oming

tr.s, GEOLOGICAL .SURVEY PROFESSIONAL PAPER io54-e
Hydrothermal Alteration in 

Research Drill Hole Y-3, 

Lower Geyser Basin, 

Yellowstone National Park, 

Wyoming

By KEITH E. BARGAR and MELVIN H. BEESON

HYDROTHERMAL STUDIES IN YELLOWSTONE NATIONAL PARK, WYOMING

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1054-C

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1985
DEPARTMENT OF THE INTERIOR

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Bargar, Keith E.

Hydrothermal alteration in research drill-hole Y-3, Lower Geyser Basin, Yellowstone National Park, Wyoming

(U.S. Geological Survey Professional Paper 1054-C)

Bibliography

Supt. of Docs. No.: I 19.16:1054-C

1. Hydrothermal deposits Wyoming Lower Geyser Basin. 2. Hydrothermal deposits Yellowstone National Park. 3. Borings 

Wyoming Yellowstone National Park. 5. Yellowstone National Park. I. Beeson, Melvin H. II. Title. III. Series: United States.

Geological Survey. Professional Paper 1054-C

QE390.5B37 1985 552'.5 85-600249

For sale by the Distribution Branch, Text Products Section, 

U.S. Geological Survey, 604 South Pickett St., Alexandria, VA 22304
CONTENTS

Abstract ________________________________ Cl

Introduction _____________________________ 1

Acknowledgments ___________________________ 2

Stratigraphy ———————————_________———— 2

Surficial deposits ________________________ 2

Volcanic rocks ________ _ ________________ 4

Hydrothermal alteration mineralogy ________________ 4

Silica minerals __________________________ 5

Opal and p-cristobalite ——_______———————— 5

Quartz and chalcedony ___________________ 5

Zeolite minerals _____________ _ _ _ _______ 5

Analcime ———————————________________ 5 

Clinoptilolite ________________________ 10 

Dachiardite _________________________ 10 

Laumontite _ _________________________ 11 

Mordenite _____________________ 11

Yugawaralite ———————________________ 12

Stilbite ____________________________ 12

Calcite _______________________________ 12

Hydrothermal alteration mineralogy—Continued

Fluorite _____________________________ C13

Clay and mica minerals ————————————————————— 13

Kaolinite ——————————————————————————— 13

Halloysite and allophane _————————————————— 14

Chlorite ____________________________ 14

Smectite ——————————————————————————— 15

Illite-smectite —————————————————--————— 15

Lepidolite —————————————————————--——— 15

Aegirine _______——_—————————- —————— - 15

Pectolite ________________—————————————— 15

Truscottite _———————————————————————————— 16

Sulfate minerals ——————————————— — ———————— 16

Gypsum ——— —— —— —— —— ———————————— — 1 6

Alunite _____-—__————————————————- 17

Hematite ___———————————————-- ———— — -- 17

Pyrite ____——————————————————————————— 17

Summary and discussion _ —— —— —— ————————————— 18

References cited ———————————————————————————— 21

ILLUSTRATIONS

FIGURE 1. Map of Lower Geyser Basin showing locations of Y-3 and other research drill holes ———___———————————————— C2

2. Plot showing depth distribution of unaltered obsidian, a-cristobalite, and hydrothermal alteration minerals from

drill core Y-3 ________________________________________________________________ 3

3. Scanning electron micrograph of euhedral, trapezohedral analcime crystals ___________________——————— 5

4. Scanning electron micrograph of intergrown tabular clinoptilolite crystals ___——______———————————————— 10

5. Ca-Na-K ternary diagram for heulandite-group zeolites from Yellowstone drill cores ———————————————————————— 10

6. Scanning electron micrograph of a large radiating cluster of dachiardite crystals ______ _______ _____————_ 11

7. Scanning electron micrograph of cavity filling __ __________________________________—— ——— —— 11

8. Ca-Na-K ternary diagram for Y-3 dachiardite compared with other published dachiardite analyses ————_ — —————— _ 11

9. Scanning electron micrograph of laumontite crystals _____________—________ — ——— —— —— —— — 12

10. Scanning electron micrograph of fibrous mordenite crystals ____ — __ — _ ——————— _ ——————— —— _—————— 12

11. Ca-Na-K ternary diagram for microprobe chemical analyses of mordenite _____________________ ———————— 13 

12-15. Scanning electron micrographs of:

12. Euhedral crystals of yugawaralite ____________________———————__—————————————————— 13

13. Blocky stilbiteC?) crystals ____________________________________________________— 13

14. A polycrystalline mat of lepidolite crystals ——__—————————————_ — —————— — _——————————— 15

15. Clusters of aegirine crystals _________________________________________————————— 16

16. Ac —Jd-Di + Hd ternary diagram for aegirine _____________________————____———————————————— 16

17. Scanning electron micrographs of fibrous and bladed pectolite —————————————__ —— — _ — __ ————————— — 18

18. Scanning electron micrograph of tabular, hexagonal crystals of truscottite ______ ___________ - —————————— 18

19. CaO-Al2O3-SiO2 molecular-proportion ternary diagram for truscottite __————————_——————————————————— 18

20. Scanning electron micrograph of pyrite needlelike crystals ______ _ __ __________________ ___—————- 19

21. Generalized paragenetic sequence of principal hydrothermal minerals in drill core Y-3 _ _________ ——————————— 19

22. A-F-M and Na2O-K2O-CaO ternary diagrams for altered volcanic rocks and glacial sediments from drill core Y-3 —————— 21

23. Plot of fluid-inclusion homogenization temperatures in quartz and fluorite crystals from drill core Y-3 ————————————— 21

III
IV

TABLES

Page 

TABLE 1. Chemical composition, pH, temperature, and calculated geothermometers of thermal water from Y-3 drill hole

compared with values from nearby Ojo Caliente Hot Spring ——————————————————————————————————— C 4

2. Chemical composition of some zeolite minerals from Y-3 drill core———————————————————————————————————— 6

3. Microprobe analyses of dachiardite from Y-3 drill core _____________————————————————————————————— 8

4. Chemical composition of chlorite from 108.3 m in drill core Y-3 ________———————————————————————————— 14

5. Microprobe analyses of aegirine from Y-3 drill core ____——————————————————————————————————————— 17

6. Microprobe analyses of truscottite from 88.6 m in drill core Y-3————————————————————————————————————— 19
HYDROTHERMAL STUDIES IN YELLOWSTONE NATIONAL PARK, WYOMING

HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, 

LOWER GEYSER BASIN, YELLOWSTONE NATIONAL PARK, WYOMING

By KEITH E. BARGAR and MELVIN H. BEESON

ABSTRACT

Y-3, a U.S. Geological Survey research diamond- drill hole in Lower 

Geyser Basin, Yellowstone National Park, Wyoming, reached a depth of 

156.7 m. The recovered drill core consists of 42.2 m of surficial (mostly 

glacial) sediments and two rhyolite flows (Nez Perce Creek flow and an 

older, unnamed rhyolite flow) of the Central Plateau Member of the 

Pleistocene Plateau Rhyolite. Hydrothermal alteration is fairly extensive in 

most of the drill core. The surficial deposits are largely cemented by silica 

and zeolite minerals; and the two rhyolite flows are, in part, bleached by 

thermal water that deposited numerous hydrothermal minerals in cavities 

and fractures. Hydrothermal minerals containing sodium as a dominant 

cation (analcime, clinoptilolite, mordenite, Na-smectite, and aegirine) are 

more abundant than calcium-bearing minerals (calcite, fluorite, Ca-smectite, and pectolite) in the sedimentary section of the drill core. In the 

volcanic section of drill core Y-3, calcium-rich minerals (dachiardite, laumontite, yugawaralite, calcite, fluorite, Ca-smectite, pectolite, and truscottite) are predominant over sodium-bearing minerals (aegirine, mordenite, 

and Na-smectite). Hydrothermal minerals that contain significant 

amounts of potassium (alunite and lepidolite in the sediments and illitesmectite in the rhyolite flows) are found in the two drill-core intervals. Drill 

core Y-3 also contains hydrothermal silica minerals (opal, fJ-cristobalite, 

chalcedony, and quartz), other clay minerals (allophane, halloysite, 

kaolinite, and chlorite), gypsum, pyrite, and hematite. The dominance of 

calcium-bearing hydrothermal minerals in the lower rhyolitic section of the 

Y-3 drill core appears to be due to loss of calcium, along with potassium, 

during adiabatic cooling of an ascending boiling water.

INTRODUCTION

Research diamond-drill hole Y-3 is one of 13 holes completed by the U.S. Geological Survey at selected sites in 

hot-spring and geyser areas of Yellowstone National Park 

(fig. 1). The holes were drilled in 1967 and 1968 in order to 

obtain detailed physical and chemical data on the shallow 

part of a high-temperature geothermal system (White and 

others, 1975). Drill hole Y-3 is located at the western margin of the Pocket Basin hydrothermal explosion crater 

debris ridge (Muffler and others, 1971). The drill-hole surface occurs at an elevation of ~2,193 m; Y-3 is about 76 m 

north of and 2 m higher than Ojo Caliente Hot Spring, a 

major thermal feature in the area (White and others, 

1975).

Drilling of Y-3 (using water as the circulating fluid) 

began on June 8, 1967, and was terminated on June 28, 

1967, after reaching a depth of 156.7 m. The drill hole was 

later plugged with cement in 1969. The core diameter is 

10.2 cm for the interval from the surface to 9.8 m, 6.0 cm for

the interval from 9.8 to 27.4 m, and 4.4 cm for the interval 

from 27.4 m to the drill-hole bottom. Core recovery, accomplished by wire-line method, averaged 65 percent from the 

surface to 28.7 m, only 3 percent from 28.5 to 41.1 m, and 94 

percent in the remainder of the drill hole.

