Stratigraphy, Regional Distribution, 

and Reconnaissance Geochemistry of 

Oligocene and Miocene Volcanic Rocks 

in the Paradise Range and Northern 

Pactolus Hills, Nye County, Nevada 

U.S. GEOLOGICAL SURVEY BULLETIN 1974 
AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY 

Instructions on ordering publications of the U.S. Geological Survey, along with the last offerings, are given in the current-year 

issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey 

publications released prior to the current year are listed in the most recent annual "Price and Availability List" Publications that are 

listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability 

List" are no longer available. 

Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated monthly, 

which is for sale in microfiche from U.S. Geological Survey Book and Open-File Report Sales, Box 25425, Denver, CO 80225. 

Order U.S. Geological Survey publications by mail or over the counter from the offices given below. 

BY MAIL 

Books 

Professional Papers, Bulletins, Water-Supply Papers, 

Techniques of Water-Resources Investigations, Circulars, publications of general interest (such as leaflets, pamphlets, booklets), single copies of periodicals (Earthquakes & Volcanoes, 

Preliminary Determination of Epicenters), and some miscellaneous reports, including some of the foregoing series that have 

gone out of print at the Superintendent of Documents, are 

obtainable by mail from 

U.S. Geological Survey, Book and Open-File Report Sales 

Box25425 

Denver, CO 80225 

Subscriptions to periodicals (Earthquakes & Volcanoes 

and Preliminary Determination of Epicenters) can be obtained 

ONLY from 

Superintendent of Documents 

U.S. Government Printing Office 

Washington, DC 20402 

(Check or money order must be payable to Superintendent 

of Documents.) 

Maps 

For maps , address mail orders to 

U.S. Geological Survey, Map Sales 

Box 25286 

Denver, CO 80225 

Residents of Alaska may order maps from 

U.S. Geological Survey, Map Sales 

101 Twelfth Ave.- Box 12 

Fairbanks, AK 99701 

OVER THE COUNTER 

Books 

Books of the U.S. Geological Survey are available over 

the counter at the following U.S. Geological Survey offices, all 

of which are authorized agents of the Superintendent of Documents. 

ANCHORAGE, Alaska--4230 University Dr., Rm. 101 

ANCHORAGE, Alaska--605 West 4th Ave., Rm G-84 

DENVER, Colorado--Federal Bldg., Rm. 169, 1961 Stout 

St. 

LAKEWOOD, Colorado-- Federal Center, Bldg. 810 

MENLO PARK, California--Bldg. 3, Rm. 3128, 345 Middlefield Rd. 

RESTON, Virginia--National Center, Rm. 1C402, 12201 

Sunrise Valley Dr. 

SALT LAKE CITY, Utah--Federal Bldg., Rm. 8105, 125 

South State St. 

SAN FRANCISCO, California--Customhouse, Rm. 504, 

555 Battery St. 

SPOKANE, Washington--U.S. Courthouse, Rm. 678, 

West 920 Riverside Ave. 

WASHINGTON, D.C.--U.S. Department of the Interior 

Bldg., Rm. 2650, 1849 C St., NW. 

Maps 

Maps may be purchased over the counter at the U.S. 

Geological Survey offices where books are sold (all addresses 

in above list) and at the following Geological Survey offices: 

ROLLA, Missouri--1400 Independence Rd. 

FAIRBANKS, Alaska--New Federal Building, 101 

Twelfth Ave. 
Stratigraphy, Regional Distribution, 

and Reconnaissance Geochemistry of 

Oligocene and Miocene Volcanic Rocks 

in the Paradise Range and Northern 

Pactolus Hi lis, Nye County, Nevada 

By DAVID A. JOHN 

U.S. GEOLOGICAL SURVEY BULLETIN 1974 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names 

in this publication is for descriptive purposes only 

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

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1992 

For sale by 

Book and Open-File Report Sales 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

library of Congress Cataloging-in-Publication Data 

john, David A. 

Stratigraphy, regional distribution, and reconnaissance geochemistry of 

Oligocene and Miocene volcanic rocks in the Paradise Range and Northern 

Pactolus hills, Nye County, Nevada I by David A. john. 

p. em. -(U.S. Geological Survey bulletin ; 1974) 

Includes bibliographical references. 

1. Volcanic ash, tuff, etc.-Nevada-Nye County. 2. Geology, 

Stratigraphic-Oligocene. 3. Geology, Stratigraphic-Miocene. 4. 

Geology-Nevada-Nye County. f. Title. If. Series. 

QE75.B9 no. 1974 557.3 s-dc20 91-4783 

[QE461] [552'.23'0979334] CIP 
CONTENTS 

Abstract 1 

Introduction 2 

Acknowledgments 2 

Previous work 4 

Geologic setting 4 

Late Cenozoic structural geology 4 

Stratigraphy of Tertiary volcanic rocks in the Paradise Range 6 

Menter Canyon section 7 

Tuff of Green Springs 7 

Tuff of Menter Canyon 8 

Tuff of Camel Spring 10 

Tuff of Gabbs Valley 10 

Tuff of Arc Dome 10 

Tuffs between the tuff of Arc Dome and the tuff of Toiyabe 12 

Tuff of Toiyabe 13 

Andesite and basaltic andesite flows 13 

Ellsworth section 14 

Tuff of Return Mine 14 

Andesite flows 14 

Tuff of Camel Spring 14 

White tuff 14 

Brown rhyolite tuff 14 

Tuff of Big Spring 14 

Other units of uncertain stratigraphic position 15 

Sheep Canyon section 15 

Tuff of Pactolus 15 

Tuff of Davis Mine 16 

Older andesite sequence 16 

Biotite lithic tuff 16 

Tuff 17 

Tuff of Goldyke 17 

Rocks between the tuff of Goldyke and the lower white tuff 17 

Lower white tuff 17 

Red tuff 18 

Gray-green tuff 18 

Blue-gray dacite breccia 18 

Upper white tuff 18 

Red rhyolite tuff 18 

Tuff of Sheep Canyon 18 

Younger andesite sequence 19 

Hornblende andesite 19 

Porphyritic dacite 19 

Silicic dikes and flow domes 20 

Breccia and conglomerate in the southwestern Paradise Range 20 

Sedimentary rocks of Stewart Valley 20 

Andesite of Stewart Valley 21 

Contents Ill 
IV Contents 

Regional distribution, sources, and volumes of major ash-flow tuff sheets 21 

Tuffs of Pactolus and Davis Mine and the Mission Spring Formation 21 

Tuff of Gabbs Valley 22 

Tuff of Arc Dome 22 

Tuff of Toiyabe and tuff of Copper Mountain 23 

Tuff of Green Springs 23 

Sources of other ash-flow tuff units in the Paradise Range 24 

Distribution and significance of the younger andesite sequence 24 

Geochemical studies 26 

Older and younger andesite sequences and the andesite of Stewart Valley 26 

Tuffs in the Menter Canyon and Ellsworth sections 29 

Tuff of Arc Dome 32 

Tuff of Toiyabe 33 

Tuffs in the Sheep Canyon section 33 

Summary of late Cenozoic volcanic and tectonic history of the Paradise Range 33 

Comparison of the Paradise Range to other highly extended terranes in the Basin and 

Range province 36 

References cited 37 

FIGURES 

1. Index map of part of Nevada 2 

2. Index map showing location of areas mapped and described in this report 3 

3. Generalized geologic map of Tertiary volcanic rocks in Paradise Range and 

northern Pactolus Hills S 

4. Simplified, composite stratigraphic sections for Tertiary volcanic rocks in Paradise 

Range and northern Pactolus Hills 7 

5. Bar graphs showing representative modal compositions for major Tertiary volcanic 

units in Paradise Range and northern Pactolus Hills 8 

6. Map of west-central Nevada showing distribution of ash-flow tuff units in Paradise 

Range and northern Pactolus Hills, andesite and intermediate lavas, and early 

Miocene normal faulting and crustal extension 11 

7-15. Graphs showing: 

7. Variations in modal mineralogy within the tuff of Arc Dome 12 

8. Variations in modal mineralogy within the tuff of Sheep Canyon 19 

9. Total alkali versus silica for Tertiary volcanic rocks in Paradise Range 25 

10. Peacock diagrams (CaO versus Si02 and N~O+~O versus Si02

) for Tertiary 

volcanic rocks in Paradise Range 27 

11. Silica versus various oxides for andesite sequences in Paradise Range, silicic 

intrusive rocks, and the andesite of Stewart Valley 28 

12. Initial 87SrJ86Sr ratio versus silica content for Tertiary volcanic rocks in 

Paradise Range 29 

13. Silica versus various oxides for ash-flow tuffs and interbedded lavas in 

Paradise Range 30 

14. Trace-element data for Tertiary volcanic rocks in Paradise Range 31 

15. Compositional variations in whole-rock samples within the tuff 

of Arc Dome 32 

16. Schematic summary of late Cenozoic volcanic-tectonic history of Paradise Range 

and northern Pactolus Hills 34 
TABLES 

1. Characteristics of maDor ash-flow tuff units in the Menter Canyon section 42 

2. Summary of modal data for ash-flow tuffs in the Paradise Range and northern 

Pactolus Hills 43 

3. Summary of K-Ar ages of Tertiary volcanic rocks in the Paradise Range 44 

4. Chemical analyses of the tuff of Arc Dome 46 

5. Chemical analyses of the tuff of Toiyabe 48 

6. Chemical analyses of the younger andesite sequence 49 

7. Characteristics of m~jor ash-flow tuff units in the Ellsworth section 53 

8. Characteristics of m~jor ash-flow tuff units in the Sheep Canyon section 54 

9. Volume estimates ofi major ash-flow tuff sheets in the Paradise Range 55 

10. Chemical analyses of the older andesite sequence 56 

11. Chemical analyses of the andesite of Stewart Valley 58 

12. Chemical analyses of silicic intrusive rocks in the Paradise Range 59 

13. Sr isotope data for Tertiary volcanic rocks in the Paradise Range 60 

14. Chemical analyses of units in the Menter Canyon and Ellsworth sections 61 

15. Chemical analyses of units in the Sheep Canyon section 63 

16. Chemical analyses of the lower white tuff 65 

17. Chemical analyses of the tuff of Sheep Canyon 67 

Contents V 

Stratigraphy, Regional Distribution, and 

Reconnaissance Geochemistry of Oligocene and 

Miocene Volcanic Rocks in the Paradise Range and 

Northern Pactolus Hills, Nye County, Nevada 

By David A. John 

Abstract 

Thick sequences of Oligocene to middle Miocene volcanic rocks form three stratigraphic sections in the 

Paradise Range and northern Pactolus Hills, northwestern 

Nye County, Nevada. At the northern end of the Paradise 

Range, five silicic ash-flow tuff units that are locally intercalated with intermediate lavas and unconformably 

overlain by intermediate to mafic lavas form the Ellsworth 

section, which is 1 ,300+ m thick. No ash-flow tuff units 

are regionally widespread. On the east side of the Paradise 

Range and in the northern Pactolus Hills as many as nine 

silicic ash-flow tuff units that are unconformably overlain 

by intermediate to mafic lavas form the Menter Canyon 

section, which is as much as 2,800 m thick. Three ashflow tuff units in this section are regionally widespread 

and have caldera sources west (tuff of Gabbs Valley) and 

east (tuffs of Arc Dome and Toiyabe) of the Paradise 

Range. The tuff of Toiyabe probably is correlative with the 

tuff of Copper Mountain as defined previously in the 

Gabbs Valley Range. The present distribution of these tuffs 

suggests approximately 35 km of post-early Miocene, rightlateral displacement on the Petrified Spring fault. On the 

southwestern side of the Paradise Range and in the northern Pactolus Hills, the Sheep Canyon section consists of 

thick accumulations of intermediate to silicic lavas (older 

andesite sequence) that are overlain by silicic ash-flow 

tuffs (middle tuff sequence) and unconformably overlain by 

intermediate to silicic lavas (younger andesite sequence). 

All three units are intruded by small hypabyssal bodies of 

intermediate to silicic composition. The total thickness of 

the Sheep Canyon section exceeds 3,500 m, and as many 

as 11 ash-flow tuff units are present. Only the oldest ashflow tuffs in this section (the tuffs of Davis Mine and 

Pactolus) may be regionally widespread and probably have 

sources in the southern Shoshone Mountains. 

Early Miocene normal faulting, locally extreme crustal 

extension, and associated synextensional to postextensional, 

dominantly intermediate-composition magmatism are 

widespread in west-central Nevada and appear to play 

Manuscript approved for publication, January 31, 1991. 

significant roles in the genesis of several major epithermal 

gold-silver deposits, including the Paradise Peak deposit in 

the southwestern Paradise Range. Tertiary volcanic rocks 

in the Paradise Range have undergone two or more periods of normal faulting; most contacts between pre-Tertiary 

and Tertiary rocks are high- or low-angle normal faults. A 

major period of normal faulting and crustal extension 

occurred approximately 22 to 19 Ma, and prominent 

angular unconformities separate earliest Miocene silicic 

ash-flow tuffs and overlying early to middle Miocene intermediate lavas (younger andesite sequence) present both on 

the east side of the Paradise Range and in the northern 

Pactolus Hills. This period of faulting also is evident in the 

Sheep Canyon section, although an angular unconformity 

is absent. 

Most ash-flow tuff in the Paradise Range is rhyolite or 

high-silica rhyolite in composition. Thick exposures of the 

tuff of Arc Dome (350+ m thick) are normally zoned from 

a high-silica rhyolite base (77 weight percent Si02 recalculated volatile-free) to normal rhyolite in its upper part (73 

weight percent Si02 ). The thick (600+ m) tuff of Sheep 

Canyon shows significant compositional zoning (68 to 

72.5 weight percent Si02), although most compositional 

changes apparently occur between cooling units. Most 

other ash-flow tuffs show little evidence for significant 

compositional zoning. No evidence is found for reverse 

compositional zoning in ash-flow tuffs exposed in the 

Paradise Range, in contrast to reverse compositional zoning reported in ash-flow tuff units in nearby ranges to the 

west. 

The older (late Oligocene) and younger (early Miocene) andesite sequences have significant compositional 

differences. Although both sequences show considerable 

compositional variation ranging from andesite or basaltic 

andesite to high-silica dacite or low-silica rhyolite (approximately 55 to 70 weight percent Si02

), the younger 

andesites have significantly higher Ca, Sr, P, and Sr/Rb, 

and lower K, Mg, Rb, K/Rb, and initial 87Sr/66Sr than the 

older andesites at a constant silica content. Comparison of 

these data to limited chemical data from adjacent areas 

suggests that the compositional differences are present regionally in early Miocene intermediate lavas and reflect 

regional changes in magma genesis that occurred about 20 Ma. 

Abstract 
Younger lavas appear spatially limited to areas that underwent early Miocene normal faulting and extension, 

suggesting that the chemical changes reflect changes in the 

tectonic environment of magma genesis. 

Comparison of the Tertiary volcanic-tectonic history of 

the Paradise Range to other highly extended terranes in the 

Basin and Range Province indicates that there are several 

significant differences in the Paradise Range, including: (1) 

there is a hiatus in volcanic activity during early Miocene 

extensional faulting in the Paradise Range; (2) 

synextensional sedimentary rocks are absent in the Paradise Range; and (3) there is little apparent systematic 

compositional variation in the synextensional to 

postextensional volcanic rocks and an absence of true basalts in the Paradise Range. It is not clear if these 

differences are minor variations on regional patterns or 

represent a fundamentally different volcanic-tectonic evolutionary style. 

INTRODUCTION 

Thick sections of Oligocene and Miocene volcanic 

rocks crop out on the north, east, and south sides of the 

Paradise Range and in the Pactolus Hills in the northwestern comer of Nye County, Nev. (figs. 1, 2). Recent 

0 20 40 60 KILOMETERS 

BASIN 

AND 

RANGE 

PROVINCE 

•Austin 

Elko• 

• Round Mountain 

Area of figure 2 

\ 

\ 

Figure 1. Index map of part of Nevada showing location of 

Paradise Range, Walker Lane (diagonal lines), and Basin 

and Range province. Outline of Walker Lane taken from 

Stewart (1988). 

detailed geologic mapping (John, 1986, 1988, unpublished data; John and Kelleher, 1987; Silberling and 

John, 1989) and K-Ar dating (McKee and John, 1987; 

John and others, 1989b) reveal that there are much 

thicker and more complex sequences of Tertiary volcanic 

rocks in these areas than previously recognized 

(Vitaliano and Vitaliano, 1972; Kleinhampl and Ziony, 

1985). Several units identified in the Paradise Range are 

regionally extensive and provide time-stratigraphic links 

with other well-studied areas to the west in the Gabbs 

Valley and Gillis Ranges (Ekren and others, 1980) and 

the Yerington district (Proffett and Proffett, 1976) and to 

the east in the southern Toiyabe Range (Brem and others, 1985; 1991) and the southern Toquima Range 

(BMen, 1986; Mills and others, 1988). Correlation of 

one regionally extensive ash-flow tuff unit allows estimation of late Cenozoic offset along the Petrified Spring 

fault, a major northwest-trending strike-slip fault on the 

east side of the Walker Lane. In addition, a sequence of 

early Miocene intermediate to silicic lava bodies are 

synextensional and provide new data on the nature of 

magmatism associated with crustal extension in the 

Great Basin. 

This paper presents detailed descriptions of the 

Tertiary volcanic stratigraphy of the Paradise Range and 

northern Pactolus Hills and discusses the regional distribution of major ash-flow tuff units present in these 

areas. Field, petrographic, modal, and chemical data are 

presented for about 40 units, and these data are compared to data from adjacent ranges and to recent descriptions of middle to late Tertiary volcanic rocks elsewhere 

in the Great Basin (Best and others, 1989a, b; Gans and 

others, 1989). The late Cenozoic volcanic and tectonic 

history of the area is discussed and compared to other 

areas in the Basin and Range province that were highly 

extended during the late Cenozoic. 

Acknowledgments 

Many people contributed to this study of the volcanic rocks in the Paradise Range. Field trips and discussions with R.F. Hardyman, G.F. Brem, NJ. Silberling, 

D.H. Whitebread, J.J. Rytuba, R.E. Thomason, P.L. 

Kelleher, J. Bosma-Douglas, and M.L. Hudson immeasurably helped. Discussions with J.H. Stewart, D.R. 

Boden, J.H. Dilles, R.P. Ashley, and M.L. Sorensen 

helped clarify some of the regional aspects of volcanism 

and tectonism in the Paradise Range. A special word of 

thanks also goes to J .S. Oldow for the inspiration he provided, when, after driving through exposures of Tertiary 

volcanic rocks in the southwestern Paradise Range during a 1983 field trip, he turned to me and asked, "Who's 

the poor sucker that has to map these rocks?" 

2 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
39°00' .---------------------------~----------------~---------.-----------,----------------------~ 

Return Mine 

~ 

Ellsworth 

• 

Gabbs Valley 

John (1988) 

Sheet 2 

~ 

Gabbs 

• 

PARADISE RANGE 

Davis Mine~ 

Goldyke 

• 

~ John and 

~ Kelleher (1987) 

Stewart Valley~ Pactolus Mine 

John and 

Kelleher 

(unpub. data) 

John (1988) 

Sheet 1 

I 

I I 

~---------- --------- ---------------- --1 

Area of Map 

lone • 

lone Valley 

0 

Whitebread and 

others (1988) 

U) 

2 

1-

2 

0 

w 

2 

0 

:r 

0 

:r 

U) 

10 KILOMETERS 

38°30' L__----------------------------------------------'------------------------------------------------' 

Figure 2. Index map showing location of Paradise Range and Pactolus Hills and areas recently mapped and described in 

this report. 

Introduction 3 
PREVIOUS WORK 

Previous descriptions of Tertiary volcanic rocks in 

the Paradise Range and the southern Shoshone Mountains were published by Vitaliano (1963), Vitaliano and 

Callaghan (1963), Vitaliano and Vitaliano (1972), and 

Kleinhampl and Ziony (1985). Vitaliano (1963) and 

Vitaliano and Callaghan (1963) presented 1:62,500-scale 

maps of Tertiary volcanic rocks in the lone and Paradise 

Peak 15-minute quadrangles, respectively. They divided 

Tertiary volcanic rocks in the Paradise Range into three 

units: lower and upper volcanic sequences and trachyandesite lavas that locally overlie the upper volcanic sequence. The lower volcanic sequence primarily consists 

of propylitized intermediate lavas, whereas the upper 

volcanic sequence consists of ash-flow tuffs locally 

intercalated with silicic to intermediate lavas. Vitaliano 

and Vitaliano (1972) presented more detailed descriptions of these two volcanic sequences and attempted to 

correlate volcanic units in the Paradise Range with units 

in the southern Shoshone Mountains. My own work reported here indicates that the stratigraphic and structural 

relations of the Tertiary volcanic rocks are much more 

complex than suggested by Vitaliano and Vitaliano 

(1972). 

Kleinhampl and Ziony (1985) generalized the maps 

of Vitaliano (1963) and Vitaliano and Callaghan (1963) 

and mapped the northern Pactolus Hills at a scale of 

1:250,000. Ekren and others (1980) described thick sections of Tertiary volcanic rocks in the Gabbs Valley and 

Gillis Ranges immediately west of the Paradise Range 

and showed the possible extent of some of these volcanic units in the southwestern Paradise Range. 

GEOLOGIC SETTING 

The Paradise Range lies in the western part of the 

Great Basin region of the Basin and Range physiographic province in west-central Nevada (fig. 1). The 

Basin and Range province is an area of alternating linear 

north- to north-northeast-trending ranges and broad . alluviated basins formed during late Cenozoic crustal extension. The basin-and-range physiography is disrupted near 

the west margin of the Great Basin by the Walker Lane, 

a northwest-trending zone of irregular topography and 

strike-slip faults (fig. 1; Locke and others, 1940; 

Stewart, 1988). The Paradise Range lies along the east 

edge of the Walker Lane. 

The oldest rocks exposed in the Paradise Range are 

early Paleozoic(?) metasedimentary rocks including dolomite, quartzite, argillite, and phyllite (Silberling and 

John, 1989). Early Paleozoic rocks are in fault contact 

with late Paleozoic and Mesozoic metavolcanic and 

metasedimentary rocks including andesitic breccia and 

tuff, volcaniclastic mudstone, sandstone, and conglomerate, metamorphosed gabbro and basalt, limestone and 

dolomite, phyllite and calcareous phyllite, and sandstone 

and quartzite (Silberling and John, 1989). These rocks 

range in age from Permian(?) to Jurassic and form several allochthons that are juxtaposed by Jurassic thrust 

faults (Oldow, 1984; Silberling and John, 1989). 

The metamorphic rocks are intruded by numerous 

plutonic bodies that range in composition from diorite 

and granite, in texture from coarse-grained coarsely porphyritic to fine-grained porphyroaphanitic, and in size 

from thin dikes to large stocks (John, 1987; Silberling 

and John, 1989). Limited radiometric dating suggests 

that most of the plutonic rocks are Late Cretaceous in 

age (John, 1987; John and McKee, 1987), although several undated, metamorphosed bodies may be Jurassic 

(Silberling and John, 1989). 

Pre-Tertiary rocks are overlain by and are in fault 

contact with thick sections of Oligocene and Miocene 

volcanic rocks (fig. 3). About 40 mappable units were 

defined by recent geologic mapping (John, 1988 and unpublished data; John and Kelleher, 1987). Total thicknesses of Tertiary volcanic sections exceed 2,800 m on 

both the east and southwest sides of the range. Figure 4 

shows generalized composite stratigraphic sections of 

Tertiary volcanic rocks in the Paradise Range and northern Pactolus Hills. 

LATE CENOZOIC STRUCTURAL GEOLOGY 

The Paradise Range has undergone a complex history of middle to late Cenozoic extensional faulting that 

strongly affected the deposition and present distribution 

of Tertiary rocks (John, 1986, 1988; John and others, 

1989b). Evidence of at least two periods of normal faulting is present throughout the Paradise Range, and most, 

if not all, contacts between pre-Tertiary basement rocks 

and Tertiary volcanic rocks are faults (John, 1988). Unlike the case in the Yerington district to the west 

(Proffett, 1977; Proffett and Dilles, 1984) and nearby 

ranges east of the Paradise Range, a prominent early 

Tertiary erosion surface and sedimentary rocks at the 

base of the Tertiary section are absent in the Paradise 

Range. 

Several sets of low- and high-angle normal faults 

cut Tertiary volcanic rocks in the Paradise Range. The 

present physiography of the range is dominantly controlled by north- to north-northeast-trending high-angle 

normal faults related to modern Basin and Range extension. These faults cut several sets of older normal faults 

related to one or more periods of Oligocene(?) and early 

4 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Qs 

Tsv 

Tbc 

Tsr 

Tr 

Tya 

Ts 

Tm 

Te 

Toa 

Tdm 

Tp 

pTu 

0 

EXPLANATION 

Surficial deposits (Quaternary) 

Andesite of Stewart Valley (Miocene) 

Breccia and conglomerate (Miocene) 

Sedimentary rocks (Miocene) 

Silicic Intrusive rocks (Miocene) 

Younger andesite sequence (Miocene) 

Middle tuff sequence of Sheep Canyon 

section (Miocene and Oligocene) 

Tuffs of Menter Canyon section (Miocene and Oligocene) 

Tuffs of Ellsworth section (Miocene and Oligocene) 

Older andesite sequence (Oligocene) 

Tuff of Davis Mine (Oligocene) 

Tuff of Pactolus (Oligocene) 

Sedimentary, volcanic, and plutonic rocks, undivided (pre-Tertiary) 

Contact 

High-angle fault- Dotted where concealed. 

Bar and ball on downthrown side 

Low-angle normal fault- Barbs on upper plate 

4 KILOMETERS 

Gabbs Valley 

Qs 

Stewart Valley 

Qs 

LodiValley 

Os 

lone Valley 

Figure 3. Generalized geologic map of Tertiary volcanic rocks in Paradise Range and northern. Pactolus Hills showing 

distribution of Menter Canyon, Ellsworth, and Sheep Canyon sections, and older and younger andesite sequences. Geology simplified from John (1988 and unpublished mapping), John and Kelleher (1987), John and others (1989b), and 

Silberling and john (1989). 

Late Cenozoic Structural Geology 5 
Miocene normal faulting and crustal extension. These 

older faults generally trend northwest to north-northwest 

and east-northeast. The northwest-trending faults commonly now dip at low angles (<20°) (John, 1988; John 

and others, 1989b). Compaction foliation in ash-flow 

tuffs in upper plates of the low-angle faults generally is 

at high angles to the fault planes, and many of the lowangle normal faults may be similar to low-angle normal 

faults in the Yerington district that Proffett (1977) has 

shown originated as ·high-angle faults and subsequently 

were rotated to their present orientation by continued extension and formation of younger sets of normal faults. 

Examples of possible rotated high-angle faults include 

the fault contact between pre-Tertiary and Tertiary rocks 

in the lower part of Menter Canyon on the east side of 

the range and numerous low-angle faults between Tertiary units in the southwestern part of the ~nge (fig. 3). 

Other low-angle normal faults, notably the Sheep Canyon fault in the southwestern part of the Paradise Range 

(fig. 3), appear to be younger than rotated high-angle 

faults and may have originated as low-angle, detachment-style faults (John, 1988; John and others, 1989b). 

The structure of Tertiary rocks varies throughout 

the Paradise Range. Tertiary rocks on the east side of the 

range generally strike north-northeast to northwest and 

have moderate dips to the east (rocks at the extreme 

north end of the range strike west-northwest and have 

moderate to steep northeast dips). The early Miocene andesite and basaltic andesite unit has notably shallower 

dips than underlying ash-flow tuff, and there commonly 

is a 10°-25° angular unconformity between these units. 

Contacts between pre-Tertiary and Tertiary rocks are 

both low- and high-angle faults. Tertiary rocks from 

Menter Canyon south generally are in low-angle fault 

contact with pre-Tertiary rocks (fig. 3). This fault contact is cut by numerous northwest-trending high-angle 

faults and has been interpreted as a rotated high-angle 

normal fault (John, 1988). 

In the southwestern Paradise Range, Tertiary rocks 

generally strike northwest and have moderate to steep 

northeast dips. Most contacts between pre-Tertiary and 

Tertiary rocks are low-angle normal faults, most notably 

the Sheep Canyon fault (fig. 3). At least five different 

sets of faults have been identified (John, 1988); the most 

prominent fault sets are northwest-trending low-angle 

normal faults and east-northeast- and north-northeasttrending high-angle normal faults. The north-northeasttrending faults generally are the youngest faults. 

In the northern Pactolus Hills, Tertiary ash-flow 

tuff generally strikes north to northwest and dips moderately to steeply to the east. Early Miocene andesite unconformably overlies these tuffs and generally dips less 

than 15° east. Several orientations of faults are present, 

including northwest-trending low-angle normal faults 

that may be rotated high-angle faults and north- to northeast-trending high-angle faults. Contacts between preTertiary and Tertiary rocks are high-angle faults that 

trend north to northeast (fig. 3). 

STRATIGRAPHY OF TERTIARY VOLCANIC 

ROCKS IN THE PARADISE RANGE 

Detailed geologic mapping of Tertiary volcanic 

rocks in the Paradise Range and northern Pactolus Hills 

shows that these rocks can be divided into three major 

stratigraphic sections: the Menter Canyon, Ellsworth, 

and Sheep Canyon sections, and a fourth composite section in the northern Pactolus Hills where the Menter 

Canyon and Section Canyon sections are juxtaposed by 

high-angle faults (fig. 4; John, 1988). The Menter Canyon section crops out on the east side of the Paradise 

Range and in the northern Pactolus Hills, the Ellsworth 

section crops out on the northeast side of the Paradise 

Range, and the Sheep Canyon section crops out at the 

south end of the Paradise Range (principally on the 

southwest side) and in the northern Pactolus Hills. Only 

one ash-flow tuff unit, the tuff of Camel Spring, is present in more than one stratigraphic section. 

Two major stratigraphic sections, the Menter Canyon and Ellsworth sections, dominantly composed of 

thick sequences of silicic ash-flow tuffs unconformably 

overlain by intermediate to mafic lavas, are present on 

the east side of the Paradise Range (figs. 3, 4). Contacts 

between these sections are faults, and only the tuff of 

Camel Spring is present in both sections. Thirteen distinct ash-flow tuff units have been recognized in these 

sections. In general, the older tuffs are relatively crystalpoor, thinner, and less widespread than the younger 

tuffs. The two thickest and most regionally widespread 

tuffs, the tuff of Arc Dome and the tuff of Toiyabe, cap 

the ash-flow tuff sequence along most of the east side of 

the range. Ash-flow tuff units in these sections locally 

are intercalated with andesitic lavas that appreciably 

thicken to the north .. In the part of the range mapped 

(south of lat 39° N.), silicic lava flows and intrusions are 

nearly absent; this is in striking contrast to the south end 

of the range, where they are relatively abundant. 

The southwestern part of the Paradise Range and 

the northern Pactolus Hills are underlain by a thick series of silicic ash-flow tuffs and intermediate to silicic 

lavas that make up the Sheep Canyon section (fig. 4). 

This section consists of a thick sequence of late Oligocene intermediate to silicic lavas overlain by a thick sequence dominantly composed of late Oligocene to early 

Miocene silicic ash-flow tuffs. Both sequences are unconformably overlain by a thick sequence of early to 

middle Miocene intermediate to silicic lavas. The Sheep 

Canyon section is locally more than 3,500 m thick. All 

three extrusive rock sequences are intruded by numerous 

small bodies of early to middle Miocene rhyolite. 

6 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Menter Canyon section 

The Menter Canyon section consists of six major 

ash-flow tuff units that locally are intercalated with three 

additional thin ash-flow tuff units (fig. 4). The ash-flow 

tuffs are unconformably overlain by a thick series of andesite and basaltic andesite lava flows. Units in this section are, from bottom to top, the tuff of Green Springs, 

the tuff of Menter Canyon, the tuff of Camel Spring, the 

tuff of Gabbs Valley, the tuff of Arc Dome, the tuff of 

Brunton Pass, two unnamed tuffs, the tuff of Toiyabe, 

and andesite to basaltic andesite lavas. Total thickness of 

this section is more than 2,800 m. Major features of ashflow tuff units in the Menter Canyon section are summarized in figure 5 and table 1. 

Tuff of Green Springs 

The tuff of Green Springs is the basal unit in the 

Menter Canyon section. It is exposed in Menter Canyon, 

where it is in low-angle fault contact with a Cretaceous(?) granitoid (porphyry of Menter Canyon; 

Silberling and John, 1989). The tuff is a compound cooling unit that consists of dark-red to reddish-brown, devitrified, densely welded, locally lithic-rich, crystal-poor 

high-silica rhyolite ash-flow tuff. Two ash-flow cooling 

units are present; the upper cooling unit contains small 

blocks of the lower cooling unit as well as clasts of 

flow-banded rhyolite. The lower cooling unit is more 

pumice-rich than the upper cooling unit and locally 

shows rheomorphic flow textures. Both cooling units 

SECTIONS AND AREAS 

AGE Sheep Canyon section Northern Pactolus Hills Menter Canyon section Ellsworth section 

Breccia and conglomerate Younger sedimentary rocks 

Miocene 

Oligocene 

PRE-TERTIARY 

(MESOZOIC and 

(PALEOZOIC) 

Green-gray tuff 

Red tuff 

Lower white tuff 

Older andesite 

sequence 

Sedimentary, volcanic, and 

intrusive rocks, undivided 

Sedimentary, volcanic, and 

intrusive rocks, undivided 

Sedimentary, volcanic, and 

intrusive rocks, undivided 

Unmapped rocks north 

of map area 

Tuff of Big Spring 

Brown rhyolite tuff 

White tuff 

Tuff of Camel Spring 

Andesite 

Tuff of Return Mine 

Sedimentary, volcanic, and 

intrusive rocks, undivided 

Figure 4. Simplified, composite stratigraphic sections for Tertiary volcanic rocks in Paradise Range and northern Pactolus 

Hills. In northern Pactolus Hills, parts of both Sheep Canyon and Menter Canyon sections are present and are juxtaposed 

by high-angle faults. Most contacts between pre-Tertiary and Tertiary rocks are faults, although there also is a significant 

erosional unconformity as portrayed in this figure. See text, table 3, and John (1988) for discussion of precise ages of 

units. Placement of Oligocene-Miocene boundary is at 23.7 Ma (Palmer, 1983). See figure 2 for area locations. 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 7 
generally contain less than 4 percent phenocrysts, which 

are mostly sanidine (fig. 5; table 2). Tpe thickness of the 

tuff of Green Springs is uncertain due to faulting but 

may be as much as 300 m. The precise age of the tuff of 

Green Springs also is unknown; it is older than the tuff 

of Gabbs Valley, which is about 26-25 Ma (nos. 22, 23, 

table 3), but regional K-Ar age data suggest that it probably is no older than about 30 Ma (Armstrong, 1970; 

McKee and others, 1971; Ekren and others, 1980; 

Kleinhampl and Ziony, 1985; McKee and John, 1987). 

The tuff of Green Springs megascopically, petrographically, and chemically resembles the Nine Hill Tuff in the 

Carson City area (Bingler, 1978; Deino, 1985). However, the apparent age of the tuff of Green Springs 

(greater than 26-25 Ma) is somewhat inconsistent with 

A 

recent high precision 40Ar-39 Ar age determinations of 

25.11±0.017 Ma on the Nine Hill Tuff (Deino, 1989), 

and possible correlation of these tuffs requires more precise dating of the tuff of Green Springs. 

Tuff of Menter Canyon 

The tuff of Menter Canyon conformably overlies 

the tuff of Green Springs in Menter Canyon and consists 

of two lithologically similar, lithic-rich, high-silica rhyolite ash-flow tuff cooling units. In Menter Canyon the 

tuff consists of black, lithic-rich, densely welded, 

crystal-poor vitrophyric ash-flow tuff that grades upward 

into white, poorly welded, devitrified pumice-rich ashflow tuff. Lithic contents commonly are 15 to 25 volume 

Menter Canyon section 

Tuff of Toiyabe (main phase) 

Tuff of Toiyabe (Cloverdale Ranch unit) 

Tuff of Brunton Pass 

Tuff of Arc Dome (upper part) 

Tuff of Arc Dome (basal zone) ~~~~~~~~~ULL.CLLL.LLLL:LL.L.J.~<.L.LLCLLL.LLLL:LillJ 

Tuff of Gabbs Valley f===.:>.:~LL.< 

Tuff of Camel Spring 

Tuff of Menter Canyon 

Tuff of Green Springs F=~~----~----~----~----~--~----~----~----~--~ 

0 10 20 30 40 

VOLUME PERCENT PHENOCRYSTS 

B 

Ellsworth section 

Tuff of Big Spring 

Brown rhyolite tuff ~---"~>...L<...£..£..£.£..jJ 

~~~~~~~~~~~~~ 

White tuff 

Tuff of Camel Spring 

Andesite 

Tuff of Return Mine 

0 10 20 30 40 

VOLUME PERCENT PHENOCRYSTS 

50 

50 

Figure 5. Representative modal compositions for major Tertiary volcanic units in Paradise Range and northern Pactolus 

Hills. Several modes representing extreme compositions are shown for units with highly variable compositions. Modes are 

based on point counts of individual thin sections (800-1 ,200 points per thin section). 

8 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
percent. Small (S2 em), rounded clasts of pink to red 

rhyolite lava are abundant and characteristic. Other lithic 

fragments include intermediate lava and granitoid rocks. 

The tuff generally contains about 1 percent phenocrysts 

mostly of fine-grained plagioclase (table 2). Outside of 

Menter Canyon only the densely welded, vitrophyric 

basal part of this unit has been found. In Menter Canyon 

this tuff is as much as 200 m thick and is underlain by a 

thin ( <2 m thick), white, aphyric, air-fall tuff that is exposed in road cuts in Menter Canyon. The tuff of Menter 

Canyon also is present locally on the east side of the 

Shoshone Mountains, where it has been included as part 

of the tuff ofUnion Canyon (Whitebread and others, 

1988). 

c 

Sheep Canyon section 

Silicic intrusions (mafic) 1iii~~~~~::~: ~: :!!)::: 

Silicic intrusions (felsic) ~ ::: 

Tuff of Sheep 

Hornblende 

PorphyrWcdacHe 

Canyon 

andesite 

(mafic) 

~~~~~~~~~~~~~~~~~~~:::::,:::,:~~~~~~ Tuff of Sheep Canyon (felsic) 

Red rhyolite tuff ~~_,_,_,._,~~~~~CLL..L<'-L..LL..<-.LLLLL..LL.L..L.4.LJ 

Upper white tuff '~~~ Blue-gray dacite breccia ~ 

Red tuff b~~~"7""7""7'"">0 

Lower white tuff t---~~.>...>.JL..<..LL..L..£..11 

Tuff~GoWyke Biotite lithic tuff '~~~~=~~~~~~~~~~~~~~~~ ~ 

Older andesite sequence (felsic) 

Older andesite sequence (mafic) 

Tuff 

Tuff of Davis Mine 

Tuff of Pactolus ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

0 

Figure 5. Continued. 

