4-J

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a-.

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^
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65-

COVER PHOTOGRAPHS

1

2

5

3
6

7

8
10

9
11

4

12

13

14

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

andUranium and Vanadium Resourcesin the Moab 1° x 2° Quadrangle,
Utah and Colorado
By A. P. BUTLER, JR., and R. P. FISCHERGEOLOGYAND

GEOLOGICALUNITED

STATESRESOURCESSURVEY

GOVERNMENTOFURANIUM

DEPOSITSPROFESSIONAL

PAPERPRINTING

WASHINGTONOFFICE,

988-A, B:

1978

UNITED STATES DEPARTMENT OF THE INTERIORCECIL 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 andMinerals Policy Act of 1970 (Public Law 91-631, Dec. 31, 1970). Total resources forpurposes 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 ofmineral resources results in approximations, subject to constant change as known
deposits are depleted, new deposits are found, new extractive technology and uses aredeveloped, 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. CATHCARTGEOLOGYAND

GEOLOGICALRESOURCESSURVEYOFURANIUM

PROFESSIONALDEPOSITS

PAPER

988-A

A study of the distribution
and occurrence of uranium inphosphate deposits of the world

UNITED

STATES

GOVERNMENTPRINTING

OFFICE,WASHINGTON

:

1978

UNITED STATES DEPARTMENT OF THE INTERIORCECIL D. ANDRUS, Secretary
GEOLOGICAL SURVEY
H. William Menard, Director

Library of Congress Cataloging in Publication Data
Cathcart, James Bachelder, 1917Uranium 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

Page

Abstract ............................................................................................. Al
Introduction ......................................................................................... 1
Guano and guano-derived deposits ...................................................... 1
Igneous apatite deposits ....................................................................... 2
Marine phosphorite ............................................................................. 2
Secondary deposits .............................................................................. 3

Other deposits ..................................................................................... A4
Lake beds ..................................................................................... 4
Offshore deposits .......................................................................... 4
Phosphate resources ............................................................................ 5
Selected references ............................................................................... 5

TABLESPage

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 DEPOSITSURANIUM IN PHOSPHATE ROCK
By JAMES B. CATHCART

ABSTRACTUranium is a trace constituent of all apatites in amounts that typicallyrange 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, andisolated 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 ofphosphoric acid by the wet process. In 1972, about 15 million tonnes (metrictons) of phosphate rock was used to make phosphoric acid in the UnitedStates. This phosphoric acid probably contained about 1,500 tonnes ofuranium. It seems likely that tonnages of uranium in phosphoric acid willreach 3,000 tonnes per year within the next 25 years because of the increased
demand for phosphatic fertilizers and increases in the amount of phosphaterock used to make phosphoric acid. About twice this amount might bepresent worldwide. Thus, marine phosphorites are a significant source ofuranium for the future.

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 inthis paper is derived from these works, and each of them
contains an extensive bibliography.
The tables that accompany this report relate only reservedata. Reserves are defined as identified mineral deposits
whose grade and tonnage are reasonably evaluated, butwhich 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 threeenvironments as guano or in deposits derived from guano,
as igneous apatite, as marine phosphate deposits and insecondary deposits formed from each of these by weathering.

GUANO AND GUANO-DERIVED DEPOSITSINTRODUCTION
Uranium is present as a trace constituent in all apatites, inamounts that typically range from 0.003 to 0.030 percent.
Strutt (1908) first discovered that phosphatic rocks andfossil 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 thelate 1920's that a shark's tooth from the Pliocene of Floridacontained 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 mentionof 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.

Guano deposits are formed from the excreta of sea birds atthe surface and of bats in caves. Guano-derived deposits areformed when the soluble phosphate in guano is dissolved byground water and reacts with the underlying rocks. Apatite
is formed when the underlying rock is limestone, and ironand aluminum phosphates are formed when igneous rocks
underlie the guano.
About 5 percent of the world's production of phosphate isfrom guano-derived deposits, and a very small amount isfrom guano deposits (table 1). Guano contains from lessthan 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 phosphatesamples from Curacao contain 0.002 percent U, and thatsamples from Nauru contain 0.005 percent. The samples
with higher uranium contents (0.005-0.008 percent) are alsohigh in fluorine; the phosphate mineral is a carbonateAlA2

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

fluorapatite, rather than a hydroxyapatite. The samples arefrom tidal zones where fluorine and uranium were addedfrom seawater.
TABLE 1. Guano and guano-derived phosphate: reserves, production, anduranium content(table 2). Thorium is not usually present, except in very
minute amounts; however, an apatite sample from apegmatite near Bahia, Brazil, contained 0.005 percent U and1,500 ppm Th (Thorium analysis by Nancy Conklin, anduranium analysis by E. J. Fennelly, U.S. Geol. Survey).
TABLE 2. Igneous apatite: reserves, production, and uranium content

Location

Reserves(tonnes)

Production(tonnes/yr)

Uranium content(percent)

Limited, renewable
Small ....................

Reserves'(tonnes)

Production2(tonnes/ yr)

Uranium content3(percent)

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

2x10'

10x10"

0.001-0.003

Dorowa, Southern Rhodesia ...

.1x10'.4x10'.1x10".15x10'.1x10"

1x10"
1x10".4x10".2x10".1x10".2X109.02x1 09
Very small.01x10".01x10"None

Location

Bird guano (surface)
Peru (Pacific Coast) .
Chile (Pacific Coast)[Leaders (...) indicate no data available]

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"

Mineville district,
New York, U.S.A.

7xl06

002

.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).

Guano-derived iron and aluminum phosphate minerals'
Malpelo Island, Colombia ...
Trauira Island, Brazil ..........
Saldanha Bay, South Africa
Kito-Daito-Jima, Ryukyu
Islands.

0.4xl06
11x10".3x10"
2x10"

None ...................
do ................
do ................
do ................

No data.
Do.
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 ofmagnitude 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 withalkalic rocks, such carbonatite, nepheline syenite, pyroxenite, and ijolite.
The apatite mineral, a fluorapatite, ranges in amount froma few percent as an accessory mineral to 80 percent in somepipes 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 ofmillion 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 phosphatecame 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 igneousrocks 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

MARINE PHOSPHORITE
Marine phosphorite deposits are known throughout theworld 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 awayfrom abundant sources of clastic material. Some deposits arevery 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 thePermian 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, inamounts 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 certainlycontain similar amounts of uranium; that is, ranging fromabout 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 ROCKTABLE 3. Marine phosphorite: reserves, production, and uranium content
Location

Production 1

Uranium content2

United States
Central Florida ...............

2.1xl09 I

North Florida
South Georgia.
North Carolina ...............
North Georgia(Savannah River).

