Ash-flow Tuffs of the Galiuro Volcanics 

in the Northern Galiuro Mountains, 

Final County, Arizona

GEOLOGICAL SURVEY PROFESSIONAL iPAPER 1104
Ash-flow Tuffs of the Galiuro Volcanics 

in the Northern Galiuro Mountains, 

Final County, Arizona

By MEDORA H. KRIEGER

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1104

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Krieger, Medora Louise Hooper, 1905-

Ash-flow tuffs of the Galiuro Volcanics in the northern Galiuro Mountains,

Final County, Arizona.

(Geological Survey Professional paper ; 1104)

Bibliography: p. 32.

1. Volcanic ash, tuff, etc. Arizona Galiuro Mountains. I. Title.

II. Series: United States. Geological Survey. Professional paper; 1104. 

QE461.K757 552'.2 79-19484

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

Washington, D.C. 20402

Stock number 024-001-03239-2
CONTENTS

Abstract —————————————————————————————————————————————————— 1 

Introduction ————————————————————————————————————————————————— 1 

Galiuro Volcanics --—-————————————————......———....——....—....—....—.— 4

Holy Joe Member ————————...—.————........—...................———.———......—— 4

Aravaipa Member ————--------------------——.——————.——....——.————.——.—-— 11

Changes in chemical composition due to zeolitization ————————-—-——-—-— 21

Conclusions —--——-——————..................—.......—————....—.—————— 23

Tuff of Bear Springs Canyon ————-—————————————..„—...—.————.—... 26

Rhyolite-obsidian member —————————————————————————————————————— 27 

Hells Half Acre Tuff Member ———-————————————.———————————— 28

Suggestions for future work ———————————————....——..........———......——.—— 31

References cited ——————————————————————————————————————————————— 32

ILLUSTRATIONS

Page

FIGURE 1. Index map showing distribution of Galiuro Volcanics ————————————————-———-———.——-———-————— 1

2. Geologic map of parts of Brandenburg Mountain, Holy Joe Peak, and Klondyke quadrangles ————————-———-—— 2

3. Correlation chart showing relations of stratigraphic units in Galiuro Volcanics —-—————————...———.——————— 4

4. Photograph of typical exposure of Holy Joe Member ———————————--—-—-———-—-————-—-—————-———— 5

5. Chart showing some physical characteristics of Holy Joe Member ———————~~————.———.—-——.—-——————— 6

6. Photomicrographs of Holy Joe Member ——————————-——-————------————.——————.———.—-—-—-— 8

7. X-ray diffractographs of selected specimens of Holy Joe and Aravaipa Members —————————————————————————— 10

8. Sketch showing effect of buried topography on zonation in Holy Joe Member ——————-———-——-—-———-————— 10

9. Photograph of typical exposure of Aravaipa Member —————————————————-—-——-—-—-——————-———— 13

10. Chart showing some physical characteristics of Aravaipa Member —————————-—————-————————-——-—-—— 14

11. Photomicrographs of specimens from interior of Aravaipa Member ——————-————-—-———-—-—————-——————-16 

12-17. Photographs of:

12. Aravaipa Member filling channel in Precambrian rocks ———-————.............—....—....—.————....—.——.—— 18

13. Vuggy zone, Aravaipa Member ——~———-—-—..........————................—.———.———————.—————-—.—— 18

14. Thunder eggs, Aravaipa Member ——————————————————..—.....—....———.—.———.———-—-—- 19

15. Platy-jointed zone, Aravaipa Member ————————————-—..........——.———......——-—-——.—.———-—-— 20

16. Distal margin of Aravaipa Member —-———————————————...........—............—......————————-——— 20

17. Change in zonation of Aravaipa Member ——————————————-————————.—-—.—.———-——-——— 22

18. Map showing location of specimens, Aravaipa Member ——————————————————-———-—-———-————— 24

19. Diagrammatic sketches of zones in Aravaipa Member —————————————————————————————————————————— 24

20. Chart showing lithologic zones and color, Aravaipa Member ———-——------——-———-——-—-——————-———— 25

21. Chart showing specific gravity, Aravaipa Member ————————————....———...............—...—.—....——.—.—— 26

22. Chart showing approximate composition, Aravaipa Member ——-———————.—.....—.——.—-———.....——.—.—— 27

23. Photomicrographs of distal margin, Aravaipa Member ———————————-———----—-——-—————-—-—-———- 28

24. Ternary diagram showing relative amounts of CaO, Na2O, and K2O in zeolitized and nonzeolitized rocks ———————— 28

25. Photograph of units of Hells Half Acre Tuff Member ———————————————————————————————————— 30

26. Diagrammatic sketch showing relations of Hells Half Acre Tuff Member, rhyolite-obsidian member, and upper andesite of

Virgus Canyon ——————————————————————————————————————————————————————————————— 30

27. Photograph of Hells Half Acre Tuff Member and rhyolite-obsidian member -——-—-—-—————-——————————— 31

28. Diagrammatic sketch showing relations of middle unit of Hells Half Acre Tuff Member and rhyolite-obsidian member -— 31

29. Chart showing approximate composition of Hells Half Acre Tuff Member ——————-—-——————-———-——-—— 32

III
IV CONTENTS

TABLES

Page

TABLE 1. Potassium-argon ages of ash-flow tuffs in Galiuro Volcanics in the northern Galiuro Mountains ————————-—-—«—- 3

2. Modes of Holy Joe Member -------—————-—————————.—————————————————————————- 7

3. Chemical composition and comparison of glassy and crystallized parts, Holy Joe Member ———————————————————— 11

4. Semiquantitative spectrographic analyses of minor elements in ash-flow tuffs and rhyolite-obsidian member, northern

	Galiuro Mountains ———-——————————.———————..—....——.......—————.———......——.———.—.—... 12

5. Modes of Aravaipa Member ——-————~——.———.————————.————.—————.—....—.————.—.—.—.— 15

6. Chemical composition and comparison of glassy and crystallized parts, Aravaipa Member —-———-—-——-——————-- 22

7. Chemical composition and comparison of zeolitized and nonzeolitized rocks ———-———-———-———-———-——————- 25
ASH-FLOW TUFFS OF THE GALIURO VOLCANICS IN THE NORTHERN 

GALIURO MOUNTAINS, FINAL COUNTY, ARIZONA

By MEDORA H. KRIEGER

ABSTRACT

The upper Oligocene and lower Miocene Galiuro Volcanics in the 

northern part of the Galiuro Mountains contains two distinctive major 

ash-flow tuff sheets, the Holy Joe and Aravaipa Members. These major 

ash-flows illustrate many features of ash-flow geology not generally exposed so completely. The Holy Joe Member, composed of a series of 

densely welded flows of quartz latite composition that make up a simple 

cooling unit, is a rare example of a cooling unit that has a vitrophyre 

at the top as well as at the base. The upper vitrophyre does not represent a cooling break. The Aravaipa Member, a rhyolite, is completely exposed in Aravaipa and other canyons and on Table Mountain. Remarkable exposures along Whitewash Canyon exhibit the 

complete change from a typical stacked-up interior zonation of an ash 

flow to a nonwelded distal margin. Vertical and horizontal changes in 

welding, crystallization, specific gravity, and lithology are exposed. 

The ash flow can be divided into six lithologic zones.

The Holy Joe and Aravaipa Members of the Galiuro Volcanics are 

so well exposed and so clearly show characteristic features of ash-flow 

tuffs that they could be a valuable teaching aid and a source of theses 

for geology students.

INTRODUCTION

The upper Oligocene and lower Miocene Galiuro Volcanics consists of andesitic to rhyolitic flows, tuffs, and 

ash-flow tuffs. Included in the sequence in the northern 

part of the Galiuro Mountains are two distinctive major ash-flow tuff sheets and two minor ash flows. The major ash-flow tuff sheets provide an excellent example of 

contrast in types of emplacement, cooling and crystallization history, and later alteration, and they illustrate some features in ash-flow tuffs not normally seen 

or exposed so completely. The older one has a vitrophyre at the top as well as at the bottom of a sequence 

of ash flows that cooled as a unit. The younger one, also 

a simple cooling unit, has a well-developed horizontal 

and vertical zonation that suggests a single ash flow, 

but that may represent at least two additional pulses. 

The nonwelded distal margin has been zeolitized.

The Galiuro Volcanics extends from the southern 

part of the Christmas quadrangle to the northern part 

of the Dragoon quadrangle (fig. 1). The first detailed 

descriptions of the Galiuro Volcanics were by Cooper

and Silver (1964) in the Dragoon quadrangle and by 

Simons (1964) in the Klondyke quadrangle. Blake 

(1902) had previously used the term Galiuro Rhyolite 

for tuffs and lavas in the central part of the Galiuro 

Mountains. Willden (1964) published a generalized 

geologic map of the Christmas quadrangle but he did 

not correlate the volcanic rocks with the Galiuro Volcanics. Detailed subdivisions of the volcanic rocks in 

the northern Galiuro Mountains—the Holy Joe Peak

110° 30'

33° 00'

5 10 15 20 KILOMETERS

FIGURE 1.—Distribution of Galiuro Volcanics (shaded), 15- 

minute quadrangles: Christmas (C), Dragoon (D), Galiuro 

Mountains (G), Holy Joe Peak (H), Klondyke (K), Mammoth (M), Reddington (R), Sierra Bonita Ranch (S), Winchester Mountains (W), and 7 1/2-minute quadrangles; 

Brandenburg Mountain (B) and Holy Joe Peak (HJ).
ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

KLONDYKE 15'

52'3CT

no-32'30" MOUNTAIN 7%' • „ M,QU.NT .

1 MILE

HOLY JOE PEAK? 1/:,'

FIGURE 2.—Geologic map of parts of Brandenburg Mountain, Holy Joe Peak, and Klondyke quadrangles 

(modified from Krieger, 1968a, b; and Simons, 1964).
INTRODUCTION

O

>Tgdv

EXPLANATION

Younger rocks 

Andesite of Table Mountain 

Apsey Conglomerate Member 

Hells Half Acre Tuff Member 

Rhyolite-obsidian Member - v, vent

Upper andesite of Virgus Canyon - 

Includes associated conglomerate

Lower andesite of Virgus Canyon - 

Includes associated conglomerate

Aravaipa Member — Includes upper 

white tuff (upper nonwelded tuff of 

earlier reports)

Lower tuff unit-Includes (oldest to youngest) tuff of Oak Springs Canyon, andesite 

of Depression Canyon (shown separately 

only in northwestern part of map area) , 

and tuff of Bear Springs Canyon (upper 

part of lower tuff unit; mostly in 

western part of map area)

Andesite of Depression Canyon — 

Includes associated conglomerate

Biotite dacite unit 

Holy Joe Member

Andesite of Little Table Mountain - 

Includes coarsely porphyritic andesite

WhitetaiK?) Conglomerate (Oligocene) - 

Beds less than 15m thick between 

prevolcanic rocks and the next 

overlying unit of the Galiuro Volcanics (porphyritic andesite, Holy 

Joe Member, andesite of Depression 

Canyon) are included in the overlying 

unit

Older rocks

Lower

Miocene

to

Upper 

Oligocene

——Contact

' — Fault — Dashed where approximately

located. Ball and bar on downthrown 

side

-*—*—*—*— Thrust fault - Sawteeth on upper plate

• Location of sections and analyzed 

specimens of Holy Joe Member

• Location of sections and analyzed 

specimens of Aravaipa Member

• Location of other analyzed specimens 

FIGURE 2.—Continued.

quadrangle1—were mapped by Krieger (1968a, b); S. 

C. Creasey (unpub. data) mapped in reconnaissance 

the central Galiuro Mountains, which contains the 

thickest section of the formation. The stratigraphy, 

lithology, chemical composition, and age of the Galiuro 

Volcanics are summarized by Creasey and Krieger 

(1978). The formation can be separated into two parts 

by an erosional unconformity. The lower part is pre1Holy Joe Peak in this report refers to the 15-minute quadrangle; four geologic maps 

cover this area (Krieger, 1968a-d). The ash-flow tuffs discussed in this report are in the 

Brandenburg Mountain and Holy Joe Peak 7Vi2-minute quadrangles and the Klondyke 

quadrangle; discussion is largely limited to the two 7^-minute quadrangles.

dominantly andesite to rhyodacite flows but it contains 

three ash-flow tuffs. The upper part is chiefly ash-flow 

tuffs, but it includes andesite flows and two areas of 

rhyolite-obsidian flows and domes, one of which is in the 

northern Galiuro Mountains. The distribution of the 

Galiuro Volcanics in parts of the Holy Joe Peak and 

Klondyke quadrangles, which is shown in figure 2, is 

modified from the published geologic maps. The terminology used in each area and my interpretation of 

the relations of members or units in the Klondyke and 

Holy Joe Peak quadrangles and in the Christmas 

quadrangle to the north are given in figure 3.

The two major ash-flow tuff sheets—Holy Joe and Aravaipa Members—and the two minor ones—tuff of 

Bear Springs Canyon and Hells Half Acre Tuff Member—illustrate many features of ash-flow geology. The 

Holy Joe Member rests on the unconformity that separates the volcanics into two parts, the tuff of Bear 

Springs Canyon underlies the Aravaipa Member, and 

the Hells Half Acre Tuff Member is in the upper part 

of the formation. The ages of the ash-flow tuffs are given 

in table 1.

The Holy Joe Member is composed of a series of 

densely welded flows of quartz latite composition that 

make up a simple cooling unit (Smith, 1960a). It is a 

rare example of a cooling unit that has a vitrophyre at 

the top as well' as at the base. The major zones recognized are, in ascending order: the lower vitrophyre, 

lower devitrified zone, central vapor-phase zone, upper 

devitrified zone, and upper vitrophyre. The absence of 

breaks in crystallization across flow boundaries and the 

gradation between zones and from crystallized to vitric 

material at the top indicate a single cooling unit. 

Dense welding and fairly uniform high specific gravity 

throughout the member indicate that the individual 

flows were hot.

The Aravaipa Member, of rhyolite composition, has 

a well-developed zonation that indicates a simple cooling unit and possibly a single ash flow. It presents a 

classic example of ash-flow geology, in that the complete 

change from the stacked-up zonation typical of the interior of the ash flow to the nonwelded distal margin, 

now zeolitized, is completely exposed in some canyon 

walls. Horizontal and vertical zonation in ash-flow tuffs 

was first recognized by Smith (1960b).

TABLE 1.—Potassium-argon ages ofash-ffow tuffs in the Galiuro 

Volcanics in the northern Galiuro Mountains (in millions of years)

[From Creasey and Krieger, 1978]

Member

Hells Half Acre Tuff Member -----

Tuff of Bear Springs Canyon1 ——

Biotite

24.6 ±0.7 

25.7 ±0.7 

23.8 ±0.7 

26.5 ±0.8

Sanidine

22.5 ±0.7 

oo Q -i- n a

oc c -i_n s

xThis analysis may be from one of the underlying tuffs in the lower tuff unit of Simons 

(1964, p. 81).
ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

Brandenburg Mountain and Holy Joe Peak 7'/2-minute 

quadrangles (Krieger, 1968a, b)

Gtiristmas 15-minute 

quadrangle (Willden, 1964)

Basalt of Gila Conglomerate

Tuff and rhyolite, undivided

Rhyolite

Along southern border of quadrangle 

includes Apsey Conglomerate and 

Hells Half Acre Tuff Members, 

\ rhyolite-obsidian member /

Basalt and andesite

Gravel, possibly Whitetail Conglomerate

METERS 

r400

-300

-200

-100

-0

\ \ \ \ 

\ \ 

\ \ \ \ 

\ \ 

\ \

\

\

Andesite of Table Mountain

Apsey Conglomerate Member

Hells Half Acre Tuff Member

Rhyolite-obsidian member

' Upper andesite of Virgus Canyon ^

' Conglomerate 1

Aravaipa\ Upper partly welded 

Member J Partly welded, welded, and lower nonwelded

g^ Tuff of Bear Springs \. 

