The Effect of Sedimentation 

And Diagenesis on Trace 

Element Composition of 

Water-Laid Tuff in the 

Keg Mountain Area, Utah 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 818-C 

The Effect of Sedimentation 

And Diagenesis on Trace 

Element Composition of 

Water-Laid Tuff in the 

Keg Mountain Area, Utah 

By DAVID A. LINDSEY 

BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 818-C 

A statistical study of the petrogenesis of 

unmineralized water-laid tuff in the 

western Utah beryllium belt 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1975 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Lindsey, David A. 

The effect of sedimentation and diagenesis on trace element composition of water-laid tuff in the Keg Mountain area, Utah. 

(Geological Survey Professional Paper 818-C: Beryllium-bearing tuffs in western Utah) 

Bibliography: PSupt. of Docs. no.: I 19.16:818-C 

L Volcanic ash, tuff, etc.-Utah-Keg Mountain region. 2. Beryllium ores-Utah-Keg Mountain region. 3. Trace elements. 

I. Title. II. Series: United States Geological Survey Professional Paper 818-C- III. Series: Beryllium-bearing tuffs in western 

Utah. 

QE46LL623 552'.2 74-30055 

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

Washington, D.C. 20402 

Stock Number 024-001-02661-9 
CONTENTS 

Page Page Abstract _________________________________ C1 Petrogenesis _____________ - __ -----_-------- C13 

Introduction _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 

Geographic and geologic setting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 

Problems in petrogenetic interpretation _ _ _ _ _ _ _ _ _ _ _ _ 13 

Methods of study --------------------------- 3 

Sampling plan -------------------------- 3 

Laboratory procedure _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

A petrogenetic model ---------------------- 15 

R-mode factor analysis --------------------- 17 

Factor analyses of the water-laid tuff data - _-------- 22 

Conclusions ______________ ----------------- 32 

Composition of the water-laid tuff _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

Lithology and petrography _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

Abundance of minerals and trace elements _ _ _ _ _ _ _ _ _ _ 8 

Sources of variation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9 

Geographic variation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 

Erosion and sedimentation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 32 

FIGURE 1. 

2. 

3. 

4. 

5-9. 

10. 

11-26 

27. 

Diagenesis ________________________ ----- 33 

Mineralization _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 34 

References cited ---------------------------- 34 

ILLUSTRATIONS 

Map showing location of the Keg Mountain study area, other geographic features, and mineral occurrences in the western 

Utah beryllium belt _______________________________________ ---------------

Map showing geographic features, distribution of water-laid tuff, and sampling stations in the Keg Mountain area 

Photographs of water-laid tuff in the Keg Mountain area ________ - __ - __ --_------------------

Map and cross sections showing classification of water-laid tuff into vitric, zeolitic, and feldspathic facies - __ ---

Histograms showing frequency distribution and maps showing mean values at each sampling station in water-laid tuff in 

the Keg Moutain area for the following: 

5. Clinoptilolite content ____________________________________ ---------------

6. Quartz content ________________________________________ ---------------

7. a-cristobalite content _________________________________ ------------------

8. Potassium feldspar content _______________________ - _____ --_---------------

~ G~~oon~~ ------------------------------------------------------- Map showing occurrence of calcite, montmorillonoid clay, and fluorite in the Keg Mountain area __ - _____ - __ 

Histograms showing frequency distribution and maps showing mean values at each sampling station in water-laid tuff in 

the Keg Mountain area for the following: 11. Barium content _____________________________________________________ _ 

12. Beryllium content ___________________________________________________ _ 

13. Chromium and lithium content -------------------------------------------- 14. Copper content _____________________________________________________ _ 

15. Iron content _______________________________________________________ _ 

16. Gallium content ____________________________________________________ _ 

17. Lanthanum content __________________________________________________ _ 

18. Manganese content __________________________________________________ _ 

19. Niobium content ____________________________________________________ _ 

20. Lead content ______________________________________________________ _ 

21. Strontium content ___________________________________________________ _ 

22. Titanium content ___________________________________________________ _ 

23. Equivalent uranium content _____________________________________________ _ 

24. Vanadium content ___________________________________________________ _ 

25. Yttrium content ____________________________________________________ _ 

26. Zirconium content ___________________________________________________ _ 

Graph showing eigenvalues and cumulative proportion of total variance explained by the first 10 principal components 

ill 

Page 

C2 

4 

5 

6 

11 

12 

13 

14 

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21 

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33 
CONTENTS 

TABLES 

Page 

TABLE 1. Stratigraphic section in the Keg Mountain area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ C3 

2. Summary statistics for mineral and trace element composition of 172 samples of water-laid tuff from the Keg Mountain area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8 

3. Estimates of total variance, variance components in a three-level nested sampling design, and variance ratios for mineral 

and trace element composition of water-laid tuff _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ 9 

4. Sum of squares of the deviations from the mean and percent reduction of the sum of squares by polynomial surfaces of 

degree 1 through 5 fitted to data on mineral and trace element composition of 164 samples of water-laid tuff _ 10 

5. Correlation coefficients based on analyses of 172 samples of water-laid tuff _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 33 

6. Communalities for two-, three-, four-, five-, and six-factor Varimax solutions compared to the percent of nonerror variance _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 33 

7. A five-factor petrogenetic model for the water-laid tuff as defined by the Varimax loadings _ _ _ _ _ _ _ _ _ _ _ _ _ _ 34 
BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

THE EFFECT OF SEDIMENTATION AND DIAGENESIS ON 

TRACE ELEMENT COMPOSITION 

OF WATER-LAID TUFF IN THE KEG MOUNTAIN AREA, UTAH 

By DAVID A. LINDSEY 

ABSTRACT 

The mineral and trace element composition of water-laid tuff in the 

Keg Mountain area was investigated as part of a study of berylliumbearing tuffs in western Utah. Keg Mountain lies within the western 

Utah beryllium belt and contains tuff similar in age and composition to 

that of Spor Mountain and the Thomas Range. Water-laid tuff at Spor 

Mountain serves as the host rock to large low-grade beryllium deposits, 

and tuff in the adjacent Thomas Range shows an extensive trace element halo which was produced by the mineralization at Spor Mountain. Mineralized tuff is not known at Keg Mountain, however, and 

this study was undertaken to assess the influence of other geologic 

processes on trace element concentration in tuff and to evaluate the 

mineral potential of the area. 

A petrogenetic model for the water-laid tuff was developed by Rmode factor analysis. The analysis shows that most of the variation in 

mineral and trace element content of the tuff can be accounted for by a 

five-factor model. The five factors are: concentration of major detrital 

minerals, concentration of minor rare earth-bearing detrital minerals, 

two stages of diagenesis (zeolitization and feldspathization), and late 

magmatic concentration(?) of the trace elements Pb, Ga, and Be. 

The two detrital factors are interpreted as indicating that erosion 

and sedimentation have played important parts in influencing the distribution of some minerals and trace elements in the tuff. Local concentration of major detrital minerals produced a detrital facies rich in 

quartz, potassium feldspar, plagioclase, and iron oxides. The concentration of the elements Ba, Fe, Cu, Mn, Ti, and V was largely controlled by this detrital factor; Ba is probably present in feldspar and 

the other elements in iron oxides. A second detrital factor concentrated 

the minor minerals sphene and zircon and operated with an intensity 

which increased eastward. This factor produced an association of the 

elements La, Nb, Y, and Zr and a pronounced easterly increase in their 

abundances. The intensity with which these two detrital factors have 

operated indicates that they may pose serious problems for 

geochemical prospecting for heavy metal and rare earth deposits in 

tuff. 

The two stages of diagenesis did not appreciably alter the trace element content of the tuff. The first stage, zeolitization, resulted in a 

clinoptilolite-rich tuff somewhat enriched with respect to Sr and impoverished with respect to U. Advanced diagenesis, marked by feldspathization, did not alter the trace element composition of the tuff. 

Regions of most intense diagenesis are located in the western and 

southeastern parts of the Keg Mountain area. Clinoptilolite and potassium feldspar are especially abundant in the western part of the range, 

and clinoptilolite is abundant in the southeastern part of the range. 

The diagenesis is similar to that which affected tuff in the Thomas 

Range and is believed to result from alkaline waters derived from 

leaching of glass. 

Three criteria indicate that there is little chance of finding beryllium 

or fluorspar deposits near Keg Mountain that are similar to those at 

Spor Mountain: (1) very little fluorite and hydrothermal clay are present; the montmorillonoid clay which occurs in vitric tuff contains no 

anomalous trace element concentrations and is probably the product of 

diagenesis; (2) the frequency distribution for Be is not highly skewed, 

in contrast to the highly skewed distribution for Be in tuff of the 

Thomas Range, and no anomalous concentrations of Be could be 

detected by trend surface analysis; and (3) Be was found by R-mode 

factor analysis to be associated with Pb and Ga, in contrast to the 

Thomas Range tuff in which Be is strongly associated with F, Cs, Li, 

Ga, Nb, and Y, and not associated with Pb. The association Pb-Be-Ga 

may be due to the concentration of these elements in the parent 

rhyolite magma; it is probably not the signature of beryllium-fluorite 

mineralization. 

INTRODUCTION 

Keg Mountain lies within the beryllium belt of 

western Utah that extends from the Sheeprock Mountains into Nevada (Cohenour, 1963) (fig. 1). Water-laid 

tuff of Pliocene age crops out extensively around Keg 

Mountain, where its deposition followed a period of ashflow eruption and caldera collapse (Shawe, 1972). The 

tuff occupies the same stratigraphic position as similar 

water-laid tuff of the Thomas Range and Spor Mountain, where it provided the host rock for beryllium and 

fluorite mineralization (Staatz and Griffitts, 1961; 

Shawe, 1968). The beryllium-fluorite mineralization at 

Spor Mountain has produced extensive areas of argillic 

and feldspathic altered tuff (Lindsey and others, 1973) 

and has imprinted a large trace element halo on adjacent 

water-laid tuff in the Thomas Range (Lindsey, 1975). 

These facts suggested that the water-laid tuff of the Keg 

Mountain area should be examined for evidence of 

beryllium-fluorite mineralization. 

An investigation of the water-laid tuff of the Keg 

Mountain area showed no evidence for beryllium-fluorite 

Cl 
C2 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

113° 

I 

I 

U GRANITE 

Be PEAK 

EXPLAN A TJON 

~Be 

Mineral occurrence 

~ I 

I 

k1 

I 

I 

I 

GREAT SALT LAKE 

DESERT 

~------------- I~~:i~~O- I 

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0 10 MILES 

0 10 K l LOMETRES 

WHITE 

VALLEY 

I 

) 

SEVIER DESERT 

FIGURE 1. - Location of the Keg Mountain study area, other geographic features, and mineral occurrences in the western Utah beryllium belt. 

or any other type of mineralization. Analyses for trace 

elements did reveal generally high concentrations of Be, 

Ga, Nb, and eU in the water-laid tuff and overlying 

alkali rhyolite, indicating that these rocks may be classified with other beryllium-bearing volcanics in western 

Utah. Statistical analysis of the mineralogic and trace 

element data on the water-laid tuff indicates the influence of numerous other petrogenetic processes, 

notably those related to the concentration of detrital 

minerals (erosion and sedimentation) and diagenesis. 

