Geochemistry of the Laramide igneous suite of theSanta Rita and Empire Mountains, southeastern Arizona

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Authors Trapp, Richard A.

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GEOCHEMISTRY'OF THE LARAMIDE IGNEOUS SUITE

OF THE SANTA RITA AND EMPIRE MOUNTAINS,

SOUTHEASTERN ARIZONA

by

Richard Allen Trapp

A Thesis Submitted to the Faculty of the

DEPARTMENT OF GEOSCIENCES

In Partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE

In the Graduate College

THE UNIVERSITY OF ARIZONA

1 9 8 7

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgement the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

Signed:

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

■ wicfstfienS. R. TITLE?

Professor of Gec^tfiences

A. MDate

ACKNOWLEDGEMENTS

I would like to thank Dr. Spencer R. Titley of the University of Arizona for his support and guidance which began before I enrolled at the University of Arizona and continued throughout the process which has culminated in this thesis. I would further like to thank Dr. Elizabeth Youngblood Anthony who guided me through the intricacies of Instrumental Neutron Activation Analysis. Finally, I would like to thank my wife, Alyce, for her support and patience during my studies.

iii

TABLE OF CONTENTS

Page

LIST OF ILLUSTRATIONS.......... : .......................... vi

LIST OF TABLES .............................................viii

ABSTRACT ............................ ...................... ix

1. INTRODUCTION .......................... ........ . . . . . 1

Scope of the Study....................................... 1Physiography and Geology of the Santa Rita/Empire

Mountains ........................................... 4Rationale for Method of S t u d y .......................... 9

2. DESCRIPTION OF THE UNITS ...................... ............ 12

Salero Formation ( S F ) ................................... 12Lower member (SFN) ................................ 13Welded-tuff member (SFS) .......................... 14

Corona and Empire stocks (KLQ) ........................ 15Josephine Canyon Diorite (JCD) ........................ 16Elephant Head Quartz Monzonite (EHQM) .................. 17Quartz latite porphyry (TKP) .......................... 18Quartz latite porphyry (GV) ............................ 19

3. ANALYTICAL METHODS .................. .. . ................. 22

Geochemical Evaluation of Weathering and Alteration . . . 23

4. DESCRIPTION OF ANALYTICAL R E S U L T S .............. 26

Major Elements ......................................... 26Mg, P, Ca, Ti, Mn, and F e .......................... 26A1 ................................................. 32Na and K ........................................... 32Ratios of Major Elements .......................... 32

Minor Elements . ......................... 36Sc, Co, Ni, Sr, Zr, and Hf ........................ 36Zn, As, Sb, and Cs ................................. 40Rb, Ba, and Ta ..................................... 40R E E .............................. 43U and Th .................................. 44

iv

V

TABLE OF CONTENTS--Continued

Ratios of K, Rb, Sr, and B a ............................ 44K/Rb ............................................... 48K/Ba ............................................... 48Rb/Sr . . . "......................................... 49S r / B a ...................... ........................ 49

5. DISCUSSION OF ANALYTICAL RESULTS .......................... 54

Major Elements ......................................... 54Mg, P, Ca, Ti, Mn, and F e .......................... 54Al ................................................. 55Na and K ........ .................... .............. 55Ratios of Major Elements .......................... 55

Minor Elements ......................................... 56Sc, Co, Ni, Sr, Zr, and Hf ......................... 56

Ratios of K, Rb, Sr, and B a ............................ 57K/Rb ........................ ...................... 57K/Ba ............................................... 57R b / S r ............................................... 58S r / B a ........................ ...................... 58General Comments ................................... 58

6. GENETIC RELATIONS BETWEEN UNITS ............................ 61

Ti and Z r ...................................... .. . . . 62K/Rb Ratios and Related Values.......................... 67Rare Earth E l e m e n t s ..................................... 68U and Th ............................................... 75Comparisons of Sierrita Samples to Santa Rita and

Empire Samples ..................................... 76

7. CONCLUSIONS............................ 79

APPENDIX 1: ANALYTICAL R E S U L T S ............................. 82

APPENDIX 2: LOCATIONS AND CORRELATIONS................ .. . 87

APPENDIX 3: MAJOR ELEMENT VALUES AND RATIOS, PETROLOGICINDICES, AND BARTH KATANORMS .................. 94

APPENDIX 4: ERRORS AND REPRODUCIBILITY .................... 113

Page

LIST OF REFERENCES 116

LIST OF ILLUSTRATIONS

1. Santa Rita and Empire Mountains and Sierrita Mountains,southeastern Arizona ................................. 5

2. Outcrop map of the study area with sample locations . . . . 7

3. MgO vs Si02". Santa Rita and Empire Mountains.............. 27

4. Ti vs SiOg: Santa Rita and Empire Mountains.............. 27

5. FegOgCt) vs SiOg: Santa Rita and Empire Mountains ........ 28

6. CaO vs D. I.: Santa Rita and Empire Mountains............ 29

7. CaO vs SiOg: Santa Rita and Empire Mountains ............ 298. Fe20g(t) vs Ti: Santa Rita and Empire M o untains.......... 31

9. Fe20g(t) vs Ti: Sierrita Mountains . ....................... 31

10. AI2O3 vs Si02: Santa Rita and Empire Mountains ............ 33

11. K2O vs Si02: Santa Rita and Empire Mountains.............. 34

12. Na20 vs Si02: Santa Rita and Empire Mountains............ 34

13. A/CNK(m) vs Si02: Santa Rita and Empire Mountains . . . . . 35

14. Na20/K20 vs Si02: Santa Rita and Empire Mountains ........ 35

15. Co vs S102: Santa Rita and Empire Mountains............... 37

16. Ni vs SiG^: Santa Rita and Empire Mountains............... 37

17. Sr vs Si02: Santa Rita and Empire Mountains............... 38

18. Zr vs Si02: Santa Rita and Empire Mountains............... 38

19. Ti vs Zr: Santa Rita and Empire Mountains................ 39

20. Sr vs CaO: Santa Rita and Empire Mountains................ 39

Figure Page

vi

LIST OF ILLUSTRATIONS--Continued

Figure Fage

21. Rb vs SiOg: Santa Rita and Empire Mountains.............. 41

22. Ba vs SlOg: Santa Rita and Empire Mountains.............. 42

23. Ta vs SiOg: Santa Rita and Empire Mountains.............. 42

24a. REE - JCD and SFS: Santa Rita and Empire Mountains . . . . 45

24b. REE - EHQM: Santa Rita and Empire Mountains....... 45

25a. REE - SFN and KLQ: Santa Rita and Empire Mountains . . . . 46

25b. REE - TKP and GV: Santa Rita and Empire Mountains . . . . 46

26. U vs SiOg: Santa Rita and Empire Mountains................ 4727. Th vs SiOg: Santa Rita and Empire Mountains.............. 47

28. K/Rb vs SiOg: Santa Rita and Empire Mountains............ 50

29. K/Rb vs SiOg: Sierrita Mountains.......................... 50

30. K/Ba vs SiOg: Santa Rita and Empire Mountains............ 51

31. K/Ba vs S102: Sierrita Mountains.......................... 51

32. Rb/Sr vs SiOg: Santa Rita and Empire Mountains ............ 52

33. Rb/Sr vs SiOg: Sierrita Mountains ........................ 52

34. Sr/Ba vs SiOg: Santa Rita and Empire Mountains ............ 53

35. Y/Sr vs SiOg: Santa Rita and Empire M o u ntains............ 60

36. Sr/Zr vs SiOg: Santa Rita and Empire Mountains............ 60

37. Ti vs Zr: Sierrita Mountains............................... 65

38. P2O5 vs total REE: Santa Rita and Empire Mountains . . . . 71

39. Zr vs total REE: Santa Rita and Empire Mountains.......... 71

40. Ti vs total REE: Santa Rita and Empire Mountains.......... 72

vii

LIST OF TABLES

1. Sampled Units with Ages and Correlations by Drewes (1981) . 3

2. Chemical Index of Alteration (C.I.A.) for Samples ........ 25

3. Ce/Yb Values and A v e r a g e s ............................ .. . 70

Table Page

viii

ABSTRACT

Laramide igneous activity in the Santa Rita and Empire

Mountains of southeastern Arizona began prior to 74 Ma and continued

until approximately 55 Ma. Eighteen samples from the Salero Formation,

Corona and Empire stocks, Josephine Canyon Diorite, Elephant Head

Quartz Monzonite, and Late Cretaceous and Paleocene stocks and dikes

were examined by Instrumental Neutron Activation Analysis to provide

reliable trace element concentrations. Ti-Zr, REE, U and Th, and K/Rb

data indicate that the Josephine Canyon Diorite and Elephant Head

Quartz Monzonite are probably genetically related, that the Corona and

Empire stocks and Late Cretaceous and Paleocene stocks and dikes are

probably related, and that the Salero Formation may be related to

either group or both. Comparison with a suite of similar age from the

Sierrita Mountains (Anthony, 1986) of southeastern Arizona indicates

distinct differences. The Sierrita Mountains contain world-class

porphyry copper deposits while the Santa Rita and Empire Mountains,

twenty miles to the east, have relatively meager metal production.

ix

CHAPTER 1

INTRODUCTION

Southeastern Arizona is one of the premier copper-producing

areas of the world. Within this region, however, some areas have had

conspicuously greater mineral production than others. This work is

part of a geochemical study of two mountain ranges which differ

markedly in metal production, yet are geographically close and have

similar intrusive histories. The Sierrita Mountains contain

world-class porphyry copper deposits in igneous rocks of Laramide age.

The Santa Rita and Empire Mountains, which lie only 20 - 30 miles to

the east, have igneous units similar to those in the Sierrita

Mountains, but are relatively meager in metal production, particularly

with respect to copper. The combination of geographic proximity,

petrologic similarity, and disparity in mineral production indicates

that a study of the trace element composition of these rocks might

suggest some differences between "productive" and "nonproductive"

plutonic complexes in the southwestern United States.

Scone of the Study

This study was conducted under the supervision of Dr. Spencer

R. Titley of the University of Arizona and was part of a larger project

aimed at placing constraints on the source regions of Laramide plutons

1V

2

in southeastern Arizona. This portion of the project concentrated on

the Santa Rita and Empire Mountains, while E. Y. Anthony and N. Hess

were conducting a study of similar units in the Sierrita Mountains. In

the Sierrita study, time- and stratigraphically restricted units that

were believed to be closely related were intensively sampled so that

geochemical modeling could be combined with isotopic analyses to typify

the sources and igneous processes which were responsible for their

formation.

In this study units from a mountain range adjacent to the

Sierrita Mountains were studied so that comparisons could be made. The

samples were chosen so that: 1) the maximum dimension of the geographic area of sampling in the Santa Rita and Empire complex was greater than

the distance between the Sierrita and Santa Rita Mountains; 2) the

sampled units in the Santa Rita and Empire complex included units both

older and younger than those sampled in the Sierrita Mountains; and, 3)

correlative units were included.

The author collected and prepared all samples from the Santa

Rita and Empire complex, with Dr..Titley advising as to which units

were appropriate to the aims of the larger project. With advice from

E. Y. Anthony, the author conducted the trace element analysis on all

but three of the samples, and assisted on those three.

APPENDIX 1 lists the results of the analyses. TABLE 1 lists

the units sampled in this study, their ages, approximate outcrop areas,

and correlations to rocks in the Sierrita Mountains according to Drewes

(1981). APPENDIX 2 is a more detailed listing of the samples in this

3

TABLE 1. Sampled Units with Ages and Correlations by Drewes (1981)

Unit: Salero Formation (SF: SFN and SFS)Age: Upper Cretaceous, upper CampanianOutcrop: Southern Santa Rita Mountains in the Salero Mountain

vicinity and an area centered between the extreme northern Santa Rita mountains and the Empire Mountains, extending into both ranges.

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

Unit: Quartz monzonite of Corona and Empire stocks (KLQ)Age: Upper Cretaceous, upper CampanianOutcrop: Corona stock outcrops at the extreme northern end of

the northern Santa Rita Mountains; Empire stock outcrops in the west-central Empire Mountains, about 6 miles southwest of the Corona stock.

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

Unit: Josephine Canyon Diorite (JCD)Age: Upper Cretaceous, MaestrichtianOutcrop: Southern Santa Rita MountainsSierrita correlative: Diorite and andesitic intrusive rocks dated

at 67 m.y. (diorite phase studied by Anthony, 1986)

Unit: Elephant Head Quartz .Monzonite (EHQM)Age: Upper Cretaceous, MaestrichtianOutcrop: Northwestern part of southern Santa Rita MountainsSierrita correlative: Diorite and andesitic intrusive rocks dated

at 67 m.y. (diorite phase studied by Anthony, 1986)

Unit: Latitic to dacitic plugs and dikes (TKP)Age: Upper Cretaceous, Maestrichtian to PaleoceneOutcrop: Several small plugs in the Salero Mountain area of the

southern Santa Rita Mountains (and dikes throughout the Santa Rita Mountains)

Sierrita correlative: None but interpreted as being emplaced atboundary between dioritic and andesitic intrusive rocks (67 m.a.) and Ruby Star Granodiorite (59-60 m.a.) and biotite rhyolite (57 m.a.)

Quartz latite porphyry (GV)PaleoceneNorthern Santa Rita and Empire Mountains as plugs and dikes.correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma.

Unit:Age:Outcrop:

Sierrita

4

study, with more precise sampling sites, units, ages, and correlations

to Sierrita units according to Drewes (1981). Figure 1 shows sample

locations and the relative positions of the Santa Rita-Empire and

Sierrita Mountains. Samples from various other units were also

analyzed to ensure that analyses of the units of interest could be

distinguished from obviously unrelated rocks. These control samples

include a mid-Tertiary rhyolitic dike from the Santa Rita Mountains

(TRD-GV-1), the Jurassic Harris Ranch Quartz Monzonite from the

Sierrita Mountains (HRQM-1), and a late Tertiary porphyry from the

Yandera porphyry copper deposit of Papua New Guinea (Y-l), collected by

Dr. Titley.

Pertinent information about the samples from the Sierrita

Mountains can be found in Anthony (1986). Discussion of those samples

is included in this report only for comparison. Unless explicitly

stated, any further references to "samples" or "units" in this report

will refer to samples collected by the author in the Santa Rita and

Empire Mountains.

Physiography and Geology of the Santa Rita and Empire Mountains

The Santa Rita, Empire, and Sierrita Mountains are within the

Basin and Range Province of Arizona, specifically within the Porphyry

Copper Block subprovince of Wilkins (1984) (Figure 1). The Santa Rita

Mountains are believed to be a tilted fault block formed during a

middle to late Tertiary period of extensional tectonics. To the west

is the Santa Cruz River valley, which is quite linear and narrow with a

5

SierritaMountains

10 miles

ARIZONA

Figure 1. Santa Rita and Empire and Sierrita Mountains, SE Arizona

6

north-south orientation, as is typical for this area (Wilkins, 1984).

It separates the Santa Rita Mountains from the Sierrita Mountains.

The Santa Rita Mountains are divided physiographically and

geologically by the Sawmill Canyon fault zone (Figure 2). This is a

major structural feature in the area and can be traced across the Santa

Cruz graben into the Sierrita Mountains to the west (Titley, 1982) and

across the Sonoita Basin into the Canelo Hills and Huachuca Mountains

to the east (Drewes, 1981). The Sawmill Canyon fault zone is marked by

a narrow linear zone of steeply tilted to overturned fault blocks of

Paleozoic and Triassic sedimentary rocks that are on strike (northwest)

and in line with a much wider zone of steeply tilted fault blocks of

Paleozoic and Triassic sedimentary rocks which compose the northern

part of the Canelo Hills.

The southern Santa Rita Mountains are characterized by: a

maximum elevation of approximately 9,500 feet; a NNW-trending outline

measuring about 10 miles by 15 miles; and igneous rocks ranging in age

from Triassic to Paleocene. The Sawmill Canyon fault zone is succeeded

southward by a wider belt of folded Cretaceous sedimentary rocks. There

is one small mid-Tertiary stock in this zone. Trending northwest to

north-northwest are semi-continuous outcrops in the following

succession (from northeast to southwest): 1) Lower Cretaceous volcanic

and sedimentary rocks that dip gently to the northeast (confined to the

east flank of the mountain range); 2) Upper Triassic to lower Jurassic

volcanic and partly coeval intrusive rocks that dip moderately to the

northeast; 3) Late Cretaceous intrusive rocks (64-68 my); 4) Upper

7

Figure 2. Outcrop map of the study area with sample locations

8

Cretaceous volcanic rocks (70-74? my); and, 5) extensive Mid-Tertiary

intrusive and volcanic rocks in the Grosvenor hills and east of the San

Cayetano Mountains.

The northern Santa Rita Mountains are characterized by: a

maximum elevation of approximately 6200 feet; a NNE-trending outline

measuring about 5 miles by 12 miles; and, extensive outcrops of

Precambrian igneous rocks, Paleozoic and Cretaceous sedimentary rocks,

and Cretaceous and Paleocene igneous rocks. From the Sawmill Canyon

fault zone northward to the Helvetia and Rosemont area, small late

Paleocene stocks, plugs, and dikes are the only manifestation of

Laramide magmatism. They intrude Precambrian igneous and metamorphic

units and lower Paleozoic and Lower Cretaceous sedimentary units. A

Laramide intrusive and extrusive complex extends from the northern

Santa Rita Mountains eastward to the middle of the Empire Mountains,

and the lithologies and pattern of outcrops of these two areas are

indistinguishable. Thus, there is no clear geological boundary between

the northern Santa Rita Mountains and the Empire Mountains, but

Davidson Canyon forms a topographic boundary.