.3xl09 (South Carolina(Beaufort County) .......
(Charleston area) .........
Florida-Georgia(Hawthorn Formation).
Idaho, Montana, Utah,
Wyoming (Phosphoria
Formation).
Utah (Brazer Dolomite,
Deep-Creek Formation,
Lodgepole Limestone).
Alaska (Permian) ............
Others (Ala., Ark., Ky.,
Iowa, Kans., Okla.,
Calif., Nev.).

35x10"( 0.003-0.030; average
concentrate 0.011;
average pebble 0.015^ .004-.011; average .006

2xl09 }
\ .004-.011;average .006
Reserves not measured;
no production- .005
resources are billions
of tonnes.
do ............................
do .............. .006
do ............................
do ............................
6xl09

do .............. .005-.037
do .............. .003-.008;average.005
4x10"'.002-.021;average .009

Measured reserves are
No production- .001-.006
small; resources,
particularly in Alaska,
are billions of tonnes.
do ............................
do .............. 4.001-.024, average .008
do ............................
do .............. Rock: .OOI-.OI4 nodules
in black shale and limestone: .009-.030
AfricaAlgeria ............................
Angola ............................
Morocco .........................
Senegal ...........................
Togo ...............................
Tunisia ............................
U.A.R. (Egypt) ...............
Spanish Sahara ...............

\
J
/
\
/
I
J
/

0.8x10"0.011-0.014
None ................. No data.
20x10".007-.023
2x10".012-.018
2x10"
No data.
4x10".004-.009.6x10".007-.012
2x10".005-.011
Asia

China (Mainland) ...........
India ............'...................
Iran .................................
Iraq .................................

IxlO9.IxlO9.05x10".1x10'

3x10"
No data.
.1x10"
50.003-0.100
None ................. No data.
do ..............
Do.

Israel ...............................
Jordan ............................
Mongolia ........................
Saudi Arabia ..................
Turkey ............................
Australia .........................

.1x10'.IxlO9IxlO9.2x10".2x10"
IxlO9

1x10"".002-.020
1.5x10"No data.
No data .............
Do.
None ................. .002-.011;average .006
do .............. .004
do .............. '.001-.013; average .006
EuropeU.S.S.R. .........................
Others (Belgium, Germany,
France, England. Spain).

1x10'
10x10"
Small .............................. .IxlO6"0.005-0.010.001-.021;average.006'

Latin America
Mexico ............................
Colombia ........................
Venezuela ........................
Peru (Sechura) ................
Brazil (Bambui) ..............

O.lSxlO9 ',Production is / No data.
.2x10" Ia few tens
I 0.004-0.012; average .008
.IxlO9 \of thousands / .005
1+xlO9 jof tonnes) .006.3xl09 ' .....................
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).

A3

replaces calcium in the apatite structure (Altschuler andothers, 1958), or is in part adsorbed as the uranyl ion toapatite crystal surfaces (Sheldon, 1959).
The uranium-apatite association is clearly demonstrated
in several ways: chemical analyses of the minerals associatedwith apatite in the Florida deposits show that they containvirtually no uranium; uranium varies directly with ?2O5
content (Cathcart, 1956, Thompson, 1953 and 1954); and theamount of uranium dissolved on acidulation of phosphaterock 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 theoverlying Bone Valley Formation were reworked from the
Hawthorn Formation in a marine environment, and theconcentrate-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 themarine environment contain as much as 0.05 percent U(Cathcart, 1956, Altschuler and others, 1958). Thus, primarypellets contain the least amount of uranium, pellets reworked once in a marine environment contain much moreuranium, and pebbles reworked several times contain themost uranium. The fine-grained pellets, highest incontent, 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 byground 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 andothers, 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. Theseabnormally 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 thelow, rather uniform content of uranium in these apatites.

SECONDARY DEPOSITSUranium 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 thelength and severity of the weathering determine the end
products of weathering and the distribution of uranium inthe products.

A4

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

When the original rock is a phosphatic limestone,
weathering removes calcite, leaving a residually enrichedphosphorite. In the residual "brown rock" deposits ofTennessee, 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, andreplaces 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 notedin the secondary apatite hardpan on the Cooper Marl ofSouth Carolina (Altschuler and others, 1958).
Replacement type deposits are known in many parts of theworld. Individual deposits tend to be small, irregular inshape, 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(tonnes/yr)

Uranium content(percent)

Calcium phosphate: replacement deposits
Florida, hardrock

0.05x10'...

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

None

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

0.001-0.017;-200 mesh from.001-.023.004

South Carolina

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

.OlxlO9.035-.12
No dataCalcium phosphate: residual deposits
Tennessee, "brown rock"30.001-0.003

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 .........

Uranium is enriched in these deposits, and it is associatedalmost entirely with the phosphate minerals, and preferentially with the calcium aluminum phosphate minerals
crandallite and millisite, or with the calcium phosphatemineral apatite. The uranium minerals autunite (fromFlorida) 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 thesepebbles. Concentrates of the calcium aluminum phosphateminerals crandallite and millisite contain as much as 0.05
percent uranium (Altschuler, 1973), but concentrates of thealuminum phosphate mineral wavellite contain an averageof 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 fromwhich it was derived.
Uranium is liberated during the solution of the apatite,remains soluble in the descending acid solutions, andenriches the crandallite and the partly leached apatite
pebbles at the base of the section. Because wavellite iscontinuously formed from crandallite in the middle parts ofthe 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.

"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 acidground water produces irregular zones of porous, vesicular,
light-colored, and lightweight rocks characterized byaluminum phosphate minerals. These zones have been
described in Florida, Nigeria, Senegal, and Siberia(Altschuler, 1973). All of the deposits are similar; they arecharacterized 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.

OTHER DEPOSITSLAKE BEDS
Tertiary lake beds in Wyoming and Nevada contain somelayers 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 ofEocene age in Wyoming and Utah contain as much as 0.27
percent U and 19 percent P2O5, although the averagecontents of both are much less (Love, 1964). Many very thinbeds containing the phosphate and uranium are present; thebeds average less than 30 cm in thickness. The uraniferous
phosphate beds are thought to be syngenetic, and althoughthese occurrences are not economic, they indicate thepossibility that in other, similar lake basins, economic bedsof 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 ofthe 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 ROCKTABLE 5.

Other phosphate deposits: reserves, production, and uranium
content
Location

Reserves(tonnes)

Production(tonnes/ yr)

Uranium content(percent)

Lake beds

Wyoming, Utah (Eocene) ......

0.10.0.12.001-.29;
average .005.

Area is large;
beds only .08
to 1.8 m thick.
Offshore

0.001-0.021

California (Monterey Bay)to Baja California.
Florida, Georgia, Southand North Carolina.

do ................
Northwest Africa (Rabat
to Mauritania).