The purpose of this report is to present a model for the 

mineral and trace element associations produced by 

sedimentation and diagenesis in the beryllium-bearing 

tuffs. This model should serve as a basis for comparison 

with the model for mineralized tuff (Lindsey, 1975); such 

comparisons should lead to more accurate identification 

of regional mineral resource potential from trace element 

anomalies in tuff. Data used in preparing this report are 

available from the U.S. Department of Commerce, 

National Technical Information Service, Springfield, 

Va. 22161 (Lindsey and others, 1974). 

I thank D. R. Shawe for information regarding the 

geology of the Keg Mountain area, and J. J. Connor, 

George Van Trump, Jr., and Josephine Boerngen, all of 

the U.S . Geological Survey, for assistance with 

statistical analysis and computer programming. Many 

other employees of the U.S. Geological Survey assisted 

in the laboratory and made chemical analyses; they are 

acknowledged in table 2. 

GEOGRAPHIC AND GEOLOGIC SETTING 

Keg Mountain lies in the Basin and Range province in 

Juab County, Utah (fig. 1). It is actually a small range 

that consists of two parts separated by Keg Pass. The 

mountains west of Keg Pass are low and extend south of 

the Jericho-Callao road; those east of Keg Pass comprise 

the highest part of the range. 

The stratigraphic section at Keg Mountain (table 1) 

consists mainly of Tertiary volcanics; these overlie 

Precambrian and Paleozoic sedimentary rocks along the 

northern edge of Keg Mountain (Erickson, 1963; Shawe, 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C3 

TABLE 1. - Stratigraphic section in the Keg Mountain area 

[Adapted from Shawe (1972); ages are from author's unpublished data ; query(?) indicates th1ckness unknown] 

Age Rock unit Maximum t hi ckness 

(ft) (m) 

Pliocene Younger volcanic group: Alkali rhyolite. 1,000 305 Water-laid tuff. 100 30 - --- - Unconformity --- - -

Rhyolite of Keg M0untains. 1,000 305 

Unconformity 

Oligocene Middle volcanic group: 

Rhyolitic welded 

ash-flow tuff. 500 152 Quartz-latitic 

welded ash-flow tuff. 200 61 Unconformi ty(?) 

Eocene Older volcanic group : Latitic and 

andesitic flows. ? ? Unconformity 

Paleozoic Marine sedimentary and 

Precambrian rocks. ? ? 

1972). The older volcanic rocks consist of (1) latitic and 

andesitic flows, (2) quartz-latitic welded ash-flow tuff, 

and (3) rhyolitic welded ash-flow tuff. These rocks were 

deposited prior to the collapse of the Keg caldera 

(Shawe, 1972). The rhyolite, water-laid tuff, and alkali 

rhyolite of Keg Mountain overlie the older volcanic rocks 

and were deposited after caldera collapse. 

The distribution of water-laid tuff is shown in figure 2 

and was compiled from the field notes of D. R. Shawe. 

The tuff overlies an erosional surface of low relief and is 

typically overlain by alkali rhyolite flows. The base of 

the alkali rhyolite commonly contains a thin brecciated 

zone; black vitrophyre is present at the base of the 

rhyolite east of Keg Pass. The tuff exceeds 100 feet (30 

m) in thickness in very few localities and is missing 

beneath the alkali rhyolite at some localities. It is cut by 

faults in a few places, notably in the southwestern and 

southeastern parts of Keg Mountain. 

METHODS OF STUDY 

SAMPLING PLAN 

Water-laid tuff throughout the area of Keg Mountain 

was sampled for this study. A stratified random sampling plan (Krumbein and Graybill, 1965, p. 156-157), 

similar to that employed for study of water-laid tuff in 

the Thomas Range (Lindsey, 1975), was used as a basis 

to select samples. Each sampling station was chosen randomly from 100 possible locations within each linear mile 

( 1.6 km) of tuff outcrop. In practice, stations were moved 

laterally to the nearest good exposure of tuff so that sampies could be obtained at every sampling station. A few 

stations were added to fill gaps left by the sampling plan. 

The stratigraphic thickness of tuff at each station was 

estimated in the field, and four 1-foot (0.3-m) intervals 

were selected from random number tables for sampling. 

The sampling program resulted in 172 samples being collected from 43 stations. The samples consisted of fresh 

chips and averaged about 2 lbs (0.9 kg). 

LABORATORY PROCEDURE 

Twenty samples were selected at random for splitting 

before any other laboratory procedures were begun. 

These splits and the original 172 samples were placed in 

random order prior to sample preparation. Samples were 

split to allow estimation of laboratory errors from 

replicate measurements on the same sample. The sample population was treated randomly to insure that 

analytical drift and other laboratory effects did not 

produce undesirable manmade trends in the data. A 

specimen for thin sectioning was removed from each 

sample before splitting and randomization. 

All 172 samples plus the 20 additional splits were 

ground to finer than 60 mesh; approximately 120 g was 

split from each sample and ground to finer than 100 

mesh. Splits of approximately 3 g and 2 g were then 

removed for X-ray diffraction and spectrographic determinations, respectively; a split of about 10 g was used for 

eU measurement. 

Mineral quantities were estimated by X-ray diffraction. The method is an application of established principles (Klug and Alexander, 1954; Schultz, 1964; Tatlock, 

1966) and is the same as that used for study of tuff in the 

Thomas Range (Lindsey, 1975). Three grams of each 

sample was ground 15 minutes in a shatterbox and 

mounted by the backpack mounting technique of McCreery (Klug and Alexander, 1954, p. 300-302). Standards were prepared and X-rayed in the same manner, 

so that the diffraction intensity of each mineral could be 

converted into percent. Amorphous glass and poorly 

crystallized minerals detected by X-ray diffraction were 

estimated by difference; that is, by adding all other components and subtracting the total from 100. 

All trace elements were determined by direct reader 

spectrometric analysis (Havens and Myers, 1973). 

Equivalent uranium (eU) was determined by a 

radiometric counting method based on the assumption 

that all beta and gamma radiation comes from decay of 

uranium. Although eU includes effects from such 

isotopes as 232Th and 4

°K, previous comparison of eU and 

chemical uranium in similar tuff indicates that much of 

the measured eU is due to uranium decay (Staatz and 

Carr, 1964, p. 115). 

COMPOSITION OF THE WATER-LAID TUFF 

LITHOLOGY AND PETROGRAPHY 

The tuff of Keg Mountain was termed "water-laid" by 

Shawe (1972) because of its stratified aspect (fig. 3A). 

The tuff contains abundant clasts derived from older 

volcanic rocks (fig. 3B); generally the clasts are only a 

few inches in diameter, but individuals as much as 16 

feet in diameter were observed at one locality in the 

southeastern part of Keg Mountain. Fragments of older 

sedimentary rocks were not observed. Massive tuff of 
C4 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

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EXPLANATION 

~ Out crop of water-laid tuff 

.2 Sampling station and number 

FIGURE 2 . - Geographic features, distribution of water-laid tuff, and sampling stations in the Keg Mountain area. 

probable air-fall origin is also present; in the eastern half 

of Keg Mountain the uppermost part of the tuff is commonly welded and overlain by dark vitrophyre (figs. 3C, 

D). 

The tuff is composed mainly of pumice, volcanic rock 

fragments, and pyroclastic crystals set in a matrix of 

glass shards, clinoptilolite, and fine-grained potassium 

feldspar, quartz, and cristobalite. Crystals of quartz, 

sanidine, and plagioclase together comprise about 5-15 

percent of the tuff; they are euhedral and commonly 

broken by transport. The tuff contains 1-2 percent each 

of biotite, magnetite, and hematite, and lesser quantities 

of sphene, hornblende, augite, zircon, and apatite. 

Euhedral shapes, often broken, are common for most of 

these minerals; sphene and augite grains are mainly 

angular, however. Iron minerals are partially oxidized to 

a red color, and locally hematite is the only iron oxide 

present. Calcite, montmorillonoid clay, and trace 

amounts of fluorite(?) are present in a few samples. 

The tuff can be divided into three facies according to 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH 

FIGURE 3. - Water-laid tuff in the Keg Mountain area: A, section of water-laid tuff overlain by alkali rhyolite, north of station 

4; note conspicuous stratification in tuff. B, detail of water-laid tuff, showing angular volcanic rock fragments; same outcrop 

as A. C, section of water-laid tuff overlain by vitrophyre at station 39. D, detail of welded zone in top of water-laid tuff, same 

outcrop as C. E, photomicrograph of zeolitic facies at station 43, showing relict shards replaced by clinoptilolite of diagenetic 

origin (plain light). F, photomicrograph of detrital facies at station 42, showing abundant quartz (Q), sanidine (8), 

plagioclase (P), and hematite (H) derived from underlying volcanic rocks and set in a fine-grained matrix of potassium feldspar and a-cristobalite of diagenetic origin (crossed polars). 

C5 
C6 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

gross mineralogy: vitric, zeolitic, and feldspathic (fig. 4). 

The vitric facies retains a large proportion of unaltered 

glass pumice and shards and represents the original 

mineralogy of the water-laid tuff. The zeolitic facies contains clinoptilolite of diagenetic origin (fig. 3E) that 

comprises nearly 100 percent of some samples. The feldspathic facies contains abundant fine-grained potassium 

feldspar, quartz, and a-cristobalite of diagenetic origin. 

The tuff at two stations, 17 and 42, also contains abundant quartz and potassium feldspar of detrital origin. 

T. 

12 

s. 

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The vitric facies is widely distributed through the 

central and northeastern parts of Keg Mountain; the 

zeolitic facies occupies much of the western and 

southeastern parts of the range; the feldspathic facies is 

present in the center of the western part of Keg Mountain and along certain horizons in the tuff of the 

northeastern part of the range, where fine-grained 

quartz, potassium feldspar, dioctahedral montmorillonoid clay, and glass occur together. Cross sections (fig. 

4) show a complex pattern of facies arrangement. The 

112°45' 

R 9 W 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 4. - Map and cross sections showing classification 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C7 

zonation of vitric-zeolitic-feldspathic facies inward from 

the margins of the range, which is well developed in the 

Thomas Range (Lindsey, 1975), is evident only in the 

western part of Keg Mountain. No zoning pattern is evident in the eastern part of the range, although the 

mineral facies there do tend to follow stratigraphic 

horizons. 

The occurrence of abundant detrital constituents at 

stations 17 and 42 indicates a fourth facies of detrital 

origin; this facies overlaps the various diagenetic facies 

in extent. The tuff at these localities contains as much as 

35 percent euhedral and broken crystals of volcanic 

quartz, sanidine, and plagioclase in a matrix of glass, 

fine-grained potassium feldspar, and a-cristobalite (fig. 

3F). Brown biotite and iron oxide minerals are also conspicuously abundant (2-3 percent). Numerous large 

clasts of gray rhyolite with conspicuous phenocrysts of 

13 

19 

quartz and plagioclase are present in the tuff at station 

42; these clasts were derived from the underlying 

rhyolite (rhyolite of Keg Mountain of Shawe, 1972). 

Abundant devitrification products, including acristobalite and potassium feldspar, indicate that 

diagenesis was also important in forming the feldspathic 

tuff at these two localities. Indications of the detrital 

facies were also observed at stations 14 and 35, where lesser quantities of crystals, including plagioclase, were 

observed in thin sections. Large clasts of the rhyolite of 

Keg Mountain are abundant in the lower part of the tuff 

at station 35. The scattered occurrence of a few percent 

plagioclase at many other localities may indicate the influence of erosion and sedimentation. 

Little evidence of hydrothermal alteration was found. 

