Mineral Resources of the

Malheur River-Bluebucket 

N

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Chapter H

Mineral Resources of the 

Malheur River-Bluebucket Creek 

Wilderness Study Area, 

Harney County, Oregon

By MICHAEL G. SAWLAN, ROBERT L TURNER, and 

ROBERT C.JACHENS 

U.S. Geological Survey

THOMAS J. PETERS and RICHARD A. WINTERS 

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 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, 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 : 1995

For sale by

U.S. Geological Survey, Map Distribution 

Box 25286, MS 306, Federal Center 

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Mineral resources of the Malheur River-Bluebucket Creek Wilderness Study Area, 

Harney County, Oregon / by Michael G. Sawlan ... [et al.].

p. cm. (U.S. Geological Survey bulletin; 1741-H) 

(Mineral resources of wilderness study areas east-central Oregon ; ch. H)

Includes bibliographical references.

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

1. Mines and mineral resources Oregon Malheur River-Bluebucket Creek 

Wilderness. 2. Malheur River-Bluebucket Creek Wilderness (Or.) I. Sawlan, 

Michael G. II. Series. III. Series: Mineral resources of wilderness study areas 

east-central Oregon; ch. H. 

QE75.B9 no. 1741-H 

[TN24.07] 

557.3 s dc20

[553'.09795'95] 94-15503

CIP
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) 

requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys 

on certain areas to determine the mineral values, if any, that may be present. Results must be 

made available to the public and be submitted to the President and the Congress. This report 

presents the results of a mineral survey of the Malheur River-Bluebucket Creek Wilderness 

Study Area (OR-002-014), Harvey County, Oregon.

CONTENTS

Summary HI 

Abstract HI 

Location and setting HI 

Identified resources HI 

Mineral resource potential H2 

Introduction H4

Location, access, and character H4 

Previous investigations H4 

Present investigations H4 

Acknowledgments H5 

Appraisal of identified resources H5 

Mining activity H5 

Diatomaceous sediment H5 

Basalt H6 

Placer samples H6

Identified resources and recommendations H6 

Assessment of mineral resource potential H6 

Geology H6

Stratigraphy H6

Structure H8 

Geochemistry H8

Introduction H8

Samples H8

Analytical methods H8

Results and interpretations H9 

Geophysics H9

Introduction H9

Gravity data H9

Aeromagnetic data H9

Radiometric data H10

Summary H10

Mineral resource potential H10 

References cited H10 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment H14 

Resource/reserve classification HIS 

Geologic time chart H16

FIGURES

1. Location of the Malheur River-Bluebucket Creek Wilderness Study Area, Haraey 

County, Oregon H2

2. Generalized geology and mineral resource potential of the Malheur RiverBluebucket Creek Wilderness Study Area, Harney County, Oregon H3

Contents

Mineral Resources of the Malheur River-Bluebucket 

Creek Wilderness Study Area, Harney County, Oregon

By Michael G. Sawlan, Robert L. Turner, and Robert C. Jachens 

U.S. Geological Survey

Thomas J. Peters and Richard A. Winters 

U.S. Bureau of Mines

SUMMARY 

Abstract

The Malheur River-Bluebucket Creek Wilderness Study 

Area (OR-002-014) is located about 40 mi northeast of the 

city of Burns in central Oregon (fig. 1). At the request of the 

U.S. Bureau of Land Management 5,560 acres of the Malheur River-Bluebucket Creek Wilderness Study Area were 

evaluated for mineral resources (known) and mineral resource potential (undiscovered). In this report, the area studied is referred to as the "Malheur River-Bluebucket Creek 

Wilderness Study Area" or the "study area."

The study area is underlain by flat-lying to gently dipping 

Neogene andesite, basalt, and tuffaceous sedimentary rocks, 

and Quaternary surficial deposits. No mineral resources are 

identified in the study area, nor are there any active mining 

claims or mineral leases. The northern part of the study area 

has low potential for gold and silver (fig. 2); gold was detected 

in one stream-sediment sample and low levels of metals associated with epithermal precious-metal deposits were found in 

nearby samples. The study area has low potential for oil and 

gas. There are no indications of oil and gas in the surface 

geology, however; if these resources are present in the study 

area, they would likely be buried by several thousand feet of 

volcanic rocks. The study area has no potential for geothermal 

resources. No young volcanic centers or active thermal springs 

are present in or near the study area. The southwestern part of 

the study area has low potential for diatomite.

Location and Setting

The Malheur River-Bluebucket Creek Wilderness 

Study Area (OR-002-014) is located in northern Harney

Manuscript approved for publication April 1,1994.

County, Oreg., about 35 mi northeast of Burns, Oreg. (fig. 

1). The study area comprises 5,560 acres of land administered by the U.S. Bureau of Land Management. Part of the 

north boundary of the study area adjoins the Malheur National Forest. The study area lies about 18 mi east of U.S. 

Highway 395, and about 15 mi north of U.S. Highway 20. 

Paved county roads and improved gravel roads provide access from the main highways to the study area.

The southern part of the study area consists of sparsely vegetated mesas 300 to 450 ft above the northwesttrending valley along Wolf Creek and the Malheur River 

to the south. The northern part of the study area includes 

forested highlands incised by steep, nigged canyons along 

the Malheur River and Bluebucket Creek.

The study area is underlain largely by flat-lying to 

gently dipping, Neogene (see "Appendixes" for geologic 

time chart) volcanic rocks and volcanogenic sedimentary 

rocks. Middle to late Miocene andesite lavas underlie the 

northern part of the study area. In the southern part of the 

study area, the andesite is completely buried beneath tuffaceous sedimentary rocks and interlayered basalt which, 

in turn, are overlain by mesa-forming basalt.

Identified Resources

No mineral resources were identified in the study 

area; there are no active mining claims or mineral leases. 

Diatomaceous sediment that is present west of the study 

area may extend into the study area beneath the basalt 

mesas of Battle Mountain. The diatomaceous sediment is 

too impure to be considered a diatomite resource. Basalt is 

abundant and could be used for construction material; 

however, it is abundant throughout the region in areas 

closer to potential markets. There are no oil and gas or 

geothermal leases or applications. No geothermal or mineral energy resources were identified.

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H1
Mineral Resource Potential

The northern part of the study area has low potential 

for gold and silver (fig. 2). One stream-sediment sample 

contains an anomalous amount of gold. Other samples

119° 00'

^ Figure 2. Generalized geology and mineral resource potential of Malheur River-Bluebucket Creek Wilderness Study 

Area, Harney County, Oregon. Geology modified from 

Greene and others (1972) for areas south of 44° N. and from 

Brown and Thayer (1966) for areas north of 44° N.

