mineralization in the 

study area include barium, beryllium, boron, cadmium, 

fluorine, lead, strontium, and uranium. 

Berger and Eimon (1983) indicated that the nature 

and economics of epithennal precious-metal deposits are 

detennined by the geometry of the fracture system, penneability and composition of the host rocks, and hydrodynamics of the fluid system. In their model, barren quartz veins 

carrying anomalous concentrations of arsenic, antimony, and 

mercury can extend hundreds of feet above an ore zone. 

Anomalies found during this study may be of this type, 

although the presence of the epithennal pathfmder suite of 

elements does not necessarily indicate the presence of an 

ore body (Nelson, 1988). 

Other low-level anomalies are probably due to lithologic controls. Anomalous concentrations of cobalt, chromiwn, and vanadiwn are probably derived from mafic flows 

and intrusions and reflect normal abundances of these elements in these rock types. Ore-grade cobalt, chromium, 

and vanadium deposits are not likely in the geological environment of the study area. Anomalous concentrations of 

lanthanum, niobium, and yttrium are probably derived from 

the chemically zoned tuff of Leslie Gulch (VanderMeulen, 

1989). 

One stream-sediment sample collected from a small 

tributary drainage in the southern part of the study area 

contains 8. 7 ppm uranium. The tributary drains landslide 

deposits in sedimentary rock. Petrified wood is abundant at 

the site but was not analyzed for uranium; however, no 

scintillometer deflection occurred over samples of petrified 

wood. A high gennanium value (100 ppm) was obtained 

from a green sandstone cobble collected at the same site. 

This and other scattered anomalous gennanium and gallium 

values probably do not indicate a resource. High anomalous zinc values, with which economic quantities of these 

metals are generally associated (Weeks, 1973), were not 

detected in the study area. 

Geophysical Studies 

Aeromagnetic Survey 

A regional aeromagnetic survey was flown over the 

study area in 1972 (U.S. Geological Survey, 1972). Data 

were collected along parallel east-west flightlines spaced at 

2-mi intervals and flown at a constant barometric elevation 

of 9,000 ft above sea level. The Earth's main field was 

subtracted from the data which were then plotted and hand 

contoured at a scale of 1:250,000. Additional aeromagnetic 

data are available at a scale of 1:500,000 for the Boise 1° 

by 2° quadrangle (geoMetries, Inc., 1979) as part of a program for the U.S. Department of Energy. These data consist of east-west proflles spaced at 3-mi intervals and flown 

at an average height of 400 ft above the ground surface. 

Magnetic minerals, where locally concentrated or depleted, may cause a high or low magnetic anomaly that 

may be a guide to mineralization. Boundaries between 

magnetic and relatively less magnetic rock units are located 

approximately at the steepest gradient on the flanks of magnetic anomalies. Most anomalies in the study area are 

probably caused by the preponderance of basalt flows and 

other volcanic rocks. The flight altitude was sufficient to 

suppress most of the short-wavelength anomalies generated 

by small rock units at or near the surface. These shortwavelength anomalies can be seen on the low-level profiles 

across the study area (geoMetries, Inc., 1979). The aeromagnetic map (U.S. Geological Survey, 1972) shows that 

the study area has relatively small magnetic highs and lows 

that are probably caused by volcanic rocks concealed below 

the surficial sediments and young lava flows rather than by 

the presence of any mineral resources. 

Gravity and Gamma Ray Surveys 

A gravity survey of this area was conducted by the 

U.S. Geological Survey in 1986 and 1987 to supplement 

data already available from the National Geophysical Data 

Center, Boulder, CO 80303. Stations were about 3 to 5 mi 

apart, and about 16 stations were used for this study. West 

of approximately 117°30' W. longitude, the study area lies 

within the eastern part of a 14-mi-wide subcircular gravity 

low having a maximum amplitude of 15 to 17 milligals (fig. 

