Mineral Resources of the 

Dominguez Canyon 

Wilderness Study Area, 

Delta, Mesa, and Montrose 

Counties, Colorado

U.S. GEOLOGICAL SURVEY BULLETIN 1736-A

Chapter A

Mineral Resources of the 

Dominguez Canyon 

Wilderness Study Area, 

Delta, Mesa, and Montrose 

Counties, Colorado

By MARGO I. TOTH, CHARLES G. PATTERSON, and 

DOLORES M. KULIK 

U.S. Geological Survey

RUSSELL A. SCHREINER 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1736

MINERAL RESOURCES OF WILDERNESS STUDY AREAS 

GRAND JUNCTION REGION, COLORADO
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U. S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE: 1987

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425

Denver, CO 80225

Library of Congress Cataloging in Publication Data

Mineral resources of the Dominguez Canyon Wilderness Study Area, Delta, 

Mesa, and Montrose counties, Colorado.

(Mineral resources of wilderness study areas Grand Junction region, 

Colorado ; ch. A) (U.S. Geological Survey bulletin ; 1736)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1736-A

1. Mines and mineral resources Colorado Dominguez Canyon 

Wilderness. 2. Dominguez Canyon Wilderness (Colo.) I. Toth, Margo 

I. II. Series. III. Series: U.S. Geological Survey bulletin ; 1736. 

QE75.B9 no. 1736-A 557.3 s [553'.09788'1] 87-600391 

[TN24.C6]
STUDIES RELATED TO WILDERNESS

Bur°au 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 a part of the 

Dominguez Canyon (CO-070-150/CO-030-363) Wilderness Study Area, Delta, Mesa, 

and Montrose Counties, Colorado.

CONTENTS

Abstract Al 

Summary Al

Introduction A2

Investigations by the U.S. Bureau of Mines A2 

Investigations by the U.S. Geological Survey A2 

Appraisal of identified resources A4 

Mining history A4 

Identified resources A4

Assessment of potential for undiscovered resources A4 

Geology A4

Geologic setting A4 

Description of rock units A5 

Structure A5 

Geochemistry A5 

Methods A5 

Results A6 

Geophysics A7

Gravity and aeromagnetic data A7 

Remote sensing A7 

Mineral and energy resources A8

Metals other than uranium A8 

Oil, gas, and coal A9 

Uranium A9 

Geothermal energy A9 

References cited A9 

Appendix All

FIGURES

1. Map showing mineral resource potential, mines, prospects, and mining claims, 

and location of the Dominguez Canyon Wilderness Study Area A3

2. Complete Bouguer gravity anomaly map of the Dominguez Canyon Wilderness 

Study Area A8

Contents V

MINERAL RESOURCES OF WILDERNESS STUDY AREASGRAND JUNCTION REGION, COLORADO

Mineral Resources of the Dominguez Canyon 

Wilderness Study Area, Delta, Mesa, and 

Montrose Counties, Colorado

By Margo I. Toth, Charles G. Patterson, and

Dolores M. Kulik

U.S. Geological Survey

Russell A. Schreiner 

U.S. Bureau of Mines

ABSTRACT

The Dominguez Canyon Wilderness Study Area 

(CO-070-150/CO-030-363) covers about 75,800 acres in 

west-central Colorado in Delta, Mesa, and Montrose Counties. A joint mineral resource study of 73,568 acres of the 

area was completed in 1983 by the U.S. Geological Survey 

and in 1986 by the U.S. Bureau of Mines. The study area has 

low mineral resource potential for metals, including uranium, 

oil and gas, coal, and geothermal energy. No identified 

resources are present.

SUMMARY

The study area is about 20 mi (miles) southeast of 

Grand Junction and is accessed by Colorado Highway 141 

and U.S. Highway 50. Within the study area, several gently 

dipping plateaus are dissected by Big Dominguez and Little 

Dominguez Creeks, which flow northeastward into the 

Gunnison River. Canyon bottoms in the wilderness study 

area expose Proterozoic (see geologic time chart in the 

Appendix) gneisses, schists, amphibolites, and granites. 

Overlying these crystalline rocks is a sequence of nearly 

flat-lying sandstones, siltstones, conglomerates, mudstones, 

and minor limestones, ranging in age from Triassic to 

Cretaceous.

Part of the Dominguez Canyon study area is in the 

Dominguez mining district; however, no production has 

been recorded for the district. No mineral resources were 

identified in the study area, but small occurrences of copper, 

amethyst, uranium, and shaly coal are present.

As a part of the resource appraisal, 68 streams were 

sampled; at each site a panned concentrate, a fine fraction 

of mud and silt, and a water sample (where water was 

present) were collected. Panned-concentrate samples were 

analyzed for 66 elements, and selected samples were also 

analyzed for gold. The fine-fraction samples were analyzed 

for 46 elements, including uranium. Water samples were 

analyzed for arsenic, selenium, molybdenum, and uranium. 

Crystalline rocks were sampled and analyzed for 66 

elements.

Stream-sediment samples from the wilderness study 

area have low concentrations of elements generally associated with mineralized systems. Except for barium, no 

localized anomalies in any of the elements are present. The 

high concentration of barium is most likely related to barite 

cement in one of the sedimentary formations. Two streams 

showed anomalous concentrations of uranium in their 

waters. These waters were sampled adjacent to the Salt 

Wash Member of the Morrison Formation, which is the likely 

source of the uranium. Rock samples from the wilderness 

study area were also low in elements associated with 

mineralization.