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 themodern oceans, as those of offshore California; others arethought 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 todata 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 thepast. 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 bringcapacity 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 usedA5

in phosphoric acid production probably contained anaverage of 0.010 percent U which would be 1,500 tonnes ofuranium. 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 ofphosphate 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 amountof recoverable uranium will increase.
Projections into the future are very speculative, but anincreasing population's need for fertilizer indicates that adoubling of production is the minimum that might berequired 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 ofnorthwest Queensland, Australia: Econ. Geology, v. 67, p. 1193-1213.
Davidson, C. F., and Atkin, D., 1953, On the occurrence of uranium inphosphate 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 decalcium: Annales des Mines Memoirs, v. 136, no. 4, p. 5-93.
Igelsrud, Iver, Stephen, E. F., Chocholak, John, Schwartz, C. M., andAustin, 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 inintermontaine 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, andSmith, 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 UnitedStates Geological Survey and Atomic Energy Commission for theUnited 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 [Theradium 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., andSankaran, 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 blackshales 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 Office, 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 thefertilizer 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. FISHERGEOLOGYAND

GEOLOGICALRESOURCESSURVEYOFURANIUM

PROFESSIONALDEPOSITS

PAPER

988-B

An outline of the geologic relations of the uranium
and vanadium deposits provides a framework forevaluating undiscovered resources of thosemetals in the Moab quadrangle

UNITED

STATES

GOVERNMENTPRINTING

OFFICE,WASHINGTON

:

1978

UNITED STATES DEPARTMENT OF THE INTERIORCECIL D. ANDRUS, Secretary
GEOLOGICAL SURVEY
H. William Menard, Director

Library of Congress Cataloging in Publication Data
Butler, Arthur Pierce, 1908Uranium 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
Page

Metric-English equivalents.
BIII
Abstract.............................
... 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

ILLUSTRATIONSPage

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

TABLESPage

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 equivalentmeter (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 DEPOSITSURANIUM AND VANADIUM RESOURCES IN THE MOAB 1° x 2°
QUADRANGLE, UTAH AND COLORADO

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

ABSTRACTThe 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 sedimentaryrocks 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 thequadrangle, 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 thecentral part of the quadrangle.
The primary 'ore minerals in the deposits consist of uranium andvanadium oxides and silicates; they mainly impregnate the sandstone. They
form tabular orebodies that average somewhat less than a meter thick andare as much as one hundred meters across. These bodies lie nearly parallel tothe bedding of the host sandstone, and they are mainly localized by
sedimentary structural features. The deposits were probably formed fromground waters moving along the beds before the host beds became deeply
buried.
Most of the deposits in the Chinle Formation are in the Big Indianmineral 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 wereactually 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 theflank of the Moab anticline and ground bordering the southwest side of
Spanish Valley. The Chinle probably contains undiscovered deposits inother places in the western part of the quadrangle, but these deposits areprobably too small and widely scattered to be a resource of economic
significance.

Deposits in the Salt Wash Member of the Morrison Formation haveyielded a little more than 9,100,000 metric tons of ore and uranium andvanadium 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 westof 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; andthose in the Salt Wash in other parts of the quadrangle about 3,440 metrictons ofINTRODUCTION
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 theColorado 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 haveyielded about 25 percent of the uranium and nearly 60
percent of the vanadium produced domestically. The known
deposits contain substantial reserves of uranium-vanadiumore, and the area has a significant resource- potential.
This report summarizes the geology of the area, andbriefly 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 forprospecting 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

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS
112°

111°

110°

109°

108°

39°

38°

i t o
5^ =Abajo
F|XV Mountains

f BOUNDARY wr
PARADOX BASIN

37

EXPLANATION
Anticline

Monocline or fold

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 informationand ideas incorporated in this report. The geology and thelocation of most of the ore deposits are shown on a map by
Williams (1964) and in simplified form by figures 3, 4, and 5of this report.

GEOLOGIC SETTING
The Moab quadrangle is in the east-central part of theColorado 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 inplaces have been broken by high-angle faults of small tomoderate 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 arecapped 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 andlocally of pegmatite. Rocks of similar lithologic character
probably underlie the entire quadrangle. Evidence from

URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO

scattered deep drill holes indicates that by the beginning ofPaleozoic time, Precambrian rocks had been reduced byerosion to a moderately flat surface.
Paleozoic rocks of pre-Pennsylvanian age are not exposedin the quadrangle. They were removed by erosion in latePaleozoic time from the area of the Uncompahgre Plateau(Cater, 1970, fig. 13) but are presumed to underlie thesouthwestern two-thirds of the quadrangle. Wherever theserocks are cut in deep drill holes or are exposed in adjoining
areas, they consist of marine carbonates and elastics andmeasure 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 verticaldisplacement 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 thesinking of the Paradox Basin southwest of the highlands.
The Hermosa Formation of Pennsylvanian age wasdeposited 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, andbordered 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 theintervening synclines. The upper member, composed mainlyof marine limestone, probably had a maximum thickness ofabout 600 m. The Hermosa Formation is exposed only along
the cores of the salt anticlines that have been breached anderoded into elongate valleys.
The Hermosa Formation grades upward into the Pennsylvanian Rico Formation, a transitional unit consisting ofas 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 anasymmetric lens that is at least 3,000 m thick near thesouthwestern front of the ancestral Uncompahgre highland,
where the formation is composed of coarse arkosic
sandstone and conglomerate of granitic pebbles andboulders 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 westernpart of the quadrangle the Cutler is composed of sandstone,
partly arkosic but predominantly muddy, with minor
amounts of conglomerate, shale, and limestone; thesandstone 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

B3

to rise and the Paradox Basin to sink. The evaporite andlimestone 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 toflow 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 theancestral Uncompahgre highland virtually stopped by theend 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 Moabquadrangle, 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 rocksof Cretaceous age, and probably also by the Morrison
Formation of Late Jurassic age. Cater (1970, p. 65) suggeststhat most or all of the evaporites had been squeezed from thesynclinal areas into the salt anticlines by Late Jurassic time.
Shawe (1970, p. C16) suggests, however, that some of thedifferences in the thickness of some Cretaceous beds between
synclinal and anticlinal areas, in the southeastern part of thequadrangle, are probably a result of continued flow of theseevaporites during the Cretaceous.
Subsequent deformation involving the Morrison andyounger 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 theMorrison and younger beds over the old salt anticlines, butevidence 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, sectionF) 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 crestalparts owing to removal of the evaporites, by erosion andsolution, as the surface of the Plateau region was lowered byerosion in the late Tertiary and the Quaternary. Erosion iscontinuing. The uplift of the present Uncompahgre Plateau,

B4

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

marked by sharp flexing of the cover of Mesozoic beds andsome faulting, occurred in the late Tertiary and Pleistocene.
The La Sal Mountains in the central part of the Moabquadrangle consist of three moderate-sized stocks andassociated 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 bysomewhat anomalous results of various methods of isotopic
age determinations; and Armstrong (1969) reported a23.5-million-year age on the basis of isotopic analysis of one
sample.

