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Geology and Geochemistry of Epithermal Systems REVieWS IN EConomiC Geology Volume 2 GEOLOGY AND GEOCHEMISTRY OF EPITHERMAL SYSTEMS CONTENTS The Geothermal Framework for Epithermal Deposits R.W. Henley A Practical Guide to the Thermodynamics of Geothermal R.W. Henley and K.L. Brown Fluids Hydrothermal Ore Deposits The Behavior of Silica in Hydrothermal Solutions R.O. Fournier Carbonate Transport and Deposition in the Epithermal Environment R.O. Fournier Fluid Inclusion Systematics in Epithermal Systems R.J. Bodnar, T.J. Reynolds, and C.A. Kuehn Light Stable-Isotope Systematics in the Epithermal Environment C.W. Field and R.H. Fifarek Geologic, Mineralogic, and Geochemical D.O. Hayba, P.M. Bethke, P. Heald, and N.K. Foley Characteristics of Volcanic-Hosted Epithermal Precious-Metal Deposits Geologic Characteristics of Sediment-Hosted, Disseminated W.C. Bagby and B.R. Berger Precious-Metal Deposits in the Western United States Relationship of Trace-Element Patterns to Alteration and M.L. Silberman and B.R. Berger Morphology in Epithermal Precious-Metal Deposits Relationship of Trace-Element Patterns to Geology in B.R. Berger and M.L. Silberman Hot-Spring Type Precious-Metal Deposits Boiling, Cooling, and Oxidation in Epithermal Systems: M.H. Reed and N. Spycher A Numerical Modeling Approach Using Geological Information to Develop Exploration S.S. Adams Strategies for Epithermal Deposits Editors B.R. Berger and P.M. Bethke SOCIETY OF ECONOMIC GEOLOGISTS, INC. Society of Economic Geologists, Inc. Reviews in Economic Geology, Vol. 2 Geology and Geochemistry of Epithermal Systems B.R. Berger and P.M. Bethke, Editors J.M. Robertson, Series Editor Additional copies of this publication can be obtained from Society of Economic Geologists, Inc. 7811 Shaffer Parkway Littleton, CO 80127 www.segweb.org ISBN: 978-1-629495-60-6 The Authors: Samuel S. Adams Robert Fournier 0. 3030 Third Street Branch of Igneous and Geothermal Processes Boulder, CO 80302 U.S Geological Survey MS 910 William C. Bagby 345 Middlefield Road Branch of Western Mineral Resources Menlo Park, CA 94025 U.S. Geological Survey MS 901 Daniel Hayba 0. 345 Middlefield Road Branch of Resource Analysis Menlo Park, CA 94025 U.S. Geological Survey MS 959, National Center B. R. Berger Reston, VA 22092 Branch of Exploration Geochemistry U.S. Geological Survey Pamela Heald Branch of Resource Analysis MS 973 . Box 25046, Federal Center U.S. Geological Survey Denver, CO 80225-0046 MS 959, National Center Reston, VA 22092 Philip M. Bethke Branch of Resource Analysis R. W. Henley U.S. Geological Survey Chemistry Divsion MS 959, National Center D.S.I.R., Private Bag Reston, VA 22092 Taupo New Zealand R. Bodnar J. Department of Geological Sciences C. A. Kuehn Virginia Polytechnic Institute and State University Department of Geosciences Blacksburg, VA 20461 The Pennsylvania State University University Park, PA 16802 K. L. Brown Chemistry Division Mark H. Reed D.S.I.R., Private Bag Department of Geology Taupo University of Oregon New Zealand Eugene, OR 97403 T. Reynolds Cyrus W. Field J. Department of Geology FLUID, Inc. Oregon State University P.O. Box 6873 Corvallis, OR 97331-5506 Denver, CO 