Mineral Resources 

Wilderness Study

the Soda Mountain

, Jackson County, Oregon

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Chapter C

Mineral Resources of the Soda Mountain 

Wilderness Study Area, Jackson County, 

Oregon

By WILLIAM J. PICKTHORN, RICHARD J. GOLDFARB, 

DONALD PLOUFF, STEVEN J. SUTLEY, and 

MARK D. WILCOX 

U.S. Geological Survey

THOMAS J. PETERS and SPENCEE L. WILLETT 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1 744

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

CENTRAL AND FAR WESTERN OREGON
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

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in this publication is for descriptive purposes only

and does not imply endorsement by the U.S. Government

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For sale by the

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the Soda Mountain Wilderness study areas, Jackson 

County, Oregon / by William J. Pickthorn ... [et al.].

p. cm. (Mineral resources of wilderness study areas south 

-central Oregon : ch. C) (U.S. Geological Survey bulletin : 1744)

Includes bibliographical references (p. ).

1. Mines and mineral resources Oregon Soda Mountain Wilderness. 

2. Soda Mountain Wilderness (Or.) I. Pickthorn, William J. 

II. Series. III. Series: U.S. Geological Survey bulletin ; 1744. 

QE75.B9 no. 1744-C 557.3 s dc20 90-13915 

[TN24.07] [553 1 .09795 '27J CIP
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Area

The Federal Land policy and Management Act (Public Land 94-579, October 21, 

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct 

mineral surveys of certain areas to determine the mineral values, if any, that may be 

present. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of mineral surveys of the Soda 

Mountain Wilderness Study Area (OR-011-017), Jackson County, Oregon.

CONTENTS

Summary Cl

Abstract Cl

Character and setting Cl

Identified resources and mineral resource potential Cl 

Introduction Cl

Area description C2

Previous and present studies C3

Acknowledgments C3 

Appraisal of identified resources C3

Mining and mineral exploration history C3

Soda Mountain prospect/mineralized area C3

Mineral economics and resources C5 

Assessment of mineral resource potential C5

Geology C5

Geochemical studies C5

Geophysical studies C6

Mineral and energy resource potential C7 

References C7 

Appendixes C9

Definitions of levels of mineral resource potential and certainty of 

assessment CIO

Resource/reserve classification Cll

Geologic time chart C12

FIGURES

1. Index map showing location of Soda Mountain Wilderness Study Area, Jackson 

County, Oregon C2

2. Map showing mineral resource potential and generalized geology of Soda Mountain 

Wilderness Study Area, Jackson County, Oregon C4

3. Aeromagnetic map of Soda Mountain Wilderness Study Area, Jackson County, 

Oregon C6

4. Gravity map of Soda Mountain Wilderness Study Area, Jackson County, Oregon C7

Contents

Mineral Resources of the Soda Mountain Wilderness 

Study Area, Jackson County, Oregon

By William J. Pickthorn, Richard J. Goldfarb, Donald Plouff, 

Steven J. Sutley, and Mark D. Wilcox 

U.S. Geological Survey

Thomas J. Peters and Spencee L. Willett 

U.S. Bureau of Mines

SUMMARY

Abstract

At the request of the Bureau of Land Management, 5,640 

acres that comprise the Soda Mountain Wilderness Study Area 

(OR-011-017), in south-central Oregon, were evaluated for 

mineral resources (known) and mineral resource potential 

(unknown). In this report the area studied is referred to as "the 

wilderness study area." The dominant rock types in the study 

area are basaltic and andesitic flows and breccia and minor 

outcrops of silicic tuff. Although there are no identified resources and there has been no significant prospecting activity, an outcrop of altered silicic tuff in the northern part of the 

study area has been prospected for gold. Much of the northern part of the study area has moderate potential for gold and 

silver. The study area has a low potential for geothermal resources. The study area has low resource potential for oil and 

gas and building stone; a small area in the south has low 

potential for gold in placer deposits.

Character and Setting

The Soda Mountain Wilderness Study Area is located 

along the west flank of the Cascade Range in Jackson County, 

Oregon, about 17 mi southeast of Ashland, Oregon (fig. 1). 