The Empire Mountains consist of scattered outcrops of

Precambrian schists and granitoids in the north, tilted fault blocks of

Paleozoic and Lower Cretaceous Bisbee Group sedimentary rocks in the

south, and the previously mentioned Laramide complex in between.

Subdued outcrops extend northward from the Empire Mountains with some

interruption across the Pantano Wash into the foothills of the Rincon

Mountains. Maximum elevation in the Empire Mountains is approximately

9

5,500 feet.

Rationale for Method of Study

Geochemical modeling using sophisticated trace-element analysis

has become a popular method of placing constraints on the petrogenesis

of igneous rocks. The fact that certain elements are "incompatible" or

are excluded from the precipitating phases of mafic-to-intermediate

rock series, has enabled the calculation of parameters involved in

crystal fractionation and partial melting. Many studies have been

conducted using calculations which are based upon accurate

determinations of both the trace element content and stoichiometric

proportions of the phases present in a mafic- to-intermediate igneous

suite.

Although such methods are widely applicable to mafic and

intermediate rock series (SiOg < 65%), all samples in this study are

felsic (SiOg > 65%). In rocks of this nature very few elements are

excluded from the precipitating phases. For instance, the REE (La to

Lu) with the exception of Eu, are strongly excluded in

mafic-to-intermediate rocks, but are strongly preferred in the

structure of minerals such as monazite, allanite, and zircon that are

common accessory minerals in the rocks of this study and other felsic

rocks. Unfortunately, even though these are common accessory minerals,

they are present in such minute amounts that it becomes an exceedingly

formidable task to separate them in sufficient quantity for accurate

analysis of their trace element content (see, for example, Fourcade and

10

Allegre, 1981, Mittlefelhdt and Miller, 1983). The uncertainties

introduced by an inability to determine accurately the exact mode of

occurrence of the REE, Zr, and other elements that are compatible in

felsic rocks make geochemical modelling based upon them problematic.

As pointed out by Hanson (1978), geochemical modelling for

felsic rocks must use elements such as K, Rb, Sr, and Ba. These

elements, however, are known to be readily mobilized under certain

conditions, many of which may possibly have occurred in the 60-70

million years that have elapsed since the rocks of this study were

formed. For a geochemical modelling study of felsic rocks, it would be

necessary to extensively sample any units studied and to analyze

mineral separates as well. Given the diversity of rocks in the Santa

Rita and Empire Laramide igneous suite, I felt that a survey of several

different units would provide more information about the nature of

Laramide magmatism in this region than a comprehensive study of two or

three units such as Anthony's (1986) Sierrita study. Without analysis

of mineral separates, rigorous geochemical modelling is not possible;

but many inferences about the petrogenesis of these rocks can still be

made.

Since the units of this study have been related to each other

in earlier studies, I will examine the analytical results by treating

the samples as members of a suite. While I do not believe that

previous work has provided conclusive proof of genetic relation, this

seems to be a reasonable approach to evaluating the data. I also do

not believe that geochemical analysis alone can provide proof of

genetic relation, but the information will add to the body of knowledge

concerning Laramide igneous rocks in southeastern Arizona.

11

CHAPTER 2

DESCRIPTION OF THE UNITS

All of the units in this study have been described by Drewes

(1971a, 1971b, 1971c, 1972, 1976, 1980, 1981) in a series of works

dealing with the Santa Rita Mountains and southeastern Arizona. Unless

otherwise stated, the samples chosen for this study are similar to

those described by Drewes. His descriptions will be summarized in the

next sections. Features of the samples from this study which differ

from Drewes' description will be noted. The capitalized letters within

parentheses that follow the title of each section will be the

abbreviation used to denote the unit in the rest of this report.

Locations of main outcrops are illustrated in Figure 2.

Salero Formation (SF1: Samples 9. 15. 16. 18

This formation consists of five members. The lowest member,

which is the oldest unit sampled in this study, is the lower andesite.

The second member is the exotic-block member. The middle unit is the

welded-tuff member. These three units comprise the bulk of the

formation. The upper two units consist mainly of sedimentary rocks.

The formation is exposed over an area of about fifteen square miles in

the southern Santa Rita Mountains and about five square miles in the

northern Santa Rita and Empire Mountains (Drewes, 1971a, 1971c, 1980;

12

13

Finnell, 1971). According to Drewes (1971c), the unit rests with

probable conformity on the Upper Cretaceous Fort Crittenden Formation

in a few places and with a highly irregular angular unconformity on the

Jurassic Squaw Gulch Granite at most visible points of contact. Lipman

and Sawyer (1985), however, believe that the lower three members of the

Salero Formation represent a thick succession of caldera fill, with blocks of varying size and lithology in a welded-tuff matrix

characterizing each of the members. Thus, the lower member contains

andesitic blocks, the exotic block member has blocks of Cretaceous

andesite and Jurassic welded-tuff and granite, and very large blocks of

Jurassic granite are contained in the welded-tuff member. These very

large blocks of Lipman and Sawyer (1985) were interpreted as buried hills by Drewes (1971c).

Lower member (SFN): Sample 9

The lower member was only sampled in the northern Santa Rita

and Empire Mountains area owing to the highly altered and quite

weathered condition of exposures in the study area. Even the sample

chosen for analysis has a significant amount of secondary epidote and

gypsum in veins, and other specimens which were examined contained

clots of massive epidote and/or abundant gypsum in veins and/or were so

altered as to be quite incompetent. The unit was considered to be

important enough that one sample was analyzed, despite its altered

condition. The sample chosen was determined to be relatively

unweathered. The lower member is described as "dacitic to andesitic

14

lava flows and tuff breccias" by Drewes (1971c). The analyzed sample

appears to be a flow (?) breccia.

Welded-tuff member (SFS): Samples 15, 16, 18The welded-tuff member of this formation was sampled more

extensively. Three samples from the southern Santa Rita Mountains were

taken from near the type locale, Salero Mountain. These samples

appeared to be quite fresh in hand sample and were quite competent.

Feldspars were lustrous on fresh surfaces. These samples are

interpreted as representative of the unit as described by Drewes

(1971c), a rhyodacite welded tuff. Drewes estimates that more than

three cubic miles of this material was erupted more-or-less continuously. Phenocrysts make up about 40% to 60% of the rock and are

about two to four millimeters long (Drewes, 1971c).

The age of this formation (SF) is Upper Cretaceous, 74.3 +/-

3.30 Ma based on a K-Ar determination of the welded-tuff member (Marvin

and others, 1973, Reynolds and others, 1985). The lower member (SFN)

is interpreted to be older than or contemporaneous with the Corona and

Empire stocks (KLQ), and the welded-tuff member (SFS) is considered to

be contemporaneous with or younger than the Corona and Empire stocks

(see below) (Drewes, 1976, 1981). The Salero Formation is considered

to be correlative with the Demetrie Volcanics and the Red Boy Rhyolite

in the Sierrita Mountains (Drewes, 1981).

15Corona and Empire stocks (KLO): Samples 10 and 11

These two stocks crop out over an area of four or five square

miles in the northernmost Santa Rita Mountains (Corona) and the Empire

Mountains (Empire) (Drewes, 1980). One sample from each of the stocks

was chosen for analysis. These two stocks are peripheral to the

largest intrusion in the Santa Rita and Empire Mountains of the Tip unit of Drewes (1981) (GV unit in this study), which is correlated with

the late quartz monzonite porphyry in the Sierrita Mountains,

associated with main-stage mineralization in the Sierrita-Esperanza

deposits. The juxtaposition of the older and younger stocks in the

Santa Rita and Empire Mountains follows the typical Laramide pattern of

repeated intrusion in a geographically restricted area. The Corona and

Empire stocks contain inclusions or roof pendants of their host rocks,

the Bisbee Group, which are contact metamorphosed to hornfels or

calc-silicate facies. The contact is sharp with no noticeable chill

zone (Drewes, 1976).

The main facies of these stocks is quartz monzonite, which is

the composition of both samples. The quartz monzonite is

hypidiomorphic-granular in texture. Drewes (1976) reports some

samples having a little mosaic, porphyritic, or porphyroblastic and

granophyric texture, with some evidence of recrystallization. The

typical grain size is 1 - 10 mm.Drewes (1976) reported wide diversity in the modes, but

chemical analysis of the two specimens in this study shows them to be

remarkably similar in most aspects. These stocks are chemically

16

similar to the Jurassic Squaw Gulch Granite (not included in this

study) and the Elephant Head Quartz Monzonite (see below). The age of

these stocks has been established as Upper Cretaceous based on

radiometric determinations of 75.5 ma and 75.3 ma for the Corona stock

and 71.9 ma for the Empire stock (Marvin and others, 1973; Reynolds and

others, 1985). Drewes (1976, 1980, 1981) has correlated these units

with the Demetrie volcanics of the Sierrita Mountains and a

granodiorite stock in the Whetstone Mountains (18 miles southeast) and

the Amole Granite and Amole Quartz Monzonite of the Tucson Mountains

and believes there to be a genetic relation between these stocks and

adjacent rhyodacite volcanics; the correlative being the Salero

Formation (SF) (see above) for the Corona and Empire stocks.

Josephine Canyon Diorite (JCD): Samples 3. 19. 20

The main outcrop of the JCD is an elongate, north-northwest

trending, pluton that extends from the-southern end of the southern

Santa Rita Mountains to just west of Mount Wrightson (Drewes, 1971a).

Samples were taken from the southern end of this pluton and are from

the dioritic phase (Kj) of Drewes (1971a, 1976). The outcrop area of

JCD is estimated to be 25 square miles by Drewes and he believes that

the sub-surface extent of the pluton is slightly larger. The main

outcrop area is divided into two segments by a narrow septum at the

approximate mid-point. The JCD intrudes the Salero Formation (SF) and

is unconformably overlain by the Gringo Gulch Volcanics and other

younger deposits. The dioritic phase generally has a subophitic

17

texture, with some occurrences of a slightly porphyritic texture, and

even fewer with a fine-grained granophyric texture. Grain size is

generally 1 - 3 mm, with very few grains being less than .1 mm or

greater than 4 mm (Drewes, 1976).

The southern portion has been dated as younger than the EHQM, but Drewes (1976) interprets the southern segment to be the youngest

and top part of the stock. Thus, Drewes argues that the northern

segment is older than the southern segment and the EHQM, thus

reconciling the radiometric data with his interpretation of the field

relations. The age of the JCD is late Late Cretaceous based on field

relations (Drewes, 1976) and a single K-Ar date of 68.7 +/- 3.00 Ma

(Marvin and others, 1973, Reynolds and others, 1985). Drewes (1981)

correlates the JCD with dioritic and andesitic intrusive rocks in the

Sierrita Mountains.

Elephant Head Quartz Monzonite (EHQM): Samples 12. 13. and 14

This pluton consists of two stocks, the Yoas and the Quantrell.

Only the Quantrell was sampled. The Quantrell stock is older and

larger than the Yoas and has two phases: a coarse-grained interior (?)

phase; and a fine-grained border (?) phase which is interpreted to be

intrusive into the coarse-grained phase (Drewes, 1976). Two samples of

the coarse-grained phase and one sample of the fine-grained phase were

analyzed.

The coarse-grained phase has a hypidiomorphic-granular texture

with a common grain size of four to eight millimeters. Drewes (1976)

18

also reports poikilitic, myrmekitic, granophyric, and perthitic

textures and one instance of a superimposed weak metamorphic texture.

The fine-grained phase has a grain size of two-tenths to two

millimeters overall, although individual specimens show less range.

The most common texture is idiomorphic- to hypidiomorphic-granular with

areas of fine-grained granophyric texture. This phase has fewer

accessory minerals than the coarse-grained phase (Drewes, 1976).

The EHQM was interpreted by Drewes (1976) to be the most

differentiated in a series which includes the JCD and the Madera Canyon

Granodiorite. It is very similar in major element composition to the

Jurassic Squaw Gulch Granite and the slightly older Late Cretaceous

quartz monzonite of the Corona and Empire stocks (KLQ). The age of the

Quantrell stock is Late Cretaceous based on K-Ar dates of 69.90 +/-

3.00 Ma and 70.80 +/- 2.90 Ma (Marvin and others, 1973, Reynolds and

others, 1985). Drewes (1971a, 1976) believes that the Josephine Canyon

Diorite (JCD) is older than the EHQM based on field relations between

the EHQM and a diorite unit which is correlated with the JCD. Drewes

(1981) correlates the EHQM with dioritic and andesitic intrusive rocks

in the Sierrita Mountains.

Quartz latite porphvrv (TKP>: Sample 17

Sample 17 was taken from a small (< 1 sq. mi.) stock that

intrudes the Salero Formation (SF) approximately 3 miles NNE of the

Salero Mine. On both fresh and weathered faces and after crushing,

this rock is a pale orange. The color probably derives from

19

pink-stained plagioclase phenocrysts. The sampled outcrop is more

resistant to weathering than the surrounding SF and forms a small knob.

Surrounding rocks do not seem to be contact metamorphosed, but the

contact is not well-exposed.

In addition to plagioclase, there are small phenocrysts of

altered mica and relatively little quartz. Groundmass of

idiomorphic-granular texture makes up 75-85% of the rock with

phenocrysts 4-7 mm long (Drewes, 1976).

Drewes (1976, 1980, 1981) interprets the stock to be older than

the Greaterville intrusives (GV - discussed below) and younger than the

JCD and the EHQM. Although the stock has not been dated, he correlates

it with other units dated at 60 - 65 Ma and indicates that its

emplacement occurred between the time of emplacement of dioritic

intrusives and the Ruby Star Granodiorite of the Sierrita Mountains.

Quartz latite porphyry (GV): Samples 4. 5. 6. 7. and 21Stocks, plugs, and dikes of quartz latite porphyry, the

youngest unit assigned to the Laramide orogeny by Drewes (1980, 1981),

outcrop in the northern Santa Rita and the Empire Mountains and the

area between them (Drewes, 1971b; Finnell, 1971). The largest stock

is central to the KLQ (see above). Two samples (7 and 21) were

analyzed from near the eastern periphery of this stock. Another group

of plugs and dikes of quartz latite porphyry occur at Greaterville,

just north of the Sawmill Canyon fault zone. Three samples were

analyzed from the Greaterville area: one from a dike (Sample 6); one

20

from the border of a plug (Sample 5); and the last (Sample 4) from

drill core from an ASARCO hole in the area. Sample 4 is somewhat

unusual in that it contains 81.5% Si02, but it appears to be a highly

differentiated member that is chemically similar to other samples.

Other outcrops of quartz latite porphyry in the northern Santa Rita

Mountains were examined, but were so altered and/or weathered that they

were not deemed suitable for this study. This unit has been informally

termed "ore porphyry" in southeastern Arizona because of its close

association with mineralization.

In the Greaterville area, the plugs and dikes intrude the

Willow Canyon and Apache Canyon Formations of the Bisbee Group. At the

other sampling locale near Davidson Canyon, the Apache Canyon and

Shellenberger Canyon Formations of the Bisbee Group have been intruded.

The intruded formations include shale and siltstone with intercalated

calcareous beds, and arkose.and conglomerate beds, all of which have

been contact-metamorphosed (Drewes, 1972, 1976).

Three of the samples, 7 and 21 from the northern stock and 6, the dike sample from Greaterville, are typical of Drewes' (1972, 1976)

description: a light-gray, closely fractured, considerably altered rock

consisting of 20-40% phenocrysts commonly 2 - 5 mm, and 60 - 80%

groundmass mostly .02mm. Sample 5 differs in that its matrix is purple

and has a glassy appearance. Sample 4 differs in that it has more

quartz and lower amounts of other minerals. The common texture is

porphyritic idiomorphic-granular.

Drewes (1972, 1976, 1981) reports that the porphyry is

chemically similar to the granitoid rocks of the Helvetia stock of

similar age. The ages for similar units range from 53-58 Ma in both

the Sierrita and Santa Rita and Empire mountain ranges. In the

northern Santa Rita Mountains K-Ar dates of 53.30 +/- 2.00, 54.80 +/-

2.00, 55.20 +/- 2.00, 57.00 +/- 2.30, 57.10 +/- 2.10, and 57.60 +/-

2.10 Ma have been determined (Marvin and others, 1973, Reynolds and others, 1985).

21

CHAPTER 3

ANALYTICAL METHODS

Samples were selected from outcrop based on competence and

examination by handlens. Examination of thin-sections in the

laboratory was the basis for selection of samples to be analyzed. An

additional criterion for selection of samples to be analyzed was the

competence of the sample during the first crushing stage and

examination by microscope as explained below.

A sample size of approximately 5-15 kg was preferred. After

hand crushing to one centimeter maximum dimension in the laboratory,

individual chips were examined under a microscope and discarded if

there were any visible signs of weathering and/or alteration. All vein

material was discarded. In this manner approximately 100 - 300 grams

of material was gathered for further crushing and analysis. All

samples except 20 and 21 were then powdered in a stainless steel shatter-box; samples 20 and 21 were crushed in a agate container by XRAL Ltd., Canada.

Analysis for major elements was performed by X-Ray Assay

Laboratories Limited, Don Mills, Ontario, Canada. Detection limits were 0.01%.

