U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2019–5077

Geochemical and Mineralogical Study of the Red Mountain 

Porphyry Copper-Molybdenum Deposit and Vicinity, 

Santa Cruz County, Arizona
Cover. Red Mountain as viewed from the south. The white cliffs near the top of the 

mountain are exposures of the altered rhyolite tuff formation. The andesite formation 

comprises all of the area below the cliffs.
Geochemical and Mineralogical 

Study of the Red Mountain Porphyry 

Copper-Molybdenum Deposit and Vicinity, 

Santa Cruz County, Arizona

By Maurice A. Chaffee

Scientific Investigations Report 2019–5077

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Suggested citation:

Chaffee, M.A., 2020, Geochemical and mineralogical study of the Red Mountain porphyry copper-molybdenum

deposit and vicinity, Santa Cruz County, Arizona: U.S. Geological Survey Scientific Investigations Report

2019–5077, 164 p., https://doi.org/10.3133/sir20195077.

Associated data for this publication:

Horton, J.D., San Juan, C.A., and Chaffee, M.A., 2020, Data to accompany U.S. Geological Survey Scientific 

Investigations Report 2019–5077—Geochemical and mineralogical study of the Red Mountain porphyry

copper-molybdenum deposit and vicinity, Santa Cruz County, Arizona: U.S. Geological Survey data release,

https://doi.org/10.5066/P9BS56JZ.

ISSN 2328-0328
iii

Acknowledgments

This report could not have been completed without the help of many individuals. W.P. Leedy and 

J.J. Quinlan, while employed by the Kerr McGee Corporation, offered helpful ideas, support, 

and encouragement during the early phases of this investigation. Many associates in the U.S. 

Geological Survey helped collect, prepare, and (or) analyze the samples collected for this study. 

They include R.J. Fairfield, D.L. Fey, R.H. Hill, H.D. King, L.S. Laudon, H.M. Nakagawa, J.C. Negri, 

R.F. Sanzolone, J.D. Sharkey, S.J. Sutley, F.W. Tippitt, and E.P. Welsch. Commercial analyses 

were determined for the U.S. Geological Survey by ActLabs of Ancaster, Ontario, Canada. 

Reviews of earlier versions of this report by K.D. Kelley and P.G. Vikre were very helpful in 

improving this final version.
iv

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................3

Location and Geologic Setting ....................................................................................................................4

Part A—Subsurface Geochemical and Mineralogical Studies of Core Sampling, Preparation, 

and Chemical Analysis of Core ......................................................................................................8

Mineralogical Analysis .................................................................................................................................9

Results and Evaluation of the Core Analyses ...........................................................................................9

R-Mode Factor Analysis .............................................................................................................................12

Distributions of Elements and Minerals in the Subsurface ..................................................................16

Mainly Hypogene Sulfide-Related Elements and Minerals.........................................................16

Mainly Lithology- and Alteration-Related Elements and Minerals ............................................34

Part B—Surface Geochemical Studies of Rock, Soil, and Vegetation...............................................57

Sampling, Preparation, and Analysis .......................................................................................................57

Results and Evaluation of the Rock Chemistry .......................................................................................59

Results and Evaluation of the Soil Chemistry..........................................................................................59

Results and Evaluation of the Vegetation Chemistry .............................................................................59

Distributions of Selected Elements in Rock and Soil Samples ............................................................70

Distribution of Percent Ash and Selected Elements in Vegetation Samples...................................109

Applications of Geochemical and Mineralogical Analyses to Geologic Mapping, 

Mineral Deposit Genesis and Models, Distribution and Zoning of Elements 

and Minerals, Exploration for Mineral Deposits, and Environmental Investigations .......154

Core.....................................................................................................................................................154

Rock and Soil.....................................................................................................................................156

Vegetation ..........................................................................................................................................156

Conclusions.................................................................................................................................................158

References Cited........................................................................................................................................159

Figures

1. Map showing location of the study area, near Patagonia, 

Santa Cruz County, Arizona.........................................................................................................2

2. Geologic map of the study area showing locations of the geologic section shown in 

figure 3 and sites for samples of rock, soil, and plants ..........................................................5

3. Geologic cross section showing locations of seven drill holes ...........................................6

4. A, Photograph of exposures of altered Gringo Gulch Volcanics, which are correlated 

with the rhyolite tuff formation on top of Red Mountain. B, Photograph of Red Mountain 

as viewed from the south. C, Photograph of the study area as viewed from the west 

with Red Mountain in the background. D, Photograph of exposures of the altered 

andesite formation overlain with indurated Tertiary gravel containing extensive 

manganese oxide cement...........................................................................................................7

5–39. Cross sections of:

5. Distributions of copper, chalcopyrite, and chalcocite in core samples...................13

6. Distribution of silver in core samples.............................................................................18
v

7. Distribution of total sulfur in core samples ...................................................................19

8. Distributions of sulfate sulfur, anhydrite, and alunite in core samples ....................20

9. Distribution of tellurium in core samples.......................................................................21

10. Distribution of molybdenum in core samples................................................................23

11. Distribution of gold in core samples...............................................................................24

12. Distribution of arsenic in core samples.........................................................................25

13. Distribution of antimony in core samples......................................................................26

14. Distribution of mercury in core samples........................................................................27

15. Distribution of lead in core samples...............................................................................29

16. Distribution of zinc in core samples ...............................................................................30

17. Distribution of bismuth in core samples ........................................................................31

18. Distribution of tin in core samples..................................................................................32

19. Distribution of tungsten in core samples.......................................................................33

20. Distribution of potassium in core samples....................................................................35

21. Distribution of thallium in core samples ........................................................................36

22. Distribution of orthoclase in core samples ...................................................................37

23. Distribution of kaolinite and other clay minerals in core samples............................38

24. Distribution of pyrophyllite in core samples..................................................................39

25. Distributions of magnetite and biotite in core samples ..............................................40

26. Distribution of cobalt in core samples ...........................................................................42

27. Distribution of pyrite in core samples ............................................................................43

28. Distribution of hematite in core samples.......................................................................44

29. Distributions of calcium and calcite in core samples .................................................45

30. Distribution of calcite in core samples ..........................................................................46

31. Distribution of sodium in core samples..........................................................................47

32. Distribution of plagioclase in core samples..................................................................48

33. Distribution of manganese in core samples..................................................................49

34. Distribution of boron in core samples............................................................................51

35. Distribution of uranium in core samples........................................................................52

36. Distribution of magnesium in core samples..................................................................53

37. Distribution of chlorite in core samples.........................................................................54

38. Distribution of quartz in core samples ...........................................................................55

39. Distribution of muscovite (sericite) in core samples...................................................56

40. Photographs showing A, Mesquite (Prosopis juliflora) tree. 

B, Oak (Quercus spp.) trees. C, Oneseed juniper (Juniperus monosperma) tree............58

41–119. Maps showing:

41. Sample locations, and the outer limit of intense, visible alteration in outcrops.....71

42. Distribution of copper in rock samples..........................................................................72

43. Distribution of copper in soil samples............................................................................73

44. Distribution of iron in rock samples................................................................................74

45. Distribution of iron in soil samples..................................................................................75

46. Distribution of molybdenum in rock samples................................................................76

47. Distribution of molybdenum in soil samples..................................................................77

48. Distribution of silver in rock samples.............................................................................78

49. Distribution of silver in soil samples...............................................................................79

50. Distribution of arsenic in rock samples .........................................................................80
vi

51. Distribution of arsenic in soil samples...........................................................................81

52. Distribution of antimony in rock samples ......................................................................82

53. Distribution of antimony in soil samples........................................................................83

54. Distribution of bismuth in rock samples.........................................................................84

55. Distribution of bismuth in soil samples ..........................................................................85

56. Distribution of thallium in rock samples.........................................................................86

57. Distribution of thallium in soil samples ..........................................................................87

58. Distribution of lead in rock samples...............................................................................88

59. Distribution of lead in soil samples.................................................................................89

60. Distribution of tellurium in rock samples.......................................................................90

61. Distribution of tellurium in soil samples.........................................................................91

62. Distribution of zinc in rock samples................................................................................92

63. Distribution of zinc in soil samples .................................................................................93

64. Distribution of cadmium in rock samples ......................................................................94

65. Distribution of cadmium in soil samples........................................................................95

66. Distribution of cobalt in rock samples............................................................................96

67. Distribution of cobalt in soil samples .............................................................................97

68. Distribution of manganese in rock samples..................................................................98

69. Distribution of manganese in soil samples....................................................................99

70. Distribution of calcium in rock samples.......................................................................100

71. Distribution of calcium in soil samples ........................................................................101

72. Distribution of magnesium in rock samples................................................................102

73. Distribution of magnesium in soil samples..................................................................103

74. Distribution of sodium in rock samples........................................................................104

75. Distribution of sodium in soil samples..........................................................................105

76. Distribution of potassium in rock samples ..................................................................106

77. Distribution of potassium in soil samples....................................................................107

78. Distribution of percent ash in mesquite samples.......................................................110

79. Distribution of percent ash in oak samples.................................................................111

80. Distribution of percent ash in juniper samples...........................................................112

81. Distribution of copper in oak ash..................................................................................113

82. Distribution of copper in mesquite ash........................................................................114

83. Distribution of copper in juniper ash............................................................................115

84. Distribution of molybdenum in mesquite ash..............................................................116

85. Distribution of molybdenum in oak ash........................................................................117

86. Distribution of molybdenum in juniper ash..................................................................118

87. Distribution of silver in mesquite ash...........................................................................119

88. Distribution of silver in oak ash.....................................................................................120

89. Distribution of silver in juniper ash...............................................................................121

90. Distribution of arsenic in mesquite ash .......................................................................123

91. Distribution of antimony in mesquite ash ....................................................................124

92. Distribution of bismuth in mesquite ash.......................................................................125

93. Distribution of arsenic in oak ash .................................................................................126

94. Distribution of antimony in oak ash ..............................................................................127

95. Distribution of bismuth in oak ash.................................................................................128
vii

96. Distribution of arsenic in juniper ash ...........................................................................129

97. Distribution of antimony in juniper ash ........................................................................130

98. Distribution of bismuth in juniper ash...........................................................................131

99. Distribution of lead in mesquite ash.............................................................................132

100. Distribution of lead in oak ash.......................................................................................133

101. Distribution of lead in juniper ash.................................................................................134

102. Distribution of zinc in mesquite ash..............................................................................135

103. Distribution of cadmium in mesquite ash ....................................................................136

104. Distribution of zinc in oak ash........................................................................................137

105. Distribution of cadmium in oak ash ..............................................................................138

106. Distribution of zinc in juniper ash..................................................................................139

107. Distribution of cadmium in juniper ash ........................................................................140

108. Distribution of selenium in mesquite ash.....................................................................142

109. Distribution of selenium in oak ash...............................................................................143

110. Distribution of selenium in juniper ash.........................................................................144

111. Distribution of sodium in mesquite ash........................................................................145

112. Distribution of sodium in oak ash..................................................................................146

113. Distribution of sodium in juniper ash............................................................................147

114. Distribution of manganese in mesquite ash................................................................148

115. Distribution of manganese in oak ash..........................................................................149

116. Distribution of manganese in juniper ash....................................................................150

117. Distribution of magnesium in mesquite ash................................................................151

118. Distribution of magnesium in oak ash..........................................................................152

119. Distribution of magnesium in juniper ash....................................................................153

Tables

1. d-Spacings and diffraction peaks used to determine peak heights used to show 

the relative abundances of minerals in drill core samples, Red Mountain, Arizona.........9

2. Summary of chemical data for 818 drill core samples and comparative background 

data, Red Mountain, Arizona, and vicinity..............................................................................10

3. Factor loading values for core samples from the hypogene and supergene zones, 

Red Mountain, Arizona ..............................................................................................................14

4. Summary of chemical data for 54 elements in 122 samples of rock outcrop and 

comparative background data, Red Mountain, Arizona ......................................................60

5. Summary of chemical data for 55 elements in 119 soil samples and comparative 

background data, Red Mountain, Arizona..............................................................................62

6. Summary of chemical data for ash and 66 elements in 57 mesquite ash samples, 

Red Mountain, Arizona ..............................................................................................................64

7. Summary of chemical data for ash and 66 elements in 108 oak ash samples, 

Red Mountain, Arizona ..............................................................................................................66

8. Summary of chemical data for ash and 66 elements in 68 juniper ash samples, 

Red Mountain, Arizona ..............................................................................................................68
viii

Conversion Factors

International System of Units to U.S. customary units

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as 

°F = (1.8 × °C) + 32.

Abbreviations

AAS atomic-absorption spectrometry

2θ two theta

Ag silver

Al aluminum

Ar-Ar argon-argon

As arsenic

Au gold

B boron

Ba barium

Be beryllium

Bi bismuth

Br bromine

Ca calcium

Cd cadmium

Ce cerium 

Co cobalt

Cr chromium

Cs cesium

Cu copper

Cu-Mo copper-molybdenum

d-spacing d is the distance between the parallel reflecting planes in a crystal as 

determined by XRD

Gd gadolinium
ix

Dy dysprosium

Er erbium

Eu europium

F fluorine

Fe iron

Ga gallium

Ge germanium

Hf hafnium

Hg mercury

I iodine

ICP-MS inductively-coupled plasma-mass spectrometry

ICP-OES inductively-coupled plasma optical-emission spectrometry

INAA instrumental neutron activation analysis

In indium

Ir iridium

K potassium

km kilometer

K-Ar potassium-argon

La lanthanum

Li lithium

Lu lutetium

m meter

Ma million years

Mg magnesium

Miller indices Integers used to indicate the orientation of a crystal face in terms 

(hkl) of its axes of reference

Mn manganese

Mo molybdenum

Na sodium

Nb niobium

Nd neodymium

ng/g nanograms per gram

Ni nickel

P phosphorus

Pb lead

PCD porphyry copper-molybdenum deposit
x

ppb parts per billion

ppm parts per million

Rb rubidium

Re rhenium

S sulfur

Sb antimony

Sc scandium

Se selenium

Si silicon

Sm samarium

Sn tin

Sr strontium

Ta tantalum

Tb terbium

Te tellurium

Th thorium

Ti titanium

Tl thallium

Tm thulium

U uranium

U-Pb uranium-lead

USGS U.S. Geological Survey

V vanadium

W tungsten

XRD X-ray diffraction

Y yttrium

Yb ytterbium

Zn zinc

Zr zirconium

Datum

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27).
Geochemical and Mineralogical Study of the Red 

Mountain Porphyry Copper-Molybdenum Deposit and 

Vicinity, Santa Cruz County, Arizona

By Maurice A. Chaffee

Abstract

The Red Mountain porphyry copper-molybdenum deposit 

(Cu-Mo deposit or PCD) is located in the northern part of the 

Patagonia Mountains, Santa Cruz County, Arizona. Extensive 

core drilling has delineated a large, deep-seated, structurally 

intact mineral system that extends from the present surface to 

depths of more than 1,765 meters. This system is hosted in a 

thick complex of predominantly felsic to andesitic volcanic 

rocks of the Cretaceous Period. This complex was intruded by 

scattered bodies of the Tertiary Period that are predominantly 

quartz monzonite porphyry; no major associated source intrusion 

has yet been found at depth. 

A total of 818 samples of core were analyzed for as many 

as 44 elements. The abundances and distributions at depth of 

at least 17 of these elements (silver [Ag], arsenic [As], gold 

[Au], boron [B], bismuth [Bi], copper [Cu], mercury [Hg], 

potassium [K], molybdenum [Mo], lead [Pb], sulfur [S], 

antimony [Sb], tin [Sn], tellurium [Te], thallium [Tl], tungsten 

[W], and zinc [Zn]) are related mostly to events that generated 

the Red Mountain system. Many of these same samples were 

also analyzed by X-ray diffraction for a suite of minerals. The 

multielement and mineralogical analyses of the core samples 

provide important information about the concentrations, 

associations, and distributions of select elements and minerals, 

including zoning patterns that may not be apparent from visual 

examination of core samples. The distributions of selected 

elements and minerals in these samples reveal an unusually 

complete mineral system that extends from a typical PCD with 

potassic alteration at depth to peripheral zones of phyllic and 

advanced argillic alteration as well as a copper-rich supergene 

enriched zone and the remnants of a leached cap. 

R-mode factor analysis was run with 34 elements for a set 

of samples from the deep part of the hypogene Cu-Mo deposit 

and another set from the part of the supergene zone with the 

highest copper enrichment. For the hypogene zone dataset, 

five factors are related to the PCD: (1) Ag, Cu, Mo, S, and Te; 

(2) As, B, Hg, and Sb; (3) Au and sodium (Na); (4) manganese 

(Mn), Pb, and Zn; and (5) K and Tl. For the supergene dataset, 

the deposit-related factors include (1) Cu, Mo, S, and Te; 

(2) Ag, As, Hg, Pb, Sb, and Tl; (3) Au and Na; and (4) K and 

rubidium (Rb). The changes in element associations between 

the two datasets indicate that some of these new associations 

are a result of formation of several suites of hypogene minerals 

in the deep part of the deposit and different hypogene mineral 

suites in the peripheral part of the deposit. Some changes may 

be because of the effects of supergene processes. 

Zones containing deposit-related elements and minerals 

common to many PCDs are present at Red Mountain. These 

zones include a crude, inverted cup-shaped shell containing 

anomalous copper accompanied by high concentrations of 

Ag, Au, K, Mo, total S, sulfate S, Sb, Te, and Tl, as well as 

local concentrations of As, B, Hg, Pb, and Zn. Hydrothermal 

minerals spatially associated with the deep hypogene Cu-Mo 

deposit include chalcopyrite, molybdenite, pyrite, plagioclase, 

orthoclase, biotite, magnetite, calcite, quartz, and anhydrite. 

Many of the hydrothermally deposited elements that are 

spatially related to the deposit are also concentrated in zones 

above the deep part of the deposit, including Ag, As, K, Pb, 

Sb, Te, Tl, and Zn. These elements are concentrated either 

(1) in generally wide, flat zones present in the upper part of the 

system or (2) in crudely arcuate peripheral zones found mainly 

in the middle part of the system and surrounding the deep part 

of the deposit. Near-surface, restricted hypogene anomalies 

are present for bismuth, mercury, tin, and tungsten.

The upper part of the deposit has been subjected to supergene 

enrichment and weathering. Deposit-related elements that remain 

anomalous in this area include Ag, As, Au, B, Bi, cobalt (Co), Cu, 

Hg, Mo, Pb, S, Sb, Sn, Te, Tl, uranium (U), and W. These positive 

concentrations indicate that, with the exception of copper and 

possibly mercury and uranium, these elements had relatively 

low chemical mobilities in the supergene enrichment and later 

weathering environments at Red Mountain. Most may have been 

deposited during one or more hypogene events and then redistributed locally during later events. Zinc is the only deposit-related 

element that has clearly been depleted as a result of supergene 

and (or) weathering events. Minerals that are common in the 

unweathered upper part of the system include chalcocite, pyrite, 

quartz, sericite, alunite, and pyrophyllite, as well as less common covellite, enargite, tennantite, tourmaline, barite, anglesite, 

and other sulfide or sulfate minerals.
2 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Subsequent to formation of the Red Mountain Cu-Mo 

deposit and supergene enrichment, chemical weathering 

produced an area of pervasive hematite and other iron oxides 

in the near-surface part of the deposit to form a leached cap. 

These iron-rich minerals formed primarily as a result of the 

oxidation of pyrite. This event was accompanied by losses of 

cobalt, mercury, magnesium, and zinc, as well as destruction 

of sericite, plagioclase, pyrite, clay minerals, and pyrophyllite. 

A total of 122 rock samples, 119 soil samples, and samples 

of three plant species (57 mesquite, 108 oak, and 68 juniper) 

were collected over and around Red Mountain. For the rock and 

soil samples, the distributions of anomalous Ag, As, Bi, Cu, Fe, 

Mo, Pb, Sb, Te, and Tl best delineated the exposed part of the 

deposit. The highest concentrations of many of these elements 

are centered on one or both of two main areas with exposures of 

quartz monzonite porphyry. The high concentrations of arsenic 

in the deposit area (as much as 390 parts per million (ppm) in 

rock and 1,500 ppm in soil) and of lead (as much as 2,370 ppm 

in rock and 1,490 ppm in soil) are particularly noteworthy.

The concentrations of various elements in the plant ash 

vary widely among the three species and are species dependent. 

Many of the deposit-related elements are either nonessential for 

plant growth or are considered toxic at certain concentration 

ranges. In spite of this, the distributions of potentially toxic Ag, 

As, Bi, Cd, Cu, Mo, Pb, Sb, selenium (Se), and Zn produce 

deposit-related anomalies for one or more of the three species.

Vegetation sampling offered no advantage over rock or 

soil sampling as an exploration tool. From an environmental 

standpoint, however, the plant analyses provide baseline data for 

both essential and nonessential elements that might be useful, 

for example, for selecting native plant species for revegetating 

mine waste areas.

The exposed part of the Red Mountain deposit has not 

been greatly disturbed as a result of mining and other activities. 

However, some of the rock, soil, and plant samples that were 

collected near the Harshaw Creek and Alum Gulch drainages, 

which are peripheral to Red Mountain, are also anomalous for 

various deposit-related elements. These anomalies are probably 

the result of dispersion of stream sediments contaminated with 

material from past mining. 

Figure 1. Location of the study area, near Patagonia, Santa Cruz County, Arizona.

Red

Mountain

Patagonia

Nogales

UNITED STATES

MEXICO

SANTA CRUZ

COUNTY

COCHISE

COUNTY

PIMA COUNTY

Study area

Patagonia Mountains

Base from U.S. Geological Survey digital data, The National Map, 2018

3D Elevation Program, 1/3 arc-second resolution Geographic projection, 

decimal degrees North American Datum of 1983

ARIZONA

SONORA

82

83

19

110°50' 110°40' 110°30' 111°10' 111°00'

111°20'

31°30'

31°40'

31°20'

SANTA CRUZ

COUNTY

Tucson

PHOENIX

ARIZONA

0 4 8 12 16 20 24 28 KILOMETERS

0 4 8 12 16 MILES
Introduction 3

Introduction

Extensive deep core drilling delineated a major, deep-seated, 

structurally intact porphyry copper-molybdenum deposit 

(Cu-Mo deposit or PCD) at Red Mountain, in the northern part 

of the Patagonia Mountains, Santa Cruz County, Arizona 

(fig. 1). This deposit is exposed in surface outcrops and continues 

downward to depths of more than 1,765 meters (m) (Corn, 1975; 

Quinlan, 1981, 1986; Lecumberri-Sanchez and others, 2013). 

The relatively complete vertical range, with all its zoning 

features, emphasizes the significance of studying this deposit. 

Additionally, the deposit area is relatively undisturbed by 

mining and other anthropogenic activities. 

Chemical and mineralogical zoning as well as 

mineralization- and alteration-related zoning typical of many 

PCDs are present at Red Mountain. These include potassic, 

phyllic, and advanced argillic zones, as well as a zone of 

supergene enrichment and the remnant of a leached cap. 

Because PCDs are the most important source of copper 

worldwide, many articles have been published describing this 

deposit type. Most articles emphasize the geology, petrography, 

and genesis of one or more deposits and commonly describe 

some of the mineral zoning and alteration assemblages on the 

surface and (or) at depth, tonnage of ore, ages of the various 

events that formed the deposit, as well as many other parameters. 

Many of the common and less common features in porphyry 

ore deposits have been described in detail (Guilbert and Lowell, 

1974; Lowell and Guilbert, 1970). However, discussion of the 

concentrations and distributions of specific elements in any of 

these reports is often limited. The elements described in published reports are usually those of economic interest, mainly 

Cu, Mo, silver (Ag), gold (Au), and sometimes lead (Pb) and 

zinc (Zn) (for example, Candela and Piccoli, 2005; Gustafson 

and Hunt, 1975; Gustafson and Quiroga G., 1995; Mason and 

MacDonald, 1978; Seedorff and others, 2005; Sillitoe and 

Perelló, 2005; Titley and Anthony, 1989; and articles in 

Brown, 1976; Pierce and Bolm, 1995; Schroeter, 1995; Titley, 

1982; Titley and Hicks, 1966).

Some published articles include tables and (or) discussion 

of analytical data that mainly relate to specific rock types associated with a PCD, but these articles typically do not illustrate 

the distribution of the elements included in the rock analyses 

(for example, Atapour and Aftabi, 2007; Chang and others, 

2011; Cox and others, 1995; Dupont and others, 2002; Lang 

and Titley, 1998; McLemore and others, 1999; Richards and 

others, 2001; Rieger and others, 2010; Teal and Benavides, 

2010; Ulrich and Heinrich, 2002). However, many elements 

may be associated with formation of a given PCD, and their 

concentrations and distributions can provide additional useful 

information on the genesis and characterization of that deposit.

 Chemical concentrations and (or) distributions have been 

described for several PCDs (for example, Carson and others, 

1976; Chaffee, 1976a; Chaffee and Hessin, 1971; Cox, 1985; 

Gott and McCarthy, 1966; Govett, 1983; Gunton and Nichol, 

1975; Jambor, 1974; Jerome, 1966; Osatenko and Jones, 1976). 

Most of these reports are limited to a few elements and most do 

not include contours of the chemical and (or) mineral zoning 

that may be present. Earlier investigations of chemical zoning 

present in the Kalamazoo, Arizona, PCD (Chaffee, 1976b, 1982) 

were more limited in scope than the one presented here, but did 

reveal several chemical zones related to that deposit. A more 

recent study of the geology and geochemistry of the Myszków 

porphyry copper-molybdenum-tungsten deposit in southern 

Poland includes detailed summaries of concentrations for 

42 elements as well as the distributions of 15 of these elements 

in cross sections (Chaffee and others, 2001; Lasoń, 2001; 

Markowiak and Habryn, 2001).

The present study identifies and evaluates both subsurface 

and surface data associated with the Red Mountain PCD. The 

subsurface data are based on core analyses and include 

concentrations and distributions of elements and minerals, 

some of which are related to the mineral deposit and some 

of which are more closely associated with the host lithologic 

units. Element concentrations and distributions on the surface 

are based on analyses of rock, soil, and vegetation samples. 

This report is divided into two parts. The focus of Part A 

is the concentrations, associations, and distributions of a large 

suite of elements and some common minerals in core samples 

collected from a fence of seven drill holes and an additional 

hole south of the fence, all of which penetrated from the surface 

to depths of as much as 1,765 m. Many of the elements determined for this investigation are not often included in published 

reports of mineral deposits, yet information on them should be 

helpful in understanding the formation of the Red Mountain 

system and may be useful in locating blind mineralized areas 

within other systems. The distributions also reflect the behavior 

and relative mobility of some of the elements and minerals.

Part B of this report describes the concentrations and 

distributions of elements in rock, soil, and vegetation samples 

collected at the surface in the vicinity of the Red Mountain 

system. These samples provide geochemical information for 

selected elements, resulting only from natural weathering and 

erosion at the top of this deposit. Because many of the elements 

may have adverse environmental effects, baseline concentrations of these elements can provide the basis for comparative 

studies. The information described in this report may also be 

useful for adding new details to PCD models such as that published by John and others (2010). The analytical data used to 

generate the tables of concentration ranges and other statistical 

information, and also the distributions of elements and minerals, 

are included for the benefit of persons interested in doing further 

studies beyond the scope of this report. It is hoped that the statistical data, as well as the element and mineral distributions shown 

on the cross sections and element distributions shown on the 

maps, will provide new baseline information for a variety of 

sample media collected in and near a relatively complete and 

undisturbed PCD.
4 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Location and Geologic Setting

The study area is located in the semiarid environment 

of southern Arizona, at the northern end of the Patagonia 

Mountains, about 80 kilometers (km) southeast of Tucson (fig. 1). 

The region is part of an aligned structural zone of Laramide 

intrusions and PCDs that extends from the Silver Bell deposit 

northwest of Tucson to the La Caridad deposit in Sonora, 

Mexico (John and others, 2010). The study area is one of 

moderate relief, with elevations ranging from about 1,940 m 

at the top of Red Mountain to about 1,235 m in the vicinity of 

Patagonia, Arizona, about 3 km northwest of Red Mountain. 

This area is centered on Red Mountain and is bounded on the 

east and south by the Harshaw Creek drainage, on the west by 

the Alum Gulch drainage, and on the north by the Patagonia 

fault (fig. 2). 

The geology of Red Mountain and the surrounding areas 

in the Patagonia Mountains has been described by Drewes 

(1971a, 1971b, 1972), Schrader (1915), and Simons (1972, 1974). 

Several geologic studies discussing the Red Mountain porphyry 

system in some detail have also been published (Bodnar and 

Beane, 1980; Corn, 1975; Kistner, 1984; Lecumberri-Sanchez 

and others, 2013; Quinlan, 1981, 1986; Vikre and others, 2014). 

The Sunnyside PCD, which is nearby and geologically similar 

to the Red Mountain deposit, has been described by Graybeal 

(1996). Only limited geologic and petrographic information 

is included in this report as these topics were not the focus of 

this investigation.

 Figure 2 shows the surface geology of the study area, 

which is generalized principally from the maps of Drewes 

(1971a, 1971b, 1972, 1996), Quinlan (1981, 1986), and 

Simons (1972, 1974). The oldest rocks in the area (J-Yh) are 

from the Mesoproterozoic Era to the Jurassic Period and crop 

out west of Red Mountain (Drewes, 1996). Formations of 

chiefly volcanic and plutonic rocks that range in age from Triassic 

to Tertiary (^m, J-^i, Kv, and TKv) crop out southwest of Red 

Mountain. A thick sequence of Cretaceous- to Tertiary-aged 

volcanic rocks, which includes both an extensive andesite 

formation (Ka) and a superjacent rhyolite tuff formation (TKr), 

host the Red Mountain PCD. These two formations are exposed 

throughout much of the study area. Indurated Tertiary terrace 

gravels are present in scattered localities, mainly north of the 

Patagonia fault, and Quaternary alluvium is present in many 

washes surrounding Red Mountain (QTag).

