Ore Textures. Recognition and Interpretation [Roger Taylor]

Ore Textures

Roger Taylor

Ore Textures Recognition and Interpretation

123

Roger Taylor Townsville Queensland 4810 Australia

ISBN 978-3-642-01782-7 e-ISBN 978-3-642-01783-4 DOI 10.1007/978-3-642-01783-4 Springer Dordrecht Heidelberg London New York Library of Congress Control Number: 2009926869 c Springer-Verlag Berlin Heidelberg 2009  This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: Bauer, Thomas Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)

Acknowledgments Given the eleven years required to produce the original five volumes, the list of contributors is considerable. They constitute numerous individuals and financial sponsor companies who deserve special acknowledgement. It is impractical to give lengthy written credit to all concerned, and the list below only outlines some of their contributions. Thank you everybody. Special thanks are extended to Dr Peter Pollard and Dr Gavin Clarke who contributed continuously via encouragement, editing, rock preparation, and their own extensive knowledge of ore textures. The outstanding plates are the work of Roger Yeldham and Brian Pump from the James Cook University ­photographic division. Although not obvious here, David Lloyd contributed the initial graphic design which made the individual volumes so attractive. The difficult and delicate task of combining five volumes into a ­single offering has been conducted by Elisabeth Sillmann of blatterwald Design. Her high quality graphic design skills are gratefully acknowleged, and will be evident to all readers. Some anonymous frogs who gracefully permitted use of their photographic images in the original volumes are also acknowledged (unfortunately only two could be included here).

INDIVIDUAL CONTRIBUTORS Dr A. Allibone Mr D. Andrews Dr E. M. Baker Professor T. H. Bell Dr N. Adshead-Bell Dr S. Beams Ms E. Caragianides Ms D. Casey Dr G. W. Clarke Dr G. Dong Ms M. Drögemuller Dr K. Hickey Mrs K. Hotschilt Dr W. P. Laing Mrs L. Laivens Ms H. Lawrie Mr D. Lloyd Ms F. McKinstry Ms M. Meyers Dr R. Meyers Dr G. W. Morrison Dr B. New Professor G. N. Phillips Dr P. J. Pollard Mr B. Pump Mr S. Richards Ms E. Sillmann Dr P. J. Williams Associate Professor S. E. Williams Dr P. J. Wormald Dr M. Worsley Mr R. Yeldham

Specimen loan and stuctural expertise Specimen loan and photography Photography Structural advice Structural advice Specimen loan Sundowners Word processing and fund raising Specimen loan, specimen preparation, photography and textural expertise Specimen loan Word processing and fund raising Structural advice Photography Specimen loan Word processing Editing Graphic design Frog photograph Editing Editing and general advice Specimen loan, photography and textural expertise Structural advice Specimen loan and general advice Specimen loan, editing, photography, textural expertise and general advice Photography Frog photograph Graphic design, typesetting Specimen loan and general advice Frog photograph Specimen loan Specimen loan Photography

V

COMMERCIAL SPONSORS

Aberfoyle Resources Limited

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ARIMCO Mining Pty Ltd

MIM Exploration Pty Ltd

Aurora Gold Pty Ltd

Mount Isa Mines Ltd

Australasian Institute of Mining and Metallurgy (North Queensland Branch)

Mount Leyshon Gold Mines Ltd

Aztec Mining Company Ltd Battle Mountain (Australia) Inc Barrick Gold Corporation (Australia) BHP Pty Ltd BHP Billiton (Cannington) Billiton Australia CRA Exploration Pty Ltd Companhia Vale Do Rio Doce (CVRD) Cyprus Gold Australia Corp. Delta Gold NL Department of Minerals & Energy (Queensland) Department of Minerals & Energy, PNG Department of Resource Industries Dominion Mining Ltd Economic Geology Research Unit (EGRU) James Cook University Freeport McMoran Copper and Gold Co Giants Reef Mining Geopeko Goldfields Exploration Gold Mines Of Australia Great Central Mines and Centaur Mining and Exploration Ltd