The drill core, which was usually obtained in 1.5- or 3-m 

intervals, was logged at the drill site by R.O. Fournier, A.H. 

Truesdell, and D.E. White as soon as possible following 

core recovery. At that time approximately 370 pieces of 

drill core were selected for detailed laboratory study on the 

basis of being representative of an interval or because of 

secondary mineral deposits in veins, vugs, or fractures. 

This "skeleton" core was systematically studied by optical 

(44 thin sections and polished thin sections), X-ray diffraction (more than 700 X-ray diffractograms), electron microprobe, and scanning electron microscope (SEM) methods. 

Whole-rock chemical analyses by rapid rock methods and 

semiquantitative spectrographic analyses for 16 selected 

Y-3 core samples are reported in Beeson and Bargar (1984). 

Bulk-rock and powdered-rock density measurements were 

also obtained for these 16 core samples. Two of the more 

abundant hydrothermal minerals (chlorite and laumontite) were concentrated by heavy liquids for conventional 

rock analysis.

Physical data for the 13 Yellowstone research drill holes 

are reported in White and others (1975). The highest temperature recorded in Y-3 was 196.0 °C at a depth of 

—150.6 m (fig. 2), and the maximum near-bottom fluid 

pressure was —1,497 kPa.

Bargar and others (1973) indicate that the Y-3 drill 

hole encountered at least two major water-producing 

zones at depths of 28 and 88 m, and they provide a 

chemical analysis of the slightly alkaline water from the 

88-m aquifer (table 1, column 2). More recently a chemical analysis of water from the bottom of the Y-3 drill hole 

was reported by Keith and others (1983), and the analysis is reproduced here in table 1, column 1. This water is 

slightly more concentrated in the major constituents 

(Na, HCO3 , and Cl) than water from the 88-m aquifer. 

Silica was not reported in either of the two analyses; 

however, SiO2 (along with Na, HCO3, and Cl) is one of 

the four main components of nearby Ojo Caliente Hot 

Spring water (table 1, column 3) (Thompson and Yadav, 

1979).

Cl
C2 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

Norris 

Geyser /Y-12 Basin 5^f:n

! ^Y-9

44°30' -

FIGURE 1.—Map of Lower Geyser Basin showing locations of Y-3 and 

other research drill holes. Index map of Yellowstone National Park 

shows the locations of Lower Geyser Basin, drill holes Y-1 through 

Y-13 drilled by U.S. Geological Survey in 1967 and 1968, and drill 

holes C-1 and C-II drilled by the Carnegie Institution of Washington 

in 1929 (Fenner, 1936).

ACKNOWLEDGMENTS

The authors would like to thank T.E.C. Keith and D.E. 

White for their critical reviews and helpful discussion of 

the manuscript. R.L. Oscarson assisted in obtaining 

SEM micrographs, and L.J.R Muffler provided us with 

his notes on the petrography of some of the Y-3 drill core.

STRATIGRAPHY

SURFICIAL DEPOSITS

The upper 1.6 m of Y-3 drill core consists of buff-towhite clayey (smectite and kaolinite) alluvial soil that 

contains some sand-sized grains of black spherical obsidian and clear botryoidal opal and angular-to-subrounded light-gray rhyolite pebbles.

Between 1.6 and 42.2 m the drill core is composed of 

red, brown, gray, or green hydrothermally cemented 

siltstone, sandstone, and conglomerate. The massive to 

thinly bedded sediments have dips that range from horizontal (perpendicular to drill core that is presumed to be 

vertical) to about 30°; several samples display crossbedding or contorted bedding. The conglomeratic material 

is poorly sorted and contains mostly rhyolite and obsidian clasts, although a few samples have sandstone pebbles. These sediments were deposited during the 

Pinedale glacial episode (^45,000-14,000 years B.P.)
INTRODUCTION C3

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SILICA ZEOLITES CLAYS AND MICA

FIGURE 2.—Plot showing depth distribution of unaltered obsidian, a-cristobalite, and hydrothermal alteration minerals from drill core Y-3. Left 

column shows a generalized stratigraphic section of rock units penetrated by the drill hole. The unnamed rhyolite flow and the Nez Perce Creek 

rhyolite flow are included in the Central Plateau Member of the Plateau Rhyolite. Horizontal lines adjacent to left column represent distribution of 

samples studied. Only a few core fragments and drill cuttings were recovered between 28.5 and 41.1 m, and the distribution of hydrothermal 

minerals in the interval, as suggested by these few samples, is shown by vertical dotted lines. Width of mineral columns given as an estimate of 

relative abundance based on X-ray diffraction analyses and microscopic observations. Vertical continuity in mineral presence between samples is 

assumed except where a mineral abundance becomes zero, in which case the zero point is arbitrarily placed 0.3 m from the last occurrence of the 

mineral. Dashed curve connects bottom-hole temperature measurements obtained as drilling progressed. Solid curve shows reference boiling 

temperature for pure water assuming a surface altitude of —2,329 m and a water table at the surface. Temperature data from White and others 

(1975).
C4 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

TABLE 1. - Chemical composition (in milligrams per liter), pH, temperature, and 

calculated geothermometers (in degrees Celsius) of thermal water from Y-3 

drill hole compared with values from nearby Ojo Caliente Hot Spring 

(Analyst: R.B. Barnes. Geothermometers calculated from formulas in table 

4.1 of Fournier (1981)]

Date collected —— - 

Temperature (°C)~

Si0 2 - - —

Y_ 3 1 

156.7 

9/25/68

8.4

Y-32 

88

174 

8.12

.1

Ojo 

Caliente 

Hot Spring2

6/10/67 

95 

8.31

230 

1.0 

.18

Recalculated 

hot-spring 

water'- 3

92

. 12

1 /, «

Mg296

14

3.6

216

290

.21 

.44

TSi02 (adiabatic)- 

TNa/K (Fournier)— 160 

TNa/K (TruesdelO- 119 

TNa-K-Ca———————— 172

.02

270

11

3.5

177

19.1

278

30

3.6

150

108

166

.02

317

9.2

4.5

249

27

331

33

176

130

84

153

.02

318

13

4.1

208

22.5

327

35

4.2

151

108

167

and others (1983). Ca value from original unpublished analysis

2 Bargar and others (1973), Fourn

Calculated, ideal composition of Ojo Caliente Hot Spring water fr

(Muffler and others, 1971; Waldrop and Pierce, 1975; 

Pierce and others, 1976; Muffler and others, 1982). 

Hydrothermal alteration is extensive in samples 

recovered throughout most of the interval, and hydrothermal minerals include opal, p-cristobalite, quartz, 

chalcedony, analcime, clinoptilolite, mordenite, calcite, 

fluorite, allophane, halloysite, kaolinite, chlorite, smectite, lepidolite, aegirine, pectolite, gypsum, alunite, 

pyrite, and hematite.

VOLCANIC ROCKS

From 42.2 to 71.2 m the drill core penetrated the Nez 

Perce Creek rhyolite flow of the Central Plateau Member of the Pleistocene Plateau Rhyolite (Christiansen 

and Blank, 1974), which was extruded about 150,000 

years ago (Waldrop and Pierce, 1975; White and others, 

1975; Leeman and Phelps, 1981). Core samples from the 

Nez Perce Creek flow frequently consist of bleached 

rhyolite flow or flow breccia that is extensively fractured 

and in some places is quite vesicular. Predominant magmatic minerals are quartz and sanidine; pyroxene, plagioclase, and magnetite are minor constituents. 

Evidence for vapor-phase mineralization is sparse, 

although a few cavities contain hydrothermal quartz 

druses that appear to be pseudomorphous after vaporphase alkali feldspar crystals. Spherulitic or microspherulitic textures are common throughout the 

rhyolite flow, but a-cristobalite, which frequently forms 

due to devitrification of cooling rhyolite flows, is rare 

and apparently has been recrystallized to quartz. 

Hydrothermal quartz and chalcedony are abundant on 

fractures and as vesicle fillings throughout much of this 

core interval. Other open-space hydrothermal minerals 

identified in the Nez Perce Creek flow include mordenite, dachiardite, aegirine, pectolite, calcite, fluorite, 

smectite, illite-smectite, chlorite, kaolinite, hematite, 

pyrite, and a 10-A mica(?).

Below 71.2 m is an older, unnamed rhyolite flow that 

apparently is not exposed anywhere at the surface 

within the Yellowstone Caldera. This flow is also correlated with the Central Plateau Member of the 

Pleistocene Plateau Rhyolite by Christiansen and 

Blank (1974). The unnamed rhyolite flow is probably not 

much older than the Nez Perce Creek flow because all of 

the lava flows of the Central Plateau Member were 

extruded about 200,000-70,000 years ago (Christiansen and Blank, 1972). In drill core Y-3, this unnamed 

rhyolite flow displays conspicuous flow banding and vesicularity. Quartz and sanidine are the most abundant 

magmatic minerals, and pyroxene, plagioclase, and 

magnetite are minor primary constituents. No vaporphase or devitrification minerals were identified, 

although parts of the drill core have a spherulitic texture. The core is extensively fractured, and hydrothermal minerals are quite abundant as vesicle and fracture 

fillings, to the extent that many of the fractures are 

completely self-sealed. Hydrothermal minerals found in 

this partially bleached rhyolite flow include quartz, 

chalcedony, dachiardite, laumontite, mordenite, 

stilbite, yugawaralite, truscottite, calcite, fluorite, 

smectite, illite-smectite, illite, chlorite, pyrite, and 

hematite.

