Heavy-Mineral Placer Deposits of the 

Ute Mountain Ute Indian Reservation, 

Southwestern Colorado and 

Northwestern New Mexico

U.S. GEOLOGICAL SURVEY BULLETIN 2061-B

Prepared in cooperation with the Ute Mountain 

Ute Tribe and the Bureau of Indian Affairs
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Heavy-Mineral Placer Deposits of the 

Ute Mountain Ute Indian Reservation, 

Southwestern Colorado and 

Northwestern New Mexico

By Robert S. Zech, Richard L. Reynolds, Joseph G. Rosenbaum, and 

Isabelle K. Brownfield

GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

U.S. GEOLOGICAL SURVEY BULLETIN 2061-B

Prepared in cooperation with the Ute Mountain 

Ute Tribe and the Bureau of Indian Affairs

Numerous small deposits of heavy minerals occur 

in the Cretaceous Point Lookout Sandstone of the 

Ute Mountain Ute Indian Reservation

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1994
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For sale by U.S. Geological Survey, Map Distribution

Box 25286, MS 306, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

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

Library of Congress Cataloging-in-Publication Data

Heavy-mineral placer deposits of the Ute Mountain Ute Indian Reservation, 

Southwestern Colorado and Northwestern New Mexico / by Robert S. Zech ... [et al.].

p. cm. (Geologic studies of the Ute Mountain Ute Indian Reservation) 

(U.S. Geological Survey bulletin ; 2061-B)

Includes bibliographical references (p. ).

Supt. of Docs, no.: 119.3:2061-B

1. Heavy minerals Ute Mountain Indian Reservation. 2. Placer deposits Ute 

Mountain Indian Reservation. I. Zech, R. S. II. Series. III. Series: U.S. Geological 

Survey bulletin ; 2061-B. 

QE75.B9 no. 2061-B 

[TN23.9] 

557.3 s dc20

[549.97882] 94-4647

CIP
CONTENTS

Abstract............................................................................................................................ Bl

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

Acknowledgments............................................................................................................ 2

Previous Investigations.................................................................................................... 2

Locating the Deposits...................................................................................................... 3

Stratigraphy and Sedimentology of Units Containing the Deposits................................ 3

Origin and Field Characteristics of Heavy-Mineral Deposits.......................................... 6

Mapping of Heavy-Mineral Deposits.............................................................................. 7

Distribution and Physical Characteristics of the Deposits............................................... 10

Southern Group........................................................................................................ 10

Airborne Anomalies 8, 9, 10, and 11............................................................... 11

Airborne Anomalies 13, 14, and 15................................................................. 13

Airborne Anomalies 16, 17, and 18................................................................. 15

Airborne Anomalies 19 and 20........................................................................ 15

Airborne Anomaly 21...................................................................................... 15

Airborne Anomaly 36...................................................................................... 15

Airborne Anomaly 37...................................................................................... 16

Anomaly FA-1................................................................................................. 16

Central Group........................................................................................................... 16

Airborne Anomaly 25...................................................................................... 16

Airborne Anomaly 26...................................................................................... 16

Airborne Anomaly 27 ...................................................................................... 16

Airborne Anomalies 30 and 31........................................................................ 16

Northern Group........................................................................................................ 17

Airborne Anomalies 38-44.............................................................................. 17

Airborne Anomaly 28...................................................................................... 18

Magnetic Studies.............................................................................................................. 18

Ground Magnetometer Survey................................................................................. 19

Magnetization of Heavy-Mineral Deposits.............................................................. 19

Magnetic Susceptibility and Natural Remanent Magnetization...................... 19

Petrologic and Rock Magnetic Investigations................................................. 20

Geochemical Studies........................................................................................................ 26

Chemical Analyses................................................................................................... 26

Energy-Dispersive X-Ray Fluorescence (XRF).............................................. 26

Instrumental Neutron-Activation Analysis (INAA)........................................ 26

Analytical Considerations................................................................................ 27

Discussion of Selected Elements............................................................................. 27

Iron................................................................................................................... 27

Titanium........................................................................................................... 28

Zirconium......................................................................................................... 28

Rare-Earth Elements........................................................................................ 29

Uranium and Thorium...................................................................................... 29

Other Elements................................................................................................. 29

Conclusions...................................................................................................................... 30

References........................................................................................................................ 30

Appendix: Chemical-Composition Data from Neutron Activation and X-Ray

Fluorescence Analyses of Whole-Rock Samples from Heavy-Mineral Deposits....... 33

III
IV CONTENTS

FIGURES

1. Map showing Ute Mountain Ute Indian Reservation............................................................................................. B2

2. Map showing locations of heavy-mineral deposits on the Reservation ................................................................. 4

3. Diagram showing idealized prograding shoreline and Point Lookout S andstone progradation ............................ 5

4. Photograph of Point Lookout Sandstone near Chimney Rock, Colo..................................................................... 6

5. Measured section of the Point Lookout Sandstone near Chimney Rock................................................................ 8

6. Photograph of heavy-mineral accumulations on a modern beach.......................................................................... 10

7. Photograph of slickensides on a rock fragment from a heavy-mineral deposit...................................................... 11

8. Map showing southern group of heavy-mineral deposits on the Reservation........................................................ 12

9. Photograph of heavy-mineral deposits AA-10 and AA-11................................................................................... 13

10. Measured section of Point Lookout Sandstone at heavy-mineral deposit AA-10................................................. 14

11-15. Maps showing:

11. Central group of heavy-mineral deposits on the Reservation ....................................................................... 17

12. Northern group of heavy-mineral deposits on the Reservation..................................................................... 18

13. Heavy-mineral deposit AA-28...................................................................................................................... 19

14. Ground magnetometer traverses 1 and 2....................................................................................................... 20

15. Ground magnetometer traverses 3, 4, and 5.................................................................................................. 20

16. Magnetic profiles from ground magnetometer traverses........................................................................................ 21

17. Upward-continuation plots at various depths for traverse 1................................................................................... 22

18. Schematic cross section of AA-10 with contours of magnetic susceptibility........................................................ 23

19. Plot of magnetic properties from deposit AA-17 samples..................................................................................... 24

20. Thermomagnetic curves for samples A A-17-3 and AA-10-3.............................................................................. 24

21. Alternating-field demagnetization plots from AA-17............................................................................................ 25

22. Plots showing acquisition of isothermal remanent magnetization for samples from AA-10 and AA-17............. 25

23. Backfield curves of isothermal remanent magnetization for samples from AA-10 and AA-17........................... 26

24. Plot of titanium versus zirconium content in analyzed samples............................................................................. 29

TABLES

1. List of airborne anomalies and Preliminary Reconnaissance Reports........................................................................... B3

2. Magnetic properties of samples from AA-17 ................................................................................................................ 23

3. Average element compositions of heavy-mineral and barren-rock samples.................................................................. 28
HEAVY-MINERAL PLACER DEPOSITS OF THE

UTE MOUNTAIN UTE INDIAN RESERVATION,

SOUTHWESTERN COLORADO AND

NORTHWESTERN NEW MEXICO

By Robert S. Zech, Richard L. Reynolds, Joseph G. Rosenbaum, and Isabelle K. Brownfield

ABSTRACT

Numerous heavy-mineral placer deposits occur in the 

upper part of the Upper Cretaceous Point Lookout Sandstone on the Ute Mountain Ute Indian Reservation of 

southwestern Colorado and northwestern New Mexico. 

Measured sections and stratigraphic observations at deposit 

outcrops confirm a foreshore or beach origin of the deposits, and alignment of their exposures defines a northwestsoutheast-oriented linear shoreline system. This depositional setting gives the deposits a predictable shape and 

trend that allows speculation about their subsurface extent. 

At least five of the known deposits have potential for subsurface extension.

A magnetization study showed that deposits that 

extend into the subsurface and undiscovered deposits that 

are covered by less than 20 m of overburden may be 

located by magnetic surveys. Magnetization of the deposits 

is provided mainly by detrital titaniferous magnetite concentrated in the centers of the deposits. Magnetite was 

apparently deposited fairly evenly throughout the deposits, 

but postdepositional alteration destroyed large quantities of 

magnetite near the margins of the deposits.

Very good induration due to iron cementation may be 

the result of humic acids from organic material in the overlying Menefee Formation mobilizing ferrous iron, particularly from titaniferous magnetite. Ferric oxide was then 

deposited interstitially in the deposits. There are relatively 

high amounts of titanium and zirconium and lesser amounts 

of rare earth elements present in the rocks. Semiquantitative analyses of whole-rock samples show that titanium 

content averages 7.9 percent and may be as much as 21 percent; zirconium content averages 1.5 percent and may reach 

as much as 6 percent.

INTRODUCTION

In 1986, the Division of Energy and Minerals of the 

Bureau of Indian Affairs began a resource assessment of the 

Ute Mountain Ute Indian Reservation at the request of the 

Ute Mountain Ute Tribe. As part of that program, the U.S. 

Geological Survey conducted this study of the heavymineral deposits on the Reservation. The investigation 

examined all of the Ute Mountain Ute Indian Reservation 

(fig. 1) but did not assess any of the known heavy-mineral 

deposits on the adjacent Navajo Indian Reservation. The 

objectives of the study included locating deposits on topographic maps and mapping their surficial extent, characterizing the processes that formed the deposits, inferring the 

presence of additional deposits in the subsurface, testing the 

feasibility of magnetic methods in locating buried deposits, 

and determining elements within the deposits. Although 

assessing the economic potential of the deposits was not part 

of the study, some economic considerations are discussed.

Because heavy-mineral deposits are present in exposures of the upper part of the Upper Cretaceous Point Lookout Sandstone, which caps many of the mesas in the central 

part of the Reservation, the extent of heavy-mineral deposits in this area is well known. Field identification is relatively easy because virtually all the deposits are darkcolored, cemented by a ferric-oxide cement, resistant to 

erosion, and radioactive. However, the true extent of some 

individual deposits could not be determined due to overburden. In the other parts of the Reservation where the Point 

Lookout Sandstone is present, deposits may exist but are 

not known because exposures are only in steep cliffs that 

greatly limit access. Heavy-mineral deposits probably 

occur in the subsurface, particularly along the depositional 

strike to the southeast on the Reservation and in the northern San Juan basin.

Bl
B2 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

109°00' 1 08*00'

37°30'

COLORADO

NEW MEXICO

UTE MOUNTAIN 

UTE INDIAN RESERVATION [_

Figure 1. Map of the Four Corners area showing the location of the Ute Mountain Ute Indian Reservation.

ACKNOWLEDGMENTS

We express our appreciation to the Division of Energy 

and Minerals of the Bureau of Indian Affairs for their support of the research and to the Energy Office of the Ute 

Mountain Ute Tribe for their cooperation. Thanks also to 

Robyn Wright Dunbar (Department of Geology, Rice University) for contributing to the fieldwork, and Gary Skipp 

(U.S. Geological Survey) for sample preparation. Contributions to the magnetization section of this report were made 

by Alien English, Anne McCafferty, Willie Rivers, and 

John Karachewski (all from the U.S. Geological Survey). 

Andrew Grosz of the U.S. Geological Survey reviewed the 

analytical data. The major-oxide XRF analyses were performed by the U.S. Geological Survey's Clay Petrology 

Laboratory, Branch of Sedimentary Processes, and Rock 

Analysis Laboratory, Branch of Central Mineral Resources. 

Bondar-Clegg & Company of Vancouver, Canada, performed the INAA analyses.

PREVIOUS INVESTIGATIONS

Heavy-mineral placer deposits were discovered in and 

around the San Juan basin of northwestern New Mexico 

and southern Colorado as a result of uranium exploration. 

Airborne gamma-ray radiometric surveys flown by the U.S. 

Atomic Energy Commission in the mid-1950's detected the 

radioactive anomalies in the Ute Mountain Ute Reservation. Investigation of these anomalies resulted in a series of 

U.S. Atomic Energy Commission Preliminary Reconnaissance Reports (PRR) written by Chenoweth (1955a-g),

Chenoweth and Carither (1955), and Blagbrough (1955a, 

b). The reports, which are available in the Field Records 

Collection of the U.S. Geological Survey Library in Denver, Colo., equate each of the radiometric anomalies with 

an airborne anomaly (AA) and give each a number. 

Because these studies served as the basis for most subsequent investigations, this numbering system is used in our 

study. Table 1 lists the airborne anomaly number and the 

PRR number for each occurrence.

Murphy (1956) documented the occurrence of heavymineral deposits on the Navajo and Ute Mountain Ute 

Indian Reservations and recommended further study of the 

economic potential of their titanium, zircon, and radioactive minerals. Chenoweth (1957) summarized the physical 

and chemical characteristics and stratigraphic distribution 

of the heavy-mineral deposits in the San Juan basin. This 

report contains the first substantial discussion of the nonradioactive elements present in the Ute Mountain Ute deposits and their economic potential.

A report by Bingler (1963) on a niobium-bearing 

deposit in the Upper Cretaceous Gallup Sandstone at 

Sanostee, N. Mex., in the Navajo Reservation, is the only 

detailed mineralogical study of a Cretaceous heavy-mineral 

deposit in the area. He identified the allogenic (zircon, garnet, tourmaline, and ilmenite) and authigenic (barite, leucoxene, and brookite) heavy minerals. Bingler's description 

of the types, sizes, distribution, and mode of occurrence of 

minerals in a shoreline heavy-mineral deposit acts as a useful guide for the Ute Mountain Ute Indian Reservation. 

R.B. O'Sullivan (U.S. Geological Survey, written commun., 1980) briefly examined these deposits as part of the 

National Uranium Resource Evaluation (NURE) program.
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B3

LOCATING THE DEPOSITS

All of the heavy-mineral deposits are in the central and 

southeastern parts of the Reservation (fig. 2). Except for 

AA-4 (an occurrence in the Upper Cretaceous Pictured 

Cliffs Sandstone; Chenoweth and Carithers, 1955), all are 

found at the top of the Point Lookout Sandstone, which commonly forms cliffs or prominent outcrops. The deposits are 

better cemented than the surrounding sandstone and form 

small knolls and ridges along the top of the Point Lookout 

outcrops. Figure 2 shows a conspicuous northwest-southeast 

alignment of the deposits that is of considerable help in 

locating other exposed deposits and inferring areas of potential buried deposits.