10 20 30 

VOLUME PERCENT PHENOCRYSTS 

EXPLANATION 

~ Plagioclase 

~ K-feldspar 

~Quartz 

D Hornblende 

D Clinopyroxene 

- Opaque minerals 

40 50 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 9 
Tuff of Camel Spring 

The tuff of Camel Spring is a compound cooling 

unit of red to orange to dark-brown, generally crystalpoor rhyolite ash-flow tuff. It is the most laterally continuous unit on the east side of the Paradise Range and 

occurs in both the Menter Canyon and Ellsworth sections. In the Menter Canyon section it overlies the tuff 

of Menter Canyon, whereas in the Ellsworth section it 

overlies andesitic lavas. In the Menter Canyon section at 

least two cooling units are present; the basal part of the 

upper cooling unit contains a thin, black vitrophyric 

zone. The tuff of Camel Spring varies from nearly aphyric to sparsely porphyritic containing about 10 percent 

phenocrysts of feldspar and minor quartz (fig. 5; table 

2). Feldspar phenocrysts vary from anorthoclase in some 

samples to mixtures of sanidine and plagioclase in others; anorthoclase appears to be more abundant in the 

upper cooling unit. Pumice and lithic contents vary from 

nearly absent to abundant. Most of the tuff is devitrified 

except for a thin vitrophyric zone at the base of the 

upper cooling unit. Most of the tuff is densely welded. 

The tuff of Camel Spring is as much as 250 m thick in 

Menter Canyon. Whitebread and others (1988) correlated 

tuffs megascopically similar to the tuff of Camel Spring 

that are present at a similar stratigraphic horizon in the 

southern Shoshone Mountains with the tuff of Camel 

Spring. The tuff of Camel Spring also may be correlative 

with a thin (15 m) ash-flow tuff exposed in Gabbs Valley and described by Ekren and Byers (1986) as a discontinuous, sporadically exposed, anorthoclase-bearing 

tuff underlying and mapped as part of the lowest member of the tuff of Gabbs Valley. 

Tuff of Gabbs Valley 

The tuff of Gabbs Valley was named by Ekren and 

others (1980) for composite flow, crystal-poor ash-flow 

tuffs that crop out in the Gabbs Valley and Gillis Ranges 

and which they inferred had sources in Gabbs Valley. 

The tuff of Gabbs Valley is correlative with the Bluestone Mine Tuff of Proffett and Proffett (1976) in the 

Yerington district (Bingler, 1978; Ekren and others, 

1980; Deino, 1985), and is possibly correlative with the 

tuff of Hackett Canyon in the Carson City area (Deino, 

1985). The lower part of the tuff of Gabbs Valley also 

megascopically resembles the Nine Hill Tuff in the 

Carson City area (Bingler, 1978; Deino, 1985). Chemical 

and modal data, however, indicate that the Nine Hill 

Tuff and the tuff of Gabbs Valley are not correlative 

(Deino, 1985). The ash-flow tuff exposed in the Paradise 

Range is the lowest of three cooling units of the tuff of 

Gabbs Valley exposed in Gabbs Valley, where it forms 

the wallrocks of a fissure vent from which the upper 

cooling unit of this tuff was erupted (fig. 6; Ekren and 

Byers, 1976). The lower cooling unit also crops out 

along the crest and east side of the southern Shoshone 

Mountains near Union Canyon, where it was included as 

part of the tuff of Union Canyon by Whitebread and others (1988). 

In the Paradise Range, the lower cooling unit of 

the tuff of Gabbs Valley is a very distinctive black to 

dark-brown, crystal-poor, pumice- and lithic-rich rhyolitic ash-flow tuff. It contains abundant black, glassy, 

strongly flattened, banded crystal-poor fiamme as much 

as 15 em long and less than 1 em thick. Many of the 

pumice bodies show contorting banding apparently resulting from rheomorphic flow. Lithic fragments of 

flow-banded rhyolite, intermediate lavas, and granitoids 

also are abundant. The tuff contains about 5 percent 

phenocrysts consisting of sanidine, plagioclase, quartz, 

and trace amounts of biotite (fig. 5; table 2). Much of 

the tuff is vitrophyric. This cooling unit is as much as 

350 m thick near Fifteenmile Spring and in Menter Canyon but is absent north of Camel Spring. This tuff appears to conformably overlie the tuff of Camel Spring 

and conformably underlie the tuff of Arc Dome. The tuff 

of Gabbs Valley in the Gillis Range has two sanidine 

K-Ar ages, 25.0 and 26.1 Ma (nos. 22, 23, table 3). 

Tuff of Arc Dome 

The tuff of Arc Dome is a thick, crystal-rich rhyolite and high-silica rhyolite ash-flow tuff that forms the 

lower flanks of Sherman Peak along the crest of Paradise 

Range. This tuff is named for thick exposures of ashflow tuff underlying Arc Dome in the southern Toiyabe 

Range (fig. 6; Brem and others, 1991; G.F. Brem, written common., 1985, 1986). In the Paradise Range, the 

tuff is a simple cooling unit that is as much as 400 m 

thick near Sherman Peak. 

The tuff of Arc Dome is a devitrified, moderately 

pumice-rich, densely welded ash-flow tuff. Crystal-rich 

pumice fragments are strongly flattened and commonly 

as much as 8 em long and less than 1 em thick. The tuff 

is characterized by abundant, 1 to 3 mm, bipyramidal 

smoky quartz phenocrysts. Phenocryst contents range 

from about 30 to 40 volume percent (figs. 5, 7; table 2). 

Modal analyses indicate that there are large variations in 

quartz and plagioclase contents, the base being richer in 

quartz and poorer in plagioclase than the upper parts of 

the tuff (fig. 7). Sanidine content is fairly constant, 

forming about 10 to 15 percent of the rock at all stratigraphic levels (fig. 7). Mafic mineral contents average 

about 1 percent biotite and trace amounts of hornblende, 

but tend to be slightly greater in the upper parts of the 

tuff (figs. 5, 7). Allanite is a common accessory mineral. 

Unlike many compositionally zoned ash-flow tuffs, this 

tuff shows little vertical variation in total phenocryst 

content (fig. 7; compare with Lipman and others, 1966; 

10 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
.. 

~ 

a aCi. 

iil 

"'0 

:r 

-< 

0 

--1 

t1) 

:l. iii. 

.. 

-< 

< 0 

r; 

~ 

::I 

;::;· 

;:10 

0 

n 

rr 

:;-

-:r 

t1) 

"'CC 

~ 

iil 

c. 

c;;· 

t1) 

;:10 

~ 

::I 

OQ 

t1) 

... 

... 

39° 

119° 

0 I 0 

\: /J YPrinntnn J 

D 

D 

-

-

~ 

* 

Inferred limit of 

tuff of Gabbs Valley 

EXPlANATION 

Andesite (early Miocene)--lncludes rocks of Mount Ferguson in 

Gabbs Valley Range 

Tuff of Toiyabe and tuff of Copper Mountain, undivided (early 

Miocene) 

Tuff of Arc Dome and tuff of Ryecroft Canyon (Oligocene) 

Tuff of Gabbs Valley (Oligocene) 

Tuff of Pactolus, tuff of Davis Mine, and the Mission Spring 

Formation of Vitaliano and Vitaliano (1972) (Oligocene) 

Contact 

Strike-slip fault. Dashed where approximately located. Arrows 

show sense of movement 

Caldera margin. Dashed where approximately located 

Vents of the tuff of Toiyabe (G.F. Brem, written commun., 1986) 

Areas of early Miocene normal faulting and crustal extension 

0 5 10 MILES 

0 10 20 KILOMETERS 

011./ <./~ 

-9-<1/V, 

0~ \ 

\ 

--

u 

118° 

-- -- -- --

Q 

11JO 

c} 

Peterson ;t"" 

Station_.....- ·ii:,:' . ........._ G ~q;: 

--- ~ ~~ ........._ ~ ~ 

-~-w. 4."'< ~ 0' 

Shoshone ~ .··• ' 

Peak,-<----:;_,\ 

/ G') ••.• . 

f. ~ ' ·• l!i..J/ "Inferred limit 1 Arc 0r of tuff of 

rth ~!$·'·. ',~·~an Juan Creek 

1\ \- Dome <"· Arc Dome 

--<....)_ \zaldere 1 D ~( 

"'-~~?~ 

~ 

I 

Dome 

/ 

-\ 

of 

Inferred 

tuff of 

limit 

c.._____../ 

~ 

Toiyabe 

Round 

Mountain • 

I.J.J 

(!) 

2 

cq,-

0: 

cq,-

:;E 

.::> 

0 

0 

1--

I ~~ ({l 

<S (S Inferred limit of tuffs of 

Pactolus and Davis Mine 

and Mission Spring Formation 

~0 f) 

~c ~ ~h C7 

Q ;s~o ~'""0 6 

Mount 

Jefferson 

... 

TuffoV 

Ryecroft 

Canyon 

38°L_--------------~------------------------------------------~--------------------------------_c=======L~------~ 

Figure 6. Distribution and inferred maximum extent of regionally extensive ashflow tuff units present in Paradise Range and northern Pactolus Hills, distribution 

of younger andesite sequence and age.-equivalent (early Miocene) intermediate 

lavas, and areas of early Miocene (approximately 20 Ma) normal faulting and 

crustal extension. Shown are inferred sources for tuffs of Davis Mine and 

Pactolus and the Mission Spring Formation, tuff of Gabbs Valley, tuff of Arc 

Dome, and tuff of Toiyabe, and major strike-slip faults in Gabbs Valley and 

Gillis Ranges. Regional distribution of tuffs and early Miocene lavas based on 

Stewart and others (1982) and references therein, Whitebread (1986 and unpublished mapping), Bonham (1970), Kleinhampl and Ziony (1985), R.F. Hardyman 

(written commun., 1989), M.L. Sorensen (written commun., 1989), and Deino 

(1985) (see text). Areas of early Miocene faulting based on John and others 

(1989b); strike-slip faults from Ekren and others (1980); locations of inferred calderas from Ekren and Byers (1986) and G.F. Brem (written commun., 1986-

1987) . 
Gans and others, 1989). Compositional zoning also is 

evident in major- and trace-element chemical analyses of 

devitrified whole-rock samples (table 4); these data indicate that the lower 50 m of the tuff is a high-silica rhyolite (Si02=77 wt percent) that abruptly changes upward 

into rhyolite (Si02=73 wt percent). A cooling break has 

not been observed, and this compositional zoning probably represents compositional zoning in the magma 

chamber. 

The basal part of the tuff of Arc Dome is marked 

by prominent, strongly flattened, 1- to 5-cm-long, black, 

glassy, crystal-rich fiamme that form 10 to 20 percent of 

the tuff; other parts of the the tuff are entirely devitrified. Quartz phenocrysts in the basal part of the tuff are 

notably darker colored than in other parts of the tuff. 

Small (~2 em) lithic fragments of silicic to intermediate 

lava and less common granitoid clasts also are abundant 

near the base of the tuff, and markedly decrease in abundance upward. 

A biotite K-Ar age of 24.9±0.6 Ma determined on 

the tuff of Arc Dome in the Paradise Range (no. 20, 

table 3) is analytically indistinguishable from a biotite 

K-Ar age of 24.4±0.4 Ma (recalculated using the new 

I.U.G.S. constants) determined by Armstrong (1970) on 

a sample of this tuff collected near lone in the southern 

Shoshone Mountains (no. 21, table 3). 

400r---~---,--~----.---~--~--~--~ 

C/) 

a: 

w 

1-

w 

::2: 300 

~ 

ui 

C/) 

< 

co 200 

w 

> 0 

co 

< 

z 

0100 

f= 

< 

> w 

_J 

w 

Upper tuff 

Basal zone 

10 20 30 

VOLUME PERCENT PHENOCRYSTS 

EXPLANATION 

o Quartz 

• K-feldspar 

o Plagioclase 

x Biotite 

• Total phenocrysts 

40 

Fig.ure 7. Variations in modal mineralogy of tuff of Arc 

Dome with increasing elevation above base of tuff. Modes 

are from thin sections of samples collected in thick section 

of densely welded tuff about 1 km south of Sherman Peak 

(fig. 3) on northeast side of Paradise Range. 

Tuffs Between the Tuff of Arc Dome and the Tuff of 

Toiyabe 

Three thin ash-flow tuffs locally are present between the tuff of Arc Dome and the tuff of Toiyabe near 

Brunton Pass on the east side of the Paradise Range. 

These units are, from oldest to youngest, the tuff of 

Brunton Pass, an unnamed black, crystal-poor vitrophyre, and an unnamed crystal- and biotite-rich tuff. 

These tuffs are only present on the east side of the Paradise Range, and the two younger tuffs have aggregate 

outcrop areas totaling less than 1 km2• However, the 

presence of these tuffs indicates that there was a significant erosional hiatus between eruptions of the tuff of 

Arc Dome and the tuff of Toiyabe and suggests that 

high-angle normal faulting may have begun on the east 

side of the Paradise Range between eruptions of these 

units. Elsewhere on the east side of the Paradise Range 

and in the southern parts of the Shoshone Mountains and 

Toiyabe Range, the tuff of Toiyabe lies directly on the 

tuff of Arc Dome. 

The tuff of Brunton Pass is the thickest and most 

widespread unit between the tuff of Arc Dome and the 

tuff of Toiyabe. It crops out discontinuously for about 12 

km between Brunton Pass and the north end of the 

Pactolus Hills and is as much as 90 m thick. It is an 

orange to dark-reddish brown, crystal-poor devitrified 

high-silica rhyolite ash-flow tuff containing 5 to 10 percent phenocrysts of sanidine and smoky quartz (table 2; 

fig. 5). The smoky quartz phenocrysts distinguish it from 

the underlying tuffs of Green Springs and Camel Spring. 

The tuff of Brunton Pass ranges from poorly to densely 

welded, probably reflecting variations in original thickness. Pumice and lithic fragments are relatively sparse. 

Locally overlying the tuff of Brunton Pass is a 

black, densely welded vitrophyric tuff containing about 

10 percent plagioclase and sanidine phenocrysts and 

trace amounts of orthopyroxene (table 2). Pumice and 

lithic fragments are very scarce. The tuff is as much as 

60 m thick. 

Locally overlying the black vitrophyre is a white, 

devitrified, densely welded, crystal-rich dacite(?) ashflow tuff that contains about 25 percent plagioclase and 

5 percent biotite phenocrysts (table 2). Quartz and sanidine phenocrysts are nearly absent, in contrast to the tuff 

of Arc Dome and the tuff of Toiyabe. This tuff contains 

abundant strongly flattened, crystal-rich pumice fragments as much as 5 em long. Maximum thickness of this 

tuff is about 20 m. The biotite tuff possibly is correlative 

with either the tuff of Sheep Canyon, which is exposed 

in the southwestern part of the Paradise Range, or with 

the Cloverdale Ranch unit of the tuff of Toiyabe, which 

is exposed in the northern Pactolus Hills. The modal 

mineralogy of the biotite tuff is similar to more mafic 

parts of the tuff of Sheep Canyon, whereas it lacks small 

amounts of hornblende and clinopyroxene phenocrysts 

12 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
that are present in the Cloverdale Ranch unit (see below). The inferred age of the biotite tuff would permit 

correlation to either of these other units. 

Tuff of Toiyabe 

Ferguson and Cathcart ( 1954) applied the name 

"Toiyabe Quartz Latite" to thick sections of crystal-rich 

ash-flow tuff exposed along the crest and west sides of 

the southern Toiyabe Range that they erroneously 

thought were lava flows. Kleinhampl and Ziony (1967, 

1985) recognized that these rocks are densely welded 

ash-flow tuff that is widely distributed in northwestern 

Nye County, and they provided modern descriptions and 

K-Ar ages for this tuff. Additional descriptions of crystal-rich tuffs that have previously been correlated with 

the herein abandoned Toiyabe Quartz Latite in the Paradise Range and Shoshone Mountains were given by 

Vitaliano (1963), Vitaliano and Vitaliano (1972), and 

Bonham (1970). 

Recent mapping in the Paradise and southern Toiyabe Ranges and in the southern Shoshone Mountains 

indicates that the many rocks heretofore mapped as the 

Toiyabe Quartz Latite belong to several different units. 

As defined by this study of the Paradise Range and mapping of the southern Toiyabe Range (Brem and others, 

1985; 1991) and of the southern Shoshone Mountains 

(Whitebread and others, 1988), the Toiyabe Quartz Latite is here abandoned owing to its previous use as a 

name for several genetically unrelated ash-flow tuff 

units, and its rocks are reassigned to several informally 

named tuff units, namely, the tuffs of Toiyabe, Arc 

Dome, Big Spring, Camel Spring, and Brunton Pass. In 

the Paradise Range, most of the rocks heretofore mapped 

as the Toiyabe Quartz Latite are assigned to the tuffs of 

Toiyabe and Arc Dome. Compared to the tuff of Arc 

Dome, the tuff of Toiyabe is notably finer grained, less 

crystal- and pumice-rich, more mafic, and lacks large 

bipyramidal smoky quartz phenocrysts (tables 1, 2; fig. 

5). Sphene, a characteristic accessory mineral in the tuff 

of Toiyabe, is absent in the tuff of Arc Dome, and allanite, common in the tuff of Arc Dome, is absent in the 

tuff of Toiyabe. There also are major chemical differences between these tuffs (compare FeO*, CaO, Ti02 , 

Rb, Sr, and Ba contents, tables 4 and 5). 

On the east side of the Paradise Range, the main 

phase of the tuff of Toiyabe appears to be a simple cooling unit of pale-lavender-gray, densely welded, devitrified, rhyolitic ash-flow tuff. The tuff contains 20 to 30 

percent phenocrysts of fine- to medium-grained plagioclase, sanidine, and quartz in about a 2:1:1 ratio, 1 to 3 

percent biotite, and about 1 percent hornblende (fig. 5; 

table 2). Sphene is a ubiquitous and characteristic accessory mineral that commonly is visible in hand specimen. 

A 5- to 10-m-thick body of dark gray to black vitrophyre 

generally is present at the base of the tuff. Small lithic 

fragments (dominantly intermediate lavas) are concentrated near the base of the tuff and decrease in abundance upward. On the east side of the Paradise Range 

near Sherman Peak, the tuff of Toiyabe has a minimum 

thickness of about 400 m. A biotite K-Ar age of 

21.4±0.7 Ma was determined on a sample of the tuff collected at Brunton Pass (no. 16, table 3). Other published 

ages of megascopically identical tuffs from the southern 

Toiyabe Range and the east side of the southern Shoshone Mountains are 22.0±0.4 and 22.5±0.7 Ma, respectively (nos. 18, 19, table 3). 

In the northern Pactolus Hills, a second ash-flow 

tuff is exposed locally beneath andesite and dacite lavas. 

This tuff is believed to be equivalent to the lower part of 

the tuff of Toiyabe and has been informally termed the 

Cloverdale Ranch unit for exposures in the southern 

Shoshone Mountains (G.F. Brem, oral commun., 1986). 

This tuff is a light-lavender-gray, densely welded, crystal-rich low-silica rhyolite. The Cloverdale Ranch unit is 

more mafic and crystal-rich than other parts of the tuff 

of Toiyabe and contains as much as 1 percent clinopyroxene, 5 percent biotite, and relatively small amounts of 

quartz and K-feldspar (figs. 5; tables 2, 5). Sphene is an 

uncommon accessory mineral. A biotite K-Ar age of 

22.9±0.7 Ma determined on a sample collected in the 

northern Pactolus Hills suggests that the Cloverdale 

Ranch unit is slightly older than the main part of the tuff 

of Toiyabe (no. 17, table 3). 

Andesite and Basaltic Andesite Flows 

Unconformably overlying the tuff of Toiyabe is a 

thick series of intermediate to mafic lava flows, flow 

breccia, volcanic debris-flow deposits (lahars), and 

minor volcaniclastic sedimentary rocks. The lava flows 

and flow breccias range from aphyric to moderately porphyritic with aphanitic to microcrystalline groundmasses. 

Most of these rocks are sparsely porphyritic containing 

fine- to medium-grained phenocrysts of plagioclase, pyroxene, and locally olivine or hornblende in pilotaxitic to 

hyalopilitic groundmasses. The more mafic flows commonly are vesicular and locally microcrystalline. Two 

whole-rock chemical analyses suggest that the lavas are 

basaltic andesite (nos. 1, 2, table 6); unanalyzed lavas 

north of Ellsworth Canyon probably are hornblende andesite or dacite, judging from their phenocryst mineralogy. Volcaniclastic sedimentary rocks and andesitic 

lahars commonly occur near the base of this unit along 

the crest of the range. This unit may be as much as 800 

m thick along the crest of the Paradise Range east of 

Sherman Peak. A whole-rock K-Ar age of 18.9±0.9 Ma 

was obtained from a basaltic andesite flow near the base 

of this unit (no. 15, table 3). 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 13 
Ellsworth Section 

The Ellsworth section consists of as many as seven 

ash-flow tuff units locally intercalated with andesite lava 

flows and unconformably overlain by andesite lava 

flows. From bottom to top, units in this section are the 

tuff of Return Mine, andesite, the tuff of Camel Spring, 

the white tuff, the brown rhyolite tuff, the tuff of Big 

Spring, and andesite and basaltic andesite (fig. 4 ). Two 

additional ash-flow tuffs, the purple tuff and the purple 

biotite tuff, and rhyolite lava flows locally crop out, but 

their ages relative to other units are unknown. Total 

thickness of the Ellsworth section exceeds 1,300 m. 

Major features of ash-flow tuff units in this section are 

summarized in figure 5 and tables 2 and 7. 

Tuff of Return Mine 

The tuff of Return Mine (fig. 2), the basal unit in 

the Ellsworth section, is a white to light-green to pink, 

poorly to moderately welded, devitrified, moderately 

crystal- and lithic-rich rhyolitic(?) ash-flow tuff. It consists of several ash flows that have variable phenocryst 

contents ranging from about 10 to 25 percent consisting 

of smoky quartz, sanidine, plagioclase, and minor biotite 

(table 2). Subangular fragments of pre-Tertiary rocks and 

older volcanic rocks as much as 6 em in diameter are 

abundant locally, particularly near the mouth of Marble 

Falls Canyon (fig. 3). This tuff commonly is strongly argillized, and pumice fragments commonly are leached 

leaving cavities partially filled with yellow and green 

clay minerals. The tuff of Return Mine is as much as 

300 m thick along the range front on the east side of 

Lodi Valley (fig. 3); elsewhere it is much thinner due to 

faulting. This tuff crops out north of Camel Spring in the 

Paradise Range and in the southern Shoshone Mountains 

near lone (Whitebread and others, 1988). The precise 

age of the tuff of Return Mine is unknown, although it 

probably is between 30 and 26 Ma given the regional 

age relations and the ages of overlying units. 

Andesite Flows 

Flows of aphyric to moderately porphyritic, locally 

vesicular hornblende and pyroxene andesite and dacite(?) 

lava lie between the tuff of Return Mine and the tuff of 

Camel Spring north of Camel Spring (fig. 3). The lavas 

are lavender-gray to reddish gray where relatively fresh, 

and white, orange-brown, or greenish gray where hydrothermally altered. They contain as much as 30 percent 

fine- to medium-grained phenocrysts consisting of plagioclase with lesser clinopyroxene or hornblende and 

local biotite in pilotaxitic groundmasses. Many of these 

lavas, particularly along the range front on the east side 

of Lodi Valley, are strongly altered either to argillic or 

propylitic assemblages. These lavas reach thicknesses of 

as much as 400 m. 

Tuff of Camel Spring 

The tuff of Camel Spring crops out between andesite flows and the white tuff in the Ellsworth section. 

See the Menter Canyon section for a complete description of this tuff. One cooling unit, believed to be the 

upper cooling unit based on the presence of anorthoclase 

phenocrysts, was recognized in the Ellsworth section. 

White Tuff 

The white tuff is a thin (0 to 50 m thick) ash-flow 

tuff that is discontinuously exposed at the north end of 

the Paradise Range. It is a moderately welded, devitrified, lithic- and pumice-poor rhyolite tuff that contains 

about 20 percent phenocrysts consisting of equal 

amounts of fine-grained quartz and sanidine, subordinate 

plagioclase, and trace amounts of biotite (fig. 5; table 2). 

It lies between the tuff of Camel Spring and the brown 

rhyolite tuff and has been identified only in the northern 

Paradise Range. 

Brown Rhyolite Tuff 

The brown rhyolite tuff is a simple cooling unit of 

light- to dark-brown, densely welded crystal-, lithic-, and 

pumice-poor high-silica rhyolite ash-flow tuff. It contains less than 10 percent phenocrysts of quartz, sanidine, . and plagioclase commonly set in a glassy matrix 

(fig. 5; table 2). This tuff locally crops out between the 

white tuff and the tuff of Big Spring at the north end of 

the Paradise Range and reaches a maximum thickness of 

about 125 m. McKee and others (1971) reported a sanidine K-Ar age of 23.7±0.7 Ma for this tuff (no. 24, table 

3). The brown rhyolite tuff has not been recognized outside of the northern Paradise Range. 

Tuff of Big Spring 

The tuff of Big Spring is a simple cooling unit of 

light-gray to bluish-gray, crystal-rich, pumice- and lithicpoor, densely welded, rhyolitic ash-flow tuff. Other authors included it as part of the herein-abandoned Toiyabe 

Quartz Latite (Vitaliano, 1963; Vitaliano and Vitaliano, 

1972; Kleinhampl and Ziony, 1985), but modal and 

chemical analyses show that it is distinct from the tuff of 

Toiyabe (table 2; fig. 5). It generally contains 35 to 45 

percent medium-grained phenocrysts of sanidine, plagio14 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
clase, and clear quartz in about a 3:3:2 ratio and 1 to 2 

percent biotite. Most of the tuff is devitrified, although 

the base of the tuff commonly is vitric. The tuff of Big 

Springs is the youngest tuff at the north end of the map 

area. It overlies the brown rhyolite tuff along a contact 

that commonly appears to be a fault contact. The tuff of 

Big Spring is younger than the brown rhyolite tuff 

(approx. 23.5 Ma, see above) and is overlain by hornblende andesite flows that probably are about 19 Ma. 

The age relation of the tuff of Big Spring to the tuff of 

Toiyabe is unknown. The tuff of Big Spring is as much 

as 200 m thick in the Paradise Range. Similar appearing 

tuffs also are present near lone in the southern Shoshone 

Mountains (Whitebread and others, 1988). 

Other Units of Uncertain Stratigraphic Position 

Small exposures of three additional volcanic units 

occur north of Ellsworth near the northeast corner of the 

area mapped. These units are the purple tuff, the purple 

biotite tuff, and rhyolite lava flows. 

The purple tuff crops out about 1.5 km west of Big 

Spring in two small fault slivers. It is a dark-purple, 

moderately pumice- and crystal-rich, densely welded, devitrified rhyolitic ash-flow tuff that contains about 15 to 

20 percent phenocrysts mostly consisting of quartz and 

sanidine with subordinate plagioclase and minor biotite 

(fig. 5; table 2). This tuff is faulted against Mesozoic 

rocks, andesite flows, and the tuff of Camel Spring and 

is intruded by a small rhyolite plug. It may be as much 

as 350m thick. 

The purple biotite tuff is exposed in four small 

outcrops about 0.5 km southeast of Big Spring, where it 

lies in depositional(?) contact on Mesozoic rocks. The 

tuff is purple to dark-red, densely welded, devitrified, 

crystal-poor, biotite- and pumice-rich rhyolite(?) ashflow tuff. It contains less than 10 percent phenocrysts 

consisting of roughly equal quantities of quartz, plagioclase, sanidine, and biotite (fig. 5; table 2). Small lithic 

fragments, including clasts of Mesozoic greenstone, are 

common near its base and decrease in abundance upward. The thickness of this tuff is unknown. 

Light-gray to red, flow-banded rhyolite lava flows 

form a small outcrop about 4 km northeast of Ellsworth 

that is fault-bounded against the tuff of Toiyabe on three 

sides and covered by alluvium on its other side. The 

flows are sparsely porphyritic containing 5 to 10 percent 

phenocrysts of fine- to medium-grained sanidine and 

quartz crystals in devitrified, locally spherulitic, aphyric 

groundmasses. The thickness and age of these flows are 

unknown, but they may be equivalent to rhyolite domes, 

plugs, flows and breccias described by Kleinhampl and 

Ziony (1984, 1985) in the Bruner district about 10 km to 

the northwest. 

Sheep Canyon Section 

The southwestern part of the Paradise Range and 

the northern Pactolus Hills are underlain by a thick series of silicic ash-flow tuff and intermediate to silicic 

lava that constitutes the Sheep Canyon section (fig. 4). 

This section consists of a thick sequence of intermediate 

to silicic lava overlain by a thick sequence of silicic ashflow tuff that locally is intercalated with intermediate 

lava and volcaniclastic sedimentary rock. Both of these 

sequences are unconformably overlain by a thick 

younger sequence of intermediate to silicic lava. John 

and others (1989b) referred to these three sequences as 

the older andesite, middle tuff, and younger andesite sequences, respectively (fig. 3). The total thickness of the 

Sheep Canyon section locally is in excess of 3,500 m. 

All three extrusive rock sequences are intruded by numerous small rhyolitic domes and dikes that are the 

same age as the younger andesite sequence. Several additional ash-flow tuff units, which may be older than the 

older andesite sequence, crop out southeast of Sheep 

Canyon in the southwestern Paradise Range and in the 

Pactolus Hills, where they are in fault contact with preTertiary rocks and the older andesite sequence. The 

sources of all of the tuff units in the Sheep Canyon section are unknown. Major features of ash-flow tuff units 

in the Sheep Canyon section are summarized in figure 5 

and tables 2 and 8. 

Tuff of Pactolus 

The tuff of Pactolus crops out in the central part of 

the Pactolus Hills near Pactolus, where it apparently is 

the oldest exposed Tertiary unit. The tuff of Pactolus 

may be correlative with the lower part of the Mission 

Spring Formation of Vitaliano and Vitaliano (1972), 

which is exposed in the southern Shoshone Mountains 

(fig. 6; G.F. Brem, oral commun., 1986; Whitebread and 

others, 1988). In the Pactolus Hills, the tuff of Pactolus 

appears to be conformably overlain by the tuff of Davis 

Mine. 

The tuff of Pactolus is a white, densely welded, 

crystal-poor to moderately crystal-rich rhyolite ash-flow 

tuff. It contains 10 to 25 percent fine- to mediumgrained phenocrysts of quartz, plagioclase, potassium 

feldspar, and biotite (fig. 3; table 2). It is everywhere 

strongly argillized or silicified. Lithic fragments are uncommon, in contrast to the overlying tuff of Davis Mine. 

This tuff is as much as 500 m thick near Pactolus but is 

exposed for only about 4 km along strike. The precise 

age of the tuff of Pactolus is uncertain, but it may be as 

old as 34 Ma (see below). 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 15 
Tuff of Davis Mine 

The tuff of Davis Mine is a distinctive, lithic-rich 

ash-flow tuff that forms prominent exposures near the 

Davis Mine and Everett Mine in the southwestern Paradise Range and in the Pactolus Hills near Pactolus (figs. 

2, 3). It is probably correlative with the ·upper part of the 

Mission Spring Formation of Vitaliano and Vitaliano 

(1972), which is exposed in the southern Shoshone 

Mountains (fig. 6; G.F. Brem, oral common., 1986; 

Whitebread and others, 1988). In the southern Shoshone 

Mountains and in the Pactolus area, the tuff of Davis 

Mine is underlain by lithic-poor tuffs (tuff of Pactolus), 

whereas in the Davis Mine area, the tuff of Davis Mine 

may be the oldest exposed Tertiary unit. 

The tuff of Davis Mine is a dark-green to black to 

white, densely welded, crystal-poor rhyolite(?) ash-flow 

tuff. It generally contains about 10 percent phenocrysts 

consisting of plagioclase and K-feldspar in roughly equal 

proportions and minor quartz and biotite (fig. 5; table 2). 

Small (generally <8 em), rounded lithic fragments of 

pre-Tertiary rocks (marble, quartzite, argillite, greenstone) and less commonly Tertiary intermediate lavas are 

abundant and characteristic throughout this tuff. The tuff 

of Davis Mine is everywhere strongly propylitized or silicified. Propylitized rock contains abundant chlorite, 

calcite, white mica, and locally, epidote. The tuff of 

Davis Mine is as much as 600 m thick near the Davis 

Mine, 600-800 m thick in the northern Pactolus Hills, 

and 350 m thick near Pactolus. 

The precise age of the tuff of Davis Mine is poorly 

known. In the southwestern Paradise Range, this tuff is 

everywhere in fault contact with pre-Tertiary rocks and 

older andesites. Compaction foliation in this tuff strikes 

north-northeast and locally has steep northwest dips. 

This orientation is unique relative to other tuff units, 

which generally strike northwest and have moderate to 

steep dips to the east. This structural orientation suggests 

that the tuff of Davis Mine may be older than the other 

tuffs and may have undergone an episode of faulting and 

tilting prior to eruption of the other tuffs. This postulated 

older age also is suggested by an imprecise, four point 

whole-rock Rb-Sr isochron age of approximately 34 Ma 

(A.C. Robinson, oral common., 1988). 

Older Andesite Sequence 

The older andesite sequence is the most widespread unit in the southwestern Paradise Range and 

commonly forms the basal Tertiary unit. It is crudely 

correlative with the older volcanic sequence of Vitaliano 

and Callaghan (1963) and Vitaliano and Vitaliano (1972) 

and consists of numerous lava flows and flow breccias 

that range in composition from andesite to low-silica 

rhyolite. Thin, laterally discontinuous beds of finegrained volcaniclastic sandstone and siltstone locally are 

present, and a thin dacite ash-flow tuff (biotite lithic tuff 

unit) is interbedded with the lavas in Sheep Canyon. A 

thicker, rhyolitic ash-flow tuff is interbedded in these 

lavas west of Goldyke, in the northern Pactolus Hills, 

and north of the Paradise Peak Mine (tuff unit of John, 

1988; see below). 

Lava flows in the older andesite sequence range 

from nearly aphyric (notably near the mouth of Sheep 

Canyon) to medium-grained porphyritic with as much as 

30 to 40 percent phenocrysts (fig. 5). Plagioclase forms 

the most common phenocryst mineral; less abundant are 

hornblende, biotite, clinopyroxene, and opaque oxides. 

Strongly resorbed quartz phenocrysts are rarely present. 

Many of the more siliceous lavas have well-developed 

flow banding. Most lavas in this sequence are weakly to 

strongly propylitically altered and contain abundant secondary calcite, chlorite, white mica, and locally, epidote. 

These altered rocks characteristically are dark purple to 

dark green, and a dark-green copper(?) oxide mineral 

commonly coats joint surfaces. 

The thickness and age range of the older andesite 

sequence are unknown. Most contacts between preTertiary rocks and the older andesites are fault contacts, 

commonly low-angle normal faults such as the Sheep 

Canyon fault (fig. 3); possible depositional contacts 

occur in an area of very poor exposure about 1 km south 

of the Gold Ledge Mine (figs. 2, 3). Structural attitudes 

of the older andesites generally are poorly known, although local flow banding in the lavas and bedding in 

thin sedimentary units suggests that the lavas are moderately to steeply tilted to the northeast similar to the 

overlying tuffs. Preliminary paleomagnetic studies also 

indicate that these lavas are steeply tilted (M.R. Hudson, 

oral common., 1989; John and Hudson, 1990). The older 

andesites have a minimum thickness of more than 400 m 

based on drilling near the Paradise Peak Mine and Davis 

Mine (fig. 2; R.E. Thomason, oral common., 1987; John 

and others, 1989b). Structural attitudes in the older 

andesites may indicate total thicknesses in excess of several kilometers in the Sheep Canyon area. McKee and 

John (1987) obtained biotite K-Ar ages of 24.4±0.7 and 

25.6±0.8 Ma (nos. 32, 33, table 3) on a dacite flow near 

the Gold Ledge Mine and on the biotite lithic tuff, respectively, and the ages of the overlying tuffs range 

from about 24 to 22 Ma (table 3). These data suggest 

that the older andesite sequence probably ranges in age 

from about 26 to 24 Ma. 

Biotite Lithic Tuff 

The biotite lithic tuff forms a distinctive marker 

unit in the older andesite sequence near the mouth of 

Sheep Canyon. This tuff is a light-gray to tan, crystalrich, pumice-poor dacite ash-flow tuff. It is more mafic 

16 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
than other ash-flow tuffs in the Paradise Range, containing 30 to 40 percent plagioclase phenocrysts, 5 to 7 percent biotite phenocrysts, and about 1 percent each 

hornblende and clinopyroxene phenocrysts (fig. 5). 

Small (less than 4 em) subrounded lithic fragments of 

intermediate lava are abundant in this tuff. The biotitelithic tuff appears to be conformably interbedded in the 

older andesites in Sheep Canyon. The tuff pinches out or 

is faulted out about 2 km south of the mouth of Sheep 

Canyon (fig. 3). McKee and John (1987) reported a biotite 

K-Ar age of 25.6±0.8 Ma on this tuff (no. 33, table 3). 

