GEOLOGICAL SURVEY PROFESSIONAL PAPER 1158-A,B,Cl
Geologic Studies in

White Pine County, Nevada

Rubidium and Strontium in Hybrid Granitoid

Rocks, Southern Snake Range, Nevada

By DONALD E. LEE and WILLIS P. DOERING

Composition of Calcium-Poor Quartzites of Late

Precambrian and Early Cambrian Age from Eastern

White Pine County, Nevada

By DONALD E. LEE, R. E. VAN LOENEN, E. L. MUNSON BRANDT,

and WILLIS P. DOERING

A Radiometric Age Study of Mesozoic-Cenozoic 

Metamorphism in Eastern White Pine County, 

Nevada, and Nearby Utah

By DONALD E. LEE, RICHARD F. MARVIN, and 

HARALD H. MEHNERT

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1158-A, B,C

UNITED STATESGOVERNMENTPRINTINGOFFICE, WASHINGTON: 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS , Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

Geologic studies in White Pine County, Nevada.

(Geological Survey Professional Paper 11 58-A, B, and C)

Supt.ofDocs.no.: I 19.16:11 58-A,B,C.

CONTENTS: Lee, D. E. and Doering, W. P. Rubidium and strontium in hybrid granitoid rocks, southern Snake 

Range, Nevada. Lee, D. E. et al. Composition of calcium-poor quartzites of late Precambrain and early 

Cambrian age from eastern White Pine County, Nevada. Lee, D. E., Marvin, R. F., and Mehnert, H. H. 

A radiometric age study of Mesozoic-Cenozoic metamorphism in eastern White Pine County, Nevada, 

and nearby Utah. 1. Geology Nevada White Pine Co. I. Lee, Donald Edward, 1921- Rubidium and 

strontium in hybrid granitoid rocks, southern Snake Range, Nevada. 1980. II. Lee, Donald Edward, 1921- 

Radiometric age study of Mesozoic-Cenozoic metamorphism in eastern White Pine County, Nevada, and 

nearby Utah. 1980. III. United States Geological Survey. IV. Composition of calcium-poor quartzites 

of late Precambrain and early Cambrain age from eastern White Pine County, Nevada. 1980. V. Series: 

United States Geological Survey Professional Paper 1158-A,B, and C.

QE138.W5G48 557.93'l5 79-607143

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

Washington, D.C. 20402 

Stock Number 024-001-03270-8
CONTENTS

[Letters designate the chapters]

Page

(A) Rubidium and strontium in hybrid granitoid rocks, southern Snake Range, Nevada, by

Donald E. Lee and Willis P. Doering —————————————————————————— i

(B) Composition of calcium-poor quartzites of late Precambrian and Early Cambrian age 

from eastern White Pine County, Nevada, by Donald E. Lee, R. E. Van Loenen, 

E. L. Munson Brandt, and Willis P. Doering —————————————————————- 9

(C) A radiometric age study of Mesozoic-Cenozoic metamorphism in eastern White Pine 

County, Nevada, and nearby Utah, by Donald E. Lee, Richard F. Marvin, and

WaralH -L.LC11.C11U W XL. Mphnprt IVLdllld. L __________- .-———................ - _______________________________ ... 1 ^ 7I

III

Rubidium and Strontium in 

Hybrid Granitoid Rocks, 

Southern Snake Range, Nevada

By DONALD E. LEE and WILLIS P. DOERING

GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1158-A
CONTENTS

Page

Introduction -----------------------------...-----------------------------------------------------————————————-—— 1

Snake Creek-Williams Canyon area —————————————————————————————— l

Pole Canyon-Can Young Canyon area —----——---———-—--———--------——-—---—------ 6

Summary ————---——-----———-------—————-———————————---———————————------ 6

JvGiGrGriCGS C1C6Q ---—-—-—-—-—-—.—...................—................_.._..—..............................._......«......._....... ^

ILLUSTRATIONS

Page

FIGURES 1-7. Graphs showing:

1. Relation between CaO and rubidium contents in granitoid rocks of

the Snake Creek-Williams Canyon area, Nevada ————————— 3

2. Relation between K:Rb ratios and CaO contents of granitoid rocks of

the Snake Creek-Williams Canyon area, Nevada ————————— 4

3. General relations between CaO content and mineralogy for granitoid

rocks of the Snake Creek-Williams Canyon area, Nevada ---——- 4

4. Distribution of rubidium among minerals in granitoid rocks of the

Snake Creek-Williams Canyon area, Nevada —————————------ 4

5. Relation between CaO and strontium in granitoid rocks of the Snake

Creek-Williams Canyon area, Nevada —————————————— 6

6. Distribution of strontium among minerals in granitoid rocks of the

Snake Creek-Williams Canyon area, Nevada —————————------ 6

7. Relation between rubidium and barium contents in granitoid rocks

of the Snake Creek-Williams Canyon area, Nevada ———————— 7

TABLES

Page

TABLE 1. Quantitative rubidium and strontium analyses and rubidium-strontium ratios

of granitoid rocks of the Snake Creek-Williams Canyon area, Nevada -— 2

2. Quantitative rubidium and strontium analyses and rubidium-strontium ratios 

of Pioche Shale, Prospect Mountain Quartzite, and Osceola Argillite, 

southern Snake Range, Nevada ————————————————————— 3

3. Distribution of rubidium among minerals in granitoid rocks of the Snake 

Creek-Williams Canyon area and the Pole Canyon-Can Young Canyon 

area, Nevada ————————————————————————————————-—— 5

4. Distribution of strontium among minerals in granitoid rocks of the Snake 

Creek-Williams Canyon area and the Pole Canyon-Can Young Canyon 

area, l\ evada ————————————————————'——————-—*-—————— o
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

RUBIDIUM AND STRONTIUM IN HYBRID GRANITOID 

ROCKS, SOUTHERN SNAKE RANGE, NEVADA

By DONALD E. LEE and WILLIS P. DOERING

ABSTRACT

In the southern Snake Range, Nevada, the equivalent of a large 

part (from 63 to 76 percent SiO2 ) of the classic differentiation sequence has resulted mainly from assimilation of chemically distinct 

host rocks. The curves for rubidium and strontium in these hybrid 

rocks resemble those expected in normally differentiated rocks, and 

the potassium-rubidium ratios tend to decline from the mafic to the 

felsic parts of the outcrop area. However, the K:Rb curve is discontinuous where the rock contains 2.5 percent CaO (about 70 percent 

SiO2 ), indicating the complexity of the igneous processes that 

resulted in the formation of this hybrid pluton.

INTRODUCTION

This paper describes the distribution of rubidium 

and strontium in hybrid granitoid rocks (Jurassic) of 

the southern Snake Range, Nevada. These intrusive 

rocks are of petrologic interest for two main reasons:

1. In the Snake Creek-Williams Canyon area the 

equivalent of a large part (from 63 to 76 percent 

SiO2) of the classic differentiation sequence has 

developed mainly from assimilation of chemically 

distinct host rocks, which are Prospect Mountain 

Quartzite (Precambrian Z and lower Cambrian), 

Pioche Shale (Lower and Middle Cambrian), and 

Pole Canyon Limestone (Middle Cambrian).

2. The Pole Cany on-Can Young Canyon area intrusive 

body is an unusual muscovite-bearing hybrid rock 

that has developed through assimilation of the upper Precambrian Osceola Argillite of Misch and 

Hazzard (1962). The distinctive nature of this intrusive is especially striking inasmuch as it is separated from the Snake Creek-Williams Canyon 

area intrusive by a septum of sedimentary rocks 

1.6 km long and only about 300 m wide. 

The Jurassic rocks studied crop out a few kilometers 

north of the Mount Wheeler mine in the southern part 

of the Snake Range, about 80 km southeast of Ely, 

Nev. These same rocks are the subject of a comprehensive field and laboratory study (Lee and Van Loenen, 

1971) that includes both a geologic map that shows 

sample localities and tables of extensive chemical data

for all the specimens discussed in the present report. 

The sample numbers used here are the same as in the 

comprehensive study, where rocks are numbered in 

order of increasing CaO content; that is, from most 

felsic to most mafic. The field numbers used in earlier 

papers cited in this report are keyed to these sample 

numbers by Lee and Van Loenen (1971, p. 11).

The samples were analyzed for rubidium and strontium on an X-ray emission spectrometer. Net counts of 

the unknown samples were compared to those of standard samples having similar major-element and 

rubidium and strontium concentrations, and values 

were corrected for mass absorption by measuring the 

Compton scattering peak. The standard samples were 

measured for rubidium and strontium on a mass spectrometer using the stable isotope dilution method.

Muscovite, feldspar, and whole-rock analyses listed 

are correct within 3 percent of the reported values for 

rubidium and strontium, but the Rb:Sr ratios are correct within 2.3 percent of the reported values because 

mass absorption effects are canceled. Biotite analyses 

listed are correct only within 4 percent of the values 

reported for rubidium and within 6 percent of the 

values reported for strontium and Rb:Sr ratios because 

these biotites are iron-rich and so have large mass absorption coefficients.

Results of semiquantitative spectrographic analyses 

are based on their identity with geometric brackets 

whose boundaries are 1.2, 0.83, 0.56, 0.38, 0.26, 0.18, 

0.12, and so forth, and are reported arbitrarily as midpoints of these brackets: 1, 0.7, 0.5, 0.3, 0.2, 0.15, and 

0.1, respectively. The precision of a reported value is 

approximately plus or minus one bracket at the 

68-percent confidence level, or two brackets at the 

95-percent confidence level.

SNAKE CREEK-WILLIAMS CANYON AREA

The influence of host rocks on the chemistry and 

mineralogy of intrusive rocks of the southern Snake 

Range is most clearly shown in the Snake Creeki
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

Williams Canyon area. There the intrusive is undeformed, probably has not been eroded to a depth of 

much more than 300 m, and is well exposed in contact 

with quartzite, shale, and limestone. Within a horizontal distance of 5 km, the intrusive grades from a quartz 

monzonite (76 percent SiO2 , 0.5 percent CaO) where the 

host rock is quartzite, to a granodiorite (63 percent 

SiO2 , 4.5 percent CaO), where the host rock is 

limestone. Other major elements vary as one would expect in a normal differentiation sequence (Lee and Van 

Loenen, 1971, fig. 4).

Most minor elements show a similar variation, the 

exceptions being the rare earths (Lee and Bastron, 

1967; Cain, 1974), zirconium (Lee and others, 1968; Lee 

and Van Loenen, 1971, fig. 6), fluorine (Lee and Van 

Loenen, 1971, fig. 7), and, most notably, barium (Lee 

and Doering, 1974).

Quantitative rubidium and strontium analyses and 

Rb:Sr ratios of the rocks are listed in table 1. In figure 

1, rubidium is plotted against CaO rather than K2O for 

a better point spread, and the equivalent ranges of K2O 

and SiO2 are indicated. The increase of rubidium contents from the mafic to the felsic parts of the pluton is, 

of course, what one would expect in a normally differentiated granitoid mass; because of the similarity of 

the two ions, Rb+ always substitutes for K+ in crystallizing silicates.

Analyses of 34 samples of sedimentary rocks that 

are in contact with (and were assimilated by) the 

hybrid granitoid rocks were listed by Lee and Van 

Loenen (1971, tables 1 and 2). For the present study, 

splits of the shales, quartzites, and argillites were 

analyzed for rubidium and strontium. The quantitative 

results are listed in table 2, and the quartzite and shale 

averages are indicated on those parts of figure 1 that 

presumably represent assimilation of the respective 

rocks by the Snake Creek-Williams Canyon area intrusive. The Pole Canyon Limestone average (20 parts 

per million rubidium) assumed (fig. 1) is based on the 

fact that the soluble portions of carbonate sediments 

contain only very minor amounts of rubidium (Heier 

and Billings, 1970, p. 37-K-l), and nine samples of the 

Pole Canyon Limestone average about 95 percent 

CaCO3 (Lee and Van Loenen, 1971, table 2).

Thus, the increase in rubidium from the mafic to the 

felsic parts of the Snake Creek-Williams Canyon intrusive appears to reflect some process of differentiation, being largely unrelated to the rubidium contents 

of the assimilated country rocks. However, barium 

shows the opposite trend (Lee and Doering, 1974, fig. 

1), tending to decrease from the mafic to the felsic 

parts of the igneous exposure, even though Ba2+, like 

Rb+, substitutes for K+ in crystallizing silicates. In a

TABLE 1. Quantitative rubidium and strontium analyses, in parts 

per million, and rubidium-strontium ratios of granitoid rocks of 

the Snake Creek- Williams Canyon area, Nevada

[W. P. Doering, analyst. Method of analysis explained 

in text. Complete analyses of rocks listed by Lee

and Van Loenen (1971, Table 5). Samples 71, 72, 77,

81, and 85 are xenoliths]

Sample Rb Sr Rb/Sr 

No.

1 263 99 2.66

2 231 106 2.18

3 353 119 2.12

4 253 119 2.12

5 219 119 1.84

6 177 140 1.23

7 269 104 2.59

8 244 100 2.44

9 179 205 .88

10 240 162 1.48

11 187 166 1.13

12 153 224 .68

13 191 212 .90

14 164 325 .50

15 148 329 .45

16 152 339 .45

17 156 356 .44

18 133 366 .36

19 131 363 .36

20 146 362 .40

21 139 368 .38

22 109 368 .30

23 155 393 .39

24 180 440 .41

25 123 373 .33

26 130 418 .31

27 136 421 .32

28 144 415 .35

29 123 470 .26

30 114 451 .25

31 121 491 .25

32 116 453 .25

33 111 457 .24

34 92.2 498 .19

35 104 507 .21

36 111 471 .24

37 95.6 498 .19

38 106 500 .21

39 113 515 .22

40 89.3 537 .17

41 96.7 538 .18

42 136 440 .31

43 102 496 .21

Sa?ple Rb Sr Rb/Sr NO.

44 105 465 0.23

45 91.6 502 .18

46 109 498 .22

47 89.4 547 .16

48 102 512 .20

49 105 582 .18

50 93.8 541 .17

51 109 486 .23

52 93.0 528 .18

53 109 471 .23

54 118 472 .25

55 111 492 .23

56 97.9 551 .18

57 101 511 .20

58 98.6 553 .18

59 151 420 .36

60 97.0 606 .16

61 83.8 713 .12

62 94.1 569 .17

63 97.2 645 .15

64 99.9 636 .16

65 89.0 701 .13

66 86.2 676 .13

67 72.6 631 .12

68 101 653 .16

69 174 471 .37

70 95.3 671 .14

71 92.6 474 .20

72 191 190 1.01

73 85.5 707 .12

74 79.0 729 .11

75 77.7 726 .11

76 77.9 742 .11

77 137 476 .29

78 67.8 854 .08

79 82.3 716 .12

80 74.4 744 .10

81 83.1 603 .14

82 87.0 725 .12

83 100 678 .15

84 76.3 763 .10

85 166 353 .47

86 70.5 822 .09

general way, the barium contents of these rocks appear

to relate to the average barium contents of the quartzite, shale, and limestone assimilated.

