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COVER PHOTOGRAPHS

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1. Asbestos ore

2. Lead ore, Balmat mine, N. Y.

3. Chromite, chromium ore, Washington

4. Zinc ore, Friedensville, Pa.

5. Banded iron-formation. Palmer, 

Mich.

6. Ribbon asbestos ore, Quebec. Canada

7. Manganese ore, banded 

rhodochrosite

8. Aluminum ore, bauxite, Georgia

9. Native copper ore, Keweenawan 

Peninsula, Mich.

10. Porphyry molybdenum ore, Colorado

11. Zinc ore, Edwards, N. Y.

12. Manganese nodules, ocean floor

13. Botryoidal f luorite ore, 

Poncha Springs, Colo. 

14. Tungsten ore. North Carolina
Uranium in Phosphate Rock

By JAMES B. CATHCART

and

Uranium and Vanadium Resources 

in the Moab 1° x 2° Quadrangle, 

Utah and Colorado

By A. P. BUTLER, JR., and R. P. FISCHER

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 988-A, B

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director
APPRAISAL OF MINERAL RESOURCES

Continuing appraisal of the mineral resources of the United States is conducted by 

the U.S. Geological Survey in accordance with the provisions of the Mining and 

Minerals Policy Act of 1970 (Public Law 91-631, Dec. 31, 1970). Total resources for 

purposes of these appraisal estimates includes currently minable resources (reserves) as 

well as those resources not yet discovered or not currently profitable to mine.

The mining of mineral deposits, once discovered, depends on geologic, economic, 

and technologic factors; however, identification of many deposits yet to be discovered, 

owing to incomplete knowledge of their distribution in the earth's crust, depends 

greatly on geologic availablity and man's ingenuity. Consequently, appraisal of 

mineral resources results in approximations, subject to constant change as known 

deposits are depleted, new deposits are found, new extractive technology and uses are 

developed, and new geologic knowledge and theories indicate new areas favorable for 

exploration.

This Professional Paper discusses aspects of the geology of uranium as a framework 

for appraising resources of this commodity in the light of today's technology, 

economics, and geologic knowledge.

Other Geological Survey publications relating to the appraisal of resources of 

specific mineral commodities include the following:

Professional Paper 820 "United States Mineral Resources"

Professional Paper 907 "Geology and Resources of Copper"

Professional Paper 926 "Geology and Resources of Vanadium"

Professional Paper 933 "Geology and Resources of Fluorine in the United States"

Professional Paper 959 "Geology and Resources of Titanium in the United States"

Uranium in Phosphate Rock

By JAMES B. CATHCART

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 988-A

A study of the distribution 

and occurrence of uranium in 

phosphate deposits of the world

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Cathcart, James Bachelder, 1917-

Uranium in phosphate rock.

(Geology and resources of uranium deposits)

(U.S. Geological Survey Professional Paper 988-A)

Bibliography: p. 5

Supt. of Docs, no.: I 19.16:988-A

1. Uranium ores. 2. Phosphate rock.

I. Title. II. Series. III. Series: United States Geological Survey Professional Paper 988-A.

TN490.U7C33 553'.493 77-608358

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-03097-7
CONTENTS

Page

Abstract ............................................................................................. Al

Introduction ......................................................................................... 1

Guano and guano-derived deposits ...................................................... 1

Igneous apatite deposits ....................................................................... 2

Marine phosphorite ............................................................................. 2

Secondary deposits .............................................................................. 3

Page

Other deposits ..................................................................................... A4

Lake beds ..................................................................................... 4

Offshore deposits .......................................................................... 4

Phosphate resources ............................................................................ 5

Selected references ............................................................................... 5

TABLES

Page

TABLE 1. Guano and guano-derived phosphate: reserves, production, and uranium content ........................................................... A2

2. Igneous apatite: reserves, production, and uranium content .............................................................................................. 2

3. Marine phosphorite: reserves, production, and uranium content ....................................................................................... 3

4. Secondary phosphate deposits: reserves, production, uranium content .............................................................................. 4

5. Other deposits: reserves, production, uranium content ....................................................................................................... 5

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

URANIUM IN PHOSPHATE ROCK

By JAMES B. CATHCART

ABSTRACT

Uranium is a trace constituent of all apatites in amounts that typically 

range from < 0.001 to 0.003 percent for guano and guano-derived deposits, 

from 0.001 to 0.010 percent for igneous apatites, and from 0.005 to 0.030 

percent for marine phosphorites. Uranium may be enriched to as much as 

0.05 percent in phosphorites reworked in a marine environment, and 

isolated bones and concretions may contain as much as 0.8 percent uranium 

as a result of enrichment by ground water.

Uranium as U(IV) replaces calcium in the apatite structure or may be 

absorbed as the uranyl ion on apatite crystal structures. Uranium is readily 

removed from apatite by weathering. Enrichment of phosphate after 

deposition may be entirely residual, as in the case of the brown rock deposits 

of Tennessee, or uranium may be added, as in the case of the lateritic 

weathering of the deposits in Florida.

Uranium has been recovered as a byproduct of the manufacture of 

phosphoric acid by the wet process. In 1972, about 15 million tonnes (metric 

tons) of phosphate rock was used to make phosphoric acid in the United 

States. This phosphoric acid probably contained about 1,500 tonnes of 

uranium. It seems likely that tonnages of uranium in phosphoric acid will 

reach 3,000 tonnes per year within the next 25 years because of the increased 

demand for phosphatic fertilizers and increases in the amount of phosphate 

rock used to make phosphoric acid. About twice this amount might be 

present worldwide. Thus, marine phosphorites are a significant source of 

uranium for the future.

INTRODUCTION

Uranium is present as a trace constituent in all apatites, in 

amounts that typically range from 0.003 to 0.030 percent. 

Strutt (1908) first discovered that phosphatic rocks and 

fossil bones are appreciably more radioactive than the 

average rocks of the crust. His data showing that certain 

British phosphorites and fossil bones contain from 0.005 to 

0.015 percent U308 were remarkably accurate. R.C. Wells of 

the U.S. Geological Survey (unpublished data) noted in the 

late 1920's that a shark's tooth from the Pliocene of Florida 

contained 0.021 percent U the first record of the uranium 

in the phosphate deposits of Florida. Hebert( 1947) reported 

that the discovery of uranium in the Cretaceous and Eocene 

phosphorites of Algeria was made in 1924. The first mention 

of uranium in the Cretaceous and Tertiary phosphate 

deposits of the U.S.S.R. was published by Rusakov (1933).

The developments of uses of uranium as an energy source 

provided the impetus for research into all potential sources, 

and apatites were tested for uranium in all parts of the world.

Detailed studies of uranium in phosphate have been made by 

Altschuler (1973), Altschuler, Clarke, and Young (1958), 

Altschuler, Jaffe, and Cuttitta (1956), Cathcart (1956), 

Davidson and Atkin (1953), McKelvey (1956), McKelvey 

and Carswell (1956), McKelvey, Everhart, and Garrels 

(1955), and Sheldon (1959). Much of the data presented in 

this paper is derived from these works, and each of them 

contains an extensive bibliography.

The tables that accompany this report relate only reserve 

data. Reserves are defined as identified mineral deposits 

whose grade and tonnage are reasonably evaluated, but 

which may not be economically recoverable under present 

conditions. All reserves are in tonnes and consist of material 

that contains at least 24 percent ?2O5.

Phosphorus is found in minable concentration in three 

environments as guano or in deposits derived from guano, 

as igneous apatite, as marine phosphate deposits and in 

secondary deposits formed from each of these by weathering.

GUANO AND GUANO-DERIVED DEPOSITS

Guano deposits are formed from the excreta of sea birds at 

the surface and of bats in caves. Guano-derived deposits are 

formed when the soluble phosphate in guano is dissolved by 

ground water and reacts with the underlying rocks. Apatite 

is formed when the underlying rock is limestone, and iron 

and aluminum phosphates are formed when igneous rocks 

underlie the guano.

About 5 percent of the world's production of phosphate is 

from guano-derived deposits, and a very small amount is 

from guano deposits (table 1). Guano contains from less 

than 0.001 to 0.003 percent U (Altschuler and others, 1958), 

but gauno-derived deposits contain as much as 0.008 percent 

U (Davidson and Atkin, 1953). Recent analytical data (U.S. 

Geol. Survey Denver laboratory: E. J. Fennelly and Johnnie 

Gardner, analysts) show that guano-derived phosphate 

samples from Curacao contain 0.002 percent U, and that 

samples from Nauru contain 0.005 percent. The samples 

with higher uranium contents (0.005-0.008 percent) are also 

high in fluorine; the phosphate mineral is a carbonate

Al
A2 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

fluorapatite, rather than a hydroxyapatite. The samples are 

from tidal zones where fluorine and uranium were added 

from seawater.

TABLE 1. Guano and guano-derived phosphate: reserves, production, and 

uranium content

Location Reserves 

(tonnes)

Production 

(tonnes/yr)

Uranium content 

(percent)

Bird guano (surface)

Peru (Pacific Coast) . 

Chile (Pacific Coast)

Limited, renewable 

Small ....................

O.lxlO" 

.01x10"

< 0.001-0.003 

<.001-.003

Bat guano (cave)

Mexico, Phillipines, 

and Africa.

Very small; total 

is about 3xl06 .

0.02-0.04x10" < 0.001-0.003

Guano-derived calcium phosphate minerals

100x10"

30x10"

10x10"

10x10"

30x10"

... ' 2x10"

7xl06

002

Guano-derived iron and aluminum phosphate minerals'

Malpelo Island, Colombia ... 

Trauira Island, Brazil ..........

Saldanha Bay, South Africa 

Kito-Daito-Jima, Ryukyu 

Islands.

0.4xl06 None ................... No data.

11x10" do ................ Do.

.3x10" do ................ Do.

2x10" do ................ Do.

'Only the largest of the aluminum and iron phosphate deposits are listed. Others are known, but 

reserves are limited and none are being mined today. The deposits of Kito-Daito-Jima have been 

mined. Uranium contents of these deposits are not known, but are thought to be small, of the order of 

magnitude of 0.001 percent.

IGNEOUS APATITE DEPOSITS

Apatite deposits of igneous origin occur as intrusive 

masses, as veins, as marginal differentiates, or as pegmatites. 

The largest deposits are intrusive masses associated with 

alkalic rocks, such carbonatite, nepheline syenite, pyroxenite, and ijolite.

The apatite mineral, a fluorapatite, ranges in amount from 

a few percent as an accessory mineral to 80 percent in some 

pipes and sheets. The apatitic masses range in size from a few 

square meters to tens of square kilometers and the amounts 

of apatite present range from a few tonnes to hundreds of 

million of tonnes. The largest deposits include the Kola 

Peninsula (U.S.S.R.), Laokay (North Vietman), Palabora 

and eastern Uganda (Africa), and Araxa (Brazil). In 1970, 

about 17 percent of the world's production of phosphate 

came from igneous apatite deposits, and about 80 percent of 

this production was from the deposits of the Kola Peninsula.

The uranium content of primary fluorapatite in igneous 

rocks typically ranges from 0.001 to 0.010 percent (Altshuler 

and others, 1958; Davidson and Atkin, 1953), although 

individual samples may contain as much as 0.079 percent U

(table 2). Thorium is not usually present, except in very 

minute amounts; however, an apatite sample from a 

pegmatite near Bahia, Brazil, contained 0.005 percent U and 

1,500 ppm Th (Thorium analysis by Nancy Conklin, and 

uranium analysis by E. J. Fennelly, U.S. Geol. Survey).

TABLE 2. Igneous apatite: reserves, production, and uranium content

[Leaders (...) indicate no data available]

Location

Kola Peninsula, U.S.S.R. ........

Dorowa, Southern Rhodesia ...

Mineville district, 

New York, U.S.A.

Reserves' 

(tonnes)

2x10' 

.1x10'

.4x10'

.1x10"

.15x10'

.1x10" 

.2X109

.02x1 09

Very small

Production2 

(tonnes/ yr)

10x10" 

1x10"

1x10"

.4x10"

.2x10"

.1x10" 

.01x10"

.01x10"

None

Uranium content3 

(percent)

0.001-0.003

.003-.004

4 .020

5 .OI3-.030

.079

'In metric tons of total rock containing more than 10 percent 

2 ln metric tons of apatite concentrate containing at least 25 percent 

'In percent, of the apatite concentrate.

4One sample, from Araxa. A sample of apatite from a pegmatite in Bahia. Brazil, contained 0.010 

percent eU, 0.005 percent U, and 1,500 ppm Th. 

'Percent ^O, from Davidson and Atkin (1953).

MARINE PHOSPHORITE

Marine phosphorite deposits are known throughout the 

world and occur in all geologic ages, from Precambrian to 

Holocene. The richest of these deposits are formed in basins, 

in warm latitudes, in areas of upwelling water, and away 

from abundant sources of clastic material. Some deposits are 

very large reserves in an individual deposit may be billions 

of tonnes; total reserves aggregate scores of billions of 

tonnes, and resources are proportionately larger (Cathcart 

and Gulbrandsen, 1973). About 84 percent of the world 

production of phosphate comes from marine phosphorites; 

from 1970 through 1972, production in the United States 

was about 40 million tonnes per year. U.S. production can be 

broken down into 83 percent from Miocene and Pliocene 

deposits in Florida and North Carolina, 11 percent from the 

Permian deposits of the Western States, and 6 percent from 

Ordovician deposits in Tennessee and Alabama. Some 

production from the Miocene of California is included in the 

total for the Western States.

Every deposit that has been analyzed contains uranium, in 

amounts that typically range from 0.005 to 0.030 percent, 

whereas the average uranium content for most deposits is in 

the range from 0.005 to 0.010 percent (table 3). The relative 

uniformity of the analytical data strongly indicates that 

deposits for which data are not available almost certainly 

contain similar amounts of uranium; that is, ranging from 

about 0.005 to 0.020 percent and averaging about 

0.006-0.008 percent uranium.

Uranium is associated with the apatite mineral (carbonate 

fluorapatite), and most workers agree that uranium as U(I V)
URANIUM IN PHOSPHATE ROCK A3

TABLE 3. Marine phosphorite: reserves, production, and uranium content

Location Production1 Uranium content2

United States

Central Florida ............... 2.1xl09 I ( 0.003-0.030; average

concentrate 0.011; 

average pebble 0.015 

North Florida .3xl09 ( 35x10" ^ .004-.011; average .006

South Georgia. 

North Carolina ............... 2xl09 } \ .004-.011;average .006

North Georgia Reserves not measured; no production- .005

(Savannah River). resources are billions

of tonnes. 

South Carolina do ............................ do .............. .006

(Beaufort County) .......

(Charleston area) ......... do ............................ do .............. .005-.037

Florida-Georgia do ............................ do .............. .003-.008;average.005

(Hawthorn Formation). 

Idaho, Montana, Utah, 6xl09 4x10" '.002-.021;average .009

Wyoming (Phosphoria

Formation). 

Utah (Brazer Dolomite, Measured reserves are No production- .001-.006

Deep-Creek Formation, small; resources,

Lodgepole Limestone). particularly in Alaska, 

are billions of tonnes. 