Approximately 75 percent of the densely vegetated study 

area comprises steep ridges and canyons forming the south 

face of Soda Mountain. Total relief of the study area is 

about 3,000 ft with a maximum elevation of 5,760 ft. The 

study area is underlain by gently northeast-dipping Oligocene (see appendixes for geologic time chart) volcanic and 

volcaniclastic rocks, principally basalt and andesite.

Manuscript approved for publication, September 4, 1990.

Identified Resources and Mineral Resource 

Potential

The Soda Mountain Wilderness Study Area has 

no identified mineral resources or significant prospecting 

activity. However, the small Soda Mountain prospect 

was located in an area of hydrothermally altered silicic 

tuff and andesite breccia on a ridge northeast of Camp 

Creek; it consists of a 7-ft-deep shaft and a nearby shallow 

pit Gold values of the altered rocks at the prospect are as 

high as 0.06 oz per ton. Geochemical data from rock and 

soil samples suggest more mineralization south of the prospect area; that area is assigned a moderate potential for 

gold. Much of the northern part of the study area is 

also assigned moderate potential for gold and silver on 

the basis of geochemical evidence. No geothermal leases 

exist in the study area and there is a low potential for 

geothermal resources. There is also low potential for oil 

and gas resources. The possibility of placer gold and building stone resources was also investigated, but no occurrences were observed; their potential is also assigned as 

low.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau of Land Management (BLM) and is a cooperative effort of 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 is 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 arMineral Resources of the Soda Mountain Wilderness Area, Jackson County, Oregon C1
eas. 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 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 the application of ore-deposit models. 

Methodology and terminology as they apply to these mineral assessment surveys were discussed by Goudarzi (1984). 

See the appendixes for the definition of levels of mineral 

resource potential and certainty of assessment and for the 

resource/reserve classification.

Area Description

The Soda Mountain Wilderness Study Area is situated along the west flank of the Cascade Range, approximately 17 mi southeast of Ashland, Oregon, immediately 

north of the California border. Best access is by an improved 

BLM dirt road that leads south from Oregon Highway 66 at 

Green Springs to a fire lookout tower and microwave relay 

facility on the peak of Soda Mountain on the north edge of 

the study area. Access is also possible by dirt roads and 

jeep trails east from Interstate Highway 5 near Siskyou, and 

north from Irongate Reservoir in northern California. Elevations in the study area range from 2,920 ft at Salt Creek 

to 5,760 ft on the flank of Soda Mountain. Most tower

122°.45' 122°30' 122°15'

O U N T A

_ _ ___ CALIFORNIA ___ jj2__

OREGON SISKIYOUCO ~

APPROXIMATE BOUNDAR Y

OF

SODA MOUNTAIN

WILDERNESS STUDY AREA

(OR-011-017)

Figure 1. Index map showing location of Soda Mountain Wilderness Study Area, Jackson County, Oregon

C2 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon
elevation slopes and stream valleys are covered by dense 

brush, and the higher ridges are vegetated by pine and fir. 

Open grasslands are present on the gentle slopes in the 

eastern part of study area.

Previous and Present Studies

Geologic mapping, geochemical sampling, geophysical studies, and mineral-assessment studies that include the 

Soda Mountain Wilderness Study Area were done on a regional scale for the Medford 1° by 2° quadrangle. These 

studies are listed and summarized in Smith and others (1986). 

Geologic mapping by Wells (1956) covered a small part of 

the west edge of the study area.

Detailed field investigations by the USGS were conducted in the Soda Mountain Wilderness Study Area during 

the summer and fall of 1988 and spring of 1989. This work 

included geologic mapping, geochemical sampling, and examination of outcrops for evidence of alteration and mineralization. The geochemical survey utilized rock and 

stream-sediment (including a fine-fraction and heavy-mineral-concentrate) samples that were analyzed for 37 elements by semiquantitative emission spectrography. All rocks 

were analyzed for gold and mercury by atomic absorption, 

and for arsenic, bismuth, cadmium, antimony, and zinc by 

inductively coupled plasma spectroscopy (ICP). Geophysical data, which consisted of gravity information collected 

during the Medford quadrangle study, and aeromagnetic 

data collected by Oregon State University and covering the 

Cascade Range were analyzed and interpreted.

The USBM examined prospects and mineralized zones 

within and adjacent to the study area to evaluate identified 

mineral resources. Prefield preparation included a library 

search of pertinent geological and mining literature, BLM 

master title plats, and current mining claim recordation data. 