We speculate that the opposite trends noted for

rubidium and barium in this igneous sequence may

have resulted from the interplay of the following two

factors:
RUBIDIUM AND STRONTIUM IN HYBRID GRANITOID ROCKS

PROSPECT MOUNTAIN 

QUARTZITE AVERAGE

ASSUMED POLE CANYON LIMESTONE

SlO2 76 . 

K20 '4.!

CaO, IN WEIGHT PERCENT 

INCREASING SiO2 AND K 2O, IN PERCENT<-

FIGURE 1.—Relation between CaO and rubidium contents in granitoid rocks of the Snake Creek-Williams Canyon area, Nevada. 

Equivalent ranges of contents of SiO2 and K2O, in weight percent, 

are indicated. Average rubidium contents of sedimentary rocks 

are indicated on parts of diagram representing assimilation of 

those rocks. Based on tables 1 and 2 and on data listed by Lee and 

Van Loenen (1971, table 5). Dot, main intrusive phase; X, xenolith.

1. Distribution coefficients for barium in biotite and 

K-feldspar are greater than 1, and those for rubidium tend to be less than 1 (Nagasawa and 

Schnetzler, 1971). We might, therefore, expect 

barium to be preferentially incorporated into the 

early-formed potassium minerals and rubidium to 

stay in the melt as long as possible.

2. Perhaps for some reason the Ba2+ ion was relatively 

immobile in the magnetic environment and thus 

the barium content of the granitoid rock reflects 

the barium content of the sedimentary rock 

assimilated.

A number of authors (for example, Taubeneck, 1965; 

the workers cited by Heier and Billings, 1970, 

p. 37-E-8) have noted that the K:Rb ratio changes progressively with concentration of felsic constituents 

over mafic constituents; that is, "differentiation." 

When a rock system undergoes some sort of differentiation, rubidium is expected to increase relative to 

potassium in the felsic fractions and the K:Rb ratio 

will decrease in a sequence from mafic to felsic rocks. 

In figure 2, K:Rb is plotted against CaO for the Snake 

Creek-Williams Canyon area intrusive. The K:Rb ratio 

for the Pole Canyon Limestone is not indicated on 

figure 2, but it is clear that this ratio involves only 

minor amounts of both elements because the average 

potassium content of nine samples of this limestone is 

only about 0.18 percent (Lee and Van Loenen, 1971, 

table 2), and, as argued earlier, the average rubidium 

content of this limestone (about 95 percent CaCO3) 

probably also is very low. The K:Rb ratios of the

TABLE 2. Quantitative rubidium and strontium analyses, in 

parts per million, and rubidium-strontium ratios of Pioche 

Shale, Prospect Mountain Quartzite, and Osceola Argillite of 

Misch and Hazzard (1962), southern Snake Range, Nevada

[W. P. Doering, analyst. Method of 

analysis explained in text. Complete analyses of rocks listed by 

Lee and Van Loenen (1971, Table 1) ]

Sample 

No.

Rb Sr Rb/Sr

Pioche Shale

51

52

53

54

55

56

57

58

59

147

78.6

396

141

273

338

217

333

105

41.1

104

359

79.1

33.2

28.4

45.9

125

82.7

3.58

.76

1.10

1.79

8.27

11.90

4.72

2.67

1.27

Average—— 225.4 99.8 2.25

Prospect Mountain Quartzite

Ql 

Q2 

Q3 

Q4

88.3

113

53.2

15.8

24.8

28.9

14.4

4.5

3.56

3.92

3.70

3.49

Average—— 67.6 18.2 3.72

Osceola Argillite

Arl 

Ar2 

Ar3 

Ar4 

Ar5 

Ar6

Average——

121

19.

148

220

18.

143

3

3

215

178

51

28

117

44

.9

.7

.8

0.

.

2.

7.

.

3.

57

11

85

67

16

20

111.6 105.9 1.05

pluton do indeed tend to decrease toward the felsic 

part of the exposure, but there is a break in the curve 

near 2.5 percent CaO. A secondary trend for barium 

also branches from the main trend where the rock contains from 2.0 to 2.5 percent CaO (Lee and Doering, 

1974). Thus, although both Rb+ and Ba2+ substitute for 

K+ in crystallizing silicates, the equivalent of a large 

part of the classic differentiation sequence (from 63 to 

76 percent SiO2 ) that has resulted from assimilation of
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

350

300-

250

200

150

100

50-

PROSPECT MOUNTAIN 

QUARTZITE AVERAGE

\

0.5 1.0 1.5 2.0 2.5 3.0 

CaO, IN WEIGHT PERCENT

3.5 4.0 4.5

FIGURE 2.—Relation between K:Rb ratios and CaO contents of 

granitoid rocks of the Snake Creek-Williams Canyon area, 

Nevada. Equivalent ranges of contents of SiO2 and K2O are shown 

in figure 1. Average K:Rb ratios of sedimentary rocks indicated 

on parts of diagram representing assimilation of those rocks are 

based on tables 1 and 2 and on data listed by Lee and Van Loenen 

(1971, tables 5 and 9). Dot, main intrusive phase; X, xenolith.

chemically distinct host rocks in the Snake CreekWilliams Canyon area displays the following relations:

1. Rubidium increases toward the felsic part of the sequence (fig. 1).

2. Barium decreases toward the felsic part of the sequence (Lee and Doering, 1974, fig. 1).

3. K:Rb ratios tend to decrease toward the felsic part 

of the sequence (fig. 2).

4. The curves for both barium and K:Rb versus CaO 

are discontinuous in that part of the sequence 

(from 2.0 to 2.5 percent CaO) representing assimilation of Pioche Shale.

The distribution of potassium in these hybrid granitoid rocks is apparent from the opposite trends for 

biotite CM).5 percent K2O) and microcline CM4-15 percent K2O) summarized in figure 3 and described in 

detail by Lee and Van Loenen (1970, p. D198; 1971, p. 

27). On the basis of data in table 3, the distribution of 

rubidium is approximated in figure 4, which resembles 

a diagram showing the distribution of barium in these 

same rocks (Lee and Doering, 1974, fig. 3).

The plot (fig. 5) of strontium (table 1) versus CaO for 

the Snake Creek-Williams Canyon intrusive agrees 

with the results of a comprehensive study by Turekian 

and Kulp (1956), who found that, for granitic rocks, 

there is an increase in strontium content with increase 

in calcium, not only for samples from a single pluton, 

but also for universal sampling. A plot of Rb:Sr ratios

4.5

WEIGHT PERCENT CaO IN ROCK

FIGURE 3.—General relations between CaO content and mineralogy 

for granitoid rocks of the Snake Creek-Williams Canyon area, 

Nevada. From Lee and Van Loenen (1971, fig. 11).

100

80

60

40

20

BIOTITE

0.5 1-0 1.5 2.0 2.5 3.0 3.5 

CaO, IN WEIGHT PERCENT

4.0 4.5

FIGURE 4.—Distribution of rubidium among minerals in granitoid 

rocks of the Snake Creek-Williams Canyon area, Nevada. Based 

on data in table 3.

listed in table 1 is not included here, but the ratio increases systematically from the most mafic to the 

most felsic parts of the exposure, as one would expect 

in a series of normal differentiates.

On the basis of the data in table 4, the distribution of 

strontium in the granitoid rocks is approximated in 

figure 6. Epidote is by far the most strontium-rich 

mineral present in these rocks (Lee and others, 1971), 

and, in the most mafic parts of the exposure, where it 

comprises about 2 percent of the rock, it contains more 

than 9 percent of the strontium present in the rock. In 

this regard, it is interesting to note that the allanite 

(cerium-epidote) present in the mafic parts of the exposure (Lee and Bastron, 1967) does not concentrate 

strontium. X-ray fluorescence analyses by Robena 

Brown showed that the constituent allanites from 

samples 22, 66, 67, 72, and 78 (table 1) each contain 

less than 100 ppm strontium. The amounts of strontium contained in apatite (table 4) are too small to be
TABLE 3. Distribution of rubidium among minerals in granitoid rocks of the Snake Creek-Williams Canyon area and the Pole Canyon-Ca

Nevada

[W. P. Doering, analyst. Method of analysis explained in text. Leaders (——) indicate no data. All analyses in we

pie 

No.

CaO 

in 

rock

Mineral in rock

BiotiteMicrocline

Muscovite

Plagioclase

Kb in pure mineral

Biotite

Microcline 1

MuscovitePlagioclase

Contribution to Kb content of the rock

Biotite

Microel ineMuscovite

Plagioclase

Total 2

BiotiteMicr

cli

Snake Creek-Williams Canyon Area

3

15

22

39

66

78

0.55

1.5

1.8

2.3

3.1

3.9

2

10

7

8

10

19

20

18

17

14

10

2

__

——

——

——

——

——

34

38

40

43

45

49

0.1082

.0781

.0569

.0648

.0442

.0356

_ _

0.0338

.0354

.0393

.0201

.0213

_ _

——

——

——

——

——

__

0.0024

.0014

.0013

.0011

.0004

0.0022

.0078

.0040

.0052

.0044

.0068

___

0.0061

.0063

.0055

.0020

.0004

_ _

——

——

——

——

——

__

0.0009

.0006

.0006

.0005

.0002

0.0353

.0148

.0109

.0113

.0069

.0074

6.2

52.7

36.7

46.0

63.8

91.9

41

57

48

29

5

Pole Canyon-Can Young Canyon Area

89

90

93

0.98

1.1

1.3

6

5

4

19

17

19

6

9

5

35

36

40

0.0740

.0888

.0950

0.0453

.0335

.0456

0.0435

.0465

.0579

0.0020

.0012

.0010

0.0040

.0044

.0038

0.0086

.0057

.0087

0.0026

.0042

.0029

0.0007

.0004

.0004

0.0159

.0147

.0158

27.0

29.9

24.1

52

38

55

Rubidium contents of microclines determined directly only for samples 66 and 78; rubidium content of other microclines ca

coexisting minerals and rubidium content of whole rocks.

Direct analyses of whole rocks gave 0.00862 and 0.00678 weight percent rubidium for samples 66 and 78, respectively.

TABLE 4.—Distribution of strontium among minerals in granitoid rocks of the Snake Creek-Williams Canyon area and the Pole Canyo

Nevada

[Quantitative Sr analyses (microclines in samples 66 and 78; plagioclases in samples 15, 22, 55, 66, 78, and 89; rocks) by W. P

analyses (apatites, epidotes, and microclines in samples 15, 22, 55, 88, 89, and 90; plagioclases in samples 90 and 93) by 

analysis explained in text. Leaders (——) indicate no data. All analyses in weight percent]

Sample 

No.

CaO 

in 

rock

Mineral in rock

ApatiteEpidoteMicrocline

Plagioclase

Sr in pure mineral

ApatiteEpidoteMicroclinePlagioclase

Contribution to Sr content of the rock

Apatite

EpidoteMicrocline

Plagioclase

Total 1

Apatite

Snake Creek-Williams Canyon Area

15

22

55

66

78

1.5

1.8

2.5

3.1

3.9

0.1

.15

.15

.2

.2

0.1

.2

.6

1.0

2.0

18

17

16

10

2

38

40

41

45

49

0.05

.05

.07

.07

.05

0.3

.3

.3

.3

.3

0.03

.03

.03

.0325

.0301

0.0600

.0644

.0904

.1383

.1180

0.0001

.0001

.0001

.0001

.0001

0.0003

.0006

.0018

.003

.006

0.0054

.0051

.0048

.0033

.0006

0.0228

.0258

.0371

.0622

.0578

0.0286 (0.0329)

.0316 ( .0368)

.0438 ( .0492)

.0686 ( .0676)

.0645 ( .0854)

0.3

.3

.2

.1

.2

Pole Canyon-Can Young Canyon Area

89

90

93

0.98

1.1

1.3

0.1

.1

.1

——

——

——

19

17

19

35

36

40

0.05

.05

.05

——

——

——

0.07

.05

.05

0.0660

.07

.07

0.0001

.0001

.0001

——

——

0.0133

.0051

.0095

0.0231

.0252

.0280

0.0365 (0.0325)

.0304 ( .0350)

.0376 ( .0352)

0.3

.3

.3

totals in parentheses are by rock analysis.
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

POLE CANYON LIMESTONE AVERAGE 

t____________________f

(1800 PARTS PER MILLION Sr)

800

700 

O 

ij 600

500

300

200

100-

SHALE AVERAGE

PROSPECT MTN. QTZ. AVERAGE

fill

0.5 1.0 1.5 2.0 2.5 3.0 3.5 

. CaO, IN WEIGHT PERCENT

4.0

FIGURE 5.—Relation between CaO and strontium in granitoid rocks 

of the Snake Creek-Williams Canyon area, Nevada. Equivalent 

ranges of contents of SiO2 and K2O are as shown on figure 1. 

Average strontium contents of sedimentary rocks are indicated 

on parts of diagram representing assimilation of those rocks. 

Based on tables 1 and 2 and on data by Lee and Van Loenen 

(1971, tables 1 and 5). Dot, main intrusive phase; X, xenolith.

100

80

60

40

O 20-

EPIDOTE

PLAGIOCLASE

1.0 1.5 2.0 2.5 3.0 3.5

CaO, IN WEIGHT PERCENT

4.0 4.5

FIGURE 6.—Distribution of strontium among minerals in granitoid 

rocks of the Snake Creek-Williams Canyon area, Nevada (based 

on data in table 4).

represented in figure 6, and the very minor amounts of 

strontium present in the constituent sphenes (Lee and 

others, 1969) are not considered here.

POLE CANYON-CAN YOUNG CANYON AREA

The unusual two-mica hybrid rock developed in the 

Pole Cany on-Can Young Canyon area through assimilation of the Osceola Argillite has been described in 

detail by Lee and Van Loenen (1971, p. 5, 38-39). 

Chemical differences in the rock from place to place are 

relatively small with no systematic spatial distribution of values for either major or minor elements.

The distribution of rubidium in three samples (Nos. 

89, 90, and 93) of this intrusive is outlined in table 3, 

which shows that a significant portion of the rubidium 

present is contained in muscovite. However, in each 

case, rubidium preferentially enters the coexisting 

biotite, which is in agreement with Heier and Billings 

(1970, p. 37-D-l). The rubidium contents of the rocks 

themselves are somewhat higher than the average 

rubidium content of six samples of the argillite 

assimilated (table 2).