When the PRR reports were written, most of the Reservation was not surveyed, and the location descriptions of the 

deposits relied on reference points such as roads, trails, and 

windmills. Many of these original reference points have 

either changed or are missing. Today, topographic maps are 

available for the area, but there are no section, township, and 

range lines. Several studies have situated the deposits using 

projected township and range lines. Unfortunately, these 

projections are derived from several baselines, and the 

deposits are still difficult to locate. This study used a combination of maps, descriptions in previous publications, air 

photos, and scintillometer traverses. Most, but not all, of the 

previously identified anomalies were found (see table 1). 

During this search for the deposits, two previously unreported, small deposits were noted (FA-1 and near AA-14; 

see detailed description of the southern anomaly group). 

Deposits located in this study are plotted on l:24,000-scale 

topographic base maps.

STRATIGRAPHY AND 

SEDIMENTOLOGY OF UNITS 

CONTAINING THE DEPOSITS

Condon (1992) and Aubrey (1991) describe the overall 

stratigraphy of the Reservation. Of most interest to this study 

are the Point Lookout Sandstone and the overlying Upper 

Cretaceous Menefee Formation. The Point Lookout is a 

shoreline deposit and the most areally extensive sandstone 

unit formed during a regression of the Late Cretaceous sea 

across the Four Corners area. It interfingers with and overlies 

offshore marine deposits of the Mancos Shale. Cyclic transgressions and regressions of the paleoshoreline built up a 

sand deposit to a thickness in excess of 90 m on the Reservation and resulted in a local landward shifting of depositional 

facies (Zech and Wright Dunbar, 1989; Wright and others, 

1989). Figure 3 compares an idealized prograding shoreline 

with the relationship of the depositional facies that results 

from one transgressive/regressive cycle, or parasequence. 

On a basin scale, the Point Lookout parasequences form sets

Table 1. List of airborne anomaly numbers and Preliminary 

Reconnaissance Report (PRR) numbers for the Ute Mountain 

Ute Indian Reservation.

Airborne anomaly number PRR number

u

'7

8,9

10,11

'12

13

14

15

16, 17, 18

19,20

'area near 21

21

1 22

'area near 23

J 23

25

26

27

28

'29

30

31

36

37

38

39

40

41

42

43

44

245

ED-R-431

ED-R-435

ED-R-433

ED-R-434

ED-R-436

ED-R-451

ED-R-452

ED-R-453

ED-R-437

ED-R-438

ED-R-473

ED-R-439

ED-R-454

ED-R-472

ED-R-454

ED-R-471

ED-R-426

ED-R-469

ED-R-468

ED-R-467

ED-R-466

ED-R-465

ED-R-440

ED-R-441

ED-R-493

ED-R-494

ED-R-495

ED-R-496

ED-R-497

ED-R-498

ED-R-499

ED-R-500

'Not located during this study. 

2Could not be accessed for this study.

that are indicative of highstand deposition (Van Wagoner 

and others, 1988). However, late-stage Point Lookout deposition (southwestern Colorado) may be of a lowstand ramp 

or shelf-margin system tract. Recent observations (Zech and 

Wright Dunbar, 1989) suggest a basinward shift in coastal 

facies and the development of a large delta near Durango, 

Colo., developed above a previously undocumented regional 

unconformity.

The Chimney Rock area (fig. 4) contains characteristic 

Point Lookout heavy-mineral deposits. The base of the Point 

Lookout measured section at Chimney Rock (fig. 5) displays 

a gradational contact with the underlying Mancos Shale (units 

1-6). The section contains at least eight coarsening-upward
B4 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

f-^CHS J^f&S'' CW.'MW

-rsk.'i. ^ OV^T! >*...: .- "sT

f^il
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO

A. IDEALIZED PROGRADING SHORELINE

B5

Mixed sandstone rand shale \-

Dominantly sandstone

Dominantly shale

Coastal plain

! " .' Foreshore . . ..' '

Upper shoreface..

Water

Lower shoreface

Offshore transition

B. POINT LOOKOUT SANDSTONE PROGRADATION

Coastal plain

Menefee Formation

rET-i

1 -*-_

L £S±

Measured section shown in figure 10

Point Lookout / 

Sandstone \

Mancos Shale

Figure 3. Comparison of an ideal shoreline progradation scheme with a typical parasequence found in the Late Cretaceous Point Lookout Sandstone in the Four Corners area. A, uninterrupted deposition results in a seaward buildout of shoreline deposits and a single coarsening-upwards vertical sequence. B, a coarsening-upwards vertical sequence is interrupted by a transgression. When deposition 

reinitiates, all sedimentary facies shift landward. Modified from Wright (1986).

cycles (B-I) within the main sand body, with most of the 

lower cycles beginning with a basal organic-rich shale or a 

silty shale. Lenticular siltstone and sandstone interbeds 

increase in number and thickness vertically until sand dominates the section, forming the base of the Point Lookout cliffs. 

Maximum grain size falls within the very fine to fine sand 

range, with individual beds displaying weakly developed, fining-upward trends. Undulatory parallel laminations and hummocky cross-stratification are the most common sedimentary 

structures, indicating deposition in the inner shelf and distant 

shoreface environment. The upper cycles contain little shale 

but are separated from each other by laterally persistent 

weathering notches. These notches probably represent 

changes in deposition that would become shale units if traced 

downdip. The top of the section (unit 25) contains coarser 

grained sandstone and trough crossbeds of the cliff-forming 

main body of the Point Lookout, indicating deposition in the 

middle to upper shoreface.

The higher (foreshore) facies are not preserved in the 

Chimney Rock section as in most of the Point Lookout, 

probably due to reworking by the fluvial and tidal processes 

of the prograding Menefee coastal plain system. However, 

the facies, some of which contain heavy-mineral deposits, 

are found in a few areas on the Reservation. Where preserved, the foreshore depositional environment is characterized by gently seaward (northeast)-dipping, even, parallel 

beds that have lateral continuity ranging from 3 to over 30 m. 

Generally, the grain size, degree and type of cement, and 

color of the foreshore beds do not significantly differ from 

shoreface beds.

The foreshore facies of the Point Lookout interfinger 

with the Menefee Formation. Fluvial and distributary sandstones of the lower part of the Menefee can be distinguished 

from sandstones of the Point Lookout on the basis of internal 

sedimentary structures, a slightly coarser grain size, poorer
B6 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Figure 4. Typical exposure of the Point Lookout Sandstone (upper, cliff-forming outcrop) overlying the Mancos 

Shale (lower, erosional slope) near Chimney Rock, Colo. The Point Lookout measured section in figure 5 is near 

the right side of the outcrop.

sorting, more carbonaceous material, (generally) more induration, and darker color. Lower coastal plain facies of the 

Menefee include carbonaceous fluvial and distributary channels, levee and overbank deposits, and coal. In areas where 

the Point Lookout and Menefee interfinger, any of these 

deposits may be found under foreshore beds, and fluvial 

channels of the Menefee commonly scour into or through the 

foreshore, resulting in sandstone-on-sandstone contact.

ORIGIN AND FIELD

CHARACTERISTICS OF

HEAVY-MINERAL DEPOSITS

Heavy-mineral deposits on the Ute Mountain Ute 

Indian Reservation define a linear depositional trend (fig. 2) 

oriented N. 55°-60° W. that is similar to trends identified by 

Hollenshead and Pritchard (1961) and Devine (1991). Virtually all of the known deposits occur at the top of the Point 

Lookout in sediments deposited in a foreshore environment. 

Interfingering of the Point Lookout foreshore facies with the 

Menefee coastal plain facies probably led to the initial conclusion in some PRR reports that some of the heavy-mineral 

deposits were in the Menefee.

Alien and Balk (1954) studied the mineral composition 

of the Point Lookout and other regressive marine sandstones 

in the San Juan basin and found them to contain about 1 percent heavy minerals, which is within the normal range for 

clastic sediments according to A.E. Grosz (U.S. Geological 

Survey, written commun., 1989). Heavy minerals included 

tourmaline, garnet, zircon, hematite, ilmenite-magnetite, 

leucoxene, biotite, and chlorite. The presence of monazite 

was not investigated. The Alien and Balk (1954) study was 

in an area where the Point Lookout sandstones were wave 

dominated (Zech, 1982), as is the case on the Ute Mountain 

Ute Indian Reservation. One difference between the two 

areas was the presence of a major(?) fluvial system in the 

area of the Reservation (Newman, 1 982; Zech and Wright 

Dunbar, 1989). This fluvial system probably originated in a 

tectonically active source area in southeastern Arizona 

(Cumella, 1983) and produced the Point Lookout delta near 

Durango (Zech and Wright Dunbar, 1989). The proximity of 

the fluvial system most likely increased the general heavymineral content of the Point Lookout beach sands.

Normally dispersed heavy minerals in the Point Lookout were concentrated in the foreshore environment by the 

repeated swash of waves on the beach. When a wave runs up 

a beach it carries both suspended light grains of sand and a
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B7

bedload of heavy grains. Although most of the landward 

flow of water returns directly to the sea, the return surface 

flow is smaller and of lesser energy due to percolation of 

some of the water into beach sands and because of local 

channelization. The lower energy return water carries back 

the lighter material but leaves some of the heavy grains in 

the most landward position, increasing the relative abundance of heavier grains in the foreshore. Repetition of the 

process concentrates the heavy minerals into a heavymineral deposit as the beach grows. Wind may further 

increase the heavy-mineral content by winnowing the deposits and removing the lighter grains. Although sedimentary 

structures in the deposits are obscured by a ferric-oxide 

cement, no eolian sedimentary structures were noted in the 

deposits on the Reservation. A modern example of heavymineral accumulation in the foreshore is shown in figure 6.

Additional information on the formation of heavymineral deposits in sedimentary rocks may be found in 

Mackie (1923), Rittenhouse (1943), Rubey (1933), Stapor 

(1973), Woolsey and others (1975), and Zenkovich (1967). 

A good overview (including depositional environments) of 

most of the known Cretaceous heavy-mineral deposits in 

the Western Interior was written by Houston and Murphy 

(1977).

All the deposits are more thoroughly cemented than 

the surrounding rock and form small, prominent topographic features. Small scarps (as high as the deposit is 

thick) will generally ring deposits exposed on the tops of 

knolls or form slope breaks on deposits exposed on hillsides. Most of the deposits are stained black or dark brown 

from ferric-oxide cement contrasting in color with the 

underlying light brown or white Point Lookout Sandstone. 

A few deposits are only moderately cemented and have a 

medium-brown color similar to the overlying Menefee 

channel sandstones. However, these deposits may be easily 

distinguished from channel sandstones by the increased 

radioactivity of the heavy minerals.

Weathering of the well-cemented deposits produces 

abundant small (marble to hand size), black, sharp-edged 

rock fragments that are generally elongate or flat. Deposits 

that are nearly covered by eolian material may be easily recognized by these fragments, which are present as a deflation 

lag on and around the deposit. Because of the resistant 

nature of the outcrop, these fragments are often the best or 

only material available for sampling. An unusual (but common on the Reservation) feature in the fragments is slickensides (fig. 7), which are not noted in overlying or underlying 

rocks. If the elongate or flat nature of the fragments reflects 

bedding, then the slickensides are at a low angle to bedding. 

A possible explanation is that leaching of minerals in the 

deposit and the subsequent induration may have caused a 

change in the volume of the deposit as a whole, producing 

slickensides as a method of accommodation.

MAPPING OF HEAVY-MINERAL 

DEPOSITS

Initially, PRRs were used to locate the airborne 

anomalies (table 1). Five airborne anomalies (AA-4, 

AA-7, AA-22, AA-23, and the area near AA-23) could 

not be located. Airborne anomaly 45 was not visited 

because of lack of access. For the anomalies that were 

located, it was necessary to confirm each deposit using a 

scintillometer because many parts of the Point Lookout 

(and the lower part of the Menefee) have similar outcrop 

characteristics to the heavy-mineral deposits. The total 

gamma-ray count of a heavy-mineral deposit is higher 

than the surrounding rock because of the increased number of radioactive minerals in the deposit, particularly 

monazite and zircon. Grosz and others (1989) showed 

that there is a strong linear relationship between heavymineral content and gamma-ray emissions and that 

gamma-ray activity is an excellent quantitative predictor 

of the economic heavy-mineral component on a bulksample basis. The scintillometer (Geometries, model GR 

101 A) was used primarily as a reconnaissance tool. It 

measured the total gamma-ray flux rate but couldn't distinguish among gamma rays produced by potassium, 

samarium, isotopes of uranium, or daughter isotopes of 

thorium. Total gamma radiation was measured in counts 

per second (cps). An average value for barren Point Lookout Sandstone taken each day was used as a background 

value. This value ranged from 90 to 120 cps. A deposit 

was identified as having a multiple radiation count (such 

as five or six times background) of the average background in the area. The scintillometer was also used to 

define poorly exposed or covered heavy-mineral deposits 

that have little surface expression. The edges of such 

deposits were determined by an abrupt decrease in the 

counts per second.

Where the exposure was good, the edge of a deposit 

was easily discernible because the increased iron and calcite cement of the deposit produced either a small escarpment or an abrupt color change. The extent of a deposit 

was determined by several traverses, and its location was 

plotted on stereo air photographs. This was transferred to 

l:24,000-scale base maps using a Kern PG-2 stereo plotter. The outlines of deposits shown on these location 

maps are schematic and should not be used to calculate 

area. The purpose of these maps is to show the general 

surface shape of the deposits and to show enough detail 

of the surrounding area to allow easy reference to their 

locations. Accurate mapping of each deposit would require 

a scale much larger than 1 :24,000.
B8 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

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BIO GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Figure 6. Heavy minerals accumulating in the swash zone of the foreshore depositional environment at Mugu 

Lagoon, Calif. Photograph courtesy of John E. Warme (Colorado School of Mines).