118° 30'

44° 00'

77~\

MALHEUR 

../^

GRANT CO _ |

"BARNEY co !

/> ?

I H 

I ffi

I W 

I &

' O

I b

7 > ' J ' I I ' I

-- -4i- J

/

\

- - -\-AT- \ '

Antelope 

\ Mountain 

\

CreekL? 1 v

Otis Mountain N

A

APPROXIMATE 

BOUNDARY

OF

MALHEUR RIVERBLUEBUCKET CREEK 

WILDERNESS 

STUDY AREA 

(OR-002-014)

"1

43° 45'

Pine Creek U Red Butte/Pine Creek 

Roadless Area '( prospect (gold)

I/

0

10 MILES 

I

AREA OF MAP

Figure 1. Index map showing location of Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon. 

Unlabeled solid lines are secondary paved roads. Unlabeled dashed lines are gravel roads or jeep trails.

H2 Mineral Resources of Wilderness Study Areas: East-Central Oregon
n 8° arso44° 00'

43° 52' 30'

L/B O,G

(entire study area)

APPROXIMATE BOUNDARY

OF

MALHEUR RIVERBLUEBUCKET CREEK 

WILDERNESS STUDY AREA 

(OR-002-014)

Tsb

Tsb

MILES

EXPLANATION

B

Area having low mineral 

resource potential

Certainty level of assessmentData only suggest level of 

potential

Commodities 

Au Gold 

Ag Silver 

O, G Oil and gas 

diat Diatomite

Map units

Qa Alluvium (Quaternary) 

Qg Gravel deposits (Quaternary) 

Tb Basalt (late Miocene and (or) Pliocene) 

Twt Welded tuff (late Miocene)

Tbl Lower basalt (middle and (or) late 

Miocene)

Tsb Tuffaceous sedimentary rocks

and basalt (middle and (or) late 

Miocene)

Ta Andesite (early and middle Miocene)

Contact

Fault Bar and ball on downthrown block

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H3
showing low levels of metals associated with preciousmetal deposits were found nearby. The southwestern part 

of the study area has low potential for diatomite. The entire study area is considered to have low potential for oil 

and gas but there are no indications in the surface geology 

to indicate the presence of either hydrocarbon source rocks 

or structural traps. There is no potential for geothermal energy resources in the study area.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau of Land Management (BLM) and is the result of a 

cooperative effort by the U.S. Geological Survey (USGS) 

and the U.S. Bureau of Mines (USBM). An introduction to 

the wilderness review process, mineral survey methods, 

and agency responsibilities was provided by Beikman and 

others (1983). The USBM evaluates identified resources at 

individual mines and known mineralized areas by collecting data on current and past mining activities and through 

field examination of mines, prospects, claims, and mineralized areas. Identified resources are classified according 

to the system modified from that described by McKelvey 

(1972) and the U.S. Bureau of Mines and U.S. Geological 

Survey (1980). Studies by the USGS are designed to provide a reasonable scientific basis for assessing the potential for undiscovered mineral resources by determining 

geologic units and structures, possible environments of 

mineral deposition, presence of geochemical and geophysical anomalies, and applicable ore-deposit models. Goudarzi (1984) discussed mineral assessment methodology 

and terminology as they apply to these surveys. See "Appendixes" for the definition of levels of mineral resource 

potential and certainty of assessment and for the resource/reserve classification.

Location, Access, and Character

The study area lies in northern Harney County in eastcentral Oregon (fig. 1). The nearest city is Burns, Oreg., 

about 35 mi southwest of the study area; the small community of Drewsey is about 11 mi to the southeast. The U.S. 

Forest Service maintains a guard station during the summer 

months at Van, about 6 mi west of the study area.

The principal access to the study area is along the 

graded and, in part, paved road between Seneca, along 

U.S. Highway 395, and Drewsey, 2 mi north of U.S. Highway 20. Along this road, the study area is about 35 mi 

from U.S. Highway 395, and about 20 mi from U.S. Highway 20 via Drewsey. A gravel road leads up to and follows the east boundary of the study area to Bluebucket 

Creek and a jeep trail is located about a mile west of the 

study area.

Relief in the area is about 1,100 ft; elevations range 

from about 4,000 ft along the Malheur River to about 

5,100 ft on the ridge west of the Malheur River in the 

northern part of the study area. The southern part of the 

study area comprises sparsely vegetated mesas 300 to 

450ft above the northwest-trending valley along Wolf 

Creek and the Malheur River to the south and southwest. 

The northern part of the study area includes forested highlands that are incised by rugged canyons along the Malheur River and Bluebucket Creek.

The study area is underlain chiefly by flat-lying to 

gently dipping Neogene volcanic rocks and volcanogenic 

sedimentary rocks (fig. 2). The northern part of the study 

area is underlain largely by andesite. Tuffaceous sedimentary rocks and interbedded basalt, locally covered by 

mesa-forming basalt, overlie the andesite from the central 

part of the study area to the south. Small areas adjacent to 

the study area are underlain by late Miocene ash-flow tuff.

Previous Investigations

The Malheur River-Bluebucket Creek Wilderness 

Study Area is included in regional reconnaissance and 

compilation geologic maps by Greene and others (1972) 

and Walker (1977). Topical studies on the widespread ashflow tuffs in this part of Oregon were undertaken by 

Greene (1973) and Walker (1979); geologic studies pertaining to the ash-flow tuffs were also done by Walker and 

Swanson (1968). The geology of the Canyon City 1° by 2° 

quadrangle, north of the study area, was mapped by 

Brown and Thayer (1966). Walker and Denton (1982) reported the results of a mineral resource appraisal of the 

Pine Creek Roadless Area, located about 10 mi south of 

the Malheur River-Bluebucket Creek Wilderness Study 

Area in the Malheur National Forest (fig. 1).

The study area is included in regional surveys aimed 

at assessing potential for uranium resources (High Life 

Helicopters, IncVQEB, Inc., 1981), oil and gas (Fouch, 

1982, 1983), and geothermal resources (Riccio, 1978).

Present Investigations

The USGS conducted field investigations in the study 

area in 1986. These consisted of geologic mapping at a 

scale of 1:24,000, field checking of existing maps, 

geochemical sampling, and examining outcrops for evidence of mineralization. Thirty-one rock samples, mostly 

from outcrop, seven stream-sediment samples, and seven 

nonmagnetic heavy-mineral-concentrate samples panned 

from stream sediment were analyzed to reveal areas having anomalous concentrations of elements of interest. All 

an-alyses were performed at USGS laboratories in Denver, 

Colo., and were reported by Erickson and others (1989).

