A geologic investigation of contact metamorphicdeposits in the Coyote Mountains, Pima County, Arizona

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Authors Carrigan, Francis John, 1941-

Publisher The University of Arizona.

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A GEOLOGIC INVESTIGATION OF CONTACT METAMORPHIC DEPOSITS IN THE

COYOTE MOUNTAINS, PIMA COUNTY, ARIZONA

byFrancis John Carrigan

A Thesis Submitted to the Faculty of the DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING

In Partial Fulfillment of the Requirements For the Degree ofMASTER OF SCIENCE

WITH A MAJOR IN GEOLOGICAL ENGINEERING In the Graduate College

THE UNIVERSITY OF ARIZONA

1 9 7 1

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of the 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 acknowledgment 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 judgment the proposed use of the material is in the interests of scholar­ship. In all other instances, however, permission must be obtained from the author.

3

APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:

Willard./£?I Lacy Professor of Mining

and Geological Engineering

S /z o /y /Date

ACKNOWLEDGMENTS

The author would like to thank Dr. W. C. Lacy, under whose direction this thesis was written, for his help and suggestions.

Sincere appreciation and thanks go to Dr. C. P. Jenney and the management of Consolidated Red Poplar Minerals, Ltd. Dr. Jenney was the consulting geologist for this project. Consolidated Red Poplar Minerals, Ltd., generously gave financial assistance as well as permission to use the data gathered for a thesis.

Drs. S. R. Titley and D. L. Bryant gave invaluable advice and suggestions regarding the correlation of the strat­igraphic section.

Dr. John F. Abel aided in the interpretation of the structural geology.

Special thanks are also due to Dr. Frederick T. Graybeal for his constant encouragement, advice, guidance, and most important, his friendship.

The excellent drafting was done by George Smith of Tucson, Arizona.

Not the least valuable was the help of my wife,Kathy, for her advice, typing and editing.

iii

TABLE OF CONTENTS

PageLIST OF ILLUSTRATIONS............................. viLIST OF T A B L E S ................................... ixA B S T R A C T .............................'........... x

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

The Problem................................... 1Location ..................................... 1History of Mining............................. 3Previous w o r k ................................. 3Procedure ..................................... 4Regional Setting ............................. 5

2. SEDIMENTARY ROCKS ................................. 7General ....................................... 7PreCambrian System .............. . . . . . . 8

Pinal S c h i s t ............................. 8Cambrian System ............................... 10

Abrigo Formation ......................... 10Devonian System ............................... 16

Martin Formation...................... 16Undifferentiated Paleozoic (?) 20

3. IGNEOUS ROCKS..................................... 2S1General ....................................... 28Quartz Monzonite............................. 28Pegmatite Dikes ............................... 31Lamprophyre Dikes .......... 31

4. STRUCTURE............................ 36General....................................... 36Sedimentary Rocks ............................. 36Igneous Rocks.................... 41

5. ALTERATION AND MINERALIZATION .................. 47

iv

V

Page6 . SUMMARY................................................ 61

APPENDIX I: GEOCHEMICAL D A T A ......................... 63

LIST OF REFERENCES................................... 66

TABLE OF CONTENTS— Continued

\

LIST OF ILLUSTRATIONS

1 . Regional Index M a p .................. 2

2. Local Index M a p ............................... 6

3. Geologic Explanation ....................... in pocket4* Geology of a Portion of the Coyote

Mountains ............................. in pocket5. Pinal Schist . . . . . . ....................... . 11

6 . Contact between Middle and Upper Members ofthe Abrigo Formation ....................... 13

7. Upper Member of. the Abrigo Formation........... 14&. Bedding in the Upper Abrigo Member............. 159. Contact between the Martin and Abrigo

Formations.............. .................. 1710. Martin Formation ............................... 1911. Biotite Actinolite Gneiss Member of the

Figure Page

Undifferentiated Paleozoic (?) Section . . . 21

12. Tremolitized Limestone Member of theUndifferentiated Paleozoic (?) Section . . . 23

13. Pyroxenite Member of the UndifferentiatedPaleozoic (?) Section............ 24

14. Pyroxenite Texture . . . . . . . . . .......... 26

15. Contact between the Pyroxenite and theQuartz Monzonite........................... 27

16. Mineralogy of the GraniticIntrusion ............................. in pocket

17* Pegmatite Dike Swarms in the QuartzMonzonite............................. 32

vi

Figure . PageIS. Contact between a Pegmatite Dike and

the Quartz Monzonite .......................... 3319. Lamprophyre Dike Intruding the Quartz

Monzonite................................... 3520. Upper Abrigo Member Pendant into Laramide

Quartz Monzonite ............................. 3721. Schmidt Plot of Bedding within the Sedimentary

P e n d a n t ..................................... 3922. Schmidt Plot of Foliation within the Sedimentary

P e n d a n t .................................... •. 40

23• Geologic Sections of the Southern Portion ofthe Coyote Mountains .................. in pocket24. Geologic Sections of the Northern Portion of

the Coyote Mountains.............. .. . in pocket25. Schmidt Plot of Igneous Fracture Pattern ......... 4226. Eye-level View of Igneous Fracture Pattern

Looking North ............................... 4327. Vertical Aerial Photograph of a Portion of

the Coyote Mountains ............ . . . . . . 442G. Flat-lying Pegmatite Dikes ....................... 4529. Main A d i t .................... 5130. Portal— Main A d i t ........ " ..................... 5231. West Adit— Upper Level ........................... 53

32. West Adit— Main L e v e l ........................... 54

33 • West Adit— Incline and Lower Level............... 55

34• Portal— West Adit— Main L e v e l ................... 56

35• Turquoise A d i t ................... 57

36. Portal— Turquoise A d i t ......................... . 5#

viiLIST OF ILLUSTRATIONS— Continued

viiiLIST OF ILLUSTRATIONS— Continued

Figure - Page37. Mineralization-Alteration Relationships . . in pocket3&. Geochemical Stream Sediment Sites and

Results................ ..............in pocket

LIST OF TABLES

1 . Mineralogy of the Sedimentary Formations . . . ' 92. Mineralogy of the Igneous R o c k s .............. 303. Results of Geochemical Stream Sediment Survey . 64

Table Page

I

ix

ABSTRACT

The northeastern portion of the Coyote Mountains con­tains a pendant of contact metamorphosed, weakly metasomatized Paleozoic sediments. The stratigraphic position of the sedimentary sequence has been identified by lithology, strati­graphic correlation, and inference. The sedimentary units found in the Coyote Mountains are the PreCambrian Pinal Schist, the Cambrian Abrigo, the Devonian Martin and an unidentified sequence labeled "Undifferentiated Paleozoic (?)."

Pre-intrusion faulting occurred within the sedimentary sequence causing a repetition of bedding. The principal in­trusive rock is a Laramide quartz monzonite whose -texture varies from aplitic to pegmatitic. The intrusion was force­ful, dilating the sediments.

Only minor post-intrusion faulting was noted.Mineralization consists of widely distributed show­

ings of oxide copper along igneous-sedimentary contacts. High-grade metallization occurs as replacement deposits in zones of silicated limestone.