The subsurface geology through the Red Mountain PCD 

is illustrated on a roughly east-west section through the area 

of the system (fig. 3). The section is located on figure 2. The 

oldest formation present in the area of the section is known 

informally as the felsite-latite unit (Kv on figures 2 and 3) and 

is at least 900 m thick. The base of this formation has not been 

found either on the surface or in drill core (Quinlan, 1986). 

This unit has been correlated with the Upper Cretaceous 

silicic volcanics of Simons (1974) and has been dated by the 

potassium-argon (K-Ar) method at about 72 million years 

(Ma) (Vikre and others, 2014). This felsite-latite unit consists 

of a succession of interlayered felsic volcanic conglomerates, 

breccias, tuffs, and possibly flows, together with andesite sills 

or flows near the top of the unit. Latite dikes and sills are 

present locally. 

The felsite-latite unit is overlain by the andesite unit 

(Ka on figures 2 and 3), which is as much as 1,300 m thick 

(Quinlan, 1986). This formation, which is composed of mostly 

porphyritic andesite and trachyandesite flows and breccias 

that have been intruded by andesite sills and dikes, has been 

correlated with the Upper Cretaceous trachyandesite of Meadow 

Valley in Simons (1972). This unit has been dated by the K-Ar 

method at about 72–71 Ma (Vikre and others, 2014). 

The rhyolite tuff unit (TKr on figures 2 and 3) overlies 

the andesite unit and caps Red Mountain. Quinlan (1986) 

states that this formation was probably at least 450 m thick, 

but because of erosion, the original thickness of this unit is 

unknown. This formation consists of a series of dacitic to 

rhyolitic tuffs, flows, and breccias called the “Volcanics of Red 

Mountain” by Drewes (1971a), and correlated by him with 

the Gringo Gulch Volcanics of the Paleocene (?). The textures 

in samples of the rhyolite tuff unit from core and outcrops 

from Red Mountain are similar to the textures of samples of 

the Gringo Gulch Volcanics that crop out along Arizona State 

Highway 82, west of Patagonia, Arizona (fig. 4A). This unit, 

which was originally thought to be Late Cretaceous to early 

Tertiary, is now suspected to be entirely from the Cretaceous 

Period. (If true, the TKr symbol used would be incorrect.) 

Although some of the dates for the two formations given in 

Vikre and others (2014) were deemed to be inconclusive, the 

uranium-lead (U-Pb) age dates from zircons indicate a common age of about 69–67 Ma for rocks from these two areas, 

which, if correct, means that this formation is Cretaceous and 

not Paleocene. The outcrop similarities, along with zircon 

dates, imply that the correlation of Drewes for these two formations is correct but his age estimate is incorrect. Although 

the three major volcanic units that host the Red Mountain 

PCD have been correlated to formations mapped outside of the 

study area, the informal names assigned to these three volcanic 

formations by Quinlan (1981, 1986) are used in this report.

The Red Mountain volcanic sequence has been 

intruded by irregularly shaped bodies that vary in composition 

from granodiorite to quartz monzonite and are commonly 

porphyritic. These intrusive bodies (Tqm, figs. 2 and 3) have 

been dated by the U-Pb method at about 62 Ma and copper 

deposit-related biotite by the argon-argon (Ar-Ar) method at 

about 60 Ma (Vikre and others, 2014). These intrusive bodies 

are probably apophyses of a stock thought to be present at depth 

but not identified by any of the deep drilling at Red Mountain 

(J.J. Quinlan, oral commun., 1987). The differences in ages 

determined for these intrusions and the copper-related 

alteration—about 62 million years compared to 60 million years—

would indicate that emplacement of the intrusive bodies is not 

associated with formation of the Red Mountain PCD. However, 

the close spatial association of the surface and subsurface 

locations of quartz monzonite porphyry and high concentrations 

of copper and other deposit-related elements, implies at least a 

probable temporal relation.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

158

151

146

156 144

145

157

23

122

112

111 110 109 24 27

108

22

107

21

65

100

20

105

99

10

9

86

85

66

97 98

9695

35

94

63

57

64

62

69 68

67

59

61 60

58

92

19 18

17

93

15 16

14

13

36

74

7

11

84

82

37 38 39

29 31 30

33

32

79 80

34

77

5

78

91 90

28

119 3

89

88

87

75

76

52

54

116

113

114

53

115

117

118

26

73

72

70

71

56 50

55 51 49 48

46

44

43 42

41 45

40

47

25

1

2

81

12

83

8

104

102

103

101

121

120

106

6

4

A

A'

Geology modified from and Simons (1974).

Base from U.S. GeologiGeographic projection, North American Datum 

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

J-YhJ-Yh

P A T A G O N I A

F A U L T

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EX

QTag Alluvi

 un

Conta infFault— or 

J-Yh Hornb

 ignSampl

Tqm Quartz 

 Int

TKv

TKr Volcan

 rhyFelsic 

Kv Silicic 

Line o

J-i Pluton

 un

m Mount 

 fel

Ka Trachy

 Ch Sim

82

Drill hMine o

158

A'A

0 .5 1 0 .5 

Figure 2. Geologic map of the study area showing locations of the geologic section shown in figure 3 and sites for samples of rock, soil, and plants. 
6 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

TKr Tqm TKr

A A'

EXPLANATION

Depth of formation unknown

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

157

NOT TO SCALE DATUM IS SEA LEVEL

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Figure 3. Geologic cross section showing locations of seven drill holes.
Figure 4. A, Photograph of exposures of altered Gringo Gulch Volcanics, which are correlated with the rhyolite tuff formation on top of Red Mountai

Mountain as viewed from the south. The white cliffs near the top of the mountain are exposures of the altered rhyolite tuff formation. The andesite forthe area below the cliffs. C, Photograph of the study area as viewed from the west with Red Mountain in the background. Exposures in the foreground terrace gravels. D, Photograph of exposures of the altered andesite formation overlain with indurated Tertiary gravel containing extensive manganese 

A BC D
8 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Lithologic contacts logged for the two westernmost drill 

holes (fig. 3) suggest that a steep, as yet unidentified, fault 

with significant offset may be present in the western part of 

the study area, between these two holes. The accompanying 

photographs illustrate typical exposures of the altered Gringo 

Gulch Volcanics (fig. 4A), the andesite and rhyolite tuff units 

(fig. 4B), the Tertiary terrace gravels (fig. 4C), and strongly 

altered andesite in the vicinity of Red Mountain (fig. 4D).

Most of the mineralization-alteration zones that are 

common to PCDs are present at Red Mountain. These zones 

include a relatively barren core surrounded by a major hypogene 

Cu-Mo deposit that is present in the form of an inverted cup that 

projects as east and west limbs in a vertical section. The deposit 

spreads upward to the surface and is accompanied by welldeveloped potassic, phyllic, and advanced argillic alteration 

zones. A supergene enrichment zone, as well as a remnant of a 

leached cap, are also present. Boundaries between these zones 

are not easily defined and often overlap or are overprinted 

and modified by later events. Quinlan (1986) describes the 

distributions of major hydrothermal sulfide minerals and silicate 

alteration minerals in the Red Mountain system in some detail. 

His model shows two separate episodes, with early, barren, widespread potassic, phyllic, and advanced argillic zones overprinted 

by later, more restricted potassic, and phyllic zones associated 

with the hypogene Cu-Mo deposit. However, the order and 

details of these two episodes have not been independently verified.

Part A—Subsurface Geochemical 

and Mineralogical Studies of Core 

Sampling, Preparation, and Chemical 

Analysis of Core

A total of 818 samples of core were collected from material 

provided by Kerr-McGee Corporation, including 708 samples 

from the fence of 7 drill holes shown in figure 3, and an 

additional 110 samples from a drill hole to the south of the 

fence. The location of the section for figure 3 is shown on 

the geologic map (fig. 2). Each sample was composited from 

typical material present in a 3-m run of core. The 3-m runs 

were spaced at approximately 15-m intervals along the entire 

length of each drill hole. Care was exercised to sample only 

the principal lithology in each sample interval. Thin crosscutting bands of different rock types or highly mineralized veins 

or fractures were not included in the sample unless they were 

distributed through most of the 3-m interval. At the time the 

sampling was done, the core was relogged to supplement 

information given in the original logs. Cores from additional 

drill holes not discussed in this report were also examined 

visually to improve the overall understanding of the geology 

and mineral zoning.

The core samples were crushed and pulverized to about 

less than (<) 0.074 millimeter (mm) (minus 200 mesh). The 

samples were submitted for analysis in a random order. 

U.S. Geological Survey (USGS) internal standards and duplicate 

samples were included in each batch of 50 or less samples to 

monitor the quality of the analyses. The samples were collected 

and thus analyzed over the period from 1980 to 2000. During 

that time the analytical methods used at the USGS and at contract laboratories changed. Thus, not all samples were analyzed 

for the same suite of elements and (or) by the same methods. 

The core samples were analyzed in the USGS Branch 

of Geochemistry laboratories in Denver for the elements 

Ag, boron (B), barium (Ba), beryllium (Be), bismuth (Bi), 

calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), 

cesium (Cs), copper (Cu), iron (Fe), lanthanum (La), 

lithium (Li), magnesium (Mg), manganese (Mn), 

molybdenum (Mo), niobium (Nb), nickel (Ni), Pb, 

rubidium (Rb), scandium (Sc), tin (Sn), strontium (Sr), 

thorium (Th), titanium (Ti), vanadium (V), tungsten (W), 

yttrium (Y), and zirconium (Zr) by semiquantitative emission 

spectrography (Grimes and Marranzino, 1968; Motooka and 

Grimes, 1976). The core samples were also analyzed for other 

elements by the following methods: arsenic (As) by colorimetry 

(Welsch, 1979); Au by atomic-absorption spectrometry (AAS) 

(Meier, 1980); mercury (Hg) by cold-vapor atomic-absorption 

(Vaughn and McCarthy, 1964); potassium (K) and sodium (Na) 

by AAS (O’Leary and Meier, 1986); total sulfur (S) by a 

combustion/titrametric method (O’Leary, 1990); antimony 

(Sb) by AAS (Welsch and Chao, 1975); Te by AAS (Chao and 

others, 1978); thallium (Tl) by AAS (Hubert and Lakin, 1973); 

uranium (U) by a modification of the fluorometric method 

of Centanni and others (1956) as described by O’Leary and 

Meier (1986); and for Zn by AAS (Ward and others, 1969). A 

few samples were analyzed for fluorine (F) by ion-selective 

analysis (Hopkins, 1977); for Sn by AAS (Welsch and Chao, 

1976); and for W by a visible spectrophotometric method 

(Welsch, 1983). All data analyzed for this study are available 

in a separate data release (Horton and others, 2020).

Prior to, and independent of, the USGS’s study, the 

Kerr-McGee Corporation collected samples from mostly 

3-m runs of core in the same set of 7 drill holes and composited them to make 379 additional samples. These samples were 

crushed, pulverized, and analyzed for a variety of elements 

for the Kerr-McGee Corporation by a commercial laboratory. 

Sulfate analyses from the Kerr-McGee Corporation dataset 

(J.J. Quinlan, Kerr-McGee Corporation, written commun., 

1980) have been used to illustrate the distribution of sulfate 

and sulfate-rich minerals.
Results and Evaluation of the Core Analyses 9

Mineralogical Analysis

During relogging, the core specimens were examined to 

visually identify the various rock types and minerals present 

and the locations of geologic contacts. Selected samples were 

analyzed by X-ray diffraction (XRD) to identify some common 

minerals present in pulverized sample material. 

The relations of the most common hypogene deposit-related 

minerals, as determined from grain boundaries and crosscutting 

veins, reveal a complex history for the Red Mountain system. 

It is beyond the scope of this report to describe in detail all of 

these relations. Only the most general and widespread mineralogical features are discussed. 

 Of the 818 core samples, 245 from the seven holes on 

the section were prepared and analyzed by XRD to identify 

selected hydrothermal- and host-rock-related minerals and 

their relative concentrations. Separate aliquots of the crushed 

core were first ground in an agate mortar to <0.062 mm 

(about minus 250 mesh). Approximately equal volumes of the 

resulting powders were mounted on glass slides and analyzed 

by XRD using a Phillips XRG-3000 generator configured with 

a copper lamp and nickel filter and run at 40 kilovolts and 

26 milliamperes. The samples were scanned over a range of 

4 to 60° two theta (2Θ) at a speed of 2° 2Θ per minute, and the 

responses were plotted as diffractograms on graph paper 

(S.J. Sutley, USGS, written commun., 1990). The relative 

concentrations of 13 minerals in each sample were estimated 

on the resulting diffractograms using the best d-spacing peak 

or peaks for which no interferences from other mineral phases 

were present (table 1). For each selected mineral, the peak 

height was recorded as the number of graph squares above 

background along a vertical line centered on the peak. For discussion purposes, this height is given in numerical “units” in 

this report. The resulting data are tabulated and available in the 

companion data release (Horton and others, 2020). No direct 

relation was established between individual peak heights and 

the actual weight percentage of a given mineral. The tabulated 

peak heights thus represent semiquantitative concentrations.

Results and Evaluation of the 

Core Analyses

The analyses for 44 elements in the 818 core samples are 

summarized in table 2 available in the data release (Horton and 

others, 2020). The median concentration values are deemed to 

provide the best measure of the typical concentration for each 

element (Reimann and others, 2008). For comparison purposes, 

the estimated abundance values for the Earth’s upper or total 

continental crust for each element are also listed. Beginning 

with Clarke (1924), many authors have attempted to compile 

estimates of abundance values for elements in the Earth’s crust, 

either for the entire crust or for the upper and lower parts of 

the crust (for example, Goldschmidt, 1954; Mason and Moore, 

1982; Parker, 1967; Rudnick and Gao, 2014; Taylor and 

McClennan, 1995; Turekian and Wedepohl, 1961; Wedepohl, 

1969–1978, 1995; Yan and Chi, 2005). 

Except for tellurium (Te), the abundance concentrations 

given in Rudnick and Gao (2014) for the upper continental crust 

are shown in table 2. Until recently, the abundance of tellurium 

in the total crust or in the upper continental crust had not been 

accurately determined, mainly because no analytical methods 

existed to accurately measure extremely low concentrations 

(nanograms per gram [ng/g], or parts per billion [ppb]) of this 

element. For purposes of this report, the value of 0.005 ppm tellurium estimated by Wedepohl (1995) for the total continental crust 

is used as an acceptable estimate of the tellurium concentration in 

the upper continental crust. 

Ratios of the median concentration values of the elements 

present at depth in the Red Mountain deposit (Column A) to 

crustal abundance concentrations, which were selected as an 

arbitrary reference database (Column B), are given in table 2. 

These ratios give first approximation estimates of the relative 

enrichment or depletion of elements in the area of the PCD at 

Red Mountain. 

Reimann and de Caritat (2000) argue that, because many 

factors affect the variability of a given element in regional 

data, comparing analytical concentrations determined in various 

media to crustal abundance concentrations is not useful, at 

least for environmental studies. However, crustal concentrations 

offer at least a qualitative reference base for estimating the 

enrichment of deposit-related elements in samples collected 

in the vicinity of the major hypogene Cu-Mo deposit at 

Red Mountain.

Table 1. d-Spacings and diffraction peaks used to determine 

peak heights used to show the relative abundances of minerals 

in drill core samples, Red Mountain, Arizona.

 [The peak heights are listed in the associated data for this publication 

(Horton and others, 2020)]

Mineral d-Spacing 

(Ångstroms)

Diffraction peak, in 

Miller indices (hkl)

Muscovite 9.95 002

Pyrophyllite 9.20 002

Hornblende 8.48 110

Kaolinite 7.15 001

Alunite group 5.70 101

Chlorite 4.73 003

Quartz 4.25 100

Orthoclase 3.24 002

Plagioclase 3.19 040

Calcite 3.03 104

Hematite 2.69 104

Magnetite 2.53 311

Hematite 1.69 116

Pyrite 1.63 311
10 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 2. Summary of chemical data for 818 drill core samples and comparative background data, Red Mountain, Arizona, and vicinity.

[All concentrations are in parts per million unless % (percent) is shown after the chemical symbol. Elements analyzed by emission spectrography unless a 

method abbreviation follows the element symbol. cm indicates colorimetric analysis. aa indicates atomic-absorption spectrometric analysis. inst indicates 

instrumental analytical technique. The analytical methods are described in the text and in the associated data for this publication (Horton and others, 2020). 

---, indicate no meaningful value. Values preceded by < or > are qualified values, which are less than or greater than, respectively, the value shown. Unqualified 

samples have no concentrations below the lower limit of determination or above the upper limit of determination. The ratios A/B, A/C, and A/D give estimates 

of the relative enrichment (>1.0) or depletion (<1.0) of each element in the core samples]

Drill core data Comparative background data

Element Range of 

values

Number 

analyzed

Percent 

analyzed 

of 818 

samples

Percent 

unqualified 

of 818 

samples

Median 

value core 

samples

(A)

Crustal

abundance1

(B)

A/B 

ratio

Median value

27 local 

andesite

samples2

 (C)

A/C 

ratio

Median value 

46 regional 

andesite

samples3 (D)

A/D 

ratio

Ag <0.5–150 818 100 75 0.70 0.053 13.2 <0.008 >8.75 <0.50 >1.4

As-cm <1.0–650 818 100 95 6.0 4.8 1.25 6 1.0 5.3 1.13

Au-aa <0.002–2.96 818 100 94 0.020 0.0015 13.33 <0.002 >10 --- ---

B <10–700 818 100 88 15 17 0.88 --- --- 15 1.00

Ba 100–5,000 818 100 100 700 628 1.11 851 0.82 1,000 0.70

Be <1.0–2.0 818 100 74 1.0 2.1 0.48 2 0.50 1 1.00

Bi <10–500 818 100 5 --- 0.16 --- <1 --- <2 ---

Ca (%) <0.05–5.00 818 100 84 0.20 2.57 0.078 3.62 0.055 1.75 0.11

Cd <20–300 818 100 3 --- 0.09 --- 0.11 --- 0.30 ---

Co <5–300 818 100 95 20 17.3 1.16 23 0.87 20 1.00

Cr <10–300 818 100 83 30 92 0.33 24 1.25 50 0.60

Cs <10–150 818 100 67 10 4.9 2.04 --- --- 50 0.20

Cu 5–20,000 818 100 100 700 28 25 47 14 40 17.5

F-inst 100–1,000 73 9 9 --- 557 --- --- --- --- ---

Fe (%) <0.05–15 818 100 99.9 5.00 3.92 1.28 5.22 0.96 3.00 1.67

Hg-inst <0.02–1.08 818 100 85 0.04 0.05 0.80 --- --- <0.02 >2.0

K (%)-aa <0.10–8.70 818 100 99.6 2.90 2.32 1.25 2.53 1.15 2.50 1.16

La <20–200 818 100 99 50 31 1.61 44 1.14 60 0.83

Li <1–200 818 100 93 10 24 0.42 40 0.25 100 0.10

Mg (%) 0.02–3.00 818 100 100 0.70 1.50 0.47 2.23 0.31 1.25 0.56

Mn 10–>5,000 818 100 99.9 500 774 0.65 826 0.61 500 1.00

Mo <5–2,000 818 100 61 5 1.1 4.55 3 1.67 <5 >1.0

Na (%)-aa <0.10–3.70 818 100 87 0.30 2.43 0.12 2.49 0.12 2.45 0.12

Nb <20–20 818 100 1 --- 12 --- 18 --- <20 ---

Ni <5–200 818 100 91 30 47 0.64 46 0.65 20 1.50

Pb <10–10,000 818 100 99.8 50 17 2.94 11 4.55 50 1.00

Rb 30–500 818 100 100 200 84 2.38 --- --- 150 1.33

S (%)-inst 0.005–17.4 818 100 100 1.70 0.06 27.4 --- --- <0.05 >34

Sb-aa <1.0–600 818 100 68 2.0 0.40 5.00 <1.0 >2.0 <2 >1.0

Sc <5–70 818 100 99 15 14 1.07 17 0.88 15 1.00

Sn <10–70 818 100 19 <10 2.1 <4.7 --- --- <10 1.00

Sn-aa <2.0–150 194 24 18 2.0 2.1 0.95 --- --- --- ---

Sr <100–2,000 818 100 83 200 320 0.625 612 0.33 300 0.67

Te-aa <0.010–6,000 818 100 98 0.25 0.005 50 <0.1 >2.5 <0.01 >25
Mineralogical Analysis 11

Table 2. Summary of chemical data for 818 drill core samples and comparative background data, Red Mountain, Arizona, and vicinity.

[All concentrations are in parts per million unless % (percent) is shown after the chemical symbol. Elements analyzed by emission spectrography unless a 

method abbreviation follows the element symbol. cm indicates colorimetric analysis. aa indicates atomic-absorption spectrometric analysis. inst indicates 

instrumental analytical technique. The analytical methods are described in the text and in the associated data for this publication (Horton and others, 2020). 

---, indicate no meaningful value. Values preceded by < or > are qualified values, which are less than or greater than, respectively, the value shown. Unqualified 

samples have no concentrations below the lower limit of determination or above the upper limit of determination. The ratios A/B, A/C, and A/D give estimates 

of the relative enrichment (>1.0) or depletion (<1.0) of each element in the core samples]

Drill core data Comparative background data

Element Range of 

values

Number 

analyzed

Percent 

analyzed 

of 818 

samples

Percent 

unqualified 

of 818 

samples

Median 

value core 

samples

(A)

Crustal

abundance1

(B)

A/B 

ratio

Median value

27 local 

andesite

samples2

 (C)

A/C 

ratio

Median value 

46 regional 

andesite

samples3 (D)

A/D 

ratio

Th <100–<100 818 100 0 --- 10.5 --- 17 --- 15.4 ---

Ti (%) 0.10–1.00 818 100 100 0.50 0.38 1.32 0.62 0.81 0.50 1.00

Tl-aa 0.20–140 818 100 100 1.50 0.90 1.67 0.2 7.5 0.18 8.33

U-inst 0.06–36 818 100 100 1.10 2.7 0.41 --- --- 1.90 0.58

V 10–700 818 100 100 100 97 1.03 93 0.52 100 1.00

W <50–150 818 100 5 --- 1.9 --- --- --- <50 ---

W-cm <1.0–100 204 25 32 5.0 1.9 2.63 --- --- --- ---

Y <10–150 818 100 96 20 21 0.95 23 0.87 20 1.00

Zn-aa <5–22,000 818 100 99.5 110 67 1.64 89 1.24 60 1.83

Zr 30–500 818 100 100 150 193 0.78 --- --- 150 1.00

1

Values, except tellurium, are from compilation of Rudnick and Gao (2014) for upper continental crust. Value for tellurium is from Wedepohl (1995) for entire 

continental crust.

2

Subset of the 122 samples in the rock dataset (table 4) consisting of analyses of unaltered or slightly propylitically-altered andesite rock samples collected 

within the study area but outside of the area of influence of the Red Mountain deposit. 

3

Subset of unaltered or slightly propylitically-altered andesite rock samples collected generally from the area immediately north of the study area. Sample 

analyses are from the U.S. Geological Survey National Geochemical Database.
12 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Because Reimann and Caritat (2000) state that crustal 

abundances do not always provide a good reference database 

for establishing estimated threshold values (the value above 

[or in some cases below] which concentrations are considered 

to be anomalous), two additional databases of median values 

for elements have been compiled to provide more localized 

threshold estimates that better determine concentration gains 

and losses in the overall Red Mountain mineral system (table 2). 

The first database consists of median values of analyses 

compiled from a subset of samples from the rock dataset of 

122 samples (table 4) collected over and around Red Mountain 

(Column C). This subset comprises 27 samples of unaltered or 

slightly propylitically altered andesite collected in the study 

area but from outside of the area affected by the Red Mountain 

deposit. The second database consists of median values of 

46 similar rock samples of the same andesite formation but 

collected from the area immediately north of the study area. 

The analyses of these samples are from the USGS National 

Geochemical Database (Column D).

The ratio values A/C and A/D (table 2) from these two 

databases provide comparisons that emphasize those elements 

mostly added to the pre-mineral host rocks during the various 

episodes of mineralization and alteration. These elements 

include, in approximate order of enrichment in A/C and (or) 

A/D: S, Te, Cu, Au, Ag, Tl, Pb, Hg, Sb, Mo, Zn, Rb, K, and As. 

(References to S in this report imply total S unless sulfate S is 

stated.) The A/B ratios, based on crustal abundance values, also 

show that most of these same elements have been added to 

the system in approximately the same order. Most of the 

deposit-related elements tend to occur in one of two common 

hydrothermal mineral associations: (1) metal-rich sulfide and 

sulfate minerals or (2) potassium-rich silicate or sulfate minerals. 

Insufficient information is available to calculate ratio values 

for four other deposit-related elements, bismuth, cadmium, tin, 

and tungsten. 

R-Mode Factor Analysis

Factor analysis is a technique that can be used with 

multielement chemical datasets to identify element associations, 

including both temporal and spatial associations, in mineral 

deposits. Such associations help to identify those elements 

related mostly to host-rock chemistry and those associated 

mostly with deposit-related minerals. Element associations can 

also be used to identify changes in these associations between 

lithologies as well as between the hypogene environment of a 

deposit and its supergene and weathering environments. 

The chemical analyses of the core samples were evaluated 

by applying R-mode factor analysis, a mathematical technique 

that is used in geochemistry to describe the covariance relations 

among element concentrations that produce subsets (factors) 

of the variables (chemical elements) in a multielement dataset. 

In the present study, the factors produced were studied to see 

whether they were related to certain lithologies, to the mineral 

deposit, or both. The relative degree with which a given element 

associates with a given factor is called its factor loading value. 

Further details about factor analysis and its applications to 

geochemistry can be found in the literature (for example, Bolivar 

and others, 1983; Davis, 1973; Howarth, 1983; Reimann and 

others, 2002; Selinus, 1983).

Analyses of two groups of core samples selected from 

samples from the fence of seven holes (Horton and others, 2020) 

were evaluated using factor analysis. The first group includes 

samples collected at depths below the zone of supergene 

enrichment that represent the deep zones of the hypogene 

Cu-Mo deposit, where copper concentrations are mostly greater 

than or equal to (≥) 2,000 ppm. Most of the 254 samples in 

this group are from the andesite unit (fig. 5). The second 

group comprises 171 samples with copper ≥2,000 ppm that 

were collected mostly from the rhyolite tuff unit in the part of 

the zone of supergene enrichment that was largely unaffected 

by later weathering. For each of the two datasets, 34 elements 

were found to have acceptable numbers of analyses above their 

respective lower limits of determination. 

Before the factor analysis was run on the two datasets, all 

analyses originally reported by the analysts with a concentration 

qualified with the letter “N” (not detected at the lower limit of 

determination accompanying the letter), “L” (detected but at 

a concentration less than the accompanying number), or “G” 

(detected at a concentration greater than the accompanying 

number) were first replaced with new concentrations, The 

concentrations qualified with an “N” were replaced by a value 

equal to 0.5 times the concentration given as the lower limit of 

determination. In a similar manner, the concentrations qualified 

with an “L” were replaced by a value equal to 0.7 times the 

lower limit of determination, and concentrations qualified with 

a “G” were replaced with a value equal to 1.4 times the upper 

limit of determination accompanying the letter. Frequency 

distribution histograms for the 34 elements were examined, 

and the type of distribution for each element was determined. 

Analyses for all but six elements (Fe, La, Rb, Tl, Y, and Zr) in 

each dataset showed distributions that most closely approximated 

a lognormal distribution. The analyses for the 28 remaining 

elements were converted to logarithms. Four other elements of 

interest (Bi, Cd, F, and W) were highly censored (that is, contained 

very few analyses not qualified with “N,” “L,” or “G”), and 

their frequency-distribution patterns could not be determined. 

The principal factor analysis method was used with a 

varimax rotation (Reimann and others, 2002). Factor models 

ranging from 7 to 10 factors were examined for each of the 

two datasets, and 8-factor models were selected as best representing known geological and chemical conditions in the study 

area. Table 3 shows the factors and their loading values for the 

hypogene zone dataset. This model accounts for 70 percent 

of the variance in the data. Table 3 also shows the factors and 

their loading values for the supergene zone dataset. This model 

accounts for 65 percent of the variance in the data. Negative 

loading values are shown where they are less than a value 

of -0.50. These negative values define those elements least 

likely to be associated with the elements loaded positively in 
R-Mode Factor Analysis 13

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of copper, in parts per million

Depth of formation unknown 

Mineralogical boundary

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of copper

Area with low concentration of copper

157

2,000

Area of copper concentrations, in parts

 per million

Greater than 2,000

1,000 to 2,000

1,000

500

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

1,000

500

500

2,000

2,000

2,000

2,000

1,000

1,000

1,000

1,000

1,000

1,000

500

500

500

500

500

500

500

2,000

1,000

2,000

1,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

TKr Tqm TKr

A A'

Copper + chalcopyrite + chalcocite

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

LOW

LOW

HIGH

LOW

LOW

LOW

HIGH

HIGH

HIGH

Top of chalcopyrite

Bottom of

chalcocite

HIGH

Top of chalcopyrite

HIGH

LOW

Bottom of chalcocite

Figure 5. Distributions of copper, chalcopyrite, and chalcocite in core samples. 
14 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

the same factor. The criteria described in Reimann and others 

(2002) require that the number of samples for a robust factor 

analysis be at least eight times the number of variables in a 

given dataset. Clearly the two datasets (254 and 171 samples, 

respectively, and 34 variables) do not meet this standard and 

thus the results must be viewed with caution.