H4 Mineral Resources of Wilderness Study Areas: East-Central Oregon
The investigation by the USBM included prefield library research and examinations of BLM and Harney 

County mining records. In July 1986, ground searches 

were made for any indication of possible mineral resources such as prospect workings, mineralized structures, alteration zones, or rock types having potential value as 

industrial minerals. Six rock samples and six alluvial samples were taken. All samples were checked for radioactivity and fluorescence. Rock samples were prepared for 

analysis at the USBM Western Field Operations Center, 

Spokane, Wash., and analyses were done by a contract 

laboratory. Alluvial samples were concentrated on a laboratory-size Wilfley table to extract possible free gold and 

other heavy minerals. Results of the USBM study were 

reported by Peters and Winters (1987).

Acknowledgments

TJ. Peters and R.J. Winters thank Roger Britton and 

Mark Hosket, BLM, Burns, Oreg., and Victor Bartkus, 

BLM, Portland, Oreg., for helpful advice on logistics and 

land status. Andrew E. Visocan, Mine and Mill Manager, 

Eagle-Picher Industries, Vale, Oreg., provided tours for 

USGS and USBM personnel of the Celatom diatomite 

mine, east of the study area, and helpful insight into diatomite resources of the region. M.G. Sawlan thanks the U.S. 

Forest Service, Burns, Oreg., for providing lodging and 

use of facilities at the Van Guard Station.

APPRAISAL OF IDENTIFIED RESOURCES

By Thomas J. Peters and Richard A. Winters 

U.S. Bureau of Mines

Mining Activity

There are no active mines, prospects, patented mining 

claims, or mineral leases in the Malheur River-Bluebucket 

Creek Wilderness Study Area. There is no record of mineral production from within the study area, and there are 

no oil and gas or geothermal leases or lease applications.

Harney County records indicate the Riley claim was 

located by George V. Riley in April 1940, 0.5 mi south of 

Sage Hen Flat in T. 18 S., R. 34 E., which includes the 

north half of the study area (fig. 2). The courthouse 

records, available maps, and a subsequent ground search 

did not disclose specific locations for Sage Hen Flat or the 

mining claim. Courthouse records indicate several scattered placer and lode claims and small claim groups for 

precious metals in the headwaters of the Malheur River 

drainage basin north of the study area.

The recently active Red Butte/Pine Creek gold prospect is located in the northern Stinking Water Mountains

south of the Malheur River, 5 to 7 mi south of the study 

area (fig. 1). Permits for exploration drilling in this area 

were issued to Battle Mountain Exploration Company in 

1990 (Wiley, 1991). Alteration occurs in and adjacent to a 

rhyolite mass shown on Greene's (1972) map as unit Trd 

("rhyodacite"). A sample of silicified rhyolite breccia from 

this unit contained anomalous amounts of gold (71 ppb) 

and molybdenum (70 ppm). The rhyolite and associated 

alteration do not extend into the study area.

About $50,000 in gold, equivalent to about 2,400 

ounces of gold (using a gold value of $20.67 per ounce for 

the late 1880's to 1934), was produced around the turn of 

the century from the Harney (Idol City-Trout Creek) Mining District about 18 mi southwest of the study area (fig. 1). 

Most production was from placer deposits although some 

lode gold apparently was also mined from andesite along a 

northwest-trending shear zone (Brooks and Ramp, 1968; 

Walker and Denton, 1982). In 1981, Noranda Exploration, 

Inc., explored for lode gold in the district (Denton, 1982, 

p. 6), and placer deposits in young valley fill were also 

being worked by seven claimants (Denton, 1981, p. 8). In 

1989, Newmont Exploration, Ltd., did exploration drilling 

for lode gold in the district (Wiley, 1991).

Eagle-Picher Industries' Celatom diatomite mine, 

Drewsey, Oreg., is 15 mi southeast of the study area 

and is the only operating mine nearby. Miocene lake 

deposits stratigraphically equivalent to those at the Celatom diatomite mine are found in the study area.

Small borrow pits in gravel deposits between Wolf 

Creek and the Malheur River (fig. 2) have probably been 

used in construction by local ranchers. There is no record 

of commercial production and the gravel deposits do not 

extend into the study area.

Diatomaceous Sediment

No diatomite or diatomaceous sediment was observed 

in the study area, but an occurrence of diatomaceous sediment as thick as 365 ft is found directly west of the study 

area, and it probably extends under part of the study area 

near Battle Mountain. The sediment is generally tan to 

cream colored and ash and silt laden. Between 10 and 20 

percent of the sediment is relatively pure white diatomite, 

which formed as 1- to 2-ft-thick beds. The diatomaceous 

sediment is covered by a 165-ft-thick basalt cap that forms 

Battle Mountain (fig. 2).

Diatomaceous sediment west of the study area is too 

impure to be considered a diatomite resource. The thin 

beds of relatively pure diatomite, which make up less 

than 20 percent of the sedimentary pile, can not be separated economically, and the cost of underground mining 

or the removal of the overlying basalt would be prohibitive. Economic exploitation of the diatomaceous sediment 

is unlikely.

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H5
Basalt Stratigraphy

Basalt and andesite are abundant in the study area. 

Five of the six rock samples taken by the USBM in the 

study area were of mafic volcanic flows; analytical results 

are presented in Peters and Winters (1987). The basalt is 

too low in alumina to be a future source of aluminum 

(Avent, 1970). It could possibly be used for products such 

as basalt fiber (Wullenwaber and Dailey, 1975), road metal, or stone products but it is not classified as a resource 

(U.S. Bureau of Mines and U.S. Geological Survey, 1980; 

see "Appendixes"), because there is no commercial demand for basalt fiber, convenient sources of road metal are 

abundant in the region, and markets for stone are remote.

Placer Samples

Six alluvial placer samples were taken but none contained free gold.

Identified Resources and Recommendations

There are no identified resources (U.S. Bureau of 

Mines and U.S. Geological Survey, 1980) in the Malheur 

River-Bluebucket Creek Wilderness Study Area. No further work is recommended.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Michael G. Sawlan, Robert L. Turner, and 

Robert C. Jachens 

U.S. Geological Survey

Geology

The Malheur River-Bluebucket Creek Wilderness 

Study Area is underlain by flat-lying to gently east-dipping 

middle and late Miocene volcanic and sedimentary rocks 

(fig. 2), which are correlative with regionally extensive 

stratigraphic units. Early and middle Miocene andesite underlies the northern part of the study area. The andesite is 

overlain by fine-grained tuffaceous sedimentary rocks that 

are locally intercalated with basalt. These sedimentary 

rocks were deposited in a narrow northwest-trending 

basin, roughly 7 to 10 mi wide, extending from several 

miles northwest of Van to southeast of Drewsey (fig. 1). 

