Regional Studies and Specific Deposits, Volume 13

Chapter 1. The Geological Association of Coal and Metallic Ores - A Review

Introduction

Categories of Coal-Ore Association

Metallic Ore Substance Directly within the Coal Seam

Uraniferous Lignites Outside of North America

Uraniferous Coals (Braunkohle to Anthracite)

Metallic Ores in Coal Association, Repetitively Present in Close Proximity to the Coal Seams

Metallic Ores in Coal Association or Adjacent to it, Accidentally Present

Metallic Ores in a Proximal Facies of Coal Associations

Metallic Mineralizations Related to the Basement on which the Coal Association Rests

Interaction of Coal and Metamorphism, Metasomatism, Igneous Intrusion: Metallogenic Implications

Spontaneous Coal Burning and Thermal Metamorphism

Contact Metamorphism/Metasomatism at Coal/Igneous Dikes and Sills Contacts

Contact Metamorphism/Metasomatism at Coal/Granitic Intrusion Contacts

Regional Metamorphism of Coal

Coal, Ores and Evolution

References

Chapter 2. Genesis of Iron Ore in Banded Iron-Formation by Supergene and Supergene-Metamorphic Processes - A Conceptual Model

Introduction

General

The Basic Conceptual Model for BIF-Derived Iron Ores

Definitions of Controversial Terms

Genesis of BIF-Derived Iron Ores

Literature Survey and Compilation of Genetic Models

Literature Features of Iron-Enrichment Ores

Genetic Models for BIF-Derived Ores - Discussion

The Hamersley Iron Province of Western Australia

General

Brief Review of Geological Investigations of Ores and BIFs

Geology of the BIFs

Formation of Ore by Supergene Processes

Textural Features of BIF

Effects of Supergene Processes on BIF Minerals

Supergene Ore Textures - Macroscopic Features

Modifications to Ore by Continuing Supergene Processes

General

Leaching of Goethite

Dehydration of Goethite

Ferricrust - Ferruginous Duricrust

Metamorphic and Post-Metamorphic Modifications to Supergene Ore

General

Regional Metamorphism

Formation of Magnetite During Regional Metamorphism

Contact Metamorphism

Textural Relationships and Interpretations

Metamorphism - Concluding Statement

Geologic and Meteoric Controls of Supergene Enrichment

General

Stratigraphic Thinning Due to Enrichment

Material Balance Between BIF and Ore

Mobility of Iron and Silica - Ore-Forming Rates

Oxidation of Iron at Depth - The Electrochemical Model

Specific Factors in Supergene Enrichment

The Environment of Supergene Enrichment

Reconstruction of an Ore Body - A Model for a Supergene Deposits

Chronology of Ore Formation

General

Stratigraphic Evidence for the Age of the Oldest Supergene Ores

Hamersley Platform

Supporting Evidence for the Age of the Oldest Supergene Ores

Later Ore Events

Phosphorus in BIF and Ore

General

Phosphorus in BIF

Phosphorus in Weathered BIF and Ores

Model for Distribution of Phosphorus in BIF-Hosted Enrichment Ores

Application of Theory

The Pilbara Iron Ore Classification (PIOC)

Exploration for High-Grade Ores

Discussion

Conclusion

Acknowledgments

References

Chapter 3. Mineral Zoning in Sediment-Hosted Copper Deposits

Introduction

Stability Relationships Between Cu and Cu-Fe Sulfide Minerals

Pyrite Replacement and Zoning Sequences

Mass Transfer Modeling as Applied to Problems of Sulfide Zoning

Transport of Copper in Aqueous Solution

Other Approaches to the Study of Reaction/Transfer Problems

General Remarks

Coupling, Feedback, Instability and Self Organization

Modeling Cu-Fe Sulfide Zoning

Overview

Simulations

Discussion

Remarks on Transport-Reaction Modeling

Conclusions

References

Chapter 4. Gossans

Introduction

Historical Background

Definitions

Processes of Gossan Formation

Sulphide Oxidation

Formation of Secondary Minerals

Behavior of Gold

Sorption Processes

Leaching

Effect of Wallrock and Gangue Minerals

The Influence of Hydrology, Climate and Geomorphology

Gossan Maturity

The Constitution of Gossans

Mineralogy

Textures

Lack of Textural Development

Colour

Geochemistry

IsotopiC Composition

The Evaluation of Gossans

Field Observations

Sampling

Preparation of Samples for Laboratory Study

Laboratory Techniques of Gossan Appraisal

Mineralogy

Texture

Case Histories

Conclusions

Acknowledgments

References

Chapter 5. Hydrothermal Karst Phenomena as a Factor in the Formation of Mississippi Valley-Type Deposits

Introduction

Underground Karst Structures - General Comments

Hydrothermal Karst - Modern Examples

Geologic Setting of MVTD

Host Rock of Ores

Solutional Disaggregation

General Premises

Karstic Nature of Ore Receptacles

Hydrothermal Origin of Sulfides

Relationship Between Hydrothermal Ores and their Karst Receptacles

Mineralization in Disaggregated Rocks - Ammoblastesis

Relationships Between Metasomatic and Karst Ores

Crevice Ores

Review of Other Hypotheses on the Origin of Karst Ores

Criticism of Hydrothermal Karst Concept

Conclusions and Implications

Acknowledgement

Glossary

References

Regional Studies and Specific Deposits deals with regional studies of strata-bound and stratiform ore deposits. Topics covered include the geological association between coal and metallic ores; the genesis of iron ores in banded iron-formation (BIF) by supergene and supergene-metamorphic processes; mineral zoning in sediment-hosted copper deposits; and the formation of gossans. The role of hydrothermal karst phenomena in the formation of Mississippi Valley-type deposits is also discussed.

Comprised of five chapters, this volume begins with a review of the geological association of coal and metallic ores, focusing in particular on which metallic accumulations could be expected to be possibly present, within or close to the coal. The next chapter examines the origin of strata-bound enrichment deposits derived from BIF and presents the basic conceptual model for BIF-derived iron ores. The evolution of sulfide mineral zonation in low-temperature, sediment-hosted copper deposits is then evaluated. The book also describes the processes underlying the formation of gossans before concluding with an analysis of the hydrothermal karst phenomena as a factor in the development of Mississippi Valley-type deposits.

This handbook will be useful to students, practitioners, and researchers in the fields of energy and earth sciences, mineralogy, mining, and metallurgy.