The study area lies on a regional gravity high 

associated with Proterozoic crystalline rocks of the core of 

the Uncompahgre uplift. Southwest of the study area, a 

northwest-trending gradient marks the transition from crystalline rocks of the Uncompahgre uplift to sedimentary rocks. 

This gradient broadens in the southwest corner of the study 

area, and it is possible sedimentary rocks extend beneath 

this area; however, they would lie at depths of 

15,000-20,000 ft (feet).

Dominguez Canyon Wilderness Study Area A1
An east-trending magnetic anomaly occurs over the 

study area and is broken by a low north-south saddle in the 

eastern half of the study area. The saddle suggests a 

variation in the composition of the underlying Proterozoic 

crystalline rocks.

Geologic, geochemical, and geophysical data indicate 

that the Dominguez Canyon Wilderness Study Area has low 

potential for all metals. Anomalous barium concentrations 

are present in stream-sediment concentrate samples, but 

these are probably related to barite cement in the underlying 

Morrison Formation. The wilderness study area lacks host 

rocks and structures favorable for the occurrence of oil, gas, 

and coal. The resource potential for these commodities is 

therefore also low. The nearest known thermal waters are 40 

mi east of the study area. The resource potential for 

geothermal energy in the study area is therefore also low.

The mineral resource potential for uranium is considered to be low because of several factors: location of the 

area outside of a known mineral belt, lack of mines or 

prospects, location within a zone of rocks unfavorable for 

uranium mineralization, and the lack of carbonaceous 

material within the Morrison Formation.

INTRODUCTION

At the request of the U.S. Bureau of Land 

Management, 73,568 acres of the Dominguez Canyon 

Wilderness Study Area were studied by the U.S. 

Geological Survey (USGS) and U.S. Bureau of Mines 

(USBM). In this report, the studied area is called the 

"wilderness study area" or simply "study area." The 

Dominguez Canyon Wilderness Study Area (CO-Q70- 

150/CO-030-363) in Delta, Mesa, and Montrose Counties, Colorado, is about 20 mi southeast of Grand 

Junction between U.S. Highway 50 and Colorado 

Highway 141 (fig. 1). Access is by unpaved roads that 

lead off highways. The Gunnison River is along the 

northeastern boundary of the wilderness study area, and 

Escalante Creek is along the southeastern boundary. 

The small towns of Escalante and Dominguez are just 

east of the wilderness study area, and the larger 

community of Delta is 10 mi to the east along U.S. 

Highway 50.

The Dominguez Canyon Wilderness Study Area 

contains a series of gently northeast-dipping plateaus 

dissected by deep, narrow canyons of the Big Dominguez 

and Little Dominguez Creeks, which drain northeastward into the Gunnison River. Vertical relief in the 

canyons is as much as 3,100 ft. The tops of the plateaus 

have a dense cover of brush and scrub, except for natural 

grass meadows and areas that have been cleared. The 

walls of the canyons are cliffs with no vegetation and (or) 

sparsely vegetated, steep slopes. Elevations range from 

4,700 ft near the Gunnison River on the northeast 

boundary to 8,176 ft on the top of the plateau.

This report presents an evaluation of the mineral 

endowment (identified resources and mineral resource 

potential) of the study area and is the product of several 

separate studies by the U.S. Bureau of Mines and the 

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

(1980), which is shown in the appendix of this report. 

Identified resources are studied by the USBM. Mineral 

resource potential is the likelihood of occurrence of 

undiscovered metals, nonmetals, industrial rocks and 

minerals, and of undiscovered energy sources (coal, oil, 

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

according to the system of Goudarzi (1984) and is shown 

in the Appendix of this report. Undiscovered resources 

are studied by the USGS.

Investigations by the U.S. Bureau of Mines

Published and unpublished literature relating to 

the study area was reviewed by the USBM to obtain 

pertinent information concerning mineral occurrences 

and mining activity. Land-status plats were acquired 

from the Bureau of Land Management State Office, 

Denver, Colorado. Twenty employee-days were spent 

mapping and sampling prospects and mineralized areas. 

Twenty-four samples were taken.

Analytical determinations were made by USBM, 

Reno Research Center, Reno, Nevada, and commercial 

laboratories. Twenty-three samples were analyzed by 

fire assay for gold and silver. Inductively coupled 

plasma-atomic emission spectroscopy was used to 

analyze for barium, copper, lead, molybdenum, vanadium, and zinc. Fluorine was determined by a wet 

chemical method and uranium by fluorimetry. X-ray 

diffraction was used to determine minerals present in a 

bentonitic mudstone. Proximate and ultimate analysisand a heat-value determination were made on a coal 

sample. At least one sample from each prospect was 

analyzed for 40 elements by semiquantitative-opticalemission spectroscopy to determine the presence of any 

unsuspected elements. Results are given in Schreiner 

(1986).

Analytical data and prospect maps are available 

for public inspection at the USBM, Intermountain Field 

Operations Center, Denver Federal Center, Denver, CO 

80225.

Investigations by the U.S. Geological Survey

A mineral resource assessment of the Dominguez 

Canyon Wilderness Study Area by the USGS in June 

and July of 1983 consisted of geologic mapping at a scale 

of 1:24,000, combined with stream-sediment, rock, anc1

A2 Mineral Resources of Wilderness Study Areas Grand Junction Region, Colorado
108°30' 108°15'

38°50' -

38°45'

38°40' 

APPROXIMATE BOUNDARY OF 

THE DOMINGUEZ CANYON 

WILDERNESS STUDY AREA

___ DOMINGUEZ

(CO-070-150/ ^^^ ^MINING

DISTRICT

COPPER, 

BLACKBIRD, 

and SUNDAY 

CLAIMS

GOLDEN 

HORSESHOE

CLAIMS

DELTA COUNTY

MONTROSE COUNTY

EXPLANATION

L/C Geologic terrane with low mineral resource potential for all metals,

oil and gas, coal, geothermal energy, and uranium, with certainty level C

Figure 1. Map showing mineral resource potential, mines, prospects, and mining claims, and location of the Dominguez 

Canyon Wilderness Study Area, Colorado.

water sampling, and subsequent analysis of the samples. 