80206 Richard H. Fifarek M. L. Silberman Department of Geology Branch of Exploration Geochemistry Southern Illinois University U.S. Geological Survey Carbondale, IL 62901 MS 912 Box 25046, Federal Center N. K. Foley Denver, CO 80225-0046 Branch of Resource Analysis U.S. Geological Survey N. Spycher MS 959, National Center Department of Geology Reston, VA 22092 University of Oregon Eugene, OR 97403 ll GEOLOGY GEOCHEMISTRY OF EPITHERMAL SYSTEMS & CONTENTS FOREWORD • X PREFACE BIOGRAPHIES xvi CHAPTER 1 THE GEOTHERMAL OF EPITHERMAL DEPOSITS FRAMEWORK Henley R. W. INTRODUCTION HYDROTHERMAL SYSTEMS IN GENERAL Collision-Related Amagmatic Hydrothermal Systems Terrestrial Magma-Related Hydro thermal Sys tems TERRESTRIAL MAGMATIC-HYDROTHERMAL SYSTEMS 4 Large Scale Structure Na tural Discharges Hydrothermal Eruption Vents Heat and Mass Flow in Geothermal Systems CHEMISTRY OF GEOTHERMAL DISCHARGES 11 EPITHERMAL ORE-FORMING SYSTEMS • • 12 Re quirememts for Ore Deposition Chemistry of Systems Responsible for Ore Formation Chemical and Physical Processes in Ore Formation Hos t-Rock Relations SUMMARY 19 EPILOGUE 21 ACKNOWLEDGMENTS 21 REFERENCES ••• 21 CHAPTER 2 A PRACTICAL GUIDE TO THE THERMODYNAMICS OF GEOTHERMAL FLUIDS AND HYDROTHERMAL DEPOSITS ORE Henley and fuoo'/Jn R. w. K. L. INTRODUCTION • • • • • • • 25 GEOLOGICAL CHARACTERISTICS OF THE BROADLANDS GEOTHERMAL SYSTEM • 25 FLUID CHEMISTRY 26 iii FLUID-MINERAL EQUILIBRIA: ALTERATION MINERALOGY . 28 FLUID-MINERAL EQUILIBRIA: TRACE-METAL CONTENTS 32 Lead Gold �r Me tals: Copper, Silver, and Arsenic MINERAL DEPOSITION . 36 Silica caiCfteMetal Sulfi des and Gold ACKNOWLEDGMENTS . 41 REV IEW QUESTIONS . 41 REFERENCES 41 APPENDIX • 43 CHAPTER 3 TBR BEHAVIOR OF SILICA HYDROTHERMAL SOLUTIONS IN Fournie1' R. 0. INTRODUCTION 45 SOLUBILITIES OF SILICA MINERALS 45 THE BEHAVIOR OF DISSOLVED SILICA IN HOT-SPRING SYSTEMS . 46 ALKALINE WATERS 48 ACID WATERS 50 REACTION WITH GLASS 51 AMORPHOUS SILICA-CHALCEDONY RELATIONS . 51 SPECULATIONS REGARDING SOME TEXTURES OF QUARTZ 51 Jasperoid and Massive Replacement of Lime stone by Silica quartz Solubility at High Tempera tures CONCLUSIONS • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 55 ACKNOWLEDGMENTS 56 REFERENCES . 56 APPENDIX • . 60 iv CHAPTER 4 CARBONATE TRANSPORT DEPOSITION IN THE EPITHERMAL ENVIRONMENT AND Four>nie1' R. 0. INTRODUCTION • • • • • • 63 CO DISSOLVED IN AQU EOUS SOLUTIONS z 63 THE SOLUBILITY OF CALCITE IN AQUEOUS SOLUTIONS 67 SUMMARY 71 RE FERENCES 71 CHAPTER 5 FLUID-INCLUSION SYSTEMATICS IN EPITHERMAL SYSTEMS R. Bodna1', ReynoLds, and Kuehn J. T. J. C. A. INTRODUCTION • • • • • • • • • • • • • • • • • • • • • 73 INFORMATION AVAI LABLE FROM FLUID-INCLU SION PETROGRAPHY 73 IDENTIFICATION OF FLUID INCLUSIONS TRAPPED FROM BOILING SOLUTIONS 79 IDENTIFICATION OF GASES IN FLUID INCLUSIONS FROM THE EPITHERMAL ENVIRONMENT • • • • • • • • • • • • • • • • • • • • • • • • 83 INTERPRETATION OF FLUID INCLU SIONS FROM THE EPITHERMAL ENVIRONMENT 93 APPLICATION OF FLUID INCLUSIONS IN EXPLORATION FOR EPITHERMAL PRECIOUS-METAL DEPOSITS • • • • • • • • • • • 94 SUGGESTIONS FOR FUTURE FLUID-INCLUSION RE SEARCH 95 REFERENCES • • • • • • 96 CHAPTER 6 LIGHT STABLE-ISOTOPE SYSTEMATICS IN THE EPITHERMAL