HYDROTHERMAL ALTERATION 

MINERALOGY

Figure 2 shows the distribution of unaltered obsidian, 

devitrification a-cristobalite, and hydrothermal minerals (opal, p-cristobalite, quartz, chalcedony, analcime, 

clinoptilolite, dachiardite, laumontite, mordenite, calcite, fluorite, kaolinite, halloysite, chlorite, smectite, 

illite-smectite, lepidolite, aegirine, pectolite, gypsum, 

pyrite, and hematite) with depth in the Y-3 drill core. 

Vapor-phase, magmatic, and a few hydrothermal minerals with only minor distribution in the drill core 

(stilbite, yugawaralite, allophane, truscottite, and 

alunite) are not shown in the figure.

The only unaltered obsidian occurs in the coarsegrained sediments of the upper 10 m of the drill core.
HYDROTHERMAL ALTERATION MINERALOGY C5

Below that depth, clastic obsidian grains are altered to 

clinoptilolite and smectite.

SILICA MINERALS

OPAL AND P-CRISTOBALITE

Sediments in the upper 14.0 m of the drill core are 

mostly cemented by clear-to-grayish opal. Opal also 

occurs in a few veins and vugs where the mineral usually has a botryoidal habit; however, one cavity at 4.7 m 

is partly filled by brown banded opal that grades upward 

to clear hyalite. X-ray diffraction analyses of two samples at 10.8 and 18.9 m show the presence of (3- 

cristobalite associated with opal cement in the shallower deposit and a chalcedony vein in the deeper sample.

QUARTZ AND CHALCEDONY

Red-to-brown, green, and white-to-clear chalcedony 

occurs throughout most of the Y-3 drill core below 

18.9 m. The cryptocrystalline silica was deposited as 

botryoidal, irregular-to-massive, or horizontally layered 

cavity and fracture fillings. In addition, chalcedony 

forms the cementing material for a few pieces of conglomerate or brecciated drill core. It also appears to be 

the earliest hydrothermal mineral deposited in the Y-3 

drill core, although some early chalcedony contains disseminated, minute pyrite crystals. A few chalcedony 

cavity fillings display microscopic convoluted bedding. 

Similar sedimentary structures in chalcedony cavity 

and fracture fillings of drill core Y-5 were interpreted by 

Keith and Muffler (1978) as being deposits of amorphous 

silica floe (opal) that later recrystallized to chalcedony.

Tiny (usually less than about 3 mm), clear quartz 

crystals are sparse to absent above 41.8 m, but the 

radiating crystal clusters are deposited in cavities and 

on fractures throughout most of the remainder of the 

drill core. Crystalline quartz appears to be an early 

hydrothermal mineral and probably was deposited 

shortly after the deposition of chalcedony. However, at 

53.8 m, quartz was deposited as more than one generation, and the paragenetic sequence is chalcedony, pyrite, 

hematite, quartz, calcite-?-fluorite, later quartz, and 

mordenite. Quartz and chalcedony can be found associated with most of the hydrothermal minerals except for 

clinoptilolite in the Y-3 drill core. A fairly close association is found between analcime and quartz or chalcedony zones, which alternate with clinoptilolite—acristobalite zones in the upper 30 m of the drill core (fig. 

2). This silica-zeolite relationship previously has been 

described for drill cores Y-l and Y-8 (Honda and Muffler, 

1970; Keith and others, 1978b), where the deposits are 

more extensive and the relationship is better defined.

ZEOLITE MINERALS

ANALCIME

Tiny (0.025-0.5 mm), isotropic, euhedral, trapezohedral analcime crystals (fig. 3) occur in the 

groundmass and as vesicle fillings in the Y-3 drill core 

from 14.2 to 15.3 m, 22.8 to 24.1 m, and 27.2 to 28.5 m. 

Quartz is closely associated with analcime and appears 

to be pseudomorphous after groundmass analcime at 

23.8 m. Six electron microprobe chemical analyses of 

analcime from 27.5 m (table 2) show that the mineral is 

a pure analcime (sodium-rich) end member. The Y-3 

analcime analyses have very high silica-to-alumina 

ratios (2.4—3.1) for analcime and are similar both to a 

microprobe analysis of analcime reported for drill core 

Y-8 (Keith and others, 1978b) and to conventional rock 

analyses of two analcime separates from drill core Y-l 

(M.H. Beeson, unpub. data, 1976). Other Yellowstone 

drill cores that contain analcime are Y-2 and Y-13. In 

drill core Y-2 the mineral appears to be a sodium-rich 

wairakite (Bargar and Beeson, 1981), and in drill core 

Y-13 both analcime and wairakite appear to be present 

in the same sample (Bargar and others, 1981). Drill cores 

Y-l and Y-8 mostly contain Na- and K-rich hydrothermal 

minerals and do not contain Ca-rich minerals (except 

for local bladed calcite) (Honda and Muffler, 1970; Keith 

and others, 1978b). Conversely, drill cores Y-2 and Y-13 

contain several Ca-rich hydrothermal minerals (Keith 

and others, 1978a; Bargar and Beeson, 1981).

FIGURE 3.—Scanning electron micrograph of euhedral, trapezohedral 

analcime crystals from 28.3 m in^ drill hole Y-3. A few scattered 

clusters of smectite crystals are later deposits (after Bargar and 

others, 1981).
C6 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

o 6 ^

c <B tl

S; o z

O O i

j CM •:•! I

E EC fa
1

Sample No. ——

Analysis No. —

Si02 — —— — ——

A1 2 03 —— —— ——

Fe 2 03 —— —— ——

MgO — —— —— ——

MnO —— —— —— —

CaO —— — —— ——

H 2 0+ —— —— — —

H 2 CT ————————

Y3-91.4 

fordenite 

9

67.56 

11.62 

.00 

.00 

.02 

3.18 

2.48 

.28 

9.10 

4.90

99.14

Y3-73. 2

Yugawaralite

1

63.93 

17.70 

.00 

.00 

.00 

9.04 

.36 

.05

——

91.08

2

63.99 

18.46 

.00 

.00 

.00 

8.97 

.37 

.07

——

91.86

3

60.74 

18.51 

.00 

.00 

.00 

9.21 

.09 

.11

——

88.66

4

63.32 

18.73 

.00 

.01 

.04 

8.95 

.40 

.06

——

91.51

4

5

63.03 

17.93 

.00 

.01 

.00 

9.06 

.33 

.05

90.41

6

Weight

64.94 

16.91 

.00 

.01 

.00 

8.01 

.82 

.25

90.94

7

percent

64.88 

18.56 

.00 

.00 

.02 

9.90 

.02 

.02

93.40

8

62.46 

16.55 

.01 

.03 

.03 

8.92 

.43 

.04

88.47

9

62.48 

17.00 

.03 

.01 

.01 

9.33 

.20 

.05

89.11

10

62.55 

16.48 

.00 

.03 

.00 

9.00 

.28 

.06

——

88.40

11

63.60 

15.88 

.00 

.02 

.03 

8.78 

.50 

.06

88.87

12

63.38 

16.36 

.02 

.02 

.01 

8.97 

.29 

.05

89.10

13

64.45 

15.46 

.04 

.01 

.00 

8.41 

.69 

.08

89.14

96 oxygens

Number of atoms on the basis of: 

56 oxygens

Si ————————— 40.11 21.15 21.00 20.71 20.88 21.03 21.48 20.97 21.30 21.17 21.33

Al ————————— 8.14 6.91 7.14 7.44 7.28 7.05 6.59 7.07 6.65 6.79 6.62

Fe ————————— .00 .00 .00 .00 .00 .00 .00 .00 .00 .01 .00

Mg ————————— .00 .00 .00 .00 .01 .00 .00 .00 .01 .01 .01

Mn ————————— .01 .00 .00 .00 .01 .00 .00 .01 .01 .00 .00 

Ca ————————— 2.02 3.21 3.16 3.37 3.16 3.24 2.84 3.43 3.26 3.39 3.29

Na —————————— 2.85 .23 .24 .06 .25 .21 .53 .01 .28 .13 .19

K —————————— .21 .02 .03 .05 .02 .02 .11 .01 .01 .02 .03

Si/Al ——————— 4.93 3.06 2.94 2.78 2.87 2.98 3.26 2.97 3.20 3.12 3.22 

Cat. bal. 

error (%) 5 —— 14.0 3.6 8.6 8.8 9.7 4.9 4.3 2.6 -2.9 -2.2 -2.8

21.55 21.43 21.74 

6.34 6.52 6.15 

.00 .01 .01 

.01 .01 .00 

.01 .00 .00 

3.19 3.25 3.04 

.33 .19 .45 

.03 .02 .04 

3.40 3.29 3.54 

-6.3 -3.1 -6.4 

^•Sample numbers correspond to depth in meters.

^Analyzed by conventional rock-analysis methods. Analysts: S. T. Neil and J. H. Christie.

-'H 2 0"f and H2 0~ determined by conventional rock-analysis method. Analyst: S. T. Neil. 

^Average of five analyses.