Alaska (Permian) ............ do ............................ do .............. 4 .001-.024, average .008

Others (Ala., Ark., Ky., do ............................ do .............. Rock: .OOI-.OI4 nodules

Iowa, Kans., Okla., in black shale and limeCalif., Nev.). stone: .009-.030

Africa

Algeria ............................ \ 0.8x10" 0.011-0.014

Angola ............................ J None ................. No data.

Morocco ......................... / 20x10" .007-.023

Senegal ........................... \ 2x10" .012-.018

Togo ............................... / 2x10" No data.

Tunisia ............................ I 4x10" .004-.009

U.A.R. (Egypt) ............... J .6x10" .007-.012

Spanish Sahara ............... / 2x10" .005-.011

Asia

China (Mainland) ........... IxlO9 3x10" No data.

India ............'................... .IxlO9 .1x10" 5 0.003-0.100

Iran ................................. .05x10" None ................. No data.

Iraq ................................. .1x10' do .............. Do.

Israel ............................... .1x10' 1x10" ".002-.020

Jordan ............................ .IxlO9 1.5x10" No data.

Mongolia ........................ IxlO9 No data ............. Do.

Saudi Arabia .................. .2x10" None ................. .002-.011;average .006

Turkey ............................ .2x10" do .............. .004

Australia ......................... IxlO9 do .............. '.001-.013; average .006

Europe

U.S.S.R. ......................... 1x10' 10x10" "0.005-0.010

Others (Belgium, Germany, Small .............................. .IxlO6 .001-.021;average.006'

France, England. Spain).

Latin America

Mexico ............................ O.lSxlO9 ', Production is / No data.

Colombia ........................ .2x10" I a few tens I 0.004-0.012; average .008

Venezuela ........................ .IxlO9 \ of thousands / .005

Peru (Sechura) ................ 1+xlO9 j of tonnes ) .006

Brazil (Bambui) .............. .3xl09 ' ..................... per year. V .001-.005;average.002

'In tonnes of recoverable phosphate product containing at least 24 percent P2®s2 Uranium, in percent, of the phosphate product, except as noted.

3 Data from Gulbrandsen (1966).

"Data from Patton and Matzko (1959).

'Data from Saraswat and others (1972).

"Data from Wurzbuger (1968).

'Data from Cook (1972).

8 Data from Bliskovskiy and Smirnov (1966).

replaces calcium in the apatite structure (Altschuler and 

others, 1958), or is in part adsorbed as the uranyl ion to 

apatite crystal surfaces (Sheldon, 1959).

The uranium-apatite association is clearly demonstrated 

in several ways: chemical analyses of the minerals associated 

with apatite in the Florida deposits show that they contain 

virtually no uranium; uranium varies directly with ?2O5 

content (Cathcart, 1956, Thompson, 1953 and 1954); and the 

amount of uranium dissolved on acidulation of phosphate 

rock varies directly with the amount of phosphate dissolved 

(Igelsrud and others, 1948).

The syngenetic character of uranium in marine phosphate 

is demonstrated by the distribution of uranium in the 

Florida phosphate deposits. Primary phosphate pellets in 

the Hawthorn Formation are low in uranium content, 

averaging about 0.005 percent. The phosphate pellets in the 

overlying Bone Valley Formation were reworked from the 

Hawthorn Formation in a marine environment, and the 

concentrate-size particles (the pellets) contain an average of 

0.011 percent U (table 3). The pebble fraction (+1 mm) 

contains an average of 0.015 percent U. The coarse pebbles 

that show evidence of several cycles of reworking in the 

marine environment contain as much as 0.05 percent U 

(Cathcart, 1956, Altschuler and others, 1958). Thus, primary 

pellets contain the least amount of uranium, pellets reworked once in a marine environment contain much more 

uranium, and pebbles reworked several times contain the 

most uranium. The fine-grained pellets, highest in 

content, always contain less uranium than the lower 

content pebble fraction, even in deposits that contain 90 

percent fine phosphate pellets and only 10 percent pebble 

size. This fact indicates that uranium was not emplaced by 

ground waters percolating through the deposits.

Uranium in ground-water solution is taken up by apatite, 

and phosphatic bones, concretions, pellets, and pebbles may 

be strongly enriched in uranium. Thus, isolated bones may 

contain as much as 0.83 percent uranium (Altschuler and 

others, 1958), individual concretions and nodules as much as 

0.1 percent (Davidson and Atkin, 1953), and individual 

samples of pellets from Florida as much as 0.5 percent. These 

abnormally high contents of uranium are cited to illustrate 

the amount of enrichment than can be accomplished under 

special conditions.

The extremely small amounts of uranium in seawater 

under normal marine conditions probably accounts for the 

low, rather uniform content of uranium in these apatites.

SECONDARY DEPOSITS

Uranium is readily leached from apatite during weathering, and under acid ground-water conditions both apatite 

and uranium are dissolved. The type of source rock and the 

length and severity of the weathering determine the end 

products of weathering and the distribution of uranium in 

the products.
A4 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

When the original rock is a phosphatic limestone, 

weathering removes calcite, leaving a residually enriched 

phosphorite. In the residual "brown rock" deposits of 

Tennessee, both the uranium and the ?2O5 contents are 

increased in the residual material by the same factor, but 

uranium shows no preferential enrichment. After the calcite 

is gone, the apatite goes into solution, moves downward, and 

replaces the underlying limestone. In replacement deposits 

there tends to be a preferential enrichment in uranium. 

Uranium contents of as much as 0.1 percent have been noted 

in the secondary apatite hardpan on the Cooper Marl of 

South Carolina (Altschuler and others, 1958).

Replacement type deposits are known in many parts of the 

world. Individual deposits tend to be small, irregular in 

shape, and high in P2®5 content. Uranium contents 

typically range from 0.001 to 0.017 percent (table 4), 

although much higher contents are known. Measured 

reserves are small, but total resources may be fairly large.

TABLE 4. Secondary phosphate deposits: reserves, production, uranium

content

Location Reserves 

(tonnes)

Production Uranium content 

(tonnes/yr) (percent)

Calcium phosphate: replacement deposits

Florida, hardrock 0.05x10' None 0.001-0.017; 

-200 mesh from 

.001-.023

South Carolina

Venezuela (Riecito area) .......

... Small ...................

.OlxlO9

do .............

do .............

.004

.035-.12

No data

Calcium phosphate: residual deposits

Tennessee, "brown rock" 3 0.001-0.003

Aluminum phosphate deposits

Florida, land-pebble 

district. .................

Senegal ....................

Nigeria .....................

Siberia, U.S.S.R. ....

0.05x10"

Very small ...........

No data, small(?)

None ............

0.1x10" 

None ............

do .........

"0.004-0.040 

No data. 

.004-.011 

No data.

'Few thousand tonnes per year.

2 Uranium analyses by E. J. Fennelly and Johnnie Gardner, U.S. Geological Survey, Denver. 

'Unaltered limestone from which the residual deposits formed contains 0.0004 percent U. 

4Typical range in uranium contents. Individual samples may contain as much as 0.3 percent U.

Intensive weathering of sandy phosphorites by acid 

ground water produces irregular zones of porous, vesicular, 

light-colored, and lightweight rocks characterized by 

aluminum phosphate minerals. These zones have been 

described in Florida, Nigeria, Senegal, and Siberia 

(Altschuler, 1973). All of the deposits are similar; they are 

characterized by the change of apatite to crandallite or 

millisite and to wavellite as an end product. These changes 

are accompanied by the change of the original clay minerals 

(montmorillonite or illite) to kaolinite.

Uranium is enriched in these deposits, and it is associated 

almost entirely with the phosphate minerals, and preferentially with the calcium aluminum phosphate minerals 

crandallite and millisite, or with the calcium phosphate 

mineral apatite. The uranium minerals autunite (from 

Florida) and torbernite (from Morocco) have been reported 

from the aluminum phosphate zones, but only in trace 

amounts and only in limited areas within the deposits. 

Uranium is highest and most enriched in the porous, partly 

leached apatite pebbles at the base of the zone of leaching; 

amounts of uranium are as high as 0.3 percent in these 

pebbles. Concentrates of the calcium aluminum phosphate 

minerals crandallite and millisite contain as much as 0.05 

percent uranium (Altschuler, 1973), but concentrates of the 

aluminum phosphate mineral wavellite contain an average 

of only about 0.003 percent uranium.

In Florida, the total zone of aluminum phosphate 

alteration may be enriched in uranium as much as 2-4 times 

over the original, unaltered calcium phosphate zone from 

which it was derived.

Uranium is liberated during the solution of the apatite, 

remains soluble in the descending acid solutions, and 

enriches the crandallite and the partly leached apatite 

pebbles at the base of the section. Because wavellite is 

continuously formed from crandallite in the middle parts of 

the zone, the uranium in the crandallite goes into solution 

and moves downward, further enriching the underlying 

apatite and accounting for the abnormally high uranium 

contents in some of this apatite.

OTHER DEPOSITS 

LAKE BEDS

Tertiary lake beds in Wyoming and Nevada contain some 

layers of uraniferous phosphate. Lake beds near Tonopah, 

Nev., contains 6.7 and 11.0 percent ?2O5 and 0.10 and 0.12 

percent eU (unpub. analyses, U.S. Geo. Survey, by Carmen 

Johnson and Maryse Delevaux) (table 5). Lake beds of 

Eocene age in Wyoming and Utah contain as much as 0.27 

percent U and 19 percent P2O5, although the average 

contents of both are much less (Love, 1964). Many very thin 

beds containing the phosphate and uranium are present; the 

beds average less than 30 cm in thickness. The uraniferous 

phosphate beds are thought to be syngenetic, and although 

these occurrences are not economic, they indicate the 

possibility that in other, similar lake basins, economic beds 

of uraniferous phosphate might be present. Tonnages are 

not known; they may be large in total because of the extent of 

the beds, but tonnages per unit area are probably small.

OFFSHORE DEPOSITS

Phosphate nodules and pellets are present on the floors of 

the modern oceans and have been investigated on the west 

coast of North America from Monterey Bay to Baja 

California, on the east coast of the United States from North 

Carolina to Florida, and along the west coast of Africa.
URANIUM IN PHOSPHATE ROCK A5

TABLE 5. Other phosphate deposits: reserves, production, 

content

Location Reserves 

(tonnes)

Production

(tonnes/ yr)

and uranium

Uranium content 

(percent)

Lake beds

Wyoming, Utah (Eocene) ...... Area is large; 

beds only .08 

to 1.8 m thick.

0.10.0.12 

.001-.29; 

average .005.

Offshore

California (Monterey Bay) 

to Baja California. 

Florida, Georgia, South 

and North Carolina.

Northwest Africa (Rabat 

to Mauritania).

do ................

0.001-0.021

No data; probably 

average .005. 

No data. 

No data. 3

'Maximum apatite content 15 percent. 

2 Apatite content 10-60 percent, reworked from older beds.

3 U content should be the same as the deposits of North Africa, from which these deposits probably 

were derived.

Some of the nodules are thought to be forming in the 

modern oceans, as those of offshore California; others are 

thought to be reworked from older phosphatic sediments, as 

those of offshore North Carolina and along the west coast of 

Africa.

Amounts of pellets and nodules in the modern sediments 

range from traces to 60 percent by volume, but probably 

average between 5 and 10 percent; resources probably 

aggregate billions of tonnes although adequate 

measurements of reserves have not been published.

Uranium contents range from 0.001 to 0.012 percent 

(Altschuler and others, 1958), but a single sample from 

offshore California contained 26.4 percent P2O5 and 0.021 

percent U (U.S. Geol. Survey analysis by M. Finch, C. 

Angelo, and P. Schuch). The analytical data are similar to 

data from older marine phosphorites, and there is no reason 

to believe that other unanalyzed deposits will contain very 

different amounts of either uranium or phosphate.

PHOSPHATE RESOURCES

Data on phosphate resources of the world are given by 

Cathcart and Gulbrandsen (1973), and it is not necessary to 

repeat the data in this paper.

Uranium has been recovered as a byproduct of the 

manufacture of phosphoric acid by the wet process in the 

past. A plant to recover uranium from wet process 

phosphoric acid was completed in Florida in 1975 and plans 

have been announced for additional plants that would bring 

capacity to 1.3 million pounds of uranium per year 

(Engineering and Mining Journal, 1975). The latest 

available data show that about 15 million tonnes, about 

one-third of the total production of phosphate rock in the 

United States, went into the manufacture of wet process 

phosphoric acid (Stowasser, 1974). The phosphate rock used

in phosphoric acid production probably contained an 

average of 0.010 percent U which would be 1,500 tonnes of 

uranium. An additional 60 million tonnes of phosphate rock 

was produced in the rest of the world, and of this, about 50 

million tonnes were from marine phosphorites. Although 

precise data are not available, it is thought that about 

one-fifth of this total was used to make wet process acid; 

therefore, about 10 million tonnes, probably containing 

0.010 percent U, was made into phosphoric acid. The total 

amount of uranium, recoverable under known processes, 

was about 2,500 tonnes in 1972. World production of 

phosphate will increase; if present trends continue, a greater 

percentage of the production will go into the manufacture of 

wet process phosphoric acid, and it follows that the amount 

of recoverable uranium will increase.

Projections into the future are very speculative, but an 

increasing population's need for fertilizer indicates that a 

doubling of production is the minimum that might be 

required in the next 25 years. The amount of uranium that 

could be recovered from wet process acid should also 

double, and a minimum of about 5,000 tonnes of uranium 

per year would be available for recovery.

SELECTED REFERENCES

Altschuler, Z. S., 1973, The weathering of phosphate

deposits geochemical and environmental aspects, in E. J. Griffith,

Alfred Beeton, J. M. Spencer, and D. J. Mitchell,eds., Environmental

phosphorus handbook: New York, John Wiley & Sons, p. 33-96. 

Altschuler, Z. S., Clarke, R. S., Jr., and Young, E. J., 1958, Geochemistry of

uranium in apatite and phosphorite: U.S. Geol. Survey Prof. Paper

314-D, p. 45-90. 

Altschuler, Z. S., Jaffee, E. B., and Cuttitta, Frank, 1956, The aluminum

phosphate zone of the Bone Valley formation, Florida, and its uranium

deposits, in Page, Stocking, and Smith, 1956: U.S. Geol. Survey Prof.

Paper 300, p. 495-504. 

Bliskovskiy, V. Z., and Smirnov, A. I., 1966, Radioactivity of phosphorites:

Geokhimiya no. 6, p. 744-747. 

Cathcart, J. B., 1956, Distribution and occurrence of uranium in the

calcium phosphate zone of the land-pebble district of Florida, in Page,

Stocking, and Smith, 1956: U.S. Geol. Survey Prof. Paper 300, p.

489-494. 

Cathcart, J. B., and Gulbrandsen, R. A., 1973, Phosphate deposits, inD. A.

Brobst, and W. P. Pratt, eds., United States mineral resources: U.S.

Geol. Survey Prof. Paper 820, p. 515-525. 

Cook, P. J., 1972, Petrology and geochemistry of the phosphate deposits of

northwest Queensland, Australia: Econ. Geology, v. 67, p. 1193-1213. 

Davidson, C. F., and Atkin, D., 1953, On the occurrence of uranium in

phosphate rock: Internal. Geol. Cong., 19th, Algiers 1952, Comptes

rendus, sec. 11, pt. 11, p. 13-31. 