DISTRIBUTION AND PHYSICAL

CHARACTERISTICS OF THE

DEPOSITS

Most of the heavy-mineral deposits on the Reservation 

formed along several Upper Cretaceous Point Lookout 

beaches. The deposits occur in three different geographic areas 

(fig. 2): the southern group in the New Mexico part of the Reservation (south of lat 37°00'), the central group near the 

Mancos Trading Post, and the northern group along the northsouth-trending cliffs east of Towaoc. This grouping of deposits resulted because the strike of the Point Lookout paleoshorelines combined with present-day structure and erosion limited 

the area where these deposits could crop out, and because only 

a few of the regressive beaches developed enough to preserve 

their foreshore deposits. Only deposits AA-4 and AA-28 fall 

outside these three groupings. Anomaly AA 4, which was not 

located during this study, is the only reported heavy-mineral 

occurrence in a rock unit other than the Point Lookout. The 

location of AA-4 reported by Chenoweth and Carithers (1955) 

places it in the Pictured Cliffs Sandstone in sec. 1 3, T. 14 W., 

R. 3 1 N. Anomaly AA-2 8 is described with the northern group 

because it is on the same depositional strike and probably 

formed along the same shoreline.

Figure 2 shows most of the deposits located in this study 

and indicates that some of the larger deposits include several 

airborne anomalies. In general, all of the deposits are subparallel and elongate in the direction of the northwest-southeast

paleoshorelines. Because of this linearity, it is probable that 

known deposits link under areas of cover, and undiscovered 

deposits exist along the identified trends or along parallel 

trends to the northeast. Unfortunately, a few centimeters of 

cover will attenuate the characteristic radioactive and magnetic signature of a deposit (Mahdavi, 1964).

SOUTHERN GROUP

The southern group includes airborne anomalies 8-11, 

13-21,36,37, and FA-1 (fig. 8). This is the largest grouping 

of airborne anomalies in number and probably in volume. 

Because the southern group overlies the Verde Oil Field 

(shown as "Oil Fields" on fig. 2), it is the most easily accessible group on the Reservation. Service roads to the oil wells 

in the area pass near most of the anomalies, and each anomaly 

is close to the elevation of nearby access roads.

The southern group formed along at least three separate 

northwest-southeast-oriented paleoshorelines. Because the 

shorelines regressed to the northeast, anomaly 36 is the oldest 

and anomalies 13-15 and 21 are the youngest. Other heavymineral occurrences along the three paleoshoreline trends are 

probable in the subsurface. The most likely areas for additional subsurface deposits are between AA-8 and AA-17 and 

between AA-13 and AA-21. The magnetic studies, which 

are discussed in a later part of this report, limit the subsurface 

potential for heavy-mineral occurrences to the area between 

AA-8 and AA-21.
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO Bll

AIRBORNE ANOMALIES 8, 9,10, AND 11

AA-8 and AA-9 are part of a series of separated occurrences at the same stratigraphic level, probably the same bed 

or within the same foreshore sequence. This is the same set 

of shorelines that forms AA-10 and AA-11. These occurrences are only 0.3-0.6 m thick, poorly exposed, and discontinuous. However, they are considerably longer than 

previously reported (Chenoweth, 1955c, d), particularly to 

the northwest. Small, black, well-cemented, chip- to fist-size 

rock fragments with total gamma-ray counts of three to eight 

times normal background characterize most of the surface 

exposures. The width of each occurrence is unknown 

because exposures crop out on only one side of a low hill. 

Because associated deposits AA-10 and AA-11 are wide 

and the northwest end of AA-8 curves to the northeast, it is 

possible that most of the occurrences remain covered and 

may thicken in the subsurface.

AA-10 is stratigraphically lower than AA-11 (fig. 9). 

As with most of the deposits, a high degree of diagenetic 

alteration and cementation obscures the sedimentary structures. However, the foreshore origin of AA-10 can be 

inferred from the gently seaward-dipping, parallel beds 

below and lateral to the deposit. The heavy-mineral occurrence forms a prominent bench to the southeast that can be 

traced to the northwest as a dark bed with anomalous 

gamma-radiation values. An overlying tidal channel locally 

eroded the heavy-mineral beds (fig. 9, C). AA-10 reaches a 

maximum thickness of 1.5-1.8 m near the center of the 

deposit and seems to thin rapidly and pinch out(?) at both 

ends. Some of the apparent thickness change may be due to 

the increasing cover. The exposed deposit reaches a maximum of 107 m long and 30 m wide. The middle of the 

deposit is well exposed on the south-facing slope, where a 

measured section was described (fig. 10).

The two areas of above-background total gamma-ray 

counts and the corresponding repetition of depositional environments in this measured section indicate that two cycles 

are present. The top of the lower cycle, about 15 m above the 

base of the section, was either poorly developed or partially 

eroded by the subsequent transgression. The mudstone 

shown in figure 10 at 18m represents part of the transgressive event shown in figure 3B. In figure 3B, the location of 

the measured section detailed in figure 10 is near the landward extent of the transgression where the depositional environments overlap. The foreshore is at the top, underlain by 

the upper shoreface, the transgressive deposits, and finally 

the foreshore and upper shoreface.

The lower part of AA-10 is not as well cemented or as 

dark colored as the upper part. Several samples (AA-10-1 to 

AA-10-13) were taken at this locality (fig. 10, appendix). 

The increase in total gamma-ray counts is due to the increase 

in heavy-mineral content. Samples AA-10 1 to AA 10-5 

were barren rock, and A A-10-6 to AA-10-13 were in the 

heavy-mineral deposit. Occurrences AA-10 and AA-11

Figure 7. A rock fragment from a Point Lookout Sandstone 

heavy-mineral deposit. Note the slickensides.

were the sites for a feasibility study of magnetic techniques 

to locate buried heavy-mineral deposits. Results of this effort 

are described in the section on magnetics.

AA-11 is divided by a small valley (fig. 8). Like many 

of the heavy-mineral deposits, AA-11 is very well 

cemented and forms the top of a hill. The upper surface of 

the deposit is covered by a 15- to 46-cm-thick mixture of 

angular rock fragments and Holocene eolian sand. Although 

the sand cover decreases the scintillometer readings over 

the deposit, a 3-10 times background level was consistently 

found. The best exposure of the deposit is at the edge of the 

outcrop on the southwest face of the hill. At this location, 

the deposit consists of thin, well-cemented, dark beds (containing heavy minerals) separated by thin, moderately well 

cemented beds of tan sandstone. Even in the best exposures, 

a pervasive, hard, black ferric-oxide cement obscures the 

internal sedimentary structures. With the exception of 

samarium, results from the analysis for this anomaly (see 

appendix) indicate the sample was from a well-cemented 

but relatively barren bed.

Rocks below AA-11 are best exposed at the southeast 

end of the hill where a small cliff exposes (from bottom to 

top) tidal-channel deposits, a few thin 2.5-5.0 cm coal beds, 

and the base of a foreshore sequence. The estimated thickness of 0.6-1.2 m is tentative because of poor outcrops and 

colluvium cover.
B12 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

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Figure 8. Locations of heavy-mineral deposits in the southern part (New Mexico) of the Ute Mountain Ute Indian Reservation. 

Topographic base from U.S. Geological Survey Heifer Point (1963) and Palmer Mesa (1983) quadrangles, scale 1:24,000. Contour 

interval is 40 ft (12.2m).
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B13

Figure 9. Site of heavy-mineral occurrences at AA-10 and AA-11. The dark-colored outcrop on the right (A) is 

AA-10, and AA-11 caps the hill on the left (B). The white sandstone (C) is a tidal-channel deposit.

AIRBORNE ANOMALIES 13,14, AND 15

AA-13 consists of two small pods located a few feet 

north of the main access road for the Verde Oil Field. 

These pods are thin, less than 0.3-0.6 m, and their total 

gamma-ray counts are four to five times the background 

level. AA-13 is on the same strike as AA-14 and AA-15 

and probably represents a continuation of the same foreshore. The deposit's thinness is due to its position on the 

paleoshoreline, which can be determined by the adjacent 

lithologies and their depositional environments. Above the 

deposit are the thin sandstone, shale, and coal beds of the 

Menefee. That part of the Point Lookout immediately 

below the deposit consists of a 0.6-m-thick, highly bioturbated sandstone bed that rests on a well-developed foreshore sequence (similar to fig. 3,4). The bioturbated bed 

indicates the termination of underlying foreshore facies. 

Therefore, the overlying heavy-mineral-bearing foreshore 

must be related to a slightly later foreshore sequence. 

Because foreshores imbricate seaward, AA-13 is probably 

the landward edge of a younger foreshore. Unless eroded 

by the Menefee fluvial systems, more and thicker heavymineral beds should be found in the subsurface to the 

northeast.

AA 14 is a few feet south of the main access road to 

the Verde Oil Field and is identified by an anomalous

scintillometer reading (two to eight times background 

level). Little remains of the deposit. Most of the radiometric anomaly seems to come from erosional remnants consisting of small, black, heavy-mineral-bearing rock 

fragments that retain a trend approximately parallel to the 

Point Lookout paleoshoreline. A small radiometric anomaly (two to six times background level) about 3 m in diameter occurs to the southeast along the depositional strike and 

across a small valley. This occurrence, which was not sampled, is an extension of the AA-14 trend and may be 

AA-12, which was reported in the area but not located in 

this study. It is difficult to determine if this small occurrence indicates additional heavy minerals of significant size 

in the subsurface. Any extension to the southeast projects 

into an area of increasing overburden.

AA-15 consists of two separate pods at the same 

stratigraphic level. Like AA-14, small, dark rock fragments 

cover the surface. Anomaly AA-15 is larger than AA-14 

but is very poorly exposed. It is overlain by Holocene 

eolian and colluvial material that is mixed with the heavymineral-bearing rock fragments. Because of the lack of outcrop, no samples were taken and the deposit was defined by 

the radioactivity measurements. The thickness and width of 

this deposit could not be determined. The subsurface lateral 

extent of this deposit may be considerably greater than the 

surface area shown in figure 8.
B14 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

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laminations

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cross strata

Trough

cross strata

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laminations

Parallel 

laminations

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cross strata 

to broad 

troughs

High-angle 

trough 

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and broad 

troughs

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strata

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Biology and 

organics

Thalassinoides 

burrows

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burrows

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burrows

Root 

mottling

Minor

burrow

mottling

Rare 

Ophiomorpha 

burrows

Plant 

fragments

Burrow 

mottling

Depositional 

environment 

and rock type

Foreshore

sandstone

Foreshore

sandstone

Foreshore 

sandstone

Upper

shoreface 

sandstone

Upper 

shoreface 

sandstone

Transgressive(?) 

mudstone

Foreshore 

sandstone

sandstone

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upper shoreface 

sandstone

Upper

shoreface 

sandstone

Middle (?) 

shoreface 

sandstone

Intertidal 

channel 

and bar 

sandstone

Lower 

shoreface 

sandstone

Figure 10. Measured section of the upper part of the Point Lookout Sandstone at location AA-10. This depositional sequence 

is represented by the rectangular area shown in figure 3B.
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO 

AIRBORNE ANOMALIES 16,17, AND 18 AIRBORNE ANOMALIES 19 AND 20

B15

Anomalies AA-16, AA-17, and AA-18 are part of 

the same foreshore deposit that has been split by Eagle 

Nest Arroyo and a small tributary (fig. 8). These occurrences make up the largest exposed heavy-mineral deposit 

in the southern group. AA-16 and AA-17 may extend into 

the subsurface to the northwest and southeast, respectively. Because of their size and probable extension into 

the subsurface (particularly to the southeast), magnetic 

investigations were attempted to identify the extent of the 

covered deposit. Results indicate that the deposit may thin 

or pinch out to the southeast. The magnetic studies are 

described in a later section.

Anomaly AA-16, although fairly large, is poorly 

exposed. Small, dark-colored rock fragments of the heavymineral deposit, mixed with Holocene alluvium and 

eolian sand, cover most of the occurrence. Thickness 

ranges from 0.3 to 2 m. Total gamma-ray counts ranged 

from two to eight times background level.

The best exposed anomaly of this group is AA-17, 

which is located in a small dry drainage about 46 m south 

to southwest of the end of a drillhole access road. Samples 

AA-17-1 to A A-17-5 (see appendix) were collected at 

this locality. AA-17-1 was barren rock from about 1.5 m 

below the dark-colored deposit. Samples A A-17-2 and 

AA-17-3, 7.6 m apart, were from the same bed at the 

base of the deposit. Samples AA-17-4 and AA-17-5 

were from 0.3 m and 1 m, respectively, above the base of 

the deposit. A few of the beds exposed in this locality 

have only background gamma-ray levels but are well 

cemented with a dark ferric cement. This could cause 

some overestimation of the deposit thickness if a scintillometer is not used. The deposit had radiation levels from 

two to six times the background level and was 0.3-2.3 m 

thick.

Both AA-16 and AA-17 are about 1.8 m thick 

where exposed by Eagle Nest Arroyo. Diagenetic cement 

and slope wash obscure the sedimentary structures within 

the deposits. A sandstone cliff in the arroyo, just below 

the deposits, exposes a sedimentary sequence that grades 

up from upper shoreface to foreshore and tidal channel. 

The proximity of these environments indicates that the 

deposit was part of a nearshore environment, probably a 

foreshore. No seaward extension for AA-17 was found.

Anomaly AA-18 is a relatively thin (0.3-0.9 m) 

deposit that is probably a seaward extension of AA-16, 

and it may extend into the subsurface to the northwest. It 

consists of concentrations of small heavy-mineral-bearing 

rock fragments and a small outcrop of the deposit at the 

edge of Eagle Nest Arroyo.

These anomalies are the erosionally separated remnants 

of a single foreshore heavy-mineral deposit, probably a 

northwest extension of AA-16 and AA-17. The surface 

exposures consist of three closely spaced, small knolls about 

30 m in diameter covered with small, dark rock fragments. 

The heavy-mineral beds are about 1 m thick and have a total 

gamma-ray count about 6 11 times higher than background. 