STRATIGRAPHY
The stratigraphy of the Mesozoic formations in the Moabquadrangle is summarized in table 1. Readers desiring more
information about the stratigraphy of these formations arereferred 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 andMorrison Formations is described in more detail below, as
these formations contain most of the known deposits ofuranium and vanadium ore in the quadrangle.
CHINLE FORMATIONThe Chinle Formation of Triassic age is widespread in the
Colorado Plateau region. It is about 600 m thick insouthwestern Utah and thins rather gradually to the east andnorth. It is composed principally of mudstone and sandstone
including some partly conglomeratic sandstone. The conditions of deposition were virtually the same throughout theregion with sediments accumulating in an environment of an
alluvial plain with meandering streams, ephemeral lakes,
and extensive mud flats. Sedimentary, metamorphic, andigneous rocks in the highland area of central Arizona and insouthwestern 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, andWilson, 1972), but only two members, the Moss Back andthe Church Rock, are clearly recognized in the area of the
Moab quadrangle; these are distinguished only in thesouthwestern 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
SystemCretaceous ...............

Jurassic

Group or formation

Thickness(meters)

Character and distribution

Mesaverde Group ....

370

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

1,200

Dakota Sandstone ...

15-60

Burro Canyon ..........
Formation
Morrison Formation

0-60

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.
Dark-gray fissile marine shale with some thin sandstone beds. Originally covered entire
quadrangle.
Gray and brown partly conglomeratic sandstone, and gray to black shale; all nonmarine;
coal-bearing in places. Originally covered entire quadrangle.
Light-colored sandstone and conglomerate, green and purplish shale, thin beds oflimestone; all nonmarine. Originally widespread, locally absent.
Brushy Basin Shale Member: varicolored bentonitic mudstone, some sandstone lenses;
nonmarine. Widespread.
Salt Wash Sandstone Member: light-colored lenticular sandstone interbedded withdominantly red mudstone; nonmarine. Widespread.
Predominantly brownish-red, gray, and green sandy shale and mudstone; nonmarine.
Widespread.
Light-colored fine- to medium-grained massive and cross bedded sandstone; predominantly eolian. Widespread.
Light-colored fine-grained massive and crossbedded sandstone; eolian. Absent in eastern
half of quadrangle.
Predominantly red irregualarly bedded shale, siltstone, and sandstone, nonmarine.
Absent in eastern part of quadrangle.
Reddish-brown fine-grained massive and crossbedded sandstone; predominantly eolian.
Widespread but thin or absent in eastern part of quadrangle.
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.
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.

75-15060-140Summerville ..............
Formation
Entrada Sandstone ...

20-170Jurassic ............
and Triassic?)
Triassic (?) .......

Navajo Sandstone .....

0-120

Kayenta Formation ...

0-75

Triassic

Wingate Sandstone ...

0-105

Chinle Formation .....

0-180

Moenkopi Formation

0-300

20-45

URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO
MOSS BACK MEMBERThe Moss Back in the southwestern part of the Moabquadrangle ranges from less than 6 m to about 30 m inthickness and averages about 16 m. Its gross lithologic
components are sandstone and mudstone, but in detail its
lithologic characteristics are quite varied. Grains in thesandstone range from fine to coarse, and some layers containpebbles 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 otherlayers 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 plantmaterial, mostly in small fragments, is sparse to abundant insome sandstone and mudstone beds.
The bedding characteristics of the Moss Back are varied,
ranging from sheetlike layers to small lenses; cut-and-fillchannels 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 themember 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 southwestof Moab; from there it is projected by interpretation
southeastward to Slick Rock, Colo., passing several
kilometers northeast of Lisbon Valley, Utah (Stewart andothers, 1959). The Moss Back is host to the importanturanium deposits in the Big Indian mineral belt along thesouthwest 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, andSimmons, 1959).
CHURCH ROCK MEMBER AND UNDIFFERENTIATED CHINLE

The Church Rock Member, in the southwestern part of
the quadrangle, and the undifferentiated Chinle, in the otherparts, 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 inthickness elsewhere. These beds are somewhat varicolored
but are dominantly brick red or reddish brown. They are
chiefly siltstone, but fine-grained sandstone is common, andthin 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 thequadrangle a quartzose grit, commonly with quartz pebbles,

B5

is present in the lower part of the undifferentiated Chinle.
Beds of this lithology may or may not be equivalent to theMoss Back (Carter and Gualtieri, 1965; Cater, 1970). Several
uranium deposits in the Sevenmile Canyon area northwestof Moab are in lenses of gray siltstone, limestone-pebble
conglomerate, and quartz-pebble conglomerate at the baseof the Chinle (Finch, 1954); these beds are interpreted to beat the base of undifferentiated Chinle and stratigraphicallyhigher than the Moss Back rather than equivalent to theMoss Back (Stewart and others, 1959, figs. 77 and 81).
MORRISON FORMATIONThe 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 thequadrangle 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 MEMBERThe Salt Wash Sandstone Member is composed ofmaterial 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 isthickest, about 180 m, and is composed almost wholly ofsandstone, which is in part conglomeratic. From there theSalt 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 Moabquadrangle the Salt Wash is composed of interbedded layersof 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 partof the quadrangle than in the western part, and Shawe (1962)
suggested that this local thickening resulted from the fillingof 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 resultof accumulation in broad shallow bodies of water in thebasin, as suggested by Shawe (1962). However, in thewestern two-thirds of the quadrangle, where the Salt Wash isore-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 ofmeters 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 thezone 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 thesandstone lenses.
The Salt Wash mudstone is indistinctly bedded and is inpart silty or finely sandy. It is predominantly red, but inplaces is gray or greenish gray. Presumably it was depositedon flood plains and in ephemeral ponds or lakes.
BRUSHY BASIN SHALE MEMBERThe 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 isvaricolored; red, purple, gray, and greenish gray arecommon. The sandstone is light colored; pebbles of red,green, white, and black chert are characteristic of theconglomeratic parts. The Brushy Basin was deposited in amixed lacustrine and fluvial environment. It ranges fromabout 90 to 120 m in thickness in the Moab quadrangle.