"^Conglomerate Canyon Conglomerate'X

^Andesite of Depression Canyon Conglomerate/"

Tuff of Oak Springs Canyon

Holy Joe Member

» , . . Latitic lavas of y< Andesite of Little Table Mountain i_^^^x Zapata Wash^

Whitetail (?) Conglomerate

\ 

\ 

\

> Klondyke 15-minute quadrangle 

\ \ (Simons, 1964)

x \

x \ 

\ x

----""

_ _ _^ ~ — -~~

''

^'''

"-^^^

Upper tuff unit

Quartz latite unit of Hawk Canyon/ 

Rhyolite-obsidian unit 

Tuff unit of Hawk Canyon-^^

Upper andesite unit 1

Intermediate andesite unit

'White tuff unit N

Upper welded tuff unit RhyolButte Blac^><^ —

Olivineandesite^^ 

Lower tuff unit ^^~- 

Hornblende andesite of Parsons Canyon^:

Biotite dacite unit

Lower welded tuff unit

^^Latite > subunit Heterogeneous siliceous''^^ ^

volcanics of Four Mile 

Lower andesite unit Canyon

Simon's (1964) upper andesite unit consists of two 

andesites one resting on rhyolite-obsidian 4n an area where 

his upper tuff unit was not deposited; the other along 

Aravaipa Canyon beneath his upper tuff unit, which he 

interpreted as also overlying rhyolite-obsidian.

2 Lower tuff unit m the Klondyke quadrangle includes 

tuff of Bear Springs Canyon,andesite of Depression Canyon, 

and a series of tuffs equivalent to or underlying tuff of Oak 

Springs Canyon.

FIGURE 3.—Correlation chart showing relations of stratigraphic units in Galiuro Volcanics, Christmas, Brandenburg Mountain, Holy 

Joe Peak, and Klondyke quadrangles. Shows maximum thickness of members or units in each area.

Suites of specimens were collected from a section 

vertically across the Holy Joe Member and from six 

vertical sections across the Aravaipa Member from the 

interior to near the distal margin. Changes in lithology, welding, crystallization, specific gravity, and composition are shown in tables and diagrammatic 

sketches. Data obtained from chemical analyses of selected specimens and from X-ray diffractographs of all 

specimens are presented.

Ac/motvJedgTnents—I thank my colleagues of the U.S. 

Geological Survey for their important contributions 

and stimulating discussions of ash-flow problems. Special thanks are due R. L. Smith and D. W. Peterson for 

interpreting and first pointing out many of the distinctive features of the ash flows in the northern Galiuro Mountains and to S. C. Creasey and F. S. Simons 

for data on the volcanic rocks in adjacent areas. D. W. 

Peterson, E. D. McKee, E. W. Heldreth, and M. G. 

Johnson made many helpful comments and suggestions during preparation of the manuscript.

GALIURO VOLCANICS

HOLY JOE MEMBER

The Holy Joe Member of the Galiuro Volcanics crops

out intermittently from 13 km west of to 8 km east of 

the boundary between the Holy Joe Peak and Klondyke quadrangles (Krieger, 1968a, b; Simons, 1964) 

and from the northernmost latitude of Aravaipa Canyon to south of the latitude of Little Table Mountain 

(fig. 2); it also crops out on a butte about 10 km south 

of Little Table Mountain. It may extend for many kilometers to the south. Its source is unknown. The member is about 100 m thick in the Klondyke quadrangle 

(Simons, 1964). Its maximum thickness around Table 

Mountain (fig. 2) in the Holy Joe Peak quadrangle 

(Krieger, 1968b) is about 80 m; to the north, the lower 

part, and locally all of it, laps out against prevolcanic 

topographic highs.

The Holy Joe Member is a cliff-forming unit that has 

strong horizontal partings (fig. 4), has a rather uniform 

appearance, and is pale brown to pale red throughout 

most of its thickness, except for a thin nearly white 

nonwelded tuff and a dark vitrophyre at the base and 

another dark vitrophyre at the top. The ash-flow tuff 

between the lower and upper vitrophyres can be divided into three lithologic zones: lower devitrified 

zone, central vapor-phase zone, and upper devitrified 

zone. The lower vitrophyre is dark gray, except for the 

basal part, which is brown due to oxidation. The lower
HOLY JOE MEMBER

FIGURE 4.—Typical exposure of Holy Joe Member, northwest end of 

Table Mountain, as viewed from northeast. Horizontal partings 

probably represent individual flows and possibly zones of denser 

welding. Andesite of Table Mountain (Tat); Apsey Conglomerate 

Member (Ta); Aravaipa Member (Tar); Holy Joe Member (Thj).

devitrified zone is reddish brown, and the upper one is 

slightly redder. The vapor-phase zone is brown to pale 

red except for the middle part, which is light brownish 

gray. The lower part of the upper vitrophyre is dark 

gray, and the upper part is red. Black glassy flattened 

pumice lapilli contrast with the red of the upper vitrophyre and the brown of the lower vitrophyre. The transition from the lower vitrophyre to the lower devitrified zone is abrupt, but that between all the other 

zones is gradational. Dense welding is characteristic 

of all the zones except the basal nonwelded zone.

A suite of specimens (H201A-Q) was collected vertically across the ash-flow sheet in Oak Springs Canyon 

(fig. 2, loc. A). The elevation above base, field units, 

color, zones of welding and crystallization, mineralogic 

composition (based on X-ray diffractographs), and specific gravities of these specimens are summarized in 

figure 5. The Holy Joe Member is composed of shards 

and pumice lapilli, very tiny crystal fragments of feldspar, quartz, and biotite, and some foreign rock and 

mineral fragments (table 2). Phenocrysts make up 

about 7 percent of the rock, and feldspar, mostly plagioclase, makes up about 71 percent of the phenocrysts. Chemical analyses (see table 3) indicate a 

quartz latite composition.

Photomicrographs (figs. 6A-J) of selected thin sections of the suite of specimens illustrate typical microscopic features of the ash-flow sheet. The basal nonwelded tuff contains undeformed shards and glass

bubbles (not illustrated). All the rocks above the nonwelded tuff show evidence of dense welding, eutaxitic 

texture due to flattening and alinement of pumice lapilli 

and shards (figs. 6B, C, E), collapse of pumice with 

elimination of most pore space but retention of pumice 

structure in frayed-out ends (fig. 6A), and molding of 

pumice and shards against phenocrysts or crystal and 

lithic fragments (figs. 6A, /, J). Shard structure (figs. 

6B, C, E, G, I) is preserved in vitrophyres and in most 

of the crystallized tuff owing to fine-grained axiolitic 

intergrowths (too small to show at scale of photomicrographs) of cristobalite and sanidine, the products of 

devitrification. Outlines of pumice lapilli are generally 

preserved, but their structure may be destroyed by 

spherulitic intergrowths around trapped gas in cavities (figs. 6D, F, H).

All the tuff between the lower and upper vitrophyre 

is devitrified, as shown by its nonvitric (stony or lithoidal) character, by a finely crystalline groundmass 

(composed of cristobalite and sanidine; see below), and 

by the alteration of biotite. The vapor-phase zone, in 

which cristobalite and sanidine are also characteristic, 

is recognized by its lighter color, the slightly cavernous 

appearance of pumice lapilli in both hand specimen 

and thin section (figs. 6D, F), and the presence of discrete microscopic crystals of tridymite in cavities. 

Crystallization in this zone is not as coarse grained as 

in less densely welded ash flows and is confined largely 

to pumice lapilli.

In addition to the study of hand specimens and thin 

sections, each specimen was X-rayed; the results are 

shown in the composition column in figure 5. X-ray 

diffractographs of the ash flows show not only the phenocrysts (feldspar, quartz, and biotite) but also the devitrification products (cristobalite and feldspar) and 

the alteration products (clay and zeolite). Because-of 

preferred orientations, degrees of crystallinity, masking by noncrystallized material, mass absorption, and 

other problems, quantitative results are impossible to 

obtain. The X-ray diffractographs show the apparent 

abundance of the constituents and are useful in identifying them, especially where thin sections were not 

available, as in parts of the Aravaipa Member. A few 

diffractographs of selected specimens of the Holy Joe 

and Aravaipa Members (fig. 7) are included to illustrate the type of peak heights involved. Noncrystalline 

material, such as glass in the vitric parts of the ash 

flow, is recognized as a "glass hump" (fig. 7A). Cristobalite is readily recognized by its characteristic peak 

(figs. IB, O. Sanidine and plagioclase can be distinguished by careful comparisons of the patterns with 

patterns prepared from pure mineral separates; they 

are identified only as feldspar in figure 7. Tridymite 

was not definitely recognized in the X-ray diffracto-
ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

60 -

50 -

40 -

30 -

20 -

10 -

—

—

—

—

-

—

-

—

—

-

—

—

—

—

Sample 

H201

Q

P

0

N

M

L

K

J

J-1

I

H

G

F

E

D 

C

A

Field 

units

Vitrophyre

Devitrified

Vapor phase

Devitrified

Vitrophyre

White tuff

Color

Red

Dark gr

Pale br to 

pale red

Pale br to 

pale red

Pale br to 

pale red

Lt br gr

Lt br gr

Pale red

Pale red to

pale br

Pale br

Pale br

Olive gr

Olive gr

Dark gr

Mod br 

Lt br

Pk gr

Zones of 

welding

ra

TMc

^

(D

§

(D 

en

C

D

Partial welding

No welding

Zones of 

crystallization

i

Vitric

'i

j

s

: >

•^ cu

.- (0

S .C

a

D "

0

a

(0

o

4J

Composition

(D4^

<D ~ 

~ 0

-Q Q N (D Q

O a) ^ £ o w>

.2 | 5 o .E £ 3

O i£ O m O o O

A 0 A A - A •

A o A A - - o

O O A A - A -

0 • 0 A - - -

• • A A - - -

0 o A A - 0 -

O O A A - - -

A o O A - A -

O O A A - A -

0 o A A - - -

O O A A - - -

- A A A - - •

A A A A - - •

- A A A - - •

- A A A - - •

- A A A - 0 •

- A A A • o -

Specific gravity

1.5 2.0

A^

Q^^.

2.5

P

°f

NJ

t

J\

J-1i

j

L

\

/

r

Abundant (more than 50 percent)

EXPLANATION

O A 

Present but not abundant Recognized Not recognized

FIGURE 5.—Some physical characteristics of the Holy Joe Member, based on specimens H201A-Q, collected at location A (fig. 2). Model data 

in table 2; chemical analyses of specimens F, H, and K in table 3. Color terms: br, brown or brownish; gr, gray; It, light; mod, moderate; 

pk, pinkish. Mineral abundance estimated from X-ray diffractographs of bulk samples. In addition to listed minerals, samples J-1 

through N contained tridymite.

graphs because it is a very minor constituent and its 

peaks (figs. IB, C) are close to some of the peaks of 

cristobalite, quartz, and feldspar. X-rays are the basis 

for most modern identification of zeolites in tuffs and 

sedimentary rocks. The zeolite, clinoptilolite, was recognized only in the X-ray of the basal nonwelded tuff

(see composition column, fig. 5); clinoptilolite extensively replaced the nonwelded distal parts of the Aravaipa Member (fig. IE).

Chemical analyses were made for samples from 

three different zones in the Holy Joe Member; the 

lower vitrophyre, lower devitrified zone, and the gray
HOLY JOE MEMBER 7 

TABLE 2.—Modes of Holy Joe Member

[Modes in volume percent. Based on thin-section studies of specimens collected vertically across the member in Oak Springs Canyon (loc. A, fig. 2); see fig. 5 for other characteristics. 

Field units: uv, upper vitrophyre; ud, upper devitrified; vp, vapor phase; Id, lower devitrified; Iv, lower vitrophyre]

Field

No.

Field 

unit

Percentage of rock exclusive of foreign fragments

Percentage of 

total rock

Matrix1

Total 

phenocrysts2

Quartz Biotite

(percentage of phenocrysts)

Foreign rock 

and mineral 

fragments4

Points 

counted

H201Q 

P 

O 

N 

M 

L 

J

J-l 

I

H 

G 

F 

E 

D 

C

uv 

ud

vp

Id 

Iv

90

87

87

90

90

92

85

92

91

89

91

88

87

92

93

10

13

13

10

10

8

15

8

9

11

9

12

13

9

6

6

4

11

6

7

9

6

9

10

6

5

(80) 

(69) 

(69) 

(60) 

(60) 

(50) 

(73) 

(75) 

(78) 

(82) 

(67) 

(75) 

(77) 

(75) 

(72)

(10)

(23)

(23)

(20)

(30)

(38)

(20)

(13)

(11)

(9)

(22)

(18)

(15)

(13)

(14)

(10) 

(8) 

(8) 

(20) 

(10) 

(12) 

(7) 

(11) 

(11) 

(9) 

(11) 

(9) 

(8) 

(12) 

(14)

27

12

11

1

4

5

4

4

7

6

7

4

9

4

9

1,062

1,006

1,003

1,007

1,044

1,052

1,046

987

956

1,064

970

971

1,000

1,062

995

Average 

Range -

90 

85-93

10 

7-15

(71) 

4-11

(20) 

1-3

(10) 

1-2 1-27

1,015

'Includes pumice lapilli, average 8 percent.

2Not counted are traces of magnetite and very tiny crystal fragments of quartz, feldspar, and biotite. Includes phenocrysts in pumice lapilli and crystal fragments in matrix.

3Largely plagioclase, includes sanidine (trace to 1 percent of total rock), may include some foreign plagioclase.

4Mostly andesite of Little Table Mountain.

part of the vapor-phase zone (table 3). Minor-element 

contents of these samples are given in table 4.

The whole-rock analyses show that chemical differences between zones in the Holy Joe Member are very 

small. The most significant differences noted are that 

the vitrophyre has more water than the crystallized 

tuffs and that the oxidation state of iron in the crystallized tuffs is higher than in the vitrophyre. Both of 

these characteristics are common in ash-flow tuffs 

throughout the western United States and elsewhere.

The high water content of the vitrophyre, most 

likely the result of secondary hydration, causes problems in comparing the abundances of the nonvolatile 

constituents (Ross and Smith, 1955, p. 1086-1088). To 

more readily compare the nonvolatile elements, table 

3 lists the analyses recalculated on a water-free basis; 

Earth cation amounts and C.I.P.W. norms are also 

listed. A comparison of the recalculated analyses 

shows a progressive but slight decline in silica and potassium upward in the section and increases in sodium 

and calcium. Without more data, however, it cannot be 

decided whether these differences are the result of progressive magmatic changes, transfer of elements during cooling or crystallization, solution during hydration, or simple coincidence.