Although the quartz monzonite is unaltered and rarely mineralized, it is believed to be the source of mineraliza­tion. A parent magma deficient in metals is presumed.

x

CHAPTER 1

INTRODUCTION

The ProblemA pendant of Paleozoic sediments located in the north­

eastern portion of the Coyote Mountains contains scattered occurrences of copper oxides over an area approximately one- half mile wide and one and one-half miles long. Since many of the mines in the Tucson area, one of the most prolific copper producing regions in the world, produce a major proportion of their ore from metamorphosed calcareous sedimentary rocks in contact with granitic intrusives, a detailed study of this area was instigated. The purpose of this study was to assess the economic potential of the Paleozoic pendant and the surrounding quartz monzonite intrusive.

LocationThe Coyote Mountains are located in southern Arizona

and comprise about thirty-five square miles of central Pima County (Fig. l). The region is about thirty miles southwest of the city of Tucson. Access is via Highway 86 to Coleman Road, then south on Coleman Road eleven miles along a good dirt road around the southern end of the Coyote Mountain range. A rough jeep road leads from the desert plain up the

1

112°

PHOENIX

RI V ER

TUCSON

C 0 U N T Y

50 0 100 MILESI i i * i l t i

Fig. 1 . Regional Index Map

3mountain to an area of old adits which constitute the main development workings.

The thesis area lies in a narrow U-shaped valley- bounded on three sides by steep ridges. The maximum relief is 2,250 feet, and the vegetation is typical of the Arizona- Sonora. Desert at this elevation in the Basin and Range Province.

History of MiningAll previous work done in this area was prior to 1928.

It consisted of limited and generally shallow underground workings developed by means of adits, and numerous surface pits and trenches. Over fifty shipments of hand-sorted ore obtained from these old workings are reported to have been sent to smelters. Smelter liquidation sheets covering twenty- eight of these shipments gave an average grade of ore running about ten per cent of copper plus approximately 1.5 ounces of silver.

All mining was done by primitive "hand-steeling" methods. No mechanical drills were used. No extensive ex­ploration was ever done. Systematic sampling and detailed mapping of these old workings are presently hindered by the backfilling of many of the older shafts and inclines as new entries were developed.

Previous WorkPrior to 1954 little more than the results of brief

reconnaissance survey work was published regarding the Coyote

4Mountains. In 1954, Joseph G. Margo prepared a thesis en­titled Geology of a Portion of the Covote-Quinlan Complex. This was followed a year later by William L. Kurtz*5 Geology of a Portion of the Coyote Mountains. The two maps were con­structed so as to fit together giving a complete geologic map of all the Coyote Mountains and a portion of the Quinlan Mountains, a total of more than forty square miles. The scale of these maps is approximately four inches to the mile. Both theses deal primarily with the internal structures of the granitic rocks and aid very little in an economic study.

' In 1966, Consolidated Red Poplar Minerals, Limited, a Canadian mining syndicate, acquired exploration rights to this land. In late 1966, and continuing into 1967, an initial exploration program was launched. Most of the work done was promotional in nature and little was learned of the geology.

ProcedureThe accompanying surface map covers the area contain­

ing the major portion of the mineralization. A series of cross sections was prepared from the surface map. Detailed surface mapping and mapping of the underground workings re­vealed the controls of mineralization.

The drill hole data were of little use in providing new geologic information since the drilling program was de­signed to intercept ore extensions.

5A total of sixty thin sections was prepared and

studied. These sections were selected from both the surface outcrops and underground workings.

Regional SettingThe Coyote Mountains are included in the Basin and

Range Province of southern Arizona. This region is charac­terized by isolated mountains rising sharply from flat, wide­spread desert plain. Figure 2 shows that the sediments in proximity to the area studied are mainly Mesozoic and have been intruded by igneous rocks and capped by Tertiary volcanics and their clastic derivatives.

The Coyote Mountains are situated at the north end of the narrow Baboquivari Mountain range which extends in a shallow reverse S-shape chain northward for forty-five miles from the Mexican border. To the west, they are separated from the granodiorites of the Quinlan Mountains by the Pan Tak fault and, to the northeast, from the volcanics of the Roskruge Mountains by the Ajo Road fault.

The narrow mountain chain continues its erratic trend northward through the Roskruge and Waterman Mountains until it is finally lost in the Silverbell Mountains thirty miles to the north.

6

n^E^TK,e THESIS AREA

AJO ROAD FAULT

EXPLANATIONisirs Alluv ie l, flood piom. Solve, channel de p se iti;

end agg lom tro tc

iii* end we dod Tuff, minor .nTcrtotddeJ sedimenri )hde$ite flews; includes rhyv it»c d «csPAN TAK FAULT

Older conglomerate; locally grades into pMfilifs.

PeCDie conglomerete, eendstor.e ond shm-bedded

Ar.dei'ie congiomerole.

Soncstone, mudstone, tyffoceous sed-menre generally fine gre ned, t» .n bedded, some cong cmerd*e; cosui oon socon# moif include rf.yel.tic tu fts mrr jood one me tom Lr-h;, *«d lo phyli te. scr s i, one f,r< - yo.r.ed gne.ss m the Ouinio.i end Comcboo* Mown*o«.*s

Biot.re gneiss Poss-bly derived from a. juicceow i

Lime silicotes Possibly derived from rolcereoul rocks, locolly includes quortutt

Crom to d rocks ~ gron i

in Coyote Mounio-n*(oiogrommotic).

Wells; number indiceies decth of we.i and thickness of olluvum penetrored.

II QT.IComp, ed by: Chor es L Fair one W. L .K -jft i

Fig. 2. Local Index MapAdapted from Galbraith, F. W., Heindl, L. A., and

Sykes, G. G., 1959, p. 256.

CHAPTER 2

SEDIMENTARY ROCKS

GeneralThe sedimentary rocks within the Coyote Mountain study

area are marble, quartzite, gneiss, homfels and skam. They form discontinuous pods, dilated by the intruding quartz monzonite, ranging up to 600 feet in length and 300 feet in width. Although they have been subjected to contact metamor­phism, they have not been extensively metasomatized. Thus, the original character of the rock has been preserved suf­ficiently to allow inferences regarding stratigraphic relationships.

Figure 2 shows the sedimentary rocks in proximity to the Coyote Mountains to be Mesozoic and Tertiary in age. The nearest recognized Paleozoic sedimentary rocks occur eighteen miles to the southeast along the west flank of the Sierrita Mountains. They are also found in the Waterman Mountains (McClymonds, 1959a) twenty-five miles to the northeast, in the Koht Kohl Hills (McClymonds and Heindl, 1965) twenty- five miles to the north, at Union Hill (Merz, 196?) thirty miles to the north, and in the El Tiro Hills (Clarke, 1965) thirty miles to the northwest. The complex structure found in the Coyote Mountains precludes all but the most general correlation with its counterparts from other locations.

7

The sedimentary section is approximately 3,340 feet thick. These sediments were subject to pre-intrusion fault­ing or folding. This process apparently repeated the upper member of the Abrigo formation three times and what is be­lieved to be the Martin formation twice. It is impossible to speculate further on other structural deformation since cor­relation of stratigraphic relationships is questionable. Fossil remains were not recognized in the contact metamor­phosed sediments. The mineralogy of the sedimentary forma­tions is shown in Table 1 .

