SOCIETY OF ECONOMIC GEOLOGISTS, INC.

TEcHNIQUES IN HYDROTHERMAL ORE DEPOSITS GEOLOGY

CONTENTS

The Thermodynamics of Hydrothermal Systems G.M. Anderson

Solubility of Ore Minerals and Complexation of Ore Metals in S.A. Wood and I.M. Samson Hydrothermal Solutions

Calculation of Activity-Activity and Log f02-pH Diagrams S.A. Wood

Magmatic Contributions to Hydrothermal Ore Deposits: P.A. Candela and P.M. Piccoli An Algorithm (MVPart) for Calculating the Composition of the Magmatic Volatile Phase

Calculation of Simultaneous Chemical Equilibria in M.H. Reed Aqueous-Mineral-Gas Systems and its Application to Modeling Hydrothermal Processes

Fluid Inclusion Techniques of Analysis T.J. Shepherd and A.H. Rankin

Fluid Inclusion Modeling for Hydrothermal Systems P.E. Brown

Introduction to Stable Isotope Applications in Hydrothermal Systems A.R. Campbell and P.B. Larson

Application of Radiogenic Isotope Systems to the Timing and J.P. Richards and S.R. Noble Origin of Hydrothermal Processes

The Influence of Geochemical Techniques on the J.W. Hedenquist and J.P. Richards Development of Genetic Models for Porphyry Copper Deposits

EditorsJ.P. Richards and P.B. Larson

REvIEwS IN EcONOMIc GEOLOGY

volume 10

Society of Economic Geologists, Inc.

Reviews in Economic Geology, Vol. 10

Techniques in Hydrothermal Ore Deposits GeologyJ.P. Richards and P.B. Larson, Editors

Additional copies of this publication can be obtained from

Society of Economic Geologists, Inc.7811 Shaffer ParkwayLittleton, CO 80127

www.segweb.org

ISBN: 978-1-629495-68-2

The Authors: G reg M. Anderson Department of G eology University of Toronto 22 Russell Street Toronto, Ontario M5S 3B1 Canada Tel.+ 1 .416 .978.4852 Fax: +1 .416 .978.3938 email:

greg@ quartz.geology.utoronto.ca

Philip E. Brown Department of Geology & Geophysics Univ. of Wisconsin-Madison 1215 W. Dayton Madison, Wisconsin 53706 USA Tel. + 1 .6 08.26 2.5954 Fax: + 1 .6 08.26 2.06 93 e mail: pbrown@ geology.wisc.edu

Philip A. Candela Department of G eology University of Maryland College Park, Maryland 20742 USA Tel. + 1 .301 .405.2783 Fax: +1 .301 .314.966 1 email: candela@geol. umd.edu

Andrew R. Campbell Department of Earth &

Environmental Sciences New Mexico Tech Socorro, New Mexico 87801 USA Tel. + 1 .505.835.5327 Fax: + 1 .505.835 .6 436 email: campbell@ mailhost.nmt.edu

Jeffrey W. Hedenquist Mineral Resources Department G eological Survey of Japan 1-1-3 Higashi, Tsukuba 305

Japan Tel. +01 1 .81 .298.54.36 49 Fax: +01 1 .81 .298.54.36 33 email: jeffrey@ gsj .goJp

Peter B . Larson Department of G eology Washington State University Pullman, Washington 9916 4-281 2 USA Tel. + 1 .509.335.3095 Fax: +1 .509.335.7816 email: plarson@wsu.edu

Steve R. Noble NIG L Kingsley Dunham Centre Keyworth, Nottingham NG 1 2 5GG United Kingdom Tel.+01 1 .5.936 .3555 Fax: +01 1 .5.936 .3302 email: SRN@wpo.nerc.ac.uk

Philip Piccoli Department of G eology University of Maryland College Park, Maryland 20742-421 1 USA Tel. + 1 .301 .405.6 966 Fax: + 1 .301 .314.966 1 email: piccoli@ geol.umd.edu

Andrew H. Rankin School of G eological Sciences Kingston University Penrhyn Road Kingston Upon Thames,

