UNDERSTANDING MINERAL DEPOSITS

U nderstanding Mineral Deposits

by

Kula c. Misra Department of Geological Sciences,

The University ofTennessee, Knoxville, U.S.A.

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

A c.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-94-010-5752-3 ISBN 978-94-011-3925-0 (eBook) DOI 10.1007/978-94-011-3925-0

Printed on acid-free paper

AII Rights Reserved © 2000 K.C. Misra

Softcover reprint of the hardcover 1 st edition 2000 No part of the material protected by this copyright notice may be reproduced

or utilized in any form or by any means, electronic or mechanical, incJuding photocopying, recording or by any information storage and

retrieval system, without written permission from the copyright owner.

To my wife, Geeta,

for her patience

during the years ofpreoccupation with the book

and the clutter it generated all around our home

TABLE OF CONTENTS

PREFACE xiii

CHAPTER 1. INTRODUCTION 11.1. Mineral Deposit versus Orebody 11.2. Styles of Mineralization and Morphology of Mineral Deposits 21.3. Distribution of Mineral Deposits 31.3. Understanding Mineral Deposits 4

CHAPTER 2. FORMATION OF MINERAL DEPOSITS 52.1. Ore-forming Processes 52.2. Orthomagmatic Processes 62.3. Examples of Orthomagmatic Deposits 182.4. Sedimentary Processes 332.5. Metamorphic Proce§§c§ 492.6. Examples of Metamorphic Deposits 542.7. Hydrothermal Processes 562.8. Examples of Hydrothermal Deposits 732.9. Summary 892.10. Recommended Reading 92

CHAPTER 3. INTERPRETATION OF MINERAL DEPOSITS - I 933.1. Introduction 933.2. Geologic Setting 943.3. Ore Minerals 943.4. Ore-Gangue Textures 953.5. Stability Relations of Ore Minerals and Assemblages 1073.6. Hydrothermal Alteration 1163.7. Zoning 1243.8. Fluid Inclusions 1313.9. Trace Element Distribution 1423.10. Recommended Reading 147

CHAPTER 4. INTERPRETATION OF MINERAL DEPOSITS - II 1484.1. Stable Isotopes 1484.2. Sulfur Isotopes 153

vii

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4.3. Carbon Isotopes 1644.4. Oxygen and Hydrogen Isotopes 1684.5. Lead Isotopes 1774.6. Strontium Isotopes 1864.7. Geothermometry and Geobarometry 1934.8. Metamorphism of Ore Assemblages 2194.9. Age of Mineralization 2284.10. A Comprehensive Example: The Creede District, Colorado, USA 2314.11. Summary 2354.12. Recommended Reading 237

CHAPTER 5. CHROMITE DEPOSITS 2385.1. Introduction 2385.2. Types of Deposits 2385.3. Distribution 2395.4. Stratiform Deposits 2405.5. Podiform Deposits 2445.6. Examples 2485.7. Chromite Composition 2565.8. Origin 2615.9. Metallogenesis 2675.10. Summary 2705.11. Recommended Reading 272

CHAPTER 6. NICKEL (-COPPER) SULFIDE DEPOSITS 2736.1. Introduction 2736.2. Distribution 2736.3. Types of Deposits 2756.4. Examples 2816.5. Ore Composition 2926.6. Hydrothermal Alteration and Metamorphism 2986.7. Origin of Kambalda-type Deposits 2996.8. Metallogenesis 3086.9. Summary 3166.10. Recommended Reading 318

CHAPTER 7. PLATINUM-GROUP ELEMENT (pGE) DEPOSITS 3197.1. Introduction 3197.2. Types of Deposits 3217.3. Examples 3237.4. Ore Composition 3357.5. Origin of Merenskky-type PGE Deposits 337

CONTENTS ix

7.6. Orgin of PGE-enriched Chromitites in Layered Intrusions 3477.7. Metallogenesis 3507.8. Summary 3517.9. Recommended Reading 352