Information was also obtained from the Oregon Department of Geology and Mineral Industries at Grants Pass, and 

the USBM Mineral Industries Location System (MILS). A 

field search was conducted for mines, prospects, and mineralized areas in and near the study area. Mineralized sites 

were examined and mapped. Ninety-eight samples were 

collected; these included 41 rock, 52 soil, and five alluvial 

samples. Rock samples were analyzed for nine major-element oxides, LOI (loss of ignition), and 34 trace elements. 

Soil samples were analyzed for 34 trace elements, and alluvial samples were analyzed for free gold and other heavy 

minerals (Peters and Willett, 1989).

Acknowledgments

The authors are grateful to Joseph G. Dauenhauer, 

owner of the Barron mine, for permission to visit the mine, 

and to John Archer for showing us the property. Edward D.

Fields, Boise Cascade Corporation, Spokane, Wash., and 

Len Ramp, Oregon Department of Geology and Mineral 

Industries, Grants Pass, provided valuable geological information. Gerry Capps, James Renthal, and Fred Tomlins, 

BLM, Medford, and Thomas Maier, U.S. Forest Service, 

Prospect, Oreg., and Steve Bulkin, U.S. Forest Service, 

Medford, Oreg., provided information and logistical support. James G. Smith of the USGS provided insight to the 

geology and resource appraisal.

APPRAISAL OF IDENTIFIED RESOURCES

By Thomas J. Peters andSpencee L. Willett 

U.S. Bureau of Mines

Mining and Mineral Exploration History

Although mining in southwest Oregon dates back to 

the 1850's, there has been relatively little activity in the 

volcanic and volcaniclastic terrane of the southern Oregon 

Cascade Range. Minor exploration activity has occurred at 

the Soda Mountain prospect, as evidenced by a 7-ft-deep 

shaft and shallow pit; the identity of the prospector(s), however, is not known. At least one company engaged in gold 

exploration has visited the prospect prior to this study.

BLM mining claim records show a lode claim was 

located in the Nl/2 of section 6, township 41 S., range 3 E., 

on November 20, 1983, by Myrle E. and Betty Dodson of 

the Medford area; the authors were unable to contact the 

Dodsons. The claim must have been in or near the west 

corner of the wilderness study area, probably along Lone 

Pine Ridge (fig. 2). A ground search of the area disclosed 

no evidence of mineralization or exploration and mining 

activity.

Mark Hermiston, BLM geologist, Medford, collected 

28 stream-sediment and five rock samples from the wilderness study area and vicinity during a reconnaissance geochemical survey (Rimal, 1985, p. 50-53).

Soda Mountain Prospect/Mineralized Area

Access to the Soda Mountain prospect is by the Soda 

Mountain Road, south from Green Springs Mountain on 

Oregon Highway 66 (fig. 2). The prospect area straddles 

the study area boundary (fig. 2). The only known workings 

consist of a 7-ft-deep, 3-ft-diameter shaft and a shallow pit. 

The prospect lies on the north edge of area underlain primarily by pervasively kaolinized and silicified rhyolite tuff.

This siliceous tuff and andesite in the prospect area 

(Peters and Willett, 1989, pi. 1) are cut by prominent steeply 

dipping joint sets trending between N. 60° W. and N. 75° 

E., and clustering at N. 70° W. and N. 80° E. Limonite, 

goethite, and hematite are present on the joints and fracMineral Resources of the Soda Mountain Wilderness Area, Jackson County, Oregon C3
R2E.R3E 122°301

122°25' R3E R4E

APPROXIMATE BOUNDARY

SODA MOUNTAIN 

^WILDERNESS STUDY AREA 

(OR-01*

EXPLANATION

Area having moderate mineral 

resource potential (M)

Deposit types 

[1] Epithermal vein 

[2] Placer 

Area having low mineral resource

potential (L) Description of map units

Qal Alluvium (Quaternary) Mostly 

Levels of certainty of assessment 

Data only suggest level of

potential TV 

Data give good indication of level

of potential 

Data clearly define level of

potential ft

Commodities 

Ag Silver 

Au Gold 

Geo Geothermal 

O, G Oil and gas 

Stone Building stone

unconsolidated stream sand

and gravel 

Volcanic rocks (Tertiary) 

Basalt, basaltic andesite, and

andesite flows and breccia;

age is Oligocene 

Tuff (Tertiary) Silicic ashflow

tuff; may be aquagene, in part

- Contact Dashed where

approximately located

Soda Mountain prospect 

Borrow pit

Figure 2. Mineral resource potential and generalized geology of Soda Mountain Wilderness Study Area, Jackson County, 

Oregon. Base from U.S. Geological Survey 1:62,000-scale Ashland (1954) and Hyatt Reservoir (1955) quadrangles, Oreg.- 

Calif. Contour interval 40 and 80 ft.