Tuff 

An unnamed crystal-poor rhyolite .tuff (tuff unit of 

John, 1988; see also John and Kelleher, 1987) crops out 

in the northern Pactolus Hills, north and northwest of 

Goldyke, and north of the Paradise Peak Mine (fig. 2). 

The tuff is gray to reddish-brown to light-blue-gray, generally densely welded, locally lithic- and pumice-rich 

rhyolite tuff that contains about 5 to 10 percent phenocrysts of plagioclase, sanidine, and quartz and sparse 3-

to 5-mm-wide biotite flakes (fig. 5; table 2). Pumice 

lapilli commonly are weathered out, giving the tuff avesicular texture. This tuff generally is devitrified and 

commonly is hydrothermally altered. Northwest of 

Goldyke, this tuff is interbedded in the older andesites 

and is overlain by about 20 m of intermediate lavas that 

are overlain by the tuff of Goldyke; elsewhere it is 

faulted against the older andesites or pre-Tertiary rocks. 

These relations suggest that this tuff is about 24 Ma. The 

tuff unit may be as much as 500 m thick in a poorly 

exposed area north of the Paradise Peak Mine; elsewhere 

it generally is between 100 and 300m thick. 

Tuff of Goldyke 

The tuff of Goldyke is a distinctive crystal-rich 

rhyolite ash-flow tuff that is exposed throughout the 

southwestern Paradise Range and northern Pactolus 

Hills. It is dark purple to light gray-green to tan, densely 

welded, devitrified, and locally pumice-rich. It contains 

20 to 35 percent phenocrysts of plagioclase, sanidine, 

quartz, and about 2 percent biotite (fig. 5; table 2). 

Quartz phenocrysts commonly are strongly resorbed and 

filled with devitrified glass inclusions, giving them a 

"wormy" or sieve texture. In the northern Pactolus Hills, 

this tuff consists of multiple ash flows, although cooling 

breaks have not been observed. There is a fairly wide 

range in phenocryst proportions (table 2), but detailed 

sampling was not done to determine if compositional 

zoning is present. The maximum exposed thickness of 

the tuff of Goldyke is about 450 m in the northern 

Pactolus Hills; elsewhere it is much thinner (S150 m) 

due to faulting and (or) a general westward thinning of 

the tuff. The tuff of Goldyke has biotite K-Ar ages of 

23.6±0.7 and 23.0±0.9 Ma (nos. 30, 31, table 3). 

Rocks Between the Tuff of Goldyke and the Lower White 

Tuff 

Discontinuous exposures of volcaniclastic and epiclastic sedimentary rocks and intermediate lavas locally 

crop out between the tuff of Goldyke and the overlying 

lower white tuff unit. The sedimentary rocks (older sedimentary rocks unit of John, 1988) consist of buff to 

light-mustard-yellow, thin-bedded shale, sandstone, and 

fine-grained conglomerate. These sedimentary rocks primarily crop out at the north end of the ridge northwest 

of the Paradise Peak Mine (Newmans Ridge, fig. 3) and 

near the Poleline Road. They have a maximum exposed 

thickness of about 30m. 

Locally overlying the sedimentary rocks are a thin 

series of medium-grained porphyritic biotite-hornblende 

andesite and dacite lava flows (rhyodacite to andesite 

unit of John, 1988). The flows are dark-gray to black, 

devitrified, medium- to coarse-grained porphyries containing 20 to 35 percent phenocrysts consisting of plagioclase with lesser fine-grained hornblende and biotite 

in microcrystalline to devitrified aphyric groundmasses. 

The flows reach a maximum thickness of about 30 m at 

the north end of Newmans Ridge. 

Lower White Tuff 

The lower white tuff is a crystal-poor rhyolite tuff 

exposed throughout the southwestern Paradise Range 

and northern Pactolus Hills; the unit is particularly thick 

and well exposed just north and west of the Paradise 

Peak Mine, where it forms most of Newmans Ridge (fig. 

3). The lower white tuff is gray to white to reddish 

brown where devitrified and black to green-gray where 

vitrophyric. It generally is pumice-rich, lithic-poor, 

densely welded near its base, and poorly welded near its 

top. A locally lithic-rich vitrophyric zone 5 to 20 m 

thick commonly is present near the base of this tuff. 

Elsewhere, the tuff is devitrified and commonly has undergone vapor-phase alteration. Chalcedony veinlets 

commonly cut the tuff in the southwestern Paradise 

Range. The tuff contains about 10 percent mediumgrained phenocrysts consisting of roughly equal 

quantities of quartz, locally iridescent sanidine, and plagioclase, and less than 1 percent biotite (fig. 5; table 2). 

Allanite is a common accessory mineral. The lower 

white tuff is as much as 250 m thick in the northern 

Pactolus Hills and may be somewhat thicker on 

Newmans Ridge. John and others (1989b) and McKee 

and John (1987) reported sanidine K-Ar ages of 

22.3±0.7, 21.8±0.7, and 25.1±1.0 Ma on this tuff (nos. 

28, 29, table 3). 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 17 
Red Tuff 

The red tuff is a prominent marker unit that is exposed throughout the southern Paradise Range and northem Pactolus Hills. In the northern Pactofus Hills the red 

tuff locally is separated from the underlying lower white 

tuff by about 5 m of medium- to coarse-grained epiclas:-

tic sandstone. The red tuff is a dark-red to lavender-gray, 

devitrified, densely welded, crystal-poor, generally 

pumice-rich rhyolite ash-flow tuff. It contains 1 to 7 percent phenocrysts of clear quartz, sanidine, and minor 

plagioclase (fig. 5; table 2). Pumice lapilli are strongly 

flattened (commonly 5 to 8 em long and less than 5 mm 

thick) and locally show rheomorphic flow textures. The 

tuff locally contains white spherulites as much as 1 em 

in diameter. The red tuff is more brittle than most other 

rocks and commonly is pervasively micro brecciated by 

faulting and partially silicified. This tuff commonly 

weathers into small chips and plates. The red tuff is as 

much as 150m thick. 

Gray-Green Tuff 

The gray-green tuff is a thin ash-flow tuff unit that 

is very locally exposed between the red tuff and the 

blue-gray dacite breccia in the southwestern Paradise 

Range and near Goldyke. It is a white to light-green, devitrified crystal-poor, locally pumice-rich rhyolite(?) tuff 

that contains about 5 to 10 percent phenocrysts of quartz 

and plagioclase (fig. 5; table 2). This tuff generally is 

weakly to strongly argillically altered. It is as much as 

50 m thick. 

Blue-Gray Dacite Breccia 

The blue-gray dacite breccia unit is a series of 

sparsely porphyritic to aphyric dacite and andesite lava 

flows and flow breccias that are present throughout most 

of the southwestern Paradise Range and northern 

Pactolus Hills. The most distinctive rocks in the unit are 

dark-blue-gray, finely brecciated dacite flow breccias 

that contain about 5 percent fine-grained phenocrysts of 

plagioclase, K-feldspar, and biotite in pilotaxitic groundmasses (fig. 5). The flow breccias locally are overlain by 

dark-gray to black, generally aphyric andesite flows. The 

total thickness of the unit is as much as 225 m in the 

southwestern Paradise Range and northern Pactolus 

Hills, but it pinches out along strike near the mouth of 

Sheep Canyon. 

Upper White Tuff 

The upper white tuff unit consists of three thin 

cooling units of crystal-poor ash-flow tuff that are present throughout most of the southwestern Paradise Range 

and northern Pactolus Hills. The lowest cooling unit has 

a prominent, greenish-black, lithic-rich basal vitrophyre 

that grades upward into devitrified, light-green-gray to 

purple, densely welded tuff containing about 5 percent 

phenocrysts of plagioclase and sanidine and trace 

amounts of biotite (table 2). The middle cooling unit is a 

devitrified, light-purple, densely welded, aphyric to 

sparsely porphyritic, pumice-poor ash-flow tuff containing less than 5 percent plagioclase phenocrysts. The 

upper part of the middle cooling unit commonly contains 

abundant white spherulites as much as 1 em in diameter. 

The upper cooling unit is a white to pale green, 

unwelded to moderately welded, devitrified crystal-poor, 

locally lithic-rich tuff. The total thickness of these tuffs 

is as much as 150m. 

Red Rhyolite Tuff 

The red rhyolite tuff consists of densely welded 

rhyolite ash-flow tuff that locally is overlain by dark-red 

epiclastic sandstone. The tuff is brick-red to light 

lavender-gray, devitrified, lithic- and pumice-poor, and 

contains 20 to 30 percent fine- to medium-grained 

phenocrysts of locally iridescent sanidine and 

bipyramidal smoky quartz (fig. 5; table 2). The tuff 

locally is overlain by as much as 10 m of irregularly 

crossbedded, fine- to medium-grained sandstone containing numerous coarser-grained crystals of sanidine and 

smoky quartz apparently derived from the underlying 

tuff. The total thickness of this unit is as much as 90 m, 

but thickness changes rapidly along strike, and this unit 

pinches out in many places. McKee and John (1987) reported a sanidine K-Ar age of 23.2±0.7 Ma on a sample 

of densely welded tuff (no. 24, table 3). 

Tuff of Sheep Canyon 

The tuff of Sheep Canyon forms the thickest and 

most complex ash-flow tuff unit in the southwestern 

Paradise Range. It is a compound ash-flow tuff consisting of as many as four cooling units, although the top 

and bottom cooling units commonly are absent. This tuff 

is white to light-pink to lavender-gray, crystal- and 

pumice-rich, devitrified, moderately to densely welded 

low-silica rhyolite and high-silica dacite and trachydacite 

tuff and lapilli tuff that contains 15 to 45 percent phenocrysts (average about 30 percent) consisting of mediumgrained plagioclase, lesser quartz and sanidine, and 1 to 

6 percent biotite (table 2; figs. 5, 8). There are notable 

vertical variations in modal mineralogy. The third cooling unit shows the greatest variability (fig. 8); within 

this cooling unit, plagioclase phenocrysts increase from 

about 20 to 30 volume percent from the base to the top 

of the unit, whereas the percentages of other phenocryst 

phases remain nearly constant or slightly decrease up18 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
ward. The tuff characteristically contains abundant, 

strongly flattened, crystal-rich pumice fragments as 

much as 25 em long. The lowest cooling unit locally is 

separated from the upper cooling units by about 10 to 15 

m of fine- to coarse-grained epiclastic sandstone and 

pebble conglomerate. A thin airfall tuff zone is present 

locally at the base of the second cooling unit above the 

sedimentary rocks. The top of the second cooling unit 

commonly has undergone strong vapor-phase alteration 

and has distinctive gas escape structures. The tuff of 

Sheep Canyon reaches a maximum thickness of about 

600 m but is exposed only for about 7 km along strike in 

the southwestern Paradise Range. McKee and John 

(1987) reported biotite K-Ar ages of 23.2±0.7 and 

24.1±0.7 Ma on this tuff (nos. 25, 26, table 3). 

Younger Andesite Sequence 

Thick piles of intermediate to silicic lava flows and 

small intrusions unconformably overlie and intrude the 

ash-flow tuffs and the older andesites in the southwestem Paradise Range and in the northern Pactolus Hills. 

These rocks are part of a large early Miocene lava field 

that extends from the Gabbs Valley Range to the east 

side of the Paradise Range (fig. 6). The younger andesite 

Cooling unit 3 

Cooling unit 2 

Cooling unit 1 

10 20 30 40 50 

VOLUME PERCENT PHENOCRYSTS 

EXPLANATION 

D Quartz x Biotite 

o Plagioclase • Hornblende 

Jt.. K-feldspar • Total phenocrysts 

Figure 8. Variations in modal mineralogy of tuff of Sheep 

Canyon with increasing elevation above exposed base of 

tuff. Modes are from thin sections of samples collected in 

a traverse across thick section of densely welded tuff that 

contains parts of four cooling units. Section is located 

about 2 km southwest of Sheep Canyon (figs. 2 and 3) in 

SEX sec. 33 and SW X sec. 34, T.11 N., R. 36 E. 

sequence is equivalent, in part, to the rocks of Mount 

Ferguson of Ekren and others (1980) and to the andesite 

and basaltic andesite unit on the east side of the Paradise 

Range. John (1988) and John and others (1989b) separated these younger lavas into two map units, hornblende 

andesite and porphyritic dacite units (figs. 4, 5). Many 

individual lava flows are present within each of these 

units. Dikes and small intrusions of hornblende andesite, 

that probably are feeders for the lavas, locally are present in Sheep Canyon. Small silicic intrusions and flow 

domes, that probably are silicic differentiates of the lavas based on chemical data and age equivalence, are 

common and intrude and overlie both the older rocks 

and the younger lavas. 

Hornblende Andesite 

Fine-grained porphyritic hornblende andesite lava 

flows crop out along the main part of the southwestern 

Paradise Range for about 6 km along strike. These unconformably overlie the tuff of Sheep Canyon, and a 

thin paleosol containing rounded granitic boulders is 

present locally along this contact. The lava flows are 

light greenish gray to black, commonly platy-weathering, 

and generally contain 5 to 20 percent fine- to mediumgrained phenocrysts of acicular hornblende and plagioclase and sparse quartz xenocrysts in pilotaxitic 

groundmasses (fig. 5). Clinopyroxene locally is present 

as a groundmass phase. Thin beds of volcaniclastic sandstone and shale locally are interbedded within the lavas. 

This unit may be as much as 750 m thick in Sheep Canyon (John, 1988). Several dikes and small intrusions of 

fine-grained andesite that locally grade into the hornblende andesite lavas are present in the Sheep Canyon 

area and are interpreted as feeders for the lavas (John, 

1988). John and others (1989b) reported a whole-rock KAr age of 20.1±0.6 Ma on a lava flow collected near the 

base of this unit (no. 14, table 3). 

Porphyritic Dacite 

The porphyritic dacite unit consists of numerous 

andesite to dacite lava flows, flow breccia, volcanic 

debris-flow deposits, and minor fine-grained volcaniclastic sedimentary rocks and block-and-ash flows. Several small intrusive plugs also have been identified about 

1 km southwest of the Paradise Peak Mine (R.E. 

Thomason, oral commun., 1987). The most abundant 

rocks in the southwestern Paradise Range are gray to 

black to red, porphyritic lava flows and flow breccias 

that contain abundant medium- to coarse-grained 

phenocrysts of plagioclase, hornblende, and biotite or 

clinopyroxene in fine-grained to aphyric, pilotaxitic to 

hyalopilitic groundmasses. Plagioclase phenocrysts commonly are tabular and as much as 1 em long. Biotite 

Stratigraphy of Tertiary Volcanic Rocks in the Paradise Range 19 
commonly forms coarse-grained books several millimeters thick. These porphyritic flows locally are overlain 

by black, sparsely porphyritic to aphyric andesite and 

dacite flows. In the northern Pactolus Hills, the basal 

flows in this sequence commonly are aphyric to sparsely 

porphyritic andesite with a trachytic groundmass that are 

overlain by porphyritic hornblende andesite and biotitehornblende dacite lava flows and flow breccia. 

Sections of the porphyritic dacite unit are best exposed in Finger Rock Wash about 8 km southwest of the 

Paradise Peak Mine (fig. 3). Here these lavas were 

mapped as the rocks of Mount Ferguson by Ekren and 

Byers (1985) and reach thicknesses of more than 500 m. 

These lavas thin to the northeast and, based on subsurface drilling, seldom exceed thicknesses of more than 

200 m in the vicinity of the Paradise Peak Mine. In the 

northern Pactolus Hills, the porphyritic dacite unit may 

be as much as 400 m thick (John, 1988). West of the 

Paradise Range, the rocks of Mount Ferguson may reach 

thicknesses in excess of 2,000 m in the Gabbs Valley 

Range (Ekren and Byers, 1985). McKee and John (1987) 

and John and others (1989b) reported 11 K-Ar ages that 

range from 19.3 to 15.5 Ma on biotite, hornblende, and 

whole-rock samples of these lavas (nos. 5-13, table 3). 

The wide range in ages is believed to be real as it is 

similar to the range in ages obtained by Ekren and others 

(1980) on the rocks of Mount Ferguson (also see John 

and others, 1989b). 

Silicic Dikes and Flow Domes 

Small rhyolite dikes and flow domes are abundant 

in the Sheep Canyon area and in the northern Pactolus 

Hills, and a large rhyolite flow dome forms the ridge 

just west of the old workings at Goldyke (fig. 3). Three 

different compositional types of rhyolite are recognized 

based on phenocryst content: (1) biotite rhyolite, (2) 

quartz rhyolite, and (3) quartz-biotite-feldspar low-silica 

rhyolite. Biotite rhyolite commonly contains about 2 to 

10 percent fine- to medium-grained phenocrysts of biotite with lesser plagioclase, K-feldspar, and quartz in 

cryptocrystalline groundmasses. Quartz rhyolite contains 

sparse, fine- to medium-grained, rounded quartz phenocrysts in aphanitic to cryptocrystalline groundmasses. 

The low-silica rhyolite contains about 10 percent fine- to 

medium-grained phenocrysts of plagioclase, biotite, 

rounded quartz, and local hornblende in cryptocrystalline 

groundmasses. Most intrusions are devitrified, although 

several glassy dikes and domes are present in the northern Pactolus Hills. Many of these rocks are strongly flow 

banded. Limited chemical analyses and K-Ar dating suggest that most of these rhyolites are silicic differentiates 

of the younger andesite sequence. McKee and John 

(1987) and John and others (1989b) reported three biotite K-Ar ages of 16.2±0.5, 16.3±0.5, and 19.2±0.6 Ma 

on dikes from the Sheep Canyon area (nos. 2-4, table 3). 

Breccia and Conglomerate in the Southwestern Paradise 

Range 

Poorly exposed, heterogeneous breccia and coarsegrained epiclastic sedimentary rocks cover about 4 

square kilometers near Willow Spring in the southwestern Paradise Range (fig. 3). Breccia consists of a heterogeneous mixture of lithic-rich tuff breccia, rhyolitic flow 

breccia, blue-gray dacite flow breccia, coarse sedimentary breccia, and large (several hundred meters) blocks of 

the lower white tuff and blue-gray dacite breccia units. 

Clasts within sedimentary breccias are as much as several meters in diameter and include pre-Tertiary rocks, 

the older andesite, the blue-gray dacite breccia, the lower 

white, red, and red rhyolite tuffs, and several unidentified volcanic units. Breccia ranges from clast- to matrixsupported, is poorly bedded and sorted, and has a 

sand-sized matrix of volcanic debris. Beds of mediumto coarse-grained sandstone and conglomerate locally are 

interstratified(?) within the breccia. Blocks of chalcedonic sinter several meters in diameter also are locally 

present near the east edge of the breccia. Many breccia 

and conglomerate beds near the east edge of the exposures are silicified and locally heavily iron stained. Disseminated pyrite locally is present in the silicified rocks. 

The breccia unit appears to unconformably overlie 

the older andesite unit and is faulted against pre-Tertiary 

rocks. Bedding generally dips at small to moderate 

angles into a major northeast-trending fault that truncates 

the Sheep Canyon detachment fault (fig. 3). The breccias 

cover an area about 1.5 by 3 km and are elongated parallel to this northeast-trending fault. Breccia fragments 

may slightly coarsen to the northeast. Breccia and associated sedimentary rocks are at least 250 m thick near 

their southwest end and probably thin to the north. The 

distribution, orientation, and lithologic characteristics of 

the breccia and interbedded conglomerate suggest that 

they formed by lithification of landslide debris and epiclastic sediments shed off the northeast-trending fault 

into a small basin or half -graben. The age of this fault is 

unknown, although it cuts the Sheep Canyon fault, 

which is younger than 16 Ma (John, 1988; John and 

others, 1989b). 

Sedimentary Rocks of Stewart Valley 

Thick sections of fine- to coarse-grained fluvial, 

lacustrine, and minor volcaniclastic sedimentary rocks 

are present in Stewart Valley between the southwest end 

of the Paradise Range and the north side of Cedar Mountain and from the Pactolus Hills on the east to the Gabbs 

Valley Range on the west (fig. 6). These rocks were de20 Geochemistry of Oligocen.e and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
posited in a middle Miocene continental basin and subsequently were faulted, uplifted, and locally folded 

(Molinari, 1984). These rocks range in age from 15 to 

11 Ma based on K-Ar dating of andesite flows that interfinger with the base of the sedimentary section, tuffs that 

are interbedded with the upper part of the section, and 

andesite lavas that overlie the sedimentary section 

(Evemden and others, 1964; Morton and others, 1977; 

Molinari, 1984; John and others, 1989b). Detailed descriptions of these rocks are given by Molinari (1984) 

and Ekren and Byers (1985, 1986). 

Only small exposures of the sedimentary rocks in 

Stewart Valley are present in the area of this report. 

They consist of white, finely laminated siltstone, sandstone, and minor pebble conglomerate cropping out in 

the northern Pactolus Hills that John (1988) and John 

and Kelleher (1987) correlated with more extensive exposures of sedimentary rocks in Stewart Valley (younger 

sedimentary rocks unit of John and Kelleher, 1987). In 

the northern Pactolus Hills, the sedimentary rocks unconformably overlie ash-flow tuff units of the Sheep 

Canyon section and the older andesite unit and locally 

bury faults including low-angle normal faults that separate the older andesite unit from tuffs of the Sheep Canyon section. The sedimentary rocks appear to be 

interstratified with undated andesite and basaltic andesite 

flows that overlie the porphyritic dacite unit in the 

southern Pactolus Hills (John and Kelleher, 1987). 

Andesite of Stewart Valley 

The andesite of Stewart Valley locally overlies the 

sedimentary rocks of Stewart Valley, the porphyritic dacite unit, and older tuff units in the central and southern 

parts of the Pactolus Hills, at the north end of Stewart 

Valley, and on the southeast side of Finger Rock Wash. 

The lavas consist of black, aphyric to sparsely porphyritic andesite lava flows and flow breccias that contain 1 to 

20 percent fine- to medium-grained phenocrysts of plagioclase, clinopyroxene, and olivine or hornblende set in 

pilotaxitic to hyalopilitic groundmasses. The flows in 

Finger Rock Wash previously were called latite by 

Ekren and Byers (1986) and John and others (1989b), 

but chemical analyses indicate that these rocks are normal calc-alkaline andesites. John and others (1989b) reported a whole-rock K-Ar age of 12.1±0.3 Ma (no. 1, 

table 3) for a hornblende andesite flow in Finger Rock 

Wash. The lavas in the Pactolus Hills and at the north 

end of Cedar Mountain are undated but probably 

younger than 11 Ma based on the age of the underlying 

sedimentary rocks. The lavas have a minimum thickness 

of about 100 m in the southern Pactolus Hills and are 

about 50 m thick in Finger Rock Wash. They are the 

youngest volcanic rocks exposed in the region. 

REGIONAL DISTRIBUTION, SOURCES, AND 

VOLUMES OF MAJOR ASH-FLOW TUFF 

SHEETS 

Five major ash-flow tuff units present in the Paradise Range and northern Pactolus Hills are widely distributed in adjacent ranges and have known or inferred 

sources outside of the Paradise Range. They are the tuffs 

of Pactolus and Davis Mine, both correlative with the 

Mission Spring Formation of Vitaliano and Vitaliano 

(1972), and the tuffs of Gabbs Valley, Arc Dome, and 

Toiyabe (fig. 6). A sixth unit, the tuff of Green Springs, 

may correlate with the Nine Hill Tuff, which is widely 

exposed in western Nevada and eastern California 

(Deino, 1985; Best and others, 1989b). Other ash-flow 

tuff units, such as the tuffs of Return Mine, Big Spring, 

Menter Canyon, and Camel Spring, are present locally in 

the southern Shoshone Mountains (Whitebread and others, 1988), but their complete extent is poorly known 

and therefore not discussed. Other ash-flow tuff units in 

the Paradise Range were not identified in adjacent 

ranges, and their sources remain unknown. 

Volumes of regionally extensive ash-flow tuff units 

are estimated on the basis of their present distributions 

and thicknesses (table 9). These estimates are subject to 

large uncertainties due to several factors including 

amount of post-eruption crustal extension, large variations in thicknesses between intracaldera and 

extracaldera facies, effects of predeposition topography 

on distribution of the tuffs, relatively few stratigraphic 

sections where thicknesses of individual tuff units have 

been accurately measured, and probable erosion of 

poorly welded parts of these tuffs. Miocene and younger 

crustal extension is the largest source of uncertainty in 

these estimates. The amount of extension varies significantly across the area where these tuffs are exposed, 

probably ranging from less than 20 percent in the southem Toiyabe Range and southern Shoshone Mountains to 

as much as 200 percent in the Yerington district 

(Proffett, 1977; Stewart, 1978). Volume estimates in 

table 9 probably are minimum estimates, because the actual amount of extension may be less than that used in 

the calculations. Because of this uncertainty, volume estimates probably are no better than ±50 percent. 

Tuffs of Pactolus and Davis Mine and the 

Mission Spring Formation 

The tuffs of Pactolus and Davis Mine and the correlative Mission Spring Formation are exposed in the 

southern Paradise Range, Pactolus Hills, and southern 

Shoshone Mountains (fig. 6). Thick sections of the tuff 

of Davis Mine are exposed in the southwestern Paradise 

Regional Distribution, Sources, and Volumes of Major Ash-Flow Tuff Sheets 21 
Range and in northern and central Pactolus Hills. In the 

Pactolus Hills, the lithic-rich tuff of Davis Mine is underlain by the lithologically similar but lithic-poor tuff 

of Pactolus. This same tuff sequence also is exposed in 

the southern Shoshone Mountains between Spanish and 

Indian Canyons (fig. 6). The tuff sequence in the 

Shoshone Mountains was named the Mission Spring Formation by Vitaliano and Vitaliano (1972; also see 

Whitebread and others, 1988) and includes numerous altered rhyolite and rhyodacite lava flows. Based on mapping by Whitebread and others (1988), the Mission 

Spring Formation may be as much as 1,100 m thick in 

the southern Shoshone Mountains, whereas the combined 

thickness of the tuffs of Pactolus and Davis Mine are no 

more than 850 m in the central Pactolus Hills and 600 m 

in the vicinity of the Davis Mine in the southwestern 

Paradise Range (fig. 6). Increasing thickness and the 

presence of abundant silicic lava flows in the southern 

Shoshone Mountains suggest that these tuffs had a 

source in or near the southern Shoshone Mountains, although existing mapping does not allow a more precise 

location of the source. 

The Mission Spring Formation and the tuffs of 

Pactolus and Davis Mine presently are exposed over an 

area covering about 475 km2• Assuming an average 

thickness of 800 m and an average of 50 percent 

posteruption extension, the approximate volume of these 

tuffs is 250 km3• This is a conservative estimate, because 

average extension may have been less than 50 percent 

and the possibility that these tuffs continue east of the 

Shoshone Mountains beneath younger volcanic rocks is 

ignored. 

Tuff of Gabbs Valley 

The tuff of Gabbs Valley is irregularly exposed in 

an east-west belt approximately 140 km long and 15-30 

km wide (fig. 6), based on geochemical data for the 

Bluestone Mine Tuff and the tuff of Gabbs Valley contained in Deino (1985) to outline the west limit of the 

tuff of Gabbs Valley, and ignoring exposures of the correlative(?), but poorly known, tuff of Hackett Canyon in 

the Virginia Range. In the Gabbs Valley Range, the tuff 

of Gabbs Valley consists ·of three cooling units of 

densely welded rhyolitic ash-flow tuff with a maximum 

exposed thickness of 630 m (Ekren and others, 1980; 

Ekren and Byers, 1986). On the east side of the Paradise 

Range and in the southern Shoshone Mountains, only the 

lowest cooling unit is exposed. Here, the tuff is as much 

as 350 m thick. At least two cooling units of the tuff of 

Gabbs Valley are present northwest of Gabbs Valley at 

the south end of the Sand Springs Range near Scheelite, 

where the tuff may be several hundred meters thick (fig. 

6). On the east side of the Yerington district, exposures 

of the Bluestone Mine Tuff tentatively correlated with 

the tuff of Gabbs Valley are as much as 300 m thick. 

Assuming an average thickness of 350 m and an average 

of 100 percent extension, the volume of tuff of Gabbs 

Valley is approximately 420 km3

• This estimate is conservative, because the thickness commonly is greater 

than 350 m and the average amount of extension may be 

considerably less than 100 percent. 

Ekren and Byers (1976) and Ekren and others 

(1980) postulated that the tuff of Gabbs Valley was 

erupted from a volcanic center located in Gabbs Valley 

and the southern Monte Cristo Range that is near the approximate center of the tuff of Gabbs Valley (fig. 6). 

Ekren and Byers (1976) described a fissure vent from 

which the upper cooling unit of these tuffs was erupted, 

and Ekren and Byers ( 1986) showed part of an inferred 

cauldron margin at the northern end of Gabbs Valley 

(fig. 6). The total thickness of the tuff of Gabbs Valley 

also is greatest near this inferred cauldron. Thus, although a well-preserved caldera is not present, it is probable that the source of the tuff of Gabbs Valley is in 

Gabbs Valley. 

Tuff of Arc Dome 

The tuff of Arc Dome is widely exposed in the 

Paradise Range, the southern Shoshone Mountains, the 

southern Toiyabe Range, the southern Sand Springs 

Range, and possibly on the east side of the Toquima 

Range (fig. 6). Ignoring small outcrops of tuff on the 

east side of the Toquima Range that are possibly correlative, the tuff of Arc Dome presently is exposed over an 

area covering about 3,350 km2

• In the Paradise Range, 

the tuff of Arc Dome crops out for about 15 km between 

Ellsworth Canyon on the north and the pediment surface 

south of Brunton Pass (fig. 3) on the south and has a 

minimum thickness of 400 m. In the Shoshone Mountains, the tuff of Arc Dome crops out discontinuously 

from near Peterson Station on old U.S. Highway 50 to 

Union Canyon about 40 km to the south and has a minimum thickness of about 450 m near North Shoshone 

Peak (Bonham, 1970). In the Toiyabe Range, the tuff of 

Arc Dome is exposed for about 35 km between the 

mouth of San Juan Creek and Arc Dome, where it may 

be more than 1 km thick. On the east side of the Toquima Range, the tuff of Ryecroft Canyon has strikingly 

similar textures, modal compositions, and an identical 

K-Ar age to the tuff of Arc Dome (fig. 6; Boden, 1986; 

D.R. Boden, oral common., 1984). In the southern Sand 

Springs Range, the tuff of Arc Dome is exposed from 

Rawhide to the vicinity of Eagleville (fig. 6), where it is 

as much as 250 m thick (M.L. Sorensen, oral common., 

1989). A conservative estimate of the volume of this tuff 

is approximately 880 km3, assuming an average thickness 

22 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
of 500 m and 25 percent extension for the east half of its 

exposures and 100 m thickness and 100 percent extension for the west half of its exposures. 

The source of the tuff of Arc ·Dome is not precisely known. G.F. Brem (oral and written commons., 

1985, 1986; Brem and others, 1991) suggested that increasing thickness of the tuff, increasing complexity of 

volcanic units within the tuff, and the presence of intrusive rocks similar to the tuff all indicate that the source 

of the tuff of Arc Dome is probably located in the southern Reese River Valley near Stewart Creek (fig. 6). 

Based on these relations and on a large gravity low centered in this area (Healey and others, 1981; Snyder and 

Healey, 1984), Brem and others (1991) inferred that a 

caldera probably is buried in the southern Reese River 

Valley. 

Tuff of Toiyabe and Tuff of Copper Mountain 

The tuff of Toiyabe is widely distributed in the 

southern Toiyabe and Paradise Ranges, southern Shoshone 

Mountains, Pactolus Hills, northern Royston Hills, and 

north Cedar Mountain (Simon area) (fig. 6). The south 

boundary of this tuff is well defined and trends nearly 

east-west across three ranges at approximately lat 38°30' 

N. West of long 118° W. the tuff of Copper Mountain is 

believed to be correlative with the tuff of Toiyabe. The 

tuff of Copper Mountain is a rhyolitic tuff named and described by Ekren and others (1980) for exposures in the 

northeastern Gabbs Valley Range (fig. 6). The tuff of Copper Mountain is megascopically, microscopically, and 

modally similar to the tuff of Toiyabe and has a majorelement composition comparable to the tuff of Toiyabe 

(R.F. Hardyman, written common., 1989). Although it has 

not been directly dated, limiting ages based on stratigraphy 

indicate that it is nearly the same age (23-22 Ma, Ekren 

and others, 1980, p. 43) as the tuff of Toiyabe (22.9-21.4 

Ma, table 3). 

The undivided tuff of Toiyabe and tuff of Copper 

Mountain presently are exposed over an approximate 

area of 4,150 km2• Thicknesses range from more than 1 

km near the source of the tuff of Toiyabe in the southern 

Toiyabe Range, to about 600 m at north Cedar Mountain, 400 m on the east side of the Paradise Range, and 

about 100m near Copper Mountain. A conservative estimate of the volume of these tuffs is approximately 1,100 

km3

, assuming an average thickness of 700 m and 25 

percent extension in the Shoshone Mountains and Toiyabe Range, an average thickness of 400 m and 50 percent 

extension in the Paradise Range, north Cedar Mountain, 

and Pactolus Hills, and an average thickness of 100 m 

and 100 percent extension further west. 

Assuming that the tuff of Toiyabe and the tuff of 

Copper Mountain are correlative, their present distribution allows estimation of offset on the Petrified Spring 

fault, the easternmost of four late Cenozoic right-lateral 

strike-slip faults mapped by Ekren and Byers (1984) in 

the eastern Walker Lane west of the Paradise Range (fig. 

6). Offset along the Petrified Spring fault is approximately 35 km based on apparent offset of the south margin of the undivided tuff of Toiyabe and tuff of Copper 

Mountain. In contrast, the tuff of Gabbs Valley, which is 

several million years older than the undivided tuff of 

Toiyabe and tuff of Copper Mountain, shows no discernible offset by this fault, although the tuff of Gabbs Valley primarily crops out north of the mapped trace of this 

fault and the distributions of individual cooling units are 

poorly known (fig. 6). Other Oligocene or early Miocene 

ash-flow tuff units are not present on both sides of the 

fault and cannot be used for estimating offset. The present distribution of 22- to 15-Ma intermediate lavas in the 

Gabbs Valley Range (rocks of Mount Ferguson) suggest 

somewhat less offset along this fault (approx. 10 km, fig. 

6), possibly indicating movement on this fault before or 

during the prolonged eruption of the rocks of Mount 

Ferguson. Synvolcanic movement along this fault also is 

suggested by the presence of landslipped debris interbedded in the rocks of Mount Ferguson (Ekren and others, 

1980). Total late Cenozoic right-lateral offset on the Petrified Spring fault probably is about 35 km; the apparent 

lack of offset on this fault shown by the tuff of Gabbs 

Valley is believed to reflect poor understanding of the 

distribution of cooling units in the tuff of Gabbs Valley. 

The source of the tuff of Toiyabe has long been 

postulated to be in the southern Toiyabe Range 

(Ferguson and Cathcart, 19 54; Kleinhampl and Ziony, 

1967, 1985). Recent mapping by G. F. Brem (oral and 

written commons., 1986; also see Brem and others, 

1985, 1991) has identified several vents for the tuff of 

Toiyabe and a partial caldera wall in the southern 

Toiyabe Range and southeastern Shoshone Mountains 

(fig. 6). 

Tuff of Green Springs 

The tuff of Green Springs is megascopically, petrographically, and chemically similar to the Nine Hill Tuff, 

which is widely distributed in western Nevada and eastern California (Deino, 1985; Best and others, 1989b). 

Apparent discrepancies in radiometric age data, however, 

do not permit correlation of these units at the present 

time; the Nine Hill Tuff has a very precise 40 Ar-39 Ar age 

of 25.11±0.017 Ma (Deino, 1989), whereas the tuff of 

Green Springs is older than the tuff of Gabbs Valley, 

which has K-Ar ages of 25.0-26.1 Ma (table 3; Ekren 

and others, 1980). Moreover, the tuff of Green Springs 

lies southeast of the known distribution of the Nine Hill 

Tuff (Deino, 1985), and the apparent thickness of the 

Regional Distribution, Sources, and Volumes of Major Ash-Flow Tuff Sheets 23 
tuff of Green Springs (as much as 300 m) is considerably greater than most sections of the Nine Hill Tuff 

which generally are less than 100 m thick and reach ~ maximum thickness of about 250 m (Deino, 1985; Best 

and others, 1989b). The source of the Nine Hill Tuff is 

unknown, although Best and others (1989b, fig. 7) inferred that the source may a caldera buried in Carson 

Sink about 100 km northwest of the Paradise Range. 

Sources of Other Ash-Flow Tuff Units in the 

Paradise Range 

Most ash-flow tuff units in the Paradise Range do 

not have readily identifiable sources. Ekren and others 

(1980) discussed the lack of known sources, specifically 

calderas, for several voluminous, widely distributed ashflow tuffs within the Walker Lane in west-central 

Nevada. They suggested several possible reasons for caldera sources not having been identified for these tuffs: 

(1) eruptions of these tuffs did not lead to formation of 

calderas; ~2) calderas were structurally dismembered by 

later ~aultmg; (3) calderas were buried beneath younger 

depostts; or (4) caldera structures have not been recognized. They suggested that a broad structural volcanotectonic depression rather than fault-bounded caldera(s) 

may have developed, possibly because the magma 

chamber(s) were at too great depths to allow formation 

of fault-bounded calderas. They speculated that reverse 

compositional zoning and strong resorption of quartz 

phenocrysts in the Mickey Pass and Singatse Tuffs are 

indicative of deep magma chambers. They also noted 

that lacustrine sediments locally are interbedded in these 

tuffs and possibly indicate local structural sags resulting 

from deep eruptions of the tuffs. 