The Holy Joe Member was made up of a series of 

very hot ash flows that erupted rapidly enough to cool 

as a unit. Dense welding, characteristic of hot ash 

flows, results in higher specific gravity than less welded 

flows. The rather uniform high specific gravity of this

ash-flow sheet supports the evidence for dense welding 

in hand specimens and thin sections.2 The specific 

gravity of the Holy Joe Member (fig. 5) contrasts markedly with the specific gravity of the Aravaipa Member 

(see fig. 10). The concentration of vapor-phase crystallization in the central part of the cooling unit, instead 

of increasing upward as in most ash flows, probably 

means that overlying possibly hotter flows trapped 

gases in this part of the ash flow, which may have been 

slightly cooler and less welded than overlying and underlying flows.

Horizontal partings in ash-flow tuffs may define individual flow boundaries, partial cooling breaks, or 

zones of dense welding. To determine the presence of 

flow boundaries, studies should be made of density, porosity, chemical and modal composition, and size distribution of phenocrysts and lithic fragments, similar 

to studies made by Ratte and Steven (1967) and Lipman, Christiansen, and O'Connor (1966). Although a 

careful search for flow boundaries was not made, an extinct fumarole, formed by escaping gas before the next

2Microprobe analyses of titanomagnetite and ilmenite from two specimens of the Holy 

Joe Member (E. W. Hildreth, oral commun., 1979) are consistent with the interpretation, 

based on dense welding and specific gravity, of high emplacement temperature. Magmatic 

equilibration temperatures and log fO2 values for the lower vitrophyre (H201C and 

H201E) are 1035° and 1065°C and -8.2 and -7.7 respectively. Temperatures of theupper 

vitrophyre could not be determined because of oxidation. The T°C and log fO2 values were 

read graphically from the Buddington-Lindsley (1964) curves, using Hildreth's analyses as 

recalculated by the method of Carmichael (1967). These are exceptionally high magmatic 

temperatures for biotite quartz latites. Since both oxide phases are abundant, homogeneous, and unaltered, however, there is no obvious reason to doubt the data. Buddington and 

Lindsley (1964) suggested an accuracy of ± 30°C, and ± 1 log unit fO2 ; reproducibilityfor 

these specimens is far better.
ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

1cm D

FIGURE 6.—Photomicrographs of Holy Joe Member. Biotite (B), holes (H), magnetite (M), plagioclase (P), pyroxene (py), pumice (pu), quartz 

(Q), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Specimen H201G, lower densely welded vitrophyre. Pumice 

collapsed, but structure retained in frayed-out end at left. Shards have dark-orange center and lighter yellow margins; some larger 

ones have dull-brown centers, representing original character of glass. Perlitic cracks common. B, Densely welded devitrified rock 

(H201I). Shard structure well preserved as dark-brown streaks, with lighter margins that are finely devitrified. Pumice and some shard 

structure destroyed (light areas) by intergrowths of cristobalite and feldspar, some spherulitic intergrowths observed with crossed nicols. 

C, Dense welding in lower brown vapor-phase zone (H201J-1) evident in alinement of shards (dark streaks) and flattened pumice (horizontal light and dark area across middle of photograph). D, Same view as C, crossed nicols. Shows spherulitic intergrowths within 

pumice and its cavernous character (black areas labeled H in O. E, Dense welding in upper brown vapor-phase zone (H201M) and large 

flattened pumice lapilli. F, Same view as E, crossed nicols. Shows crystallization within pumice and its cavernous character. Shard 

matrix devitrified but mostly too fine grained to show in photograph. G, Dense welding in upper brown vapor-phase zone (H201N). 

Shard structure retained (dark streaks in dark areas). It and pumice structure destroyed by aggregates of feldspar and cristobalite 

(light areas). H, Same view as G, crossed nicols. Fine-grained devitrification barely visible in dark areas contrasts with coarser grained 

devitrification and vapor-phase crystallization of shards and pumice in light area. Note alteration of biotite. /, Dense welding in upper 

devitrified part of ash flow (H201O). Shards (dark streaks) molded against large phenocrysts and crystal fragments; pumice flattened. 

Spherulitic intergrowths of cristobalite and feldspar developed in pumice; apparent with crossed nicols. J, Densely welded upper vitrophyre (H201P), containing numerous small and large crystal and lithic fragments. Shard structure and flattened pumice structure 

preserved.

overlying flow was erupted, occurs in Oak Springs Canyon (fig. 2, loc. A). A short distance below the upper 

vitrophyre (between specimens H201O and P, see fig. 

5) the boundary between two flows is marked by a concentration of lump pumice that was rafted on top of the

underlying flow. This boundary is interpreted as representing the base of the last flow. Elsewhere, contrasts 

in abundance of crystal and lithic fragments and in the 

character of pumice fragments suggest different flows. 

Because there is no change in crystallization of the
HOLY JOE MEMBER

1cm 1cm H

1cm 1cm

^-*1 *«f.

1cm 1cm

FIGURE 6.—Continued.

groundmass across the two recognized flow boundaries ' The vitrophyre at the top of the Holy Joe Member

and the gradation from one zone of crystallization to 

another, the partings are not believed to define partial 

cooling breaks.

deserves special comment. Vitrophyres commonly occur near the base of cooling units; a second vitrophyre 

in a sequence of ash flows is generally interpreted as
10 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

10

26, IN DEGREES 

20 30

40

30

20

10

70

30

50

40

30

20

10

80

70

60

50

40

30

20

10

100

90

80

70

60

50

40

30

20

10

BO 

70 

60 

50 

40 

30 

20 

10

i——i——i i

B

TT T

8.8 4.4 3.0 

I.NTERPLANAR SPACINGS, IN ANGSTROMS

B-Biotite 

C-Cristobalite

EXPLANATION 

Cl-Clinoptilolite 

F-Feldspar

Vitrophyre

Older rocks

Q-Quartz 

T-Tridymite

H—————APPROXIMATE SCALE 0.4 KILOMETER ——————>]

FIGURE 8.—Sketch showing effect of buried topography on zonation in Holy Joe Member. 

Lower and upper vitrophyres merge as ashflow sheet thins against prevolcanic topographic 

highs. Basal part of ash flow remains vitric and 

replaces devitrified and vapor-phase zones 

(dv). Dashed lines below and parallel to upper 

vitrophyre diagrammatically represent a few 

boundaries between individual flows. Aravaipa 

Member (Tar) and a thin basal tuff (not shown) 

overlie Holy Joe Member. Looking northwest 

across Oak Springs Canyon, from south of loc. 

6A, fig. 2.

indicating the base of an overlying cooling unit and a 

break in cooling history. The following evidence suggests that the upper vitrophyre does not represent a 

cooling break: the boundary marked by the lump pumice horizon, described above, is within the upper devitrified zone. No break in groundmass crystallization 

was recognized across this boundary. The devitrified 

material above the flow boundary grades upward into 

the upper vitrophyre. This last flow was hot enough to 

weld, but it cooled too rapidly, in contact with the air, 

to devitrify. Although a vitrophyre at the top of a cooling unit is rare, Lipman, Christiansen, and O'Connor 

(1966) have described a similar occurrence. I am indebted to R. L. Smith (oral commun., 1963) for first 

pointing out many of the features that led to the interpretation of this ash-flow sheet. Further evidence of 

a single cooling unit can be seen where the ash-flow 

sheet laps against prevolcanic topographic highs and 

the lower vitrophyre crosses flow lines until it merges 

with the upper vitrophyre (fig. 8).

FIGURE 7.—X-ray diffractographs of selected specimens of Holy Joe 

and Aravaipa Members, showing type of peak heights involved 

in estimation of composition. Calculated positions of major tridymite peaks also shown. Peak intensity (maximum) = 100. 

Cu/Ni radiation, A CuKa = 1.5418 A. Scan from 4° to 36° at 

1° 26/minute. A, Vitrophyre, H201E, Holy Joe Member. B, Devitrified zone, H201H, Holy Joe Member. C, Vapor-phase zone, 

H201M, Holy Joe Member. D, Vapor-phase zone, H202Q, Aravaipa Member. E, Zeolitized tuff, A3, Aravaipa Member.
ARAVAIPA MEMBER 11 

TABLE 3.—Chemical composition and comparison of glassy and crystallized parts, Holy Joe Member

[Major oxide analyses (weight percent) by P. Elmore, S. Botts, and C. Chloe by rapid methods described by Shapiro and Brannock (1962). See table 4 for minor-element analyses]

Original analyses

SiO2 — — — -

AI Al POJ3 —— —— — ——

FeO ____ -

MgO CaO — — —

Na2O —— —— -

K

/-v

H /~» 1 H f\

Tin

MnO

Total -

i

en 9

.......... 14.4

i ^

CQ

........ .. .77

.......... i.i

Q C.

.......... 5.4

q E

.......... .40

.......... .48

.......... .07

^

.......... 99

2

68.5 

15.2 

2.5 

.30 

.80 

1.3 

3.8 

5.7 

.53 

.32 

.56 

.16 

.08 

<.05

100

3

67.1 

15.4 

2.6 

.33 

.77 

1.8 

4.0 

5.2 

.58 

.56 

.60 

.19 

.05 

<.05

99

Recalculated without H2O and CO2

SiO2 — —— ——

Al n

Fe203 -----

FeO —— — ——

MgO —— ——

CaO ———.-

Na2O — — ——

K20 —— — —

Tin

M2n6

Total -

1

_ .. 70 f»

.... —— . 15.1

.......... 1.6

.......... .66

.......... .81

.......... 1.1

.......... 3.8

.......... 5.7

.......... .50

1 3

.... ...... .07

2

69.3 

15.4 

2.5 

.30 

.81 

1.3 

3.8 

5.8 

.57 

.16 

.08

100.02

3

68.4 

15.7 

2.7 

.34 

.79 

1.8 

4.1 

5.3 

.61 

.19 

.05

99.98

Rutile — — — — —

Total — — -

Si — —— —— ... ——

Al -—-—————

Fe+3 ———————

Mg -———-—

—————————

Ti ———————.

P —— —— —— ——

Mn 

Total — —

Fe total —— — — - —

Fe + 2/Fe total — — --

CIPW norms

1

OO E

qq E

q9 fl

4 Q

1.0 9 n

1.0

1.0

100.1

Earth cations

1

/?E E

16.6

1.1

.51

1.1

o. /

• — .00

.10

.Do

QQ 99

1.61

q9

2

21.3 

34.1 

32.5 

5.5 

.8 

2.0

2.5 

.8 

.1 

.4

100.0

2

64.4 

16.8 

1.8 

.24 

1.1 

1.3 

6.9 

6.8 

.40 

.13 

.06

99.93

2.04 

.12

3

19.9 

31.3 

34.5

7.8 

.4 

2.0

2.7 

.8 

.2 

.5

100.1

3

63.5 

17.2 

1.9 

.26 

1.1 

1.8 

7.3 

6.3 

.43 

.15 

.04

99.98

2.16 

.12

NOTE: Samples 1-3 from Oak Springs Canyon, NE corner sec. 6, T. 7 S., R. 18 E. (loc. A, fig. 2). 1, Lower vitrophyre, H201F, lab no. 159526. 

2, Lower devitrified zone, H201H, lab. no. 159527. 3, Vapor-phase zone, H201K, lab no. 159528.

ARAVAIPA MEMBER

The Aravaipa Member of the Galiuro Volcanics covers or underlies an area of more than 144 km2 , from 

the northernmost latitude of Aravaipa Canyon (fig. 2) 

for about 11 km to the south side of Table Mountain 

(fig. 2), and from about 6 km west of to 6 km east of 

the boundary between the Holy Joe Peak and Klondyke quadrangles. The southernmost exposures on Table Mountain are about 75 m thick—and they show 

zoning typical of the central part of the ash-flow sheet. 

The absence of the member farther south, therefore, 

suggests its removal by erosion rather than thinning 

at a distal margin; this interpretation is further supported by the gentle north to northeast dip of the member and by its southward projection upward above the 

present land surface. The Aravaipa Member may, however, be present in some of the thick accumulations of

ash flows to the southeast that have not yet been divided 

into separate units (Creasey and Krieger, 1978). To the 

east and probably to the southwest, the member lias 

been downfaulted and buried by younger deposits. Its 

distal edge is exposed to the northwest. North of Aravaipa Canyon it is buried by younger members of the 

Galiuro Volcanics. Except at its distal margin, where 

it has been eroded, or where it thins, or is absent over 

topographic highs of older rocks, the member has a 

fairly uniform thickness of about 75 m.

The Aravaipa Member is an ash-flow tuff of rhyolitic 

composition that has a well-developed interior zonation; this zonation indicates that it has an uninterrupted cooling history but it may be composed of two 

or more ash flows. Excellent exposures of the interior 

vertical zonation occur in near-vertical cliffs along Aravaipa Canyon (fig. 9) and along Oak Springs and up-
12 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

TABLE 4.—Semiquantitative spectrographic analyses of minor elements in ash-flow tuffs and rhyolite-obsidian member, northern Galiuro

Mountains, Ariz.

[Minor-element analyses by semiquantitative spectrographic methods by I. H. Barlow (nos. 1-8) and C. H. Heropoulos (nos. 9-13); values reported as the nearest in the series 1.5, 2,

3, 5, 7, 10. Comparison with quantitative analyses indicates that the same class interval is assigned in about 30 percent of the samples. N, not detected; leaders (--), not looked for;

<, less than. Looked for but not found: As, Au, Bi, Cd, Eu, Ge, He, In, Li, Pd, Pt, Re, Sb, Sm, Ta, Te, Th, Tl, U, W]

Quadrangle

Member

Unit

Number

Laboratory

No. 

Field No.

\a

g

ga ______ 

Be — — — — -

Ce

Co ----- 

Cu —— ----- -

Qa _________

/"U

La --— —— -

Mo — — —— —

Nb — —— — —

Nd

Ni — ——— — -

Pb —— —— ——

Sc —— —— — -

Sn -—— ——

Sr —— —— —— 

V _______ 

Y — ——— ——

Yb — --—— 

Zn — —— — —

Zr

Holy Joe Peak

Holy Joe Member

Vitrophyre

1

159526 

H201F

<0.00007 

<.003 

.1 

.0003 

.03 

.0003 

.0005 

.005 

.0015 

N 

.01 

.0003 

.0015 

.01 

.002 

.003 

.0005 

N 

.03 

.002 

.005 

.0005 

N 

.1

De vitrified

2

159527 

H201H

<0.00007 

N 

.2 

.0003 

.03 

.0005 

.002 

.002 

.002 

.003 

.015 

.0003 

.002 

.015 

.003 

.003 

.001 

N 

.05 

.005 

.007 

.0007 

N 

.1

Vaporphase

3

159528 

H201K

<0.00007 

N 

.2 

.0003 

.03 

.0005 

.0015 

.0015 

.002 

N 

.01 

<.0003 

.002 

.01 

.005 

.003 

.0007 

N 

.05 

.007 

.005 

.0005 

N 

.07

Brown 

vitrophyre

4

159529 

H202E

<0.00007 

<.003 

.03 

.0003 

.015 

N 

.0015 

.0003 

.0015 

N 

.007 

.0005 

.002 

N 

.0015 

.007 

.0005 

.0005 

.005 

.0005 

.003 

.0005 

N 

.015

Brandenburg Mtn.