ENVIRONMENT FieLd and Fifa1'ek C. W. R. H. INTRODUCTION 99 CONVENTIONS , SYSTEMATICS , AND RATIONALE 99 Fractionation Equilibrium Reaction Appl ications GEOLOGIC DI STRIBUTIONS •••••••••••••••••••••••••••••••••• 110 Hydrogen and Oxygen Carbon Sulfur EPITHERMAL DEPOSITS • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 113 Carbon Sulfur v Hydrogen and Oxygen SUMMARY 124 RE FERENCES 125 CHAPTER 7 GEOLOGIC, MINERALOGIC, AND GEOCHEMICAL CHARACTERISTICS OF VOLCANIQ-HOSTED EPITHERMAL PRECIOUs-METAL DEPOSITS Hayba, Bethke, Heatd, and Fotey D. 0. P. M. P. N. K. INTRODUCTION • 129 SUMMARY OF THE CHARACTERISTICS OF VOLCANI C-HOSTED EPITHERMAL ORE DEPOSITS 129 Characteristics of Adularia- Sericite-Type Deposits Characteristics of Ac id-Sulfate-Type Deposits Summary of Characteristics THE ADULARIA-SERICITE ENVIRONMENT : CREEDE AS AN EXAMPLE • • • • • • • • • • • • • • • • • 136 Creede as an Exemplar Summary of Important Studies Geologic and Mineralogic Characteristics Geochemical Environment Hydrologic Environment Boiling and Mixing in the Ore Zone Summary of Creede Mineralization THE ACID- SULFATE ENVIRONMENT : SUMMITVILLE AS AN EXAMPLE • • • • • • • • • • • • • • • • • 151 Geologic and Mineralogic Characteristics Geochemical Environment Summary of Summitville Mineralization GEOTHERMAL INTERPRETATION OF VOLCANI C-HOSTED EPITHERMAL nEPOSITS • • • • • • • • • • • • • 158 Adularia-Sericite Deposits Ac id-Sulfate Deposits MECHANISMS OF ACID- SULFATE ALTERATION 159 ACKNOWLEDGMENTS 162 REFERENCES • • • 162 CHAPTER 8 GEOLOGIC CHARACTERISTICS OF SEDIMENT-HOSTED, DISSEMINATED PRECIOUs-METAL DEPOSITS IN THE WESTERN UNITED STATES Bagby and B. R. Berger W. C. INTRODUCTION • • 169 CLASSIFICATION 169 REGIONAL GEOLOGIC CHARACTERISTICS OF DEPOSITS IN MINERAL TRENDS ISOLATED DEPOSITS • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • AND 172 The Getchell Trend The Carlin Trend vi The Cortez Trend Isolated Deposits GEOLOGIC CHARACTERISTICS OF THREE END-MEMBER, SEDIMENT-HOSTED , DISSEMINATED PRECIOU S-METAL DEPOSITS • • • • • • • • • • • • • • • • • • • • • • • • • • 183 Carlin Taylor Preble GENERAL ASPECTS OF TRACE ELEMENT AND STABLE-ISOTOPE GEOCHEMISTRY • 189 SUMMARY OF GEOLOGIC CHARACTERISTICS 192 Re gional and District Scale Deposit Scale ENVIRONMENT OF FORMATION 195 EXPLORATION APPLICATION 195 INFLUENCE OF GEOLOGIC CHARACTERISTICS ON MINING 196 Grade and Tonnage Mineability REFERENCES • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 199 CHAPTER 9 :RELATIONSHIP OF TRACE-ELEMENT PATTERNS TO ALTERATION AND MORPHOLOGY IN EPITHERMAL PRECIOUs-METAL DEPOSITS Silberman and B. Berger M. L. R. INTRODUCTION • • • 203 GEOTHERMAL SYSTEMS • 204 Morphology and Characteristics Al teration Patterns Geochemical Zones EPITHERMAL ORE DEPOSITS ••••••••••••••••••••••••••• 208 Morphology and Characteristics Al teration Patterns NATURE OF FLUID S INVOLVED IN GEOTHERMAL SYSTEMS AND EPITHERMAL ORE DEPOSITS 21 3 TIMING • • • • 214 GEOCHEMICAL ZONING IN EPITHERMAL DEPOSITS 214 BODIE MINING DISTRI CT 215 Large-scale Vertical Zoning at Bodie Bluff--The Big Picture Detailed Lateral Zoning PARAMOUNT MINING DISTRICT--VERTICAL ZONING 224 SUMMARY 227 vii ACKNOWLEDGMENTS
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