Identifying the mineral host or hosts for the selected 

elements determined for this study helps in understanding the 

genesis of the formation of the Red Mountain Cu-Mo deposit. 

However, no chemical analyses of the host minerals have been 

done for most of the elements described below. Comments for 

many element and mineral associations and mineral hosts in 

the succeeding paragraphs are based on information presented 

in published reports or on observations of core specimens 

or outcrops. In many cases the mineral hosts have not been 

determined. Possible hosts noted in the literature have been 

Table 3. Factor loading values for core samples from the hypogene and supergene zones, Red Mountain, Arizona.

[Negative loading values shown where they are less than a value of -0.50. Negative loading values define those elements least likely to be associated with the 

elements loaded positively on the same factor]

Hypogene zone

Factor 1

(Andesite

accessory

minerals)

Factor 2

(Copper 

associated

minerals)

Factor 3

(Andesite accessory

minerals)

Factor 4

(Alkali-earth 

accessory

minerals)

Factor 5

(Sphalerite-galena 

suite)

Factor 6

(Potassium-rich 

minerals)

Factor 7

(Gold factor)

Factor 8

(Sulfide 

associated

minerals)

Ni 0.906 Ag 0.827 Zr 0.747 Rb 0.748 Mn 0.738 K 0.476 Au 0.659 Sb 0.790

V 0.887 Cu 0.824 Y 0.735 Cs 0.727 Zn 0.671 Tl 0.426 Na 0.514 As 0.727

Co 0.876 S 0.768 La 0.727 Li 0.655 Pb 0.526 B 0.629

Cr 0.866 Te 0.637 Ba 0.700 _______ _______ Hg 0.441

Fe 0.823 Mo 0.402 U -0.700 Sr -0.810

Sc 0.814 Ca -0.873

Ti 0.781

Mg 0.728

Supergene zone

Factor 1

(Rhyolite tuff

lithology

minerals)

Factor 2

(Rhyolite tuff

accessory

minerals)

Factor 3

(Lead-rich sulfosalt

minerals)

Factor 4

(Rhyolite tuff

accessory

minerals)

Factor 5

(Copper-associated

minerals)

Factor 6

(Rhyolite tuff

accessory

minerals)

Factor 7

(Gold factor)

Factor 8

(Rhyolite tuff

potassium-rich

minerals)

Mn 0.911 Ni 0.841 Sb 0.667 Zr 0.704 Cu 0.722 La 0.822 Na 0.765 K 0.708

Li 0.818 Cr 0.799 Hg 0.637 Ba 0.445 Mo 0.611 Y 0.620 Au 0.513 Rb 0.684

Ca 0.779 V 0.797 Pb 0.624 B 0.351 Te 0.508 U 0.605

Mg 0.757 Sc 0.730 As 0.617 S 0.322

Cs 0.703 Ti 0.690 Ag 0.561

Zn 0.335 Co 0.590 Tl 0.440

_______ Fe 0.548

S -0.598

Sr -0.732

given where appropriate, but for the most part, these hosts are 

considered speculative. 

The hypogene zone dataset (table 3) shows two factors 

(Factors 1 and 3) that are predominantly related to accessory 

minerals in the andesite lithology and six factors (Factors 2, 4, 

5, 6, 7, and 8) containing elements related to hypogene sulfide 

minerals or to associated alteration minerals. The elements in 

Factor 1 include (in order of loading values from highest to 

lowest) Ni, V, Co, Cr, Fe, Sc, Ti, and Mg. When these ferride 

elements occur together, it usually means that they are mostly 

associated with igneous iron-rich accessory minerals such 

as magnetite, micas, and amphiboles. These minerals have 

been observed in cores from the andesite unit. Iron is also a 

major constituent of the copper-associated minerals, pyrite 

and chalcopyrite; however, iron is most strongly associated 

only with the suite of ferride elements. Unpublished analyses 
R-Mode Factor Analysis 15

of pyrite concentrates from the Red Mountain area generally 

show relatively high concentrations of cobalt; thus, cobalt may 

also be hosted in pyrite. The elements in Factor 3 (Zr, Y, La, 

and Ba) are commonly found in accessory minerals that here 

are related to host-rock lithology. Factor 2 includes most of 

the hypogene copper-associated elements (in order, Ag, Cu, 

S, Te, and Mo). All of these elements except molybdenum are 

known to be hosted in chalcopyrite. Analyses of rocks from 

PCDs in Russia (Sindeeva, 1964) describe the presence of tellurium. Unpublished data of the author indicate that tellurium 

is also present in pyrite at Red Mountain. Molybdenum is also 

associated with this copper factor, confirming observations 

in core samples that chalcopyrite and molybdenite occur in 

veins together. The elements in Factor 4 (rubidium, cesium, 

lithium) can proxy for potassium in minerals such as orthoclase (Heier and Billings, 1970a, 1970b, 1970c); however, 

their respective mineral residences at Red Mountain have not 

been determined.

Factor 5 includes manganese, zinc, and lead. In the hypogene zone, lead and zinc commonly occur together in veins 

as galena and sphalerite, respectively. Manganese is known to 

proxy in both sphalerite and galena (Wedepohl, 1978). Factor 

6 includes the elements potassium and thallium. Thallium 

commonly proxies for potassium in potassium-bearing minerals (Albuquerque and Shaw, 1972). These two elements are 

mainly associated with hydrothermal orthoclase and biotite 

in the potassic alteration zone and with sericite in the phyllic 

zone. The large negative values for calcium and strontium in 

Factor 6 suggest a common depletion of these elements during 

potassium metasomatism. Factor 7 includes gold and sodium. 

The reason for this association is not clear but could possibly 

represent gold deposition associated with sodium-rich inclusions or with sodic feldspars. It may also be just a default 

association assigned by the mathematical technique, because 

in hypogene parts of PCDs, gold tends to be hosted in chalcopyrite and (or) pyrite (Crocket, 1974). 

Factor 8 includes other deposit-related elements: Sb, 

As, B, and Hg. Antimony and arsenic commonly substitute 

together in sulfides such as sphalerite, galena, chalcopyrite, 

and pyrite (Onishi, 1969), and are also commonly found 

in minerals such as enargite, famatinite, tetrahedrite, and 

tennantite. Most of these minerals are present at Red Mountain. Boron in PCDs is most commonly found in the mineral 

tourmaline, which has been identified in samples of core 

from scattered locations and is known to occur in the strongly 

mineralized part of PCDs (Cox, 1986). The overall concentrations of mercury are low in the Red Mountain system, and the 

mineral residence of this element is unknown. The association 

of boron with mercury, arsenic, and antimony in factor 8 is not 

entirely understood but implies a common time and (or) place 

of deposition for all four elements. These four elements are all 

associated spatially in high concentrations in the west limb of 

the deep part of the hypogene deposit.

The eight factors for the supergene zone dataset are also 

listed in table 3. In many cases, it is not certain whether the 

element associations in this zone are (1) related wholly or 

partly to lithology of the rhyolite tuff; (2) a result of hypogene 

processes, with or without modification by later supergene 

processes; or (3) entirely the result of supergene events. The 

elements in Factors 1, 2, 4, and 6 are related mostly to minerals 

associated with the rhyolite tuff lithology. The elements in 

Factors 3, 5, 7, and 8 are related mostly to minerals associated 

with the peripheral parts of the hypogene Cu-Mo deposit. 

Factor 1 includes six positively loaded elements (in order 

of factor-loading values: Mn, Li, Ca, Mg, Cs, and Zn) that exhibit 

relatively low concentrations in the supergene-affected part of the 

rhyolite tuff. The low concentrations for zinc indicate that this element, which is highly mobile chemically, has been leached from 

this zone. The relative low concentrations of the other elements 

are mainly related to the bulk, pre-mineralization chemistry 

of the rhyolite tuff unit. In contrast, the negatively-loaded 

elements on this factor (strontium and sulfur) have relatively 

high concentrations in this same area and are mostly associated 

with minerals that are common to the area and are relatively 

chemically immobile, such as clay minerals (strontium) 

(Stueber, 1976) and alunite (sulfur). Factor 2 includes a group 

of ferride elements (Ni, Cr, V, Sc, Ti, Co, and Fe) that are 

commonly associated with iron-rich accessory minerals, 

especially in the andesite unit. The association in the rhyolite 

tuff unit is not as clear. The intense alteration in that formation 

makes visual identification of accessory minerals difficult. 

Alternatively, at least some of this factor may be related to 

iron-rich pyrite and chalcopyrite.

Factor 4 includes zirconium, barium, and boron. Boron 

and barium are commonly associated with tourmaline and barite, 

respectively, both of which have been observed in drill core 

associated with the advanced argillic alteration zone, similar 

to that described for other PCDs (Guilbert and Park, 1986; 

Gustafson and Hunt, 1975; Knight, 1977; Sillitoe, 1983). 

Zirconium likely reflects the accessory mineral zircon. 

Factor 6 includes lanthanum, yttrium, and uranium; 

these three trace elements are often found in minerals such as 

biotite, hornblende, apatite, or monazite (Rogers and Adams, 

1974). However, their host minerals at Red Mountain have not 

been determined. 

Factor 5 contains many of the hydrothermal 

copper-associated elements (Cu, Mo, Te, and S). Minerals 

such as chalcopyrite, molybdenite, enargite, and tennantite 

have been observed in core samples from this upper part of the 

deposit. Also observed have been supergene-related chalcocite 

and ferrimolybdite, the latter of which is probably related to 

formation of the leached cap (Vikre, 2010). Both ferrimolybdite 

and molybdenite are present in outcrops on Red Mountain. As 

noted previously, tellurium can proxy in chalcopyrite.

The hypogene-related elements in Factor 3 for the 

supergene zone (Sb, Hg, Pb, As, Ag, and Tl) have also not 

been strongly leached during supergene enrichment and are 

thought to be mostly associated with generally insoluble 

lead-rich minerals. In the supergene zone, observations in core 

samples indicate that some of the lead is still present as galena. 

Although not noted in core logs for the fence of drill holes, 

core logs for other holes have noted the presence of anglesite 
16 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

and other lead minerals such as plumbojarosite. As noted for 

the hypogene zone, the mineral residence for mercury is not 

known. In this upper part of the deposit system, both 

mercury and thallium may be substituting in hypogene- or 

supergene-generated, lead-rich minerals (Albuquerque and 

Shaw, 1972). 

Factor 7 again shows an association of gold with 

sodium that is not clearly understood in this environment 

and further suggests a misleading default association assigned 

by the mathematical technique. In both the hypogene and 

supergene zones of this deposit, the residency of gold has not 

been identified. 

Factor 8 includes potassium and rubidium. Rubidium 

commonly proxies in potassium-rich minerals (Heier and Billings, 

1970a; 1970b). Both elements probably occur in this part of 

the supergene zone mostly in potassium-rich minerals such as 

sericite, alunite, and jarosite. 

Distributions of Elements and Minerals 

in the Subsurface

Plots of element and mineral concentrations have been 

made on cross sections for selected elements and minerals 

(Horton and others, 2020) present in the fence of seven drill holes. 

The location of this section is shown on figure 2. The individual 

sections (figs. 5–39) provide a two-dimensional view of the 

distribution of various elements and minerals through the approximate vertical center of the Red Mountain PCD. The figures 

are classified into two general categories: (1) mainly hypogene 

sulfide-related elements and minerals and (2) mainly lithology- or 

alteration-related elements and minerals. 

The distributions and concentrations of elements and 

minerals shown on the sections represent a culmination of the 

original distributions and concentrations in the volcanic host 

rocks that have been overprinted by two or more hydrothermal 

events related to formation of the PCD, followed, at least 

locally, by a supergene event and then by weathering in 

the near surface part of the deposit. In conjunction with the 

information provided by the factor analyses, the sections 

were examined to determine the element distributions that are 

mostly related to lithology, those that are related to hypogene 

or supergene events, those that are related to the leached cap, 

those that might reflect multiple origins, and (or) those that 

show no obvious spatial relations. Of the 44 elements listed 

in table 2, 14 (Ba, Be, Cr, Cs, La, Li, Ni, Rb, Sc, Sr, Ti, V, Y, 

and Zr) do not show any meaningful analytical variation or do 

not clearly delineate areas of element concentration that can 

be consistently related either to specific lithologic units or to 

hypogene or supergene alteration or mineralization. 

The analyses for three additional elements (bismuth, tin, 

and tungsten) are too highly censored (have too few analyses 

above their respective lower limits of determination) to provide 

meaningful data for factor analysis or for detailed element 

plots for the entire area of the section. However, they do show 

restricted but meaningful anomalies, which are described in 

the succeeding paragraphs. 

 At Red Mountain, some elements, particularly some 

of the major elements, contain a component related to the 

pre-mineralization host-rock chemistry and a component 

resulting from the chemical overprinting of the host-rock 

units during formation of the mineral deposit. For comparison 

purposes, two subsets of analyses were compiled to provide 

estimates of the pre-mineralization concentration values for 

selected elements in the andesite unit. The first was established 

by using analyses of 27 samples of unaltered or weakly 

propylitically altered andesite from the rock dataset (Horton and 

others, 2020) that were collected in the study area but outside 

of the area of the Red Mountain deposit. A second subset was 

compiled using analyses of 46 similar andesite samples in the 

USGS National Geochemical Database that were collected 

generally in the area immediately north of the study area. 

Table 2 summarizes the range of concentrations and median 

values for the selected elements, as well as the median concentrations of these two andesite datasets. The median concentration 

values are deemed to estimate the original or typical threshold 

concentrations of elements in the andesite unit.

The contour lines were manually drawn, not computer 

generated, in order to best approximate the effect of the host rock 

chemistry. Because of local variations in element distributions, 

the locations of the contour lines should be considered as 

approximate.

Mainly Hypogene Sulfide-Related Elements 

and Minerals

Elements in this category include Cu, Ag, S (as both total 

S and sulfate S), Te, Mo, Au, Pb, Zn, Hg, As, and Sb. Minerals 

that contain high concentrations of these elements, and for 

which enough data exist to plot their distributions, include 

chalcopyrite, chalcocite, anhydrite, and alunite.

Copper, Chalcopyrite, and Chalcocite—Figure 5 shows 

the distribution of copper, as well as those of visible chalcopyrite 

and chalcocite, in the core samples. The estimated threshold 

concentration for copper ranges from 40 to 47 ppm (table 2). 

Copper exhibits concentrations greater than (>) 100 ppm 

throughout almost all of the area of the section but is clearly 

more concentrated in the vertical center of the section. The 

extent of copper concentrations at depth is controlled by the 

depth of drilling and has not been completely defined. The 

lateral extent of anomalous copper concentrations beyond the 
Distributions of Elements and Minerals in the Subsurface 17

section is unknown but clearly extends to the right (east) of 

drill hole 158, in which many samples exhibit concentrations 

exceeding 100 ppm copper (Horton and others, 2020). 

For purposes of discussion, the hypogene and supergene 

parts of the Cu-Mo deposit are defined to include areas 

containing ≥1,000 ppm of copper. These areas have been 

added to all of the succeeding sections (figs. 6–39) for reference. 

The two limbs of the deep part of the hypogene deposit, are 

part of the crude, inverted cup configuration of this deposit 

in two dimensions that are best defined by 2,000-ppm copper 

contours. These limbs are generally associated spatially with 

quartz monzonite porphyry intrusive bodies. A second, more 

restricted mid-level zone (≥2,000 ppm Cu), which contains 

both chalcopyrite and chalcocite, is present above the deep 

part of the hypogene deposit, mainly in the andesite unit. This 

mid-level zone represents an overlapping of hypogene and 

supergene copper minerals. 

In the rhyolite tuff unit, a distinct area outlined by 

1,000- and 2,000-ppm copper contours delineates the area 

most enriched in copper as a result of supergene processes 

(fig. 5). It is noteworthy that chalcopyrite is still present in the 

center of the section almost to the present surface, indicating 

that hypogene mineralization extended at least to that elevation. 

Visible chalcocite extends to depths of as much as 950 m below 

the present surface. The overall depth of chalcocite is shown 

as an approximate boundary line on figure 5. Below this line, 

copper occurs almost entirely as chalcopyrite, occasionally 

accompanied by bornite. Above this line, chalcocite is commonly 

observed. Other copper-rich minerals observed in core in this 

area include enargite, chalcopyrite, tennantite, and minor 

amounts of covellite. Both 500- and 1,000-ppm copper contours 

surround the entire deposit, emphasizing that copper concentrations are continuous and anomalous over a large area. In spite of 

weathering, copper is highly concentrated at the present surface, 

especially directly above the hypogene Cu-Mo deposit. The 

distributions of copper, chalcopyrite, and chalcocite are in 

general agreement with those of Lecumberri-Sanchez and 

others (2013).

Silver.—The factor analyses (table 3) show silver associated 

with copper in the hypogene zone and with lead and other 

elements in the supergene zone. The estimated threshold value 

for silver is <0.008 ppm (table 2). The distributions at depth 

of high (>1 ppm) silver concentrations (fig. 6) correlate well 

spatially with the distributions of copper in the deep part of 

the hypogene deposit (fig. 5). The distributions of similar high 

silver concentrations in the upper part of the system form a 

wide zone that is spatially associated with peripheral hypogene 

and supergene copper and lead minerals. Like copper, silver is 

anomalous at the present surface.

Total Sulfur, Sulfate Sulfur, Anhydrite, and Alunite.—The 

threshold value for total sulfur is estimated to be <0.05 percent 

(table 2). Figure 7 shows the distribution of total sulfur, which 

includes sulfides, sulfates, and other minor mineral forms such 

as sulfosalts. As observed for copper, sulfur is highly concentrated throughout the entire area of the section. Examination 

of the drill core indicates that almost all of the sulfide sulfur 

occurs in pyrite, chalcopyrite, molybdenite, or chalcocite; 

the amounts of enargite, tennantite, sphalerite, galena, and 

other sulfur-rich species are relatively minor. A total sulfur 

anomaly (>2.0 percent) correlates spatially with the deep part 

of the hypogene Cu-Mo deposit. The upper part of the system 

exhibits the highest concentrations of total sulfur (generally 

>4.0 percent), partly reflecting the more intense pyritization 

present near the top of the system, as described later for pyrite. 

The highest sulfur concentrations in this area are also related 

to chalcocite formed during supergene enrichment. Sulfur is 

anomalous at the present surface, mainly in the form of sulfate 

minerals such as alunite. Alunite and both pyrite and molybdenite have been observed locally in outcrops.

Figure 8 shows the distribution of sulfate sulfur, anhydrite, 

and alunite. The area with the highest (>0.40 percent) concentrations of sulfate in the deeper part of the system correlates 

spatially with the general area of the deep part of the hypogene 

Cu-Mo deposit, and the 0.20-percent contour correlates spatially, at least in the vertical center of the deposit, with the 

top of the area containing visible anhydrite. The anhydrite 

line was determined on the basis of its presence or absence in 

core samples and not on its relative concentrations. Pervasive 

hypogene alunite associated with advanced argillic alteration 

occurs throughout the area above the line marking the base 

of XRD alunite. Alunite also occurs in the upper 100 m of the 

system in younger veins that cut areas of pervasive alunite. 

This relation can also be seen locally in outcrops. Gypsum, 

anglesite, jarosite, and barite are also locally present in the 

upper part of the deposit. 

Tellurium.—The estimated threshold value for tellurium 

ranges from <0.01 to <0.1 ppm and may be as low as the 

crustal abundance value of 0.005 ppm (table 2). Anomalous 

(>0.5 ppm) tellurium is spatially associated with the limbs 

of the deep part of the hypogene deposit and is more concentrated in the (left) west limb (fig. 9). High concentrations 

of tellurium (>1 ppm) in the upper part of the system are 

mostly confined to the rhyolite tuff unit and occur in the area 

exhibiting the highest concentrations of total sulfur (fig. 7) 

and pyrite. 

The broad tellurium anomaly (>0.5 ppm) in the upper 

part of the deposit extends locally to the present surface, 

especially directly above the deep part of the hypogene 

Cu-Mo deposit, indicating that tellurium is relatively 

immobile chemically in the weathering environment. This 

near-surface tellurium distribution corroborates the description by Sillitoe (1983) of several porphyry copper deposits 

that contain tellurium in the enargite zones associated with 

advanced argillic alteration.
18 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of silver, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of silver

Area with low concentration of silver

157

2

Area of silver concentrations, in parts per million

Greater than 2

1 to 2 

1

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

1

1

1

1

1

2

2

2

2

2

2

1

1

1

2

2

2

2

1

1

1

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Silver

LOW

LOW

HIGH

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH

HIGH

HIGH

Figure 6. Distribution of silver in core samples.
Distributions of Elements and Minerals in the Subsurface 19

NOT TO SCALE DATUM IS SEA LEVEL

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

EXPLANATION

Concentrations of total sulfur, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of total sulfur

Area with low concentration of total sulfur

157

6.00

Area of sulfur concentrations, in percent

Greater than 6.00

4.00 to 6.00 

4.00

2.00

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

2.00

2.00

2.00

2.00

4.00

4.00

4.00

4.00

2.00

2.00

2.00

2.00

2.00

4.00

4.00

4.00

2.00

2.00

2.00

4.00

6.00

6.00

4.00

4.00

4.00

4.00

4.00

4.00

2.00

2.00

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Total sulfur

HIGH

LOW

LOW

LOW

HIGH

HIGH

HIGH

LOW

LOW

Figure 7. Distribution of total sulfur in core samples.
20 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

EXPLANATION

Mineralogical boundary

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of sulfate sulfur, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of sulfate sulfur

Area with low concentration of sulfate sulfur

157

0.40

Area of sulfate concentrations, in percent

Greater than 0.40

0.20 to 0.40

0.20

0.10

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

0.10

0.20

0.20

0.10

0.10

0.10

0.10

0.10

0.40

0.40

0.40

0.40

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

TKr Tqm TKr

A A'

Sulfate sulfur + anhydrite and alunite

Top of visible anhydrite

Base of X-ray diffraction alunite

Base of X-ray diffraction

alunite

LOW

LOW

LOW

LOW

LOW

LOW

High X-ray diffraction alunite

Top of visible anhydrite

HIGH

HIGH

HIGH

Figure 8. Distributions of sulfate sulfur, anhydrite, and alunite in core samples.
Distributions of Elements and Minerals in the Subsurface 21

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of tellurium, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of tellurium

Area with low concentration of tellurium

157

3

Area of tellurium concentrations, in parts

 per million

Greater than 3

1 to 3

1

0.5

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

1

3

3

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

1

1

1

1

1

1

1

1

1 

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm

TKr

TKr

A A'

Tellurium

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

LOW

LOW

HIGH

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH

LOW

Figure 9. Distribution of tellurium in core samples. 
22 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Molybdenum.—The estimated threshold value for 

molybdenum is about 3 ppm (table 2). Figure 10 shows the 

distribution of molybdenum. The relatively few observations 

of visible molybdenite in core samples and the relatively 

low chemical concentrations of molybdenum together make 

defining the complete distribution of molybdenite difficult. 

High concentrations (>20 ppm) of molybdenum are present in both limbs of the deep part of the hypogene deposit 

(fig. 10). Unlike some other elements, molybdenum is more 

concentrated in the right (east) limb and above the east limb. 

In the deep part of the hypogene deposit, all of the molybdenum occurs as molybdenite. High concentrations (>50 ppm) 

of molybdenum are present in the near-surface area directly 

above the deep hypogene Cu-Mo deposit. These distributions are in general agreement with the spatial associations 

of molybdenum noted by Lecumberri-Sanchez and others 

(2013). The high concentrations of molybdenum in the nearsurface area are composed of both hypogene molybdenite 

and ferrimolybdite, the latter of which is probably related to 

formation of the leached cap (Vikre, 2010).

Gold.—Gold is present in the Red Mountain system. 

However, overall concentrations are low, as is typically the 

case for molybdenum-rich PCDs formed in the continental 

crust environment of the southwestern United States 

(Kesler, 1973). The estimated threshold value for gold is 

<0.002 ppm (table 2). Figure 11 shows the distribution of 

gold. The overall distribution of the highest concentrations 

(>0.05 ppm) of gold generally correspond spatially to the 

areas of deep and mid-level chalcopyrite concentrations 

(fig. 5) and generally agree with the distribution of gold 

shown by Lecomberri-Sanchez and others (2013). This 

distribution implies that gold is probably associated with 

chalcopyrite. However, pyrite is another possible host. Vikre 

(2010) notes that supergene enrichment of gold has not been 

documented in PCDs. However, supergene enrichment of 

gold has been identified in deposits in deeply weathered 

laterite terrains in Western Australia, Africa, and South 

America (Butt, 1988; Monti, 1987). The concentrations 

(>0.02 ppm) of gold in the near-surface part of the Red 

Mountain deposit, in an area that coincides approximately 

with supergene-related copper >1,000 ppm, may have 

therefore resulted from supergene enrichment. More likely, 

this near-surface gold concentration represents a separate 

zone of hypogene gold. Gold is anomalous (>0.02 ppm) at 

the present surface.

Arsenic.—The estimated threshold value for arsenic is 

about 5–6 ppm (table 2). High concentrations (>50 ppm) of 

arsenic (fig. 12) generally correlate spatially with the left 

(west) limb of the deep part of the hypogene deposit but not 

with the right (east) limb at this concentration level. A small 

mid-level zone containing similar high concentrations of 

arsenic is also present above the west limb.

The highest concentrations of arsenic (>100 ppm) are 

found in a broad zone in the uppermost, near-surface part 

of the system, that may be a broad hypogene halo above 

the deep hypogene Cu-Mo deposit in which arsenic has not 

migrated as a result of supergene enrichment and (or) 

weathering. Arsenic is highly concentrated at the present 

surface, including in the leached cap weathered zone. The 

factor analysis (table 3), as well as the common distributions 

of elements, imply that much of the arsenic and antimony 

concentrations are associated with lead minerals in the 

uppermost part of the hypogene deposit. Enargite/famatinite 

and tennantite/tetrahedrite are additional minerals that contain 

arsenic and (or) antimony. Pyrite is another possible host.

Antimony.—The estimated threshold value for antimony 

at Red Mountain is not well defined but is probably <1 ppm 

(table 2). At depth, antimony exhibits concentrations (>2 ppm) 

(fig. 13) that are spatially coincident with the limbs in the 

deep part of the hypogene deposit. Like arsenic, the left 

(west) limb has higher (>10 ppm) antimony concentrations 

than does the right (east) limb. Similar to arsenic, high antimony concentrations (>10 ppm) are found in a broad area in 

the uppermost part of the deposit that may represent a hypogene halo above the deep part of the deposit. In this upper 

part of the system, the area with >4 ppm antimony broadly 

overlaps the >10 ppm arsenic zone. Like arsenic, antimony 

anomalies extend to the present surface. This distribution 

confirms the data of Levinson (1974, 1980) that antimony 

tends to be relatively immobile. 

Mercury.—The threshold value for mercury is estimated 

to be <0.02 ppm (table 2). Similar to distributions for arsenic 

and antimony, high concentrations (>0.06 ppm) of mercury 

show a close spatial association with the west limb of the 

deep part of the hypogene deposit (Fig. 14). A restricted area 

of high concentrations (>0.06 ppm) of probable hypogenerelated mercury is present in part of the uppermost part of the 

system, directly above the deep part of the hypogene Cu-Mo 

deposit. This restricted area might also represent the remnants of a crude halo around the deep part of the hypogene 

deposit. Mercury concentrations are low in the near-surface, 

right (eastern) side of the section, probably because of dispersion of this element in the weathering environment that 

produced the leached cap.
Distributions of Elements and Minerals in the Subsurface 23

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of molybdenum, in parts

 per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of molybdenum

Area with low concentration of molybdenum

157

50

Area of molybdenum concentrations, in parts

 per million

Greater than 50

20 to 50

20

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

20

20

20 

20

20

20

20

20

20

20

20

50

50

20

20

20

20

50

50

50

50

20

20

50

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

Tqm

TKr

TKr

A A'

Molybdenum

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

LOW

LOW

HIGH

HIGH

HIGH

LOW

HIGH

LOW

Figure 10. Distribution of molybdenum in core samples.
24 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of gold, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of gold

Area with low concentration of gold

157

0.10

Area of gold concentrations, in parts

 per million

Greater than 0.10

0.05 to 0.10

0.05

0.02

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

0.02

0.05

0.10

0.02

0.05

0.05

0.05

0.05

0.05

0.05

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.05

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

Tqm TKr

TKr

A A'

Gold

LOW

LOW

HIGH

HIGH

LOW

LOW

LOW

LOW

HIGH

HIGH

LOW

Figure 11. Distribution of gold in core samples.
Distributions of Elements and Minerals in the Subsurface 25

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of arsenic, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of arsenic

Area with low concentration of arsenic

157

100 

Area of arsenic concentrations, in parts

 per million

Greater than 100

50 to 100

50

10

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

50

50

50

10

10

10

10

10

10

10

10

10

10

10

10

50

100

10

10

10

50

50

50

50

50

50

50

10

10

50

50

50

50 100

100

100

100

10

HIGH

HIGH

HIGH

LOW

LOW

LOW

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm TKr TKr

A A'

Arsenic

Figure 12. Distribution of arsenic in core samples.
26 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of antimony, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of antimony

Area with low concentration of antimony

157

10

Area of antimony concentrations, in parts

 per million

Greater than 10

4 to 10

4

2

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

10

10

4

4

4

4

4

4

4

4

4

2

2

2

2

4

2

2

4

4

4

2

2

2

2

4

10

10

10

2

2

2

2

2

LOW

LOW

LOW

LOW

LOW

HIGH

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm TKr TKr

A A'

Antimony

HIGH

Figure 13. Distribution of antimony in core samples.
Distributions of Elements and Minerals in the Subsurface 27

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of mercury, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of mercury

Area with low concentration of mercury

157

0.10

Area of mercury concentrations, in parts

 per million

Greater than 0.10

0.08 to 0.10

0.08

0.06

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

0.08

0.08

0.06

0.06

0.08

0.08

0.06

0.06

0.08

0.08

0.08

0.08

0.1

0.1

0.06

0.06

0.06

0.06

0.06

0.06

0.08

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.08

0.1

0.1

0.1

0.08

0.08

0.1

0.1

0.08

HIGH

LOW

LOW LOW

LOW

HIGH

HIGH

HIGH

HIGH

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158 TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm TKr TKr

A A'

Mercury

Figure 14. Distribution of mercury in core samples.
28 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Lead.—The estimated threshold value for lead ranges 

from 11 to 50 ppm (table 2). The distribution of lead (fig. 15) 

suggests that the value is probably <30 ppm and thus closer 

to the crustal abundance value of 17 ppm. Concentrations of 

lead between 30 and 100 ppm are present in parts of the right 

(east) limb in the deep part of the deposit but are more highly 

concentrated (>100 ppm) in and west of the left (west) limb. 