URANIUM AND VANADIUM DEPOSITSUranium 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 arenearly concordant to the bedding of the host sandstone; theterm "peneconcordant" has been applied to this type ofdeposit (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), theChinle Formation about 39 percent, and the Cutler Formation about 3.6 percent. The Brushy Basin Member of theMorrison 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 arewidespread in sparse amounts and conspicuous in a few
places. Accessory minerals are mainly sulfides; pyrite andmarcasite are common but not abundant, and trace amountsof galena and sphalerite are widespread. Minerals containing molybdenum, selenium, chromium, nickel, cobalt,
and silver are also present; only in a few places are some ofthese 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 ofoxidation, but montroseite and the two primary uranium
minerals oxidize readily, and the contained metals areconverted to a soluble higher valent state. Where sufficient
vanadium is available, however, uranium is fixed.almost inplace as carnotite [K2(UO2)2V2O5-3H2O] or tyuyamunite[Ca(UO2)2V2O5- 5-8!/2 H2O], both of which are quite stablein 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 thedeposit at and near the surface. On the other hand, indeposits that are low in vanadium, either the uranium ismobilized or it forms a variety of secondary minerals. Someof these secondary minerals are not very stable themselves,and migration of uranium may have impoverished parts ofsome 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 andnearly concordant to bedding but do not follow beds indetail. These bodies range from 0.3 m to several meters inthickness and average about 1 m thick; they range frombodies only 1 or 2 m across, which contain only a few tons ofore-bearing rock, to those that are many tens of metersacross 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 andthe 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 theabsence 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. Alteredsandstone below the zone of surface oxidation is light gray toB7

URANIUM AND VANADIUM IN THE MOAB QUADRANGLE, UTAH AND COLORADO

buff and contains sparsely disseminated pyrite; recent
oxidation of this pyrite imparts a yellowish cast to the alteredsandstone at and near the surface. In contrast, unalteredsandstone is pale red to red, both above and below the zoneof 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 alarger target for subsurface exploration than do the deposits
themselves.
Stratigraphic, lithologic, and sedimentary structural factors are significant in the localization of many of theuranium 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 theuppermost sandstone unit of the Salt Wash Member. (2)Almost all deposits are in permeable sandstone beds, andalmost all except those in the Entrada Sandstone atPlacerville 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 thecourses of the streams that deposited these lenses. In
contrast, igneous activity, hydrothermal mineralization, andtectonic 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 theera and those in the Morrison during the late part. Geologic
field relations indicate a pre-Laramide age; the folds andfaults 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 Morrisonin the Uravan area probably formed about 110 million years
ago (during the Early Cretaceous).
Various theories have been proposed to explain the originof the peneconcordant uranium and vanadium deposits of
the Colorado Plateau region. The concept currently favoredby geologists assumes that the mineralizing solutions wereground waters that leached trace amounts of metals from theore-bearing beds and associated strata and transported these
metals in their high-valent states to places where they wereprecipitated by reduction; carbonaceous material orhydrogen 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 haveoccurred whenever and wherever these geochemical
processes were operative; the movement of solutions andbacterial 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 tointensive subsurface exploration in the vicinity of thedeposits that crop out, and many buried deposits have beenfound. 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 bediscovered near known deposits. On the other hand, there ismuch 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 mainlyon this ground. Our resource appraisal and suggestions forprospecting are based oh our understanding of the habits,
distribution, and localization of the known deposits. The
resources included in our appraisal are hypotheticalresources as defined by Pratt and Brobst (1974, p. 2) in thatthey consist of material in undiscovered deposits like thenumerous identified deposits in the same general area andgeologic 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 theresource 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 anddowndip 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 thedowndip 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 informations 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 FORMATIONThe Chinle Formation is the principal host to deposits inthe southwestern part of the Moab quadrangle (fig. 3). The
formation is present in most places in the rest of thequadrangle, 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 3 O8 in 6,920,0001 of ore, had been minedby 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 depositionaledge of the Moss Back; the Moss Back in this ore-bearingzone is thinner and more lenticular than it is to thesouthwest, where the unit is apparently barren (Johnson andThordarson, 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 thequadrangle, undiscovered resources in this member areprobably small, and further intensive exploration of thesebeds 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 themcan be selected, deep exploration for them would bejustified. If such deposits are present, they probably werelocalized 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 significanceare 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 theunderlying 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 thebeds 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 historyof 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 ofsalt and gypsum in the Hermosa Formation. This upwelling
occurred in two major stages, the first during the latePaleozoic 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 wascompletely 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 thatminor 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°

LISBON VALLEY ANTICLINEEXPLANATION
Intrusive rocks of the La Sal Mountains(mid-Tertiary)Contact
Fault Bar and ball on downthrown side

Chinle Formation and post-Chinle formations-4 I
Zone where Moss Back Member of Chinle
Formation is thin and lenticular (modified
from Johnson and Thordarson, 1966)
Pre-Chinle formations

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.

B9

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

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.

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-A f).
The localization of the Big Indian mineral belt can be
explained if a minor upward movement of the salt andgypsum during Chinle time is assumed. Ground water
seeping downward along the crest of the anticline could haveleached 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(fig. 4, section B-B"). This flow of ground water may havecontinued 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 thatlithologically favorable host beds were deposited there by
Moss Back streams. In recent years, exploration near thenorthwest 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

Favorable for
uranium production!?)

1500-

1000-

B

Crest of Late Triassic anticline
Water tablePh

4 KILOMETERS

being mined from these shafts are a downfaulted northerly
extension of the Big Indian mineral belt or the northerly endof 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 justificationfor exploration drilling on the northeast flank of the
anticline. Actually, some exploratory drilling has been doneon this flank, and is reported to have shown mineralized rockand 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 exploitabledeposit that might confirm the existence of a belt of deposits
on the northeast side of the anticline, it is possible that notenough drilling has been done to negate the possibility of amineral 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 theLisbon Valley anticline, has a thickened core of salt andgypsum, but these evaporites probably did not penetrate theoverlying beds and the crest of the anticline has not beenbreached to expose the evaporites (Shawe, 1970). There is no
definite evidence of up welling of salt and gypsum along theDolores 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 arethicker in the adjoining Disappointment syncline, northeastof 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 thatsuggested 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 thesandstone 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 isreasonably favorable for uranium deposits. Three small
deposits are exposed in the Moss Back in the Dolores River
canyon, and anomalous radioactivity was detected at otherplaces 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 beappraised accurately; they could range from insignificant tothe same order of magnitude as'those along the Lisbon
Valley anticline (about 29,0001 of l^Og). These beds on theflanks of the Dolores anticline, however, are judged to bereasonably 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 U3 Og in thethree 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, thecalculated 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 ofsuch deposits would be about 1 in every 16 km2 . Exploration
to find such deposits in the Moss Back, which lies at depthsof 240-365 m in most of the area, would be so costly that theestimated 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 andothers, 1959, figs. 77 and 81). The deposits are on thesouthwest flank of the Moab anticline near its northwesternend. 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 ofthe 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 Indianmineral belt. The likely projection of this hypothetical belt,
however, is not exposed, and it has not been tested bysubsurface exploration because the basal beds of the Chinle
are deeply buried and the topography is so rough that accessby drill rigs would be difficult. Nevertheless, exploration totest the basal beds of the Chinle might be fruitful along thesouthwest 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 asthat of the Lisbon Valley anticline, but the presently known
deposits are confined to about the northwest one-fifth of thesouthwest flank. The average size of deposits in the Moabanticline area is only one-twentieth that of the averagedeposit in the Lisbon Valley area. Thus, although thesouthwest flank of the Moab anticline is very incompletely
explored and although the extent of host rocks that might befavorable for deposits is only approximately delineated, it isunlikely 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 Moabanticline and the northwest end of the Lisbon Valley
anticline is about twice the length of the latter. The Chinle islargely 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 thesouthwest side of Spanish Valley. If so, resources between
the northwest end of the- Lisbon Valley anticline and theColorado River are probably no more, and may be muchless, 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 generalestimate 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 FORMATIONThe 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