Precambrian System

Pinal SchistThe oldest rock unit cropping out within the thesis

area is believed to originally have been Pinal Schist. It is now a chloritic biotite gneiss. The main criteria for naming this Pinal Schist was its composition and homogeneity over a thickness ranging from two to five thousand feet.

The chloritic biotite gneiss occurs only as a few minor outcrops (Figs. 3 and 4, in pocket). It does, however, extend as far as the most easterly ridge of the Coyote Mountains. -

The gneiss is very easily weathered and only scattered exposures remain. In general, these outcrops exist only where the intruding quartz monzonite has partially engulfed it, thus protecting it from erosion.

Table 1. Mineralogy of the Sedimentary Formations

SedimentaryLithology Qu

artz

Ortho-

clase

Albite

Andesine

Labra-

dorite

Sericite

Biotite

Pinal Schistchloritic biotite gneiss 20 15 44Lower & Middle Abrigor.arbleized limestonequartzite 75hornblende gneiss 54 30 5banded homfels 55homfels 5 50 5Upper Abrigoaltered quartzite 35 10Martin Formationhornblende gneiss 10 15 19 5 1marbleized limestonemarbleized limestoneUndifferentiated Paleozoicbiotite gneiss 10 20 . 15 30tremolitized limestone 15pyroxenite 5 3 3

O r> oO 5 i O

5o 3 o1 *3 i d i ©l TJ U e o o to O eH o o Q *3 o 43E g o

r—( 3 d 8 5 OH 3 a,5 5 5 E pu <y

3d AS i 6 5S 3 u H d a, H O d •o L, =2 S 3 XU O H O u w O O N o CO H H O a,

20 tr 1

10 40 5 30 5 101- 4 20 tr

1015 10 20

1

tr 40tr

20 3530 5 94 10 5

83 5 110 5 1 1

25 tr tr tr55 2 3 25

5 2

Composition expressed in percentages

Apatiti

10The foliation trends N. 27°W. dips 44°SV/-. The over-

lying sediments generally strike N.24°W. and dip 44°SV/.In hand specimen (Fig. 5) the rock is a friable,

moderately foliated biotite gneiss. Microscopic examination, however, reveals an overall texture of lepidoblastic biotite and chlorite within an equant, hypidiomorphic groundmass com­posed essentially of orthoclase and albite.

Cambrian SystemAbrigo Formation

The Abrigo formation is in fault contact with the Pinal Schist. The Bolsa quartzite has been removed by fault­ing. The sedimentary sequence in contact with the chloritic biotite gneiss consists of marbleized limestone, homfels and quartzite. This is not Bolsa lithology but is more charac­teristic of the lower portion of the Abrigo formation.

In this report the Abrigo has been divided into two units; the upper member and a middle and lower member.

The nearest known exposure of the Abrigo formation is in the Waterman Mountains. McClymonds (1957, p . 145- 151) divided this section into three members. The lowest member is 275 feet of alternating, thin beds of lime silt- stones, shales, and calcareous sandstones. Above the lowest member is a 262-foot section of limestone, and above the limestone lies the upper member of 171 feet of thin-bedded alternating limy marls and siltstones. Similarly, in the

11

Fig. 5. Pinal Schist(A) Texture, (B) Pinal Schist cut by lamprophyre

dike

12northern Waterman Mountains, Ruff (1951, p. 16-23) reports 288

feet of thin-bedded, alternating limy shales and sandstones as a basal member, overlain by 239 feet of limestone, which, in turn, is overlain by 104 feet of alternating, thin-bedded limy sandstones, shales and limestones.

In the Coyote Mountains it is not possible to differen­tiate between the lower and middle members. This unit consists primarily of marbleized limestone and homfels in its upper part while quartzites (some metamorphosed to gneiss) and horn- fels along with minor marbleized limestone constitute the basal portion. The thickness of the combined units is 586 feet.

The distinctive, differentially weathered, upper Abrigo is 279 feet thick above its contact with the middle Abrigo. Figure 6 shows the sharpness of this contact.

The upper Abrigo at this location is a quartzite with calcareous layers. Thin section studies show that the cal­careous laminae have been metamorphosed to diopside and garnet.

According to Dr. D. L. Bryant (personal communication, December, 1970) only the upper Abrigo weathers to the distinct texture shown in Figures 7 and 8 . This is an important fact since the unit is repeated twice without any evidence of faulting or folding.

Total thickness of the Abrigo in the Coyote Mountains is 865 feet, at Silverbell 420 feet (Merz, 1967, p. 27), whereas in the Waterman Mountains the Abrigo is reported

13

Fig. 6. Contact between Middle andUpper Members of the Abrigo Formation

14

Fig. 7 Upper Member of the Abrigo Formation

Fig. 8. Bedding in the Upper Abrigo Member

16to be 708 feet thick (McClymonds, 1957, p. 15-22) and 631

feet thick (Ruff, 1951, p. 16-23)•

AreaUpper Abrigo

MemberMiddle Abrigo

MemberLower Abrigo

MemberCentralWatermanMountains

171* marls and siltstones

262* limestone 275' thin- bedded limy sandstones and shales

NorthWatermanMountains

1041 limyshales,sandstones

239* limestone 288* limy shales and sandstones

UnionHillVicinity

100*+ of metas edimentary limy rocks

1 2* limestone 200*(?) .thin- bedded hom- fels

CoyoteMountains

279* quartzite with stringers of diopside and garnet

586* marble, quartzite and hornfels

Despite insufficient evidence to make an absolute cor­relation, it is felt that the distinctive texture of the upper member, coupled with similar lithologies and thicknesses, makes a tentative correlation with the Abrigo formation plausible.

Devonian System

Martin FormationThe Martin formation of Late Devonian age overlies

the Abrigo disconformably (Fig. 9)• Although the time lapse between the deposition of the Abrigo and Martin represents the Ordovician, Silurian, and early part of the Devonian

Fig. 9. Contact between the Martin and Abrigo Formations

periods, the contact between the two formations appears to be almost gradational.

The identification of the Martin was based upon two criteria. The first is the lithology of the metamorphosed Martin formation. The second, less indicative, is the rela­tionship of the Martin to the more readily identified, under­lying upper member of the Abrigo formation.

The nearest outcrop of recognized Martin formation is in the Waterman Mountains twenty-five miles to the northeast. Here it is 364 to 3&5 feet thick as compared to 685 feet in the Coyote Mountains (McClymonds, 1959a, p. 71)• The Martin is present at Silverbell, although Merz (1967, p. 29) does not give a thickness. The unusual thickness in the Coyote Mountains can be attributed probably to repetition of the bedding. Wilson (1962, p. 29), however, lists thicknesses for the Martin ranging from 200 to 615 feet throughout southern Arizona.

The Martin in this locale is a marbleized dolomitic limestone (Fig. 10) whose lower half is laced with beds of hornblende gneiss up to three feet thick. The hornblende gneiss appears to be the metamorphosed equivalent of a shale interbedded with the limestone.