CHAPTER 8. PORPHYRY DEPOSITS 3538.1. Introduction 3538.2. Porphyry Copper Deposits 3538.3. Porphyry Molybdenum Deposits 3978.4. Porphyry Tin Deposits 4098.5. Summary 4128.6. Recommended Reading 413

CHAPTER 9. SKARN DEPOSITS 4149.1. Introduction 4149.2. Skarns and Skarn Deposits 4149.3. Types of Skarns and Skarn Deposits 4179.4. Examples 4289.5. Origin 4379.6. Metallogenesis 4419.7. Summary 4489.8. Recommended Reading 449

CHAPTER 10. VOLCANIC-ASSOCIATED MASSIVE SULFIDE 450(VMS) DEPOSITS

10.1. Introduction 45010.2. Distinguishing Features 45110.3. Distribution 45210.4. Types of Deposits 45510.5. Examples 46410.6. Ore Composition 47010.7. Hydrothermal Alteration 47310.8. Metamorphism and Deformation 47710.9. Origin 47810.10. Metallogenesis 48710.11. Summary 49510.12. Recommended Reading 496

CHAPTER II. SEDIMENT-HOSTED MASSIVE ZINC-LEAD 497SULFIDE (SMS) DEPOSITS

11.1. Introduction 49711.2. Distinguishing Features 498

x CONTENTS

11.3. Distribution 50011.4. Types of Deposits 50411.5. Examples 50411.6. Ore Composition 52111.7. Hydrothennal Alteration 52311.8. Origin 52411.9. Metallogenesis 53011.10. Summary 53811.11. Recommended Reading 538

CHAPTER 12. SEDIMENT-HOSTED STRATIFORM COPPER (SSC) 539DEPOSITS

12.1. Introduction 53912.2. Distinguishing Features 54012.3. Distribution 54112.4. Types of Deposits 54412.5. Examples 54512.6. Ore Composition 55912.7. Origin 56112.8. Metallogenesis 56712.9. Summary 57112.10. Recommended Reading 572

CHAPTER 13. MISSISSIPPI VALLEY-TYPE (MVT) ZINC-LEAD 573DEPOSITS

13.1. Introduction 57313.2. Distinguishing Features 57313.3. Distribution 57513.4. Examples 57813.5. Ore Composition 58813.6. Alteration 59013.7. Brecciation 59113.8. Origin 59313.9. Metallogenesis 60213.10. Summary 60713.11. Comparison of VMS, SMS, SSC, and MVT Deposits 60813.12. Recommended Reading 612

CHAPTER 14. URANIUM DEPOSITS 61314.1. Introduction 61314.2. Types of Deposits and Distribution 61314.3. Examples 627

CONTENTS

14.4. Mineralogy and Textures14.5. Origin14.6. Metallogenesis14.7. Summary14.8. Recommended Reading

CHAPTER 15. PRECAMBRIAN IRON-FORMATIONS15.1. Introduction15.2. Iron-formation15.3. Distribution15.4. Iron-formation Facies15.5. Types of Iron-formations15.6. Examples15.7. Ore Composition15.8. Metamorphism15.9. Secondary Enrichment15.10. Origin15.11. Time-bound Distribution ofIron-formations15.12. Summary15.13. Recommended Reading

CHAPTER 16. GOLD DEPOSITS16.1. Introduction16.2. Distribution16.3. Types of Gold Deposits16.4. Examples16.5. Origin of Hydrothermal Gold Deposits16.6. Metallogenesis16.7. Summary16.8. Recommended Reading