Surrey KTI 2E United Kingdom Tel. +01 1 .0181 .54 7. 7245 Fax: +01 1 .0181 .547.7419 email: a.rankin@kingston.ac.uk

Mark H. Reed Department of G eological Sciences Unversity of Oregon Eugene, Oregon 97403- 1272 USA Tel: + 1 .541 .346 .5587 Fax: + 1 .541 .346 .46 92 email: mhreed@ oregon.uoregon.edu

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Jeremy P. Richards Department of Earth &

Atmospheric Sciences University of Alberta Edmonton, Alberta T6G 2E3 Canada Tel: + 1 .403.492.3430 Fax: + 1 .403.492.2030 email: J eremy.Richards@ ualberta.ca

lain M. Samson Earth Sciences University of Windsor Windsor, Ontario N9B 3P4 Canada Tel. +1 .519.253.4232 Fax: +1 .519.973.7081 email: ims@ uwindsor.ca

Tom J. Shepherd British G eological Survey Keyworth, Nottingham NG 12 5GG United Kingdom Tel. +01 1 .5.936 .3100 Fax: +01 1 .5.936 . 3302 email: TJS@wpo.nerc.ac.uk

Scott A. Wood Department of G eology &

G eological Engineering University of Idaho Moscow, Idaho 83844-3022 USA Tel.+ 1 .208.885.5966 Fax: + 1 .208.885.5724 email: swood@ uidaho.edu

PREFACE

One of the best things about being an "economic geol­ogist" is the fact that the term almost defies definition. The only requirements are that one should be a geol ogist (preferably a good one ! ) , and have an interest in the eco­nomic applications of that science to the minerals indus­try. Consequently, we can be mineralogists, geochemists, geophysicists, exploration geologists, mine geologists, pa­leontologists, ge ochronologists, geomorphologists, sedi­mentologists, structural geologists-the list could go on, but we are all unified by that interest in mineral deposits. To be fully conversant with this broad science, however, it is not sufficient for us to operate exclusively within our own specialization: the isotope geochemist cannot afford to ignore the paragenetic information available from pe­trography and mineralogy; the fluid inclusionist can eke far more information out of microthermometric or ana­lytical data by fitting them to thermodynamic models. This requirement can be both a blessing and a curse, however. On the one hand, it encourages us to be geologists in the broadest sense, with a full appreciation of the mechanics of our planet and how they affect ore formation. On the other hand, we cannot possibly hope to be experts in all of these fields in the space of one lifetime.

The solution, therefore, must be interdisciplinary col­laboration, combined with more effective communica­tion, so that, although we may not become experts, we at least have a working knowledge of the full range of disci­plines at our disposal.

The impetus for this volume arises from the editors' own feelings of inadequacy when confronted with certain aspects of our science, and also our experiences in trying to communicate this subject to our students and col­leagues. We all know that the easiest lectures to give are those based on our own specializations and research; how­ever, these are not necessarily the easiest lectures to give well, particularly if the target audience is non-expert in our field. Likewise in our writings: as professionals we are ex­pected to write succinct papers focusing solely on our new results and interpretations, with no room for background explanations, and lots of unspoken pressure to impress our peers. However, such writings are opaque to a broader readership, and do little to help expose our science to other scientists, let alone the general public.

In an attempt to address these problems, at least within the broader circle of economic geologists, we have sought contributions from user-friendly expert authors on spe­cific aspects of geochemical data collection and modeling as applied to hydrothermal ore deposits. Our intention was not to compete with Hubert Barnes' milestone vol­umes (G eochemistry of Hydrothermal Ore Deposits ) . Rather, we wished to insert a stepping stone in front of

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these volumes, to enable a wider audience to access and appreciate their wealth of information. Thus, our target audience is very broad, and includes everyone from final­year undergraduate students to industry geologists and academics with specializations in other fields.

Each chapter is self-contained, but the reader may find that he or she needs to read an earlier chapter to brush up on some background theory. However, a specialist's knowledge is not required at any point. The chapters aim to provide the basic principles of the topic, and then to ex­plore the practical applications of the techniques in the study of ore deposits. The volume is thus both a reference book and a handbook, with practical information ranging from the construction and interpretation of commonly used geochemical diagrams, to the size and type of sam­ples required for geochronological analyses.