In the Paradise Range, many of the ash-flow tuffs 

appear to represent small-volume localized units that 

may not have formed calderas and whose vents could 

easily be concealed beneath basin-filling alluvium. Many 

~f the tuffs appear to be distal outflow sheets; pyroclastic textures suggestive of near-vent facies or intracaldera 

rocks, megabreccias, and dikes and lava flows genetically related to the tuffs are not apparent. These relations 

suggest that caldera sources for most of these tuffs are 

not present in the Paradise Range. An exception may be 

the tuff of Sheep Canyon, which contains as many as 

four cooling units, reaches thicknesses in excess of 600 

m, and locally contains very coarse pumice fragments. 

H~we~er, this tuff is exposed only for about 7 km along 

strike m the southwestern Paradise Range, has not been 

r~ognized in adjacent ranges, and also may be a relatively small volume, albeit very thick, ash-flow tuff unit. 

In the Paradise Range, most of the tuffs present in 

the Sheep Canyon section represent a relatively short 

time period (less than 2 m.y.), and many features are 

common to different ash-flow tuff units, which suggests 

that several of these tuffs may have had common 

sources. For example, the lower white, red, gray-green, 

and upper white tuffs are all relatively thin, crystal-poor 

rhyolitic(?) tuffs that have very similar textural and petrographic characteristics and could have a common 

source. The tuffs of Goldyke and Sheep Canyon also 

share many characteristics and possibly have a common 

source. Additional petrologic, geochemical, and geochronologic data are required to test these hypotheses, 

but the actual number of sources for the ash-flow tuffs in 

the Paradise Range may be far fewer than suggested by 

the number of mappable ash-flow tuff units. 

Ekren and others (1980) noted several features that 

are present in the Gabbs Valley and Gillis Ranges, including reverse compositional zoning and resorption of 

quartz phenocrysts, which they inferred were indicative 

of deep magma chambers. These features are not present in the Paradise Range. Reverse compositional zoning 

is not obvious in ash-flow tuff in the Paradise Range. 

The only tuffs showing substantial compositional zoning 

are the tuffs of Arc Dome and Sheep Canyon. The tuff 

of Arc Dome shows normal (felsic to mafic) zoning 

(figs. 5, 7; see below). Zoning in the tuff of Sheep Canyon is less well defined, but most zoning may occur between different cooling units rather than within 

individual cooling units (fig. 8; see below). In addition, 

strong resorption of quartz phenocrysts is only evident in 

one ash-flow unit (the tuff of Goldyke). 

Sources for many of the ash-flow tuff units in the 

Paradise Range remain unidentified. Problems in identifying sources for the tuffs include the lack of depositional contacts between pre-Tertiary and Tertiary rocks, 

the complex faulting history, and locally strong hydrothermal alteration of the tuffs. However, extensive K-Ar 

dating of fresh rocks (table 3), modal data (fig. 5; table 

2), and geochemical data (see below) indicate that most 

tuffs in the Paradise Range, whose sources are not 

known, are not correlated with tuffs in adjacent ranges. 

For example, most of the tuffs in the Sheep Canyon section are substantially younger and less mafic than tuffs 

in the Gabbs Valley and Gillis Ranges. Similarly, tuffs 

in the lower part of the Menter Canyon section and in 

the Ellsworth section are much less mafic than ageequivalent tuffs in the Gabbs Valley and Gillis Ranges. 

The inability to correlate many tuff units in the Paradise 

Range with units in adjacent ranges and the absence of 

rocks with textures indicative of near-vent facies in the 

Paradise Range indicate that it is highly unlikely that 

sources for the tuffs are exposed in the Paradise Range. 

DISTRIBUTION AND SIGNIFICANCE OF THE 

YOUNGER ANDESITE SEQUENCE 

The younger andesite sequence (20- to 15-Ma intermediate lavas) in the Paradise Range and Pactolus Hills is 

24 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
part of an early Miocene volcanic field that may have covered more than 1,000 km2 in the Gabbs Valley and Paradise Ranges (fig. 6). These lavas include the rocks of 

Mount Ferguson in the Gabbs Valley Range and the hornblende andesite, porphyritic dacite, and andesite and basaltic andesite units in the Paradise Range. These lavas were 

erupted during or shortly after a brief period of early Miocene normal faulting and, at least locally, extreme crustal 

extension (John and others, 1989a, b). In the Paradise 

Range, this episode of faulting is marked by major angular 

unconformities between earliest Miocene ash-flow tuff 

units and the overlying younger andesite sequence (as 

much as 75° in the northern Pactolus Hills) and changes in 

the orientation and abundance of faults cutting the older 

rocks and the younger andesites (John, 1988). Similar field 

relations were described by Ekren and Byers (1984) in the 

Gabbs Valley Range and appear to be widespread throughout west-central Nevada (fig. 6; see data compilation in 

John and others, 1989b). 

There are several other early Miocene (approximately 22 to 18 Ma) volcanic centers composed dominantly of 

1- 10 

z 

UJ 

() 

a: 

UJ 9 

a_ 

1-

I 

CJ 8 

w 

3: 

z 7 

~---

z 

UJ 

1- 6 z 

0 

() 

0 

'::2 5 

+ 0 

ro 

z 4 

54 

A 

• 

T rachydacite 

• • 

• 

Rhy?lite 

.. 

58 62 66 70 74 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

e Andesite of Stewart Valley 

• Silicic intrusive rocks 

_. Porphyritic dacite 

x Hornblende andesite 

• Andesite and basaltic andesite 

0 Older andesite sequence 

78 

Figure 9. Total alkali-silica diagrams for Tertiary volcanic 

rocks in Paradise Range. All analyses recalculated to 100 

percent on volatile-free basis. Analyses of samples that 

have undergone obvious hydrothermal alteration (Si02

>78 

weight percent, high K20, low Na20, or low AI 0 3

) are not 

plotted. Rock names are I.U.G.S. classification fLe Bas and 

others, 1986) except for dashed line at Si02

=75 percent 

separating high-silica rhyolite (>75 percent Si02

) from 

rhyolite. BA, basaltic andesite; TB, trachybasalt. A, Older 

intermediate lavas in west-central Nevada including Goldfield, Tonopah-San Antonio Mountains, Candelaria HillsMonte Cristo Range, Terrill Mountains, southern Cocoon 

Mountains, and the northern Yerington district (Lincoln 

Flat area) (fig. 6; John and others, 1989b). There is a good 

correlation between areas of early Miocene faulting and 

the distribution of early Miocene intermediate lavas; intermediate lavas are mostly restricted to regions that underwent extensive normal faulting (fig. 6). Early Miocene 

andesite in the Paradise Range is chemically distinct from 

the older andesite (fig. 9A), which appears to be genetically related to the ash-flow tuffs (fig. 9B). 

Early Miocene intermediate magmatism and the 

plumbing system provided by extensive high-angle faults 

played important roles in the genesis of several major, 

early Miocene, epithermal gold-silver deposits including 

the Tonopah, Goldfield, and Paradise Peak deposits (John 

and others, 1989a, b, 1991). In particular, the deposits 

formed during or just after a period of early Miocene normal faulting and are spatially, temporally, and probably 

genetically related to intermediate magmatism. 

1-

z 

UJ 

() 

a: 

UJ 

a_ 

1-

I 

CJ 

w 

3: 

z 

~---

z 

UJ 

1-

z 

0 

() 

0 

'::2 

+ 0 

rn 

z 

9 

8 o: 

& : () 

.or» o: ~ Trachydacite • : sP 

• I<> 

>l • 

+ +-if.~ ~<> 8 I 0 X :0 

+: ~ I 

+ .tl + I 0 

0 

7 

I 

BA Andesite Rhy?lite 

6 

54 58 62 66 70 74 78 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

o Tuff of Arc Dome 

+ Tuff of Toiyabe 

o Brown rhyolite tuff 

<> Tuff of Green Spring 

• Tuff of Sheep Canyon 

o Lower white tuff 

... Tuff of Goldyke 

t::. Dacite breccia 

• Tuff of Brunton Pass 

• Tuff of Gabbs Valley 

Ill Tuff of Big Spring 

x Tuff of Camel Spring 

andesite sequence from the Sheep Canyon section, 

younger andesite sequence from throughout the Paradise 

Range and northern Pactolus Hills (hornblende andesite, 

porphyritic dacite, and andesite and basaltic andesite 

units), silicic intrusive rocks from southwestern Paradise 

Range and northern Pactolus Hills, and andesite of Stewart 

Valley. 8, Ash-flow tuffs and interbedded lavas from 

Menter Canyon, Ellsworth and Sheep Canyon sections. 

Distribution and Significance of the Younger Andesite Sequence 25 
GEOCHEMICAL STUDIES 

Approximately 120 whole-rock chemical analyses 

were obtained for volcanic rocks in the Paradise Range. 

These samples represent most major volcanic units, except those pervasively hydrothermally altered. Most ashflow tuff samples were densely welded and devitrified, 

and no attempt was made to separate the strongly flattened, devitrified pumice blobs from matrix material. 

Many samples were weakly altered (generally deuteric or 

propylitic alteration). Glass in vitrophyric samples was 

hydrated, and irregular and low sodium contents of many 

hydrated glasses suggest that partial sodium loss 

occurred during hydration (Noble, 1970). In addition, 

several ash-flow tuff samples that megascopically appear 

unaltered showed alkali metasomatism, probably due to 

vapor-phase alteration. Because of these limitations, detailed petrochemical discussion of volcanic rocks in the 

Paradise Range is not warranted, and chemical analyses 

are used only to define general trends and as an aid in 

correlation of rock units. 

Major elements in most samples were analyzed by 

wavelength-dispersive X-ray fluorescence spectroscopy 

(Taggert and others, 1987), and minor elements (Nb, Rb, 

Sr, Zr, Y, Ba, Ce, La, Cu, Ni, Zn, and Cr) were analyzed 

by energy-dispersive X-ray fluorescence spectroscopy 

(Johnson and King, 1987). FeO, H2

0+, H20-, C02

, and F 

were determined by conventional wet chemical methods 

(Jackson and others, 1987). Major elements for a few 

samples were determined by single-solution rapid rock 

analysis (Shapiro, 1975). Sr-isotopes were measured for 

about 25 samples using standard mass spectrometry techniques (see Kistler and others (1986) for a description of 

analytical procedures). Geochemical data are presented 

in tables 4, 5, 6, 10, 11, 12, 13, 14, 15, 16, and 17. 

Older and Younger Andesite Sequences and the 

Andesite of Stewart Valley 

Analyses of the older and younger andesite sequences and the andesite of Stewart Valley are given in 

tables 6, 10, and 11. Rocks in the older andesite sequence range in composition from 59 to 70 weight percent Si02 (major elements are recalculated to 100 percent 

on a volatile-free basis), have fairly high total alkali contents (6.0 to 7.3 weight percent Na2

0 + K20), and are 

andesites, trachyandesites, dacites, trachydacites, and 

rhyolites using the I.U.G.S. chemical classification (fig. 

9A; Le Bas and others, 1986). They have an alkali-lime 

index of about 55 (fig. 10C) and thus are alkali-calcic 

(Peacock, 1931). They form a high-K series using Gill's 

(1981) classification of orogenic andesites (fig. 11). 

Lava flows intercalated in the tuffs in the Sheep Canyon 

and Ellsworth sections (andesite and rhyodacite to andesite 

units) are andesite and dacite compositionally similar to 

the older andesite sequence (figs. 9-11, tables 14, 15). 

Silica content in the younger andesite sequence 

ranges widely from 54 to 70 weight percent. Using the 

I.U.G.S. classification, these rocks range from basaltic 

andesite to high-silica dacite (fig. 9A). They have an 

alkali-lime index of about 60 and are calc-alkalic using 

Peacock's (1931) classification. Using Gill's (1981) classification these rocks straddle the medium- and high-K 

series boundary and generally have notably lower K20 

contents than the older andesites (fig. 11). 

Limited chemical data for the silicic intrusive 

rocks that are equivalent in age to the younger andesite 

sequence suggest that the silicic intrusive rocks probably 

are silicic differentiates of the younger andesite sequence 

(figs. 9-12, tables 12, 13). In particular, the relatively 

low Rb and K2

0 contents and initial strontium ratio and 

relatively high K/Rb and Sr/Rb ratios are generally similar to the younger andesites and dissimilar to the older 

andesites. 

Four analyses of the andesite of Stewart Valley 

range from 56.6 to 59.7 weight percent Si02 (table 11) 

and are andesites and basaltic trachyandesites using the 

I.U.G.S. classification (fig. 9A). Their compositions are 

very similar to the younger andesite sequence (figs. 9-

11), and they also have relatively low initial strontium 

ratios similar to the younger andesites (87

Sr/"6Sri=0.7047; 

table 13; fig. 12). 

Although the range of silica contents of the older 

and younger andesite sequences are broadly similar, 

there are many compositional differences between these 

lava sequences (figs. 9-11). The older andesites tend to 

have higher ~0, MgO, Rb, and Rb/Sr contents at a 

given Si02 value than the younger andesites, whereas the 

younger andesites generally have higher CaO, P20!5, Sr, 

K/Rb, and FeO* /MgO than the older andesites. Initial 

strontium ratios generally are higher for the older 

andesites (

87Sr/"6

Sri=O. 7049-0.7054) than for the younger 

andesites (

87Sr/"6

Sri=0.7042-0.7051) and are comparable 

to those of the ash-flow tuffs (

87Sr/"6

Sri=0.7050-0.7055) 

(table 13; fig. 12). 

Compositional differences between the two groups 

of andesites in the Paradise Range are very similar to 

chemical variations between different ages of andesites 

elsewhere in the Walker Lane (Silberman and others, 

1976) and are similar to differences described in detail 

by Mellot and Hart (1987) for two series of Miocene andesitic lavas in the northern Basin and Range in Nevada. 

Mellot and Hart ( 1987) suggested that these compositional differences arise from a complex tectonic history 

involving magmas from multiple or heterogeneous 

sources and variable interaction of these magmas with 

evolved subcontinental mantle or heterogeneous crust. 

Similar complex magmatic histories may have occurred 

in the Paradise Range, although a lack of Pb and Nd isotopic 

26 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
data and rare-earth element data preclude formulation of 

a detailed model for generation of the andesitic magmas. 

However, the chemical data and the different tectonic 

settings of the two groups of andesites in the Paradise 

Range suggest that their magmas had different origins. 

In particular, lower K and Rb contents and initial strontium ratios and higher Ca, Sr, and P contents and K/R.b 

and Sr/Rb ratios of the younger andesite sequence and the 

silicic intrusive rocks indicate that they are less highly 

evolved than the older andesite sequence and suggest 

that they have a more primitive source (possibly a larger 

component of mantle or subducted oceanic crust) or 

have undergone less interaction with continental crust 

during ascent than the older andesites. The lack of correlation between silica content and initial strontium ratio 

(fig. 11) indicates that simple mixing of melts derived 

1-

z 

UJ 10 

0 

a: 

UJ 

a.. 0 1-

I 8 

CJ 

UJ 

~ + + 

z 

~ 6 + 

z 

UJ + 1- + z 

0 4 () 00 

0 

~ 0 

+ 

0 2 

n1' 0 z 0 0 

a: A 0 

0 0 CCI 50 54 58 62 66 70 74 78 () 

Si02 CONTENT, IN WEIGHT PERCENT 

Si02 CONTENT, IN WEIGHT PERCENT 

from the continental crust and from the upper mantle is 

not a reasonable mechanism to explain the compositional 

variation seen in the Paradise Range (compare to figure 

14 of Gans and others, 1989). 

There are relatively few chemical data for late 

Oligocene and early Miocene intermediate lavas from adjacent areas. Intermediate lavas in the Mizpah Trachyte 

(24-23 Ma) in the Tonopah district are trachyandesites 

that have major-element compositions very similar to the 

older andesites (Bonham and Garside, 1979). Early Miocene (mostly 22-20.5 Ma) lavas from the Goldfield district 

dominantly have intermediate compositions with calc-alkaline affinities that also appear similar to the older andesites 

in the Paradise Range (Ashley, 1979; R.P. Ashley, written 

commun., 1989). In contrast, the andesite of Lincoln Flat 

(19-18 Ma) in the northern Yerington district consists of 

1-

z 

UJ 10 

0 

a: 

UJ 

a.. 

1-

I 8 

CJ 

UJ 

~ 

z 

~6 

z 

UJ 

1-

z 

0 4 0 

0 

~ 

+ 

0 2 

n1' 

z 

a: c 0 

~ 0 

0 50 

+ + + +i + 

+ + 

-t + + 

+0 

0 

0 

0 

0 

54 58 62 66 70 74 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

o CaO 

+ Na20+K 20 

78 

Figure 10. Peacock (1931) diagrams (CaO versus Si02 and 

Na20+K20 versus Si02

) for Tertiary volcanic rocks in the 

Paradise Range. All analyses recalculated to 100 percent 

on volatile-free basis. Analyses of samples that have undergone obvious hydrothermal alteration are not plotted. Peacock index is silica content where lines through CaO and 

Na20+K20 intersect. A, Younger andesite sequence, silicic 

intrusive rocks, and andesite of Stewart Valley. 8, Ash-flow 

tuffs and interbedded lavas from Menter Canyon, 

Ellsworth, and Sheep Canyon sections. C, Older andesite 

sequence. 

Geochemical Studies 27 
~ 20.-~-.--~-,--~-.~--,-~--.-~-, 

z 

UJ 

() 

a: 

UJ 

a.. 

19 ..... 

• 

I- 18 I 

(9 

w 17 

3: 

~ 

~- 16 

z 

UJ I- 15 

z 

0 

() 14 

Q 

0 0 

0 o. 

. 

. <( 13 5'--4--~--'58--~-6--'-2---'---6-'--6 --~-'70 __ ~_7_._4 __ _._____.J78 

1--

z 

UJ 

() 

a: 

UJ 

a.. 

II 

(9 

w 

3: 

~ 

~ 

z 

UJ 

1--

z 

0 

() 

b 

Q) 

u. 

1--

z 

UJ 

() 

a: 

UJ 

a.. 

II 

(9 

w 

3: 

~ 

~ 

z 

UJ 

~ 

z 

0 

() 

0 

0> 

~ 

~ 

z 

UJ 

() 

a: 

UJ 

a.. 

II 

(9 

w 

3: 

~ 

1---

z 

UJ 

~ 

z 

0 

() 

0 

ctl 

() 

6 

4 

0 

0 54 58 62 66 

0 

. .. 

70 74 

.. 

78 

5.-~~--~-.--~-.--~.-~--.-~-. 

.... 

0 54 

0 0 

... . ~ ...... .. X f.i!~£ 

£ X£ 

. ... Do ... jJD 0 

... ... ... 

,.. ... ,.. ,.. .._oo 

58 62 66 

0 

.. 

70 74 78 

10,-~~--.--.-----.~~.-~--.-~-. 

... 8 r-. 

... . 

o• 

Si02 CONTENT, IN WEIGHT PERCENT 

1--

z 

UJ 

() 

a: 

UJ 

a.. 

II 

S2 

UJ 

3: 

~ 

~ 

z 

UJ 

1--

z 

0 

() 

0 

~ 

z 

4 

. . ... 

2 54 

• 

., 

58 

0 

0 ......... 

·~ ... o,.. 

o Jlj Do fl 0 

LA' .. ... 

.... ... ... 0 

62 66 

0 

... . 

0 

70 74 78 

1--

z 5--~~--~~--~-.--~.-~~.-~-. 

UJ 

() 

a: 

UJ 

a.. 

II 

(9 

w 

3: 

~ 

1---

z 

UJ 

1--

z 

0 

() 

0 

-:2 

3 

1 54 

I- 1.5 

z 

UJ 

() 

a: 

UJ 

a.. 

j: 1.0 

S2 

UJ 

3: 

~ 

1---

z 0.5 

UJ 

1--

z 

0 

() 

0 

i= 0.0 54 

58 

58 

o o Do o 

0 ~ 0 0 

El 

.............. X 0 ~£ £ 

... ... ...... 

...... 0 

62 

62 

66 

66 

0 

0 

70 

0 

70 

. . 

.. High-K 

Medium-K 

74 

.. 

74 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

e Andesite of Stewart Valley 

• Silicic intrusive rocks 

£ Porphyritic dacite 

x Hornblende andesite 

• Andesite and basaltic andesite 

0 Older andesite sequence 

78 

78 

Figure 11. Silica variation diagrams for the older and younger andesite sequences in Paradise 

Range and northern Pactolus Hills, silicic intrusive rocks, and andesite of Stewart Valley. All 

analyses recalculated to 100 percent on volatile-free basis. Samples that have undergone obvious 

hydrothermal alteration are not plotted. Line separating high-K and medium-K series from Gill 

(1981 ). 

28 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
andesite, trachyandesite, and trachydacite with alkali 

contents between those of the older and younger andesite 

sequences, but with Rb and Sr concentrations and Sr/Rb 

and K/Rb ratios similar to the younger andesite sequence 

(Proffett and Proffett, 1976). Lavas in the Alta Formation (approx. 20-14.5 Ma; Vikre and others, 1988) in the 

Virginia City area about 150 km northwest of the Paradise Range mostly are andesite with major- and traceelement compositions similar to the younger andesite 

sequence (Whitebread, 1976; M.L. Silberman, written 

commun., 1990). These data suggest that compositional 

changes seen in intermediate lavas in the Paradise Range 

occurred regionally and that major changes in andesite 

chemistry, and presumably magma genesis, occurred at 

about 20 Ma in the west-central Great Basin. Notably, 

this change in magma chemistry occurred during an episode of widespread crustal extension, and the compositional changes are consistent with a larger component of 

mantle source material in the early Miocene magmas. 

Numerous authors have noted that the tectonic environment of the Great Basin changed across the region 

during the early to middle Miocene (approximately 20 to 

17 Ma) from subduction-related, dominantly andesitic 

magmatism, generally occurring in areas of intra- and 

back-arc extension, to fundamentally bimodal basalt0.706 .-----.---,-----r-------.-----.-------, 

In 

<D 

~ C/') 

r--. 

00 0.705 .....J 

<( 

i= 

~ 

• 

0 ... • 0 

m 

In 0 

0 

0 

60 

0 

• 

... D 

0 

70 

• 

... 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

!.:::, Andesite of Stewart Valley 

D Rhyolite intrusion 

0 Younger andesite sequence 

• Tuffs 

e Older andesite sequence 

80 

Figure 12. Plot of initial 87Sr/86Sr ratio versus silica content for Tertiary volcanic rocks in Paradise Range and 

northern Pactolus Hills. See table 13 for Sr-isotope data. 

rhyolite magmatism associated with oblique extension 

east of the San Andreas transform and its result, modem 

Basin and Range faulting (see for example McKee, 

1971; Christiansen and Lipman, 1972; Silberman and 

others, 1976; Snyder and others, 1976). The Walker 

Lane area in the western Great Basin is anomalous, however, because it is characterized throughout the Miocene 

by intermediate calc-alkaline volcanism that may be the 

southward continuation of the Cascade volcanic arc, and 

the transition to bimodal magmatism occurred much later 

than in most other areas of the Great Basin (see for example Silberman and others, 1976; Snyder and others, 

1976). The Paradise Range lies along the east side of the 

Walker Lane, and compositional changes seen in early 

Miocene intermediate magmatism in the Paradise Range 

and nearby ranges to the west apparently reflect the 

change from andesitic magmatism associated with backarc extension to andesitic magmatism related to the Cascade arc (for example, Silberman and others, 1976). 

However, the role of crustal extension played in the genesis of these magmas and how early Miocene extension 

fits into tectonic models for the western Great Basin remain unclear. 

Tuffs in the Menter Canyon and Ellsworth 

Sections 

With the exception of the more mafic Cloverdale 

Ranch unit of the tuff of Toiyabe, all analyzed tuffs in 

the Menter Canyon and Ellsworth sections are rhyolites 

or high-silica rhyolites (tables 4, 5, and 14; fig. 13) . 

Most of these tuffs have unremarkable major- and traceelement compositions and trends that are similar to other 

Oligocene and early Miocene, broadly calc-alkaline ashflow tuff sheets in the Great Basin (for example, Ekren 

and others, 1974; Bonham and Garside, 1979; Boden, 

1986, 1989; Gans and others, 1989; Best and others, 

1989a, b) and dissimilar to Oligocene trachytic tuffs in 

the central Great Basin (for example, lsom Formation, 

Best and others, 1989a, b) and peralkaline rhyolitic ashflow tuffs associated with middle and late Miocene magmatism in the northern and southern Great Basin (for 

example, Noble and Christiansen, 1974; Christiansen and 

others, 1977; Rytuba and McKee, 1984; Conrad, 1984). 

Tuffs on the east side of the Paradise Range are in general more siliceous than age-equivalent tuffs in the 

Gabbs Valley, Gillis, and Singatse Ranges to the west 

(Proffett and Proffett, 1976; Ekren and others, 1980). 

Notably absent are the "monotonous intermediates" (dacitic tuffs) of Hildreth (1981) that characterize many 

Oligocene and early Miocene ash-flow tuff sequences 

elsewhere in the Great Basin (for example, Gans and 

others, 1989; Best and others, 1989a, b). 

Geochemical Studies 29 
~ 2o.-~--.-~~--~~--~~--~~--~~ 

z 

UJ 

0 

cr: 

UJ 18 a.. 

tI 

C) 

iJj 16 

~ 

~ 

~ 

z 

UJ 

0 

cr: 

UJ 

a.. 

~ 

I 

C) 

w 

~ 

~ 

t--

z 

UJ 

~ 

z 

0 

0 

b 

(]) 

u. 

4 

3 

2 

~ 1.2 

z 

UJ 

~ 1.0 

UJ 

a.. 

j: 0.8 

S2 

UJ 

~ 0.6 

~ 

t--

z 0.4 

UJ 

~ 

z 0 0.2 

0 

0 

. . .-+-" 

. 

. 

+ + 

++ + 

~ 0.0 L.._~--L.._~___JL_--'-___J----'--.....J---'-----'----'-----'-

~ ~ ~ ~ ro ~ n 

~ 

z 

UJ 

0 

a: 

UJ 

a.. 

~ 

I 

C) 

w 

~ 

~ 

,_: 

z 

UJ 

tz 

0 

0 

0 

cu 

0 

. .. 

. 

+ 

~ 

+ 

o~~--~~--L-~--L-~--L---'--.....J----'--.....J 

54 58 62 66 70 74 78 

Si02 CONTENT, IN WEIGHT PERCENT 

tz 

UJ 

0 

cr: 

UJ 

a.. 

~ 

I 

C) 

iJj 

3: 

~ 

~­

z 

UJ 

~ 

z 

0 

0 

4 

. . 

" 

0 

® 

[ 

0 

cU 

z 2L_~--L_~L_L_~___JL_~___JL_--'-----'----'-~ 

~ ~ ~ M ro ~ n 

~ 

z 

UJ 

0 

cr: 

6--~--,-~--.-~-,.-~-,.-~-.~e-~-, 

UJ 

a.. 

~ 

I 

S2 

UJ 

s 

~ 

~­

z 

UJ 

~ 

z 

0 

0 

0 

-2 

~ 0.8 

z 

UJ 

0 

cr: :f 0.6 

~ 

I 

S2 

UJ 3: 0.4 

~ 

~­

z 

~ 0.2 

z 

0 

0 

0 

. 

. 

+ 

. .. 

+ .. 

• 

• + o .. oao 

~ ++oEB 0 

+-W ~0 :j: 0< + + X 

X 0 [):l 

0 

[ 

i= 0.0 54 58 62 66 70 74 78 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

o Tuff of Arc Dome 

+ Tuff of Toiyabe 

c Brown rhyolite tuff 

o Tuff of Green Spring 

• Tuff of Sheep Canyon 

o Lower white tuff 

.. Tuff of Goldyke 

" Dacite breccia 

• Tuff of Brunton Pass 

• Tuff of Gabbs Valley 

EB Tuff of Big Spring 

x Tuff of Camel Spring 

* Rhyodacite-andesite 

lSI Tuff of Menter Canyon 

Figure 13. Silica variation diagrams for ash-flow tuffs and interbedded lavas in Paradise Range and 

northern Pactolus Hills. All analyses recalculated to 100 percent on volatile-free basis. Analyses of 

samples that have undergone obvious hydrothermal alteration are not plotted. 

30 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
The tuff of Green Springs is a high-silica rhyolite 

(75-77 weight percent Si02

) that is highly enriched in 

z 200 

0 A 

:J 

__J 

~ 

a: 150 w 

a_ 

Cl) 

1- D 

a: § B DO <( 100 a_ D D D D 

z X D 

~---- D D 0 ~ 

z ... "'14 ............ ... w 50 ! ~ ...... -· 1-

z •• X ·~ 0 ... ... 0 ... .0 

a: 0 

54 58 62 66 70 74 78 

600 

8 

... 

... JJ."' 

.0 .... ... a: 400 .. X ... ... X D • 

~ ... .......... ... 

• ... ... ~ 

... ... D c:PD D A. X D [JJ 

... CJ DO D 

D 

200 

54 58 62 66 70 74 78 

59 c ... 

40 ... 

• 30 -tl X 

.0 • ... 

a: 

-.:::: ... . ...... Cl) 

20 ' X •!J ... • ... ~ ... ... D ...... ... 10 X D D 

D D 08 o• oCI D . 

. . ~ 

0 

54 58 62 66 70 74 78 

Si02 CONTENT, IN WEIGHT PERCENT 

EXPLANATION 

• Andesite of Stewart Valley 

. Silicic intrusive rocks 

... Porphyritic dacite 

X Hornblende andesite 

. Andesite and basaltic andesite 

D Older andesite sequence 

Ce, La, Nb, Zn, and Zr relative to other tuffs in the Paradise Range (table 14; fig. 14) and is compositionally 

comparable to the Nine Hill Tuff (fig. 14; Deino, 1985). 

Analyses of samples from both cooling units of the tuff 

of Green Springs from two localities indicate that the 

lower cooling unit is more highly evolved than the upper 

cooling unit as it is enriched in Si02, ~0, Ce, Nb, Rb, 

Y, Zn, and Zr relative to the upper cooling unit, which is 

enriched in all other elements (table 14). The high Zr 

content, low phenocryst content, and secondary flowage 

textures of the tuff of Green Springs suggest that it 

erupted at relatively high temperatures as did the Nine 

Hill Tuff, which also has these features (Deino, 1985) . 

Trace-element analyses of samples of the lower 

cooling unit of the tuff of Gabbs Valley collected in the 

Paradise Range are similar to analyses obtained by 

Deino (1985) for other exposures of the tuff of Gabbs 

Valley. The relatively low Zr and Nb contents of the tuff 

z sao D 

0 

:J 

__J 

~ 400 

a: 

w 

a_ 

Cl) 

1-

a: 

<( 

a_ 

z 

1--

z 

w 

1-

z 

0 

0 

300 

200 

100 

T"ffmG~~ 

¢ 

0 0 Tuff of Green Springs 

0 8 

0 . 0 lSI . 0 + & 0 

t>O~:j:~+! ~ 8 ooo +!xD 

X X 

N a~--~--~--~--~--~--~--~--~ 

0 10 20 30 40 

Nb CONTENT, IN PARTS PER MILLION 

EXPLANATION 

0 Tuff of Arc Dome 

+ Tuff of Toiyabe 

o Tuff of Green Springs 

o Tuff of Sheep Canyon 

D Lower white tuff 

• Tuff of Goldyke 

t> Dacite breccia 

• Tuff of Brunton Pass 

• Tuff of Gabbs Valley 

x Tuff of Camel Spring 

lSI Tuff of Menter Canyon 

~ Rhyodacite to andesite flows 

Figure 14. Plots of trace-element data for Tertiary 

volcanic rocks in Paradise Range and northern 

Pactolus Hills. A, Rb versus Si02 for older and 

younger andesite sequences. 8, K/Ro versus Si02 for 

older and younger andesite sequences. C, Sr/Rb versus Si02 for older and younger andesite sequences. 

D, Zr versus Nb for ash-flow tuffs from Menter Canyon, Ellsworth, and Sheep Canyon sections. Also 

shown are average compositions for the Nine Hill 

Tuff and Unit D of the Bates Mountain Tuff from 

Deino (1985). Note that analyses of tuff of Green 

Springs are similar to the Nine Hill Tuff and Unit D 

of the Bates Mountain Tuff and that analyses of tuff 

of Gabbs Valley from the Paradise Range are distinct 

from the Nine Hill Tuff and Unit D of the Bates 

Mountain Tuff. 

Geochemical Studies 31 
of Gabbs Valley clearly indicate that the tuff exposed in 

the Paradise Range and elsewhere is not correlative with 

the Nine Hill Tuff (fig. 14; Deino, 1985), despite their 

strikingly similar and distinctive megascopic textures. 

Tuff of Arc Dome 

The tuff of Arc Dome shows pronounced normal 

compositional zoning with the basal 50 m of the tuff enriched in Si02, Rb, Nb, and Zn relative to the fairly 

homogeneous upper 300+ m of the tuff, which has 

higher concentrations of most other elements (fig. 15; 

table 4 ). Changes in bulk composition are reflected in 

phenocryst mineralogy: the basal zone contains more 

quartz and sanidine relative to the upper parts of the tuff, 

which have greater plagioclase and mafic mineral contents (fig. 7). As noted above, no cooling break has been 

(f) 

a: 

w 

1-

w 

~ 300 

z 

w 

(f) 

~ 

co 200 

w 

> 0 

co 

~ 

z 100 

0 

i= 

~ 

> w 

.....J 

w o~~~~~~~~~~~~~~~~~ 

w 

(f) 

~ 

co 

70 

w 200 

> 0 

co 

~ 

5 100 

i= 

~ 

> w 

.....J 

w 

71 72 73 74 75 76 77 78 

Si02 CONTENT, IN WEIGHT PERCENT 

200 400 600 800 1000 1200 

Ba (•) OR Sr (o) CONTENT, IN PARTS PER MILLION 

observed between the basal, black fiamme-rich part of 

the tuff and the homogeneous upper part of the tuff. 

These trends probably reflect compositional zoning in 

the magma chamber. 

Compositional and mineralogical trends in the tuff 

of Arc Dome are similar to trends reported for other 

large-volume, middle Tertiary ash-flow tuff sheets in the 

western Great Basin (for example, the Windous Butte 

Formation and the tuffs of Williams Ridge and Morey 

Peak, Ekren and others, 1974; tuff of Mount Jefferson, 

Boden, 1986, 1989). However, the upper parts of many 

other tuffs are much more mafic than the exposed top of 

the tuff of Arc Dome. The lack of more mafic ash flows 

in exposures of outflow-facies rocks of the tuff of Arc 

Dome in the Paradise Range and southern Shoshone 

Mountains may reflect differences between outflowfacies and intracaldera-facies rocks, with only the more 

(f) 

a: 

w 

1-

w 

~ 300 

z 

w-

(1) 

~ 

co 200 

w 

> 0 

co 

~ 

z 100 

0 

i= 

~ 

> w 

.....J 

w o~~~~--~~--~--~~--~--~~ 

0 2 3 4 5 

CaO (o) OR Na20 (•) CONTENT, IN WEIGHT PERCENT 

(f) 400 

a: 

w 

1-

w 

~ 

z 300 

w-

(1) 

~ 

co 

w 200 

> 0 

co 

~ 

z 100 0 

i= 

~ 

> w 

.....J 

w 0~--~-----L---*~----~--~----~ 

0 100 200 300 

Rb (~)OR Zr (•) CONTENT, IN PARTS PER MILLION 

Figure 15. Compositional variations in whole-rock samples of tuff of Arc Dome. 

32 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
siliceous upper part of the magma chamber represented 

in the outflow facies tuff. 

Tuff of Toiyabe 

Although a detailed sampling traverse across the 

tuff of Toiyabe was not made, there is little evidence for 

significant compositional zoning within the part of the 

tuff of Toiyabe exposed in the eastern Paradise Range 

(compare analyses of the basal part of the tuff (nos. 1-3, 

table 5) to the other analyses (nos. 4-6)). The tuff of 

Toiyabe has notably higher CaO, Sr, and Sr/Rb and 

lower total alkalis, Zr, Ba, Ce, and La than the upper 

part of tuff of Arc Dome, although they have similar 

silica contents (tables 4, 5). The tuff of Toiyabe exposed 

in the Simon area at the north end of Cedar Mountain is 

slightly more mafic than the tuff exposed on the east 

side of the Paradise Range (nos. 7, 8, table 5) but is considerably less mafic than its Cloverdale Ranch unit exposed in the northern Pactolus Hills (nos. 9, 10, table 5). 

Major-element analyses of the probably correlative tuff 

of Copper Mountain from the Gabbs Valley Range and 

Barnett Hills are nearly identical to analyses of the tuff 

of Toiyabe from the east side of the Paradise Range 

(R.F. Hardyman, written commun., 1989). 

Tuffs in the Sheep Canyon Section 

Ash-flow tuffs in the Sheep Canyon section show 

more compositional variation than tuffs on the east side 

of the Paradise Range ranging from trachydacite to highsilica rhyolite, although all of the analyzed units except 

the tuff of Sheep Canyon are rhyolite or high-silica 

rhyolite. Many tuffs are weakly to strongly altered (notably the lower white tuff, red tuff, and red rhyolite tuff 

units). Altered tuffs commonly have high ~0 and Si02 

and low Na20 (nos. 4-6, table 14, and nos. 2 and 7-11, 

table 16). This alteration probably reflects vapor-phase 

alteration as the tuffs cooled, because it does not affect 

underlying units or the hydrated basal vitrophyre of the 

lower white tuff (compare nos. 1 and 2, table 16) and it 

does not appear to be structurally controlled as is potassium metasomatism, which results in similar chemical 

changes (Brooks, 1986; Glazner, 1988). Some alteration 

of the red tuff may be due to partial silicification during 

tectonic brecciation, because it has relatively normal 

K20 and N~O but very high Si02 and very low Al20 3 

(no. 4, table 15). 