B13

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
(metric tons)
Ore

Estimated (hypothetical) resources(metric tons)
U 308

U 3O8
minimum

maximum

minimum

maximum

Moss Back Member

Lisbon Valley anticline ......
Dolores anticline ................
Area tributary to Colorado
and Green Rivers.

1,491,000
0
8,378

5,853
0
23

360,000 4,500,000
Neg.
7,200,000'1,800,000

900
Neg.

18,00027,000'5,000

Undifferentiated Chinle

Moab anticline ....
Southwest side of
Spanish Valley.
Total (rounded for resources)

1,499,378

5,876'1,360'450,000
450,000

Neg.

1,360

1,700,000 '13,500,000

7,300

53,000Neg.

'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.

(fig. 2). The formation has been eroded from much of thewestern part of the quadrangle. Although it is present inmuch of the eastern part, no deposits are known and theformation is judged to be unfavorable for deposits there.
Most of the deposits in the Morrison are in sandstone in theuppermost 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, thanelsewhere. Several deposits occur in sandstone lenses in the
Brushy Basin Member; they are widely scattered andalthough 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 thelong axes of the host sandstone lenses. The sandstone andassociated mudstone layers in these patches have certain
geologic characteristics that are rather consistently
associated with ore deposits; for that reason thesecharacteristics are thought to be indicative of favorable
ground and collectively are useful guides in exploration andresource 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 lightgray to buff in color and contains sparse and finely
disseminated pyrite and in the zone of oxidation it has ayellowish cast, in contrast to a light pink or pale redcolor in unfavorable ground in both zones.
(3) The mudstone that occurs as thin layers or pebbles in thesandstone 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 disseminatedpyrite below the zone of oxidation.
(4) The sandstone contains more coalified fossil wood in andnear ore deposits than remote from deposits.
Weir (1952) has suggested a scheme of numerical evaluationof 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 Moabquadrangle. About 80 percent of the ore found had been
mined and the remaining 20 percent was in reservesconsidered 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 percentof the ore produced.
The U3Og contained in ore was apportioned amongdeposits 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 totalof the amounts entered in the table is larger than the amountgiven above for the Moab quadrangle. Distribution of U3Qg
by size ranges of deposits in the Salt Wash Member of theMorrison 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°00'109°4539°

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

Rock, a distance of about 115 km (fig. 5). The patches offavorable ground in which the deposits occur, the orebodies
themselves, and the so-called ore rolls
small, podlike
Intrusive rocks of the La Sal Mountains (mid-Tertiary)bodies of ore
tend to be elongate normal to the trend of
Morrison Formation and post-Morrison formations
the belt. In addition, sedimentary structures in the host rock,such as current-lineation marks and the dip of crossbedding
Base of Morrison Formation and borders of intrusive
planes and fossil logs, which were rafted into place, arerocks Dashed where covered
generally oriented normal to the belt. The belt crosses
tectonic structures which show little or no apparent localizPre-Morrison formations
ing influence on the belt; some deposits, however, lie outside
Fault Dashed where covered
the general limits of the belt near fault zones in Gypsum
Valley and southeast of Slick Rock.
Significant uranium deposit or group of deposits
The area of the mineral belt probably was made especially
Approximate area of ground favorable for uranium
favorable
for ore by geologic conditions extant during thedeposits
accumulation of the Salt Wash Member of the Morrison.
Edge of alluvial fan and area of subsidence
The favorable host rocks are sandstone lenses that wereformed by streams. The trend of these lenses perpendicular
General direction of flow of Salt Wash distributary
to the arcuate mineral belt (fig. 5) resembles the pattern ofstreams in area of fan
ribs of a fan, the apex of which would be a vaguely defined
Dominant trend of ore rolls, fossil logs, and sedpoint
several tens of kilometers west of the belt. Shawe
imentary structures(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 theSize range
No. ofContained J308
Deposits(pounds L^Og)
Total pounds
Percent of total . larger fan that formed the entire Salt Wash Member;perhaps this smaller fan formed in an area of shallow
0-200
322
22,4780.027
subsidence that developed during Salt Wash time, for the200-2,000
282
235,969.28
2,000-20,000
317
2,562,569
3.05
member is a little thicker in this area than in other places. A
309
20,000-200,000
22,001,658
26.2
few miles east of the belt the host sandstone beds are finer
200,000-2,000,00085
45,127,918
53.7
More than 2,000,000
514,154,675
16.8
grained and more thinly and evenly bedded, as if they were1319
Totals84,105,267
100.037
deposited in a shallow body of standing water. Immediately
west of the belt, coalified fossil plants are not present inmany of the Salt Wash sandstone lenses; either the plant
As can be seen from the table, nearly 97 percent of theuranium contained in known deposits in the Salt Wash is in material was never present, or it was destroyed after burial in
the larger deposits, those that contain at least 20,000 pounds the beds. Where deposits occur west of the belt, however,(9.11) of 1)305 each, and 70 percent of the total uranium is in coalified fossil plants are present and probably were
deposits that contain at least 200,000 pounds (911) each. In preserved by locally high water tables.
The observed relations and the hydrologic system thatview of the rather wide distribution of deposits, as shown in
wouldlikely develop in this geologic environment permit thefigure 5, and because the size-range distribution of known
following
hypothesis regarding belt localization: The belt
deposits in each of the principal areas of their occurrence isextendedalong the toe of an east-facing alluvial fan.
fairly similar to the distribution of all deposits, as shown inStanding
water
persisted a short distance east of the belt; as a
the table, it is likely that undiscovered deposits are apporresult,
the
water
table along the belt was virtually at thetioned among the size intervals in about the same proporsurface
while
the
host
sandstone lenses accumulated, preventions as the known deposits.
ting
destructionbyoxidationof plant material buried in the
Several areas potentially favorable for significant
sand.
Becauseoftheoriginal
sedimentary
dip of the beds, aresources in the Morrison will now be discussed.
gravity flow of ground water in an easterly direction would
URAVAN MINERAL BELT
have started during the accumulation of the Salt Wash sand
Uravan mineral belt is the name applied to a narrow, lenses and probably would have been most active from thenelongate area in southwestern Colorado in which the until the invasion of Mancos seas in the Late Cretaceous.
uranium-vanadium deposits in the Morrison Formation The deposits probably formed from these ground waters ingenerally are closer spaced, larger in size, and higher in grade this interval.
Undiscovered resources in the part of the Uravan mineralthan those in adjoining areas (Fischer and Hilpert, 1952).
The belt extends from Gateway through Uravan to Slick belt within the Moab quadrangle as estimated by methods
EXPLANATIONB16