The volume editors would like to thank all of the authors for their efforts in taming their science, the re­viewers for providing an excel lent test of our successes and failures and thereby significantly improving the volume, and Mike Lesher, who as former Series Editor provided the lift and encouragement required to turn an idea into a reality.

Finally, we remember and thank Werner G iggenbach, who was preparing a manuscript for this volume at the time of his death in November 1997.

LIST OF REVIEWERS An tonio Arribas, Jr. Mark D. Barton William L. Bourcier Douglas E. Crowe John H. Dilles Christopher H. G ammons Thomas H. G iordano Larry M. Heaman G aham D. Layne Jacob B. Lowenstern Jon A. Naden David I . Norman David A. Polya W. I an Ridley Edward M. Ripley Edward T.C. Spooner Holly J. Stein James A. Wh itney An thony E. Williams-J ones Thomas J. Wolery

Jeremy P. Richards Peter B. Larson

BIOGRAPHIES

GREG M. ANDERSON be gan his caree r as a mining e ngi­nee r and e xploration geologist before he discove re d the joy of ge oche mistry. After completing his Ph.D. at Toronto with F.G . Smith, he spe nt five ye ars at Pe nnsylvania State Unive rsity in Wayne Burnham's lab, doing e xpe rime ntal work on mine ral solubilitie s. Afte rward he re turned to Toronto, whe re he has divided his time betwee n studies of mine ral solubilities, MVf deposits, and theoretical geochem­istry. He is the author of tw o textbooks on thermodynamics - The rmodynamics in Geochemistry, with D.A. Crerar (Ox­ford) , and Thermodynamics of Natural Systems (Wiley) .

PHILIP E. BROWN re ce ive d a B.A. de gree i n ge ology from Carle ton Colle ge in 1974, and M.S. ( 1976 ) and Ph.D. ( 1980) de gree s from the Unive rsity of Michigan, whe re he spe cialize d in e conomic geology, in ge ne ral, and the Pine Cree k, California, tungste n skarn, in particular. Afte r a one-ye ar post-doctoral appointme nt at the U.S. Ge ological Survey in Re ston, Virginia, he acce pted a position at the Unive rsity of Wisconsin-Madison in 1981 and has bee n the re since . His re se arch inte rests ce nter around fluids in the Earth's crust and Arche an gold de posits, me tamorphic and me tamorphose d ore bodies, fluid inclusions, skarns and the Proterozoic massive sulfide deposits of Wisconsin. A six-month sabbatical in Western Australia in 1991 be gan a collaborative re se arch program with the the n 'Key Ce n­tre ' at the University of We ste rn Australia - this continues today, with Dr. Brown holding an Adjunct Faculty position in Pe rth. Re ce ntly his interests include e xploring the role that compute r visualization te chnology can play in geo­logical e ducation.

ANDREW R. CAMPBELL re ce ived a B.S. in ge ology from Indiana Unive rsity in 1977 and a Ph.D. in ge ology from Harvard University in 1983. Since the n, he has bee n te ach­ing at New Me xico Te ch in Socorro, N.M., whe re he is cur­re ntly Profe ssor of Geology. He has se rved the Socie ty as an Associate Editor for Economic Ge ology and as Editor of the Newsle tte r. Dr. Campbell's re se arch inte rests in­clude fluid inclusion and stable isotope studies of ore de­posits as well as application of stable isotope ge oche mistry to othe r topics. He pionee red the use of infrare d mi­croscopy to study fluid inclusions in opaque ore mine rals.