3). The east edge of this low is marked by a steep gravity 

gradient that slopes down to the west and is probably caused 

by a concealed fault striking north at about 117°30' W. longitude. The fault appears to be the southernmost end of a 

major fault zone extending at least 70 mi north of the study 

area (Lillie, 1977). The accompanying subcircular gravity 

low west of this fault, and lying outside the study area, does 

not have an easily identified source. The low extends 15 mi 

west and northwest of the study area, across the Owyhee 

River canyon. Its lowest point is near the canyon bottom 

where the thickest section of silicic welded tuff is exposed 

(Evans and others, 1990). Explanations for the gravity low 

include a small concealed granitic batholith, a concealed 

basin filled with low-density sedimentary rocks, or a concealed caldera that contains low-density sedimentary and 

volcanic rocks. The third explanation is the most likely 

because it offers a possible source for the tuff of Birch Creek 

and for thick sequences of rhyolite and welded tuff exposed 

8 mi southeast of the study area. Such a caldera might have 

associated mineralization. Another smaller gravity low approximately 6 mi in diameter lies within and east of the 

study area (fig. 3). This low is probably caused by a thick 

sequence of tuffs and sedimentary rocks that flll the western 

part of the Mahogany Mountain caldera. 

G18 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
Aerial gamma-ray spectrometer measurements are 

available along the 3-mi-spaced east-west profiles illustrated 

by geoMetries, Inc. (1979). Statistically significant anomalies for uranium were not found within the borders of the 

study area. 

Mineral and Energy Resource Potential of the 

Blue Canyon Wilderness Study Area 

Gold prospects have been located by several exploration companies that are prospecting north and east of the 

Blue Canyon Wilderness Study Area (ftg. 1) where hotspring gold mineralization is commonly associated with 

intersecting north-, northwest-, and northeast-trending fault 

zones, localized silicic volcanism, hydrothermal explosion 

breccia, caps of siliceous sinter, and syndepositional arkosic 

0 

Figure 3. Bouguer gravity anomaly map of part of the Lake 

Owyhee volcanic field, eastern Oregon. Contour interval, 

2 milligals; hachured in direction of gravity low. Cross ( +) 

indicates gravity station. Heavy lines indicate approximate 

boundaries of Blue Canyon (BC) and Owyhee Breaks (08) 

5 

sandstone and conglomerate beds. These criteria were 

used to rate the resource potential for gold in the study area. 

A lithic-rich rhyolite ash-flow tuff exposed in the 

northern part of the study area is locally altered and silicified. The tuff ranges from 5 to 80 ft thick and typically 

caps the sedimentary sequence. Samples of the silicified 

tuff collected along a north-trending fault contain anomalous concentrations of gold, silver, mercury, and molybdenum. Silicified parts of the tuff, therefore, have high 

mineral resource potential for gold, silver, mercury, and 

molybdenum, certainty level C (fig. 2). 

In the central part of the study area, samples of 

silicified and brecciated tuff collected along two northtrending fault zones contain anomalous concentrations of 

gold, mercury, molybdenum, and barium. At the Red 

Butte gold prospect to the north, a similar sample of brecciated rock collected along a north-trending fault zone 

10 MILES 

Wilderness Study Areas (shaded area). Heavy dotted lines 

indicate inferred margins of the Three Fingers (TF) and 

Mahogany Mountain (MM) calderas. Open-circle dotted 

line indicates approximate margin of a possible caldera 

based on geophysical data. 

Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon C19 
contains anomalous concentrations of gold, silver, mercury, 

arsenic, antimony, molybdenum, and barium. Therefore, 

silicified and brecciated rocks along these fault zones have 

high potential for gold, mercury, and molybdenum resources, 

certainty level C. 

Because mineral associations for epithermal hot-spring 

gold deposits have been identified in the study area, and 

because the general volcanic and sedimentary stratigraphy 

and structure can be traced into the study area from known 

gold prospects in the region, the the rest of study area has 

moderate potential for volcanic- and sediment-hosted gold 

resources, certainty level C. 

Samples of the tuff of Leslie Gulch have extraordinarily high zinc concentrations (Vander Meulen and others, 

1987a), which are associated with pumice fragments in the 

tuff. Volcanogenic disseminated zinc deposits of this type 

were previously unrecognized in the world. Areas underlain 

by this tuff unit have low potential for zinc resources, certainty level B. 