The tuff of Sheep Canyon shows the most compositional variation and is the most mafic tuff analyzed in 

the southwestern Paradise Range (68 to 72.5 weight percent Si02

), which is consistent with its phenocryst mineralogy (table 2; figs. 5, 8). As noted above, there are 

substantial variations in modal mineralogy of samples 

collected along a detailed traverse across the four cooling units in this tuff (fig. 8). Because of strong deuteric 

or propylitic alteration of this tuff, chemical analyses of 

most samples collected in this traverse were not made, 

and the total compositional variation of this tuff is unknown. Modal data suggest that compositional zoning is 

normal (felsic to mafic) in the thickest (third) cooling 

unit (fig. 8). Comparison of modal data of chemically 

analyzed samples with modal data from samples in this 

traverse suggests that greater compositional variation 

occurs between cooling units than within individual 

cooling units. 

SUMMARY OF LATE CENOZOIC 

VOLCANIC AND TECTONIC HISTORY 

OF THE PARADISE RANGE 

Tertiary volcanic rocks exposed in the Paradise 

Range and northern Pactolus Hills record a complex history of late Cenozoic volcanism and tectonism that is 

summarized in figure 16. The earliest Tertiary volcanic 

eruptions preserved in the Paradise Range are the tuffs 

of Davis Mine and Pactolus in the southwestern part of 

the range and in the Pactolus Hills, the tuff of Return 

Mine at the north end of the range, and the lower part of 

the Menter Canyon section (tuffs of Green Springs and 

Menter Canyon) on the east side of the range. The tuffs 

of Davis Mine and Return Mine both locally contain 

abundant lithic fragments of pre-Tertiary rocks, 

indicating that they were erupted through or traveled 

across areas containing exposed pre-Tertiary rocks. They 

also contain clasts of Tertiary(?) intermediate lavas. 

These relations suggest that the tuffs of Davis Mine and 

Return Mine are some of the earliest Tertiary units in the 

region. In contrast, most other ash-flow tuff units lack 

abundant pre-Tertiary lithic components (the tuffs of 

Menter Canyon and Gabbs Valley are exceptions). The 

tuffs of Pactolus and Davis Mine may have been erupted 

from the southern Shoshone Mountains and may date 

from about 34 Ma. The tuff of Return Mine and tuffs in 

the lower part of the Menter Canyon section are undated 

but probably date from 30 to 26 Ma. Sources for these 

latter tuffs have not been identified. Compositions of the 

tuffs of Pactolus, Davis Mine, and Return Mine are unknown due to extensive hydrothermal alteration, but 

modal analyses suggest that they are rhyolites similar to 

other Oligocene calc-alkaline ash-flow tuffs exposed 

throughout the Great Basin (for example, Best and others, 1989a, b; Gans and others, 1989). 

In the southern part of the Paradise Range and in 

the Pactolus Hills, eruption of the tuffs of Pactolus and 

Davis Mine may have been followed by a period of normal faulting and tilting. These tuffs, particularly the tuff 

of Davis Mine, have a different structural orientation 

Summary of Late Cenozoic Volcanic and Tectonic History of the Paradise Range 33 
w 

ol:lo 

Ellsworth section (north side Paradise Range) Menter Canyon section (east side Paradise Range) Sheep Canyon section (southwestern Paradise Range 

n and northern Pactolus Hills) ~ 

C) Time Volcanic Tectonic Time Volcanic Tectonic Time Volcanic Tectonic n 

:::r" Events Events Events Events Events Events ~ 

3 01 • 01 • 0 

=.· 

.. 

-< 

C) 

..... 

Q 

41 I Modern Basin and Range faulting, 41 I Modern Basin and Range faulting, 

4l I ciQ' uplift of Paradise Range, and erosion uplift of Paradise Range, and erosion Modern Basin and Range faulting, C) uplift of Paradise Range, and erosion n 

~ 

= ~ 

Dol 

= Q. 8 I 8 • 8- ~ C'-· 

I I I cs· C'-· C'-· 

n I I I ~ I C'-· 

= ~ I I 

~ C'-· C'-· I I Eruption of andesite of Stewart Valley 12 I 12 I 12 ;:; 

Dol U) I I Sedimentation in Stewart Valley; form-

= a: C'-· C'-· 

r;· <( I I ation of breccia and conglomerate in 

jill:! w Sheep Canyon; formation of Sheep 

C) >- Canyon fault 

n LL I I I ~ 0 16 C'-· 16 C'-· 16 

~ U) I I I Eruption of younger andesite sequence; .. 

Dol z I Eruption of andesite and basaltic I Eruption of andesite and basaltic I normal faulting and tilting caused by 

Q. 

Dol 0 crustal extension(?) ::J andesite flow unit andesite flow unit 

~· I I I .....J ('o· 

jill:! :::2: 20 20 Erosion, normal faulting, tilting, and 20 I Dol Erosion, normal faulting, tilting, and crustal extension Erosion and local exposure of pre- = z crustal extension(?) OQ 

~ - Tertiary rocks 

ui I I Dol Eruption of tuff of Big Spring Eruption of tuff of Toiyabe I = :::2: I Eruption of middle tuff sequence Q. i= I z Eruption of brown rhyolite tuff Erosion, normal faulting and emplace- C) 24 24 ment of local volcanic units 24 .. Eruption of tuff of Camel Spring and I -:::r" middle Eruption of tuff of Arc Dome Eruption of older andesite sequence part of the Ellsworth section ~ 

3 I I Eruption of tuff of Gabbs Valley I 

~ C'-· Local normal faulting C'-· Local normal faulting ('o· 

~ I I I I I 

- 28 I Eruption of lower parts of Ellsworth 28 I Eruption of lower parts of Menter 28 C) I 

c section C'-· Canyon section ('o· 

Erosion, faulting, and tilting of tuffs of Ill I I I Pactolus and Davis Mine E I I I ... ;' 

I I ('o· 

I 

z 32 32 32 -< I ~ ('o· 

Q Erosion Erosion I I C'-· Eruption of tuffs of Pactolus and Davis Mine 

c I I = 

- Erosion -::< 36 36 36 z 

~ 

< !. Figure 16. Schematic summary of late Cenozoic volcanic-tectonic history of Paradise Range and northern Pactolus Hills. Dol 
compared to younger rocks in the same area, suggesting 

that the older tuffs may have undergone a period of 

faulting and tilting prior to eruption of the younger 

rocks. 

Oligocene faulting and extension also have been 

suggested for several areas near the Paradise Range. 

Boden (1986) and Mills and others (1988) presented data 

on the orientation of Oligocene faults and dikes near 

Round Mountain in the southern Toquima Range and 

suggested that the orientation of these features indicates 

a period of Oligocene normal faulting and extension(?). 

R.F. Hardyman (written commun., 1987) described a 

major angular unconformity between Oligocene ash-flow 

tuff units in the Dicalite Summit area at South Cedar 

Mountain. Seedorff (1981, 1991) also described a major 

angular unconformity between Oligocene ash-flow tuff 

units in the Royston area and suggested that a widespread episode of crustal extension occurred about 27 

Ma. 

In the southwestern Paradise Range and in northern 

Pactolus Hills, voluminous eruptions of an older sequence of intermediate to silicic lavas occurred between 

about 26 and 24 Ma. The lavas are not widespread in 

adjacent ranges and therefore probably had fairly local 

sources. However, most contacts with pre-Tertiary rocks 

are faults whose displacement are unknown, which precludes accurate reconstruction of the original distribution 

of these lavas. These lavas were conformably(?) overlain 

by a thick sequence of silicic ash-flow tuff and less 

abundant intermediate to felsic lava that erupted during a 

short period of time about 23 Ma. Differences in chemistry and petrography suggest at least three sources for the 

tuffs, but vents have not been identified. The older andesite sequence and ash-flow tuffs form a broadly calcalkalic, high-K series that is petrochemically similar to 

other calc-alkaline sequences erupted throughout much 

of the Great Basin during the Oligocene and earliest 

Miocene (approx 36 to 22 Ma). 

On the east side of the Paradise Range, ash-flow 

tuff erupted from several major sources was deposited 

between about 26 and 24.5 Ma. These tuffs were erupted 

from Gabbs Valley (tuff of Gabbs Valley) and from the 

west side of the Toiyabe Range (tuff of Arc Dome). Following eruption of the tuff of Arc Dome, there was a 

major period of erosion lasting until about 22 to 23 Ma. 

Erosion may have resulted from local uplift due to faulting as suggested by the local preservation of small exposures of tuffs overlying the tuff of Arc Dome near 

Brunton Pass and the formation of a volcanic-tectonic 

trough in the southern Toiyabe Range at this time (Brem 

and others, 1985, 1991). About 22 to 23 Ma, eruptions 

of the tuff of Toiyabe covered most of the east side of 

the Paradise Range and the Pactolus Hills. Although exposed far west and south of the Paradise Range, this tuff 

is not present in the southwestern Paradise Range, possibly because that part of the range was a topographic 

high. 

Following eruption of the tuff of Toiyabe and the 

tuffs in the Sheep Canyon section at about 22 Ma, there 

was a hiatus in volcanic activity that lasted about 2 m.y. 

in the southwestern Paradise Range and about 3 m.y. in 

the northern Pactolus Hills and on the east side of the 

Paradise Range. A similar hiatus in volcanic activity is 

widespread in west-central Nevada and generally marks 

the end of voluminous silicic ash-flow tuff eruptions at 

this latitude (see discussion and references in John and 

others, 1989b ). 

In the Paradise Range, and in most ranges to the 

west where the Oligocene and early Miocene tuff is preserved, there is evidence for a major period of normal 

faulting and, locally, extreme crustal extension that 

began during or shortly after the early Miocene hiatus in 

volcanic activity. In the Paradise Range, this faulting 

event is marked by major unconformities between Oligocene to early Miocene tuffs and the younger andesite sequence and changes in the abundance and orientation of 

faults. The tuff of Toiyabe and overlying basaltic andesite lavas are separated by a 10°-25° angular unconformity on the east side of the range. In the northern Pactolus 

Hills, there is as much as a 75° angular unconformity 

between the Cloverdale Ranch unit of the tuff of 

Toiyabe and overlying hornblende andesite lava flows 

and flow breccias. 

Normal faulting and intermediate to felsic volcanism occurred simultaneously in the southwestern Paradise Range during the early Miocene. Numerous 

low-angle faults, which may have originated as highangle faults, formed at this time. There is a pronounced 

unconformity between the tuffs and overlying hornblende andes,ite and porphyritic dacite units, and a 

paleosol containing rounded granitic boulders locally 

separates the tuff of Sheep Canyon from the overlying 

hornblende andesite unit, suggesting uplift of the range 

and exposure of the pre-Tertiary basement prior to eruption of the hornblende andesite unit. Andesite dikes, 

interpreted as feeders for the upper part of the hornblende andesite unit, cross-cut low-angle faults between 

the older andesites and tuffs. Preliminary paleomagnetic 

data suggest that these dikes are untilted (M.R. Hudson, 

oral commun., 1989). Rhyolite dikes, interpreted as silicic differentiates of the younger andesites, also cross-cut 

low-angle faults. Elsewhere in the southwestern Paradise 

Range, lava flows in the hornblende andesite unit are 

steeply tilted and are in low-angle fault contact with the 

tuff sequence. 

Near the end of eruption of the younger sequence 

of intermediate lavas, a large basin formed in Stewart 

Valley. Subsidence and sedimentation in this basin lasted 

from about 15 to 12-11 Ma. Sedimentary rocks in 

Stewart Valley are at least 445 m thick (Molinari, 1984). 

Summary of Late Cenozoic Volcanic and Tectonic History of the Paradise Range 35 
In the southwestern Paradise Range and in the northern 

Pactolus Hills, these sedimentary rocks locally lap up 

against the older rocks and cover older faults. The Sheep 

Canyon detachment fault in the southwestern Paradise 

Range may have formed at this time, perhaps as a large 

gravity slide, as this fault cuts rhyolite dikes dated at 19 

to 16 Ma and the hornblende andesite unit (20 to >16 

Ma). The breccia and conglomerate unit exposed near 

Willow· Spring in the southwestern Paradise Range also 

may have formed during this time from landslide debris 

shed into a small half-graben that formed either along a 

northeast-trending fault that cuts the Sheep Canyon fault 

or along the Sheep Canyon fault. Blocks of sinter in the 

breccia and conglomerate unit, and local silicification 

and pyritic alteration along the margin of these rocks 

where they were deposited against a northeast-trending 

fault, suggest that hydrothermal activity occurred during 

formation of these rocks and that they probably are not 

much younger than the youngest volcanic rocks in the 

area (approximately 15.5 Ma in the southwestern Paradise Range). 

The latest volcanic activity in the area occurred 

south of the Paradise Range at the north end of Stewart 

Valley, in the southern Pactolus Hills, and at the north 

end of Cedar Mountain, where 50--100 m of andesite 

lava and lahars locally cap the sedimentary rocks. These 

rocks are about 12 Ma at the north end of Stewart Valley 

(John and others, 1989b), but rocks further south are undated and may be slightly younger. 

The present physiography of the Paradise Range 

and northern Pactolus Hills is mainly controlled by 

north- to north-northeast-trending high-angle normal 

faults that are modern Basin and Range structures. These 

faults resulted in the uplift of the Paradise Range and 

Pactolus Hills relative to Gabbs, Lodi, and Stewart Valleys (fig. 2). It is unknown when movement on these 

faults began, but movement probably has continued into 

the Quaternary (J.C. Dohrenwend, oral commun., 1989). 

COMPARISON OF THE PARADISE RANGE TO 

OTHER HIGHLY EXTENDED TERRANES IN 

THE BASIN AND RANGE PROVINCE 

Gans and others (1989) described early Oligocene 

synextensional magmatism in eastern Nevada and summarized tectonic and volcanic features of other highly 

extended terranes in the Basin and Range province. They 

recognized six features that are common to most highly 

extended terranes: (1) multiple generations of imbricated 

normal faults with older faults cut and rotated to low 

angles by younger high-angle normal faults; (2) volcanic 

sequences that show broad compositional zonation upward from intermediate composition at the base to more 

silicic composition at the top (andesite or basaltic andesite at the base to dacite or rhyolite at the top); (3) relatively short duration of volcanism (several million years) 

and high rate of volcanic eruption; (4) beginning of extension either synchronous with, or immediately after, 

peak magmatic activity; (5) a marked decrease or cessation of volcanic eruption shortly after initiation of 

extension with deposition of thick sections of coarse 

sedimentary rocks during extension; and (6) local presence of gently dipping sequences of basalt (±rhyolite) inter stratified with fanglomerates. These capping 

sequences overlie older volcanic rocks along an angular 

unconformity. Several of these features are present in the 

Paradise Range, although there are notable differences. 

Oligocene and early Miocene rocks in the Paradise 

Range show evidence for multiple generations of normal 

faults formed during a period of early Miocene faulting; 

the oldest faults now dip at low angles and are cut by 

younger normal and strike-slip faults. Upper plate rocks 

generally dip at moderate to high angles into the fault 

planes suggesting that the low-angle faults may be rotated high-angle faults. The oldest faults generally trend 

northwest, whereas the youngest faults generally trend 

north-northeast to northeast. The origin of many of the 

low-angle faults remains unclear. The amount of stratal 

rotation of lower plate rocks for many of the low-angle 

faults is indeterminate. Preliminary paleomagnetic studies of rocks beneath the Sheep Canyon fault suggest that 

the lower plate rocks of this fault have not been tilted as 

much as upper plate rocks (John and Hudson, 1990; 

M.R. Hudson, oral commun., 1989). Thus, the Sheep 

Canyon fault may have originated as a low-angle structure. In addition, depositional contacts between preTertiary and Tertiary rocks are absent in the Paradise 

Range, and therefore restored cross sections showing 

pre-Cenozoic faulting cannot be constructed. These relations preclude a unique interpretation of the faulting history in the Paradise Range, but it is likely that at least 

some low-angle normal faults are rotated high-angle 

faults. 

Synextensional magmatic rocks in the Paradise 

Range may show gross overall compositional zonation 

from intermediate to more silicic compositions with decreasing age, although the volume of siliceous rocks is 

small and mostly consists of small rhyolitic intrusions. 

Compositions of syn- to post-extensional intermediate 

lavas do not appear to change systematically with time. 

The oldest lavas in the southwestern part of the Paradise 

Range, the hornblende andesite unit, are compositionally 

similar to many of the younger lavas (approximately 

58.7--61.7 weight percent Si02; table 6). Lavas in a wellexposed, 500+m-thick section of intermediate lavas in 

Finger Rock Wash range from about 55 to 63 weight 

percent Si02

, although there is almost no variation between the lowest and uppermost exposures that contain 

approximately 61 weight percent Si02

• In a 200-m-thick 

36 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
section of the youngest part of the younger andesite sequence exposed about 2 km southwest of the Paradise 

Peak Mine, lavas decrease from about 70 weight percent 

Si02 at the base of the section to about 64 weight percent 

Si02 at the top of the section. In the Pactolus Hills, Si02 

increases from about 58 to 62.5 weight percent from the 

base to the middle of the section. However, many of the 

youngest rocks in the southwestern Paradise Range are 

small rhyolitic intrusions that are distinctly more siliceous than the lavas (Si02 content of the intrusions is 

71.5-76 weight percent), suggesting that there may be a 

general tendency toward more siliceous compositions 

with decreasing age. 

Synextensional volcanism in the southwestern 

Paradise Range lasted about 4.5 m.y., somewhat longer 

than in most areas discussed by Gans and others (1989). 

In other parts of the Paradise Range and in the northern 

Pactolus Hills, the duration of volcanism is unknown. In 

comparison to the southwestern Paradise Range, most of 

the synextensional volcanic rocks in the Yerington district were erupted in about 2 m.y. (between 19 and 17 

Ma) (Proffett, 1977; Proffett and Proffett, 1976), and in 

eastern Nevada most of the synextensional rocks were 

erupted in 1-2 m.y. (Gans and others, 1989). 

Early Miocene normal faulting and extension 

occurred during a hiatus in magmatic activity and prior 

to onset of large-volume intermediate volcanism on the 

east side of the Paradise Range and in the Pactolus Hills. 

Major angular unconformities separate Oligocene to earliest Miocene tuff from overlying early Miocene lavas. 

The early Miocene lavas generally are tilted less than 

15-20°, in contrast to the underlying tuffs that locally 

are tilted as much as 75°. In the southwestern Paradise 

Range, relative timing between faulting and intermediate 

volcanism is less well constrained, but the lower part of 

the younger andesite sequence is tilted as much as the 

ash-flow tuffs, and thus large-volume, intermediate volcanism began prior to extensional faulting. 

In the Paradise Range, intermediate-composition 

magmatism continued well after extension started, and 

synextensional sedimentary rocks are absent. These relations are well exposed on the east side of the range and 

in the northern Pactolus Hills, where thick sequences of 

intermediate lava appear to entirely postdate early Miocene extensional faulting, and sedimentary horizons are 

virtually absent. Gently dipping sedimentary horizons in 

the central and southern Pactolus Hills grade laterally 

into thick sequences of sedimentary rocks in Stewart 

Valley. The sedimentary rocks of Stewart Valley lap 

over low-angle faults and steeply tilted tuffs and appear 

to entirely postdate early Miocene faulting. Farther west 

on the east side of the Gabbs Valley Range, the base of 

the sedimentary rocks section has been dated at about 15 

Ma, whereas faulting occurred between 22 and 19 Ma. 

In the southwestern Paradise Range, coarse sedimentary 

breccia locally is present, but its age and origin are unclear. The breccia probably is younger than the major 

period of early Miocene faulting as it appears to lap over 

low-angle faults and steeply tilted tuffs and is inferred to 

have filled a half-graben formed by a fault that cuts the 

Sheep Canyon fault. 

In summary, the late Cenozoic volcanic-tectonic history of Paradise Range differs from that of other highly 

extended terranes in the Basin and Range province. Much 

extensional faulting occurred during a hiatus in magmatic 

activity in the early Miocene. Extension was followed by a 

relatively long episode of dominantly intermediate composition magmatism that is geochemically distinct from earlier, dominantly silicic magmatism common throughout 

west-central Nevada during the Oligocene and early Miocene. There is little systematic compositional variation in 

intermediate lavas erupted during or just after extensional 

faulting, and true basalts are absent in the Paradise Range. 

Major horizons of synextensional sedimentary rocks also 

are absent in the Paradise Range. It is not clear whether 

these differences between the Paradise Range and highly 

extended terranes in the Basin and Range province represent local variations or fundamentally different styles of 

crustal extension and volcanism. 

REFERENCES CITED 

Armstrong, R.L., 1970, Geochronology of Tertiary igneous 

rocks, eastern Basin and Range Province, western Utah, 

eastern Nevada, and vicinity, U.S.A.: Geochimica et 

Cosmochimica Acta, v. 34, p. 203-232. 

Ashley, R.P., 1979, Relation between volcanism and ore deposition at Goldfield, Nevada: Nevada Bureau of Mines and 

Geology Report 33, p. 77-86. 

Best, M.G., Christiansen, E.H., and Blank, R.H., Jr., 1989a, 

Oligocene caldera complex and calc-alkaline tuffs and 

lavas of the Indian Peak volcanic field, Nevada and Utah: 

Geological Society of America Bulletin, v. 101, p. 1076-

1090. 

Best, M.G., Christiansen, E.H., Deino, A.L., Gromme, C.S., 

McKee, E.H., and Noble, D.C., 1989b, Excursion 3A: Eocene through Miocene volcanism in the Great Basin of the 

Western United States: New Mexico Bureau of Mines and 

Geology Resources Memoir 47, p. 91-133. 

Bingler, E.C., 1978, Abandonment of the name Hartford Hill 

Rhyolite Tuff and adoption of new formation names for 

middle Tertiary ash-flow tuffs in the Carson City-Silver 

City area, Nevada: U.S. Geological Survey Bulletin 1457-

0,19 p. 

Boden, D.R., 1986, Eruptive history and structural development of the Toquima caldera complex, central Nevada: 

Geological Society of America Bulletin, v. 97, p. 61-74. 

--1989, Evidence for step-function zoning of magma and 

eruptive dynamics, Toquima caldera complex, Nevada: 

Journal of Volcanology and Geothermal Research, v. 37, 

p. 39-57. 

References Cited 37 
Bonham, H.F., Jr., 1970, Geologic map and sections of a part 

of the Shoshone Mountains, Lander and Nye Counties, 

Nevada: Nevada Bureau of Mines and Geology Map 32, 

scale 1:62,500. 

Bonham, H.F., Jr., and Garside, L.J., 1979, Geology of the 

Tonopah, Lone Mountain, Klondike, and northern Mud 

Lake quadrangles, Nevada: Nevada Bureau of Mines and 

Geology Bulletin 92, 142 p. 

Brem, G.F., John, D.A., Nash, J.T., Poole, F.G., and Synder, 

D.B., 1991, Mineral resources of the Arc Dome Wilderness Recommendation Area, Nye County, Nevada: U.S. 

Geological Survey Bulletin 1961, 21 p. 

Brem, G.F., Purdy, T.L., and Snyder, D.B., 1985, Oligocene 

and Miocene volcanic-tectonic history of the southern 

Toiyabe and Shoshone Mountains [abs.]: Geological Society of America Abstracts with Programs, v. 17, p. 343. 

Brooks, W.E., 1986, Distribution of anomalously high ~0 

volcanic rocks in Arizona: Metasomatism at the Picacho 

Peak detachment fault: Geology, v. 14, p. 339-342. 

Christiansen, R.L., and Lipman, P.W., 1972, Cenozoic volcanism and plate-tectonic evolution of the Western United 

States-Part II-Late Cenozoic: Philosophical Transactions of the Royal Society of London, v. 271, p. 249-284. 

Christiansen, R.L., Lipman, P.W., Carr, W.J., Byers, F.M., Jr., 

Orkild, P.P., and Sargent, K.A., 1977, Timber MountainOasis Valley caldera complex of southern Nevada: Geological Society of America Bulletin, v. 88, p. 943-959. 

Conrad, W.K., 1984, The mineralogy and petrology of compositionally zoned ash flow tuffs, and related silicic volcanic 

rocks, from the McDermitt caldera complex, NevadaOregon: Journal of Geophysical Research, v. 89, no. B10, 

p. 8639-8664. 

Deino, A.L., 1985, Stratigraphy, chemistry, K-Ar dating, and 

paleomagnetism of the Nine Hill Tuff, California-Nevada: 

Part 1: Berkeley, University of California, Ph.D. thesis, 

338 p. 

---1989, Single-crystal 40 ArP9 Ar dating as an aide in correlation of ash flows: Examples from the Chimney 

Spring/New Pass Tuffs and the Nine Hill/Bates Mountain 

Tuffs of California and Nevada [abs.]: New Mexico Bureau of Mines and Mineral Resources Bulletin 131, p. 70. 

Ekren, E.B., and Byers, F.M., Jr., 1976, Ash-flow fissure vent 

in west-central Nevada: Geology, v. 4, p. 247-251. 

---1984, The Gabbs Valley Range-A well exposed segment of the Walker Lane in west-central Nevada, in Lintz, 

Joseph, Jr., ed., Western geological excursions, volume 4, 

1984, Annual Meeting of the Geological Society of 

America: Boulder, Geological Society of America, p. 203-

215. 

---1985, Geologic map of the Gabbs Mountain, Mount 

Ferguson, Luning and Sunrise Flat quadrangles, Mineral 

and Nye Counties, Nevada: U.S. Geological Survey Miscellaneous Investigations Map Series 1-1577, scale 

1:48,000. 

---1986, Geologic map of the Mount Annie NE, Mount 

Annie, Ramsey Spring, and Mount Annie SE quadrangles, 

Mineral and Nye Counties, Nevada: U.S. Geological Survey Miscellaneous Investigations Map Series 1-1579, 

scale 1:48,000. 

Ekren, E.B., Byers, F.M., Jr., Hardyman, R.F., Marvin, R.F., 

and Silberman, M.L., 1980, Stratigraphy, preliminary petrology, and some structural features of Tertiary volcanic 

rocks in the Gabbs Valley and Gillis Ranges, Mineral 

County, Nevada: U.S. Geological Survey Bulletin 1464, 

54p. 

Ekren, E.B., Quinlivan, W.D., Snyder, R.P., and Kleinhampl, 

F.J., 1974, Stratigraphy, structure, and geologic history of 

the Lunar Lake caldera of northern Nye County, Nevada: 

U.S. Geological Survey Journal of Research, v. 2, p. 599-

608. 

Evernden, J.F., Savage, D.E., Curtis, G.H., and James, G.T., 

1964, Potassium-argon dates and the Cenozoic mammalian 

chronology of North America: American Journal of Science,v. 262,p. 145-198. 

Ferguson, H.G., and Cathcart, S.H., 1954, Geologic map of the 

Round Mountain quadrangle, Nevada: U.S. Geological 

Survey Geologic Quadrangle Map GQ-40, scale 

1:125,000. 

Gans, P.B., Mahood, G.A., and Schermer, Elizabeth, 1989, 

Synextensional magmatism in the Basin and Range Province; a case study from the eastern Great Basin: Geological Society of America Special Paper 233, 53 p. 

Gill, J.B., 1981, Orogenic andesites and plate tectonics: New 

York, Springer-Verlag, 385 p. 

Glazner, A.F., 1988, Stratigraphy, structure, and potassic alteration of Miocene volcanic rocks in the Sleeping Beauty 

area, central Mojave Desert, California: Geological Society of America Bulletin, v. 100, p. 424-435. 

Hardyman, R.F., 1980, Geologic map of the Gillis Canyon 

quadrangle, Mineral County, Nevada: U.S. Geological 

Survey Miscellaneous Investigations Series Map 1-1237, 

scale 1:48,000. 

Healey, D L., Snyder, D.B., and Wahl, R.R., 1981, Bouguer 

gravity map of Nevada: Tonopah sheet: Nevada Bureau of 

Mines and Geology Map 73, scale 1:250,000. 

Hildreth, Wes, 1981, Gradients in silicic magma chambers: Implications for lithospheric magmatism: Journal of Geophysical Research, v. 86, p. 10,153-10,192. 

Jackson, L.L., Brown, F.W., and Neil, Sarah, 1987, Major and 

minor elements requiring individual determination, classical whole rock analysis, and rapid rock analysis, in 

Baedecker, P.A., ed., Methods for geochemical analysis: 

U.S. Geological Survey Bulletin 1770, p. G1-G23. 

John, D.A., 1986, Geology of Tertiary volcanic rocks in the 

Paradise Range and northern Pactolus Hills, Nye County, 

Nevada [abs.]: U.S. Geological Survey Open-File Report 

86-467. p. 13. 

---1987, Map showing the distribution and characteristics 

of plutonic rocks in the Tonopah 1° by 2° quadrangle, 

central Nevada: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1877-J, scale 1:250,000. 

---1988, Geologic map of Oligocene and Miocene volcanic rocks in the Paradise Peak and western part of the 

lone quadrangles, Nye County, Nevada: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-2025, scale 

1:24,000, 2 sheets. 

John, D.A., and Hudson, M.L., 1990, Paleomagnetic evidence 

for the geometry and chronology of Tertiary tectonic rotations, Paradise Range, western Nevada [abs.]: Eos, v. 71, 

no. 43, p. 1295. 

38 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
John, D.A., and Kelleher, P.L., 1987, Bedrock geologic map of 

the Goldyke quadrangle, Nye CoWlty, Nevada: U.S. Geological Survey Miscellaneous Field Studies Map MF1963, scale 1:24,000. 

John, D.A., and McKee, E.H., 1987, K-Ar ages of granitic plutonism and hydrothermal alteration in the western part of 

the Tonopah 1° by 2° quadrangle, Nevada: lsochron/West, 

no. 48, p. 16-18. 

John, D.A., Nash, J.T., Clark, C.W., and Wulftange, W.H., 

1991, Geology, hydrothermal alteration, and mineralization at the Paradise Peak gold-silver-mercury deposit, Nye 

CoWlty, Nevada, in Raines, G.L., Lisle, R.E., Schafer, 

R.W., and Wilkinson, W.H., eds., Symposium on the geology and ore deposits of the Great Basin, symposium proceedings: Reno, Geological Society of Nevada and U.S. 

Geological Survey, p. 1020-1050. 

John, D.A., Thomason, R.E., Clark, C.W., and McKee, E.H., 

1989a, Volcanic-tectonic setting and geology of the Paradise Peak gold-silver-mercury deposit, Nye County, 

Nevada [abs.], in Schindler, K.S., ed., USGS research on 

mineral resources-1989 program and abstracts: U.S. 

Geological Survey Circular 1035, p. 37-38. 

John, D.A., Thomason, R.E., and McKee, E.H., 1989b, Geology and K-Ar geochronology of the Paradise Peak Mine 

and the relationship of pre-Basin and Range extension to 

early Miocene precious-metal mineralization in westcentral Nevada: Economic Geology, v. 84, p. 631-649. 

Johnson, R.G., and King, B.S.L., 1987, Energy-dispersive 

x-ray fluorescence spectrometry, in Baedecker, P.A., ed., 

Methods for geochemical analysis: U.S. Geological Survey Bulletin 1770, p. Fl-F5. 

Kistler, R.W., Chappell, B.W., Peck, D.L., and Bateman, P.C., 

1986, Isotopic variation in the Tuolumne Intrusive Suite, 

central Sierra Nevada, California: Contributions to Mineralogy and Petrology, v. 94, p. 205-220. 

Kleinhampl, F.J., and Ziony, J.I., 1967, Preliminary geologic 

map of northern Nye County, Nevada: U.S. Geological 

Survey Open-File Map, scale 1:200,000. 

---1984, Mineral resources of northern Nye County: 

Nevada Bureau of Mines and Geology Bulletin 99B, 

241 p. 

---1985, Geology of northern Nye County, Nevada: 

Nevada Bureau of Mines and Geology Bulletin 99A, 

172p. 

Le Bas, M.J., Le Maitre, R.W., Streckeisen, A., and Zanettin, 

B., 1986, A chemical classification of volcanic rocks 

based on the total alkali-silica diagram: Journal of Petrology, v. 27, p. 745-750. 

Lipman, P.W., Christiansen, R.L., and O'Connor, T.J., 1966, A 

compositionally zoned ash-flow sheet in southern Nevada: 

U.S. Geological Survey Professional Paper 524-F, 47 p. 

Locke, Augustus, Billingsley, P.R., and Mayo, E.B., 1940, Sierra Nevada tectonic patterns: Geological Society of 

America Bulletin, v. 51, p. 513-540. 

Ludwig, K.R., 1987, Isoplot200, a plotting and regression program for isotope geochemists, for use with HP Series 200 

computers: U.S. Geological Survey Open-File Report 85-

513, 102 p. 

McKee, E. H., 1971, Tertiary igneous chronology of the Great 

Basin of the western United States: Implications for teetonic models: Geological Society of America Bulletin, 

v.82,p. 3497-3502. 

McKee, E.H., and John, D.A., 1987, Sample locality map and 

potassium-argon ages and data for Cenozoic igneous rocks 

in the Tonopah 1 o x 2° quadrangle, central Nevada: U.S. 

Geological Survey Miscellaneous Field Studies Map MF1877-I, scale 1:250,000. 

McKee, E.H., Silberman, M.L., Marvin, R.E., and Obradovich, 

J.D., 1971, A summary of radiometric ages of Tertiary 

volcanic rocks in Nevada and eastern California, Part 1: 

Central Nevada: lsochron/West, no. 2, p. 21-42. 

Mellot, M.G., and Hart, W.K., 1987, Petrogenesis and tectonic 

significance of andesites from the northern Basin and 

Range, Nevada [abs.]: Geological Society of America Abstracts with Programs, v. 19, p. 770. 

Mills, B.A., Boden, D.R., and Sander, M.V., 1988, Alteration 

and precious metal mineralization associated with the Toquima caldera complex, Nye County, Nevada, in Schafer, 

R.W., Cooper, J.J., and Vikre, P.G., eds., Bulk mineable 

precious metal deposits of the Western United States, 

symposium proceedings: Reno, Geological Society of 

Nevada, p. 303-331. 

Molinari, M.P., 1984, Late Cenozoic structural geology of 

Stewart and Monte Cristo Valleys, Walker Lane of west 

central Nevada, in Lintz, Joseph, Jr., ed., Western geological excursions, volume 4, 1984 Annual Meeting of the 

Geological Society of America: Boulder, Geological Society of America, p. 219-231. 

Morton, J.L., Silberman, M.L., Bonham, H.F., Jr., Garside, 

L.J., and Noble, D.C., 1977, K-Ar ages of volcanic rocks, 

plutonic rocks, and ore deposits in Nevada and eastern 

California: Isochron/West, no. 20, p. 19-29. 

Noble, D.C., 1970, Loss of sodium from crystallized comendite 

welded tuffs of the Miocene Grouse Canyon member of 

the Belted Range Tuff, Nevada: Geological Society of 

America Bulletin, v. 81, p. 2677-2688. 

Noble, D.C., and Christiansen, R.L., 1974, Black Mountain 

volcanic center, in Guidebook to the geology of four Tertiary volcanic centers in central Nevada: Nevada Bureau 

of Mines and Geology Report 19, p. 22-34. 

Oldow, J.S., 1984, Evolution of a late Mesozoic back-arc fold 

and thrust belt, northwestern Great Basin, U.S.A.: Tectonophysics, v. 102, p. 245-274. 

Palmer, A.R., compiler, 1983, The Decade of North American 

Geology 1983 time scale: Geology, v. 11, p. 503-504. 

Peacock, M.A., 1931, Classification of igneous rock series: 

Journal of Geology, v. 39, p. 54-67. 

Proffett, J.M., Jr., 1977, Cenozoic geology of the Yerington 

district, Nevada and implications for the nature and origin 

of basin and range faulting: Geological Society of 

America Bulletin, v. 88, p. 247-266. 

Proffett, J.M., Jr., and Dilles, J.H., 1984, Geologic map of the 

Yerington district, Nevada: Nevada Bureau of Mines and 

Geology Map 77, scale 1:24,000. 

Proffett, J.M., Jr., and Proffett, B.H., 1976, Stratigraphy of the 

Tertiary ash-flow tuffs in the Yerington district, Nevada: 

Nevada Bureau of Mines and Geology Report 27,28 p. 

Rytuba, J.J., and McKee, E.H., 1984, Peralkaline ash flow tuffs 

and calderas of the McDermitt volcanic field, southeast 

Oregon and north central Nevada: Journal of Geophysical 

References Cited 39 
Research, v. 89, p. B8616-8628. 

Seedorf f. C.E., 1981, Geology of the Royston porphyry copper 

prospect, Nye and Esmeralda Counties, Nevada: Stanford, 

California, Stanford University, M.S. thesis, 106 p. 

---1991, Royston district, western Nevada: A Mesozoic 

porphyry copper system that was tilted and disrupted by 

Tertiary normal faults, in Geological Society of Nevada 

Symposiwn; The Geology and Ore Deposits of the Great 

Bas in (in press). 

Shapiro, Leonard, 1975, Rapid analysis of silicate, carbonate, 

and phosphate rocks-Revised edition: U.S. Geological 

Survey Bulletin 1401, 76 p. 

Silberling, N.J., and John, D.A., 1989, Geologic map of preTertiary rocks of the Paradise Range and southern Lodi 

Hills, west-central Nevada: U.S. Geological Survey Miscellaneous Field Studies Map MF-2062, scale 1:24,000, 2 

sheets. 

Silberman, M.L., Stewart, J.H., and McKee, E.H., 1976, Igneous activity, tectonics, and hydrothermal precious-metal 

mineralization in the Great Basin during Cenozoic time: 

Society of Mining Engineers of the AIME Transactions, 

v.260,p. 253-263. 

Snyder, D.B., and Healey, D.L., 1984, Interpretation of the 

Bouguer gravity map of Nevada: Tonopah sheet: Nevada 

Bureau of Mines and Geology Report 38, 14 p. 

Snyder, W.S., Dickinson, W.R., and Silberman, M.L., 1976, 

Tectonic implications of space-time patterns of Cenozoic 

magmatism in the Western United States: Earth and Planetary Science Letters, v. 32, p. 91-106. 

Steiger, R.H., and Jager, E., 1977, Subcommission on geochronology: Convention on the use of decay constants in geoand cosmochronology: Earth and Planetary Science Letters, v. 36, p. 359-362. 