Analysis for minor elements was performed by Instrumental

Neutron Activation Analysis (INAA) at the laboratories of Dr. W. V.

22

23

Boynton at the University of Arizona. Irradiation of the samples was

accomplished at the TRIGA reactor at the University of Arizona: three

hours at a flux of 7 x 1 0 ^ neutrons/cm^/sec. Three standard rocks,

W-l, NBS 278, and NBS 688A were used in addition to chemical standards

for calibration and error-checking. Counting was done with an anti-Compton spectrometer for 8 hours at 5 to 10 days after irradiation

and for 4 hours at 30 to 40 days after. Error and reproducibility

figures are noted in APPENDIX 4. The reproducibility figures are

comparisons of splits from the same samples: two powder aliquots (taken

after crushing) of Sample 7, QLP-DC-1, were analyzed; Sample RS-MR-6

was re-analyzed after an earlier run; and Sample JCD-SM-1 was split

into two samples (3 and 19) before crushing.

Geochemical Evaluation of Weathering and Alteration

The main criteria for evaluation of weathering and alteration

of the samples was examination of thin-sections. In addition,

geochemical criteria were used to evaluate the degree of weathering and

alteration in the analyzed samples. Several different methods of

detecting weathering and alteration were used on these samples. Among

these are the criteria discussed by Condie and Shadel (1984), Beswick

and Soucie (1978), and Nesbitt, Marcovics and Price (1980).

The Chemical Index of Alteration (CIA) (Nesbitt and Young,

1982, Taylor and McLennan, 1985) was developed to give an indication of

chemical weathering in the upper crust. This index is based on the

fact that feldspars are the most abundant of the minerals considered

24

reactive during weathering and that calcium, sodium, and potassium are

generally more easily removed than aluminum. Thus, the proportion of

alumina to alkalies generally increases during weathering. The formula

uses molecular proportions as follows:

CIA - [Al203/(Al203+Ca0*+Na20+K20)] x 100

where CaO* is the amount of CaO incorporated in silicates (Nesbitt and

Young, 1982). Typical values for some minerals and rock types are

given with the calculated values for these samples in TABLE 2. As can

be seen, all of the samples except 6 (GV) are less than the suggested upper limit of fresh granites and granodiorites.

As shown in APPENDIX 3, significant amounts of corundum appear

in the norm of Sample 6 combined with an A/CNK ratio much higher than any other of the samples, probably indicative of weathering. The thin

section of Sample 6 also showed it to be weathered, but it was the best sample from the dikes in the Greaterville area and was included both

for that reason and to give an indication of the effects of weathering.

25

TABLE 2. Chemical Index of Alteration (C.I.A.) for Samples (Nesbitt and Young, 1982)

CIA MATERIAL

Typical Values for Minerals

50 Unaltered albite, anorthite, and potassic feldspars0 diopside75 idealized muscovite75-85 illite100 kaolinite and chlorite

Typical Values for Rocks

30-45 fresh basalts45-55 fresh granites and granodiorites55-70 loess70-75 shales

Samples (ordered by age)

49 9 (SEN)45 10 (KLQ)49 11 (KLQ)49 15 (SFS)49 16 (SFS)50 18 (SFS)45 3 (JCD)46 19 (JCD)44 20 (JCD)50 12 (EHQM)50 13 (EHQM)50 14 (EHQM)50 17 (TKP)49 4 (GV)51 5 (GV)57 6 (GV)49 7 (GV)43 21 (GV)

CHAPTER 4

DESCRIPTION OF ANALYTICAL RESULTS

This section will be a brief summary of the results of

analysis in the form of describing various geochemical plots. Because

a common way to describe geochemical trends of igneous rocks is by

relating them to some index of differentiation, the data have been

shown in diagrams comparing an index of differentiation with selected

elements. As mentioned earlier, an assumption of genetic relation is

being made so that the geochemical properties of the samples can be

compared. Major elements are discussed first, followed by minor

elements. The final section deals with K, Rb, Sr, and Ba: elements of

major importance in geochemical modelling of suites of granitic

composition (Hanson, 1978).

Manor Elements

Analysis for major elements was performed by X-Ray Assay

Laboratories Limited, Don Mills, Ontario, Canada. Groups of elements

that behave similarly with respect to SiOg % are described together.

Mg, P, Ca, Ti, Mn, and Fe

These elements all decrease systematically with increases in

SiOg content and the Differentiation Index (D. I.) (e.g., Figures 3, 4,

26

27

Figure 3. MgO vs SiOg: Santa Rita and Empire Mountains

o. m7 21 10

Figure 4. Ti vs SiOg: Santa Rita and Empire Mountains

U. 2-

Figure 5. FegOgft) vs SiOg: Santa Rita and Empire Mountains

29

Figure 6. CaO vs D. I.: Santa Rita and Empire Mountains

Figure 7. CaO vs SiOg: Santa Rita and Empire Mountains

30

5, and 6). Comparison of Figures 3, 4, and 5, with Figure 7 reveals

significantly more scatter in the plot of CaO vs. SiOg (Figure 7). A

much smoother curve results when CaO is plotted against the D.I.

(Figure 6). In general, the values of this group of elements in the

three samples of JCD and, to a lesser extent, in the single sample of

SFN are somewhat higher than the values in the other samples (e.g.,

Figures 3, 4, and 5).

In contrast, the lowest values for this group of elements

belong to the GV and EHQM samples. One of the samples of EHQM, 12,

shows lower values of the Differentiation Index (D.I.) and higher

values of CaO than the other two EHQM samples (see Figures 6 and 7).Very good correspondence is also apparent in interelement plots

of Mg, P, Ca, Ti, Mn, and Fe. There is a striking correspondence

between Fe and Ti in all samples except for 10 (KLQ) and 21 (GV)

(Figure 8). The samples from the Sierrita study of Anthony (1986) also

show a positive correspondence between Fe and Ti but significantly more

scatter (Figure 9).

All of these plots have a concave-up appearance. Minor

elements which display the same behavior include Sc, Co, Ni, Sr, Zr,

Hf, and probably Cr.

In comparison with the samples from the Sierrita Mountains

(Anthony, 1986), the behavior of Mg, P, Ca, Ti, Mn, and Fe is the same

in both suites except for one aspect. The values of Mg, Ca, Ti, Mn,

and Fe for Samples 3, 19, and 20 (JCD) and, to a lesser extent, 9 (SFN)

are greater than the same values for the Sierrita samples.

31

(Thousands)Ti ppmFigure 8. Fe203(t) vs Ti: Santa Rita and Empire Mountains

(Thousands) Ti ppm

Figure 9. FegOgft) vs Ti: Sierrita Mountains

32

A1AI2O3 values show a gradual decrease with respect to increases

in SiC>2 content and differentiation (Figure 10). There is a slight

indication of an inflection point between the JCD samples and the rest,

giving a concave-down pattern. The AI2O3 values for the Sierrita samples (Anthony, 1986) are virtually indistinguishable from those of

the Santa Rita and Empire complex and taken together all these samples

form an extremely smooth curve that extends from 56% to 81.5% Si02.

Na and K

These two elements show considerable scatter against all

measures of differentiation. K (Figure 11) tends to increase somewhat

with increasing differentiation, while Na (Figure 12) remains

relatively constant. Sample 12 (EHQM) has lower values of Na and

Sample 9 (SF) has lower values of K than the other samples. There are

slightly higher values of K in samples 15 and 18 (SF) and 13 and 14

(EHQM). There is a close correspondence between the behavior of K and

Rb. The plots for K and Na for the Sierrita samples are quite similar

to the Santa Rita and Empire samples in all respects.

Ratios of Major Elements

Al/Ca+Na+K (molar) values are steady, varying from .8 to 1 in all samples but one, sample 6 (GV) (Figure 13). This places these

samples in the metaluminous to mildly peraluminous range. Na20/K20(Figure 14) values are also quite steady averaging about 1. These

Figure 10. AlgO] vs S102: Santa Rita and Empire Mountains

34

Figure 11. KgO vs SiOg: Santa Rita and Empire Mountains

35

Figure 13. A/CNK(m) vs SiOg: Santa Rita and Empire Mountains

Figure 14. NagO/KgO vs SiOg: Santa Rita and Empire Mountains

36

plots provide an interesting contrast to the Marker variation plots of

the same elements which show considerable scatter. Again the Sierrita

values for these ratios are very similar as shown in Anthony (1986).

Minor Elements

Groups of elements that behave similarly with respect to Si02 %

are described together.

Sc, Co, Ni, Sr, Zr, and Hf

All of these elements mimic the behavior of Mg, P, Ca, Ti, Mn,

and Fe: that is, a fairly constant decline with increasing values of

the differentiation index (Figures 15, 16, 17, and 18). There is a

particularly good correspondence between Hf and Zr. The plot of Ti vs.

Zr (Figure 19) shows discrete groupings of the various rock units of

this study.

The interelement plot of Sr vs. CaO (Figure 20) shows good

correspondence, except for sample 12 (EHQM), which shows pronounced

lower values of Sr.

There are much higher values of Ni in Samples 3, 19, and 20

(JCD) compared to the rest of the samples (Figure 16).

Samples 3, 19, and 20 (JCD) and 9 (SFN) have higher values of

Sc, Co, Ni, and Hf (although maximum values for Zr are equivalent) than

the samples from Sierrita (Anthony, 1986). This pattern mimics the

behavior of these four samples and the Sierrita samples with respect to

Mg, Ca, Ti, Mn, and Fe. Two andesites from Sierrita and Sample 21 (GV)

Ni

ppm

2

Co

ppm

37

145 0

Si02 wt%15. Co vs SiOg: Santa Rita and Empire Mountains

Figure 16. Ni vs SIO2: Santa Rita and Empire Mountains

Zr

ppm

g

Sr

ppm

38

400-

200-

17. Sr vs SiOg: Santa Rita and Empire Mountains

250-

200-

SiOm w*%Figure 18. Zr vs SiOg: Santa Rita and Empire Mountains

7

65-

11Pi4-

3-

2-

I-

20

93 19

460-0 40 80 120 160 200 240

Zr ppm

Figure 19. Ti vs Zr: Santa Rita and Empire Mountains

0.400-

200-

CaO w t%

Figure 20. Sr vs CaO: Santa Rita and Empire Mountains

40

have higher Sr values than any of the other samples.

Zn, As, Sb, and Cs

While these elements show the same general behavior as the

previous group and the related group of major elements (Mg, P, Ca, Ti,

Mn, and Fe), some samples have elevated values compared to the rest.

Samples 15, 16, 18 (SF), 17 (TKP) and 12 (EHQM) have higher values of

As and Sb; samples 15, 16, and 18 (SF) of Cs; and samples 15 and 16

(SF) of Zn. Samples 15, 16, 17, and 18 are from the same geographical

area which is known to contain economic base- and precious-metal

deposits. These elements differ from the previous group in that the

highest values do not belong to the most mafic units, but generally to

the andesites.

Rb, Ba, and Ta

The only major element (excepting Si) that increases in

concentration with an increase in differentiation in this study is K.

While the behavior of Rb (Figure 21) would seem rather equivocal at

this stage of the discussion, I have included it with Ba and Ta

(Figures 22 and 23), which show a general positive correspondence with

SiOg, owing to the extreme similarity of the behavior of K and Rb with

respect to certain samples and differentiation (compare Figures 11 and

21). Samples 15 and 18 (SFS) and 12, 13, and 14 (EHQM) have higher

values of K and Rb than the rest of the samples while Samples 4 (GV)

and 9 (SFN) have lower values. Sample 4 (GV) has a higher

300

Eo.CLAcc

250-

200

I50H

100

50

% 16

9

II7 21 10

13

1214

l7s 6

70Si02 w t%

I78

Figure 21. Rb vs SiOg: Santa Rita and Empire Mountains

42

S i02 w t%

Figure 22. Ba vs SiOg: Santa Rita and Empire Mountains

Figure 23. Ta vs Si02: Santa Rita and Empire Mountains

43

concentration of Ba than the other samples while Sample 12 has a lower

concentration. With regard to Ta, Sample 12 (EHQM) has a higher

concentration than the other samples while Samples 4 (GV) and 9 (SEN)

have lower concentrations. The samples from the Sierrita Mountains

(Anthony, 1986) are very similar with respect to these elements: there is a close correspondence between the extreme values of Rb, Ba, and Ta

exhibited by Sample 12 (EHQM) and the extreme values exhibited by some

of the rhyolites and aplites of the Sierrita group.

REE

The REE show no consistent pattern when all the samples are

evaluated as a single group. The majority of samples show a relatively

steep LREE-enriched, HREE-depleted trend with a small negative

Eu-anomaly. Sample 4 (GV) differs by having a slight positive

Eu-anomaly. All three of the EHQM samples are significantly different

from the others: while maintaining the relative enrichment of LREE over

HREE, the levels of both are relatively elevated and there is a strong

negative Eu-anomaly. The patterns of all samples hinge on Tb with EHQM

showing rising values to Lu. SF and JCD show a slightly flatter slope

than the rest from La to Tb but still show declining values to Lu.

KLQ, TLP, and TKP show essentially flat curves from Tb to Lu.

It must be noted that the units from the southern Santa Rita

Mountains, excepting TKP, show steadily increasing LREE and HREE when

considered in decreasing age as interpreted by Drewes (1971a, 1971c,

1976) and that the youngest unit, EHQM, shows a significant negative

44

Eu-anomaly (Figures 24a and 24b). The behavior of SFS is equivocal in

that it matches very closely the very tight pattern displayed by the

two KLQ samples and would fit nicely in a sequence of SFN-->KLQ-->SFS

(the symbol --> denotes decreasing age and a postulated genetic relation) which matches the genetic grouping of Drewes (1981) (compare

Figures 24a and 25a). The units from the northern Santa Rita and

Empire Mountains plus the TKP sample show steadily decreasing REE

values with the most felsic sample, 4 (GV), showing a slight positive

Eu-anomaly when considered in decreasing age (Figures 25a and 25b).

The LREE values from the Sierrita units (Anthony, 1986) closely

match the range in Figure 25a (SFN and KLQ). With respect to the HREE

(Tm to Lu), the Sierrita samples more closely resemble the TKP and GV

units from the Santa Rita Mountains (Figure 25b).

U and Th

Values for both U and Th (Figures 26 and 27) show a general

decrease with increasing differentiation for all samples except EHQM

which have significantly higher values for both elements. Sample 9

(SFN) has the lowest values of U.

Ratios of K. Rb. Sr. and Ba

Of major interest in the interpretation of felsic igneous

suites are the elements K, Rb, Sr, and Ba because their general

partitioning behavior among the typical minerals is well known (Hanson,

1978). These elements are present only in the major silicate minerals

norm

aliz

ed t

o ch

ondr

itic

valu

es

SFN and KLQ fromfigure 25a

La Ce Sm Eu Yb Lu

Figure 24a REE - JCD and SES: Santa Rita and Expire Mountains

--------- JCD and SFS fromfigure 24 a

EHQM

Yb LuLa Ce

Figure 24b. REE - EHQM: Santa Rita and Empire Mountains

norm

aliz

ed t

o ch

ondr

itic

valu

es

La Ce Sm Eu Yb Lu

Figure 25a REE - SFN and KLQ: Santa Rita and Enpire Mountains

— SFN ond KLQ from figure 25a

La Ce Sm Eu Yb Lu

Figure 25b. REE - TKP and GV: Santa Rita and Enpire

Mountains

47

Figure 26. U vs SiOg: Santa Rita and Empire Mountains

F 20-

Figure 27. Th vs SiOg: Santa Rita and Empire Mountains

48

and not in any of the accessory minerals, unlike the REE whose

concentration can be totally dependent upon exceedingly minute amounts

of minerals such as monazite (McCarthy and Hasty, 1976, Mittlefelhdt

and Miller, 1983). K differs from the others in that it is a major

element, but it can be treated as a trace element if there is no

residual phase present such as biotite or K-feldspar in which K is an

essential structural constituent (Hanson, 1978). The behavior of these

elements will be described mainly with respect to various ratios

between them.

K/Rb

In the plot of K/Rb vs SiOg (Figure 28), Samples 3, 19, and 20

(JCD), Sample 9 (SFN), Samples 15 and 18 (SFS), and Samples 12, 13, and

14 (EHQM) have values of K/Rb which are distinctly lower than all the

other samples. This values of K/Rb within this sub-group decrease with

increasing differentiation while all the other samples show a slight

increase. The samples from the Sierrita Mountains (Anthony, 1986) show

a similar negative correlation, but have higher values (Figure 29).

K/Ba

The ratios are low and constant at values between 20 and 40

except for samples 12 and 13 (EHQM), which are considerably higher

(Figure 30). The values are identical for the Sierrita samples (Figure

31) (Anthony, 1986) , except for the higher values of the aplites and

rhyolites.

49

Rb/Sr

The slope of these ratios plotted against SiOg is opposite to

that of K/Rb: the sequence JCD-->(SFS)-->EHQM shows a sharp increase in

values of Rb/Sr while all the other samples show constant values

(Figure 32). The samples from Sierrita (Anthony, 1986) show a modest

increase with increasing SiOg except for the aplites and rhyolites (Figure 33), some of which again have elevated values comparable to the

EHQM of the southern Santa Rita Mountains.

Sr/Ba

The trends and ranges of values for both the Santa Rita (Figure

34) and Sierrita samples (Anthony, 1986) are identical: a steady

decrease with increasing differentiation.