The interbedded sedimentary rocks and basalt unit is 

capped by basalt that forms northwest-trending elongate 

mesas. The Devine Canyon Ash-Flow Tuff is found locally 

in and near the study area.

The oldest rocks exposed in the study area are andesitic lavas (unit Ta, fig. 2), that underlie the northern part of 

the study area along Malheur River and Bluebucket Creek. 

The stack of andesite and basaltic andesite lavas along the 

Malheur River is at least 800 ft thick, and may be as much 

as 3,000 ft thick judging from the thickness of correlative 

volcanic sections in and around Harney Basin (Walker and 

Denton, 1982). The andesitic lavas are mostly sparsely 

porphyritic basaltic andesite containing phenocrysts of olivine±plagioclase±clinopyroxene and abundantly porphyritic andesite containing mostly plagioclase phenocrysts. 

These rocks dip gently, less than about 5° to the north, and 

are part of a regionally extensive andesite unit named the 

Strawberry Volcanics (Brown and Thayer, 1966). Although 

this unit consists of lavas in the northern part of the study 

area, are lavas, it is largely composed of andesite tuff 

breccia formed from volcanic debris flows southwest of 

the study area. The age of andesite in the study area is not 

known precisely but is probably early and middle Miocene 

on the basis of potassium-argon (K-Ar) ages ranging from 

about 19 to 12 million years (Ma) on correlative andesite 

within the surrounding region (Greene and others, 1972; 

Walker and Denton, 1982) (see "Appendixes" for geologic 

time scale).

Tuffaceous sedimentary rocks with local intercalated 

basalt underlie the southern part of the study area (unit 

Tsb, fig. 2). The tuffaceous rocks are mostly poorly bedded, weakly lithified, and friable siltstone and fine-grained 

sandstone. The siltstone is locally diatomaceous, and thin, 

relatively pure diatomite interbeds are found in the area 

between Battle Mountain and Coyote Creek (fig. 2). These 

poorly lithified rocks are easily eroded, characteristically 

form recessive slopes, and are poorly exposed. Attitudes 

of these strata are best seen in the basalt layers which, in 

the area south of Moffit Table, dip 5 to 10° northeast. The 

age of this unit is probably between 12 and 9 Ma (late 

middle Miocene and (or) early late Miocene) given the 

age of the underlying andesite is 19 to 12 Ma (Greene and 

others, 1972; Walker and Denton, 1982), and that the age 

of the Devine Canyon Ash-Flow Tuff which overlies these 

rocks is about 9 Ma (Walker, 1979; Greene and others, 

1972).

North of Battle Mountain, basalt horizons appear to 

be absent from the tuffaceous sediment and basalt unit. 

Basalt is intercalated with sedimentary rocks mostly south, 

southeast, and southwest of the study area and consists of 

lava flows, 10 to 20 ft thick, that form thin lenses that can 

be traced laterally for about a mile or less. A sequence of 

four to five flows, each separated by sedimentary interbeds, is present southwest of Moffit Table. These flows are 

characteristically vesicular, strongly weathered, and are 

aphyric or sparsely porphyritic with olivine phenocrysts. 

Locally, these flows have pahoehoe (ropey) surface texH6 Mineral Resources of Wilderness Study Areas: East-Central Oregon
tures. Basalt of this unit was mapped separately in the area 

southwest of Battle Mountain along Coyote Creek (unit 

Tbl, fig. 2), where dissected remnants of basalt vents comprising agglutinated lava, cinders, and feeder dikes are 

found. Basalt from the vent area west of Coyote Creek is 

distinctive in that it contains abundant large phenocrysts of 

olivine and plagioclase. Palagonite tuff is present locally.

These sediments and lavas were deposited in a northwest-trending basin extending from near Van to at least 20 

mi southeast (fig. 1). The tuffaceous sedimentary rocks 

and basalt unit is at least 1,000 ft thick in the area southwest of Battle Mountain but pinches out against andesite 

beneath Moffit Table and north of Battle Mountain. These 

deposits apparently lap onto the andesite in erosional unconformity but no outcrops were found that explicitly 

show this relation. Gravity data (see "Geophysics" section) suggest that the northeast to southwest increase in 

thickness of the tuffaceous sedimentary rocks is gradual 

across the basin's northeast margin, which trends northwest across the center of the study area. That is, there appear to be no significant bounding faults that controlled 

basin formation. The basin in the vicinity of the study area 

most likely represents an erosional landform or a homoclinal downwarp of the andesitic basement, dipping about 

10° southwest.

Welded ash-flow tuff underlies areas northeast and 

east of the study area, and small areas southwest of the 

study area at the confluence of Wolf Creek and the Malheur River (unit Twt, fig. 2). Two tuff units are represented: the Devine Canyon Ash-Flow Tuff, which erupted at 

about 9.2 Ma, and the Rattlesnake Ash-Flow Tuff, which 

erupted at about 6.5 Ma (Walker, 1979; Greene and others, 

1972). The younger Rattlesnake Ash-Flow Tuff crops out 

at elevations about 400 ft higher than the Devine Canyon 

Ash-Flow tuff. The Devine Canyon Ash-Flow Tuff underlies small areas at elevations around 4,500 ft in and adjacent to the central part of the study area north of Battle 

Mountain, and to the east along Bluebucket Creek. This 

tuff is crystal-rich and contains 25 to 30 percent crystals 

and crystal fragments mostly of alkali feldspar (sanidine 

and anorthoclase(?)) and minor amounts of quartz. Welded 

tuff, tentatively correlated with the Rattlesnake Ash-Flow 

Tuff, crops out in small areas northeast of the study area, 

about 1 mi north of Bluebucket Creek and 1 mi east of the 

Malheur River, at elevations around 4,900 ft. This tuff is 

generally thin (3-6 m thick) and crystal poor; it contains 

less than 2 percent phenocrysts mostly of alkalic feldspar, 

quartz, clinopyroxene (pale green in thin section) and rare 

grains of oxidized biotite(?). Both tuffs are regionally extensive and thicken southwest toward Harney Basin where 

the tuffs erupted from a caldera that is now buried by 

younger sediments (Walker, 1979).