Stewart, J.H., 1978, Basin-range structure in western North 

America: A review: Geological Society of America Memoir 152, p. 1-31. 

---1988, Tectonics of the Walker Lane Belt, western Great 

Basin-Mesozoic and Cenozoic deformation in a zone of 

shear, in Ernst, W.G., ed., Metamorphism and crustal evolution of the Western United States, Rubey Volume VII: 

Englewood Cliffs, New Jersey, Prentice-Hall, p. 683-713. 

Stewart, J.H., Carlson, I.E., and Johannesen, D.C., 1982, Geologic map of the Walker Lake 1° by 2° quadrangle, California and Nevada: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1382-A, scale 1:250,000. 

Taggert, J.E., Lindsay, J.R., Scott, B.A., Vivit, D.V., Bartel, 

A.J., and Stewart, K.C., 1987, Analysis of geological materials by wavelength-dispersive x-ray fluorescence spectrometry, in Baedecker, P.A., ed., Methods for geochemical analysis: U.S. Geological Survey Bulletin 1770, p. E1-

E19. 

Vitaliano, C.J., 1963, Cenozoic geology and sections of the 

lone quadrangle, Nye County, Nevada: U.S. Geological 

Survey .Mineral Investigations Field Studies Map MF-255, 

scale 1:62,500. 

Vitaliano, C.J., and Callaghan, Eugene, 1963, Geology of the 

Paradise Peak quadrangle, Nevada: U.S. Geological Survey Geologic Quadrangle Map GQ-250, scale 1:62,500. 

Vitaliano, C.J., and Vitaliano, D.B., 1972, Cenozoic volcanic 

rocks in the southern Shoshone Mountains and Paradise 

Range, Nevada: Geological Society of America Bulletin, 

v. 83,p. 3269-3280. 

Vikre, P.G., McKee, E.H., and Silberman, M.L., 1988, Chronology of Miocene hydrothermal and igneous events in 

the western Virginia Range, Washoe, Storey, and Lyon 

Counties, Nevada: Economic Geology, v. 83, p. 864-874. 

Whitebread, D.H., 1976, Alteration and geochemistry of Tertiary volcanic rocks in parts of the Virginia City quadrangle, Nevada: U.S. Geological Survey Professional Paper 936, 43 p. 

---1986, Generalized geologic map of the Tonopah 1° by 

2° quadrangle, Nevada: U.S. Geological Survey Open-File 

Report 86-462, scale 1:250,000. 

Whitebread, D.H., Silberling, N.J., Brem, G.F., and Andrews, 

T.D., 1988, Preliminary geologic map of the eastern half 

of the lone quadrangle, Nye County, Nevada: U.S. Geological Survey Open-File Report 88-48, scale 1:62,500. 

40 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
TABLES 1-17 
~ 

N 

C') 

2 

n 

:r 

I'D 

3 

=: .. 

-< 

= -

Q 

ciQ' 

= n 

I'D 

= I'D 

Ill 

&. 

~ o' 

n 

I'D 

= I'D 

< 

= ;:;-

Ill 

= ;::;-

;a 

n = 

~ ., 

Ill 

!. 

iii' 

I'D 

CIQ 

~ I'D 

Ill 

= c. 

z 

= ::::. 

:r 

~ 

., 

= 

~ 

S' 

c 

WI 

~ .. iii 

z 

"< I'D 

n 

= c 

= 

~ 

z 

I'D 

< 

~ Ill 

Table 1. Characteristics of major ash-flow tuff units in the Menter Canyon section 

Unit Tuff of Green Springs Tuff of Menter Canyon Tuff of Camel Spring Tuff of Gabbs Valley Tuff of Arc Dome Tuff of Brunton Pass 

Composition1 High-silica Ihyolite Rhyolite Rhyolite Rhyolite Rhyolite-high- High-silica Ihyolite 

silica Ihyolite 

Percent phenocrysts 1-6 I 0-10 5-7 30-40 6--8 

Major phenocrysts2 s p A,P,S S,P,Q S,Q,P,B Q,P 

Aattened pumice clasts Locally abundant Locally abundant Locally abundant Abundant, to 15 em Abundant, Locally abundant 

crystal-rich; 

black glass at 

base 

Welding Dense Poor to dense Poor to dense Dense Dense Poor to dense 

Lithics Locally abundant Abundant Abundant Abundant Sparse except at Sparse 

base 

Simple or compound Compound Compound Compound Simple (in Paradise Simple Simple 

cooling unit Range) 

Notable characteristics Local secondary Abundant pink Anorthoclase Extremely densely Abundant smoky Smoky quartz 

flow structures Ihyolite lithic phenocrysts welded; abundant quartz phenocrysts 

fragments granitic clasts phenocrysts 

Thickness3 (m) 300(?) 200 250 350 400 90 

Age (Ma) (see table 3) >26 >26 >26 26-25 25-24.5 <25 and >22 

Areal distribution4 PR PR,SM PR, SM, GV(?) PR, SM, GV, GR, PR, SM, T, TQ(?), PR 

ss. y ss 

Source Unknown Unknown Unknown Gabbs Valley Southern Reese Unknown 

River Valley 

Comments Upper cooling unit Commonly - Only lower member Smoky quartz - commonly vitrophyric present in member of 

contains Paradise Range; Toiyabe Quartz 

fragments of commonly Latite of former 

lower cooling vitrophyric usage (see 

unit Kleinhampl and 

Ziony, 1985; 

Bonham, 1970) 

1

Classification is lUGS chemical classification (Le Bas and others, 1986) based on total alkali and silica contents of whole-rock samples recalculated to 100 percent volatile-free. 

2s, sanidine; P, plagioclase; A, anorthoclase; Q, quartz; B, biotite; H, hornblende. 3

Maximum thickness in the Paradise Range. 

Tuff of Toiyabe (main phase) 

Rhyolite 

14-30 

P,Q,S,B, H 

Locally abundant, crystal 

rich 

Dense 

Sparse except a1 base 

Simple 

Abundant accessory 

sphene 

400+ 

23-22 

PR, SM, T, RH, PH, CM, 

GV(?), BH(?) 

Southern Toiyabe Range 

Correlative with the tuff 

of Copper Mountain of 

Ekren and others (1980) 

4

PR, Paradise Range; SM, Southern Shoshone Mountains; GV, Gabbs Valley Range; GR, Gillis Range; SS, Southern Sand Springs Range; Y, Yerington district; T, Toiyabe Range; TQ, Toquima Range; RH, Northern 

Royston Hills; PH, Pactolus Hills; CM, North Cedar Mountain; BH, Barnett Hills. 
Table 2. Summary of modal data for ash-flow tuffs in the Paradise Range and northern Pactolus Hills 

[Numbers give range and (mean) values for all samples. Accessory minerals typically present in trace (tr) amounts; all, allanite; ap, apatite; cpx, clinopyroxene; sph, sphene; z, zircon] 

Number Opaque Accessory 

Unit of samples Quartz Plagioclase K-feldspar Ground mass Biotite Hornblende minerals minerals 

Menter Canyon section 

Tuff of Toiyabe (main phase) - 22 1.7-11.5 (6.3) 7.1-25.1 (10.9) 1.8-7.8 (5.2) 61.1-85.6 (73.8) 0.9-3.4 (2.1) 0.0-2.9 (1.1) 0.1-1.1 (0.6) sph (cpx, z) 

Tuff of Toiyabe 

(Cloverdale Ranch unit)--- 3 0.4-4.4 (2.2) 20.6-26.3 (23.8) 2.3-3.6 (3.1) 62.1-66.6 (64.9) 3.3-3.9 (3.5) 0.4-1.4 (0.9) 0.5-1.6 (0.9) cpx::0.6, z, (sph) 

Biotite tuff------------------------- 2 0.2-0.4 22.6-24.3 0.3-0.8 68.0-71.3 4.1-5.2 0.0 1.3-1.5 ap, z 

Tuff of Brunton Pass ------------ 6 2.7-4.3 (3.4) 0.0-0.9 (0.4) 2.2-3.1 (2.5) 92.7-94.1 (93.5) 0.0-0.1 (0.0) 0.0-0.1 (0.0) 0.1-0.3 (0.2) 

Tuff of Arc Dome --------------- 21 4.2-15.3 (8.4) 2.8-16.0 (9.1) 11.2-15.4 (13.0) 61.6-72.0 (67.8) 0.1-1.7 (1.0) 0.0-1.0 (0.3) 0.1-0.9 (0.3) all, z 

Tuff of Gabbs Valley ----------- 3 0.5-1.0 (0.8) 1.4-2.4 (1.8) 2.4-3.7 (3.0) 93.5-95.3 (94.1) tr-0.1 (0.1) 0.0-0.1 (0.0) tr-0.1 (tr) (cpx) 

Tuff of Camel Spring ----------- 8 0.0-2.0 (0.5) 0.1-10.4 (5.6)* * 89.2-99.7 (93.7) 0.0-0.2 (tr) 0.0-tr tr-0.8 (0.3) (z, cpx) 

Tuff of Menter Canyon --------- 2 0.2-0.3 0.6-0.8 0.2 98.8-98.9 0.0 0.0 tr 

Tuff of Green Springs----------- 5 tr -0.6 (0.2) 0.0-0.7 (0.4) 1.2-5.3 (2.5) 93.6-98.7 (96.8) 0.0-0.1 (0.0) 0.0 tr-0.4 (0.2) (z) 

Ellsworth section 

Tuff of Big Spring--------------- 8 4.9-14.4 (8.7) 6.9-17.4 (12.6) 9.7-18.0 (13.7) 55.7-68.6 (63.0) 0.3-2.3 (1.4) 0.0-0.6 (0.2) tr-0.6 (0.3) z, (all) 

Brown rhyolite tuff -------------- 3 1.0-3.3 (2.4) 0.8-1.8 (1.4) 0.6-2.9 (2.1) 92.9-96.5 (94.1) 0.0-0.1 (tr) 0.0-tr (0.0) 0.1-0.2 (0.1) z, (all) 

White tuff-------------------------- 3 7.8-10.3 (8.9) 1.2-4.0 (2.6) 7.5-10.4 (9.0) 77.1-80.2 (79.0) 0.1-0.7 (0.4) 0.0 tr-0.2 (0.1) z 

Tuff of Camel Spring ----------- See above in Menter Canyon section 

Tuff of Return Mine------------- 10 3.9-13.9 (6.4) 0.5-10.3 (4.1) 1.9-8.9 (6.2) 74.7-89.0 (83.5) 0.1-2.0 (0.5) 0.0 tr-0.3 (0.1) (all, z) 

Purple biotite tuff ---------------- 1 1.9 1.3 1.8 92.7 2.2 0.0 0.1 

Purple tuff ------------------------- 1 7.5 1.9 5.9 84.1 0.3 0.0 0.3 z 

Sheep Canyon section 

Tuff of Sheep Canyon ---------- 29 0.1-9.0 (3.1) 6.8-32.1 (18.3) 0.0-10.3 (4.0) 55.7-86.1 (70.9) 0.5-5.8 (2.6) 0.0-1.4 (0.3) tr-1.3 (0.8) z (all, ap, cpx, sph) 

Red rhyolite tuff------------------ 4 9.3-14.4 (11.4) 0.0-2.3 (0.7) 10.8-13.9 (12.8) 71.3-79.5 (74.8) tr-0.3 (0.1) 0.0 0.1-0.4 (0.2) z (all) 

Upper white tuff------------------ 6 0.0-0.5 (0.2) tr-5.2 (3.6) 1.6-2.5 (2.0) 92.8-98.0 (94.1) 0.0-0.3 (0.1) 0.0 0.1-0.4 (0.2) (z) 

Gray-green tuff------------------- 1 0.0 0.8 3.3 95.9 0.0 0.0 tr z 

Red tuff ---------------------------- 14 tr-3.0 (2.1) 0.1-1.6 (0.3) 0.2-4.9 (2.7) 92.8-99.2 (94.8) tr-0.1 (tr) 0.0 tr-0.3 (0.1) (z) 

Lower white tuff ----------------- 36 0.0-3.5 (2.1) 0.0-7.8 (2.3) 0.2-5.7 (3.3) 83.4-96.1 (92.0) 0.0-1.4 (0.3) 0.0-0.2 (0.0) 0.1-0.5 (0.2) (all, sph, z) 

Tuff of Goldyke ------------------ 19 1.0-8.7 (5.1) 3.3-28.1 (11.6) 1.6-13.9 (9.7) 63.6-90.6 (72.0) 0.2-2.1 (1.1) 0.0-0.4 (0.1) 0.2-1.0 (0.4) z, (all, ap, sph) 

Tuff --------------------------------- 6 tr-2.5 (1.1) 0.3-5.2 (2.1) 0.3-3.4 (1.7) 92.0-99.4 (94. 7) 0.0-0.4 (0.2) 0.0-0.3 (tr) tr-0.4 (0.2) z 

Biotite-lithic tuff ----------------- 1 1.9 32.1 1.8 58.5 2.8 0.8 1.1 cpx=l.O, z 

Tuff of Davis Mine -------------- 2 0.5-0.6 4.1-5.7 2.1-2.6 91.2-92.3 0.3 0.0 0.1-0.2 z -f 

Dl Tuff of Pactolus ------------------ 3 2.5-7.9 (5.1) 2.5-10.2 (7.5) 3.0-7.4 (4.6) 73.4-92.0 (81.6) tr-2.0 (1.0) 0.0 tr-0.1 (0.1) z f:f' 

;-

Ill 

... *Most feldspar is anorthoclase. 

I 

... 

...... 

.,. 

CN 
~ 

~ 

C') 

~ 1'1 

::r 

I'D 

3 

=.· 

.. 

"< 

0 

-

g Table 3. Summary of K-Ar ages of Tertiary volcanic rocks in the Paradise Range, Nevada OQ 

~ [Pre-1976 ages recalculated using new I.U.G.S. constants (Steiger and Jager, 1977)] I'D 

:I 

I'D 

~ 

:I 

Q. 

~ 

cs· 

1'1 

I'D 

:I 

I'D 

< 0 

;:r 

~ 

:I 

;::;· 

~ 

0 

1'1 

~ .., 

~ 

i 

iii" 

I'D 

Rock type or unit location 

Hornblende andesite flow----- North end of Stewart Valley 

2 Rhyolite dike --------------------

3 Rhyolite dike --------------------

4 Rhyolite dike --------------------

1 km east of Sheep Canyon, 

Paradise Range. 

Mouth of Sheep Canyon, 

Paradise Range. 

2 km west of Willow Spring, 

Paradise Range. 

Material dated Reported age (Ma) 

Andesite of Stewart Valley 

Whole rock 12.1±0.3 

Silicic intrusive rocks 

Biotite 16.2±0.5 

Biotite 19.2±0.6 

Biotite 16.3±0.5 

Comments 

Caps sedimentary rocks of 

Stewart Valley. 

Cut by Sheep Canyon faulL 

Cut by Sheep Canyon faulL 

~ 

~ 

:I 

0,: Porphyritic dacite, hornblende andesite, and andesite and basaltic andesite units 

~ Q. 

z 

~ 

:;. 

I'D 

.. 

:I 

.., 

~ 

8" 

c 

Ill 

~ ~iii 

z 

"< I'D 

n 

0 

c 

:I 

~ 

z 

I'D 

i 

~ 

5 Porphyritic dacite flow --------

6 Porphyritic dacite flow --------

7 Andesite flow --------------------

8 Porphyritic dacite flow --------

9 Hornblende andesite flow -----

10 Porphyritic dacite flow --------

11 Andesite porphyry flow -------

12 Porphyritic hornblende 

andesite flow. 

13 Andesite flow--------------------

14 Hornblende andesite------------

15 Basaltic andesite flow----------

1.5 km east of Paradise 

Peak Mine. 

1 km southeast of Paradise 

Peak Mine. 

3 km southwest of Paradise 

Peak Mine . 

1.5 km south of Paradise 

Peak Mine. 

Paradise Peak Mine 

1 km east of Paradise 

Peak Mine. 

1 km southeast of Paradise 

Peak Mine. 

Northern Pactolus Hills 

2 km west of Paradise 

Peak Mine. 

Sheep Canyon, Paradise 

Peak Mine. 

3 km north of Brunton 

Pass, Paradise Range. 

Biotite 18.7±0.6 

Biotite 17.1±0.5 

Whole rock 15.6±0.8 

Whole rock 15.5±0.6; 

17.3±0.9 

Whole rock 17.6±0.9 

Whole rock 17.9±0.9; 

17.6±0.7 

Whole rock 18.2±1.0 

Hornblende 18.9±0.6 

Whole rock 19.3±0.9 

Whole rock 20.1±0.6 

Whole rock 18.9±0.9 

Caps younger andesite sequence. 

Replicate analyses from different labs. 

Replicate analyses from different labs. 

Base of hornblende andesite unit. 

Base of andesite and basaltic andesite 

unit. 

References 

John and others (1989b) 

McKee and John (1987) 

John and others (1989b) 

McKee and John (1987) 

McKee and John (1987) 

McKee and John (1987) 

John and others (1989b) 

John and others (1989b) 

John and others (1989b) 

John and others (1989b) 

John and others (1989b) 

McKee and John (1987) 

John and others (1989b) 

John and others (1989b) 

McKee and John (1987) 
"""' Cll 

c:r 

;-

WI 

.... 

!. 

"" 

~ 

U'l 

16 Tuff of Toiyabe ----------------- Near Brunton Pass, 

Paradise Range. 

17 Tuff of Toiyabe 

(Cloverdale Ranch unit). Northern Pactolus Hills 

18 Tuff of Toiyabe ----------------- Peavine Canyon, southern 

Toiyabe Range. 

19 Tuff of Toiyabe ----------------- Shoshone Mountains southwest 

of Black Mountain. 

20 Tuff of Arc Dome -------------- Green Springs Summit, 

Paradise Range. 

21 Tuff of Arc Dome -------------- Mouth of lone Canyon, 

Shoshone Mountains. 

22 Tuff of Gabbs Valley ---------- Gillis Range 

23 Tuff of Gabbs Valley ---------- Gillis Range 

24 Brown rhyolite tuff------------- North end of Paradise Range 

25 Tuff of Sheep Canyon --------- Sheep Canyon, Paradise Range 

26 Tuff of Sheep Canyon --------- Sheep Canyon, Paradise Range 

27 Red myolite tuff ---------------- Sheep Canyon, Paradise Range 

28 Lower white tuff ---------------- Northern Pactolus Hills 

29 Lower white tuff---------------- 2 km northwest of Paradise 

Peak Mine. 

30 Tuff of Goldyke ----------------- 2 km southwest of Paradise 

Peak Mine. 

31 Tuff of Goldyke ----------------- Northern Pactolus Hills 

32 Porphyritic rhyolite flow ------ 0.5 km east of Gold Ledge 

Mine, Paradise Range. 

33 Dacite tuff (biotite-lithic tuff) Sheep Canyon, Paradise Range 

Tuffs in Menter Canyon section 

Biotite 21.4±0.7 

Biotite 22.9±0.7 

Biotite 22.0±0.4 

Biotite 22.5±0.7 

Biotite 24.9±0.6 

Biotite 24.4±0.4 

Sanidine 25.0±1.0 

Sanidine 26.1±0.8 

Tuffs in the Ellsworth section 

Sanidine 23.7±0.7 

Tuffs in the Sheep Canyon section 

Biotite 

Biotite 

Sanidine 

Sanidine 

Sanidine 

Biotite 

Biotite 

24.1±0.7 

23.2±0.7 

23.2±0.7 

22.3±0.7 

21.8±0.7; 

25.1±1.0 

23.0±0.9 

23.6±0.7 

Older andesite sequence 

Biotite 24.4±0.7 

Biotite 25.6±0.8 

--

--

Base of tuff of Toiyabe. 

Vent for tuff of Toiyabe. 

--

Previously assigned to Toiyabe Quartz 

Latite by Armstrong (1970). 

--

--

Sample identification and location 

from F.J. Kleinhampl (oral commun., 

1986). 

Age considered 1 m.y. too young. 

Replicate analyses from different labs. 

McKee and John (1987) 

McKee and John (1987) 

Silberman and McKee (1972) 

McKee and John (1987) 

McKee and John (1987) 

Armstrong (1970) 

Ekren and others (1980) 

Ekren and others (1980) 

McKee and others (1971) 

McKee and John (1987) 

McKee and John (1987) 

McKee and John (1987) 

McKee and John (1987) 

McKee and John (1987); 

John and others (1989b) 

John and others (1989b) 

McKee and John (1987) 

McKee and John (1987) 

McKee and John (1987) 
~ Table 4. Chemical analyses of the tuff of Arc Dome 

[All analyses except sample 83-DJ-97 by X-ray fluorescence spectroscopy (analysts: A. Bartel, J. Evans, D. Siems, J. Taggart, and D. Vivit; chemical determination of FeO, ~o+.~o-, 

~ and C02 by W. Crandell, L. Espos, and H. Smith). Sample 83-DJ-97 analyzed by rapid rock analysis (analyst: N Rait). FeO*, total Fe as FeO; LOI, loss on ignition at 900°C) 

~ 

0 

, 

:::r 1 2 3 4 5 6 7 8 9 10 11 ~ 

3 Sample number 83-0j-96 83-DJ-97 86-0j-79A 86-0j-798 86-0j-79C 86-0j-790 86-0j-79E 86-0j-79F 87-0J-151 85-SH-4 85-SH-5 

.. 

~ 

-< Major elements normalized to 100 percent volatile-free (weight percent) 0 

-

Q 

~~0 :~~~~~~~~~~~~~~~~~~~~~~ 77.18 77.26 77.01 73.55 73.17 73.68 73.43 73.81 74.48 76.99 74.31 C"iQ' 

, 

0 12.85 12.71 12.89 14.46 14.39 14.25 14.30 14.15 13.58 12.53 13.48 ~ FeO ----------------------- .10 .16 .20 .29 .28 .24 .37 .35 .36 .16 .52 = ~ Fe2

0 3 ---------------------- .95 .99 .83 1.37 1.69 1.51 1.48 1.21 1.21 .86 1.21 AI 

= Q.. MgO ---------------------- .21 .18 .20 .29 .32 .23 .26 .25 .25 .17 .25 

~ CaO ----------------------- .56 .71 .59 1.09 1.16 1.13 1.06 1.13 1.31 .58 .99 

=· ~ 60 -~~~~=~~=~~=~~=~=~~=~~= , 3.17 3.33 3.52 3.81 3.83 3..83 3.84 4.05 3.57 3.49 2.94 ~ 4.78 4.44 4.59 4.81 4.76 4.79 4.86 4.70 4.99 5.08 5.99 

= ~ Ti02 ----------------------- .09 .12 .09 .21 .25 .22 .23 .18 .18 .12 .22 

< 0 

~6 -~:~~:~~:~~:~~:~:~~:~~: .02 .06 .03 .06 .09 .06 .09 .06 <0.05 <0.05 <0.05 

;:;-

AI .07 .05 .03 .03 .03 .03 .03 .05 .04 <0.02 .03 

;;· = 

~ LOI ------------------------ -1.25 - .87 1.12 0 1.00 1.12 .62 1.13 .91 .54 2.16 , 

~ Total (volatile-free .., 

e: before normalization) 98.08 99.15 99.34 98.17 98.68 98.26 98.60 99.22 98.69 98.97 97.16 AI 

Q.. 

iii' 

~ H2 Q+ ---------------------- .58 .54 .47 .64 .46 .56 .37 .29 .50 .13 1.30 ~ 

AI H2o- ---------------------- .44 .58 .25 .37 .42 .33 .20 .37 .30 .32 .77 OQ = C02 ------------------------ .11 .03 .08 .09 .05 .38 .05 .07 .41 .01 <0.01 ~ 

AI F --------------------------- - .042 

= Q.. 

z Minor elements (parts per million) 0 

.. 

~ 

~ Nb ------------------------- 25 21 24 20 20 20 18 20 17 18 17 .. 

= Rb ------------------------- 240 141 240 160 160 170 160 160 175 195 204 .., 

AI Sr ------------------------- 36 123 30 160 160 150 140 160 124 52 119 , 

S' a------------------------- 140 165 140 220 270 250 270 240 174 153 195 

c y -------------------------- 30 26 28 25 25 20 28 32 21 25 24 Ill 

:::z:: Ba ------------------------- 260 - 200 1,000 970 900 900 890 707 310 650 

.. iii Ce ------------------------- 65 - 75 80 90 65 80 95 87 87 98 

z La ------------------------- 30 - <30 45 55 40 45 55 45 61 64 

~ Cu ------------------------- <20 - <20 <20 <20 <20 <20 <20 12 8 <5 

n Ni ------------------------- <20 - <20 <20 <20 <20 <20 <20 <5 <5 <5 0 

c Zn ------------------------- 45 - 50 50 56 56 60 42 50 56 64 

= Cr ------------------------- <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 ~ -

z 

~ K/Rb ---------------------- 165 261 159 249 247 234 252 244 236 216 244 < AI 

Q.. Sr/Rb ---------------------- .15 .87 .13 1.00 1.00 .88 .88 1.00 .71 .27 .58 AI FeO* ---------------------- .96 1.05 .95 1.52 1.80 1.60 1.70 1.44 1.45 .94 1.61 
~ 

Dl 

C"' 

;-

WI 

..... 

.!... 

..... 

... 

..... 

Table 4. Chemical analyses of the tuff of Arc Dome-Continued 

Sample descriptions 

1 (83-DJ-96) Partially devitrified, densely welded basal part of the tuff of Arc Dome collected about 300 m east of Green Spring Summit, east side of the Paradise Range at lat 

38°53'50"N., long 117°46'56"W. 

2 (83-DJ-97) Devitrified, densely welded tuff of Arc Dome about 50 m above exposed base collected about 300m east of Green Spring Summit, east side of the Paradise Range at lat 

38°53'50"N., !ong 117°46'57"W. 

3 (86-DJ-79A) Partially devitrified, densely welded basal part of the tuff of Arc Dome about 35 m above base collected on the east side of the Paradise Range about 3 km south of 

Sherman Peak at lat 38°54'23"N., long 117°46'16"W. 

4 (86-DJ-79B) Devitrified, densely welded tuff about 65 m above the base collected on the east side of the Paradise Range about 3 km south of Sherman Peak at lat 38°54'23"N., long 

117°46'14"W. 

5 (86-DJ-79C) Devitrified, densely welded tuff about 130m above the base collected on the east side of the Paradise Range about 3 km south of Sherman Peak at lat 38°54'23"N., long 

117°46'12"W. 

6 (86-DJ-79D) Devitrified, densely welded tuff about 200m above the base collected on the east side of the Paradise Range about 3 km south of Sherman Peak at lat 38°54'23"N., long 

117°46'10"W. 

7 (86-DJ-79E) Devitrified, densely welded tuff about 260m above the base collected on the east side of the Paradise Range about 3 km south of Sherman Peak at lat 38°54'23"N., long 

117° 46'08"W. 

8 (86-DJ-79F) Devitrified, densely welded tuff at top of section (approximately 350m above the base) collected on the east side of the Paradise Range about 3 km south of Sherman 

Peak at lat 38°54'23"N., long 117°46'04"W. 

9 (87-DJ-151) Devitrified, densely welded tuff collected at the south end of the Sand Springs Range approximately 1 km north of Scheelite at lat 39°01'20"N., long l18°18'45"W. 

10 (85-SH-4) Partially devitrified, densely welded basal part of the tuff collected in Peterson Canyon in the Shoshone Mountains at lat 39°10'15"N., long 117°30'05"W. 

11 (85-SH-5) Devitrified, densely welded upper part of the tuff collected in Peterson Canyon in the Shoshone Mountains at lat 39°10'15"N., long l17°30'00"W. 
Table 5. Chemical analyses of the tuff of Toiyabe 

[All analyses except sample 83-DJ-100 by X-ray fluorescence spectroscopy (analysts: A. Bartel, J. Kent, D. Siems, and J. Taggart; chemical 

determination of FeO, ~0+, ~o-. C02 and F by W. Crandell, C. Papp, and H. Smith.) Sample 83-DJ-100 analyzed by rapid rock analysis 

(analyst: N. Rait). FeO*, total Fe as FeO; LOI, loss on ignition at 9000C] 

1 2 3 4 5 6 7 8 9 10 

Sample Number 83-DH5 83-Dj-99 86-0j-80 83-DJ-32 83-DH2 83-Dj-100 85-Dj-125 85-Dj-196 85-DJ-204 85-Dj-153 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 -----·------------------- 74.40 74.61 73.72 74.73 74.32 74.71 69.93 72.37 73.77 69.93 

Al2 0 3 -----------·----------- 13.20 13.09 13.59 13.42 13.33 p.55 15.51 14.43 13.63 16.20 

FeO ------·------------------ .56 .40 .44 .32 .44 .28 .53 .36 .40 .23 

Fe2 0 3 ----------------------- 1.19 1.49 1.41 1.58 1.48 1.52 2.22 1.66 2.04 2.51 

MgO ------------------------ .64 .68 .66 .41 .44 .48 .84 .59 .75 .54 

CaO ---··----·-------------·· 1.53 1.60 1.67 1.35 1.50 1.52 2.72 2.23 1.56 2.29 

N ~0 -----------------------· 3.18 3.10 2.99 3.23 3.41 3.03 3.43 3.48 2.84 3.60 

~0 ------------------------- 4.87 4.64 5.12 4.49 4.66 4.45 4.31 4.36 4.59 4.52 

Ti02 -------·-----·------··--- .25 .25 .26 .25 .26 .28 .36 .34 .29 .37 

p 2 0' ------------------------- .07 .07 .07 .16 .08 .13 .12 .10 .08 .12 

MnO ----·----------------·-- .04 .04 .03 .02 .03 .05 .02 .05 .02 <0.02 

Total (volatile-free 

before normalization) 97.72 97.04 97.13 98.36 99.03 98.91 97.38 98.39 97.60 96.94 

LOI ------------------------- 1.81 2.20 2.51 .98 .42 1.50 .96 1.62 2.20 

H20+ ------------------------ 1.30 1.70 2.10 .37 .16 .46 .57 .26 .80 .86 

H2o-------------------------- .35 .29 .46 .55 .30 .44 .71 .70 1.50 .93 

C02 ------------------------- .01 .03 .01 .01 .01 .08 .09 .16 .01 <0.01 

F ----------------------------- .022 .020 

Minor elements (parts per million) 

Nb ------------------------- 12 11 14 13 13 11 11 11 10 

Rb ------------------------- 148 156 157 145 145 108 137 129 136 116 

Sr -------------------------- 226 258 269 245 241 378 408 396 284 465 

Zr ------------------------- 123 122 136 125 134 163 154 131 188 

y -------------------------- 18 16 17 19 19 20 14 13 10 

Ba ------------------------- 702 762 737 835 821 1,000 1,290 1,100 1,500 

Ce ------------------------- 56 54 67 62 64 110 53 58 30 

La ------------------------- 40 28 35 28 26 45 27 26 50 

Cu ------------------------- <5 7 7 10 16 9 <5 <5 <20 

N i ------------------------- <5 <5 <5 <5 <5 5 <5 <5 <20 

Zn ------------------------- 47 51 49 49 45 67 54 46 50 

Cr ------------------------- <20 <20 <20 <20 <20 <10 <20 <20 <20 

K/R.b ---------------------- 273 247 271 257 266 342 261 281 280 323 

Sr/Rb --------------------- 1.53 1.65 1.71 1.69 1.66 3.50 2.98 3.07 2.09 4.01 

Feo• --------------------- 1.63 1.73 1.71 1.74 1.76 1.65 2.53 1.86 2.23 2.40 

Sample descriptions 

1 (83-DJ-45) Densely welded glaasy tuff from near base of tuff of Toiyabe on the east side of the Paradise Range about 3 km south of Sherman Peak at lat 

38°55'00"N., long 1l7°46'10"W. 

2 (83-DJ-99) Densely welded basal vitrophyre of tuff of Toiyabe collected about 1 km south of Brunton Pass at lat 38°53 '30"N., long 117°46' 1 O"W. 

3 (86-DJ-80) Densely welded basal vitrophyre of tuff of Toiyabe collected about 3 km south of Shennan Peak at lat 38°55'10"N., long 117°46'00"W. 

4 (83-DJ-32 Devitrified densely welded tuff from the middle part of the tuff of Toiyabe collected about 4 km south of Shennan Peak along the crest of the east side 

of the Paradise Range at lat 38°54'30"N., long 117°46'00"W. 

5 (83-DJ-42) Devitrified densely welded tuff from the middle part of the tuff of Toiyabe collected about 4 km south of Shennan Peak along the crest of the east 

side of the Paradise Range at lat 38°54'15"N., long 117°45'40"W. 

6 (83-DJ-100) Devitrified densely welded tuff about 15 m above base of tuff of Toiyabe collected about 1 km south of Brunton Pass at lat 38°53'30"N., long 

117°44 '09"W. 

7 (85-DJ-125) Devitrified, densely welded Cloverdale Ranch unit of the tuff of Toiyabe collected in the northern Pactolus Hills at lat 38°45'05"N., long 

117°47'50"W. 

8 (85-DJ-196) Devitrified, densely welded upper part of the tuff of Toiyabe from north Cedar Mountain about 3.5 km northwest of Simon at lat 38°35'20''N., long 

117°54 'OO"W. 

9 (85-DJ-204) Devitrified, densely welded upper part of the tuff of Toiyabe from north Cedar Mountain about 5 km northwest of Simon at lat 38°35'40"N., long 

117°53 'OO"W. 

10 (85-DJ-153) Devitrified, densely welded Cloverdale Ranch unit of the tuff of Toiyabe collected in the northern Pactolus Hills at lat 38°38'20"N., long 

117°47'45"W. 

48 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Table 6. Chemical analyses of the younger andesite sequence 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, L. Espos, J. Kent, B. King, R. Mendes, S. Pribble, K. Stewart, J. Taggart, D. Vivit; chemical 

determinations for FeO, ~()+. Hp-. 002

, and F by N. Elsheimer and S. Neil). FeO*, total Fe as FeO; LOI,Ioss on ignition at 900°C] 

1 2 3 4 5 6 7 8 9 10 11 

Sample number 84-0J-232 84-0J-150 84-0j-127 86-0j-122A 87-DJ-7 87-0j-8 84-0J-114 85-0J-67 06-J-119 86-0J-120 86-0j-121 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ------------------- 55.18 54.46 61.65 58.72 59.17 58.59 62.33 62.24 61.49 62.24 61.17 

A~03 ------------------ 19.07 18.97 18.11 18.19 17.71 18.69 17.11 17.30 17.48 17.38 16.65 

FeO ------------------- 3.59 4.70 .42 1.12 1.43 1.30 1.11 .41 .17 .22 .42 

Fe20 3 ------------------ 4.11 3.12 5.23 5.67 5.34 4.96 4.44 4.58 5.32 5.79 5.64 

MgO ------------------ 3.35 4.07 2.44 2.67 3.17 3.03 2.77 1.86 2.80 1.79 3.46 

CaO ------------------- 7.89 7.98 4.91 4.99 4.85 6.04 5.47 5.85 5.76 5.40 5.54 

N~O ------------------ 3.51 3.49 3.94 4.29 4.50 4.28 3.48 4.04 4.01 3.49 3.25 

~g2 ~~~~~~~~~~~~~~~~~~~ 1.58 1.47 2.38 2.89 2.48 1.75 2.24 2.45 1.91 2.57 2.79 

1.12 1.12 .60 .80 .76 .79 .72 .65 .64 .71 .74 

P20 5 ------------------- .50 .51 .27 .45 .33 .46 .28 .36 .32 .33 .29 

MnO ------------------ .10 .11 .06 .09 .10 .10 .06 .08 .10 .08 .05 

Total (volatilefree before 

normalization)-- 98.58 98.05 95.54 96.22 97.69 95.75 96.43 98.85 97.25 96.08 95.47 

LOI -------------------- .72 1.50 4.04 3.13 2.63 2.96 3.26 .59 2.00 3.38 4.26 

~Q+ ------------------ .43 .71 1.37 2.14 1.52 .90 .94 .22 .71 1.24 1.14 

~o- ------------------ .39 1.08 2.07 1.18 .84 1.69 1.93 .14 1.25 1.40 2.58 

C02 -------------------- .06 <.05 . 53 .49 .19 .16 .14 .15 .05 . .15 .15 

F ----------------------- .020 - .040 - .030 - .050 .030 

Minor elements (parts per mHlion) 

Nb --------------------- - <10 5 11 10 10 9 - <10 <10 <10 

Rb --------------------- 36 40 41 81 52 36 17 60 30 62 62 

Sr ---------------------- 1,193 1,200 700 724 926 1,100 787 1,226 850 820 740 

a ---------------------- - 138 97 100 140 152 130 - 160 130 150 

y ---------------------- - 10 15 11 14 18 19 - 20 24 14 

Ba --------------------- - 1,000 - 900 1,150 850 - - 1,150 1,100 990 

Ce ---------:------------- - 46 - 28 56 42 - - 45 55 45 

La --------------------- - 30 - 11 42 32 - - <30 <30 <30 

-1 Cu --------------------- - <20 - 10 <20 <20 - - <20 <20 26 a! 

Ni ---------------------- - <20 6 <20 <20 <20 <20 <20 e:r - - - r Zn --------------------- - 82 - 67 72 80 - - 82 85 83 .... 

I Cr ---------------------- - 22 - <20 <20 <20 - - <20 <20 20 .... 

....... 