The highest lead concentrations (>500 ppm) are in the upper 

part of the system within a broad area of >100 ppm lead. 

Both hypogene galena and supergene- or weathering-related 

anglesite have been observed in cores from the near-surface 

part of the deposit. This broad area could thus be interpreted as 

a hypogene halo above the deep part of the hypogene deposit 

that may have been partly altered and enriched by supergene 

or weathering processes. Lead is relatively immobile in the 

supergene and weathering environments at Red Mountain and 

is present in high concentrations at the present surface. 

Zinc.—The estimated threshold value for zinc ranges from 

60 to 89 ppm (table 2). Like lead and some other elements, 

zinc is not noticeably concentrated (>100 ppm) in parts of the 

right (east) limb of the deep part of the deposit (fig. 16) but is 

most highly concentrated (>500 ppm) in the area of the left 

(west) limb. Zinc is also generally concentrated in a broad, 

roughly horizontal zone that extends across the upper mid-level 

part of the system. As is the case for other elements, this zone 

may represent the remnants of a broad hypogene halo above 

the deep part of the Cu-Mo deposit. Unlike lead, zinc is highly 

mobile in the low pH environment associated with oxidizing 

pyrite; thus, the zone of low zinc concentrations at the top of 

the system reflects leaching of zinc during supergene enrichment and (or) during post supergene weathering related to 

formation of the leached cap.

Other elements.—Three other analyzed elements (bismuth, 

tin, and tungsten) are associated with the hypogene events of 

the PCD at Red Mountain. These elements were not included 

in the factor analysis because their respective datasets contained too few analyses above their respective lower limits 

of determination. Accordingly, only the samples with high 

concentrations of these elements can be evaluated and plotted.

Bismuth.—The mineral residence of bismuth at Red 

Mountain is not known. It is a common constituent of sulfide 

minerals such as galena, sphalerite, chalcopyrite, and pyrite 

(Ahrens and Erlank, 1969), all of which are present in the 

deposit area. The estimated threshold value for bismuth is not 

well established but is probably <1 ppm, as compared to the 

crustal abundance value of 0.16 ppm (table 2). Anomalous 

concentrations of bismuth in the deep part of the hypogene 

Cu-Mo deposit occur in a few scattered localities (fig. 17). 

These concentrations range from “10L” (less than the lower 

limit of determination of 10 ppm, which is plotted as 7 ppm) 

to 20 ppm except for one sample in the deep part of drill hole 

145 that was reported as 500 ppm (Horton and others, 2020). 

This sample occurs within a 10-ppm contour near the top of 

the felsite-latite formation. The highest bismuth concentrations, 

however, are centered mostly in the near-surface part of the 

system directly above the deep part of the hypogene deposit. 

This distribution most closely matches that of lead (fig. 15), 

with the highest area of bismuth concentrations in a more 

restricted area than that of lead. This anomalous area is similar 

to the anomalies of elements such as mercury, tin, thallium, 

and tungsten. High bismuth concentrations in the uppermost 

part of the Red Mountain system agree with similar observations 

noted by Sillitoe (1983) for the Lepanto, Philippines, copper 

deposit. Bismuth is one of the elements at Red Mountain that 

represents the most distant manifestations of the deep part of 

the hypogene deposit. The distribution of near-surface bismuth 

implies that it is probably located where originally deposited 

and has not been significantly remobilized by supergene 

enrichment or subsequent weathering processes.

Tin.—The mineral residence of tin at Red Mountain is not 

known. No tin minerals were identified in the drill core logs 

reviewed for this study. Tin is known to occur in micas and 

other rock-forming minerals and in sulfide minerals (Hamaguchi and Kuroda, 1969). An estimated threshold value for tin 

could not be determined from the Red Mountain data but is 

clearly <10 ppm and probably closer to the crustal abundance 

value of 2.1 ppm (table 2). Concentrations of tin were detected 

in a few scattered localities in the area of the deep part of the 

hypogene Cu-Mo deposit (fig. 18). High tin concentrations 

(including reported concentrations between “10L” [less than 

the lower limit of determination of 10 ppm, plotted as 7 ppm] 

and 70 ppm [Horton and others, 2020], which is within the 

plotted area of the 20-ppm contour) are more widely concentrated in a broad zone in the upper part of the deposit. This 

latter area corroborates similar observations of Sillitoe (1983) 

for tin concentrations in the upper parts of other PCDs. The 

distribution of tin at Red Mountain implies that it may be 

associated with lead-rich minerals or possibly molybdenum 

minerals. Some of the tin may also be associated with accessory minerals present in the rhyolite tuff unit. Like bismuth, tin 

is probably located where it was originally deposited during 

formation of the hypogene Cu-Mo deposit. Tin is also relatively immobile with respect to supergene enrichment and (or) 

weathering processes and is anomalous at the present surface. 

Tungsten.—A reliable estimated threshold value for tungsten 

could not be determined, but it is clearly <50 ppm and probably 

is closer to the crustal abundance value of 1.9 ppm (table 2). 

The mineral residence of tungsten at Red Mountain is also not 

known. At low concentrations, such as those present there, 

tungsten can substitute for molybdenum. This substitution 

may be the case at Red Mountain because tungsten anomalies, 

including reported concentrations between “50L” (less than 

the lower limit of determination of 50 ppm, plotted as 30 ppm) 

and 150 ppm ([Horton and others, 2020], which is within the 

plotted area of the 50-ppm contour) (fig. 19), particularly in 

the near-surface part of the deposit, generally occur where 

molybdenum is most highly concentrated (fig. 10). This 

restricted near-surface tungsten anomaly is probably located 

where tungsten was originally deposited. Tungsten, another 

element that is relatively immobile with respect to supergene 

enrichment and (or) weathering processes at Red Mountain, is 

anomalous at the present surface.
Distributions of Elements and Minerals in the Subsurface 29

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of lead, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of lead

Area with low concentration of lead

157

500

Area of lead concentrations, in parts

 per million

Greater than 500

100 to 500

100

30

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

30

30

30

100

100

100

100

30

30

30

100

100

100

100

100

100

500

500

100

100

100

100

500

500

100

100

30

30

30

30

30

500

500

500

100

100

HIGH

LOW

LOW

LOW

LOW

HIGH

HIGH

HIGH

LOW

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm Tqm

TKr TKr

A A'

Lead

Figure 15. Distribution of lead in core samples.
30 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of zinc, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of zinc

Area with low concentration of zinc

157

1,000

Area of zinc concentrations, in parts

 per million

Greater than 1,000

500 to 1,000

500

200

100

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

500

500

200

500

1,000

500

500

500

500

500

500

500

500

200

100

500

500

200

200

200

200

200

200

500

1,000

1,000

500

100

100

100

100

100

100

100

1,000

200

200

100

100

100

100

200

200

500

500

1,000

1,000

HIGH

LOW

LOW

LOW

HIGH HIGH

LOW

HIGH

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm Tqm

TKr TKr

A A'

Zinc

Figure 16. Distribution of zinc in core samples.
Distributions of Elements and Minerals in the Subsurface 31

NOT TO SCALE DATUM IS SEA LEVEL

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

EXPLANATION

Concentrations of bismuth, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of bismuth

Area with low concentration of bismuth

157

10

Area of bismuth concentrations, in parts per million

Greater than 10

7 to 10

7

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

HIGH

LOW

LOW

LOW

LOW LOW

7

7

7

7

7

7

10

10

10

10

10

10

10

10

7

10 7

7

7

10

7

7

7

10 7

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Bismuth

Figure 17. Distribution of bismuth in core samples.
32 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of tin, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of tin

Area with low concentration of tin

157

20

Area of tin concentrations, in parts

 per million

Greater than 20

15 to 20

15

10

7

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

20

15

20

15

10

7

10

10

10

7

15

10 7

7

7

7

7

7

7

7

10

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm

TKr TKr

A A'

Tin

Figure 18. Distribution of tin in core samples.
Distributions of Elements and Minerals in the Subsurface 33

NOT TO SCALE DATUM IS SEA LEVEL

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

EXPLANATION

Concentrations of tungsten, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of tungsten

Area with low concentration of tungsten

157

50

Area of tungsten concentrations, in parts per million

Greater than 50

30 to 50

30

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

30

30

30

30 50

50

30

30

30

30

30

30

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm TKr Tqm TKr

A A'

Tungsten

Figure 19. Distribution of tungsten in core samples.
34 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Mainly Lithology- and Alteration-Related 

Elements and Minerals

 Selected elements in this group of mainly lithology- and 

alteration-related elements include K, Tl, Co, Ca, Na, Mn, B, 

U, and Mg. Selected minerals include orthoclase, kaolinite 

and clay minerals, pyrophyllite, magnetite, pyrite, hematite, 

calcite, plagioclase, chlorite, quartz, and mica, as described in 

the succeeding paragraphs. 

Potassium and Thallium.—The analytical ranges of 

potassium and thallium concentrations are limited compared 

to many of the other selected elements. As a consequence, it is 

difficult to contour concentrations of these two elements in any 

detail. The estimated threshold value for potassium is about 

2.50 percent and for thallium is about 0.20 ppm (table 2). The 

distributions of potassium and thallium are shown on figures 

20 and 21, respectively. In both the deep and mid-level areas, 

most of the potassium is associated with orthoclase (fig. 22). 

Other potassium minerals include sericite, alunite, and jarosite, 

which are mostly present in the rhyolite tuff unit. Biotite, 

another potassium-rich mineral, is commonly accompanied with 

magnetite and is widely disseminated throughout the andesite 

unit, probably as a result of the early potassic alteration phase. 

These two minerals produce a distinct black color in drill core 

samples. In the deep part of the hypogene Cu-Mo deposit, high 

concentrations (>3.00 percent) of potassium coincide spatially 

with both limbs (fig. 5). Similar concentrations extend in an 

arcuate halo over the mid-level part of the deposit. 

The high (>3.00 percent) potassium concentrations in the 

westernmost drill hole 157 and in the bottom of adjacent hole 

145 are related to higher overall potassium and orthoclase 

contents in the felsite-latite unit and not to the hypogene 

Cu-Mo deposit.

Both potassium and thallium exhibit relatively low concentrations in the “barren” core area of the deposit. Thallium 

(fig. 21) exhibits weak concentrations (1–2 ppm) in the area of 

both limbs of the deep hypogene deposit, where it likely substitutes for potassium in orthoclase. Thallium is most highly 

concentrated (>3 ppm) in a broad zone in the upper part of the 

system, with the highest concentrations found directly above 

the deep part of the hypogene deposit. The factor analysis for 

the hypogene dataset shows thallium associated with potassium (table 3), whereas thallium in the supergene dataset is 

associated with lead and other elements (table 3). Thallium is 

known to be hosted in lead minerals (Albuquerque and Shaw, 

1972). In agreement with this observation, the thallium distribution in the upper part of the deposit is spatially similar to the 

zone containing high lead concentrations (fig. 15). In contrast 

to orthoclase, thallium, like lead, is concentrated at the present 

surface of the deposit, which is probably its original location. 

Thus, thallium has not been significantly mobilized as a result 

of supergene enrichment or weathering processes.

Orthoclase.—The highest orthoclase concentrations 

(50-unit contour line) (fig. 22) encompass areas that are 

closely associated with the quartz monzonite porphyry, and 

with areas with high concentrations of potassium and thallium 

(figs. 20 and 21). The 20-unit contours form an extensive halo 

peripheral to the areas of quartz monzonite porphyry, and 

mainly in the andesite unit. This distribution may define the 

general limit of the late-stage potassic alteration zone. Only 

relatively low concentrations (<20-unit contour) of orthoclase 

are present in the “barren” core area of the hypogene Cu-Mo 

deposit, where sodium and plagioclase concentrations are 

both relatively high. Orthoclase is found in relatively high 

concentrations (>20-unit contour) in the felsite-latite unit. 

Both potassium and orthoclase are present in relatively low 

concentrations in the rhyolite tuff unit. The 10-unit contour for 

orthoclase in the andesite unit roughly defines the lower limit 

of supergene effects in this deposit. Above this line both premineralization and deposit-related orthoclase has been largely 

replaced by sericite, clay minerals, and alunite.

Kaolinite and Other Clay Minerals.—This category 

includes all clay minerals, with kaolinite being the dominant 

species. Only a few scattered, weak clay-related anomalies are 

present in the deep part of the system. In contrast, the rhyolite tuff unit exhibits relatively high concentrations (>10-unit 

contours) of clay minerals (fig. 23), which are thought to be 

primarily a product of advanced argillic alteration (Guilbert 

and Park, 1986). However, it is possible that the rhyolite tuff 

may have contained some pre-mineralization clay minerals. 

Clay minerals are generally absent in the near-surface area as a 

result of weathering during formation of the leached cap.

Pyrophyllite.—Pyrophyllite was detected by XRD analyses in only a few samples. However, it was easily identifiable 

in drill core by its appearance and greasy feel. This mineral is 

present in a distinct, nearly horizontal zone in the upper part of 

the deposit (fig. 24), which is almost entirely confined to the 

rhyolite tuff unit and is associated with the zone of advanced 

argillic alteration (Guilbert and Park, 1986). Pyrophyllite has 

also been destroyed near the surface as a result of weathering 

related to formation of the leached cap.

Magnetite and Biotite.—Figure 25 shows the upper limit 

of visible black biotite and XRD-determined magnetite and the 

distribution of magnetite. Both magnetite and biotite are found 

mostly in the andesite unit. The unaltered andesite unit is normally a medium to dark gray, whereas hydrothermally altered 

andesite is black because of a combination of high contents of 

magnetite and fine-grained biotite that are related to the early 

potassic alteration event (Quinlan, 1986; Lecumberri-Sanchez 

and others, 2013). The upper limit of this mineralogical boundary 

also marks the approximate depth of supergene enrichment. The 

deep zone of high (>10-unit contour) magnetite concentrations 

roughly encompasses the area containing high concentrations 

for many of the elements associated with the hypogene Cu-Mo 

deposit, including copper, silver, molybdenum, and sulfur. 
Distributions of Elements and Minerals in the Subsurface 35

NOT TO SCALE DATUM IS SEA LEVEL

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

EXPLANATION

Concentrations of potassium, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of potassium

Area with low concentration of potassium

157

4.00

Area of potassium concentrations, in percent

Greater than 4.00

3.00 to 4.00

3.00

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

LOW

LOW

HIGH

HIGH

HIGH

HIGH

LOW

LOW

4.00

4.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

4.00

4.00

4.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00 3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

4.00

3.00

3.00

3.00

3.00

4.00

4.00

4.00

4.00

3.00

4.00

4.00

4.00

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Potassium

Figure 20. Distribution of potassium in core samples.
36 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of thallium, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of thallium

Area with low concentration of thallium

157

5

Area of thallium concentrations, in parts

 per million

Greater than 5

3 to 5

3

2

1

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

3

3

2

1

1

1

1

1

1

2

2

2

2

2

2

2

2

2

2

3

3

5

5 5

3

LOW

LOW

HIGH

HIGH

HIGH

HIGH

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm

TKr TKr

A A'

Thallium

Figure 21. Distribution of thallium in core samples.
Distributions of Elements and Minerals in the Subsurface 37

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of orthoclase, based on X-ray

 diffraction peak heights

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of orthoclase

Area with low concentration of orthoclase

157

50

Area of orthoclase concentrations, based on X-ray

 diffraction peak heights

Greater than 50

20 to 50

20

10

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of copper, in parts per million

2,000

1,000

10

10

10

20

20

20

20

20

20

50

50

50

50

50

10

50

50

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Orthoclase

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

HIGH

HIGH

LOW

LOW

LOW

HIGH

LOW

Figure 22. Distribution of orthoclase in core samples.
38 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

IGSKAHCMVSFS002\Jeff\den18-0050_maurice\den18-0050_working-files\den18-0050_report_figures\den18-0050_fig023.ai

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of kaolinite and clays, based

 on X-ray diffraction peak heights

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of kaolinite and clays

Area with low concentration of kaolinite and clays

157

20

Area of kaolinite and clays concentrations,

 based on X-ray diffraction peak heights

Greater than 20

10 to 20

10

0

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of copper, in parts per million

2,000

1,000

0

0

0

0

0

0

0

0

0

0

20

10

20

10

20

0

10

10

0

0

0

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Kaolinite and clays

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

LOW

LOW

LOW

LOW

LOW

LOW

LOW

HIGH

HIGH

HIGH

Figure 23. Distribution of kaolinite and other clay minerals in core samples.
Distributions of Elements and Minerals in the Subsurface 39

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Pyrophyllite zone boundary

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

157 Zone of significant visible pyrophyllite in

 drill core

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of copper, in parts per million

2,000

1,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm

TKr

TKr

A A'

Pyrophyllite

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

Figure 24. Distribution of pyrophyllite in core samples.
40 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of magnetite, based on

 X-ray diffraction peak heights

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of magnetite

Area with low concentration of magnetite

157

20

Area of magnetite concentrations, based on

 X-ray diffraction peak heights

Greater than 20

10 to 20

10

0

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of copper, in parts per million

2,000

1,000

0

0

0

0

0

0

10

10

20

20

20

10

20

20

20

10

10

0

10

10

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr

TKr

A A'

Magnetite and biotite

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

LOW

LOW

HIGH

LOW LOW

HIGH

HIGH Approximate Upper Limit of Visible

LOW Biotite and X-ray diffraction Magnetite

Mineralogical boundary

Figure 25. Distribution of magnetite and biotite in core samples.
Distributions of Elements and Minerals in the Subsurface 41

In contrast, however, magnetite concentrations are high 

(>20-unit contour) in the “barren” core zone of the deposit 

where many of the hypogene deposit-related elements exhibit 

relatively low concentrations as compared to the two limbs 

of the deposit.

Cobalt, Pyrite, and Hematite.—The estimated threshold 

value for cobalt is about 20–23 ppm (table 2). The distribution 

of cobalt (fig. 26) generally shows no clear pattern associated 

with the deep part of the hypogene Cu-Mo deposit. Relatively 

low (<20 ppm) concentrations seem to be spatially associated 

with quartz monzonite porphyry bodies. 

In the area of the mid-level and deep parts of the hypogene 

deposit, pyrite (fig. 27) is present in an arcuate zone between 

the 5- and 10-unit contours that corresponds spatially with the 

1,000–2,000 ppm copper zone (fig. 5). Pyrite concentrations are 

markedly higher in the upper part of the system, corroborating 

distributions noted in the drill core. This area of high pyrite 

concentrations is associated with the phyllic alteration zone. 

High concentrations (50–100 ppm) of cobalt form a broad 

zone, which correlates spatially with the distribution of high 

(>20-unit contours) concentrations of pyrite, suggesting that 

cobalt proxies in pyrite. Additionally, the zone of near-surface 

low (<20 ppm) cobalt concentrations correlates spatially 

with low concentrations of pyrite and high concentrations of 

hematite (fig. 28). This near-surface zone likely represents the 

remnant of a leached cap that formed by circulation of oxidizing groundwater. During this process, cobalt was most likely 

leached and pyrite was oxidized to hematite, as observed in 

core and outcrop.

Calcium and Calcite.—The estimated threshold value for 

calcium in the andesite unit varies from 1.75 to 3.62 percent 

(table 2). The concentrations of calcium (fig. 29) are low 

(<1.00 percent) in the areas of the left (west) limb and the lowermost part of the right (east) limb of the hypogene Cu-Mo deposit. 

This distribution reflects the relative loss of calcium (mainly 

because of the destruction of calcium-rich plagioclase) corresponding to a relative increase in potassium as orthoclase, 

particularly in the areas of the quartz monzonite porphyry. 

Higher in the system, in the upper part of the andesite unit, 

calcium concentrations decrease rapidly above the 1.00-percent 

calcium contour. This distribution indicates that calcium, which 

is highly mobile chemically, has been leached, especially 

above the 0.15-percent contour, mostly during the time of 

supergene enrichment.

The approximate upper limit of calcite (identified by XRD) 

generally falls between the 0.70- and 0.15-percent calcium 

contours (fig. 29). The 0.05-percent calcium contour coincides 

closely with the base of XRD-identified alunite (fig. 8), a mineral 

mostly associated with advanced argillic alteration and the supergene zone (Guilbert and Park, 1986). The low (<0.05 percent) 

calcium concentrations in the rhyolite tuff unit probably result 

from a combination of (1) low pre-mineralization calcium 

concentrations, (2) later remobilization of this element associated with formation of the Cu-Mo deposit, including supergene 

enrichment, and (3) later weathering. 

The highest concentrations (>10-unit contours) of calcite 

form an arcuate zone that is spatially associated with the deep 

hypogene deposit and with quartz monzonite porphyry bodies 

(fig. 30). Calcite is present in core samples in association with 

many of the hypogene deposit-related elements and minerals. 

Calcite is known to be associated with potassic alteration in 

PCDs (Guilbert and Park, 1986). The absence of calcite in the 

upper part of the section mostly reflects its destruction during 

supergene enrichment and subsequent weathering. 

Sodium.—The estimated threshold value for sodium 

in the andesite unit is about 2.45 to 2.49 percent (table 2). 

Concentrations of sodium (>1.00 percent) (fig. 31) form 

an arc centered on the deep part of the hypogene Cu-Mo 

deposit. The highest sodium concentrations (>2.00 percent) 

are present in the “barren” core area of the deposit between 

the limbs of the hypogene deposit. Although not verified 

petrographically, these high sodium concentrations may 

represent relatively high sodic plagioclase concentrations 

in the “barren” core of the hypogene deposit (fig. 5), where 

potassium metasomatism has not replaced the plagioclase of 

the host andesite unit. The 0.50-percent sodium contour at 

the mid-level of the section roughly defines the base of the 

supergene zone in the andesite unit. 

Plagioclase.—The highest (>50-unit contour) plagioclase 

concentrations are in the area of the “barren” core and left (west) 

limb of the deep part of the deposit. High concentrations 

(>20-unit contours) of plagioclase (fig. 32) define an area in 

the andesite unit that is spatially similar to that of the deep and 

mid-level parts of the hypogene Cu-Mo deposit, indicating 

that plagioclase has not been hydrothermally altered totally 

to orthoclase, sericite, or other minerals. This zone coincides 

roughly with that of high sodium concentrations (fig. 31), 

suggesting the presence of sodic plagioclase in that area. Like 

sodium, plagioclase exhibits relatively low concentrations 

in the upper part of the andesite unit and in the rhyolite tuff 

unit. As was the case for cobalt and pyrite (figs. 26 and 27), as 

well as other elements and minerals, plagioclase is absent in 

the near-surface area where it has been destroyed as a result 

of weathering that formed the leached cap, as defined by the 

distribution of hematite (fig. 28).

Manganese.—The estimated threshold value for 

manganese in the andesite unit varies from 500 to 826 ppm 

(table 2). Manganese shows relatively low concentrations 

(<500 ppm) at depth in the area of both limbs of the hypogene 

deposit that are probably related mostly to the bulk chemistry 

of the quartz monzonite porphyry (fig. 33). In agreement 

with the calculated threshold value for the andesite unit, 

manganese concentrations are relatively high (>500 ppm) in 

much of this formation and are mostly in the 500–1,000 ppm 
42 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of cobalt, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of cobalt

Area with low concentration of cobalt

157 Area of cobalt concentrations, in parts

 per million

Greater than 50

20 to 50 HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

100

50

20

10

Concentrations of copper, in parts per million

2,000

1,000

10

10

20

20

20

20

50

50

50

50

50

50

20

50

50

20

50

100

20

20

LOW

LOW

HIGH HIGH

LOW

LOW

LOW

LOW

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Cobalt

Figure 26. Distribution of cobalt in core samples.
Distributions of Elements and Minerals in the Subsurface 43

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of pyrite

Area with low concentration of pyrite

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

20

15

10

5

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of pyrite, based on X-ray diffraction

 peak heights

Area of pyrite concentrations, based on x-ray

 diffraction peak heights

Greater than 20

15 to 20

5

5

5

5

5

5

5

5

5

5

10

10

10

10

20

15

15

15

15

15

15

20

20

HIGH

LOW

LOW

LOW

HIGH

LOW

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Pyrite

Figure 27. Distribution of pyrite in core samples.
44 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of hematite

Area with low concentration of hematite

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Greater than 0

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of hematite, based on X-ray

 diffraction peak heights

Area of hematite concentrations, based on X-ray

 diffraction peak heights

Greater than 0

>0

>0 >0

>0

>0

>0

>0

>0

>0

HIGH

LOW

LOW

LOW

LOW

LEACHED CAP ZONE

HIGH

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Hematite

Figure 28. Distribution of hematite in core samples.
Distributions of Elements and Minerals in the Subsurface 45

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of calcium, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of calcium

Area with low concentration of calcium

157

Area of calcium concentrations, in percent

Greater than 1.00

0.70 to 1.00

HIGH

LOW

Area in with calcium is nearly or completely

 absent

VERY LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

1.00

0.70

0.15

0.05

Concentrations of copper, in parts per million

2,000

1,000

Mineralogical boundary

0.05

0.15

1.00

1.00

1.00

1.00

1.00

0.05

0.15

1.00

0.70

0.70

0.70

0.70

0.70

0.70

0.70

0.70

1.00

1.00

HIGH

VERY LOW

HIGH

HIGH

HIGH

VERY LOW

LOW LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Calcium and calcite

Approximate Upper Limit

of X-ray diffraction Calcite

Figure 29. Distributions of calcium and calcite in core samples.
46 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of calcite

Area with low concentration of calcite

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

20

10

5

0

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of calcite, based on X-ray

 diffraction peak heights

Area of calcite concentrations, based on X-ray

 diffraction peak heights

Greater than 20

10 to 20

0

0

0

10

10

10

10

10

5

5

5

5

5

5

10

10

10

10

10

20

20

0

5

5

20

20

10

20

10

LOW

LOW

LOW

HIGH

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Calcite

Figure 30. Distribution of calcite in core samples.
Distributions of Elements and Minerals in the Subsurface 47

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of sodium, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of sodium

Area with low concentration of sodium

Area of sodium concentrations, in percent 157

Greater than 2.00

1.00 to 2.00

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

2.00

1.00

0.50

Concentrations of copper, in parts per million

2,000

1,000

2.00

2.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

0.50

1.00

1.00

1.00

1.00

0.50 

0.50

0.50

1.00

1.00

1.00

1.00

0.50

1.00

LOW

LOW

HIGH

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

TKr TKr Tqm

A A'

Sodium

Figure 31. Distribution of sodium in core samples.
48 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of plagioclase

Area with low concentration of plagioclase

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

50

20

5

0

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of plagioclase, based on X-ray

 diffraction peak heights

Area of plagioclase concentrations, based on X-ray

 diffraction peak heights

Greater than 50

20 to 50

Area in with plagioclase is nearly or completely

 absent

VERY LOW

20

0

0

50

50

50

50

50

20

20

20

20

20

20

20

20

20

50

50

5

5

5

50

20

5

5

5

5

5

HIGH

LOW

LOW

VERY LOW

LOW

HIGH

HIGH

LOW

HIGH

LOW

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm TKr TKr Tqm

A A'

Plagioclase

Figure 32. Distribution of plagioclase in core samples.
Distributions of Elements and Minerals in the Subsurface 49

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of manganese, in parts per

 million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of manganese

Area with low concentration of manganese

157

1,000

Area of manganese concentrations, in parts

 per million

Greater than 1,000

500 to 1,000

500

300

50

Concentrations of copper, in parts per million

2,000

1,000

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

50

50

50

500

500

500

500

500

500

500

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

300

300

300

300

300

300

LOW

LOW

HIGH

LOW

LOW

LOW

HIGH

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

Tqm

TKr TKr

A A'

Manganese

Figure 33. Distribution of manganese in core samples.
50 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

range in the felsite-latite unit, irrespective of the distribution 

of elements related to the Cu-Mo deposit. In contrast to the 

concentrations of manganese in these two units, the overall 

manganese concentration in the entire area of the rhyolite tuff 

unit is consistently below 50 ppm. The coincidence of this 

sharp change in concentration at the rhyolite tuff-andesite 

contact indicates that the contrasting manganese contents of 

these two formations are related mostly to their differences 

in bulk chemistry. The 500-ppm manganese contour near the 

top of the andesite unit is thought to locally approximate the 

base of the zone of supergene enrichment. 

Boron.—The estimated threshold value for boron in the 

andesite unit is 15 ppm (table 2). Relatively high concentrations 

(30–50 ppm) of boron (fig. 34) are present at depth in the area 

of the left (west) limb of the hypogene deposit, where arsenic, 

antimony, mercury, and other elements are also concentrated. 