Further detailed mapping and study of the Salt Wash 

Member of the Morrison Formation was undertaken to 

determine its resource potential for uranium. Color 

aerial photographs were used to supplement the 

geologic mapping and determine regional structures. 

The results of this study are given in detail in Toth and 

others (1983). Parts of this report present a summarized 

version of that study.

Acknowledgments. The geologic mapping, geochemical sampling, interpretation, and manuscript preparation were facilitated by many people in the USGS. 

L.L. Davis, RJ. Stoneman, S.J. Soulliere, A.M. Leibold, 

and M.A. Arnold assisted in geologic mapping. L.R. 

Layman, D.B. Hatfield, L.L. Coles, and K.K. Wise 

assisted in the stream-sediment and water sampling.

Further invaluable support was provided by L.L. 

Jackson and J.L. Seeley of the USGS. D.B. Hatfield and 

J.L. Seeley developed the analytical method for the 

uranium determination in acetic acid extracts, with D.B. 

Hatfield performing the analyses. C.G. Patterson assisted in the uranium evaluation. Thanks go to the

Dominguez Canyon Wilderness Study Area A3
personnel in the U.S. Bureau of Land Management 

office in Grand Junction for their assistance and 

cooperation.

APPRAISAL OF IDENTIFIED RESOURCES

By Russell A. Schreiner, 

U.S. Bureau of Mines

Mining History

Part of the Dominguez Canyon study area is in the 

Dominguez mining district (fig. 1). The area was 

probably first prospected about the same time period as 

the Unaweep mining district approximately 6 mi to the 

northwest, where copper-bearing veins were noted in the 

1870's. The Unaweep district had recorded production 

of 4,650 Ibs (pounds) of copper in 1899 and was 

reported also to have been worked for amethyst 

(Schwochow, 1978). The Dominguez district also contains copper-bearing veins on similar structural trends 

(approximately N. 70° W.) and appears to be an 

extension of the Unaweep district. The Copper, Blackbird, and Sunday claims are located on copper and 

amethyst occurrences in Big Dominguez Creek (fig. 1). 

No production has been recorded for the Dominguez 

mining district.

The Morrison Formation, which contains major 

uranium deposits in the Uravan Mineral Belt approximately 20 mi to the southwest, was explored extensively 

in the study area during the 1950's. Drilling operations 

were reported in the late 1970's, but no significant 

discoveries were made (Toth and others, 1983). Four 

minor uranium occurrences in the Morrison Formation 

and one in the Dakota Sandstone were identified in the 

study area. The Bronco and Golden Horseshoe claims 

are located on or near two of these occurrences (fig. 1).

Identified Resources

No mineral resources were identified, but small 

occurrences of copper, amethyst, uranium, and shaly 

coal exist in the Dominguez Canyon study area.

Copper prospects are located in the Precambrian 

rocks on the Copper, Blackbird, and Sunday claims in 

Big Dominguez Creek (fig. 1). The two principal mineral 

occurrences in the area are present on these claims. One 

occurrence consists of veinlets, as wide as J/2 in. (inch), 

containing chalcopyrite, malachite, azurite, hematite, 

quartz, calcite, and barite within a granite dike. The 

second, a vein 0.8 ft wide, contains chalcopyrite, 

malachite, hematite, calcite, barite, fluorite, and quartz,

including the variety amethyst, within a pegmatite dike. 

The amethyst is of poor clarity and therefore not of 

gemstone quality, but it could be sold as specimens. 

Copper values in chip samples were as high as 3.0 

percent, but gold, lead, molybdenum, silver, and zinc 

values were near or below detection limits of the 

analytical methods. Resources were not identified due to 

the small size of the occurrences and low metal values.

Small, localized uranium concentrations, as much 

as 900 ppm (parts per million), are associated with fossil 

bone fragments and calcareous siltstone and mudstone 

in the Morrison Formation, and a carbonaceous shale in 

the Dakota Sandstone. Five areas emitted radioactivity, 

and the scintillometer measured 50-300 cps (counts per 

second) above a background of 25 cps. Previous 

prospecting in these areas consists of shallow bulldozer 

cuts and pits. No resources were identified because of 

the small size of the occurrences and low metal values.

A 7-ft-thick bed of shaly coal is exposed inside the 

study area near the top of Star Mesa in the Dakota 

Sandstone (fig. 1). A channel sample of the bed, on an 

"as received basis," contained 11.59 percent moisture, 

46.15 percent ash, 19.55 percent volatile matter, 22.71 

percent fixed carbon, 0.22 percent sulfur, and had a heat 

value of 4,383 Btu/lb (British thermal units/pound). 

Calculation of heat value to determine the apparent rank 

(ASTM designation D-388-82, American Society for 

Testing and Materials, 1982) of the sample was made on 

a moist mineral-matter-free basis. The calculated value 

was 8,906 Btu/lb, and the apparent rank of the coal is 

subbituminous C. The high ash content, more than 33 

percent, would exclude it as a resource according to the 

coal resource classification system of the USGS (Wood 

and others, 1983).

Small volumes of sand and gravel occur in the 

wilderness study area but are not considered an 

identified resource.