A thin sequence of fluvial sandstone and pebble conglomerate caps the tuffaceous sedimentary rocks and directly underlies mesa-forming basalt. Owing to generally

poor exposure and thinness, these deposits are included in 

the tuffaceous sedimentary rocks and basalt unit in mapping but are probably penecontemporaneous with the overlying mesa-forming basalt. These fluvial deposits, about 

15 to 40 ft thick, show numerous sedimentary structures 

including channels, scour and fill structures, crossbedding, 

and soft-sediment load structures. These rocks contain 

abundant vesicular basalt detritus most likely derived from 

pyroclastic material associated with eruptions that produced the mesa-forming basalt.

Basalt lavas cap mesas in a northwest-trending belt 

across the southern part of the study area (unit Tb, fig 2). 

Moffit Table and Battle Mountain are two prominent 

mesas that are mostly included in the southern parts of the 

study area and stratigraphically equivalent basalt overlies 

andesite and ash-flow tuff north and northeast of the study 

area. Mesa-forming basalt in the region has been mapped 

as the Drinkwater Basalt (Greene and others, 1972), which 

was named by Bowen and others (in Shotwell, 1963, p. 

31-32). Greene and others (1972) reported a K-Ar age of 

6.91+1.09 Ma on Drinkwater Basalt from 40 mi south of 

the study area. The mesa-forming basalt in the study area 

is, therefore, probably late Miocene and (or) Pliocene in 

age; these basalts have not been dated in or near the study 

area. The mesa-forming basalts typically comprise one to 

four flows having a composite thickness of 30 to 150 ft. 

They are aphyric or contain phenocrysts of olivine+plagioclase, and commonly show a diktytaxitic (spongy) groundmass texture. These basalts are nearly flat lying or dip 

gently, less than 2 to 3° southeast. They lie in slight angular unconformity over the tuffaceous sedimentary rocks 

and basalt unit which, southwest of Moffit Table, dips to 

the northeast 5 to 10°.

Basalt-capped mesas are found at elevations that differ 

by as much as 440 ft. Individual flows cannot be correlated 

across these mesas and the number and thickness of flows 

differ between adjacent mesas. Three levels of mesas are 

present in the area. The highest level of mesa basalt, at 

about 4,840 ft, includes Moffit Table and narrow mesas 

of the northeast side of Battle Mountain; the middle level, 

at about 4,700 ft, is represented by the large basalt mesa 

of Battle Mountain; and the lowest level, at about 4,450 

to 4,500 ft, includes basalt on the northwest side of Battle 

Mountain and mesas to the west. The basalts most likely 

flowed into shallow, elongate, fluvial drainages that possibly 

were established by normal faulting. Erosion of poorly lithified tuffaceous sediments not covered by basalt lavas likely 

occurred between emplacement of individual flow units 

of the mesa basalt sequence. Thus, the basalt lavas forming 

the highest mesas are the oldest, and those forming the 

lower mesas are younger, having flowed into more deeply 

incised drainages adjacent to older lavas. The northwest 

trend of the mesas, and the gentle southwest dip of the 

mesas suggests that a northwest to southeast drainage pattern 

covered this area during eruption of the mesa basalts.

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H7
Differences in elevations of the mesas that cannot be attributed to faulting suggest that the mesa basalts erupted 

during an extended period of time during which the tuffaceous unit was incised by erosion. The presence of fluvial 

sandstone and gravel, as well as the basalt debris within 

these gravels beneath the basalt mesa of Moffit Table suggest 

that these basalts were deposited in fluvial channels.

Quaternary alluvial gravels locally form low dissected 

benches about 10 to 20 ft thick along the Malheur River 

near the confluence with Coyote Creek, southwest of the 

study area (unit Qg, fig. 2). Recent alluvium (unit Qa, fig. 

2) comprises coarse angular gravel, sand, and silt in and 

along active streams.

Structure

The sedimentary rocks and interbedded basalt were 

deposited in a narrow northwest-trending basin roughly 7 

to 10 mi wide, floored by Miocene andesite, extending 

from several miles northwest of Van to southeast of Drewsey (fig. 1). Although depth to underlying andesite increases, from northeast to southwest, more than 800 ft over a 

distance of about 1 mi, no significant offsets of the andesite basement to the basin are suggested in the gravity 

data. If bounding faults along the northeast margin of the 

basin exist, these have been covered by the tuffaceous sedimentary rocks and basalt. As noted above, the basin 

probably represents an erosional surface, or possibly a 

homoclinal downwarp of the andesitic basement, dipping 

about 10° southwest. Local and minor tilting of ash-flow 

tuff, from 15 to 25°, is observed only in small areas adjacent to faults south of the study area near Wolf Creek.

The mesa basalts appear to be younger than northnorthwest-trending faults mapped by Brown and Thayer 

(1966) in adjacent areas to the north. The elongation and 

northwest trend of basalt mesas of a given height (broadly 

correlative with age) may be explained as the result of lavas 

flowing into shallow northwest-trending basins that deepened by about 400 ft during the time in which the mesaforming basalts erupted. Deepening of the basins is probably 

the result of erosion because the mesa basalts are not faulted.

Geochemistry

Introduction

A reconnaissance geochemical survey was conducted in 

the Malheur-Bluebucket Creek Wilderness Study Area by the 

USGS in the summer of 1986. This study consisted of collecting, analyzing, and evaluating rock, minus-80 mesh (0.18 

mm) stream sediment, and nonmagnetic heavy-mineral 

panned-concentrate (hereafter referred to as heavy-mineral 

concentrate) samples. Seven sites were sampled for stream 

sediments and 31 sites were sampled for rocks; heavy-mineral concentrates were obtained at six of the seven streamsediment sites.

The stream-sediment and heavy-mineral concentrate 

samples are collected primarily for their ability to reveal 

metal anomalies within drainage basins. Stream sediments 

represent a composite of the rock and soil exposed upstream from the sample site. The processing of heavy-mineral concentrates tends to remove common rock-forming 

minerals and to concentrate ore and ore-related minerals. 

The selective concentration of minerals permits determination of some elements that are not easily detected in bulk 

stream-sediment samples (if mineralization has occurred in 

the study area).

The rock samples, nearly all of which appeared unaltered and unmineralized, were collected from outcrop and 

stream float to determine if analysis might reveal an indication of mineralization. Samples that appeared fresh and unaltered were collected to provide information on geochemical 

background values. Anomalous values were determined by 

statistical methods, by comparison of mineralized and altered 

samples with their unaltered equivalents, and by comparison 

with published data for common rock types.