Boron is most highly concentrated (50–>100 ppm) in the 

general area of the rhyolite tuff unit, where it is thought to be 

related to a combination of the bulk chemistry of the rhyolite 

tuff lithology as well as to deposit-related tourmaline. Boron is 

also known to occur in micas such as sericite (Harder, 1974). 

The high concentrations of boron near the present surface 

of the deposit area imply that boron is relatively immobile 

chemically in that area. 

Uranium.—Cox (1986) notes that weak uranium anomalies 

are sometimes present in PCDs. The estimated threshold value 

for uranium is 1.9 ppm (table 2). The concentrations of uranium 

are relatively high (>2 ppm) in the area of the left (west) limb 

of the hypogene deposit (fig. 35). An area with high uranium 

concentrations (1–>3 ppm) is also present in the rhyolite tuff 

unit. This area of high concentrations suggests that uranium 

either was locally highly concentrated in the pre-mineralization 

rhyolite tuff unit, or was mobilized and concentrated in this 

area, probably as a result of supergene enrichment and 

possibly later weathering. 

Magnesium and Chlorite.—The estimated threshold value 

for magnesium in the andesite ranges from 1.25 to 2.23 percent 

(table 2). Most magnesium concentrations in the area of the 

section are below the threshold value. Magnesium concentrations 

and those of chlorite are largely determined by the contrasting 

chemistry of the andesite, felsite-latite, and rhyolite tuff units. 

The highest magnesium concentrations (>0.70 percent) are 

found in the andesite unit; lower concentrations (<0.50 percent) 

are associated with the rhyolite tuff and felsite-latite units, and 

locally, with the quartz monzonite porphyry (fig. 36). In the 

near-surface part of the deposit, magnesium, like cobalt, has 

clearly been removed during formation of the leached cap, 

probably as a result of circulation of oxidizing acidic 

groundwater. 

Similarly, chlorite is concentrated (>4-unit contours) 

throughout most of the andesite unit (fig. 37), exhibits lower 

concentrations (<4-unit contours) in the felsite-latite unit, 

and is in less than detectable concentrations or totally absent 

in the rhyolite tuff unit. Thus, the presence or absence of chlorite can generally be used to define the andesite-rhyolite tuff 

boundary. Examination of core samples indicates that the 

high (>7-unit contours) chlorite concentrations on the right

 (eastern) side of the section formed mostly from biotite that 

was altered to chlorite during the supergene enrichment event. 

However, chlorite distributions in the overall area of this 

section also suggest a peripheral propylitic alteration zone 

related to the hypogene Cu-Mo deposit. Typical propylitic 

alteration, which may or may not be related to the mineral 

deposit, is exposed locally in andesite outcrops on the eastern 

side of Red Mountain (Kistner, 1984) and is present regionally 

in scattered outcrops of this unit.

Quartz.—The distribution of quartz is hard to interpret 

because this mineral occurs in many forms with different 

ages, including forms that are related to pre-deposit host-rock 

chemistry and other forms that are related to hydrothermal 

events. Examination of drill core indicates that disseminated 

pre-mineral deposit quartz is present in the rhyolite tuff and 

felsite-latite units (fig. 38). Abundant quartz (>30-unit contour) 

is spatially related to the quartz monzonite porphyry. Core 

samples clearly show abundant, hydrothermally related, complex 

crosscutting quartz veins with and without various sulfide 

and other minerals. Non-vein, hydrothermal, disseminated 

silicification is also common. The highest (>60-unit contour) 

quartz concentrations are mostly found in the rhyolite tuff unit 

in the central, near-surface part of the section, where the quartz 

is a combination of a non-vein quartz-rich lithology and superimposed hydrothermal quartz veins related to the hypogene 

Cu-Mo deposit. Quartz veins are also present in the most 

altered outcrops on Red Mountain.

Muscovite (Sericite).—Muscovite mica (determined by 

XRD) at Red Mountain is predominantly sericite. A welldefined peripheral arcuate zone of high (>15-unit contour) 

mica concentrations is present above the deep part of the 

hypogene Cu-Mo deposit (fig. 39). This zone of sericite 

defines pervasive phyllic alteration. The lack of mica concentrations in the near surface reflects the destructive effects of 

weathering in the leached cap area as defined by the distribution of hematite (fig. 28).
Distributions of Elements and Minerals in the Subsurface 51

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of boron, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of boron

Area with low concentration of boron

157 Area of boron concentrations, in parts per million

Greater than 100

50 to 100 

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

100

50

30

Concentrations of copper, in parts per million

2,000

1,000

30

30 

30

30

30

30

30

30

30

30

30

30

50

50

50

50

100

50

30

LOW

LOW

LOW

LOW

LOW

HIGH HIGH

LOW

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm TKr

A A'

Boron

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

Figure 34. Distribution of boron in core samples.
52 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of uranium, in parts per million

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of uranium

Area with low concentration of uranium

157 Area of uranium concentrations, in parts per million

Greater than 3

2 to 3 

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

3

2

1

Concentrations of copper, in parts per million

2,000

1,000

1

1

1

1

1

1 3

1

1

2

3

2

2

1

1

3

2

1

1

3

1

1

1

2

2

2

1

2

3

1

LOW

HIGH

LOW

LOW

LOW

LOW

LOW

LOW

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm TKr

A A'

Uranium

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

Figure 35. Distribution of uranium in core samples.
Distributions of Elements and Minerals in the Subsurface 53

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Concentrations of magnesium, in percent

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of magnesium

Area with low concentration of magnesium

157 Area of magnesium concentrations, in

 percent

Greater than 1.50

0.70 to 1.50 HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

1.50

0.70

0.50

0.10

Concentrations of copper, in parts per million

2,000

1,000

Area in with magnesium is nearly or completely

 absent

VERY LOW

0.10

1.50

1.50

1.50

1.50

1.50

1.50

0.70

0.70

0.70

0.70

0.70

0.70

0.70

0.70

0.70

0.70

0.10

0.50

0.50

0.50

0.50

1.50

1.50

0.70

0.70

HIGH

HIGH

HIGH

LOW

VERY LOW

LOW

LOW LOW

LOW

VERY LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

Tqm TKr TKr

A A'

Magnesium

Figure 36. Distribution of magnesium in core samples.
54 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

EXPLANATION

NOT TO SCALE DATUM IS SEA LEVEL

Concentrations of chlorite, based on x-ray

 diffraction peak heights

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of chlorite

Area with low concentration of chlorite

157

7

Area of chlorite concentrations, based on x-ray

 diffraction peak heights

Greater than 7

4 to 7

4

0

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

Concentrations of copper, in parts per million

2,000

1,000

4

4

4

4

4

4

4

4

4

4

4

4

0

0

7

7

7

7

7

7

7

LOW

LOW

LOW

LOW

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH

HIGH

HIGH

HIGH

LOW

LOW

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Kv

Kv

Tqm

Tqm Tqm TKr TKr

A A'

Chlorite

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

Figure 37. Distribution of chlorite in core samples.
Distributions of Elements and Minerals in the Subsurface 55

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of quartz

Area with low concentration of quartz

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

60

50

30

20

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of quartz, based on X-ray diffraction

 peak heights

Area of quartz concentrations, based on X-ray

 diffraction peak heights

Greater than 60

50 to 60

50

30

60

20

20

20

20

30

30

30

30

30

30

30

30

30

50

50

50

50

50

50

50

50

50

60

60

60

60

30

30

50

50

20

30

30

60

60

60

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH HIGH

HIGH

HIGH

LOW

LOW

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158 TKr

TKr

TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm Tqm TKr

A A'

Quartz

Figure 38. Distribution of quartz in core samples.
56 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

METERS

NOT TO SCALE DATUM IS SEA LEVEL

EXPLANATION

Depth of formation unknown 

Tqm Quartz monzonite porphyry—Intrusive rocks

TKr Volcanics of Red Mountain—Chiefly rhyolite tuff

Kv Silicic volcanics—Felsite-latite

Ka Trachyandesite of Meadow Valley—Chiefly

 andesite porphyry

Drill hole and identifier

Area with high concentration of muscovite (sericite)

Area with low concentration of muscovite (sericite)

157

HIGH

LOW

Approximate contact—Lithologic contacts logged

 for the two westernmost drill holes suggest that

 a steep, as yet unidentified, fault with significant

 offset may be present in the western part of the

 study area, between these two holes

40

20

15

2

Concentrations of copper, in parts per million

2,000

1,000

Concentrations of muscovite (sericite), based on

 X-ray diffraction peak heights

Area of concentrations, based

 on X-ray diffraction peak heights

Greater than 40

20 to 40

Muscovite (sericite)

20

20

20

20

20

2

2

2

2

15

15

15

15

15

15

15

15

40

20

15

20

15

15

15

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0 0

FEET

157

145

156

144

146

151

158 TKr

TKr TKr

Tqm

Tqm

Tqm

Tqm

Tqm

Ka

Ka

Ka

Kv

Kv

Tqm

Tqm

Tqm

Tqm TKr

A A'

Figure 39. Distribution of muscovite (sericite) in core samples.
Sampling, Preparation, and Analysis 57

Part B—Surface Geochemical Studies 

of Rock, Soil, and Vegetation

Surface geochemical sampling included samples of rock, 

soil, and three species of plants. The analyses of these samples 

provide detailed chemical information over a relatively 

undisturbed area known to be highly mineralized both at the 

surface and at depth. Information derived from these analyses 

provides base line data that may be useful for both exploration 

and environmental purposes.

Sampling, Preparation, and Analysis

The rock samples were collected from throughout the 

study area from typical outcrops of both visually fresh and 

altered rocks in order to characterize the chemical differences 

in rocks in surface exposures and identify element distributions relative to the known Cu-Mo deposit. Soil samples 

were collected to identify changes in element concentrations 

relative to the adjacent rocks, as well as to document element 

distributions. The plant samples were collected to establish a 

multielement baseline reference database and to learn more 

about their chemistry relative to the underlying hypogene 

Cu-Mo deposit. 

A total of 122 rock samples were collected in the vicinity 

of the deposit. The samples were composited from outcrops 

within about 10 m of each sample site. Only material representative of the outcrops near each site was collected. Each 

sample was hand cobbed when necessary to remove any visibly 

weathered surface material not typical of the sample as a whole. 

Before being submitted to the laboratory, the samples were 

first crushed in a jaw crusher and then ground in a ceramic 

pulverizer to material <0.15 mm (minus 100 mesh).

A total of 119 soil samples were also collected, mostly 

close to the corresponding rock sample sites. The soil samples 

were also composited from several subsites. The samples were 

collected below any obvious organic layer. Prior to submitting 

the samples to the laboratory, each bulk sample was sieved 

through stainless-steel sieves, and a <0.18-mm (minus 80-mesh) 

fraction was pulverized in a manner similar to that used for the 

rock samples.

Samples from three species of trees common to the 

region were also collected, mostly from near the corresponding 

rock and (or) soil sample sites. The combination of the three 

species collected at any given site depended on the local 

environment. At lower elevations, which are within the Lower 

Sonoran Life Zone, mesquite (Prosopis juliflora (Sw.) DC) 

(fig. 40A) and oak (Emory’s oak, Quercus emoryi Torr.; and 

Mexican blue oak, Q. oblongifolia Torr.) (fig. 40B) are the 

most common species. At higher elevations, which are within 

the Upper Sonoran Life Zone, oak and oneseed juniper 

(Juniperus monosperma (Engelm.) Sarg.) (fig. 40C) are the 

most common species (Integrated Taxonomic Information 

System, https://itis.gov, accessed August 15, 2019). A total 

of 57 mesquite samples, 108 oak samples, and 68 juniper 

samples were collected. Each sample was composited from 

material collected around each tree, generally at about 1.2 to 

1.8 m above the ground surface. At each site, samples were 

collected from more than one tree of each species if they were 

available. In the case of the oak and mesquite, each sample 

consisted of twigs less than about 6 mm in diameter from 

which all leaves had been removed. For the juniper samples, 

entire branches, for which the stems did not exceed about 6 mm 

in diameter, were collected. All samples were air dried and 

cut into small pieces. This material was then macerated in a 

stainless-steel blender to produce a fine powder. An aliquot 

of this powder was slowly ashed in a muffle furnace for about 

22 hours at temperatures that did not exceed about 450 °C. 

The rock, soil, and plant samples were submitted to the 

respective laboratories in a random order. Duplicate samples 

and internal standards were added to each batch to monitor the 

quality of the analyses. The rock and soil samples numbered 

PT001–PT019 were analyzed by a commercial laboratory for 

As, Au, Ba, bromine (Br), cerium (Ce), Co, Cr, Cs, europium 

(Eu), Fe, hafnium (Hf), Hg, iridium (Ir), La, lutetium (Lu), Na, 

neodymium (Nd), Rb, Sb, Sc, selenium [Se], samarium (Sm), 

Sn, tantalum (Ta), terbium (Tb), Th, U, W, and ytterbium 

(Yb) by instrumental neutron activation analysis (INAA), 

for 19 elements (Ag, aluminum [Al], beryllium [Be], Bi, Ca, 

cadmium [Cd], Cu, K, Mg, Mn, Mo, Ni, phosphorus [P], Pb, 

Sr, Ti, V, Y, and Zn) using a 4-acid (hydrofluoric, perchloric, 

nitric, and hydrochloric acids [HF, HClO4

, HNO3, and HCl, 

respectively]) digestion followed by inductively-coupled 

plasma optical-emission spectrometry (ICP-OES) (ActLabs, 

2000). They were also analyzed in the USGS Branch of 

Geochemistry laboratory in Denver for Te and Tl by atomicabsorption spectrometry (AAS) (O’Leary, 1996). Some of the 

soil samples were also analyzed in the same USGS laboratory 

for S by an infrared, instrumental method. The rest of the rock 

and soil samples (PT020-PT122) were analyzed in a commercial 

laboratory for 35 elements (Al, As, Ba, Be, Ca, Ce, Co, Cr, Cu, 

Eu, Fe, Ga, Ho, K, La, Li, Mg, Mn, Mo, Na, Nb, Nd, Ni, P, Pb, 

Sc, Sr, Ta, Th, Ti, U, V, Y, Yb, and Zn) by a modification of the 

inductively-coupled plasma-mass spectrometry (ICP-MS) 

method of Briggs and Meier (2002) (ActLabs, 2000) and in 

the USGS Branch of Geochemistry laboratories for Ag, Au, Bi, 

Cd, and Sb by the inductively-coupled plasma-atomic emission 

spectrometry (ICP-AES) method of Motooka (1996) and for 

Te and Tl by AAS (O’Leary, 1996). The analyses for the rock 

and soil samples are tabulated and are available in a separate 

data release (Horton and others, 2020).
58 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

A

B

C

Figure 40. Photographs showing A, Mesquite (Prosopis juliflora) tree. B, Oak (Quercus spp.) trees. C, Oneseed juniper 

(Juniperus monosperma) tree.
Results and Evaluation of the Vegetation Chemistry 59

All samples of plant ash were analyzed in a commercial 

laboratory. Samples PT001–PT019 for each species were 

analyzed for 29 elements (As, Au, Ba, Br, Ce, Co, Cr, Cs, Eu, 

Fe, Hf, Hg, Ir, La, Lu, Na, Nd, Rb, Sb, Sc, Se, Sm, Sn, Ta, Tb, 

Th, U, W, and Yb) by INAA and for 19 elements (Ag, Al, Be, 

Bi, Ca, Cd, Cu, K, Mg, Mn, Mo, Ni, P, Pb, Sr, Ti, V, Y, and Zn) 

using the same 4-acid (HF, HClO4, HNO3, and HCl) digestion 

followed by ICP-OES. Samples PT020–PT122 were analyzed 

for as many as 66 elements (Ag, Al, As, Au, B, Ba, Be, Bi, Br, 

Ca, Cd, Ce, Co, Cr, Cs, Cu, dysprosium [Dy], erbium [Er], Eu, 

Fe, gallium [Ga], gadolinium [Gd], germanium [Ge], Hf, Hg, 

Ho, iodine [I], indium [In], Ir, K, La, Li, Lu, Mg, Mn, Mo, Na, 

Nb, Nd, Ni, P, Pb, Pr, Rb, rhenium [Re], Sb, Sc, Se, silicon 

[Si], Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, thulium [Tm], U, V, 

W, Y, Yb, Zn, and Zr) using a nitric acid + hydrogen peroxide 

(HNO3+H2O2) digestion followed by ICP-MS (ActLabs, 2000). 

Listings of the chemical analyses for the plants are available in 

a separate data release (Horton and others, 2020).

Results and Evaluation of the 

Rock Chemistry

Table 4 summarizes information for 54 elements in 

122 rock samples. The median concentration values for the 

surface rock samples were compared to median concentration 

values for the same two datasets of andesite samples that are 

listed for the drill core samples in table 2 and described in the 

section, Results and Evaluation of the Core Analyses. Because 

median values for the dataset of 122 samples, which includes 

samples from both the andesite and rhyolite tuff units, are 

being compared to two datasets of only andesite samples, the 

resulting ratio values (columns A/B and A/C, respectively) may 

not be meaningful for some elements related mostly to lithology 

but likely are valid for most of the elements introduced during 

formation of the hypogene Cu-Mo deposit. For the dataset 

of surface rock samples (table 4), the median ratio values for 

deposit-related elements are generally smaller than those noted 

for the subsurface core samples (table 2) because the surface 

samples are from the uppermost remaining part of the deposit 

system where concentrations for many of the deposit-related 

elements are relatively low as compared to their concentrations 

at depth. The median ratio values for the rock samples 

(columns A/B ratio and (or) A/C ratio, table 4) show that the 

deposit-related elements As, Pb, Te, and Tl are clearly more 

concentrated in these samples as compared to one or the other 

of the two andesite datasets. The data for other deposit-related 

elements (Ag, Cu, Mo, Sb, and Zn) are inconclusive. 

Results and Evaluation of the 

Soil Chemistry

Table 5 summarizes, for 55 elements in 119 soil samples, 

the same columns of data shown in table 4. Examination 

of the columns listing A/B and A/C ratios show that the 

deposit-related elements Ag, As, Cu, Mo, Pb, Sb, Te, and Zn 

are more concentrated in the soil as compared to one or the 

other of the two andesite datasets. The data for bismuth and 

cadmium are inconclusive.

Results and Evaluation of the 

Vegetation Chemistry

Many elements are considered essential to normal plant 

growth. Some of these essential elements are part of the suite 

of deposit-related elements at Red Mountain and some are not. 

Similarly, many other elements are nonessential for plant growth, 

including elements both related to, and unrelated to, the hypogene 

Cu-Mo deposit. Nevertheless, nonessential elements can be taken 

up by plants, even when they may be considered potentially toxic 

to the plants. Elements essential for plant growth that were analyzed for this study include Ca, Cu, Fe, K, Mg, Mn, Mo, Na, P, 

and Zn (Brooks, 1983). Elements analyzed that are probably nonessential, or those that are considered potentially toxic to plants, 

depending on their concentrations and probably other factors, 

include Ag, As, Ba, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Te, 

Tl, V, Zn, and probably others (Brooks, 1983; Levinson, 1974). 

Note that copper, manganese, molybdenum, and zinc, which are 

found on both lists, may be essential in low concentrations but 

can be toxic at higher concentrations.

Tables 6, 7, and 8 summarize data for percent ash and 

for 66 elements analyzed in the ash of 57 mesquite twigs, 

108 oak twigs, and 68 juniper branches, respectively. For the 

plant samples, the median concentration values in the ash 

provide a means of comparing the degree of accumulation of 

a given element among the three species.

The concentration of a given element in plant ash is here 

deemed to be comparable to the concentration of that element 

in soil. Therefore, the ratio column (A/B) provides at least qualitative estimates of the relative concentration of each element 

in the ash of a given plant species (column A) as compared to 

its substrate soil (column B). These ratios provide an estimate 

of which elements are being accumulated in each of the three 

species. For mesquite, these elements are (in order, with ratio 

values in parentheses): Ca (60), P (21), Sr (9.1), K (5.1), Mg (5.0), 

Zn (5.0), Cd (2.2), Cu (1.6), and Mo (1.3) (table 6). Similarly, 

the elements accumulated in oak ash are: Ca (64), Cd (47), 

P (22), Mn (8.8), Mg (6.8), Sr (5.4), K (>3.0), Ni (2.3), Zn (2.2), 
60 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 4. Summary of chemical data for 54 elements in 122 samples of rock outcrop and comparative background data, 

Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratios A/B and A/C give estimates of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

outcrop samples]

Rock outcrop data Comparative background data

Element Range of

values

Number

analyzed

Percent

analyzed of 

122 samples

Percent 

unqualified of 

122 samples

Median value

rock samples 

(A)

Median value of 

27 local andesite 

samples2

 (B)

A/B 

ratio

Median value of 46 

regional andesite 

samples3 (C)

A/C 

ratio

Ag1 <0.08–54.5 122 100 48 <0.5 <0.008 --- <0.5 ---

Al (%) 2.81–12.5 122 100 100 8.36 --- --- --- ---

As1 <1.0–390 122 100 80 12 6 2.0 5.3 2.26

Au1 <0.002–0.712 122 100 10 --- --- --- --- ---

Ba 83–2,490 122 100 100 764 851 0.90 1,000 0.76

Be1 <1.0–6.0 122 100 52 1.0 2 0.50 1.0 1.00

Bi1 <1–32 122 100 30 <1.0 <1 --- <10 ---

Br <0.5–<0.5 19 16 0 --- --- --- --- ---

Ca (%) 0.01–6.98 122 100 100 0.12 3.62 0.033 1.75 0.069

Cd1 <0.05–5.28 122 100 59 0.06 0.11 0.55 0.30 0.20

Ce 22–160 122 100 100 76 --- --- --- ---

Co1 <1.0–37 122 100 70 5 23 0.28 20 0.25

Cr1 <2.0–150 122 100 64 5.5 24 0.23 50 0.11

Cs 2–36 19 16 16 --- --- --- 50 ---

Cu <2–417 122 100 98 44 47 0.94 40 1.10

Eu1 <0.9–4 122 100 43 <2 --- --- --- ---

Fe (%) 0.12–9.16 122 100 100 3.54 5.22 0.68 3.00 1.18

Ga 7–55 103 84 84 20 --- --- --- ---

Hf 4–13 19 16 16 --- --- --- --- ---

Hg <1–<1 19 16 0 --- --- --- <0.02 ---

Ho <4–10 103 84 7 --- --- --- --- ---

Ir (ppb) <5–<5 19 16 0 --- --- --- --- ---

K (%) 0.03–6.31 122 100 100 2.56 2.53 1.01 --- ---

La 5–82 122 100 100 42 44 0.95 60 0.70

Li <2–95 103 84 70 10 40 0.25 --- ---

Lu 0.23–1.22 19 16 16 --- --- --- --- ---

Mg (%) 0.01–3.91 122 100 100 0.32 2.23 0.14 1.25 0.26

Mn <4–1930 122 100 84 144 826 0.17 500 0.31

Mo <2–176 122 100 82 3 3 1.00 <5 >0.60

Na (%) 0.01–4.22 122 100 100 0.38 2.49 0.15 2.45 0.16

Nb <4–31 103 84 57 8.0 18 0.44 <20 >0.40

Nd <9–71 122 100 91 31 --- --- --- ---

Ni1 <2–123 122 100 61 5.0 46 0.11 20 0.25

P (%) 0.005–0.26 122 100 100 0.080 --- --- --- ---

Pb1 <4–2,370 122 100 97 39 11 3.55 50 0.78

Rb <5–310 19 16 15 --- --- --- --- ---
Results and Evaluation of the Rock Chemistry 61

Table 4. Summary of chemical data for 54 elements in 122 samples of rock outcrop and comparative background data, 

Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratios A/B and A/C give estimates of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

outcrop samples]

Rock outcrop data Comparative background data

Element Range of

values

Number

analyzed

Percent

analyzed of 

122 samples

Percent 

unqualified of 

122 samples

Median value

rock samples 

(A)

Median value of 

27 local andesite 

samples2

 (B)

A/B 

ratio

Median value of 46 

regional andesite 

samples3 (C)

A/C 

ratio

Sb1 <0.5–261 122 100 57 1.0 <1.0 >1.0 <2 >0.5

Sc <2–28 122 100 99 11 17 0.65 15 0.73

Se <3.0–3.0 19 100 1 --- --- --- --- ---

Sm 3.2–12 19 16 16 --- --- --- --- ---

Sn <100–<50 122 100 0 --- <10 --- <10 ---

Sr <1–1,760 122 100 99 285 612 0.47 300 0.95

Ta1 <0.5–2.0 122 100 5 --- --- --- --- ---

Tb <0.5–1.9 19 16 3 --- --- --- --- ---

Te <0.1–4.60 122 100 66 0.2 <0.1 >2.0 <0.01 >20

Th 6–58 122 100 100 18 17 1.06 --- ---

Ti (%) 0.023–0.75 122 100 100 0.35 0.62 0.56 0.50 0.69

Tl <0.1–9.4 122 100 93 1.0 0.2 5.00 0.18 5.56

U1 <2–18 122 16 16 --- --- --- 1.90 ---

V 3–461 122 100 100 113 93 1.22 100 1.13

W <1–6 19 16 2 --- --- --- <50 ---

Y <2–44 122 100 95 14 23 0.61 20 0.70

Yb <1.0–9 122 100 73 2.0 --- --- --- ---

Zn <2–765 122 100 99 74 89 0.83 60 1.23

1

More than one lower limit of determination reported. The lowest value is shown. 

2

Subset of the 122 samples in the rock dataset (table 4) consisting of analyses of unaltered or slightly propylitically-altered andesite rock samples collected 

within the study area but outside of the area of influence of the Red Mountain deposit. 

3

Subset of unaltered or slightly propylitically-altered andesite rock samples collected generally from the area immediately north of the study area. Sample 

analyses are from the U.S. Geological Survey National Geochemical Database.
62 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 5. Summary of chemical data for 55 elements in 119 soil samples and comparative background data, Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratios A/B and A/C give estimates of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

soil samples]

Soil data Comparative background data

Element Range of

values

Number

analyzed

Percent 

analyzed of 

119 samples

Percent 

unqualified of 

119 samples

Median 

value soil 

samples (A)

Median value of 

27 local andesite 

samples2

 (B)

A/B 

ratio

Median value of 46 

regional andesite 

samples3 (C)

A/C 

ratio

Ag1 <0.10–14.8 119 100 75 0.3 <0.008 >37.5 <0.50 >0.60

Al

 (%) 4.12–13.22 119 100 100 8.4 --- --- --- ---

As1 3–1,500 119 100 100 34 6 5.67 5.3 6.42

Au1 <0.002–0.143 119 100 17 --- --- --- --- ---

Ba 263–5,250 119 100 100 735 851 0.86 1,000 0.74

Be1 <1.0–5.0 119 100 58 1 2 0.50 1.0 1.00

Bi1 <1–15 119 100 64 1.0 <1 >1.0 <10 >0.10

Br <0.5–15 19 16 11 --- --- --- --- ---

Ca (%) 0.04–9.78 119 100 100 0.45 3.62 0.12 1.75 0.26

Cd1 <0.05–6.95 119 100 83 0.25 0.11 2.27 0.30 0.83

Ce 36–174 119 100 100 76 --- --- --- ---

Co1 2–53 119 100 100 9 23 0.39 20 0.45

Cr1 <5–200 119 100 99 29 24 1.21 50 0.58

Cs 6–94 19 16 16 --- --- --- 50 ---

Cu 18–483 119 100 100 91 47 1.94 40 2.28

Eu1 1.0–4.7 119 100 47 <2 --- --- --- ---

Fe (%) 1.92–12.4 119 100 100 4.62 5.22 0.89 3.00 1.54

Ga 10–45 100 84 84 23 --- --- --- ---

Hf 4–13 19 16 16 --- --- --- --- ---

Hg <1–<1 19 16 0 --- --- --- <0.02 ---

Ho <4–10 100 84 8 --- --- --- --- ---

Ir (ppb) <5–<5 19 16 0 --- --- --- --- ---

K (%) 0.88–4.26 119 100 100 2.19 2.53 0.87 --- ---

La 20–84 119 100 100 39 44 0.87 60 0.65

Li 6–84 100 84 84 19 40 0.48 --- ---

Lu 0.17–0.97 19 16 16 --- --- --- --- ---

Mg (%) 0.12–3.25 119 100 100 0.47 2.23 0.21 1.25 0.38

Mn 32–5,840 119 100 100 571 826 0.38 500 1.14

Mo <2–136 119 100 87 4 3 1.33 <5 >0.80

Na (%) 0.05–2.42 119 100 100 0.52 2.49 0.21 2.45 0.21

Nb 4–31 100 84 84 14 18 0.78 <20 >0.70

Nd <9–85 119 100 97 34 --- --- --- ---

Ni1 <3–142 119 100 87 15 46 0.33 20 0.75

P (%) 0.020–0.253 119 100 100 0.08 --- --- --- ---

Pb1 8–1,490 119 100 100 112 11 10.2 50 2.24

Rb 37–270 19 87 16 --- --- --- --- ---

S (%) 0.027–2.48 7 6 6 --- --- --- --- ---
Results and Evaluation of the Rock Chemistry 63

Table 5. Summary of chemical data for 55 elements in 119 soil samples and comparative background data, Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratios A/B and A/C give estimates of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

soil samples]

Soil data Comparative background data

Element Range of

values

Number

analyzed

Percent 

analyzed of 

119 samples

Percent 

unqualified of 

119 samples

Median 

value soil 

samples (A)

Median value of 

27 local andesite 

samples2

 (B)

A/B 

ratio

Median value of 46 

regional andesite 

samples3 (C)

A/C 

ratio

Sb1 <1.0–40 119 100 89 3.0 <1.0 >3.0 <2 >1.5

Sc 4–44 119 100 100 12 17 0.71 15 0.80

Se <3.0–<3.0 19 16 0 --- --- --- --- ---

Sm 4.2–14 119 100 16 --- --- --- --- ---

Sn <200–<100 119 100 0 --- <10 --- <10 ---

Sr 72–1,420 119 100 100 268 612 0.44 300 0.89

Ta1 <0.5–2.4 119 100 6 --- --- --- --- ---

Tb <0.5–1.7 19 16 5 --- --- --- --- ---

Te <0.1–8.3 119 100 87 0.6 <0.1 >6.0 <0.01 >60

Th 6–72 119 100 100 18 17 1.06 --- ---

Ti (%) 0.128–0.980 119 100 100 0.37 0.62 0.60 0.50 0.74

Tl 0.1–11.7 119 100 99 1.5 0.2 7.50 0.18 8.33

U1 <2.0–19 19 16 16 --- --- --- 1.90 ---

V 26–405 119 100 100 131 93 1.41 100 1.31

W <1–12 19 16 3 --- --- --- <50 ---

Y 4–56 119 100 100 16 23 0.70 20 0.80

Yb <1.0–5.9 119 100 86 2 --- --- --- ---

Zn 23–1,260 119 100 100 103 89 1.16 60 1.72

1

More than one lower limit of determination reported. The lowest value is shown. 