The beryllium deposits in tuff at Spor Mountain are associated with abundant fluorite and montmorillonoid 

'26 

21 FEET METRES 

0 0 

22 

10 

50 

20 

100 30 

EXPLANATION 

GLASS 

•

6 Sampling station and station number 

x Sample eleva tron in section 

CLJNOPTJLOLITE POTASSIUM FELDSPAR 

of water-laid tuff into vitric, zeolitic, and feldspathic facies. 
C8 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

clay. Very little fluorite was detected in the tuff of the 

Keg mountain area, however, and the montmorillonoid 

clay which is widely distributed is probably of diagenetic 

origin. The lowermost outcrop of tuff at station 19 is 

much altered to dioctahedral montmorillonoid clay, but 

spectrographic analyses failed to reveal evidence of 

mineralization. Samples from prospect pits in tuff near 

stations 13 and 30 were examined for evidence of alteration or mineralization; no clay minerals, fluorite, or 

anomalous trace element concentrations were found. 

ABUNDANCE OF MINERALS AND TRACE ELEMENTS 

The mineral and trace element compositions of the 

tuff are summarized in table 2. Although no analyses for 

major chemical constituents were made, the composition 

of the tuff is probably rhyolitic, similar to that of the 

water-laid tuff in the Thomas Range (Lindsey, 1975). 

The trace elements Be (5 ppm), Ga (26 ppm), Nb (29 

ppm), and U (33 ppm eU) are probably more abundant 

than in other tuffaceous and volcanic rocks, although Be, 

Ga, and U are less abundant than in the water-laid tuff 

of the Thomas Range. 

The frequency distributions of each mineral and trace 

element (hereafter referred to collectively as variables) 

are summarized by moment estimates and histograms 

(Freund, 1960, p. 3-105). Central tendency was estimated by the arithmetic and geometric means and by 

the median (50th percentile); variation was estimated by 

the standard deviation, geometric deviation, and the difference between the lOth and 90th percentiles (table 2). 

Estimates of means and variation for censored frequency 

distributions- that is, where the concentration of a particular mineral or element is below the limit of detection 

for some samples- were made by the methods of Cohen 

TABLE 2. - Summary statistics for mineral and trace element composition of 172 samples of water-laid tuff from the Keg Mountain area 

rMineral composition determined by X-ray diffraction by K. A. Buzard; equivalent uranium (eU) determined by beta-gamma scaler by E. J. Fennelly; Li determined by six-step semi- quantitative spectrographic analysis by L. D. Forshey; all other elements determined by direct reading spectrograph by R. G. Havens, N. M. Conklin, and L. M. Lee. Elements 

looked for but not found , with their detection limits in parts per million, are Ag (4), Au (20), Bi (20), Cd (100), Co (8), Ge (100), In (20), Mo (20), Pd (10), He (70), Sb (300), Tl (50), W (500) , and Zn (300). Leaders indicate not calculated] 

Mineral or trace element 

Number of 

samples below the limit of 

detection 

Montmorillonoid clay ________ 139 

Mica - ---- - --- ---- ----- 99 Clinoptilolite _ ___ __ _______ 61 

Quartz ---------- ------ 0 a-cristobalite _ _ _ _ _ _ _ _ _ _ _ _ _ 17 

K-feldspar -------------- 0 

Plagioclase ______________ 164 

Calcite ________________ 157 

Fluorite ________________ 162 

Glass _________________ 121 

B ____________________ W9 

Ba ------------------- 1 

Be ------------------- 11 Cr ___________________ 147 

Cu ------------------- 0 

Fe _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ 0 

Ga _____ __ _ _ ___ _ _ ____ _ 0 

La Li --

__ ---_ _________ --- - ----_ ------__ ____ 151 ~ 

Mn ------------- - ---- 0 

Nb _____ ___ ___________ 8 

Ni _________ ________ __ 171 

Pb ------------------- 6 Sc __ _______________ _ _ 170 

Sn __________________ _ 171 

Sr _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 0 

TI ------------------- 0 

eU ------------------- 1 

v -------------------- 73 y ____________________ ~ 

Zr --- - --------------- 0 

1

ltalics indica te arithmetic mean and standard deviation. 

Bimodal distribution. 

Lower limit of detection 

10 

1 

5 

1 

1 

1 

5 

1 

0.5 

30 

30 

10 

4 

5 

1 

500 

10 

50 

50 

7 

20 

7 

20 

10 

20 

10 

20 

10 

10 

20 

20 

Geometric 

mean 1 

219.9 

12.1 

3.7 

19.9 

160 

5.2 

3.7 

7,219 

26.1 

57.4 

332 

28.6 

29.3 

302 

1,001 

33.4 

10.9 

26.0 

112 

Percentile 

Geometric 

deviation 1 lOth 50th 90th 

Mineral composition (weight percent) 

13.0 

2.2 

4.81 49.0 83.2 

1.62 6.0 12.6 24.2 

2.56 2.2 3.8 12.1 

1.65 9.7 20.1 38.3 

1.0 

62 

Trace element composition (parts per million) 

2.39 51 170 577 

1.27 4.1 5.6 7.8 

5.0 

1.62 2.1 4.2 6.2 

1.46 4,264 7,038 11,650 

1.14 21.5 25.6 31.0 

1.47 57.8 86.0 

50 

1.56 185 342 554 

4.8 21.7 29.5 36.3 

1.27 19.4 29.1 37.3 

2.33 86 319 926 

1.53 585 961 1,753 

9.2 25.3 38.6 49.5 

1.67 10.0 22.8 

1.43 25.2 38.1 

1.25 87 107 158 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C9 

and Sichel (Miesch, 1967a, p. B5-B8). Statistical 

parameters were not computed for variables for which 

more than 30 percent of the samples are below the limit 

of detection, although data for some are summarized 

later in histograms and maps. 

Study of the skewness revealed that frequency distributions for most variables depart significantly from 

the normal model. Normal distributions are symmetrical 

with a skewness near 0 and if the frequency distribution 

deviates significantly from the normal, various transformations of the data (Miesch, 1967a, p. B5) are necessary 

before further statistical analysis. Logarithmic transformations were helpful in normalizing the data for all 

variables except Nb and eU; the frequency distributions 

of these two variables were found to be nearly normal 

without transformation. Transformation of data to 

logarithms prior to other statistical calculations is indicated in the tables following table 2 by referring to 

variables as "log clinoptilolite," etc. The geometric 

mean and geometric deviation are given in table 2 as estimates of central tendency and variation for those 

variables which tend to exhibit log normal frequency distributions. They are the antilogarithms of the arithmetic 

mean and standard deviation of the log concentrations. 

The arithmetic mean and standard deviation of Nb and 

eU are given in table 2 as the best estimate of central 

tendency and variation for these two variables. 

Histograms, or bar diagrams, were constructed for 

most variables (figs. 5-26). The data were divided into 

classes of equal width for normally distributed data and 

into geometric classes for log normal data. The geometric 

class interval was usually selected so that six classes per 

order of magnitude were plotted, with the series 1, 1.5, 2, 

3, 5, 7, 10, etc. serving as class midpoints. For Ga and Zr, 

as many as 20 classes per order of magnitude were necessary to display the data adequately (figs. 16, 26). The 

histogram for Be (fig. 12) is based on arithmetic classes 

because that trace element was reported as integers in 

the range of 4-9 ppm. 

SOURCES OF VARIATION 

The total variance of each mineral and trace element 

can be understood as the sum of numerous sources of 

natural and manmade variation. The observed value of 

each measurement is influenced by each of these sources 

of variation. The magnitude of each of these sources of 

variation can be determined by analysis of variance. In 

this study, the sampling design outlined earlier provides 

the basis for a three-level nested analysis of variance 

(Krumbein and Graybill, 1965, p. 215). 

The statistical model of variation is: 

Xijk=f.l +ai+{3ij+'Yijk, 

where Xijk=the kth measurement on the jth sample from 

the ith station where l:::;;k:::;;2, 1:::;;j:::;;4, and 1:::;;i:::;;43. Thus 

each measurement may be viewed as the sum of a grand 

mean (f.l) and deviations introduced by a particular station (aJ, sample ({3ij), and laboratory measurement 

('Yijk). The latter term is identified with laboratory error 

and the preceding term (f3i) may be called sampling 

error. A more extensive discussion of sampling models 

in geochemistry is given by Miesch (1967b). 

Analysis of variance was used to partition the total 

variance of each variable into three components; these 

components are assigned to variance among stations 

(s 0 ?}, among samples within stations (sr/), and among 

splits within samples (s 1

?) (table 3). The analysis is 

based on the assumptions that ai, {3ij, and 'Yijk are 

random variables with means of zero and variances of 

sa 2, sr/, and s,./ and that the variance components 

are additive: 

sT2=sa2+sr/+s,?' 

where sT2 is the total variance. Station variance (sa2) is a 

measure of geographic variation; sample variance (sr/) is 

a measure of sampling error; and the split variance, (s,.?), 

is a measure of laboratory error and includes effects due 

to grinding, splitting, and analytical error. 

Calculations for the analysis of variance were made in 

two stages. In the first stage, a two-level model consisting of 40 splits (20 samples) was used to compute estimates of the among-splits variance component (s/). 

In the second stage, another two-level model consisting 

of all 43 stations and 172 samples was used to compute 

estimates of the among-stations variance component 

(s 1/) and the sum of among-samples and amongTABLE 3. - Estimates of total variance, variance components in a 

three-level nested sampling design, and variance ratios for mineral 

and trace element composition of water-laid tuff 

[Significant differences (0.05 level) among stations were found for all variables. 

sa' ------, the ratio of among-stations variance to the variance of the (sfj'+s,_,')/4 

station mean) 

Mineral or trace element 

Log clinoptilolite ____ _ Log quartz _______ _ 

Log a-cristobalite ___ _ Log K-feldspar _____ _ Log glass ________ _ 

LogBa _______ ,_ __ LogBe __________ _ LogCu _________ _ 

Log Fe __________ _ LogGa _________ _ 

Log La __________ _ Log Mn _________ -

Nb ------------- Log Ph _________ _ Log Sr ______ - ___ _ 

LogTi __________ _ 

eU ____ - ___ ----- LogV __________ _ 

LogY __________ _ 

LogZr __________ _ 

Components of variance as percent of total variance 

Total among 

variance stations 

(percent)' 

0.466 

.044 

.167 

.047 

.041 

(ppm)' 

0.144 

.011 

.044 

.027 

.003 

.028 

.037 

23.5 

.011 

.135 

.034 

85.5 

.049 

.024 

.010 

(sa') 

79 

60 

38 

55 

69 

59 

29 

22 

53 

33 

34 

57 

35 

23 

64 

44 

35 

57 

51 

47 

among 

samples 

(sfj') 

21 

25 

58 

31 

27 

36 

28 

20 

38 

33 

24 

26 

24 

59 

33 

42 

<1 

36 

3 

<1 

among 

splits 

(s-/l 

<1 

15 

4 

14 

4 

5 

43 

58 

9 

34 

42 

17 

41 

18 

3 

14 

65 

7 

46 

53 

Variance 

ratios 

Vm 

15.05 

6.00 

2.45 

4.89 

8.90 

5.76 

1.63 

1.13 

4.51 

1.97 

2.06 

5.30 

2.15 

1.19 

7.11 

3.14 

2.15 

5.30 

4.16 

3.55 
ClO BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

splits variance components (s_i+s./). The amongsamples variance component (s_i) was determined by 

difference. Data on total crystalline material were used 

to estimate the variance components of glass in the 

analysis; glass has a highly censored frequency distribution and was computed as 100 minus total crystalline 

material when a glass hump was noted in the X-ray 

pattern. 