Newcrest Mining Ltd Newmont Gold Company Normandy Exploration Ltd North Ltd North Flinders Exploration Nuigini Mining (Australia) Pty Ltd Pac Min Mining Company Ltd Pancontinental Mining Ltd Pasminco Exploration Placer Exploration Ltd Plutonic Mining Phelps Dodge Australia Inc P. T. Freeport Indonesia Reynolds Australia Metals Ltd RGC Ltd Rio Tinto Ross Mining NL RTZ (South America) Sons of Gwalia Ltd Teck Cominco Ltd The Key Centre for Economic Geology, James Cook University Western Mining Corporation

VII

Preface

This text has resulted from some forty years of experience during which the author has puzzled over the meaning of ore textures. The learning process has been slow and is still incomplete. The bemusement began directly upon leaving the academic confines, which in retrospect left one keen young geologist very ill-equipped to interpret the mineralising process via field or hand lens style observation of the rocks. Enlightenment has proceeded via a series of events:1. The slow process of field observation as an industry-based mine and exploration geologist. 2. The opportunity to visit numerous different styles of ore deposit both as an academic and consultant. 3. The need to answer questions from several generations of enquiring students. 4. The privilege of being able to conduct research. 5. The good fortune to be associated with a few top class economic geologists who actually knew what they were doing! Professor Willard C. Lacy deserves the most credit for quietly demonstrating the value of first principles concerning fluid channelways, combined with an ability to look properly at the textures. Despite rapid technological advances this skill remains fundamental both to the practicing exploration geologist and to the academic researcher who is interested in understanding ore forming processes. The five volumes comprising this presentation were originally compiled individually over a period of eleven years, and aimed to progressively guide the observer though the principles of recognition concerning infill, alteration, overprinting, and finally to ore-related breccias. Most observers have no significant problems with infill and alteration concepts in relation to narrow veins, but frequently flounder when the same components are repackaged as breccias. The plates have been carefully chosen to illustrate recognition procedure whilst giving a visual guide to a wide range of examples. The plate captions have been specifically written in a lengthy simplistic form to assist the genuine beginner. They contain a wealth of detail which is intended to lay a foundation for good textural observational methodology. A few more complex plates have been sporadically included to add appeal for those at connoisseur level. The book is not intended as a rigorous academic text. However, it is noted that the subject of textural interpretation still remains absent from most institutional training courses, and it is thus hoped that this contribution will be of direct assistance to many enquiring readers. Townsville, March 2009

Roger G. Taylor

IX

Contents Ore Textures – Recognition and Interpretation

Volume 1 • Infill Textures 1



List of Plates

1 2 2.1 2.1.1 2.1.2 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5

Introduction Recognition Criteria Incomplete Infill Remaining Void Space Crystals Projecting Into a Cavity Complete Infill Euhedral or Partially Euhedral Crystal Outlines Zoned Crystals Banded or Layered Textures Large-Scale Triangular Textures Small-Scale Triangular or Partially Triangular Textures

3 3.1 3.2 3.3 3.4

Problems and Working Techniques Common Misconceptions Problems with the Well-Formed Crystal Criterion The Edge Problem The Working Backwards Technique

4 4.1 4.2 4.3 4.4 4.4.1 4.4.2 4.4.3

How and Where to Look for Infill Textures – Channelway Recognition General Approach Vein Styles Breccia Styles Other Styles Miarolitic Igneous Interstitial Mineralisation Dissolution within Granite Systems

3 5 5 5 5 5 6 6 8 10 12 16



21 21 21 21 22



Volume 2 • Alteration Textures



25 25 25 25 26 26 30 30

35



List of Plates



37

1

Introduction



39

2

Basic Principles

3 3.1 3.2 3.3 3.4 3.5 3.5

Approach to Alteration Alteration Recognition The Movement Principle – Observational Positioning Mineral Identification – Nomenclature Changeover Observations – Transitional Zones Textural Observation Channelway Identification