The distribution of strontium in the same three 

samples of this intrusive is outlined in table 4. These 

two-mica rocks are devoid of epidote, and practically 

all of the strontium present is contained in plagioclase 

and microcline. The strontium contents of the rocks 

themselves are appreciably greater than the average 

strontium content of six samples of the argillite 

assimilated.

SUMMARY

The Snake Creek-Williams Canyon area intrusive is 

an ideal subject for a study of igneous processes. The 

chemistry and mineralogy of this intrusive are highly 

variable over a horizontal distance of 5 km; these variations involving major elements are those expected in a 

series of differentiates. However, from references 

already cited, it is apparent that the trends for the rare 

earths, fluorine, zirconium, and barium, are the opposite of those expected in normally differentiated 

rocks. Moreover, the breaks in the curves for barium 

and K:Rb versus CaO near the part of the intrusive 

outcrop that presumably represents assimilation of 

shale indicate a discontinuity in the transition between 

the mafic and felsic parts of the Snake Creek-Williams 

Canyon igneous sequence not apparent from our previous work on these rocks.

Puchelt (1972, p. 56-D-15) stated, "A useful index 

of fractionation is the ratio Ba/Rb." In this connection, 

we present figure 7, in which rubidium is plotted 

against barium for granitoid rocks of the Snake CreekWilliams Canyon area, and the course of crystalliza-
RUBIDIUM AND STRONTIUM IN HYBRID GRANITOID ROCKS

350

300

250

200

150

100 -

/ * x

'\

I • Xv

/ • . \ AVERAGE PIOCHE SHALE 

\

"ASSIMILATION OF PROSPECT ~—- 

MOUNTAIN QUARTZITE 

AVERAGE PROSPECT 

MOUNTAIN QUARTZITE

EXPLANATION

Whole-rock CaCO, 

in percent

• 0.47-1.9 

A 2.0-2.5 

o 2.6-4.5 

x Xenollth

ASSIMILATION OF 

PIOCHE SHALE

50 - AVERAGE POLE

CANYON LIMESTONE

6

J____L

ASSIMILATION OF POLE 

CANYON LIMESTONE

2362 

PPM Ba

0 200 400 600 800 1000 1200 1400 1600 1600 

Ba, IN PARTS PER MILLION

FIGURE 7.—Relation between rubidium and barium contents in 

granitoid rocks of the Snake Creek-Williams Canyon area, Nevada (based on tables 1 and 2 of this report, on tables 1 and 2 of 

Lee and Doering, 1974, and on data listed by Lee and Van Loenen, 

1971).

tion from the mafic (assimilation of limestone) to the 

felsic (assimilation of quartzite) parts of the igneous sequence is indicated. The concentration of points in 

rather well-defined fields presumably representing 

assimilation of limestone, shale, and quartzite shows 

little relation to the averages indicated for the 

sedimentary rock types themselves.

Any attempt to explain the behavior of both 

rubidium (figs. 1, 4, 7) and barium (Lee and Doering, 

1974, fig. 1) during crystallization of these contaminated rocks becomes contrived. Thus, it is clear 

that we have much to learn about the distribution coefficients of both elements under various conditions 

such as those discussed by Puchelt (1972, p. 56-D-15). 

We note, finally, that a mineralogical study of the igneous biotites recovered from these rocks (Lee and Van 

Loenen, 1970) shows a number of regular chemical 

changes from the mafic to the felsic parts of the exposure, indicating complete reworking of the detrital 

mica present in the assimilated Pioche Shale.

REFERENCES CITED

Cain, D., 1974, The determination and interpretation of rare-earth 

abundances in hybrid granitoid rocks of the southern Snake 

Range, Nevada: Colorado School Mines M.S. thesis, 94 p.

Heier, K. S., and Billings, G. K., Rubidium, in Wedepohl, K. H., ed., 

Handbook of geochemistry: New York, Springer-Verlag, v. 11/3, 

p. 37-B-l to 37-E-10 and 37-K-l to 37-N-l.

Lee, D. E., and Bastron, Harry, 1967, Fractionation of rare-earth 

elements in allanite and monazite as related to geology of the 

Mount Wheeler mine area, Nevada: Geochemica et Cosmochimica Acta, v. 31, no. 3, p. 339-356.

Lee, D. E., and Doering, W. P., 1974, Barium in hybrid granitoid 

rocks of the southern Snake Range, Nevada: U.S. Geological 

Survey Journal of Research, v. 2, no. 6, p. 671-675.

Lee, D. E., Mays, R. E., Van Loenen, R. E., and Rose, H. J., Jr., 

1969, Accessory sphene from hybrid rocks of the Mount 

Wheeler mine area, Nevada, in Geological Survey research 

1969: U.S. Geological Survey Professional Paper 650-B, p. 

B41-B46.

___1971, Accessory epidote from hybrid granitoid rocks of the 

Mount Wheeler mine area, Nevada, in Geological Survey research 1971: U.S. Geological Survey Professional Paper 750-C, 

p.C112-C116.

Lee, D. E., Stern, T. W., Mays, R. E., and Van Loenen, R. E., 1968, 

Accessory zircon from granitoid rocks of the Mount Wheeler 

mine area, Nevada, in Geological Survey research 1968: U.S. 

Geological Survey Professional Paper 600-D, p. D197-D203.

Lee, D. E., and Van Loenen, R. E., 1970, Biotites from hybrid granitoid rocks of the southern Snake Range, Nevada, in Geological 

Survey research 1970: U.S. Geological Survey Professional 

Paper 700-D, p. D196-D206.

___1971, Hybrid granitoid rocks of the southern Snake Range, 

Nevada: U.S. Geological Survey Professional Paper 668, 48 p.

Misch, Peter, and Hazzard, J. C., 1962, Stratigraphy and metamorphism of Late Precambrian rocks in central northeastern 

Nevada and adjacent Utah: American Association of Petroleum 

Geologists Bulletin, v. 46, no. 3, pt. 1, p. 289-343.

Nagasawa, Hiroshi, and Schnetzler, C. C., 1971, Partitioning of rare 

earth, alkali and alkaline earth elements between phenocrysts 

and acidic igneous magma: Geochimica et Cosmochimica Acta, 

v. 35, p. 953-968.

Puchelt, H., 1972, Barium, in Wedepohl, K. H., ed., Handbook of 

geochemistry: New York, Springer-Verlag, v. 11/3, p. 56-D-l to 

56-E-9.

Taubeneck, W. H., 1965, An appraisal of some potassium-rubidium 

ratios in igneous rocks: Journal of Geophysical Research, v. 70, 

no. 2, p. 475-478.

Turekian, K. K., and Kulp, J. L., 1956, The geochemistry of strontium: Geochimica et Cosmochimica Acta, v. 10, nos. 5-6, p. 

245-296.

Composition of Calcium-Poor 

Quartzites of Late Precambrian and 

Early Cambrian Age from 

Eastern White Pine County, Nevada

By DONALD E. LEE, R. E. VAN LOENEN, E. L. MUNSON BRANDT, 

and WILLIS P. DOERING

GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1158-B
CONTENTS

ILLUSTRATIONS

Page

Abstract -----------------------------------------------------------------------««——«—-———~TM«———««««——~~TM—~ Q

Chemistry and mineralogy of the quartzites -—--——----—--—————————_____ 9

x\,eier ences citeci ••••'"'•-••""TMTM—-—-———TMTM-TMTM-TM————TMTMTM—TMTM~—TM~—-"—-——-«—«--—"•« J.D

Page

FIGURE 8. Map of localities of quartzite samples analyzed — -- —— - —— -- ——— — —— -- —— — - 10 

9. Diagram of relation between (K2O + Na2O) and A12O3 contents of quartzites in

10. Diagram of relation between K2O and Na2O contents of quartzites in table 5 -— 16

TABLES

TABLE 5. Analytical data for quartzites from eastern White Pine County, Nevada —-—- 12 

6. Petrographic data for quartzites from eastern White Pine County, Nevada —-- 14
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

COMPOSITION OF CALCIUM-POOR QUARTZITES

OF LATE PRECAMBRIAN AND EARLY CAMBRIAN AGE

FROM EASTERN WHITE PINE COUNTY, NEVADA

By DONALD E. LEE, R. E. VAN LOENEN, E. L. MUNSON BRANDT,

and WlLLIS P. DOERING

ABSTRACT

The 18 samples of quartzites of late Precambrian and Early Cambrian age described are remarkable for their very minor contents of 

CaO, especially in relation to the amounts of SiO2 , A12O3 , Fe2O3 , 

FeO, MgO, K2O, and TiO2 present. The Na2O contents of these 

quartzites are also low, and the average K2O:Na2O ratio is 20:1. The 

original miogeosynclinal shelf sediments were mixtures of (1) sand 

with a fair degree of mineralogical maturity and a low degree of textural maturity, and (2) argillaceous material. In most rocks described, the bulk chemistry of the argillaceous material apparently 

was appropriate for the crystallization of metamorphic mica(s) 

under conditions of metamorphism that were essentially 

isochemical, except for depletion of pore fluids. There is no evidence 

of metasomatism either in the field or in thin section. It is concluded 

that the sediments were derived from a deeply weathered 

crystalline terrane. This type of Precambrian source rock probably 

was present on the craton to the east at the time the original shelf 

sediments were transported westward and deposited.

INTRODUCTION

During study of age relations in eastern White Pine 

County, Nev., samples of Precambrian and Cambrian 

quartzite selected for their contents of metamorphic 

mica were analyzed chemically and found to be almost 

devoid of CaO, even though their average SiO2 content 

is less than 90 percent. The Na2O contents of these 

quartzites also are low, and the average K2O:Na2O 

ratio is 20:1. The purpose of this report is to describe 

the chemistry and mineralogy of 2 samples of Precambrian quartzite and 16 samples of Precambrian 

and Cambrian Prospect Mountain Quartzite and to 

comment on the provenance of the original sediments.

Barium values were determined according to the 

X-ray fluorescence method described by Lee and Doering (1974, p. 671). An X-ray emission spectrometer was 

used to measure rubidium and strontium values. The 

unknown sample net counts were compared to those of 

standard samples having similar rubidium, strontium, 

and major-element concentrations. Mass absorption effects were corrected by measuring the Compton scattering peak. The standard samples were analyzed for

rubidium and strontium on a mass spectrometer using 

the stable isotope dilution method, which has an uncertainty of 1.5 percent at the 95-percent confidence level. 

The values reported for rubidium and strontium (table 

1) have an uncertainty of 3.0 percent at the 95-percent 

confidence level. The Rb:Sr ratios reported are correct 

to 2.3 percent with 95-percent confidence, because 

mass absorption effects are canceled.

Semiquantitative spectrographic results are based 

on their identity with geometric brackets whose 

boundaries are 1.2, 0.83, 0.56, 0.38, 0.26, 0.18, 0.12 percent, and so forth; and the results are reported arbitrarily as midpoints of these brackets, 1.0, 0.7, 0.5, 0.3, 

0.2, 0.15, and 0.1 percent, respectively. The precision 

of a reported value is approximately one bracket at 

68-percent or two brackets at 95-percent confidence.

CHEMISTRY AND MINERALOGY 

OF THE QUARTZITES

The quartzites described were derived from Precambrian crystalline and sedimentary rocks exposed on the 

craton to the east (Stewart and Poole, 1974), and 

deposited as shelf sediments in the Cordilleran miogeosyncline during late Precambrian and Early Cambrian 

time. By early Triassic time a total of from 10,000 to 

13,000 m of strata was deposited in the Cordilleran 

miogeosyncline (Hose and Blake, 1976, p. 3), resulting 

in deep burial and some static metamorphism of the 

Cambrian and older sediments. During Mesozoic and 

(or) Tertiary time some of the clastic sediments of late 

Precambrian and Early Cambrian age were also subjected to a dynamic metamorphism, resulting from tectonic overpressures related to movement along the 

regional thrust faults. Finally, some of these quartzites may have been subjected to thermal metamorphism related to the intrusion of the Mesozoic and Tertiary rocks exposed in the area of the sample sites (fig. 

8). (See the map of Hose and Blake, 1976.)

9
10 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

114°30' 15' 114°00'

39°30' —

39°00'

FIGURE 8.—Localities of quartzite samples analyzed. Precise latitudes and longitudes of localities listed in table 5. Base 

from U.S. Geological Survey 1:250,000 Ely, Nevada, Utah (1956, rev. 1971).
COMPOSITION OF CALCIUM-POOR QUARTZITES 11

The nature of the metamorphism affecting each of 

these quartzites still is being studied, but apparently 

the metamorphism was essentially isochemical, except 

for depletion of pore fluids, for no evidence of metasomatism exists either in the field or in thin section. 

Thus the analyses (table 5) probably are representative 

of the chemistry of the original sediments. Petrographic data are summarized in table 6.

As a group these quartzites are remarkable for their 

very minor contents of CaO, especially when viewed in 

relation to the amounts of SiO2 , A12O3 , Fe2O3 , FeO, 

MgO, K2O, and TiO2 present. The difficulties encountered in determining very small amounts of CaO 

by means by gravimetric analysis were discussed by 

Peck (1964, p. 34, 35), and he stated: "A better alternative, if calcium must be determined, is to make a 

spectrographic analysis on a portion of the sample." 

We have therefore included in table 5 the spectrographically determined values of Ca. These (semiquantitative) results confirm the dearth of CaO in these 

quartzites. Spectrographic values for Ca range from 

0.015 to 0.05 percent (^0.02-0.07 percent CaO) for the 

12 quartzites that were shown to be devoid of CaO by 

gravimetric analysis.

The literature contains other examples of quartzites 

with such low contents of CaO (for example, Pettijohn, 

1963, table 2; Ketner, 1966, table 3), but they are orthoquartzites, very mature sands consisting almost entirely of detrital quartz cemented with silica and containing only minor amounts of all oxides other than 

silica.

The quartzites in table 5 also contain only minor 

amounts of Na2O, and their average K2O:Na2O ratio exceeds 20:1. Such a high K2O:Na2O ratio is unusual in 

clastic sedimentary rocks, except for some arkoses and 

argillites. (See Pettijohn, 1963, figs. 2, 3.)