Aravaipa Member

Black 

vitrophyre

5

159530 

H202F

<0.00007 

<.003 

.03 

.0003 

.01 

N 

.0005 

.0002 

.0015 

N 

.005 

.0005 

.002 

N 

.001 

.007 

.0002 

.0007 

.003 

.0005 

.003 

.0003 

N 

.02

De vitrified

6

159531 

H202L

<0.00007 

<.003 

.05 

.0005 

.01 

N 

.0003 

.0003 

.002 

N 

.005 

<.0003 

.002 

N 

.001 

.003 

.0003 

N 

.007 

.001

.0003 

N 

.02

Platyjointed

7

159532 

H202M

<0.00007 

<.003 

.07 

.0005 

.02 

N 

<,0003 

.0003 

.002 

N 

.007 

<.0003 

.002 

N 

.0015 

.002 

.0005 

N 

.01 

.0007 

.003 

.0003 

N 

.02

Columnarjointed

8

159533 

H202O

<0.00007 

<.003 

.07 

.0005 

.02 

N 

.0003 

.001 

.002 

N 

.007 

.0003 

.002 

N 

.001 

.003 

.0005 

.0003 

.007 

.001 

.005 

.0005 

N 

.02

Pink 

tuff

9

M126691W 

A-4

N 

.007 

.02 

.0007

N 

.00015 

.0005

.005 

N 

.003

.00007 

.003 

.0005 

N 

.01 

.0007 

.003

.003 

.03

Pink 

tuff

10

M126692W 

H343M

N 

.001 

.02 

.0007

N 

.003 

.0007

.01 

N 

.005

.00007 

.003 

.0007 

N 

.02 

.002 

.003

.003 

.03

Klondyke

Tuff of Bear 

Springs Can.

Pink 

tuff

11

M101324W 

H414

<0.00007 

N 

.05 

.0003 

.01 

N 

.0001 

.0003 

.0015 

N 

.005 

N 

.002 

N 

N 

.003 

.0005 

N 

.03 

.0015 

.003 

.0003 

N 

.015

Brandenburg Mtn.

Hells Hf. 

Acre Tuff

Middle 

unit

12

M101323W 

H410

<0.00007 

.0015 

.02 

.0003 

.007 

N 

.00015 

.0005 

.0015

.005 

N 

.002 

N 

.00015 

.003 

.0003 

N 

.05 

.0015 

.003 

.0003 

N 

.01

Rhyoliteobsidian

Rhyolite

13

M101317W 

H409

<0.00007 

.001 

.005 

.0005 

.01 

N 

N 

.0003 

.002

.007 

.0002 

.003 

N 

N 

.005 

.0005 

N 

.0007 

N 

.003 

.0003 

N 

.02

1-3. Oak Springs Canyon, NE corner sec. 6, T. 7 S., R. 18 E., loc. A, fig. 2.

4-5. East of Oak Springs Canyon, near center sec. 5, T. 7 S., R. 18 E., loc. 6A, fig. 2.

6-8. Upper Bear Springs Canyon, center sec. 4, T. 7 S., R. 18 E., loc 6B, fig. 2.

9. Between Whitewash and Bear Springs Canyons, NWV4 sec. 30, T. 6 S., R. 18 E., loc. 2A, fig. 2.

10. Cave Canyon, W edge, N ^ sec. 18, T. 6 S., R. 18 E., loc. 3, fig 2.

11. West of Virgus Canyon, loc. 7, fig. 2.

12. Aravaipa Canyon, east of Cave Canyon, loc. 8, fig 2.

13. Aravaipa Canyon, east of Javalina Canyon, SWV4 sec. 8, T. 6 S., R. 18 E., loc. 9, fig. 2.

per Bear Springs Canyons. The ash flow can be separated into six lithologic zones, in ascending order, the 

lower nonwelded to partially welded tuff, densely 

welded vitrophyre, vuggy, platy-jointed, and columnar-jointed zones, and the upper partially welded 

white tuff. The lower tuff is pale orange, becoming 

very light brown at the top. The lower part of the vitrophyre is pale brown from oxidation; the rest of it is 

dark gray, except for brown spots at the top from incipient devitrification. The vuggy zone is light brownish gray except at the base, where it is pale brown. The 

platy-jointed zone is also light brownish gray. The columnar-jointed zone is slightly lighter in color. The upper white tuff grades from pinkish gray at the base to 

white at the top.

A suite of specimens, representing a vertical section 

across the ash flow, was collected in Oak Springs Canyon (specimens H202A-H) and upper Bear Springs 

Canyon (specimens H202I-R) (locations 6A and 6B, 

fig. 2). The approximate elevation of each specimen 

above the base of the ash flow, the field units or lithologic zones, color, zones of welding and crystallization, 

approximate mineralogic composition (based on X-ray 

diffractographs), and specific gravity of these specimens are summarized in figure 10.

The ash flow is composed of shards and pumice lapilli, 

phenocrysts of feldspar, quartz, and biotite, and foreign rock and crystal fragments. Phenocrysts average 

about 6 percent of the rock, and feldspars (plagioclase 

and sanidine) make up about 62 percent of the phenocrysts (table 5). Most of the lithic fragments are from 

older andesites, but in the upper part of the ash flow 

many of them are rhyolite, probably derived from earlier crystallization of the ash-flow magma.

Photomicrographs (fig. 11) of selected thin sections 

of the suite of specimens show the microscopic features 

of the ash-flow sheet. The lower tuff is completely nonwelded (fig. 11 A) and vitric, except for the basal few 

meters, which has been altered to clinoptilolite (see 

composition column, fig. 10). The vitrophyre (fig. 115) 

is densely welded and completely glassy, except for 

phenocrysts and xenoliths. Oxidation was considered 

the cause of the brown spots in specimens from the top 

of the vitrophyre (fig. HO. However, they probably 

are due largely to incipient devitrification, as seen 

through crossed nicols (fig. 11D). The lighter areas, in 

contrast, are largely vitric. Where the ash flow filled a 

channel in older rocks, rapid chilling of the tuff against 

the channel walls caused the vitrophyre to reflect the 

underlying topographic irregularities (fig. 12).
ARAVAIPA MEMBER 13

The vuggy zone (fig. 9) consists of densely welded 

and devitrified rock that is composed largely of cristobalite and feldspar, some of it in spherulitic intergrowths (fig. HE). Biotite is altered, as it is in all crystallized parts of the ash flow; it is fresh only in vitric 

and zeolitized parts. The vuggy zone contains abundant large (as much as 10 cm in diameter), somewhat 

flattened vugs or lithophysae. The cavities are lined 

with inward-projecting acicular quartz crystals; locally 

centers contain calcite crystals. The abundance and 

size of the lithophysae (fig. 13) suggest that this ash 

flow had retained an uncommonly large proportion of 

volatiles in solution in the glass (Ross and Smith, 

1961, p. 38). The volatiles were released after dense 

welding and during devitrification. Quartz and calcite 

were deposited in the vugs after the ash flow had partly 

crystallized and cooled. Thunder eggs (fig. 14), a distinctive type of lithophysae, formed along the contact 

between the vitrophyre and devitrified zone near Oak 

Springs Canyon (loc. 6A, fig. 2). They have a maximum 

diameter of 15 cm. Gases released during devitrification accumulated within the spheres and produced sufficient pressure to fracture them. Small brown crystals 

of andradite garnet (identified by X-ray diffraction) 

occur within some of the voids (fig. 14 G) and locally 

formed larger masses. To my knowledge, andradite has 

not been reported from rhyolite ash-flow tuffs; possibly 

it represents metamorphosed calcareous xenoliths.

The platy-jointed zone is similar to the vuggy zone, 

except for closely spaced subhorizontal joints (fig. 15), 

a slightly lighter color, and fewer or no vugs. It is 

densely welded and completely devitrified (figs. 11F, 

G), with some coarse-grained devitrification products 

not only in pumice, but in some of the finer grained 

shard areas. Platy joints commonly develop near the 

zone of maximum compaction. A second thin slightly 

vuggy zone overlain by a thin platy-jointed zone was 

observed in many places, especially along Aravaipa 

Canyon. It was not studied in detail or traced so its 

significance is not understood. Its presence suggests 

the possibility of a second pulse of the ash flow.

The columnar-jointed zone (figs. 9, 15, see also fig. 

25) is a cliff-forming light-brownish-gray devitrified 

rock, much of which is also quite densely welded. 

Coarse-grained vapor-phase crystallization is mainly 

confined to pumice lapilli (fig. llfl). The columnar 

joints are contraction joints that develop during cooling; they are common in densely welded parts of ash 

flows and are also common in some vapor-phase zones.

Welding, crystallization, composition based on X-ray 

diffractographs, and specific gravity of the lithologic 

units of the central part of the ash flow will be included 

with the discussion of the distal margin of the ash flow.

The upper white tuff (fig. 9; see also fig. 27) is a soft,

Approximate scale

FIGURE 9.—Typical exposure of Aravaipa Member (Tar) on north side of Aravaipa Canyon showing normal vertical zonation (see sketch): 

vuggy (V), platy-jointed (Pj), and columnar-jointed (Cj) zones, overlain, across Horse Camp Canyon, by upper white tuff (Taru). Vitrophyre below level of creek. Lower andesite (Tlav) and conglomerate (Tcv) of Virgus Canyon overlie upper white tuff at top center.
14 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

80 -

60 -

40 -

20 -

Specimen

location

above 

base

H202

— R

— Q

— P

— O

— N

- M

— L

— K

— J

— 1 — H

— G

— F

— E

— D

— C

— B

— A

Field units

Upper 

white 

tuff

Columnarjointed

Platyjointed

Vuggy zone

Vitrophyre

Lower

white 

tuff

Color

White

White

Pk gr

V It br gr

Lt br gr

Lt br gr

Lt br gr

Lt br gr

Lt br gr

Lt br gr

Pale br

Gr and br

Gr black

Pale br

V It br

Pale orange

Pale orange

Pale orange

Zones of 

welding

Slight 

welding 

(decreasing 

upward)

O)

c

"CD

§

CD

C

CD

C3

Slight

welding

No welding

Zones of 

crystallization

I 

"* 

•

CD 

in

flj

£

Q.

O

Q.

ro

3

)

—— 

CD 1 c *

i

i

4-

•^

J

j

Composition

CD

CD .-

~ O 

CD *- —

o %• V 2 °-

K "D ro *? c > S

TM ~JII 3 O — TO _

U u. O bo U U O

• 0 o A - — -

- • • A - - —

A • • A - - -

O o O A - A -

0 0 o A - - -

o o o A - - —

O o O A - A —

o o o A — — —

0 0 0 A - - -

O O O A - - —

• • A A - - -

A A A A - - •

- A A A - - •

_ A - A - - •

A A - A - o •

A A A - - A •

A A A A - A •

- A A - • - 0

Specific grav

1.5 2.0

\

4

*

f^^

B

VA

ty

2.5

\

f

V

0

'N

M

L

I

V

J

Abundant (more than 50 percent)

EXPLANATION

Present but not abundant

A 

Recognized Not recognized

FIGURE 10.—Some physical characteristics of interior parts of Aravaipa Member based on specimens collected at locality 6A(H202AH) and 6B (H202I-R), figure 2. Modal data in table 5, chemical analyses of some specimens in table 6. Color terms: br, brown or 

brownish; gr, gray or grayish; It, light; pk, pinkish; v, very. Abundance of minerals estimated from X-ray diffractographs of bulk 

samples. In addition to listed minerals, sample H202O contained tridymite.

slope-forming, slightly welded unit that was referred 

to in the quadrangle reports as the upper nonwelded 

zone (Krieger, 1968a, b) and the white tuff unit (Simons, 1964). It is shown separately on the quadrangle 

maps, but not in figure 2 of this report. It is welded 

(figs. Ill, J), but welding decreases rapidly upward as 

shown by hand specimens and thin sections. Little 

welding has occurred at the very top (figs. UK, L). The 

rock is devitrified, with some coarse-grained crystallization in pumice lapilli. The nonwelded vitric top was

largely eroded before deposition of younger rocks. The 

tuff, in places, is pockmarked by wind erosion, a characteristic feature of vapor-phase zones in ash-flow 

sheets, according to Ross and Smith (1961, p. 30). A 

low cliff occurs at the top of the white tuff in many of 

the southern exposures. The induration is due to silicification and represents exposure for a long period of 

time before deposition of younger rocks. The cliff was 

not observed along Aravaipa Canyon, where the tuff 

probably was exposed to erosion and weathering for a
ARAVAIPA MEMBER 15

TABLE 5.—Modes of Aravaipa Member

[Modes in volume percent. Based on thin-section studies of specimens H202A-H, loc. 6A, and H202I—R, loc. 6B (fig. 2). See figure 10 for lithologic zones and other characteristics. 

Field units: ut, upper tuff; cj, columnar jointed; pj, platy jointed; vug, vuggy; vit, vitrophyre; It, lower tuff. T = trace]

Percentage of rock exclusive of foreign fragments

Field

No.

H202R

H202Q

H202P

H202O

H202N

H202M

H202K

H202I

H202H

H202F

H202E

H202D

Average

Range

Field

unit

Ut

CJ

PJ

vug

vit

It

Matrix'

95

96

95

94

91

86

94

93

96

96

97

99

94

86-99

Total

phenocrysts2

5

4

5

6

9

14

6

7

4

4

3

1

6

1-14

Feldspar3 Quartz Biotite

(percentage of phenocrysts)

3

2

2

5

7

9

4

5

2

3

2

T

4

T-9

(60)

(50)

(40)

(83)

(78)

(64)

(67)

(71)

(50)

(75)

(67)

(40)

(62)

--

1

2

3

1

1

4

2

1

1

1

1

T

2

T-^

(20)

(50)

(60)

(17)

(11)

(28)

(33)

(15

(25)

(25)

(33)

(30)

(29)

1

T

T

T

1

1

T

1

1

T

T

T

T

T-l

(20)

-

~

~

(11)

(8) —

(14)

(25)

-

—

(30)

(9)

--

Percentage of 

total rock

Foreign rock 

and mineral

fragments4

1

2

T

T

T

T

T

T

T

T

T

T

T

T-2

Points

counted

1,011

1,025

1,005

1,001

1,004

1,007

1,002

1,003

1,003

1,019

1,005

1,010

1,008

—

'Includes pumice lapilli; H202D has more pore space than overlying specimens.

2Not counted are traces of magnetite and very tiny crystal fragments. Includes phenocrysts in pumice lapilli and crystal fragments in matrix.

3Largely plagioclase, includes sanidine (trace to 2 percent of total rock); may include some foreign plagioclase.

4Older volcanic rock, mostly andesite, except for rhyolite in H202P-R.

shorter time. Because a zone of "solidly welded" tuff 

(Simons, 1964, p. 84-85) occurs at the top of the unit 

west of Parsons Canyon (east-central part of fig. 2, 

north of latitude 32°52'30"), Simons concluded that 

the white tuff was not part of his upper welded unit. 