-"Determined by method of Passaglia (1970).
C8 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

g o Z W w o
1

Sample No. —— Analysis No. -- Si02 —— —— -—— A1 2 03 - ————— MgO ————————— MnO ————————— K2 0 — —— —— —— 

Total —— - S i ____________ Al —— —— —— —— Fe — — — —— —— Mg ————————— Mn —— —— —— —— Si/Al ~— —— —— 

Cat.bal. 

error U)4 —— Y3-73.2 6 64.34 14.09 .00 .00 .00 7.92 .11 .05 86.51 19.04 4.91 .00 .00 .00 2.51 .07 .02 3.88 -3.8 7 65.30 15.81 .00 .03 .00 7.69 .18 .08 89.09 18.76 5.36 .00 .01 .00 2.37 .10 .03 3.50 9.7 8 63.99 16.62 .00 .02 .00 8.38 .03 .04 89.08 18.46 5.65 .00 .01 .00 2.59 .02 .01 3.27 8.1 9 61.72 15.59 .00 .01 .00 8.18 .05 .02 85.57 18.54 5.52 .00 .00 .00 2.63 .03 .01 3.36 4.0 2 10 64.33 62 14.97 15 .00 .00 .00 8.12 7 .05 .02 87.49 86 Numbers 18.84 18 5.17 5 .00 .00 .00 2.55 2 .03 .01 3.65 3 .7 5 11.50 .64 .01 .01 .00 .74 .10 .05 .05 of .76 .31 .00 .00 .00 .49 .06 .02 .53 .0 12 Weight 67.06 16.42 .09 .00 .01 8.09 .18 .11 91.96 atoms on 18.70 5.40 .02 .00 .00 2.42 .10 .04 3.46 9.0 3 13 percent 66.10 15.86 .00 .00 .00 8.23 .16 .06 90.41 the basis 18.75 5.30 .00 .00 .00 2.50 .09 .02 3.53 3.7 14 62.84 15.22 .01 .02 .03 8.22 .09 .06 86.49 15 64.26 14.41 .00 .03 .01 8.24 .08 .05 87.08 16 63.43 14.74 .00 .02 .02 8.14 .12 .09 86.56 17 61.34 14.40 .01 .05 .00 8.12 .08 .04 84.04 18 64.76 14.72 .00 .03 .00 8.15 .09 .07 87.82 19 63.07 15.03 .00 .00 .01 8.35 .10 .04 86.60 20 61.26 14.83 .03 .02 .00 8.06 .13 .05 84.38 21 62.55 15.03 .01 .06 .00 8.25 .05 .05 86.00 22 63.84 15.14 .00 .04 .01 8.43 .09 .03 87.58 of 48 oxygens 18.67 5.33 .00 .01 .01 2.62 .05 .02 3.50 -.2 18.93 5.00 .00 .01 .00 2.50 .05 .02 3.78 -5.4 18.81 5.15 .00 .01 .01 2.59 .05 .03 3.65 -3.0 18.75 5.19 .00 .02 .00 2.66 .05 .02 3.61 -4.4 18.90 5.06 .00 .01 .00 2.55 .05 .03 3.73 -2.7 18.71 5.26 .00 .00 .00 2.65 .06 .02 3.56 -2.4 18.66 5.24 .01 .01 .00 2.63 .08 .02 3.56 -2.6 18.69 5.29 .00 .03 .00 2.64 .03 .02 3.53 -1.5 18.73 5.24 .00 .02 .00 2.65 .05 .01 3.58 -3.0

^•Sample numbers correspond to depth in meters.

^Average of two analyses.

^Average of five analyses.

^Determined by method of Passaglia (1970).

oco
CIO HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

CLINOPTILOLITE

Clinoptilolite, usually associated with devitrification 

a-cristobalite in drill core Y-3 (fig. 2), was identified by Xray diffraction analyses as the cementing material in 

finer grained sediments at 7.3—14.2 m. Clinoptilolite is 

the only zeolite mineral in this interval. The nearly 

isotropic mineral also occurs as cement in finer grained 

siltstone and sandstone and was deposited as tiny 

(0.005—0.012 mm), clear, tabular crystals that line cavities (fig. 4) in conglomerate between 16.2 and 26.3 m. Xray diffraction traces of 12 samples from these two zones 

showed no change in position or intensity of the (020) Xray peak at about 9 A after heating according to the 

method of Mumpton (1960), and the mineral was identified as Clinoptilolite.

A single microprobe chemical analysis of Clinoptilolite 

was obtained from 12.4 m (table 2). This analysis indicates that Clinoptilolite at this depth is low in silica, 

contains very little calcium, and is rich in sodium and, 

in particular, potassium. The Y-3 Clinoptilolite is much 

lower in calcium than most other heulandite-group 

zeolites from Yellowstone drill cores, and it is nearly as 

rich in potassium as some clinoptilolites from drill cores 

Y-7 and Y-8 (Keith and others, 1978b) (fig. 5).

Three core samples from 24.2 to 26.3 m and drill 

cuttings recovered from about 29—30 m are characterized by splitting of the (020) X-ray peak into three 

peaks at about 8.9, 8.7, and 8.3 A following heat treatment. No chemical analyses were obtained for the three

FIGURE 4.—Scanning electron micrograph of intergrown tabular 

Clinoptilolite crystals from 14.0 m in drill core Y- 3 (after Bargar and 

others, 1981).

core samples; however, we would predict that they contain more calcium than the above Clinoptilolite samples 

and are probably intermediate heulandites (Alietti, 

1972; Boles, 1972).

DACHIARDITE

Clear dachiardite crystals are widely scattered 

between 60.2 and 80.9 m in the Y-3 drill core. The rare, 

radiating, blocky crystals are found deposited in cavities 

along with earlier quartz, later mordenite, and smectite 

(figs. 6 and 7), and they are later than chalcedony in a 

few vein fillings.

Microprobe chemical analyses of dachiardite crystals 

from 60.4 and 73.2 m in drill core Y-3 are given in table 

3. A ternary plot of the exchangeable cations (Ca-Na-K) 

content in Y-3 dachiardite compared with other published dachiardite analyses is shown in figure 8. The 

published analyses are divided into two groups: (1) 

sodium-rich dachiardite, and (2) intermediate dachiardite (Alberti, 1975; Wise and Tschernich, 1978; Bonardi, 

1979; Bonardi and others, 1981). A drill core Y-2 dachiardite analysis (Bargar and Beeson, 1981) plots near the 

latter group and several dachiardite analyses from sample Y3-60.4 plot near the intermediate group, but these 

crystals are more calcium rich. Chemical analyses of 

water from the Y-3 drill hole (table 1) suggest that calcium is lost (precipitates) as the water ascends to the 

surface (Bargar and others, 1973). The Y3-73.2 sample is 

very calcium rich, and, to the best of our knowledge, this

EXPLANATION

Drill core (See fig. 1 for location)

+ C-I 

AY-1 

AY-2

• Y-3 

DY-6 

OY-7

• Y-8

Na K

FIGURE 5.—Ca-Na-K ternary diagram for heulandite-group zeolites 

from Yellowstone drill cores. Data sources as follows: C-I (Fenner, 

1936), Y-l (Honda and Muffler, 1970), Y-2 (Bargar and Beeson, 1981), 

Y-7 and Y-8 (Keith and others, 1978b), Y-6 (Bargar and Beeson, 

1984), Y-3 (table 3, this report).
HYDROTHERMAL ALTERATION MINERALOGY Cll

sample is the only naturally occurring Ca-rich dachiardite ever reported. Ca-rich dachiardite has been produced in the laboratory using devitrified rhyolite as the 

starting material (Knauss and Beiriger, 1984).

LAUMONTITE

Many fractures and cavities below 73.2 m in the Y-3 

drill core contain white prismatic laumontite crystals 

that are up to about 1 mm in length. SEM studies show 

that laumontite was deposited later than quartz and 

earlier than mixed-layer illite-smectite. Some laumontite crystals appear to have been subjected to partial 

leaching, and the illite-smectite was deposited in the 

resulting cavities (fig. 9).

Chemical analyses of laumontite from 73.2 and 126.9 

m (by electron microprobe and conventional rock analysis methods) are given in table 2. The Y-3 laumontite is 

calcium rich and is very similar to several microprobe 

analyses of hydrothermal, burial metamorphic, and 

surficial hot-spring-deposited laumontite (McCulloh 

and others, 1981). The measured temperature range at 

which Y-3 laumontite was found was about 167-196 °C.

MORDENITE

Mordenite is the most abundant zeolite mineral found 

in the Y-3 drill core. Scattered mordenite deposits occur

FIGURE 6.—Scanning electron micrograph of a large radiating cluster 

of dachiardite crystals deposited on hydrothermal quartz crystals 

(top and right side of photo) in a vug at 60.2 m in the Y-3 drill core. 

Smectite crystal cluster (s) was deposited later than dachiardite 

(after Bargar and others, 1981).

in many vugs and fractures throughout much of the drill 

core as radiating, long, thin, fibrous crystals (fig. 7), as

FIGURE 7.—Scanning electron micrograph of cavity filling from 60.2 m 

in the Y-3 drill core. Micrograph shows, in apparent depositional 

sequence, quartz crystals (upper left and lower right), dachiardite 

(blocky crystals extending diagonally from lower left to right center), radiating fibrous mordenite crystals, and numerous tiny smectite crystal clusters (after Bargar and others, 1981).

EXPLANATION

Drill

hole Depth (m) 

O Y2-20.7

• Y3-60.4

• Y3-73.2

D Italy

A Pacific Northwest

• Canada

FIGURE 8.—Ca-Na-K ternary diagram for Y-3 dachiardite compared 

with other published dachiardite analyses. Data sources as follows: 

Y3-60.4 and Y3-73.2 (table 3, this report), Y2-20.7 (Bargar and 

Beeson, 1981), Pacific Northwest (Wise and Tschernich, 1978), Italy 

(Bonardi, 1979; Alberti, 1975), Canada (Bonardi and others, 1981).
C12 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

mats of interwoven fibers, or as needlelike crystals 

(fig. 10). SEM studies show that mordenite formed later 

than silica and most other zeolite minerals and earlier 

than some clay deposits (figs. 7 and 10).