AA-20 does not extend beyond its surface exposure because 

of erosion. However, AA-19 probably does continue into the 

subsurface to the southeast. This extension of AA-19 is 

important because it would indicate the possibility of a much 

larger occurrence with relatively thin overburden between 

AA-19 and AA-16, a distance of about 1,520 m (fig. 8).

AIRBORNE ANOMALY 21

Anomaly AA-21 has a surface exposure consisting of 

mostly ferric-oxide-cemented rock fragments with little 

exposure along the edge of the nearby canyon (fig. 8). 

Holocene eolian sand covers much of the upper surface of 

the deposit. AA-21 is estimated to be 0.6-1.2 m thick, with 

a total gamma-ray count six to nine times background level. 

The heavy-mineral deposit may continue into the subsurface 

to the northwest under unconsolidated colluvium and a 

thickening overburden of the Menefee Formation. This is the 

youngest deposit in the southern group, and it does not correlate with the paleoshoreline trend of AA-13, AA-14, and 

AA-15, which are 7.2 km to the southeast. The upper part of 

the Point Lookout exposed across the arroyo to the southeast 

showed no extension of the heavy-mineral trend.

AIRBORNE ANOMALY 36

Anomaly AA-36 is the oldest and longest continuous 

heavy-mineral deposit exposed in the southern group. It 

forms the top of a ridge capped by fist-size and smaller 

rock fragments of the dark-colored, ferric-oxide-cemented 

heavy-mineral deposit. There is very little outcropping. 

However, the rock-fragment cover is thinnest along the 

northern edge of the ridge, where the deposit is 1.0-1.2 m 

thick and scintillometer values are five to eight times background level. A drillhole marker near the southeast end of 

the deposit shows the following information: 660FSL, 790 

PEL, 32N, 16W, #1 NAV/UTE. The deposit was sampled 

at each end. As a result of erosion of the surrounding area, 

there is no possibility of any subsurface extension of the 

deposit. However, remnants of the deposit may form a 

prominent northwest-southeast trending ridge about 3,000 

m to the southeast (shown in fig. 8).
B16 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

AIRBORNE ANOMALY 37

The surface expression of AA-37 is similar to the previously described deposits, except that it is smaller and more 

circular (about 12 m in diameter and about 0.6-0.9 m thick). 

Some of the foreshore beds beneath the dark, well-cemented 

deposit register minor increases in total gamma-ray count 

(one to four times background level) and have a mottled 

hematite and limonite staining. The upper part of the deposit 

has a 10-12 times background emissions level. The deposit 

may extend in the subsurface to the southeast but not to the 

northwest because of local erosion.

ANOMALY FA-1

This is a small, isolated anomaly that was not reported 

in the PRRs or in subsequent reports. Like the rest of the 

southern group, it forms the top of a small knoll, is about 30 

m in diameter, and is covered with well-cemented, blackcolored rock fragments. Scintillometer values 6-11 times the 

background level were measured across the deposit. The 

sample analyzed from this deposit (see appendix) was from 

a well-cemented but relatively barren bed in the deposit. This 

anomaly is on the same trend as AA-20, AA-19, and AA-16 

and probably represents an extension of the same shoreline 

deposit. Parallel, laminated seaward-dipping foreshore beds 

are exposed just beneath the deposit.

CENTRAL GROUP

The central group of anomalies (fig. 11) probably relate 

to the older shorelines of the southern group, but the distance 

between the groups makes correlation difficult. Deposits in 

this group are at the top of the massive Point Lookout Sandstone and are part of an underlying foreshore. Anomalies 25, 

27, 30, and 31 are related to the same shoreline and are the 

oldest in the group. This foreshore sequence is progressively 

wider to the southeast. In general, the deposits have less of 

the black to dark-brown color and are more brown to darkred, indicating a leaching of iron from the deposit (see the 

petrologic and magnetic descriptions). Like the southern 

group of deposits, this group is well exposed, has little overburden, and is mostly accessible by existing roads. Except 

for AA-29, all previously reported anomalies in this group 

were located. Anomaly AA-29 was described by Chenoweth 

(1955f) along the Point Lookout-Menefee contact, about 1.5 

km east of the eastern border of figure 11. Although the contact was traversed, the anomaly could not be found.

AIRBORNE ANOMALY 25

The deposit at AA-25 is well exposed, about 312 m 

long by 14 m wide and 0.2-0.8 m thick. A 12-m diameter 

small erosional remnant of the deposit is present to the

southeast. Total gamma-ray counts range from 7 to 15 times 

background level. Because of the degree of erosion, this 

trend probably does not continue to the northwest. Anomaly 

AA-27 is a continuation of this deposit to the southeast. 

Two samples were taken because of the good exposure, 

length, and proximity to AA 26.

AIRBORNE ANOMALY 26

Radiometrically and geochemically, AA-26 is the most 

notable deposit on the Reservation. It is 335 m long and may 

continue to the northwest in the subsurface. Most of the 

deposit is 4.5-6.0 m wide and covered by 0.6-0.9 m of 

unconsolidated Holocene eolian sand. However, where 

blowouts in the eolian sand expose the deposit, the heavymineral deposit is observed to be as much as 12 m wide and 

0.6-0.9 m thick. Total gamma-ray counts range from 4 to 30 

times background level the highest value of any of the 

deposits. Although the gamma-ray emissions for this deposit 

have a considerable range, the overall values are generally 

higher than those of other deposits. The highest values are in 

the southeast part of the deposit. Because of the higher than 

average gamma-ray values, the deposit was sampled twice. 

One sample was taken near the northwest end of the deposit 

and the other near the southeast end. The southeast sample 

(AA-26-SE) contained almost 6 percent zirconium and 0.1 

percent thorium (see appendix). Based on scintillometer 

traverses and one analysis, this deposit probably contains 

higher concentrations of zirconium and thorium than any 

other heavy-mineral deposit on the Reservation.

AIRBORNE ANOMALY 27

This deposit is the least accessible of the central group. 

The closest access is a road that stops at AA-25, about 914 

m to the northwest. AA-27 is part of the same foreshore that 

forms AA-25 but is separated from it by erosion. AA-27 

consists of one main body of heavy minerals (about 137 m 

long, 10.6 m wide, and 0.6-0.9 m thick) and three smaller 

bodies (each about 30.4 m long, 10.6 m wide, and 0.3-0.6 m 

thick). The three smaller remnants are shown in figure 11 as 

one outlier north west of the main body. The main body of the 

deposit has a total gamma-ray count that ranges from 4 to 16 

times background level. The smaller bodies range from 4-12 

times the background level. Local erosion divides all the 

deposits.

AIRBORNE ANOMALIES 30 AND 31

These two anomalies represent the same heavy-mineral 

deposit, the central part of which is covered by Holocene 

eolian sand. It is an unusual deposit because of its large (76 

m) width, which gives it a more rounded than elongate 

shape in map view. The deposit reaches a maximum length
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B17

37° 108°42'30" 108°40'

C^rv,^,r Can^S

figure 11. Locations of heavy-mineral deposits in the central part (Colorado) of the Ute Mountain Ute Indian Reservation. Topographic base from U.S. Geological Survey Tanner Mesa (1966) quadrangle, scale 1:24,000. Contour interval is 40 ft (12.2 m).

of 457 m and varies in thickness from 0.6 to 1.1 m. The total 

gamma-ray counts ranged from 5 to 20 times background 

level both in the northern (AA-30) and southern (AA-31) 

outcrops. This deposit is probably related to the same foreshore sequence that forms AA-27 and AA-25. Because of 

erosion, there is no possible subsurface extension of the 

deposit on the Reservation. However, this is the same trend 

that hosts some of the heavy-mineral deposits on the Navajo 

Reservation, just to the southeast.

NORTHERN GROUP

The northern group of anomalies is shown in figures 

12 and 13. The deposits are parts of two separate foreshore 

sequences that are younger than other heavy-mineral 

deposits on the Reservation. These two foreshore sequences 

have very restricted outcrops. However, every outcrop contains a heavy-mineral deposit.

AA-45 (shown only in fig. 2) is the northernmost 

anomaly on the Reservation. It was not sampled because of

restricted access. However, its reported location (Chenoweth, 1955g) indicates that the deposit has minor surface 

exposure and, if it does extend into the subsurface, it would 

project into an area of thick overburden.

AIRBORNE ANOMALIES 38^14

These seven anomalies (fig. 12) represent one foreshore sequence and the longest exposed heavy-mineral 

deposit on the Reservation. Including the width of the three 

small tributaries that cut through the deposit, the total 

length from AA-44 to AA-39 is about 2,286 m. Anomaly 

AA-38, the southeasternmost anomaly of the group, is 

about 122 m in length and is separated from the other 

deposits by a 610-m-wide canyon. This is the only anomaly 

of the group that shows slight iron staining and relatively 

weak induration. If it was not partially eroded, the total 

length of the exposed linear deposit would be 3.4 km. Total 

gamma-ray counts average four to eight times background 

level. The thickness of this deposit is 0.3-1.2 m.
B18 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

108°40'

Figure 12. Locations of heavy-mineral deposits in the northern part (Colorado) of the Ute Mountain Ute Indian Reservation. Topographic base from U.S. Geological Survey Towaoc (1966) quadrangle, scale 1:24,000. Contour interval is 40 ft (12.2 m).

An unusable, abandoned road approaches this group of 

deposits from the north. Rusting tools and minor excavations 

in the vicinity of AA-41 are evidence of prospecting, possibly for uranium.

AIRBORNE ANOMALY 28

AA-28 may be an extension of the foreshore sequence 

that produced anomalies 38-44. It is a very small occurrence, about 15 cm thick and 7.6 m in diameter. It is not as 

dark colored (less ferric cement) as the other deposits, and 

the total gamma-ray count is two to four times the background level. The down-dip (northwest) continuity cannot be 

determined because of a thick cover of alluvium from the 

Mancos River.

MAGNETIC STUDIES

Magnetic analyses of two areas (encompassing anomalies AA-10, AA-11, and AA-17) were undertaken to determine the feasibility of using magnetic methods to locate 

buried heavy-mineral deposits on the Ute Mountain Ute 

Indian Reservation. Heavy-mineral deposits typically have 

higher magnetization than surrounding sediments because 

they contain concentrations of detrital magnetic minerals. 

Moreover, the association of magnetite, the most common 

detrital magnetic mineral, with ilmenite, the primary host for

titanium, may link magnetization and titanium content in the 

heavy-mineral deposits. Anomalies AA-10 and AA-17 were 

chosen because of their good exposures and potential for 

extension into the subsurface. AA-11 was included because 

of its proximity to AA 10.

The magnetic studies consisted of: (1) measurement of 

the total magnetic field along ground traverses over and 

between exposed deposits; (2) upward continuation of a totalfield profile from an exposed deposit to determine the 

expected magnetic signals from the deposit at different burial 

depths; (3) measurements of magnetic susceptibility of the 

deposits at the outcrops to map the distributions of magnetic 

minerals in the deposits; (4) laboratory measurements of 

magnetic susceptibility and remanent magnetization of samples taken in and adjacent to heavy-mineral deposits; and (5) 

petrologic study and rock magnetic tests to identify the magnetic minerals in the deposits and to explain variations in 

magnetic properties. The results of this investigation showed 

that these methods can be used to locate deposits similar to 

AA-10 if they are buried less than 20 m deep and that magnetization is dominated by authigenic ferric-oxide minerals 

at the margins and by detrital magnetite and possibly titanohematite in the interiors of the deposits.

Many of the sample sites for the magnetic studies coincide with the sample sites for the geochemical tests. They also 

share the same sample number, such as AA-17-1. Magneticanalyses samples that do not share the same sample site begin 

with the prefix 7UM.
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B19

1(F35'

2 KILOMETERS

J

Figure 13. Location of heavy-mineral deposit AA-28 in the northern part (Colorado) of the Ute Mountain Ute Indian Reservation. 

Topographic base from U.S. Geological Survey Moqui Canyon (1966) quadrangle, scale 1:24,000. Contour interval is 40 ft (12.2 m).

GROUND MAGNETOMETER SURVEY

The total magnetic field was measured using a protonprecession magnetometer along five traverses. Traverses 1 , 

2, and 4 (figs. 14 and 15) crossed exposed deposits, and 

traverses 3 and 5 (fig. 15) crossed projected trends of the 

deposits. Line 1 delineates deposit AA-10 with a peak 

amplitude of about 100 nanoteslas (nT) (fig. 16^4). AA-11 is 

marked by a more subdued peak of about 30 nT (fig. 165). 

Line 3 was about 2,010 m northwest of AA-10 and 1,100 m 

southeast of AA-17. The magnetic profile (fig. 16Q, which 

covers about 1,370 m, lacks obvious magnetic anomalies but 

displays numerous minor features that have wavelengths of 

about 15 m and amplitudes of about 5-10 nT. Line 4, across 

the exposed part of AA-17, reveals a peak of about 75 nT 

(fig. 16/)). Line 5, about 520 m southeast of line 4, did not 

detect deposit AA-17 (fig.!6£). The only magnetic feature 

detected is probably a pipeline beneath the road that was also 

detected in the profile of line 4.

The lack of prominent peaks (except for the pipeline) in 

the profiles of lines 3 and 5 may be attributed to either the 

absence of buried deposits or to burial at sufficient depth to 

mask or eliminate magnetic signals at the surface. It is 

believed that AA 17 pinches out between lines 4 and 5 

because geologic evidence, such as bedding attitude or structure that would indicate an abrupt change in depth of the 

deposit between the two closely spaced lines, is lacking.

Burial depth must be considered as a possible cause of 

the subdued magnetic field along line 3, which is remote 

from deposit exposures. This possibility was evaluated by 

determining the effects of different burial depths on the 

magnetic profile obtained in line 1. Using the upwardcontinuation method, we generated the magnetic-field profiles (fig. 17) that would have been observed had AA-10 

been buried between 3 and 21m. The analysis yielded the 

approximate depths to which magnetic detection of deposits

of the type in the study area is feasible. For example, at 3-, 

9-, and 21-m-separation increments between observer and 

source, the peak amplitudes decrease from about 100 nT to 

about 60 nT, 30 nT, and 10 nT, respectively.