Engineering and Mining Journal, 1975, Large scale uranium recovery from

phosphoric acid looks promising: Eng. and Mining Jour., v. 176, no.

11, p. 32. 

Gulbrandsen, R. A., 1966, Chemical composition of phosphorites of the

Phosphoria Formation: Geochim. et Cosmochim. Acta, v. 30, no. 8, p.

769-778. 

Hubert, Claude, 1947, Contribution a" I'e'tude de la chimie de phosphates de

calcium: Annales des Mines Memoirs, v. 136, no. 4, p. 5-93. 

Igelsrud, Iver, Stephen, E. F., Chocholak, John, Schwartz, C. M., and

Austin, A. E., 1948, Chemical process to recover uranium from

phosphate rock:. U.S. Atomic Energy Comm., BMI-JDS-126, 29 p.
A6 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

Love, J. D., 1964, Uraniferous phosphatic lake beds of Eocene age in 

intermontaine basins of Wyoming and Utah: U.S. Geol. Survey Prof. 

Paper 474-E, 66 p.

McKelvey, V. E., 1956, Uranium in phosphate rock, in Page, Stocking, and 

Smith, 1956: U.S. Geol. Survey Prof. Paper 300, p. 477-481.

McKelvey, V. E., and Carswell, L. D., 1956, Uranium in the Phosphoria 

formation, in Page, Stocking, and Smith, 1956: U.S. Geol. Survey 

Prof. Paper 300, p. 483-488.

McKelvey, V. E., Everhart, D. L., and Garrels, R. M., 1955, Origin of 

uranium deposits, in Part 1 of A. M. Bateman, ed.. Fiftieth 

Anniversary volume, 1905-1955: Econ. Geology, p. 464-533.

Page, L. R., Stocking, H. E., and Smith, H. B., compilers, 1956, 

Contributions to the geology of uranium and thorium by the United 

States Geological Survey and Atomic Energy Commission for the 

United Nations International Conference on Peaceful Uses of Atomic 

Energy, Geneva, Switzerland, 1955: U.S. Geol. Survey Prof. Paper 

300, 739 p.

Patton, W. W., Jr., and Matzko, J. J., 1959, Phosphate deposits in northern 

Alaska: U.S. Geol. Survey Prof. Paper 302-A, 17 p.

Rusakov, V. P., 1933, O soderzhanii radiya i toriya v fosforitakh [The 

radium and thorium content of phosphates]: Acad. Nauk. SSSR, 

Leningrad, Doklady (Compte rendus) ser. A, no. 3, p. 25-33.

Saraswat, A. C., Varada Rajo, H. N., Taneja, P. C, Bargaja, V. B., and

Sankaran, A. V., 1972, Geochemical data on the uraniferous

phosphorites of Musoorie, Dehra Dun district, Uttar Pradesh, India:

ECAFE-UNESCO Doc. GSM (2)/36, 13 p. 

Sheldon, R. P., 1959, Geochemistry of uranium in phosphorites and black

shales of the Phosphoria Formation: U.S. Geol. Survey Bull. 1084-D,

p. 83-115. 

Stowasser, W. F., 1974, Phosphate rock, in U.S. Bureau of Mines, Minerals

Yearbook, 1972, volume 1: Washington, U.S. Govt. Printing Off ice, p.

1027-1041. 

Strutt, R. J., 1908, On the accumulation of helium in geological time: Royal

Soc. London Proc., ser. A, v. 81, p. 272-277. 

Thompson, M. E., 1953, Distribution of uranium in rich phosphate beds of

the Phosphoria formation: U.S. Geol. Survey Bull. 988-D, p. 45-67. 

______ 1954, Further studies of the distribution of uranium in rich

phosphate beds of the Phosphoria formation: U.S. Geol. Survey Bull.

1009-D, p. 107-123. 

Wurzburger, U.S., 1968, A survey of phosphate deposits in Israel, in

Proceedings of the seminar on sources of mineral raw materials for the

fertilizer industry in Asia and the Far East: U.N. ECAFE Mineral

Resources Devel. Ser. no. 32, p. 152-165.
Uranium and Vanadium 

Resources in the 

Moab 1° x 2° Quadrangle, 

Utah and Colorado

By A. P. BUTLER, JR., and R. P. FISHER

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 988-B

An outline of the geologic relations of the uranium 

and vanadium deposits provides a framework for 

evaluating undiscovered resources of those 

metals in the Moab quadrangle

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Butler, Arthur Pierce, 1908-

Uranium and vanadium resources in the Moab 1°X2° quadrangle, Utah and Colorado.

(Geology and resources of uranium deposits)

(U.S. Geological Survey Professional Paper 988-B)

Bibliography: p. 22

Supt. of Docs, no.: I 19.16:988-6

1. Uranium ores Utah. 2. Uranium ores Colorado. 3. Vanadium ores Utah.

4. Vanadium ores Colorado. 5. Geology Utah 6. Geology Colorado.

I. Fischer, Richard Philip, 1910- joint author. II. Title. III. Series. IV. Series:

United States Geological Survey Professional Paper. 988-B 

TN490.U7B83 553'.493 77-608350

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-03097-7
CONTENTS

Metric-English equivalents. 

Abstract.............................

Page

BIII 

... i

Introduction.......................................................................................... 1

Geologic setting.................................................................................... 2

Stratigraphy.......................................................................................... 4

Chinle Formation.......................................................................... 4

Moss Back Member ............................................................... 5

Church Rock Member and undifferentiated Chinle............... 5

Morrison Formation...................................................................... 5

Salt Wash Sandstone Member............................................... 5

Brushy Basin Shale Member.................................................. 6

Uranium and vanadium deposits .......................................................... 6

Resource appraisal................................................................................ 7

Deposits in the Chinle Formation................................................. 8

Moss Back Member............................................................... 8

Undifferentiated Chinle.......................................................... 12

Resource appraisal Continued

Deposits in the Morrison Formation...........................................B12

Uravan mineral belt................................................................ 15

La Sal Mountain-Island Mesa area........................................ 16

Sage Plain area....................................................................... 16

Thompson area....................................................................... 17

Summary of resources in the Salt Wash Member.................. 17

Summary of resources................................................................... 18

Methodologies...................................................................................... 18

Methods of estimating resources in the Salt Wash

Member of the Morrison Formation ......................................... 18

Uravan mineral belt................................................................ 18

La Sal Mountain-Island Mesa area........................................ 19

Sage Plain area....................................................................... 21

References cited.................................................................................... 22

ILLUSTRATIONS

Page

FIGURE 1. Tectonic sketch map of part of Colorado Plateau showing Moab quadrangle...................................................................B2

2. Outline map of Moab I°x2° quadrangle, Utah-Colorado, showing areas where uranium deposits occur in the Chinle

and Morrison Formations ............................................................................................................................................. 7

3. Simplified geologic map of the western two-thirds of the Moab quadrangle showing uranium deposits in the

Chinle Formation and in some other formations ......................................................................................................... 9

4. Simplified geologic map and cross sections of the Lisbon Valley area uranium deposits of the Big Indian mineral belt.. 10

5. Simplified geologic map showing uranium-vanadium deposits in the Morrison Formation.............................................. 14

6. Index map of areas used to estimate resources in the Salt Wash Member, Morrison Formation..................................... 20

TABLES

Page

TABLE 1. Generalized section of Mesozoic formations in the Moab quadrangle................................................................................B4

2. Resources of uranium in the Chinle Formation in the Moab quadrangle, Utah-Colorado ............................................... 13

3. Resources in the Salt Wash Member of the Morrison Formation in the Moab quadrangle, Utah-Colorado ..........:........ 17

METRIC-ENGLISH EQUIVALENTS

Metric unit English equivalent

meter (m) 

kilometer (km) 

square kilometer (km2 ) 

cubic meter (m3 ) 

kilogram (kg) 

metric ton (t)

3.28 feet

.62 mile

.386 square mile 

35.31 cubic feet 

2.2 pounds 

1.1 short tons

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

URANIUM AND VANADIUM RESOURCES IN THE MOAB 1° x 2° 

QUADRANGLE, UTAH AND COLORADO

By A. P. BUTLER, JR., and R. P. FISCHER

ABSTRACT

The Moab quadrangle, Utah and Colorado, includes highly productive 

uranium and uranium-vanadium deposits and has a significant resource 

potential.

Rocks in the quadrangle range in age from Precambrian to Cenozoic, but 

those exposed over much of the quadrangle consist of bedded sedimentary 

rocks of Paleozoic and Mesozoic ages. The Chinle Formation of Triassic 

age and the Morrison Formation of Jurassic age contain most of the known 

uranium deposits. The Chinle is ore-bearing in the western part of the 

quadrangle, where it is composed of light-colored conglomeratic sandstone 

at and near its base and overlying reddish-brown or varicolored mudstone, 

siltstone, and sandstone; ore deposits occur in the conglomeratic sandstone. 

The Morrison Formation is divided into the underlying Salt Wash 

Sandstone Member composed of light-colored lenticular sandstone strata 

interbedded with dominantly red mudstone, and the overlying Brushy Basin 

Shale Member, composed mainly of varicolored mudstone. Most of the ore 

deposits are in the uppermost sandstone lenses of the Salt Wash and in the 

central part of the quadrangle.

The primary 'ore minerals in the deposits consist of uranium and 

vanadium oxides and silicates; they mainly impregnate the sandstone. They 

form tabular orebodies that average somewhat less than a meter thick and 

are as much as one hundred meters across. These bodies lie nearly parallel to 

the bedding of the host sandstone, and they are mainly localized by 

sedimentary structural features. The deposits were probably formed from 

ground waters moving along the beds before the host beds became deeply 

buried.

Most of the deposits in the Chinle Formation are in the Big Indian 

mineral belt on the southwest side of the Lisbon Valley anticline. These 

deposits have yielded ore containing uranium worth about $500 million. 

They were probably formed in Late Triassic time, when the Chinle covered 

the anticline and was slightly arched owing to a minor upwelling of 

evaporites in the underlying core of the anticline. If these deposits were 

actually formed in this geologic situation, then the northeast flank of the 

anticline might also contain significant deposits, provided Chinle streams 

deposited favorable host beds there. Favorable locations for similar 

deposits might also be the flanks of the Dolores anticline and possibly the 

flank of the Moab anticline and ground bordering the southwest side of 

Spanish Valley. The Chinle probably contains undiscovered deposits in 

other places in the western part of the quadrangle, but these deposits are 

probably too small and widely scattered to be a resource of economic 

significance.

Deposits in the Salt Wash Member of the Morrison Formation have 

yielded a little more than 9,100,000 metric tons of ore and uranium and 

vanadium worth more than $600 million; more than 80 percent of this ore 

came from the Uravan mineral belt. The belt was probably localized along 

the toe of a subsidiary alluvial fan, which was formed by a distributary 

stream system on part of the main fan in an area of minor subsidence during 

Salt Wash time. The deposits in the belt and on the mid-slope of the fan west 

of the belt occur in sandstone lenses that formed along the courses of the 

major distributary streams; deposits outside the area of this alluvial fan also 

occur in sandstone lenses formed in major stream courses. The ore deposits 

were probably formed before burial by marine sedimentary beds in Late 

Cretaceous time. Reserves plus undiscovered resources in deposits in the 

Uravan mineral belt probably contain about 12,700 metric tons of U3Og; 

those in the fan area west of the belt about 7,900 metric tons of ^Og; and 

those in the Salt Wash in other parts of the quadrangle about 3,440 metric 

tons of

INTRODUCTION

The Moab Ix2-degree quadrangle is in east-central Utah 

and west-central Colorado. The area of the quadrangle 

includes many of the major uranium and uranium-vanadium 

deposits and mining districts in the central part of the 

Colorado Plateau region (fig. 1). It also includes two of the 

major mineral belts in the Plateau region, namely the 

Uravan and Big Indian mineral belts. These deposits have 

yielded about 25 percent of the uranium and nearly 60 

percent of the vanadium produced domestically. The known 

deposits contain substantial reserves of uranium-vanadium 

ore, and the area has a significant resource- potential.

This report summarizes the geology of the area, and 

briefly describes the habits of the uranium and vanadium 

deposits. An appraisal is made of the uranium and vanadium 

resources of the area, and suggestions are made for 

prospecting several of the more favorable parts of the area.

This study is based on the knowledge and experience of 

the writers, on many published reports, and on production 

and reserve data obtained from the U.S. Atomic Energy

Bl
B2

112°

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

111° 110° 109° 108°

39° 

38° 

i t o 

 5^ =Abajo F|XV Mountains

f BOUNDARY wr 

PARADOX BASIN

EXPLANATION 

Anticline

Monocline or fold

37

FIGURE 1. Tectonic sketch map of part of the Colorado Plateau (modified from Cater, 1970) showing location of the Moab Ix2-degree quadrangle.

Commission. In addition, many people in the U.S. 

Geological Survey, the U.S. Atomic Energy Commission, 

and in the mining industry have contributed information 

and ideas incorporated in this report. The geology and the 

location of most of the ore deposits are shown on a map by 

Williams (1964) and in simplified form by figures 3, 4, and 5 

of this report.

GEOLOGIC SETTING

The Moab quadrangle is in the east-central part of the 

Colorado Plateau physiographic and structural province. 

Rocks in the area range in age from Precambrian to 

Cenozoic, but those exposed over much of the quadrangle

are sedimentary rocks of Paleozoic and Mesozoic ages. The 

beds have been gently to moderately tilted by folding, and in 

places have been broken by high-angle faults of small to 

moderate displacement; in the central part of the quadrangle 

the rocks were invaded by moderate-sized bodies of magma, 

parent to the igneous rocks that form the cores of the La Sal 

Mountains, and in the northeast part of the quadrangle are 

capped by igneous rocks on Grand Mesa.

In the Moab quadrangle, Precambrian rocks are exposed 

only in places on the Uncompahgre Plateau; these rocks 

consist predominantly of granite, gneiss, and schist and 

locally of pegmatite. Rocks of similar lithologic character 

probably underlie the entire quadrangle. Evidence from
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B3

scattered deep drill holes indicates that by the beginning of 

Paleozoic time, Precambrian rocks had been reduced by 

erosion to a moderately flat surface.

Paleozoic rocks of pre-Pennsylvanian age are not exposed 

in the quadrangle. They were removed by erosion in late 

Paleozoic time from the area of the Uncompahgre Plateau 

(Cater, 1970, fig. 13) but are presumed to underlie the 

southwestern two-thirds of the quadrangle. Wherever these 

rocks are cut in deep drill holes or are exposed in adjoining 

areas, they consist of marine carbonates and elastics and 

measure several tens of meters thick.

The rocks of the Moab quadrangle and surrounding 

region were disturbed by deformation in Pennsylvanian time 

(Cater, 1955). The deformation consisted mainly of vertical 

displacement of crustal blocks along northwest-trending 

faults; it resulted in the uplift of the ancestral Uncompahgre 

highland in the northeastern part of the quadrangle and the 

sinking of the Paradox Basin southwest of the highlands. 