PHILIP A. CANDELA re ce ive d his Ph.D. from Harvard Unive rsity in 1982. Since the n he has bee n at the Unive r­sity of Maryland, whe re he is now Professor of Ge ology and co-dire ctor of the Laboratory for Mine ral Deposits Re­se arch. He has also bee n a Visiting Fe llow at the De part­me nt of Ge ology at the Australian National Unive rsity, and is a Fe llow of the Ge ological Socie ty of Ame rica, the Min­e ralogical Socie ty of Ame rica, and the Socie ty of Eco­nomic Geologists. His rese arch involves: the study of e le­me nt partitioning in me lt-vapor-brine-crystal syste ms, with spe cial refe re nce to the be havior of ore me tals, including Au and Cu; fie ld and the ore tical studie s of the mass trans­fe r dynamics in devolatilizing magma chambe rs; textural

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studies in igneous rocks; expe rime ntal studies of wall-rock alte ration in ore de posits and ge othe rmal syste ms; e xpe ri­me ntal studie s of sulfides in magmatic-hydrothe rmal e nvi­ronme nts; and ore deposits and tectonics of the Appalachian Oroge n. At the University of Maryland, he te aches gradu­ate leve l classe s in the rmodynamics, advance d e conomic ge ology, and igne ous pe trology; he is also the dire ctor the unde rgraduate se nior thesis program in Geology.

JEFFREY W. HEDENQUIST is a geologist with the Ge o­logical Survey of Japan, in the De partme nt of Mine ral and Fuel Resource s. He began graduate studie s on an Arche an gold de posit, and at the same time worke d for the U.S. Ge­ological Survey on coastal se dime ntology, granite s, and lunar pe trology. He comple te d his graduate study on gold mine ralization of an active ge othe rmal syste m while at the Unive rsity of Auckland, New Ze aland, on a Fulbright fe l­lowship. He joine d Che mistry Division, DSIR New Ze aland, in 1982, and while base d at Wairake i was involve d in ge ot­he rmal e nergy developme nt and epithe rmal gold e xplo­ration in the we ste rn Pacific. He move d to Japan in 1989 to e xpand his epithe rmal re se arch to the porphyry e nvi­ronme nt, and also to study me tals in volcanic discharge s.

PETER B. LARSON is Chair of the Ge ology De partme nt at Washington State University, whe re he has se rve d on the faculty since e arning his Ph.D. from Calte ch in 1983. His primary research intere sts are wate r-rock interaction in hy­drothe rmal e nvironme nts, and igneous pe troge nesis, to which he applie s stable isotope analyses. He was born and raise d in the midst of the Michigan native coppe r district, and re ce ive d his B.Sc. in geology from Michigan Te ch in 1973.

STEPHEN R. NOBLE re ceive d a B.Sc. (geological e ngi­neering) in 1980 and an M.Sc. (ge ology) in 1992 from the University of Toronto. During this time he was involve d in re search associated with porphyry Mo-W and relate d skarn deposits in the Yukon and Northwest Te rritorie s. Noble re­ce ived a Ph.D. in geoche mistry in 1989 from the Unive rsity of Toronto, whe re his work involved investigating the U-Pb ge ochronology, and geoche mical and Sm-Nd isotope char­acteristics of Archean granite-greenstone te rrane s in north­west Ontario. Since then he has bee n a rese arch ge ologist, responsible for establishing the U-Pb ge ochronology labo­ratory at the Natural Environme nt Re search Council Iso­tope Geoscie nces Laboratory, now part of the British Ge o­logical Survey. Curre nt rese arch focuse s on high pre cision U-Pb ge ochronology in the Himalayas and Scottish High­lands, Lu-Hf isotope syste matics, and the deve lopme nt of ICP-MS and lase r ablation ge ochronology technique s.

PHILIP M. PICCOLI is a Research Scie ntist at the Labo­ratory for Mine ral De posits Research, Unive rsity of Mary­land. His inte rests include fie ld studies of silicic volcanic and plutonic rocks; the use of acce ssory phases in the de­te rmination of magmatic, hydrothe rmal, and ore-forming

processes; chemical modeling of ore-forming processes; microanalysis of minerals; and experimental simulation of magmatic-ore systems involving Au, Cu, etc. Piccoli em­ploys a multidimensional approach involving field obser­vations, modeling, and experimentation to solve problems in ore-genesis.