50

400

300-

cr200-

100

Figure 29. K/Rb vs SiOg: Sierrita Mountains

51

Si02 w t%Figure 30. K/Ba vs SiOg: Santa Rita and Empire Mountains

64 62 70Si02 W t%

Figure 31. K/Ba vs SiOg: Sierrita Mountains

Rb

/Sr

2 R

b/S

r52

Si CL w t%

32. Rb/Sr vs SiOg: Santa Rita and Empire Mountains

Figure 33. Rb/Sr vs SiOg: Sierrita Mountains

53

Figure 34. Sr/Ba vs SiOg: Santa Rita and Empire Mountains

CHAPTER 5

DISCUSSION OF ANALYTICAL RESULTS

This section will includes interpretations by the author and

various other authors of the geochemical characteristics displayed by

the samples. As mentioned earlier, an assumption of genetic relation

is being made so that the geochemical properties of the samples can be

compared. The structure of this chapter parallels the previous

chapter. Major elements are discussed first, followed by minor

elements. The final section deals with K, Rb, Sr, and Ba.

Major Elements

Most of the major elements behave similarly with respect to

Si(>2 content and are described under the first heading of this section.

Mg, P, Ca, Ti, Mn, and Fe

The plot of CaO vs. D. I. (Figure 6) shows less scatter than the plot of CaO vs. SiOg (Figure 7). I do not believe that the scatter

indicates a significant problem with alteration or weathering. It

seems likely that Samples 10 (KLQ), Sample 12 (EHQM), and Sample 21

(GV) have had small additions of CaO relative to the rest of the

samples. For instance, Sample 12 (EHQM) has a low D.I. and high CaO

content, but its Eu/Eu* value indicates that it is the most

54

55

differentiated in the EHQM.

The high values for this group of elements of the three JCD

samples (3, 19, and 20) and the single sample of SEN (9) likely reflect

the more mafic character of these four samples. The GV and EHQM

samples show the lowest values for this group of elements, reflecting

the more evolved or felsic nature of these units.

The striking positive correspondence between Fe and Ti in the

samples from the Santa Rita and Empire Mountains (Figure 8) seems to

suggest that Ti in the Santa Rita/Empire samples may be more closely

associated with Fe, possibly as ilmenitic magnetite, an ubiquitous

mineral in most units according to Drewes (e.g., 1976).

A1

The very good correlation with SiOg is mostly likely a

reflection of feldspar precipitation.

Na and K

Weathering or alteration as the cause for the low Na value of

Sample 12 (EHQM) is supported by some elevated values of Na for the

aplites and rhyolites of Sierrita (Anthony, 1986); in most other

aspects the aplites and rhyolites behave similarly to EHQM.

Ratios of Major Elements

Steady values of NagO/KgO averaging about 1 are a good

indication that these rocks have not been subjected to K-metasomatism

56

(Chapin and Lindley, 1986).

Minor Elements

Groups of elements that behave similarly with respect to SiOg %

are described together.

Sc, Co, Ni, Sr, Zr, and Hf

The excellent correspondence between Hf and Zr is undoubtedly

due to the presence of Hf in zircon in these samples. The discrete

grouping of the various units shown by the plot of Ti vs. Zr is

considered important evidence of genetic relation because these two

elements are considered to be immobile under most conditions occurring

after crystallization (Pearce and Norry, 1979).

In another study (Perfit and others, 1980) in which fractional

crystallization was believed to be an important process in the

evolution of a magma system, large differences in Ni and Cr content

between earlier and later members of a rock suite were interpreted as

indicating significant fractionation of olivine and clinopyroxene

between the time of removal of the units . Although Cr contamination

from the shatterbox used in sample preparation prevented the use of Cr

values in this study (see Anthony, 1986), there are definite

indications that the Cr values of these three samples are relatively

much higher than any of the other samples.

57

Ratios of K. Rb. Sr. and Ba

These four elements are of major importance in the

interpretation of felsic igneous suites. This section will include

accepted interpretations of the ratios and relations between these

elements as expressed by several authors (with appropriate references).

K/Rb

Perfit and others (1980) predict declining K/Rb if a large

amount of potassium-bearing amphibole (e.g. hornblende) is removed from

a magma. In contrast, Hanson (1978) maintains that only the removal of

potassium feldspar or biotite significantly affects the K/Rb ratio. In

addition, Hanson states that removal of potassium feldspar,

particularly in the case of a relatively pure phase, contributes

greatly to the reduction of the K/Rb ratio of the melt relative to the

parent and that plagioclase in the residue does not greatly affect the

K/Rb ratio. Finally, Hanson believes that hornblende in the residue

could lead to a minor reduction in the K/Rb ratio.

K/Ba

Hanson (1978) states that K/Ba is also not affected by the

removal of any minerals except biotite and potassium feldspar. He also

states that K and Ba are retained by potassium feldspar.

58

Rb/Sr

Hanson (1978) states that the Rb/Sr ratio of progressive melts

is increased by the presence of plagioclase and less so by potassium

feldspar in the residue; biotite in the residue decreases the Rb/Sr

ratio.

Sr/Ba

Hanson (1978) states that the Sr/Ba ratio in the melt is

reduced by crystallization of plagioclase, but increased slightly by

crystallization of potassium feldspar, and increased even more by

biotite in the residue.

General Comments

Perfit and others (1980) state that constant ratios of K/Rb

(Figure 28) with increasing Rb/Sr ratio (Figure 32) and Ba content

(Figure 22) exclude biotite and orthoclase as fractionating phases.

They also indicate that constant enrichment of K (Figure 11) with

decreasing Ti (Figure 4) severely limits the crystallization of biotite

during fractional crystallization. Hanson (1978) predicts that biotite

in the residue would maintain a constant K, reduce the Rb/Sr ratio, and

increase the Sr/Ba ratio (Figure 34) in the melt owing to the fact that

biotite retains K, Rb, and Ba. Hanson further notes that potassium

feldspar can be distinguished from plagioclase as a residual phase

because it does not increase the Rb/Sr ratio in the melt as much as

plagioclase, but leads to a much greater Sr/Ba ratio.

Perfit and others (1980) predict that increasing Rb/Sr, Y/Sr,

and Ba (Figures 32, 35, and 22) and decreasing Sr/Zr (Figure 36) and '

Eu/Eu* with increasing SiOg indicate that plagioclase with lesser

pyroxene, amphibole, and possibly olivine were principal phases

crystallizing during fractional crystallization. This would appear to

be the case for the sequence JCD-->EHQM. Hanson (1978) states that

plagioclase as a residual phase depletes the melt in Sr. Figure 17 may

indicate that all the samples of EHQM are depleted relative to the

other samples and certainly relative to JCD with respect to Sr.

59

Figure 35. Y/Sr vs SiOg: Santa Rita/Empire Mountains

SI On Wt%

Figure 36. Sr/Zr vs SiOg: Santa Rita/Empire Mountains

CHAPTER 6

GENETIC RELATIONS BETWEEN UNITS

One of the principal objectives of this study is to test the

hypothesis that the sampled units are genetically related. Previous

studies (e.g., Drewes, 1981) have suggested this to be the case. The

analytical results have been presented using this assumption. This

study and most others, unfortunately, cannot derive unequivocal

relations; some interpretation and supposition are required. The

remainder of this thesis will contain interpretation: some by the

author of his own results; and some by other authors.

The results of this study suggest that there are four principal

interelement relations which indicate that the studied units can be

divided into genetically-related groups. The most striking geochemical

similarities seem to exist between JCD and EHQM. In addition to

geochemical evidence, this association is consistent with the similar

radiometric ages and field evidence (Drewes, 1976). Further, it

appears that SFS may be related to these two, although the geochemical

evidence is not as consistent as that linking JCD and EHQM. Another

possibility suggested from the data is that the units SFN (one sample),

SFS, and KLQ are related, which again supports previous interpretations

by Drewes, and is further substantiated by similar ages for these

units. The geochemical evidence is permissive of a relationship

61

62

beginning with SFN and KLQ, with or without SFS, continuing through the

TKP unit (only one sample) to the GV (youngest) unit.

Deducing solely from the geochemical evidence, it is possible

that the two differing trends of compositional change result from

different magma sources. SFS may have properties similar to both

trends due to a mixing of two different sources. It is possible that

the source for the JCD-->EHQM units began to interact with the source

of the other units at some time prior to the eruption of SFS. Isotopic

study is necessary before reaching a conclusion such as this, but the

geochemical evidence which is consistent with this possibility will be

presented.

Ti and Zr

Ti and Zr are unlikely to be subject to remobilization and/or

transport by aqueous species owing to their high field strength

(charge/radius ratio). Therefore, they are usually considered to be

immobile (e.g., Pearce and Norry, 1979, Condie and Shadel, 1984).

Thus, they should be ideally suited to discriminating between separate

units in a given area. In this particular instance, it has already

been shown that the behavior of Ti is predictable in terms of a major

element, Fe (vis-a-vis the excellent correspondence between the two

elements). This relation takes on added import when compared to the

relatively poor correlation between the two elements in the suite from

the Sierrita Mountains (Figure 9). Anthony (1986) has demonstrated an

intrinsically oxidizing nature for the parent magma in the Sierrita

63

Mountains, one manifestation of which was the pre-eminence of titanite

over ilmenite and related species. The presence of Fe-Ti oxides with

the indication of a close relationship between Fe and Ti may indicate a

more reducing nature for the parent magma(s?) in the Santa Rita and

Empire Mountains. The decrease in Ti with increasing differentiation

suggests that amphibole and/or small quantities of Fe-Ti oxides may

have been fractionating phases (Perfit and others, 1980) in the Santa

Rita and Empire complex.

The importance of the role of zircon in the formation of felsic

magmas has recently been studied, most notably by the experimental work

of Watson (1979). Owing to its effect on REE abundances, zircon

fractionation must be considered in geochemical modelling, particularly

in the case of felsic, non-peralkaline magmas, the types described

here.

A Ti-Zr plot (Figure 19) of the samples shows excellent

discrimination of the various units and a general decrease of Zr and Ti

with increasing differentiation and decreasing age. The JCD samples

plot in a discrete area which is assumed to represent a minimal area

for a unit. Two of these samples were from the same outcrop and the

other from only a few hundred yards away and all indications are that

these were among the least-weathered of all the samples. It should

also be noted that these three samples show the most consistent

grouping of any of the other units on virtually all other plots. There

is quite good grouping within other related samples: the three SFS

samples plot almost as a single point as do the two KLQ samples. In

64

addition, the EHQM samples, which show the most intra-unit variability

in all other plots, are very tightly spaced. Samples 4, 5, and 6, from the same unit (GV) and geographical area, show a grouping comparable to

JCD. The intra-unit variation of the whole GV unit, samples of which

are widely separated geographically, compares quite favorably to the

JCD unit samples which came from a more restricted area. Thus it

appears that the Ti - Zr values support relations among the individual

samples which are consistent with previous assignments to rock units.

The majority of values of the samples fall on a line between

approximately 6500 ppm Ti, 240 ppm Zr and 500 ppm Ti, 60 ppm Zr. A

similar plot for the Sierrita samples (Figure 37) (Anthony, 1986) shows

that they also lie on a line that terminates at 500 ppm Ti, 60 ppm Zr.

This decreasing trend to a value of 60 ppm Zr corresponds very nicely

with Watson's (1979) prediction that melting in a region of the crust

containing >100 ppm Zr would result in a decrease of the total

abundance of Zr in the system, an increase in the abundance of Zr in

the residue, and a buffering of the concentration in the liquid at a

value of approximately 60 ppm. Anthony (1986) has attempted to show

the importance of assimilation for the Sierrita samples and the 100%

crustal character of the latest differentiates there. It would seem

reasonable that the correspondence of minimum Zr values might also

indicate the importance of assimilation in the Santa Rita and Empire units also.

The EHQM samples do not fall on this trend and appear to have

been enriched in Zr as opposed to depleted in Ti (relative to the other

a. m

Zr ppm

Figure 37. Ti vs Zr: Sierrita Mountains

66

samples) although both may be possible. Owing to other indications,

such as their negative Eu-anomalies and high Differentiation Indices,

it would seem more likely that the EHQM samples should have plotted

near the low-Zr, low-Ti end of the plot. If they are enriched in Zr,

there are many possible explanations, none of which are exclusive.

Based on Watson's (1979) work, the EHQM samples may be related to the

residue in view of their increased Zr values. In addition he states

that unmelted zircon in the residual rock of this type of melting event

would impart to the residue a U- or V-shaped REE pattern. Watson

(1979) further predicts that Zr concentrations >100 ppm in felsic,

non-peralkaline rocks do not represent Zr abundances in liquids, but rather a composite value of melt + zircon crystals. Drewes (1976)

notes that the zircon crystals in the EHQM are euhedral, fairly large

and abundant when compared to other igneous units in the area. The

field relations combined with some of the geochemical evidence also

suggest an assimilation connection. The fine-grained border phase is

interpreted as intruding both the host rocks (diorite correlated with

the JCD) and the coarse-grained phase of the EHQM. On many plots the

fine-grained Sample 14 seems to be more closely related to the values

displayed by the other units rather than the extremes exhibited by

Samples 12 and 13 (e.g., Figures 21, 22, 26, 27, 28, 30, 32, and 35).

The most likely explanation is that both assimilation and

fractional crystallization played a part in the origin of the EHQM. In

view of the REE patterns of the EHQM and the decidedly more mafic

character of its precursor, JCD (assuming a genetic connection), one is

67

almost compelled to conclude that EHQM was subjected to extensive

fractionation. However, other evidence such as that mentioned above

seems to support assimilation or partial melting.

K/Rb Ratios and Related Values

The K/Rb values are also strongly supportive of the relation of

JCD to EHQM and possibly to the SF and indicative of the fundamental

difference between these units and all of the others. Other related

diagrams that were discussed above seem to indicate that plagioclase,

amphibole, clinopyroxene, olivine, zircon, and Fe-Ti oxides were the

most probable fractionating phases during magma formation in the JCD--

>EHQM sequence. It appears most clear that biotite was not a

fractionating phase, but the case for potassium feldspar is not so

clear. The reduction in K/Rb seems to indicate potassium feldspar

removal, but the reduction could also be due to amphibole removal. If

Sample 12 is the most differentiated of the EHQM, then its reduced

values for Ba and Sr would support potassium feldspar removal: Ba would

be low due to retention by potassium feldspar; and the anomalously low

Sr value relative to CaO in Sample 12 could be explained by its

incorporation into both plagioclase by substitution for Ca and

potassium feldspar by substitution for K due to its intermediate ionic

radius (Krauskopf, 1979). The general decrease of the Sr/Ba ratio with

increasing differentiation does not support potassium feldspar as a

precipitating phase.

With regard to the other units, the declining Sr/Ba values seem

68

to indicate plagioclase as a fractionating phase but all the other

factors that indicate substantial fractional crystallization in the

sequence JCD-->EHQM are not as pronounced in the other units. There do

not seem to be indications of substantial assimilation either though.

For instance, as mentioned above, it is the EHQM that shares

characteristics with the late differentiates from the Sierrita

Mountains which Anthony (1986) has inferred are 100% crustal in nature.

The Ti - Zr data does appear to indicate that these other units in the

Santa Rita and Empire Mountains were liquids that were continuously

declining toward a felsic liquid derived by partial melting.

Plagioclase with lesser amphibole, and Fe-Ti oxides are the

precipitating phases indicated by this group of values for the units

KLQ, SFN, SFS (possibly or partially), TKP and GV, but the REE and U

and Th provide evidence for other precipitating phases.

Rare Earth Elements

. The REE values were discussed above: indications are that JCD

and EHQM behaved quite differently than the rest with regard to these

elements. For instance, the sequence JCD-->EHQM shows rising values for

the HREE; this would appear to limit the roles of garnet, zircon, and

hornblende as residual phases in this sequence. On the other hand the

rest of the units, taken as a sequence, show a slight decline in HREE

with time; this would appear to be permissive of garnet, hornblende,

and zircon as residual phases. Further supporting evidence for

discriminating between JCD-->EHQM and the other units can be seen by

69

examining Ce/Yb ratios in Table 3 which give a value for LREE

preference relative to HREE. There is a general decline of Ce/Yb in

JCD-->EHQM indicating that garnet, zircon, and hornblende were not

involved as residual phases, and a general increase in Ce/Yb for all

the rest, permissive of garnet, zircon, and hornblende as residual

phases (Perfit and others, 1980). Note that Sample 21 (GV) is

considerably lower than the other four GV values. In addition, the

elevated REE contents and lowered Ce/Yb ratio of EHQM are not

consistent with dominant plagioclase removal (Perfit and others, 1980).

If plagioclase removal was not dominant in this sequence, potassium

feldspar removal, mentioned in the previous section, seems more

plausible.

The relation of PgOg vs. total REE (Figure 38) is remarkably

similar to Zr vs. total REE (Figure 39) and also, surprisingly, to Ti

vs. total REE (Figure 40). There is a positive correspondence with

some scatter for all units from JCD to GV but does not include Samples

12 and 13 (EHQM) and 21 (GV). The only samples which change relative

position in the three diagrams are Samples 12, 13, and 14 (EHQM) which

have equal y-values (P2O5, Zr, Ti) but varying x-values (total REE), defining a horizontal line on the plots with Sample 14 having values

close to the other samples. It is tempting to speculate in view of

Drewes' (1976) interpretation that the fine-grained phase of EHQM is

younger than the coarse-grained phase of EHQM and JCD that this effect

is due to greater levels of assimilation of the country rock.

