The geochemistry and mineralogy of the Gies gold-silver telluride deposit, central Montana

226 Pages·2017·3.53 MB·English

Iowa State University Capstones, Theses and
Retrospective Theses and Dissertations
Dissertations
1992
The geochemistry and mineralogy of the Gies gold-
silver telluride deposit, central Montana
Xiaomao Zhang
Iowa State University
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Recommended Citation
Zhang, Xiaomao, "The geochemistry and mineralogy of the Gies gold-silver telluride deposit, central Montana " (1992).Retrospective
Theses and Dissertations. 10164.
https://lib.dr.iastate.edu/rtd/10164
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The geochemistry and mineralogy of the Gies gold-silver telluride
deposit, central Montana
Zhang, Xiaomao, Ph.D.
Iowa State University, 1992
U M I
300 N. Zeeb Rd.
Ann Arbor, MI 48106

The geochemistry and mineralogy of the Gies gold-silver
telluride deposit, central Montana
by
Xiaomao Zhang
A Dissertation Submitted to the
Graduate Faculty in Partial Fulfillment of the
Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Department: Geological and Atmospheric Sciences
Major: Geology
Approved: Members of the Committee:
Signature was redacted for privacy.
Signature was redacted for privacy.
Signature was redacted for privacy.
For the MajiSr Department
Signature was redacted for privacy.
For the Graduate College
Iowa State University
Ames, Iowa
1992
ii
TABLE OF CONTENTS
page
GENERAL INTRODUCTION 1
PAPER I. MINERALOGICAL, FLUID INCLUSION, AND STABLE
ISOTOPE STUDIES OF THE GIES GOLD-SILVER
TELLURIDE DEPOSIT, JUDITH MOUNTAINS, MONTANA 5
INTRODUCTION 6
GEOLOGY OF THE JUDITH MOUNTAINS 8
LOCAL GEOLOGY 12
PETROCHEMISTRY OF INTRUSIVE IGNEOUS ROCKS 13
MINERALIZATION OF THE GIES DEPOSIT 28
MINERALOGY OF THE VEIN SYSTEMS 32
FLUID INCLUSION STUDY 52
STABLE ISOTOPE STUDIES 57
DISCUSSION 66
PHYSICO-CHEMICAL CONDITIONS OF ORE FORMATION 71
GENETIC MODEL FOR MINERALIZATION 77
CONCLUSIONS 82
REFERENCES 84
APPENDIX. MICROPROBE ANALYSES OF MINERALS 112
iii
PAPER II. AQUEOUS TELLURIUM SPECIATION AND THE
STABILITY OF GALA VERITE AND HESSITE AT
ELEVATED TEMPERATURES 119
INTRODUCTION 120
PREVIOUS STUDIES OF AQUEOUS TELLURIUM SPECIES 122
THE PRINCIPLE OF BALANCE OF IDENTICAL LIKE CHARGES 126
EQUILIBRIUM REACTIONS IN THE SYSTEM Te-O-H 129
STABILITIES OF GOLD AND SILVER TELLURIDES 137
APPLICATIONS TO THE CONDITIONS OF FORMATION OF THE GIES
GOLD-SILVER TELLURIDE DEPOSIT, JUDITH MOUNTAINS, MONTANA 149
CONCLUSIONS 151
REFERENCES 153
PAPER III. MINERAL STABILITIES AND SULFUR ISOTOPE
DISTRIBUTION IN log fOj-pH SPACE AT
ELEVATED TEMPERATURES 166
INTRODUCTION 167
MINERAL STABILITIES IN log fOz-pH SPACE 169
SULFUR ISOTOPE DISTRIBUTION IN log fOj-pH SPACE 178
CONSTANT: EQUILIBRIUM CONSTANTS OF MINERAL-GASEOUS-
AQUEOUS PHASE REACTIONS 181
REFERENCES 187
APPENDIX 1. PROGRAM LISTING 191
APPENDIX 2. USERS MANUAL 203
iv
GENERAL SUMMARY 212
REFERENCES 215
ACKNOWLEDGEMENTS 217
1
GENERAL INTRODUCTION
This dissertation focuses on the geochemistry and origin of gold and silver telluride
mineralization at the Gies mine, Montana, where gold and silver telluride-bearing quartz
veins occur along the contact between Cretaceous-Tertiary alkaline intrusive rocks and a
sequence of sedimentary rocks of Cambrian to Cretaceous age.
Gold and silver telluride mineralization is most common in mesothermal deposits of
Archean age (e.g., Kalgoorlie, Australia (Markham, 1960; Nickel, 1977), and Sigma,
Canada (Robert and Brown, 1986)), and epithermal deposits of Tertiary age (e.g.,
Cripple Creek, Colorado (Thompson et al., 1985), Emperor, Fiji (Ahmad et al., 1987)
and Little Rocky Mountains, Montana (Wilson and Kyser, 1988)). Although most
epithermal gold deposits were genetically related to the circulation of meteoric water
(Taylor, 1979; Ohomoto, 1986), there is considerable evidence that some components of
epithermal gold-silver telluride deposits were derived from igneous source(s) (Porter and
Ripley, 1985; Saunders and May, 1986; Ahmad et al., 1987). The relationship between
the supposed igneous source and gold mineralization, however, is unclear.
In considering the potential source of the ore-forming fluids, the Gies deposit
provides an excellent opportunity to evaluate the genetic relationship between magmatic
alkaline intrusion and gold-silver telluride mineralization. The possible contribution of
magmatic and/or other components (e.g., meteoric water) to the ore-forming fluid will be
assessed, and the origin and the physical and chemical conditions of the gold-silver
telluride formation will be determined.