ANDY H. RANKIN received his B.Sc. in chemistry and his Ph.D. in geology from the University of Leicester, UK. Prior to his curre nt appointment in 1991 as Professor of Applied G eology and Head of the School of G eological Sciences at Kingston University, UK, he held various fac­ulty positions in the Royal School of Mines, Imperial Col­lege, London, over the period 197 4-1991 , first as lecturer in Mining G eology, then as Reader in Applied Mineralogy and Head of the Fluid Process Research G roup. His main research interests are in hydrothermal and magmatic processes in ore genesis and in the development and ap­plication of fluid inclusion methods to a range of prob­lems in the G eosciences. He has published widely on these topics and has organized and participated in a number of successful short courses in fluid inclusion in the UK, USA, and South America. Until recently he was president of the Mineralogical Society of G reat Britain and Ireland.

MARK H. REED received B.A. degrees in chemistry and ge­ology from Carleton College in 197 1 , followed by an M.S. in 1974 and a Ph.D. in 1977 from University of California, Berkeley. His Ph.D. research focused on the origin of mas­sive sulfide mineralization in seafloor settings, for which studies he developed original forms of two computer pro­grams for multicomponent, multiphase chemical equilib­rium calculations. Reed worked as a staff geologist and project geologist for the Anaconda Company in Butte, Montana, from 1977 through 1979. During that period, he mapped underground exploration crosscuts and under­ground and surface drill core, focusing on describing the hydrothermal alteration and mineralization in the large porphyry copper- molybdenum system at Butte. From 1980 to the present, Reed has been on the faculty of the Depart­ment of G eological Sciences, University of O regon, special­izing in studies of ore deposits and in modeling geochemi­cal processes in geothermal systems, hydrothermal ore systems, volcanic gas fumaroles, and sediment diagenesis.

JEREMY P. RICHARDS received his B.A. ( 1 983) in geol­ogy from the University of Cambridge, UK, his M.Sc. ( 1986 ) in economic geology from the University of Toronto, Canada, and a Ph.D. ( 1990) in economic geology from the Australian National University. Mter a two-year post-doc­toral position at the University of Saskatchewan, Canada, he joined the faculty at the University of Leicester, UK, in 1992. He has since recently moved back to Canada, where he is currently an Associate Professor in economic geology at the University of Alberta. His research focuses on the genesis of hydrothermal ore deposits, and previous and ongoing investigations include studies of the Keweenawan basalt-hosted copper deposits in Michigan and O ntario, sed­iment-hosted stratiform copper deposits in the Democratic

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Republic of Congo (formerly Zaere ) , porphyry copper de­posits in Chile and Ecuador, and alkalic intrusive-related gold deposits in Papua New G uinea.

lAIN M. SAMSON received a B.Sc. in applied geology in 1979 and Ph.D. in economic geology in 1983 from the University of Strathclyde. From 1983 until 1986 he was a Research Associate with the Mineral Exploration Research Institute (IREM-MERI) at McG ill University. In 1986 he joined the faculty of the University of Windsor where he is currently an Associate Professor in the Department of Earth Sciences. His research interests are in the genesis of hydrothermal mineral deposits and the geochemistry of hydrothermal systems. He has published papers on a vari­ety of types of mineral deposits, including SED EX Pb-Zn, granite-related W, Mo, Sn, and Cu deposits and Precam­brian Au-Ag deposits. His current research is focused on the genesis of REE and other rare-element deposits, par­ticularly those associated with alkalic igneous rocks, and on the micro beam analysis of fluid inclusions.

TOMJ. SHEPHERD received his B.Sc. and Ph.D. in geol­ogy from the University of Durham, UK. Following a two­year period as an exploration geologist working from Com­inca's European office he joined the G eochemical Division of the British G eological Survey (Institute of G e­ological Sciences) , where his initial brief was to develop methods for fluid inclusion analysis. He has maintained his current interest in the development and application of fluid inclusion methods, especially in relation to mineral and petroleum exploration and ore genesis, since joining the survey in 1971 . He currently holds a Cabinet O ffice In­dividual Merit Position at the BG S, Nottingham, UK, which permits him to further develop his research inter­ests in these fields. He has published widely in these and related fields, including a textbook on fluid inclusions, co­authored with Andy Rankin and Dave Alderton.