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

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. Muchof 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
LA SAL MOUNTAIN-ISLAND MESA AREA
found in the Salt Wash high on the flanks of the mountains,
The La Sal Mountain-Island Mesa area is west of the where exposures, because of more soil and vegetation, are
Uravan mineral belt and near its eastern side straddles the not as good as in other parts of the Moab quadrangle.
Utah-Colorado State line (fig. 5). It is roughly triangular in Nevertheless, continued exploration by surface methods
shape with its base along the irregular line of Morrison around the La Sal Mountains might find a few deposits or
outcrops that extend from Island Mesa northward to a point patches of ground lithologically favorable for ore, in which
about 16 km southwest of Gateway, and its apex is in the case subsurface exploration behind the outcrop might
vicinity of Kane Springs. If the Uravan mineral belt lies be rewarding; without these guides, subsurface exploration
along the toe of an alluvial fan, as suggested above, most of would be blind and probably not justifiable.
the La Sal Mountains-Island Mesa area would be on theUndiscovered resources in the La Sal Mountains-Island
mid-slope and apex parts of this fan; the Kane Mesa area, as estimated in the manner described in the
Springs-Wilson Mesa part of the area might be north and section on methodologies, are about 8,200 t of U3Og inwest of the fan (fig. 5).
2.7-3.2 million t of ore. Much of this, perhaps 75 percent, isjudgedto be in the central part of the area, extending from
Significant deposits have been found at and near theLa
Sal
Creek on the east to Kane Springs on the west,
outcrop along La Sal Creek. These deposits are in an
includingthe ground between the Rattlesnake mine and theeast-trending patch of favorable ground, similar to the
Yellow
Circlemines (fig. 5). This area is about 337 km2, andfavorable patches in the Uravan mineral belt. Presumably
the
known
deposits
at the two ends permit an estimate withthe host rock of the La Sal Creek deposits accumulated
moderateconfidence
that undiscovered resources are about
along one of the distributary streams that formed the
6,800
t
of
U3Og
in
2,300,000
t of ore. The moderately large
supposed alluvial fan; the presence of coalified fossil wood in
deposits
recently
foundinthe middle of this area by
the ore indicates that at least locally the water table duringsubsurface
exploration
supportthis optimistic appraisal.
accumulation of the host rock was high enough to prevent
The
southern
part
of
the
La
Sal
Mountains-Island Mesa
destruction of the plant fossils by oxidation.
area, roughly bounded by lines connecting the Rattlesnake
A large deposit at the Rattlesnake mine has been mine, Island Mesa, and La Sal Creek, probably contains one
exploited, and numerous deposits, mostly small but some of or more favorable patches of ground, like those known in themoderate size, have been found at and near the outcrops La Sal Creek-Kane Springs trend. On this assumption, andnear the Yellow Circle mines (fig. 5). In addition, at least two by comparison with an adjoining area on the east describedlarge deposits have been found by subsurface exploration in the section on methodologies, resources of 900 t or more
midway between the Rattlesnake mine and the deposits of U3Og have been assigned to the southern part of the La
along La Sal Creek. It will not be known until exploration Sal Mountains-Island Mesa area. The scant exposures of theand mine development progresses farther whether these Salt Wash in this part of the area do not permit appraisalgroups of deposits are all on a continuous favorable trend, as with much confidence.
suggested by Johnson and Thordarson (1966), or in separate
Appraisal of the ground on the east, north, and northwest
favorable patches that are approximately alined, because the flanks of the La Sal Mountains, where virtually no deposits
Salt Wash does not crop out along this trend.
have been found, is made with even less confidence;
South of the trend between La Sal Creek and the nevertheless, as explained in the section on methodologies,
Rattlesnake and Yellow Circle mines the Salt Wash is not resources containing about 540 t of U3Og are estimated for
exposed, except in the vicinity of Island Mesa, where some this part of the area.
small- to medium-sized deposits occur, and along the line of
SAGE PLAIN AREA
outcrop from Island Mesa to La Sal Creek, where only a few
The Sage Plain area is along the southern edge of thesmall deposits are known. In the concealed Salt Wash of thisarea, however, there is room for one or more favorable Moab quadrangle, partly in Colorado but mostly in Utah. It
patches or trends. If present, the favorable patches or trends is west of the Uravan mineral belt and probably southwest of
are probably elongate in a southeasterly direction, more or the mineral belt fan. Exposures are limited to the northern
less radial from the apex of the alluvial fan. This part of the edge of the area. These exposures have not been studied
La Sal Mountains-Island Mesa area could be tested for adequately to permit a sound interpretation of the geologic
described in the section on methodologies are about 6,8001
of U3Og, contained in about 2,700,0001 of ore. Most of theseresources are judged to be in deposits in and close to thepatches of favorable ground that contain most of the known
deposits (fig. 5). These undiscovered resources amount toonly about 20 percent of the total rescmrces originallypresent in the area of the belt.

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 beenfound in the upper sandstone layer of the Salt Wash at andnear 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 thatthe northeast-flowing streams that deposited the host lenses
in these ore-bearing trends were deflected southeastward byslightly higher ground over the ancestral Lisbon Valley salt
anticline, and that these trends perhaps connect with theore-bearing northwest-trending patches of ground in the
Uravan mineral belt of Slick Rock (fig. 5). This relationshipis possible, and perhaps likely, and it permits optimism thatground favorable for uranium deposits lies in the Sage Plainarea and suggests the pattern and orientation of thisfavorable 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 amethod 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 beenfound by subsurface exploration in the eastern part of thearea near the Uravan mineral belt; if these deposits are morenearly representative of part or all of this area, resources
could be somewhat larger.

in the vicinity of the principal groups, where some deposits
are in sandstone beds higher in the Salt Wash and some arein sandstone in the basal part of the Brushy Basin Member.
All of the larger deposits are in rather well-defined sandstonelenses that trend northeasterly or easterly. Favorable groundmight continue northeast of the known deposits in thevicinity of the Yellow Cat group, but the Salt Wash iscovered by an increasing thickness of younger beds in thisdirection, 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, inan area of about 78 km2 adjoining it on the north, along thegeneral trend of the lenses of ore-bearing sandstone, thedepth to the base of the formation is mostly less than 300 m
and probably averages no more than 150 m. It is possiblethat undiscovered deposits in this unexplored area containproportionately about as much uranium as in the fully
explored area or about 5401 of ^Og in 240,0001 of rock. Ifuranium is apportioned among undiscovered deposits as it isamong those that have been discovered, about two-thirds ofthe estimated amount would be in those containing
9,070-90,700 kg.