The Hermosa Formation of Pennsylvanian age was 

deposited in this basin. It comprises two members, a lower 

one, the Paradox, and an unnamed upper member. The 

Paradox Member consists mainly of salt and sulfate 

evaporites. Originally this member was probably over a 

thousand meters thick in the deeper part of the basin, which 

was in the central part of the Moab quadrangle, and 

bordered on the southwest flank of the ancestral Uncompahgre highland. The original thickness of this member is 

not known, however, because its beds have subsequently 

been squeezed laterally into several large anticlines from the 

intervening synclines. The upper member, composed mainly 

of marine limestone, probably had a maximum thickness of 

about 600 m. The Hermosa Formation is exposed only along 

the cores of the salt anticlines that have been breached and 

eroded into elongate valleys.

The Hermosa Formation grades upward into the Pennsylvanian Rico Formation, a transitional unit consisting of 

as much as 50 meters of marine and nonmarine limestone, 

sandstone, and siltstone; the Rico in turn grades upward into 

the Permian Cutler Formation. The Cutler forms an 

asymmetric lens that is at least 3,000 m thick near the 

southwestern front of the ancestral Uncompahgre highland, 

where the formation is composed of coarse arkosic 

sandstone and conglomerate of granitic pebbles and 

boulders derived from the highland (Cater, 1970, p. 10-11). 

The Cutler pinches out abruptly to the northeast, thins 

gradually to the west, and has a maximum thickness of about 

300 m in the western part of the Moab quadrangle. The grain 

size of the formation also decreases westward. In the western 

part of the quadrangle the Cutler is composed of sandstone, 

partly arkosic but predominantly muddy, with minor 

amounts of conglomerate, shale, and limestone; the 

sandstone beds are dominantly dark red, purple, or brown, 

but some are light-colored (McKnight, 1940).

While the Hermosa and Cutler Formations were being 

deposited, the ancestral Uncompahgre highland continued

to rise and the Paradox Basin to sink. The evaporite and 

limestone members of the Hermosa were warped by tilting 

fault blocks under the basin, forming gentle anticlines above 

the uplifted edges of the blocks. Because of erosion or 

nondeposition along these anticlines, the limestone member 

was'thinner on them than in the intervening synclines. The 

heavier loading on the synclines caused the evaporites to 

flow laterally from them to the anticlines and thence upward, 

initiating the salt anticlines. The added weight of the Cutler 

beds enhanced this movement of the evaporites, squeezing 

this material upward into and through the Cutler (Cater, 

1970, fig. 13, sections B, C, and D).

The crustal movements associated with the uplift of the 

ancestral Uncompahgre highland virtually stopped by the 

end of Cutler time. Throughout the Mesozoic Era the entire 

Colorado Plateau region remained relatively stable except 

for a gradual subsidence that kept the region close to sea 

level. During this time about 2,400 m of sedimentary beds, 

mostly nonmarine, were deposited. In the area of the Moab 

quadrangle, however, minor upwelling of the evaporites 

along the salt anticlines was recurrent at least until Late 

Jurassic time; as a result, some beds of Triassic and Jurassic 

ages thin or wedge out by nondeposition or erosion along the 

upturned flanks of the anticlines (Cater, 1970, fig. 13, section 

£). In most places, these anticlines were covered by the rocks 

of Cretaceous age, and probably also by the Morrison 

Formation of Late Jurassic age. Cater (1970, p. 65) suggests 

that most or all of the evaporites had been squeezed from the 

synclinal areas into the salt anticlines by Late Jurassic time. 

Shawe (1970, p. C16) suggests, however, that some of the 

differences in the thickness of some Cretaceous beds between 

synclinal and anticlinal areas, in the southeastern part of the 

quadrangle, are probably a result of continued flow of these 

evaporites during the Cretaceous.

Subsequent deformation involving the Morrison and 

younger beds in the quadrangle probably resulted primarily 

from tectonic movements of the deep-seated fault blocks, 

rather than the flowage of the Hermosa evaporites. The 

conspicuous deformation consisted of arching of the 

Morrison and younger beds over the old salt anticlines, but 

evidence to date this folding is scant. Significant movements 

may have occurred during Laramide time in the Late 

Cretaceous and early Tertiary (Cater, 1970, fig. 13, section 

F) or in the early to middle Tertiary (Shawe, 1970, p. C17); 

probably the Lisbon Valley anticline was broken by its 

conspicuous fault during the Late Cretaceous to mid-Tertiary interval. Possibly some tectonic deformation occurred 

during the epeirogenic uplift of the entire Colorado Plateau 

region in middle to late Tertiary time. Certainly the 

anticlines were modified in detail by collapse of the crestal 

parts owing to removal of the evaporites, by erosion and 

solution, as the surface of the Plateau region was lowered by 

erosion in the late Tertiary and the Quaternary. Erosion is 

continuing. The uplift of the present Uncompahgre Plateau,
B4 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

marked by sharp flexing of the cover of Mesozoic beds and 

some faulting, occurred in the late Tertiary and Pleistocene. 

The La Sal Mountains in the central part of the Moab 

quadrangle consist of three moderate-sized stocks and 

associated laccoliths composed mainly of dioritic, monzonitic, and syenitic porphyries (Hunt, 1958). The parent 

magma of these igneous bodies invaded and domed sedimentary beds of late Paleozoic and Mesozoic ages. Hunt (1958, 

p. 314) favored a middle Tertiary age for the intrusions, on 

the basis of the geologic record; Stern and others (1965) 

favored an age of about 25 million years, or about the end of 

the middle Tertiary, for the intrusions, as indicated by 

somewhat anomalous results of various methods of isotopic 

age determinations; and Armstrong (1969) reported a 

23.5-million-year age on the basis of isotopic analysis of one 

sample.

STRATIGRAPHY

The stratigraphy of the Mesozoic formations in the Moab 

quadrangle is summarized in table 1. Readers desiring more 

information about the stratigraphy of these formations are 

referred to reports by Baker (1933), Dane (1935), McKnight 

(1940), Bush, Bromfield, and Pierson (1959), Carter and 

Gualtieri (1965), Shawe, Simmons, and Archbold (1968), 

and Cater (1970). The stratigraphy of the Chinle and

Morrison Formations is described in more detail below, as 

these formations contain most of the known deposits of 

uranium and vanadium ore in the quadrangle.

CHINLE FORMATION

The Chinle Formation of Triassic age is widespread in the 

Colorado Plateau region. It is about 600 m thick in 

southwestern Utah and thins rather gradually to the east and 

north. It is composed principally of mudstone and sandstone 

including some partly conglomeratic sandstone. The conditions of deposition were virtually the same throughout the 

region with sediments accumulating in an environment of an 

alluvial plain with meandering streams, ephemeral lakes, 

and extensive mud flats. Sedimentary, metamorphic, and 

igneous rocks in the highland area of central Arizona and in 

southwestern New Mexico were probably the principal 

source of these sediments. The Chinle is divided into several 

members in the southern and western parts of the Plateau 

region (Stewart and others, 1959; Stewart, Poole, and 

Wilson, 1972), but only two members, the Moss Back and 

the Church Rock, are clearly recognized in the area of the 

Moab quadrangle; these are distinguished only in the 

southwestern part of the quadrangle. In most of the area the 

Chinle is not formally subdivided.

TABLE 1. Generalized section of Mesozoic formations in the Moab quadrangle

System Group or formation Thickness 

(meters)

Character and distribution

Cretaceous ............... Mesaverde Group ....

Mancos Shale ..........

Dakota Sandstone ...

Jurassic

Burro Canyon ..........

Formation 

Morrison Formation

Summerville ..............

Formation 

Entrada Sandstone ...

Jurassic ............

and Triassic?) 

Triassic (?) .......

Triassic

Navajo Sandstone ..... 

Kayenta Formation ... 

Wingate Sandstone ... 

Chinle Formation .....

Moenkopi Formation

370 Thick-bedded light-colored marine and nonmarine sandstone and shale; coal-bearing.

Originally covered entire quadrangle; may have been thicker than that remaining in

northeast and northwest corners. 

1,200 Dark-gray fissile marine shale with some thin sandstone beds. Originally covered entire

quadrangle. 

15-60 Gray and brown partly conglomeratic sandstone, and gray to black shale; all nonmarine;

coal-bearing in places. Originally covered entire quadrangle. 

0-60 Light-colored sandstone and conglomerate, green and purplish shale, thin beds of

limestone; all nonmarine. Originally widespread, locally absent. 

75-150 Brushy Basin Shale Member: varicolored bentonitic mudstone, some sandstone lenses;

nonmarine. Widespread. 

60-140 Salt Wash Sandstone Member: light-colored lenticular sandstone interbedded with

dominantly red mudstone; nonmarine. Widespread. 

20-45 Predominantly brownish-red, gray, and green sandy shale and mudstone; nonmarine.

Widespread.

20-170 Light-colored fine- to medium-grained massive and cross bedded sandstone; predominantly eolian. Widespread. 

0-120 Light-colored fine-grained massive and crossbedded sandstone; eolian. Absent in eastern

half of quadrangle. 

0-75 Predominantly red irregualarly bedded shale, siltstone, and sandstone, nonmarine.

Absent in eastern part of quadrangle. 

0-105 Reddish-brown fine-grained massive and crossbedded sandstone; predominantly eolian.

Widespread but thin or absent in eastern part of quadrangle. 

0-180 Reddish-brown or varicolored mudstone, siltstone, and sandstone, in part bentonitic,

commonly with light-colored conglomeratic sandstone at or near the base; nonmarine.

Widespread but locally absent along the salt anticlines. 

0-300 Chocolate-brown, reddish-brown, and purple shale, mudstone, and sandstone, in part

arkosic and conglomeratic; marine and marginal marine. Widespread but locally absent

along the salt anticlines and in the eastern part of the quadrangle.
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B5

MOSS BACK MEMBER

The Moss Back in the southwestern part of the Moab 

quadrangle ranges from less than 6 m to about 30 m in 

thickness and averages about 16 m. Its gross lithologic 

components are sandstone and mudstone, but in detail its 

lithologic characteristics are quite varied. Grains in the 

sandstone range from fine to coarse, and some layers contain 

pebbles and less commonly cobbles. Some beds are composed dominantly of quartz, some are highly feldspathic, 

and some contain abundant grains of calcareous siltstone 

and limestone. The pebbles in some conglomeratic layers are 

predominantly quartz, quartzite, and chert, and in other 

layers are mainly siltstone and limestone. The mudstone 

beds consist of siltstone, claystone, and argillaceous 

limestone. The sandy beds are dominantly light gray and the 

muddy beds are chiefly greenish gray. Coalified plant 

material, mostly in small fragments, is sparse to abundant in 

some sandstone and mudstone beds.

The bedding characteristics of the Moss Back are varied, 

ranging from sheetlike layers to small lenses; cut-and-fill 

channels are not conspicuous although some of small size 

occur at the base of the member. Crossbedding is common 

but not omnipresent. Sandy beds, especially the conglomeratic ones, are more abundant in the lower part of the 

member and muddy beds are more common in the upper 

part of the member. Sedimentary structures indicate deposition by streams flowing generally northwestward.

The northeastern limit of the Moss Back is recognized in 

exposures along the Colorado River about 16 km southwest 

of Moab; from there it is projected by interpretation 

southeastward to Slick Rock, Colo., passing several 

kilometers northeast of Lisbon Valley, Utah (Stewart and 

others, 1959). The Moss Back is host to the important 

uranium deposits in the Big Indian mineral belt along the 

southwest side of Lisbon Valley (Wood, 1968), to several 

dozen small deposits along the Green and Colorado Rivers 

in the west-central part of the quadrangle, and to three small 

deposits south of Slick Rock (Shawe, Archbold, and 

Simmons, 1959).

CHURCH ROCK MEMBER AND UNDIFFERENTIATED CHINLE

The Church Rock Member, in the southwestern part of 

the quadrangle, and the undifferentiated Chinle, in the other 

parts, are lithologically similar and probably largely 

equivalent. These units are absent in places along the salt 

anticlines; they average about 30 m thick on the Uncompahgre Plateau; and they range from about 90 to 180 m in 

thickness elsewhere. These beds are somewhat varicolored 

but are dominantly brick red or reddish brown. They are 

chiefly siltstone, but fine-grained sandstone is common, and 

thin layers of limestone-pebble conglomerate are present. 

The siltstone and sandstone are somewhat tuffaceous. They 

occur in thick, poorly defined layers that are massive or only 

vaguely laminated. In many places in the central part of the 

quadrangle a quartzose grit, commonly with quartz pebbles,

is present in the lower part of the undifferentiated Chinle. 

Beds of this lithology may or may not be equivalent to the 

Moss Back (Carter and Gualtieri, 1965; Cater, 1970). Several 

uranium deposits in the Sevenmile Canyon area northwest 

of Moab are in lenses of gray siltstone, limestone-pebble 

conglomerate, and quartz-pebble conglomerate at the base 

of the Chinle (Finch, 1954); these beds are interpreted to be 

at the base of undifferentiated Chinle and stratigraphically 

higher than the Moss Back rather than equivalent to the 

Moss Back (Stewart and others, 1959, figs. 77 and 81).

MORRISON FORMATION

The Morrison Formation (fig. 5) in the Moab quadrangle 

comprises two members, the Salt Wash Sandstone Member 

at the base and the Brushy Basin Shale Member at the top. 

Each originally extended throughout the area of the 

quadrangle and beyond it in all directions. The Salt Wash 

Member has yielded most of the vanadiferous uranium ore 

in the quadrangle, and contains most of the known reserves.

SALT WASH SANDSTONE MEMBER

The Salt Wash Sandstone Member is composed of 

material derived mainly from preexisting sedimentary rocks 

from a source area of moderate elevation in western Arizona 

and the adjacent part of California. This material was 

probably carried by a major river that entered the Colorado 

Plateau region in an area about where the present Colorado 

River crosses the Utah-Arizona line. There the Salt Wash is 

thickest, about 180 m, and is composed almost wholly of 

sandstone, which is in part conglomeratic. From there the 

Salt Wash was spread to the east and north by a distributary 

river system as a broad alluvial fan, becoming finer grained 

and thinning gradually in these directions. In the Moab 

quadrangle the Salt Wash is composed of interbedded layers 

of sandstone and mudstone in about equal amounts, ranging 

from about 90 to 120 m in thickness (Craigand others, 1955, 

fig. 21). The Salt Wash is slightly thicker in the eastern part 

of the quadrangle than in the western part, and Shawe (1962) 

suggested that this local thickening resulted from the filling 

of a shallow basin that had developed in southwestern 

Colorado during Salt Wash time.

In the eastern part of the quadrangle the sandstone layers 

in the Salt Wash tend to be evenly bedded, perhaps the result 

of accumulation in broad shallow bodies of water in the 

basin, as suggested by Shawe (1962). However, in the 

western two-thirds of the quadrangle, where the Salt Wash is 

ore-bearing, the sandstone layers are ill-defined lenses that 

presumably were deposited by shifting streams. These lenses 

are commonly 1.5-8 km wide and as much as a few tens of 

meters thick; they interfinger laterally with mudstone, which 

probably accumulated on flood plains. Fluvial crossbedding 

and scour-and-fill bedding are conspicuous sedimentary 

structural features in the sandstone, and thin lenses of 

mudstone and mudstone-pebble conglomerate are common. 