Stream-sediment and nonmagnetic panned concentrate 

samples from areas underlain by sedimentary rocks contain 

anomalous fluorine. Authigenic fluorite in lacustrine and 

tuffaceous sedimentary rocks is reported by Sheppard and 

Gude (1969) 25 mi south of the study area near Rome, Oreg. 

Similar deposits of diagenetic fluorite may occur in the study 

area; therefore, sedimentary rocks within the study area have 

low potential for fluorite resources, certainty level B. 

In the northern part of the study area, beds of bentonite and diatomite are intercalated with a thick sequence of 

lacustrine sedimentary rocks. The bentonite units typically 

form low subdued hills and have estimated maximum thicknesses of 50 ft. Two swelling clay minerals, smectite and 

illite, were identified. Diatomite beds are exposed primarily 

in the northern and northwestern parts of the study area. 

The beds are typically 2 to 4 in. thick but are locally as thick 

as 5 ft. The thicker beds are very clean and possibly of 

industrial quality. Northern and western parts of the study 

area underlain by the sedimentary rocks have moderate potential for bentonite and diatomite resources, certainty level C. 

In the adjoining Owyhee Breaks Wilderness Study 

Area, a thermal spring issues from a north-trending fault 

zone (fig. 2). Another thermal spring issues from a northtrending, high-angle normal fault about 2.5 mi east of the 

Blue Canyon Wilderness Study Area on the south edge of 

Lake Owyhee. Recorded temperature of this spring water 

is 50 oc (Bliss, 1983). Several thermal springs and wells 

are about 27 mi northeast of the study area (Oregon Department of Geology and Mineral Industries, 1982). An area 

less than 20 mi northeast of the study area may be underlain at shallow depth (less than 3,280 ft) by thermal water 

of sufficient temperature for direct-heat applications (Oregon Department of Geology and Mineral Industries, 1982). 

Although no thermal springs were identified in the study 

area, geothermal waters may exist at depth along northtrending fault zones. Areas adjacent to these fault zones 

have moderate potential for geothermal energy resources, 

certainty level C. 

Sedimentary rocks in the northern part of the study 

area could serve as source rocks for oil and gas resources. 

An estimated 650-ft-thick sequence of fmely laminated carbonaceous claystone and siltstone contains intercalated lenticular horizons of carbonaceous material and organic-rich 

detritus. The sedimentary rocks directly north of the study 

area are folded to form several anticlines (fig. 2). These 

north- to northeast-trending, south-plunging anticlines could 

be excellent traps for oil and gas reservoirs. No geologic 

evidence suggests that these sedimentary rocks and trap 

structures are of greater extent at depth. A drilling program 

in conjunction with seismic studies is needed to test the 

rocks for their oil and gas potential. Sedimentary rocks in 

the northwestern part of the study area have low potential 

for oil and gas energy resources, certainty level B. 

Mineral and Energy Resource Potential of the 

Owyhee Breaks Wilderness Study Area 

Gold prospects have been located by several exploration companies that are prospecting north and east of the 

Owyhee Breaks Wilderness Study Area (fig. 1) where hotspring gold mineralization is commonly associated with 

intersecting north-, northwest-, and northeast-trending fault 

zones, localized silicic volcanism, hydrothermal explosion 

breccia, caps of siliceous sinter, and syndepositional arkosic 

sandstone and conglomerate beds. These criteria were used 

to rate the resource potential for gold in the study area. 

In the central part of the study area, samples of silicified tuff, conglomerate, and black chert (siliceous sinter) 

contain anomalous concentrations of gold. These altered 

and mineralized rocks are exposed along north- and northwest-trending fault zones. The altered rocks and faults are 

similar to those exposed at the Red Butte gold prospect to 

the north; therefore, this area and a similar one just outside 

the east border have high mineral resource potential for 

gold in fault-controlled volcanic- and sediment-hosted hotspring gold deposits, certainty level C. 

Because mineral associations for epithermal hot-spring 

gold deposits have been identified in the study area, and 

because the general volcanic and sedimentary stratigraphy 

and structure can be traced into the study area from known 

gold prospects in the region, the entire study has moderate 

potential for volcanic- and sediment-hosted gold resources, 

certainty level C. 