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Margo I. Toth, Charles G. Patterson, and

Dolores M. Kulik

U.S. Geological Survey

Geology

Geologic Setting

The Dominguez Canyon Wilderness Study Area is 

on the northeast flank of the Uncompahgre Plateau, a 

major landform and structural feature of western

A4 Mineral Resources of Wilderness Study Areas Grand Junction Region, Colorado
Colorado. The plateau is approximately 100 mi long by 

25 mi wide, and trends northwest-southeast from Grand 

Junction and Colorado National Monument to near 

Ridgway and the San Juan Mountains. Structurally, it is 

a large arch with a steeper southwest limb and a gentler 

northeast limb, bordered by the Paradox Basin to the 

southwest, Douglas Arch and Piceance Creek Basin to 

the north and northeast, and the Gunnison Uplift and 

San Juan Volcanic Field to the southeast and south. The 

plateau contains Proterozoic igneous and metamorphic 

rocks overlain by nearly flat lying to monoclinally folded 

sedimentary rocks of Paleozoic and Mesozoic age. 

West-northwest- and northwest-trending, high-angle 

faults are found mostly along the western margin of but 

also within the Uncompahgre Plateau.

Description of Rock Units

A detailed geologic map and description of rock 

units is given in Toth and others (1983). The following is 

a summary of that work.

Proterozoic crystalline rocks crop out in the study 

area only in the deeper canyon bottoms and consist of 

biotite schist, gneiss, hornblende-biotite granite, and 

amphibolite. Diabase dikes crosscut the Proterozoic 

granite in Big Dominguez Creek; the age of the diabase 

is unknown, but Schwochow (1978) indicated that many 

of the diabase dikes in the Unaweep and Dominguez 

districts may be Cambrian, based upon correlation with 

other similar diabase dikes in the Dominguez district. 

Ogden Tweto (oral commun., 1983), however, indicated 

that the diabase dikes in Big Dominguez Creek are 

probably Proterozoic in age, based upon their physical 

similarities to other Proterozoic diabase dikes in the 

area.

Pegmatite dikes crosscut the diabase in a dense 

array in Big Dominguez Creek and range in thickness 

from a few inches to 20 ft, averaging 2 ft in thickness. 

Almost all of the pegmatites strike northwest. Sparse 

copper mineralization occurs along the contacts between 

some of the pegmatite and diabase dikes in Big 

Dominguez Creek. The age of the pegmatites is 

unknown, but they clearly postdate the diabase and 

predate the overlying Triassic sedimentary rocks.

The Triassic Chinle Formation directly overlies the 

crystalline rocks and ranges from 30 to 160 ft thick, 

thinning to the northeast. The formation consists of 

brick-red, interlayered siltstones, shales, and finegrained sandstones.

The Triassic Wingate Sandstone lies unconformably on the Chinle Formation and forms steep, slabby 

cliffs ranging from 80 to 100 ft high. In some places it 

forms arches and in almost all exposures it has vertical 

joints. Overlying the Wingate Sandstone, the Jurassic

Entrada Sandstone is salmon pink and very fine grained; 

the total thickness ranges from 70 to 120 ft.

The Jurassic Wanakah Formation unconformably 

overlies the Entrada Sandstone and consists of thin and 

evenly bedded sandy shale and mudstone with nodular 

limestone and chert layers. The formation commonly 

forms a talus-covered slope and ranges in thickness from 

20 to 45 ft thick.

The Jurassic Morrison Formation overlies the 

Wanakah and is divided into three members in the 

wilderness study area. The lower or Tidwell Member 

consists of about 40-50 ft of flat-bedded, fine-grained 

sandstone, mudstone, and a few nodular limestones. The 

middle or Salt Wash Member consists of fine- to 

medium-grained sandstone; mudstone with scattered, 

thin limestone beds: and white, medium- to fine-grained 

eolian sandstone at the base. The lower half of the Salt 

Wash Member has a distinct gray-green color. The 

member ranges from 285 to 425 ft thick, thickening to 

the west, and generally forms ledges; it is the uraniumbearing unit of the Morrison Formation. The overlying 

upper or Brushy Basin Member contains red, green, and 

buff variegated bentonitic shales and mudstones with 

interbeddcd red, fine-grained sandstones and conglomerate. The Brushy Basin Member ranges from 285 to 

approximately 400 ft thick and generally forms gentle 

slopes.

The Cretaceous Burro Canyon Formation overlies 

the Morrison Formation and consists of fine-grained, 

well-indurated sandstones that are locally crossbedded, 

and crossbedded conglomerate with interbedded green 

and purplish shale. Conformably overlying the Burro 

Canyon Formation, the Cretaceous Dakota Sandstone 

consists of sandstone and conglomerate with interbedded carbonaceous shale and impure coal. The Dakota 

Sandstone and the Burro Canyon Formation together 

are at least 140 ft thick in the study area.

Structure

The major structural features in the wilderness 

study area are two northwest-trending, high-angle, 

normal faults that may have a small component of 

left-lateral, strike-slip movement. A major northwesttrending fault, the north side down dropped, is just to the 

east of the study area. The sedimentary rocks in the 

study area strike northwest and are nearly flat-lying with 

a maximum clip of 8° to the northeast. Where foliation in 

the Proterozoic rock is evident, the rocks show variable 

strikes and dips.

Geochemistry

Methods

The geochemical survey included sampling stream 

sediments, water, and rocks for chemical analysis.

Dominguez Canyon Wilderness Study Area A5
Detailed methods of analysis are in Toth and others 

(1983), and sample localities are also given in that 

report.