C4 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon
tures. Epidote alteration and weak arsenopyrite mineralization were also observed. Flow banding is not apparent in 

most places, but in the prospect area it dips 30° E. where 

observed.

Mineral Economics and Resources

Gold concentrations in rock and soil samples from 

the Soda Mountain prospect (Peters and Willett, 1989) delineate a 10-acre gold-bearing mineralized zone. Three rock 

samples from the southern part of the prospect area contained 280, 210, and 2,100 parts per billion (ppb) (0.008, 

0.006, and 0.06 oz per ton) gold, respectively, worth $3.30, 

$2.40, and $24.80 per ton at a $400 per oz gold price.

Possible occurrences of placer gold and building stone 

resources were also investigated (Peters and Willett, 1989, 

p. 11), but no resources were identified. Five alluvial samples 

from streambeds draining the study area contained placer 

gold with an in situ value of 0,2,2, 5, and 20 cents per yd3 

at a $400 per oz gold price; no extensive alluvial bars were 

observed. None of the stone observed had special physical 

properties, such as splitting into flat slabs useful for facing 

stone, nor special chemical properties, such as an extraordinarily high alumina content suitable as an alternative source 

of aluminum ore in the distant future. The stone appears to 

have value only as road metal, a low-value, high-volume end 

use economically suitable for local application only; ample 

supplies of stone are present locally outside the study area.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By William J. Pickthorn, Richard J. Goldfarb, Donald Plouff, 

Steven J. Sutley, and Mark D. Wilcox 

U.S. Geological Survey

Geology

The Soda Mountain Wilderness Study Area lies along 

the west flank of the Cascade Range and the geology consists 

of volcanic and volcaniclastic rocks of the Cascade Volcanic 

Arc. These rocks were erupted during the Oligocene and 

early Miocene Epochs (Smith and others, 1986). This sequence is collectively called the volcanic rocks of the western Cascade Range. In southern Oregon the volcanic rocks 

of the western Cascade Range are structurally simple, forming a homoclinal sequence that dips gently north-northeast. 

Because of shifting eruptive centers and the interfingering 

and overlapping of volcanic and sedimentary units, a simple 

stratigraphic sequence does not exist. Rapid facies changes 

are common within a single unit

The study area lies entirely within a single regional 

reconnaissance volcanic unit mapped by Smith and others

(1982) as Oligocene basalt, basaltic andcsite, and andesite. 

Individual depositional units have varying appearance due 

to textural changes, rather than compositional changes, and 

thus were not mapped separately. Much of the study area is 

covered by dense brush and extensive soils are developed 

on the slopes. Smith and others (1982) indicate no major 

faults in their mapping, and none were noted in this study. 

Small landslides are present on the steeper slopes and on 

the south face of Soda Mountain.

Several outcrops of a recently mapped silicic tuff (Peters and Willett, 1989) are present in the northern part of 

the study area, along a tributary to Camp Creek. The tuff 

unit appears to pinch and swell and the thickness could not 

be accurately determined. The unit appears to be dominantly bedded, suggesting an aquagene origin in pan. Fragments of the tuff present along Camp and Dutch Oven Creeks 

suggest that the tuff may extend to the west but no outcrops 

were observed in the thick brush.