THOMPSON AREA

SUMMARY OF RESOURCES IN THE SALT WASH MEMBER

In the Thompson area, Utah, the Morrison Formation
crops out for about 50 km along a west-trending line from apoint 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 othergroups a short distance east of the Yellow Cat group, most ofthem are small. Almost all of these deposits are in the lowest
sandstone in the Salt Wash Member of the Morrison, except

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 Moabquadrangle 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 andresources 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)

V 205

Ore

Uravan mineral belt ................................ 2,053,500
La Sal MountainsIsland Mesa:
Central part ..................................... 105,600
South part ...............................
North part ...............................
Sage Plain ............................................... 203,300
Thompson ...............................................
19,300Totals (rounded for resources).

2,381,700

Estimated (hypothetical) resources(metric tons)
Ore

U30g

V 205

5,790

30,8002,700,00

6,800

41,000

299

1,590

322
57

3,050
290

2,450,000
450,000
240,000
1,200,000
240,000

6,700
900
590
2,000
540

36,0006,800
3,600
18,000
3,600

6,468

35,7307,300,000

17,500109,000

B18

GEOLOGY AND RESOURCES OF URANIUM DEPOSITS

estimated in 1971 that uranium could be recovered atforward 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 thisleaner rock is in the same deposits as and adjoins the richer
rock composing those resources. Data about leaner rockobtained 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 theestimate of hypothetical resources, the amount of contained
U3Og would probably be from 25 to 50 percent, 4,500-9,000t 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 Moabquadrangle 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 andMorrison Formations which are the hosts to the bulk of theresources 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 discoveredresources in the Cutler, it is probably only a fraction of theamount in the other two formations as mentioned earlier inthe 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 besomewhat 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 amountin rock that would have constituted ore under conditions
that prevailed in 1970-71. In addition, a substantial volumeof 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 theamount of such leaner rock and its UjOg content suggeststhat the estimates of resources given above would be larger
by 25 to 50 percent if such leaner rock were included.

METHODOLOGIESMETHODS OF ESTIMATING RESOURCES IN THE
SALT WASH MEMBER OF THE
MORRISON FORMATION
Two basic methods were used to estimate the hypotheticalresources in the Salt Wash Member of the Morrison
Formation; each was applied in different parts of the Moabquadrangle, distinguished in figure 6. One method makes useof a factor derived by dividing the aggregate length ofoutcrop of exposed ore deposits in the Salt Wash by the total
length Salt Wash outcrop in a given area. It is assumed thatthe 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 theoutcrop is related. The length of ore-bearing outcrop relative
to the total outcrop represents the percentage of groundunderlain by ore behind the outcrop. Multiplying this factor
by the measured size of an area yields an estimate of thenumber 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 factorof 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 ofmineralized 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 inwell-explored parts of a general area are indicative of thetons-per-unit-area in the adjoining sparsely explored partsof 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 generalvicinity of the Uravan mineral belt where numerous deposits
are exposed along many tens of kilometers of outcrop on thesides 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, theBull 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 otherparts 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

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 themineral belt. This lack of continuity for the outcroppingedge of the ore-bearing interval precludes determing thefractional length of the outcrop that is ore-bearing, as anindex of the adjoining area that may be ore-bearing. Hencethe 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 toapproximately the same extent and that the ratio of ore
in known deposits (including production) to that inundiscovered deposits, and hence to total resources,
was about the same for the Gypsum Valley area as it wasfor the East Gateway area.
2. Strobell and others (1954) and C. G. Gilbert (U.S.
Geological Survey, written commun., 1954) used resultsof 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 totalmineralization 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)

Estimated area
underlain by ore
as percent of
total area

145
212 .
373
370
96
130
243

0.38
.61
1.10
.92
.54
.21
1.11

B19

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 bywhich the estimate of the resources originally present in thearea 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 theSalt 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 theundiscovered 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 thesouthern 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 theMorrison northwestward from the vicinity of the
Rattlesnake mine is assumed to be generally representativeof 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 theaverage amount of ore that may be present in the unexploredground between La Sal Creek and Kane Springs, theundiscovered 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 thesouthern part of the La Sal Mountain-Island Mesa area.
Nearly all are small and confined to the immediate vicinity ofthe outcrop. If these deposits are truly representative of thearea 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 arewithin an arbitrarily outlined rectilinear block of groundabout 5 km wide extending 20.3 km north from the southedge 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°00'109°45108°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

SAGE PLAIN AREA
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 thesouthern subarea near the north end of that valley by thearea of the arbitrary index block yields a quantity of 3,000
kg/km2 . Assuming that the incidence of deposits in thisarbitrarily 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 partof 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, aremostly small. All but one are distributed along the outcropsof the Morrison from Kane Springs to Wilson Mesa on thenorthwest side of the mountains. As the largest of thesecontained only a little more than 1,3601 of ore it is assumed
that the maximum extent of fully explored ground in thispart of the area is a strip no more than 0.16 km wide adjacentto 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 ofstrip 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, resourcesin undiscovered deposits within it are about 5901 of l^Og ina little more than 230,000 t of mineralized rock. The size ofdeposits in the sample strip suggests that estimated undiscovered resources might be in similarly small deposits;
however, the general distribution of discovered resourcesamong deposits in different ranges of size in the other partsof 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.

Deposits in the part of the Sage Plain area within the
Moab quadrangle are irregularly distributed mostly at orclose to 72 linear kilometers of outcrop of the Salt Wash
Member of the Morrison Formation along the north edge ofthe plain. Most of these deposits had some exposure at theoutcrop 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 offully explored ground bordering the outcrop, is considered
to indicate the amount of uranium present per unit area inthe unexplored part of the Sage Plain. In the absence ofspecific information about exploration in the area, the widthof the strip of ground considered to be fully explored isassumed to be not less than the estimated length of thelargest deposit and not more than twice that length. The
mass of ore discovered in the largest outcropping deposit is34,172 t. Calculated at 0.437 m3 /t and an average thicknessof 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 towidth ratio of 4 to 1. For the area calculated above thelength 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 isabout 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 thesealternatives 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 thisamount of resources would be possible only if the Salt Wash
Member were as favorable for deposits in this portion of theSage Plain as it is on the average in the Uravan mineral belt.
The position of the Sage Plain relative to the inferred edge ofthe subsidiary Salt Wash fan (fig. 5) suggests, however, thatthe 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 undiscoveredresources 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

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