The estimates of variance components in table 3 show 

that two trace elements, Cu and Ph, have only slightly 

more than a 20 percent geographic (among-stations) 

variation; the remainder of the variation observed for 

these elements is due to sampling and laboratory error. 

The mineral cristobalite and the trace elements Be, Ga, 

La, Nb, and U (as eU) also exhibit weak geographic 

variation. All other minerals and the trace elements Ba, 

Fe, Mn, Sr, V, and Y have a large (>50 percent) 

geographic-variance component. 

Variation among samples (sampling error) in the 

design is equivalent to small-scale stratigraphic variation, since each station consists of four samples drawn at 

random from a stratigraphic section through the tuff. 

Thus the large (>50 percent) among-samples component 

of variance observed for cristobalite and Pb may be interpreted as being due to major variation up and down 

tuff sections. The variance component among splits 

(laboratory error) is especially large for Cu, eU, and Zr; 

for Be, La, Nb, andY it also approaches 50 percent of the 

total variance. 

GEOGRAPHIC VARIATION 

Regional patterns, or trends, are of special interest in 

this study because they may be used to help identify 

petrogenetic processes and to search for evidence of 

beryllium-fluorite and other mineralization (Lindsey, 

1975). The geographic distributions of each variable are 

shown in figures 5-26. Only presence or absence is noted 

for calcite, montmorillonoid clay, and fluorite (fig. 10) 

and Cr and Li (fig. 13). The distributions of all other 

variables are summarized by symbols for the arithmetic 

or geometric mean at each sampling station. 

The potential for definition of geographic variation 

was estimated by computing V m' the ratio of the 

among-stations variance to the variance of the station 

mean (table 3) (Connor and others, 1972). In general, 

V m values below about 1.00 indicate that the error in 

any station mean based on four samples is so high that 

comparisons among stations may be unreliable, and 

further sampling at each station is necessary if stable 

maps are to be constructed. Values of V m above 1.00 indicate greater potential for constructing stable maps. 

Although the sampling design was adequate to yield a 

V m ratio greater than 1.00 for all of the variables 

measured the ratios for Cu and Ph are near 1.00. 

Therefore there is some doubt whether any geographic 

variation of these two trace elements can be detected 

with the available data. Beryllium and Ga have 

somewhat higher V m ratios, but geographic variation of 

these elements may also be difficult to demonstrate. 

Clinoptilolite, quartz, potassium feldspar, glass, Ba, Fe, 

Mn, Sr, V, andY all show high ratios (~4.00), indicating 

a high potential for defining geographic variation. 

Polynomial trend surfaces provide an objective 

method for studying the nature of geographic variation. 

Methods of least-squares surface fitting are described by 

Krumbein and Graybill (1965, p. 319-340). Trend surfaces of degrees 1 through 5 were fitted to data for all 

variables. The model for the 5th degree polynomial is: 

x ii = f3oo+ f3w Ui+ /301 Vi + /3 2oUi 2 

+/3nUiVj+/3o2V/ + ... +f3o5V/, 

where xij is the predicted value of some variable observ~d 

in the sample collected at map coordinates ( Ui, Vj). xij 

has the structure Xij=xii+eij' where Xij is the observed 

value and eii is the residual. {300, {3 10 , ••• , f3o5 are the 

numerical coefficients chosen to minimize the variance 

of eij· For polynomials of lesser degree, the number of 

coefficients and terms is accordingly fewer. Thus it is impossible to partition the variance into two parts: (1) that 

due to a regional trend as expressed by a polynomial 

equation and (2) that due to local variation (the 

residual). The proportion of variance explained by the 

TABLE 4. - Sum of squares of the deviations from the mean and 

percent reduction of the sum of squares by polynomial surfaces of 

degree 1 through 5 fitted to data on mineral and trace element composition of 164 samples of water-laid tuff 

[Italic numbers indicate percent reduction of sum of squares above Howarth's (1967) limits for random data (linear, quadratic, and cubic surfaces only). Asterisks (*) indicate signifi- cant reduction of the sum of squares (0.05 level)] 

Cumulative percent reduction of sum of squares 

Mineral or Sum of Quadtrace element squares Linear ratic Cubic Quartic Quintic 

(percent)' 

Log clinoptilolite _____ 76.29 25* 38* 42* 47* 50 

Log quartz --------7.152 2 6 20* 24. 25 

Log a-cristobalite ____ 27.42 4* 6 12* 25* 26 

LogK-feldspar ______ 7.885 6* 17* 20 26 

Log glass - - - - - - - - - 6. 783 21* 30* 31 34 36 

(ppm)' 

LogBa ----------24.49 8* 13* 33* 38* 39 

Log Be ___________ 2.032 0 3 11* 14 16 

LogCu ----------7.063 0 6* 13* 17 21 

Log Fe ___________ 4.336 0 6* 19* 22 22 

LogGa ----------5.514 9* 12 19* 20 

Log La ___________ 5.678 19* 20 23 26 27 

LogMn __________ 6.147 2 7* 16* 20 21 

Nb __________ 4,084 13* 19* 30* 35* 35 

LogPb ----------2.040 3 8* 11 14 16 

Log Sr ___________ 22.08 2 13* 20* 27* '41* 

Log Ti ___________ 5.340 12* 15 19 

eU __________ 14,093 5* 11 14 24* 

LogV -----------6.735 2 12* 24* 31* 34 

LogY -----------4.764 40* 41 53* 54 54 

LogZr ___________ 1.518 18* 19 23 27 29 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH Cll 

T. 

12 

s. 

45' 

(/) 

UJ 

_J 

"-

:::. 

60 

;;; 40 

u. 

0 

a: 

~ 20 

:::. 

::l 

z 

112.45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

CLINOPTILOLITE, IN PERCENT 

0 N 

0 10 

0 15 

0 20 

0 30 

0 50 

070 

0100 

-30-

CLINOPTILOLITE, IN PERCENT 

lsopleth for clinoptiloli te, in percent 

(quartic surface, 4 7-percent reduction of sum of squares) 

R 9 W R. 8 W. 

0 SMILES 

0 5 KILOMETRES 

FIGURE 5. - Clinoptilolite content of water-laid tuff in the Keg Mountain area. 

trend should not exceed that due to the among-stations 

variance component listed in table 2. 

The relative strengths of the trends fitted to data on 

minerals and trace elements are presented in table 4. 

Stations 1 and 2 were omitted from data fitted to trend 

surfaces because they lie well outside the region covered 

by the remaining stations. Random effects can also give 

rise to weak trends, and Howarth (1967) considered that 

reductions in the percent sum of squares smaller than 

6.0, 12.0, and 16.2 for linear, quadratic, and cubic surfaces respectively can be taken as an upper limit for 

trends which may arise with random data. In the present 

study, a-cristobalite, Be, Cu, Ga, Mn, Ph, Ti, and eU 

show weak trends which could be ascribed to random effects. Either linear, quadratic, or cubic trends for the 

remaining variables account for a sufficiently large 

percentage reduction of the sum of squares so as to suggest that the trends are real. 

Another method of evaluating trend surfaces is by 

analysis of variance of the sums of squares (Krumbein 

and Graybill, 1965, p. 333-337). This method was applied, and the percent reduction values marked by 
C12 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

12 

S. 

45' 

II 

II 

I) 

(/ 

/j 

-7-;/ 

;j 

I;\\ 

/; ,, 1- \\ ,;.~ \\ 

-7 \\ 

• " " \\ 

II 

\I 

\I 

\1 

II 

II 

11 

II 

II 

II 

II 

II 

lll 

(J) 

Q 

Q 

; 

~~ II 

~,~~~~ -~ ·~ 

II 

" 

60 

Vl 

w 

_J 

"-:;;; 

<( 40 Vl 

lL 

0 

a: 

w 

:;;; "'

::> 

z 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

QUARTZ, IN PERCENT 

0 5 

0 

0 10 

015 

020 

030 

-to5 7 1 0 15 20 30 50 

QUARTZ, IN PERCENT 

Isopleth for quartz, in percent 

(cubic surface , 20 percent reduction of sum of squares) 

R 9 W. R. 8 W 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 6. - Quartz content of water-laid tuff in the Keg Mountain area. 

asterisks (*) in table 4 indicate those surfaces which 

result in a significant (0.05 level) reduction of the sum of 

squares. Both Howarth's (1967) limits and analysis of 

variance were used to select trend surfaces for mapping 

on figures 5-26. Only variables having surfaces which exceed Howarth's limits were considered for mapping; the 

highest degree surface which shows a significant reduction in the sum of squares was chosen as the best 

representation of the geographic trend. 

The geographic trends of certain minerals confirm the 

facies classification presented in figure 4. The constituents clinoptilolite (fig. 5) and glass (fig. 9) show 

strong trends that parallel the geographic distribution of 

zeolitic and vitric facies, respectively. Quartz (fig. 6) and 

potassium feldspar (fig. 8), on the other hand, show 

relatively weak trends whereas a-cristobalite (fig. 7) 

shows no significant trend at all; these major detrital 

and late-stage diagenetic minerals are not distributed as 

well-defined regional facies, but instead occur largely as 

local and discontinuous facies. 

The absence of any regional trend for beryllium (fig. 

12) is noteworthy. The very low reduction of the sum of 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C13 

T 

11 

s 

45' 

I 

I 

" ~:-:-;:;::::;::;:.~.~ 

I '\. 

Ul 

w 

-' "-

::;; 

<1: 

Ul 

u. 

0 

a: 

w 

m 

::;; 

::J 

z 

~ 

60 

40 

20 

\1 

II 

II 

II 

II 

I) 

., 

ti' 

/f 

I< 

il 

II 

I; 

112°45' 

EXPLANATION 

., 

( STATION GEOMETRIC MEAN 

4 ~) a-CRISTOBALITE , IN PERCENT 

0 N 

0 1.5 

0 2 

03 

05 

0 7 

010 

015 

1~ r~---~~ ()~ II l? 

39° 

1

\ ~~ N 1 1.5 2 3 5 7 10 15 20 30 50 

0 20 

0 30 

a-CRISTOBA LITE , IN PE RC ENT 

40' R. 10 w --'------- R 9 W R. 8 W 

0 5 MILES 

0 5 KI LOMETRES 

FIGURE 7 . - a -cristobalite content of water-laid tuff in the Keg Mountain area. 

squares for various trend surfaces fitted to data on beryllium in tuff of the Keg Mountain area indicates that no 

concentration attributable to mineralization is present. 

In the southern part of the Thomas Range, polynomial 

trend surfaces were used to define a pronounced beryllium halo around the Spor Mountain beryllium and 

fluorspar district (Lindsey, 1975). 

The trends for La, Nb, Y, and Zr (table 4; figs. 17, 19, 

25, and 26, respectively) are of interest because they exhibit some degree of similarity. All four trace elements 

have significant linear trends with an easterly increase in 

concentration. This information anticipates a finding of 

the next section, that these elements reflect an eastward 

increase in sphene and zircon. 

PETROGENESIS 

PROBLEMS IN PETROGENETIC INTERPRETATION 

Interpretation of mineralogical and chemical change 

from bulk rock analyses is complicated by several important considerations. All concentrations are reported as 

ratios, as either percent or parts per million, and 
C14 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

\1 

1\ 

I} 

d 

/J -7-:/ 

/( 

1/\\ 

I; ,, 

1- \\ -'}--7 \\ 

-r \\ 

" " " 1\ 

\\ 

\\ 

\\ 

II 

1\ 

II 

II 

II 

II 

1

ll 

r

""'"'-- ;' 45' --~~, , 

,\ 

II 

T. 