Geochemical Studies

The geochemical survey of the Soda Mountain Wilderness Study Area consisted of the collection and analysis 

of eight stream-sediment and heavy-mineral-concentrate 

samples and 31 rock samples from inside, and immediately 

adjacent to, the study area. Stream-sediment samples were 

air-dried and sieved to minus-80-mesh fractions. All concentrate samples were panned from 1.5 to 2 Ib of minus-10- 

mesh sediment using a gold pan. In the laboratory, the 

concentrates were air-dried, the lighter material was removed 

using bromoform, and the magnetic heavy-mineral fractions 

were removed using a magnetic separator. Sediment and 

rock samples were analyzed for 35 elements and 

nonmagnetic concentrate samples were analyzed for 37 elements using optical emission spectrography according to 

the method outlined by Grimes and Marranzino (1968). In 

addition, all rocks and sediments were analyzed by atomicabsorption spectrometry for gold, all rocks were analyzed 

by atomic-absorption spectrometry for mercury, and all 

sediments and selected altered rocks were analyzed by ICP 

for arsenic, bismuth, cadmium, antimony, and zinc. Complete analytical data and a detailed discussion of the sampling 

and analytical methods are given in Sutley and others (1990).

With the exception of samples collected from the Soda 

Mountain prospect, most of the lithogeochemical data for 

basalt, andesite, vein quartz, and jasperoid samples show 

background levels for all elements studied. Gold concentrations were below the 50 ppb lower determination limit and 

most mercury concentrations were less than 100 ppb. One 

quartz vein, however, contained 120 ppb mercury with no 

other anomalous element values. The only significant geochemical anomalies were for hydrothermally altered siliceous volcanic breccia and tuff samples collected at the 

Soda Mountain prospect These altered rocks contain as

Mineral Resources of the Soda Mountain Wilderness Area, Jackson County, Oregon C5
much as 1.5 parts per million (ppm) silver, 127 ppm arsenic, 

greater than 2,000 ppm boron, 10 ppm bismuth, 2.9 ppm 

mercury, 100 ppm lead, and 28 ppm antimony. Some 

samples are slightly enriched in copper, molybdenum, and 

tin compared to samples from the rest of the study area. 

None of the anomalous rocks, however, contained detectable 

gold at the 50-ppb lower determination limit. However, Peters and Willett (1989) report as much as 2.10 ppm gold, as 

well as 19 ppm, silver, 11,200 ppm arsenic, 2.3 ppm mercury, 1,724 ppm lead, and 76 ppm antimony, for altered 

tuff from the prospect. This discrepancy in reported chemical 

analyses is most likely due to "nugget effect."

Stream-sediment and heavy-mineral-concentrate data 

suggest other areas of weakly altered volcanic rocks elsewhere within the study area. The three stream sediments 

collected along the east edge of the study area are weakly 

anomalous in silver, arsenic, and (or) zinc. Sediment and 

concentrate samples collected near the junction of Camp 

and Dutch Oven Creeks contain above-background concentrations of silver, arsenic, boron, and (or) lead, a suite of 

elements similar to those elements present in anomalous 

concentrations in the altered rock samples. Microscopic examination of the most anomalous heavy-mineral-concentrate sample, collected on Dutch Oven Creek about 100 yd 

above its junction with Camp Creek, revealed the presence 

of grains of pyrite, arsenopyrite, and galena.

Geophysical Studies

Geophysical evaluation of the mineral resources of 

the study area was based on interpretations of aeromagnetic 

and gravity surveys.

As part of the USGS Geothermal Program, Oregon 

State University was funded to collect aeromagnetic data in 

the Cascade Range. The area surrounding the study area 

was flown at an elevation at 9,000 ft above sea level along 

east-west flightlines spaced approximately 1 mi apart (Couch 

and others, 1981; Couch, 1982) (fig. 3). Most of the study 

area lies along the south and southwest edges of an eastwest-elongated aeromagnetic high (fig. 3). The shape and 

location of the aeromagnetic high generally reflects moderate magnetization of underlying andesite to basalt flows 

(Smith and others, 1982), as confirmed by the presence of a 

local magnetic crest of the magnetic high over Soda Mountain. Magnetic gradients extending over horizontal distances 

of nearly 2 mi near the study area suggest that the thickness 

of the causative magnetic body or bodies substantially exceeds that of volcanic rocks that crop out near the study 

area. The aeromagnetic high centered north of the study 

area is situated near the south edge of a prominent set of 

magnetic highs that extend north-northwestward for about 

60 mi. Blakely (1986) interpreted the set of magnetic highs 

as possibly being caused by a fault-bounded underlying ultramafic sheet or a thick sequence of Tertiary volcanic rocks.