2

Subset of the 122 samples in the rock dataset (table 4) consisting of analyses of unaltered or slightly propylitically-altered andesite rock samples collected 

within the study area but outside of the area of influence of the Red Mountain deposit. 

3

Subset of unaltered or slightly propylitically-altered andesite rock samples collected generally from the area immediately north of the study area. Sample 

analyses are from the U.S. Geological Survey National Geochemical Database.
64 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 6. Summary of chemical data for ash and 66 elements in 57 mesquite ash samples, Red Mountain, Arizona.

 [All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

mesquite samples]

Element or

variable Range of values Number analyzed

Percent analyzed 

of 57 samples

Percent unqualified 

of 57 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Ash (%) 2.90–7.90 57 100 100 5.70 --- ---

Ag1 <0.40–2.30 57 100 82 0.27 0.30 0.90

Al 70–2,580 42 74 74 843 84,000 0.010

As <0.5–30.7 57 100 95 1.7 34 0.05

Au (ppb) <2.0–7.0 13 23 9 <2.0 --- ---

B 179–376 44 77 77 282 --- ---

Ba 87–2,570 57 100 100 710 735 0.97

Be1 0.016–0.548 57 100 77 0.041 1.0 0.041

Bi1 0.050–6.0 57 100 81 0.07 1.0 0.07

Br 43–130 13 23 23 64 --- ---

Ca (%) 13.57–35.77 42 74 74 26.61 0.45 60

Cd1 0.19–6.60 57 100 75 0.54 0.25 2.2

Ce1 2.08–8.95 57 100 88 3.18 76 0.042

Co 0.85–10.0 57 100 100 1.51 9.0 0.17

Cr1 0.6–8.0 57 100 82 1.50 29 0.052

Cs1 0.3–1,220 57 100 98 42 --- ---

Cu 64–211 57 100 100 147 91 1.6

Dy 0.053–0.876 44 77 77 0.159 --- ---

Er 0.030–0.341 44 77 77 0.075 --- ---

Eu1 0.054–0.823 57 100 77 0.202 <2.0

Fe (%) 0.13–0.485 57 100 100 0.24 4.62 0.052

Ga 0.171–1.002 44 77 77 0.314 23 0.014

Gd 0.102–1.541 44 77 77 0.333 --- ---

Ge <0.010–0.045 44 77 75 0.022 --- ---

Hf1 <0.010–0.055 57 100 61 0.018 --- ---

Hg <1.0–1.0 13 23 2 --- --- ---

Ho 0.010–0.149 44 77 77 0.028 --- ---

I <0.10–0.20 15 26 2 --- --- ---

In (ppb)1 0.963–8.30 44 77 75 4.89 --- ---

Ir (ppb) <5.0–<5.0 13 23 0 --- --- ---

K (%) 3.87–>11.10 42 74 39 11.10 2.19 5.1

La 0.69–6.17 57 100 100 1.40 39 0.036

Li <1.00–9.0 44 77 70 2.0 19 0.11

Lu1 0.004–0.024 57 100 77 0.007 --- ---

Mg (%) 1.08–7.58 57 100 100 2.35 0.47 5.0

Mn 176–1,200 57 100 100 381 571 0.67

Mo 1.20–83.8 57 100 100 5.3 4.0 1.3

Na (%) 0.03–0.18 57 100 100 0.07 0.52 0.14

Nb1 0.025–0.087 44 77 54 0.033 14 0.0024
Results and Evaluation of the Rock Chemistry 65

Table 6. Summary of chemical data for ash and 66 elements in 57 mesquite ash samples, Red Mountain, Arizona.

 [All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified 

values, which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination 

or above the upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the 

mesquite samples]

Element or

variable Range of values Number analyzed

Percent analyzed 

of 57 samples

Percent unqualified 

of 57 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Nd1 0.51–5.05 57 100 77 1.08 34 0.032

Ni 2.0–43 57 100 100 8.9 15 0.59

P (%) 1.180–2.492 13 23 23 1.69 0.080 21

Pb1 1.1–203 57 100 91 4.6 112 0.04

Pr 0.140–1.294 44 77 77 0.299 --- ---

Rb 29–1,070 57 100 100 137 --- ---

Re 2.0–150 44 77 77 16.7 --- ---

Sb1 0.05–5.90 57 100 98 0.12 3.0 0.04

Sc 0.18–1.23 42 74 74 0.335 12 0.028

Se1 0.57–10.0 19 33 82 1.10 --- ---

Si 294–625 29 51 51 416 --- ---

Sm 0.100–1.02 19 33 100 0.26 --- ---

Sn1 1.0–1.0 57 100 61 1.0 --- ---

Sr 807–6,800 57 100 100 2430 268 9.1

Ta1 0.001–0.002 57 100 11 <0.01 --- ---

Tb1 0.001–0.196 19 33 77 0.027 --- ---

Te1 0.012–0.066 29 51 51 0.043 0.60 0.072

Th1 0.089–0.70 57 100 86 0.176 18 0.0098

Ti1 43–226 57 100 91 83 3,690 0.022

Tl1 0.005–0.683 44 77 60 0.020 1.5 0.013

Tm 0.004–0.032 44 77 77 0.010 --- ---

U1 0.020–0.36 57 100 77 0.046 --- ---

V1 0.78–7.20 57 100 95 1.80 131 0.014

W1 <0.1–<1.0 42 74 0 --- --- ---

Y 0.34–6.75 57 100 100 1.54 16 0.096

Yb1 0.023–0.179 44 77 77 0.048 2.0 0.024

Zn 128–2,710 57 100 100 511 103 5.0

Zr1 0.381–1.202 44 77 54 0.50 --- ---

1

More than one lower limit of determination reported. The lowest reported value is shown.
66 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 7. Summary of chemical data for ash and 66 elements in 108 oak ash samples, Red Mountain, Arizona.

 [All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified values, which 

are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination or above the 

upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the oak samples]

Element or

variable Range of values Number analyzed

Percent analyzed 

of 108 samples

Percent unqualified 

of 108 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Ash (%) 1.31–9.50 108 100 100 3.95 --- ---

Ag1 0.05–2.89 108 100 93 0.42 0.30 1.4

Al 300–3,600 57 53 53 1,240 84,000 0.015

As1 <0.5–50.6 108 100 94 5.0 34 0.47

Au (ppb) <2.0–26 16 15 9 6.5 --- ---

B 194–759 92 85 85 338 --- ---

Ba <50–4,040 108 100 98 622 735 0.85

Be1 0.049–1.76 108 100 85 0.178 1.0 0.18

Bi1 0.059–21 108 100 90 0.159 1.0 0.16

Br <3–27 16 15 14 14 --- ---

Ca (%) 13.59–37.58 57 53 53 28.79 0.45 64

Cd1 <0.50–154 108 100 97 11.75 0.25 47

Ce1 2.44–37.32 108 100 96 6.89 76 0.091

Co 0.95–64 108 100 100 5.01 9.0 0.56

Cr1 0.7–31 108 100 91 2.26 29 0.079

Cs1 0.4–588 108 100 99 4.92 --- ---

Cu 24–506 108 100 100 87 91 0.96

Dy 0.068–2.81 92 85 85 0.293 --- ---

Er 0.040–1.38 92 85 85 0.139 --- ---

Eu1 0.090–1.44 108 100 89 0.223 <2.0 >0.11

Fe (%) 0.06–1.13 108 100 100 0.21 4.62 0.045

Ga 0.164–1.44 92 85 85 0.458 23 0.020

Gd 0.150–4.30 92 85 85 0.630 --- ---

Ge 0.013–0.070 92 85 85 0.032 --- ---

Hf1 <0.010–0.100 108 100 84 0.020 --- ---

Hg <1.0–<1.0 16 15 0 --- --- ---

Ho 0.013–0.514 92 85 85 0.051 --- ---

I <0.10–1.29 51 47 16 <0.10 --- ---

In (ppb) 2.819–23.1 92 85 85 12.48 --- ---

Ir (ppb) <5.0–<5.0 16 15 0 --- --- ---

K (%)2 1.67–9.04 57 53 23 >6.60 2.19 >3.0

La 0.82–26.7 108 100 100 2.99 39 0.077

Li 2.35–48 92 85 85 10.23 19 0.54

Lu1 0.004–0.111 92 85 85 0.014 --- ---

Mg (%) 0.87–10.15 108 100 100 3.20 0.47 6.8

Mn2 112–20,980 108 100 98 5,025 571 8.8

Mo1 0.47–22.9 108 100 92 1.6 4.0 0.39

Na (%) 0.03–0.36 108 100 100 0.09 0.52 0.18

Nb1 0.019–0.140 92 85 57 0.040 14 0.0029

Nd1 0.66–15.7 108 100 86 2.43 34 0.071
Results and Evaluation of the Rock Chemistry 67

Table 7. Summary of chemical data for ash and 66 elements in 108 oak ash samples, Red Mountain, Arizona.

 [All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified values, which 

are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination or above the 

upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the oak samples]

Element or

variable Range of values Number analyzed

Percent analyzed 

of 108 samples

Percent unqualified 

of 108 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Ni 1.9–516 108 100 100 35 15 2.3

P (%) 0.498–3.53 16 15 15 1.72 0.080 22

Pb1 3.0–1,510 108 100 98 13 112 0.12

Pr 0.186–4.37 92 85 85 0.774 --- ---

Rb <15–1,910 108 100 98 95.9 --- ---

Re 0.001–0.230 92 85 85 5.25 --- ---

Sb1 0.06–6.40 108 100 96 0.18 3.0 0.06

Sc 0.13–3.60 57 53 53 0.41 12 0.034

Se1 0.37–4.92 108 100 85 0.89 --- ---

Si 205–1,550 41 38 38 479 --- ---

Sm 0.100–3.83 108 100 100 0.59 --- ---

Sn1 <1.0–1.77 108 100 69 0.09 --- ---

Sr 197–5,580 108 100 100 1,445 268 5.4

Ta1 <0.001–0.006 108 100 32 <0.01 --- ---

Tb1 0.016–0.592 108 100 85 0.059 --- ---

Te1 0.014–0.109 92 85 41 <0.10 0.60 <0.17

Th1 0.072–3.10 108 100 93 0.201 18 0.011

Ti1 38–218 108 100 97 86 3,690 0.023

Tl <0.010–2.40 92 85 71 0.025 1.5 0.017

Tm 0.005–0.147 92 85 85 0.017 --- ---

U1 0.023–1.02 108 100 86 0.109 --- ---

V1 0.84–7.00 108 100 98 2.25 131 0.017

W <0.1–<1.0 58 54 0 --- --- ---

Y 0.40–16.8 108 100 100 1.95 16 0.12

Yb1 0.028–0.905 108 100 88 0.094 2.0 0.047

Zn 58–4,040 108 100 100 226 103 2.2

Zr1 0.380–1.37 92 85 64 0.59 --- ---

1

More than one lower limit of determination reported. The lowest reported value is shown. 

2

More than one upper limit of determination reported. The highest reported value is shown.
68 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Table 8. Summary of chemical data for ash and 66 elements in 68 juniper ash samples, Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified values, 

which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination or above the 

upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the juniper samples] 

Element or

variable Range of values Number analyzed

Percent analyzed 

of 68 samples

Percent unqualified 

of 68 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Ash (%) 3.15–7.40 68 100 100 4.78 --- ---

Ag1 0.04–0.70 68 100 87 0.15 0.30 0.50

Al 884–10,100 38 56 56 1,875 84,000 0.022

As 0.8–19 68 100 100 5.3 34 0.16

Au (ppb) <2.0–7.0 12 18 12 4.5 --- ---

B 193–482 56 82 82 322 --- ---

Ba 76–4,230 68 100 100 818 735 1.1

Be1 0.022–4.33 68 100 82 0.233 1.0 0.23

Bi1 0.053–0.68 68 100 82 0.106 1.0 0.11

Br 20–55 12 18 18 33 --- ---

Ca (%) 23.41–33.36 38 56 56 28.20 0.45 63

Cd1 0.23–5.90 68 100 81 1.03 0.25 4.1

Ce1 2.31–66.0 68 100 99 7.02 76 0.092

Co 1.46–61.9 68 100 100 3.66 9.0 0.41

Cr1 1.6–12.0 68 100 93 3.17 29 0.11

Cs1 0.6–77 68 100 96 2.04 --- ---

Cu 39–137 68 100 100 62 91 0.68

Dy 0.082–4.90 56 82 82 0.297 --- ---

Er 0.044–3.66 56 82 82 0.163 --- ---

Eu1 0.076–2.55 68 100 84 0.222 <2.0 >0.11

Fe (%) 0.15–0.74 68 100 100 0.33 4.62 0.071

Ga 0.457–1.82 56 82 82 0.766 23 0.033

Gd 0.158–6.47 56 82 82 0.558 --- ---

Ge 0.019–0.097 56 82 82 0.037 --- ---

Hf1 0.013–1.00 68 100 84 0.023 --- ---

Hg <1.0–<1.0 12 18 0 --- --- ---

Ho 0.015–1.17 56 82 82 0.057 --- ---

I <0.10–0.43 30 44 4 <0.10 --- ---

In (ppb) 2.531–45.5 56 82 82 10.1 --- ---

Ir (ppb) <5.0–<5.0 12 18 0 --- --- ---

K (%) 3.74–>14.40 38 56 51 10.05 2.19 4.6

La 1.12–42.3 68 100 100 3.02 39 0.077

Li 2.3–18 56 82 82 5.72 19 0.30

Lu1 0.006–0.370 68 100 85 0.016 --- ---

Mg (%) 0.10–9.57 68 100 100 4.04 0.47 8.6

Mn 300–12,300 68 100 100 1,090 571 1.9

Mo 1.87–22.0 68 100 100 5.0 4.0 1.3

Na (%) 0.04–0.36 68 100 100 0.12 0.52 0.23

Nb <0.050–0.231 56 82 81 0.093 14 0.0066

Nd1 0.82–31.5 68 100 82 2.03 34 0.060
Results and Evaluation of the Rock Chemistry 69

Table 8. Summary of chemical data for ash and 66 elements in 68 juniper ash samples, Red Mountain, Arizona.

[All concentrations are in parts per million unless % (percent) or ppb (parts per billion) is shown after the chemical symbol. Analytical methods are described 

in the text and in the associated data for this publication (Horton and others, 2020). ---, indicate no meaningful value. Values preceded by < or > are qualified values, 

which are less than or greater than, respectively, the value shown. Unqualified samples have no concentrations below the lower limit of determination or above the 

upper limit of determination. The ratio A/B gives an estimate of the relative enrichment (>1.0) or depletion (<1.0) of each element in the juniper samples] 

Element or

variable Range of values Number analyzed

Percent analyzed 

of 68 samples

Percent unqualified 

of 68 samples

Median value 

in ash (A)

Median value

in soils (B) A/B ratio

Ni 3.0–174 68 100 100 19 15 1.3

P (%) 0.763–2.44 12 18 18 1.45 0.080 18

Pb 1.8–62 68 100 100 6.6 112 0.06

Pr 0.231–8.25 56 82 82 0.070 --- ---

Rb1 <15–121 68 100 96 31 --- ---

Re 0.067–12.92 56 82 82 300 --- ---

Sb1 0.08–5.00 68 100 97 0.22 3.0 0.07

Sc 0.40–3.00 38 56 56 0.85 12 0.071

Se1 0.56–8.00 68 100 84 1.06 --- ---

Si 773–2,940 26 38 38 1,270 --- ---

Sm 0.153–5.60 68 100 100 0.51 --- ---

Sn1 <1.0–1.3 68 100 53 1.00 --- ---

Sr 427–5,260 68 100 100 2,175 268 8.1

Ta1 0.001–0.017 68 100 47 <0.5 --- ---

Tb1 0.018–0.904 68 100 82 0.060 --- ---

Te1 0.004–0.16 56 82 41 <0.10 0.60 <0.17

Th <0.200–1.80 68 100 97 0.501 18 0.028

Ti 92–700 68 100 100 152 3,690 0.041

Tl1 0.007–0.135 56 82 81 0.023 1.5 0.015

Tm 0.006–0.445 56 82 82 0.024 --- ---

U1 0.028–0.60 68 100 85 0.094 --- ---

V1 1.51–19.0 68 100 99 3.81 131 0.029

W <0.1–<1.0 38 56 0 <0.1 --- ---

Y 0.47–51 68 100 100 2.50 16 0.16

Yb1 0.035–2.58 68 100 88 0.113 2.0 0.057

Zn 86–2,430 68 100 100 202 103 2.0

Zr1 0.468–1.36 56 82 68 0.62 --- ---

1

More than one lower limit of determination reported. The lowest reported value is shown.
70 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

and Ag (1.4) (table 7). For juniper, the elements accumulated 

are: Ca (63), P (18), Mg (8.6), Sr (8.1), K (4.6), Cd (4.1), Zn 

(2.0), Mn (1.9), Ni (1.3), Mo (1.3), and Ba (1.1) (table 8). These 

ratio values show that in addition to concentrating some of the 

deposit-related elements, the three plant species all tend to accumulate the common essential, nontoxic- and nondeposit-related 

elements, although to differing degrees. 

The median concentration values in the ash (tables 6–8) 

indicate that the three plant species do not concentrate a given 

element to the same degree. For example, cadmium is about 

10 times more concentrated in oak ash than in juniper ash, and 

at least 20 times more in oak ash than in mesquite ash. Zinc is 

more than twice as concentrated in mesquite ash than it is in the 

other two species. Similarly, cesium is about 8 times more concentrated in mesquite ash than in oak ash and at least 20 times 

more than in juniper ash. Other examples can be found. Clearly, 

these observations indicate that plant genetics must control the 

overall chemical uptake of different elements by each species.

Distributions of Selected Elements in 

Rock and Soil Samples

Maps related to the rock and soil chemistry (figs. 41–77) 

show the distributions for selected elements overlaid on a 

geologic base. The sample sites used for contouring are shown 

on each of the figures. The element distributions are shown 

using contours. Contours are shown with a solid line where 

the sample density is high. Where sample density is low, the 

contours are dashed.

Deposit-related elements with positive anomalies in 

both the rock and soil samples include Ag, As, Bi, Cu, Fe, 

Mo, Pb, Sb, Te, and Tl. Select elements exhibiting negative 

anomalies in both media include the deposit-related elements 

Cd, Co, and Zn, and the mostly lithology-related elements 

Ca, K, La, Mg, Mn, and Na. Localized anomalies for 

deposit-related elements in the Tertiary indurated terrace 

gravels are caused by fragments of altered rock included in 

samples collected from this unit.

Outer Limit of Visible Alteration in Outcrops.—The 

boundary outlining the outer limit of visible strong alteration 

in rock samples defines an area, which helps to interpret 

anomaly sources (fig. 41). The area containing most of the 

altered samples is largely centered on the rhyolite tuff and 

quartz monzonite porphyry exposures but extends locally 

into the surrounding formations. The lateral extent at depth 

of alteration related to the Red Mountain PCD is not precisely 

known, but at the surface visible strong alteration extends 

more than 6 km in an east-west direction and about 4 km in a 

north-south direction (fig. 41).

There are also some scattered, small isolated altered 

areas outside of the altered rock boundary. Anomalies of any 

deposit-related elements in rock samples collected outside 

of this boundary (except for the few isolated, altered sites) 

probably do not have a source related to the hypogene 

Cu-Mo deposit. This source is most likely contamination 

from material from past mining activity (Chaffee and others, 

1981) in the region that has been dispersed by wind and 

(or) water.

Copper.—The median values for copper in the rock and 

soil databases are 44 and 91 ppm, respectively (tables 4 and 5), 

indicating that copper has been concentrated during soil 

formation. The distribution of copper in rock samples is 

shown in figure 42. The highest copper concentrations are 

found in two areas labeled “A” and “B,” which are within 

the alteration boundary and clearly related to the hypogene 

Cu-Mo deposit. Anomaly “A” is over the main exposure of 

the quartz monzonite porphyry. Anomaly “B” is farther to 

the east and is associated with the cluster of small outcrops 

of the same formation that is directly above the deep part 

of the hypogene deposit. The widespread anomaly labeled 

“C” is outside of the area of visible alteration and generally 

includes samples of visibly unaltered andesite collected along 

or near the Harshaw Creek drainage. A few samples from 

area “C” have copper concentrations exceeding 100 ppm. 

The source for these relatively high copper concentrations 

is not entirely clear, because obvious signs of alteration, 

such as veins, silicification, bleaching, or the presence of 

hydrothermal biotite or magnetite, are lacking. 

The distribution of copper in soil samples (fig. 43) differs from that of copper in rock samples in that the highest 

soil concentrations are only present in the area surrounding 

the main quartz monzonite porphyry intrusive center (area 

“A” on fig. 42). The soil anomaly in area “B” is offset somewhat to the east of the quartz monzonite porphyry outcrops, 

possibly because of weathering-related chemical migration. 

The area of the anomaly labeled “C” on the rock map is also 

anomalous in general for the soils and is almost certainly 

caused by dispersion of sediments in the Harshaw Creek 

drainage contaminated by past mining activity (Chaffee and 

others, 1981). 

Iron.—Major rock-forming elements, such as iron, 

are difficult to contour because the range of values is more 

restricted than those of minor or trace elements. The overall 

distribution of this element reflects a combination of the 

bulk chemistry of the andesite and rhyolite tuff units and 

the hydrothermal introduction of iron, mainly in the form of 

pyrite, magnetite, and chalcopyrite. The median values for 

iron in the rock and soil databases are 3.54 and 4.62 percent, 

respectively (tables 4 and 5), indicating that iron has been 

concentrated during soil formation. The highest concentrations 
Figure 41. Sample locations and the outer limit of intense, visible alteration in outcrops. Harshaw Creek

Harshaw Creek

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Figure 42. Distribution of copper in rock samples.
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Figure 43. Distribution of copper in soil samples.
Patagonia

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Figure 44. Distribution of iron in rock samples.
Patagonia

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Figure 45. Distribution of iron in soil samples.
Harshaw Creek

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Figure 46. Distribution of molybdenum in rock samples.
Harshaw Creek

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Figure 47. Distribution of molybdenum in soil samples.
Harshaw Creek

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Figure 48. Distribution of silver in rock samples.
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Figure 49. Distribution of silver in soil samples.
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Figure 50. Distribution of arsenic in rock samples.
Harshaw Creek

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Figure 51. Distribution of arsenic in soil samples.
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Figure 52. Distribution of antimony in rock samples.
Harshaw Creek

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Figure 53. Distribution of antimony in soil samples.
Harshaw Creek

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low

5.03.01.0

Geology modified from Dand Simons (1974).

0 .5 1 10 .5 

Figure 54. Distribution of bismuth in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum oGeology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

5.03.01.0

0 .5 1 10 .5 

Figure 55. Distribution of bismuth in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

4.02.01.0

0 .5 1 10 .5 

Figure 56. Distribution of thallium in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact infeFault— or in

J-Yh Hornble

 igne

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu part with  dens low, 

6.0

4.03.0

Sample 

1.5

0 .5 1 10 .5 

Figure 57. Distribution of thallium in soil samples.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low

50030010040

0 .5 1 10 .5 

Figure 58. Distribution of lead in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igne

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

800500300

Sample 

100

0 .5 1 10 .5 

Figure 59. Distribution of lead in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu part with  dens low, 

3.0

1.00.30.2

0 .5 1 10 .5 

Figure 60. Distribution of tellurium in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu part with  dens low, 

2.0

1.00.6

0 .5 1 10 .5 

Figure 61. Distribution of tellurium in soil samples.
Harshaw Creek Harshaw Creek Sonoita CreekRed Mountain QTag QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

20010070

0 .5 1 10 .5 

Figure 62. Distribution of zinc in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igne

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

400200100

Sample 

80

0 .5 1 10 .5 

Figure 63. Distribution of zinc in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

0.500.100.05

0 .5 1 10 .5 

Figure 64. Distribution of cadmium in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm Tqm

Tqm TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or in

J-Yh Hornble

 igne

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low

0.700.500.25

Sample 

0.20

0 .5 1 10 .5 

Figure 65. Distribution of cadmium in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

1052

0 .5 1 10 .5 

Figure 66. Distribution of cobalt in rock samples. 
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low, 

20105

0 .5 1 10 .5 

Figure 67. Distribution of cobalt in soil samples.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact inferFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu in pa show dens low, 

300150205

0 .5 1 10 .5 

Figure 68. Distribution of manganese in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm Tqm

Tqm TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact inferFault— or in

J-Yh Hornble

 igne

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu in pa show dens low, 

1,000500200

Sample 

100

0 .5 1 10 .5 

Figure 69. Distribution of manganese in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag QTag

QTag

QTag

Tqm

Tqm Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum oGeology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or i

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount 

 fels

Ka Trachya

 Chie Sim

Distribu per soli high con

0.500.100.05

0 .5 1 0 .5 

Figure 70. Distribution of calcium in rock samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

82

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

Alum

Gulch

Base from U.S. GeologicGeographic projection, dNorth American Datum 

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EX

QTag Alluviu

 und

Contac infFault— or 

J-Yh Hornb

 ignSampl

Tqm Quartz 

 Int

TKv

TKr Volcan

 rhyFelsic 

Kv Silicic 

J-i Pluton

 und

m Mount 

 fels

Ka Trachy

 Ch Sim

Distrib pe sol hig co

0.500.250.15

0 .5 1 0 .5 

Figure 71. Distribution of calcium in soil samples.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag QTag

QTag

QTag

Tqm

Tqm Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact infeFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcani

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu in pe solid  high cont

0.500.300.10

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Figure 72. Distribution of magnesium in rock samples.
Harshaw Creek

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Figure 73. Distribution of magnesium in soil samples.
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Figure 74. Distribution of sodium in rock samples.
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Figure 75. Distribution of sodium in soil samples.
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Figure 76. Distribution of potassium in rock samples.
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Figure 77. Distribution of potassium in soil samples.
108 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

of iron in rock samples are centered over the cluster of small 

quartz monzonite porphyry outcrops that is directly above 

the deep hypogene Cu-Mo deposit (fig. 44). As discussed 

previously for copper, the widespread anomaly for iron along 

Harshaw Creek is likely a result of past mining contamination 

but some of the anomaly may be because of differences in 

iron concentrations because of lithologic variations within 

the andesite unit. In contrast to the distribution of iron in the 

rock samples, the highest iron concentrations in the soils are 

located over and around the main outcrop of quartz monzonite 

porphyry (fig. 45). 

Molybdenum.—The median values for molybdenum 

in the rock and soil databases are 3 and 4 ppm, respectively 

(tables 4 and 5), indicating that molybdenum has probably 

been concentrated during soil formation. The highest molybdenum concentrations in both rock and soil samples are 

spatially associated with both the main outcrop of the quartz 

monzonite porphyry unit to the west and the cluster of small 

outcrops farther east (figs. 46 and 47). The rock map also identifies sites with molybdenum concentrations in the Harshaw 

Creek drainage that are probably related to contamination 

from past mining activities (Chaffee and others, 1981). 

Silver, Arsenic, Antimony, Bismuth, Thallium, Lead, and 

Tellurium.—The median values for Ag, As, Sb, Bi, Tl, Pb, 

and Te in rock are <0.5, 12, 1.0, <1.0, 1.0, 39, and 0.2 ppm, 

respectively (table 4) and for these elements in soil are 0.3, 

34, 3.0, 1.0, 1.5, 112, and 0.6 ppm, respectively (table 5). 

Although the data for silver are not clear, it is likely that all of 

these elements have been concentrated during soil formation. 

The distributions of these deposit-related elements in the rock 

and soil samples are shown in figures 48-61. The rock maps all 

show complex distributions that are similar, positive anomalies, 

with the highest concentrations commonly in the general area 

of the cluster of small quartz monzonite porphyry outcrops 

in the center of the rhyolite tuff unit (figs. 48, 50, 52, 54, 56, 

58, and 60 for Ag, As, Sb, Bi, Tl, Pb, and Te, respectively). In 

contrast, the anomalies for many of these same seven elements 

in soil samples are somewhat more widespread than those seen 

for the comparable rock samples. Anomalies for most of these 

elements in soils include both the area of the main outcrop 

of quartz monzonite porphyry and that containing the cluster 

of small outcrops of the same unit (figs. 49, 51, 53, 55, 57, 

59, and 61 for Ag, As, Sb, Bi, Tl, Pb, and Te, respectively). 