13 

S. 

/

II 

II 

II 

I{ 

II 

II 

~ II 

II 

/{ 

.S II 

;;oo " 

0~ 

\1 

" \1 

~~?;==~r= " " ~~ 

~ ::~ {( 

It 

1/ 

II 

/I 

1\ 

II 

II 

1\ 

,-y 

\__/ " \1 

Vl 

w 

_J 

ll. 

:;; 

II 

60 

<( 40 Vl 

u.. 

0 

oc 

w 20 

:;; "' 

::J 

z 

if 

/J 

It 

/i 

/{ 

II 

\\ 

\\ 

II 

172 samples 

Ol-J...-""""'"""""" N 5 

Geometric mean 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

POTASSIUM-FELDSPAR, 

IN PERCENT 

0 10 

0 15 

0 20 

0 30 

050 

p 

Stations with as much as 

20 percent plagioclase 

-/5-

\\ 

\\ 

POTASSIUM FELDSPAR , IN PERCENT 

lsopleth for potassium-feldspar, in 

percent (cubic surface, 17 percent reduction of sum of squares) 

39° 40'L_ __________ R--IO~W-,-. -L~~-L-----------------------R.-9 W ______ L_ ________________ --------R-.-8.-W~.----------~ 

0 5MILES 

0 5 KILOMETRES 

FIGURE 8. - Potassium feldspar content of water-laid tuff in the Keg Mountain area . Also shown is the occurrence of plagioclase. 

therefore variations in concentration of minerals and 

trace elements among samples of a rock type represent 

changes in the ratios as determined by (1) addition and 

removal, or (2) residual concentration and dilution of the 

various constituents. For example, a trace element may 

be present at unusually high concentrations in some 

samples of tuff because either it was actually added to 

the rock or other constituents were removed (residual 

enrichment). The problem is further complicated by 

changes in the bulk density and volume of the rock. For 

example, an increase in bulk density could be due either 

to exchange of light elements for heavier elements or to 

addition of constituents by filling of pore space. If compaction of the rock occurred during alteration, the bulk 

density could decrease without chemical change. These 

problems are discussed more fully in an earlier paper 

(Lindsey, 1975). 

Percentage and parts per million data also affect the 

interpretation of correlation among the minerals and 

trace elements. High positive correlation is usually interpreted as an indication of a common origin, whereas 

noncorrelation is an indication of independent origin. An 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C15 

50' 112 °45' ---,---

) I 

I ¥-'/.-;:--:=....:.~=:::.:.1 

"<j/ ! 

I 

100 

Vl 

w 

_J EXPLANATION 80 0.. 

:;;; 

<( GLASS, IN PERCENT Vl 

( u.. 0 N 0 60 

0:: 0 w 30 !Il 

:;;; 0 :;) 40 50 z 

20 070 

-20-

0 

39.1 

N 30 50 70 100 

GLASS, IN PERCENT 

lso pleth fo r glass, in percent (quadratic surface , 30 percent reduction of sum of squares) 

40'~· -- R 10 Vv R 9 W R 8 W 

0 5 Ml LES 

0 5 KILOMETRES 

FIGURE 9. - Glass content of water-laid tuff in the Keg Mountain area. 

important constraint upon such interpretations is the effect of closure (Chayes, 1960). Data on mineral and 

chemical constituents form two groups of variables, each 

of which sum to 100 percent under ideal conditions. In a 

two-component closed array, one component must increase as the other component decreases, inducing a 

perfect negative correlation. Similar but more complicated effects exist in multicomponent arrays such as 

the mineral and trace element composition of the tuff 

samples. Although there is currently no satisfactory 

solution to the problem of closure (Miesch, 1969), an attempt will be made in this study to identify its obvious 

effects on the covariation of major constituents. 

A PETROGENETIC MODEL 

A petrogenetic model has been proposed for the origin 

of water-laid tuff in the Thomas Range (Lindsey, 1975). 

Likewise, the origin of water-laid tuff at Keg Mountain 

can be stated in terms of a model which accounts for the 

various petrogenetic processes, or factors, that are 

believed to have been important in producing the 

observed mineral and trace element variation. A general 
C16 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

45'! 

_JL ' __ \ ___£__ 

'\ 

,, 

\ 

50' 

11...-----

c: 

5600,, 

- ) 

/ 

I ___ ./ 

\ 

11 2°45' 

\\ I 

\ c.:! ~ \ ~-= 

\~ ) ~--7 

::r·\''"""/ 

,, I 

:: II \ 

___ ) 

I 

'-, 

) 

( 

EXPLANATION 

Occurrence of minor: 

c Calcite 

M Montmorillonoid clay 

F Fluorite(< 1 percent) J " ·' ::'~~ ;,~,~t"''" "".'" I 

L ~.t j__ -----· 39°' 

4 0' t< I;) Vv R 9 W R 8 W 

0 

I 

0 

5MILES 

5 KILOMETRES 

FIGURE 10. - Occurrence of calcite, montmorillonoid clay, and fluorite in the Keg Mountain area. 

model may be stated as follows: 

where Xji is the value of the ith sample for the jth variable 

and is a linear function of p common factors (F). Each 

factor (F) operates with an intensity of the coefficients 

Cl.ji, aj2 , . .. , ajp, and Uji is a unique factor accounting 

for the remaining variation in the data (Cooley and 

Lohnes, 1962, p. 160). 

The identity of some of the factors in the general 

model can be anticipated from information already 

presented on the petrography and the mineral and trace 

element content of the water-laid tuff. Processes of erosion and sedimentation obviously were active in forming 

the detrital facies of crystal-rich tuff; and the processes 

of zeolitization and potassium feldspar diagenesis are 

known to have been responsible for corresponding zeolite 

and potassium feldspar facies in the tuff (fig. 4). The 

mineralization-related trace elements Be, Ga, and Y are 

present in lower concentrations in the water-laid tuff of 

Keg Mountain (table 2) than in the Thomas Range 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA. UTAH C17 

T 

12 

s 

45' 

I 

\ 

v 

I 

\ 

\\ 

I 

It 

I 

I 

\ ,/ ··- -----;- _/ .,, lj 

,, 

,, 

I 

'I 

N 10 15 20 

'I 

112"45' 

--,---------, 

STATION GEOMETRIC MEAN 

BARIUM, IN PPM 

0 30 

0 50 

0 70 

0 100 

0 150 

0 200 

0 300 

0 500 

0700 

01000 

-300-

BARIUM , IN PPM 

Isopleth for barium, in ppm (quartic 

surface, 38 percent reduction of 

sum of squares) 

------------

R 10 'lv R 8 W 

0 5 MILES 

0 5 KI LOMETRES 

FIGURE 11. - Barium content of water-laid tuff in the Keg Mountain area. 

(Lindsey, 1975), suggesting that a mineralization factor, 

if present, operated only at a very weak intensity. 

R-MODE FACTOR ANALYSIS 

Petrogenetic parameters (a's, F's) in the model may 

be defined by a method known as R-mode factor 

analysis; detailed discussions of factor analysis were 

presented by Harman (1960), Cooley and Lohnes (1962, 

p. 151-172) and Miesch, Chao, and Cuttitta (1966). The 

method was used to develop a model which would account for the variation of physical properties, 

mineralogy, and chemical composition observed in 

water-laid tuffs of the Thomas Range (Lindsey, 1975), 

and the account in that report is repeated here. The 

method involves four major steps: 

1. An m X m correlation matrix (R-matrix) is computed, where m is the number of measured variables. 

2. The R-matrix is solved for m roots (eigenvalues) 

and the number of large roots (p) is selected as the 

minimum number necessary to account for a major part 

of the total variance in the system. 

3. A provisional coefficient matrix (the factor 
C18 

I II 

,, 

~ ,, 1/ 

' /j 

~ «·::/-

j( 

/; 11 

/j \\ 

"" 1\ 

L /-"" 1\ .r"" \\ 

\\ 

r 

"' 