The magnetic gradients in the study area apparently reflect 

a steeply dipping or fault-bounded interface between deepseated plutonic or volcanic rocks and surrounding, less 

magnetic basement rocks. The magnetic gradient is interrupted along the south edge of the study area by a magnetic 

low. The magnetic low probably is caused by rocks of low 

magnetization in and beneath a 1-mi-diameter outcrop of 

mafic intrusive rocks of Tertiary age centered at the south 

edge of the study area (Smith and others, 1982).

The USGS established eight gravity stations in and 

within 3 mi from the border of the study area during a 

regional mineral appraisal of public lands in the Medford 

1° by 2° quadrangle (R.J. Blakely, written commun., 1989). 

These data were supplemented with gravity data obtained 

from Oregon State University as part of Blakely's compilation. Locations, elevations, and terrain corrections for these 

data were revised to reflect topography on 7 1/2-minute 

topographic maps published since the original gravity data 

were collected. North-northwest-trending contours in the 

region generally reflect thickening of the crust away from 

the Pacific coast and a decrease of the local gravity anomaly 

toward a regional gravity trough along the Cascade Range 

(Blakely and others, 1985). The most prominent feature of 

the gravity map of the study area is a gravity high centered 

near the southwest edge of the study area and its enclosing 

gravity contours (fig. 4). The shape of the contours and the 

position and orientation of the gravity high are uncertain 

because there are only a few stations in the area. The location of the gravity high and, consequently its source, is also 

uncertain because its effect is superimposed on a strong

12 2°30' 122°2C'

Figure 3. Aeromagnetic map of Soda Mountain Wilderness 

Area, Oregon (shaded). Values of magnetic intensity of Earth's magnetic field in nanoTeslas (nT) (1 nT=1 gamma) at arbitrary datum; 

International Geomagnetic Reference Field has been removed. Contour interval 40 nT; dot, magnetic station; contours hachured in 

direction of lower magnetic intensities. Dashed line, center of magnetic low discussed in text.

C6 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon
regional gravity gradient We speculate that the source of 

the gravity high that interrupts the regional gradient also is 

associated with the underlying source of the mafic intrusive 

rocks that crop out nearby.

Mineral and Energy Resource Potential

Geologic, geochemical, and geophysical investigations 

suggest potential for epithermal precious metal mineralization in the Soda Mountain Wilderness Study Area. Singer 

and others (1983) indicate much of the area on the Medford 

1° by 2° quadrangle that is underlain by Tertiary volcanic 

rocks is favorable for epithermal vein mineralization. One 

such area, based on rock samples with anomalous boron, 

mercury, and tellurium concentrations, is present approximately 1 mi north of the study area boundary. Also, the 

Barron mine, a past producer of gold and silver, is located 

within the Tertiary volcanic rocks about 10 mi northwest of 

the study area.

Hydrothermally altered silicic tuff and andesite breccia samples collected by the USBM and USGS from the 

area of the Soda Mountain prospect contain significant concentrations of gold and silver. This area has moderate resource potential for gold and silver, certainty level D. 

Stream-sediment and heavy-mineral-concentrate samples 

containing anomalous concentrations of many elements 

characteristic of epithermal mineralization suggest that other 

parts of the study area, lacking adequate outcrop exposure, 

may contain similar zones of alteration and possibly underwent gold-silver mineralization. These areas, along the north 

edge of the study area and within the Dutch Oven Creek

12 2° 30' 122° 20 1

Figure 4. Bouguer gravity anomaly map of Soda Mountain Wilderness Study Area, Oregon (shaded). Gravity values in milliGals; 

contour interval 2 milliGals; dot, station location; contours hachured 

in direction of lower gravity values. Reduction density 2.67 g/cm3.

watershed, have a moderate resource potential for gold and 

silver, certainty level B.

The potential for geothermal resources in the study 

area is low, certainty level C. Areas of active geothermal 

energy and exploration are associated with silicic volcanism less than 2 Ma (million years) (Smith and Shaw, 1975) 

or areas of high heat flow, neither of which are present 

here.

The potential for oil and gas resources in the study 

area is low, certainty level C. This evaluation is based on 

the absence of suitable source or reservoir rocks.

The potential for building stone is also low, certainty 

level C.

A small area in the southern part of the study area has 

low potential for gold in placer deposits, certainty level C.

REFERENCES

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 Land Management Wilderness Study 

Areas: U.S. Geological Survey Circular 901,28 p.