However, I found no evidence of a break in crystallization across the contact in this area. I interpret this 

densely welded zone as representing an additional 

pulse that was hot enough so that it became more 

densely welded than the underlying part. Crystallization appears gradational, and there is no evidence 

of any vitric material at the base of this last flow. The 

contact between the columnar-jointed and white tuff 

zones wherever observed is completely gradational. 

Lithology, specific gravity, and degree of welding and 

crystallization support the conclusion that the upper 

white tuff is part of the same cooling unit as the underlying ash flow.

The vertical zonation described above is characteristic of the Aravaipa Member throughout most of the 

Holy Joe Peak and Klondyke quadrangles. In the 

northwestern part of the outcrop area, however, near 

the distal margin of the ash flow, a marked change in 

zonation occurs. A remarkable exposure (fig. 16) of the 

distal margin of the welded part of the ash flow occurs 

on the north side of lower Whitewash Canyon. The 

slightly welded, columnar-jointed vapor-phase zone 

thins rapidly and pinches out. Pink nonwelded tuff 

underlies, locally overlies, and extends beyond the 

welded part of the ash flow. This same change can be 

seen on the northwest side of Bear Springs Canyon, 

near a small canyon between Hells Half Acre and

Whitewash Canyons, and in Cave Canyon north of 

Aravaipa Canyon. Another view (fig. 17) shows the 

complete change from the stacked-up zonation typical 

of the interior of the ash flow at the right to the nonwelded distal margin, the view shown in figure 16, at 

the extreme left. The nonwelded basal tuff becomes 

progressively thicker away from the interior and successively replaces the vitrophyre, the vuggy, and the 

platy-jointed zones. Similarly, the columnar-jointed 

zone increases in thickness but farther outward is entirely replaced by nonwelded tuff.

Detailed studies of the ash flow were made at selected 

localities from the interior toward the northwestern 

distal margin, and a suite of specimens was collected 

at each locality (fig. 18; also fig. 2). Figure 19 is a diagrammatic summary of the studies made; it illustrates 

the general distribution, both horizontally and vertically, of lithology, welding, crystallization, mineralogy, and specific gravity from the southeast (loc. 6A 

and 6B) to the northwest (loc. IB). Because no specimens were collected from Whitewash Canyon north 

(loc. IB), data from Bear Springs Canyon north (loc. 

1 A, 2A, 2B) have been used. Details from the east side 

of Cave Canyon (loc. 3) are also inserted between 

Whitewash Canyon north and south (loc. IB and 4). 

This section is of interest because it is one of the few 

places where the nonwelded zeolitized top has been 

preserved and because the nonwelded basal tuff has 

been replaced by mordenite, instead of clinoptilolite, 

the zeolite that largely replaces nonwelded parts of the 

ash flow elsewhere. Details of the lithology and color, 

specific gravity, and mineralogy are shown in figures
16 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

1cm

.. ^.^..i^r,,; ,.

'1-fA *' :S*'fc-.y • j ' < S*L ' ' v< ' :4

»^rt, '^ | ^'.1 '//f - ,% ,%i3. .,S^ I

J'l-T --*-"• - 'vUi ' • * ' ! * 1

1cm

r

1cm

pu

1cm

FIGURE 11.—Photomicrographs of specimens from interior of Aravaipa Member. Biotite (B), magnetite (M), plagioclase (P), pumice (pu), 

quartz (Q), vug (V), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Lower white tuff (H202B); completely nonwelded 

with undeformed shards and unbroken glass bubbles. B, Strongly welded vitrophyre (H202F). Shards molded against crystal fragments. 

Large shards have dull-brown centers, representing original character of glass, and colorless margins. Groundmass contains much fine 

dust. Other parts of thin section show flattened pumice lapilli. C, Densely welded vitrophyre (H202G) with well-preserved shard structure. 

Shows part of one brown spot (darker area) in lighter colored vitrophyre. D, Same view as C, crossed nicols. Shows that areas that were 

darker in plane polarized light are clearly devitrified. E, Welded tuff from vuggy zone (H202J), crossed nicols. Show spherulitic intergrowths of cristobalite and feldspar in pumice. Shard structure visible in plane light. Black areas (except in plagioclase) are vugs and 

are lined with quartz. F, Strongly welded, platy jointed tuff (H202N). Excellent preservation of shard structure, with dark streak down
ARAVAIPA MEMBER

1cm

H

1cm 1cm

centers of shards, tube structure visible in large flattened pumice lapillus. G, Same view as E, crossed nicols. Intergrowths of cristobalite 

and feldspar transect pumice and shard structure; intergrowths meet to form dark line through center of pumice lapillus. H, Columnarjointed vapor-phase zone (H202O), crossed nicols. Shows contrast in texture between shard (finer grained) and pumice (coarser grained) 

areas. Fine-grained devitrification products are cristobalite and feldspar, but coarse-grained vapor-phase products in pumice include 

small tridymite crystals (too small to recognize in picture). In plane light, shard structure can be recognized. /, Slightly welded upper 

white tuff (H202P), showing shard structure and part of large pumice lapillus. J, Same view as /, crossed nicols. Vapor-phase minerals, 

tridymite and cristobalite, converted to quartz (see fig. 10, composition column). K, Nearly nonwelded tuff (H202R) from near top of 

upper white tuff. Shard structure defined by very fine grained axiolitic intergrowths of cristobalite and feldspar; pumice structure partly 

destroyed by coarse-grained spherulitic intergrowths. L, Same view as K, crossed nicols.
18 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

^

i

m

f?.t I if -3* /* *""**' "••" *"" f '"' '\> r , «i*V>^fciJ*'

r ''jt«^.t_M« -^7* -' * z.*'" V " ,« - ^-: >" :s5> *^W L^^

Approximate scale

FIGURE 12. — Aravaipa Member filling channel in Precambrian rocks 

(or). Sketch shows stratigraphic relations. Basal white tuff (wt) 

and vitrophyre (vit) reflect underlying topographic irregularities. 

Vuggy zone (v) occupies central part of channel and is overlain by 

columnar-jointed zone (c). Also shown are undifferentiated Aravaipa Member (Tar) and upper tuff unit (Taru), rhyolite-obsidian 

member (Tro) and middle unit of Hells Half Acre Tuff Member 

(Thh-2). View north across Aravaipa Canyon from west of mouth 

of Virgus Canyon. Contact dashed where inferred.

*»*

FIGURE 13.—Vuggy zone, Aravaipa Member showing quartz lining 

cavities. See pocket knife for scale. East of Oak Springs Canyon 

(loc. 6A, fig. 2).

20-22. Photomicrographs of selected thin sections (fig. 

23) show the microscopic features.

The trends shown in figures 19-22 were caused by 

the decrease in temperature of the ash flow with distance from its source and by the rapid thinning of the 

ash flow against preexisting topographic highs (see fig. 

2 where, west of Cave Canyon, Hells Half Acre Tuff 

Member overlaps Aravaipa Member onto the underlying andesite of Depression Canyon.)

At Bear Springs Canyon south (loc. 5) and Whitewash Canyon south (loc. 4), the lithologic zones (figs. 

19A, 20) are essentially the same as in the interior of 

the ash flow (loc. 6A, B), except that at Bear Springs 

Canyon south the vitrophyre extends to, or nearly to, 

the base of the ash flow, probably because of a topographic high, and at Whitewash Canyon south, pink 

tuff underlies the vitrophyre. The upper white tuff has 

been removed by erosion from location 4. The specific 

gravities (figs. WE and 21) of the lithologic zones at 

locations 4 and 5 are similar to those at location 6, except that in the upper part of the columnar-jointed 

zone at location 4, specific gravity is as low as it is in 

the upper part of the white tuff at locations 5 and 6. 

Northwest of Whitewash Canyon south (loc. 4), only 

columnar-jointed tuff and pink tuff remain, and specific gravity (figs. 19E and 21) decreases in both zones, 

reflecting in part a decrease in welding towards the dis-
ARAVAIPA MEMBER 19

G

FIGURE 14.—Thunder eggs from near contact between vitrophyre and vuggy zone, Aravaipa Member. Cauliflowerlike surface (A) 

caused by spotty incipient devitrification. Upper surface of thunder egg, as originally oriented, is cut by fractures filled with chalcedony that form low ridges. Upper and lower halves are separated by a fracture, also filled with chalcedony. Fractures, typically 

three in number, in upper half generally do not extend into lower half. Incipient devitrification extends inward for about 0.5 cm, 

inside of which ash-flow tuff is completely devitrified into spherulitic intergrowths of cristobalite and feldspar (B-G). Vertical sections 

(B-E) through typical thunder eggs show irregular, angular character of partly filled voids in which chalcedony was deposited, and 

concentration of chalcedony in upper part of voids (especially D and E). Angular fragments of detrified tuff occur within voids (B 

and O. Finer grained material in lower part of some voids (C, D, E) consists of quartz, cristobalite, clay, and locally clinoptilolite. 

Variations in openings and fillings occur in some thunder eggs (F and G). Small crystals of andradite garnet locally occur in or 

partly fill voids (G).

tal margin. The tip of the columnar-jointed zone at location 1A is nearly nonwelded (fig. 23H). Thin sections 

(figs. 23A-G) also show the complete absence of welding in the pink tuff. Shards and glass bubbles are generally well preserved because of axiolitic replacement, 

regardless of whether the zeolite is clinoptilolite (figs.
20 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

FIGURE 15.—Platy-jointed zone (P), between vuggy (V) and columnar-jointed (C) zones, Aravaipa Member, showing closely spaced 

subhorizontal joints. Exposed thickness of member, approximately 

30 m. North side of Bear Springs Canyon, location 5 (fig. 2).

23A-D) or mordenite (figs. 23E, F). The specific gravity 

of the pink tuff may have been less than 1.5 before it 

was zeolitized; Hoover (1966) found that bulk densities 

of tuffs increase during zeolitization. The specific gravity of the pink tuff is low but somewhat variable, in 

part owing to variations in the number of lithophysae 

and pumice lapilli, which tend to decrease specific 

gravity.

Each of the specimens collected was X-rayed; the results are shown in figure 22 and summarized diagrammatically in figure 19D. X-ray diffractographs of the 

ash flow show not only the phenocrysts (feldspar, quartz,

and biotite) but also devitrification products (cristobalite and feldspar), secondary quartz, and alteration 

products (clay and zeolite). The problems related to 

determination of mineral composition by X-ray diffractographs have been discussed in the section on the 

Holy Joe Member (p. 5). X-ray diffractographs were 

very useful in studying the Aravaipa Member, especially the many specimens for which no thin sections 

were available and those that had been zeolitized. The 

X-ray patterns indicate that quartz, rather than cristobalite, is the principal silica mineral in the columnar-jointed zone at locations 2B, 3, 4, and 5, and in 

most of the upper white tuff at locations 5 and 6 (see 

fig. 7 for diffractograph of H202Q; this also shows that 

the principal tridymite peaks may have been masked 

by peaks of other minerals). At the distal margin of 

the columnar-jointed zone (Iocs. 1A, 2A) and in the top 

of the upper white tuff (Iocs. 5 and 6), cristobalite is 

the dominant silica mineral.

The common devitrification products developed during crystallization of a cooling ash flow are cristobalite 

and feldspar. They start growing at grain boundaries 

and meet at a central zone of discontinuity that forms 

a dark line (figs. 11F, G), producing the typical axiolitic texture that preserves the shard structure.

Vapor-phase crystallization is superimposed on devitrification and may obscure shard structure. Vaporphase crystals develop first in pumice lapilli, where 

they are coarser than devitrification products. Tridymite, together with cristobalite and feldspar, is a common vapor-phase mineral in all younger Tertiary and 

Quaternary ash-flow tuffs. Tridymite was recognized in 

thin sections of specimens from the vapor-phase zone 

(columnar-jointed zone and lower part of upper white 

tuff at loc. 6) but not from the columnar-jointed zone

FIGURE 16.—Distal margin of welded zone of Aravaipa Member, showing change from section composed mostly of columnar-jointed zone 

to completely nonwelded zone at left (see accompanying sketch). Lower part of cliff (right) is slightly darker, indicating denser welding 

and development of vuggy zone (vug), which to left has been replaced by columnar-jointed zone (c). Nonwelded pink tuff (p) farther left 

replaces lower part of columnar-jointed zone and still farther left overlies and extends beyond columnar-jointed tuff. Aravaipa Member
ARAVAIPA MEMBER 21

at Iocs. 1A, 2A, and 3. It was not definitely recognized 

in the X-ray diffractographs because it is a minor constituent where present, and its peaks are close to some 

of the peaks of cristobalite, quartz, and feldspar (see 

figs. 1C, D).

Quartz rather than cristobalite (and tridymite?) occurs in most of the vapor-phase zone (see figs. 19C, D). 

The cristobalite and tridymite probably inverted to 

high-temperature quartz during a prolonged spell at 

temperatures just below the inversion temperature. 

The quartz represents neither the granophyric crystallization that occurs in some very thick ash flows nor 

the conversion of cristobalite and tridymite that occurs 

in older ash flows. Most of the cristobalite detected by 

X-ray in the nonwelded pink tuff (fig. 22) probably represents devitrification that formed around lithophysae.

Chemical analyses (table 6) were made for two samples of the 'vitrophyre (one brown and one black) and 

one each of the devitrified, platy-jointed, and vaporphase zones. Minor-element contents of these samples 

are given in table 4.

The whole-rock analyses show that chemical differences between zones in the Aravaipa Member are very 

small. The most significant differences are the higher 

water content in vitrophyre than in the crystallized 

tuff and a high oxidation state of iron in the crystallized tuff than in the black vitrophyre. Both these 

characteristics are observed in ash-flow tuffs throughout the western United States and elsewhere.

The high water content of the vitrophyre causes 

problems in comparing relative abundance of the nonvolatile constituents, and probably is the result of secondary hydration rather than of magmatic, depositional, or cooling processes (Ross and Smith, 1955, p. 

1086-1088). To more readily compare the nonvolatile 

elements, the analyses have been recalculated on a 

water-free basis; CIPW norms and Earth cation 

amounts are also listed. The recalculated analyses 

show a decrease in sodium in the vitrophyre compared 

to the crystallized rocks. Solution of sodium, some of 

it in greater amounts than reported here, has been reported from vitric parts of many rhyolitic rocks (Lipman and Christiansen, 1964; Lipman, 1965). The other 

changes are minor and may reflect random variations 

among the samples or crystal and lithic fragments. 

Silica shows an increase; aluminum, magnesium, and 

calcium show very slight decreases in the vitrophyre 

compared with the crystallized parts of the ash flow. 

These changes are the reverse of those found by Lipman and Christiansen (1964), who explain the higher 

aluminum, magnesium, and calcium content of the 

glassy nonwelded tuff by the presence of 5-10 percent 

of calcic montmorillonitic clay coating glass shards. 

The vitrophyres in the Aravaipa Member were too 

densely welded for clay to have developed. The relative 

amounts of CaO, Na2O, and K2O in the five analyzed 

samples have been plotted on figure 24 (Nos. la-5a) 

and show a slight but progressive upward increase in 

Na2O and decrease in K2O.