This analysis indicates that deposits having magnetizations equivalent to those of AA-10 are undetectable at the 

surface if buried by more than about 20 m. Considering the 

elevations of lines 1 and 3, the bedding attitudes, and the lack 

of known faults in the study area, it is unlikely that AA-10 

occurs below line 3 at depths greater than 20 m; more likely, 

this deposit does not even extend to the vicinity of line 3.

MAGNETIZATION OF 

HEAVY-MINERAL DEPOSITS

MAGNETIC SUSCEPTIBILITY AND 

NATURAL REMANENT MAGNETIZATION

Magnitudes of magnetic susceptibility (MS) at the outcrop and magnitudes of natural remanent magnetization 

(NRM) of samples returned to the laboratory from AA-10 

were measured to investigate the variability of these properties in the deposit (table 2). Magnetic susceptibility is a measure of the magnetization induced in rock in the presence of 

a weak, low-amplitude magnetic field. Natural remanent 

magnetization is the entire permanent magnetization of a 

rock. The magnetic properties were found to vary systematically with respect to the geometry of the deposits and they 

yielded information on postdepositional alteration.

Magnetic susceptibility was measured at the outcrops of 

AA-10 and AA-17 using a portable susceptometer having a 

sensitivity of about 5* 10~5 SI (Systeme Internationale units). 

At both exposures, MS was relatively low at the margins of 

the deposits and increased toward the interior. The spatial 

change of MS is illustrated in a schematic cross section of
B20 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

KILOMETER

Figure 14. Ground magnetometer survey traverse lines 1 and 2 

across anomalies AA-10 and AA-11. Topographic base from U.S. 

Geological Survey Waterflow (New Mexico) quadrangle, scale 

1:24,000. Contour interval is 40 ft (12.2 m).

AA-10 with contoured MS values, shown in figure 18. Laboratory measurement of MS and NRM of samples from 

AA-17 bear out the observations made at the outcrop and 

indicate that the NRM magnitude, which commonly mimics 

variations in MS, is also highest in the center of the deposit 

(table 2; fig. 19).

The high MS and NRM in the centers of the heavymineral deposits suggests that magnetite is relatively more 

abundant in the interior parts than at the margins. The variations in magnetic properties correlate with variations in the 

colors of the deposits in the outcrops. In general, black rocks 

are characteristic of the interior zones of high magnetization, 

whereas brown and brown-red hues characterize the margins 

that have substantially lower magnetization.

PETROLOGIC AND ROCK 

MAGNETIC INVESTIGATIONS

The causes of variation in magnetization in the deposits 

were investigated using a combination of petrologic and rock 

magnetic methods. These methods included reflected-light 

microscopic examination of polished thin sections and of 

polished grain mounts of magnetic separates, thermomagnetic analysis, and rock magnetic tests that, for our purposes, 

allow distinction primarily between hematite and magnetite. 

In thermomagnetic analysis, magnetic grains are heated and 

then cooled in the presence of a strong magnetic field, and 

the resulting changes in magnetization enable mineral identification by defining, for example, the Curie temperatures of

the grains. The Curie temperature is the temperature at which 

a ferrimagnetic substance loses its ferrimagnetism, or spontaneous magnetic ordering. Together, the results and observations from the petrologic and rock magnetic methods 

enable identification of the minerals responsible for magnetization of the deposits and yield information on their distributions.

Petrographic examination of polished thin sections confirmed the presence of abundant titanium-bearing magnetite 

in the highly magnetic interior portions of the deposits; magnetite was not observed in samples from the more weakly 

magnetized margins. Instead, the weakly magnetized rocks 

contain abundant grains of titaniferous magnetite that has 

been postdepositionally altered by leaching of iron, leaving 

relict titanium-rich minerals such as anatase.

The zones of high and low magnetization have different 

interstitial cements. Calcite cement occurs in the strongly 

magnetized sandstones that contain magnetite and other 

detrital oxide minerals that lack obvious or extreme postdepositional alteration. The calcite contains sparse framboids of pyrite that appear to have formed during early 

diagenesis. In contrast, ferric-oxide phases completely fill 

interstitial areas in sandstones in which titaniferous magnetite was strongly altered by leaching of iron. Relicts of framboidal pyrite are rarely found within the oxide cement, but 

there is no evidence of another generation of sulfide minerals that would postdate the pyrite seen in the interior zones 

of the deposits.

108°30'

Figure 15. Ground magnetometer survey traverse lines 3, 4, and 

5 in the vicinity of anomaly AA-17. Topographic base modified 

from U.S. Geological Survey Heifer Point (New Mexico) quadrangle, scale 1:24,000. Contour interval is 40 ft (12.2 m).
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B21 

52,900 ,

52,850 

52,800 

CO

CO 

LLJ

AA-10

A

Line 1

52,850

52,800

50 100 150

52,870 |

52,850

Line 3

LU 52,870 -

O

52,850

Line 3 (continued)

52,870 

52,850

750

Line 3 (continued)

1,250

250

1,000

100 150 200

500

52,958

52,900 

52,850 

50

52,900 

52,850 

Road

100 150 0 50 

DISTANCE, IN METERS

Line 5

100 150

Figure 16. Magnetic profiles from ground magnetometer traverses conducted in the southern group of anomalies (lines shown 

in figs. 14 and 15). Profiles begin at the southwest end of each line.
B22 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

52,900

52,850

52,800

52,900

52,850

52,800

CO

< 52,900

CO

52,850

52,800

52,900

52,850

 52,800

0 52,900

52,850

52,800

52,900

52,850

52,800

52,900

52,850

52,800

3 meters

6 meters

x x

9 meters

x x x

12 meters

X x

x Xx x x xx x

15 meters

DO OO O o

1 °°o o o o99»< 

x x x x x

18 meters

x x

x x

21 meters

X X

Figure 17. Plots generated 

using the upward-continuation 

method in which the magnetic 

profile obtained from line 1 

(fig. 16/4), shown here with 

crosses, is plotted against the 

synthetic profiles (circles) at 

the various depths indicated.

50 100 

DISTANCE, IN METERS

150
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO 

Table 2. Magnetic properties of samples from AA-17.

[Magnetic sample numbers start with 7UM; corresponding geochemical sample numbers are given in parentheses. Mj^y^,, magnetic dipole moment in SI units of 

amperes per meter (A/m; 1 A/m=l(T3 emu/cc); K, magnetic susceptibility in volume SI units (1 vol SI unit of K is equivalent to l/4n emu/cc in COS units); FeTO3, 

total iron oxide expressed as Fe2O3; ( ), none detected]

B23

Sample 

number

7UM-27

(AA-17-5)

7UM-26

(AA-17^)

7UM-25

(AA-17-3)

27UM-24

7UM-23

(AA-17-1)

27UM-22

Location

White sandstone above deposit

Upper part of deposit; 1.3m below

7UM-27

Interior of deposit; 0.3 m below

7UM-26

Adjacent to 7UM-25

Lower in deposit; 0.7 m below

7UM-24

Lowermost exposure of deposit (base

is covered); 0.3 m below 7UM-23

MNRM

(xl(T2 A/m)

0.3

1.7

100

94

1.7

16

K

(xl(T3)

0.2

0.7

65

60

0.5

0.4

FeTO3 'TiOj 

(percent) (percent)

5.89 3.98

14.61 5.71

34.91 5.56

--

15.42 0.45

__

'Data from appendix.

2No corresponding geochemical samples.

Figure 18. Schematic cross section of deposit AA-10 showing magnetic susceptibility values, in volume SI units (1 volume SI unit is 

equivalent to 1/471 electromagnetic units per cubic centimeter in the COS system), contoured from portable-susceptometer readings 

taken at the outcrop. Rocks of highest susceptibility occur in the center of the deposit.
B24 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

MAGNETIC SUSCEPTIBILITY, IN VOLUME SI

10-* io-3 10- 2 10-1

7UM-27

7UM-26

^ 7UM-24/ 

< 7UM-25

7UM-23 

7UM-22

10-3 10-2

1CH 10

MAGNETIC DIPOLE MOMENT OF NATURAL REMANENT 

MAGNETIZATION, IN AMPERES PER METER

Figure 19. Plot of magnetic properties of samples from deposit at 

AA-17 showing highest values of magnetic susceptibility (crosses) 

and magnetic dipole moment of natural remanent magnetization 

(NRM) (circles) in the center of the deposit. See table 2 for descriptions of the samples.

Detrital iron-titanium oxides other than magnetite are 

common in the heavy-mineral suite, especially minerals of 

the ilmenite-hematite series (titanohematites). Over a range 

of intermediate compositions (20-40 mol percent hematite), 

the titanohematites are ferrimagnetic (strongly magnetic). A 

polished grain mount of the magnetic separate from sample 

AA-10-9 indicates abundant titanohematite that contributes 

to the magnetization of the deposits.

Thermomagnetic analysis confirms the petrographic 

identification of titanohematite in sample AA-10-3 (fig. 

20). The thermomagnetic curve for AA-10-3 shows an 

abrupt initial loss of magnetization at the onset of heating 

and an abrupt gain in magnetization upon cooling below 

about 250°C. Such behavior is diagnostic for ferrimagnetic 

titanohematite when considered with the petrographic observations (Reynolds, 1977). The parts of the heating and cooling paths at temperatures above about 300°C and the 

irreversibility of the curves are difficult to explain. Irreversibility refers to the failure of the cooling curve to trace back 

on or near the heating curve. Magnetite was absent in the 

original sample, but apparently it was produced from the 

sample during heating, as indicated by the minor increase in 

magnetization from 490 to 510°C. The absence of a sharp 

increase in magnetization near 580°C, the Curie temperature 

for magnetite upon cooling, indicates that the magnetite was 

oxidized to ferric oxide shortly after its formation. The cause 

of the production of magnetite is not known. Pyrite is present 

in very minor amounts in the sample, but it is not a precursor 

of the magnetite because under the experimental conditions 

of the instrument, pyrite converts to magnetite at temperatures near 350°C. The abundant interstitial ferric-oxide

cement in this sample probably is responsible for the magnetization above 580°C.

The thermomagnetic curve for AA-17-3 (fig. 20), a 

sample known to contain abundant magnetite, is irreversible 

and shows a remarkably abrupt and unusual increase in magnetization at 490°C that resulted from the production of an 

additional large quantity of magnetite. In this case, the magnetite was preserved and perhaps continued to grow despite 

continued heating to 620°C, as indicated by the strong gain 

in magnetization upon cooling below 580°C. Again, oxidation of pyrite to form magnetite cannot account for the formation of additional magnetite. Sample AA-17-3 contains 

abundant calcite cement and is devoid of ferric-oxide 

cement. The high-temperature oxidation of other irontitanium-oxide minerals such as titanomagnetite or titanomaghemite may have generated magnetite during the 

experiments.

Other rock magnetic tests were conducted to supplement the petrographic and thermomagnetic analyses. These 

tests included the alternating-field (AF) demagnetization of 

NRM, the acquisition of isothermal remanent magnetization 

(IRM), and the removal of the IRM in a strong magnetic 

induction field directed opposite to the induction in which 

the IRM was acquired. These tests yield information on the 

coercivity (or magnetic "hardness") of the rocks and their 

magnetic minerals. Coercivity, the opposing applied magnetic field that reduces the remanent magnetization of a substance to zero, varies for different magnetic minerals. The 

results from these tests elucidate qualitatively the contributions to magnetization from the titanomagnetites and titanohematites, which have relatively low coercivities, and from 

hematites (and perhaps other ferric oxides), which have 

higher coercivities. In this study, the results mainly reflect 

the distribution of detrital titanomagnetite and titanohematite 

relative to that of the interstitial ferric oxide that occurs antipathetically with magnetite.

1.0

< 0.5

N

AA-17-3

1.0

0.5

AA-10-3

0 200 400 600 0 200 400 600 

TEMPERATURE. IN DEGREES CELSIUS

Figure 20. Thermomagnetic curves for samples AA-17-3 and 

AA-10-3.
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO

1.0

B25

20 40 60 

DEMAGNETIZATION FIELD, IN MILLITESLAS

80

Figure 21. Alternating-field (AF) demagnetization plots of samples from AA-17 showing decay of the magnetic dipole moment of 

NRM (normalized magnetization) with respect to the demagnetization field.

High coercivities of magnetic minerals are revealed in 

plots of AF demagnetization by a low decay of NRM magnitude with increase in the demagnetization field, whereas relatively low coercivities are indicated by a substantial 

decrease in magnetization with higher demagnetization 

fields (fig. 21). Samples 7UM-22 and 7UM-23, which are 

from the lower part of AA-17, show the dominantly high 

coercivity behavior characteristic of hematite. In contrast, 

samples 7UM-24 and 7UM-25, from the highly magnetized 

center of the deposit, have low coercivities typical of magnetite-bearing rocks. AF demagnetization curves for samples 

7UM-26 (upper part of deposit) and 7UM-27 (above the 

deposit) lie close to but above those for samples 7UM-24 

and 7UM-25. Samples 7UM-26 and 7UM-27 thus appear to 

contain a combination of magnetite and ferric oxide (even 

small quantities of magnetite dominate magnetic signals in 

rocks that contain volumetrically more hematite).

Curves of IRM acquisition (fig. 22) show the distinction between magnetization carried dominantly by magnetite and that carried dominantly by ferric oxide. In IRM 

acquisition tests, the magnetization is imparted to a sample 

in the presence of an incrementally increased magnetic 

induction instead of reduced from the sample as in the AFdemagnetization method. In this procedure, magnetite is

0.2 0.4 0.6 0.8 

MAGNETIC INDUCTION, IN TESLAS

1.0

Figure 22. Curves of acquisition of isothermal remanent magnetization (IRM) showing magnetization (normalized) plotted against 

magnetic induction. Sample 7UM-18 is from AA-10; others are 

from AA-17.

more readily magnetized than the magnetically "harder" ferric oxide. Thus, magnetite-bearing rocks acquire a greater 

portion of their saturation IRM at low inductions relative to 

hematite-bearing samples. Again, the magnetite-dominant 

magnetization in sample 7UM 25 contrasts with the ferricoxide-dominant magnetization in sample 7UM-22 (fig. 22). 