Considering the minor amounts of CaO and large 

amounts of K2O present in these quartzites, analytical 

results for Sr, Rb, and Ba (table 5) are about what 

would be expected. Sr2+ substitutes for Ca2+ in rockforming minerals, and these quartzites contain only 

about 4-84 ppm Sr. On the other hand Rb+ and Ba2+ 

substitute for K+, and these quartzites contain about 

16-258 ppm Rb and 133-1757 ppm Ba. Excepting the 

two samples of Precambrian quartzite (428 and 476), 

the Rb and Ba values (table 5) plot (not shown) near a 

line representing a Ba:Rb ratio of about 5; comparative 

data are rare in the literature. The semiquantitative 

values for the various trace elements (table 5) generally 

conform to the ranges reported for sandstones by 

Pettijohn (1963, table 10).

The modal analyses listed in table 5 and the data 

summarized in table 6 show that the original 

sediments were sands with various amounts of admixed argillaceous materials. The degree of mineralogical maturity of the detrital grains varies, but plagioclase is either absent or present in only minor amounts, 

as shown by both the chemical and modal analyses 

listed in table 5. Some of these assemblages contain appreciable amounts of potassium feldspar, whereas 

others are composed almost entirely of quartz. The 

detrital grains generally show a low degree of textural 

maturity. Samples in which size and shape are still apparent are composed of poorly sorted and poorly 

rounded grains that have suffered relatively little attrition during transport and deposition.

The mineralogy of the argillaceous materials present 

in the original sediments is a matter of conjecture, for 

these materials have crystallized to metamorphic 

micas. Stewart (1970, p. 24, 25) reported the presence 

of muscovite, chlorite, "mica clay," potassium 

feldspar, and quartz in many upper Precambrian and 

Lower Cambrian pelitic rocks of the southern Great 

Basin. Harrison and Grimes (1970, p. O13) reported 

illite-sericite, chlorite, potassium feldspar, and quartz 

in argillitic rocks of the Belt Supergroup in northwestern Montana that date from a period of sedimentation about 1,100 m.y. ago. It is possible that the 

argillaceous materials of interest in the present study 

were composed mainly of chlorite, micas, illite, quartz, 

and potassium feldspar. For most of the rocks included 

in tables 5 and 6, it also appears that the bulk 

chemistry of the argillaceous material was appropriate 

for the crystallization of one or more metamorphic 

micas under conditions of metamorphism that were 

essentially isochemical, except for the depletion of pore 

fluids—for no evidence of metasomatism exists. Some 

of the chemical relations are shown in figures 9 and 10. 

In figure 9 we have plotted K2O+Na2O versus A12O3 

for the quartzites listed in table 5. The points fall between or near the lines indicating the ratios of these oxides present in the metamorphic micas recovered from 

four of these quartzites (Lee and Van Loenen, 1969). In 

figure 10, K2O is plotted against Na2O for these quartzites, and the ratio of these oxides in the metamorphic 

micas is indicated. Moreover, the published analyses 

(Lee and Van Loenen, 1969) of micas from four of these 

quartzites are generally representative of our unpublished analyses of micas recovered from 14 of the 

quartzites listed in tables 5 and 6.

PROVENANCE

In brief, we may consider the original miogeosynclinal shelf sediments as composed of various proportions of two sedimentary rock types: (1) sandstone 

with a fair degree of mineralogical maturity but a 

rather low degree of textural maturity, not nearly as 

well sorted and well rounded as the Ordovician quartz-
12 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

TABLE 5.—Analytical data for quartzites

[Chemical analyses of samples 552, 554, 558, and 562 by S. Botts, using single solution procedure described by Shapiro 

Rb, Sr, and Ba analyses by W. P. Doering, using methods described in text. Semiquantitative spectrographic analyses 

by methods described by Lee and Van Loenen (1971, p. 10,11). Leaders (---), not applicable or not determined. ND, 

Precambrian and are Cambrian prospect mountain quartzite. Muscovite and biotite are metamorphic in these rocks]

Sample

Lat N.

Long W.

146-DL-62

39°01 '14"

114°15'05"

380-DL-66 39°01 '20"

114-16'H"

418-DL-67 38°54'48"

114°10'50"

419-DL-67 39°13'05"

114°04'15"

428 39°22'30"

114°3T25"

*476

39°03'02"

114°20'55"

478

39°13'00"

114°24'35"

503

39°29'05"

114°19'10"

505

39°30'30"

114°19'40"

Chemical analyses (weight percent)

Si02 ————

A1 20 3 ———

Feo0 3— — 

FeO —————

MgO ——————

Na 2 0 ———— 

Kn

LI r\ i . \ H 2 0(+) ———

H 2 0(-)~ —

Ti02 ————

P2 05— — - 

MnO —————

F ———————

Subtotal — 

Less 0 ———

Total ———

96.53

1.30

.55

1 Q

.09

.00

no

.41

.14

.02

45

.02

.00

.01

.00

.02

99.80 

.01

99.79

90.74

.72

.24

.00

no

.47

03

.10

.01

.01

.00

.00

.01

99.74 

.00

99.74

85.74

6.65

1

O£

.46

.49

.02

.17

3

r o

.60

.02

.65

.07

.01

.01

.00

.02

99.79 

.01

99.78

91.14

4 55

.47

.12

.07

.00

.17

2

-1 Q

.24

.02

.06

.03

.02

.01

.00

.01

99.69 

.00

99.69

81.44

8.90

1 10

2 57

.57

.09

.12

2.84

1.31

.05

.61

.09

.01

.01

.01

.06

99.86 

.03

57.40

23.19

3 27

2.10

^ C. Q

no

32

6.60

3.72

.13

Q r

13

.07

.02

.00

.07

99.63 

.03

99.60

77.08

11.71

2.71

.40

.67

.14

no

4 35

1 CQ

.05

.79

.01

.01

.12

.00

.03

99.73 

.01

99.72

95.18

2

r -j

30

1 Q

.10

.02

.04

.92

.21

.02

.10

.01

.00

.02

.00

.01

99.68 

.00

99.68

80.93

10.74

.77

Q C

.39

.00

.12

4.44

1.01

.04

.16

.03

.01

.02

.00

.12

99.63 

.05

99 58

Quantitative X-ray fluorescence analyses (parts per million)

Rb —————— -

Sr--- ---.

p -.

Rb/Sr —— -

1C Q

45

Ttt

3 49

14.4

421

3.70

113

28.9

465

3.92

—— 112

—— 1757

—— 7.27

O C Q

Q O C

C C. O

3 09

141

7.6

499

18.58

9.5

279

3 64

1 7 Q

on o

972

5.80

Semiquantitative spectrographic analyses (weight percent)

Be ———— -

Ca- —— --

rp _ _ ____

Co ————

La— — -

Mo ————

Mb ————

Pb ————

Sr -------

V ——————

Y —————

Zr ————

0

0

.03

0

0

.0003

.0005

0

0

.0005

0

0

0

0

.001

.001

.0002

.05

0

0

.015

0

.0005

.0015

.0005

.0007

0

0

0

.0007

0

0

0

0

0

.007

0

0

.05

0

.0005

.001

.010

.001

0

0

0

.001

.0015

.0005

.007

.0015

.003

.07

0

0

.03

0

.0003

.0003

.0003

.0007

0

0

0

.0005

0

0

0

0

0

.007

0.005

.00015

.15

<.02

.0007

.003

.0003

.0015

<.005

0

.002

.002

.0015

.0007

.007

.0015

.0002

.02

0.05

.0005

.1

<.02

.003

.01

.003

.003

.007

.0003

.002

.007

.0015

.002

.015

.003

.005

.03

0.003

.0003

.15

<.02

.001

.003

.001

.0015

<.005

0

.0015

.002

0

.001

.007

.0015

.0002

.03

0.002

0

.03

0

.0003

.0015

.0003

0

0

0

.0015

0

0

0

.0007

.0015

.0002

.007

0.002

.0003

.03

0

.0005

.002

.0003

.0015

0

0

.0015

.0007

.001

.0005

.002

.001

.0001

.01

X-ray modal analyses (weight percent)

Quartz —— -

Plagioclase

Muscovite —

Biotite ——

95

<1

ND

4

°

89

4

<1

7

ND

72

13

ND

13

2

79

15

ND

6

ND

69

ND

2

21

8

20

ND

3

70

ND

70

4

<1

26

ND

89

ND

ND

11

ND

69

5

<1

25

°

^Sample 476 contains chlorite and illite(?). 

•Sample 558 contains about 1 percent garnet.
COMPOSITION OF CALCIUM-POOR QUARTZITES 

from eastern White Pine County, Nevada

(1967). All other chemical analyses by E. L. Munson Brandt by methods described by Peck (1964). Quantitative 

by L. A. Bradley; general limitations of method described in text. X-ray modal analyses by R. E. Van Loenen, 

detected. <, less than amount shown. Samples 428 and 476 are Precambrian in age; all other samples are

13

506 39°32'55" 

114°19'45"

547 39°14'35" 

114°04'50I

548 39°15'15" 

11 114°07'15

549 39°14'55" 

" 114°07'10'

552 38°59'09" 38 C 

1 114°18'50" 114

554 2 558 •59'35" 39°20'35" 

°19'13" 114°14'05"

562 39°18'45" 

114 0 13'00"

569 39°02'22" 

114°34'09"

Chemical analyses (weight percent) — Continued

94.

2.

.

•

.

.

.

•

.

.

•

.

.

.

•

99.

99!

98

48

35

34

24

00

01

81

12

03

13

02

01

03

00

05

60

02

58

91.

3.

1.

•

.

.

1.

,

.

•

.

.

•

99.

99.

88

78

84

18

13

00

03

32

41

02

10

02

01

02

01

01

76

00

76

92.74

3.57

1.38

.18

.10

.00

.03

1.21

.29

.02

.10

.03

.01

.01

.00

.01

99.68

.00

99.68

86.

5.

2.'

1.

.

.

1.

.

.

•

.

.

•

99.

99.

08

97

82

72

37

00

27

44

69

04

31

03

04

02

00

03

QOOO

01

82

89.5 89

5.3 5

1.0

.08

.19

.03

.31

2.6 2

.56

.04

.29

.04

.02

.01

.00

.01

100 99

Quantitative X-ray fluorescence analyses

40.

11.

189

3.

5

4

55

44.

9.

221

5.

0

00

39.0

3^7

1 Q7 1 O/

10.49

75.

oc ob.

177

2.

Semiquantitative

0.

.

.

0

•

.

.

.

0

0

.

.

0

0

.

•

90

ND

<1

9

<1

002

0003

05

0005

0003

0003

0005

001

0007

0007

001

0001

007

0.

0

.

0

0

.

.

0

0

.

.

0

0

.

.

.

•

89

<1

<1

10

ND

002

03

0007

0003

0007

001

0005

0007

001

0001

007

0.002

0

.03

0

.0003

.0005

.0001

.0007

0

0

.001

.0005

0

0

.0007

.001

.0001

.01

88

ND

ND

12

ND

0.

0

.

<.

•

.

.

<•

0

.

.

0

.

.

.

•

X-ray

82

ND

ND

10

8

1

5

06

QQ ------ oo

——— 24

3

.4

.5

.55

.16

.16

.00

.12

.3

.86

.01

.06

.02

.01

.02

.00

.01

95.4

1.2

.70

.40

.22

.00

.00

.31

.67

.00

.11

.03

.04

.02

.01

.01

99

94.0

2.6

.31

.12

.06

.00

.09

1.1

.54

.00

.17

.02

.02

.01

.00

.01

99

79.83

9.99

1.83

.41

.55

.00

.11

5.10

1.04

.03

.74

.04

.01

.05

.00

.02

99. 73

.01

99.72

(parts per million) — Continued

.3

.56

spectrographic analyses (weight

002

05

02

001

002

003

0007

005

0015

0015

0007

003

0015

0002

015

modal

0.002 0

0 0

.02

<.02 0

.0003

.0007

.0003

.0007

0 0

0 0

.001

.0005

.0015

0 0

.0015

.0015 0

.0002

.015

analyses (weight

78 79

15 10

3 <1

2 10

2 ND

.002

.015

.0003

.0002

.0003

.0007

.001

.0005

.001

.0007

.0001

.007

19.4

3.9

52

5.02

32.9

56.1

465

.59

131

41.4

695

3.17

percent)--Continued

0.002

0

.05

<.02

.0003

.0003

.0015

0

.0030

0

.001

.0005

0

0

.0007

.0015

.0001

.02

0.002

0

.03

<.02

0

.0005

.0001

0

0

0

.001

.0005

.001

0

.0007

0

.0001

.01

0.003

.0003

.05

0

.0005

.0015

.0001

.0010

.0030

0

.0020

.001

.001

.0007

.003

.002

.0003

.05

percent) --Continued

95

ND

ND

2

2

91

3

ND

6

ND

63

10

<1

27

ND
14 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA 

TABLE 6.—Petrographic data for quartzites from eastern White Pine County, Nevada

Sample 

Number Original sediment Present rock

'146-DL-62 

'380-DL-66

'418-DL-67 

'419-DL-67

2428

2476

478

503

505

506

547

548

549

552

Quartz sandstone with about 4 percent argillaceous cement. Quartz 

grains subangular to subrounded, with grain size 0.2-0.5 mm.

Quartz sandstone with about 4 percent detrital potassium feldspar and 

7 percent argillaceous cement. Quartz, potassium feldspar grains 

subangular and poorly sorted, with grain size 0.06-0.5 mm.

Argillaceous quartz, potassium feldspar sandstone. Detrital grains 

subangular to subrounded and poorly sorted, with grain size 0.03- 

0.4mm.

Quartz, potassium feldspar sandstone with argillaceous cement. Original grains obscured by a pronounced directional element and sutured contacts.

Argillaceous quartz sandstone. Poorly sorted subangular quartz grains 

0.05-1.0 mm in size.

Mudstone with chert fragments less than 1.0 mm in size.

Argillaceous quartz, potassium feldspar sandstone. Quartz partly recrystallized, but original grains, still visible, subangular to subrounded 

and 0.05-1.0 mm in size.

Argillaceous quartz sandstone. Quartz completely recrystallized. Sutured contacts between grains. Original grains obscured.

Argillaceous quartz, potassium feldspar sandstone. Original quartz 

grains obscured during complete recrystallization.

Argillaceous quartz sandstone. Quartz completely recrystallized, with 

sutured contacts between grains. Original grains obscured.

Argillaceous quartz sandstone. Original grains obscured by complete 

recrystallization and development of pronounced directional element.

- do

Quartz, potassium feldspar sandstone with argillite cement. Quartz, 

potassium feldspar grains subangular to subrounded and 0.05-0.4 mm

Light-gray massive 

quartzite.

Do.

Thin-bedded muscovite quartzite.

Gray quartzitic flagstone.

Dark-gray schistose 

quartzite.

Greenish-gray phyllite.

Thin-bedded muscovite quartzite.

Coarsely crystalline 

quartzite.