CHANGES IN CHEMICAL COMPOSITION 

DUE TO ZEOLITIZATION

The Aravaipa Member presents an excellent opportunity to compare the chemical composition of a nonzeolitized tuff with that of its zeolitized parts. Zeolitization took place only in the nonwelded parts of the

4 «* It-fiw^ •*• 4> » % -- ?^$0sgigffi3&$b&£;

? 04 n fi kTII DM FTP R

Approximate scale

is separated locally from overlying Hells Half Acre Tuff Member (upper unit, Thh-3) by thin lenses of conglomerate (Tcv) derived from 

lower andesite of Virgus Canyon and is underlain by tuff of Bear Springs Canyon (Ttb), which consists of pink tuff, except for columnarjointed tuff (Cj) at right. Beneath tuff of Bear Springs Canyon are andesite of Depression Canyon (Tad), Holy Joe Member (Thj), and 

WhitetaiK?) Conglomerate (Tw). Photograph taken from near loc. 1A; end of welded part at loc. IB (fig. 18).
22 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

"_s^_

FIGURE 17.—Change from interior zonation in Aravaipa Member (right) to distal margin of ash flow (left). Most of photograph shows interior 

vertical zonation from vitrophyre (V) at base through vuggy zone (vug) to columnar-jointed zone (C) at top (see accompanying sketch). 

Platy-jointed zone not recognized in photograph; upper tuff has been removed by erosion. To the left, first vitrophyre and then vuggy 

zone are replaced by pink tuff (P). Part of exposure to left of vitrophyre and vuggy zones also shown in figure 16. Apsey Conglomerate

TABLE 6.—Chemical composition and comparison of glassy and crystallized parts, Aravaipa Member

(Major oxide analyses (weight percent) by P. Elmore, S. Bolts, and G. Chloe by rapid methods described by Shapiro and Brannock (1962). See table 4 for minor-element analyses!

Original analyses

Si02 -----

Al O

Fe 1 K2^3O — — — -—

FeO ____ ——

MgO —————

CaO —————

>JQ n

K

/~,

H f~l _L

H

/~>

TiO —————

P2o4 ...............

MnO — — — — -

L,U2 ——————

Total -----

i

73.4 

12.7 

1.1 

.13 

.25 

.38 

3.2 

5.4 

3.0 

.40 

.21 

.03 

.07 

<.05

100

2

73.2 

12.8 

.83 

.34 

.24 

.39 

3.3 

5.0 

3.1 

.38 

.22 

.04 

.11 

<.05

100

3

73.4 

13.6 

1.2 

.08 

.47 

.44 

3.6 

5.2 

.93 

.93 

.24 

.06 

.08 

<.05

100

4

74.0 

13.6 

1.2 

.05 

.39 

.38 

3.8 

5.0 

.80 

.44 

.24 

.04 

.08 

<.05

100

5

74.1 

13.5 

1.2 

.04 

.35 

.46 

3.8 

4.9 

.77 

.61 

.24 

.04 

.07 

<.05

100

Si02 ------ 

A1A! 2Un3 — — — ----- 

Fe 1 C2O W3 — — ----- —

FeO ——————

MgO —————

PnO

INdgV^ 

Kf\

^2^5

MnO

Total ——

la

76.0 

13.1 

1.1 

.13 

.26 

.39 

3.3 

5.6 

.22 

.03 

.07

100.20

Recalculated without H2O and CO2

2a

75.8

13.3 

.86 

.35 

.25 

.40 

3.4 

5.2 

.23 

.04 

.11

99.94

3a

74.6 

13.8 

1.2 

.08 

.48 

.45 

3.7 

5.3 

.24 

.06 

.08

99.98

4a

74.9 

13.8 

1.2 

.05 

.39 

.38 

3.8 

5.1 

.24 

.04 

.08

99.98

5a

75.1 

13.7 

1.2 

.04 

.35 

.47 

3.9 

5.0 

.24 

.04 

.07

100.11

Orthoclase — —

Alhitp

Rutile

Total — ~

i

34.1 

32.9 

28.0 

1.7 

1.0 

.64 

.04 

1.1 

.41

.07

99.96

2

35.0 

30.6 

28.9 

1.7 

1.4 

.62 

.85 

.28 

.43

.10

99.88

CIPW norms

3

31.6 

31.2 

31.0 

1.8 

1.4 

1.0

1.2 

.35 

.06 

.14

99.75

Earth cations

4

31.9 

29.9 

32.6 

1.6 

1.4 

.98

1.2 

.28 

.10 

.10

100.06

5

32.3 

29.3 

32.6 

2.1 

1.2 

.88

1.2 

.24 

.12 

.10

100.04

Si ——————

Al _________

Fe +3 —————

JV2 ——— .... ....

Mg ---—— -

Po

TSJo ____

Ti ——————

P ...—————

Mn ——————

Total ——

Fe total — — — -

Fe" 2 /Fe total — -

i

71.0 

14.5 

.80 

.11 

.36 

.39 

6.0 

6.7 

.15 

.02 

.06

100.09

.91

.12

2

71.0 

14.6 

.61 

.28 

.35 

.41 

6.2 

6.2 

.16 

.03 

.09

99.93

.89

.31

3

69.6 

15.2 

.86 

.06 

.66 

.45 

6.6 

6.3 

.17 

.05 

.06

100.01

.92

.06

4

69.8 

15.1 

.85 

.04 

.55 

.38 

7.0 

6.0 

.17 

.03 

.06

99.98

.89

.04

5

70.0 

15.0 

.85 

.03 

.49 

.47 

7.0 

5.9 

.17 

.03 

.06

100.00

.88

.03

NOTE: Samples 1, 2 from east of Oak Springs Canyon, near center sec. 5, T. 7 S., R. 18 E., loc. 6A, fig. 18. Samples 3-5 from upper 

Bear Springs Canyon, center sec. 4, T. 7 S., R. 18 E., loc. 6B, fig. 18. 1, Brown vitrophyre, H202E, Lab no. 159529. 2, Black vitrophyre, 

H202F, Lab no. 159530. 3, Devitrified zone, H202L, Lab no. 159531. 4, Platy-jointed zone, H202M, Lab no. 159532. 5, Vapor-phase zone, 

H202O, Lab no. 159533.
ARAVAIPA MEMBER

Member (Ta) forms hills in right distance. Hells Half Acre Tuff Member (upper unit, Thh-3) is separated locally from Aravaipa Member 

by thin lenses of conglomerate (Tcv) derived from lower andesite of Virgus Canyon. Tuff of Bear Springs Canyon (Ttb) underlies Aravaipa Member and is underlain by andesite of Depression Canyon (Tad). Photograph taken from south of loc. 4 (fig. 18). Distance from 

left to right side of photograph approximately 2 km.

ash flow that had remained vitric during cooling. None 

of the devitrified or vapor-phase zones were altered 

(see figs. 22, 19C, D; and the X-ray diffractographs, 

figs. 7 D, E) South of Aravaipa Canyon (fig. 22, Iocs. 

1A, 2A, 2B, and 4), and in the west side of Cave Canyon, north of Aravaipa Canyon (Krieger, Johnson, and 

Bigsby, 1979), the nonwelded tuff was altered to clinoptilolite. On the east side of Cave Canyon, however 

(fig. 22, loc. 3), it was altered to mordenite below and 

to clinoptilolite above the columnar-jointed zone. Hoover and Shepard (1965) found that clinoptilolite, mordenite, and analcime formed in progressively deeper 

but overlapping zones. Mordenite, rather than clinoptilolite, may have formed below the columnar-jointed 

zone on the east side of Cave Canyon because this part 

of the ash flow was buried more deeply than it was to 

the west and south, owing to the gentle north-northeastward dip of the ash flow and to a thicker section of 

overlying Hells Half Acre Tuff Member. Zeolitization 

is believed to have occurred in an unsaturated zone 

above the water table and above impermeable rocks, 

conditions similar to those found by Hoover (1968) at 

the Nevada Test Site. Sheppard and Gude (1965), who 

compared vitric and zeolitized tuff by assuming constant A12O3 , concluded that formation of pure clinoptilolite from pure rhyolite glass should involve mainly 

gains in H2O and CaO and losses in SiO2 and K2O.

The chemical analysis of the devitrified tuff (no. 3 

from table 6) is compared to the analyses of the tuff 

that has been altered to clinoptilolite and to mordenite 

(table 7, nos. 1-3; also shown on table 7 are the analyses of tuff of Bear Springs Canyon, no. 4; the middle 

unit of Hells Half Acre Tuff Member, no. 5, both altered to clinoptilolite; and the unaltered rhyolite-obsidian member, no. 6). The assumption is made that 

the devitrified tuff is the closest available approximation to the original composition of the magma. The 

major change is a large increase in H2O. To more readily compare the nonvolatile constituents, the analyses 

have been recalculated on a water-free basis. In addition to H2O, the major changes during alteration to 

both clinoptilolite and mordenite have been an increase in CaO (greater when altered to mordenite) and 

losses in Na2O (greater when altered to clinoptilolite) 

and K2O (greater when altered to mordenite). Clinoptilolite shows a small increase in MgO and SiO2 , 

whereas mordenite shows little change; some of these 

differences may be due to minute xenoliths or xenocrysts. The relative amounts of CaO, Na2O, and K2O 

in all the zeolitized and nonzeolitized rocks (from table 

7) are plotted in figure 24. The relative amounts of 

these constituents in the five samples of the Aravaipa 

Member (from recalculated analyses, table 6, columns 

1—5) are also plotted as nos. la-5a.

CONCLUSIONS

The Aravaipa Member is an outstanding example of 

vertical and horizontal zonation in an ash-flow tuff that 

cooled as a unit. The remarkable exposures, especially 

along Whitewash Canyon, make it posssble to trace 

the complete change from the typical stacked-up interior zonation to the nonwelded distal margin. The 

Aravaipa Member is a classic area for study of ash-flow 

tuffs. Vertical and horizontal changes in welding, crystallization, specific gravity, and lithology of the ash
24 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

110°32'30

EXPLANATION

Locality Location

1A Bear Springs Canyon north

1 B Whitewash Canyon north

2A Bear Springs Canyon north

2B Bear Springs Canyon north

3 Cave Canyon

4 Whitewash Canyon south

5 Bear Springs Canyon south

6A Near Oak Springs Canyon

6B Upper Bear Springs Canyon

Specimen number 

A-7,H341K, N, O, P

H341A-H, J

A-1-6

H343A-H, J-M

A-8-16

A-17-25

H202A-H

H202I-R

FIGURE 18.—Map showing outcrop of Aravaipa Member (shaded), 

location of specimens, and approximate position of distal margin 

of columnar-jointed zone (heavy dashed line).

flow are due to decrease in temperature as distance from 

its source increased and as thinning of the ash flow 

against topographic highs caused more rapid cooling. 

The Aravaipa Member maintains its typical interior 

zonation for a minimum of 9 km in a east-west direction. The rapid thinning of the ash flow and the short 

distance (less than 0.7 km) in which the change takes 

place doc. 4 to loc. 1A, fig. 18) suggest that cooling was 

due more to the thinning against older rocks than to

1B 2 4

jjwt

A '

Approximate top of ash flow.

Present erosion surface*

Upper white tuff 

Columnar-jointed zone 

Platy-jointed zone

Vuggy zone 

Vitrophyre 

White tuff, pink tuff

EXPLANATION

Partial welding 

Dense welding 

No welding

EXPLANATION

Vapor-phase zone 

Devitrified zone 

Vitric zone

Quartz and feldspar 

Cristobalite and feldspar

METER 

50

2 KILOMETERS

EXPLANATION

1.0-1.5 

1.5-2.0 

2.0-2.5

FIGURE 19.—Diagrammatic sketches of zones in Aravaipa Member. 

A, Lithology. B, Welding. C, Crystallization. D, Mineralogy. E, 

Specific gravity. C and D show probable features prior to zeolitization. Numbers and ticks at top show specimen localities (see fig. 

18). Ticks (at right) represent boundaries of lithologic zones: uwt, 

upper white tuff; cj, columnar-jointed; pj, platy-jointed; v, vuggy; 

vit, vitrophyre; wt, white tuff; and (at left) pk, pink tuff.
ARAVAIPA MEMBER 25

EXPLANATION

Illllllll

V*« to«"*°'«'*« c>

AV//»'.:.

1A

H:

pk gr

: or p c

Upper tuff 

Columnar-jointed 

Platy-jointed 

Vuggy 

Vitrophyre 

Lower tuff-White 

Pink tuff

2A ^

341^-^" H3/l

O 

N

K ;

'\ A-7 ;

\ ;

\: 

Tuff of j

Bear Springs < 

Canyon

pk gr

to |

V It

br gr

;: :r or plf 

lilt i>V"gr|

igr or pk 

:v pa or:

:::::: w: :::::::

2

n/

j 

\

H

\G 

E \-: --

D ;;; ;;| 

B ! gr b

A ::: :::

B4-, ;;;;!;!;

5 6

A

3

H343

ft-""""

A ^-"

v 6

_/

;;i!T; ; 4

r'pk:

;;;;;;; ?/

gr or pk

w • o 

pk gr

pa red 

jr or pk

B3 Columnar-jointed

B2 

•^j — Pink tuff

111

^^^-^_

D

- E

- F 

G

H

- - • - \l 5-

- - - : I *J\ —

: :: : \\ v i:

iiii^ t

^ V; Y"'

\ ;......

si-

-=_s-i=-=. — — —

o^ 3

4 /

Tl.

or jk

or pk

°0 °. S»l

r gr " «

:::gr pk;:

'^r&^^

15

/

|J4/-

I* 13 /

•»'/

=^<5/ 

ii^

i;;i:;S;S;i;;s8;i;:?§: :tsff;::;:m*fi*im.

I111I3I1I

:iilllll;l;i mmmmZmtm

nil

m

' br gr ml

oog'r or pk° •

'Z'frgftl

METERS

r 20

_ n

25

24

23A 

23

22

21

\

19

\ 

\\ \

\ 

\

H202

:i?^SS:?S;:: :§S:S:;;S-:if 

iifi5jS-SWS?Si^'iS-

:- : 8S: P k gr Wv.»:

v It br

lllllll

u

II

E-EIfbr grid

r^O^-=3-£jO^-Si

0 * * o * % o°tt . o * ** c 

«V? *0*«o* **

; 0 lt o br grV.

i\

v It br 

pa or

: : : : pa- • or ; ; ; ; ;

R

Q 

P

O

N

M 

L 

K

J

1 H 

G

D 

C 

B 

A

FIGURE 20.—Lithologic zones and color, Aravaipa Member, showing change from interior sequence doc. 6) to distal margin 

of ash flow (loc. 1A) (see fig. 18 for locations). Color terms: bl, black; br, brown or brownish; d, dark; gr, gray orgrayish; 

It, light; or, orange; pa, pale; pk, pink or pinkish; v, very; w, white. Underlying tuff of Bear Springs Canyon (bottom 

of loc. 2A) also shown.