Sample 7UM-18, shown in figures 22 and 23, is from the 

magnetite-rich part of AA-10.

Similar information is obtained from examination of 

curves generated by removing IRM. The magnetic induction at which the IRM is reduced to zero, termed the coercivity of remanence, is sensitive in this application to 

magnetic mineralogy. IRM of magnetite-bearing rocks is 

more easily eliminated, giving low negative values of the 

coercivity of remanence relative to hematite-bearing samples. Curves showing the removal of IRM in figure 23 

illustrate the hematite dominance in sample 7UM-22 and 

the magnetite dominance in samples 7UM-25 and 

7UM-18.

Thus, the rock magnetic results show that ferric-oxide 

minerals dominate the magnetization of samples from the 

weakly magnetized margins of the deposits, and that magnetite (and perhaps titanohematite the relative contributions of the two species cannot be discerned in these 

analyses) dominates the magnetizations of the interiors of 

the deposits. Therefore, the rock magnetic data corroborate 

the petrographic observations and results from MS and 

NRM measurements.
B26 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

1.00

-0.25

-0.20 -0.15 -0.10 -0.05 

MAGNETIC INDUCTION, IN TESLAS

0.00

Figure 23. Backfield curves of isothermal remanent magnetization (IRM) showing magnetization (normalized) plotted 

against magnetic induction. Negative induction values indicate 

application of the induction in a direction opposite to that applied 

for acquisition of the IRM. Sample 7UM-18 is from AA-10; others are from AA-17.

the deposit as a whole. A specific analysis can provide 

insight to the unique characteristics of particular deposits, 

such as the high zirconium and titanium content of AA-26. 

Although relatively large samples were collected, an economic evaluation would require larger samples taken systematically through each occurrence.

Each field sample was cut with a rock saw for thin sections and whole-rock specimens. A split of the remaining 

sample was pulverized with a ceramic shatterbox laboratory 

mill to -200 mesh for analysis. Pulverized samples were split 

using a mechanical splitter; one split was for instrumental 

neutron-activation analysis (INAA) and the other was 

pressed into pellets for energy-dispersive x-ray fluorescence 

spectroscopy (XRF) analysis.

CHEMICAL ANALYSES

Results of chemical analyses are shown in the appendix. XRF analysis was used to identify the major elements 

and the trace elements Cu, Ga, Nb, Pb, and Y. INAA analyzed the remaining trace elements. The major elements are 

given in percent oxide. INAA trace-element results are 

reported in alphabetical order in parts per million. The 

results of the XRF and INAA analyses are from whole-rock 

samples, reported as received and are not rounded to significant numbers.

GEOCHEMICAL STUDIES

One or two 0.5-1.5 kg grab samples were taken from 

each deposit except for AA-10 and AA-17, which were sampled more thoroughly because their outcrops facilitated the 

collection of a vertical series of samples. A total of 51 samples were collected. The intent was to sample an area that 

would best represent the deposit; however, several characteristics of these deposits made this quite difficult. First, many 

have limited outcrops with only the upper(?) part exposed 

above the surrounding Holocene colluvium or eolian sand. In 

such areas, the relation of the outcrop to the rest of the deposit 

is unknown. Second, the high degree of induration made 

sampling difficult. Commonly, only sites of intense fracturing and weathering or areas of less induration were available 

for sampling. Because of this, many of the samples are from 

the tops of the deposits or nearby. Third, visual and radiometric observations indicated that the heavy-mineral content of 

a deposit varied from one horizon to another. This is supported by the findings of the magnetic part of our study and 

by the multiple samples of AA-10 (see appendix). A deposit 

may contain relatively barren beds that may be mistaken as 

heavy-mineral accumulations because of the degree of diagenetic iron cement present (such as in AA-11 and FA 1). 

Thus, no single sample represents an entire deposit. Each 

group of samples should be viewed as broadly characterizing

ENERGY-DISPERSIVE X-RAY FLUORESCENCE (XRF)

XRF analysis uses two sources to irradiate the samples. 

Rhodium radiation was used to analyze for major oxides, and 

109Cd was used to obtain semiquantitative values for the 

trace elements Cu, Ga, Nb, Pb, and Y. Johnson and King 

(1987) summarize the method:

X-ray fluorescence analysis entails the excitation of X-rays within a sample and their subsequent detection and measurement. * * * During sample 

irradiation, inner shell electrons of the elements in the sample absorb specific X-ray photons and are ejected from the atom. Rearrangement of the 

remaining electrons to fill these vacancies causes the emission of so-called 

fluorescent X-rays, whose energies are characteristic of the elements from 

which they originate. * * * X-rays emitted by the sample are absorbed in 

the detector, which acts as a diode in converting these incident X-rays to 

electronic pulses whose amplitudes are proportional to the energies of the 

corresponding X-rays. Pulses then are processed and sorted according to 

amplitude: * * * The intensity, or number of counts in a peak, is a direct 

result of the number of fluorescing atoms of that element in the sample; 

thus, the area under a peak is proportional to the concentration of that element in the sample.

INSTRUMENTAL NEUTRON-ACTIVATION 

ANALYSIS (INAA)

The INAA technique is well summarized by Baedecker 

andMcKowen(1987):
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B27

Instrumental activation analysis with thermal neutrons (INAA) is a versatile technique for elemental analysis because it has a high sensitivity for 

many elements, * * * and provides precise data for many major, minor, 

and trace elements in a single sample aliquant without chemical treatment. 

* * * The method is based on the irradiation of samples and standards in a 

reactor neutron flux and the measurement of the induced radioactivity 

using high resolution gamma-ray spectrometry. The technique has a sensitivity ranging from 0.1 to 10 parts per million for a wide range of elements 

including many of the first row transition elements, rare earths, alkali, and 

alkaline earths.

ANALYTICAL CONSIDERATIONS

In XRF analysis, sample composition and preparation, 

relative elemental concentrations, and major concentrations 

of an element (such as iron) affect the analytical results. 

The most conspicuous effect is that the total of major 

oxides in the samples is considerably less than 100 percent. 

The reasons for this are discussed in the following paragraphs. Although the lower oxide values are noteworthy, 

titanium, which is the most important economic element in 

the oxides, is relatively unaffected.

The lower oxide values of the deposit samples are 

caused by several factors. One cause is the trace elements, 

which may exceed 6 percent of the sample. Another is the 

XRF method, which does not account for the large massabsorption contributions of Na, Mg, and Fe and the mineralogic effects due to differences in standards and samples. This 

is particularly important as the Fe content increases in the 

samples. A third cause is the mineralogic effect that significantly reduces the SiC>2 values in the oxide analysis. This 

was confirmed by XRF analysis on selected fused duplicate 

samples. The analysis showed an SiC>2 value that was consistently 10 percent lower in the packed-powder samples (other 

oxide values remained fairly constant). And fourth, XRF is 

incapable of analyzing all of the major elements, in particular carbon (in CO2 and organic carbon) and hydrogen (in 

H2O+). This results in lower oxide totals because: (1) CC>2 

contained in carbonates including calcite (CaCC^), siderite 

(FeCO3 ), ankerite [Ca(Fe,Mg,Mn,)(CO3 )], and dolomite 

[CaMg(CO3)2J will not be detected; and (2) structural water 

is not detected, and deposit samples have some clay and 

higher quantities of mica compared to the barren samples. 

Loss on ignition, which quantifies the volatile fraction, 

ranged from 6.1 to 14.7 percent on six random samples.

In the INAA method, composition, preparation, and 

relative elemental concentrations affect the detection limits 

because of elemental sparsity and overlap of detection 

peaks. Major concentrations of an element such as iron 

have an effect on the detection limits and accuracy. It is 

believed that samples with relatively high levels of iron (>5 

percent) give analyses with higher detection limits and 

lower accuracy for some elements. This interference, however, will not affect discrimination between the elements.

In general, the values for the elements in high-iron samples 

are expected to have a precision of ±20 percent. Because 

the purpose of the analysis is to indicate potentially economic elemental abundance, errors in the detection level 

are not significant, and precision errors of as much as 20 

percent will still show concentration trends of interest.

DISCUSSION OF SELECTED ELEMENTS

The elements considered in this section (Fe, Ti, Zr, U, 

Th, Y, Cr, Au, and rare-earth elements) were selected 

because of their economic potential. However, the appendix includes all the analyzed elements because they may 

have value in understanding the chemistry or mineralogy of 

the deposit and may have some importance in future evaluations.

Table 3 shows the oxide and trace-element average 

compositions for barren samples (AA-10-1, AA-10-2, 

AA-10-3, AA-10-5, and AA-17-1) and mineralized samples. All barren rock samples were determined by field criteria and confirmed by analytical results. Anomalies 

AA-11 and FA-1 were identified in the field as heavymineral deposits, but analyses later showed that their samples were from iron-cemented but relatively barren beds 

within the deposits. These samples were not included in the 

average values shown in table 3.

IRON

Except for SiC>2, iron oxide is the dominant compound 

in the deposits, ranging from 0.7 to 35 percent of the whole 

rock. The presence of large amounts of iron has a substantial negative impact on the economics of a heavy-mineral 

deposit because it introduces additional costs to mining, 

disaggregation, and milling. The iron occurs mostly as a 

ferric-oxide cement. This degree of iron cementation is 

unusual in Holocene heavy-mineral deposits even though it 

is common in fossil deposits (Wedow and Hobbs, 1968; 

Dow and Batty, 1961). Although some of the induration is 

due to calcite cement and part of the characteristic color is 

due to manganese, the iron content of the rock is mostly 

responsible for these qualities. The dark color is a primary 

field guide because it is always present in areas of maximum heavy-mineral concentrations. However, it is not 

always present in areas of moderate concentrations. As an 

example, sample AA-10-6 (see appendix) was collected 

from a light-colored bed but has a relatively high Zr value 

(4,200 ppm) and TiC>2 value (4.34 percent). A scintillometer is a useful reconnaissance tool in such situations 

because it detects the radioactivity associated with the 

heavy-mineral concentrations.
B28 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Petrographic observations suggest reducing conditions 

of alteration under which iron was leached from titaniferous magnetite and ilmenite, leaving relict grains rich in titanium dioxide. Iron was subsequently redeposited as ferricoxide phases in interstitial areas between the detrital heavy 

minerals. Leaching of iron may have been facilitated (by 

complexing, for instance) with organic acids derived from 

the overlying Menefee Formation. For additional information on the Eh/pH behavior of iron and iron solubility, see 

Garrels and Christ, (1965, fig. 7.11).

TITANIUM

Table 3. Average compositions of oxides and trace elements from 

semiquantitative analyses of the barren and heavy-mineral samples 

from the Ute Mountain Ute Indian Reservation.

Titanium (in the form of TiC^) is the primary economic element in many modern heavy-mineral placers. On 

the Reservation, TiC>2 ranges from about 0.4 to 21 percent 

and averages 7.9 percent. Titanium is contained in ilmenite, 

titanomagnetite, titanohematites, and small amounts of titanium-oxide minerals including rutile, anatase, and brookite. 

The relative abundance of these minerals varies depending 

on the deposit, degree of iron alteration, and the location of 

the sample (see section on petrology and rock magnetic 

investigations).

TiC>2 may constitute as much as one-fifth of a lithified 

heavy -mineral deposit (Wedow and Hobbs, 1968). The 

TiC>2 content is greater in older deposits, primarily because 

of increased leaching of iron from ilmenite and the alteration of ilmenite to leucoxene (U.S. Bureau of Mines, 

1985; Staatz and others, 1980). Some of the heavy-mineral 

deposits in the San Juan basin average 16 percent TiC>2, 

with a maximum of 32 percent (Chenoweth, 1957). In the 

same article, Chenoweth reported a 2 1 .5 percent TiC>2 value 

from a Ute Mountain Ute Indian Reservation sample (probably from AA-17 or AA-18).

One unusual titanium occurrence (4.51 percent TiO2) 

on the Reservation is in a sandy mudstone in AA-10, 

about 19.8 m above the base of the section (fig. 10). This 

mudstone lies on a ravinement surface where sediments 

were transgressed and eroded (see description of airborne 

anomaly AA-10 in the discussion of the southern anomaly 

group). The mudstone is part of a minor transgressive 

event and contains some of the heavy minerals from the 

eroded and reworked underlying foreshore sediments. The 

areal extent and patterns of heavy-mineral concentrations 

in these transgressive mudstones are unknown. Future 

investigations of heavy-mineral deposits should include 

this facies.

ZIRCONIUM

Zirconium, from the mineral zircon, may be the second 

most valuable element in these deposits. Zircon has risen in 

value and in many mines is considered a coproduct instead

Substance Barren samples 1 Mineralized samples2

Oxides (percent)

SiO2

A12O3

3FeTO3

MnO

MgO

CaO

Na20

K2O

Ti02

P205

S03

Total

81.76

10.09

4.46

0.05

0.36

0.48

1.70

1.84

0.46

0.09

0.03

101.32

38.80

4.16

18.75

0.51

0.68

5.38

0.40

0.25

7.93

0.34

0.29

77.49

Trace elements (parts per million)

Ag

As

Au

Ba

Br

Ce

Co

Cr

Cs

Cu

Eu

Ga

Hf

La

Lu

Mo

Nb

Ni

Pb

Rb

Sb

Sc

Se

Sm

Sr

Ta

Tb

Th

U

W

Yb

Y

Zn

Zr

1

3.34

0.09

544

1.32

50.6

8.2

96

1.54

47.2

0.5

11.8

3.8

30

0.32

0.6

6.2

10

12.6

55.8

0.74

7.28

2.5

3.98

64.6

0.34

0.53

7.64

1.99

0.9

1.8

14.8

50

224

3.80

4.70

0.03

411.62

2.24

1,157.65

49.28

856.76

0.71

99.81

3.11

54.08

340.05

740.54

6.84

1.32

172.73

28.14

97.11

13.45

1.59

49.16

3.96

85.03

39.00

14.27

8.60

278.11

46.57

13.77

38.70

255.73

236.62

14,490.00

Samples AA-10-1, AA-10-2, AA-10-3, AA-10-5 and AA-17-1. 