Sixty-eight streams in the study area were sampled, 

and two types of stream sediments were collected at each 

sampling locality. Panned-concentrate samples were 

collected to analyze for the heavier metallic elements 

such as copper, lead, and zinc, and fine fractions of mud 

and clay were collected to analyze for metals such as 

molybdenum and uranium, which typically adhere to 

clays. When water was present, it was also collected for 

analysis. Conductivity, temperature, and acidity of the 

water were also measured at each site.

Rock samples were collected at two types of 

localities within the wilderness study area. The first were 

any localities containing mineralized or altered rock, or 

areas with characteristics indicative of related mineralized rock. The second were localities with outcrops of 

Proterozoic crystalline rocks. These were sampled at 

random intervals to establish background values of the 

various elements and to look for any trends or values 

that indicate presence of mineralized rock.

Panned-concentrate samples were analyzed semiquantitatively for 66 elements by optical-emission 

spectrography (Myers and others, 1961). Panned concentrates were additionally analyzed for gold by atomicabsorption spectroscopy (Thompson and others, 1968). 

Ten grams of sample are normally used in this 

procedure, with a resultant limit of determination of 0.1 

ppm gold. When only smaller amounts of sample were 

available, the limit of determination was increased 

proportionately.

The fine fraction of the stream-sediment samples 

was sieved through a minus-100 mesh (0.0059 in.) screen 

and analyzed for 45 elements using inductively coupled 

plasma atomic emission spectroscopy (ICP) (Taggart 

and others, 1981). Uranium in the fine fraction of the 

stream sediments was determined by fluorimetry and 

had a determination limit of 0.2 ppm.

Rock samples were crushed, pulverized, and 

analyzed by semiquantitative emission spectrography for 

66 elements, similar to the method used for panned 

concentrates as discussed above.

The water samples were analyzed for arsenic, 

selenium, molybdenum, and uranium. Arsenic and 

selenium were determined using procedures of Crock 

and Lichte (1982). Samples were analyzed for molybdenum by ICP methods, and uranium in the waters was 

determined by fluorescence methods (Thatcher and 

Janzer, 1977).

The analyses were done by N.M. Conklin and D.B. 

Hatfield under project leader J.L. Seeley. Albert Yang of 

the USGS did the uranium analysis of the waters.

Results

The panned-concentrate samples from the Dominguez Canyon Wilderness Study Area were analyzed 

for 66 elements but only showed detectable amounts of 

boron, barium, cobalt, chromium, copper, nickel, niobium, lead, scandium, strontium, vanadium, yttrium, and 

zirconium, mainly in low concentrations near the 

detection limits. The analytical data for each of these 

elements were composited into histograms to look for 

anomalous concentrations. Except for barium and 

possibly zirconium, none of the elements was present in 

anomalous concentration. The elements were in general 

characterized by a very wide range of low concentrations, 

possibly reflecting the high variability in the lithologies of 

the source rocks.

The concentration of barium in the panned 

concentrates ranged from 1,500 ppm to > 100,000 ppm, 

with a median value of 20,000 ppm. Two samples along 

the east and northeast sides of the wilderness study area 

contained 100,000 ppm barium and were collected 

where the streams cut through outcrop of Wingate 

Sandstone and Morrison Formation. A third sample 

from the northeast side of the wilderness study area 

contained > 100,000 ppm barium and was collected 

where the stream cut through outcrop of Wingate 

Sandstone. Barite was identified in the panned concentrates by visual examination and by X-ray diffraction.

Because the streams drained an area with a variety 

of rock types, it is not possible to identify the source of 

the barium. However, because the samples were 

collected above outcrops of the Chinle Formation, the 

source of the barium must also be above the Chinle. 

Barite could be contained in barite cement, barite 

nodules, or barite veinlets. Fred Peterson (oral commun., 1983) stated that the Salt Wash Member of the 

Morrison locally contains a barite cement, so this 

member may be a source of the barium.

Two samples from the wilderness study area 

contained 20,000 ppm zirconium in the panned concentrates. The source for the high zirconium is probably 

zircon in the Proterozoic crystalline rocks.

Panned-concentrate samples from drainages with 

substantial amounts of Proterozoic outcrop were also 

analyzed for gold. No gold was detected in any of the 

samples (detection limit 0.1 ppm).

The fine fraction of the stream sediments had no 

anomalous concentrations of any elements. Very few of 

ihe samples contained concentrations of elements above 

the detection limits. Uranium values ranged from <0.2 

to 0.5 ppm, with almost three-fourths of all values being 

<0.2 ppm.

Water samples from the Dominguez Canyon 

Wilderness Study Area showed no anomalous concentrations of the analyzed elements, except for two

A6 Mineral Resources of Wilderness Study Areas Grand Junction Region, Colorado
samples, which contained 48 and 34 ppb (parts per 

billion) uranium/conductivity X 1000, respectively. 

These waters were sampled adjacent to the Salt Wash 

Member of the Morrison Formation, which was a likely 

source for the uranium.

The rock samples from the wilderness study area 

are low in elements associated with mineralization. Of 

the elements looked for in the rocks, only barium, 

beryllium, cobalt, chromium, copper, lanthanum, lead, 

scandium, strontium, vanadium, yttrium, and zirconium 

were present, and most of these were in low concentrations near the detection limit for each element.

Geophysics

Gravity and Aeromagnetic Data

Gravity and aeromagnetic studies were undertaken as part of the mineral resource evaluation of the 

Dominguez Canyon Wilderness Study Area. These 

studies provide information on the subsurface distribution of rock masses and the structural framework.