I \ \ 

T. ~:,i, l 

1~ 1 . ~\ ~ 

\I 

II 

II 

II 

~~~-- \1 

45' - --~~"" , .',\ ~ 11 

~ 

\I 

II 

II 

BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

_-::r- / \\ 

\\ 

I! 

II 

1'. 

II 

"' 1! 

/1 " 

II 

1\ 

II 

II 

II 

II 

!; 

,, 

/J 

/f 

!I 

II 

/I 

112°45' 

EXPLANATION 

STAT ION GEOMET RIC M EAN 

T. 

13 

s 

0 

0 

If) 

w 

_J 

"-

:;; 

<( 

If) 

"-

0 

a: 

w 

CD 

:;; 

::;) 

z 

60 

40 

20 

0 N 4 5 6 8 9 

BERYL L IUM, IN PPM 

R 9 W. 

5 MILES 

5 KILOMETRES 

F IGURE 12. - Beryllium content of water-laid tuff in the Keg Mountain area. 

loadings) used to define the principal components is 

computed. 

vs/sk2 

BERY LLIUM, IN PPM 

0 N 

0 4 

Q5 

06 

0 

Qs 

R 8 W. 

4. A final coefficient matrix defined by the V arimax 

criterion (Harman, 1960, p. 301) is derived from the 

factor-loadings matrix. The Varimax loadings are arbitrarily accepted as the a-coefficients in the model. 

where Sjk• the covariance, is computed by 

N 

The data matrix, Xij, is N by m in size where N is the 

number of samples and m is the number of variables. 

The degree of linear association between two variables j 

and k is measured by the correlation coefficient: 

~ X .. X.k 

'1 ' i= 1 

N 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C19 

T. 

12 

S. 

45' 

17 

" II 

II 

II 

II 

II 

II 

II 

II ~ ll "'I eli 

3 II 

II 

II 

II 

II 

II 

u. 

0 

cr: 

w 

~ z 

0 

0 

50' 

172 samples 

N 50 70 100 150 

LITHIUM, IN PPM 

5 Kl LOMETRES 

5 MILES 

112°45' 

EXPLANATION 

•6 Sampling station and station number 

Cr Dete table ~ 5 ppm chromium 

Li Detectable 2 50 ppm lithium 

FIGURE 13. - Chromium and lithium content of water-laid tuff in the Keg Mountain area. 

and sf , the variance, is computed by 

N 

~X .2 

I) 

i== 1 

------------------------- -xjz 

N 

Linear covariation between the variables is expressed by 

the m X m matrix of correlation coefficients, or Rmatrix. A correlation coefficient of r == 1.0 indicates 

perfect linear interdependence, r == 0 indicates no linear 

dependence, and r == -1.0 indicates perfect inverse 

linear dependence. Because the genetic significance of 

the correlation coefficients is subject to the restrictions 

of closure, the correlation coefficients between the 

petrologic variables in this study must be viewed as 

descriptive measures of covariation. 

Factor analysis commonly begins with principal components extraction. Such analysis may be understood in 

terms of m-dimensional space, where m is the number of 
C20 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

12 

s 

T. 

13 

S. 

;j "' 1/\\ 

I; \\ 

1- \\ 

-.<-

4-~ \\ 

-7 \\ 

,, 

1/ 

II 

lj 

\\ 

\\ 

\\ 

II 

II 

\I 

II 

I! 

I! 

I 

II 

II 

II 

II 

!I 

II 

II 

.s il 

""'o ~ " 

" 

II 

II 

li 

II 

II 

II 

II 

II 

II 

\_/'\\ 

(/) 

UJ 

_j 

"-:;; 

<t 

(/) 

u.. 

0 

a: 

UJ 

co 

:;; 

:::J 

z 

80 

60 

40 

20 

\1 

1\ 

1\ 

II 

II 

II 

\1 

I! 

" II 

II 

It 

lj 

It 

II 

II 

,, 

\I 

1\ 

II 

" 

/.1 

/j 

lj 

5 

50' 112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

COPPER , IN PPM 

0 1.5 

\\ 

\\ 

\\ COPPER, IN PPM 

R. 8 W 

0 5MILES 

0 5 KILOMETRES 

FIGURE 14. - Copper content of water-laid tuff in the Keg Mountain area. 

original variables. Each variable defines a dimension in 

them-space and the position of each of N samples can be 

plotted in terms of the m coordinates. Presumably theN 

samples will tend to cluster as an elongate swarm of 

points in the m-space. The object of the principal component analysis is to find new uncorrelated variables 

which measure what the original variables have in common and which produce a maximum variance among 

samples. The first principal component is located along 

the major axis of the sample cluster so that the sample 

projections onto it are maximized. This axis is a new 

variable which describes the largest possible proportion 

of the variance. A second axis is located at right angles to 

the first so that the next largest proportion of variance is 

explained, and so on. As many as m axes are possible, 

but some number p<m will commonly account for most 

of the variance. The variances of the principal components are equal to their eigenvalues. The principal components, following standardization to unit variance, are 

related to original variables by a new set of coefficients, 

the factor loadings. 

If some number p <m axes accounts for most of the 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C21 

T 

11 

s 

12 T.r 

s. 

l~, " "'~~"'- \\ I 

45' -~

~ II 

II 

I! 

II 

\I 

60 

CJ) 

UJ 

__J 

0.. 

:> 

<{ 40 CJ) 

u.. 

0 

a: 

UJ 20 CD 

:> 

::J 

z 

II 

/j 

/j 

it 

II 

II 

\\ 

1\ 

\\ 

172 samples 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

IRON, IN PPM 

0 3000 

0 5000 

0 7000 

0 10,000 

015,000 

-7000-

II 

\I 

0 1000 2000 5000 1 0,000 20,000 lsopJeth for iron , in ppm (cubic surface , 19 percent reduction of sum 

of squares) \1 

\1 

1\ 

1500 3000 7000 15,000 

IRON, IN PPM 

0 5 MILES 

0 5 KI LOMETRES 

FIGURE 15. - Iron content of water-laid tuff in the Keg Mountain area . 

variance (that is, the N points occur largely in pdimensional space), it is often desirable to rotate the p 

axes so that they may be more readily interpreted. Rotation may be done in any manner which facilitates interpretation, but the most commonly used objective 

method of rotation utilizes the Varimax criterion 

(Harman, 1960, p. 301). The Varimax criterion requires 

that the variance of the squared factor loadings be maximized and this tends to simplify the resulting factors by 

yielding large positive or negative loadings for only a few 

variables on each factor. The rest of the loadings in each 

factor tend to be near zero. The resulting close association of a few variables with the Varimax factors will allow them to be more readily interpreted. The V arimax 

loadings specify the relationship of the original variables 

to the Varimax axes (factors); the axes may be used as a 

reference system to plot the original variables as vectors. 

If the sum of the first p eigenvalues of the R-matrix approaches m, the cosines of the angles between vectors in 

the p-space will approximate the original correlation 

coefficients. 

Because only p<m axes are retained in the model, less 
C22 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

12 

s. 

,, 

\\ ,, 

" \\ ,, 

\I 

1\ 

II 

II 

\1 

112"55' T- -~~-

\\ 

1\ 

II 

1\ 

II 

II 

II 

,, 

•.' 

•I 

If 

172 samples 

112"45' -------'---'----,--- ------, 

EXPLANATION 

STATION GEOMETR IC MEAN 

GALLIUM, lN PPM 

0 21 (20.0-22.4) 

0 24 (22.4- 25.2) 

0 27 (25.2-28 .2) 

0 30 (28.2-31.7) 

0 34 (31.7-35.5) 

R9W R. 8 W 

0 5MILES 

0 5 KILOMETRES 

FIGURE 16. - Gallium content of water-laid tuff in the Keg Mountain area. 

than 100 percent of the total variance will be explained. 

The proportion of variance explained for each variable in 

the factor solution is termed its "communality" (h2 ). 

Geometrically, the square of the vector length of the 

original variable plotted in the p -space of the factor solution will be h2 • The remaining, unexplained variance 

(1-h2) is termed the unique component; it consists of 

unrecognized factors and laboratory error. 

FACTOR ANALYSES OF THE WATER-LAID TUFF DATA 

Correlation coefficients were calculated between all 

minerals and trace elements for which more than 30 percent of the data was above the detection limit (table 5). 

In addition, the variable "glass" was included because it 

proved to be helpful in the interpretation. All other 

variables were not included in the analysis because their 

frequency distributions were more than 30 percent censored. As before, a log transformation was made on all 

variables except Nb and eU prior to calculation of the Rmatrix. 

A principal components analysis of the data was then 

performed on a 19Xl9 R-matrix with unities in the 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C23 

I 

I 

13 

T Ll ~~"'=="or--= ~ i1 ~ L 

s --7"' :: <:::J _____:) 

I' II I n~ II \ 

::~ 

172 samples 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

LANTHANUM, IN PPM 

0 N 

0 50 

0 70 

0100 

0150 

-50-

:: \? (~ 

39°,' -------"~ _ 

N 50 70 100 150 200 300 500 700 

LANTHANUM , IN PPM 

Isopleth for lanthanum, in ppm 

(linear surface, 19 percent reduction of sum of squares) 

-- _______________ _i _______________ __ __ .J......____ ____ _ 

40' - R 10 W R. 9 W R 8 W 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 17. - Lanthanum content of water-laid tuff in the Keg Mountain area. 

diagonal. The p largest principal components to be 

preserved for rotation and interpretation were selected 

by examining the magnitude of the eigenvalues and the 

communalities for various solutions. The eigenvalues, 

which measure the proportion of the total variance explained by each principal component, are plotted in 

figure 27 for the 10 largest principal components (factors). Visible declines occur after the second and sixth 

eigenvalues, suggesting that from two to six principal 

components might be considered for rotation. Various 

experiments were conducted by Varimax rotation of two 

through six axes and the communalities of all variables 

for each solution were compared (table 6) with the 

percentage of nonerror variance as estimated in table 3. 

Study of the communalities for each solution led to 

selection of a five-factor model as the most suitable 

choice. Communalities of some elements (La, Nb, and 

Zr) already exceed the nonerror variance in the threefactor model, but the communalities for many other 

variables (a-cristobalite, potassium feldspar, Be, Ph, 

and Sr) remain quite low until four or five components 

are rotated. When six components are rotated, the com-
C24 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

60 (/) 

w 

_J 

<l. 

:;; 

<( 40 Ul 

lL 

0 

a: 

w 20 al 

:;; 

::J 

z 

EXPLANATION 

STATION GEOMETRIC MEAN 

MANGANESE, IN PPM 

0 200 

0 

0 

300 

500 

1 00 150 200 300 500 700 1000 

MANGANESE, IN PPM 0700 

R. 9 'lv R 8 W 

0 5M ILES 

0 5 Kl LOMETRES 

FIGURE 18. - Manganese content of water-laid tuff in the Keg Mountain area. 

munalities of 10 elements exceed the nonerror variance; 

the increase of the communality for eU from 36 to 68 percent in the face of only 35 percent "real" or nonerror 

variance indicates that the six-factor solution is "explaining" variance in eU that is actually error in large 

part. The five-factor model appears to be more desirable 

than the four-factor model; the communalities of acristobalite and potassium feldspar are much higher in 

the five-factor model; other communalities are likewise 

improved while the number of elements with excessively 

high communalities does not increase. The excessively 

high communality of Zr throughout all experiments is 

bothersome, although as will be shown shortly, the location of Zr with respect to the factor axes results in a 

reasonable interpretation. The five-factor model accounts for 72 percent of the total variance in the normalized data. 

The five principal components were rotated by the 

Varimax method and the loadings of each variable on 

the five Varimax factors are shown in table 7; the 

Varimax loadings may be accepted as the a-coefficients 

of the petrogenetic model. Each factor (F1, F 2 ..• Fp) 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C25 

T. 

12 

s 

45'-

T. l 13 

S. ~;;~ 

,. 

li IIG 

II 

II 

,, 

112°45' 

EXPLANATION 

STATION ARITHMETIC MEAN 

NIOB IUM, IN PPM 

0 <20 

0 20-25 

0 25- 30 

030-35 

-30-

1\ 

,, 

II 