Samples of the tuff of Leslie Gulch have extraordinarily high zinc concentrations (Vander Meulen and others, 

1987a), which are associated with pumice fragments in the 

tuff. Volcanogenic disseminated zinc deposits of this type 

were previously unrecognized in the world. Areas underlain by this tuff unit have low potential for zinc resources, 

certainty level B. 

G20 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
Stream-sediment and nonmagnetic panned-concentrate 

samples from areas underlain by sedimentary rocks contain 

anomalous fluorine. Authigenic fluorite in lacustrine and 

tuffaceous sedimentary rocks is reported by Sheppard and 

Gude (1969) 25 mi south of the study area near Rome, Oreg. 

Similar deposits of diagenetic fluorite may occur in the study 

area; therefore, sedimentary rocks within the study area have 

low potential for fluorite resources, certainty level B. 

In the northern part of the study area, beds of bentonite and diatomite are intercalated with a thick sequence 

of lacustrine sedimentary rocks. Locally, bentonitic clay 

beds form low subdued hills and the underlying slip surfaces for large landslide deposits. A sample of bentonitic 

clay collected near the north boundary of the study area 

contains 80 to 95 percent smectite, a clay mineral that has 

swelling properties. Thin beds of diatomaceous earth are 

also exposed in the northern and northwestern parts of the 

study area. Therefore, parts of the study area underlain by 

the sedimentary rocks have moderate potential for bentonite 

and diatomite resources, certainty level C. 

In the central part of the study area along the Owyhee 

River, a thermal spring issues from a north-trending fault 

zone (fig, 2). Another thermal spring issues from a northtrending, high-angle normal fault approximately 6.5 mi 

northeast of the study area on the south side of Lake Owyhee. 

Recorded temperature of this spring water is 50 °C (Bliss, 

1983). Several thermal springs and wells are about 30 mi 

northeast of the siudy area (Oregon Department of Geology 

and Mineral Industries, 1982). An area less than 24 mi 

northeast of the study area may be underlain at shallow 

depth (less than 3,280 ft) by thermal water of sufficient 

temperature for direct-heat applications (Oregon Department 

of Geology and Mineral Industries, 1982). In the study 

area, geothermal waters issue from one north-trending fault 

zone and may exist at depth along similar fault zones. Areas adjacent to these fault zones have moderate potential 

for geothermal resources, certainty level C. 

In the northern part of the study area, a 1 ,000-ft-thick 

sequence of lacustrine and fluvial sedimentary rocks overlies two ash-flow tuff units. These middle to upper Miocene sedimentary rocks could serve as source rocks for oil 

and gas resources. However, no current geologic evidence 

suggests that these rocks are of greater extent at depth or 

that they have trapped any oil and gas. A drilling program 

in conjunction with seismic studies is needed to test the 

sedimentary rocks for their oil and gas potential. Sedimentary rocks in the northern part of the study area have low 

potential for oil and gas resources, certainty level B. 

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Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study Areas, Malheur County, Oregon G23 

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. 

l ...J 

< i= 

z 

w 

0 

Cl.. 

w 

u 

c.:: 

:) 

0 

V') 

w 

c.:: 

u.. 

0 

...J 

w 

> w 

...J 

A 

U/A 

UNKNOWN POTENTIAL 

Abstracted with minor modifications from: 

B c 

. H/B H/C 

HIGH POTENTIAL HIGH POTENTIAL 

M/B .M/C 

MODERATE POTENTIAL MODERATE POTENTIAL 

L)B L)C 

LOW POTENTIAL LOW POTENTIAL 

LEVEL OF CERTAINTY 

D 

H/D 

HIGH POTENTIAL 

MID 

MODERATE POTENTIAL 

L)D 

LOW POTENTIAL 

N/D 

NO POTENTIAL 

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

Taylor, R. 8., 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. 