40



43 43 43 43 44 44 44

XI

3.7 3.8

Chemical Awareness Examples of Alteration Types and Structural Style Types Sericite Greisen, Silica-Sericite Phyllic, Silica -Sericite Chlorite Chlorite Silica Propylitic, Chlorite-Epidote Propylitic, Chlorite-Epidote, Silica, Sulphide Potassic (K-Feldspar, Potassium Feldspar) Adularia (Potassium Feldspar) Potassic (Biotite) Albite Argillic Clay-Carbonate, Sulphide Advanced Argillic, Pyrophyllite, Silica-Alunite Hematite – Red Rock Magnetite-Albite, Chlorite-Epidote Silica-Pyrite-Carbonate Silica-Pyrite-Carbonate Sulphide-Silica-Pyrite, Silica-Magnetite Sulphide-Pyrrhotite Topaz Albite, Chlorite (Granite)

4

Alteration minerals – Some General Observations

5

Assessment Sheet

6

References

45 45

Structural Style Vein Pipe Stockwork-Vein Miarolitic Fault Breccia-Vein Fault Breccia-Vein Vein Intrusive Breccia Stockwork Breccia Intrusive Breccia Vein Pervasive-Vein-Breccia Vein (Ductile Style) Layer Controlled, Vein Vein Vein Vein Breccia Layer Controlled, Vein Fault Breccia-Vein Background, Selective Semi-Pervasive



90



95



97

Volume 3 • Overprinting Textures

XII



47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89

99



List of Plates



101

1

Introduction



103

2 2.1 2.2 2.2.1 2.2.2 2.3 2.3.1 2.3.2 2.3.3 2.4 2.5

Overprinting criteria General First Order Criteria – Confidence Building Mineral Superimposition – Sequential Infill Structural Superimposition – Crosscutting Veins, Breccia Second Order Criteria – Suspicion Arousing Mismatches Between Alteration and Infill Components Inconsistent Alteration Configurations Alteration of Alteration Third Order Criteria – Indirect Overprinting – Mineral Assemblages Fourth Order Criteria – Indirect Overprinting – Temperature Indicators

3 3.1 3.2

Overprinting Textures – Broader-Scale Perspectives Broad-Scale Perspectives Recording Observations

Ore Textures  •  Recognition and Interpretation  •  Contents





105 105 105 105 105 105 105 106 106 106 106 107 107 107



4 4.1 4.2

First Order Criteria – Mineral Superimposition Sequential Infill Textures and Problems

109 109 109

5 5.1 5.2

First Order Criteria – Structural Superimposition Crosscutting Veins – Stockwork Styles Textures and Problems

6 6.1 6.2

First Order Criteria – Structural Superimposition Breccia – Fragments of Early Stage Mineralisation Contained within Later Stages Textures and Problems

135

7 7.1 7.2

Second Order Criteria Suspicion Arousing, Parallel Overprinting Veins Alteration Mismatching – Inconsistent Alteration and/or Infill Sequences, Alteration of Alteration

145 145

8

References



117 117 117

135

145



161

Volume 4 • Broken Rocks – Breccias I

163



List of Plates



165

1

Introduction



169

2

Observation of Broken Rock Patterns

3

Approach to Understanding Broken Rock Patterns

4 4.1 4.2 4.3 4.4

Arrangement of Plates – Design Philosophy General Patterns of Broken Rocks and Problems Involved with Recognition, Scale Perception, and Overprinting Systems/Rocks with Pronounced Shear (Brittle – Ductile, Ductile Components) Systems/Rocks with Pronounced Brittle Components Textures of Related/Miscellaneous Interest