Although massive and resistant to weathering, the Martin is subdued in topographic expression. The bedding ranges from six inches to two feet in thickness. The light- to-dark gray, coarse-grained, equigranular Martin varies

19

Fig. 10 Martin Formation

20from limestone to dolomitic limestone to dolomite. It weathers from a yellowish to a chocolate brown color.

In the western section of the thesis area, the Martin is repeated. There it is again sandwiched between two seg­ments of the upper member of the Abrigo formation.

Undifferentiated Paleozoic (?)In the western portion of the thesis area above the

third and final repetition of the upper Abrigo lie three unidentified lithologic units.

The lower unit consists of 243 feet of biotite gneiss. As illustrated in Figures 3 and 4 (in pocket), this unit is highly discontinuous. Individual blocks have been randomly scattered by the intruding magma. The thickness given should be regarded as a very rough approximation.

Close to its contact with the Abrigo, the gneiss (Fig. 11), because of its very fine-grained, poorly-foliated texture, has a salt-and-pepper appearance. Here, the rock weathers easily and outcrops are scarce and poorly defined. Higher in the section the laminations become more distinct and the rock coarser-grained. The light tan-to-gray outcrops are better defined but still have a sandy, granular texture. Approximately forty-five to seventy per cent of the gneiss is composed of orthoclase, andesine, and quartz, the remainder being two-thirds biotite and one-third actinolite. The lepidoblastic biotite and actinolite are set in a mylonitic

21

Fig. 11. Biotite Actinolite Gneiss Member of the Undifferentiated Paleozoic (?) Section

22groundmass of quartz and feldspar. Perhaps originally this rock was an argillaceous sandstone or quartzite.

A white limestone (Fig. 12) weathered to a gray color, with a distinctively pitted surface, overlies the friable biotite gneiss. Individual pits may be up to 1.5 inches deep and three inches long.

The fresh crystalline limestone is creamy white with a pale green cast. The pale green color is a result of the metamorphic process changing the calcite to tremolite and diopside.

The general texture, as viewed through a microscope, is one of aligned, equant, xenoblastic grains of tremolite and granoblastic grains of diopside cut by veinlets of sericite.

The limestone is 205 feet thick. A bed of altered quartzite is found midway through the section. It has been highly silicified and converted to epidote and garnet.

In discussing the correlation of both the gneiss and limestones with Drs. S. R. Titley and D. L. Bryant, it was sug­gested they be designated as undifferentiated Paleozoic (?).The distinctive texture of the limestone does not provide the key to identity but appears to be a result of the metamorphism rather than an original feature of the rock (Dr. D. L. Bryant, personal communication, December, 1970).

A body of pyroxenite (Fig. 13) is found in the north­west and northern portions of the thesis area. It is composed

23

24

Fig. 13• Pyroxenite Member of the Undifferentiated Paleozoic (?) Section

25predominantly of coarse (1-2 cm), equant, augite crystals (Table 1 ; Fig. 14)• Although massive and resistant to weathering, the pyroxenite is subdued in topographic ex­pression. Outcrops occur as large (up to 150 x 400 feet), discontinuous masses. No bedding is apparent.

The contact between the quartz monzonite and the pyroxenite is illustrated in Figure 15. The contact is sharp, no baking was noted, no inclusions of pyroxenite were found in the intrusion nor intrusive rock within the pyroxenite.

The pyroxenite, where present, is always found above the third repetition of the upper member of the Abrigo forma­tion. The long axis of the pyroxenite trend parallels the general strike of the sedimentary pendant. It never cuts the sediments in the manner of a dike.

Dr. W. C. Lacy (personal communication, January, 1971) advanced the idea that the pyroxenite originally was a sedi­ment whose chemistry enabled it to react radically when metamorphosed. He felt that the pyroxenite originally might have been a member of the Naco group, specifically the Earp formation.

Its relationship to both the quartz monzonite as well as the sedimentary pendant is indicative of a sedimentary origin for the pyroxenite. There is no field evidence sub­stantiating a wholly igneous origin for this rock.

26

Fig. 14. Pyroxenite Texture A quarter is used for size comparison

27

Fig. 15. Contact between the Pyroxenite and the Quartz Monzonite

CHAPTER 3

IGNEOUS ROCKS

GeneralFour igneous rock types are recognized within the

confines of the area studied. The oldest, classified in the field as a quartz monzonite, was emplaced during the Laramide Revolution (Wilson, Moore, O'Haire, I960). Thin section examination revealed the intrusive rock in the central portion of the mapped area to be granite. Since it was not possible to distinguish between the two, this igneous rock will be referred to by its field classifica­tion, quartz monzonite. Associated with and related to the quartz monzonite are many narrow pegmatite dikes. The youngest intrusive activity is evidenced by a few north- striking lamprophyre dikes.

Quartz MonzoniteThe block of sediments previously discussed appears

to be a roof pendant into the quartz monzonite. It is assumed that the intrusion was emplaced as part of the large plutons of granitic rock which now form the Baboquivari Mountains. On the basis of the small area mapped, it is notpossible to speculate on the original form of the intrusive rock.

29The quartz monzonite has a highly variable texture

with some variations noted in composition. Thirteen thin sections of the quartz monzonite were prepared from surfaceoutcrops. Table 2 gives a specific analysis of the thin sections and Figures 3 and 16 (in pocket) shows the location of the sample sites.

Texturally, the quartz monzonite ranges from aplitic to pegmatitic. The rock is primarily pegmatitic with crystals averaging 3 cm in diameter. The change from aplitic to pegmatitic texture cannot be mapped since there appears to be no definable relationship explaining why the texture is in one place very fine and a few feet away extremely coarse.The mineralogic composition in either textural extreme re­mains the same.

In general, the pegmatitic quartz monzonite is white, weathering to a light gray and forming massive, highly resistant outcrops.

In hand specimen the most distinguishing aspect of the quartz monzonite is the complete absence of mafic minerals. This is a primary feature since hydrothermal alteration has not taken place.

Although the intrusion dilated the sediments, rarely has an igneous dike pierced a sedimentary bed. More commonly,the quartz monzonite maintains very sharp contacts with the sedimentary pods.

Table 2. Mineralogy of the Igneous Rocks

Igneous Rocks

N

ncy

0)CO3oOuo

CDCOctfrHOO•H

!a.

CD•P•H

<D•SCO0)3

<DP•HO3aco

CDp•HPo•HPQ

CDP•HPcda,

CDp•H

(DTj•HCOAO•HQ

P0)

5

CDP•H3OrHO

CDP•HP<DI

Intrusivequartz monzonite 45 40 15 tr trquartz monzonite 55 15 30 tr trquartz monzonite 50 15 28 5 1 1quartz monzonite 35 40 20 1 tr 4 trgranite 28 60 10 tr tr 2quartz monzonite 189 10 10 tr tr 1granite 25 57 15 1 1 1 trgranite 44 45 10 tr tr tr 1quartz monzonite 35 35 25 5 trquartz monzonite 29 45 25 tr 1quartz monzonite 55 20 20 1 3 trgranite 28 60 10 tr tr 2granite 50 40 10 tr tr tr tr

Pegmatite 40 45 5 10Lamprophyre 5 10 27 tr 20 7

11

1 30

Composition expressed in percentages.