Electron microprobe chemical analyses of coarse mordenite fibers from 91.4 m are given in table 2 along with 

H2O values that were determined by conventional rock 

analysis methods. None of the microprobe analyses

total to 100 n wii-V. ,r>^^^ TJ r\

chlorite also occur in the yugawaralite-bearing samples. 

The idealized unit cell content of yugawaralite is 

Ca4(Al8Si20056)16H2O (Barrer, 1982). Several microprobe chemical analyses of yugawaralite from the Y-3 

drill core at 73.2 m (table 2) show that calcium is the 

dominant cation and that only minor amounts of sodium 

and potassium are present. The Y-3 chemical analyses 

are very similar to analyses of yugawaralite made by

C14 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

formed as a result of acid-sulfate alteration. A similar 

mineral assemblage occurs in Yellowstone drill core Y-ll 

from a vapor-dominated geothermal system (Muffler 

and Bargar, 1974; Bargar and Muffler, 1982). Schoen and 

others (1974) also attributed a similar assemblage of 

minerals from Steamboat Springs, Nevada, to surficial 

acid (H2SO4) alteration. Two additional kaolinite zones 

(41.7—44.4 m and 68.7—71.3 m) contain associated smectite and pyrite and are nearly coincident with stratigraphic breaks between the glacial sediments and the 

top of the Nez Perce Creek rhyolite flow and between the 

Nez Perce Creek flow and the older, unnamed rhyolite 

flow. However, fossil zones of surficial acid alteration are 

precluded in these two zones because the kaolinite is a 

late hydrothermal product and is deposited on top of 

quartz. The kaolinite may have formed due to alteration 

of K-feldspar by descending meteoric waters that were 

acidified by oxidation of pyrite. Fenner (1936) describes a 

similar process for kaolinite formation in drill core C-II 

(fig. 1).

HALLOYSITE AND ALLOPHANE

At 1.7 m, kaolinite is the predominant clay mineral; 

however, some halloysite and allophane are also present. Halloysite has a broad X-ray diffraction peak at 

about 7.7 A, which, upon heating to 140 °C for 15 hours, 

becomes sharper, higher, and shifts to about 7.3-A 

(Birkeland, 1969). In addition, one of the X-ray traces of 

this sample contained a low, broad —11.5 A peak that 

was not affected by heating and might be an allophane 

peak; allophane is commonly associated with kaolinite 

and halloysite (Deer and others, 1962). Subsequent testing, involving a small amount of powdered sample 

placed upon phenolpthalein-treated filter paper to 

which a drop of 1M NaF was later added, confirmed the 

identification of allophane by turning the indicator 

paper to a pinkish-red color (Fieldes and Perrott, 1966).

CHLORITE

Chlorite occurs throughout most of the two rhyolite 

flows as fillings in fractures and cavities and as wholerock alteration adjacent to a few fractures. Open-space 

chlorite deposits formed later than chalcedony,

TABLE 4.— Chemical composition of chlorite 

from 108.3 m in drill core Y-3 1* 2

Weight percent

S iO 2 ————————————

FeO ———————-——-

MnO ----- —— ----- —

MgO —————————————

\_>aw

Na2 0 ————————————

K2 0 ——————————————

TT /-V+ __ ____

F

-. — —. ~_

-0=¥

——————— .15

————————— 20.55

3

Q1

• 7 J

O Q 11

————————— 1.47

————————— 1.49

/ 1

————————— .44

————————— 1.64

j . \j 1 ——————— .74

—————————— .12

99.79 

.05

Total- 99.74

Numbers of atoms on the basis of 36 oxygens

SiAlAlTiFe2+- 

Mn—— 

Mg—— 

Ca——

Na—- 

K———

6.86 ^

1.14 )r

4.11

.03

.64

5.10

.03

.48

.10

.18

.45

$.00

11.12

OHF—

14.18

.08

14.26

1-X-ray diffraction shows ^1-2 percent 

quartz and hematite impurities.

2Analysts: S. T. Neil and J. H. Christie. 

Analysis by conventional rock-analysis 

methods .
HYDEGTHRRMAL ALTERATION MINERALOGY C15

SMECTITE

White, light-gray, or green smectite is the predominant clay mineral in much of the upper 80.6 m of the Y-3 

drill core. The smectite commonly occurs as an alteration product of glass, and it was deposited iu cavities and 

on fractures. X-ray diffraction analyses show that the 

smectite basal (001) spacing varies from about; 12 to 15 A 

and expands to about 17 A when treated with ethylene 

glycol for 1 hour at 60 °C. In the lower part of this range 

(12,5 A) sodium is the exchangeable cation, and at the 

upper end of the range (14.5-15.5 A) calcium should be 

the exchangeable cation (Grim, 1968). Using these criteria, calcium is the predominant cation in the smectite 

above 11,3m and from 48.8 to 80.6 m in the Y-3 drill core; 

between these depths (11.3-48.8 m), sodium is the major 

cation, with occasional calcium-rich samples.

ILLITE-SMECTITE

Mixed-layer illite-smectite occurs as open-space fillings and whole-rock alteration below 80.6 m and can be 

found in a few shallower samples. X-ray diffraction 

traces show an air-dried basal (001) peak at about 10-12 

A for the mixed-layer clay that splits into two peaks at 

about 11-14 A and 9.1-9.9 A following glycolaticn. 

According to data given by Hower (1981), these samples 

appear to contain about 80-80 percent illite layers and 

are probably allevardite ordered.

LEPIDOLITE

Lepidolite, generally considered to be a high-temperature vein, pegmatite, granite, or aplite-associated 

deposit (Deer and others, 1966), was identified as an 

intergranular cavity filling in conglomerate and coarsegrained sandstone at 23.8 rn and between 27.2 and 28,5 

m in the Y-3 drill core, where the temperature was about 

130-140 °C (Bargar and others, 1973). The polycrystalline lepidolite mats (fig. 14) appear to have been 

deposited later than analcime and quartz and earlier 

than pectolite and aegirine. Other hydrothermal minerals identified in the lepidolite-bearing samples include 

chalcedony, calcite, fluorite, kaolinite, and pyrite. X-ray 

diffraction and chemical data for the polylithionite (a 

lepidolite end member) are given in Bargar and others 

(1973). According to Bargar and others (1973), the water 

that deposited lepidolite in the Y-3 drill hole is anomalously rich in lithium and fiuoride, which are the two j 

chemical constituents necessary for the4 formation of 

lepidolite. A barely perceptible 10-A mica X-ray diffraction peak was noted in a few scattered samples at 1,4. 

13.0-15.2, 43.8-47,0, and 65.5-66.1 m. The 10-A mica 

was not observed in thin section, and its origin is uncertain.

AEGIRINE

In drill core Y-3, bright-green, pleochroic aegirine 

occurs as spherical or radiating clusters of euhedral

bladed-to-prismatic crystals tt at are up to about 15 jxm 

in length (figs. 15A, JB ). Aegir'ne is closely associated 

wiili pectolite at depths of 26.3 -28.5 and 65.5-66.3 m; 

in the shallower zone, the two n inerals were deposited 

in intergranular cavities in coar se sediments, whereas 

in the deeper zone, the minerals vere deposited in fractures and cavities formed by leaching of sanidine phenocrysts. Aegirine is a fairly ran; mineral in modern 

geothermal systems; previously, it #as identified in Yellowstone drill cores Y-1 (Honda an 1 Muffler, 1970), Y-2 

(Bargar and Beeson, 1981), and Y-H (Keith and others, 

1978a).

Figure 16 is a ternary diagram of ac nite-jadite-hedenbergite + diopside (Ac — Jd — Hd + Di) electron microprobe compositions of aegirine from d 'ill core Y-3 (table 

5) compared with analyses of Y-2 hydrt thermal aegirine 

(Bargar and Beeson, 1981). End-menu >er compositions 

were calculated according to the method of Cawthorn 

and Collerson (1974).

PECTOLITE

Pectolite is not an uncommon hydrothermal mineral, 

but, according to Diowne (1978), this cacium-sodium 

silicate hydrate mineral is rare in activt geothermal 

fields and has been identified only in the ?-3 drill core 

(at depths of 26.3-28.5 and 65.5-66.3 m) and in discharge pipes and channels of the New Zeab nd volcanic 

zone. In dxill core Y-3, pectolite occurs as w lite fibrous 

crystals (figs. 15A, 15JB, and 17A) or as radiat ng clusters 

of bladed crystals (fig. 17B) that were deposited later 

than aegirint' and quartz.

FIGURE 14.—Scanning electron micrograph of a polycrystalliiie mat of 

lepidolite crystals frora 2S.3 m in drill core Y-3,
C16 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

TRUSCOTTITE

Truscottite, another calcium silicate hydrate mineral, 

was identified in the Y-3 drill core from between 87.8 

and 89.8 m, where the temperature measured during 

drilling was about 175 °C. (Truscottite has been formed 

in the laboratory from gyrolite and silica at 180 °C 

(Minato and Kato, 1967).) Clear, tabular truscottite crystals (fig. 18) were deposited in cavities and on fractures

FIGURE 15.—Scanning electron micrographs from drill core Y-3 at 

65.5 m. A, Spherical cluster of aegirine crystals and later pectolite 

fibrous crystals. B, Radiating clusters of aegirine crystals and later 

pectolite fiber.

and are associated with earlier chalcedony, quartz, calcite, and laumontite, and later smectite and mordenite; 

Y-3 truscottite-bearing samples also contain chlorite 

and pyrite. Truscottite previously had been identified in 

three other Yellowstone drill cores (Y-2, Y-13, and C-I) 

(Keith and others, 1978a; Bargar and Beeson, 1981; Bargar and others, 1981). Several microprobe analyses of 

truscottite from 88.6 m in drill core Y-3 (table 6) suggest 

that this occurrence is slightly more calcium rich (chemical analyses of Y-3 drill-hole water compared with 

water from nearby Ojo Caliente Hot Spring, shown in 

table 1, suggest that calcium is precipitated during 

ascent of the water to the surface), is silica deficient, and 

has slightly greater alumina content than is found in 

most published analyses of the mineral (Minato and 

Kato, 1967; Juan and others, 1970) (fig. 19).