SCOTT A WOOD received a B.A. degree in both geology and chemistry from Hamilton College in Clinton, New York, in May 1980. He then went on to obtain an M.A. ( 1982) and a Ph.D. ( 1985) in G eochemistry from Princeton University under the supervision of Dr. David Crerar. From January 1985 until December 1991 he was first an Assistant and then Associate Professor at McG ill University in Mon­treal. Since then he has been at the University of Idaho where he is currently Professor of G eochemistry . Starting with his Ph.D., he has been involved in experimental and theoretical research into the solubility of ore minerals and the speciation of ore metals in hydrothermal solutions, and has had particular interests in the platinum-group ele­ments, the rare earth elements, tungsten, gold, bery llium, and zirconium. He has also been involved in field-based geochemical studies of the origin of ore deposits, including hydrothermal REE, epithermal Ag-Au and porphyry Cu mineralization. In recent years he has devoted a significant proportion of his research effort to environmental geo­chemistry. Since 1989, Dr. Wood has been an Associate Edi­tor of the journal G eochimica et Cosmochimica Acta.

CONTENTS

Chapter 1-The Thermodynamics of Hydrothermal Systems INTRODUCTION ................................................................... 1 THE THREE LAWS OF THERMODYNAMICS .... ........................ 3 SoLUTIONS AND AcTMTIES ............................ .................. !! OPEN SYSTEMS ...... ............ .......................... ...................... 1 8 THE HKF MoDEL FoR AQuEous ELECTROLYTES ............... 20 PHASE SEPARATION ............................................. ............... 22 REDOX REACTIONS ..................................................•......... 24 PROCESS MODELING .......................................................... 25 CONCLUDING REMARKS ..................................................... 30 ACKNOWLEDGMENTS ............................................. ............. 30 REFERENCES ...................................................................... 31

Chapter 2-Solubility of Ore Minerals and Complexation of Ore Metals in Hydrothermal Solutions INTRODUCTION .... ................... .......................................... 33 COMPLEXATION ........................................ ........ ......... ........ 33 MoRE COMPLICATED SOLUBILI1Y CALCULATIONS .............. 39 METHODS OF EXTRAPOLATION OF EQUILIBRIUM

CONSTANTS ............................................................... ..... 42 ESTIMATING STANDARD STATE EQUILIBRIUM CONSTANTS .. .48 REVIEW OF THERMODYNAMIC DATA FOR

SELECTED METALS .. .. ........................ ............................. 49 CONCLUDING REMARKS ........... ........................ .................. 70 ACKNOWLEDGMENTS .................... ...................................... 70 REFERENCES ................................ ...................................... 70 APPENDIX ..................................... ..................................... 77

Chapter 3-Calculation of Activity-Activity and Log /02-pH Diagrams INTRODUCTION ............................. . ................................... 81 ACTM1Y-ACTM1Y DIAGRAMS ............................................ 81 LOG f02-pH DIAGRAMS ...................................................... 87 CONCLUDING REMARKS ..................................................... 95 ACKNOWLEDGMENTS ......................... ....... .................. . . ...... 95 REFERENCES ...................................................................... 96

Chapter 4-Magmatic Contributions to Hydrothermal Ore Deposits: An Algorithm (MVPart) for Calculating the Composition of the Magmatic Volatile Phase INTRODUCTION .................................................... ............. 97 INTRODUCTION TO THE ALGORITHM ................................. 99 ESTIMATION OF GEOLOGICAL PARAMETERS .... .................... 99 MODELING THE PARTITIONING OF Cu: AN OVERVIEW ..... 103 SUMMARY .......................................... ..... ......................... I 05 REFERENCES .............................................. ...................... l 05 APPENDIX I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l 06 APPENDIX 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 08

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Chapter 5-Calculation of Simultaneous Chemical Equilibria in Aqueous-Mineral-Gas Systems and its Application to Modeling Hydrothermal Processes INTRODUCTION ............................................................... 109 WHOLE-SYsTEM GEOCHEMISTRY AND