The sandstone is light colored, generally grayish yellow or
B6 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

pale red at the outcrop and pale gray or pale red below the 

zone of ozidation. It is composed of fine to medium grains 

predominantly of quartz and subordinately of some feldspar 

and chert. Pieces of coalified fossil plants ranging from small 

fragments to large logs are scattered through the sandstone 

but are most abundant in the thicker central parts of the 

sandstone lenses.

The Salt Wash mudstone is indistinctly bedded and is in 

part silty or finely sandy. It is predominantly red, but in 

places is gray or greenish gray. Presumably it was deposited 

on flood plains and in ephemeral ponds or lakes.

BRUSHY BASIN SHALE MEMBER

The Brushy Basin Shale Member is composed 

predominantly of bentonitic claystone, which is in part silty 

and sandy. It also contains a minor amount of partly 

conglomeratic lenticular sandstone. The claystone is 

varicolored; red, purple, gray, and greenish gray are 

common. The sandstone is light colored; pebbles of red, 

green, white, and black chert are characteristic of the 

conglomeratic parts. The Brushy Basin was deposited in a 

mixed lacustrine and fluvial environment. It ranges from 

about 90 to 120 m in thickness in the Moab quadrangle.

URANIUM AND VANADIUM DEPOSITS

Uranium and vanadium deposits in sandstone are 

numerous and widespread in the Moab quadrangle. These 

deposits have yielded about 17 million t (metric tons) of ore, 

and they contain known reserves (minable under conditions 

prevailing in 1971-72) that total about 4.2 million t of ore. 

Almost all of the ore has come from tabular deposits that are 

nearly concordant to the bedding of the host sandstone; the 

term "peneconcordant" has been applied to this type of 

deposit (Finch, 1959). A little ore has come from vein 

deposits along fractures in sandstone and limestone. All of 

the known reserves are in peneconcordant deposits. The Salt 

Wash Member of the Morrison Formation is host to about 

57 percent of the known ore (production plus reserves), the 

Chinle Formation about 39 percent, and the Cutler Formation about 3.6 percent. The Brushy Basin Member of the 

Morrison Formation, the Entrada Sandstone, the Wingate 

Sandstone, and the upper member of the Hermosa Formation are host to some small deposits that collectively 

represent a fraction of one percent of the total known ore.

The ore minerals below the zone of oxidation are 

low-valent oxides and silicates of uranium and vanadium: 

uraninite [UO2+], coffinite [U(SiO4)i-x(OH)4x], montroseite [VO(OH)] or paramontroseite, and vanadium-bearing mica, chlorite, and clay. The common copper sulfides are 

widespread in sparse amounts and conspicuous in a few 

places. Accessory minerals are mainly sulfides; pyrite and 

marcasite are common but not abundant, and trace amounts 

of galena and sphalerite are widespread. Minerals containing molybdenum, selenium, chromium, nickel, cobalt, 

and silver are also present; only in a few places are some of

these minerals abundant enough to be recognized. Introduced gangue minerals other than those that commonly 

cement sandstone are inconspicuous or absent.

The vanadium silicates are virtually stable in the zone of 

oxidation, but montroseite and the two primary uranium 

minerals oxidize readily, and the contained metals are 

converted to a soluble higher valent state. Where sufficient 

vanadium is available, however, uranium is fixed.almost in 

place as carnotite [K2(UO2)2V2O5-3H2O] or tyuyamunite 

[Ca(UO2)2V2O5- 5-8!/2 H2O], both of which are quite stable 

in the zone of oxidation. Hence, in the vanadium-rich 

deposits, the mineralogy in the zone of oxidation is simple, 

and there has been little or no migration of either uranium or 

vanadium to cause enrichment or impoverishment of the 

deposit at and near the surface. On the other hand, in 

deposits that are low in vanadium, either the uranium is 

mobilized or it forms a variety of secondary minerals. Some 

of these secondary minerals are not very stable themselves, 

and migration of uranium may have impoverished parts of 

some deposits near the outcrop, perhaps with some secondary enrichment at some place behind the outcrop.

The ore minerals mainly coat the sand grains, partly filling 

the pore spaces of the sandstone; however, in places they 

replace the sand grains, and interstitial clay and the original 

calcite cement of the sandstone, and some of the coalified 

plant remains. The ore minerals are epigenetic, and they 

form orebodies that are crudely tabular or lenticular and 

nearly concordant to bedding but do not follow beds in 

detail. These bodies range from 0.3 m to several meters in 

thickness and average about 1 m thick; they range from 

bodies only 1 or 2 m across, which contain only a few tons of 

ore-bearing rock, to those that are many tens of meters 

across and contain many thousands of tons of ore. The 

orebodies are irregular in plan but tend to be elongate, 

generally parallel to the long axes of the host lenses. The 

grade of the ore varies considerably from place to place 

within an orebody, but the ore is mixed during mining and 

the product is rather uniform in grade and averages a few 

tenths of 1 percent l^Og; orebodies in the Morrison 

Formation commonly average about 1.5 percent V205, 

whereas those in the Chinle Formation contain only a few 

tenths of 1 percent or less V2O5- Characteristically, 

orebodies have well-defined edges, and the grade drops 

within a few inches at the edges; large halos of low-grade 

material are not common, although thin layers of ore-grade 

material are much more extensive than minable ore.

The uranium deposits in the Moab quadrangle are 

restricted to places where the enclosing rocks retain 

characteristics indicative of reduction in contrast to the 

absence of such characteristics in the surrounding rocks; 

these reduced rocks are generally referred to as "altered." 

The altered rock extends a few hundred meters laterally and 

up to several meters vertically from ore deposits. Altered 

sandstone below the zone of surface oxidation is light gray to
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B7

buff and contains sparsely disseminated pyrite; recent 

oxidation of this pyrite imparts a yellowish cast to the altered 

sandstone at and near the surface. In contrast, unaltered 

sandstone is pale red to red, both above and below the zone 

of oxidation. Mudstone associated with the near surface 

altered sandstone is gray or green, whereas the unaltered 

mudstone is dominantly red; the altered mudstone contains 

disseminated pyrite below the zone of oxidation. These 

altered halos are a useful guide in exploration, as they 

indicate ground favorable for uranium deposits and offer a 

larger target for subsurface exploration than do the deposits 

themselves.

Stratigraphic, lithologic, and sedimentary structural factors are significant in the localization of many of the 

uranium and vanadium deposits in the Moab quadrangle: 

(1) The known deposits in the Chinle are all in the basal 

sandstone beds, and most of those in the Morrison are in the 

uppermost sandstone unit of the Salt Wash Member. (2) 

Almost all deposits are in permeable sandstone beds, and 

almost all except those in the Entrada Sandstone at 

Placerville contain coalified plant fossils. (3) Many deposits, 

especially those in the Morrison, are in the thicker central 

parts of sandstone lenses and are elongate parallel to the 

courses of the streams that deposited these lenses. In 

contrast, igneous activity, hydrothermal mineralization, and 

tectonic structures show no similarly consistent influence on 

localization.

The time of ore deposition is not definitely established, but 

it seems likely that the deposits are of Mesozoicage; perhaps 

the deposits in the Chinle formed during the middle of the 

era and those in the Morrison during the late part. Geologic 

field relations indicate a pre-Laramide age; the folds and 

faults of Laramide and Tertiary age show no obvious 

influence on the distribution and localization of the deposits, 

and all of the faults that cut the deposits displace the ore 

layers. Isotopic data permit interpretation of ages of ore 

emplacement that include Cenozoic as well as Mesozoic 

times. On the basis of their latest studies, however, Miller 

and Kulp (1963) suggest that the deposits in the Chinle in the 

Lisbon Valley area probably formed about 210 million years 

ago (during the late Triassic) and that those in the Morrison 

in the Uravan area probably formed about 110 million years 

ago (during the Early Cretaceous).

Various theories have been proposed to explain the origin 

of the peneconcordant uranium and vanadium deposits of 

the Colorado Plateau region. The concept currently favored 

by geologists assumes that the mineralizing solutions were 

ground waters that leached trace amounts of metals from the 

ore-bearing beds and associated strata and transported these 

metals in their high-valent states to places where they were 

precipitated by reduction; carbonaceous material or 

hydrogen sulfide formed by anaerobic bacteria are assumed 

to be the most likely reducing agents (Hostetler and Garrels, 

1962; Motica, 1968; Wood, 1968). Ore formation could have

occurred whenever and wherever these geochemical 

processes were operative; the movement of solutions and 

bacterial activity may have been greater before deep burial of 

the ore-bearing beds.

RESOURCE APPRAISAL

Many uranium deposits, some with significant amounts of 

vanadium, occur in the Moab quadrangle (fig. 2). Much of 

the area has been intensively prospected by surface-exploration methods, and probably all or nearly all of the deposits 

that crop out have been found. There has been moderate to 

intensive subsurface exploration in the vicinity of the 

deposits that crop out, and many buried deposits have been 

found. Continued subsurface exploration in the vicinity of 

the known deposits will find other buried deposits, but 

probably only a moderate amount of ore remains to be 

discovered near known deposits. On the other hand, there is 

much unexplored and partially explored ground farther 

away that could contain undiscovered ore deposits in the 

Moab quadrangle; attention from the standpoint of resource 

appraisal and suggestions for prospecting is focused mainly 

on this ground. Our resource appraisal and suggestions for 

prospecting are based oh our understanding of the habits, 

distribution, and localization of the known deposits. The 

resources included in our appraisal are hypothetical 

resources as defined by Pratt and Brobst (1974, p. 2) in that 

they consist of material in undiscovered deposits like the 

numerous identified deposits in the same general area and 

geologic setting. The data about ore produced and in reserve 

were obtained from records made available by the U.S. 

Atomic Energy Commission.

About 96 percent of the known ore (production plus 

reserves) is in the Chinle and Morrison Formations, and the 

resource potential of only these formations will be discussed 

in detail. Undiscovered deposits undoubtedly occur in other

80 KILOMETERS

FIGURE 2. Outline map of the Moab Ix2-degree quadrangle 

showing generalized areas within which deposits occur in 

the Chinle Formation (horizontal lines) and Morrison 

Formation (vertical lines).
B8 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

stratigraphic units in the area, but with the possible 

exception of the Cutler Formation, the undiscovered 

deposits in these units are judged to be too small and widely 

scattered to justify intensive search for them. In recent years 

a few significant deposits have been found in the Cutler 

Formation. They are a short distance southwest of and 

downdip from deposits in the Chinle in the central part of the 

Big Indian mineral belt, Lisbon Valley area, Utah (fig. 4). It 

is possible that other deposits occur in the Cutler on the 

downdip side of this mineral belt, but we cannot adequately 

appraise this possibility without more knowledge of the 

known deposits in the Cutler. The known deposits in the 

Cutler are shown in figure 3. A few known deposits in 

formations other than the Cutler, Chinle, and Morrison in 

the Moab quadrangle are shown on a map by Williams 

(1964, sheet 2).

DEPOSITS IN THE CHINLE FORMATION

The Chinle Formation is the principal host to deposits in 

the southwestern part of the Moab quadrangle (fig. 3). The 

formation is present in most places in the rest of the 

quadrangle, but it is not known to be ore-bearing, and it 

generally lacks beds that are lithologically favorable for 

uranium deposits.

About 31,100,000 kg of l^Og in 8,420,0001 of ore had 

been found in the Chinle Formation in the southwest part of 

the quadrangle by mid-1971. A large part of this, about 

25,240,000 kg of U 3O8 in 6,920,0001 of ore, had been mined 

by that time. Reserves as of July 1, 1971, amounted to about 

5,900,000 kg of U3Og in 1,500,000 t of ore.

MOSS BACK MEMBER

The bulk of the known deposits in the Chinle are in the 

'Moss Back Member, which is the basal member of the 

Chinle in the southwestern part of the quadrangle. The Moss 

Back is a unit of varied lithology. Known deposits in the 

Moss Back are restricted to a northwest-trending zone 16-32 

km wide (fig. 3) that borders the northeastern depositional 

edge of the Moss Back; the Moss Back in this ore-bearing 

zone is thinner and more lenticular than it is to the 

southwest, where the unit is apparently barren (Johnson and 

Thordarson, 1966). Almost all of the deposits in the Moss 

Back are in the basal sandstone beds; the deposits are tabular 

layers that lie nearly parallel to the bedding, but are not 

restricted by the bedding, and they show little or no 

preference for sandstone of a particular composition.

Highly productive deposits that have yielded uranium 

worth nearly $500 million have been mined from the Moss 

Back in the Big Indian mineral belt in the Lisbon Valley area 

(Wood, 1968). These deposits represent nearly 98 percent of 

the known resources in the Chinle within the quadrangle. If 

this group of deposits is unique to the Moss Back in the 

quadrangle, undiscovered resources in this member are 

probably small, and further intensive exploration of these 

beds would not be justifiable. If, on the other hand,

undiscovered deposits similar to those in the Big Indian belt 

are present, substantial undiscovered resources would exist, 

and if target areas of ground geologically favorable for them 

can be selected, deep exploration for them would be 

justified. If such deposits are present, they probably were 

localized in geologic conditions similar to those in the belt. 

Although the geologic relations that localized the belt are 

not definitely recognized, some ideas of possible significance 

are discussed below. It is hoped that these ideas will help 

select target areas for fruitful exploration.

The Big Indian mineral belt is about 0.8 km wide and 24 

km long. It is on the southwest flank of the Lisbon Valley 

anticline, and it trends virtually parallel to the structure 

contours on the base of the Chinle along this flank (fig. 4). 

The lower beds of the Chinle and the upper part of the 

underlying Cutler Formation have been altered ("bleached") 

by reduction along the mineral belt (Wood, 1968, p. 779). 

Miller and Kulp (1963, p. 627) suggested a Triassic age 

(about 210 million years) for these deposits, on the basis of 

isotopic age data. Wood (1968) suggested that the uranium 

was derived by ground waters from the volcanic ash in the 

beds in the upper part of the Chinle and it was moved by 

downward percolation into the permeable Moss Back beds, 

where the ore minerals were precipitated by reduction. He 

suggested that the leaching, movement, and precipitation 

began during diagenesis of the Chinle beds and continued 

during the deposition of the later Traissic and Jurassic beds, 

but that they ended prior to Laramide deformation. These 

relations and ideas are compatible with the geologic history 

of the anticline, and they permit optimism that similar 

deposits occur in Moss Back beds in other places where 

geologic relations are similar in the Moab quadrangle.

The Lisbon Valley anticline is one of several 

northwest-trending anticlines in this part of the Colorado 

Plateau region (fig. 1). All were arched by the up welling of 

salt and gypsum in the Hermosa Formation. This upwelling 

occurred in two major stages, the first during the late 

Paleozoic and the second during Laramide time or later. 