Hema

tite

31Pegmatite Dikes

Swarms of pegmatite dikes occur in the southeast portion of the thesis area. These dikes occur only in the intrusive and do not cut the sediments or the later lamprophyre dikes. .

The pegmatites are white and stand out in marked con­trast to the host rock (Figs. 17 and IS). The grain size ranges from 1 to 5 cm. The mineralogy of the pegmatite is simple and similar to that of the granite (Table 2). Intergrowths of orthoclase and plagioclase (perthite) and of orthoclase and quartz (graphic intergrowth) are common.

The pegmatite-quartz monzonite contacts show no de­formation. The contact is gradational with the host rock being incorporated into the pegmatite. There is no zoning.

On the basis of similar mineralogy, textural relationships, and general field relations, the author be­lieves that the pegmatite dikes were a late segregation from the intrusive.

Lamprophyre DikesThe most recent period of intrusive action is

responsible for the emplacement of lamprophyre dikes.The lamprophyres are dark to light green and have an

aphanitic texture. In thin section, the rock has an overall lepidoblastic texture formed by tabular plagioclase with intergranular occurrences of chlorite and quartz. The

32

Fig. 17. Pegmatite Dike Swarms in the Quartz Monzonite

33

Fig. 18. Contact between a Pegmatite Dike and the Quartz MonzoniteA 6-inch scale is used for comparison

plagioclase has been extensively altered (probably by weather­ing) to kaolinite.

These dikes occur in both the intrusive complex (Fig. 19) and the sedimentary pendant with widths varying from a few to ten feet. They are passive intrusions occur­ring along possible fault planes. The host rock shows no evidence of deformation by the lamprophyres. They are highly discontinuous, pinching and swelling at random but always trending in a north-south direction while maintaining a near­vertical dip.

34

35

CHAPTER 4

STRUCTURE

GeneralThe structural history of this portion of the

Coyote Mountains is complicated. This fact is not notice­able upon preliminary examination but becomes apparent when the stratigraphy is examined in detail.

Generally, this area contains large blocks of dis­continuous sedimentary rock constituting a pendant into a quartz monzonite stock (Fig. 20).

Mo post-intrusion folding was noted.Post-intrusion faulting is inferred by the presence

of lamprophyre dikes. These dikes, present in both the igneous and sedimentary rocks, appear to follow fault planes.

Sedimentary RocksWithin the region covered by this thesis sedimentary

rocks occur over a length of 4,600 feet. The trend of the long axis of the sediments is M.24°W. The thickness of the section is highly variable. Total thickness of sediment present, excluding what is believed to be Pinal Schist, is 3,33^ feet. These rocks as mapped by Kurtz (1955) extend '

36

Fig. 20. Upper Abrigo Member Pendant into Laramide Quartz Monzonite

36approximately three-quarters of a mile further north of the area under discussion.

The pendant occurs as discontinuous pods of varying size separated by forcefully intruded quartz monzonite. The discontinuity of the pods is due to the dilation of the sedi­mentary rocks by the intruding igneous mass and to the fact that this may be the remaining portions of a once larger sedimentary block.

Throughout its length the pendant strikes N.24°W. while dipping 44°SWe This indicates that while the quartz monzonite forced itself into the sedimentary mass, dilating individual blocks, the entire process occurred in a stress field great enough to insure a consistent strike and dip.

According to Dr. D. L. Bryant (personal communication, December, 1970), the upper member of the Abrigo formation is the only lithology that weathers i'n the manner shown in Figure 7« This distinctive unit is repeated twice, each time separated by what is thought to be Martin formation.The consistency of the strikes and dips (Figs. 21 and 22), the distinctive Abrigo lithology and the cross sections (Figs. 3, 23, and 24, in pocket) give credence to the idea of repeated faulting or possible very tight folding prior to intrusion. There is no other way to account for the recurrence of both the Abrigo and Martin formations.

Other events prior to intrusion are subject to specula tion, and field evidence does not justify further postulations

Fig. 21. Schmidt Plot of Bedding within the Sedi­mentary Pendant

The sedimentary rocks exhibit a consistent strike of N.24°W* and dip 44°SW.

Number of Points per 1% Area

6-11

12-17

18-23

5* 24

Based upon 171 points

39

Fig. 21. Schmidt Plot of Bedding within the Sedimentary Pendant

Fig. 22. Schmidt Plot of Foliation within the Sedimentary- Pendant

The foliation is almost identical to the sedimentary strike* and dip. Foliation strikes N.27°V/. and dips 44USVZ.Number of Points per 1% Area

1

2

Based upon 17 points

40

Fig. 22. Schmidt Plot of Foliation within the Sedimentary Pendant

41Igneous Rocks

The main structural feature found in the intrusive complex is two sets of tension fractures. One set trends north-south; the other east-west. Figure 25 graphically illustrates these trends in a Schmidt plot. Some differences are noted from the general trends. These variations are due to the fact that geologic structures do not normally occur along perfectly straight lines.

According to Mayo (1942, p. 171), this type of fracture may be due to the stretching of the rigid outer shell over a rising and expanding inner magma core.

Figure 26 is an eye-level view of the north-south fracture pattern. The joint spacing shown in this picture ranges from three to five feet.

Figure 27 depicts both sets of tension breaks as seen from the air.

One of the most unusual structural features of this region is the prominent pegmatite dike swarm in the south­east comer of the thesis area. These are not found in any other portion of this area. Further to the south and west of the study area, however, they become abundant. Figure 2# looks westward and is situated about one-half mile south of the mapped area. The peak in the .far background is streaked with flat-lying pegmatite dikes. In the right foreground, the dikes dip to the east. These flat-lying pegmatite dikes, which are primary flat-lying structures, are what Balk

Fig. 25• Schmidt Plot of Igneous Fracture Pattern

Number of Points per Area

15-24

25-34

35-44

45-54

> 55

Based upon 757 points

42

Fig. 25• Schmidt Plot of Igneous Fracture Pattern

Fig. 26. Eye-level View of Igneous Fracture Pattern Looking NorthThe joint spacing ranges from 3-5 feet

Fig. 2?. Vertical Aerial Photograph of a Portion of t.h« Coyote Mountains e

Explanation

Trace of Tension Fractures

Linears

---- Area Mapped1 inch = 1,477 feet

44

Fig, 27* Vertical Aerial Photograph of a Portion of the Coyote Mountains

45

Fig. 28. Flat-lying Pegmatite DikesSouth of the thesis area looking west. Note

how the dip of the dikes has increased in the fore ground.

(1937, p. 40) calls Lager, The dikes change orientation; flat-lying westward, they dip easterly along the eastern flank of the Coyote Mountains. This raises the possibility that the eastern flank of the Coyote Mountains is at the edge of a dome.

CHAPTER 5

ALTERATION AND MINERALIZATION

In the Coyote Mountains the alteration and minerali­zation are spatially and genetically related to the intrusion of quartz monzonite.

The principal manifestation of alteration in the intrusive rocks is the development of clay and sericite at the expense of sodic feldspars. Altered igneous rock is found only in the West and Turquoise adits where it is in contact with skarn. These adits constitute the major de­velopment work and were the source of all the ore shipped. With these minor exceptions the quartz monzonite is de­void of hydrothermal alteration, silication or extensive fracturing.