The high concentrations of arsenic in the deposit area (as 

much as 390 ppm in rock and 1,500 ppm in soil; Horton and 

others, 2020) and of lead (as much as 2,370 ppm in rock and 

1,490 ppm in soil; Horton and others, 2020) are particularly 

noteworthy and emphasize that these two potentially toxic 

elements, in particular, have not been leached from the top 

of the deposit as a result of supergene enrichment and later 

weathering. The three scattered rock sites to the south of Red 

Mountain with highly anomalous silver, lead, and antimony 

in the rock samples are related to small areas prospected for 

base-metal silver deposits that may be part of a zone peripheral 

to the Red Mountain mineral system. 

The high concentrations of arsenic (>100 ppm) and 

lead (>800 ppm) in soil samples are particularly notable and 

emphasize that these elements, as well as many of the other 

deposit-related elements in this group have been relatively 

immobile chemically during weathering at Red Mountain. The 

effects of contamination for most of these elements in both 

sample types are only present in the upper part of the Harshaw 

Creek drainage.

All seven elements in this group also showed positive 

anomalies in core samples at the top of the section. Very few 

rock and soil samples were analyzed for tin and tungsten. 

However, their high, near-surface concentrations in the core 

samples imply that these two elements would also show 

deposit-related positive anomalies in the rock and soil samples.

Zinc and Cadmium.—The median values for zinc and 

cadmium are 74 and 0.06 ppm, respectively, in the rock database 

(table 4), and 103 and 0.25 ppm, respectively, in the soil 

database (table 5). These values clearly indicate that both 

elements have been concentrated during soil formation. These 

two elements in rock and soil samples (figs. 62–65) exhibit low 

concentrations over the hypogene Cu-Mo deposit, consistent with 

the observation that low concentrations of zinc (and probably 

cadmium, for which data at depth are lacking) are present in 

core samples from the near-surface part of the deposit. These 

negative anomalies are present in both the rhyolite tuff and 

andesite units and locally in adjacent formations to the west. 

Some of this negative anomaly effect may be a result of 

pre-mineralization chemical differences between contrasting 

lithologies. Positive anomalies for cadmium and zinc are present 

locally for both media in the area surrounding the boundary for 

altered rocks and may represent a crude halo effect surrounding 

the central negative anomalies. Contamination effects have 

produced local negative anomalies in the peripheral drainage 

channels for both elements in both media, suggesting leaching 

of both elements.

Cobalt and Manganese.—The median values for cobalt 

and manganese are 5 and 144 ppm, respectively, in the rock 

database (table 4), and 9 and 571 ppm, respectively, in the soil 

database (table 5). Again, the soil values for both elements are 

distinctly higher than the rock values. These two elements also 

exhibit negative anomalies over the hypogene Cu-Mo deposit 

in both rock and soil samples (figs. 66–69). The negative 

anomaly for cobalt is mainly a result of leaching of this element 

during the period of near-surface weathering that formed the 

leached cap. In the case of manganese, the distributions at 

depth (fig. 33), as well as at the surface, are mostly related to 

initially low concentrations of this element in the rhyolite tuff 

unit but may also include the effects of low concentrations as 

a result of leaching during formation of the leached cap. 

Manganese oxides are widely distributed in the indurated 

terrace gravels in the study area (fig. 4D).

Calcium, Magnesium, and Sodium.—The median values 

for calcium, magnesium, and sodium in rock samples are 0.12, 

0.32, and 0.38 percent, respectively (table 4), and the values 

in soil samples are 0.45, 0.47, and 0.52 percent, respectively 
Distribution of Percent Ash and Selected Elements in Vegetation Samples 109

(table 5). All three elements have higher concentrations in the 

soils than rocks. These three major rock-forming elements 

exhibit distributions at depth that are closely related spatially 

to alteration associated with the hypogene Cu-Mo deposit as 

well as to chemical differences because of weathering and 

contrasting lithologies. On the surface directly over the deposit 

area, all three elements exhibit complex negative anomalies in 

both the rock and soil samples (figs. 70–75). 

Potassium.—Potassium is also a major constituent of the 

bulk chemistry of the various volcanic host rocks, as well as 

being associated with hydrothermal potassic alteration and 

with the major sulfide mineralization events at Red Mountain. 

The median value for potassium is 2.56 percent in rock (table 4) 

and 2.19 percent in soil (table 5). Unlike all of the other selected 

elements, potassium is somewhat depleted in the soil samples 

as compared to the rock samples. Potassium concentrations 

in both rock and soil samples exhibit complex, mostly 

lithology-associated negative anomalies that are generally 

centered on the rhyolite tuff unit but extend locally into the 

andesite unit (figs. 76 and 77). The high concentrations 

(>2.50 percent for rocks and >2.10 percent for soils) of potassium 

outside of the area of visible alteration on both plots are thought 

to simply represent relatively high but normal concentrations of 

potassium in the generally unaltered parts of the andesite unit. 

Distribution of Percent Ash and 

Selected Elements in Vegetation 

Samples

The elements selected for illustrating distributions in 

vegetation include 10 hypogene deposit-related elements (Ag, 

As, Bi, Cd, Cu, Mo, Pb, Sb, Se, and Zn) and 3 elements more 

closely related to lithology (Mg, Mn, and Na). Some elements 

highlighted in the rock and soil discussion are not included in 

this section because they did not show any interpretable distributions or had restricted ranges of values. Percent ash maps 

for the mesquite, oak, and juniper are included to demonstrate 

that their distributions are totally independent of the effects of 

the chemical history of the hypogene Cu-Mo deposit and also 

of the various lithologies. 

The distributions for percent ash and these 13 elements in 

the 3 plant species are shown in figures 78–119. Contour values 

for each vegetation map were chosen somewhat arbitrarily in 

order to best illustrate the distribution of a given element in 

each species. In general, the lowest contour value plotted on 

each map is close to the median concentration value for that 

element. As was the case for rock and soil samples, some of the 

vegetation maps show anomalies associated with the Harshaw 

Creek and Alum Gulch drainages that are likely a result of 

water, soil, and (or) airborne contamination related to past 

mining (Chaffee and others, 1981).

Percent Ash—Because of the limited ranges of values for 

percent ash in the three plant species, the distributions are difficult 

to contour. The median values for percent ash in mesquite, oak, 

and juniper samples are 5.70, 3.95, and 4.78 percent, respectively 

(tables 6–8), The mesquite and oak ash produced positive 

anomalies that are centered mostly east (mesquite) or south 

(oak) of Red Mountain (figs. 78 and 79, respectively). In contrast, juniper ash produced a negative anomaly that is roughly 

centered over and south of the rhyolite tuff unit (fig. 80). These 

distributions are species dependent and are not associated with 

the chemical distributions related either to the mineral deposit 

or to specific lithologies. The distributions are thus mostly 

related to physical environmental conditions, such as annual 

precipitation, annual temperature, elevation, slope angle, 

aspect, and available groundwater.

Copper, Molybdenum, and Silver.—Copper and molybdenum are essential elements for plants; silver is considered 

to be nonessential (Brooks, 1983). The A/B (ash/soil) ratios 

exceed 1.00 for copper and molybdenum in mesquite, for 

silver in oak, and for molybdenum in juniper (tables 6–8). 

Previous studies have also shown accumulation of copper 

and molybdenum in mesquite (Chaffee, 1976a; Huff, 1970). 

Published data for oak and juniper are lacking. 

The median values for copper are 147, 87, and 62 ppm for 

mesquite, oak, and juniper ash, respectively; for molybdenum 

are 5.3, 1.6, and 5.0 ppm, respectively; and for silver are 0.27, 

0.42, and 0.15 ppm, respectively (tables 6–8). Positive anomalies 

of copper, molybdenum, and silver in ash samples of all three 

species are generally centered over the rhyolite tuff unit and, 

in many cases, directly over the hypogene Cu-Mo deposit 

(figs. 81–89, respectively). The distributions of anomalies in 

the mesquite ash samples are not well defined in the center of 

the rhyolite tuff unit because of the lack of sample sites in that 

formation at the higher elevations. High concentrations of all 

three elements in oak ash samples are mostly centered over the 

main exposure of quartz monzonite porphyry and, to a lesser 

extent, over the area with the cluster of small outcrops of this 

same formation. In contrast to their distributions in mesquite 

and oak ash, the copper, molybdenum, and silver anomalies 

for juniper ash (figs. 83, 86, and 89, respectively) are mostly 

centered over the cluster of small quartz monzonite porphyry 

outcrops in the middle of the rhyolite tuff unit. The reason for 

these differences among the species is not clear.

Arsenic, Antimony, and Bismuth.—These three elements 

are an important part of the hydrothermal mineral suite at Red 

Mountain, but they are not essential for plants; they are generally considered to be toxic (Levinson, 1974). This nonessential 

nature of these elements is emphasized with the mostly low 

ash/soil ratio values (columns A/B) for these elements, which 

range from 0.04 to 0.07 in mesquite ash, from 0.06 to 0.47 in 

oak ash, and from 0.07 to 0.16 in juniper ash (tables 6–8). The 

low ratio values emphasize that these species are not strongly 

accumulating these potentially toxic elements. Despite this 

fact, all of these elements, except for antimony in mesquite, 

exhibit well-defined positive anomalies (figs. 90–98), 
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Figure 80. Distribution of percent ash in juniper samples.
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Figure 81. Distribution of copper in oak ash.
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Figure 82. Distribution of copper in mesquite ash.
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Figure 83. Distribution of copper in juniper ash.
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Patagonia

82

Base from U.S. GeologicGeographic projection, dNorth American Datum 

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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m Mount 

 fels

Ka Trachy

 Chi Sim

Distrib ash are  sam den

Sampl

4020105

0 .5 1 0 .5 

Figure 84. Distribution of molybdenum in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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E

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 rhyolite tFelsic volca

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m Mount Wrigh

 felsic vol

Ka Trachyandes

 Chiefly a Simons, 

Distribution  per millio line wher Where sa are dash

2.5

2.01.5

0 .5 1 10 .5 

Figure 85. Distribution of molybdenum in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, deNorth American Datum o

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110°46' 110°44' 110°42'

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 Chief Simo

Distribut in pa with  is hig conto

9

75

0 .5 1 10 .5 

Figure 86. Distribution of molybdenum in juniper ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

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m Mount W

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 Chie Sim

Distribu part with  den low, 

1.00.50.3

0 .5 1 10 .5 

Figure 87. Distribution of silver in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, deNorth American Datum o

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110°46' 110°44' 110°42'

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m Mount W

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 Chiefl Simon

Distributi millio line w Wher are da

1.0

0.70.5

0 .5 1 10 .5 

Figure 88. Distribution of silver in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Patagonia

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Alum

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Base from U.S. GeologicGeographic projection, dNorth American Datum 

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

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31°30'31°28'

EXP

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Distribu per  solid  high cont

9.0

7.05.0

0 .5 1 0 .5 

Figure 89. Distribution of silver in juniper ash.
122 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

indicating that all three species are taking up most of these 

elements to some degree in response to the concentrations 

in the substrate soils. Armienta and others (2008) note that, 

in spite of the potential toxicity of arsenic, mesquite is 

arsenic tolerant and can accumulate considerable amounts in 

both leaves and stems. This tolerance for arsenic seems to be 

present for oak and juniper trees as well.

The median values for arsenic are 1.7, 5.0, and 5.3 ppm 

for mesquite, oak, and juniper ash, respectively; for antimony 

are 0.12, 0.18, and 0.22 ppm, respectively; and for bismuth are 

0.074, 0.159, and 0.106 ppm, respectively (tables 6–8). The 

distributions of arsenic, antimony, and bismuth in mesquite 

ash are shown on figures 90–92. Those for arsenic and bismuth 

exhibit high concentrations that are associated mostly with 

the rhyolite tuff unit (figs. 90 and 92). The distributions of 

antimony in mesquite ash (fig. 91) do not match those of the 

other two elements and probably do not reflect any meaningful 

anomalies. The distributions of high concentrations of all three 

elements in oak ash are generally highest over the western 

area containing the main outcrops of quartz monzonite porphyry 

(figs. 93, 94, and 95, respectively). In contrast, the distributions 

of all three elements in juniper ash (figs. 96, 97, and 98, 

respectively) are similar to those of copper and silver (figs. 83 

and 89) and are centered farther to the east, over the cluster of 

small quartz monzonite porphyry outcrops. The distributions of 

antimony in all three species also exhibit anomalies near washes 

that probably are related to contamination from past mining.

Lead.—Lead is toxic when present in relatively high 

concentrations and is nonessential for plants (Levinson, 1974). 

The corresponding ash/soil ratio values for the three plant 

species reflect that, with low values ranging from 0.04 to 0.12 

(tables 6–8). However, concentration ranges show that lead 

has been highly concentrated, especially in oak ash, which 

indicates a high tolerance for lead for that species.

The median values for lead in mesquite, oak, and juniper 

samples are 4.6, 13, and 6.6 ppm, respectively (tables 6–8). 

Lead is present in much lower concentrations in the mesquite 

ash (fig. 99) than in the ash of oak or juniper (figs. 100 and 101, 

respectively). That fact, plus the lack of sufficient sample sites 

over the deposit, explains why the distributions of high concentrations of lead in mesquite ash do not show meaningful 

anomalies related to the hypogene Cu-Mo deposit. High concentrations of lead in oak and juniper ash show patterns that 

are similar to those of lead in soil (fig. 59). Anomalous lead 

concentrations for these two species are approximately centered 

over the cluster of quartz monzonite porphyry outcrops in the 

middle of the rhyolite tuff unit. Concentrations exceeding 

100 ppm lead in oak ash samples are more common than those 

for juniper, probably because of the relatively higher overall 

concentrations of lead in oak ash as reflected in the median 

values. Anomalous lead that is a result of contamination from 

past mining is present in major drainages for all three species.

Zinc and Cadmium.—These two elements commonly 

occur together in many natural substances. In low concentrations, zinc is considered essential for plants and cadmium may 

also be essential (Brooks, 1983; Shacklette, 1972). Both zinc 

and cadmium exhibit high ash/soil ratios for all three species 

(tables 6–8). In particular, the ratio value for zinc in mesquite 

ash samples (5.0) and for cadmium in the oak ash samples 

(47) are unusually high. These two high ratio values indicate 

that mesquite trees in the environment at Red Mountain have a 

higher accumulation rate and tolerance for zinc, and oak trees 

have a high accumulation rate and tolerance for potentially 

toxic cadmium.

The median values for zinc are 511, 226, and 202 ppm for 

mesquite, oak, and juniper ash, respectively; and for cadmium 

are 0.54, 11.75, and 1.03 ppm, respectively (tables 6–8). The 

distributions of zinc and cadmium in the three species are 

shown on figures 102–107. Concentrations in the mesquite 

ash show positive anomalies for both elements that are 

centered over the general area of the deposit (figs. 102 and 

103, respectively). Positive anomalies of zinc and cadmium 

occur in oak ash in the area of the main quartz monzonite 

porphyry outcrop (figs. 104 and 105, respectively). Zinc in 

juniper ash exhibits a positive anomaly that is mostly concentrated over the northwestern part of the rhyolite tuff unit and 

includes the two main areas of quartz monzonite porphyry 

(fig. 106). In contrast, cadmium in juniper ash exhibits a 

negative anomaly over this same area as well as over a wide 

area to the southeast (fig. 107).

Selenium.—This element is essential in many plant species 

but may not be essential for all species (Brooks, 1983). Ash/soil 

ratios could not be calculated for any of the plant species because 

selenium was not determined in most rock or soil samples. 

The median values for selenium are 1.10, 0.89, and 1.06 ppm 

for mesquite, oak, and juniper ash, respectively (tables 6–8). 

Because of the lack of sample sites, the distribution of selenium 

in mesquite ash is not meaningful in terms of delineating 

anomalies related to the hypogene Cu-Mo deposit. The only 

significant selenium anomaly in mesquite ash is located 

southeast of the main surface exposures of the deep copper 

deposit, in a mostly altered area in the andesite unit (fig. 108). 

The highest concentrations of selenium in oak ash are centered 

over the area of the rhyolite tuff unit and especially over the 

main quartz monzonite porphyry outcrop (fig. 109). In contrast, 

the distribution of high selenium concentrations in juniper ash 

is more widespread and encompasses the rhyolite tuff unit and 

also adjacent parts of the andesite unit, mainly to the south of 

the rhyolite tuff unit (fig. 110). 
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

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82

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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110°40'

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EXP

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Distribu part with  den low

10

42

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Figure 90. Distribution of arsenic in mesquite ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, dNorth American Datum oGeology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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Distribu part with  den low

0.20

0.150.10

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Figure 91. Distribution of antimony in mesquite ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

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Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

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m Mount 

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 Chie Sim

Distribu part with  den low

0.15

0.130.07

0 .5 1 0 .5 

Figure 92. Distribution of bismuth in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXPL

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Ka Trachyan

 Chief Simon

Distribut millio line w Wher are d

20

105

0 .5 1 0 .5 

Figure 93. Distribution of arsenic in oak ash.
Harshaw Creek

Sonoita Creek

Harshaw Creek

Red

Mountain

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Alum Gulch

Base from U.S. Geological Geographic projection, decNorth American Datum of 

Geology modified from Dreand Simons (1974).

110°46' 110°44' 110°42'

31°32'

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EXPLA

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Ka Trachyand

 Chiefly  Simons

Distributio million line wh Where  are das

0.250.200.15

0 .5 1 1.0 .5 

Figure 94. Distribution of antimony in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

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 undiv

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m Mount W

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Ka Trachyan

 Chief Simon

Distribut millio line w Wher are d

0.300.250.200.15

0 .5 1 0 .5 

Figure 95. Distribution of bismuth in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

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m Mount W

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 Chief Simo

Distribu per m solid  high.  cont

15105

0 .5 1 0 .5 

Figure 96. Distribution of arsenic in juniper ash.
Harshaw

Creek

Sonoita Creek

Harshaw

Creek

Red

Mountain

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

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Distribu parts  with  is hig cont

1.00

0.500.20

0 .5 1 0 .5 

Figure 97. Distribution of antimony in juniper ash.
Figure 98. Distribution of bismuth in juniper ash.

Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Patagonia

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

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EXPL

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TKv

TKr Volcanics 

 rhyolitFelsic vol

Kv Silicic vo

J-i Plutonic a

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chiefl Simon

Distributi per m solid l high.  conto

0.400.200.10

0 .5 1 0 .5 
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

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Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

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J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or i

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount 

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low

15

105

0 .5 1 0 .5 

Figure 99. Distribution of lead in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Ka

Ka

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Ka

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m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

TKv

TKr Volcanic

 rhyoliFelsic vo

Kv Silicic vo

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut millio line w Wher are d

100502010

0 .5 1 0 .5 

Figure 100. Distribution of lead in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Ka

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Ka

Ka

Ka

Ka

Ka

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J-i

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J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum oGeology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undiv

Contact— inferFault—D or in

J-Yh Hornble

 igne

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic vo

Kv Silicic v

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachya

 Chief Simo

Distribu per m solid  high.  cont

Sample 

502096

0 .5 1 0 .5 

Figure 101. Distribution of lead in juniper ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag

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Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or i

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount 

 fels

Ka Trachya

 Chie Sim

Distribu per  soli high con

1,5001,000500

Geology modified from Dand Simons (1974).

0 .5 1 0 .5 

Figure 102. Distribution of zinc in mesquite ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag QTag

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Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, deNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or in

J-Yh Hornble

 igne

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount W

 fels

Ka Trachya

 Chie Sim

Distribu part with  den low

Sample 

2.01.51.00.5

0 .5 1 10 .5 

Figure 103. Distribution of cadmium in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Tqm Tqm

TKr TKr

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TKr

TKr

TKr

TKr

TKr

TKr

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TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

TKv

TKr Volcanic

 rhyoliFelsic vo

Kv Silicic vo

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut millio line w Wher are d

600400200

0 .5 1 0 .5 

Figure 104. Distribution of zinc in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

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Tqm

Tqm

Tqm Tqm

TKr

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TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

TKv

TKr Volcanic

 rhyoliFelsic vo

Kv Silicic vo

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut per m solid  Wher are d

503015

0 .5 1 0 .5 

Figure 105. Distribution of cadmium in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

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Tqm

Tqm

Tqm Tqm

TKr TKr

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TKr

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TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum Gulch

Base from U.S. Geological Geographic projection, decNorth American Datum of 

Geology modified from Dreand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPLA

QTag Alluvium a

 undivid

Contact— inferreFault—Da or infe

J-Yh Hornblend

 igneouSample si

Tqm Quartz mo

 Intrusi

TKv

TKr Volcanics 

 rhyolitFelsic volc

Kv Silicic vol

J-i Plutonic a

 undivid

m Mount Wr

 felsic v

Ka Trachyand

 Chiefly  Simons

Distributio per mi solid li high. W contou

500

300200

0 .5 1 1.5 0 .5 

Figure 106. Distribution of zinc in juniper ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

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TKr TKr

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Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum Gulch

Base from U.S. GeologicGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact inferFault—D or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic vo

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsic 

Ka Trachya

 Chie Simo

Distribu parts  with  is hig cont

1.51.00.5

0 .5 1 0 .5 

Figure 107. Distribution of cadmium in juniper ash.
Distribution of Percent Ash and Selected Elements in Vegetation Samples 141

Sodium.—This major element is essential for plants 

(Brooks, 1983). However, the ash/soil ratios for the three 

species are very low, ranging from 0.14 to 0.23 (tables 6–8), 

implying that sodium is not highly concentrated by these 

species. The median values for sodium are 0.07, 0.09, and 

0.12 percent for mesquite, oak, and juniper ash, respectively 

(tables 6–8). The rock and soil distributions for sodium 

exhibit negative anomalies centered over the rhyolite tuff 

unit (figs. 74 and 75). In contrast, the distributions of all 

three plant species show low-level but distinct positive 

anomalies over this unit (figs. 111–113). However, the 

distribution of sodium in oak ash is more concentrated over 

the main outcrops of quartz monzonite porphyry than it is 

in mesquite and juniper ash. The discrepancy between the 

negative rock and soil distributions and the positive plant 

distributions seems to reflect the essentiality of sodium in 

plants even though the ash/soil ratios are low.

Manganese.—This minor element is also essential for 

plants (Brooks, 1983). The ash/soil ratios for manganese 

in mesquite and juniper ash are 0.67 and 1.9, respectively 

(tables 6 and 8). In the case of oak ash, the ratio is an unusually high 8.8, with manganese concentrations ranging as high 

as 20,980 ppm, or about 2.1 percent, in ash (table 7). These 

differences in manganese ash/soil ratios indicate that this 

element is accumulated quite differently in each of these 

three plant species, probably as a result of genetic differences.

The median values for manganese are 381, 5,025, and 

1,090 ppm for mesquite, oak, and juniper ash, respectively 

(tables 6–8). The distribution of manganese in soils (fig. 69) 

exhibits a negative anomaly centered over the rhyolite tuff 

unit. The distributions for all three plant species show broad 

areas of low manganese concentrations that differ for each 

species. The low areas are not entirely confined to the area 

of visible alteration (fig. 41) or to the area of the rhyolite 

tuff unit (figs. 114–116). The area of low manganese 

concentrations for all three species in the andesite unit south 

of the rhyolite tuff unit is not present in the distribution of 

manganese in soils (fig. 69) and is thus thought to be a result of 

elevation-related climate parameters or possibly groundwater 

regimens rather than to the chemical effects of deposit-related 

minerals or lithology. Negative anomalies, especially for 

manganese in oak ash, are also present along the Harshaw 

Creek drainages. Their possible association with contamination 

from past mining is implied but not clearly understood.

Magnesium.—This major element is also essential for 

plants (Brooks, 1983). The ash/soil ratios for the three species 

range from 5.0 to 8.6 (tables 6–8), indicating that magnesium 

is strongly accumulated in all three of these species; however, 

all three species exhibit negative anomalies.

The median values for magnesium are 2.35, 3.20, and 

4.04 percent for mesquite, oak, and juniper ash, respectively 

(tables 6–8). Sample sites for magnesium in the mesquite ash 

are lacking over the rhyolite tuff unit; thus, it is not possible 

to accurately describe the overall distribution of magnesium 

for this species (fig. 117). The distributions of magnesium 

in the ash of oak and juniper (figs. 118–119) show negative 

anomalies that are centered over the rhyolite tuff unit and are 

similar to the distribution of magnesium in soil samples 

(fig. 73). However, unlike the distribution of magnesium in 

soils, distributions of low concentrations for all three plant 

species extend in a broad area to the southeast of Red Mountain, 

suggesting that factors other than lithology are affecting the 

magnesium concentrations in plants in that area.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag

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Tqm

Tqm

Tqm

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TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or i

J-Yh Hornbl

 igne

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount 

 fels

Ka Trachya

 Chi Sim

Distrib par with  den low

Sample 

4.02.01.51.0

0 .5 1 0 .5 

Figure 108. Distribution of selenium in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

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Tqm

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Tqm

TKr TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

TKv

TKr Volcanic

 rhyoliFelsic vo

Kv Silicic vo

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut per m solid  Wher are d

2.52.01.51.0

0 .5 1 0 .5 

Figure 109. Distribution of selenium in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

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Tqm

Tqm

Tqm Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undiv

Contact— inferFault—D or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic vo

Kv Silicic v

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachya

 Chief Simo

Distribu parts  with  is hig cont

2.0

1.51.0

0 .5 1 0 .5 

Figure 110. Distribution of selenium in juniper ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

QTag QTag

QTag

QTag

QTag QTag

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Tqm

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, dNorth American Datum oGeology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluviu

 und

Contac infeFault— or i

J-Yh Hornble

 igneSample 

Tqm Quartz 

 Intr

TKv

TKr Volcan

 rhyoFelsic v

Kv Silicic 

J-i Plutoni

 und

m Mount 

 fels

Ka Trachya

 Chie Sim

Distribu per soli high con

0.150.100.07

0 .5 1 0 .5 

Figure 111. Distribution of sodium in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

QTag

Tqm

Tqm

Tqm Tqm

TKr TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPLA

QTag Alluvium a

 undivid

Contact— inferreFault—Da or infe

J-Yh Hornblend

 igneouSample sit

Tqm Quartz mo

 Intrusiv

TKv

TKr Volcanics 

 rhyolite Felsic volc

Kv Silicic vol

J-i Plutonic a

 undivid

m Mount Wr

 felsic v

Ka Trachyand

 Chiefly  Simons

Distributio Contou the sam density 

0.20

0.150.09

0 .5 1 0 .5 

Figure 112. Distribution of sodium in oak ash.
Harshaw

Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

QTag

QTag

QTag

QTag

QTag

QTag

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Tqm

Tqm

Tqm

Tqm

TKr TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m Kv

Kv

Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

TKv

TKr Volcanic

 rhyoliFelsic vo

Kv Silicic vo

J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut perce line w Wher are d

0.300.200.10

0 .5 1 0 .5 

Figure 113. Distribution of sodium in juniper ash.
Harshaw Creek

Creek

Alum

Gulch

Sonoita Creek

Harshaw

Red

Mountain

QTag

QTag

QTag

QTag

QTag QTag

QTag

QTag

Tqm

Tqm

Tqm

Tqm

Tqm

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKr

TKv

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

Ka

J-i

J-i

J-i

J-Yh

J-Yh

J-Yh

m

m

m

m

m

m

Kv

Kv

Patagonia

82

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXP

QTag Alluvium 

 undi

Contact inferFault— or in

J-Yh Hornble

 igneSample 

Tqm Quartz m

 Intru

TKv

TKr Volcanic

 rhyoFelsic v

Kv Silicic v

J-i Plutonic 

 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu in pa show dens low, 

500400300

0 .5 1 10 .5 

Figure 114. Distribution of manganese in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

QTag

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Patagonia

82

Alum Gulch

Base from U.S. Geological Geographic projection, decNorth American Datum of 

Geology modified from Dreand Simons (1974).

110°46' 110°44' 110°42'

31°32'

110°40'

31°30'31°28'

EXPLA

QTag Alluvium a

 undivid

Contact— inferreFault—Da or infe

J-Yh Hornblend

 igneouSample sit

Tqm Quartz mo

 Intrusiv

TKv

TKr Volcanics 

 rhyolite Felsic volc

Kv Silicic vol

J-i Plutonic a

 undivid

m Mount Wr

 felsic v

Ka Trachyand

 Chiefly  Simons

Distributio per mi solid li Where  are das

10,000

5,0003,000

0 .5 1 1.0 .5 

Figure 115. Distribution of manganese in oak ash.
Harshaw

Creek

Sonoita Creek

Harshaw

Creek

Red

Mountain

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Patagonia

82

Alum

Gulch

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Drand Simons (1974).

110°46' 110°44' 110°42'

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EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

J-Yh Hornblen

 igneoSample s

Tqm Quartz m

 Intrus

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 rhyolFelsic vo

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J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simo

Distribut parts  with  is hig conto

1,4001,100700

0 .5 1 10 .5 

Figure 116. Distribution of manganese in juniper ash.
Harshaw Creek

Harshaw

Creek

Alum

Gulch

Sonoita Creek

Red

Mountain

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82

Base from U.S. GeologicaGeographic projection, deNorth American Datum of 

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

QTag Alluvium 

 undi

Contact infeFault— or in

J-Yh Hornble

 igneSample 

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 Intru

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 undi

m Mount W

 felsi

Ka Trachya

 Chie Simo

Distribu in pe solid  high cont

2.50

2.001.50

0 .5 1 10 .5 

Figure 117. Distribution of magnesium in mesquite ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Alum

Gulch

Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXPL

QTag Alluvium 

 undiv

Contact— inferrFault—D or inf

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 igneoSample s

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 Intrus

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J-i Plutonic 

 undiv

m Mount W

 felsic 

Ka Trachyan

 Chief Simon

Distribut perce line w Wher are d

4.003.002.00

0 .5 1 0 .5 

Figure 118. Distribution of magnesium in oak ash.
Harshaw Creek

Harshaw

Creek

Sonoita Creek

Red

Mountain

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Patagonia

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Base from U.S. GeologicaGeographic projection, dNorth American Datum o

Geology modified from Dand Simons (1974).