Relative quiescence prevailed during the Mesozoic Era, 

although minor upwelling and arching occurred occasionally. The ancestral (late Paleozoic) Lisbon Valley anticline 

probably was a rather symmetrical structure that was 

truncated by erosion before Chinle time. It probably was 

completely covered by the Moss Back and overlying parts of 

the Chinle, but small variations in the thickness of these beds 

on the southwest flank of the present anticline suggest that 

minor uplift of parts of the anticline might have occurred 

during Chinle sedimentation. The anticline and Chinle beds 

were then covered by about 2,400 m of younger Mesozoic 

sedimentary rocks. During deformation in Laramide time, 

or later, the anticline was broken by an axial fault of about 

900 m of displacement; the southwest flank was tilted to its 

present attitude, but the northeast flank was relatively 

undisturbed. Regional uplift and subsequent erosion has
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO

109°

B9

LISBON VALLEY ANTICLINE

EXPLANATION

Intrusive rocks of the La Sal Mountains 

(mid-Tertiary)

Chinle Formation and post-Chinle formations

Zone where Moss Back Member of Chinle 

Formation is thin and lenticular (modified 

from Johnson and Thordarson, 1966)

Pre-Chinle formations

 Contact

 Fault Bar and ball on downthrown side 

-4 I Anticline Showing plunge

Uranium deposit or group of deposits in the Chinle 

Formation or other formations PC, Cutler Formation; "Rw, Wingate Sandstone; and "Rkw, 

Kayenta Formation and Wingate Sandstone

FIGURE 3. Simplified geologic map of the western two-thirds of the Moab Ix2-degree quadrangle showing uranium deposits in the 

Chinle Formation, except those in Lisbon Valley, and in some other formations as indicated by letter symbol. Only those faults 

mentioned in text are shown.
BIO GEOLOGY AND RESOURCES OF URANIUM DEPOSITS 

_____109°15'______ __________________

38°15'

JTif

5 KILOMETERS

FIGURE 4. Simplified geologic map of the Lisbon Valley area, Utah 

(modified from Wood, 1968), showing uranium deposits (black) of the 

Big Indian mineral belt projected vertically to surface, and structure 

contours in feet (1,000 feet equals 305 m) on the base of the Chinle 

Formation on the southwest side of the anticline. Section A-A' shows 

present geologic relations; section B-B' shows hypothetical relations

exposed the Chinle on the southwest flank of the anticline, 

but these beds are about 760 m below the present surface on 

the northeast flank (fig. 4, section A-Af).

The localization of the Big Indian mineral belt can be 

explained if a minor upward movement of the salt and 

gypsum during Chinle time is assumed. Ground water 

seeping downward along the crest of the anticline could have 

leached uranium from the upper Chinle beds and moved it 

downward along the Moss Back to a favorable reducing 

environment, probably somewhere below the water table

during Late Triassic time. Kf, mostly Cretaceous formations; J~pf, 

Jurassic and Triassic formations; T?c, Chinle Formation; PC, Permian 

Cutler Formation; (?)IPh, Pennsylvanian Hermosa Formation. U, 

upthrown block; D, downthrown block. Arrows indicate relative 

movement of fault blocks.

(fig. 4, section B-B"). This flow of ground water may have 

continued for a while after Chinle time.

From a practical standpoint, the model shown on figure 4, 

section B-B', suggests that the northeast flank of the anticline 

is also favorable for uranium deposits, provided that 

lithologically favorable host beds were deposited there by 

Moss Back streams. In recent years, exploration near the 

northwest end of the northeast flank of the anticline has 

found enough ore in the Moss Back to justify sinking two 

shafts, each about 760 m deep. Whether the ore deposits
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO Bll

1500-

1000-

Favorable for 

uranium production!?)

B Crest of Late Triassic anticline

Water table

Ph

4 KILOMETERS

being mined from these shafts are a downfaulted northerly 

extension of the Big Indian mineral belt or the northerly end 

of a belt on the northeast flank of the anticline cannot be 

determined at the present stage of exploration and development. But the presence of these deposits, and the geologic 

rationale presented above, would seem to offer justification 

for exploration drilling on the northeast flank of the 

anticline. Actually, some exploratory drilling has been done 

on this flank, and is reported to have shown mineralized rock 

and sandstone beds resembling those that are ore-bearing in 

the Big Indian mineral belt. Although this exploration has 

not resulted in an announced discovery of an exploitable 

deposit that might confirm the existence of a belt of deposits 

on the northeast side of the anticline, it is possible that not 

enough drilling has been done to negate the possibility of a 

mineral belt. Should such a belt exist, resources in the Moss 

Back on the northeast side of this anticline might be as 

significant as those on the southwest side, which contained 

about 25,000 t l^Og.

The Dolores anticline extends from the Lisbon Valley 

anticline southeastward beyond the southern edge of the 

Moab quadrangle (fig. 1). The Dolores anticline, like the

Lisbon Valley anticline, has a thickened core of salt and 

gypsum, but these evaporites probably did not penetrate the 

overlying beds and the crest of the anticline has not been 

breached to expose the evaporites (Shawe, 1970). There is no 

definite evidence of up welling of salt and gypsum along the 

Dolores anticline during Chinle time or immediately 

afterward, which might have arched the Chinle over the 

anticline, as was suggested in the case of the Lisbon Valley 

anticline. Nevertheless, some other units of Mesozoic age are 

thicker in the adjoining Disappointment syncline, northeast 

of the Dolores anticline, than they are over the anticline, 

suggesting that some flowage of evaporites recurred at times 

during the Mesozoic (Shawe, 1970, p. C7). Perhaps during 

Chinle time and shortly afterwards ground-water flow in the 

Chinle beds over the Dolores anticline was similar to that 

suggested in the Chinle beds over the Lisbon Valley 

anticline; if favorable host beds are present, deposits similar 

to those in the Big Indian mineral belt might have formed. 

Where the Moss Back is exposed in the Dolores River 

canyon south of Slick Rock, it is composed of gray limy 

arkosic and quartzose sandstone, which is in part conglomeratic, with some gray and reddish mudstone. Coalified
B12 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

and silicified plant fossiles are locally abundant in the 

sandstone and mudstone. Beds of similar lithology were cut 

in drill holes in Summit Canyon (Shawe and others, 1968, p. 

A28 and pis. 2 and 4). The lithology of these beds is 

reasonably favorable for uranium deposits. Three small 

deposits are exposed in the Moss Back in the Dolores River 

canyon, and anomalous radioactivity was detected at other 

places in these beds along the river and in some drill holes in 

Summit Canyon (Shawe and others, 1968, p. A29).

Without more information, the uranium resources of the 

Moss Back beds along the Dolores anticline cannot be 

appraised accurately; they could range from insignificant to 

the same order of magnitude as'those along the Lisbon 

Valley anticline (about 29,0001 of l^Og). These beds on the 

flanks of the Dolores anticline, however, are judged to be 

reasonably favorable exploration targets. Any exploratory 

drilling should be done with an initial pattern of holes spaced 

300 m to 1,000 m apart, and they should have the principal 

objective of obtaining geologic information, such as determining if altered beds of favorable lithologic characteristics 

are present. If favorable ground is found, closer spaced 

drilling to seek ore deposits should be justifiable.

About three dozen deposits have been found along 460 km 

of outcrop of the Moss Back along the Colorado and Green 

Rivers and their tributaries west and south of Moab (fig. 3), 

an area of about 1,300 km2 . Most of these deposits are small, 

but five of them are of medium size. These five deposits 

contained at least 45,000 kg or l^Og each, and collectively 

account for 95 percent of the total 350,000 kg of U3Og in the 

three dozen deposits. If it is assumed that the outcrop 

exposes a true sample of deposits by size and distribution, 

and this assumption is judged to be reasonable, the 

calculated total U^Og in deposits in the 1,300-km2 area 

amounts to about 5,3001. If most of this l^Og is in deposits 

that contain about 45,000 kg each, the average incidence of 

such deposits would be about 1 in every 16 km2 . Exploration 

to find such deposits in the Moss Back, which lies at depths 

of 240-365 m in most of the area, would be so costly that the 

estimated amount of uranium in them could be considered 

an economically viable resource only if the likely positions of 

the deposits could be more closely defined than is possible 

with information now available.

UNDIFFERENTIATED CHINLE

Lenses of gray siltstone, limestone-pebble conglomerate, 

and quartz-pebble conglomerate are host to several uranium 

deposits in or near Sevenmile Canyon northwest of Moab 

(Finch, 1954). These beds are interpreted to be at the base of 

the undifferentiated part of the Chinle and to be 

stratigraphically higher than the Moss Back (Stewart and 

others, 1959, figs. 77 and 81). The deposits are on the 

southwest flank of the Moab anticline near its northwestern 

end. This structure, like the Lisbon Valley anticline, is a salt 

anticline that was broken by an axial fault of large 

displacement, and the southwest flank was uplifted relative

to the northeast flank. These deposits occupy about the same 

position on the Moab anticline as does the northwest part of 

the Big Indian mineral belt on the Lisbon Valley anticline. 

By analogy, the deposits in the Sevenmile Canyon area 

might be part of a mineral belt similar to the Big Indian 

mineral belt. The likely projection of this hypothetical belt, 

however, is not exposed, and it has not been tested by 

subsurface exploration because the basal beds of the Chinle 

are deeply buried and the topography is so rough that access 

by drill rigs would be difficult. Nevertheless, exploration to 

test the basal beds of the Chinle might be fruitful along the 

southwest flank of the Moab anticline, and even farther 

southeast along the southwest flank of the structures 

bordering Spanish Valley on the southwest.

The axial length of the Moab anticline is about the same as 

that of the Lisbon Valley anticline, but the presently known 

deposits are confined to about the northwest one-fifth of the 

southwest flank. The average size of deposits in the Moab 

anticline area is only one-twentieth that of the average 

deposit in the Lisbon Valley area. Thus, although the 

southwest flank of the Moab anticline is very incompletely 

explored and although the extent of host rocks that might be 

favorable for deposits is only approximately delineated, it is 

unlikely that resources along that flank would be more than 

5 percent of the resources on the southwest side of the Lisbon 

Valley anticline.

The distance between the southeast end of the Moab 

anticline and the northwest end of the Lisbon Valley 

anticline is about twice the length of the latter. The Chinle is 

largely concealed throughout this distance. Direct evidence 

about the characteristics of rocks near the base is lacking, 

but Johnson and Thordarson (1966, pi. 1) imply that the 

Moss Back Member, which is host to the Lisbon Valley 

deposits, pinches out only about 8 km northwest of the 

Lisbon Valley deposits.

If Johnson and Thordarson are correct, beds low in the 

Chinle that are favorable for deposits may be confined, as 

indicated on their map (1966, pi. 1), to a relatively narrow 

strip on the southwest flank of the structures on the 

southwest side of Spanish Valley. If so, resources between 

the northwest end of the- Lisbon Valley anticline and the 

Colorado River are probably no more, and may be much 

less, than on the southwest flank of the Moab anticline.

Estimates of resources of l^Og in the Chinle Formation 

are summarized in table 2.

Information about vanadium content of deposits in the 

Chinle is too incomplete to warrant more than a general 

estimate for the Chinle as a whole. To judge from incomplete 

data about vanadium produced from deposits in the Lisbon 

Valley (Wood, 1968, p. 776), resources of V2<35 are probably 

not more than two-thirds those of

DEPOSITS IN THE MORRISON FORMATION

The Morrison Formation is the principal host to deposits 

in the central and northwestern part of the Moab quadrangle
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO 

TABLE 2. Resources of uranium in the Chink Formation in the Moab quadrangle, Utah-Colorado

[Reserves compiled from data made available by Grand Junction office, ERDA (formerly U.S. Atomic Energy Commission). Neg., negligible]

Area Reserves as of July 1, 1971 Estimated (hypothetical) resources

(metric tons) (metric tons)

Ore U 3O8 U 308

minimum maximum minimum maximum

Moss Back Member

Lisbon Valley anticline ......

Dolores anticline ................

Area tributary to Colorado 

and Green Rivers.

1,491,000 5,853 360,000 4,500,000 900 18,000

0 0 Neg. 7,200,000 Neg. 27,000

8,378 23 '1,800,000 '5,000

Undifferentiated Chinle

Moab anticline ....

Southwest side of

Spanish Valley.

'450,000 

Neg. 450,000

'1,360 

Neg. 1,360

Total (rounded for resources) 1,499,378 5,876 1,700,000 '13,500,000 7,300 53,000

'Where only one number is given for a particular area that quantity is included in the sum of both the maximum and minimum columns. 

See text discussion of individual areas for explanation of range in estimate for some areas. 

^Included with area tributary to Colorado and Green Rivers to avoid disclosing information about individual properties.

B13

(fig. 2). The formation has been eroded from much of the 

western part of the quadrangle. Although it is present in 

much of the eastern part, no deposits are known and the 

formation is judged to be unfavorable for deposits there. 

Most of the deposits in the Morrison are in sandstone in the 

uppermost part of the Salt Wash Member. A moderate 

number of deposits, most of them small but a few of medium 

size, occur in sandstone beds lower in the Salt Wash; 

deposits at this stratigraphic position are more abundant in 

the Bull Canyon and the Carpenter Ridge-Martin Mesa 

areas, Colorado, and the Thompson area, Utah, than 

elsewhere. Several deposits occur in sandstone lenses in the 

Brushy Basin Member; they are widely scattered and 

although most are small, a few are of medium size.

The uranium-vanadium deposits in the uppermost 

sandstone of the Salt Wash Member tend to be clustered in 

ill-defined patches of ground (fig. 5). These patches range 

from several hundred meters to several kilometers; they are 

irregular in shape but they tend to be elongate parallel to the 

long axes of the host sandstone lenses. The sandstone and 

associated mudstone layers in these patches have certain 

geologic characteristics that are rather consistently 

associated with ore deposits; for that reason these 

characteristics are thought to be indicative of favorable 

ground and collectively are useful guides in exploration and 

resource appraisal. These characteristics are as follow:

(1) The sandstone is generally about 12 m or more thick.

(2) Below the zone of surface oxidation the sandstone is light 

gray to buff in color and contains sparse and finely 

disseminated pyrite and in the zone of oxidation it has a 

yellowish cast, in contrast to a light pink or pale red 

color in unfavorable ground in both zones.

(3) The mudstone that occurs as thin layers or pebbles in the

sandstone and the mudstone in contact with the bottom 

or top surfaces of the sandstone is altered to gray or 

green, in contrast to a red color in unaltered mudstone; 

the altered mudstone contains finely disseminated 

pyrite below the zone of oxidation. 

(4) The sandstone contains more coalified fossil wood in and

near ore deposits than remote from deposits. 

Weir (1952) has suggested a scheme of numerical evaluation 

of these geologic guides as they can be recognized in drill 

holes.

By the middle of 1971 nearly 12,200,0001 of ore containing 

almost 31,500 t of 113 Og had been found in the Salt Wash 

Member of the Morrison Formation within the Moab 

quadrangle. About 80 percent of the ore found had been 

mined and the remaining 20 percent was in reserves 

considered by the Atomic Energy Commission to be minable 

at $8 per pound of L^Og. The areas that are comprised by 

the Uravan mineral belt (fig. 5) and ground in Colorado 

immediately adjoining the belt account for about 90 percent 

of the ore produced.