Schistose quartzite.

Coarsely crystalline 

quartzite.

Do.

Do.

Schistose quartzite. 

Gray quartzite.

554

558

562

569

Argillaceous quartz, potassium feldspar sandstone. Quartz, potassium 

feldspar grains subangular to subrounded and 0.05-1.0 mm in size.

Quartz sandstone with argillaceous cement. Original grains obscured 

by complete recrystallization and development of pronounced directional element.

do --

Argillaceous quartz, potassium feldspar sandstone. Quartz, potassium 

feldspar grains subangular to subrounded and 0.05-0.4 mm in size.

Light-gray quartzite.

Gray quartzite.

Gray quartzitic flagstone.

Schistose quartzite.

'Chemistry of constituent metamorphic micas in Lee and Van Loenen (1969). Radiometric K-Ar ages of micas presented by Lee and 

others (1970). Radiometric K-Ar ages of constituent micas from all other quartzites presented in Chapter C, this report. 

2Samples 428 and 476 are Precambrian in age; all others are Precambrian and Cambrian Prospect Mountain Quartzite.
COMPOSITION OF CALCIUM-POOR QUARTZITES 15

1623.19

12.0

10.0-

0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

K2 0+Na2 0, IN WEIGHT PERCENT 

*

FIGURE 9.—Relation between K2O+Na2O and A12O3 contents of quartzites listed in table 5. Phengite and biotite ratios indicated based 

on analyses in Lee and Van Loenen (1969). Much or all of the K2O and Na2O present in each rock contained in metamorphic mica 

that crystallized from argillaceous material.

ites of the area described by Ketner (1966, 1968); and 

(2) argillaceous material, possibly composed mainly of 

chlorite, micas, illite, quartz, and potassium feldspar. 

Stewart (1970) showed that these sediments were 

derived from Precambrian terrane exposed on the 

craton to the east. The character of these sediments 

suggests that they may have been derived from a deeply weathered crystalline mass composed mainly of 

quartz, weathered potassium feldspar, and clay 

minerals. Stewart and Poole (1974, fig. 4) showed that 

this type of terrane was available as source material in 

a pregeosynclinal exposure of metamorphic rocks 

about 300 km to the east. The inferred paleoequator

passed very near the area of study during Cambrian 

time (Smith and others, 1973, fig. 13), indicating that 

the sediments were at least transported and deposited 

in a tropical climate, under conditions conducive to the 

rapid destruction of ferromagnesian minerals and 

plagioclase.

Other data suggest that the original miogeosynclinal 

shelf sediments could have been derived from the terrane just described. During our study of age relations 

in eastern White Pine County, Nev., we have obtained 

K-Ar radiometric ages for five clastic micas recovered 

from unmetamorphosed Lower Cambrian detrital sediments. Four of these samples were collected from the
16 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

PHENGITE, BIOTITE RATIO

2.0 3.0 4.0 

K2O, IN WEIGHT PERCENT

5.0 6.0 7.0

FIGURE 10.—Relation between K2O and Na2O contents of quartzites listed in table 5. Phengite, biotite ratio based on analyses in 

Lee and Van Loenen (1969). Much or all of the K2O and Na2O present in each rock is contained in metamorphic mica that 

crystallized from argillaceous material. Compare Pettijohn (1963, figs. 2, 3).

Schell Creek Range-Duck Creek Range area, within 20 

km west of the area of figure 8, and one was collected 

about 50 km east of the area of figure 8. All five of 

these clastic micas give K-Ar age results (chapter C, 

this report) within the range 1,182-1,242 m.y.

REFERENCES CITED

Harrison, J. E., and Grimes, D. J., 1970, Mineralogy and 

geochemistry of some Belt rocks, Montana and Idaho: U.S. 

Geological Survey Bulletin 1312-O, 49 p.

Hose, R. K., and Blake, M. C., 1976, Geology of White Pine County, 

Nevada: Nevada Bureau of Mines and Geology Bulletin 85, pt. 1, 

p. 1-35.

Ketner, K. B., 1966, Comparison of Ordovician eugeosynclinal and 

miogeosynclinal quartzites of the Cordilleran geosyncline, in 

Geological Survey research 1966: U.S. Geological Survey Professional Paper 550-C, p. C54-C60.

_____1968, Origin of Ordovician quartzite in the Cordilleran miogeosyncline, in Geological Survey research 1968: U.S. Geological 

Survey Professional Paper 600-B, p. B169-B177.

Lee, D. E., and Doering, W. P., 1974, Barium in hybrid granitoid 

rocks of the southern Snake Range, Nevada: U.S. Geological 

Survey Journal of Research, v. 2, no. 6, p. 671-675.

Lee, D. E., Marvin, R. F., Stern, T. W., and Peterman, Z. E., 1970, 

Modification of potassium-argon ages by Tertiary thrusting in 

the Snake Range, White Pine County, Nevada, in Geological

Survey research 1970: U.S. Geological Survey Professional Paper 

700-D, p. D92-D102.

Lee, D. E., and Van Loenen, R. E., 1969, Phengitic micas from the 

Cambrian Prospect Mountain Quartzite of eastern Nevada, in 

Geological Survey research 1969: U.S. Geological Survey Professional Paper 650-C, p. C45-C48.

___1971, Hybrid granitoid rocks of the southern Snake Range, 

Nevada: U.S. Geological Survey Professional Paper 668, 48 p.

Peck, L. C., 1964, Systematic analysis of silicates: U.S. Geological 

Survey Bulletin 1170, 89 p.

Pettijohn, F. J., 1963, Chemical composition of sandstones—excluding carbonate and volcanic sands, Chap. S in Data of 

geochemistry, 6th ed.: U.S. Geological Survey Professional Paper 

440-S, 21 p.

Shapiro, Leonard, 1967, Rapid analysis of rocks and minerals by a 

single-solution method, in Geological Survey research 1967: U.S. 

Geological Survey Professional Paper 575-B, p. B187-B191.

Smith, A. G., Briden, J. C., and Drewry, G. E., 1973, Phanerozoic 

world maps—Special papers in paleontology no. 12, in Hughes, 

N. F., ed., Organisms and continents through time—a symposium 

volume of 23 papers: London Paleontological Association, 39 p.

Stewart, J. H., 1970, Upper Precambrian and Lower Cambrian 

strata in the southern Great Basin, California and Nevada: U.S. 

Geological Survey Professional Paper 620, 206 p.

Stewart, J. H., and Poole, F. G., 1974, Lower Paleozoic and uppermost Precambrian Cordilleran Miogeocline, Great Basin, western 

United States, in Dickinson, W. R., ed., Tectonics and Sedimentation: Society of Economic Paleontologists and Mineralogists 

Special Publication no. 22, p. 28-57.
A Radiometric Age Study of 

Mesozoic-Cenozoic Metamorphism in 

Eastern White Pine County, 

Nevada, and Nearby Utah

By DONALD E. LEE, RICHARD F. MARVIN, and 

HARALD H. MEHNERT

GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1158-C
CONTENTS

Page

---.....-...-......-..-.....-.-......-—»....-.—...-.-———-—-——-——---—---.«•••• ................ .............. . 17j^ i

———•«TMTMTM«TM-TMTM—«——•-—«-TM«TM«—.....................——.*--—............. j^ j

---TM-—-TM--TM-—---—---—--»-TM-»-TM-TM-TM--TM———-..........—«..•«••.......................... j^ ^

XJ.OUSG JXcHlgjG, U tclil •••"——"—-———..«.-.«.-...-««-«««««———«——-«——•.................................. j^ f

Northern Snake Range, Nevada ———————————————————————.....—...——... 20

xVern JViounLainsf JNevacla ano utaxi————————•—————*—•—————————•—•——— ^^

Precambrian rocks, southern Snake Range, Nevada ——————————-——....———..... 23

Wheeler Peak area, southern Snake Range, Nevada ————————————--——...——— 24

Mount Wheeler mine area, southern Snake Range, Nevada —————————————...— 24

Lexington Creek area, southern Snake Range, Nevada ————————————————— 24

McCoy Creek area, Schell Creek Range, Nevada ——————————————————— 24

Other areas, Schell Creek Range, and Duck Creek Range, Nevada ——————————— 25

Egan Range, Nevada————————————————————————————————————————— 26

Toana Range, Nevada——————————————————————————————————— 26

j_/iscussion —-««««—TM——TM«TM««««-—-«-«««««««»..-...«-.———TM««.TM——«——.-............................. ^ j

\_/oricrusions ——"-——-—-"""—•——--——-——-------••••-•«•««.«..———.—•« ..............................I-.*............. ^ ^

xxGTGiGliCGS C1CGQ. •—«TM-TM—-""——TM———•-——TM---TM-TMTM-TM-—-•-----------—-«--•—.-«««««««»——————- ^o

ILLUSTRATIONS

FIGURE 11. Map of part of eastern Nevada and western Utah, showing sample localities — 21

TABLES

Page

TABLE 7. Potassium-argon ages of selected minerals from the northeastern part of the

Basin and Range province -«——————————-——--—————-———— 18

8. Whole-rock rubidium and strontium data for samples 244 and 245 ———-——-- 22
GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

A RADIOMETRIC AGE STUDY OF MESOZOIC-CENOZOIC METAMORPHISM 

IN EASTERN WHITE PINE COUNTY, NEVADA, AND NEARBY UTAH

By DONALD E. LEE, RICHARD F. MARVIN, 

and HARALD H. MEHNERT

ABSTRACT

A total of 58 K-Ar radiometric ages have been determined for igneous, detrital, and metamorphic minerals, mostly from eastern 

White Pine County, Nev., and nearby Utah. A surprising agreement 

among results for five detrital muscovites from Lower Cambrian 

sediments indicate a Precambrian provenance that crystallized at 

least 1,182-1,242 m.y. ago. It is probably more useful to regard the 

metamorphism in the area as spotty and diverse, rather than 

regional, for no area-wide metamorphic event is apparent. Tertiary 

K-Ar ages determined on micas from Precambrian and Cambrian 

metasedimentary rocks are generally interpreted to have resulted 

from loss of argon, caused by thermal stresses related to Tertiary 

activity along the regional thrust faults. However, the time of 

original crystallization of any one of these metamorphic micas remains an important and unanswered question. Where an intrusive 

is exposed near the level of a regional thrust fault, K-Ar ages for the 

igneous micas might reflect postcrystallization movement along the 

thrust fault. A working hypothesis as to the history of plutons exposed in and near the area is proposed.

INTRODUCTION

A previous study (Lee and others, 1970) presented 

more than 70 radiometric ages for samples of Jurassic 

and Tertiary igneous rocks and upper Precambrian to 

Lower Cambrian metasedimentary rocks from the 

southern and central Snake Range of eastern Nevada. 

Potassium-argon ages determined on micas recovered 

from the Jurassic igneous terrane were found to range 

from 17.4 to 159 m.y.; ages determined on micas from 

the Precambrian and Cambrian metasedimentary 

rocks ranged from 22.7 to 264 m.y. (Ages quoted from 

the previous study are recalculated using the new 

decay constants listed in table 7.) The main conclusion 

reached in the previous study was that the lower K-Ar 

ages result from loss of argon due to stress related to 

Tertiary activity along the Snake Range decollement.

The present study reports 58 new K-Ar ages for 

metamorphic, detrital, and igneous minerals, mostly 

from eastern White Pine County, Nev. Sampling for 

this study was designed to meet two closely related objectives:

1. To test the possibility that the main conclusion 

reached in the previous study also applies to parts 

of the region other than the southern and central 

Snake Range. In other words, has there been a 

modification of K-Ar ages near the level of 

thrusting in some of the other ranges of eastern 

White Pine County?

2. To investigate further the metamorphism apparent 

in parts of eastern White Pine County. Is it 

regional, as proposed by Misch and Hazzard 

(1962), and referred to by Armstrong and Hansen 

(1966), Nelson (1966), and Drewes (1967), or is it 

rather irregular and spotty, related in part to tectonic elements such as the Snake Range de*collement and other thrust faults?

In conjunction with the age investigation, we have 

obtained chemical analyses of highly purified fractions 

of 16 of the metamorphic micas dated by K-Ar. A comprehensive discussion of these analyses is beyond the 

scope of this report, but we can state that they are 

generally similar to analyses of four phengitic 

muscovites and one biotite listed by Lee and Van 

Loenen (1969), who also described the methods of 

mineral purification used in the present study.

Standard techniques for potassium and argon 

analysis were used (Evernden and Curtis, 1965). 

Analytical error for individual K-Ar ages was 

evaluated in the manner described by Cox and Dalrymple (1967). Throughout this report a given sample 

number refers to the whole rock and to the mineral or 

minerals recovered from that rock. Potassium-argon 

ages are listed in table 7.

POTASSIUM-ARGON AGES

HOUSE RANGE, UTAH

Before proceeding to an area-by-area discussion of 

the geochronology, consider the age determined for a 

muscovite recovered from a sample of Lower Cambrian

17
TABLE 1 .—Potassium-argon ages of selected minerals from the northeastern part of the Basin and Range prov

[Analyzed by R. F. Marvin, H. H. Mehnert, Viola Merritt, W. T. Henderson, Lois Schlocker. and R. E. Zartman, U.S. 

Constants: ^°YAe = 0.581 x 10~10 yr" 1 ; X g « 4.962 x 10~ l0 yr-1 . 

Atomic abundance: l|0 K = 1.167 x 10"1*. ^"Ar = radiogenic isotope, columns 7 and 9]

Sample 

Number

471

471

Location 

Lat N. Long W.