SULFATE MINERALS

GYPSUM

Gypsum occurs in a few scattered samples above 21.5 

m in the Y-3 drill core. In the shallowest samples, white 

gypsum fibrous crystals line cavities and veins at less 

than 57 °C (the greatest temperature at which gypsum 

is the stable calcium sulfate phase) (Holland, 1967), and 

the mineral may be of hydrothermal origin. However, in 

deeper samples the gypsum is mostly deposited in association with pyrite and was probably formed by oxidation after the drill core was brought to the surface.

EXPLANATION

Drill hole

OY-2 

• Y-3

Hd+Di

FIGURE 16.—Ac - Jd — Di + Hd ternary diagram for aegirine from drill 

core Y-3 (data from table 5, this report) compared with Y-2 aegirine 

reported by Bargar and Beeson (1981).
HYDROTHERMAL ALTERATION MINERALOGY C17

ALUNITE

Alunite, a potassium sulfate mineral, occurs in a single sample at 1.6 m in drill core Y-3 in association with 

opal, kaolinite, allophane, and halloysite. White and 

others (1975, table 3) indicate that the depth to the water 

table in drill hole Y-3 was about 2.4 m. Thus, alunite in 

Y-3 appears to have formed in the unsaturated zone of 

the drill core as a result of near-surface acid alteration, 

as described by Schoen and others (1974).

HEMATITE

Orange-red-reddish-brown iron oxide is sparse above 

46 m and has a sporadic distribution throughout the 

remainder of the Y-3 drill core. Iron oxide (hematite 

where identified by X-ray diffraction) commonly occurs 

as pigment that stains chalcedony fracture fillings and 

vug deposits; however, occasional earthy or clayey

hematite was noted. Hematite is an early hydrothermal 

mineral and appears to have formed later than chalcedony and pyrite, probably as a result of pyrite oxidation.

PYRITE

Tiny cubic pyrite crystals are found throughout much 

of the Y-3 drill core as deposits disseminated in 

groundmass or earlier green chalcedony. In Y-3, pyrite 

commonly lines fractures and vugs where the euhedral 

crystals or thin massive deposits are sometimes associated with later hematite. A few massive pyrite fracture 

fillings have crude hexagonal-appearing crystal cluster 

shapes that hint of a possible sulfide (pyrrhotite?) precursor. Pyrrhotite was identified in nearby Yellowstone 

drill core Y-2 (Bargar and Beeson, 1981). Y-3 pyrite crystals are typically small (about 0.1 mm); however, at 

about 4.5 m a thin, black, powdery pyrite deposit consists of 0.02-0.03 mm cubic crystals. At 45.5 m, pyrite

TABLE 5. — Microprobe analyses of aegirine from Y-3 drill core

Sample No. — Y3-27.5 Y3-66.1

Analysis No.- 1

Weight percent

SiC>2 — -—— 

A12 03 —— —

Fe203 -----

MgO —— — —

MnO ----- —

41 a t\j

K2 0 —— — —

52.60

.19 

29.42

.94

1.05

QQ

12.64

.12

51.39

.23 

29.29

.94

.99

Q <i

13.08

no

50.26

.10 

29.22

1.23

1.37

.70

11.09

Q /:

51.27 

.16 

29.37

.99

.61

1.25

12.53

nO

50.58 

.22 

28.53

.95

.61

1.55

12.72

.07

50.68

.50 

28.81

.77

.64

1 f.O

.23

50.31

.19 

28.82

.74

.64 

Iofi

13.01

.07

49.70

1.28 

27.60

OQ

.50

1.09

11.71 

on

Total- 97.84 96.85 94.24 96.26 95.23 96.17 95.06 93.31

Numbers of atoms on the basis of 6 oxygens

Si —— — —

Fe — — ——

Mg ————— -

Mn —————

Po

.01

Q£.

.05

.03 

.04

.95

.01

2.03 

.01

Q~7

.06

.03

.04

1.00

.00

2.03

.00

.89

.07

.05

.03

fi7

.02

2.01

.01

Q7

.06

.02

.05

1.05

.00

2.03

.01

O£

.06

.02

.07

.99

.00

2.02

.02

O£

.05

.02

.07

.99

.01

2.02 

.01

O7

.04

.02 

.06

1.01

.00

2.02 

.06

.84

.05

.02 

.05

.92

.04

^Sample numbers correspond to depth in meters.
C18 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

displays an unusual needlelike crystal structure; the 

brassy needles (deposited later than quartz) are up to 

about 0.25 mm in length (fig. 20).

SUMMARY AND DISCUSSION

The Y-3 drill hole penetrated about 42 m of surficial 

deposits consisting primarily of Pinedale glacial sediFIGURE 17.—Scanning electron micrographs from drill core Y-3. A, 

Clusters of fibrous pectolite crystals deposited on top of hydrothermal quartz crystals at a depth of 28.3 m. B, Cluster of bladed 

pectolite crystals deposited later than quartz at 27.5 m (after Bargar and others, 1981).

ments that were deposited 2=45,000-14,000 years B.P. 

(Christiansen and Blank, 1974; Pierce and others, 1976). 

Below 42 m are two rhyolite flows, the Nez Perce Creek 

flow and an older, unnamed rhyolite flow, that ChrisFIGURE 18.—Scanning electron micrograph of tabular, hexagonal 

crystals of truscottite deposited later than quartz at 88.6 m in drill 

core Y-3 (after Bargar and others, 1981).

AI2O3

EXPLANATION

Y-3

O Minato & Kato (1967) 

A Juan & others (1970)

CaO SiO2

FIGURE 19 —CaO-Al2O3-SiO2 molecular-proportion ternary diagram 

for truscottite from 88.6 m in drill core Y- 3 (data from table 6, this 

report) compared with published analyses of truscottite reported by 

Minato and Kato (1967) and Juan and others (1970).
SUMMARY AND DISCUSSION C19

TABLE 6. — Microprobe analyses of truscottite from 88.6 m in drill core Y-3

Analysis No.— 10

Weight percent

Si02 —————

A 1 2 03 ————

Fe2 03 ————

MgO —————— 

MnO ——————

CaO ——————

50.99 

4.29

.19

.04

.04

1.91

.76

5.15 

.14

.06

.02

27.51

1

f\Q

.56

52.53 

4.54

f 0

.09

.05

29.33

f r)

.59

Q Q

.07

.09

29.17 

.41

.50

55.03

3

f\Q

.21

.06

.05 

30.14

.27

.67

50.97

3.72

1 fi

.11

.06

27.04

1.51

.69

53.20

4.70 

.19

.15

.03

29.35

f Q

7C

51.66 

4.59

.19

f\Q

.01

29.47 

.65

1.14

49.19

4.47

.14

.07 

.04

00 00

.61

1.02

51.56 

4.40

.13

.10 

.06

1.30

.53

Total——— 84.11 88.80 83.37 87.75 89.51 84.28 89.08 87.79 83.86 83.55

Number of atoms on the basis of 11 oxygens

Si ——————

Fe ——————

Mg —————— 

Mn —————— • Ca ——————

Na ——————

—— 4.01

——— .40

—— .01

——— .00

—— .00

2

1 fi

—— .29

f\Q

4.01

.45

.01

.01

.00

.15

.05

3.95

.40

.04

.01

.00

2

0 £

.09

.06

4.05

.30

.02

.01

.01

2.35

.06

.05

4.07

.27

.01

.01

.00

2.39 

.04

.06

4.01

.34

.01

.01

.00

.23

.07

3.96

.41

.01

.02

.00

.10

.07

3.93

.41

.01

.01

.00

2.40

.10

.11

3.92

.01

.01 

.00

2.42

.09

.10

4.04

.41 

.01

.01

.00

2.14

.20

.05

1Average of three analyses.

FIGURE 20.—Scanning electron micrograph of pyrite needlelike crystals deposited on top of quartz crystals that line a cavity at 45.5 m in 

drill core Y-3. Threadlike material may be mordenite. Smectite 

crystal clusters also appear to be present.

Early Late

chalcedony

pyrite

hematite

quartz

clays

calcite

chlorite

fluorite

zeolites

FIGURE 21.—Generalized paragenetic sequence of principal hydrothermal minerals in drill core Y-3. Length of lines is not indicative of 

duration of mineral deposition.
C20 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

tiansen and Blank (1974) correlated with the Central 

Plateau Member of the Pleistocene Plateau Rhyolite. 

The Nez Perce Creek flow has K-Ar dates between 

140,000 and 160,000 years B.P., as reported in White and 

others (1975), Waldrop and Pierce (1975), and Leeman 

and Phelps (1981). Other rhyolite flows of the Central 

Plateau Member were extruded between about 200,000 

and 70,000 years ago (Christiansen and Blank, 1972). 

Thus the unnamed rhyolite flow in drill core Y-3 is 

probably not much older than the overlying Nez Perce 

Creek flow.