Samples

The stream-sediment samples were collected from active alluvium in the stream channel. Each sample was 

composited from several localities along a channel length 

of approximately 50 ft. The stream sediments were sieved 

through an 80-mesh screen. The heavy-mineral concentrates were obtained by sieving stream sediment through a 

10-mesh screen and then panning the passing fraction until 

most of the quartz, feldspar, clay-sized material, and organic matter were removed. The remaining light minerals 

were separated from the heavy minerals with a heavy liquid (bromoform, specific gravity 2.8). Magnetite and ilmenite were removed from the material having a specific 

gravity greater than 2.8 using an electromagnet. Before 

analysis, the stream-sediment, heavy-mineral concentrate, 

and rock samples were ground to a fine powder.

Analytical Methods

All samples were analyzed for 31 elements by directcurrent arc, semiquantitative emission spectrographic analysis routinely used by the USGS (Grimes and Marranzino, 

1968; Crock and others, 1983). The rock and stream-sediment samples were, in addition, analyzed for arsenic, bismuth, cadmium, antimony, and zinc (O'Leary and Viets, 

1986), gold (Thompson and others, 1968), and mercury 

(Koirtyohann and Khalil, 1976). We were unable to analyze 

the heavy-mineral concentrate samples by these additional 

methods because of insufficient amounts of sample material. 

Analytical data and description of the sampling and analytical 

techniques are given in Erickson and others (1989).

H8 Mineral Resources of Wilderness Study Areas: East-Central Oregon
Results and Interpretations

Anomalous geochemical values were found in samples 

from three sites in the corner of the study area. Gold 

(0.2 ppm) was detected in one stream-sediment sample, bismuth (3 ppm) in one heavy-mineral concentrate, and zinc 

(200 ppm) and molybdenum (5 ppm) in a boulder of basalt 

or andesite. The sample sites are short drainages west of the 

Malheur River, in an area underlain principally by andesite 

(fig. 2). Although gold was found in only one sample, detection of gold in a stream-sediment sample (as opposed to 

a heavy-mineral concentrate) is notable. The low but anomalous values of bismuth, molybdenum, and zinc do not suggest the possible occurrence of deposits of these metals; they 

are, however, commonly associated with epithermal precious-metal deposits. These data suggest that mineralized 

rock containing gold and associated silver may be present 

in andesitic rocks in the northern part of the study area.- 

Andesite, cut by a northwest-trending shear zone, is the host 

for gold in the Harney Mining District (Brooks and Ramp, 

1968, p. 160). Thin hyalite veins are present as coatings on 

fractures in the andesite; no geochemical anomalies were 

detected in analyses of these veins.

Geophysics

Introduction

Three types of geophysical data (gravity, magnetic, 

and radiometric) from east-central Oregon were compiled 

and examined to aid in assessment of the mineral resource 

potential of the Malheur River-Bluebucket Creek Wilderness Study Area. The sparsely distributed nature of the 

three data sets makes them adequate for addressing only 

the regional structural and tectonic setting of the study 

area and it does not permit statements about mineral resource potential at the deposit scale.

Gravity Data

Gravity data for the region surrounding the study area 

were obtained from the National Geophysical Data Center, 

National Oceanic and Atmospheric Administration, Boulder, Colo. Data points are scattered at 3- to 5-mi spacings 

in the region but no data points fall within the study area. 

The observed gravity data, based on the International 

Gravity Standardization Net datum (Morelli, 1974), were 

reduced to free-air gravity anomalies using standard formulas (Telford and others, 1976). Bouger, curvature, and 

terrain corrections (to a distance of 103.6 mi from each 

station) at a standard reduction density of 2.67 g/cm3 were 

added to the free-air anomaly at each station to determine 

complete Bouguer gravity anomalies.

The Bouguer gravity field over the study area and surrounding regions reflects both shallow density contrasts and

deep-crustal density distributions that correlate with the topography in a manner consistent with the concept of isostasy. 

To isolate that part of the gravity field that arises from 

upper crustal density distributions, an isostatic residual-gravity map was constructed from the Bouguer gravity data by 

removing a regional gravity field computed from a model 

of the crust-mantle interface, assuming Airy-type isostatic 

compensation (Jachens and Griscom, 1985). A regional gravity perspective of the setting of the study area can be seen 

on the map of Jachens and others (1985).

The study area lies near the center of a gravity gradient 

that connects a 40-mi-long by 15-mi-wide east-northeasttrending gravity high to the south with a roughly circular 

20-mi-diameter gravity low to the north. Gravity contours 

near the study area are nearly perpendicular to the structural 

grain defined by numerous north-northwest-trending normal 

faults that cut the exposed Tertiary volcanic rocks. The contours also cut across the northwest-trending basin filled with 

tuffaceous sedimentary rocks that lies south of and includes 

the southern half of the study area.

The gravity gradient that crosses the study area probably 

is caused by a combination of two sources, both related to the 

pre-Tertiary basement that lies beneath the volcanic cover. 

Part of the gradient most likely reflects a southward increase 

in density of the basement rocks from mainly clastic strata of 

the Forearc Basin terrane (Brooks, 1979) on the north, to 

denser rocks to the south that may be part of the Huntington 

volcanic-arc terrane (Brooks, 1979). The contact between 

these two terranes is exposed 45 mi northeast of the study 

area where it is marked by a gravity gradient that tentatively 

can be followed southwest to near the study area.

An additional contribution to the gravity gradient in 

the vicinity of the study area probably arises from a northward 

dip of the basement surface and the associated northward 

thickening of the overlying volcanic section. Geologic mapping (Brown and Thayer, 1966) indicates a large depression 

filled with Tertiary volcanic rock north of the study area; 

the associated gravity low of about 30 milliGals (mGal) 

in this area suggests this basin may be 10,000 ft or more deep.

Although the gravity data are sparsely distributed near 

the study area, the lack of a recognizable gravity low associated with the tuffaceous sedimentary rocks that fill the 

basin south of the study area suggests that these sedimentary 

rocks are not thicker than 1,000 ft.

Aeromagnetic Data

An aeromagnetic survey of east-central Oregon, including the study area, was flown and compiled under contract to 

the USGS in 1983 (U.S. Geological Survey, 1984). Total field 

magnetic data were collected along east-west flightlines 

spaced approximately 3 mi apart and at a constant barometric 

elevation of 7,000 ft. Corrections were applied to the data to 

compensate for diurnal variations of the Earth's magnetic 

field, and the international Geomagnetic Reference Field

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H9
(updated to the month that the data were collected) was 

subtracted to yield a residual magnetic field.