110°46' 110°44' 110°42'

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EXP

QTag Alluvium 

 undiv

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 undiv

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Ka Trachya

 Chief Simo

Distribu perc solid  high.  cont

5.004.003.00

0 .5 1 0 .5 

Figure 119. Distribution of magnesium in juniper ash.
154 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Applications of Geochemical and 

Mineralogical Analyses to Geologic 

Mapping, Mineral Deposit Genesis 

and Models, Distribution and Zoning of 

Elements and Minerals, Exploration for 

Mineral Deposits, and Environmental 

Investigations

Many different topics can be investigated for a mineral 

deposit. For the Red Mountain PCD, authors have described 

host-rock geology (Drewes, 1971a; 1972; 1996; Quinlan, 

1981; 1986; Simons, 1972; 1974); the Red Mountain mineral 

deposit (Lecumberri-Sanchez and others, 2013; Quinlan, 1981; 

1986; Vikre and others, 2014); ages of host rock formations and 

mineralization (Drewes, 1971a; 1972; Vikre and others, 2014); 

remote sensing and alteration (Berger and others, 2003); vein 

structure (Kistner, 1984); and fluid inclusions (Bodnar and 

Beane, 1980; Lecumberri-Sanchez and others, 2013). The 

current study emphasizes and discusses the concentrations 

and distributions of selected elements and minerals in the 

subsurface and of elements in rocks, soils, and plants over 

the deposit. 

Element concentrations and distributions complement 

other parameters that can be determined for a PCD. Elements 

are commonly not mineral specific, and unlike mineral phases, 

do not provide data such as pressure and temperature of 

formation of the deposit. However, the concentrations and 

distributions do locate areas of enrichment and depletion and 

can show the results of the multiple events in the formation 

of a given deposit. 

For most of the elements discussed here, the concentrations 

are based on a near-total analysis. Thus, one cannot distinguish 

between oxidation states and their differing mobilities. Element 

concentrations and distributions do, however, provide base 

line information that is particularly useful for mining feasibility, 

exploration, and environmental studies.

The timing of events that formed the Red Mountain PCD 

are not completely established. Not resolved is the apparent 

difference between the age of the mineralizing events and the 

age of the quartz monzonite porphyry bodies. The differences 

in ages determined for these intrusions and the copper-related 

alteration (about 62 Ma compared to 60 Ma) (Vikre and others, 

2014) would imply that the emplacement of the intrusive 

bodies is not associated with formation of the Red Mountain 

PCD. However, the close spatial association of the surface and 

subsurface locations of quartz monzonite porphyry and high 

concentrations of copper and other deposit-related elements, 

suggests at least a probable temporal relation.

Core

As part of this study, as many as 44 elements and 

13 minerals were determined in core samples. The concentrations and distributions of both elements and XRD-determined 

minerals provide important information not readily obtainable 

from core logging. These data are also independent of any 

biases of different individuals logging the same or similar 

core. Although the mineral data have little temporal value, 

they help in interpreting mineral zoning.

Factor analysis is used here to classify the mineral-depositrelated elements into groups that may represent different events 

and (or) zones resulting from mineralization and alteration 

processes. This mathematical technique thus helps separate the 

chemical associations related to lithology (1) from those related 

to hypogene events and (2) from those related to supergene 

enrichment and later weathering. The element associations 

determined by factor analysis can also sometimes identify 

which trace and minor elements are probably substituting in 

the structures of visible minerals.

Factor analysis was run with 34 elements on a hypogene 

dataset that includes samples from the deep part of the deposit 

and on a supergene dataset with samples from the area of most 

intense supergene enrichment that includes both hypogene- and 

supergene-related elements and minerals. The results show that 

four factors classify the hypogene mineral deposit associations. 

These four factors include (1) Ag, Cu, S, Te, and Mo; (2), Mn, 

Zn, and Pb; (3) Au and Na; and (4) Sb, As, B, and Hg. Another 

factor includes potassium and thallium, which are related to 

potassic alteration. Three deposit-related factors classify the 

supergene zone: (1) Sb, Hg, Pb, As, Ag, and Tl; (2) Cu, Mo, Te, 

and S; and (3) Au and Na. An additional factor contains potassium and rubidium, which are related mostly to potassium-rich 

alteration minerals.

The fact that all of the elements related to altered and 

mineralized rocks can be classified into separate groups is 

important. In an earlier study, a regional multielement soil 

survey was conducted in the vicinity of Eureka, Nevada, an 

area with a history of overlapping mineralizing events. Factor 

analysis successfully identified and classified two suites of elements: a silver-rich base-metal suite (Ag, Cu, Pb, Sb, and Zn) 

of the Cretaceous Period and a Carlin-type gold suite (Au, As, 

Hg, and Sb) of the Tertiary Period (Chaffee, 1987; Shawe and 

Nolan, 1989). 

Because all the deposit-related elements at Red Mountain 

are not loaded on just one or possibly two factors, one can 

speculate that their separation into four or five different factors 

is partly a result of separate mineralizing events and (or) partly 

due to the effects of different spatial and (or) concentration zoning 

of the respective elements represented in each of these factors.

A comparison of the element associations between the 

hypogene and supergene factors illustrates changes in associations due partly to different mineral species at different levels of 
Geochemical and Mineralogical Analyses to Geologic Mapping, Models, and Distribution of Elements and Minerals 155

the deposit, partly to addition or depletion of certain elements 

as a result of supergene and later weathering events, and 

partly to differences in the bulk pre-mineralization chemistry 

of the rhyolite tuff and andesite lithologies. As examples, 

zinc in the hypogene zone is associated with a deposit-related 

factor that includes lead and manganese. Because of different 

chemical mobilities, zinc has been leached in the supergene 

zone while lead has not. Thus, zinc becomes associated with 

lithology-related elements that are present in comparatively 

low concentrations in the rhyolite tuff-dominated supergene zone. 

In the hypogene zone, silver and lead are associated with 

copper and zinc, respectively. In the supergene zone, lead is 

associated with silver, arsenic, mercury, antimony, and thallium. 

probably in lead-rich base-metal sulfide or sulfate minerals. 

Some of these new associations are a result of formation of 

several suites of hypogene minerals in the deep part of the 

deposit and different hypogene mineral suites in the peripheral 

part of the deposit. Some changes may be a result of the effects 

of supergene processes. 

Element and mineral distributions can be classified into 

zones in the Red Mountain deposit. Present in the copper-poor 

“barren” core in the deep part of the Cu-Mo deposit (fig. 5) are 

relatively low concentrations of copper and other copper-related 

elements, including silver, arsenic, gold, molybdenum, sulfur, 

antimony, tellurium, and thallium, and only sparse distributions 

of pyrite, calcite, and chlorite. This core area is characterized 

by relatively high concentrations of calcium, manganese, 

sodium, plagioclase, and magnetite. 

The distributions of elements in the mid-level to deep 

part of the hypogene deposit project in cross section as two 

limbs in the general area of intrusive lenses of quartz monzonite 

porphyry (figs. 3 and 5). These limbs are part of a crude, 

inverted, cup-shaped shell (Quinlan, 1986) that is typical of 

many PCDs. Based on observations of crosscutting vein sets, 

the deposit was formed during several separate mineralizing 

events that produced a PCD that is confined mostly to the 

andesite unit but continues locally upward to the present top 

of the overlying rhyolite tuff unit. For some elements, their 

concentrations differ markedly between the two limbs of the 

cup-shaped shell. Because no deposit is perfectly symmetrical, 

such differences are to be expected.

Elements most closely associated spatially with the potassic 

alteration zone and the deep part of the hypogene Cu-Mo deposit 

include Ag, Au, K, Mo, total S, sulfate S, Sb, Te, and Tl, with 

weaker spatial associations of As, B, Hg, Pb, and Zn. Minerals 

spatially associated with this part of the deposit include chalcopyrite, molybdenite, pyrite, orthoclase, biotite, magnetite, 

calcite, quartz, and anhydrite. 

Minerals representing other classic zones associated with 

PCDs are also present above the deep part of the hypogene 

deposit and its potassic alteration mineral assemblage at Red 

Mountain. The phyllic zone is represented by pyrite, sericite, 

and quartz. The advanced argillic zone, which is mostly 

confined to the rhyolite tuff unit, is typical of those described 

for other PCDs and includes the minerals enargite, tennantite, 

alunite, pyrophyllite, kaolinite, quartz, tourmaline, and barite 

(Guilbert and Park, 1986; Gustafson and Hunt, 1975; Hemley 

and Jones, 1964; Hemley and others, 1969; Knight, 1977; 

Sillitoe, 1983). These three major alteration zones generally 

overlap and thus do not exhibit well-defined boundaries.

Supergene enrichment and subsequent weathering altered 

many of the hypogene elements and minerals. Supergene 

enrichment produced extensive chalcocite deposition. Chalcocite, 

which occurs mainly as coatings on pyrite but also as veinlets 

filling fractures, is most highly concentrated in a blanket 

deposit, which is defined by the 1,000 and 2,000 ppm copper 

contours, and is present in the rhyolite tuff unit vertically above 

the deep part of the Cu-Mo deposit (fig. 5). As seen in the section, 

the effects of the circulating fluids related to this event extended 

from the present surface downward for a distance of about 

1,220 m for many elements and minerals on the east side of the 

section in the vicinity of drill hole 158, traversing the rhyolite 

tuff unit and well into the andesite unit.

Deposit-related elements that are concentrated in the area 

of the supergene zone and (or) above that zone include Ag, As, 

Au, B, Bi, Co, Cu, Hg, Mo, Pb, S, Sb, Sn, Te, Tl, U, and W. 

The only deposit-related element that has clearly been leached 

in this upper part of the system is zinc. With the exception 

primarily of copper and possibly mercury and uranium, these 

concentrations in the area affected by supergene enrichment 

indicate that most of these elements have relatively low chemical mobilities in this environment at Red Mountain. Because 

most of these elements are hypogene in origin and are essentially in their original locations at the top of the deposit, they 

should be especially effective to use in both reconnaissance 

and detailed geochemical surveys conducted in areas affected 

by similar metallogenic events and climatic environments. 

Many of these same elements are present in the peripheral 

zones of other PCDs.

Subsequent to supergene enrichment, near-surface chemical 

weathering produced a leached cap consisting of pervasive 

hematite and other iron oxides in the uppermost part of the 

rhyolite tuff unit. These minerals formed primarily as a result 

of the oxidation of pyrite. This event was accompanied by 

considerable losses of cobalt, mercury, magnesium, zinc, and 

possibly other elements, as well as the destruction of sericite, 

plagioclase, pyrite, clay minerals, and pyrophyllite. No copper 

oxide minerals have been observed in the leached cap area. If 

present, they are rare.

The distributions of some of the elements and minerals 

determined for this study can help locate the contacts between 

the andesite and rhyolite tuff formations. This contact is sometimes difficult to identify in subsurface core samples and to some 

extent in surface rock samples because of intense alteration 

effects. The best elements for defining this contact are calcium, 

magnesium, manganese, and sodium. The upper limits of the 
156 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

distributions of biotite, magnetite, and calcite also help to 

define this contact except where later events have destroyed 

these minerals. Where biotite has been altered to chlorite, the 

upper limit of chlorite occurrences marks the contact (fig. 37). 

The presence of low but anomalous concentrations of 

mercury in the deep hypogene part of the Cu-Mo deposit, 

along with evidence of anomalous mercury in the upper parts 

of the system directly above the deep part of the deposit (fig. 14), 

suggest that mercury, and possibly other volatile elements and 

compounds, warrant consideration in geochemical exploration 

surveys looking for deep-seated mineral deposits.

Although tellurium has been recovered in the processing 

of PCD ores from some deposits, its distribution has not been 

adequately appreciated as a pathfinder element in the search 

for PCDs. The high median values for tellurium in core, rock, 

and soil samples, and high ratio values relative to estimated 

threshold concentrations in andesite samples are noteworthy. 

The high concentrations of tellurium at Red Mountain tend to 

form a widespread halo well outside the deep and mid-level 

parts of the Red Mountain deposit (fig. 9), a zoning first noted 

by Gott and McCarthy (1966) for the Ely, Nevada, copper 

deposit. Additionally, the regional stream-sediment survey of 

the Patagonia Mountains (Chaffee and others, 1981) revealed 

high concentrations of tellurium in the vicinity of Red Mountain. 

Tellurium is relatively immobile in the weathering environment 

so that its halo remains even when other deposit-related 

elements have been leached or dispersed. The high incidence 

of PCDs in southern Arizona imply that this region is a 

tellurium-rich metallogenic province. Thus, the regional distribution of this element may be a useful exploration guide in the 

search for undiscovered PCDs. 

Rock and Soil

A total of 122 rock and 119 soil samples were analyzed 

for this study. The concentrations and distributions of selected 

elements in these samples (1) provide information about 

the surface expression of the Red Mountain deposit, and 

(2) provide element databases useful for both exploration and 

environmental purposes.

Although the rock and soil distributions provide a good 

indication of what is actually anomalous on the surface of the 

Red Mountain deposit and in the surrounding area, the boundary 

line defining the limit of visible alteration (fig. 41) also helps to 

define and explain the areas containing anomalous concentrations 

of various elements that are related to this deposit. 

Most of the rock samples collected outside this boundary 

did not appear to be visually altered. Thus, it was somewhat 

surprising to find “anomalies” for some mineral deposit-related 

elements—notably copper but also including cadmium, iron, 

molybdenum, and zinc—in the rock samples collected in the 

vicinity of the major drainages surrounding Red Mountain. 

Most of these “anomalous” samples are from the andesite unit. 

The lateral extent of anomalous copper at depth is unknown 

but extends to the right (east) of the area of drill hole 158 (fig. 5). 

The core from this drill hole includes many samples that 

contain copper concentrations exceeding 100 ppm. These 

anomalous concentrations could extend to the area of the 

Harshaw Creek drainage.

Taylor (1969) reports typical copper concentrations in 

andesites ranging as high as 60 ppm. The summaries by 

Wedepohl (1974) of the copper content of andesites show a 

range of 3 to 150 ppm, with average values between 34 and 

67 ppm and an arithmetic mean value of 55 ppm. Thus, at 

least some of the high copper contents in the andesite samples 

collected east of Red Mountain could be the result of unusually 

copper-rich andesitic rocks. 

Mining for base and precious metals has occurred 

throughout the Patagonia Mountains since the late 1800s 

(Schrader, 1915). In the past, little attention was given to 

controlling contamination. As a result, the major drainages 

surrounding Red Mountain are highly contaminated with 

mineralized material related to past mining (Chaffee and others, 

1981). This contamination is apparently reflected in the 

rock and soil samples collected in and near these drainages. 

Contamination may also result from erosion of exposures of 

altered rocks and soils from higher on Red Mountain. Thus, 

it is likely that such soil and sediment has been dispersed by 

gravity, winds, rain, or possibly flash-flood waters and has 

locally contaminated the rock surfaces where the samples were 

collected in spite of an effort during sampling to remove any 

visibly altered surface material from each sample. 

The distributions of the deposit-related elements Ag, As, 

Bi, Cu, Fe, Mo, Pb, Sb, Te, and Tl in rock and soil samples 

show positive anomalies within and adjacent to the boundary 

of the area containing visibly altered rock. Within the boundary, many of these deposit-related elements exhibit anomalies 

spatially related to exposures of one or both of two centers of 

quartz monzonite porphyry. The easternmost center contains 

a cluster of scattered small outcrops of this formation that 

crop out directly above the deep part of the hypogene Cu-Mo 

deposit. The westernmost center is associated with the largest 

area of quartz monzonite porphyry outcrops. However, no 

holes were drilled in this westernmost center, and thus no drill 

core was available to test for the presence or absence of an 

extension of the hypogene deposit below this location. 

In addition to the positive anomalies noted above, some 

elements in the rock and soil samples (Ca, Cd, Co, K, La, Mg, 

Mn, Na, and Zn) exhibit negative anomalies on the surface 

above the area of the hypogene deposit. Of these, cadmium, 

cobalt, and zinc are related to the deposit and have been 

leached from the near surface during supergene enrichment or 

during formation of the leached cap. In contrast, the negative 

anomalies of Ca, K, La, Mg, Mn, and Na mostly reflect the 

bulk pre-mineralization chemistry of the rhyolite tuff unit as 

compared to that of the underlying andesite unit. 
Geochemical and Mineralogical Analyses to Geologic Mapping, Models, and Distribution of Elements and Minerals 157

Vegetation

The ash of 57 mesquite, 108 oak, and 68 juniper samples 

were analyzed for this study. The concentrations and distributions 

of selected elements in a plant can provide useful guidance in 

biogeochemical surveys conducted for mineral deposit exploration 

or for environmental studies. 

Because of the relatively high relief present in the Red 

Mountain area, the three species of plants sampled were not evenly 

distributed throughout the study area. In areas of relatively low 

relief, such as the Lower Sonoran Life Zone, phreatophytes such 

as mesquite have proved useful in reconnaissance and detailed 

biogeochemical studies undertaken to find blind or poorly exposed 

copper deposits in low-relief pediment areas of Arizona that 

contain abundant drainage channels (Chaffee, 1976a; Huff, 1970). 

Field studies by the author and many others indicate 

that mesquite is native throughout much of southern Arizona, 

southern New Mexico, and northern Mexico. This commonly 

riparian species is particularly useful as a sample medium near 

washes, where it is deep rooted and can tap the groundwater 

table. This groundwater may contain elements related to a 

blind mineral deposit. 

Examination of the distribution of sample sites shows that 

mesquite, a common species in the Lower Sonoran Life Zone, 

is generally found growing only at lower elevations around 

Red Mountain, and thus grows mostly in areas underlain by 

andesite (for example, fig. 78). In contrast, oak and juniper 

trees, which are more common in the Upper Sonoran Life 

Zone, are less restricted by elevation and are found growing 

throughout most of the study area and over several different 

rock types (for example, figs. 79 and 80). These observations 

explain why it has been difficult in this study to define anomalies 

for many elements using mesquite samples.

Comparisons of concentrations of a given element in the 

ash of the three plant species (tables 6–8) show that the uptake 

of some elements varies substantially among the species. For 

example, median values for Br, Cs, and Zn in mesquite ash; 

median values for Cd, Co, Li, Mn, and Ni in oak ash; and the 

median value for Re in juniper ash are all much higher than 

the respective values of the other two species. These contrasting concentrations among the three species support the idea 

that plant genetics must play a role in element uptake. Faulty 

conclusions may thus occur if different species are combined 

in a vegetation survey. As a result, it is important in a biogeochemical survey to be able to identify specific species and to 

compile database on only one specific species at a time. 

Of the elements analyzed, some (B, Ca, Cu, Fe, K, Mg, Mn, 

Mo, Na, S, Se, and Zn) are known to be essential for plant growth 

when present in limited concentrations, and some (Ag, Co, Li, 

and U) are known to be nonessential (Brooks, 1983). Those 

elements analyzed for this study that can be severely toxic when 

present in significant concentrations include Ag, As, Co, Cu, Pb, 

and Tl. Those elements that can be moderately toxic include Bi, 

Cd, Mn, Mo, Sb, Se, Sn, U, W, and Zn. In spite of their potentially 

toxic effects, many of the deposit-related elements were taken 

up by the three species in high enough concentrations to produce 

positive anomalies over the deposit. These observations indicate 

that the deposit-related elements Ag, Cd, Cu, Mo, and Zn likely 

are the most useful for biogeochemical studies related to PCDs 

in environments such as that in the vicinity of Red Mountain. 

Past studies (Chaffee, 1976a; Huff, 1970) confirm these findings, 

at least for copper, molybdenum, and zinc in mesquite ash. Data 

are lacking in the literature for biogeochemical studies of oak 

and juniper. The concentration levels of these five deposit-related 

elements (Ag, Cd, Cu, Mo, and Zn) in the plants must not be high 

enough to poison these three species. Field observations in the Red 

Mountain vicinity did not identify any areas with clearly stunted 

trees or areas devoid of a given species that could be related to high 

concentrations of any of the elements determined for this study.

Comparisons of anomalies generated in the ash of the 

three plant species with those of the rock and soil samples 

show that some element anomalies in the plant ash are positive 

when the corresponding rock and (or) soil distributions show 

what appear to be negative anomalies. Again, plant genetics 

must play a part. 

All three species produced anomalies related to the 

underlying Red Mountain deposit for most of the elements 

studied. Of the three species, the distributions in oak ash most 

consistently identified in detail the anomalies in the soil substrate.

The anomalies identified for the various elements in the ash 

of the three plant species are not substantially more widespread 

than those of the rock and soil samples. Vegetation sampling in 

the Red Mountain environment thus offers no obvious advantage 

as a sample medium for exploration purposes. From an environmental standpoint, however, the plant analyses provide baseline 

data that might be useful, for example, for selecting plant species 

for revegetating mine waste areas.

Anomalies for some elements in one or more species are 

also present in the Harshaw Creek drainage basin. As was the 

case for rock and soil samples, anomalies for at least some 

of the elements in plant samples from that area are almost 

certainly related to contamination from past mining.

Surface anomalies are present for many elements in rock, 

soil, and vegetation samples and include many potentially toxic 

elements. From an environmental standpoint, it is worth noting 

that, with the exception at Red Mountain of samples collected 

from sites in and near stream channels, these relatively high 

concentrations are natural, for the most part, and not caused 

by any past mining activity or other man-made activity. Thus, 

before the start of any mining venture, a thorough multielement 

geochemical survey can provide baseline data that characterize 

the natural distributions and abundances of elements of interest. 

These data can be used subsequently for environmental 

mitigation when mining is completed. 

Because mineral and chemical zoning in mineral systems 

results from the physical and chemical processes responsible 

for the system, such zoning is generally present to some 

degree in the vicinity of most hydrothermal mineral deposits. 

The acquisition and interpretation of multielement chemical 

data, as well as mineralogical data, warrant consideration as an 

integral part in the study of most any kind of mineral system. 

The observations described in this report provide only a part 

of the information that could be obtained about the remarkably 

complete mineral deposit system at Red Mountain.
158 Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona

Conclusions

Extensive core drilling at Red Mountain, Arizona, has 

delineated a large, deep seated, structurally intact porphyry 

copper-molybdenum deposit (Cu-Mo deposit or PCD) that 

extends from the present surface to depths of more than 

1,765 meters. Unlike some other deposit types, porphyry 

Cu-Mo deposits typically exhibit a well-documented pattern 

of element and mineral zoning. The distribution of elements 

and minerals determined for this study provide a zoning 

model of the Red Mountain system that can be applied to 

other PCDs and can aid in the search for new deposits. 

Multielement chemical information can thus be especially 

useful as part of an exploration program where only the less 

mineralized and less altered outer zones of an entire system 

are present or where the zones are not clearly exposed or are 

not recognized. 

Following deposition of the thick sequence of predominantly felsic to andesitic volcanic host rocks at Red Mountain 

in the Late Cretaceous, several major events occurred to form 

the Red Mountain PCD during the early Tertiary. These events 

are recorded in the chemistry and mineralogy of core samples 

and reveal a complexly zoned hypogene system with multiple 

stages of chemical and mineralogical overprinting. 

In spite of the depths to which the Red Mountain deposit 

has been explored, no associated pluton has yet been identified. 

Only small intrusive bodies have been found. The apparent 

difference in ages of the mineralizing events and the known 

quartz monzonite porphyry bodies has not been resolved. The 

differences in ages determined for these intrusions and the 

copper-related alteration—about 62 million years compared 

to 60 million years—would indicate that emplacement of the 

intrusive bodies is not associated with formation of the Red 

Mountain PCD. However, the close spatial association of the 

surface and subsurface locations of quartz monzonite porphyry 

and high concentrations of copper and other deposit-related 

elements, implies at least a probable temporal relation.

Samples of drill core, rock outcrops, soils, and three species 

of plants were collected and analyzed. Additional core samples 

were analyzed by X-ray diffraction for 13 minerals. The analyses 

show that the deep part of the hypogene deposit at Red Mountain consists of a potassic alteration zone that includes an arcuate zone of high copper concentrations in the form of a crude, 

inverted cup-shaped shell surrounding a relatively “barren” 

core that is typical of many PCDs. The two limbs of this shell 

contain anomalous but varying concentrations of silver (Ag), 

arsenic (As), gold (Au), boron (B), copper (Cu), potassium 

(K), molybdenum (Mo), lead (Pb), total and sulfate sulfur (S), 

antimony (Sb), tellurium (Te), thallium (Tl), and zinc (Zn). 

Minerals associated with the shell include chalcopyrite, bornite, 

molybdenite, pyrite, sphalerite, galena, orthoclase, biotite, 

magnetite, calcite, quartz, and anhydrite.

Higher in the system, several hypogene-related elements 

form broad, peripheral, flat to arcuate zones. These elements 

include Ag, As, cobalt (Co), iron (Fe), Pb, Sb, Te, Tl, and Zn. 

Near-surface restricted zones are present for bismuth (Bi), 

mercury (Hg), tin (Sn), and tungsten (W). Minerals concentrated 

in the phyllic alteration zone include pyrite, sericite, and quartz. 

Typical minerals in the advanced argillic zone include enargite, 

tennantite, alunite, pyrophyllite, clay minerals, quartz, tourmaline, and barite. Supergene enrichment re-mobilized hypogene 

copper and probably zinc and produced a blanket deposit 

of chalcocite and minor covellite. Subsequent weathering 

produced a leached cap zone in which hematite and other iron 

oxides replaced pyrite; molybdenite was locally altered to 

ferrimolybdite; cobalt, mercury, molybdenum, zinc, and possibly 

other elements were leached; and sericite, plagioclase, clay 

minerals, and pyrophyllite were destroyed. No copper oxide 

minerals have been observed. If present, they are rare. The 

near-surface part of the system also contains anglesite locally, 

which formed during supergene and (or) later weathering events. 

Other minerals related to these events are also probably present 

but have not been identified because they could not be easily 

identified as a result of the intense alteration in the upper part 

of the deposit.

Factor analysis helps classify the mineral-deposit-related 

elements into groups that may represent different episodes 

and (or) zones resulting from mineralization and alteration 

processes. This technique was run on a hypogene dataset that 

includes samples from the deep part of the deposit and on a 

supergene dataset with samples from the area of most intense 

supergene enrichment that includes both hypogene- and 

supergene-related elements and minerals. Five of the eight 

factors in the hypogene dataset have associations related to 

the mineral deposit: (1) Ag, Cu, S, Te and Mo; (2), manganese 

(Mn), Zn, and Pb; (3) Au and sodium (Na); (4) Sb, As, B, and 

Hg; and (5) K and Tl. Four of the eight factors in the supergene 

dataset have associations related to the mineral deposit: 

(1) Sb, Hg, Pb, As, Ag, and Tl; (2) Cu, Mo, Te, and S; (3) Au 

and Na; and (4) K and rubidium (Rb). The changes in element 

associations between the two datasets mostly reflect changes 

in mineral species at different levels in the deposit. 

The concentrations and distributions of selected elements 

in rock and soil samples (1) provide information about the 

surface expression of the Red Mountain deposit, and 

(2) provide element databases useful for both exploration 

and environmental projects.

Of the deposit-related elements studied, Ag, As, Bi, Cu, 

Fe, Mo, Pb, Sb, Te, and Tl exhibit positive anomalies over the 

deposit in samples of both rock and soil. The highest concentrations for these elements are generally spatially associated 

with either one or both of two areas with exposures of the 

quartz monzonite porphyry. Zinc, cadmium, and cobalt exhibit 

negative anomalies that are the result of chemical leaching 

related to supergene and (or) weathering events. Other elements, 

such as calcium (Ca), K, magnesium (Mg), Mn, and Na, also 

exhibit negative anomalies, but these distributions are mainly 

the result of relatively low concentrations in the rhyolite tuff 

host rock as compared to the andesite unit. 

The high concentrations of relatively immobile tellurium 

at Red Mountain, which mostly occur in a peripheral zone in 

the uppermost part of the system, and the high incidence of 
References Cited 159

similar PCDs in southern Arizona, together suggest that this 

region is a tellurium-rich metallogenic province. Thus, the 

regional distribution of this element may be a useful exploration 

guide in the search for undiscovered PCDs. 

The concentrations of many elements in samples of mesquite, 

oak, and juniper trees vary from one species to another, apparently 

because of genetic differences that largely determine whether a 

given element is essential, nonessential, or toxic to a plant. The 

high tolerance of oak trees to potentially toxic arsenic and lead 

is especially noteworthy. 

The distributions of high concentrations of elements in the 

three plant species generally mimic those of their substrate soils. In 

spite of their potentially toxic effects, many of the deposit-related 

elements, including Ag, As, Bi, cadmium (Cd), Cu, Mo, Sb, and 

Zn, were taken up by the three species in high enough concentrations to produce positive anomalies over the deposit. 

Vegetation sampling in the Red Mountain environment 

offered no obvious advantage as a sample medium for exploration purposes. From an environmental standpoint, however, 

the plant analyses provide baseline data that might be useful, 

for example, for selecting plant species for revegetating mine 

waste areas.

Mining for base and precious metals has occurred 

throughout the Patagonia Mountains since the late 1800s. In 

the past, little attention was given to controlling contamination. 

As a result, the major drainages surrounding Red Mountain are 

highly contaminated with mineralized material related to past 

mining. This contamination is locally reflected in the rock, soil, 

and some plant samples collected in and near these drainages.

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Chaffee—Red Mountain Porphyry Copper-Molybdenum Deposit and Vicinity, Santa Cruz County, Arizona—Scientific Investigations Report 2019–5077

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20195077