The effects of hydrothermal alteration are evident 

throughout the Y-3 drill core. Silica and zeolite minerals 

provide the cementing material for much of the surficial 

deposits. Parts of the two rhyolite flows were bleached 

by thermal waters, and the entire drill core contains 

hydrothermal minerals lining vugs and filling fractures. A generalized paragenetic sequence for the principal hydrothermal minerals found in drill core Y-3 is 

shown in figure 21. The glacial sediments and both 

rhyolite flows probably have been subjected to hydrothermal alteration throughout their histories, because 

the duration of hydrothermal activity in the Yellowstone 

region appears to extend over the last 266,000 years and 

may possibly date back to about 600,000 years B.P. 

(Silberman and others, 1979). Consequently, some of the 

hydrothermal minerals in drill core Y-3 probably predate the Pinedale glacial sedimentary deposits of the 

upper 42.2 m. Chalcedony, pyrite, hematite, quartz, and 

clay minerals (smectite and mixed-layer illite-smectite) 

are early hydrothermal deposits in the volcanic section 

of the drill core (listed in order of deposition); calcite, 

chlorite, fluorite and zeolite minerals are later deposits, 

although the depositional sequence of calcite, chlorite, 

and fluorite was not determined. Chalcedony, pyrite, 

hematite, quartz, and clays are also shown as late 

hydrothermal deposits in figure 21 because these minerals are found in the younger sedimentary section of the 

drill core, as well as in the volcanic section. In addition, 

pyrite was deposited both earlier and later than quartz, 

and quartz occurs both earlier and later than calcite in 

the same sample.

Porosity, based on the difference between bulk- and 

powder-density measurements, was computed for 16 

selected samples of Y-3 drill core. The calculated porosity ranged from 15.7 to 45.8 percent (average 35.1 percent) in the glacial sediments and from 3.7 to 36.9 

percent (average 15.3 percent) in the rhyolite flows. The 

porosity and effective permeability of the volcanic rocks 

appear to have been greatly reduced owing to precipitation of hydrothermal minerals, particularly quartz and 

chalcedony, in vugs and fractures. In fact, many of the 

fractures in the lower, unnamed rhyolite flow have been 

completely closed (self-sealed) by silica deposition.

According to Pierce (1979, pi. 1), as much as 600 m of 

Pinedale glacial ice may have covered the ground surface about 10 km north of the Y-3 drill hole. In the 

thermal areas of Lower Geyser Basin, a significant portion of the ice probably melted and formed an ice-dammed lake (Muffler and others, 1971), the possible extent 

of which is shown by Pierce (1979, fig. 35). Muffler and 

others (1971) suggest that the triggering mechanism for 

the nearby hydrothermal explosion crater at Pocket 

Basin (fig. 1) may have been a sudden release of pressure 

caused by breaching of the ice dam and rapid draining of 

the lake. Prior to failure of the dam, the confining pressure at a given depth beneath the ground surface would 

have greatly exceeded present-day hydrostatic or 

lithostatic pressures, and the temperature at that depth 

would have been significantly warmer than the temperature measured during drilling of Y-3. Presumably, 

the fluid-inclusion homogenization temperature measurements for the Y-3 drill core (and other drill cores in 

Lower Geyser Basin) that exceed the temperatures measured during drilling reflect the higher temperaturepressure conditions that existed as a result of increased 

overburden during the Pinedale glacial time (Bargar 

and others, 1984).

In the sedimentary section of the Y-3 drill core, hydrothermal minerals containing sodium as a dominant 

cation (analcime, clinoptilolite, mordenite, Na-smectite, 

and aegirine) are more abundant than calcium-bearing 

minerals (calcite, fluorite, Ca-smectite, and pectolite). 

Conversely, in the volcanic section of the drill core, calcium-rich minerals (dachiardite, laumontite, 

yugawaralite, calcite, fluorite, Ca-smectite, pectolite, 

and truscottite) are predominant over sodium-bearing 

minerals (aegirine, mordenite, and Na-smectite). A few 

hydrothermal minerals that contain significant 

amounts of potassium (alunite, illite-smectite, and lepidolite) occur in both sections of the drill core.

Rhyolite flows of the Central Plateau Member are 

similar in chemical composition to the Summit Lake 

flow (Keith and others, 1978b) and to glass from the Nez 

Perce Creek flow (Leeman and Phelps, 1981). The analyses of the latter two flows show abundant sodium and 

potassium and little calcium. Twelve hydrothermally 

altered rocks from the Nez Perce Creek flow and the 

underlying unnamed rhyolite flow were analyzed by 

rapid rock methods and reported by Beeson and Bargar 

(1984). Figure 22 shows A-F-M and Na2O-K2O-CaO 

diagrams for these Y-3 volcanic rocks, as well as for 

hydrothermally altered glacial sediments from the 

upper part of the Y-3 drill core. All of the rocks are alkali 

rich (especially potassium) and calcium poor. As such, 

the dominance of calcium-bearing hydrothermal minerals in the lower rhyolitic volcanic section of Y-3 would 

appear to be due to the waters that deposited the miner-
REFERENCES CITED C21

als. In fact, a comparison of chemical analyses of water 

from the Y-3 drill hole and from nearby Ojo Caliente Hot 

Spring (table 1) suggests that calcium, along with 

potassium, is probably lost during adiabatic cooling of 

an ascending boiling water, whereas sodium remains 

unchanged after correcting for boiling (Bargar and others, 1973).

The silica geothermometer for Ojo Caliente Hot 

Spring water (176°C) is in good agreement with the 

measured temperature (174°C) for water from the 88-m 

aquifer in drill hole Y-3 (table 1, column 2). Other geothermometer calculations in table 1 give temperatures 

that are too low for Y-3. Calculated geothermometers for 

the bottom-water (table 1, column 1) are significantly 

lower than the 196°C measurement at the bottom of the 

drill hole. At the time the Y-3 bottom water sample was 

collected, White and others (1975) concluded that the 

region below 80 m in the drill hole was influenced by 

downflow of cooler water from the upper part of the drill 

hole.

Fluid-inclusion homogenization temperatures were 

measured in quartz (48 fluid inclusions in 4 samples) 

and fluorite (47 fluid inclusions in 3 samples) crystals 

from the Y-3 drill core. Most of the liquid-rich fluid 

inclusions appear to be secondary (?) or pseudosecondary and have homogenization temperatures that plot 

very close to the present-day measured temperature 

curve (fig. 23). One homogenization temperature measurement of 313.5°C at 45.8 m was not reported in figure 

23 because the value obviously was too high owing to 

necking-down of the fluid inclusion by precipitation of 

later silica (Roedder, 1984). Similarly a few other small, 

irregular fluid inclusions, some with "tails," may give 

erroneous (either too high or too low) homogenization 

temperatures. Probably the most reliable homogenizaK0O

Glacial sediment

Nez Perce Creek 

flow

Unnamed flow

Na0O

CaO

FIGURE 22.—A-F-M and Na2O-K2O-CaO ternary diagrams for altered 

volcanic rocks and glacial sediments from drill core Y-3.

CO

oc

LJJ hLLJ

fill] 

Q

50

100

150

Reference

boiling-point

curve

Measured

temperature

curve

Q

i i i i\i

100 200 

TEMPERATURE, IN DEGREES CELSIUS

FIGURE 23.—Plot of fluid-inclusion homogenization temperatures in 

quartz (Q) and fluorite (F) crystals from seven samples in drill core 

Y-3. Horizontal line segments give range of homogenization temperature measurements, which are shown as short vertical tick 

marks.

tion temperatures shown in figure 23 are the clustered 

measurements, which usually plot less than about 

20-40°C from the measured temperature curve. From 

these data we infer that the temperature of the water 

that deposited the quartz and fluorite crystals studied 

was a little warmer than the temperatures measured 

during drilling.

REFERENCES CITED

Alberti, A., 1975, Sodium-rich dachiardite from Alpe de Siusi, Italy: 

Contributions to Mineralogy and Petrology, v. 49, p. 63-66.

Alietti, A., 1972, Polymorphism and crystal-chemistry of heulandites 

and clinoptilolites: American Mineralogist, v. 57, p. 1448-1462.

Bargar, K.E., and Beeson, M.H., 1981, Hydrothermal alteration in 

research drill hole Y-2, Lower Geyser Basin, Yellowstone National 

Park, Wyoming: American Mineralogist, v. 66, p. 473-490.

————1984, Hydrothermal alteration in research drill hole Y-6, Upper 

Firehole River, Yellowstone National Park, Wyoming: U.S. Geological Survey Professional Paper 1054-B, 24 p.

Bargar, K.E., Beeson, M.H., Fournier, R.O., and Muffler, L.J.P., 1973, 

Present-day deposition of lepidolite from thermal waters in Yellowstone National Park: American Mineralogist, v. 58, p. 901-904.
C22 HYDROTHERMAL ALTERATION IN RESEARCH DRILL HOLE Y-3, WYOMING

Bargar, K.E., Beeson, M.H., and Keith, T.E.C., 1981, Zeolites in Yellowstone National Park: Mineralogical Record, v. 12, p. 29-38.

Bargar, K.E., Fournier, R.O, and Theodore, T.G., 1984, Particles 

resembling bacteria in fluid inclusions from Yellowstone National 

Park, Wyoming: Geological Society of America Abstracts with 

Programs, v. 16, p. 436-437.

Bargar, K.E., and Muffler, L.J.P, 1982, Hydrothermal alteration in 

research drill hole Y-ll from a vapor- dominated geothermal system at Mud Volcano, Yellowstone National Park, Wyoming: Wyoming Geological Association Annual Field Conference, 33d, 

Mammoth Hot Springs, Wyoming, Guidebook, p. 139-152.

Barrer, R.M., 1982, Hydrothermal chemistry of zeolites: New York, 

Academic Press, 360 p.