2A11 samples except barren samples and those from FA-1 and AA-11. 

3Total iron oxide expressed as Fe2O3 .
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B29

U 4 

oc

10 15 

TITANIUM, IN PERCENT

20

Figure 24. Plot of zirconium versus titanium content in heavymineral samples analyzed. Line represents a linear best-fit curve to 

the data.

of a byproduct. The average zirconium content in deposit 

samples is 1.4 percent. A sample from AA-26 contained 

almost 6 percent zirconium, the highest amount found in any 

of the deposits on the Reservation. By comparison, Wedow 

and Hobbs (1968) have reported zircon values in other lithified titanium-rich heavy-mineral deposits in the United 

States ranging from 5.5 to 9 percent (2.6-4.4 percent zirconium).

In general, the amounts of titanium and zirconium in 

Reservation deposits increase and decrease together in a 

ratio of about 5:1 (see appendix). This is shown by plotting 

titanium versus zirconium content in Reservation samples 

(fig. 24).

RARE-EARTH ELEMENTS

Rare-earth elements (REE) is a collective term for 15 

elements with atomic numbers from 57 to 71 (the lanthanides). Yttrium, scandium, and thorium (atomic numbers 

39,21, and 90, respectively) are commonly included with the 

REE because they have similar chemical properties and generally occur with the other REE.

Most REE are obtained from monazite, which is a 

byproduct of heavy-mineral mining for titanium and zirconium. Monazite is a rare-earth phosphate that commonly contains 50-60 percent rare-earth oxides and 2 percent yttrium 

oxide (U.S. Bureau of Mines, 1989). Monazite has a wide 

range of compositions because of appreciable REE substitutions. Its chemical formula is commonly shown as (Ce, La, 

Y, Th) PC>4, but it may contain varying amounts of other 

REE. Monazite was identified in several samples from the

Reservation by its characteristic fluorescence under a mercury vapor lamp, x-ray diffraction techniques, and energydispersive fluorescence using a scanning-electron microscope. Using oxide and trace-element averages (table 3), the 

monazite content of mineralized samples was calculated and 

found to constitute as much as 0.2 weight percent. Other 

heavy minerals that can contain REE include apatite, zircon, 

sphene, and epidote.

URANIUM AND THORIUM

The average uranium and thorium values (46.57 ppm 

and 278.11 ppm, table 3) are relatively low. Most of the uranium and some of the thorium in the deposits probably reside 

in zircon, where they are minor constituents. Zircon is generally used without separation of the uranium and thorium, 

which are tolerated but not desired components in commercial applications. Uranium may also be present in monazite, 

and some uranium may be absorbed by ferric oxides.

Most of the thorium probably occurs in monazite, 

which may contain as much as 12 percent thorium (Deer and 

others, 1966). Thorium is produced as a byproduct in monazite processing. Thorium in monazite and uranium and thorium in zircon are responsible for the characteristic 

radioactivity of heavy-mineral deposits.

OTHER ELEMENTS

Yttrium is found in xenotime (YPO4) and in monazite. 

Because xenotime was not found in the Reservation samples, 

the yttrium probably occurs in the monazite. Yttrium is a lowvolume but high-value commodity. Except for AA-26-SE, 

the yttrium values are relatively low.

Chromium is found in fairly high quantities for whole 

rock. It may be in ilmenite, or it may be complexed with some 

of the other oxides in the deposits. Chromium is important 

because it may negatively affect the marketability of ilmenite 

or adversely affect the milling of other elements (Grosz, 

1987).

Gold is present in very small amounts in most samples. 

The average gold content is 0.09 ppm in barren samples and 

0.03 ppm in mineralized samples (table 3). The higher barrensample value is probably due to the sparsity of gold in the 

samples, the small sample size, and the relatively few barren 

samples. Larger samples are required for economic evaluation. Depending on the mineralogic occurrence, gold may or 

may not be economically important.

Zinc, like gold, is found in small quantities in many samples. Zinc may occur in magnetite and other ferromagnetic 

minerals in the heavy-mineral deposit. Zinc is a noneconomic 

element in these deposits and is of interest only if it occurs as 

gahnite, a zinc spinel that is difficult to separate from rutile.
B30 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

CONCLUSIONS REFERENCES

Measured sections and stratigraphic observations at 

each anomaly site on the Reservation show that virtually 

all the heavy-mineral deposits are at the top of the Point 

Lookout Sandstone. Sedimentary structures and adjacent 

sedimentary environments indicate that the heavy-mineral 

deposits are in foreshore (beach) facies. The alignment of 

the deposits (fig. 2) defines a linear shoreline system oriented N. 55°- 60° W. that allows extrapolation of the 

trend to the northwest, where little is known about the 

deposition of equivalent rocks. This alignment and depositional setting gives the deposits a predictable shape and 

trend and allows speculation about their subsurface extent.

If there is any subsurface extension from the northern heavy-mineral group, it would lie between airborne 

anomalies AA-38 and AA-28, an area of significant overburden. In the central group, only anomaly AA-26 has , 

the possibility of subsurface extension. In the southern 

group, subsurface extensions are possible between airborne anomalies AA-13 and AA-21 and between AA-8 

and AA-17, but the potential for a subsurface heavymineral deposit between AA-8 and AA-17 is limited by 

negative magnetization results.

The magnetic portion of this study indicates that 

such surveys are potentially useful tools for locating 

heavy-mineral deposits that are buried by less than 20 m 

of overburden. The magnetization is provided mainly by 

detrital titaniferous magnetite concentrated in the centers 

of the deposits. Magnetite was apparently deposited relatively evenly throughout the deposits, but postdepositional alteration destroyed large quantities of the magnetite 

near the margins. Iron cementation may be the result of 

humic acids migrating from organic material in the overlying Menefee Formation. Such acids may have mobilized 

iron from minerals, especially titaniferous magnetite, in 

the section. Ferric oxide was then deposited interstitially 

in the deposit.

The heavy-mineral deposits on the Reservation are 

of economic importance because of, primarily, their relatively high titanium and zirconium content and, secondarily, their various REE byproducts. Semiquantitative 

analysis showed that titanium content averages 7.9 percent and may reach as much as 21 percent in the wholerock samples. Zirconium averages 1.5 percent and can 

make up as much as 6 percent of the whole rock. However, the limited volume of the individual deposits, high 

iron content, degree of cementation, and distance to 

water, mills, and markets are factors that negatively affect 

the economic potential of heavy-mineral deposits on the 

Reservation.

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HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B31

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conference, September 5-7, 1957, p. 212-217.

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A o/'Zech, R.S., ed., Geology and mineral resources of the 

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Cumella, S.P., 1983, Relation of Upper Cretaceous regressive sandstone units of the San Juan basin to source area tectonics, in 

Reynolds, M.W., and Dolly, E.D., eds., Mesozoic paleogeography of the west-central United States: Denver, Colo., Society 

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Dow, V.T., and Batty, J.V., 1961, Reconnaissance of titaniferous 

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Garrels, R.M., and Christ, C.L., 1965, Solutions, minerals, and 

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Grosz, A.E., 1987, Nature and distribution of potential heavymineral resources offshore of the Atlantic coast of the United 

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and Lowder, W.M., eds., The natural radiation environment: 

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B32 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

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tool Point Lookout Sandstone, southeastern San Juan basin, 

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Published in the Central Region, Denver, Colorado 

Manuscript approved for publication January 25, 1994 

Graphics prepared by Robert Zech and Carol Quesenberry 

Photocomposition by Carol Quesenberry 

Edited by John Synnefakis
APPENDIX
B34 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

APPENDIX Chemical-composition data from neutron activation and x-ray fluorescence analyses of selected

[FeTO3 , total iron oxide expressed as Fe2O3 . Cd, Ir, Sm, and Te not detected. Major oxides analyzed by x-ray fluorescence (XRF); trace 

(detection limit follows < symbol)]

Sample

numbers

AA-8 AA-9 AA-10-1 AA-10-2 AA-10-3 AA-10-4 AA-10-5

Major oxides (percent)

SiO2

TiO2

A1203

FeTO3

MnO

MgO

CaO

Na2O

K20

P2O5

SO3

Total

16.43

9.36

1.37

32.22

0.8

0.35

4.4

0.32

0.06

0.35

0.37

66.03

18.44

14.71

3.04

18.88

0.83

1.04

9.71

0.28

<0.01

0.67

0.07

67.66

73.01

0.69

15.49

2.27

0.01

0.82

0.49

2.54

2.61

0.13

0.03

98.09

96.6

0.37

6.4

1.87

0.05

0.23

0.54

1.05

0.9

0.1

0.01

108.12

81.6

0.4

12.89

1.58

0.01

0.45

0.45

2.39

2.8

0.07

<Q.Q1

102.64

68.53

4.51

11.99

2.75

0.05

1.62

0.98

0.48

0.31

0.06

3.04

94.32

93.66

0.41

8.3

1.15

0.01

0.12

0.39

1.18

1.44

0.05

<Q.Q1

106.68

Trace elements (parts per million)

Ag

As

Au

Ba

Br

Ce

Co

Cr

Cs

Cu

Eu

Ga

Hf

La

Lu

Mo

Nb

Ni

Pb

Rb

Sb

Sc

Se

Sm

Sr

Ta

Tb

Th

U

W

Yb

Y

Zn

Zr

14

10

0.011

540

3.7

1680

81

890

<1.5

116

<4

37

513

814

7.6

<4

147

96

230

<25

2.5

42.4

<13

121

56

14

16

602

100

7

34

300

<260

26900

<10

<4.9

0.02

690

5.1

2740

50

1500

<1.6

283

8

144

727

1710

14

<5

385

<45

136

<27

1.5

92.7

<14

161

50

32

18

608

85.3

<12

82

511

500

30000

<2

3.2

0.02

720

<2

60

8

91

2.8

34

<1

6

6

32

0.4

<1

11

<20

8

70

1

9.3

<5

5

89

0.7

0.6

11

3

2

3

19

<100

430

<2

3.4

0.13

340

<2

43

<5

77

1.2

31

<1

7

5

25

0.2

<1

6

<20

8

35

0.7

3.7

<5

3.8

36

<0.5

0.6

6.6

1.6

<1

<2

10

<100

<200

<2

7.7

0.16

740

<2

42

7

66

1.8

59

<1

16

2

25

0.2

1

6

<20

18

76

1.1

3.8

<5

3.2

94

<0.5

<0.5

7.2

2.1

1

<2

10

<100

<200

<2

4.4

0.036

290

6.5

280

55

400

3.3

71

<1

24

90

150

2

4

71

37

33

24

3.1

24.6

<5

18

21

6.3

2.1

94.3

14

3

12

72

120

3900

<2

0.7

0.14

410

<2

47

<5

96

1

60

<1

17

3

28

0.3

<1

5

<20

15

49

0.4

3.6

<5

3.6

54

<0.5

0.6

6.3

1.6

<1

<2

20

<100

<200
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO

whole-rock samples from heavy-mineral deposits on the Ute Mountain Ute Indian Reservation.

elements were analyzed by neutron activation except for Cu, Ga, Nb, Pb, and Y, which were analyzed by XRF. (<), below detection limit

B35

AA-10-6 AA-10-7 AA-10-8 AA-10-9 AA-10-10 AA-10-11 AA-10-12 AA-10-13

Major oxides (percent) Continued

70.7

4.34

9.96

5.00

0.04

0.97

0.42

0.83

0.77

0.31

0.01

93.35

28.93

4.86

3.6

13.25

0.62

0.63

19.33

0.41

0.47

0.29

0.12

72.51

68.32

5.15

6.08

6.45

0.07

0.75

1.6

0.54

0.29

0.59

<0.01

89.82

8.57

11.29

0.68

31.87

0.77

0.8

9.77

0.24

<0.01

0.23

0.38

64.61

15.47

10.09

1.24

31.43

0.9

1.11

5.15

0.29

0.06

0.2

0.37

66.31

68.69

2.84

7.42

10.11

0.08

1.13

0.35

0.77

0.88

0.05

0.02

92.34

49.04

13.22

9.38

8.57

0.06

0.78

0.7

0.52

0.74

0.23

0.04

83.28

29.89

6.27

1.7

27.56

0.73

0.43

5.71

0.3

<0.01

0.44

0.44

73.39

Trace elements (parts per million) Continued

<6

2.8

<.005

410

<2

586

36

520

<0.5

8

<4

<26

86

3100

2.4

<1

88

<29

26

46

1.2

35.4

<5

36.8

32

7.7

4.2

88.5

15

6

16

112

180

4200

<7

<2.0

<.007

290

<2

723

53

700

<1.2

60

<5

<26

189

417

4.1

<3

108

<33

63

<20

1.2

43.5

<10

42.7

31

8.8

4.7

161

28.7

7

25

141

330

8200

<2

<1.1

0.026

200

<2

595

9

400

<0.5

32

<2

<26

87

355

2.7

<1

120

<20

18

11

0.7

33.9

<5

31.5

13

11

3.8

94.6

18

5

17

107

<100

3600

<9

9

<.009

<190

<2

1170

86

1600

<1.5

139

6

73

489

715

10

<4

192

<43

243

<25

2.3

55.2

<11

76.2

65

16

9.2

353

62.4

5

50

291

320

20500

<11

<3.0

<.010

320

<2

1010

130

1300

<1.8

67

<6

<26

362

572

6.7

<4

171

<50

162

<29

2

50.8

<12

59.5

53

14

7

268

51

6

39

225

360

16000

<2

5.5

0.02

410

<2

280

29

350

1.6

73

4

<26

71

160

1.4

<1

47

32

32

33

2

18

<5

16

37

3.9

1.6

62.4

10

<2

8

46

140

3100

<10

<2.9

0.014

470

2.1

1840

<11

1200

<1.6

118

<7

86

555

1120

13

<5

278

<46

154

<29

2.1

59.1

<17

128

70

18

13

567

81.7

9

63

398

450

27400

<5

2.5

0.089

790

2.5

1100

40

840

<0.5

180

<3

76

298

652

6.5

<1

156

<22

131

<13

0.7

42.7

<5

60.8

36

12

7.7

223

41.8

5

38

242

180

13000
B36 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

APPENDIX Chemical-composition data from neutron activation and x-ray fluorescence analyses of selected