REFERENCES

INDEX

Xl

635636647658659

660660660661662667669675678680680694696697

698698699699725731749756759

761

839

PREFACE

Mineral deposits have supplied useful or valuable material for human consumptionlong before they became objects of scientific curiosity or commercial exploitation. Infact, the earliest human interest in rocks was probably because of the easily accessible,useful (e.g., red pigment in the form of earthy hematite) or valuable (e.g., native goldand gemstones) materials they contained at places. In modern times, the study ofmineral deposits has evolved into an applied science employing detailed fieldobservations, sophisticated laboratory techniques for additional information, andcomputer modeling to build complex hypotheses. Understanding concepts that wouldsomeday help geologists to find new mineral deposits or exploit the known ones moreefficiently have always been, and will continue to be, at the core of any course onmineral deposits, but it is a fascinating subject in its own right, even for students whodo not intend to be professional economic geologists. I believe that a course onmineral deposits should be designed as a "capstone course" that illustrates acomprehensive application of concepts from many other disciplines in geology(mineralogy, stratigraphy and sedimentation, structure and tectonics, petrology,geochemistry, paleontology, geomorphology, etc.).

This book is intended as a text for such an introductory course in economicgeology, primarily for senior undergraduate and graduate students in colleges anduniversities. It should also serve as a useful information resource for professionaleconomic geologists. The overall objective of the book is to provide the reader with acritical understanding of selected classes mineral deposits: how are they distributed inspace and geologic time, what are their distinguishing and general characteristics, andwhat can be inferred about their genesis from the available data. The expectation isthat the information and discussions in this text will provide students with an insightinto the formulation of appropriate exploration strategies for various classes of mineraldeposits and kindle their interest in further research on aspects of mineral deposits thatare poorly understood or that remain unresolved.

As an applied discipline, the study of economic geology requires a background inother disciplines of geology (particularly mineralogy, petrology, structural geology,and stratigraphy and sedimentation) as well as in allied sciences, such as physics andchemistry. It is assumed that the student has had one or more courses in these subjectsand is in a position to appreciate the applications of various principles taught in thosecourses to issues related to mineral deposits. There is an emphasis on geochemistrythroughout the book; this is necessary because the formation of almost all mineral

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deposits ultimately involves the chemical precipitation of minerals from fluids ofappropriate characteristics.

Considering the vast spectrum of mineral deposits that are either of potentialeconomic interest or are actually being exploited for our use, it is practicallyimpossible to include a comprehensive treatment of mineral deposits in an introductorytext of this kind constrained by page limitations. The selection included here is basedon what I perceive as the more interesting (and usually controversial) classes ofdeposits, especially from the points of view of origin and crustal evolution in space andtime. This does not imply that the classes of deposits excluded from consideration hereare not interesting or that their origins are devoid of controversy, but I had to draw theline somewhere.

A recurring problem I have had to deal with in writing this book is to keep itupdated with the latest information, which is being produced at an ever increasing rate.In addition, space limitation has compelled me to a selection of the references I haveused, a judgement, which I am afraid, is probably not totally devoid of personal bias.

Kula C. MisraKnoxville, Tennessee

August, 1999

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ACKNOWLEDGMENTS

The information contained in this book has come from a variety of sources: thousandsof journal articles, scores of books, visits to many mines around the world, and a life­time of endeavor to understand mineral deposits. I am thankful to all those authorswho have shared their knowledge, the publishers who have been instrumental indisseminating the information, the mine geologists and mine managers who have madethe mine visits a rewarding experience, and the teachers, such as Samar Sarkar, AsokeMookherjee, Sisir Sen, and Michael Fleet, who taught me to think critically.

A book of this length and effort does not happen without the sustained cooperationand help of a substantial number of individuals. In addition to the anonymousreviewers selected by the publisher, I am grateful to my colleagues Harry Y. McSween,Jr., Otto C. Kopp, Robert D. Hatcher, and Marvin Bennett for critically reviewingseveral of the chapters. I am particularly indebted to Hap McSween for his continuedsupport throughout the writing of this book.

I thank Marvin Bennett for all the help with the computer softwares I have used forthis book, especially for graphics. The Office of Research, The University ofTennessee, Knoxville, is gratefully acknowledged for a generous grant toward thecompletion of this project.

This book would not have been completed without the encouragement of my wife,Geeta, our children, Lolly and Anand, and our son-in law, Tom, or published withoutthe patience of the publishers.

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