PROCESS MODELING .................................................... I I 0 INTRODUCTION TO THE COMPUTATIONAL APPROACH ...... I l l THE CoRE SYsTEM oF EQUATIONS ... ............................... l l2 SOLVING THE SYSTEM OF EQUATIONS .............................. 1 15 ACTM1Y COEFFICIENTS ................................................... 1 16 PHASE AsSEMBLAGE SELECTION AND GAS BUFFERING ...... l l 7 PROCESS MODELS ............................................................ l l8 CONCLUDING STATEMENT .................................. .............. 1 22 ACKNOWLEDGMENTS ........................................................ l 22 REFERENCES .................................................................... 123

Chapter 6-Fluid Inclusion Techniques of Analysis INTRODUCTION ............................................................... 1 25 BULK METHODS FOR VOLATILE ANALYSIS ............ ............ 1 30 BULK METHODS FOR SOLUTE ANALYSIS ................... . ....... l 33 SINGLE INCLUSION TECHNIQUES .. ................................... 1 36 CONCLUDING REMARKS ................................................... 146 ACKNOWLEDGMENTS .............................................. .......... l46 REFERENCES .................... ..... ............... . . ................ .......... 146

Chapter 7-Fluid Inclusion Modeling for Hydrothermal Systems INTRODUCTION ...................... ..... . ................................... 1 5 1 MICROTHERMOMETRY ...................................................... l 52 DATA HANDLING .......................................................... ... l6 0 INTERPRETATION .......................... ............... .................... 16 4 AN EXERCISE ....................................... ............................ l6 7 ACKNOWLEDGMENTS .................. .......... ............................ l6 9 REFERENCES .............................. ...................................... 16 9

Chapter 8-Introduction to Stable Isotope Applications in Hydrothermal Systems INTRODUCTION ............................................... ................ 1 73 SAMPLE PREPARATION AND ANALYSIS ..... ..... ..................... 1 75 GENERAL RANGE OF ISOTOPE VALUES

FOUND IN NATURE ... .......................... .......................... l 76 ISOTOPE FRACTIONATION ....................... .... ..................... 1 77 GEOTHERMOMETRY ........................................ ................. l 79 PROCESSES AND RESERVOIRS ............... ..... ........................ 181 APPLICATIONS TO HYDROTHERMAL ALTERATION .............. 1 84 FLUID INCLUSIONS ............................ ..... ......................... 1 89 CLOSING STATEMENT ....................................................... 190 ACKNOWLEDGMENTS ........................................................ l90 REFERENCES .............. . . . ............. ...... ................................ 190 APPENDIX ............ ............................... . .... ........................ 192

Chapter 9-Application of Radiogenic Isotope Systems to the Timing and Origin of Hydrothermal Processes INTRODUCTION ............................................................... 195 RADIOGENIC ISOTOPE SYSTEMATICS ................................. 195 RB-SR DATING TECHNIQUES ............................................ 199 SM-ND DATING ................................................................ 203 U-(TH)-PB DATING ......................................................... 205 PB-PB DATING ................................................................. 2 1 1 K-A.R DATING .................................................................. 2 1 5 40ARj39AR DATING ........................................................... 218 RE-Os DATING ................................................................ 222 ISOTOPIC SOURCE TRACING ............................................. 223 SUMMARY ........................................................................ 228 ACKNOWLEDGMENTS ........................................................ 228 REFERENCES .................................................................... 228

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Chapter 10-The Influence of Geochemical Techniques on the Development of Genetic Models for Porphyry Copper Deposits INTRODUCTION ............................................................... 235 PORPHYRY COPPER DEPOSITS ........................................... 235 GEOCHEMICAL STUDIES ................................................... 239 STABLE ISOTOPIC STUDIES: SOURCES OF WATER .............. 243 RADIOGENIC AND OTHER ISOTOPIC STUDIES:

SOURCES OF SOLUTES .................................................. 247 GEOCHRONOLOGIC STUDIES: TIMING OF

ORE FORMATION ......................................................... 249 PHYSICAL AND CHEMICAL MODELING .............................. 250 SUMMARY ........................................................................ 251 FUTURE DIRECTIONS ....................................................... 251 EPILOGUE: ORE DEPOSITS, FLUIDS, AND CRUSTAL

PROCESSES ................................................................... 252 ACKNOWLEDGMENTS ........................................................ 252 REFERENCES .................................................................... 252