The sedimentary rocks have been subject to very minor metasomatism and low-grade contact matamorphism. The term metasomatism is used here to indicate not only the introduc­tion of material from external sources, but also the almost simultaneous solution and deposition on an atomic scale. Inthe Coyote Mountains the hydrothermal alteration is asso­ciated with the contact between a favorable sedimentarylithology and the intrusion of quartz monzonite. The hydro- thermal solutions may have come directly from the intrusive or from depth with the contact acting as a channel way for

47

the introduction or removal of material. With the exceptions of the West and Turquoise adits, the intrusive rock is un­altered adjacent to altered sediments.

Occasionally, within the sedimentary rock, altered zones surrounded by unaltered rock were encountered. Often "these isolated zones appear to have no channel ways, veins or fissures leading to them to account for the introduction of hydrothermal fluids. Here, the movement of material is inferred to be along capillary or subcapillary openings. Metasomatism rather than metamorphism is proposed to account for most of the changes in the sedimentary rocks'.

The original rocks present prior to the Laramide metamorphic period were schists, quartzites, limestone, dolomite, argillaceous-dolomitic limestones and shales. These rocks are now gneisses, quartzites, marble, skara, and hom- fels.

The changes in what is believed to have been the Pinal Schist were due primarily to thermal metamorphism rather than metasomatism. The Pinal Schist exhibits minor effects of the hydrothermal alteration and contains rare occurrences of copper oxide where it is in contact with the quartz monzonite.

The quartzites in the lower and middle members of the Abrigo formation have re-crystallized and additional silica has been introduced in the form of quartz veinlets. The shales are now hornfels while the limestones have beenmarbleized

49The marbleized limestone is the only lithology to

exhibit any copper mineralization and related alteration. Epidote, garnet, and diopside form the alteration assemblage, and copper oxides reflect the mineralization. Both are re­lated to the igneous contact.

Alteration in the upper member of the Abrigo formation is confined to the calcareous layers. These have been thoroughly converted to diopside and garnet, and only minor calcite remains. The amount of garnet present is variable, but the alteration of calcite to diopside is pervasive. Only minor copper mineralization is associated with this portion of the Abrigo.

The Devonian -Martin formation is the sedimentary unit most strongly affected by metamorphism and metasomatism. The majority of copper occurrences, including the producing workings, are found in the Martin.- The development of epidote, garnet, and diopside is fairly common. The alteration is not always related to a visible igneous contact. Rocks of the undifferentiated Paleozoic (?) section have been modified to varying degrees: the biotite gneiss is unaltered, the lime­stone member has been extensively altered, garnet is abundant, calcite has been altered to tremolite, and the quartzite stringer found in the center of the limestone has been highly silicified and garnetized.

50The pyroxenite may have formed solely as a result

of contact metamorphism; however, the effects of meta­somatism upon this lithology are unknown.

Each of the sedimentary units originally composed of clean massive limestone or quartzite were only slightly affected by the intrusion of quartz monzonite. The units which were originally dolomitic, shaly or otherwise impure limy sediments were more affected by the contact meta­morphism and metasomatism.

The sedimentary strata originally composed of fairly pure limestone or quartzite have little copper mineraliza­tion, while the less .pure, more strongly metamorphosed and metasomatized units are more favorable hosts. Figures 29 through 33 show mineralization in the Main and West adits.The Lower West and Main adits both have mineralized skam zones developed between the fresh limestone and the quartz monozonite. Where present, the skarn makes a" sharp contact with the fresh limestone (Fig. 34)• The skarn rarely exceeds twenty-five feet in thickness and is highly irregular in shape. These two adits produced the major portion of the ore. In the Turquoise adit (Figs. 35 and 36), no skam zone was developed. Here the mineralizing fluids selectively replaced specific beds within the dolomitic limestone.

Metals involved in the mineralization in the Coyote Mountains are chiefly copper with minor silver, molybdeniteand zinc.

51

I N A C C E S S I B L E IN C L I N E B A C K F I L L E D

++M A S S IV E M A G N E T IT E

S T O R E D B E L O W

+ + C H R Y S O C O L L A , M A L A C H IT E ,

+ +/2M A G N E T I T E , A Z U R I T E C O N F IN E D

T O B E D D IN G IN S K A R N

S T O R E D A B O V E - S K A R N

^ + / 4 + / 4M A L A C H IT E , L IM O N I T E S T A IN O N C O N T A C T

C H A L C O C IT E + + , M A L A C H IT E ^ , C H R Y S O - 3 5+ +/4 +/2

C O L L A , A Z U R I T E , H E M A T I T E , 8 2

+ / 4M A G N E T I T E C O N F I N E D T O

B E D D IN G S U R F A C E

5 0 F E E T

___I

S T O R E D A B O V E - H O R N B L E N D E G N E S I S - V E R Y W E A K RO C K , D ID N O T E N T E R

P Y R I T E ^ C H A L C O P Y R IT E + , D IS S E M IN A T E D

IN H O R N B L E N D E G N E IS S

u \ M A L A C H I T E S T A IN IN Q U A R T Z " 5 0 V . M O N Z O N I T E

| 3 3 \ S T O R E D A B O V E - S K A R N

1™ ^ + / 4C H R Y S O C O L L A S T A IN

+/2 + / 4G A R N E T , C H L O R IT E D IS S E M IN A T E D

^ 7 T H R O U G H O U T T H E L I M E S T O N E

+ / 4C H R Y S O C O L L A ON C O N T A C T

ROAD

E X P L A N A T I O N

Q U A R T Z M O N Z O N I T E

M A R T I N L I M E S T O N E

H O R N B L E N D E G N E IS S

A L T E R A T I O N , T Y P E N O T E D

M IN E R A L IZ A T IO N , T Y P E N O T E D

S K A R N

S T O R E

V

W

I N C L I N E

* D U M P

O P E N C U T

1 W B A C K F IL L E D W O R K IN G S

- L - S T R I K E A N D DIP O F S E D IM E N T S

j o i n t

R E L A T I V E Q U A N T IT IE S OF M I N E R A L I Z A T I O N /

A L T E R A T I O N , L E A S T + / 4 , + / 2 , + , + + ,

G R E A T E S T , T R T R A C E

Fig. 29. Main Adit

O Q

52

Fig. 30. Portal— Main Adit(A) Mineralized skara, (B) Lamprophyre dike,

Unmineralized/unaltered Martin limestone, Unmineralized/unaltered quartz monzonite.