The gravity data were obtained in and adjacent to 

the study area in 1986 and 1987 and were supplemented 

by data maintained in the files of the Defense Mapping 

Agency of the U.S. Department of Defense. Stations 

measured in this study were established using the 

Worden gravimeter W-1771 . The data were tied to the 

International Gravity Standardization Net 1971 (U.S. 

Defense Mapping Agency, Aerospace Center, 1974) at 

base station ACIC 4023-1 at Delta, Colo. Station 

elevations were obtained from benchmarks, spot elevations, and estimates from topographic maps at a scale of 

1:24,000 and are accurate to ±20 ft. The error in the 

Bouguer anomaly is less than 1.2 mGal (milligals) for 

errors in elevation control. Bouguer anomaly values 

were computed using the 1967 gravity formula (International Association of Geodesy, 1967) and a reduction 

density of 2.67 g/cm3 (grams/cubic centimeter). Mathematical formulas are given in Cordell and others (1982). 

Terrain corrections were made by computer for a 

distance of 100 mi from the station using the method of 

Plouff (1977). The data are shown on figure 2 as a 

complete Bouguer anomaly map with a contour interval 

of 5 mGal.

A regional gravity high is associated with Proterozoic crystalline rocks of the core of the Uncompahgre

lTJse of brand names in this report is for descriptive purposes 

only and does not constitute endorsement by the U.S. Geological 

Survey.

uplift. Case (1966) attributed the large regional anomaly 

of over 50 mGal to a combination of structural relief of 

16,000 to 19,000 ft on the Proterozoic rocks, the 

northeastward wcdgeout of Paleozoic sedimentary rocks, 

and density variations of the Proterozoic rocks. A 

northwest-trending gradient in the southwest corner of 

the map area marks the transition from crystalline rocks 

in the uplift to sedimentary rocks of the Paradox Basin 

southwest of the map area. Data from two wells 

approximately 50 mi northwest of the study area, the 

Mobil-American Petrofina Elba Flats Unit No. 1-30 and 

the Mobil No. 1 McCormick Federal "C", along with 

seismic data, were used to estimate the clip of the fault 

plane beneath the uplift at about 30° to the northeast, 

overhanging the sedimentary rocks in the Paradox Basin 

(Frahme and Vaughn, 1983). The northwest-trending 

gravity gradient between the crystalline rocks of the 

uplift and the sedimentary rocks of the basin is located 

between the wells. Well control data and preliminary 

gravity models suggest that underlying sedimentary 

rocks of the Paradox Basin do not extend northeast of 

the area bounded by the gradient. The gradient broadens 

across the southwest corner of the study area, and it is 

possible that sedimentary rocks with lower relative 

density extend beneath this area (A on fig. 2); if so, they 

would lie at depths of at least 15,000-20,000 ft if the 

fault bounding the uplift is projected at 30°. A northeast 

trend, apparent in the gravity data at the southeast 

margin of the study area, extends at least 25 mi to the 

northeast and about the same distance to the southwest 

near where the axis of the uplift shows a change in 

direction of plunge (fig. 2). The gravity trend and the 

warp in the uplift are probably associated with a warp or 

ramp in the underlying crystalline basement rocks. 

Gravity measurements were obtained on widely spaced 

traverses, and no small features are apparent in the data. 

A relatively high east-trending magnetic anomaly 

(U.S. Department of Energy, 1983) occurs over the 

study area and extends approximately 10 mi to the east 

and 40 mi to the west. The anomaly is broken by a low 

saddle less than 30 gammas in amplitude which trends 

north-south through the eastern half of the study area. A 

nosing of the contours of the regional gravity high occurs 

in the same area (B on fig. 2). The magnetic saddle and 

gravity nose suggest a variation in composition of the 

Precambrian rocks as discussed by Case (1966) in the 

northwestern Uncompahgre Plateau.

Remote Sensing

A remote sensing study of the Dominguez Canyon 

Wilderness Study Area was based on Landsat 2 

Multispectral Scanner imagery and is given in detail in 

Lee (1987). These data were processed and analyzed for 

lineaments and for limonite anomalies that might relate

Dominguez Canyon Wilderness Study Area A7
ftfff-W

APPROXIMATE BOUNDARY 

OF THE DOMINGUEZ CANYON 

WILDERNESS STUDY AREA

38°30'

EXPLANATION

 Gravity station location 

 < > Axis of Uncompahgre Uplift - Arrows show direction of plunge

Figure 2. Complete Bouguer gravity anomaly map of the Dominguez Canyon Wilderness Study Area. Letters are referred to 

in text. Contour interval 5 mGal; hachures indicate gravity low.

to mineralization, hydrothermal alteration, migrating 

hydrocarbons, or uranium.

From the lineament analysis, a major basement 

fault is interpreted to the east of the wilderness study 

area, with probable down-to-the-northeast displacement. 

No limonite anomalies of interest are apparent in the 

imagery, but the narrow outcrop widths compared with 

the image resolution suggest that any such anomalies 

probably would go undetected.

Mineral and Energy Resources

Metals Other Than Uranium

Geologic, geochemical, and geophysical data indicate that the Dominguez Canyon Wilderness Study Area 

has low potential for all metals, with certainty level C. 

Anomalous barium concentrations are present in 

panned-concentrate samples and are probably related to

A8 Mineral Resources of Wilderness Study Areas Grand Junction Region, Colorado
barite cement in the underlying Morrison Formation; 

barite does not constitute a resource. Although mineralized rock is present at two locations in Big Dominguez 

Creek in Proterozoic crystalline rock, the extent of 

mineralization is extremely local.