The U3Og contained in ore was apportioned among 

deposits of a wide range in size as shown in the tabulation 

below. The table includes deposits in the extreme 

southwestern part of the Uravan mineral belt, which extends 

into the adjoining Cortez quadrangle, and therefore the total 

of the amounts entered in the table is larger than the amount 

given above for the Moab quadrangle. Distribution of U3Qg 

by size ranges of deposits in the Salt Wash Member of the 

Morrison Formation, based on production to July 1, 1971, 

and reserves, mostly of that data are tabulated below. 1

'Compiled primarily from information supplied by the Grand Junction Office, ERDA (formerly 

U.S. Atomic Energy Commission); supplemented in some areas by field inspection and estimates 

adapted from published data.
B14 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

109°45 39°

109°00' 108°45'

Yellow Circle 

mines 

£ Apex of 

ralluvial

FIGURE 5. Simplified geologic map of the central part of the Moab Ix2-degree quadrangle showing uranium-vanadium deposits in the 

Morrison Formation and the significant geologic relations of these deposits.
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B15

EXPLANATION

Intrusive rocks of the La Sal Mountains (mid-Tertiary) 

Morrison Formation and post-Morrison formations

Base of Morrison Formation and borders of intrusive 

rocks Dashed where covered

Pre-Morrison formations

Fault Dashed where covered

Significant uranium deposit or group of deposits

Approximate area of ground favorable for uranium 

deposits

Edge of alluvial fan and area of subsidence

General direction of flow of Salt Wash distributary 

streams in area of fan

Dominant trend of ore rolls, fossil logs, and sedimentary structures

Size range

(pounds L^Og)

0-200

200-2,000

2,000-20,000

20,000-200,000

200,000-2,000,000

More than 2,000,000

Totals

No. of

Deposits

322

282

317

309

85

5

1319

Contained

Total pounds

22,478

235,969

2,562,569

22,001,658

45,127,918

14,154,675

84,105,267

J308

Percent of total .

0.027

.28

3.05

26.2

53.7

16.8

100.037

As can be seen from the table, nearly 97 percent of the 

uranium contained in known deposits in the Salt Wash is in 

the larger deposits, those that contain at least 20,000 pounds 

(9.11) of 1)305 each, and 70 percent of the total uranium is in 

deposits that contain at least 200,000 pounds (911) each. In 

view of the rather wide distribution of deposits, as shown in 

figure 5, and because the size-range distribution of known 

deposits in each of the principal areas of their occurrence is 

fairly similar to the distribution of all deposits, as shown in 

the table, it is likely that undiscovered deposits are apportioned among the size intervals in about the same proportions as the known deposits.

Several areas potentially favorable for significant 

resources in the Morrison will now be discussed.

URAVAN MINERAL BELT

Uravan mineral belt is the name applied to a narrow, 

elongate area in southwestern Colorado in which the 

uranium-vanadium deposits in the Morrison Formation 

generally are closer spaced, larger in size, and higher in grade 

than those in adjoining areas (Fischer and Hilpert, 1952). 

The belt extends from Gateway through Uravan to Slick

Rock, a distance of about 115 km (fig. 5). The patches of 

favorable ground in which the deposits occur, the orebodies 

themselves, and the so-called ore rolls small, podlike 

bodies of ore tend to be elongate normal to the trend of 

the belt. In addition, sedimentary structures in the host rock, 

such as current-lineation marks and the dip of crossbedding 

planes and fossil logs, which were rafted into place, are 

generally oriented normal to the belt. The belt crosses 

tectonic structures which show little or no apparent localizing influence on the belt; some deposits, however, lie outside 

the general limits of the belt near fault zones in Gypsum 

Valley and southeast of Slick Rock.

The area of the mineral belt probably was made especially 

favorable for ore by geologic conditions extant during the 

accumulation of the Salt Wash Member of the Morrison. 

The favorable host rocks are sandstone lenses that were 

formed by streams. The trend of these lenses perpendicular 

to the arcuate mineral belt (fig. 5) resembles the pattern of 

ribs of a fan, the apex of which would be a vaguely defined 

point several tens of kilometers west of the belt. Shawe 

(1962, fig. 62.2) suggested that this pattern of sedimentary 

structure along the mineral belt resulted from deposition 

along the toe of a subsidiary fan locally superposed on the 

larger fan that formed the entire Salt Wash Member; 

perhaps this smaller fan formed in an area of shallow 

subsidence that developed during Salt Wash time, for the 

member is a little thicker in this area than in other places. A 

few miles east of the belt the host sandstone beds are finer 

grained and more thinly and evenly bedded, as if they were 

deposited in a shallow body of standing water. Immediately 

west of the belt, coalified fossil plants are not present in 

many of the Salt Wash sandstone lenses; either the plant 

material was never present, or it was destroyed after burial in 

the beds. Where deposits occur west of the belt, however, 

coalified fossil plants are present and probably were 

preserved by locally high water tables.

The observed relations and the hydrologic system that 

would likely develop in this geologic environment permit the 

following hypothesis regarding belt localization: The belt 

extended along the toe of an east-facing alluvial fan. 

Standing water persisted a short distance east of the belt; as a 

result, the water table along the belt was virtually at the 

surface while the host sandstone lenses accumulated, preventing destruction by oxidation of plant material buried in the 

sand. Because of the original sedimentary dip of the beds, a 

gravity flow of ground water in an easterly direction would 

have started during the accumulation of the Salt Wash sand 

lenses and probably would have been most active from then 

until the invasion of Mancos seas in the Late Cretaceous. 

The deposits probably formed from these ground waters in 

this interval.

Undiscovered resources in the part of the Uravan mineral 

belt within the Moab quadrangle as estimated by methods
B16 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

described in the section on methodologies are about 6,8001 

of U3Og, contained in about 2,700,0001 of ore. Most of these 

resources are judged to be in deposits in and close to the 

patches of favorable ground that contain most of the known 

deposits (fig. 5). These undiscovered resources amount to 

only about 20 percent of the total rescmrces originally 

present in the area of the belt.

LA SAL MOUNTAIN-ISLAND MESA AREA

The La Sal Mountain-Island Mesa area is west of the 

Uravan mineral belt and near its eastern side straddles the 

Utah-Colorado State line (fig. 5). It is roughly triangular in 

shape with its base along the irregular line of Morrison 

outcrops that extend from Island Mesa northward to a point 

about 16 km southwest of Gateway, and its apex is in the 

vicinity of Kane Springs. If the Uravan mineral belt lies 

along the toe of an alluvial fan, as suggested above, most of 

the La Sal Mountains-Island Mesa area would be on the 

mid-slope and apex parts of this fan; the Kane 

Springs-Wilson Mesa part of the area might be north and 

west of the fan (fig. 5).

Significant deposits have been found at and near the 

outcrop along La Sal Creek. These deposits are in an 

east-trending patch of favorable ground, similar to the 

favorable patches in the Uravan mineral belt. Presumably 

the host rock of the La Sal Creek deposits accumulated 

along one of the distributary streams that formed the 

supposed alluvial fan; the presence of coalified fossil wood in 

the ore indicates that at least locally the water table during 

accumulation of the host rock was high enough to prevent 

destruction of the plant fossils by oxidation.

A large deposit at the Rattlesnake mine has been 

exploited, and numerous deposits, mostly small but some of 

moderate size, have been found at and near the outcrops 

near the Yellow Circle mines (fig. 5). In addition, at least two 

large deposits have been found by subsurface exploration 

midway between the Rattlesnake mine and the deposits 

along La Sal Creek. It will not be known until exploration 

and mine development progresses farther whether these 

groups of deposits are all on a continuous favorable trend, as 

suggested by Johnson and Thordarson (1966), or in separate 

favorable patches that are approximately alined, because the 

Salt Wash does not crop out along this trend.

South of the trend between La Sal Creek and the 

Rattlesnake and Yellow Circle mines the Salt Wash is not 

exposed, except in the vicinity of Island Mesa, where some 

small- to medium-sized deposits occur, and along the line of 

outcrop from Island Mesa to La Sal Creek, where only a few 

small deposits are known. In the concealed Salt Wash of this 

area, however, there is room for one or more favorable 

patches or trends. If present, the favorable patches or trends 

are probably elongate in a southeasterly direction, more or 

less radial from the apex of the alluvial fan. This part of the 

La Sal Mountains-Island Mesa area could be tested for

favorable ground with a pattern of drill holes 300 to 600 m 

apart.

The Salt Wash underlies a considerable part of the east, 

north, and northwest flanks of the La Sal Mountains. Much 

of this part of the area probably is also on the midslope of the 

Uravan mineral belt alluvial fan (fig. 5); therefore, this area 

might also contain some patches of favorable ground. 

Appraisal, however, is difficult. No deposits have been 

found in the Salt Wash high on the flanks of the mountains, 

where exposures, because of more soil and vegetation, are 

not as good as in other parts of the Moab quadrangle. 

Nevertheless, continued exploration by surface methods 

around the La Sal Mountains might find a few deposits or 

patches of ground lithologically favorable for ore, in which 

case subsurface exploration behind the outcrop might 

be rewarding; without these guides, subsurface exploration 

would be blind and probably not justifiable.

Undiscovered resources in the La Sal Mountains-Island 

Mesa area, as estimated in the manner described in the 

section on methodologies, are about 8,200 t of U3Og in 

2.7-3.2 million t of ore. Much of this, perhaps 75 percent, is 

judged to be in the central part of the area, extending from 

La Sal Creek on the east to Kane Springs on the west, 

including the ground between the Rattlesnake mine and the 

Yellow Circle mines (fig. 5). This area is about 337 km2 , and 

the known deposits at the two ends permit an estimate with 

moderate confidence that undiscovered resources are about 

6,800 t of U3Og in 2,300,000 t of ore. The moderately large 

deposits recently found in the middle of this area by 

subsurface exploration support this optimistic appraisal.

The southern part of the La Sal Mountains-Island Mesa 

area, roughly bounded by lines connecting the Rattlesnake 

mine, Island Mesa, and La Sal Creek, probably contains one 

or more favorable patches of ground, like those known in the 

La Sal Creek-Kane Springs trend. On this assumption, and 

by comparison with an adjoining area on the east described 

in the section on methodologies, resources of 900 t or more 

of U3Og have been assigned to the southern part of the La 

Sal Mountains-Island Mesa area. The scant exposures of the 

Salt Wash in this part of the area do not permit appraisal 

with much confidence.

Appraisal of the ground on the east, north, and northwest 

flanks of the La Sal Mountains, where virtually no deposits 

have been found, is made with even less confidence; 

nevertheless, as explained in the section on methodologies, 

resources containing about 540 t of U3Og are estimated for 

this part of the area.

SAGE PLAIN AREA

The Sage Plain area is along the southern edge of the 

Moab quadrangle, partly in Colorado but mostly in Utah. It 

is west of the Uravan mineral belt and probably southwest of 

the mineral belt fan. Exposures are limited to the northern 

edge of the area. These exposures have not been studied 

adequately to permit a sound interpretation of the geologic
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B17

environment of deposition of the Morrison Formation 

relative to its mineral potential, even though numerous 

small- to medium-sized and a few large deposits have been 

found in the upper sandstone layer of the Salt Wash at and 

near its outcrops. A conspicuous, ore-bearing, 

northeast-trending sandstone lens is exposed on both sides 

of East Canyon (fig. 5), and two other ore-bearing northeast 

trends are suggested by Johnson and Thordarson (1966, pi. 

1) nearby. These authors (1966, p. H46) also suggested that 

the northeast-flowing streams that deposited the host lenses 

in these ore-bearing trends were deflected southeastward by 

slightly higher ground over the ancestral Lisbon Valley salt 

anticline, and that these trends perhaps connect with the 

ore-bearing northwest-trending patches of ground in the 

Uravan mineral belt of Slick Rock (fig. 5). This relationship 

is possible, and perhaps likely, and it permits optimism that 

ground favorable for uranium deposits lies in the Sage Plain 

area and suggests the pattern and orientation of this 

favorable ground.

If the deposits that have been found at the outcrop along 

the northern edge of this area are a representative sample of 

the area, undiscovered resources in the area estimated by a 

method described in the section on methodologies, probably 

total about 2,000 t of l^Og in about 1,200,000 t of ore. On 

the other hand, a few moderately large deposits have been 

found by subsurface exploration in the eastern part of the 

area near the Uravan mineral belt; if these deposits are more 

nearly representative of part or all of this area, resources 

could be somewhat larger.

THOMPSON AREA

In the Thompson area, Utah, the Morrison Formation 

crops out for about 50 km along a west-trending line from a 

point several kilometers west of the State line (fig. 5). 

Numerous deposits have been found along these outcrops. 

Except for some in the Yellow Cat group and in two other 

groups a short distance east of the Yellow Cat group, most of 

them are small. Almost all of these deposits are in the lowest 

sandstone in the Salt Wash Member of the Morrison, except

in the vicinity of the principal groups, where some deposits 

are in sandstone beds higher in the Salt Wash and some are 

in sandstone in the basal part of the Brushy Basin Member. 

All of the larger deposits are in rather well-defined sandstone 

lenses that trend northeasterly or easterly. Favorable ground 

might continue northeast of the known deposits in the 

vicinity of the Yellow Cat group, but the Salt Wash is 

covered by an increasing thickness of younger beds in this 

direction, and any deposits present might not be large 

enough to justify the cost of deep exploration and development.

About 270,000 kg of UaOg in 122,000 t of ore have been 

discovered in deposits in the Thompson area. These deposits 

are distributed in an area of about 39 km2 underlain by the 

Morrison Formation that is estimated to be fully explored. 

The Morrison Formation becomes progressively deeper 

northward from the fully explored ground. Nevertheless, in 

an area of about 78 km2 adjoining it on the north, along the 

general trend of the lenses of ore-bearing sandstone, the 

depth to the base of the formation is mostly less than 300 m 

and probably averages no more than 150 m. It is possible 

that undiscovered deposits in this unexplored area contain 

proportionately about as much uranium as in the fully 

explored area or about 5401 of ^Og in 240,0001 of rock. If 

uranium is apportioned among undiscovered deposits as it is 

among those that have been discovered, about two-thirds of 

the estimated amount would be in those containing 

9,070-90,700 kg.

SUMMARY OF RESOURCES IN THE SALT WASH MEMBER

Hypothetical resources of uranium and vanadium estimated to be present in undiscovered deposits in the Salt 

Wash Member of the Morrison within the area of the Moab 

quadrangle are about 18,000 t of U3Og and 110,000 t of 

¥205 contained in about 7,300,000 t of mineralized rock. 

The estimates for each area are summarized in table 3.

The resources listed in table 3 correspond approximately 

to material from which the U.S. Atomic Energy Commission

TABLE 3. Resources in the Salt Wash Member of the Morrison Formation in the Moab quadrangle,

Utah-Colorado

[Reserves complied from data made available by Grand Junction Office, ERDA (formerly U.S. Atomic Energy Commision). Reserves and 

resources of V2O5 calculated by using an average content of 1.5 percent as given in the text in the section "Uranium and vanadium deposits"]

Reserves as of July 1, 1971 

(metric tons)

Estimated (hypothetical) resources 

(metric tons)

Ore V205 Ore U30g V205

Uravan mineral belt ................................ 2,053,500 5,790 30,800 2,700,00 6,800 41,000

La Sal MountainsIsland Mesa:

Central part ..................................... 105,600

South part ...............................

North part ...............................

Sage Plain ............................................... 203,300

Thompson ............................................... 19,300

Totals (rounded for resources). 2,381,700 6,468 35,730 7,300,000 17,500 109,000

105,600

203,300

19,300

299

322

57

1,590

3,050

290

2,450,000

450,000

240,000

1,200,000

240,000

6,700

900

590

2,000

540

36,000

6,800

3,600

18,000

3,600
B18 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

estimated in 1971 that uranium could be recovered at 

forward costs of $8 per pound.