TABLE 7.—Chemical analyses and comparisons of nonzeolitized and zeolitized Aravaipa Member, zeolitized tuff of Bear Springs 

Canyon and Hells Half Acre Tuff Member, and nonzeolitized rhyolite-obsidian member

(Major oxide analyses (weight percent), No. 1 by P. Elmore, S. Botts, and G. Chloe; Nos. 4-6 by P. Elmore, L. Artis, G. Chloe, J. Glenn, S. Botts, H. Smith, and D. Taylor by rapid 

methods described by Shapiro and Brannock (1962); Nos. 4-6 supplemented by atomic absorption; Nos. 2, 3 by H. Smith by methods described by Shapiro (1967). See table 4 for 

minor-element analyses]

Mineral

Si02 — — —

Fe2 03 --—— ——

FeO ----- — — - — -

MgO —— —— —

CaO —— —— ——

Na O

K

f~l

H

/~» +

H

/~» -

TiO —————

P2 05 -— — — 

MnO —— — — -

^*_»2

Total

Original analyses

1

73.4 

13.6

1.2 

.08 

.47 

.44 

3.6 

5.2 

.93 

.93 

.24

.08 

<.05

100

2

67.0 

12.5 

1.2 

.12 

1.0 

2.6 

.78 

3.5 

7.6 

4.0 

.16 

.15 

.07 

.22

100.90

3

63.6 

12.1 

1.0 

.08 

.40 

3.0 

1.9 

3.0 

7.9 

5.6 

.12 

.04 

.06

99

4

65.5 

12.4 

1.2 

.16 

1.5 

2.9 

.80 

1.3 

3.3 

10.3 

.21 

.03 

.06 

<.05

100

5

69.3 

11.5

.16

.72 

2.3 

1.4 

3.6 

2.2 

7.5 

.15 

.04 

.07 

.11

99.97

6

74.6 

13.5 

1.3 

.12 

.11 

.38 

4.2 

4.5 

.42 

.10 

.21

.10 

<.05

100

i

74.6 

13.8 

1.2 

.08 

.48 

.45 

3.7 

5.3

.24 

.08

99.99

Recalculated without H2O and CO2

2

75.2 

14.0 

1.4 

.13 

1.1 

2.9 

.88 

3.9

.18 

.06 

.08

99.83

3

74.4 

14.1 

1.2 

.09 

.47 

3.5

3.5

.14 

.05 

.07

99.72

4

76.1 

14.4 

1.4

1.7 

3.4

.24 

.03 

.07

99.96

5

76.6

12.8 

1.0 

.18 

.8 

2.5 

1.5 

4.0

.17 

.04 

.08

99.87

6

75.3 

13.6 

1.3 

.12 

.11 

.38 

4.2 

4.5

.21 

.03 

.01

99.76

1. Aravaipa Member, devitrified, H202L, Lab 159531, upper Bear Springs Canyon, center sec. 4, T. 7 S., R. 18E., loc. 6B, fig. 18.

2. Aravaipa Member altered to clinoptilolite, A-4, Lab M126691W, NWy4 sec. 30, T. 6 S., R. 19 E., between Whitewash and Bear 

Springs Canyons, loc. 2B, fig. 18.

3. Aravaipa Member, altered to mordenite, H343M, Lab M126692W, west edge NV2 sec. 18, T. 6 S., R. 18 E., Cave Canyon, loc. 3, fig. 

18.

4. Tuff of Bear Springs Canyon(?), altered to clinoptilolite, H414, Lab M101324W, east edge, NVi sec. 4, T. 7S., R. 18 E., loc. 7, fig. 2.

5. Hells Half Acre Tuff Member, middle unit, altered to clinoptilolite, H410, Lab M101323W, north of Aravaipa Canyon, east of Cave 

Canyon, NWV4 sec. 18, T. 6 S., R. 18 E., loc. 8, fig. 2.

6. Rhyolite-obsidian member, unaltered, H409, Lab M101317W, north of Aravaipa Canyon, east of Javalina Canyon, SE cor. sec. 7, 

T. 6 S., R. 18 E., loc. 9, fig. 2.
26 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

1A 2A 2B 3 4 5 6

1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 2.5 1.5 2.0 2.5 1.5 2.0 2.5

A-25

Upper

24

V<23

\

^-join

zone

ophyr

white

3A

22 

\21

20\ 

ted I

18\}

e"'

; \

tuff

Tuff of

Bear Springs <J Pink 

Canyon

METERS 

r20

H202

I P

white 

tuff

L 0

FIGURE 21.—Specific gravity, Aravaipa Member, superimposed on lithologic zones, showing change from interior 

sequence (loc. 6) to distal margin (loc. 1A) (see fig. 18 for locations). Also shows underlying tuff of Bear Springs 

Canyon (bottom of loc. 2A).

distance from the source. The distal margin of the ash 

flow cooled so rapidly that it remained vitric, and this 

nonwelded vitric part was later completely zeolitized 

by ground water.

TUFF OF BEAR SPRINGS CANYON

The tuff of Bear Springs Canyon (25 m) between 

Bear Springs and Whitewash Canyons is a rhyolite 

ash-flow tuff that is nearly coextensive with the overlying Aravaipa Member (figs. 16 and 17). It is composed of shards, pumice lapilli, crystal and accidental 

fragments, and small lithophysae. The lower part (0- 

15 m) is pink tuff, largely altered to clinoptilolite; the 

upper part (0-10 m) is very light olive-gray to lightbrownish-gray columnar-jointed tuff whose groundmass is composed largely of quartz and feldspar. The 

lithologic zones, specific gravities, and mineral compositions of four specimens collected vertically across 

the tuff are shown in figures 20-22, loc. 2A, below the 

Aravaipa Member. The pink tuff represents the nonwelded part, and the gray columnar-jointed tuff represents the zone of vapor-phase crystallization of an 

ash flow that was erupted at temperatures not far above 

the minimum necessary for welding, as indicated by

the very minor welding and the absence of a vitrophyre. The higher specific gravity in the columnarjointed zone may be due to slight welding. The lower 

specific gravity in the middle part of the pink tuff may 

be caused by large pumice lapilli, common in this part 

of the tuff. Both parts of the ash flow closely resemble 

the overlying pink tuff and columnar-jointed parts of 

the distal margin of the Aravaipa Member, but the 

lower columnar-jointed zone is not so extensive as the 

upper one. The two ash flows probably are similar in 

composition and closely related, but they are separated 

by a period of erosion, as evidenced by channels cut 

into or through the tuff of Bear Springs Canyon. No 

chemical analyses of the zeolitized tuff in this area are 

available. A chemical analysis of a pink tuff collected 

near the west edge of the Klondyke quadrangle (loc. 

7, fig. 2) is included in table 7 (column 4). It may be 

tuff of Bear Springs Canyon, but it probably is one of 

the tuffs in the lower part of Simon's (1964, p. 81) lower 

tuff unit. This specimen is composed of clinoptilolite 

with traces of quartz, feldspar, and biotite, similar to 

the pink tuff of Bear Springs Canyon (fig. 22, loc. 2A). 

Its recalculated analysis, however, suggests that it 

originally may not have had the same composition as 

the tuff of Bear Springs Canyon or Aravaipa Member;
RHYOLITE-OBSIDIAN MEMBER 27

• A A A A - -

• o A A - - -

• O A A - - -

Lower pink 

tuff

0 0 A A o - -

A A A A • - -

P

O

N

K

A-7

\

Tuff of 

BearSprings - 

Canyon

\

• 0 0 A

• O A A

O O A A 

A AAA

AAAA AA -

A AA - 

A AAA

- AA-

_ _ _

A - -

• - -

• - - 

• - -

• - - 

• - -

• - -

Columnar- jointed

AAA- • - - 

- A A - • - -

J

H

F\

E 

D

C

B

A 

B4,

B3 

B2

B1

Ao

Columnar 

jointed

o o A - - -

AA A A • - -

Lower pink

tuff

A o A A • - - 

AA o A • - - 

- A A A • - -

A 0 A - - -

- O - A • A -

Lower pink 

tuff

- A A A • - -

- A A A • - - 

A A A A • - -

Abundant ( 50-100 percent)

Clinoptilolite 

in upper pink 

tuff; mordenite 

in lower pink 

tuff

EXPLANATION

Present but not abundant

0) <D .t;

•- o

<u ^- —

o|»*| „

~ |j § 0 .E m tO

OL-O COOOU

0 0 • A - - -

A • • A - - -

jointed

A 0 • A - - -

Vuggy zone

• 0 0 A - - -

o A A A - - •

A A A A - - •

A A A - • o -

- A - A • 0 -

16

15

/

/

14X

/

y/ j

0) o) .t:

* 0

££"<•>£

'^ o> 3 .2 — <° ro

ou-O coooo

0 A o A - - -

A O o A - A -

- 0 • A - - -

- O • A - - -

A 0 • A - A -

A O • A - A -

0 0 0 A - A -

Platy-jointed

o A A A - - • 

A A A A - - • 

Vitrophyre

A

25

24

23A 

23

22

21

20^

\

19

\18 

17 

\

MFTFRC: V \

11y '""~ '20 \\ \

10 \\

9 \\

/8 -10 \

\

0)

O

CD i_ —

f SN»S

~ 5 5 o .E m <S

OL.OODOOO

O O O A - - -

Upper white

tuff

- • • A- - -

A • o A - - -

O O o A - A -

0 0 0 A - - -

0 o 0 A - - -

O o O A - A -

0 o 0 A - - -

O O O A - - -

o o o A - - -

o • A A - - -

A A A A - - o

AAA •

- A - A - - •

A A - A - O •

Lower tuff

0 A A A - A •

- A A - • - 0

H202

R

Q

P

O

N

M

L

K

J

I

H

G

F

E

D

C

B

A

L 0

A 

Recognized Not recognized

FIGURE 22.—Approximate composition of Aravaipa Member, superimposed on lithologic zones, showing change from interior sequence doc. 

6) to distal margin (loc. 1A) of ash flow. Apparent abundance estimated from X-ray diffractographs of bulk samples. In addition to 

minerals listed, specimens H202O and P contain tridymite, and specimens H341L and M (between locations 1A, 2A) appear to contain 

about equal parts of cristobalite and feldspar, with traces of biotite and quartz. Also shows underlying tuff of Bear Springs Canyon 

(loc. 2A).

it has a higher MgO and CaO and lower K2O content 

than the tuff of Bear Springs Canyon, and the relative 

amounts of CaO, Na2O, and K2O are different (see fig. 

24). Additional data on tuff of Bear Springs Canyon 

are given in Krieger, Johnson, and Bigsby (1979).

RHYOLITE-OBSIDIAN MEMBER

Although the rhyolite-obsidian member is not an 

ash-flow tuff, it is described here briefly because of its 

probable close relationship to the Hells Half Acre Tuff 

Member. The rhyolite-obsidian member underlies an 

area of about 100 km2, about half of it in the northwest 

part of the Klondyke quadrangle. It extends from the 

north side of Aravaipa Canyon (fig. 2) to the southeastern part of the Christmas quadrangle (fig. 1). The 

member consists of gray and black flow-banded to massive perlitic to lithophysal obsidian and obsidian breccia, and finely laminated to contorted gray stony (devitrified) locally lithophysal rhyolite flow and flow 

breccia. A chemical analysis is given in table 7; see 

table 4 for minor-element content. The member was 

extruded as stubby flows and domes (see figs. 26, 27, and 

28); only a few of the lowest ones reached the vicinity 

of Aravaipa Canyon. The member has an estimated 

maximum thickness of about 300 m. It probably was 

erupted from at least two sources: one just north of the 

canyon on the boundary between the Klondyke and 

Holy Joe Peak quadrangles (fig. 2) and the other in the 

northeast part of the Holy Joe Peak quadrangle (Krieger, 1968a). Any other earlier sources have been buried by younger flows. The stratigraphic relations of the 

rhyolite-obsidian member to other members of the Galiuro Volcanics and their correlation with units in the 

Christmas quadrangle are given in figure 3 (see especially footnote 1, in Klondyke quadrangle) and discussed briefly by Creasey and Krieger (1978).
28 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

1cm

1cm 1cm D

FIGURE 23.—Photomicrographs of specimens from near distal margin of Aravaipa Member. Biotite (B), hole (H), lithophysa (L), magnetite 

(M), plagioclase (P), pumice (pu), quartz (Q), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Nonwelded pink tuff 

(H341A) from base of location 2A. Altered to clinoptilolite. Shard, glass bubble, and pumice structure well preserved. Some dark spots 

are grinding material. B, Same view as A, crossed nicols. Structure preserved because of axiolitic replacement by clinoptilolite. C, 

Nonwelded pink tuff (H341D). Excellent preservation of shard structure in tuff that has been altered to clinoptilolite. D, Same view 

as C, crossed nicols. Crystallization coarser grained in large shard fragment. Tube structure (not shown) preserved, even though finely

CaO 

EXPLANATION

• NONZEOLITIZED ROCKS 

1a-5a Aravaipa Member 

from table 6, 

3a = 1 in table 7 

6 Rhyolite-obsidian 

Member

HELLS HALF ACRE TUFF MEMBER

The Hells Half Acre Tuff Member (0-150 m), of 

rhyolite composition, extends from the northeastern 

part of the Holy Joe Peak quadrangle (fig. 2) to about 

1.6 km north of Aravaipa Canyon and eastward into 

the Klondyke quadrangle for about 3.5 km (fig. 2). It 

crops out intermittently beneath the Apsey Conglomerate Member north of Aravaipa Canyon to the northwest corner of the Brandenburg Mountain quadrangle 

(Krieger, 1968a). North and south of the canyon, the 

member is thinner because the lower part laps against 

topographic highs of older members of the volcanic sequence and of prevolcanic rocks. Along Aravaipa Canyon the member can be readily separated into three

XZEOLITIZEDTUFFS 2~l

Na2O
HELLS HALF ACRE TUFF MEMBER

MpK^MHmjnH ^wKX>-" *~^r* */^V ^Sc "V

»?*?_«!? *1

P^??P5rr: :* >„

», ^ ^ -S«^ ./"

1cm 1cm

1cm

crystalline. E, Nonwelded pink tuff (H343J) altered to mordenite, showing shard structure. Abundant dust (dark). F, Same view as E, 

crossed nicols. Axiolitic intergrowths permit recognition of shard structure. G, Pink tuff (H343K), altered to mordenite; shard and 

pumice tube structure clearly defined. H, Specimen (H341P) from distal margin of columnar-jointed tuff (loc. 1A). Tuff only slightly 

welded, even though it still shows columnar jointing. With crossed nicols rock is finely devitrified; but X-ray diffractograph indicates 

that some birefringence is due to replacement by clinoptilolite.

units that are completely exposed in nearly inaccessible cliffs (fig. 25).

The lowest unit (0 to at least 15 m) is a well-bedded 

cliff-forming porous yellowish-brown to brown rhyolite 

tuff with pumice lapilli and grains of quartz, feldspar, 

and biotite in a matrix of shards. Most of the vitric 

material has been altered to clinoptilolite. The unit, 

which was deposited in water impounded behind a 

tongue of rhyolite-obsidian (see figs. 2 and 26), is present along Aravaipa Canyon from about 0.7 km west of 

the mouth of Javalina3 Canyon to or nearly to the east

^Spelling is that used on Brandenburg Mountain topographic map.

FIGURE 24.—Relative amounts of CaO, Na2O, and K2O in zeolitized 

and nonzeolitized samples of Aravaipa Member, tuff of Bear 

Springs Canyon, Hells Half Acre Tuff Member, and rhyolite-obsidian member.

edge of the quadrangle and up Virgus Canyon for 

about 1.6 km. Simons (1964, p. 91) describes a similar 

water-laid tuff at the base of his lowest subunit, just 

south of Aravaipa Canyon, about 2.4 km east of the 

quadrangle boundary.