0 ' ii 0 ' it

39 14 55

39 14 55

113 25 40

113 25 40

Rock type 1

P

P

Mineral

Western House Range,

Western House Range,

K2 0 l|0Ar RadioMesh size (Weight (10~ 10 genie l|0 Ar 

percent) moles/g) (percent)

Millard County,

-100 , +140

Millard County,

-100 , +140

Utah

8.78

Utah

8.78

226.0

226.0

98

98

Northern Snake Range, Nevada

478 

501

503 

505 

506

547 

548

549

558 

560 

561 

562

RM-1 

244 

245 

564 

566

567

39 13 00 

39 29 00 

39 29 00 

39 29 05 

39 30 30 

39 32 55 

39 32 55 

39 14 35 

39 15 15 

39 15 15 

39 14 55 

39 14 55 

39 14 55 

39 20 35 

39 19 05 

39 19 00 

39 18 45

39 44 00 

39 35 55 

39 35 55 

39 38 05 

39 38 15 

39 38 15 

39 38 30

114 24 35 

114 18 10 

114 18 10 

114 19 10 

114 19 40 

114 19 45 

114 19 45 

114 04 50 

114 07 15 

114 07 15 

114 07 10 

114 07 10 

114 07 10 

114 14 05 

114 12 00 

114 12 35 

114 13 00

114 14 00 

114 07 55 

114 07 55 

114 03 35 

114 03 05 

114 03 05 

114 02 30

-bp — ————————— ——————

—— do ———————————

p€€pm —————————————— 

—— do ——————————————

—— do ——————————————

—— do ———————————————

—— do ——— ———— ——— — ——

— An _____ ____ ___ .____

—— do ———— ———— ——— —

_ An — — — .—————————

—— do —————————————— 

—— do ——————————————

—— do ——————————————

—— do —— ———— ——— —— —

Cataclastic intrusive — 

Mafic sill in marble ——

—— do ————————————

Cataclastic intrusive —

—— do ———— ————— —

Muscovite ————————

—— do —— — —— ————

Muscovite ————————

—— do — — ——— ————

Muse ov i t e — — ——— —

Muscovite ————————

—— do — ——— —— — ——

Kern Mountains,

—— do ———————————

—— do ——— ———— ———

Muscovite + quartzBiotite + quartz ——

Biotite + quartz ——

-150 

-100 

-100 

-60 

-100 

-100 

-100 

-30 

-60 

-60 

-60 

-60 

-60 

-60 

-60 

-60 

-60

2 

2

, +100 2 

2

2

, +60 

, +100 2 

, +100 2 

, +140 

, +140 

, +140 

, +140 

, +140 

, +100 2 

, +140

10.99 

10.79 

2 9.41 

10.86 

11.03 

11.02 

7.42 

10.54 

10.80 

10.80 

7.18 

2 7.12 

2 9.07 

9.99 

8.73 

10.69 

10.56

14.16 

8.056 

5.940 

9.062 

8.712 

8.895 

5.440 

3.177 

3.545 

3.522 

3.177 

3.142 

6.234 

5.924 

3.895 

5.731 

5.602

95 

92 

82 

90 

63 

90 

90 

67 

71 

75 

48 

35 

86 

83 

84 

74 

68

Nevada and Utah

-10 

-100 

-100 

-100 

-200 

-200 

-60

Precambrian rocks, southern

472 

473 

476 

499 

536

39 02 20 

39 02 20 

39 03 02 

39 03 05 

39 08 35

114 20 25 

114 20 25 

114 20 55 

114 20 45 

114 22 00

p€pw ——————————————

—— do ———— — ——— ———

p€s t r ( ? ) ———————————

———An—— ____________

-200 

-100 

-100 

-100 

-230

Wheeler Peak area, southern

552 

554 

<;<;<;

38 59 09 

38 59 35 

•*a nn n<;

114 18 50 

114 19 13

1 1 A 10 1 S

—— do ————————————

__ j.-, _______ _ . _ .__

__do—— — — — — — — ——

——— An _____——————————

-100 

-100 

-inn

, +30 

2

2 

, +100

10.07 

10.78 

10.79 

6.31 

6.63 

.553 

8.22

10.22 

8.012 

7.545 

2.264 

2.754 

.2752 

3.040

69 

56 

45 

83 

56 

61 

82

Snake Range, Nevada

, +200

Snake Range,

7.62 

9.16 

8.56 

8.39 

6.92

Nevada

5.82 

9.00

0. 01

12.21 

65.26 

13.27 

23.24 

7.503

28.01 

13.22 

•>r\. 07

94 

93 

91 

97 

87

96 

92

07
Mount Wheeler mine area, southern Snake Range, Nevada

2-MW-60 38 53

378 

531 

532

38 51 

38 51 

38 51

52

29 

12 

40

114 19 12

114 13 04 

114 12 05 

114 10 56

—— do ————————————

—— do ————————————

Sericite ————————— -100

Lex ing ton Creek

__ ___/1n_ — - .___.

,__ —— do ———— •

8.48 25.30 98 

area, southern Snake Range, Nevada

——————— _100, +200

—————— _100, +200

——————— _100, +200

McCoy Creek area, Schell Creek Range

427 

428

430 

435 

571 

572

368 

393 

394

538 

569 

575 

576

39 22 

39 22 

39 22 

39 22 

39 22 

39 21 

39 22

39 14 

39 15 

39 15 

39 15 

39 28 

39 02 

39 15 

39 15

30 

30 

30 

26 

21 

36 

25

00 

43 

43 

43 

19 

22 

32 

36

114 31 25 

114 31 25 

114 31 25 

114 31 40 

114 34 08 

114 35 36 

114 31 58

114 32 13 

114 30 35 

114 30 35 

114 30 35 

114 37 00 

114 34 09 

114 43 43 

114 44 02

—.ft

—— do ————————————

—— do ————————————

Other

_r»

Xeno 1 i th ——————————

—— do ————————————

-ep _________________

__ —— do ———— •

do

——————— -100, +200 

_________ _i nn -i-9nn

——————— _100

on

quartz — -100 

f.n

— Amphibole5 ———————— -200

10.72 

10.47 

10.32

, Nevada

2 10. 50 

8.51 

2 10. 36 

2 10.48 

8.54 

10.09 

.332

areas, Schell Creek Range, and Duck Creek Range,

__ ———Ar\——————.

—— ___, do ——————— •

_ . __ _1A<"»

—————— _140

—————— _140

_________ _i nn

—————— _60

____ .— —i on

8.41 

8.72 

8.45 

1.03 

9.86 

2 10.89 

10.41 

9.93

13.67 

12.67 

11.83

9.792 

5.680 

9.356 

13.30 

90.37 

241.1 

.4815

Nevada

11.19 

4.463 

4.260 

.5356 

241.5 

10.68 

256.8 

238.6

88 

89 

89

88 

79 

85 

90 

99 

99 

61

83 

84 

86 

64 

99 

93 

98 

99

Egan Range, Nevada

383 

384 

386 

439

39 38 

39 37 

39 48 

39 22

05 

40 

20 

13

114 53 20 

114 52 55 

114 53 25 

114 52 58

Sheared intrusive ——

_— — An— ___ ___ ___ ___ ___

— Muscovite + quartz — -100

____ _ ._ _ _i nn

100

—————— _100

10.44 

10.46 

10.30 

8.12

3.807 

5.503 

5.218 

7.787

89 

90 

84 

84

Toana Range, Nevada

511 

512

41 00 

41 00

55 

55

114 17 30 

114 17 30 __ —— do ———— •

i nn 2 10.89 

2 10.85

11.59 

12.06

92 

93

1 p€€pm, Precambrian and Cambrian Prospect Mountain Quartzite. €p, Cambrian Pioche Shale. p€pw, unnamed Precambrian 

Quartzite of Misch and Hazzard (1962)). p€str, Precambrian Strawberry Creek Formation of Misch and Hazzard (1962). p€, 

Creek Group of Misch and Hazzard (1962).

2 Potassium determinations are part of complete mineral analyses by methods described by Peck (1964); Elaine L. Muns

Except as noted, each of the other potassium values is an average of two determinations made with a Perkin-Elmer flame p

lithium internal standard. (Brand names in this report are for illustration purposes only and do not constitute endorsem

Geological Survey.)

^Subjected to ultrasonic vibration for 1 hour.

4 Specific gravity less than 2.86.

5Potassium determined by mass spectrometry.
20 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

Pioche Shale collected on the west flank of the House 

Range, Millard County, Utah. As shown on the geologic map of southwestern Utah compiled by Hintze 

(1963), no thrust faults are exposed in the area, 

although it should be noted that Hose and Danes 

(1973) have shown that the House Range itself should 

be underlain by a thrust of very large magnitude. No 

evidence of metamorphism has been seen in the field, 

and petrographic evidence shows clearly that the 

dated mica is detrital in the Pioche Shale. The age 

(1,242 m.y.) of this mica is of more than passing interest, for, as brought out in the discussion to follow, 

four other detrital micas recovered from Lower Cambrian clastic rocks of eastern White Pine County, Nev., 

gave similar Precambrian Y ages.

NORTHERN SNAKE RANGE, NEVADA

In the northern Snake Range, erosion has exposed 

hundreds of square kilometers of Lower Cambrian 

metasediments which originally were less than a few 

hundred meters below the sole of the Snake Range 

decollement. (See the map of Hose and Blake, 1976.) 

From field, petrographic, and radiometric age evidence 

described below, we interpret the metamorphism to 

have resulted from the heat and tectonic overpressures 

developed during inception of the decollement and 

from subsequent movements on the decollement.

Sample 478 (fig. 11), Prospect Mountain Quartzite, 

was originally a poorly sorted impure sandstone with 

quartz grains less than 1 mm in diameter. The original 

argillaceous impurities have recrystallized into a finegrained metamorphic muscovite, now surrounding detrital quartz grains and comprising about 27 percent of 

the rock. The lower plate appears to have been eroded 

to a depth of about 200 m at the sample site. 

Muscovite 478 gave a Late Cretaceous age of 87.4 

m.y., appreciably older than any of the other samples 

from the northern Snake Range discussed below or included in the study of Lee and others (1970).

Samples 501, 503, 505, and 506 were collected from 

lower plate rocks on the northwestern flank of the 

northern Snake Range (fig. 11). Sample 501 is Pioche 

Shale; the others are Prospect Mountain Quartzite. 

Nelson (1966, p. 922, and map, p. 924, 925) noted the 

presence of staurolite in these rocks. In the area of 

these samples (fig. 11), which covers a horizontal 

distance of about 6 km, we did not detect any 

staurolite, either in the field or during petrographic 

and mineral separation work in the laboratory.

The metamorphic micas in these samples are so 

abundant and well crystallized that it was easy to 

recover clean concentrates for analyses. The quartz 

grains in samples 503, 505, and 506 (Prospect Mountain Quartzite) show evidence of pronounced strain and 

recrystallization, with sutured contacts except where 

shielded by mica. The orientation of the micas is determined mainly by the outlines of the original detrital 

quartz grains, but in sample 506 a faint directional element is evident in thin section. The four muscovite 

ages (table 7) all are in the range 51.1-57.1 m.y., 

whereas biotites 501 and 506 gave ages of 43.3 and 

50.2 m.y., respectively. Many studies (for example, Lee 

and others, 1970) have shown that muscovite is 

superior to biotite in retaining argon during periods of 

geothermal stress. We interpret these ages as hybrid, 

related to heat produced by movement along the 

thrust.

Samples 547, 548, and 549, all Prospect Mountain 

Quartzite, were collected from the Hampton Creek 

drainage on the east side of the range. This is a highgrade metamorphic terrane unique among the areas 

discussed here. Between sample sites 547 and 548 is 

abundant development of garnet and staurolite in 

rocks of appropriate composition. No detailed study of 

this metamorphism has been made.

Sample 547 is from a relatively undisturbed outcrop 

of coarsely crystalline quartzite within a mass of contorted quartzite. The rock is about 90 percent quartz 

and 10 percent muscovite. The muscovite is arranged 

in thin layers. The quartz has been recrystallized and 

shows pronounced strain in thin section. Sample 548 is 

somewhat richer in muscovite than 547, but is otherwise very similar. Sample 549 is a quartz-muscovitebiotite schist. In thin section the rock shows a very 

strong planar element. The quartz has been recrystallized and shows pronounced strain; sparse amounts of 

garnet and staurolite have formed.

Muscovite 547 gave an age of 20.8 m.y. During the 

mineral separation process many of the micas in table 

7 were subjected to ultrasonic vibration for a few 

minutes. To check for possible loss of radiogenic argon 

during this procedure, muscovite 548 was split into 

two fractions. One part received no ultrasonic treatment, and the other was subjected to an hour of ultrasonic vibration. The two fractions gave practically 

identical ages of 22.7 and 22.5 m.y.

As emphasized by Lee and Van Loenen (1969), the 

metamorphic (phengitic) muscovites recovered from 

these Lower Cambrian metasediments are homogeneous and fractionate over a very narrow specific 

gravity range during centrifuging in heavy liquids. 

Muscovite 549 proved to be an exception, so one fraction lighter and one heavier than specific gravity 2.86 

were analyzed. The two fractions gave practically identical ages of 30.4 and 30.5 m.y. Both fractions were 

very clean; the low K2O values listed in table 7 result 

from the fact that this muscovite contains about 38
A RADIOMETRIC AGE STUDY OF MESOZOIC-CENOZOIC METAMORPHISM 21

114°56'

39°49'

114°00'

38°50'

FIGURE 11.—Map of part of eastern Nevada and western Utah, showing sample localities. Sample locality 471 is about 50 km 

east of the map area, localities 511 and 512 are about 133 km north. The 2500-m contour lines are not shown in the 

southwestern part of the map area. Base from U.S. Geological Survey 1:250,000 Ely, Nevada, Utah (1956, rev. 1971); 

Lund, Nevada, Utah (1956, rev. 1970).
22 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

percent of the paragonite molecule. Sample 549 is 

unusual in another respect: The biotite gave an age of 

47.1 m.y., much higher than the coexisting (paragonitic) muscovite. As already noted, the opposite relation 

is normally expected. It is possible that distortion of 

the muscovite structure due to the presence of the 

paragonite molecule led to unusually easy diffusion of 

radiogenic argon when the mica was under thermal 

stress.

It is difficult to interpret the apparent ages of these 

micas. They probably indicate Miocene movement on 

the overlying thrust, possibly complicated and (or) 

complemented by the presence of a Miocene hot spot.

Sample 558 appears to be from a quartzite horizon 

within the Pioche Shale; 560 is from a knob of 

Cretaceous-Tertiary (Hose and Blake, 1976) granodiorite just north of Deadman Creek, and 561 and 562 

are Prospect Mountain Quartzite, both collected less 

than 2 km southwest of 560. Sample sites 560, 561, and 

562 probably are not more than a few meters below the 

sole of the thrust. Sample 558 is from a rather massive 

quartzite, and samples 561 and 562 are from quartzitic 

flagstones. Petrographic study shows the quartz to be 

completely recrystallized and drawn out to express a 

planar element approximately parallel with the present 

surface and presumably with the overlying thrust. The 

micas are alined in the same plane. Sample 561 is about 

94 percent quartz and 6 percent muscovite; sample 562 

contains slightly less quartz and a few percent 

potassium feldspar. Sample 558 is more iron rich; it 

contains metamorphic biotite, and a few scattered 

grains of garnet and staurolite were detected during 

mineral separation. Thin-section study of 560 (intrusive) shows incipient cataclasis.

Muscovites 558, 561, and 562 gave ages of 40.7, 36.9, 

and 36.5 m.y., respectively. Biotite 560 gave 30.7 m.y. 

The muscovite ages are hybrid, related to heat produced by movement along the thrust and distance 

below the sole. The biotite age probably also is hybrid. 