K/Rb ------------------ 365 305 481 296 395 405 1,094 339 529 344 373 

"" IC Sr/Rb ----------------- 33.14 30.00 17.07 8.94 17.81 30.56 46.29 20.43 28.33 13.23 11.94 

FeO* ------------------ 7.29 7.21 5.13 6.22 6.24 5.76 5.10 4.54 4.96 5.43 5.49 
Table 6. Chemical analyses of the younger andesite sequence-Continued 

VI 

= [All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, L. Espos, J. Kent, B. King, R. Mendes, S. Pribble, K. Stewart, J. Taggart, D. Vivit; chemical detenninations for FeO, H:P+, H,Q-, C02

, and F by N. Elsheimer and S. Neil). FeO•, total Fe as FeO; LOI, loss on ignition at 900"C] 

~ 

~ 

0 12 13 14 15 16 17 18 19 20 21 22 t'l 

:r 

~ Sample number 86-DJ-122 86-DJ-123 86-DJ-124 86-DJ-125 86-Dj-126 86-DJ-127 86-DJ-128 86-DJ-129 86-DJ-131 86-DJ-132 86-DJ-133 

3 

.. 

s: Major elements normalized to 100 percent volatile-free (weight percent) "< 

0 

- Si02 ------------------- 60.44 55.46 60.71 61.31 61.42 62.33 62.99 60.75 70.22 64.77 65.43 0 

aa· A~ 0 3 ------------------ 17.79 18.00 17.42 16.61 16.89 16.82 16.61 16.99 14.52 17.37 16.99 0 FeO ------------------- 1.53 1.43 1.26 1.50 1.40 .29 .00 1.00 0.22 1.80 .78 t'l 

~ Fe2

0 3 ------------------ 4.39 6.34 4.22 4.15 3.87 6.38 5.53 4.87 3.74 2.06 3.35 = ~ 

1.24 I» MgO ------------------ 2.48 4.14 2.88 3.07 2.82 1.32 1.12 3.19 .86 1.67 

c. =CaO ------------------- 6.37 8.53 6.50 6.11 6.62 5.25 5.69 6.04 3.77 4.53 4.32 

~ N ~ 0 ------------------ 3.50 3.42 3.92 3.59 3.86 4.02 4.16 3.95 3.33 3.58 4.12 

c;· ~0 ------------------- 2.33 1.29 1.99 2.57 2.09 2.40 2.80 2.11 2.55 3.39 2.91 t'l 

~ Ti02 ------------------- .75 .97 .65 .66 .59 .76 .67 .68 .53 .54 .57 = ~ P2

0 5 ------------------- .34 .31 .35 .33 .32 .37 .33 .32 .24 .22 .21 

< 0 MnO ------------------ .08 .11 .10 .11 .13 .05 .09 .10 .03 .07 .06 nI» 

;:;· = Total (volatile- ;11:1 

0 free before t'l normalization)-- 97.79 96.11 98.17 97.54 99.50 96.91 98.11 98.27 97.12 97.88 98.27 ~ 

""C' 

I» 

LOI -------------------- 1.87 3.75 1.25 1.75 2.75 2.88 1.38 .87 2.88 1.88 1.50 .. 

I» 

c. 

;;;· 

~ H2

0+ ------------------ .70 1.07 .42 1.05 .78 .29 27 .72 .94 1.48 .39 ;11:1 

I» ~o- ------------------ 1.23 1.91 .58 .32 1.46 1.77 51 .38 1.70 .52 1.13 CJQ = C02 ~ -------------------- .09 .47 .25 .14 .27 .07 49 .06 .21 .02 .03 

I» F ----------------------- c. =

z Minor elements (parts per mUlion) 0 

::. 

:r 

~ 

.. Nb ---------------------< 10 <10 <10 <10 <10 10 10 <10 <10 10 <10 

= Rb --------------------- 60 22 40 52 40 52 52 43 58 62 60 ""C' 

~ Sr ---------------------- 880 860 890 770 830 810 810 930 660 790 730 

0 a ----------------------130 120 150 160 160 160 160 160 130 180 180 2'" 

WI y ---------------------- 17 17 18 20 14 20 20 16 <10 16 20 

~ Ba ---------------------890 800 980 980 970 1,100 1,100 1,050 970 1,250 1,300 

F Ce --------------------- 45 40 50 55 45 40 40 30 35 <30 35 

z La --------------------- <30 <30 <30 <30 <30 <30 <30 <30 <30 <30 <30 "< 

~ Cu ---------------------<20 40 <20 <20 <20 <20 <20 <20 <20 <20 <20 

t"'l Ni ----------------------<20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 0 

c Zn --------------------- 80 90 70 70 63 86 78 70 68 66 72 

= 

~ Cr ---------------------- 28 40 <20 <20 <20 <20 <20 <20 <20 <20 <20 

z 

~ 

< K/Rb ------------------ 323 487 412 411 433 384 408 407 365 454 403 I» 

c. Sr/Rb ------------------ 14.67 39.09 22.25 14.81 20.75 15.58 13.33 21.63 11.38 12.74 12.17 I» 

FeO* ------------------ 5.48 7.13 5.06 5.23 4.88 6.03 4.98 5.38 3.58 3.66 3.80 
Table 6. Chemical analyses of the younger andesite sequence-Continued 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, L. Espos, J. Kent, B. King, R. Mendes, S. Pribble, K. Stewart, J. Taggart, D. Vivit; chemical 

determinations for FeO, H2

0+, Hp-, C02

, and F by N. Elsheimer and S. Neil). FeO*, total Fe as FeO; LOI, loss on ignition at 900°C] 

23 24 25 26 27 28 29 30 31 32 33 

Sample number 86-Dj-134 86-Dj-135 86-Dj-136 86-Dj-137 86-Dj-138 86-Dj-139 86-Dj-140 86-Dj-14 88-PP-157 88-PP-158 88-PP-159 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ------------------- 64.18 65.04 63.96 63.57 61.70 60.45 62.47 61.57 57.65 57.86 57.67 

A~03 ------------------ 17.39 17.36 17.36 16.28 17.86 17.20 17.31 18.18 17.74 17.70 17.72 

FeO ------------------- .78 .14 1.74 .83 1.11 .72 2.14 .56 2.55 1.88 2.19 

Fe20 3 ------------------ 4.03 4.46 2.79 5.09 4.39 6.29 2.97 5.44 4.46 5.17 4.83 

MgO ------------------ 1.13 .49 1.61 2.00 1.59 2.19 2.56 1.16 3.13 2.97 3.13 

CaO ------------------- 4.56 4.35 4.80 4.97 6.01 6.24 5.65 5.72 7.30 7.26 7.33 

N~O ------------------ 4.18 4.36 4.02 3.48 3.60 3.38 3.38 3.68 3.76 3.78 3.74 

~0 ------------------- 2.80 2.84 2.77 2.60 2.52 2.32 2.45 2.43 1.91 1.95 1.93 

Ti02 ------------------- .64 .62 .62 .79 .78 .82 .65 .83 .84 .83 .85 

P20 5 ------------------- .24 .26 .24 .36 .37 .32 .34 .36 .27 .27 .27 

MnO ------------------ .07 .08 .08 .04 .06 .06 .08 .07 .11 .10 .10 

Total (volatilefree before 

normalization) -- 98.32 97.94 98.50 97.68 97.40 95.95 97.64 96.80 99.22 98.86 99.35 

LOI -------------------- 1.50 1.75 1.37 2.25 2.38 3.75 2.12 3.13 .66 .90 .74 

H20+ ------------------ .48 .35 .73 .39 .54 .87 1.17 .69 .81 .95 .90 

H2o- ------------------ .98 1.31 .71 1.23 1.40 2.99 .93 2.11 .20 .22 .22 

C02 -------------------- .15 .11 .13 .04 .26 .04 .03 .07 <.01 <.01 <.01 

F -----------------------

Minor elements (parts per mlllion) 

Nb --------------------- <10 10 <10 12 10 10 <10 11 <10 <10 <10 

Rb --------------------- 52 56 52 58 60 53 62 55 54 45 61 

Sr ---------------------- 800 780 790 760 920 870 790 920 1,030 1,010 1,050 

a ---------------------- 1so 180 170 130 170 150 130 160 105 91 105 

y ---------------------- 14 17 16 22 15 14 13 16 12 9 15 

Ba ---------------------1,350 2,250 1,350 1,200 1,200 930 1,000 1,150 855 862 880 

Ce --------------------- 40 <30 <30 45 40 45 50 <30 50 44 55 

La --------------------- <30 <30 <30 <30 <30 <30 <30 40 25 20 20 

Cu --------------------- <20 20 <20 <20 <20 <20 <20 <20 14 9 11 

Ni ---------------------- <20 <20 <20 <20 <20 <20 <20 <20 5 <5 <5 -1 

Dol Zn --------------------- 69 70 73 82 80 88 60 94 76 67 66 r:r 

;- Cr ---------------------- <20 <20 <20 24 32 52 30 36 <20 <20 <20 WI 

.... 

.!... K/Rb ------------------ 446 421 442 372 348 364 328 366 294 360 263 ...... Sr/Rb ------------------ 15.38 13.93 15.19 13.10 15.33 16.42 12.74 16.73 19.07 22.44 17.21 

VI FeO* ------------------ 4.41 4.16 4.25 5.41 5.06 6.38 4.81 5.46 6.56 6.54 6.53 .... 
1.1'1 

N 

~ 

~ 1'1 

::r 

~ 

3 

.. =: 

"< 

e 

-

Q 

oe· 

e 

1'1 

~ 

= 

~ 

AI 

= Cl. 

~ 

c:;· 

1'1 

~ 

= ~ 

< e 

rr 

AI 

= ;:r 

;:iiC 

e 

1'1 

~ 

~ 

AI 

!. 

;· 

~ 

CJQ 

~ ~ 

AI 

= Cl. 

z 

e 

~ 

::r 

~ .. 

= 

~ 

~ 

S' 

c 

Ut 

~ ... iii 

z 

1 

~ c 

= 

~ 

z 

~ 

< 

~ AI 

Table 6. Chemical analyses of the younger andesite sequence-Continued 

Sample descriptions 

1 (84-DJ-232) Vesicular, fmc-grained basaltic andesite lava containing plagioclase, clinopyroxene, and altered olivine phenocrysts in a microcrystalline groundmass collected near the base of the andesite 

and basaltic andesite unit on the east side of the Paradise Range at lat 38°54'15"N., long 117°49'48"W. 

2. (84-DJ-150) Fine-grained basaltic andesite lava containing plagioclase, clinopyroxene, and altered olivine phenocrysts in a microcrystalline groundmass collected near the base of the andesite and 

basaltic andesite unit on the east side of the Paradise Range at lat 38°54'10"N., long ll7°47"05"W. 

3. (84-DJ-127) Fine- to medium-grained, devitrified hornblende andesite lava collected in Sheep Canyon at lat 38°47'12"N., long ll7°49'48"W. (hornblende andesite unit) 

4. (86-DJ-122A) Propylitized, fmc- to medium-grained porphyritic hornblende andesite dike intruding older andesite lavas and tuffs in the Sheep Canyon section collected in the southwestern Paradise Range 

along the range front about 2 km south of Sheep Canyon at lat 38°48'06"N., long 117°56'24"W. (hornblende andesite unit) 

5. (87-DJ-7) Weakly propylitized fmc-grained hornblende andesite lava collected in Sheep Canyon at lat 38°48'08"N.,long ll7°55'10"W. (hornblende andesite unit) 

6. (87-DJ-8) Devitrified, fine- to medium-grained hornblende-plagiolcase andesite lava from the base of the hornblende andesite unit collected in Sheep Canyon at lat 38°42'02"N., 117°54'47"W. 

7. (84-DJ-114) Vitrophyric, coarse-grained porphyritic biotite hornblende plagioclase andesite lava collected along the old Poleline Road in the southwestern Paradise Range at lat 38°44'59"N., long 

117°59'00"W. (porphyritic dacite unit) 

8. (85-DJ-67) Devitrified, medium-grained hornblende plagioclase andesite flow breccia collected near the base of the porphyritic dacite unit in the northern Pactolus Hills at lat 38°44'48"N., long 

117°47'02"W. 

9. (86-DJ-119) Devitrified, medium-grained porphyritic biotite-hornblende-plagioclase andesite porphyry flow breccia from Finger Rock Wash collected at lat 38°42'14"N.,long ll8°01'42"W. (porphyritic 

dacite unit) 

10. (86-DJ-120) Devitrified, coarse-grained porphyritic hornblende-plagioclase andesite lava from Finger Rock Wash collected at lat 38°42'14"N., long 118°01 '40"W. (porphyritic dacite unit) 

11. (86-DJ-121) Devitrified, medium-grained, sparsely porphyritic hornblende-plagioclase andesite lava from Finger Rock Wash collected at lat 38°42'19"N.,long 118°0l'35"W. (porphyritic dacite unit) 

12. (86-DJ-122) Devitrified, medium-grained, sparsely porphyritic clinopyroxene-hornblende-plagioclase andesite lava from Finger Rock Wash collected at lat 38°42'20"N., long 118°01'28"W. (porphyritic 

dacite unit) 

13. (86-DJ-123) Devitrified, medium-grained, sparsely porphyritic basaltic andesite lava from Finger Rock Wash collected at lat 38°42'22"N.,long 118°01 '25"W. (porphyritic dacite unit) 

14. (86-DJ-124) Devitrified, medium-grained porphyritic hornblende andesite porphyry flow breccia from Finger Rock Wash collected at lat 38°42'21 "N., long 118°01 '17"W. (porphyritic dacite unit) 

15. (86-DJ-125) Devitrified, medium-grained porphyritic hornblende-plagioclase andesite porphyry from Finger Rock Wash collected at lat 38°42'24"N., long 118°01 '14"W. (porphyritic dacite unit) 

16. (86-DJ-126) Devitrified, medium-grained hornblende andesite lava from Finger Rock Wash collected at lat 38°42'24"N., long 118°01 '09"W. (porphyritic dacite unit) 

17. (86-DJ-127) Devitrified, medium-grained hornblende andesite lava from Finger Rock Wash collected at lat 38°42'23"N.,long ll8°01'02"W. (porphyritic dacite unit) 

18. (86-DJ-128) Devitrified, medium-grained hornblende-plagioclase andesite lava from Finger Rock Wash collected at lat 38°42'27"N., long 118°00'50"W. (porphyritic dacite unit) 

19. (86-DJ-129) Devitrified, medium-grained hornblende-plagioclase andesite porphyry from Finger Rock Wash collected at lat 38°42'27"N., long ll8°00'50"W. (porphyritic dacite unit) 

20. (86-DJ-131) Devitrified, coarsely porphyritic plagioclase rhyolite flow breccia collected on the southwest side of Newman's Ridge at lat 38°43'17"N.,long 117°59'18"W. (porphyritic dacite unit) 

21. (86-DJ-132) Devitrified, fine-grained sparsely porphyritic hornblende dacite lava collected on the southwest side of Newman's Ridge at lat 38°43'16"N., long 117°59'10"W. (porphyritic dacite unit) 

22. (86-DJ-133) Devitrified, fine-grained sparsely porphyritic hornblende dacite lava collected on the southwest side of Newman's Ridge at lat 38°43'20"N., long ·117°59'10"W. (porphyritic dacite unit) 

23. (86-DJ-134) Devitrified, fine-grained sparsely porphyritic hornblende dacite lava collected on the southwest side of Newman's Ridge at lat 38°43'25"N., long 117°58'59"W. (porphyritic dacite unit) 

24. (86-DJ-135) Devitrified, fine-grained sparsely porphyritic hornblende dacite lava collected on the southwest side of Newman's Ridge at lat 38°43'33"N., long 117°58'57"W. (porphyritic dacite unit) 

25. (86-DJ-136) Devitrified, fmc-grained sparsely porphyritic hornblende dacite lava collected on the southwest side of Newman's Ridge at lat 38°43 '48"N., long 117°58'53"W. (porphyritic dacite unit) 

26. (86-DJ-137) Devitrified, coarse-grained biotite-hornblende-plagioclase dacite porphyry collected about 500 m east of the Paradise Peak Mine at lat 38°45'07"N., long 117°57'35"W. (porphyritic dacite 

unit) 

27 (86-DJ-138) Devitrified, coarse-grained hornblende-plagioclase andesite lava collected about 500 m east of the Paradise Peak Mine at lat 38°45'07"N., long 117°57'39"W. (porphyritic dacite unit) 

28. (86-DJ-139) Devitrified, sparsely porphyritic hornblende-plagioclase andesite flow breccia collected about 500 m east of the Paradise Peak Mine at lat 38°44'55"N., long 117°57'36"W. (porphyritic dacite 

unit) 

29. (86-DJ-140) Vitric, flow banded, hornblende andesite lava collected about 500 m east of the Paradise Peak Mine at lat 38°44'55"N., long 117°57'36"W. (porphyritic dacite unit) 

30. (86-DJ-141) Devitrified, sparsely porphyritic, hornblende-plagioclase andesite lava collected about 500 m east of the Paradise Peak Mine at lat 38°44'55"N., long 117°57'39"W. (porphyritic dacite unit) 

31. (88-PP-157) Devitrified, fmc-grained clinopyroxene-plagioclase andesite lava collected in the northern Pactolus Hills at lat 38°46'34"N., long 117°47'00"W. (porphyritic dacite unit) 

32. (88-PP-158) Devitrified, fine-grained clinopyroxene-plagioclase andesite lava collected in the northern Pactolus Hills at lat 38°46'34"N., long 117°47'02"W. (porphyritic dacite unit) 

33. (88-PP-159) Devitrified, fine-grained clinopyroxene-plagioclase andesite lava collected in the northern Pactolus Hills at lat 38°46'34"N., long 117°47'01 "W. (porphyritic dacite unit) 
Table 7. Characteristics of major ash-flow tuff units in the Ellsworth section 

Tuff of Return Tuff of Camel Brown rhyolite Tuff of Big 

Unit Mine Spring White tuff tuff Spring 

Cornposition1 --------------Rhyolite(?) Rhyolite Rhyolite(?) Rhyolite Rhyolite 

Percent phenocrysts ------11-25 1-11 20-23 4-7 31-44 

Major phenocrysts2 -------Q, S, P, B A,P,S Q,S,P Q,S,P S,P,Q,B 

Pumice clasts --------------Abundant Locally abundant Sparse Sparse Sparse 

Welding --------------------Poor to moderate Poor to dense Poor to Dense Dense 

moderate 

Lithic fragments ----------Locally abundant Locally abundant Sparse Sparse Sparse 

Simple or compound 

cooling unit --------------Compound Compound Simple Simple Simple 

Notable characteristics --Smoky quartz Anorthoclase Commonly Base 

phenocrysts, phenocrysts vitrophyric commonly 

commonly vitrophyric 

strongly argillized 

Thickness3 (m) ------------ 300 250 50 125 200 

Age (Ma) (see table 3) -->26 >26 >23 23-24 ~23 

Areal distribution4 --------PR, SM PR, SM, GV(?) PR PR PR,SM 

Source ----------------------Unknown Unknown Unknown Unknown Unknown 

Comments ----------------- Also present in 

Menter Canyon 

section 

1

Classification is lUGS chemical classification (Le Bas and others, 1986) based on total alkali and silica contents of 

whole-rock samples recalculated to 100 percent volatile-free. 

lQ, quartz; S, sanidine; P, plagioclase; B, biotite; A, anorthoclase. 3

Maximum thickness in Paradise Range. 4

PR, Paradise Range; SM, Southern Shoshone Mountains; GV, Gabbs Valley Range. 

Tables 1-17 53 
U1 Table 8. Characteristics of major ash-flow tuff units in the Sheep Canyon section ~ 

C") 

tD 

~ 

if 

3 iii • 

.5' 

0 

-

Q 

;· 

,., 

tD 

:I 

tD 

II 

:I 

Q. 

~ 

cr 

,., 

tD 

:I 

tD 

< 0 

;;-

~~ 

:I 

;:;· 

:Ia 

~ ,. 

-a 

e: 

!. 

xr 

:Ia 

II 

, :I 

i 

z 

0 

::l 

:r 

tD 

... 

:I 

-a 

~ 

S' 

c 

Ill 

~ ,Wi 

z 

~ 

Q 

c 

:I 

~ 

z 

tD 

i 

II 

Unit 

Composition1 

Percent phenocrysts 

Major phenocrysts2 

Pumice clasts 

Welding 

Lithic fragments 

Simple or compound 

cooling unit 

Notable characteristics 

Thickness' (m) 

Age (Ma) (see table 3) 

Areal distribution• 

Source 

Comments 

Unit 

Composition1 

Percent phenocrysts 

Major phenocrysts2 

Pumice clasts 

Welding 

Lithic fragments 

Simple or compound 

cooling unit 

Notable characteristics 

Thickness' (m) 

Age (Ma) (see table 3) 

Areal distribution• 

Source 

Comments 

Tuff of Pactolus 

Rhyolite 

10-25 

Q,P,S,B 

Locally abundant, crystal-rich 

Dense 

Sparse 

Compound(?) 

Strongly altered throughout 

(argillic or silicic). 

500 

<!:34(7) 

PH,SM 

Southern Shoshone Mountains(?) 

Correlative(?) with lower part 

of Mission Spring Formation 

of Vitaliano and Vitalino (1972). 

Lower white 

tuff 

Rhyolite 

4-15 

Q,S,P,B 

Abundant 

Dense to poor 

Sparse except at base 

Simple 

Persistant basal vitrophyre; 

sanidine commonly iridescent. 

250 

approx. 23 

PR,PH 

Unknown 

-

Rhyolite 

8-9 

P,S 

Tuff of 

Davis Mine 

Locally abundant 

Extremely dense 

Abundant 

Simple(?) 

Abundant pre-Tertiary lithic 

fragments; strongly altered 

(propylitic). 

600 

approx. 34 (7) 

PR, PH, SM 

Southern Shoshone Motmtains (7) 

Correlative(?) with upper part 

of Mission Spring Formation 

of Vitaliano and Vitaliano (1972). 

Red tuff 

Rhyolite 

1-7 

Q,P 

Generally abundant 

Dense 

Sparse 

Simple 

Local secondary flow structures; 

commonly spherulitic. 

150 

approx. 23 

PR,PH 

Unknown 

-

Rhyolite 

1-8 

P,S,Q 

Abundant 

Dense 

Tuff 

Locally abundant 

Simple(?) 

Commonly vesicular due to 

weathered-out pumice lapilli. 

500 

approx. 24(7) 

PR 

Unknown 

Upper white tuff 

Rhyolite(?) 

2-7 

P,S 

Generally sparse 

Poor to moderate 

Sparse except at base of 

lowest cooling tmit. 

Compound 

Middle member spherulitic; 

basal vitrophyres in lower 

and upper members. 

150 

approx. 23 

PR,PH 

Unknown 

3 cooling units 

Biotite-lithic 

tuff 

Dacite(?) 

40 

P,B,H,C 

Sparse 

Dense 

Abundant 

Simple 

Very lithic-rich; more mafic 

than other tuffs with abundant 

hornblende and clinopyroxene. 

60 

25.6 

PR 

Unknown 

Red rhyolite 

tuff 

Rhyolite 

20-30 

S,Q 

Sparse 

Dense 

Sparse 

Simple 

Virtually no plagioclase or 

biotite phenocrysts; local 

sandstone overlying tuff. 

90 

23 

PR,PH 

Unknown 

Rhyolite 

20-35 

Tuff of 

Go I dyke 

P,Q,S,B 

Locally abundant 

Dense 

Sparse 

Compound 

Sieve-textured quartz 

450 

23.5-23.0 

PR,PH 

Unknown 

Tuff of Sheep 

Canyon 

Dacite-rhyolite 

15-45 

P,S,Q,B 

Abundant, crystal-rich, 

as long as 25 ern. 

Moderate to dense 

Generally sparse 

Compound 

Four cooling units; pumice 

contains abundant biotite. 

600 

appox. 23 

PR 

Unknown 

1

Classification is lUGS chemical classification (Le Bas and others, 1986) based on total alkali and silica contents of whole-rock samples recalculated to 100 percent volatile-free. 

2Q, quartz; P, plagioclase; S, sanidine; B, biotite; H, hornblende; C, clinopyroxene. 

'Maximum thickness in Paradise Range. 4

PR, Paradise Range; PH, Pactolus Hills; SM, Southern Shoshone Mountains. 
Table 9. Volume estimates of major ash-flow tuff sheets in the Paradise Range 

Unit Present area (km2) Restored area (km2) Restored volume (km3) 

Tuffs of Davis Mine and Pactolus 

and Mission Spring Formation --------------475 

Tuff of Gabbs Valley --------------------------2,100 

Tuff of Arc Dome------------------------------ 3,350 

Tuff of Toiyabe ---------------------------------4,150 

325 

1,050 

2,300 

2,650 

250 

370 

800 

1,100 

Tables 1-17 55 
Table 10. Chemical analyses of the older andesite sequence 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, R. Mendes, K. Stewart, _J. Taggart; chemical 

determinations for FeO, ~0+, ~o--. and C02 by N. Elsheimer and S. Neil). FeO*, total Fe as FeO; LOI, loss on ignition at 

900°C] 

1 2 3 4 5 6 

Sample Number 84-Dj-38 84-Dj-41 84-DJ-49 84-Dj-58 87-DJ-10 87-Dj-11 

Major elements normalized to 100 percent volatile-free (weight percent) 

SiO ---------------------

A~ 0 3 --------------------

66.08 

16.01 

FeO --------------------- .20 

Fe20 3 -------------------- 4.77 

MgO -------------------- 1.12 

CaO --------------------- 3.73 

~ 6 0 -~~~~~~~~~~~~~~~~~~~~ 3.67 

3.59 

Ti02 --------------------- .53 

~~6 -~~~~~~~~~~~~~~~~~~~~ .22 

.05 

Total (volatile-free 

before normalization) 98.06 

LOI ---------------------- 1.38 

Hl Q+ --------------------

H20- --------------------

C02 ----------------------

Nb ----------------------- 12 

Rb ----------------------- 104 

Sr ------------------------ 520 

'Z;r ------------------------ 126 

y ------------------------ 14 

.63 

.37 

.38 

Ba ----------------------- 1,000 

Ce ----------------------- 60 

La ----------------------- 48 

Cu ----------------------- 24 

Ni ------------------------ <20 

Zn ----------------------- 62 

Cr ------------------------ 92 

K/Rb -------------------- 286 

Sr/Rb ------------------- 5.00 

FeO* -------------------- 4.49 

Sample descriptions 

62.68 61.39 70.60 62.76 

17.61 17.81 15.07 17.24 

.46 1.36 .18 1.64 

5.25 4.23 3.00 3.57 

1.86 2.69 .79 2.35 

3.81 4.66 2.90 4.98 

3.63 3.93 2.97 4.39 

3.61 2.59 3.93 1.96 

.73 .79 .38 .63 

.27 .35 .14 .22 

.04 .06 .02 .08 

96.52 96.60 96.88 98.00 

3.50 3.62 2.68 1.88 

1.58 1.73 .68 1.30 

1.30 .63 1.30 .50 

.38 .48 .31 <0.05 

Minor elements (parts per million) 

12 12 

116 70 

560 720 

215 176 

18 16 

1,450 1,200 

68 72 

54 52 

24 <20 

<20 <20 

74 78 

34 42 

258 307 

4.83 10.29 

5.18 5.16 

<10 

83 

539 

121 

15 

393 

6.49 

2.88 

10 

68 

840 

215 

16 

1,050 

48 

36 

22 

<20 

72 

<20 

239 

12.35 

4.85 

60.17 

17.63 

2.54 

3.36 

3.28 

5.72 

3.49 

2.54 

.66 

.25 

.09 

97.56 

2.00 

1.71 

.33 

<0.05 

10 

70 

720 

188 

18 

1,150 

48 

38 

28 

<20 

78 

<20 

301 

10.29 

5.56 

7 8 

87-Dj-12 87-Dj-2 

61.57 63.34 

17.65 16.76 

2.12 .26 

2.96 5.37 

2.67 1.85 

4.54 4.30 

4.21 3.60 

3.12 3.56 

.64 .64 

.23 .25 

.08 .07 

97.45 97.25 

2.25 2.37 

1.73 .88 

.41 1.08 

.23 .53 

10 12 

104 100 

800 560 

210 192 

20 20 

1,250 1,250 

42 54 

30 40 

26 22 

<20 <20 

74 78 

<20 <20 

249 295 

7.69 5.60 

4.77 5.07 

l (84-DJ-38) Devitrified, flow-banded, medium-grained biotite-hornblende-plagioclase dacite lava collected along the range 

front in the southwestern Paradise Range at lat 38°48'00"N., long ll7°56'2l"W. 

2 (84-DJ-41) Devitrified, medium-grained (biotite)-homblende-plagioclase andesite lava collected along the range front in the 

southwestern Paradise Range at lat 38°47'35"N., long 1l7°56'09"W. 

3 (84-DJ-49) Propylitized, medium-grained (biotite)-hornblende-plagioclase andesite lava collected near the Poleline Road in 

southwestern Paradise Range at lat 38°46'45"N., long 117°57'45"W. 

4 (84-DJ-58) Weakly propylitized, flow-banded, medium-grained biotite-hornblende-plagioclase rhyolite lava collected about 

300m east of the Gold Ledge Mine, southwestern Paradise Range at lat 38°47'12"N., long 38°47'12"W. 

5 (87-DJ-10) Propylitized, medium-grained clinopyroxene-hornblende-plagioclase andesite lava collected near the Davis Mine 

in the southwestern Paradise Range at lat 38°45'13"N., long 1l7°53'15"W. 

6 (87-DJ-11) Propylitized, medium-grained hornblende-plagioclase andesite lava collected near the Davis Mine in the 

southwestern Paradise Range at lat 38°45'16"N., long ll7°53'04"W. 

7 (87-DJ-12) Propylitized, medium-grained, flow foliated clinopyroxene-hornblende-plagioclase andesite lava collected near 

the Davis Mine in the southwestern Paradise Range at lat 38°45'17"N., long 117°52'58"W. 

8 (87-DJ-2) Propylitized, fine-grained clinopyroxene-hornblende-plagioclase dacite lava collected near the mouth of Sheep 

Canyon at lat 38°49'17"N., long 117°55'36"W. 

56 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Table 10. Chemical analyses of the older andesite sequence-Continued 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, R. Mendes, K. Stewart, J. 

Taggart; chemical determinations for FeO, }\Q+, }\Q-, and C02 by N. Elsheirner and S. Neil). FeO*, total Fe as 

FeO; LOI, loss on ignition at 900°C] 

Sample Number 

9 

87-Dj-3 

10 

87-DH 

11 

87-DJ-5 

12 

87-Dj-6 

13 

87-Dj-9 

14 

88-Dj-66 

Major elements normalized to 100 percent volatile-free (weight percent) 

SiO --------------------- 61.57 68.34 63.35 66.43 59.22 60.76 

A~03 -------------------- 16.61 15.87 17.04 15.31 17.98 16.59 

FeO --------------------- .29 .30 .42 .10 2.10 3.10 

Fe1 0 3 -------------------- 5.52 2.92 4.53 5.29 3.74 2.28 

MgO -------------------- 3.70 .93 2.26 1.35 3.72 2.91 

CaO --------------------- 4.80 3.86 4.13 3.95 4.71 6.14 NhO -------------------- 3.60 3.81 4.00 3.41 3.62 3.56 

~ --------------------- 3.05 3.30 3.29 3.27 3.66 3.49 

Ti01 --------------------- .59 .39 .62 .58 .66 .78 

~6 -~~~~~~~~~~~~~~~~~~~~ .19 .19 .25 .23 .27 .30 

.06 .06 .08 .07 .09 .09 

Total (volatile-free 

before normalization) 94.52 97.01 97.40 96.65 96.76 92.82 

LOI ---------------------- 4.88 2.62 2.25 3.12 2.62 6.24 

~Q+ -------------------- 2.08 .82 .92 1.09 1.68 2.09 

~o- -------------------- 2.19 1.08 1.01 .74 .31 .17 

C01 ---------------------- .30 .51 <0.05 .92 .46 3.42 

Minor elements (parts per mlllion) 

Nb ----------------------- 12 12 12 <10 10 12 

Rb ----------------------- 102 90 106 94 96 94 

Sr ------------------------1,650 500 610 600 1,150 580 

a------------------------ 150 118 205 134 270 114 

y ------------,------------ 18 12 20 12 20 14 

Ba ----------------------- 1,450 1,000 1,200 1,000 2,150 1,000 

Ce ----------------------- 40 46 48 44 50 34 

La ----------------------- 34 36 30 36 38 <30 

Cu ----------------------- 30 <20 22 <20 22 <20 

Ni ------------------------ <20 <20 <20 <20 <20 <20 

Zn ----------------------- 78 54 82 60 78 68 

Cr ------------------------ 32 <20 <20 <20 88 <20 

K/Rb -------------------- 248 304 257 289 316 308 

Sr/Rb -------------------- 16.18 5.56 5.75 6.38 11.98 6.17 

FeO* -------------------- 5.24 2.92 4.49 4.86 5.46 5.16 

15 

84-Dj-132 

65.06 

16.70 

1.20 

3.28 

1.81 

4.19 

3.68 

3.18 

.57 

.23 

.10 

97.60 

1.93 

1.11 

.61 

.29 

<10 

104 

690 

172 

14 

1,200 

34 

48 

<20 

<20 

68 

44 

253 

6.63 

4.15 

9 (87-DJ-3) Weakly propylitized, coarsely porphyritic hornblende-clinopyroxene-plagioclase andesite flow 

breccia containing clots of medium- to coarse-grained plagoclase crystals collected near the mouth of Sheep 

Canyon at lat 38°49'18"N., long ll7°56'01"W. 

10 (87-DJ-4) Devitrified, flow banded, fine- to medium-grained (quartz)-biotite-hornblende-plagioclase dacite 

lava collected near the mouth of Sheep Canyon at lat 38°49'18"N., long 117°56'06"W. 

11 (87-DJ-5) Devitrified, sparsely porphyritic hornblende-plagioclase dacite lava collected near the mouth of 

Sheep Canyon at lat 38°49'10"N., long ll7°56'00"W. 

12 (87-DJ-6) Propylitized, medium-grained (quartz)-biotite-hornblende-plagioclase dacite lava collected near 

the mouth of Sheep Canyon at tat 38°48'47"N., long 117°55'38"W. 

13 (87-DJ-9) Propylitized, medium-grained clinopyroxene-hornblende-plagioclase andesite lava collected near 

the Davis Mine in the southwestern Paradise Range at lat 38°45' 19"N., long ll7°53'30"W. 

14 (8~DJ-66) Propylitized, medium-grained biotite-hornblende-plagioclase andesite dike in the footwall of the 

Sheep Canyon fault, southwestern Paradise Range collected at lat 38°47'34"N., long 117°54'09"W. 

15 (84-DJ-132) Devitrified, flow foliated, medium-grained hornblende-plagioclase dacite lava collected near the 

Poleline Road in the southwestern Paradise Range at lat 38°47'20"N., long ll7°55'20"W. 

Tables 1-17 57 
Table 11. Chemical analyses of the andesite of Stewart Valley 

[All analyses by X-ray fluorescence spectroscopy (analyst: M. Dyslin; 

chemical determinations of FeO, f40+, f4o-, and C01 by S. Neil and S. 

Pribble). FeO*, total Fe as FeO; LOI, loss on ignition at 900°C] 

Sample number 314-4K 

2 

346-12K 

3 

346-3K 

4 

87-DJ-146 

Major elements normalized to 100 percent volatile-free (weight 

percent) 

SiO -----------------

A~63 ---------------- FeO -----------------

Fe203 ----------------

MgO ----------------

CaO -----------------

N ~0 ----------------

~0 -----------------

Ti02 -----------------

p 0 ----------------- MnO ----------------

Total (volatilefree before 

57.45 

18.61 

3.13 

3.52 

2.95 

7.16 

3.86 

1.83 

.94 

.43 

.12 

59.74 

17.81 

3.02 

3.25 

3.21 

6.23 

3.31 

2.24 

.81 

.29 

.09 

56.68 

18.89 

1.26 

5.97 

2.04 

7.19 

4.19 

2.10 

1.08 

.49 

.10 

57.85 

17.60 

3.89 

3.40 

2.88 

6.53 

3.81 

2.10 

1.01 

.78 

.15 

normalization) - 98.34 

=================== 

96.59 97.92 97.15 

LOI ------------------ .88 3.25 2.00 

~Q+ ---------------- .73 1.75 .83 

~ o------------------ .31 .39 .98 

C02 ------------------ <0.05 .96 <0.05 

Minor elements (parts per million) 

Nb ----------------- < 10 

Rb ----------------- 38 

Sr ------------------ 1 ,300 

7:r ------------------ 166 

y ------------------ 16 

Ba ----------------- 1,150 

Ce ----------------- 72 

La ----------------- 62 

Cu ----------------- <20 

Ni ------------------ <20 

Zn ----------------- 86 

Cr ------------------ <20 

K/Rb -------------- 400 

Sr/Rb -------------- 34.2 

FeO* -------------- 6.27 

Sample descriptions 

<10 

50 

760 

134 

14 

1,050 

54 

46 

<20 

<20 

82 

42 

372 

15.2 

5.95 

12 

44 

1,250 

174 

18 

1,150 

64 

42 

<20 

<20 

80 

<20 

396 

28.4 

6.63 

1.55 

18 

50 

920 

260 

26 

1,300 

90 

78 

<20 

<20 

92 

<20 

.96 

.70 

.09 

349 

18.4 

6.75 

1 (314-4K) Fine-grained, porphyritic clinopyroxene-plagioclase andesite lava flow with a microcrystalline groundmass collected in the 

southern Pactolus Hills at Iat 38°36'54"N., ll7°47'13"W. 

2 (346-12K) Devitrified, coarsely porphyritic biotite-clinopyroxenehornblende-plagioclase andesite lava flow. Mafic minerals partially 

chloritized and plagioclase partially sericitized. Collected in the 

southern Pactolus Hills at lat 38°36'54"N., long ll7°49'35"W. 

3 (346-3K) Fine-grained, porphyritic olivine-clinopyroxene-plagioclase andesite lava flow with a microcrystalline groundmass. Olivine 

altered to bowlingite. Collected in the southern Pactolus Hills at lat 

38°38'20"N., long ll7°49'33"W. 

4 (87-DJ-146) Devitrified, sparsely porphyritic fine-grained hornblende 

andesite lava collected in Finger Rock Wash at lat 38°44'05"N., long 

ll7°59'25"W. 