The middle unit (up to 120 m maximum thickness 

between Javalina and Cave Canyons) is a massive 

cliff-forming white to very pale pink tuff. It is separated into two parts by a narrow bench or slope; the 

upper part thickens to the east and the lower part 

thickens to the west of Virgus Canyon. The unit is 

composed of pumice lapilli, some obsidian and rhyolite 

lapilli, and grains of quartz, feldspar, and minor biotite 

in a matrix of shards; some of the vitric material has 

been altered to clinoptilolite. The unit, at least the 

lower part, is considered a nonwelded or slightly
30 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

Tar

0.2 KILOMETERS

Approximate scale

FIGURE 25.—Outcrop of units of Hells Half Acre Tuff Member (upper 

air-fall and reworked tuff, Thh-3; middle ash-flow(?) tuff, Thh-2; 

and lower water-laid tuff, Thh-1). Vague columnar jointing in 

lower part of middle unit suggests ash-flow tuff origin. Hells Half 

Acre Tuff Member overlain by Apsey Conglomerate Member (Ta) 

and underlain by a slope that largely conceals upper andesite 

(Tuav) and conglomerate (Tcv) of Virgus Canyon; lower andesite 

(Tlav) only at right side of picture. Lower cliff is Aravaipa Member 

(Tar, columnar-jointed (cj) and vuggy (v) zones; and Taru, upper 

slightly welded zone). View northeast across Aravaipa Canyon 

from just west of mouth of Virgus Canyon; Horse Camp Canyon 

in lower left.

welded ash-flow tuff because it shows vague columnar 

jointing (fig. 25), a feature common in ash-flow tuffs but 

not in air-fall tuffs, and because it is massive (fig. 27) 

and unsorted. Furthermore, the subunit thins against 

older rocks (rhyolite-obsidian, figs. 27 and 28, and andesite of Depression Canyon west of Cave Canyon, fig. 

2) instead of maintaining a more uniform thickness as 

would an air-fall tuff.

The upper unit (up to 10 m or more), the most extensive unit, is a cliff- and slope-forming white to tan 

air-fall and partly reworked lithic tuff containing large 

angular lapilli of lump pumice and rhyolite-obsidian. 

It is characterized by northeast- and northwest-trending joints along which narrow, deep crevices have developed, especially on Hells Half Acre, between Whitewash and Hells Half Acre Canyons (fig. 2).

The Hells Half Acre Tuff Member was not studied 

in detail, so the extent and amount of zeolitization are

0.6 KILOMETER

600 METERS

APPROXIMATE SCALE

FIGURE 26.—Diagrammatic sketch of northwest wall of Horse Camp 

Canyon, above Aravaipa Canyon, showing units of Hells Half Acre 

Tuff Member (air-fall and reworked tuff, Thh-3; ash-flow(?) tuff, 

Thh-2; water-laid tuff, Thh-1) and relations of rhyolite-obsidian 

member (Tro) to Hells Half Acre Tuff Member and to upper andesite of Virgus Canyon (Tuav). Exposed contacts (only locally covered with talus) are solid lines; inferred contacts are dashed. Upper andesite of Virgus Canyon locally separated from rhyoliteobsidian by conglomerate (eg) and from lower unit of Hells Half 

Acre Tuff Member by a wedge of crossbedded sandstone, washed 

out from the brecciated nose of rhyolite-obsidian flow. Conglomerate 

of Virgus Canyon (Tcv); lower andesite of Virgus Canyon (Tlav), 

and Aravaipa Member (Tar, showing vuggy and columnar-jointed 

zones and overlying slightly welded zone, Taru).

not known. The compositions of six random specimens 

of the tuff, estimated from X-ray diffractographs, are 

shown in figure 29. Four of the specimens (all from the 

middle unit) have been largely altered to clinoptilolite; 

the others are vitric. The altered tuff is pink or white; 

the pumice lapilli are pink, white, or pale brown. A 

chemical analysis of a specimen of altered tuff and an 

analysis of a specimen of unaltered rhyolite-obsidian 

are listed in table 7 together with the analyses recalculated without H2O. The zeolitic alteration of the tuff 

accounts for the higher CaO and lower Na2O content. 

Relative amounts of CaO, Na2O, and K2O are plotted 

in figure 24. The minor-element analysis is given in 

table 4. Zeolitic alteration makes it impossible to tell 

if the two were originally chemically similar. Additional data on Hells Half Acre Tuff Member is given 

in Krieger, Johnson and Bigsby (1979).

The Hells Half Acre Tuff Member may be part of the 

same volcanic episode as the rhyolite-obsidian member, although eruption of flows and tuffs may have alternated. The relations on the north side of Aravaipa 

Canyon east of Javalina Canyon (fig. 27) suggest that 

an obsidian flow and the overlying middle unit of Hells 

Half Acre Tuff are contemporaneous. Obsidian breccia 

underlies, overlies, and wraps around the nose of the 

flow. Immediate burial by the tuff probably preserved 

the breccia from erosion. The relations between rhyolite-obsidian and the lowest unit of the tuff, as exposed 

in Horse Camp Canyon (fig. 25), however, suggest sufficient time for erosion to form the wedge of crossbed-
SUGGESTIONS FOR FUTURE WORK 31

0.15 KILOMETER

Approximate scale

FIGURE 27.—Massive lower part of middle unit (Thh-2a) of Hells 

Half Acre Tuff Member and its relation to rhyolite-obsidian member (Tro) (see sketch). Unit thins over irregular surface of flow, but 

maintains a horizontal top. This flow impounded water in which 

lower unit (Thh-1) of tuff was deposited. Flow consists of brecciated (br) and nonbrecciated (Tro) material. Upper part of middle 

unit (Thh-2b) is overlain by upper unit (Thh-3). Aravaipa Member (upper slightly welded tuff, Taru, and cliff-forming, columnarjointed and vuggy zones, Tar) underlies talus-covered slope concealing conglomerate and possibly andesite of Virgus Canyon. 

View northeast from west of mouth of Virgus Canyon.

ded sandstone that is composed of material derived 

from the brecciated rhyolite-obsidian flow. Finally, 

some of the large angular airborne(?) lapilli of rhyolite-obsidian and lump pumice that are abundant in 

the upper unit of the tuff may have come from the vent

0.05 K'LOMETER

0 50 METERS 

APPROXIMATE SCALE

FIGURE 28.—Diagrammatic sketch showing relations of middle unit 

(Thh-2) of Hells Half Acre Tuff Member and rhyolite-obsidian 

member (Tro). Massive lower part of middle unit has horizontal 

top and very irregular base, suggesting ash-flow rather than air-fall 

origin. Interior of obsidian flow (Tro) is flow banded; its margins are 

brecciated. Preservation of fragmented nose and top of obsidian 

flow suggests that it was almost immediately covered by Hells Half 

Acre Tuff Member. Aravaipa Member (Tar) underlies rhyolite-obsidian member. Composite of exposures on north side of Aravaipa 

Canyon east of Javalina Canyon.

in the rhyolite-obsidian near the boundary between 

the Klondyke and Holy Joe Peak quadrangles north of 

Aravaipa Canyon. These may represent the last major 

eruption of this sequence. To date no conclusive proof 

of intermittent eruption of rhyolite-obsidian flows has 

been found. The relations shown in figure 27, however, 

suggest that the rhyolite-obsidian flow here may be 

slightly older than both the lower and middle units of 

the tuff.

SUGGESTIONS FOR FUTURE WORK

The Holy Joe and Aravaipa Members of the Galiuro 

Volcanics are so well exposed and so clearly show characteristic features of ash-flow tuffs that they could be a 

valuable teaching aid, and a source of theses for geology students. Many detailed studies could be undertaken, for instance: (1) searching for flow boundaries 

and lithologic and chemical changes across flows in the
32 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, FINAL COUNTY, ARIZONA

Sample

number

H180A

H276

H342A

H344

H410

H410A

0) •M 

ID

.Q 

O

•M

O

-

-

-

-

-

-

^

ID

a

•o

0> 

LL

A

A

O

A

A

A

N

•H

<0

3

a

A

O

O

0

A

A

0>•H 

'£

O

bo

-

-

A

A

A

-

0>

"o

a

O w

.E £ J3 

0 0 O

A — •

• — —

• — —

• — —

• — —

— — •

• Abundant (more than

50 percent)

O Present but not abundant

A Recognized

— Not recognized

Upper unit (air-fall tuff)

Middle(?) unit

Middle unit (ash-flow tuff)

Middle unit (ash-flow tuff)

Middle unit (ash-flow tuff)

Upper(?) unit (air-fall tuff)

FIGURE 29.—Approximate composition of Hells Half Acre 

Tuff Member, estimated from X-ray diffractographs of 

bulk samples. H180A, middle branch, Hells Half Acre 

Canyon, center sec. 20, T. 6 S., R. 18 E. (fig. 2). Contains 

trace of calcite. H276, Ash Creek, east of Lyon Camp, sec. 

21, T. 5 S., R. 18 E., NWV4 Brandenburg Mountain quadrangle; H342A, Cave Canyon, NWVi sec. 18, T. 6 S., R. 19 

E. (fig. 2); H344, Aravaipa Canyon, east of Cave Canyon, 

NWV4 sec. 18, T. 6 S., R. 18 E. (fig. 2); H410, Aravaipa 

Canyon, near mouth of Cave Canyon, NWVi sec. 18, T. 6 

S., R. 18 E. (no. 12, fig. 2). (Chemical analysis, see table 

7); H410A, Horse Camp Canyon, SW cor. sec. 9, T. 6 S., 

R. 18 E. (fig. 2).

Holy Joe Member, as well as more detailed study of 

the upper vitrophyre and its distribution than has 

been made; (2) studying the ash-flow tuff sheet of the 

Aravaipa Member to determine if it is made up of more 

than one flow; making a careful selection of samples so 

as to obtain more meaningful results of changes in 

chemical composition of glassy and crystalline parts of 

both ash-flow tuffs and of changes due to zeolitization 

in the Aravaipa Member; (3) examining the relation 

of the tuff of Bear Springs Canyon to the tuff of Aravaipa Member to determine if they make up a composite sheet (Smith, 1960a); (4) determining the age 

relations of rhyolite-obsidian member and Hells Half 

Acre Tuff Member and the distribution of zeolitization 

in the tuff.

REFERENCES CITED

Blake, W. P., 1902, The geology of the Galiuro Mountains, Ariz., and 

of the gold-bearing ledge known as Gold Mountain: Engineering 

Mining Journal, v. 73, p. 546-547.

Buddington, A. F., and Lindsley, D. H., 1964, Iron-titanium oxide 

minerals and synthetic equivalents: Journal of Petrology, v. 5, 

p. 310-357.

Carmichael, I. S. E., 1967, The iron-titanium oxides of salic volcanic 

rocks and their associated ferromagnesian silicates: Contributions to Mineralogy and Petrology, v. 14, p. 36-64.

Cooper, J. R., and Silver, L. T., 1964, Geology and ore deposits of the 

Dragoon quadrangle, Cochise County, Arizona: U.S. Geological 

Survey Professional Paper 416, 196 p.

Creasey, S. C., and Krieger, M. H., 1978, The Galiuro Volcanics, 

Final, Graham, and Cochise Counties, Arizona: U.S. Geological 

Survey Journal of Research, v. 6, no. 1, p. 115-131.

Hoover, D. L., 1966, Physical and chemical changes during zeolitization of vitric tuffs and lava flows, Nevada Test Site [abs.]: Geological Society of America Special Paper 87, p. 286-287.

————1968, Genesis of zeolites, Nevada Test Site, in Eckel, E. B.,

ed., Nevada Test Site: Geological Society of America Memoir 

110, p. 275-284.

Hoover, D. L., and Shepard, A. O., 1965, Zeolite zoning in volcanic 

rocks at the Nevada Test Site, Nye County, Nevada [abs.]: 

American Mineralogist, v. 50, nos. 1—2, p. 287.

Krieger, M. H., 1968a, Geologic map of the Brandenburg Mountain 

quadrangle, Final County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-668, scale 1:24,000.

————1968b, Geologic map of the Holy Joe Peak quadrangle, Final 

County, Arizona: U.S. Geological Survey Geologic Quadrangle 

Map GQ-669, scale 1:24,000.

————1968c, Geologic map of the Lookout Mountain quadrangle, 

Final County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-670, scale 1:24,000. 

-1968d, Geologic map of the Saddle Mountain quadrangle,

Final County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-671, scale 1:24,000.

Krieger, M. H., Johnson, M. G., and Bigsby, P. R., 1979, Mineral 

resources of the Aravaipa Canyon Designated Wilderness area. 

Final and Graham Counties, Arizona: U.S. Geological Survey 

Open-File Report 79-291, 183 p.

Lipman, P. W., 1965, Chemical comparison of glassy and crystalline 

volcanic rocks: U.S. Geological Survey Bulletin 1201-D, 24 p.

Lipman, P. W., and Christiansen, R. L., 1964, Zonal features of an 

ash-flow sheet in the Piapi Canyon Formation, southern Nevada, 

in Geological Survey Research, 1964: U.S. Geological Survey 

Professional Paper 501-B, p. B74-B78.

Lipman, P. W., Christiansen, R. L., and O'Connor, J. T., 1966, A 

compositionally zoned ash-flow sheet in southern Nevada: U.S. 

Geological Survey Professional Paper 524-F, 47 p.

Ratte, J. C., and Steven, T. A., 1967, Ash flows and related volcanic 

rocks associated with the Creede caldera, San Juan Mountains, 

Colorado: U.S. Geological Survey Professional Paper 524-H, 

58 p.

Ross, C. S., and Smith, R. L., 1955, Water and other volatiles in volcanic glasses: American Mineralogist, v. 40, nos. 11-12, p. 1071- 

1089. 

1961, Ash-flow tuffs—Their origin, geologic relations, and identification: U.S. Geological Survey Professional Paper 366, 81 p.

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

single solution method, in Geological Survey Research 1967: 

U.S. Geological Survey Professional Paper 575-B, p. B187- 

B191.

Shapiro, Leonard, and Brannock, W. W., 1962, Rapid analysis of silicate, carbonate, and phosphate rocks: U.S. Geological Survey 

Bulletin 1144-A, 56 p.

Sheppard, R. A., and Gude, A. J., 3d, 1965, Zeolitic authigenesis of 

tuffs in the Ricardo Formation, Kern County, California, in Geological Survey Research, 1965: U.S. Geological Survey Professional Paper 525-D, p. D44-D47.

Simons, F. S., 1964, Geology of the Klondyke quadrangle, Graham 

and Final Counties, Arizona: U.S. Geological Survey Professional Paper 461, 173 p.

Smith, R. L., 1960a, Ash flows: Geological Society of America Bulletin, 

v. 71, no. 6, p. 795-841.

1960b, Zones and zonal variations in welded ash flows: U.S.

Geological Survey Professional Paper 354-F, p. F149-F159. 

Willden, Ronald, 1964, Geology of the Christmas quadrangle, Gila 

and Final Counties, Arizona: U.S. Geological Survey Bulletin 

1161-E, 64 p.

GPO689-143