53

N

S H A F TB A C K F I L L E D

M I N E R A L I Z A T I O N C O N F I N E D TO

3 ' Z O N E A R O U N D C O N T A C T .+ +

M A L A C H I T E , C H R Y S O C O L L A ,

+ +/2 L I M O N I T E , E P I D O T E

C O N T A C T P L U N G E S N 2 0 ° W AT 5 3 °

A

*0

S H E A R IN G N E S I S L A Y E R IN

L I M E S T O N E , U N M I N E R A L I Z E D

L I M E S T O N E B E D D IN G I N D I S T I N C T NO

A T T I T U D E P O S S I B L E

E X P L A N A T I

Q U A R T Z M O N Z O N I T E

M A R T I N L I M E S T O N E

M I N E R A L I Z A T I O N , T Y P E N O T E D

0 N

B3

'\AZ>

♦x

V E R T I C A L S H A F T

S H E A R

J O I N T

R E L A T I V E Q U A N T IT IE S OF M I N E R A L I Z A T I O N /

A L T E R A T I O N , L E A S T + / 4 , + / 2 , + , + + ,

G R E A T E S T , T R T R A C E

0 5 0 F E E T

I________________ _ J

Fig. 31, West Adit— Upper Level

5/f

C H L O R I T E , G A R N E T , E P I D O T E

S E R C I T E

L I M O N I T E ^ E P I D O T E ^ C H R Y S O C O L L A + ,/ 2 M A G N E T I T eY 2 A Z U R I T E ^ 4\ 8 0

i l S E R C I T E ^ 4 S E C O N D A R Y B I O T I T E , M A G N E T I T E ^ 4

S H A F TB A C K F IL L E D

S H A F T B A C K F I L L E D

~ C H R Y S O C O L L A - , E P I D O T E ^ ^ A Z U R I T E + 2 M A G N E T ITE ^2

^ T H R O U G H O U T S K A R N

E X P L A N A T 1 0 N

Q U A R T Z M O N Z O N I T E & I N C L I N E

M A R T I N L IM E S T O N E H V E R T I C A L S H A F T

A L T E R A T I O N , T Y P E N O T E D ^ 4 ^ / D U M P

M IN E R A L IZ A T IO N , T Y P E N O T E D \ \ O P E N C U T

S K A R N < W ‘ S H E A R

R E L A T I V E Q U A N T IT IE S O F M I N E R A L IZ A T IO N /

A L T E R A T I O N , L E A S T + / 4 , + / 2 , + , + + ,

G R E A T E S T , T R T R A C E

S T R IK E A N D D IP O F S E D I M E N T S

J O I N T

0 5 0 F E E TI__________|

Fig. 32. West Adit— Main Level

55

N

S T O R E D B ELO W . A N D B A C K F IL L E D

A L L V E R T I C A L S H A F T A N D

IN C L I N E S B A C K F IL L E D

C O PP ER O X ID E STAIN

L I M 0 N I T E + / 4 ,

M A N G A N E S E O X ID E

IN A C C E S S IB L E

. 4 / 4

MAGNETITE*™!" E P ID O T E + , G A R N E T ^ 2

S T O R E D A B O V E

M A L A C H I T E * , E P I D O T E * * M A G N E T IT E

E X P L A N A T I O N

M IN E R A L IZ A T IO N , T Y P E N O T E D

Q U A R T Z

M A R T I N

S K A R N

I I S T O R E

M O N Z O N I T E

L IM E S T O N E

6 I N C L I N E

V E R T I C A L S H A F T

B B O T T O M O F S H A F T

<\A/' F A U L T

N J O I N T

R E L A T I V E Q U A N T I T I E S OF M I N E R A L I Z A T I O N /

A L T E R A T I O N , L E A S T 4 / 4 , 4 / 2 , 4 , 4 4 ,

G R E A T E S T , T R T R A C E

0 5 0 F E E T1 __________|

Fig. 33• West Adit— Incline and Lower Level

Fig. 34. Portal— West Adit— Main Level(A) Sericitized quartz monzonite, (B) Mineralized skam, (C) Unaltered/ unmineralized Martin limestone, (D) Unmineralized/unaltered quartz monzonite.

VlOn

57I N C L I N E B A C K F I L L E D

+/4C H R Y S O C O L L A , L I M O N I T E ,

.4 -/4E P I D O T E

S T O R E D A B O V E - Q U A R T Z M O N Z O N IT E H IG H L Y , B L E A C H E D , E P I D O T E ,

L I M O N I T E + / 2

C H R Y S O C O L L A

C O N T A C T N 5 5 ° E , 4 0 ° N W ; H IG H L Y

F R A C T U R E D , B L E A C H E D ; L IM O N IT E

H IG H F R A C T U R E D , A R G I L L I C A L L Y A L T E R E D+/2

Q U A R T Z M O N Z O N I T E . M A L A C H I T E

C H R Y S O C O L L A + f 2 H E M A T I T E ^ 2 C O N F IN E D

TO F R A C T U R E S

+ + +/2 C H A L C O C I T E , H E M A T I T E , C H R Y S O C O L L A ,

+ / 4E P I D O T E , z B E D D I N G C O N T R O L L E D

S T O R E D A B O V E

S T O R E D A B O V E W IT H V E R T I C A L S H A F T T O S U R F A C EC H A L C O C I T E ^ C O N F I N E D TO B E D D IN G

IN S T O R E

R OAD + + ^I \ H E M A T I T E , C H A L C O C IT E

R O A DB E D D IN G C O N T R O L E D

5 0 F E E T

___IE X P L A N A T I O N

Q U A R T Z M O N Z O N I T E

M A R T I N L IM E S T O N E

A L T E R A T IO N ,T Y P E N O T E D

M IN E R A L IZ A T IO N , T Y P E N O T E D

6 I N C L I N E

0 F O O T O F V E R T I C A L S H A F T

XXD U M P

O P E N C U T

,--------»------- , S T O R E

R E L A T I V E Q U A N T I T I E S OF M I N E R A L I Z A T I O N /

A L T E R A T I O N , L E A S T + / 4 , + / 2 , + , + + ,

G R E A T E S T , T R T R A C E

S T R I K E A N D D IP O F S E D IM E N T S

J O I N T

Fig. 35 Turquoise Adit

w yB

eep -7 B

' '5< i J

Fig. 36. Portal— Turquoise Adit(A) Argillically altered quartz monzonite, (B) Mineralized

zone, (C) Unmineralized/unaltered Martin limestone.

vn00-

59Mineralization is associated with the igneous­

sedimentary interface (Figs. 3 and 37, in pocket) and the intrusive rock is felt to be the source of this mineraliza­tion. Nevertheless, the quartz monzonite exhibits only rare occurrences of oxide copper stain and is devoid of sulfide mineralization.

Pyrite, chalcopyrite, bornite, covellite, and chal-' cocite were the only sulfides observed from underground workings. On the surface these sulfides have been altered to chrysocolla, malachite, azurite, and hematite.

In thin section, the ore sulfides appear to be associated with the metamorphic assemblage occurring to a greater extent in silicated zones. They are generally found at grain boundaries, or cavities in garnets, and have re­placed the adjacent silicates. The replacement of the silicates indicates a metasomatic process for the minerali­zation as well as the alteration.

Economic interest in the Coyote Mountains was based upon expectation of mining by nonselective bulk methods. It has been postulated that the quartz monzonite is the source of mineralization and that the selective replacement of silicated rock formed the pods of high-grade ore.

The intrusive rock, however, exhibits no pervasive al­teration, sulfide mineralization or intense fracturing, charac­teristics normally associated with porphyry deposits. The

limited amount of metallization (Figs. 3, 37, 38 /In pocket/, and Appendix I) and the absence of alteration result from deficiencies in the parent magma. The mineralizing fluids present reacted with the sedimentary pendant along contactsor selectively replaced zones of silicated limestone.