That it indicates the time of emplacement of the pluton 

is unlikely, for the incipient cataclasis noted above indicates a cooled and completely crystallized magma.

KERN MOUNTAINS, NEVADA AND UTAH

Intrusive rocks crop out over an area of about 

130 km2 in the Kern Mountains of Nevada and Utah. 

Previous attempts to date these rocks radiometrically 

have met with frustration (Best and others, 1974, p. 

1283). Our data (tables 7, 8) do not resolve the problem, 

but they do point up some striking similarities between the Kern Mountains and the southern Snake 

Range, Nevada.

Most of the Kern Mountains intrusive is an unusual 

two-mica granite, practically identical to the Pole Canyon-Can Young Canyon granitoid rock of the southern 

Snake Range described by Lee and Van Loenen (1971, 

p. 5, 38). Muscovite RM-1, from a rock of this type, 

gave an age of 69.2 m.y.

Samples 244 (two-mica granite) and 245 (aplite) were 

collected less than 3 m apart. Muscovites 244 and 245 

gave K-Ar ages of 50.9 and 47.9 m.y., respectively. 

Whole-rock rubidium and strontium data for samples 

244 and 245 are listed in table 8. A two-point wholerock isochron (not shown) based on these data gives an 

apparent age of 71±6 m.y. and an initial 87Sr/86Sr ratio 

of 0.719. Such a high initial ratio suggests that the 

pluton originated from melting of the crust. Best and 

others (1974) found similarly high initial 87Sr/86Sr ratios 

and postulated a minimum age of 60 m.y. for the 

granite.

TABLE 8.— Whole-rock rubidium and strontium data for samples 244

and 245

[zell Peterman, U.S. Geological Survey, analyst. Decay 

constants for 87 Rb: Ag =1.42xlO~11yr~ 1 . Isotope 

abundance: 87 Rb/Rb=0.283 g/g]

Sample 

No.

Rb Srr 

(in ppm)

87 Sr/86Sl

245 

244

213 

123

14.6 

313

42.1 

1.14

0.7614 

.7204

Nelson (1966, p. 938) stated: "The rocks in the 

easternmost part of the Kern Mountain pluton have 

been subjected to cataclasis and shearing which, as 

determined from the orientation of the shear planes, is 

believed to be related to the eastward-directed decollement thrusting ..." Although in the eastern part of 

the Kern Mountains the main decollement has been 

completely eroded away (R. K. Hose, written commun., 

1978), the cataclasis described by Nelson is practically 

identical to that described by Lee and Van Loenen 

(1971, p. 6, 40) for the Can Young Canyon-Kious Basin 

area of the southern Snake Range, where it has clearly 

resulted from late (17-19 m.y., Lee and others, 1970) 

movement on the Snake Range decollement. Muscovite 564 and biotite 567, recovered from cataclasized 

Kern Mountains intrusive rocks, gave ages of 24.7 and 

25.5 m.y., respectively. Sample 566 was collected from 

a mafic sill in marble closely associated with 

cataclastic intrusives. The biotite and amphibole from 

this rock gave ages of 28.6 and 34.3 m.y., respectively. 

The pattern of K-Ar ages listed for the Kern Mountains in table 7 is similar to the pattern found in the intrusive rocks of the southern Snake Range and lends 

itself to a similar interpretation. The ages (24.7 and 

25.5 m.y.) on the cataclastic (eastern) portion of the 

Kern Mountains intrusive date a late movement on the
A RADIOMETRIC AGE STUDY OF MESOZOIC-CENOZOIC METAMORPHISM 23

overlying decollement, which effected the cataclasis. 

Farther to the west, in undeformed intrusive, where 

the muscovites were less completely degassed by thermal stresses related to the thrusting, the apparent 

ages increase to as much as 69.2 m.y. However, in the 

Kern Mountains there is an additional complication 

not encountered in the southern Snake Range—the 

protoclastic border facies described by Best and others 

(1974). The biotite and muscovite dated (23.3 and 48.2 

m.y., respectively) by Armstrong (1970) apparently 

were collected very near this border facies; these micas 

probably have been partially degassed by the protoclasis. Two other muscovite K-Ar ages listed by Best 

and others (1974) are 63.9 and 47.1 m.y.

Best and others (1974) postulated two intrusive 

events, with the younger being Oligocene in age, about 

31 m.y. ago. The 34.3-m.y. age given by amphibole 566 

may be related to this younger event. Our data indicate a minimum age of 70 m.y. for the main Kern 

Mountains intrusive event. A U-Pb age on zircon 

seems the next likely step. However, if sample 244 is 

representative of the main intrusive event, zircons will 

be difficult to obtain, for they are present mainly as 

tiny acicular inclusions in sparsely distributed apatite 

(Lee and others, 1973). Pending accumulation of further data, we can only conclude as Best and others 

(1974, p. 1285) did: "We are only beginning to realize 

how complex the Mesozoic-Tertiary magmatic and 

metamorphic history of the hinterland of the Sevier 

erogenic belt is and to study the rocks in the detail 

they deserve."

PRECAMBRIAN ROCKS, SOUTHERN SNAKE RANGE, NEVADA

Five samples were collected from the upper Precambrian sequence of the southern Snake Range described 

by Misch and Hazzard (1962). No high-grade metamorphic minerals such as garnet and staurolite were 

detected in any of these rocks, either in the field or in 

the laboratory.

Sample 472 is from the unnamed unit underlying the 

Willard Creek Quartzite of Misch and Hazzard (1962). 

This rock was originally a rather clean, poorly sorted 

sandstone composed of quartz grains less than 3 mm 

across. The original argillaceous cement has crystallized to a very fine grained muscovite sparsely 

distributed between the grains of clastic quartz, which 

now show evidence of strain and some recrystallization. Muscovite 472 furnished an age of 108 m.y.

Sample 473 is a minor variant of the unnamed unit. 

The rock was originally a very impure sandstone. It is 

present in outcrop as a massive dark-green chloritic 

rock with spotty brown stains resulting from altered 

pyrite. Flakes of clastic mica as much as 2 mm across 

are visible in hand specimen. Some very fine grained 

and sparsely distributed metamorphic mica is visible

in thin section, but all of this metamorphic mica probably was eliminated by taking only the +200 mesh 

material for analysis. The clastic mica from this rock 

gave an age of 437 m.y.

Sample 476 is from a greenish-gray phyllitic interval 

in the Strawberry Creek Formation of Misch and Hazzard (1962). The original sediment was probably a 

mudstone containing a few chert fragments less than 1 

mm across. As seen in thin section it is now a felt of extremely fine grained metamorphic muscovite laid in 

quartz and peppered with many tiny tourmaline euhedra that clearly grew in place. Muscovite 476 gave 

an age of 105 m.y.

Sample 499 also is from the Strawberry Creek Formation. The rock was originally a fairly well sorted 

sandstone with subangular quartz grains mostly about 

0.3 mm across. In thin section the quartz shows 

evidence of strain and partial recrystallization. The 

clastic quartz grains are surrounded by a fine-grained 

metamorphic mica that gave an age of 183 m.y.

Sample 536 was collected just below a thrust surface 

in Precambrian rocks mapped by Hose and Blake 

(1976). It probably is part of the Strawberry Creek Formation. The original sediment was a silty chert. It is 

now a greenish-gray phyllite, seen in thin section as a 

crinkled felt of very fine grained muscovite set in 

chert-like material. The muscovite gave an age of 73.8 

m.y.

In addition to these samples, metamorphic muscovite 330 (Lee and others, 1970), collected from the 

Strawberry Creek Formation about 1.5 km east of sample locality 499, gave an age of 125 m.y.

Misch and Hazzard (1962, p. 297, 300) described 

both contact and regional metamorphism in the area of 

these samples. Any contact metamorphism would be 

due to the intrusive referred to as the Osceola stock by 

Armstrong (1966). Several K-Ar ages determined on 

micas from this stock range from 51.2 to 154 m.y. (Lee 

and others, 1970) and show a general tendency to increase from east to west. The intrusive ages determined suggest a history similar to that of the Jurassic 

(160 m.y.) granitoid rocks exposed a few kilometers to 

the south (Snake Creek-Williams Canyon area), and on 

the basis of available information, it is reasonable to 

suppose that the Osceola stock crystallized about 160 

m.y. ago.

Interpretation of the ages of these muscovites from 

Precambrian metasediments is difficult because of 

their wide age range—437 to 73.8 m.y. It appears that 

diagenesis, contact, load, and dynamic metamorphism, 

and detrital mica have all had some effect on the age of 

each sample. The oldest age is predominantly a detrital 

age, and the youngest results mainly from dynamic 

metamorphism related to Tertiary thrust faulting. The
24 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

last event, dynamic metamosphism, was not intense 

enough to re-equilibrate the earlier formed detrital, 

diagenetic, and (or) metamorphic micas.

WHEELER PEAK AREA, SOUTHERN SNAKE RANGE, NEVADA

In the earlier paper (Lee and others, 1970), we had 

difficulty explaining the 264-m.y. age obtained for a 

muscovite recovered from a sample of Prospect Mountain Quartzite near the top of Wheeler Peak. In order 

to check this result, we collected three additional 

samples of Prospect Mountain Quartzite: sample 552 

from the top of Wheeler Peak (elevation about 3,982 

m), sample 554 (at 3,640 m), and sample 555 (at 3,440 

m). Petrographic study of these samples, as well as the 

264-m.y. sample from near the top of Wheeler Peak, 

shows that all four have these features in common:

1. All are rather clean quartzites. (Samples 552 and 

554 contain about 90 percent SiO2 .)

2. The original sediments were poorly sorted, with subrounded to subangular detrital grains of quartz 

and minor feldspar less than 1 mm in diameter.

3. The original argillaceous cement has crystallized to 

an extremely fine grained muscovite surrounding 

the detrital quartz.

4. There has been little if any recrystallization of the 

detrital quartz.

5. The detrital quartz shows little evidence of strain;

most grains extinguish sharply under crossed

nicols.

Muscovites 552, 554, and 555 gave ages of 307, 99.3, 

and 141 m.y., respectively, showing little relation to 

present altitude, position within the stratigraphic section, or distance below any eroded thrust fault. The 

evidence would seem to indicate a very low grade static 

or load metamorphism. The lack of agreement among 

these ages probably is due to: (1) the presence of small 

amounts of detrital mica in some samples, and (or) (2) 

local differences in chemical conditions (i.e., PH2O) conducive to the crystallization of metamorphic mica during burial.

MOUNT WHEELER MINE AREA, SOUTHERN SNAKE RANGE, 

NEVADA

Sample 2-MW-60 was collected from an irregularly 

shaped beryl veinlet about 1,195 m back in the Pole 

Canyon adit of the Mount Wheeler mine. The occurrence of beryllium at this mine was described by 

Stager (1960), and Lee and Erd (1963) described the 

phenakite (Be2SiO4 ) present in sample 2-MW-60. A 

concentrate of sericite from this sample gave an age of 

196 m.y., suggesting that the plutonic history of this 

area may have been initiated by an Early Jurassic 

episode of mineralization. However, this idea is tentative, and further data on the age of this mineralization 

are needed.

LEXINGTON CREEK AREA, SOUTHERN SNAKE RANGE, 

NEVADA

Samples 378, 531, and 532 were collected from a 

small quartz monzonite pluton exposed in the lower 

reaches of the north fork of Lexington Creek. The map 

of Whitebread (1969) shows this intrusive cut by a 

thrust fault, and both Whitebread and Drewes (1958) 

noted the foliated nature of the intrusive. Except for 

variations near the margins of the pluton, most of this 

foliation tends to strike NW. and dip moderately NE. 

The predominantly NW. strike of this foliation is 

almost normal to the direction of movement of the upper plate of the thrust as deduced by Drewes (1958, p. 

230), and the foliation may have been caused by movement on the thrust before the pluton was completely 

crystallized. Muscovites 378, 531, and 532 gave Late 

Cretaceous ages of 86.3, 82.2, and 77.9 m.y., respectively.

The Snake Creek-Williams Canyon intrusive mass 

exposed 10-20 km to the north has been dated as Middle Jurassic (~160 m.y., Lee and others, 1968), and was 

completely crystallized and "dry" (Lee and Van 

Loenen, 1971, p. 6, 40) when partially cataclasized by 

late (17-19 m.y., Lee and others, 1970) movement on 

the Snake Range decollement. If, as seems likely in 

view of the other Jurassic intrusive, the Lexington 

Creek pluton also is Jurassic in age, the observations 

noted above may be explained by the following sequence of events:

1. Penecontemporaneous Jurassic thrusting and emplacement of the pluton, with development of 

foliation in the pluton by movement along the 

overlying thrust surface.

2. A period of quiescence, with cooling and complete 

crystallization of the foliated pluton.

3. Partial loss of radiogenic argon from the igneous 

muscovite, resulting from thermal stresses 

related to renewed (post-Cretaceous) movement 

on the thrust surface. All three sample sites probably are within about 20 m of the eroded thrust 

surface.

MCCOY CREEK AREA, SCHELL CREEK RANGE, NEVADA

More than 2,500 m of upper Precambrian section and 

at least 1,200 m of overlying uppermost Precambrian 

and Lower Cambrian Prospect Mountain Quartzite are 

exposed in the McCoy Creek area (Misch and Hazzard, 

1962, p. 309). Samples 427 and 428 are the quartzite 

and mica schist, respectively, of Misch and Hazzard's 

(1962, p. 308, 309) A, of unit A. Both were collected 

about 100 m above a thrust surface within the Precambrian section. (See the map of Hose and Blake, 1976.) 

Both 427 and 428 were from originally poorly sorted 

sediments, with subangular quartz grains from 0.05 to
A RADIOMETRIC AGE STUDY OF MESOZOIC-CENOZOIC METAMORPHISM 25

1.0 mm across. The original argillaceous impurities 

now are well-crystallized metamorphic micas that tend 

to surround the detrital quartz. Muscovites 427 and 

428 gave ages of 63.6 and 61.7 m.y., respectively, and 

biotite 428 gave 45.8 m.y.

Sample 430, from the upper quartzite of Misch and 

Hazzard's A2 of unit A, was collected about 150 m 

stratigraphically above 427 and 428, and about 250 m 

above the thrust. Most of the detrital quartz in 430 is 

less than 0.5 mm in diameter. The metamorphic 

muscovite is not as well crystallized as in 427 and 428, 

and a few of the larger flakes of muscovite are detrital. 

Thus the age (86.1 m.y.) probably was determined on a 

mixture of clastic and metamorphic mica.