The contoured magnetic data near the study area 

show a "birds-eye" pattern of highs and lows with characteristic dimensions of about 5 mi that is typical of the 

magnetic field over the volcanic terrane of east-central Oregon. Depth-to-source estimates based on the steep gradients that flank some of the anomalies and the presence of 

magnetic highs over some topographic highs indicate that 

the exposed Tertiary volcanic rocks are magnetic and 

probably can account for most of the anomalies. Highs 

and lows within mapped volcanic units probably reflect 

differing magnetic properties of individual flows or sets of 

lows within the units. The lack of a spatial correlation between the magnetic and gravity anomalies in the areas 

suggests that any magnetic anomalies caused by magnetization variations within the basement rocks are masked by 

anomalies owing to the overlying volcanic rocks.

Radiometric Data

A radiometric survey of the Burns 1° by 2° quadrangle, 

Oreg., was flown and compiled under contract to the U.S. 

Department of Energy as part of the National Uranium Resource Evaluation (NURE) program (High Life Helicopters, 

IncVQEB, Inc., 1981). Recordings were made of gammaray flux from radioactive isotopes of potassium, thorium, 

and uranium along east-west flightlines spaced approximately 6 mi apart and at a height of 400 ft above average 

terrain. One flightline from the survey crossed the study 

area at lat. 43°58.63' N. Count rates were low along this 

line over the study area and gave no indication of anomalous 

amounts of radioactive elements. However, because only 

one flightline crossed the study area and because gamma 

rays are strongly attenuated by passage through earth materials, these data do not preclude the presence of anomalous 

amounts of radioactive elements away from the flightline 

or buried more than a few feet beneath the ground surface.

Summary

The geophysical data provide no constraints on the 

distribution of mineralized areas in the study area. Altered 

areas are typically only several feet wide and these features can not be resolved with geophysical data based on 

widely spaced flightlines or stations. No areas were identified that might contain altered or mineralized rock.

MINERAL RESOURCE POTENTIAL

The mineral resource potential of the Malheur RiverBluebucket Creek Wilderness Study Area was assessed on 

the basis of geologic investigations, geochemical and geophysical studies, and studies of prospects and claims in 

areas of reported mineral occurrences and of deposits in 

nearby regions. The northern part of the study area has low 

potential for gold and silver resources in epithermal deposits, with a certainty level of B. This area includes all parts 

of the study area underlain by andesite. This assignment is 

based on the detection of gold in one stream-sediment sample and low amounts of related metals in nearby samples.

There is low potential for oil and gas in the entire 

study area (Fouch, 1982,1983). The tuffaceous sedimentary 

rocks, the only likely exposed source rock for hydrocarbons, 

do not contain significant amounts of organic material. There 

are no geologic indications of oil and gas or structural traps 

for hydrocarbon accumulation in or around the study area; 

hence, the assessment of low potential may be too high. 

If oil and gas are present at depth in the area, they are 

buried by volcanic rocks as much as several thousand feet 

thick, and they could only be found with detailed geophysical 

surveys. The certainty of assessment, therefore, is B.

The Malheur River-Bluebucket Creek Wilderness 

Study Area has no geothermal energy potential (Muffler, 

1979). No young volcanic centers are present in or near 

the study area. The youngest volcanic rocks in the study 

area are the basalts capping mesas, which are probably 

older than 5 Ma, and no fossil or active hot springs are 

present in the study area. Therefore, the level of certainty 

of this assessment is D. The study area has no potential 

for mineral energy resources.

REFERENCES CITED

Avent, J.C., 1970, Correlation of the Steens-Columbia River basalts: some tectonic and petrogenetic implications, in Proceedings of 2nd Columbia River Basalt Symposium, Cheney, 

Eastern Washington State College Press, p. 133-157.

Beikman, H.M., Hinkle, M.E., Frieders, Twila, Marcus, S.M., 

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

Survey and the Bureau of Mines of Bureau of Land Management Wilderness Study Areas: U.S. Geological Survey Circular 901, 28 p.

Brooks, B.C., 1979, Plate tectonics and the geologic history of 

the Blue Mountains: Oregon Geology, v. 41, p. 71-80.

Brooks, H.C., and Ramp, Len, 1968, Gold and silver in Oregon: Oregon Department of Geology and Mineral Industries Bulletin 61, 337 p.

Brown, C.E., and Thayer, T.P., 1966, Geologic map of 

the Canyon City quadrangle, northeastern Oregon: U.S. 

Geological Survey Miscellaneous Geologic Investigations 

Map 1-447, scale 1:250,000.

Crock, J.G., Lichte, F.E., and Briggs, PH., 1983, Determination of elements in National Bureau of Standards Geological References Material SRM 278 obsidian and SRM 668 

basalt by induction coupled argon plasma-atomic emission 

spectrometry: Geostandards Newsletter, no. 7, p. 335-340.

Denton, D.K., 1981, Mineral resources of the Pine Creek 

RARE II Area (no. 6248), Barney County, Oregon: U.S.

H10 Mineral Resources of Wilderness Study Areas: East-Central Oregon
Bureau of Mines [file report, Western Field Operations 

Center, Spokane, WA, 10 p.]

Denton, O.K., 1982, Mineral investigation of the Pine Creek 

RARE H Area (no. 6248), Harney County, Oregon: U.S. 

Bureau of Mines Open File Report, MLA 101-82, 7 p.

Erickson, M.S., Jones, Janet, Kennedy, Kay, and Gent, Carol, 

1989, Analytical results and sample locality map of streamsediment and heavy-mineral-concentrate samples from the 

Malheur-Bluebucket Wilderness Study Area (OR-002-014), 

Harney County, Oregon: U.S. Geological Survey Open-File 

Report 89-164, 10 p.

Fouch, T.D., 1982, Petroleum potential of wilderness lands 

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

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

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

Goudarzi, G.H., 1984, Guide to preparation of mineral survey 

reports on public lands: U.S. Geological Survey Open-File 

Report 84-787, 51 p.

Greene, R.C., 1973, Petrology of the welded tuff of Devine 

Canyon, southeast Oregon: U.S. Geological Survey Professional Paper 797, 26 p.

Greene, R.C., Walker, G.W., and Corcoran, R.E., 1972, Geologic map of the Burns quadrangle, Oregon: U.S. Geological Survey Miscellaneous Investigations Map 1-680, scale 

1:250,000.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc 

and alternating-current spark emission spectrographic field 

methods for the semiquantitative analysis of geologic materials: U.S. Geological Survey Circular 591, 6 p.