Beeson, M.H., and Bargar, K.E., 1984, Major and trace element analyses of drill cores from thermal areas in Yellowstone National Park, 

Wyoming: U.S. Geological Survey Open-File Report 84-373,40 p.

Birkeland, P.W., 1969, Quaternary paleoclimatic implications of soil 

clay mineral distribution in Sierra Nevada-Great Basin Transect: 

Journal of Geology, v. 77, p. 289-302.

Boles, J.R., 1972, Composition, optical properties, cell dimensions, and 

thermal stability of some heulandite-group zeolites: American 

Mineralogist, v. 57, p. 1463-1493.

Bonardi, M., 1979, Composition of type dachiardite from Elba: a reexamination: Mineral Magazine, v. 43, p. 548-549.

Bonardi, M., Roberts, A.C., and Sabina, A.P., 1981, Sodium-rich 

dachiardite from the Francon Quarry, Montreal Island, Quebec: 

Canadian Mineralogist, v. 19, p. 285-289.

Browne, P.R.L., 1978, Hydrothermal alteration in active geothermal 

fields: Annual Review of Earth and Planetary Sciences, v. 6, p. 

229-250.

Cawthorn, R.G., and Collerson, K.D., 1974, The recalculation of pyroxene end-member parameters and the estimation of ferrous and 

ferric iron content from electron microprobe analyses: American 

Mineralogist, v. 59, p. 1203-1208.

Christiansen, R.L., and Blank, H.R., Jr., 1972, Volcanic stratigraphy of 

the Quaternary rhyolite-plateau in Yellowstone National Park: 

U.S. Geological Survey Professional Paper 729-B, 18 p.

————1974, Geologic map of the Madison Junction quadrangle, Yellowstone National Park, Wyoming: U.S. Geological Survey Geologic Quadrangle Map GQ-1190, scale 1:62,500.

Deer, W.A., Howie, R.A., and Zussman, J., 1962, Rock-forming minerals: Vol. 3 sheet silicates: London, Longmans, 270 p.

———-1963, Rock-forming minerals: Vol. 4 framework silicates: New 

York, John Wiley, 435 p. 

-1966, An introduction to the rock-forming minerals: London,

Longmans, 528 p.

Eberlein, G.D., Erd, R.C., Weber, F, and Beatty, L.B., 1971, New occurrence of yugawaralite from the Chena Hot Springs area, Alaska: 

American Mineralogist, v. 56, p. 1699-1717.

Fenner, C.N., 1936, Bore-hole investigations in Yellowstone Park: 

Journal of Geology, v. 44, p. 225-315.

Fieldes, M., and Perrott, K.W, 1966, The nature of allophane in soils: 

Part 3. Rapid field and laboratory test for allophane: New Zealand 

Journal of Science, v. 9, p. 623-629.

Fournier, R.O., 1981, Application of water geochemistry to geothermal 

exploration and reservoir engineering, in Rybach, L., and Muffler, 

L.J.P, eds., Geothermal Systems: Principles and Case Histories: 

New York, John Wiley, p. 109-143.

Grim, R.E., 1968, Clay mineralogy: San Francisco, McGraw-Hill, 

596 p.

Holland, H.D., 1967, Gangue minerals in hydrothermal deposits, in 

Barnes, H.L., ed., Geochemistry of Hydrothermal Ore Deposits: 

New York, Holt, Rinehart & Winston, p. 382-436.

Honda, S., and Muffler, L.J.P., 1970, Hydrothermal alteration in core 

from research drill hole Y-l, Upper Geyser Basin, Yellowstone 

National Park, Wyoming. American Mineralogist, v. 55, p. 

1714-1737.

Hower, J, 1981, X-ray diffraction identification of mixed-layer clay 

minerals: Mineralogical Association of Canada Short Course, p. 

39-59.

Juan, V.C., Vouh, C.-C., and Lo, H.-J., 1970, The dehydration reaction 

of natural truscottite: Proceedings of the Geological Society of 

China, v. 13, p. 34-40.

Keith, T.E.C., Beeson, M.H., and White, D.E., 1978a, Hydrothermal 

minerals in U.S. Geological Survey research drill hole Y-13, Yellowstone National Park, Wyoming [abs.]: Geological Society of 

America Abstracts with Programs, v. 10, p. 432-433.

Keith, T.E.C., and Muffler, L.J.P, 1978, Minerals produced during 

cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5: Journal of Volcanology and Geothermal 

Research, v. 3, p. 373-402.

Keith, T.E.C., Thompson, J.M., and Mays, R.E., 1983, Selective concentration of cesium in analcime during hydrothermal alteration, 

Yellowstone National Park, Wyoming: Geochimica et Cosmochimica Acta, v. 47, p. 795-804.

Keith, T.E.C., White, D.E., and Beeson, M.H., 1978b, Hydrothermal 

alteration and self-sealing in Y-7 and Y-8 drill holes in northern 

part of Upper Geyser Basin, Yellowstone National Park, Wyoming: U.S. Geological Survey Professional Paper 1054-A, 26 p.

Knauss, KG., and Beiriger, W.J, 1984, Dachiardite formation by 

hydrothermal alteration of a devitrified high silica rhyolite [abs.]: 

Geological Society of America Abstracts with Programs, v. 16, p. 

561.

Leeman, W.P., and Phelps, D.W, 1981, Partitioning of rare earths and 

other trace elements between sanidine and coexisting volcanic 

glass: Journal of Geophysical Research, v. 86, no. Bll, p. 10193- 

10199.

McCulloh, T.H., Frizzell, V.A., Jr., Stewart, R.J., and Barnes, I., 1981, 

Precipitation of laumontite with quartz, thenardite, and gypsum 

at Sespe Hot Springs, Western Transverse Ranges, California: 

Clays and Clay Minerals, v. 29, p. 353-364.

Minato, H., and Kato, A., 1967, Truscottite from the Toi Mine, 

Shizuoka prefecture: Mineralogical Journal, v. 5, p. 144-156.

Muffler, L.J.P, and Bargar, K.E., 1974, Hydrothermal alteration of 

rhyolitic ash-flow tuff in the vapor-dominated geothermal system 

at Mud Volcano, Yellowstone National Park, U.S.A. [abs.]: International Symposium on Water-Rock Interaction, Prague, Czechoslovakia, Abstract Volume, p. 52.

Muffler, L.J.P, White, D.E., and Truesdell, A.H., 1971, Hydrothermal 

explosion craters in Yellowstone National Park: Geological 

Society of America Bulletin, v. 82, p. 723-740.

Muffler, L.J.P., White, D.E., Truesdell, A.H., and Fournier, R.O, 1982, 

Geologic map of Lower Geyser Basin, Yellowstone National Park, 

Wyoming: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-1373, scale 1:24,000.

Mumpton, FA., 1960, Clinoptilolite redefined: American Mineralogist, 

v. 45, p. 351-369.

Passaglia, E., 1970, The crystal chemistry of chabazites: American 

Mineralogist, v. 55, p. 1278-1301.

Pierce, K.L., 1979, History and dynamics of glaciation in the northern 

Yellowstone National Park area: U.S. Geological Survey Professional Paper 729-F, 90 p.

Pierce, K.L., Obradovich, J.D., and Friedman, I., 1976, Obsidian 

hydration dating and correlation of Bull Lake and Pinedale 

Glaciations near West Yellowstone, Montana: Geological Society 

of America Bulletin, v. 87, p. 703-710.
REFERENCES CITED C23

Pongiluppi, D., 1977, A new occurrence of yugawaralite at Osilo, Sardinia: Canadian Mineralogist, v. 15, p. 113-114.

Roedder, E., 1984, Fluid inclusions: v. 12 of Reviews in Mineralogy: 

Mineralogical Society of America, 644 p.

Schoen, R., White, D.E., and Hemley, J.J., 1974, Argillization by 

descending acid at Steamboat Springs, Nevada: Clays and Clay 

Minerals, v. 22, p. 1-22.

Sheppard, R.A., and Gude, A.J., 3d, 1969, Diagenesis of tuffs in the 

Barstow Formation, Mud Hills, San Bernardino County, California: U.S. Geological Survey Professional Paper 634, 35 p.

Silberman, M.L., White, D.E., Keith, T.E.C., and Dockter, R.D., 1979, 

Duration of hydrothermal activity at Steamboat Springs, Nevada, 

from ages of spatially associated volcanic rocks: U.S. Geological 

Survey Professional Paper 458-D, 14 p.

Thompson, J.M., and Yadav, S., 1979, Chemical analyses of waters 

from geysers, hot springs and pools in Yellowstone National Park, 

Wyoming from 1974 to 1978: U.S. Geological Survey Open-File 

Report 79-704, 49 p.

Waldrop, H.A., and Pierce, K.L., 1975, Surficial geologic map of the 

Madison Junction quadrangle, Yellowstone National Park, Wyoming: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-651, scale 1:62,500.

White, D.E., Fournier, R.O., Muffler, L.J.P, and Truesdell, A.H., 1975, 

Physical results of research drilling in thermal areas of Yellowstone National Park, Wyoming: U.S. Geological Survey Professional Paper 892, 70 p.

Wise, W.S., 1978, Yugawaralite from Bombay, India: Mineralogical 

Record, v. 5, p. 296.

Wise, W.S., and Tschernich, R.W, 1978, Dachiardite-bearing 

assemblages in the Pacific Northwest, in Sand, L.B., and 

Mumpton, FA., eds., Natural zeolites: occurrence, properties, 

use: New York, Pergamon Press, p. 105-111.

Zeng, Y, and Liou, J.G., 1982, Experimental investigation of 

yugawaralite-wairakite equilibrium: American Mineralogist, v. 

67, p. 937-943.

GPO 687-049/45005