The positive correspondence in the case of Zr and total REE is

70

TABLE 3. Ce/Yb Values and Averages

Ce/Yb Unit Sample

34.4 JCD 326.7 GV 430.8 GV 526.0 GV 636.4 GV 723.7 SEN 927.4 KLQ 1025.7 KLQ 1117.9 EHQM 1236.8 EHQM 1328.3 EHQM 1429.5 SFS 1530.2 SFS 1635.1 TKP 1730.5 SFS . 1834.9 JCD 1935.2 JCD 2020.4 GV 21

Average Unit

34.8 JCD 127.7 EHQM . 1 V

falling values with decreasing age, increasing differentiation

23.7 SEN26.6 KLQ28.5 SF (SEN + SFS)30.0 SFS35.1 TKP28.1 GV (all)30.0 GV (4,5,6,7)

Vrising/steady values with decreasing age, increasing differentiation

* single samples

Zr ppm

m P2°

5

0.4

0.3-

0.2-

0 .1-

40 80 120 160 200 240total REE ppm

38. P2O5 vs total REE: Santa Rita and Empire Mountains

200-

120 160 total REE ppm

Figure 39. Zr vs total REE: Santa Rita and Empire Mountains

72

total REE ppm

Figure 40. Ti vs total REE: Santa Rita and Empire Mountains

73

apparently due to zircon being a residual phase as mentioned above.

Zircon, of course, does contain significant levels of REE, but mainly

the HREE. The positive correspondence in the case of PgOg is probably

due to apatite as a residual phase. Apatite contains REE, both LREE

and (even greater amounts of) MREE. In the case of Ti, I am unaware of

any mineral phase that would explain this relationship. The value for

total REE was arrived at by simply summing the ppm values for La, Ce,

Nd (LREE), Sm, Eu, Tb (MREE), and Tm, Yb, Lu (HREE). In all these

samples, the LREE account for greater than 90% of total REE. It is

difficult to explain the similarity in plots for Zr, PgOg, and Ti vs.

total REE in terms of either zircon (preference for HREE), apatite

(preference for MREE and less for LREE), or Fe-Ti oxides (no known

preference for REE) being the chief phase responsible for distribution

of REE. All show exactly the same relationship, even Ti for which

there is no plausible REE-retaining phase! Similarly, it is unlikely

that zircon and apatite could be displaying a similar affinity for

total REE when their preferences for the subdivisions of the REE are so

different. One possible explanation is that zircon, apatite, Fe-Ti

oxides, and some REE-retaining phase were important residual phases

throughout the crystallization history of all units. The fine-grained

phase of EHQM (Sample 14) is similar to the other samples, but the

coarse-grained phase of EHQM (Samples 12 and 13) shows extremely high

REE values, indicating a possible difference in source or process or

This series of diagrams also indicates that Sample 21 (GV)

both.

74

differs from the other samples in its lower LREE abundances. According

to Hanson (1978) apatite is the only common mineral which would cause a

reduction in LREE abundances and, indeed, there are two relations which

could indicate that apatite is a residual phase for most or all the of

the units. The graph of PgOg vs. total REE (Figure 38) was discussed

in the previous paragraph. The possibility of apatite as a residual is

further strengthened by the general decline in LREE abundance for all

units except JCD-->EHQM. However, there is another possibility which

is suggested by the extreme behavior of LREE in Sample 21. As

mentioned above, the Ce/Yb value of this sample is considerably lower

than other samples of this unit (GV). While the LREE abundances are

considerably lower, the MREE abundances of this sample are not

significantly lower than other samples of this unit. Thus,

fractionation of apatite is not a likely cause as apatite (and sphene)

would result in more striking depletions of the MREE than the LREE

(Miller and Mittlefehldt, 1982). Other samples show no indication of

depletion of MREE relative to LREE as would be expected if apatite were

the controlling phase (e.g., compare SEN and KLQ to GV in Figure 25b).

The most likely cause of reduction in REE values with time is

significant fractionation of allanite and monazite since the LREE are

stoichiometric constituents of these minerals and the MREE are not,

thus LREE abundances are significantly affected while MREE are not

(Miller and Mittlefehldt, 1982). This again supports the supposition

that the units other than JCD-->EHQM are behaving as a felsic liquid

crystallizing significant amounts of REE minerals such as monazite and

75

allanite (Miller and Mittlefehldt, 1982).

U and Th

These two elements (Figures 26 and 27), behave similarly with

respect to differentiation: with the exception of EHQM the U and Th

concentrations of all samples decrease with differentiation. This decrease is significant in view of the scattered but definite increase

of U and Th with differentiation displayed by the samples from Sierrita

(Anthony, 1981). In the case of JCD, although the difference in

differentiation is slight between the three samples, 3, 19, and 20,

both U and Th values increase with differentiation. In both cases, a

line drawn through the three JCD samples passes through the space

occupied by EHQM. This relation is especially striking in the case of

Th, where the values of JCD are higher than any of the other samples

(except EHQM). The JCD samples also form an endpoint for the values of

the rest of the samples. It is also probably significant that the most

mafic samples from the Sierrita Mountains show lower values of both U

and Th than the most mafic samples from the Santa Rita and Empire

complex whereas the most felsic samples from the Sierrita Mountains

show higher values of U and Th than all the Santa Rita and Empire

samples except EHQM.

The behavior of Th and U point up a fundamental difference

between the Sierrita magmas and those of the Santa Rita and Empire

complex. If we disregard, for the moment, the behavior of JCD and EHQM

and assume that all the other units in the Santa Rita and Empire

76

complex are genetically related, then it seems clear that U and Th were

compatible elements in this series (i.e, monazite was crystallizing).

It also seems clear beyond doubt that these same elements were

incompatible in the Sierrita series. The evidence indicates that the

Sierrita series was considerably more mafic in character than the Santa

Rita and Empire series (excluding JCD and EHQM) and that allanite (U)

and monazite (Th) were not being removed from the Sierrita magma.

Comparisons of Sierrita Samples to Santa Rita and Empire Samples

If we now return our attention to the postulated relationship

JCD-->EHQM, it is obvious that there is a definite similarity between

the Sierrita samples (Anthony, 1986) and these two units. The ages of

both series are equivalent and they were emplaced within 20 miles of each other. Both series show similar initial and final values of U and

Th at the same values of differentiation. It is at this point,

however, that the similarity breaks down. The plots of the Sierrita

samples show declining REE values with differentiation (Anthony, 1986)

whereas the JCD-->EHQM shows a tremendous increase. For the Sierrita

samples, removal of allanite and monazite could not have been

responsible for declining REE values because U and Th increase; the

decline must be due to other species such as apatite, hornblende, and

clinopyroxene. With JCD-->EHQM both REE and U and Th increase while

Eu/Eu* decreases, which is highly indicative of fractional

crystallization with strong exclusion of phases which are fractionating

phases in felsic magmas (Miller and Mittlefehldt, 1982). This evidence

seems to indicate that JCD-->EHQM was developed by fractional

crystallization of a mafic magma.

Returning to the K/Rb data, it appears that the Sierrita series

(Anthony, 1986) is the more mafic of the two, by virtue of its higher

(initial) K/Rb values. However, the Ni, Co, and Sc, (and probably Cr)

values would seem to indicate that JCD-->EHQM had the more mafic

character initially.

If it is true, as Anthony (1986) has concluded, that

assimilation played an important role in the Sierrita series, then

fractional crystallization may have been the dominant process in the

JCD-->EHQM series. In the Sierrita series, rising U and Th values may

have been caused by large-scale assimilation of U- and Th-rich upper

crust by a mafic magma. In the JCD-->EHQM series, rising U and Th

values may have resulted from fractional crystallization of a mafic

magma without large-scale assimilation of upper crust. Another

possibility is that the EHQM is the residual of a magma that developed

by assimilation of a U- and Th-rich source with a negative Eu-anomaly.

With regard to the other units from the Santa Rita and Empire

complex, it seems clear that fractional crystallization did play some

role in their formation. The steadily decreasing REE and U and Th

indicate fractional crystallization of a felsic magma (Miller and

Mittlefehldt, 1982). In addition, the Ti-Zr values indicate partial

melting in a region of the crust with Zr values >100 ppm producing a

granitic magma (Watson, 1979) and the trend is similar to but higher

than that of the Sierrita samples (Anthony, 1986).

77

Perhaps the Sierrita samples represent one extreme, large-scale

assimilation, and the JCD-->EHQM series another extreme, fractional

crystallization. The other units of the Santa Rita and Empire complex

may represent a mixture of both processes. In this context it must be

noted that in the southern Santa Rita Mountains, where the SFS, JCD,

and EHQM samples were collected, there have been no porphyry copper

deposits discovered; in the northern Santa Rita and Empire Mountains,

where the SFN, KLQ, and GV samples were collected, there have been

significant finds which have not been fully exploited. Is assimilation

the key?

78

CHAPTER 7

CONCLUSIONS

While isotopic study is considered necessary to verify genetic

relations between units, in this section I will present

interpretations based solely upon the geochemical evidence. The

geochemical data from the Santa Rita and Empire suite is interpreted as

follows:

1) The units JCD and EHQM are probably related genetically. This is

supported by previous work (e.g., Drewes, 1976) and K/Rb data

directly, and suggested by U and Th data; other data is permissive.

2) The sequence JCD-->EHQM is distinctly different from the other units

in the Santa Rita and Empire Mountains. This is supported by Ti-Zr,

K/Rb, REE, and U and Th data.

3) The unit SFS may be genetically related to or may have been

geochemically influenced (mixing) by JCD and EHQM. REE is

permissive of a sequence SFS-->JCD-->EHQM. K/Rb and U data is

permissive of a sequence JCD-->SFS-->EHQM. Other data, discussed

previously, indicate that SFS is intermediate in the sequence JCD--

>EHQM.

4) Assuming that JCD and EHQM are genetically related, the JCD-->EHQM

sequence, although of similar age, is distinctly different from the

Sierrita series studied by Anthony (1986). This is supported by

79

80

Ti-Zr, K/Rb, and REE data.

5) The sequence JCD-->EHQM is probably derived mainly by fractional

crystallization of a basic magma. This is supported by REE and U

and Th data and by Ti-Zr data. In addition, the high Ni, Co, and Sc

(and probably Cr) values of JCD indicate that this unit was more

mafic or had retained a more mafic character prior to emplacement

than either the Sierrita series or the other units from the Santa

Rita and Empire complex.

6) Despite these elevated values, the JCD unit is an endpoint for virtually all geochemical plots for the Santa Rita and Empire

complex and is very similar to the oldest unit, SEN. This suggests

that the JCD is related genetically to all the other units. All

major element data is permissive of all units in the Santa Rita and

Empire complex being related. In particular, the Fe-Ti relation

seems to indicate a very close relation. Since the EHQM is

considered to be more closely related to the JCD than the other

Santa Rita and Empire units, a two-stage process may be responsible

with the second stage resulting in the profound differences between

the EHQM and all the other units. Alternatively, the interpreted

age difference combined with the geochemical similarity of JCD and

SEN may indicate the ascent of two separate magma batches from the

same source. In the traditional view of porphyry copper generation,

successive magma batches ascend along earlier-prepared (heated)

conduits to form the surface expression of repeated intrusion about

a center. This process would seem to be conducive to assimilation

81

(of previously heated country rock). Perhaps in the case of JCD--

>EHQM ascent did not occur along a previously prepared conduit, but

rather along a zone of profound crustal weakness (Sawmill Canyon

fault zone??) that allowed (relatively rapid?) ascent without

wholesale assimilation. An emplacement mechanism for JCD which

involved limited assimilation might also result in greater heat

retention at higher crustal levels, delaying crystallization. Thus

JCD and SFN might have been derived from the same magma source at

the same time despite the interpreted age difference. The

indications of partial melting and assimilation exhibited by EHQM

may thus have resulted from interaction at relatively shallow

crustal layers at the time of final emplacement rather than at

deeper layers during ascent.

7) The other units of the Santa Rita and Empire complex exhibit

behavior consistent with a felsic liquid derived partially or wholly

by partial melting in a region of the crust with Zr values

considerably higher than 100 ppm and being subjected to fractional crystallization with removal of REE-enriched species such as

allanite and monazite. This is supported by Ti-Zr, REE, and U and

Th data.

8) Based on the data derived from this report, it seems likely that assimilation is a critical process in the formation of porphyry

copper deposits. The crustal level at which assimilation takes

place is probably also critical.

APPENDIX 1

ANALYTICAL RESULTS

Analytical results for the individual samples are listed in

this appendix. Samples are grouped by formation. See main text for

explanation of analytical methods. The last page of this section lists

the analytical results for the three control samples.

82

83SALERO FORMATION (SF) CORONA/EMPIRE

STOCKS (KLQ)(SFS) (SFS)

BSM-KSW-1 BSM-KSW-2 #15 #16

Si02 % AI2O3 % CaO %MgO %NagO %K20 % Fe203(t)% MnO %Ti02 % P205 %LOI %

SUM

Sc ppm Ti ppm Co ppm Ni ppm Zn ppm As ppm Rb ppm Sr ppm Y ppm Zr ppm Nb ppm Sb ppm Cs ppm Ba ppm La ppm Ce ppm Nd ppm Sm ppm Eu ppm Tb ppm Yb ppm Lu ppm Hf ppm Ta ppm Th ppm U ppm

(SFN)SF-DC-4

#9

59.0016.705.202.233.292.026.280.120.820.244.31

100.21

11.8604915.0814.3005.198

71.0601.72779.27

512.3020.00181.9620.000.8818.435

605.6834.44558.70631.2805.9341.4810.7512.4740.4125.2470.4217.6370.907

61.2016.203.471.553.174.784.450.070.560.184.3199.94

6.0953356.6410.7705.549

190.8005.217

213.85470.9530.00

172.0410.003.492

22.1471041.3131.99351.07125.1324.3121.1204.7631.7330.3045.2070.8319.7395.123

61.8016.603.621.664.323.514.280.070.570.203.47

100.10

5.6623416.58

9.73211.140239.500

6.813124.15595.6520.00

169.7610.001.56317.7601146.3830.63250.98724.8294.5291.051 0.458 1.691 0.296 5.183 0.7699.051 4.618

(SFS)SM-KSW-3#18

62.0016.702.951.323.495.074.380.120.560.193.31

100.09

6.1203356.6410.4108.945

75.3704.413274.45399.7820.00

171.5410.004.196

43.6941295.7733.46154.51425.4574.5191.1240.4691.7910.3155.4610.89510.5405.446

KLQ-ES-2#1068.4015.40 4.68 1.883.81 3.70 1.34 0.04 0.47 0.14 0.31

100.17

6.7022817.184.1185.944

25.5601.494112.25474.14

5.00145.6430.000.6184.815787.8132.00952.10523.3614.0601.0120.4601.9040.3194.8220.8009.1343.659

KLQ-CS-1#1168.6015.203.261.343.593.833.500.040.470.140.47

100.44

6.4602817.18

9.3015.47934.050 0.932139.15403.8210.00140.0410.00 0.170

. 6.091 891.49 29.238 48.334 22.262 3.928 0.891 0.456 1.879 0.322 4.506 0.80011.050 3.441

84JOSEPHINE CANYON DIORITE

(JCD)

JCD-SM-1 JCD-SH-1X JCD-SM-5 #3 #19 #20

Si02 % 58.40 58.90 57.00AI2O3 % 16.50 16.50 15.50CaO % 5.69 5.60 5.87MgO % 3.54 3.42 4.25NagO % 3.90 3.80 3.61k2o % 2.87 2.94 3.05Fe203(t)% 6.82 6.57 8.17MnO % 0.11 0.10 0.17Ti02 % 0.91 0.88 1.08P205 % 0.24 0.23 0.31LOI % 1.08 1.08 1.16

SUM 100.06 100.02 100.17

Sc ppm 13.070 12.940 16.470Ti ppm 5454.54 5274.72 6473.52Co ppm 22.010 21.540 24.530Ni ppm 37.620 39.060 44.650Zn ppm 86.030 85.500 104.200As ppm 4.357 4.223 4.428Rb ppm 126.15 122.70 134.50Sr ppm 555.15 549.15 491.28Y ppm 30.00 20.00 20.00Zr ppm 218.26 239.35 226.00Nb ppm 30.00 30.00 10.00Sb ppm 0.699 0.669Cs ppm 6.196 6.445 8.196Ba ppm 805.89 819.86 798.73La ppm 37.661 ‘ 37.993 35.578Ce ppm 62.877 63.348 69.492Nd ppm 32.669 32.848 34.242Sm ppm 5.990 5.956 6.515Eu ppm 1.313 1.345 1.350Tb ppm 0.597 0.604 0.732Yb ppm 1.827 1.818 1.973Lu ppm 0.301 0.304 0.304Hf ppm 6.326 6.860 6.730Ta ppm 0.678 0.719 0.650Th ppm 18.680 18.820 16.250U ppm 5.694 5.916 4.605

ELEPHANT HEAD QUARTZ MONZONITE(EHQM)

AC-EH-1 AC-EH-2 AC-EH-3#12 #13 #1473.70 72.50 73.0013.90 14.20 14.004.47 0.74 1.330.54 0.40 0.420.70 4.31 4.024.26 5.32 4.641.61 1.69 1.730.05 0.03 0.020.25 0.22 0.250.07 0.06 0.060.85 0.70 0.62