60

CHAPTER 6

SUMMARY

The geology of the Coyote Mountains involves a series of contact metamorphosed, weakly metasomatized blocks of Paleozoic sedimentary rocks.

Within the study area are four major stratigraphic units: the PreCambrian Pinal Schist, the Cambrian Abrigoformation, the Devonian'Martin formation, and a sequence of undifferentiated Paleozoic rocks. These have been intruded by a Laramide pegmatitic quartz monzonite.

Scattered oxide copper mineralization is found throughout the area. Most mineralization occurs along the sedimentary-igneous interface. High-grade ore zones were developed in selectively replaced skam zones within the Martin formation. These are of limited size and irregular in nature.

The Laramide intrusion exhibits no pervasive alter­ation, sulfide mineralization or fracturing. The intrusion is considered to be the source of mineralization. The lack of alteration/mineralization is attributed to the nature of the parent magma.

The sedimentary units, composed predominantly of massive monomineralic rock, limestone, quartzite, or shale,

61

were affected only slightly by metamorphism or mineralization. The favorable host strata are those units with varied composi­tion, such as the Martin formation,' a series of alternating dolomites, limestones, limy shales, and argillaceous lime­stones.

Because of limited mineralization or indications of hydrothermal activity within the quartz monzonite, the area appears to be of little economic interest.

62

APPENDIX I GEOCHEMICAL DATA

63

64Table 3• Results of Geochemical Stream Sediment SurveySampleNumber

Copper(in narts oer million)

Molybdenum(in parts per million)

SS- 1 90 3SS- 2 135 2

SS- 3 70 1

SS— if 135 1

ICOco 220 2

SS— 6 85 -

SS- 7 75 1

SS— 8 420 3SS- 9 130 1

SS-10 110 2

SS-11 320 1

SS-12 140 2

SS-13 650 1

SS—14 4,000 7ss-15 3,000 4SS-16 500 2

ss-17 100 2

ss-ia 90 1

s s -1 9 80 1

ss-21 440 1

ss-22 105 -1

ss-23 85 -1

ss-24 440 -1

65Table 3-SampleNumberSS-25SS-26

SS-27SS-28

SS-29SS-30SS-31SS-32SS-33SS-34

SS-35SS-36

SS-37

SS-3S

-ContinuedCopper Molybdenum

(in parts per million) (in parts per million)6060

34027020090210150403535354040

-1-1112112

-1-1-111

-1

SELECTED BIBLIOGRAPHY

Balk, Robert, 1937• Structural behavior of igneous rocks: Geol. Soc. America, Mem. 5, 177 p.

Clarke, Craig W., 1965. The geology of the El Tiro Hills, west Silverbell Mountains, Pima County, Arizona: unpublished Master's thesis. University of Arizona,51 p.

Darke, Kenneth H., 1968. Summary report on the CoyoteMountain property, Pima County, Arizona: privatereport to Consolidated Red Poolar Minerals, Ltd.,17 p.

Galbraith, F. V/., Heindl, L. A., and Sykes, G. G., 1959*Volcanic craters of the Pinacate Mountains, Sonora, Mexico, trip VI, road log, in Arizona Geological Society. Guidebook II, p. 253-270.

Hogue, V/. G., 1940. Geology of the northern part of theSlate Mountains, Pinal County, Arizona: unpublishedMaster's thesis, University of Arizona, 43 p.

Jenney, C. P., 1968. Evaluation of the Coyote Mountainproperty, Pima County, Arizona: private report toConsolidated Red Poplar Minerals, Ltd., 14 p.

Krieger, Medora H., 1968. Stratigraphic relations of theTroy Quartzite (Younger PreCambrian) and the Cambrian formations in southeastern Arizona, in Titley, S. R. (ed.): Southern Arizona Guidebook III: ArizonaGeological Society, p. 23-43•

Kurtz, William L., 1955* Geology of a portion of the Coyote Mountains, Pima County, Arizona: unpublishedMaster's thesis, University of Arizona, 62 p.

Mayo, Evans B., 1942. Structures associated with igneousintrusion, in Nevin, C. M. (3d.), Structural geology: New York, John Wiley and Sons, p. 164-185.

McClymonds, Neal E., 1957• The stratigraphy and structure of the Waterman Mountains, Pima County, Arizona: un­published Master's thesis. University of Arizona,157 p.

66

67________, 1959a. Paleozoic stratigraphy of the Waterman

Mountains, Pima County, Arizona, .in Arizona Geological Society, Guidebook II: p. 66-76.

________, 1959b. Precambrian and Paleozoic sedimentary rockson the Papago Indian Reservation, Arizona, in Arizona Geological Society, Guidebook II, p. 77-84.

________, and Heindl, L. A., 1965. Stratigraphic sections ofyounger Precambrian and Paleozoic formations, Papago Indian Reservation, Arizona: U.S. Geol. Survey,Tucson, Arizona, open file report, 10.p.

Merz, Joy J., 1967• The geology of the Union Hill area, Pima County, Arizona: unpublished Master’s thesis, Uni­versity of Arizona, 58 p.

Ransome, Frederick Leslie, 1903. Geology of the Globe copper district, Arizona: U.S. Geol. Survey Prof. Paper 1*2,168 p.

_______ , 1916. Some Paleozoic sections in Arizona and theircorrelation: U.S. Geol. Survey Prof. Paper 98-K,p. 133-166.

Ruff, Arthur V/., 1951• The geology and ore deposits of theIndiana Mine area, Pima County, Arizona: unpublishedMaster’s thesis, University of Arizona, 64 p.

Shride, A. F., 1961. Some aspects of younger Precambrian geology in southern Arizona: unpublished Doctoralthesis, University of Arizona, 234 p.

Stoyanovj, A. A., 1936. Correlation of Arizona Paleozoic formations: Geol. Soc. America Bull., vol. 37,p. 459-540.

Wargo, Joseph G., 1954* Geology of a portion of the Coyote- Quinlan complex, Pima County, Arizona: unpublishedMaster’s thesis, Univeristy of Arizona, 67 p.

Wilson, E. D., Moore, R. T., and O ’Haire, R. T., I960.Geologic map of Pima and Santa Cruz Counties,Arizona: Arizona Bur. Mines.

Wilson, Eldred D., 1962. A resume of the geology of Arizona: Arizona Bur. Mines Bull. 171, 140 p.

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FIGURE 24. GEOLOGIC SECTIONS OF THE NORTHERN PORTION OF THE COYOTE MOUNTAINS.CARRIGAN, GEOLOGICAL

THESIS, 197 1ENGINEERING

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FIGURE 38. GEOCHEMICAL STREAM SEDIMENT SITES AND RESULTS.CARRIGAN, GEOLOGICAL ENGINEERING

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I I NCH = 100 F E E T

CONTOUR I N T E R V A L , 10 F E E T ; D A T U M IS M E A N SEA L E V E L

FIGURE 3. GEOLOGIC EXPLANATION.CARRIGAN, GEOLOGICAL

THESIS, • 1971ENGINEERING

6973 (