20 25 30 35 40 45 50 

N IOBIUM, IN PPM 

Isopleth for niobium, in ppm (quartic 

surface, 35 percent reduction of 

sum of squares) 39° 

40'L_ _________ R--10~~-,--L--L--L-----------------------R--9W----~---------------------------R-.-8.-W~------------' 

0 5 M I LES 

0 5 KILOMETRES 

FIGURE 19. -- Niobium content of water-laid tuff in the Keg Mountain area. 

can be interpreted from the association of variables 

which load most heavily on it. The factor interpretations 

are as follows: 

Factor I (F1 ): Concentration of major detrital 

minerals. Barium, Fe, V, Ti, Cu, and quartz, and to a 

lesser extent Mn, Zr, and potassium feldspar have high 

positive loadings on factor I. 

Factor II (F2 ): Initial diagenesis (zeolitization). 

Clinoptilolite and Sr have high positive loadings; glass 

and to a lesser extent eU have negative loadings. 

Factor III (F3 ): Concentration of minor rare earthbearing detrital minerals. Lanthanum, Nb, Y, and Zr 

have positive loadings on factor III. 

Factor IV (F4 ) : Late magmatic concentration of trace 

elements(?). Lead, Ga, Be, and to a lesser extent Mn and 

Nb have positive loadings on factor IV. 

Factor V (F5 ): Advanced diagenesis (feldspathization). Cristobalite and potassium feldspar have positive 

loadings on factor V. 

Factor I, representing concentration of major detrital 

minerals, clearly reflects the processes of erosion and 

sedimentation whereby detrital quartz, feldspar, and 
C26 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

~--~--------------l~l~2r~=5'------ , 

Geometric mean 

100 

80 EXPLANATION (/) 

w 

...J 

a.. STATION GEOMETRIC MEAN 

/ ::;; 

<( 60 

(, (/) 

u.. 172 samples 

LEAD , IN PPM 

0 20 

0 

__ ) I a: 

w 40 0 30 

<Il 

::;; 

::::> 

z Qso 20 

N 20 30 50 70 1 00 

LEAD , IN PPM 

R 10 W R 9 W R. 8 W 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 20. -- Lead content of water-laid tuff in the Keg Mountain area. 

iron oxides are concentrated to form the detrital facies 

described earlier. Tuff samples which have high concentrations of quartz, potassium feldspar, Ba, Cu, Fe, 

Mn, V, Ti, and Zr and thus would be expected to score 

high on factor I include those of the detrital facies. These 

trace elements are abundant in many samples, indicating that the influence of detrital processes in the 

water-laid tuff was widespread. 

The association of trace elements with factor I is 

probably due to substitution of some of these elements 

(Mn, Ti, and V) in magnetite (Deer, Howie, and Zussman, 1962, v. 5, p. 68-77). As much as 2 percent 

magnetite and hematite was recovered from samples 

with high concentrations of factor I trace elements. 

Perhaps some of the trace elements are also present in 

unusually large amounts of other minerals, such as feldspar, barite, and zircon. No barite has been identified in 

heavy mineral separates, however, and it seems more 

likely that Ba may reside in detrital plagioclase. 

Concentrates of magnetite and hematite from tuff sam-
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C27 

50' -· -

\\ ./ II 11 \l 1\ 

\l, // 

\l If 

\\ / /- ., It (Jfl' 

T. 

12 

s. 

Vl 

w 

_J 

a. 

:;;; 

<( 

Vl 

lL 

0 

a: 

w 

OJ 

:;;; 

::J 

z 

60 

40 

20 

II II I\ il/ 

'' _/f!- ao- (\.f..v~~ 50 

II 

!I 

\\ 

1\ 

172 samples 

0

/ EXPLANATION 'lj 

STATION GEOMETRIC MEAN 

STRONTIUM, IN PPM 

0 50 

0 70 

0 100 

0 150 

0 200 

0 300 

0 500 

0700 

01000 

-300- ,.[_ 70 100 150 200 300 500 700 1000 1500 lsopleth for strontium, in ppm 

(q uintic surface , 41 percent 

STRONTIUM, reduction of sum of squares) IN PPM 

40' R R 9 W R. 8 W 10 W 

0 5 MILES 

0 5 KI LOMETRES 

FIGURE 21. - Strontium content of water-laid tuff in the Keg Mountain area. 

ples rich in these minerals were analyzed by 

spectrographic methods to determine the extent of association of factor I trace elements with the iron oxides. 

High concentrations of Co (as much as 50 ppm), Cr (as 

much as 200 ppm), Cu (7-15 ppm), Mn (3,000 ppm), Ti 

(7,000-15,000 ppm), V (300-500 ppm), and Zn (700 ppm) 

were found in four magnetite concentrates. A single concentrate of hematite showed generally lower concentrations of these elements, except Cu and Zn, which showed 

the same degree of concentration as in magnetite. These 

results indicate that the high loadings of Cu, Mn, Ti, 

and V on factor I are due in part to their presence in 

magnetite. Given sufficiently sensitive analytical 

methods, the elements Co, Cr, and Zn might also be expected to associate with factor I. 

Factor II, the factor for initial diagenesis (zeolitization), involves the alteration of glass to clinoptilolite and 

accounts for the widespread distribution of the zeolitic 

facies in the tuff. The inverse relationship between glass 

and zeolite in factor II illustrates the effect of closure, 
C28 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

T. 

13 

S. 

II 

II 

II 

.s /1 ""o II 

1~ ~~ :G 

II " 

112'45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

TITANIUM, IN PPM 

0 500 

0 700 

0 1000 

0 1500 

0 2000 II 

II 

1\ 

II 

II 

1\ 

200 500 1000 2000 5000 300 700 1500 3000 03000 

3 9' TITANIUM, IN PPM 

0'L-----------~--_L~~~-----------------------------L------------------------~~~i----------~ 

1\ 

\\ 

R 10 W R. 9 W R. 8 W. 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 22. - Titanium content of water-laid tuff in the Keg Mountain area. 

but nevertheless is understandable in that it corresponds 

to the alteration of vitric to zeolitic tuff. The relative 

concentrations of Sr and U (as eU) in the tuff were increased and decreased respectively as zeolitization occurred. 

Factor III is interpreted as the concentration of minor 

detrital minerals. The association of the trace elements 

La, Nb, Y, and Zr with factor III indicates that the concentration process involves selection of rare earthbearing minerals. Mineral separates were prepared from 

tuff samples which contained high concentrations of 

these elements and sphene and zircon were found to be 

abundant relative to other tuff samples. Substitution of 

numerous elements, including rare earths, in sphene has 

been reported (Deer and others, 1962, v. 1, p. 69-76). 

Spectrographic analyses of two sphene concentrates 

show high concentrations of La (1,500-3,000 ppm), Nb 

(500- 1,500 ppm), Ti (>2 percent), and Y (1,500-7,000 

ppm). Other rare earths were also found, including Ce 

(3,000-7,000 ppm), Dy (300-1,500 ppm), Er (150-1,000 

ppm), Gd (300-1,500 ppm), Ho (70-300 ppm), Lu (as 

much as 70 ppm), Nd (3,000-7,000 ppm), Pr (500-2,000 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C29 

II 

II 

~ II " "'o ~,, " 

c=;;-- ,, 

Ul 

w 

_J 

Cl. 

:;;; 

< Ul 

u.. 

0 

a: 

w 

aJ 

2 

:::J 

z 

\1 

II 

\1 

II 

II 

II 

:• 

II 

II 

II 

\1 

II 

If 

1 

112'45' 

EXPLANATION 

STATION ARITHMETIC MEAN 

EQU IVALENT URANIUM, IN PPM 

0 10-20 

0 20-30 

0 30-40 

10 20 30 40 50 60 70 

EQUIVAL ENT URANIUM , IN PPM 0 4o- 5o I 

_________ _L_ _ _j 

R 9 W R 8 W 

0 5 MI L ES 

0 5 KILOMETRES 

FIGURE 23. - Equivalent uranium content of water-laid tuff in the Keg Mountain area. 

ppm), Sm (700-2,000 ppm), Tm (as much as 100 ppm), 

and Yb (150-500 ppm); these elements were not included 

in the direct reading spectrographic analysis of the tuff 

samples. These results confirm that the high loading of 

La, Nb, Y, and Zr on factor III is due in part to the concentration of sphene and zircon. 

Heavy minerals in the underlying volcanic rocks were 

examined also, in order to determine which rock units 

might be likely sources of the sphene and zircon. Abundant sphene was recovered from rhyolitic welded ashflow tuff in the central part of the Keg Mountain area, 

and abundant pink zircon, similar to some observed in 

the water-laid tuff, was recovered from the rhyolite of 

Keg Mountain in the southeastern part of the area. 

These rock units underlie the tuff throughout the eastern 

half of the Keg Mountain area and could be the source of 

the easterly concentration of the trace elements La, Nb, 

Y, and Zr. 

Another aspect of interpretation is the possibility of 

systematic laboratory error among the trace elements associated with factor III. The communalities of La, Nb, 

and Zr are all substantially in excess of the nonerror 
C30 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

I 

I 

i'\ if 

If 

" 

~~ v" \\ 

1\ 

" \I 

II 

11 

" II 

II 

II 

0 

i! 

!i 

,, 

II " 

I! 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

VANADIUM, IN PPM 

0 N 

0 10 

015 

0 20 

030 

-10-

N 10 15 20 30 50 

VANADIUM , IN PPM 

lsopleth for vanadium, in ppm 

(quartic surface, 31 percent 

reduction of sum of squares) 

R 10 W R 9 W R 8 W 

0 5 MILES 

0 5 Kl LOMETRES 

FIGURE 24. - Vanadium content of water-laid tuff in the Keg Mountain area. 

variance (table 6), indicating that factor III "explains" 

considerable error. The specific cause of laboratory error 

is unknown. The fact that Y is also included among the 

trace elements associated with factor III (the communality of Y does not exceed the nonerror variance) 

and that all of these elements show similar geographic 

trends indicates that the association is real and not 

merely an artifact. 

Factor IV is the most difficult to interpret. The high 

positive loadings of Ga and Be, and to a lesser extent Mn 

and Nb, at once suggest that factor IV represents the effeet of beryllium mineralization on the tuff. Lead was 

not concentrated by mineralization of tuff in the Thomas 

Range (Lindsey, 1975), however, and its high loading on 

factor IV suggests that some process other than beryllium mineralization is responsible. Another feature of 

tuff near areas of beryllium mineralization is the high 

degree of skewness shown by the frequency distribution 

for beryllium; nearly half of the samples of tuff that were 

studied from the Thomas Range contain 10 ppm or more 

Be and a few samples were found to contain more than 

100 ppm Be (Lindsey, 1975). In contrast, the berllium 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C31 

T. l 

121 s. 

(J) 

w 

.J 

0.. 

:::;: 

<l: 

(J) 

u. 

0 

a: 

w 

:::;: "' 

:J 

z 

'I 

.I 

II 

II 

/j 

,, 

" II 

,, 

\I 

') 

60 

40 

20 

0 

112°45' 

EXPLANATION 

STATION GEOMETRIC MEAN 

YTTRIUM, IN PPM 

0 N 

0 20 

030 

050 

-20-

N 20 30 50 70 1 00 

Isopleth for yttrium, in ppm (cubic I 

surface , 53 percent red uction of 

YTTRIUM, IN PPM sum of squares) 

_____ _L_. _I 

R 10 W R 9 W R 8 W 

0 5 MILES 

0 5 KILOMETRES 

FIGURE 25. - Yttrium content of water-laid tuff in the Keg Mountain area. 

concentration in water-laid tuff of the Keg Mountain 

area never exceeds 10 ppm and the frequency distribution for Be is skewed very little (fig. 12). Hence comparison of frequency distributions for beryllium indicates that effects of beryllium mineralization at Keg 

Mountain are weak or absent. 

An alternative interpretation of factor IV is that it 

represents concentration of trace elements in the original 

rhyolite magma. The rhyolites of the Thomas Range, 

which might approximate the composition of the original 

magma, are well known for the occurrence of topaz, 

beryl, and bixbyite in lithophysae (Staatz and Carr, 

1964, p. 102-106); these minerals indicate a tendency 

toward concentration of F, Be, and Mn in the vapor 

phase of the magma. Spectrographic analyses of 

rhyolites in the western Utah beryllium belt show a 

general enrichment of Be (3-20 ppm), Ga (15-50 ppm), 

Nb (30-100 ppm), Pb (40-60 ppm), and Sn (as much as 

50 ppm) (Shawe, 1966, table 3); older, less silicic rocks 

from the same area usually contain notably less of these 