Blakely, R.J., 1986, Maps showing aeromagnetic data and interpretation of the Medford 1° by 2° quadrangle, Oregon-California: U.S. Geological Survey Miscellaneous Field Studies 

Map MF-1383-B, 2 sheets, scale 1:250,000.

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

1985, Tectonic setting of the southern Cascade Range as interpreted from its magnetic and gravity fields: Geological 

Society of America Bulletin, v. 96, p. 43-48.

Couch, R.W., 1982, Maps showing total-field aeromagnetic 

anomalies and topography of the Cascade Mountain Range, 

northern California: U.S. Geological Survey Open-File Report 82-198,2 sheets, scale 1:250,000.

Couch, R.W., Gemperle, M., McLain, W.H., and Conrad, G.G., 

1981, Total field aeromagnetic anomaly map Cascade Mountain Range, southern Oregon: Oregon Department of Geology and Mineral Industries, Geological Map Series Map GMS17,1 sheet, scale 1:250,000.

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.

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.

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

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

Peters, T.J., and Willett, S.L., 1989, Mineral resource of the Soda 

Mountain Wilderness Study Area, Jackson County, Oregon: 

U.S. Bureau of Mines Open-File Report MLA 32-89,24 p.

Rimal, Durga, coordinator, 1985, Preliminary geochemical data 

on some BLM-administered lands including Wilderness Study 

Areas in Oregon and Washington: U.S. Bureau of Land Management unnumbered report, Oregon State Office, Portland, 

52 p.

Singer, D.A., Page, N.J, Smith, J.G., Blakely, R.J., and Johnson,

Mineral Resources of the Soda Mountain Wilderness Area, Jackson County, Oregon C7
M.G., 1983, Mineral resource assessment maps of the Medford 

1° x 2° quadrangle Oregon-California: U.S. Geological Survey Miscellaneous Field Studies Map MF-1383-C, scale 

1:250,000,2 sheets.

Smith, J.G., Blakely, R.J., Johnson, M.G., Page, N.J, Peterson, 

JA., Singer, D.A., and Whittington, C.L., 1986, The Conterminous United States Minerals Appraisal Program: Background information to accompany folio of geologic, geochemical, geophysical, and mineral resource maps of the 

Medford 1° by 2° quadrangle, Oregon and California: U.S. 

Geological Survey Circular 976.

Smith, J.G., Page, NJ, Johnson, M.G., Moring, B.C., and Gray, 

Floyd, 1982, Preliminary geologic map of Medford 1° by 2° 

quadrangle, Oregon and California: U.S. Geological Survey 

Open-File Report 82-955,1 sheet, scale 1:250,000.

Smith, R.L., and Shaw, H.R., 1975, Igneous-related geothermal 

systems, in White, D.L., ed., Assessment of geothermal resources of the United States 1975: U.S. Geological Survey 

Circular 76, p. 58-83.

Sutley, S.J., Goldfarb, R.J., and Pickthorn, W.J., 1990, Analytical 

results and sample locality map of stream-sediment, heavymineral-concentrate, and rock samples from the Soda Mountain Wilderness Study Area, Jackson County, Oregon: U.S. 

Geological Survey Open-File Report 90-450,13 p.

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.

Wells, F.G., 1956, Geology of the Medford quadrangle, OregonCalifornia: U.S. Geological Survey Geologic Quadrangle Map 

GQ-89, scale 1:62,500.

C8 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon
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.

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

L/C

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

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

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

Geological Survey Bulletin 1638, p. 40-42. 

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

C10 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

»rves

I 

Marginal 

Reserves

Demonstrated 

Subeconomic 

Resources

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

1

1

1

1 

i

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

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

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

Mineral Resources of the Soda Mountain Wilderness Area, Jackson County, Oregon C11
GEOLOGIC TIME CHART

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

EON

Phanerozoic

Proterozoic

pre-Archean2

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Neogene

Subperiod

Tertiary ,

r dltx/c^i IL,

C- rctscGO u s

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

------ . . (3800?)- - -

EPOCH

Holocene

" Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

AGE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (Ma)

 0.010

 1.7

 5

 jo

 55

 66

yb 

1 10

 205

~?4O

290 

 -330

 360

 410

*** J / V

 1600

 2500

JL/UU 

t Af\f\

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

informal time term without specific rank.

C12 Mineral Resources of Wilderness Study Areas: Central and Far Western Oregon


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