26 Mineral Resources of Wilderness Study Areas: East-Central Oregon 
RESOURCE/RESERVE CLASSIFICATION 

IDENTIFIED RESOURCES UNDISCOVERED RESOURCES 

Demonstrated Probabi I ity Range 

Inferred 

Measured Indicated Hypo~hetical Speculative 

I Inferred I 

ECONOMIC Reserves Reserves 

I I ----~---- r---------- - -~-

MARGINALLY Marginal Inferred 

Marginal ECONOMIC Reserves Reserves 

I 1----------- I 

----,---- -~-

SUB- Demonstrated Inferred 

Subeconomic Subeconomic 

ECONOMIC Resources Resources I I I 

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

resource estimates and pub I ic 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 Blue Canyon and Owyhee Breaks Wilderness Study Areas, Oregon 27 
GEOLOGIC TIME CHART 

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

EON ERA PERIOD EPOCH 

Quaternary 

Holocene 

Pleistocene 

Neogene Pliocene 

Cenozoic Subperiod Miocene 

Tertiary Paleogene Oligocene 

Subperiod Eocene 

Paleocene 

Cretaceous Late 

Early 

Late 

Mesozoic jurassic Middle 

Early 

Late 

Triassic Middle 

Early 

Permian Late 

Phanerozoic Early 

Late 

Pennsylvanian Middle 

Carboniferous Early Periods 

Mississippian Late 

Early 

Late 

Devonian Middle 

Paleozoic Early 

Late 

Silurian Middle 

• Early 

Late 

Ordovician Middle 

Early 

Late 

Cambrian Middle 

Early 

Late Proterozoic 

Proterozoic Middle Proterozoic 

Early Proterozoic 

Late Archean 

Archean Middle Archean 

Early Archean 

--------------- - - - - - - - - - - - - - - - - - - - - - - - - - - (38001}- - - - - - - - - - - - - - - - - - -

pre-Archean2 

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

21nformal time term without specific rank. 

28 ~ineral Resources of Wilderness Study Areas: East-Central Oregon 

AGE ESTIMATES OF 

BOUNDARIES IN 

Ml LLION YEARS (Ma) 

0.010 

1.7 

5 

24 

38 

55 

66 

- 96 

138 

205 

-240 

290 

-330 

360 

410 

435 

500 

1

-570 

900 

1600 

2500 

3000 

3400 

4550 
Mineral Resources of 

Wilderness Study Areas: 

East-Central Oregon 

This volume was published as separate chapters A-G 

U.S. GEOLOGICAL SURVEY BULLETIN 1741 
U.S. 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 Honeycombs Wilderness Study Area, Malheur County, 

Oregon, by Dean B. VanderMeulen, J.J. Rytuba, H.D. King, D. Plouff, and 

Douglas F. Scott. 

(B) Mineral Resources of the Sheep Mountain Wilderness Study Area, Baker 

County, Oregon, by Roger P. Ashley, Robert C. Roback, Robert L. Turner, 

Robert C. Jachens, Terry J. Close, and Richard L. Rains. 

(C) Mineral Resources of the Camp Creek and Cottonwood Creek Wilderness Study 

Areas, Malheur County, Oregon, by William J. Keith, Robert L. Turner, 

Andrew Griscom, John R. Benham, and Michael S. Miller. 

(D) Mineral Resources of the Upper Leslie Gulch and Slocum Creek Wilderness 

Study Areas, Malheur County, Oregon, by Dean B. VanderMeulen, Andrew 

Griscom, Harley D. King, and John R. Benham. 

(E) Mineral Resources of the Gold Creek and Sperry Creek Wilderness Study 

Areas, Malheur County, Oregon, by James G. Evans, James G. Frisken, Andrew 

Griscom, Don L. Sawatzky, and Michael S. Miller. 

(F) Mineral Resources of the Lower Owyhee Canyon Wilderness Study Area, 

Malheur County, Oregon, by James G. Evans, Robert L. Turner, Andrew 

Griscom, Don L. Sawatzky, and J. Douglas Causey. 

(G) Mineral Resources of the Blue Canyon and Owyhee Breaks Wilderness Study 

Areas, Malheur County, Oregon, by Dean B. VanderMeulen, Vincent E. 

Barlock, Patrick S. Plumley, James G. Frisken, Andrew Griscom, and J. 

Douglas Causey. 
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