High Life Helicopters, Inc./QEB, Inc., 1981, Airborne gammaray spectrometers and magnetometer survey, Burns quadrangle, Oregon: U.S. Department of Energy Open-File Report 

GJBX 240 (81), v. 2, variously paged.

Jachens, R.C., and Griscom, Andrew, 1985, An isostatic residual gravity map of California A residual map for interpretation of anomalies from intracrustal sources, in Hinze, 

W.J., ed., The utility of regional gravity and magnetic 

anomaly maps: Tulsa, Okla., Society of Exploration Geophysicists, p. 347-360.

Jachens, R.C., Simpson, R.W., Blakely, R.J., and Saltus, R.W., 

1985, Isostatic residual gravity map of the United States, 

exclusive of Alaska and Hawaii: National Geophysical 

Data Center (NOAA), Boulder, Colo., on clear film with 

interpretative text, 2 sheets, scale 1:2,500,000.

Koirtyohann, S.R., and Khalil, Moheb, 1976, Variables in determination of mercury by cold vapor atomic absorption: Analytical Chemistry, 48, p. 136-139.

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

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

Morelli, C.E., ed., 1974, The international gravity standardization 

net 1971: International Association of Geodesy Special Publication no. 4, 194 p.

Muffler, L.J.P., ed., 1979, Assessment of geothermal resources of 

the United States 1978: U.S. Geological Survey Circular 

790, 163 p.

O'Leary, R.M., and Viets, J.G., 1986, Determination of antimony, 

arsenic, bismuth, cadmium, copper, lead, molybdenum, silver and zinc in geologic materials by atomic absorption 

spectrometry using a hydrochloric acid-hydrogen peroxide 

digestion: Atomic Spectroscopy, 7, p. 4-8.

Peters, T.J., and Winters, R.A., 1987, Mineral resources of the 

Malheur River-Bluebucket Wilderness Study area, Lake and 

Harney Counties, Oregon: U.S. Bureau of Mines Minerals 

Land Assessment Open-File Report MLA 67-87, 11 p.

Riccio, J.F., 1978, Preliminary geothermal resource map of Oregon: Oregon Department of Geology and Mineral Industries 

Geological Map Series GMS-11, scale 1:500,000.

Shotwell, J.A, 1963, The Juntura Basin Studies in earth history 

and paleoecology: American Philosophical Society Transactions, v. 53, pt. 1, 77 p.

Telford, W.M., Geldart, L.P., Sheriff, R.E., and Keyes, D.A., 

1976, Applied Geophysics: New York, Cambridge University 

Press, 960 p.

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

Rapid analysis for gold in geologic materials, in Geological 

Survey Research, 1968: U.S. Geological Survey Professional 

Paper 600-B, p. B130-B132.

U.S. Geological Survey, 1984, Aeromagnetic map of east-central 

Oregon: U.S. Geological Survey Open-File Report 84-512, 

scale 1:250,000.

U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of a resource/reserve classification for minerals: U.S. 

Geological Survey Circular 831, 5 p.

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

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

Walker, G.W., 1979, Revisions to the Cenozoic stratigraphy of 

Harney Basin, southeastern Oregon: U.S. Geological Survey 

Bulletin 1475, 35 p.

Walker, G.W., and Denton, D.K., 1982, Mineral resource 

potential of the Pine Creek Roadless Area, Harney County, Oregon: U.S. Geological Survey Open-File Report 82- 

822, 7 p.

Walker, G.W., and Swanson, D.A., 1968, Summary report on the 

geology and mineral resources of the Harney Lake and Malheur Lake areas of the Malheur National Wildlife Refuge, 

north-central Harney County, Oregon: U.S. Geological Survey Bulletin 1260-L, 17 p.

Wiley, T.J., 1991, Mining and exploration in Oregon during 

1990: Oregon Geology, v. 53, no. 3, p. 63-70.

Wullenwaber, Dean, and Dailey, R.T., 1975, Economic criteria 

for producing basalt fibers in the Pacific northwest: Center 

for Business Development and Research, College and Business and Economics, University of Idaho, Moscow, Idaho, 

CBDR 75-9,47 p.

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Harney County, Oregon H11

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 t 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, an (or) where an application of mineraldeposit 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 

not 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.

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

17B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

tyc

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

17D

LOW POTENTIAL

N/D

NO POTENTIAL

JZ

LU

5

a.

O

LU 

>

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

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

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

Geological Survey Bulletin 1638, p. 40-42. 

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

H14 Mineral Resources of Wilderness Study Areas: East-Central Oregon
RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

ECONOMIC Reserves Inferred 

Reserves

MARGINALLY 

ECONOMIC

Marginal 

Reserves

Inferred 

Marginal 

Reserves

SUBECONOMIC

Demonstrated

Subeconomic

Resources

Inferred

Subeconomic

Resources

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

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

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

Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study Area, Hamey County, Oregon HIS
GEOLOGIC TIME CHART

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

EON

Phanerozoic

Proterozoic

Archean

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Neogene 

Subperiod

Tertiary 

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Periods 

Mississippian

Devonian

Silurian

Ordovician

Cambrian

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

pre-Archean2

AGE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (MA)

 0.010

1.7

 5

*> A

OQ

 55

...... ftk

 96

205

1 A f\

 ?QO

-330

 -360

 410

 435

cnn

 ^570

 -900

 1600

 2500

 3000

3400

 Accn 

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

Informal time term without specific rank.

HI 6 Mineral Resources of Wilderness Study Areas: East-Central Oregon
Mineral Resources of 

Wilderness Study Areas: 

East-Central Oregon

This volume was published as separate chapters A-H

U.S. GEOLOGICAL SURVEY BULLETIN 1741
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the Honeycombs Wilderness Study Area, Malheur County, 

Oregon, by Dean B. Vander Meulen, JJ. 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 

Area, 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 Area, Malheur County, Oregon, by Dean B. Vander Meulen, Andrew 

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

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

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 

Sawatzky, and J. Douglas Causey.

(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, Andrew Griscom, and J. Douglas Griscom.

(H) Mineral Resources of the Malheur River-Bluebucket Creek Wilderness Study 

Area, Harney County, Oregon, by Michael G. Sawlan^ Robert L. Turner, Robert 

C. Jachens, Thomas J. Peters, and Richard A. Winters.

*u.s. oovnoMair PRINTING OFFICE: 1995-683-048A0016



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