58 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Table 12. Chemical analyses of silicic intrusive rocks in the Paradise Range 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, J. Kent, D. Siems, J. Taggart; chemical determinations of FeO, H2

0+, H1Q-, and C02 by C. Papp). FeO*, total Fe as FeO; LOI, loss on ignition at 900°C] 

2 3 4 5 6 7 

Sample number 84-Dj-11 84-DHO 84-Dj-113 84-DJ-115 87-DJ-1 85-DJ-126 89-Dj-38 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ----------------- 71.42 75.66 73.78 75.86 71.58 72.61 76.28 

A~03 ---------------- 14.94 13.97 14.34 13.77 15.58 14.69 13.37 

FeO ----------------- .36 .28 .48 .23 .14 0.26 

Fe2 0 3 ---------------- 1.57 1.06 1.40 1.15 1.56 1.45 .97 

MgO ---------------- .72 .42 .72 .51 .43 .32 .24 

CaO ----------------- 3.03 1.14 1.57 1.46 3.59 1.20 .31 

N~O ---------------- 4.36 3.34 2.76 2.96 3.33 4.10 3.74 

~ 0 ----------------- 3.21 3.85 4.57 3.79 3.29 4.99 4.92 

Ti02 ----------------- .25 .18 .26 .17 .24 .31 .12 

P20 s ----------------- .11 .06 .11 .08 .13 .06 <0.05 

MnO ---------------- .03 .03 <0.02 <0.02 .03 <0.02 .04 

Total (volatilefree before 

normalization) - 97.03 98.07 96.91 97.28 93.04 98.74 98.72 

LOI ------------------ 2.04 1.38 2.40 2.68 5.85 .56 .71 

H2O+ ---------------- .56 1.08 1.01 1.09 1.41 .28 .47 

H20------------------ .59 .60 1.08 .81 2.35 .34 .18 

C02 ------------------ .87 .01 .20 .64 1.80 <0.01 .13 

Minor elements (parts per million) 

Nb ------------------- < 10 <10 10 11 <10 12 14 

Rb ------------------- 70 102 140 95 68 166 180 

Sr -------------------- 460 250 230 249 310 240 52 

Zx -------------------- 144 124 126 136 136 260 160 

y -------------------- 10 12 10 14 <10 18 20 

Ba -------------------1,300 1,200 1,100 1,100 1,500 480 

Ce ------------------- 66 32 46 56 72 70 

La ------------------- 34 36 52 66 52 48 

Cu ------------------- <20 <20 <20 <20 <20 <10 

Ni -------------------- <20 <20 <20 <20 <20 <10 

Zn ------------------- 62 40 46 48 58 68 

Cr -------------------- <20 <20 <20 <20 <20 <20 

K/Rb ---------------- 380 314 271 331 401 250 227 

Sr/Rb ---------------- 1.54 2.45 1.64 2.62 4.56 1.45 .29 

FeO* ---------------- 1.77 1.23 1.74 1.26 1.54 1.57 .87 

Sample descriptions 

1 (84-DJ-11) Devitrified, sparsely porphyritic fine-grained biotite rhyolite dike collected in Sheep Canyon at lat 

38°48'21 "N., long 117°56'15"W. 

2 (84-DJ-40) Devitrified, sparsely porphyritic fine-grained biotite rhyolite dike collected in Sheep Canyon at lat 

38°47'20"N., long 117°56'10"W. 

3 (84-DJ-113) Devitrified, medium-grained quartz-biotite-K-feldspar-plagioclase rhyolite dike collected in Sheep 

Canyon at lat 38°46'50"N., long 117°54'25"W. 

4 (84-DJ-115) Devitrified, sparsely porphyritic fine-grained biotite rhyolite dike collected near Sheep Canyon at 

lat 38°47'29"N., long 117°55'33"W. 

5 (87-DJ-1) Devitrified, sparsely porphyritic fine-grained biotite rhyolite dike collected in Sheep Canyon at lat 

38°49'20"N., long 117°55'10"W. 

6 (85-DJ-126) Glassy, medium-grained biotite rhyolite dike collected in the northern Pactolus Hills at lat 

38°45'05"N., long 117°47'50"W. 

7 (89-DJ-38) Devitrified, flow-banded, sparsely porphyritic rhyolite dome collected about 1 km southwest of 

Goldyke at lat 38°43'50"N., long 117°52'42"W. 

Tables 1-17 59 
Table 13. Sr isotope data for Tertiary volcanic rocks in the Paradise Range 

[Rb and Sr analyses by X-ray fluorescence spectroscopy and Rb and Sr isotopic ratios by mass 

spectrometry (analyst: A. C. Robinson). -, approximately] 

Sample number Unit1 Rb(ppm) Sr(ppm) 17Rb/"Sr 17Sr/"Sr Age(Ma) (

17Sr/"Sr)1 

87-DJ-146 ------- Tsv 50.7 951 .154 .704753 12 .70473 

314-4K ----------- Tsv 36.8 1,278 .0833 .70475 12? .704735 

87-DJ-1 ---------- Tri 75.9 314 .699 .705206 19 .705017 

84-DJ-127 ------- Tha 48.0 696 .199 .704715 -18 .704664 

86-DJ-129 ------- Tpd 49.4 920 .155 .704859 -18 .70482 

84-DJ-114 ------- Tpd 31.7 849 .108 .704969 19 .70494 

86-DJ-119 ------- Tpd 23.9 897 .077 .704845 -19 .70482 

85-DJ-67 -------- Tpd 59.5 1,226 .14 .704223 -19 .704185 

86-DJ-131 ------- Tpd 70.2 641 .317 .704978 -19 .704895 

86-DJ-123 ------- Tpd 14.6 934 .0452 .704575 -19 .704563 

87-DJ-7 ---------- Tha 50.4 926 .157 .704435 -19 .70438 

84-DJ-232 ------- Tha 36.0 1,193 .0873 .705112 19 .705088 

83-DJ-1 00------- Tt 163 217 2.17 .705851 22 .70517 

84-DJ-119 ------- Tsc 137 167 2.37 .706257 23 .70548 

84-DJ-121 ------- Tsc 178 317 1.62 .705536 23 .70507 

85-DJ-125 ------- Tt 137 408 .971 .705348 23 .705031 

85-DJ-151------- Tg 164 138 3.44 .706292 23.5 .70516 

84-DJ-58 -------- Toa 92.3 480 .556 .705544 24.5 .70535 

87-DJ-10 -------- Toa 67.4 820 .238 .705156 -25 .70507 

87-DJ-11 -------- Toa 70.6 727 .281 .704985 -25 .704885 

87-DJ-12 -------- Toa 101 759 .385 .705178 -25 .705041 

87-DJ-5 ---------- Toa 96.6 594 .47 .705258 25-26 .705088 

87-DJ-3 ---------- Toa 81.6 1,874 .126 .705354 -26 .705307 

84-DJ-137 ------- Tdm 156 133 3.39 .706698 

84-DJ-174 ------- Tdm 160 227 2.04 .706199 

84-DJ-175 ------- Tdm 149 403 1.07 .705561 33.82 .705122 

85-DJ-170 ------- Tdm 147 293 1.45 .705823 

1

Tsv=Andesite of Stewart Valley; Tri=Rhyolite intrusion; Tha=Hornblende andesite; 

Tpd=Porphyritic dacite; Tba=Andesite and basaltic andesite; Tt=Tuff of Toiyabe; Tsc=Tuff of Sheep 

Canyon; Tg=Tuff of Goldyke; Toa=Older andesite sequence; Tdrn=Tuff of Davis Mine. 1

Weighted linear regression using equations of Ludwig (1987) and four samples of the tuff of 

Davis Mine. 

60 Geochemistry of Oligocene and Miocene Volcanic Rocks, Paradise Range and Northern Pactolus Hills, Nye County, Nevada 
Table 14. Chemical analyses of units in the Menter Canyon and Ellsworth sections 

[All analyses except samples 83-DJ-94, 83-DJ-95, and 83-DJ-98 by X-ray fluorescence spectroscopy (analysts: 

A Bartel, J. Kent, R. Mendes, K. Stewart, D. Siems, and J. Taggart; chemical determination of FeO, IJ,O+, IJ,Q-, 

C02 by C. Papp and S. Neil); samples 83-DJ-94, 83-DJ-95, and 83-DJ-98 analysed by rapid rock analysis 

(analyst: N. Rait). FeO*, total Fe as FeO; LOI, loss on ignition at 9000C] 

Sample number 

1 

83-Dj-26 

2 

83-Dj-27 

3 

85-Dj-1 

4 

85-Dj-2 

5 

83-Dj-94 

6 

83-Dj-50A 

Major elements normalized to 100 percent volatile-free (weight percent) 

SiO -----------------

A~63 ---------------- FeO -----------------

Fe203 ----------------

MgO ----------------

CaO -----------------

Na,_O ----------------

~0 -----------------

Ti02 -----------------

p 0 -----------------

~6 ----------------

Total (volatilefree before 

75.39 

13.13 

.13 

2.10 

.23 

.51 

3.42 

4.85 

.22 

<0.05 

.02 

75.79 

12.75 

.05 

2.07 

.14 

.30 

3.66 

5.07 

.17 

<0.05 

<0.02 

77.57 

11.71 

.07 

1.91 

.11 

.31 

3.52 

4.61 

.16 

<0.05 

.03 

77.85 

11.53 

.13 

1.82 

.25 

.71 

2.96 

4.52 

.21 

<0.05 

.02 

76.51 

12.96 

.25 

1.24 

.10 

.53 

3.11 

5.08 

.09 

.06 

.06 

75.15 

13.55 

.18 

1.39 

.39 

1.14 

3.65 

4.37 

.13 

<0.05 

.04 

7 

89-DHO 

74.10 

13.90 

1.99 

.44 

1.42 

3.65 

4.21 

.18 

.06 

.04 

normalization) - ::97::::.4::9=====9=8=.04====98::.2::4::::===97::::.::11::::===96::.::::46::::===9:::8::.8::7=====9=7=.84 

LOI ------------------

H20+ ----------------

H.,O------------------

Cb2 ------------------

F ---------------------

Cl --------------------

1.94 

.77 

.88 

<0.01 

Nb ------------------- 28 

Rb ------------------- 174 

Sr -------------------- 60 

il-------------------- 355 

y -------------------- 34 

Ba ------------------- 540 

Ce ------------------- 64 

La ------------------- 82 

Cu ------------------- <20 

Ni -------------------- <20 

Zn ------------------- 48 

Cr -------------------- <20 

K/Rb ---------------- 231 

Sr/Rb ---------------- .34 

FeO* ---------------- 2.02 

Sample descriptions 

1.13 

.40 

.71 

<0.01 

1.15 

.22 

.83 

<0.01 

2.30 

.74 

1.07 

<0.01 

2.90 

.43 

.03 

.025 

Minor elements (parts per million) 

30 

190 

28 

435 

46 

182 

116 

74 

<20 

<20 

98 

<20 

221 

.15 

1.91 

26 

168 

28 

390 

38 

168 

92 

58 

<20 

<20 

82 

<20 

228 

.17 

1.79 

18 

146 

90 

300 

28 

680 

110 

78 

<20 

<20 

82 

<20 

257 

.62 

1.77 

23 

197 

31 

203 

31 

200 

160 

68 

<20 

<20 

73 

<10 

214 

6.35 

1.37 

.75 

.05 

.40 

<0.01 

18 

188 

118 

92 

22 

220 

42 

<30 

<20 

<20 

46 

<20 

193 

.63 

1.43 

1.18 

.35 

.57 

.04 

14 

170 

180 

108 

24 

340 

30 

<30 

10 

<10 

64 

<20 

206 

1.06 

1.79 

1 (83-DJ-26) Devitrified, densely welded upper cooling unit of the tuff of Green Springs from Green 

Springs collected at lat 38°53'30"N., long ll7°46'56"W. 

2 (83-DJ-27) Devitrified, densely welded lower cooling unit of the tuff of Green Springs from Green 

Springs collected at lat 38°53'28"N., long ll7°46'45"W. 

3 (85-DJ-1) Devitrified, densely welded lower cooling unit of the tuff of Green Springs from Menter 

Canyon collected at lat 38°52'48"N., long 117°47'30"W. 

4 (85-DJ-2) Devitrified, densely welded upper cooling unit of the tuff of Green Springs from Menter 

Canyon collected at lat 38°52'47"N., long 117°47'35"W. 

5 (83-DJ-94) Vitrophyric, densely welded tuff of Menter Canyon from lower cooling unit in Menter Canyon 

collected at lat 38°54'23"N., long ll7°47'45"W. 

6 (83-DJ-50A) Devitrified, densely welded upper part of the lower cooling unit of the tuff of Camel Spring 

collected about 1 km west of Fifteenmile Spring on the east side of the Paradise Range at lat 38°53'07"N., long 

ll7°46'30"W. 

7 (89-DJ-40) Devitrified, densely welded upper part of the lower cooling unit of the tuff of Camel Spring 

collected near Fifteenmile Spring on the east side of the Paradise Range at lat 38°51 '53"N., long ll7°48'07"W. 
Table 14. Chemical analyses of units in the Menter Canyon and Ellsworth sections-Continued 

[All analyses except samples 83-DJ-94, 83-DJ-95, and 83-DJ-98 by X-ray fluorescence spectroscopy (analysts: A 

Bartel, J. Kent, R. Mendes, K. Stewart, D. Siems, and J. Taggart; chemical determination of FeO, ~Q+, ~o-. C01 by 

C. Papp and S. Neil); samples 83-DJ-94, 83-DJ-95, and 83-DJ-98 analysed by rapid rock analysis (analyst: N. Rait). 

FeO*, total Fe as FeO; LOI, loss on ignition at 900°C) 

Sample number 

8 

89-Dj-41 

9 

83-Dj-95 

10 

83-Dj-98 

11 

83-Dj-35 

12 

83-DH7 

13 

85-Dj-119A 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ----------------- 74.82 

A~ 0 3 ---------------- 13.71 

FeO -----------------

Fe20 3 ----------------

MgO ----------------

CaO -----------------

N~O ----------------

~g2 ~~~~~~~~~~~~~~~~~ P20 s -----------------

MnO ----------------

Total (volatile1.29 

.40 

1.32 

3.53 

4.69 

.14 

.05 

.04 

73.72 76.92 

14.06 12.67 

.62 .16 

1.24 1.21 

.41 .18 

1.24 .50 

3.10 3.52 

5.27 4.62 

.18 .11 

.08 .06 

.07 .05 

77.05 65.07 77.24 

12.44 18.39 12.89 

.05 .87 .38 

1.44 2.60 .70 

.13 .70 .12 

.30 4.33 .73 

3.67 4.09 3.56 

4.82 3.10 4.27 

.08 .54 .07 

<0.05 .25 <0.05 

.02 .04 .04 

14 

85-Dj-117 

76.00 

13.38 

.28 

.83 

.17 

.87 

3.48 

4.80 

.19 

<0.05 

<0.02 

free before 

normalization) - 97.03 

======================================= 

96.72 99.46 98.90 96.79 94.64 97.90 

LOI ------------------ 2.54 

H20• ---------------- 2.14 

H20------------------ .22 

C02 ------------------ .02 

F ---------------------

Cl --------------------

Nb ------------------- 12 

Rb ------------------- 176 

Sr -------------------- 15 6 

a -------------------- 92 

y -------------------- 22 

Ba ------------------- 235 

Ce ------------------- 50 

La ------------------- 38 

Cu ------------------- < 10 

Ni -------------------- < 10 

Zn ------------------- 56 

Cr -------------------- <20 

K/Rb ---------------- 221 

Sr/Rb ---------------- .90 

FeO* ---------------- 1.16 

Sample descriptions 

.68 2.81 

2.30 .55 .31 1.48 

.44 .60 .42 1.18 

.02 .06 <0.01 <0.01 

.026 .027 

Minor elements (parts per mlllion) 

12 35 34 10 

130 202 245 92 

182 42 24 690 

216 221 205 220 

21 63 42 24 

540 150 110 1,500 

160 140 78 94 

58 50 74 30 

<20 <10 <20 <20 

<20 <10 <20 <20 

68 100 94 90 

13 <10 <20 <20 

337 190 163 280 

.71 4.81 .10 7.50 

1.74 1.25 1.32 3.10 

4.82 1.18 

3.79 .37 

.74 .54 

.08 <0.05 

.020 .020 

.072 .022 

14 

148 

112 

168 

24 

870 

105 

54 

<10 

<10 

43 

<10 

269 

1.32 

1.01 1.02 

8 (89-DJ-41) Vitrophyric, densely welded basal vitrophyre of the upper cooling unit of the tuff of Camel Spring 

collected near Fifteenmile Spring on the east side of the Paradise Range at lat 38°51'53"N., long l17°48'07"W. 

9 (83-DJ-95) Vitrophyric, densely welded pumice-rich tuff. Lower cooling unit of the tuff of Gabb Valley 

collected in Menter Canyon at lat 38°54'07"N., long 117°47'23"W. 

10 (83-DJ-98) Devitrified, densely welded part of the tuff of Brunton Pass from Brunton Pass collected at lat 

38°52'18"N., long l17°44'13"W. 

11 (83-DJ-35) Devitrified, densely welded part of the tuff of Brunton Pass from Green Spring Summit collected 

at lat 38°53'20"N., long 117°47'00"W. 

12 (83-DJ-47) Devitrified, fine-grained porphyritic lava containing about 15 percent plagioclase, 2 percent 

clinopyroxene and 1 percent hornblende phenocrysts. From andesite unit that is between the tuff of Return Mine 

and the tuff of Camel Spring collected about 1 km south of Sherman Peak at Iat 38°54'05"N., long ll7°46'20"W. 

13 (85-DJ-119A) Vitrophyric, densely welded brown rhyolite tuff collected about 1 km north of Fairview Peak in 

the northern Paradise Range at lat 38°59'56"N., long 117°46'09"W. 

14 (85-DJ-117) Partially devitrified, densely welded basal part of the tuff of Big Spring collected about 1 km 

northeast of Big Spring at lat 38°59'40"N., long 117°45'09"W. 
Table 15. Chemical analyses of units in the Sheep Canyon section 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin, J. Kent, R. Mendes, K. Stewart. J. Taggart, and T. Vercoutre; chemical determination of FeO, 

Hp+, }\O-, C02

, F, and Cl by N. Elsheimer, S. Neil, C. Papp, and S. Pribble.) FeO*, total Fe as FeO; LOI, loss on ignition at 900°C] 

2 3 4 5 6 7 8 9 10 11 

Sample number 85-DJ-54 85-0J-151 88-PP-53 84-DJ-33 85-DJ-14 84-DJ-118 84-DJ-117 88-PP-52 88-PP-54 88-PP-55 88-PP-56 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ----------------- 75.50 75.07 74.61 80.93 79.39 78.92 69.59 66.86 67.14 62.48 63.64 

A~03 ---------------- 13.47 13.92 14.65 9.98 11.24 10.72 14.73 16.06 17.60 16.21 18.20 

FeO ----------------- .36 .15 .24 .12 .99 .16 .19 1.61 .25 .31 4.46 

Fe20 3 ---------------- 1.09 1.26 1.62 .79 .35 .60 3.77 3.04 3.22 5.02 .99 

MgO ---------------- .30 .32 .36 .41 .17 .25 .70 .42 <0.20 .54 .72 

CaO ----------------- 1.29 .99 .60 1.33 .33 .95 3.41 3.67 3.81 7.82 3.45 

N~O ---------------- 3.66 3.13 1.56 2.58 1.37 1.17 3.00 3.55 3.58 3.44 3.91 

~0 ----------------- 4.15 4.93 5.99 3.73 6.10 7.18 3.68 3.55 3.50 3.11 3.78 

Ti02 ----------------- .13 .22 .29 .08 .06 .05 .61 .71 .63 .64 .53 

P20S ----------------- <0.05 <0.05 .08 .05 <0.05 <0.05 .25 .29 .25 .24 .25 

MnO ---------------- .04 <0.02 <0.02 <0.02 <0.02 <0.02 .08 .25 .02 .19 .06 

Total (volatilefree before 

normalization)-- 93.51 96.97 96.24 97.98 97.87 97.95 95.71 95.87 97.71 93.15 97.26 

LOI ------------------ 5.61 2.14 3.49 1.61 1.53 1.89 4.43 3.28 1.39 6.36 3.01 

~: g: -~~~~~~~~~~~~~~~~ 3.56 .79 1.61 .41 .79 .62 1.11 1.43 .63 .93 .96 

1.64 .96 1.41 .40 .29 .34 1.72 .48 .45 1.33 1.15 

C02 ------------------ .21 .13 <0.01 .94 .25 .94 1.24 1.43 .16 3.5 .26 

F --------------------- .01 .02 - .01 <0.01 .02 .03 

Cl -------------------- .038 <0.005 - .008 .008 .012 .004 

Minor elements (parts per million) 

Nb ----------------- 14 17 14 35 - 19 8 16 12 10 14 

Rb ----------------- 345 154 150 238 - 189 96 84 92 72 102 

Sr ------------------ 287 139 80 66 - 45 453 385 620 485 550 

a------------------ 153 163 170 224 - 132 128 148 136 126 156 

y ------------------ 30 25 22 37 - 40 22 20 16 16 18 

Ba ----------------- 400 950 1,000 - - - - 1,200 990 870 920 

Ce ----------------- 75 85 50 - - - - 58 <30 58 <30 

La ----------------- 28 40 <30 - - - - <30 <30 30 <30 

Cu ----------------- < 10 <10 <20 - - - - <20 20 <20 <20 -1 

I» Ni ------------------ <10 <10 <20 - - - - <20 <20 <20 <20 c:r Zn ----------------- 56 52 96 58 42 52 50 ii" - - - - WI 

..... Cr ------------------ < 10 11 <20 - - - - <20 54 24 <20 I 

..... 

...... K/Rb -------------- 100 266 331 130 - 315 318 350 316 359 308 

~ Sr/Rb -------------- .83 .90 .53 .28 - .24 4.72 4.58 6.74 6.74 5.39 w FeO• -------------- 1.35 1.29 1.70 .83 1.30 .71 3.58 4.34 3.15 4.83 5.35 
CTI 

'"' 

C) 

I'D 

0 

l"l 

::r 

I'D 

3 

~-

-< 

0 

-

Q 

o"Q' 

0 

l"l 

I'D 

I'D = 

I» 

= Cl.. 

~ 

c:;· 

l"l 

I'D 

I'D = 

< 0 

rr 

I» 

;::;· = 

;lie 

0 

l"l 

F 

""1:::1 

I» 

.. 

~ ;· 

I'D 

;lie 

I» 

OQ = 

I'D 

I» 

= Cl.. 

z 

0 

.. 

;. 

I'D 

.. 

= 

""1:::1 

I» 

l"l 

8' 

c 

Cll 

~ 

F 

z 

~ 

Q 

c 

a 

-:c 

z 

I'D 

< 

!. 

I» 

Table 15. Chemical analyses of units in the Sheep Canyon section-Continued 

Sample descriptions 

1 (85-DJ-54) Densely welded, vitrophyric lapilli tuff. Part of the Tuff unit of John (1988) collected about 2 km north of the Paradise Peak mine at lat 38°45'57"N., long 

117°59'20"W. 

2 (85-DJ-151) Densely welded devitrified pan of the tuff of Goldyke collected in the northern Pactolus Hills at lat l17°59'20"N., long 117°48'36"W. 

3 (88-PP-53) Densely welded devitrified part of the tuff of Goldyke collected on the east side of Newmans Ridge at lat 38°45'16"N., long ll7°59'18"W. 

4 (84-DJ-33) Devitrified, weakly brecciated densely welded ash-flow tuff. Part of the red tuff unit of John (1988) collected in Sheep Canyon at lat 38°48'21"N., long 

117°56'12"W. 

5 (85-DJ-14) Devitrified, densely welded ash-flow tuff. Part of the red rhyolite tuff unit of John (1988) collected in Sheep Canyon at lat 38°46'44"N., long 117°54'33"W. 

6 (84-DJ-118) Devitrified, densely welded ash-flow tuff. Part of the red rhyolite tuff unit of John (1988) collected in Sheep Canyon at lat 38°46'22"N., long 117°54'40"W. 

7 (84-DJ-117) Devitrified, sparsely porphyritic dacite flow breccia. Pan of the blue-gray dacite breccia unit of John (1988) collected in Sheep Canyon at lat 38°46'22"N., long 

117°54'57"W. 

8 (88-PP-52) Devitrified, sparsely porphyritic dacite flow breccia. Pan of the blue-gray dacite breccia unit of John (1988) collected on the east side of Newmans Ridge at lat 

38°45'20"N., long 117°59'16"W. 

9 (88-PP-54) Weakly propylitized, moderately porphyritic hornblende-biotite-plagioclase dacite lava flow. Part of the rhyodacite to andesite unit of John (1988) collected on 

the north side of Newmans Ridge at lat 38°45'26"N., long 117°59'40"W. 

10 (88-PP-55) Weakly propylitized, moderately porphyritic hornblende-biotite-plagioclase dacite lava flow. Part of the rhyodacite to andesite unit of John (1988) collected on 

the north side of Newmans Ridge at lat 38°45'26"N., long 117°59'41"W. 

11 (88-PP-56) Weakly propylitized, moderately porphyritic hornblende-biotite-plagioclase dacite lava flow. Part of the rhyodacite to andesite unit of John (1988) collected on 

the north side of Newmans Ridge at lat 38°45'26"N., long ll7°59'42"W. 
Table 16. Chemical analyses of the lower white tuff 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, M. Dyslin. J. Kent, R. Mendes, K. Stewart, J. Taggart, and T. Vercoutre; chemical determination of 

FeO, ~0+, ~o-. C02

, and F by N. Elsheimer, S. Neil, C. Papp. and S. Pribble). FeO*. total Fe as FeO; LOI. loss on ignition at 900°C] 

1 2 3 4 5 6 7 8 9 10 11 

Sample number 84-0j-200 84-0j-204 85-0j-133 85-0j-58 88-0j-69 88-0j-70 88-PP-57 88-PP-58 88-PP-59 88-PP-60 88-PP-61 

Major elements normalized to 100 percent volatile-free (weight percent) 

Si02 ----------------- 76.71 79.76 76.32 77.84 76.87 76.83 77.91 77.86 78.64 75.05 76.39 

A~03 ---------------- 13.05 13.09 13.19 12.80 13.24 13.07 14.02 14.20 13.91 14.25 15.28 

FeO ----------------- .31 .16 .28 .33 .22 .18 .06 .07 .09 .33 .10 

Fe20 3 ---------------- .89 .26 .77 .62 .97 1.13 .65 .82 .41 1.43 .52 

MgO ---------------- .28 .18 .17 .16 <0.20 <0.20 <0.20 <0.20 <0.20 <0.20 <0.20 

CaO ----------------- 1.11 .13 .75 .54 1.22 1.26 .44 .25 .25 1.49 .35 

Na20 ---------------- 2.92 .89 3.32 3.96 3.31 2.95 1.04 .89 .95 1.40 1.14 

~0 ----------------- 4.57 5.44 5.03 3.63 3.91 4.26 5.73 5.78 5.59 5.79 5.99 

Ti02 ----------------- .11 .09 .12 .07 .13 .13 .10 .10 .12 .17 .19 

P20S ----------------- <0.05 <0.05 <0.05 <0.05 .02 .04 .04 .02 .04 .04 .04 

MnO ---------------- .05 <0.02 .05 .05 .12 .15 <0.02 <0.02 <0.02 .04 <0.02 

Total (volatilefree before 

normalization) - 94.25 97.04 95.52 93.78 93.67 94.88 96.27 96.46 97.03 92.61 96.22 

WI------------------ 5.74 2.81 3.95 5.44 6.24 4.49 3.10 3.05 2.85 6.73 3.35 

H20+ ---------------- 2.68 2.00 2.82 4.34 3.17 1.73 1.55 1.69 1.81 3.30 1.94 

H2o------------------ 2.59 .66 .79 .80 2.47 2.11 .72 .62 .41 2.68 .52 

C02 ------------------ .21 .07 .13 .07 .04 <0.01 .08 <0.01 .21 .06 .13 

F --------------------- .030 .030 .020 .010 

Trace elements (parts per million) 

Nb ------------------- 14 17 16 15 22 18 18 20 20 20 20 

Rb -------------------255 181 224 262 295 154 174 178 166 186 168 

Sr --------------------175 26 57 51 94 118 10 16 20 305 24 

Zr -------------------- 139 180 140 117 138 138 128 136 144 200 172 

y -------------------- 26 21 26 27 30 22 18 22 20 26 22 

Ba ------------------- - - 235 76 164 245 106 120 220 1,300 360 

Ce ------------------- - - 88 75 <30 80 46 68 58 64 110 

La ------------------- - - 37 36 <30 44 <30 <30 <30 36 44 

Cu ------------------- - - <1 <1 <20 <20 <20 <20 <20 <20 <20 

Ni -------------------- - - <1 0 <20 <20 <20 <20 <20 <20 <20 -1 

Dl Zn ------------------- - - 75 57 56 56 30 30 <20 118 <20 "a" Cr -------------------- - 6 0 <20 <20 <20 <20 <20 <20 <20 ~ -

.... 

.... 

I K/Rb ----------------149 250 186 115 110 229 274 270 279 258 296 ..... Sr/Rb --------------- .69 .14 .25 .19 .32 .77 .06 .09 .12 1.64 .14 

Cl"' FeO* ---------------- 1.11 .40 .98 .89 1.10 1.19 .65 .81 .46 1.62 .57 U1 
0'1 

0'1 

~ 

11'1 

Q 

n 

:r 

11'1 

3 

s: 

.. 

"< 

Q 

-

Q 

;· 

n 

11'1 

= 11'1 

I» 

= c.. 

~ 

c;· 

n 

11'1 

11'1 = 

< Q 

rr 

I» 

= r;· 

~ 

Q 

n 

~ .., 

I» 

i 

;;· 

11'1 

:IICI 

I» 

, = 

~ c.. 

z 

Q 

:=. 

:r 

11'1 

.. 

.., = 

~ 

Q 

c 

WI 

~ 

F 

z 

"< 11'1 

(') 

Q 

c 

~ =-

z 

11'1 

< !. 

I» 

Table 16. Chemical analyses of the lower white tuff-Continued 

Sample descriptions 

1 (84-DJ-200) Densely welded, basal vitrophyre from Newman's Ridge collected at lat 38°45'16"N., long ll7°59'20"W. 

2 (84-DJ-204) Devitrified, moderately welded tuff from Newman's Ridge collected at lat 38°45'28"N., long ll7°59'29"W. 

3 (85-DJ-133) Densely welded, basal vitrophyre from northern Pactolus Hills collected at lat 38°45'15"N., long ll7°48'13"W . 

4 (85-DJ-58) Densely welded basal vitrophyre from the northern end of Newman's Ridge collected at lat 38°45'23"N., long ll7°59'30"W. 

5 (88-DJ-69) Densely welded basal vitrophyre from the Poleline Road collected at lat 38°47'12"N., long ll7°57'33"W. 

6 (88-DJ-70) Densely welded basal vitrophyre from the Poleline Road collected at lat 38°47'12"N., long ll7°57'32"W. 

7 (88-PP-57) Devitrified, moderately welded tuff from east side of Newman's Ridge collected at lat 38°45'24"N., long ll7°59'30"W. 

8 (88-PP-58) Devitrified, moderately welded tuff from east side of Newman's Ridge collected at lat 38°45'24"N., long ll7°59'30"W. 

9 (88-PP-59) Devitrified, moderately welded tuff from east side of Newman's Ridge collected at lat 38°45'20"N., long ll7°59'29"W. 

10 (88-PP-60) Densely welded, basal vitrophyre from the east side of Newman's Ridge collected at lat 38°45'18"N., long l17°59'22"W. 

11 (88-PP-61) Devitrified, moderately welded tuff from east side of Newman's Ridge collected at lat 38°45'19"N., long ll7°59'32"W. 
Table 17. Chemical analyses of the tuff of Sheep Canyon 

[All analyses by X-ray fluorescence spectroscopy (analysts: A. Bartel, J. Kent, R. Mendes, D. Siems, K. Stewart, and J. 

Taggart; chemical determination of FeO, ~()+, ~o-. C02

, F, and Cl by N. Elsheimer and S. Neil.) FeO*, total Fe as FeO; 

LOI, loss on ignition at 900°C) 

1 2 3 4 5 6 7 

Sample number 84-DJ-119 84-DJ-120 84-DJ-121 84-Dj-126 85-DJ-13 85-Dj-167G 85-DJ-167j 

Major elements normalized to 100 percent volatile-free (weight percent) 

SiO ----------------- 72.54 68.05 69.48 69.12 70.09 69.88 67.93 

A~63 ---------------- 14.47 16.09 15.74 15.99 15.60 15.59 16.17 

FeO ----------------- .30 .60 .26 .34 .35 .45 .51 

Fe20 3 ---------------- 1.91 2.56 2.75 2.52 2.44 2.71 2.82 

MgO ---------------- .46 .76 .46 1.01 .50 .91 .98 

CaO ----------------- 1.50 3.17 2.89 3.32 2.63 2.57 3.02 NhO ---------------- 3.41 3.41 3.09 2.84 3.48 3.17 3.80 

~ ----------------- 5.11 4.82 4.75 4.05 4.43 4.14 4.02 

Ti02 ----------------- .23 .40 .40 .54 .36 .39 .42 

~6 -~~~~~~~~~~~~~~~~ .07 .14 .16 .13 .12 .14 .26 

<0.02 <0.02 .03 .14 <0.02 .04 .08 

Total (volatilefree before 

normalization)- 96.78 98.17 97.87 93.17 97.45 96.88 98.34 

LOI ------------------ 2.63 1.71 1.94 5.46 1.34 2.58 .92 

H20+ ---------------- .81 .54 .73 1.40 .55 .93 .45 

H20------------------ 1.01 .52 .50 2.84 .42 1.34 .31 

C02 ------------------ .75 .58 .55 .99 .28 .05 .05 

F --------------------- .05 .04 .04 .03 .01 

Cl-------------------- .009 .021 .007 .007 .010 

Minor elements (parts per mlllion) 

Nb ------------------- 18 12 <10 12 14 10 <10 

Rb ------------------- 160 148 177 116 131 130 116 

Sr -------------------- 164 450 328 274 412 405 520 

Zc -------------------- 236 146 130 250 155 140 166 

y -------------------- 29 21 18 22 20 16 12 

Ba ------------------- 1,900 1,275 1,100 1,400 

Ce ------------------- 76 95 54 36 

La ------------------- 56 55 50 <30 

Cu ------------------- <20 <20 <20 <20 

Ni -------------------- <20 <20 <20 <20 

Zn ------------------- 65 43 40 44 

Cr -------------------- <20 <20 <20 <20 

K/Rb ---------------- 265 270 223 290 281 264 287 

Sr/Rb --------------- 1.03 3.04 1.85 2.36 3.15 3.12 4.48 

FeO* ---------------- 2.02 2.90 2.73 2.61 2.55 2.89 3.05 

Sample descriptions 

1 (84-DJ-119) Devitrified, densely welded tuff from the lower part of the second cooling unit collected in Sheep Canyon at 

lat 38°46'24"N., long 117°54'37"W. 

2 (84-DJ-120) Devitrified, densely welded tuff from the lower part of the third cooling unit collected in Sheep Canyon at 

lat 38°46'28"N., long 117°54'34"W. 

3 (84-DJ-121) Devitrified, densely welded tuff from the lower part of the fourth cooling unit collected in Sheep Canyon at 

lat 38°47'53"N., long ll7°54'32"W. 

4 (84-DJ-126) Devitrified, densely welded tuff from the second cooling unit collected in Sheep Canyon at lat 38°48'34"N., 

long 117°55'32"W. 

5 (85-DJ-13) Devitrified, densely welded tuff from the second cooling unit collected in Sheep Canyon at lat 38°46'48"N., 

long ll7°54'33"W. 

6 (85-DJ-167G) Devitrified, densely welded tuff from the middle part of the third cooling unit collected in Sheep Canyon at 

lat 38°46'28"N., long 117°54'32"W. 

7 (85-DJ-1671) Devitrified, densely welded tuff from the upper part of the third cooling unit collected in Sheep Canyon at 

lat 38°46'28"N., long ll7°54'30"W. 

Tables 1-17 67 



SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS 

Periodicals 

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly). 

Technical Books and Repons 

Professional Papers are mainly comprehensive scientific reports of 

wide and lasting interest and importance to professional scientists and engineers. Included are reports on the results of resource studies and of 

topographic, hydrologic, and geologic investigations. They also include 

collections of related papers addressing different aspects of a single scientific topic. 

Bulletins contain significant data and interpretations that are of lasting scientific interest but are generally more limited in scope or 

geographic coverage than Professional Papers. They include the results 

of resource studies and of geologic and topographic investigations; as well 

as collections of short papers related to a specific topic. 

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrogeology, 

availability of water, quality of water, and use of water. 

CII'culars present administrative information or important scientific 

information of wide popular interest in a format designed for distribution 

at no cost to the public. Information is usually of short-term interest. 

Water-Resources Investigations Reports are papers of an interpretive nature made available to the public outside the formal USGS publications series. Copies are reproduced on request unlike formal USGS 

publications, and they are also available for public inspection at 

depositories indicated in USGS catalogs. 

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at 

depositories. They are a nonpermanent form of publication that may be 

cited in other publications as sources of information. 

Maps 

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 7 1/2- or 15-minute quadrangle formats (scales mainly 1:24,000 or 1 :62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only. 

Geophysical Investigations Maps are on topographic or planimetric 

bases at various scales; they show results of surveys using geophysical 

techniques, such as gravity, magnetic, seismic, or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology. 

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 7 1/2-minute quadrangle photo geologic maps on planimetric bases 

which show geology as interpreted from aerial photographs. Series also 

includes maps of Mars and the Moon. 

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy, and structural relations in certain coal-resource areas. 

Oil and Gas Investigations Charts show stratigraphic information 

for certain oil and gas fields and other areas having petroleum potential. 

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations. 

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric., bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; principal scale 

is 1:24,000 and regional studies are at 1:250,000 scale or smaller. 

Catalogs 

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List) 

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982, 1983, 1984, 1985,1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form. 

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only. 

"Price and Avallablllty List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only. 

Selected copies of a monthly catalog "New Publications of the U.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092. 

Note.--Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.