In addition to the resources discussed thus far, a relatively 

substantial amount of uranium oxide is present in leaner 

rock containing at least 0.02 percent l^Og. Most of this 

leaner rock is in the same deposits as and adjoins the richer 

rock composing those resources. Data about leaner rock 

obtained by the U.S. Geological Survey in the 1950's in 

exploring for deposits by drilling is somewhat scanty but 

suggest that, if all such leaner rock were included in the 

estimate of hypothetical resources, the amount of contained 

U3Og would probably be from 25 to 50 percent, 4,500-9,000 

t more than the amount in table 3. Similarly, the amount of 

¥205 would be increased by 27,000-54,000 t.

SUMMARY OF RESOURCES

Undiscovered (hypothetical) resources in the Moab 

quadrangle are probably at least 22,7001 of U3Og, and may 

be a few times more than that; those of ¥205 are about 

113,000 t. Most of the U3Og resources are in the Chinle and 

Morrison Formations which are the hosts to the bulk of the 

resources already discovered, and most of the ¥205 

resources are in the Morrison Formation. A small but 

indeterminate amount of ^Og resources is probably 

present in the Cutler Formation. Like the discovered 

resources in the Cutler, it is probably only a fraction of the 

amount in the other two formations as mentioned earlier in 

the section "Uranium and vanadium deposits."

Undiscovered resources in the Chinle Formation could be 

about twice the 30,800 t of ^Og already found in it, if the 

.Dolores anticline and the northeast flank of the Lisbon 

Valley anticline should prove to be as favorable for deposits 

as the southwest flank of the Lisbon Valley anticline. 

Otherwise, undiscovered resources in the Chinle may be 

somewhat less than 9,000 t.

Resources in the Salt Wash Member of the Morrison 

Formation are estimated to be about 18,000 t of U3Og and 

109,0001 of V2O5. Approximately three-fourths of the totals 

are about evenly divided between the Uravan mineral belt 

and the central part of the La Sal Mountains-Island Mesa 

area. The other one-fourth is distributed unevenly among 

the other areas listed in table 3.

The resources of U3Og summarized represent the amount 

in rock that would have constituted ore under conditions 

that prevailed in 1970-71. In addition, a substantial volume 

of mineralized rock adjacent to ore in most deposits contains 

at least 0.02 percent ^Og, but less than the 0.10 percent 

U3Og cutoff grade for ore. Incomplete data about the 

amount of such leaner rock and its UjOg content suggests 

that the estimates of resources given above would be larger 

by 25 to 50 percent if such leaner rock were included.

METHODOLOGIES

METHODS OF ESTIMATING RESOURCES IN THE

SALT WASH MEMBER OF THE

MORRISON FORMATION

Two basic methods were used to estimate the hypothetical 

resources in the Salt Wash Member of the Morrison 

Formation; each was applied in different parts of the Moab 

quadrangle, distinguished in figure 6. One method makes use 

of a factor derived by dividing the aggregate length of 

outcrop of exposed ore deposits in the Salt Wash by the total 

length Salt Wash outcrop in a given area. It is assumed that 

the outcrop is random relative to the distribution of deposits, 

and therefore, it serves as a slice exposing a representative 

sample of the deposits present in the area to which the 

outcrop is related. The length of ore-bearing outcrop relative 

to the total outcrop represents the percentage of ground 

underlain by ore behind the outcrop. Multiplying this factor 

by the measured size of an area yields an estimate of the 

number of square meters occupied by ore within the area. 

The volume of ore was calculated by applying an assumed 

average thickness of ore ranging from 0.5 to 0.6 m. A factor 

of 0.437 m3 /t was used to convert volume to tons of ore. As 

used in connection with this scheme, ore consists of a layer of 

mineralized rock at least 0.3 m thick containing at least 0.1 

percent U3Og or 1 percent V2O5 (Bush and Stager, 1956).

In the second method it is assumed that the tons of ore 

discovered (reserves plus production) per unit area in 

well-explored parts of a general area are indicative of the 

tons-per-unit-area in the adjoining sparsely explored parts 

of that area judged to be equally favorable for ore. The 

application of both of these methods in various areas will be 

described in the following paragraphs. The areas will be 

discussed in the same order as in the main text.

URAVAN MINERAL BELT

The first of the methods just described is particularly well 

adapted to estimating resources of the area in the general 

vicinity of the Uravan mineral belt where numerous deposits 

are exposed along many tens of kilometers of outcrop on the 

sides of canyons and valleys. The percentage of area 

underlain by ore was estimated individually by this method 

for all but two of the subareas related to the mineral belt. The 

percentages were determined indirectly for the other two, the 

Bull Canyon and Gypsum Valley areas (fig. 6).

By the mid-1950's, results of exploration and geologic 

study suggested that the incidence and sizes of deposits in the 

Bull Canyon area were probably at least intermediate 

between those characteristics of the East Gateway and 

Uravan segments. Thus, rather than assembling the detailed 

information that is the basis for estimating resources in other 

parts of the belt, it is assumed that the fraction of the area 

underlain by ore in this segment of the belt is the mean of the
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B19

fractions of the Uravan and East Gateway areas as given in a 

subsequent list, weighted according to their respective areas. 

Much of the Morrison Formation in the Gypsum Valley 

area is in structural blocks downfaulted as the result of 

collapse of a salt-cored anticline. Margins of many tracts 

underlain by the Morrison are faults along which it abuts 

against older rocks so that the edges of its component beds 

are not exposed to the extent that they are elsewhere in the 

mineral belt. This lack of continuity for the outcropping 

edge of the ore-bearing interval precludes determing the 

fractional length of the outcrop that is ore-bearing, as an 

index of the adjoining area that may be ore-bearing. Hence 

the simple method based on the mineralized fraction of total 

outcrop cannot be used to estimate resources for this area. 

Instead, that method was used indirectly, by comparing the 

Gypsum Valley area with the East Gateway area, as follows:

1. We believe that in 1954 both areas had been explored to 

approximately the same extent and that the ratio of ore 

in known deposits (including production) to that in 

undiscovered deposits, and hence to total resources, 

was about the same for the Gypsum Valley area as it was 

for the East Gateway area.

2. Strobell and others (1954) and C. G. Gilbert (U.S. 

Geological Survey, written commun., 1954) used results 

of mine mapping and drilling to estimate the percentage 

of each total area that was then known to be ore-bearing. According to these estimates, the percentage of the 

Gypsum Valley area known to be ore-bearing was only 

about one-third of the percentage of the East Gateway 

area known to be ore-bearing; that is, the Gypsum 

Valley area was mineralized only about one-third as 

much, per unit area, as the East Gateway area.

3. On the assumption that this ratio of one-third, derived 

from known mineralization, also applies to total 

mineralization in the two areas, it follows that the total 

percentage of the Gypsum Valley area underlain by ore 

(that is, production + reserves + undiscovered resources) 

is 0.20 or about one-third of the percentage of the East 

Gateway area underlain by ore.

The percent of each subarea estimated to be underlain by 

the Salt Wash Member, mineralized with a content of at least 

0.1 percent l^Og across a thickness of 0.3 m, and the area of 

the Salt Wash in each are listed in the following table.

Name of subarea

Gypsum Valley .................................

Slick Rock ........................................

Area 

(sq. km)

145

212 .

373

370

96

130

243

Estimated area 

underlain by ore 

as percent of 

total area

0.38

.61

1.10

.92

.54

.21

1.11

The fraction of each area underlain by ore as set forth in 

the list yields a rounded estimate of 13,500,000 t of ore 

originally present in the Salt Wash Member of the Morrison 

Formation in about 1,550 km2 of the Uravan mineral belt 

within the Moab quadrangle.

The estimate of resources still undiscovered in mid-1971 is 

6,800 t of U3Og in 2,700,000 t of ore. It is the amount by 

which the estimate of the resources originally present in the 

area of the mineral belt exceeds the resources discovered 

(production plus reserves) up to that time.

LA SAL MOUNTAIN-ISLAND MESA AREA

If the distribution of deposits close to the outcrop of the 

Salt Wash Member at places along the periphery of the La 

Sal Mountain-Island Mesa area is a general indication of the 

distribution of concealed deposits, about 75 percent of the 

undiscovered resources are probably in the central part of 

the area on the south and west sides of the La Sal Mountains 

(fig. 6). Most of the remainder is thought to be in the 

southern part south of a line extending generally eastward 

from the Rattlesnake mine.

The distribution of discovered deposits in the vicinity of 

La Sal Creek and along the western belt of outcrop of the 

Morrison northwestward from the vicinity of the 

Rattlesnake mine is assumed to be generally representative 

of the general distribution and incidence of deposits 

throughout the 344 km2 of the central part of the area. The 

known deposits along La Sal Creek occupy an area of about 

57 km2 . Production plus reserves total about 980,000 kg of 

U3Og, or about 17,100 kg/km2 . The deposits between the 

Rattlesnake and Yellow Circle mines occupy an outcrop 

length of about 32 km; assuming that a strip averaging 0.65 

km wide behind this outcrop has been reasonably well 

explored, these deposits occupy an area of 21 km2 . Production plus reserves total about 966,000 kg ^Og, or about 

46,800 kg/km2 . If the average of these amounts, weighted 

according to the area of each, is used as an index of the 

average amount of ore that may be present in the unexplored 

ground between La Sal Creek and Kane Springs, the 

undiscovered resources should be about 6,700 t of ^Og in 

2,500,000 t of ore. i

Identified deposits in the Salt Wash Member are few in the 

southern part of the La Sal Mountain-Island Mesa area. 

Nearly all are small and confined to the immediate vicinity of 

the outcrop. If these deposits are truly representative of the 

area the hypothetical resources in the area are trivial.

On the other hand, the cluster of deposits in Gypsum 

Valley near its northwest end may be a better indication of 

the amount of resources in the southern part of this area. 

These deposits are just outside the area on the east and are 

within an arbitrarily outlined rectilinear block of ground 

about 5 km wide extending 20.3 km north from the south 

edge of the cluster to the north edge of this southern area. 

The Morrison Formation is present in about 85 km2 of the
B20 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

109°45 109°00' 108°45'

LA SAL MOUNTAINSISLAND MESA AREA

FIGURE 6. Map showing outlines of areas distinguished in estimating resources in the Salt Wash Member of the Morrison Formation.
URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO B21

EXPLANATION

Intrusive rocks of the La Sal Mountains (mid-Tertiary) 

Morrison Formation and post-Morrison formations

Base of Morrison Formation and borders of intrusive 

rocks Dashed where covered

Pre-Morrison formations

Fault Dashed where covered

Significant uranium deposit or group of deposits

Approximate area of ground favorable for uranium 

deposits

Edge of alluvial fan and area of subsidence

Boundaries of areas distinguished for resource estimation Solid line, major division in table 3; 

dashed lines, subareas

arbitrary block. Dividing the amount of L^Og discovered in 

the Gypsum Valley cluster and in one deposit within the 

southern subarea near the north end of that valley by the 

area of the arbitrary index block yields a quantity of 3,000 

kg/km2 . Assuming that the incidence of deposits in this 

arbitrarily defined area is indicative of the incidence of 

deposits in the adjoining area, uranium resources in undiscovered deposits within the 310 km2 of the southern part 

of the La Sal Mountain-Island Mesa area would be about 

900 t of U3Og in 360,000 to 450,000 t of mineralized rock.

Deposits in the part of the La Sal Mountains-Island Mesa 

area north of the belt extending west from La Sal Creek, are 

mostly small. All but one are distributed along the outcrops 

of the Morrison from Kane Springs to Wilson Mesa on the 

northwest side of the mountains. As the largest of these 

contained only a little more than 1,3601 of ore it is assumed 

that the maximum extent of fully explored ground in this 

part of the area is a strip no more than 0.16 km wide adjacent 

to 60 km of outcrop of the Salt Wash Member. Nearly 11,000 

kg of U3Og has been found in deposits within the 9.6 km2 of 

strip of about 1,130 kg/km2 . If the sample strip adjacent to 

the outcrop is representative of the whole 520 km2 underlain 

by the Salt Wash Member in this part of the area, resources 

in undiscovered deposits within it are about 5901 of l^Og in 

a little more than 230,000 t of mineralized rock. The size of 

deposits in the sample strip suggests that estimated undiscovered resources might be in similarly small deposits; 

however, the general distribution of discovered resources 

among deposits in different ranges of size in the other parts 

of the La Sal Mountains-Island Mesa area suggests that if 

the estimated amount of resources is actually present, at least 

80 percent may be in 10 to 15 deposits with masses of 3,200 to 

32,000 t.

SAGE PLAIN AREA

Deposits in the part of the Sage Plain area within the 

Moab quadrangle are irregularly distributed mostly at or 

close to 72 linear kilometers of outcrop of the Salt Wash 

Member of the Morrison Formation along the north edge of 

the plain. Most of these deposits had some exposure at the 

outcrop and were delimited by exploration in their immediate vicinity. The amount of uranium in discovered 

deposits, presumed to have had some outcrop expression, 

when recalculated as the amount per unit area of a strip of 

fully explored ground bordering the outcrop, is considered 

to indicate the amount of uranium present per unit area in 

the unexplored part of the Sage Plain. In the absence of 

specific information about exploration in the area, the width 

of the strip of ground considered to be fully explored is 

assumed to be not less than the estimated length of the 

largest deposit and not more than twice that length. The 

mass of ore discovered in the largest outcropping deposit is 

34,172 t. Calculated at 0.437 m3 /t and an average thickness 

of 0.61 m, the area of such a deposit would be 24,480 m2 . The 

actual shape is not known, but as many deposits in the 

Morrison are somewhat elongate, although not excessively 

so, it is assumed to be generally rectilinear with a length to 

width ratio of 4 to 1. For the area calculated above the 

length would be about 0.32 km. The amount of l^Og 

discovered in deposits within a strip considered to be fully 

explored along 72 km of outcrop of the Salt Wash Member is 

about 360,000 kg. This is equivalent to 15,650 kg/km2 in the 

23 km2 of the strip, if the width of the strip equals the 

maximum dimension of the largest deposit, and 7,800 

kg/ km2 if the width of the strip is assumed to be twice that 

dimension.

Resources mostly in undiscovered deposits in the remaining unexplored portion of the area for each of these 

alternatives would be 4,300 of UsOg in 2,500,0001 of rock or 

1,950 of UsOg in 1,200,000 t of rock in areas of 275 or 251 

km2 respectively. The larger estimate is probably an upper 

limit for resources in the area, because the presence of this 

amount of resources would be possible only if the Salt Wash 

Member were as favorable for deposits in this portion of the 

Sage Plain as it is on the average in the Uravan mineral belt. 

The position of the Sage Plain relative to the inferred edge of 

the subsidiary Salt Wash fan (fig. 5) suggests, however, that 

the portion of the plain within the Moab quadrangle is not as 

favorable for deposits as the Uravan mineral belt.

If, as seems probable, the amount of undiscovered 

resources is closer to the lesser of the amount given above, 

1,950 t of UsOg in 1,200,000 t of rock and if the number of 

undiscovered deposits of different sizes is proportionately 

about the same as that of discovered deposits, nearly 1,8001 

of U3Og would be in 22 deposits that contain at least 91 of 

U3Og. Of these five or six would be likely to contain at least 

90 t of
B22 GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

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