Oil, Gas, and Coal

The Dominguez Canyon Wilderness Study Area 

lacks host rocks and structures favorable for the 

occurrence of oil, gas, and coal resources. The total 

sedimentary rock section is exposed, eliminating sealed 

structural or stratigraphic traps. Although the gravity 

data indicate that sedimentary rocks could underlie the 

crystalline rocks at the southwestern part of the study 

area, the sedimentary rocks would be at a depth of 

15,000-20,000 ft. No oil and gas leases are present in the 

wilderness study area (Schreiner, 1986). Spencer (1983) 

rated the study area as having zero to low hydrocarbon 

potential. Coal beds in the Dakota Sandstone are thin, 

discontinuous, and have a high ash content. The 

resource potential for oil, gas, and coal is therefore low, 

with certainty level C.

Uranium

Isopach data for the Salt Wash Member of the 

Morrison Formation in the Dominguez Canyon Wilderness Study Area reveal a trend shown first by Craig and 

others (1955) and by Mullens and Freeman (1957). 

Total thickness and limestone thickness outline a trough 

or synclinal feature oriented approximately transverse to 

ancient flow directions in the Salt Wash Member. This 

may be due to deflection and ponding of Salt Wash 

paleodrainages by a remnant of the ancestral Uncompahgre highland. Fred Peterson (oral commun., 1983) 

thought that the downstream edge of the cross-trending 

trough is the most favorable location for generation of 

uranium-trapping humate substances generated in anoxic, swampy lakes, now represented by gray mudstones. 

A dolomite, rather than calcite, cement that is highly 

persistent in the Salt Wash Member throughout the 

Dominguez Canyon Wilderness Study Area at approximately 75 ft below the top of the uppermost rim 

sandstone coincides with a level of very sparse 

carbonaceous material. Intersections of carbonaceous 

material with areas of high concentrations of dolomite 

cement are considered favorable indicators of mineralization (Northrop, 1982). Slight uranium mineralization 

was observed in and near the carbonaceous material. 

Two factors, however, argue against larger deposits. 

First, erosion by the Gunnison River may have removed 

the most favorable rocks; and second, the extreme 

scarcity of carbonaceous debris and favorable gray

mudstones in the upper or lower rims of the Salt Wash 

diminished opportunities for uranium-bearing solutions 

to precipitate the uranium.

Anomalous uranium concentrations were detected 

in water samples collected for this study and by the 

National Uranium Resource Evaluation investigation 

(Campbell and others, 1980). Field mapping revealed 

these to be associated with a northwest-trending fault 

system. Because the Salt Wash is known to contain 

widespread but extremely low-grade amounts of uranium, it is likely that the anomaly is due to leaching and 

secondary concentration of uranium along the fault, and 

does not necessarily indicate the presence of a resource.

The mineral resource potential for uranium in the 

Dominguez Canyon Wilderness Study Area is considered low, with certainty level C. In summary, this is 

because of extremely sparse carbonaceous material, lack 

of favorable gray mudstones, location outside of a known 

mineral belt, lack of uranium mines or prospects, and 

location in a zone of unfavorable facies for these types of 

deposits.

Geothermal Energy

The nearest known thermal waters are about 40 mi 

to the east, between Hotchkiss and Paonia (Pearl, 1980). 

No warm springs were observed in the wilderness study 

area, and no known geothermal sources are present. The 

entire study area therefore has low resource potential 

for geothermal energy, with certainty level C.

REFERENCES CITED

American Society for Testing and Materials, 1982, Standard 

classification of coals by rank (ASTM Designation 

D-388-82): 1982 Annual book of ASTM Standards, pt. 

26, p. 242-246.

Campbell, JA., Franczyk, K.J., Lupe, R.D., and Peterson, 

Fred, 1980, National uranium resource evaluation, 

Moab quadrangle, Colorado and Utah: U.S. Department 

of Energy Report PGJ/F-056(82), 68 p. text, 855 p. 

microfiche.

Case, J.E., 1966, Geophysical anomalies over Precambrian 

rocks, northwestern Uncompahgre Plateau, Utah and 

Colorado: Amerian Association of Petroleum Geologists 

Bulletin, v. 50, no. 7, p. 1423-1443.

Cordell, Lindreth, Keller, G.R., and Hildenbrand, T.G., 1982, 

Bouguer gravity map of the Rio Grande Rift, Colorado, 

New Mexico, and Texas: U.S. Geological Survey 

Geophysical Investigations Map GP-949, scale 

1:1,000,000.

Craig, L.C., Holmes, C.N., Cadigan, R.A., Freeman, V.L., 

Mullens, T.E., and Weir, G.W., 1955, Stratigraphy of the 

Morrison and related formations, Colorado Plateau 

Region, a preliminary report: U.S. Geological Survey 

Bulletin 1009-E, p. 125-168.

Dominguez Canyon Wilderness Study Area A9
Crock, J.G., and Lichte, F.E., 1982, An improved method for 

the determination of trace levels of arsenic and antimony 

in geological materials by automated hydride generationatomic absorption spectroscopy: Analytica Chimica 

Acta, v. 144, p. 223-233.

Frahme, C.W., and Vaughn, E.B., 1983, Paleozoic geology and 

seismic stratigraphy of the northern Uncompahgre front, 

Grand County, Utah, in Lowell, J.D., and Gries, R., eds., 

Rocky Mountain foreland basin and uplifts: Rocky 

Mountain Association of Geologists, p. 201-218.

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

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

Survey Open-File Report 84-787, 42 p.

International Association of Geodesy, 1967, Geodetic Reference System, 1967: International Association of Geodesy 

Special Publication No. 3, 116 p.