[FeTO3, total iron oxide expressed as Fe2O3 . Cd, Ir, Sm, and Te not detected. Major oxides analyzed by x-ray fluorescence (XRF); trace 

(detection limit follows < symbol)]

Sample

numbers

AA-11 AA-13 AA-14 AA-16 AA-17-1 AA-17-2 AA-17-3

Major oxides (percent)

SiO2

TiO2

A12O3

FeTO3

MnO

MgO

CaO

Na203

K2O

P2O5

SO3

Total

54.59

0.48

0.78

23.51

1.37

0.13

4.99

0.3

0.03

0.1

0.03

86.31

56.78

8.06

3.69

14.5

0.06

0.23

0.7

0.4

0.18

0.58

0.28

85.46

36.75

4.47

1.96

22.69

0.76

0.13

6.03

0.3

0.04

0.34

2.04

75.51

12.42

12.67

2.17

18.65

0.59

1.05

17.84

0.28

<0.01

0.41

0.12

66.15

63.95

0.45

7.37

15.42

0.19

0.2

0.54

1.35

1.46

0.09

0.08

91.1

22.68

8.68

2.01

31.02

0.67

0.31

2.16

0.34

0.24

0.27

<0.01

68.38

18.91

5.56

1.49

34.91

0.4

0.62

3.13

0.37

0.03

0.23

0.05

65.70

Trace elements (parts per million)

Ag

As

Au

Ba

Br

Ce

Co

Cr

Cs

Cu

Eu

Ga

Hf

La

Lu

Mo

Nb

Ni

Pb

Rb

Sb

Sc

Se

Sm

Sr

Ta

Tb

Th

U

w

Yb

Y

Zn

Zr

7

3.7

0.04

290

<2

90

35

100

0.7

88

1

29

7

54

0.6

<1

3

30

36

11

0.5

12

<5

580

16

0.8

1.3

9.5

10

<1

3

17

<100

430

<5

<2.7

0.059

350

<2

1140

<5

1000

<0.5

89

4

78

342

673

5.9

<2

178

<21

74

14

1.8

53.9

<5

68.7

30

14

7.9

284.7

41.9

11

36

249

<100

1400

10

2.7

<.005

210

<2

947

30

330

<0.5

13

3

19

173

452

3.8

<1

103

28

56

<15

1

40

<5

47.7

18

11

6.6

162

32.2

5

23

150

180

8400

12

5.1

0.029

450

2.9

2080

92

1300

<1.6

279

5

93

712

1080

12

<4

299

87

166

<28

3.9

71.6

<18

105

54

24

16

494

87

14

66

417

<2

1.7

0.011

510

2.6

61

21

150

0.9

52

<1

13

3

40

0.5

<1

3

<20

14

49

0.5

16

<5

4.3

50

<0.5

0.6

7.1

<3.3

<1

3

15

360 <100

31200 390

<8

6.5

0.019

410

<2

870

90

1000

<1.2

29

<4

60

279

559

6.1

<3

146

67

173

28

1.8

49.1

<11

49.2

46

13

6.2

210

38

6

36

193

320

12000

<6

<1.8

0.012

<120

<2

570

50

750

1.6

66

<3

<26

180

342

3.7

<2

90

<28

100

<17

1

29.9

<5

34.3

34

8

3.4

149

24.8

<3

24

107

<100

8400
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO

whole-rock samples from heavy-mineral deposits on the Ute Mountain Ute Indian Reservation Continued 

elements were analyzed by neutron activation except for Cu, Ga, Nb, Pb, and Y, which were analyzed by XRF. (<), below detection limit

B37

AA-17-4 AA-17-5 AA-19 AA-20 AA-21 AA-25-NW AA-25-SE AA-26-NW

Major oxides (percent) Continued

49.18

5.71

5.17

14.61

2.54

0.34

1.64

0.67

0.97

0.24

0.01

81.08

63.69

3.98

12.73

5.89

0.14

0.49

0.47

0.93

1.18

0.21

0.02

89.73

26.6

5.6

2.16

31.09

0.55

0.44

4.88

0.4

0.25

0.3

0.02

72.29

23.62

8.57

2.31

32.67

0.57

0.03

1.5

0.38

0.27

0.36

0.03

70.31

49.99

3.79

2.46

3.88

0.34

0.24

19.49

0.35

0.05

0.28

<0.01

80.87

62.57

5.46

4.21

10.33

0.07

0.48

1.18

0.44

0.45

0.3

0.75

86.24

68.95

3.26

3.2

10.29

0.05

0.3

5.5

0.31

0.09

0.44

0.13

92.52

51.53

2.29

5.54

16.44

1.29

1.2

3.88

0.6

0.75

0.18

0.07

83.77

Trace elements (parts per million) Continued

<7

4.2

0.014

890

2.9

678

170

740

<1.2

72

<5

<26

194

411

3.7

<3

102

100

53

<22

1.6

30.3

<11

44.7

48

8.9

5.9

174

30.1

6

20

180

<230

8400

<5

10

0.013

370

4.9

523

12

460

<0.5

14

<3

<26

125

298

3

<1

72

<22

17

35

1.6

30

<5

32.5

35

6.1

4.4

112

20

9

18

106

160

5200

<2

4.3

0.09

650

<2

726

66

490

<0.5

31

3

<26

186

373

3.9

<1

106

49

86

13

1.5

34

<5

37.3

35

8.9

5.2

150

31.4

5

22

139

160

8500

<6

2.4

0.038

290

<2

1210

77

750

<1.1

135

5

48

408

580

7.3

<2

139

48

136

<19

1.6

47.2

<11

69.1

62

12

10

318

59.4

9

42

250

250

18000

<5

<2.3

0.078

270

<2

1380

9

530

<0.5

130

5

38

304

111

5.9

<3

136

<23

46

<14

0.5

30.6

<5

89.5

32

12

9.4

325

43.4

<6

37

261

<100

12000

<6

<1.9

0.007

<130

2.6

1070

13

530

<1.0

9

<4

<26

182

627

5.2

<3

148

<29

23

<18

0.8

42.4

<5

55.7

24

13

6.6

223

31.1

9

32

169

210

8000

<5

6.4

0.008

220

<2

684

26

330

0.9

<60

<3

<26

84

430

2.4

<1

103

<22

<19

<13

0.8

40.2

<5

35

12

20

3.6

142

18

221

17

90

150

3700

<2

3.8

<.002

720

2

370

71

340

0.7

<60

<2

<26

66

200

2.5

<1

48

51

<19

25

0.6

28.2

<5

22.7

27

4.5

2.8

67.4

15

<2

16

85

240

2900
B38 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

APPENDIX Chemical-composition data from neutron activation and x-ray fluorescence analyses of selected 

Continued

[FeTO3 , total iron oxide expressed as Fe2O3 . Cd, Ir, Sm, and Te not detected. Major oxides analyzed by x-ray fluorescence (XRF); trace 

(<), below detection limit (detection limit follows < symbol)]

Sample

numbers

AA-26-SE AA-27 AA-28 AA-30 AA-36-NW AA-36-SE AA-37

Major oxides (percent)

SiO2

TiO2

A1203

FeTO3

MnO

MgO

CaO

Na2O

K20

P205

S03

Total

21.76

21.89

7.7

10.82

0.19

1.52

6.31

0.31

<0.01

0.61

0.18

71.29

66.72

5.58

3.52

10.37

0.11

0.63

1.94

0.37

0.15

0.22

0.08

89.69

30.79

7.72

2.32

28.3

0.97

0.3

0.99

0.47

0.42

0.26

<0.01

72.54

48.15

10.68

1.41

16.28

0.09

0.13

1.03

0.36

<0.01

0.55

1.61

80.29

14.89

5.83

1.34

23.71

0.27

0.17

20.95

0.32

0.01

0.34

0.15

67.98

15.02

5.16

1.59

28.21

0.41

0.25

17.09

0.34

0.1

0.29

0.16

68.62

67.47

6.25

5.48

7.95

0.51

0.78

0.62

0.36

0.05

0.2

0.01

89.68

Trace elements (parts per million)

Ag

As

Au

Ba

Br

Ce

Co

Cr

Cs

Cu

Eu

Ga

Hf

La

Lu

Mo

Nb

Ni

Pb

Rb

Sb

Sc

Se

Sm

Sr

Ta

Tb

Th

U

w

Yb

Y

Zn

Zr

<7

<3.6

0.025

<140

<2

3890

23

2230

<1.1

471

10

412

1470

2530

29.2

<5

672

<33

239

<19

1

119

<11

265

105

42

31

1080

180

<9

150

1205

270

59800

<2

4.4

0.039

130

<2

1260

10

480

<0.5

117

3

65

360

588

6.1

<1

162

<20

21

25

0.8

39.6

<5

65

19

14

8.5

286

42.1

7

33

255

<100

16000

<5

12

0.059

480

<2

856

82

920

1.3

<60

4

<26

310

490

5.7

<2

126

57

133

14

2.1

48.9

<5

55.5

50

10

7

223

38.2

<5

35

194

330

13000

<2

2.7

0.041

1100

<2

2350

<5

900

<0.5

159

2

111

770

1250

12

<1

300

<20

85

<11

1.2

62.2

<5

128

45

26

17

559

82.5

10

65

475

<100

36300

<6

29

0.085

870

7.1

949

88

1200

<0.5

78

<3

<26

342

559

7

<2

112

<25

85

<15

3.1

50.5

<5

63.5

34

13

8.3

284

48.1

62

39

199

570

15000

<4

6.1

<.004

500

10

645

66

780

1

141

3

40

206

381

4.5

<1

101

<20

81

<12

1.3

34.4

<5

36.4

33

7.9

5

163

28.9

3

25

146

240

8600

<6

<1.3

0.059

360

<2

1150

20

640

<1.0

98

6

67

324

577

6.9

<3

162

<29

59

<18

0.7

43.7

<10

63.9

30

13

8.2

255

41.5

7

44

300

270

14000
HEAVY-MINERAL PLACERS, UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO B39 

whole-rock samples from heavy-mineral deposits on the Ute Mountain Ute Indian Reservation 

trace elements were analyzed by neutron activation except for Cu, Ga, Nb, Pb, and Y, which were analyzed by XRF.

AA-38 AA-39 AA^O AA-41 AA-43 AA-W FA-1

Major oxides (percent) Continued

56.84

10.4

9.95

6.72

0.09

0.86

0.51

0.42

0.41

0.35

0.09

86.64

56.05

14

6.74

6.06

0.12

1

0.97

0.38

0.32

0.52

0.01

86.17

28.35

16.49

9.1

15.93

0.16

2.39

1.48

0.29

0.3

0.68

<0.01

75.17

15.44

9.3

1.39

31.84

0.61

1.05

6.29

0.26

<0.01

0.36

<0.01

66.54

27.42

7.27

3.04

28.26

0.7

0.91

2.67

0.31

0.16

0.4

0.02

71.16

13.95

10.29

1.36

30.81

0.55

0.73

6.91

0.26

<0.01

0.31

0.02

65.10

54.65

0.51

3.47

23.76

0.44

0.42

1.35

0.55

0.68

0.06

0.03

85.92

Trace elements (parts per million) Continued

<8

3.6

0.041

270

3

1340

17

1000

1.6

23

<5

65

397

764

8.7

<3

218

<36

68

<21

2

68.1

<12

80.5

40

16

10

274

52

12

48

359

300

17000

<7

4.5

0.08

430

3.1

1620

17

1200

<1.1

52

4

85

511

946

10

<3

331

<30

113

<18

2.2

87.2

<5

97.1

46

23

12

324

59.4

13

65

469

190

20800

<8

<3.2

0.021

380

2.4

1870

44

1500

<1.2

63

5

76

388

1140

10

<4

324

<34

89

<20

2.6

93.9

<10

107

34

26

13

295

51.6

14

62

348

500

15000

<6

<2.7

0.049

370

<2

1060

67

1100

1.2

137

<3

32

363

633

6.8

<4

166

<27

140

<16

1.7

54

<5

63.1

38

14

8.8

243

42.8

<7

40

260

330

16000

<7

<1.8

0.11

550

<2

791

43

810

<1.1

60

<4

49

189

463

4.8

<2

135

<30

104

<18

1.5

46.9

<5

46.3

30

11

5.3

149

29.1

6

28

177

370

8400

<8

<3.6

0.06

390

<2

990

55

940

<1.3

175

<5

25

314

623

6.4

<3

193

<35

195

<21

2.3

51

<12

67.8

39

16

9

275

16.6

5

33

263

320

14000

<2

<1.4

0.015

400

<2

82

53

170

0.9

98

<1

7

4

71

0.5

<1

6

40

33

28

0.4

15

<5

637

33

0.5

1.3

8.6

31.4

<3

3

22

190

<200

Geologic Studies of the

Ute Mountain Ute Indian Reservation

U.S. GEOLOGICAL SURVEY BULLETIN 2061

This volume was published as separate chapters A and B

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1994
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For sale by U.S. Geological Survey, Map Distribution

Box 25286, MS 306, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

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

A. Distribution and Properties of Clinoptilolite-Bearing Tuffs in the Upper Jurassic 

Morrison Formation on the Ute Mountain Ute Reservation, Southwestern Colorado 

and Northwestern New Mexico

By Paula L. Hansley and Richard A. Sheppard

B. Heavy-Mineral Placer Deposits of the Ute Mountain Ute Indian Reservation, 

Southwestern Colorado and Northwestern New Mexico

By Robert S. Zech, Richard L. Reynolds, Joseph G. Rosenbaum, and 

Isabelle K. Brownfield

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