100.40 100.17 100.09

3.116 2.744 2.7161498.50 1318.68 1498.502.001 2.298 1.1412.467 5.611 3.544

26.870 22.150 16.9003.742 1.342 1.318

238.90 276.75 205.7593.04 93.68 141.1960.00 30.00 20.00

156.60 163.10 151.6310.00 10.00 20.001.118 0.431 0.2214.574 3.618 4.486218.93 560.41 1060.5758.843 68.754 39.702101.142 103.500 58.76341.925 34.956 20.7928.002 5.379 3.4740.418 0.606 - 0.5231.076 0.565 0.3765.645 2.812 2.0790.948 0.507 0.3775.565 5.586 4.9032.101 0.797 1.057

40.450 48.940 31.89011.360 7.431 6.974

85QUARTZ LATITE GREATERVILLE INTRUSIVES AND QUARTZ LATITE PORPHYRY (TLP) PORPHYRY UNITS (GV)BSM-QL-1 GV-AG32-#17 #4

Si02 % 72.80 81.50AI2O3 % 13.40 9.40CaO % 1.84 1.31MgO % 0.71 0.29NagO % 3.59 2.67k2o % 3.71 2.88Fe202(t)% 2.31 0.92MnO % 0.05 0.02Ti02 % 0.36 0.17P2O5 % 0.13 0.05LOI % 1.39 0.70

SUM 100.29 99.91

Sc ppm 3.205 1.197Ti ppm 2157.84 1018.98Co ppm 6.067 3.115Ni ppm 7.385 4.035Zn ppm 38.420 11.570As ppm 6.401 0.993Rb ppm 128.60 99.20Sr ppm 350.04 255.42Y ppm 20.00 20.00Zr ppm 126.34 83.49Nb ppm 20.00 20.00Sb ppm 1.377 0.196Cs ppm 7.264 1.701Ba ppm 1217.37 2054.76La ppm 34.828 18.161Ce ppm 50.595 28.326Nd ppm 22.721 12.053Sm PPm 3.538 2.211Eu ppm 0.843 0.716Tb ppm 0.343 0.258Yb ppm 1.444 1.061Lu ppm 0.257 0.174Hf ppm 3.872 2.409Ta ppm 0.831 0.398Th ppm 10.120 5.028U ppm 4.737 1.799

GV-GMN-5 GV-GMW-1 QLP-DC-1 QLP-PM-:#5 #6 #7 #21

73.60 75.80 65.60 67.0014.30 14.20 15.30 15.602.59 0.17 2.52 4.920.55 0.21 1.49 1.653.00 3.83 4.53 4.733.88 3.98 3.41 3.800.96 0.71 3.55 0.820.02 0.01 0.06 0.070.19 0.11 0.46 0.470.10 0.05 0.16 0.160.62 1.00 3.16 1.1699.81 100.06 100.27 100.38

1.840 1.476 5.223 5.6931138.86 659.34 2757.24 2817.18

1.042 0.581 9.582 2.0323.630 2.741 12.455 11.090

40.180 15.770 55.090 36.4000.828 1.091 1.360 2.701116.90 124.95 108.43 106.95318.47 111.62 499.01 697.2820.00 5.00 10.00 10.00123.01 75.98 126.99 126.6020.00 10.00 10.00 5.000.568 0.536 0.4826.257 3.020 4.777 3.317834.76 1291.31 962.86 839.5928.150 19.096 24.935 12.35749.008 35.862 41.822 26.68922.096 16.104 21.759 17.3463.838 3.215 3.810 3.3940.838 0.684 0.965 0.8620.478 0.443 0.392 0.4021.594 1.379 1.148 1.3100.257 0.215 0.192 0.2044.239 3.406 3.942 4.1600.695 0.806 0.659 0.6115.418 5.019 6.390 6.9811.827 1.405 2.464 2.811

86

CONTROL SAMPLES

Si02 % AI0O3 % CaO %MgO %Na20 %K20 % Fe203(t)% MnO %Ti02 % P2O5 %LOI %

SUM

Sc ppm Ti ppm Co ppm Ni ppm Zn ppm As ppm Rb ppm Sr ppm Y ppm Zr ppm Nb ppm Sb ppm Cs ppm Ba ppm La ppm Ce ppm Nd ppm Sm ppm Eu ppm Tb ppm Yb ppm Lu ppm Hf ppm Ta ppm Th ppm U ppm

TRD-GV-1#22

77.8012.100.140.213.213.950.850.010.090.021.85

100.23

2.768539.460.1341.294

71.2000.603262.55 82.10 60.00175.55 60.00

5.352192.7824.70641.39914.9742.8770.2180.6844.4010.6878.4943.73623.6809.617

HRQM-1#23

66.2015.702.181.084.554.883.680.100.590.200.85

100.01

8.2333536.46

6.1072.820

71.3005.685

221.30258.4930.00

211.2330.00

8.473975.9844.16078.60434.2576.2191.3720.8093.0840.4866.8610.90918.4404.022

Y-l#25

63.2216.254.773.245.091.154.740.080.540.181.05

100.31

9.3783237.3012.32826.849

152.550I. 013 16.37

758.27II. 0098.50

0.729255.9811.86323.66713.8332.8550.8840.3360.9900.1542.9200.1561.8740.620

APPENDIX 2

LOCATIONS AND CORRELATIONS

Sample numbers are given as they appear in the text and in the figures. Locations are given first as latitude and longitude (estimated from map locations), second as a cadastral description with the appropriate quadrangle name, and third as a description using local features, natural and man-made. Units are given first as the original unit name as described by Drewes (for the Sahuarita and Mt. Wrightson 7-1/2" quadrangles) or Finnell (for the Empire 15" quadrangle) during the 1970's, and second as listed by Drewes (1980, 1981) in later works on the tectonics of southeastern Arizona (in brackets). Ages are listed first according to Drewes (1980) with radiometric determinations (in brackets) by Marvin and others (1973) as recalculated by Reynolds and others (1985). Sierrita correlatives are listed according to Drewes (1981).

87

88

Field no: JCD-SM-1

SAMPLE 3

Location: 31°32,45" 110°49' SE1/4,SW1/4,SW1/4,SEC4,T22S,R15E(Patagonia 7-1/2") South Santa Rita Mts., 1/4 mile ESE of Weatherhead Ranch, at concrete bridge over Patagonia - Alto road.

Unit: Kj (Drewes, 1971a) - Josephine Canyon Diorite, moderately coarse-grained quartz diorite [ Kd (Drewes, 1980) - Main Cordilleran (Laramide) Igneous Rocks, diorite and quartz diorite ].

Age: Upper Cretaceous (Drewes, 1980) [ 68.70 +/- 3.00 Ma, K-Ar(Marvin and others, 1973, Reynolds and others, 1985) ]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at 67 Ma.

SAMPLE 4

Field no: GV-AG32-1Location: (approximate) 31°45'30" 110°46' NW1/4,SEC25,T19S,R15E

Unit:

(Helvetia 7-1/2") North Santa Rita Mts., drill core from Granite Mountain in the Greaterville district.Tql (Drewes, 1971b) - Quartz latite porphyry stocks and dikes [ Tip (Drewes, 1980) - Uppermost Cordilleran (Laramide)

Igneous Rocks, quartz latite porphyry ].Age: Upper Paleocene (Drewes, 1980) [ 55.2 +/- 2.00 Ma, 57.0 +/-

2.30 Ma, 57.1 +/- 2.10 Ma, 57.6 +/- 2.10 Ma, K-Ar (Marvin andothers, 1973, Reynolds and others, 1985)]

Sierrita correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma (Drewes, 1981)

SAMPLE 5

Field no: GV-GMN-5Location: 31°46' 110°46'45" NW1/4,SE1/4,SE1/4,SEC23,T19S,R15E

Unit:

(Helvetia 7-1/2") North Santa Rita Mts., outcrop on south side of the Forest Service road from the Greaterville site to Melendrez Pass where the road cuts the westernmost of the main stocks in the Greaterville area.Tql (Drewes, 1971b) - Quartz latite porphyry stocks and dikes [ Tip (Drewes, 1980) - Uppermost Cordilleran (Laramide)

Age:Igneous Rocks, quartz latite porphyry ].Upper Paleocene (Drewes, 1980) [ 55.2 +/- 2.00 Ma, 57.0 +/- 2.30 Ma, 57.1 +/- 2.10 Ma, 57.6 +/- 2.10 Ma, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma

89

Field no: GV-GMW-1Location: 31°45'45" 110°47' NW1/4,NW1/4,NE1/4,SEC26,T19S,RISE

(Helvetia 7-1/2") North Santa Rita Mts., northwestern end of the northwest-striking long dike on the southwestern side of the Greaterville district.

Unit: Tql (Drewes, 1971b) - Quartz latite porphyry stocks and dikes[ Tip (Drewes, 1980) - Uppermost Cordilleran (Laramide)

Igneous Rocks, quartz latite porphyry ].Age: Upper Paleocene (Drewes, 1980) [ 55.2 +/- 2.00 Ma, 57.0 +/-

2.30 Ma, 57.1 +/- 2.10 Ma, 57.6 +/- 2.10 Ma, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma

SAMPLE 6

SAMPLE 7

Field no: QLP-DC-1Location: 31°37'30" 110°52'30" SW1/4,NE1/4,NW1/4,SEC26,T17S,R16E (Mt.

Fagan 7-1/2') North Santa Rita Mts., 1 mile NNE of Pauline Mine adjacent to wash which can be reached by going south on the dirt road immediately east of the intersection of Sahuarita and Coronado Roads.

Unit: Tql (Finnell, 1971) Quartz latite porphyry [ Tip (Drewes,1980) - Uppermost Cordilleran (Laramide) Igneous Rocks, quartz latite porphyry ].

Age: Upper Paleocene (Drewes, 1980) [ 55.2 +/- 2.00 Ma, 57.0 +/-2.30 Ma, 57.1 +/- 2.10 Ma, 57.6 +/- 2.10 Ma, K-Ar (Marvin and others, 1973, Reynolds and othersj 1985)]

Sierrita correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma

SAMPLE 9

Field no: SF-DC-4Location: 31°51'45" 110°41'15" SE1/4,SE1/4,SEC15,T18S,R16E (EMPIRE

RANCH 7-1/2") North Santa Rita/Empire Mts.,Davidson Canyon, roadcut Arizona State Highway 83, 1 mile N of Rosemont Junction road.

Unit: Kse (Finnell, 1971) - Salero Fm., andesitic to dacitic flowsand flow breccias [ Ka (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, andesitic to dacitic volcanic breccia ].

Age: Upper Cretaceous (older than Kr) (Drewes, 1980).Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

90

Field no: KLQ-CS-1Location: 31°57' 110°43' CORNER,SEC16,17,20,21,1178,R16E (Mt. Fagan

SAMPLE 10

Unit:

7-1/2") North Santa Rita Mts., 1 mile S of intersection of Wentworth and Sahuarita Roads (Corona stock).Tkm (Finnell, 1971) - Quartz monzonite, light-to-medium-gray quartz monzonite stock [ Klq (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, lower quartz monzonite and granodiorite ].

Age: Upper Cretaceous (Drewes, 1980) [ 75.30 +/- 2.90 Ma, 75.50 +/- 2.70Ma, K-Ar (Marvin and others, 1973, Reynolds andothers, 1985)]

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

SAMPLE 11

Field no: KLQ-ES-2Location: 31°45'15" 110°39' SW1/4,SW1/4,SEC31,T17S,R17E (Mt. Fagan

Unit:

7-1/2") Empire Mts., 3/4 mile E of Arizona State Highway 83 above Davidson Canyon.Ke (Finnell, 1971) - Quartz monzonite of Empire Mountains stock [ Klq (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, lower quartz monzonite and granodiorite ].

Age: Upper Cretaceous (Drewes, 1980) [ 71.90 +/- 2.50, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

SAMPLE 12

Field no: AC-EH-1Location: 31°42' 110o55' NE1/4,NW1/4,NW1/4,SEC16,T20S,R14E (Mt.

Unit:Hopkins 7-1/2") South Santa Rita Mts., Agua Caliente Canyon. Keqc (Drewes, 1971a) - Elephant Head Quartz Monzonite, quartz monzonite of the Quantrell stock, coarse phase [ Kq (Drewes, 1980) - Main Cordilleran (Laramide)Igneous Rocks, quartz monzonite ].

Age: Upper Cretaceous (Drewes, 1980) [ 69.90 +/- 3.00, 70.80 +/- 2.90, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at 67 Ma

91

Field no: AC-EH-2Location: 31°42'10" 110°55' SW1/4,SW1/4,SEC9,T20S,R14E (Mt. Hopkins

7-1/2") South Santa Rita Mts., Agua Caliente Canyon.Unit: Keqc (Drewes, 1971a) - Elephant Head Quartz Monzonite, quartz

monzonite of the Quantrell stock, coarse phase [ Kq (Drewes, 1980) - Main Cordilleran (Laramide)Igneous Rocks, quartz monzonite ].

Age: Upper Cretaceous (Drewes, 1980) [ 69.90 +/- 3.00, 70.80 +/-2.90, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at 67 Ma

SAMPLE 13

SAMPLE 14

Field no: AC-EH-3Location: 31°41'45" 110°56' SE1/4,NW1/4,SEC17,T20S,R14E (Mt. Hopkins

7-1/2") South Santa Rita Mts., Agua Caliente Canyon.Unit: Keqf (Drewes, 1971a) - Elephant Head Quartz Monzonite, quartz

monzonite of the Quantrell stock, fine-grained phase [ Kq (Drewes, 1980) - Main Cordilleran (Laramide) Igneous Rocks, quartz monzonite ].

Age: Upper Cretaceous (Drewes, 1980) [ 69.90 +/- 3.00, 70.80 +/-2.90, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at 67m.y.

SAMPLE 15

Field no: BSM-KSW-1Location: 31°38'30" 110°54'30" SE1/4,SW1/4,SE1/4,SEC33,T20S,R14E (Mt.

Hopkins 7-1/2") South Santa Rita Mts., unnamed canyon NE of Josephine Canyon, 1/2 mile WNW of Bull Springs Mine.

Unit: Ksw (Drewes, 1971a) - Salero Fra., rhyodacite welded tuffmember [ Kr (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, rhyodacite tuff and welded tuff ].

Age: Upper Cretaceous (Drewes, 1980) [ 74.30 +/- 3.30, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

92

Field no: BSM-KSW-2Location: 31°38'20" 110°53'40" NW1/4,NE1/4,SEC3,T21S,R14E (Mt. Hopkins

7-1/2") South Santa Rita Mts., Josephine Canyon, 1/2 mile E of Bull Springs Mine.

Unit: Ksw (Drewes, 1971a) - Salero Fm., rhyodacite welded tuffmember [ Kr (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, rhyodacite tuff and welded tuff ].

Age: Upper Cretaceous (Drewes, 1980) [ 74.30 +/- 3.30, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

SAMPLE 16

SAMPLE 17

Field no: BSM-QL-1Location: 31°38'10" 110°53' NW1/4,SE1/4,NUl/4,SEC2,T21S,R14E (Mt.

Hopkins 7-1/2") South Santa Rita Mts., 1 mile ESE of Bull Springs Mine and 3/4 mile NNE of Helvetia Mine.

Unit: Kip (Drewes, 1971a) - Quartz latite porphyry, stocks, dikes,and a sill [ Tkp (Drewes, 1980) - Main Cordilleran (Laramide) Igneous Rocks, porphyritic and aplitic intrusive rocks ].

Age: Paleocene and Upper Cretaceous (Drewes, 1980)Sierrita correlative: None but interpreted (Drewes, 1980) as being

emplaced at the boundary between diorite and intrusive andesitic rocks (67 m.a.) and Ruby Star Granodiorite (59 - 60 m.a.) and biotite rhyolite (57 m.a.)

SAMPLE 18Field no: SM-KSW-3Location: 31°37'15" 110°52,30" SE1/4,NE1/4,SECll,T21S,R U E (Patagonia

7-1/2") South Santa Rita Mts., .8 mile N of Baca Float No. 5 boundary on road between Bull Springs Mine and Alto.

Unit: Ksw (Drewes, 1971a) - Salero Fm., rhyodacite welded tuffmember [ Kr (Drewes, 1980) - Lower Cordilleran (Laramide) Igneous and Sedimentary Rocks, rhyodacite tuff and welded tuff ].

Age: Upper Cretaceous (Drewes, 1980) [ 74.30 +/- 3.30, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Demetrie Volcanics and Red Boy Rhyolite

93

SAMPLE 19

Field no: JCD-SM-1XLocation: same as JCD-SM-1 (this sample was a split taken prior to

crushing).Unit: Kj (Drewes, 1971a) - Josephine Canyon Diorite, moderately

coarse-grained quartz diorite [ Kd (Drewes, 1980) - Main Cordilleran (Laramide) Igneous Rocks, diorite and quartz diorite ].

Age: Upper Cretaceous (Drewes, 1980) [ 68.70 +/- 3.00 Ma, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at Ma

SAMPLE 20

Field no: JCD-SM-5Location: 31°32'45" 110°49' SE1/4,SW1/4,SW1/4,SEC4,T22S,RISE

(Patagonia 7-1/2") South Santa Rita Mts., 1/4 mile ESE of Meatherhead Ranch, 200 yards NW of concrete bridge (sampling site for JCD-SM-1 and -IX) over Patagonia - Alto road.