elements. Thus the association of Pb-Ga-Be, and to a 

lesser extent Mn and Nb, could be interpreted as due to 
C32 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

w "' __J 

,_ 

:;; 

<t 

"' "-

0 

a: 

w 

co 

:;; 

::;) 

z 

\>-~---

60 

40 

20 

\\ 

,, 

1\ 

,, 

,, 

II 

I! 

\I 

1\ 

II 

,, 

" 

1\ 

II 

II 

II 

1 

172 samples 

112 '45' 

(__ EXPLANATION 

S STATION GEOMETRIC M EAN 

t ZIRCONIUM , IN PPM 

0 84 (79-89) 

0 94 (89-100) 

0 106 (100-112) 

0 119 (112-126) 

0 133 (126- 141) 

0 150 (141-158) 

0 168 (158- 178) 

0 188 (178-200) 

0 211 (200-224) 

-106-

0 75 84 94 106 119 133 150 168 188 211 237 

ZIRCONIUM, IN PPM 

Isopleth for zirconium, in ppm 

(linear surface, 18 percent reduction of sum of squares) 

R 9 W. R 8 W. 

0 5MILES 

0 5 Kl LOMETRES 

FIGURE 26. - Zirconium content of water-laid tuff in the Keg Mountain area. 

concentration in the more silicic, vapor-rich portions of a 

parent rhyolite magma. 

Factor V is the association of cristobalite and potassium feldspar and represents the final stage of 

diagenesis. The concentration of trace elements was not 

affected by advanced diagenesis. 

CONCLUSIONS 

EROSION AND SEDIMENTATION 

A petrogenetic model derived by R-mode factor 

analysis of mineral and chemical data shows that concentration of detrital minerals by erosion and sedimentation is the dominant process in controlling the distribution of many metallic elements in the water-laid 

tuffs of western Utah. Detrital heavy minerals containing AI, Fe, Mg, Mn, Ti, and Zr are concentrated mainly 

in local areas (1-2 mi, 1.6-3.2 km) of tuff in the southern 

part of the Thomas Range (Lindsey, 1975). In the Keg 

Mountain area, a detrital assemblage of heavy minerals 

containing Fe, Cu, Mn, Ti, V, and Zr is associated with 

abundant quartz and feldspar derived from older 

volcanic rocks. This detrital facies also forms local (1-2 
TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C33 

TABLE 5. - Correlation coefficients based on analyses of 172 samples of water-laid tuff from the Keg Mountain area 

Log 

Log Log a-cris- K- Log 

quartz tobalite feldspar glass LogBa Log Be LogCu Log FP Log Ga Log La Log Mn Nb Log Pb Log Sr Log Ti eU Log V LogY Log Zr 

Log clinoptilolite ____ -0.22 -0.02 -0.18 -0.78 -0.28 

.61 

.24 

.50 

.02 

-0.30 

.13 

.19 

.19 

.29 

-0.21 

.37 

.18 

.25 

.12 

-0.47 -0.51 -0.13 .05 

.00 

.08 

.03 

-0.52 .38 

.24 

.36 

.34 

-0.22 -0.17 0.57 -0.35 -0.37 .12 

.00 

.25 

.36 

-0.08 .46 

.21 

.30 

-0.19 .02 

-.09 

.00 

.24 

-0.33 .21 

.16 

.27 

.21 

Logquartz ___________ .21 .67 -.15 .60 .16 -.20 -.05 .20 .47 Log a-cristobalite _ _ _ _ _ _ _ _ _ _ _ _ .40 -.18 .27 .08 .01 

-.01 

.28 

-.04 -.13 .23 LogK-feldspar _____ ____ _____ _____ -.11 .54 .21 -.03 .01 .45 Log glass __________________________ _ .20 .50 .24 -.50 .11 -.09 

.30 .36 -.06 -.07 .19 .77 .07 .67 .19 

-.01 .45 .27 .25 -.16 .18 .18 .07 -.02 

.19 .37 .13 .16 .07 .48 .16 .50 .13 

.34 .65 .16 .14 .00 .88 .30 .72 .10 

.20 .53 .38 .47 -.26 .34 .36 .25 .12 

.50 .12 .27 .46 .51 .34 .43 -.02 

.23 .24 .00 .45 .04 .30 .06 .22 .03 -.26 .32 -.02 

LogTi _____________ ------------------- __________ ------------ _ __ _ _ _ _ _ _ _ __ ___ _____ _____ _ ____ .20 .76 .17 .76 

eU ------------------------------------------------------------------------------------------- -~2 ~4 .M LogV ---------------------------------------------------------------------------------------------- .00 .42 LogY --------------------------------------------------------------------------------------------------- -~ 

They might present serious problems in geochemical ex100 ploration for heavy metal and rare earth deposits, 

however, and the evaluation of trace element anomalies 

in tuffs should take into consideration the effect of erosion and sedimentation on trace element concentration. 

8 

w 7 ::J 

....J 

<( 

~ 6 w 

(.!) 

w 5 

4 

3 

2 

II Ill IV v VI VII VIII IX X 

PRINCIPAL COMPONENT 

80 

w 

u 

z 

<( 

a: 

<( 

60 > 

....J 

<( 

1-

0 

ILL. 

0 

40 1-

z 

w 

u 

a: 

w 

a... 

w 

> 20 1-

<( 

....J 

::J 

~ 

::J 

u 

FIGURE 27. - Eigenvalues and cumulative proportion of total 

variance explained by the first 10 principal components. 

mi, 1.6-3.2 km) concentrations in the tuff. A second 

detrital assemblage consists of the heavy minerals 

sphene and zircon; these are defined by a regional 

eastward increase in the abundance of La, Nb, Y, and 

Zr. 

The effects of erosion and sedimentation on concentration of various heavy elements in the water-laid tuffs 

should pose no threat to defining halo effects of beryllium and fluorite mineralization in tuffs of western Utah. 

DIAGENESIS 

Diagenetic alteration of the water-laid tuff in the Keg 

Mountain area was approximately the same type as that 

which affected the tuff in the Thomas Range. Factor 

analysis of mineral and chemical data showed that three 

stages of diagenetic alteration could be distinguished in 

tuff of the Thomas Range (Lindsey, 1975). The initial 

stage involved alteration of glass to clinoptilolite, accompanied by relative loss of alkalis, (N azO, K20, and Rb) 

eU, F, and Mn, and relative gain of Sr and MgO. Thesecond stage involved formation of additional clinoptilolite 

as well as potassium feldspar and quartz. The concentraTABLE 6. - Communalities (in percent) for two-, three-, four-, five-,. 

and six-factor Varimax solutions, compared to the percent of nonerror variance 

[Italic numbers indicate communalities which exceed the nonerror variance] 

Number of rotated factors Nonerror ____________ variance 

Log clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ 60 Log quartz _____ _ _____ _____ 57 

Log a-cristobalite __ -· _ _ _ _ _ _ _ _ _ 15 Log K-feldspar _ _ _ _ _ _ _ _ _ _ _ _ _ _ 43 Log glass _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 66 

Log Ba _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 76 

Log Be------------------- 27 LogCu ------------------ 42 LogFe ___________________ 00 

LogGa _____ ---------- ___ 59 

Log La------------------- 22 LogMn ------------------- 52 Nb ____ ---------- _______ 41 

Log Ph ______ ------------ 29 Log Sr _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 38 

LogTi ------------------- 82 eU --------------------- 33 

LogV ------------------- 68 LogY ------------------- 17 Log~------------------- u 

68 

64 

22 

50 

69 

76 

41 

42 

91 

63 

72 

66 

65 

30 

48 

86 

34 

69 

54 

71 

4 

84 

64 22 

51 

76 

81 

58 

49 

91 

72 

73 

68 

71 

66 

72 

88 

34 

71 

56 

77 

87 

64 

70 

69 

86 

84 

60 

53 

92 

72 

75 

69 

79 

66 

78 

88 

36 

78 

56 

79 

6 

87 

79 

79 

82 

87 

84 

64 

56 

92 

73 

75 

69 

80 

71 

82 

90 

68 

82 

65 

81 

>99 

85 

96 

86 

96 

95 

57 

42 

91 

66 

58 

83 

59 

82 

97 

86 

35 

93 

54 

47 
C34 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

TABLE 7. - A five-factor petrogenetic model for the water-laid tuff as 

defined by the Varimax loadings 

[Coefficients:::: -0.50 or 20.50 are shown in italic type] 

Variable 

Log Mn _________ _ Log Cu _________ _ 

Log quartz _______ _ Log Ti __________ _ Log V __________ _ 

Log Fe __________ _ Log Ba _________ _ 

Log clinoptilolite ____ _ Log Sr __________ _ ell ____________ _ 

Log glass ________ _ LogLa __________ _ Nb ____________ _ LogY __________ _ 

Log Zr __________ _ 

Log Ph _________ _ LogGa _________ _ 

Log Be __________ _ 

Log a-cristobalite ___ _ Log K-feldspar _____ _ 

0.51 

.61 

. 71 

.83 

.84 

.85 

.88 

-.28 

.27 

.06 

.01 

.24 

-.13 

.02 

.49 

-.05 

.27 

.12 

.13 

.48 

II 

-.36 

.00 

.01 

-.13 

.20 

-.22 

-.04 

.87 

.80 

-.45 

-.82 

.03 

-.10 

-.13 

-.22 

.00 

-.39 

-.21 

.03 

.08 

Factors 

III 

-0.07 

.05 

-.17 

.38 

.08 

.17 

.16 

-.08 

-.04 

.20 

.09 

.82 

.72 

.72 

.68 

.24 

.10 

-.10 

-.01 

-.02 

IV 

0.50 

.38 

-.01 

.04 

.11 

.23 

-.12 

-.15 

.01 

.29 

.26 

.02 

.47 

.01 

.00 

.76 

.69 

.68 

.07 

.02 

v 

0.17 

-.01 

.32 

.14 

-.01 

.20 

.11 

.04 

-.22 

.13 

-.33 

.00 

.04 

-.13 

.14 

-.12 

.00 

.21 

.82 

.66 

tion of Na20 and Ph declined while that ofBa and Cr increased. The advanced stage of diagenesis was 

characterized by the formation of a-cristobalite and additional potassium feldspar with no further chemical 

change. Bulk density increased and porosity decreased 

as diagenesis proceeded, and so the final product is a 

dense tuff composed mainly of potassium feldspar and 

cristobalite. The three stages of diagenesis probably 

represent a continuum that results from the action of 

ground water. Leaching of alkalis from glass results in an 

ever increasing ratio of alkali/hydrogen ion concentrations as ground water percolates downward through 

vitric tuff (Hay, 1963), with the result that first clinoptilolite and then potassium feldspar is formed. 

Two stages of diagenetic alteration (zeolitic and feldspathic) are distinguished in the water-laid tuff of the 

Keg Mountain area. They correspond approximately to 

the initial and advanced stages of diagenesis identified 

in tuff of the Thomas Range. Data are not available to 

record the leaching of alkalis from glass in tuff of the Keg 

Mountain area, but inasmuch as this mechanism is 

thought to be responsible for diagenetic alteration, 

removal of alkalis seems probable. As with the tuff of the 

Thomas Range, the concentration of uranium (as eU) 

appears to decline during zeolitization whereas Sr increases. The increase in Sr is probably due to its 

presence in clinoptilolite (Hawkins, 1967a; 1967b). Possible Ba uptake by clinoptilolite was noted in the 

Thomas Range tuff (Lindsey, 1975), but Ba concentration is controlled principally by detrital processes in the 

tuff at Keg Mountain. As was the case for the Thomas 

Range tuff, the advanced stage of diagenesis of waterlaid tuff at Keg Mountain is marked by feldspathization 

with little relative change in chemical composition. 

MINERALIZATION 

No evidence for mineralization in the Keg Mountain 

area was found by study of the mineralogy and trace element content of the water-laid tuff. Little fluorite was 

found, and the occurrences of argillic tuff do not contain 

unusual concentrations of trace elements known to be 

associated with beryllium or other mineralization. The 

frequency distribution for Be is nearly symmetrical, in 

contrast to the highly skewed frequency distribution for 

Be in the tuff of the Thomas Range (Lindsey, 1975). No 

regional concentrations of beryllium in tuff were discerned by trend surface analysis. The association of PbGa-Be, discovered by R-mode factor analysis of data on 

the Keg Mountain tuff, probably reflects concentration 

in the silicic, vapor-rich parent magma. 

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Cohenour, R. E., 1963, The beryllium belt of western Utah, in Beryllium and uranium mineralization in western Juab County, Utah: 

Utah Geol. Soc. Guidebook to the Geology of Utah, no. 17, p. 4-7. 

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__ 1967b, Zeolites studies-[Pt.]2, Ion-exchange properties of some 

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Hay, R. L., 1963, Stratigraphy and zeolitic diagenesis of the John Day 

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Howarth, R. J., 1967, Trend-surface fitting to random data-An experimental test: Am. Jour. Sci. v. 265, no. 7, p. 619-625. 

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TRACE ELEMENTS OF WATER-LAID TUFF, KEG MOUNTAIN AREA, UTAH C35 

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-trU.S. GOVERNMENT PRINTING OFFICE: 1975-677-311/54