5

References



171



173



176 198 204 218

223





List of Plates



Introduction, Scope and Arrangement of Volume

1

Initial Recognition

2

General Features – Range in Styles and Scale of Intrusive Breccia

3

Multistage Structural and Hydrothermal Overprinting

4

Special Features Associated with Selected Intrusive Breccias

5

Intrusive Breccia Associated with Maar-Volcanoes and Associated Structures

6

Intrusive Breccia in Other Epithermal Systems

7

References

Index



222

Volume 5 • Broken Rocks – Breccias II



175

225



229



231





244



256



264



274 280 282

283

Ore Textures  •  Recognition and Interpretation  •  Contents

XIII

Mfcld\(Æ@eÔccK\okli\j

Mfcld\=ifekGX^\ Specimen of vein material from the St Patrick tin mine, near lrvinebank, Queensland (Herberton tinfield), Australia. The specimen illustrates many of the criteria which can be utilised to identify infill mineralogy: (a) (b) (c) (d) (e)

Cavities (several styles) Cavities containing partially euhedral minerals (quartz) Euhedral (or partially euhedral) crystals (quartz and dark cassiterite) Layered textures – crustiform banding (quartz) Triangular textures – small scale acute angle forms of cassiterite (dark) towards the top centre where cassiterite has infilled between pre-existing quartz crystals.

The wall rocks are silicified metasediments (not visible). The paragenesis (depositional sequence) is obviously complex, with the many different forms of silica presumably reflecting changing physical and chemical conditions of precipitation. It is possible that the thin curving style cavities which are prevalent towards the bottom of the plate have formed by selective leaching of an infill mineral (siderite?).

1

Mt Gibson topaz-tin region, Mt Garnet, Queensland, Australia. Void space, projecting crystals.

7

Mt Misery (Mt Tin – Morning Cloud deposit) Mowbray Creek, Queensland (Herberton tinfield), Australia. Euhedral mineral growth.

7

Mt Carbine tungsten mine? Mt Carbine, Queensland, Australia. Euhedral mineral growth.

9

4

Selwyn-Cloncurry Region, Queensland, Australia. Euhedral mineral growth.

9

5

Cleveland tin mine, North West Tasmania, Australia. Euhedral mineral growth.

11

6

Snow Flake mine, San Juan (silver, lead, zinc, gold) district, Colorado, United States of America. Euhedral mineral growth, layered texture.

11

7

Quartz Hill gold prospect, Collinsville, Queensland, Australia. Layered texture.

13

8

Comeno (silver, lead, zinc) mine, Mt Albion, Queensland, Australia. Layered texture.

13

Mt Leyshon gold mine, Charters Towers, Queensland, Australia. Large scale triangular textures.

15

Mt Leyshon gold mine, Charters Towers, Queensland, Australia. Large scale triangular textures.

15

Wirralie gold mine, Mt Coolon, Queensland, Australia. Large scale triangular textures.

17

Black King tin mine, Herberton, Queensland, Australia. Small scale triangular textures.

17

Unknown locality. Possibly Cooktown, Queensland, Australia. Small scale triangular textures.

19

Idarado mine? San Juan (silver, lead, zinc, gold) district, Colorado, United States of America. Small scale triangular textures.

19

15

Isobella (silver, lead, zinc) mine, Herberton, Queensland. Edge effects – breccia.

23

16

Mt Petersen tin mine, Irvinebank, Queensland, Australia. Edge effects – breccia.

23

17

Southern Cross tin mine, Herberton, Queensland, Australia. Edge effects – breccia.

27

18

Ardlethan tin mine, Ardlethan, New South Wales, Australia. Breccia – small scale triangular textures.

29

Ardlethan tin mine, Ardlethan, New South Wales, Australia. Breccia – small scale triangular textures.

29

20

Herberton, Queensland, Australia. Miarolitic-pegmatitic texture.

29

21

Zaaiplaats tin-mine, Limpopo, South Africa. Mineralised miarolitic-texture.

31

Zaaiplaats tin-mine, Limpopo, South Africa. Interstitial infill.

31

Maggs Pipe, Zaaiplaats tin-mine, Limpopo, South Africa. Dissolution-infill.

33

2 3

9 10 11 12 13 14

19

22 23

*

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