Unit: Kj (Drewes, 1971a) - Josephine Canyon Diorite, moderatelycoarse-grained quartz diorite [ Kd (Drewes, 1980) - Main Cordilleran (Laramide) Igneous Rocks, diorite and quartz diorite ].

Age: Upper Cretaceous (Drewes, 1980) [ 68.70 +/-3.00 MA, K-Ar(Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Diorite and andesitic intrusive rocks dated at 67 Ma

SAMPLE 21

Field no: QLP-PM-2Location: 31°55'30" 110o4 V SW1/4,NE1/4,SW1/4,SEC26,T17S,R16E (Mt.

Fagan 7-1/2") 3/4 mile east of Pauline Mine just east (or north) of heavily fractured and mineralized area.

Unit: Tql (Finnell, 1971) Quartz latite porphyry [ Tip (Drewes,1980) - Uppermost Cordilleran (Laramide) Igneous Rocks, quartz latite porphyry ].

Age: Upper Paleocene (Drewes, 1980) [ 55.2 +/- 2.00 Ma, 57.0 +/-2.30 Ma, 57.1 +/- 2.10 Ma, 57.6 +/- 2.10 Ma, K-Ar (Marvin and others, 1973, Reynolds and others, 1985)]

Sierrita correlative: Quartz monzonite porphyry stocks and dikes (ore porphyry) 54-56 Ma

APPENDIX 3

MAJOR ELEMENT VALUES AND RATIOS, PETROLOGIC INDICES, AND BARTH KATANORMS

94

95

SAMPLE: 3 IDENTIFIER: JCD-SM-1

OXIDE WT PCT CAT.PCT FACTOR WT PCT CAT PCT

SI02 58.40 54.79 A 39.43 51.82t i o2 0.91 0.64 F 39.95 23.83AL9O1 16.50 18.25 M 20.62 24.36FE203 6.86 1.70FEO 0.0 3.14MNO 0.11 0.08 A 35.04 49.92MGO 3.54 4.95 C 29.45 27.12CAO 5.69 5.72 F 35.51 22.96NA20 3.90 7.09k 2o 2.87 3.44C02 0.0 0.0 NA 31.30 43.66p2°5 0.24 0.19 K 23.03 21.14S 0.0 0.0 CA 45.67 35.20H20 1.08TOTAL 100.10 A/CNK 0.83

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 20.49 Q 9.16THETA (SUGIMORA) 31.28 A 21.69SIGMA (RITTMANN) 2.98 P 69.16DIFFERENTIATION INDEX 59.90 F 0.0LARSON FACTOR 6.94MODIFIED LARSON FACTOR 5.29AGPAITIC COEFFICIENT(KN/A) 0.58

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 79.20 PERCENT ALBITE 35.47ANORTH 19.30ORTHO 17.18QUARTZ 7.25

FEMIC MINERALS 20.80 PERCENTENSTAT 9.90FERROS 3.47WOLLAS 3.08MAGNET 2.55ILMEN 1.28APATIT 0.51

MINERAL DISTRIBUTION

PLAGIOCLASE 54.77 PCT AN- 35. AB- 65.CPX 6.17 PCT EN- 37. FS- 13.OPX 10.29 PCT EN- 74. FS- 26.

WO- 50.

96

SAMPLE: 4 IDENTIFIER: GV-AG32-1

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 81.50 78.28 A 82.59 89.00t i o2 0.17 0.12 F 13.10 6.66AL203 9.40 10.64 M 4.32 4.35lFE203 0.88 0.64FEO 0.0 0.0MNO 0.02 0.01 A 71.71 81.08MGO 0.29 0.42 C 16.93 12.86CAO 1.31 1.35 F 11.37 6.07n a2o 2.67 4.97k 2o 2.88 3.53C02 0.0 0.0 NA 38.92 50.48P205 0.05 0.04 K 41.98 35.83s 0.0 0.0 CA 19.10 13.69h 2o 0.70TOTAL 99; 87 A/CNK 0.95

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 4.30 Q 51.10THETA (SUGIMORA) 43.96 A 18.03SIGMA (RITTMANN) 0.80 P 30.88DIFFERENTIATION INDEX 92.51 F 0.0LARSON FACTOR 27.66MODIFIED LARSON FACTOR 13.99AGPAITIC COEFFICIENT(KN/A) 0.80

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 97.87 PERCENT QUARTZ 50.01ALBITE 24.86ORTHO 17.64ANORTH 5.36

FEMIC MINERALS 2.13 PERCENTENSTAT 0.83HEMAT 0.64WOLLAS 0.42APATIT 0.11RUTILE 0.11ILMEN 0.03

MINERAL DISTRIBUTION

PLAGIOCLASE 30.22 PCT AN- 18. AB- 82.CPX 0.84 PCT EN- 50. FS- 0.OPX 0.41 PCT EN-100. FS- 0.

WO- 50

97

SAMPLE: 5 IDENTIFIER: GV-GMN-5OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 73.60 69.59 A 82.40 87.69TI02 0.19 0.14 F 11.02 5.64AL9O3 14.30 15.94 M 6.59 6.68FE2O3 0.92 0.65FEO 0.0 0.0MNO 0.02 0.01 A 66.22 75.64MGO 0.55 0.78 C 24.93 19.50CAO 2.59 2.62 F 8.85 4.86n a2o 3.00 5.50k 2o 3.88 4.68C02 0.0 0.0 NA 31.68 42.95P2O5 0.10 0.08 K 40.97 36.55S 0.0 0.0 CA 27.35 20.49H20 0.62TOTAL 99.77 A/CNK 1.03

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 6.57 Q 34.45THETA (SUGIMORA) 43.58 A 24.21SIGMA (RITTMANN) 1.55 P 41.34DIFFERENTIATION INDEX 84.98 F 0.0LARSON1 FACTOR 24.45MODIFIED LARSON FACTOR 12.52AGPAITIC COEFFICIENT(KN/A) 0.64

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)SALIC MINERALS 97.43 PERCENTQUARTZ 33.29ALBITE 27.50ORTHO 23.40ANORTH 12.45CORUND 0.78

FEMIC MINERALS 2.57 PERCENTENSTAT 1.55HEMAT 0.65APATIT 0.21RUTILE 0.12ILMEN 0.03

MINERAL DISTRIBUTION

PLAGIOCLASE 39.95 PCT AN- 31. AB- 69.OPX 1.55 PCT EN-100. FS- 0.

98

SAMPLE: 6 IDENTIFIER: GV-GMW-1OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 75.80 71.39 A 89.98 93.92t i o2 0.11 0.07 F 7.60 3.73AL203 14.20 15.77 M 2.42 2.35FE20] 0.66 0.47FEO 0.0 0.0MNO 0.01 0.00 A 90.39 94.85MGO 0.21 0.29 C 1.97 1.38GAO 0.17 0.17 F 7.64 3.77NA20 3.83 6.99k 2o 3.98 4.78C02 0.0 0.0 NA 47.99 58.54P205 0.05 0.04 K 49.87 40.03S 0.0 0.0 CA 2.13 1.44h 2o 1.00TOTAL 100.02 A/CNK 1.30

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 2.42 Q 37.44THETA (SUGIMORA) 40.69 A 25.18SIGMA (RITTMANN) 1.86 P 37.38DIFFERENTIATION INDEX 98.23 F 0.0LARSON FACTOR 28.27MODIFIED LARSON FACTOR 14.88AGPAITIC COEFFICIENT(KN/A) 0.75

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 98.75 PERCENTQUARTZ 35.56ALBITE 34.97ORTHO 23.91CORUND 3.78ANORTH 0.53

FEMIC MINERALS 1.25 PERCENTENSTAT 0.59HEMAT 0.47APATIT 0.11RUTILE 0.07ILMEN 0.01

MINERAL DISTRIBUTION

PLAGIOCLASE 35.50 PCT AN- 1. AB- 99.OPX 0.59 PCT EN-100. FS- 0.

99

SAMPLE:OXIDE

7WT PCT CAT PCT

IDENTIFIER: QLP-DC-1 FACTOR WT PCT CAT PCT

SI02 65.60 62.52 A 61.03 72.77t i o2 0.46 0.33 F 27.52 14.93a l2o3 15.30 17.19 M 11.45 12.30FE203 3.58 1.41FEO 0.0 1.16MNO 0.06 0.04 A 56.55 70.89MGO 1.49 2.12 C 17.95 14.57CAO 2.52 2.57 F 25.50 14.54n a2o 4.53 8.37k 2o 3.41 4.15C02 0.0 0.0 NA 43.31 55.47P205 0.16 0.13 K 32.60 27.47s 0.0 0.0 CA 24.09 17.05h 2o 3.16TOTAL 100.27 A/CNK 0.97PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 11.40 Q 19.49THETA (SUGIMORA) 31.38 A 22.47SIGMA (RITTMANN) 2.79 P 58.04DIFFERENTIATION INDEX 80.57 F 0.0LARSON FACTOR 18.05MODIFIED LARSON FACTOR 10.36AGPAITIC COEFFICIENT(KN/A) 0.73

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 92.26 PERCENT ALBITE 41.86ORTHO 20.73QUARTZ 17.98ANORTH 11.68

FEMIC MINERALS 7.74 PERCENTENSTAT 4.23MAGNET 2.11ILMEN 0.66FERROS 0.35APATIT 0.34WOLLAS 0.04

MINERAL DISTRIBUTION

PLAGIOCLASE 53.54 PCT AN- 22. AB- 78.CPX 0.08 PCT EN- 46. FS- 4.OPX 4.55 PCT EN- 92. FS- 8.

WO- 50.

100

SAMPLE: 9 IDENTIFIER: SF-DC-4

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 59.00 57.72 A 38.31 52.58t i o2 0.82 0.60 F 45.60 27.91ALpO^ 16.70 19.26 M 16.09 19.51f e2o3 6.32 1.71FEO 0.0 2.94MNO 0.12 0.09 A 31.55 46.45MGO 2.23 3.25 C 30.90 28.89CAO 5.20 5.45 F 37.55 24.66n a2o 3.29 6.24k 2o 2.02 2.52C02 0.0 0.0 NA 31.30 43.91p2°5 0.24 0.20 K 19.22 17.74S 0.0 0.0 CA 49.48 38.35H20 4.31TOTAL 100.25 A/CNK 0.98

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 15.95 Q 19.07THETA (SUGIMORA) 37.62 A 14.70SIGMA (RITTMANN) 1.76 P 66.23DIFFERENTIATION INDEX 60.43 F 0.0LARSON FACTOR 8.57MODIFIED LARSON FACTOR 5.82AGPAITIC COEFFICIENT(KN/A) 0.45

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 86.03 PERCENTALBITE 31.21ANORTH 25.60QUARTZ 16.36ORTHO 12.61CORUND 0.26

FEMIC MINERALS 13.97 PERCENTENSTAT 6.50FERROS 3.17MAGNET 2.56ILMEN 1.21APATIT 0.53

MINERAL DISTRIBUTION

PLAGIOCLASE 56.80 PCT AN- 45. AB- 55.OPX 9.68 PCT EN- 67. FS- 33.

101SAMPLE:

OXIDE

10WT PCT CAT PCT

IDENTIFIER: KLQ-CS-1 FACTOR WT PCT CAT PCT

SI02 68.60 64.11 A 60.52 71.90TI02 0.47 0.33 F 28.55 15.98a l2o3 15.20 16.75 M 10.93 12.12FE203 3.50 1.39FEO 0.0 1.08MNO 0.04 0.03 A 52.33 65.91MGO 1.34 1.87 C 22.99 19.43CAO 3.26 3.26 F 24.68 14.65n a2o 3.59 6.51k 2o 3.83 4.57C02 0.0 0.0 NA 33.61 45.38P205 0.14 0.11 K 35.86 31.85S 0.0 0.0 CA 30.52 22.77H20 0.47TOTAL 100.44 A/CNK 0.95

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 10.89 THETA (SUGIMORA) 37.53 SIGMA (RITTMANN) 2.15 DIFFERENTIATION INDEX 78.39 LARSON FACTOR 18.95 MODIFIED LARSON FACTOR 10.74 AGPAITIC COEFFICIENT(KN/A) 0.66

QAPF

24.8724.6650.460.0

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 92.58 ALBITE 32.53QUARTZ 23.03ORTHO 22.83ANORTH 14.19

PERCENT

FEMIC MINERALS 7.42 PERCENTENSTATMAGNETILMENWOLLASAPATITFERROS

3.732.080.660.480.300.17

MINERAL DISTRIBUTION

PLAGIOCLASE 46.72 PCT AN- 30. AB-CPX 0.97 PCT EN- 48. FS-OPX 3.42 PCT EN- 96. FS-

70.2.4.

WO- 50.

102

SAMPLE: 11 IDENTIFIER: KLQ-ES-2

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 68.40 63.35 A 70.12 76.14TI02 0.47 0.33 F 12.32 6.25AL203 15.40 16.81 M 17.55 17.62FE203 1.32 0.92FEO 0.0 0.0MNO 0.04 0.03 A 55.59 66.84MGO 1.88 2.59 C 34.64 27.68CAO 4.68 4.64 F 9.77 5.48NA20 3.81 6.84k 2o 3.70 4.37C02 0.0 0.0 NA 31.26 43.15P205 0.14 0.11 K 30.35 27.57s 0.0 0.0 CA 38.39 29.29h 2o 0.31TOTAL 100.15 A/CNK 0.82

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 17.49 Q 22.08THETA (SUGIMORA) 37.06 A 24.31SIGMA (RITTMANN) 2.22 P 53.62DIFFERENTIATION INDEX 75.92 F 0.0LARSON1 FACTOR 18.75MODIFIED LARSON FACTOR 9.26AGPAITIC COEFFICIENT(KN/A) 0.67

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 89. ALBITE • 34.21 ORTHO 21.86QUARTZ 19.85ANORTH 14.00

92 PERCENT

FEMIC MINERALS 10.08 PERCENTENSTATWOLLASHEMATRUTILEAPATITILMEN

5.193.320.920.300.290.06

MINERAL DISTRIBUTION

PLAGIOCLASE 48.21 PCT AN- 29. AB- 71.CPX 6.64 PCT EN- 50. FS- 0 .OPX 1.87 PCT EN-100. FS- 0 .

WO- 50.

103

SAMPLE: 12 IDENTIFIER: AC-EH-1

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 73.70 70.88 A 69.76 77.11t i o2 0.25 0.18 F 22.64 13.75AL2O3 13.90 15.76 M 7.59 9.14FE2°3 1.61 1.17FEO 0.0 0.0MNO 0.05 0.04 A 44.93 53.09MGO 0.54 0.77 C 40.49 37.44CAO 4.47 4.61 F 14.58 9.47NA20 0.70 1.31k 2o 4.26 5.23C02 0.0 0.0 NA 7.42 11.72P205 0.07 0.05 K 45.17 46.93s 0.0 0.0 CA 47.40 41.35H20 0.85TOTAL 100.40 A/CNK 1.00PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 7.54 Q 42.90THETA (SUGIMORA) 54.22 A 27.03SIGMA (RITTMANN) 0.80 P 30.07DIFFERENTIATION INDEX 74.36 F 0.0LARSON FACTOR 22.37MODIFIED LARSON FACTOR 11.51AGPAITIC COEFFICIENT(KN/A) 0.41

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 96.91 PERCENTQUARTZ 41.49ORTHO 26.14ANORTH 22.56ALBITE 6.53CORUND 0.21

FEMIC MINERALS 3.09 PERCENTENSTAT 1.55HEMAT 1.17APATIT 0.15RUTILE 0.14ILMEN 0.08

MINERAL DISTRIBUTION

PLAGIOCLASE 29.08 PCT AN- 78. AB- 22.OPX 1.55 PCT EN-100. FS- 0.

104

SAMPLE: 13 IDENTIFIER: AC-EH-2OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 72.50 67.61 A 82.66 89.30t i o2 0.22 0.15 F 13.91 7.19AL203 14.20 15.61 M 3.43 3.52FE203 1.62 1.14FEO 0.0 0.0MNO . 0.03 0.02 A 80.32 88.27MGO 0.40 0.56 C 6.17 4.62CAO 0.74 0.74 F 13.51 7.11n a2o 4.31 7.79k 2o 5.32 6.33C02 0.0 0.0 NA 41.56 52.44P205 0.06 0.04 K 51.30 42.59s 0.0 0.0 CA 7.14 4.98H20 0.70TOTAL 100.10 A/CNK 1.00PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 3.42 Q 24.02THETA (SUGIMORA) 29.98 A 32.53SIGMA (RITTMANN) 3.14 P 43.45DIFFERENTIATION INDEX 94.15 F 0.0LARSON FACTOR 26.89MODIFIED LARSON FACTOR 14.96AGPAITIC COEFFICIENT(KN/A) 0.90

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 97.45 PERCENTALBITE 38.97ORTHO 31.65QUARTZ 23.36ANORTH 3.30CORUND 0.17

FEMIC MINERALS 2.55 PERCENT HEMAT 1.14ENSTAT 1.11RUTILE 0.13APATIT 0.13ILMEN 0.04

MINERAL DISTRIBUTION

PLAGIOCLASE 42.27 PCTOPX 1.11 PCT

AN- 8. AB- 92.EN-100. FS- 0.