Lee, Keenan, 1987, Remote sensing study in support of 

mineral resource appraisal of the Dominguez Canyon 

Wilderness Study Area, Montrose, Mesa, and Delta 

Counties, Colorado: U.S. Geological Survey Open-File 

Report 87-421.

Mullens, T.G., and Freeman, V.L., 1957, Lithofacies of the Salt 

Wash Member of the Morrison Formation, Colorado 

Plateau: Geological Society of America Bulletin, v. 68, 

no. 4, p. 505-526.

Myers, A.T., Havens, R.A., and Dunton, P.J., 1961, A 

spectrochemical method for the semiquantitative analysis of rocks, minerals, and ores: U.S. Geological Survey 

Bulletin 1084-1, p. 207-229.

Northrop, H.R., 1982, Origin of the tabular-type vanadiumuranium deposits in the Henry structural basin, Utah: 

Golden, Colorado School of Mines, Ph.D. thesis, 340 p.

Pearl, R.H., 1980, Geothermal resources of Colorado: Colorado Geological Survey Map Series 14, scale 1:500,000.

Plouff, Donald, 1977, Preliminary documentation for a 

FORTRAN program to compute gravity terrain corrections based on topography digitized on a geographic 

grid: U.S. Geological Survey Open-File Report 77-535.

Schwochow, S.D., 1978, Mineral resources survey of Mesa 

County a model study: Colorado Geological Survey, 

Department of Natural Resources, series 2, 110 p.

Spencer, C.W., 1983, Petroleum potential of wilderness lands 

in Colorado, in Miller, B.M., ed., Petroleum potential of 

wilderness lands in the Western United States: U.S. 

Geological Survey Circular 902-A-P, p. E1-E8.

Schreiner, R.A., 1986, Mineral investigation of a part of the 

Dominguez Canyon Wilderness Study Area (CO070-150), Delta, Mesa, and Montrose Counties, Colorado: U.S. Bureau of Mines Open File Report MLA 

65-86, 13 p.

Taggart, J.E., Lichte, F.E., and Wahlberg, J.S., 1981, Methods 

of analysis of samples using X-ray fluorescence and 

induction coupled plasma spectroscopy: U.S. Geological 

Survey Professional Paper 1250, p. 683-687.

Thatcher, L.L., and Janzer, V.J., 1977, Methods for determination of radioactive substances in water and fluvial 

sediments, U.S. Geological Survey Techniques of water 

resources investigations TWI 05 A5, 95 p.

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

1968, Rapid analysis for gold in geological materials: 

U.S. Geological Survey Professional Paper 600-B, p. 

130-132.

Toth, M.I., Davis, L.L., Patterson, C.G., and Seeley, J.L., 1983, 

Geology and mineral resource potential of the Dominguez Canyon Wilderness Study Area, Delta, Mesa, 

and Montrose Counties, Colorado: U.S. Geological 

Survey Open-File Report 83-797, 44 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.

U.S. Defense Mapping Agency, Aerospace Center, 1974, 

World Relative Gravity Reference Network, North 

America, Part 2: Defense Mapping Agency Aerospace 

Center Reference Publication 25, with supplement 

updating Gravity Standardization Net, 1971, 1,635 p.

U.S. Department of Energy, 1983, Moab Quadrangle: Residual Intensity Magnetic Anomaly Contour Map, GJM 

406, pi. 4.

Wood, G.H., Kehn, T.M., Carter, M.D., and Culbertson, W.C., 

1983, Coal resource classification system of the U.S. 

Geological Survey: U.S. Geological Survey Circular 891, 

65 p.

A10 Mineral Resources of Wilderness Study Areas Grand Junction Region, Colorado
APPENDIX
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

Definitions of Mineral Resource Potential

LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is unlikely. This broad 

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

or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations 

of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of 

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

HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of 

data indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit 

models indicating presence of resources, and where evidence indicates that mineral concentration has 

taken place. Assignment of high resource potential to an area requires some positive knowledge that 

mineral-forming processes have been active in at least part of the area.

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

moderate, or high levels of resource potential.

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

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B 

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D 

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

a: 

D 

O CO

B C 

LEVEL OF CERTAINTY

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

B. Available information suggests the level of mineral resource potential.

C. Available information gives a good indication of the level of mineral resource potential.

D. Available information clearly defines the level of mineral resource potential.

Abstracted with minor modifications from:

Taylor, R. B., and Steven, T. A., 1983, Definition of mineral resource potential: Economic Geology,

v. 78, no. 6, p. 1268-1270. 

Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential

of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p.

40-42. 

Goudarzi, G. H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S.

Geological Survey Open-File Report 84-0787, p. 7, 8.
RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

Inferred

UNDISCOVERED RESOURCES

Hypothetical

Probability Range 

'(or)'

Speculative

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

Reserves Inferred Reserves

Marginal Reserves

Demonstrated 

Subeconomic Resources

Inferred 

Marginal Reserves

Inferred

Subeconomic

Resources

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

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

minerals: U. S. Geological Survey Circular 831, p. 5.
GEOLOGIC TIME CHART 

Terms and boundary ages used in this report

EON

Phanerozoic

Proterozoic

Archean 

pre-Ar

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

;hean2

PERIOD

Quate

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 _3B007 -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

 -

BOUNDARY AGE 

IN 

MILLION YEARS

- 0.010

- 1.7

- 5

- 24 

10

- 55

- 66

- 96

1 *5t>

-~ 240

- 290 

-~ 330

oen

- 410

- 500 

-~ 570 1

- 900 

- 1600

- 2500

- 3000 

- 3400 *

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

1 Informal time term without specific rank.

V U.S. GOVERNMENT PRINTING OFFICE:1987- 573-047/66017