Drainage Geochemistry (eBook)

Front Cover 1
Drainage Geochemistry 
4 
Copyright Page 5
Table of Contents 18
Editor's Foreword 6
Preface 8
List of Contributors 12
PART I: PRINCIPLES UNDERLYING DRAINAGE GEOCHEMSTRY 28
Chapter 1. Introduction: the foundations of modern drainage geochemistry 30
Drainage geochemistry in exploration and mapping 31
Regional geochemistry and resource evaluation 34
Modern methods in drainage geochemistry 35
Chapter 2. Mineral deposit models and primary rock geochemical characteristics 38
Introduction 38
Classifications of ore deposits and their settings 39
Mineral deposit models 43
Primary geochemical signatures of igneous rocks in relation to tectonic setting 75
Conclusions 99
Chapter 3. Modifications to the geochemical signatures of ore deposits and their associated rocks in different surface environments 100
Introduction 100
Processes of formation of secondary dispersion patterns 103
Element affinities and associations 118
Different surface environments 123
General implications for sampling 132
Chapter 4. Strategic choices in drainage geochemistry 138
Introduction 138
Survey objectives 138
Survey logistics 163
Survey budget 166
Conclusions 171
PART II: DRAINAGE GEOCHEMISTRY SAMPLE MEDIA 172
Chapter 5. Stream sediments in mineral exploration 174
Introduction 174
Theoretical considerations 176
Practical considerations 195
Summary 210
Chapter 6. Heavy-mineral concentrates in geochemical exploration 212
Introduction 212
Theoretical considerations 215
Practical considerations 231
Summary and conclusion 248
Chapter 7. Lake sediment sampling in mineral exploration 254
Introduction 254
Nature of the lake environment 255
Dispersion of elements into lakes 264
Lake sediment survey procedures 284
Summary 293
Acknowledgements 293
Chapter 8. Natural waters as sample media in drainage geochemistry 296
Introduction 296
Theoretical considerations 298
Properties and constituents of natural waters: application to exploration 303
Practical considerations 326
Conclusions 329
PART III: DRAINAGE GEOCHEMSTRY FOR DIFFERENT NATURAL ENVIRONMENTS 332
Chapter 9. Drainage geochemistry in glaciated terrain 334
Introduction 334
Climate and physiography 335
Geology and mineral deposits 339
Glacial and postglacial geology 343
Methods 348
Survey designs 354
Comparison between media in low-density surveys 356
Examples of technical success 362
Conclusions 366
Chapter 10. Drainage geochemistry in tropical rain forest terrains 368
Introduction 368
Regional geology and mineral deposits 369
Geomorphology and the development of drainage systems 371
Weathering and dispersion processes 375
Sample media 388
Practical problems related to the tropical rain forest environment 396
Case histories 398
Evaluation of the exploration record and topics for future research 404
Chapter 11. Drainage geochemistry in arid regions 406
Introduction 406
Theoretical considerations 408
Stream sediment surveys in arid regions 414
Playa lake geochemistry surveys 439
Summary and conclusions 440
Chapter 12. Drainage geochemistry in young folded mountain belts 442
Characteristics of young folded mountain belts 442
Factors influencing morphology and dispersion in young mountain areas 445
Geochemical dispersion trains in different climatic zones 452
Recommendations for geochemical exploration in high mountain areas 467
Conclusions 470
PART IV: DRAINAGE GEOCHEMISTRY FOR SPECIFIC APPLICATIONS 472
Chapter 13. Drainage geochemistry in contaminated terrains 474
Introduction 474
Major sources of contamination and their impact on drainage samples 479
Identification and discrimination of contaminated samples 506
Diagnostic signatures of contaminants 521
Conclusions 523
Chapter 14. Drainage geochemistry in gold exploration 526
Introduction 526
Background 526
Geology of gold deposits 527
Geochemistry of gold in the surface environment 528
Sedimentology of gold in drainage sediments 535
Sample representativity considerations 548
Analysis of geochemical samples for gold and pathfinders 560
Case histories 561
Discussion and conclusions 580
Design of gold exploration programmes using geochemistry 581
Acknowledgements 584
Chapter 15. Drainage geochemistry in uranium exploration 586
Introduction 586
Geochemical considerations 587
Practical considerations 593
Case histories 596
Discussion 608
Conclusions 626
Chapter 16. Selective extractions and contrasting sample media in drainage geochemistry 628
Introduction 628
Partial dissolution of stream sediments 629
Physically-separated fractions of stream sediments 636
Contrasting sample types 638
Discussion and conclusions 659
References 662
Author index 736
Geographical index 758
Mineral deposit index 766
Subject index 770