105

SAMPLE: 14 IDENTIFIER: AC-EH-3

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 73.00 68.36 A 80.56 87.93TI02 0.25 0.18 F 15.53 8.06AL203 14.00 15.46 M 3.91 4.01FE203 1.67 1.18FEO 0.0 0.0MNO 0.02 0.01 A 74.27 83.64MGO 0.42 0.59 C 11.41 8.69CAO 1.33 1.33 F 14.32 7.66NA20 4.02 7.30k 2o 4.64 5.54C02 0.0 0.0 NA 40.24 51.49P205 0.06 0.04 K 46.45 39.10s 0.0 0.0 CA 13.31 9.41H20 0.62TOTAL 100.03 A/CNK 1.00PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) THETA (SUGIMORA)SIGMA (RITTMANN) DIFFERENTIATION INDEX LARSON FACTOR MODIFIED LARSON FACTOR AGPAITIC COEFFICIENT(KN/A)

3.90 Q 27.5033.95 A 28.512.50 P 43.9991.06 F 0.025.72 14.03 0.83

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 97.33 PERCENTALBITE 36.50ORTHO 27.72QUARTZ 26.74ANORTH 6.28CORUND 0.10

FEMIC MINERALS 2.67 PERCENTHEMAT 1.18ENSTAT 1.17RUTILE 0.16APATIT 0.13ILMEN 0.03

MINERAL DISTRIBUTION

PLAGIOCLASE 42.77 PCT AN- 15.OPX 1.17 PCT EN-100.

AB- 85.FS- 0.

106

SAMPLE: 15 IDENTIFIER: BSM-KSW-1

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

sio2 61.20 59.67 A 56.95 68.37t i o2 0.56 0.41 F 31.95 18.74AL2Og 16.20 18.62 M 11.10 12.90FE20] 4.46 1.51FEO 0.0 1.76MNO 0.07 0.05 A 50.06 63.38MGO 1.55 2.25 C 21.85 19.25CAO 3.47 3.63 F 28.09 17.37n a2o 3.17 5.99k 2o 4.78 5.95C02 0.0 0.0 NA 27.76 38.51p2°5 0.18 0.15 K 41.86 38.20S 0.0 0.0 CA 30.39 23.29H20 4.31TOTAL 99.95 A/CNK 0.97

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) THETA (SUGIMORA)SIGMA (RITTMANN) DIFFERENTIATION INDEX LARSON FACTOR MODIFIED LARSON FACTOR AGPAITIC COEFFICIENT(KN/A)

11.05 Q 15.7031.07 A 32.803.47 P 51.5073.93 F 0.016.15 10.10 0.64

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 90.63 PERCENT ALBITE 29.97ORTHO 29.73ANORTH 16.71QUARTZ 14.23

FEMIC MINERALS 9.37 PERCENTENSTAT 4.50MAGNET 2.27FERROS 1.30ILMEN 0.82APATIT 0.40WOLLAS 0.07

MINERAL DISTRIBUTION

PLAGIOCLASE 46.67 PCT AN- 36. AB- 64.CPX 0.14 PCT EN- 39. FS- 11.OPX 5.74 PCT EN- 78. FS- 22.

WO- 50.

107

SAMPLE: 16 IDENTIFIER: BSM-KSW-2

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 61.80 59.16 A 56.86 69.30TI02 0.57 0.41 F 31.08 17.36AL203 16.60 18.74 M 12.06 13.34FE2°3 4.28 1.49FEO 0.0 1.59MNO 0.07 0.05 A 49.78 64.42MGO 1.66 2.37 C 23.01 19.44CAO 3.62 3.71 F 27.21 16.14NA20 4.32 8.02k 2o 3.51 4.29C02 0.0 0.0 NA 37.73 50.06P205 0.20 0.16 K 30.66 26.76s 0.0 0.0 CA 31.62 23.18h 2o 3.47TOTAL 100.10 A/CNK 0.95PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 11.99 Q 14.09THETA (SUGIMORA) 30.93 A 23.73SIGMA (RITTMANN) 3.26 P 62.18DIFFERENTIATION INDEX 74.26 F 0.0LARSON FACTOR 14.98MODIFIED LARSON FACTOR 8.96AGPAITIC COEFFICIENT(KN/A) 0.66BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 90.33 PERCENT ALBITE 40.10ORTHO 21.44ANORTH 16.07QUARTZ 12.73

FEMIC MINERALS 9.67 PERCENTENSTAT 4.74MAGNET 2.24FERROS 0.99ILMEN 0.82WOLLAS 0.46APATIT 0.43

MINERAL DISTRIBUTION

PLAGIOCLASE 56.17 PCT AN- 29. AB- 71.CPX 0.91 PCT EN- 41. FS- 9.OPX 5.27 PCT EN- 83. FS- 17.

WO- 50

108

SAMPLE: 17 IDENTIFIER: BSM-QL-1OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 72.80 69.04 A 71.01 80.87t i o2 0.36 0.26 F 22.08 11.81AL203 13.40 14.98 M 6.91 7.32FE2°3 2.27 1.33FEO 0.0 0.29MNO 0.05 0.04 A 63.98 76.07MGO 0.71 1.00 C 16.13 12.82CAO 1.84 1.87 F 19.89 11.11n a2o 3.59 6.60k 2o 3.71 4.49C02 0.0 0.0 NA 39.28 50.94P2O5 0.13 0.10 K 40.59 34.64s 0.0 0.0 CA 20.13 14.43h 2o 1.39TOTAL 100.25 A/CNK 1.01PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) THETA (SUGIMORA)SIGMA (RITTMANN) DIFFERENTIATION INDEX LARSON FACTOR MODIFIED LARSON FACTOR AGPAITIC COEFFICIENT(KN/A)

6.87 Q 32.9238.01 A 23.551.79 P 43.5387.32 F 0.023.38 x12.69 0.74

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 95.80 PERCENTALBITE 33.01QUARTZ 31.37ORTHO 22.44ANORTH 8.48CORUND 0.50

FEMIC MINERALS 4.20 PERCENTENSTAT 2.01HEMAT 1.18ILMEN 0.51APATIT 0.28MAGNET 0.23

MINERAL DISTRIBUTION

PLAGIOCLASE 41.48 PCT AN- 20. AB- 80.OPX 2.01 PCT EN-100. FS- 0.

109

SAMPLE: 18 IDENTIFIER: SM-KSW-3

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 62.00 59.61 A 60.15 71.64t i o2 0.56 0.40 F 30.57 17.72AL9O1 16.70 18.93 M 9.28 10.65FE2O3 4.35 1.49FEO 0.0 1.66MNO 0.12 0.09 A 53.97 67.29MGO 1.32 1.89 C 18.60 16.07CAO 2.95 3.04 F 27.43 16.64n a2o 3.49 6.51k 2o 5.07 6.22C02 0.0 0.0 NA 30.32 41.27P2O5 0.19 0.15 .K 44.05 39.45s 0.0 0.0 CA 25.63 19.28h 2o 3.31t o t a l 100.06 A/CNK 1.01PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 9.20 Q 14.71THETA (SUGIMORA) 30.40 A 34.20SIGMA (RITTMANN) 3.86 P 51.08DIFFERENTIATION INDEX 77.65 F 0.0LARSON FACTOR 17.55MODIFIED LARSON FACTOR 10.97AGPAITIC COEFFICIENT(KN/A) 0.67

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 91.55 PERCENTALBITE 32.53ORTHO 31.10ANORTH 13.90QUARTZ 13.38CORUND 0.64

FEMIC MINERALS 8.45 PERCENTENSTAT 3.78MAGNET 2.24FERROS 1.21ILMEN 0.81APATIT 0.41

MINERAL DISTRIBUTION

PLAGIOCLASE 46.44 PCT AN- 30.OPX 4.99 PCT EN- 76.

AB- 70.FS- 24.

110

SAMPLE: 19 IDENTIFIER: JCD-SM-1X

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 58.90 55.34 A 40.34 52.59TI02 0.88 0.62 F 39.20 23.31AL203 16.50 18.28 M 20.47 24.11FE203 6.55 1.68FEO 0.0 2.95MNO 0.10 0.08 A 35.68 50.43MGO 3.42 4.79 C 29.65 27.22CAO 5.60 5.64 F 34.67 22.35NA20 3.80 6.92k 2o 2.94 3.52C02 0.0 0.0 NA 30.79 43.04P205 0.23 0.18 K 23.82 21.91S 0.0 0.0 CA 45.38 35.05H20 1.08to t a l 100.00 A/CNK 0.84

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 20.35 Q 10.47THETA (SUGIMORA) 32.03 A 21.97SIGMA (RITTMANN) 2.86 P 67.56DIFFERENTIATION INDEX 60.63 F 0.0LARSON FACTOR 7.66MODIFIED LARSON FACTOR 5.56AGPAITIC COEFFICIENT(KN/A) 0.57

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 80.20 PERCENT ALBITE 34.61ANORTH 19.57ORTHO 17.62QUARTZ 8.40

FEMIC MINERALS 19.80 PERCENTENSTAT 9.58FERROS 3.13WOLLAS 2.83MAGNET 2.52ILMEN 1.24APATIT 0.49

MINERAL DISTRIBUTION

PLAGIOCLASE 54.19 PCT AN- 36. AB- 64.CPX 5.67 PCT EN- 38. FS- 12. WO- 50.OPX 9.87 PCT EN- 75. FS- 25.

Ill

SAMPLE: 20 IDENTIFIER: JCD-SM-5OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 57.00 53.69 A 34.89 46.58t i o2 1.08 0.77 F 42.85 26.33AL^Oq 15.50 17.21 M 22.26 27.09FE2O3 8.18 1.83FEO 0.0 3.97MNO 0.17 0.14 A 32.16 46.67MGO 4.25 5.97 C 28.34 26.95CAO 5.87 5.92 F 39.50 26.38NA20 3.61 6.59k 2o 3.05 3.67C02 0.0 0.0 NA 28.81 40.74P2O5 0.31 0.25 K 24.34 22.65S 0.0 0.0 CA 46.85 36.61H20 1.16TOTAL 100.18 A/CNK 0.78

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 22.07 Q 7.46THETA (SUGIMORA) 28.99 A 24.69SIGMA (RITTMANN) 3.17 P 67.85DIFFERENTIATION INDEX 56.83 F 0.0LARSON FACTOR 4.57MODIFIED LARSON FACTOR 4.66AGPAITIC COEFFICIENT(KN/A) 0.60

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 74.21 PERCENT ALBITE • 32.97ORTHO 18.33ANORTH 17.38QUARTZ 5.54

FEMIC MINERALS 25.79 PERCENTENSTAT 11.93FERROS 4.85WOLLAS 4.07MAGNET 2.74ILMEN 1.53APATIT 0.66

MINERAL DISTRIBUTION

PLAGIOCLASE 50.35 PCT AN- 35. AB- 65.CPX 8.14 PCT EN- 36. FS- 14.OPX 12.71 PCT EN- 71. FS- 29.

WO- 50.

112

SAMPLE: 21 IDENTIFIER: QLP-PM-2

OXIDE WT PCT CAT PCT FACTOR WT PCT CAT PCT

SI02 67.00 61.90 A 78.11 82.30t i o2 0.47 0.33 F 6.78 3.27ALfOq 15.60 16.99 M 15.11 14.43FE203 0.74 0.51FEO 0.0 0.0MNO 0.07 0.05 A 60.11 70.63MGO 1.65 2.27 C 34.67 26.56CAO 4.92 4.87 F 5.21 2.81n a2o 4.73 8.47k 2o 3.80 4.48C02 0.0 0.0 NA 35.17 47.54P2O5 0.16 0.13 K 28.25 25.13s 0.0 0.0 CA 36.58 27.33h 2o 1.16TOTAL 100.30 A/CNK 0.75

PETROLOGIC INDICES FACTOR

SOLIDIFICATION INDEX (KUNO) 15.01 Q 15.84THETA (SUGIMORA) 31.17 A 25.18SIGMA (RITTMANN) 3.03 P 58.98DIFFERENTIATION INDEX 78.85 F 0.0LARSON FACTOR 18.90MODIFIED LARSON FACTOR 9.09AGPAITIC COEFFICIENT(KN/A) 0.76

BARTH NORMATIVE MINERALOGY (IN ORDER OF ABUNDANCE)

SALIC MINERALS 88.94 PERCENT ALBITE 42.36ORTHO 22.39QUARTZ 14.09ANORTH 10.10

FEMIC MINERALS 11.06 PERCENTWOLLAS 5.28ENSTAT 4.54HEMAT 0.51APATIT 0.33RUTILE 0.27ILMEN 0.11

MINERAL DISTRIBUTION

PLAGIOCLASE 52.46 PCT AN- 19. AB- 81.CPX 9.09 PCT EN- 50. FS- 0. WO- 50.

APPENDIX 4

ERRORS AND REPRODUCIBILITY

An indication of analytical error is derived from the

analytical results for three standard rocks which were analyzed with

the samples. These results are listed first. Reproducibility of

results is indicated by comparison of results for aliquots of the same

sample. The nature of the aliquots is discussed in the main text.

Reproducibility is listed second.

113

9S?SEegB&g&B*88f?f?8ir!?S85?8&S

Errors in analysis of Standard Rocks

elementunit

%%

ppn %PE*n PPn PPn PPn PPn ppn ppn PPn PPn ppn PPn ppn ppn ppn PPn ppn ppn ppn FPn PPn PPn U ppn

W1rprtdvalue diff

1.58 0.6%7.82 -2.3%35.00 0.6%7.79 0.3%

46.00 1.3%75.00 2.0%84.00 1.4%2.20 -3.6%

21.42 -1.4%187.00 1.4%100.00 -1.1%

1.05 0.9%0.95 —0.6%

162.00 6.4%10.90 7.5%23.00 —21.6%15.00 -9.0%3.50 -4.9%1.11 -5.3%0.65 -8.9%2.12 -2.6%0.34 1.8%2.60 6.0%0.50 -10.8%2.40 —6.5%0.57 -7.7%

NBS278rprtdvalue diff

3.59 0.0%0.70 0.8%5.24 -4.3%1.43 2.4%1.50 2.0%

5.06 1.4%127.50 2.7%

1.61 7.0%

35.40 -3.7%59.40 0.2%28.20 1.0%

0.76 -0.9%

4.54 2.4%0.84 -6.0%8.82 0.6%1.23 7.1%12.40 1.0%4.58 2.4%

NBS688Arprtdvalue diff

1.60 -1.1%8.70 1.0%36.10 -0.4%7.24 -0.6%49.70 -0.4%150.00 -1.5%

2.68 -5.5%

169.20 5.0%59.00 -3.3%0.47 -77.3%

4.90 16.0%

2.31 2.7%0.92 0.4%0.46 9.7%

0.34 3.5%1.58 1.9%0.25 -0.4%0.33 -6.7%

average averagediff (absol)

|diff|

-0.2% 0.6%-0.2% 1.4%-1.4% 1.8%0.7% 1.1%1.0% 1.2%0.3% 1.8%1.4% 1.4%

-2.6% 3.5%0.7% 2.1%3.2% 3.2%

-2.2% 2.2%-23.1% 28.4%-0.6% 0.6%6.4% 6.4%6.6% 9.1%

—10.7% 10.9%-4.0% 5.0%—1.1% 3.8%-1.9% 2.2%0.4% 9.3%

—0.1% 2.5%-0.2% 3.8%2.8% 2.8%

-1.4% 6.1%-4.1% 4.7%-2.7% 5.1% HH

£39

115Reproducibility in Sample Splits

element

NaCaScFeCoNiZnAsRbSrZrSbCsBaLaCeNdSmEu

HfTaThU

QLP-DC-1 RS -MR-6 JCD -SM-1average (absol) average (absol) average (absol)unit value |diff| value |diff| value |diff|

% 4.53 0.7% 2.18 0.6% 3.90 0.3%% 2.52 6.8% 0.50 2.8% 5.69 1.1%ppm 5.22 2.0% 0.83 2.7% 13.07 1.0%% 3.55 1.7% 0.47 2.0% 6.82 2.9%ppm 9.58 2.3% 0.80 3.8% 22.01 2.2%ppm 12.46 27.9% 5.25 59.2% 37.62 3.8%ppm 55.31 1.0% 4.59 6.5% 86.03 0.6%ppm 1.36 20.8% 0.51 4.36 3.1%ppm 108.43 3.2% 190.70 0.2% 126.15 2.5%ppm 499.01 0.3% 55.54 12.9% 555.15 1.1%ppm 126.99 3.8% 75.44 14.8% 218.26 9.0%ppm 0.48 3.1% 0.07 0.70 4.4%ppm 4.78 0.9% 2.46 9.2% 6.20 3.9%ppm 962.86 2.0% 201.16 0.7% 805.89 0.3%ppm 24.94 10.3% 26.13 9.1% 37.66 0.9%ppm 41.82 7.4% 28.92 0.9% 62.88 0.7%ppm 21.76 4.3% 6.80 3.0% 32.67 0.5%ppm 3.81 3.4%. 0.84 9.7% 5.99 0.7%ppm 0.97 0.8% 0.19 4.4% 1.31 2.4%ppm 0.39 7.1% 0.60 1.2%ppm 1.15 2.3% 0.44 6.1% 1.83 0.5%ppm 0.19 1.6% 0.09 6.7% 0.30 1.0%ppm 3.94 0.7% 2.73 8.9% 6.33 8.1%ppm 0.66 4.5% 0.51 5.7% 0.68 5.9%ppm 6.39 5.6% 32.57 5.1% 18.68 30.1%ppm 2.46 2.6% 4.65 1.8% 5.69 3.8%

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