Sample YAG 192B of Armstrong and Hansen (1966, 

p. 123), a "very fine-grained carbonaceous phyllite" 

that gave a whole-rock K-Ar age of 39 m.y., apparently 

was collected from Misch and Hazzard's unit C, stratigraphically above 430.

Sample 435, a phyllitic argillite, is from the upper 

part of Misch and Hazzard's unit E, about 1500 m 

stratigraphically above sample 430, and far removed 

from any thrust fault mapped by Hose and Blake 

(1976). Petrographic study shows that the muscovite 

in this rock is clearly detrital. The muscovite (with 

quartz) concentrate recovered gave an age of 617 m.y.

Sample 571 is from the Prospect Mountain Quartzite, from what was originally a shaly sandstone. Although some cryptocrystalline white mica has formed 

in the rock, this material is so fine grained that it 

was undoubtedly lost in the washing and separation 

processes, and the age determined (1,177 m.y.) must be 

ascribed to the coarser grained clastic mica readily apparent in thin section.

Finally, sample 572 is from an amphibolite that intrudes the central part of Misch and Hazzard's unit B, 

about 300 m stratigraphically above sample 430. The 

amphibole recovered from sample 572 gave an age of 

98.0 m.y.

Taken as a group, the six mica ages determined for 

samples collected in the McCoy Creek area are difficult 

to reconcile with the idea of a regional metamorphism 

of Mesozic age. Nor do they lend themselves to a 

unique interpretation. They increase with distance above 

the thrust fault, which is up-section. The increase of 

apparent ages within a distance of 1,700—1,800 mof 

Precambrian section, from 45.8 m.y. (biotite 428) to 

617 m.y. (muscovite 435) is too large to be explained on 

the basis of cooling with uplift. Those ages determined 

on the well-crystallized metamorphic micas 427 and 

428 most probably relate to Tertiary movement along 

the thrust fault within the upper Precambrian section. 

The 86.1-m.y. age (muscovite 430) is a mixed metamorphic-detrital mica age, and the 617-m.y. age

(muscovite 435) is a mixed detrital-authigenic age. The 

age of detrital muscovite 471 (1,177 m.y.) is similar to 

the age (1,242 m.y.) determined for detrital muscovite 

471, from the western House Range, Utah. The 

98.0-m.y. age (amphibole 472) is a minimum age for the 

amphibolite.

OTHER AREAS, SCHELL CREEK RANGE, 

AND DUCK CREEK RANGE, NEVADA

Eight mineral ages were obtained for other areas in 

the Schell Creek Range and the contiguous Duck Creek 

Range. Sample 368 was collected near the top of the 

Precambrian section, south of the mouth of Indian 

Creek, about 2 km north of Cleve Creek. The rock was 

originally a rather clean, poorly sorted sandstone, with 

quartz grains and chert fragments from less than 0.01 

to more than 1.0 mm across. The original argillaceous 

material is now a well-crystallized metamorphic 

muscovite that tends to outline the clastic quartz 

grains, which show evidence of strain. Where not 

shielded by muscovite the contacts between quartz 

grains have been recrystallized. Muscovite 368 gave 

an age of 90.2 m.y.

Samples 393 and 394 (a xenolith) were collected 

about 6 km NE. of 368, from a granodiorite only a few 

hundred square meters in outcrop area. Biotite 393 

gave an age of 35.2 m.y.; biotite and amphibole 394, 

34.7 and 35.8 m.y., respectively. The intrusive appears 

to be early Oligocene in age.

Sample 538, unmetamorphosed Lower Cambrian 

Pioche Shale, was collected on the north side of upper 

Piermont Creek canyon. The clastic muscovite recovered from this rock gave an age of 1,190 m.y., very 

similar to the ages obtained for the Lower Cambrian 

clastic micas already described.

Sample 569 was collected from a shaly unit within 

the Prospect Mountain Quartzite, about 1.7 km north 

of Majors Place. About 23 percent of the rock is a very 

homogeneous, well-crystallized metamorphic muscovite that shows preferred orientation and gave an age 

of 66.9 m.y.

Samples 575 (Prospect Mountain Quartzite) and 576 

(Pioche Shale) were collected just below a thrust fault. 

(See the map of Hose and Blake, 1976.) Despite the fact 

that these samples were collected from the uppermost 

part of the lower plate, petrographic study shows the 

rock to be practically unmetamorphosed. The clastic 

muscovites recovered from samples 575 and 576 gave 

ages of 1,205 and 1,182 m.y., respectively, very similar 

to the ages obtained for the three other Lower Cambrian clastic micas already noted.

The ages discussed in this section lend little support 

either to the idea of a regional metamorphic event, or 

to the idea of cooling with uplift. Muscovite 368 (90.2 

m.y.) was collected only a few hundred meters from
26 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

where the upper Precambrian section rises above the 

valley fill. We can only speculate that results for this 

sample indicate some thermal stress (degassing), 

resulting either from Tertiary movement on a concealed thrust fault, or from the contact effects of a concealed pluton, related in age to the Oligocene pluton 

about 6 km to the northeast (samples 393 and 394).

The map and cross section O-O' of Drewes (1967) indicate that sample 569 was collected about 600 m 

below the eroded sole of the Schell Creek Range thrust. 

We ascribe the apparent age of muscovite 569 (66.9 

m.y.) to Tertiary movement on this thrust fault.

The three clastic micas (538, 575, and 576) discussed 

in this section and the two described in earlier sections 

(471, western House Range, and 571, McCoy Creek 

area) all were recovered from the Pioche Shale or Prospect Mountain Quartzite; and all gave ages in the 

range 1,182-1,242 m.y. The surprising agreement 

among these results indicate an approximate minimum age for the crystalline terrane that provided the 

source material for the Lower Cambrian clastic sediments in this region.

The lack of metamorphism of samples 575 and 576, 

collected just under the sole of a thrust, is difficult to 

explain. We speculate that an irregular interface between the upper and lower plates at the time of movement, with sample sites 575 and 576 on the lee side of a 

rise, might have sheltered these rocks from tectonic 

overpressures, and might thus account for this lack of 

metamorphism.

EGAN RANGE, NEVADA

Samples 383 and 384 are from a quartz monzonite 

pluton in the Warm Springs area of the northern Egan 

Range, Nevada. The intrusive has been sheared and 

deformed where these samples were collected. The map 

and cross section E-E' of Fritz (1968) show the intrusive exposed just below the level of Fritz's thrust 

sheet /. In his explanatory text, Fritz concluded that 

the thrusting is Mesozoic in age, and that the intrusions in the area postdate the thrusting and may have 

been guided by one or more of the thrust faults. Muscovites 383 and 384 gave ages of 25.2 and 36.2 m.y., 

respectively. Armstrong (1966, p. 596) listed a date of 

38 m.y. for a biotite from this same intrusive, determined on a sample apparently collected about 1 km 

SW. of our sample 384. We attribute the shearing and 

deformation noted above to stresses related to late 

movement on the overlying (eroded) thrust fault. Moreover, we regard the ages to be spuriously young, reflecting degassing of the micas at the time of this late 

thrusting. The intrusive may have crystallized much 

earlier than 38 m.y. ago.

Sample 386 is from the "Big Rock" area of intrusive 

outcrop in the southern part of the Cherry Creek district of the northern Egan Range. The intrusive is cut 

by shears in the area of the sample site, which is about 

100 m east of a fault within the intrusive that dips 

about 30° E-NE. (See the map of Adair, 1961.) The 

alteration and deformation of parts of this intrusive 

were clearly recognized by Adair (1961, p. 43), who 

stated: "The fact that thrust faults exist in and around 

this igneous body can hardly be questioned." Muscovite 386 gave an age of 34.9 m.y. Again, we interpret 

this age to be spuriously young and suggest that the 

intrusive may actually have crystallized much earlier.

Sample 439 is from the Prospect Mountain Quartzite 

on the south flank of Heusser Mountain in the central 

Egan Range. The rock was originally an argillaceous 

sandstone, with poorly sorted, mostly subangular 

quartz grains. Metamorphism has resulted in development of a finely crystalline mica arranged around and 

between the clastic quartz grains that show evidence 

of strain. Where not shielded by metamorphic mica, 

the quartz has been recrystallized along grain boundaries.

Muscovite 439 gave an age of 65.4 m.y. The sample 

was collected about 1 km south of an exposed pluton 

(map of Woodward, 1964), which Armstrong (1970, p. 

215) dated as 33.6 m.y. (biotite K-Ar age). One might 

conclude that the 65.4-m.y. age we obtained reflects 

heating and degassing by the intrusive. However, 

Woodward mapped and described a major Mesozoic 

thrust fault that before erosion extended over both the 

site of sample 439 and the Heusser Mountain pluton to 

the north. Thus it is possible that both ages (65.4 and 

33.6 m.y.) have been modified by stresses related to 

Tertiary movement on the Mesozoic thrust fault. With 

the data now available, we prefer the latter interpretation.

TOANA RANGE, NEVADA

Samples 511 and 512 are Prospect Mountain Quartzite. In outcrop 511 is somewhat lighter in color than 

512, but microscope study shows both to be rather 

clean quartzites. Recrystallization has resulted in 

sutured contacts between quartz grains, which show 

evidence of strain. Sparse, well-crystallized metamorphic mica occurs. Muscovites 511 and 512 gave ages of 

72.5 and 75.6 m.y., respectively. A Tertiary-Jurassic 

pluton has intruded the Prospect Mountain Quartzite, 

and Cambrian carbonate rocks have been thrust over 

the quartzite (map of Stewart and Carlson, 1974). If 

the intrusive is Tertiary, the ages (72.5 and 75.6 m.y.) 

may reflect degassing by heat stress resulting from 

contact action; if it is Jurassic, the ages may indicate 

the time of latest movement on the thrust.
A RADIOMETRIC AGE STUDY OF MESOZOIC-CENOZOIC METAMORPHISM 27

DISCUSSION

Here we draw on the data in table 7 and those listed 

by Lee and others (1970) in order to suggest a working 

hypothesis relating to the history of plutons in the 

region of figure 11, comment on the nature of the 

metamorphism in the region of figure 11, and point up 

an important unanswered question regarding the apparent K-Ar ages of micas recovered from the metasedimentary rocks.

We propose a working hypothesis to help interpret 

the history of plutons exposed in the region of figure 

11 and adjacent parts of the eastern Great Basin. It is 

based on a sequence of events as exemplified in the 

southern Snake Range:

1. Intrusion of plutonic rocks penecontemporaneous 

with and spatially related to thrust faulting during the Mesozoic orogeny postulated by Misch 

and Hazzard (1962). This would imply a genetic 

relation between the thrust faulting and the 

magmatic activity.

2. A period of quiescence, with cooling and complete 

crystallization of the plutonic rocks.

3. Renewed thrusting (as recent as 17-19 m.y. ago in 

the southern Snake Range), leading to stress, 

shearing, or even cataclasis in the associated 

plutons, with partial to total degassing of the constituent micas, and consequent postcrystallization K-Ar ages for those micas. This would suggest that other plutons in and near the region of 

figure 11 might be much older than indicated by 

K-Ar age results for the constituent micas. 

In addition to the southern Snake Range, we have in 

this study noted that thrust faults and plutons are exposed in close proximity at the present level of erosion 

in the northern Snake Range, the Kern Mountains, the 

northern and central Egan Range, and the Toana 

Range. A study of relevant maps shows the same 

spatial relation in many other parts of the eastern 

Great Basin.

A regional metamorphism in the area of figure 11 

was postulated by Misch and Hazzard (1962), and the 

concept has been adopted by many other students of 

the area. We regard the metamorphism of the area as 

spotty rather than regional. Contact metamorphism is 

associated with the plutons, low-grade static metamorphism occurs in some of the clastic sediments, and a 

dynamic metamorphism resulted from movement 

along the regional thrust faults; in places dynamic 

metamorphism is superimposed on the contact and (or) 

static types of metamorphism. Some of the Lower 

Cambrian clastic rocks show very little evidence of recrystallization (538 and 571), even where exposed 

beneath the sole of a thrust (575 and 576). In the

Hampton Creek area of the northern Snake Range, an 

area of perhaps less than 100 km2 might be regarded as 

staurolite-grade regional metamorphic terrane.

We prefer the concept of a spotty rather than 

regional metamorphism because it more nearly indicates the problems we face in our efforts to understand the geologic history of the area. Misch and Hazzard (1962, p. 289) themselves recognized static, thermal, and dynamic metamorphism in the area, with different combinations of the three having produced 

"various kinds of polymetamorphic rocks." Hose and 

Blake (1976, p. 25) stated: "The metamorphic rocks in 

White Pine County are extremely diverse in character 

and origin." Similar observations could no doubt be 

culled from the literature. Our purpose here is to stress 

these observations, as opposed to the idea of an areawide metamorphic event.

Where micas from lower plate metasedimentary 

rocks gave Tertiary K-Ar age dates, we consider that 

they indicate a maximum date for the time of most recent movement along the overlying thrust surface. 

However, we immediately face the question: When did 

any one of these metamorphic micas first crystallize 

from argillaceous material in the original clastic sediment? The importance of this question can hardly be 

overemphasized, for the Tertiary date might indicate 

the actual time of formation of the mica, or might result from degassing of a much older mica (formed originally perhaps as a result of tectonic overpressures during earlier movement along the thrust surface), or in 

some cases, it might be the result of another type of 

metamorphism. For now we can only delineate the 

problem.

CONCLUSIONS

Based on the results of this study, and the data 

listed by Lee and others (1970), we conclude:

1. Where an intrusive is exposed near a level of 

thrusting, uncorroborated K-Ar age data are 

suspect as being spuriously young.

2. The distribution of Tertiary K-Ar ages in upper Precambrian and Lower Cambrian metasedimentary 

and Jurassic igneous terrane is incompatible with 

the idea of cooling with uplift, but relates instead 

to Tertiary movement along the regional thrust 

faults.

3. An important and unanswered question with regard 

to any one of the micas from lower plate metasedimentary rocks is this: Does the K-Ar age obtained 

for the mica indicate the time of crystallization, or 

merely that of degassing of the mica in response 

to stresses resulting from late movement along 

the overlying thrust surface?
28 GEOLOGIC STUDIES IN WHITE PINE COUNTY, NEVADA

4. In the present state of our knowledge it is probably 

more useful to regard the metamorphism in the 

area of figure 11 as spotty and diverse rather than 

regional, which tends to connote a widespread 

metamorphic event.

5. The surprising agreement (1,182-1,242 m.y.) among 

the K-Ar ages determined for five unmetamorphosed clastic micas recovered from Lower Cambrian sediments would seem to indicate a Precambrian Y provenance that crystallized at least 

1,182-1,242 m.y. ago.

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