Regolith Exploration Geochemistry in Tropical and Subtropical Terrains

About this book

The use of exploration geochemistry has increased enormously in the last decade. The present volume specifically addresses those geochemical exploration practices appropriate for tropical, sub-tropical and adjacent areas - in environments ranging from rainforest to desert. Practical recommendations are made for the optimization of sampling, and analytical and interpretational procedures for exploration according to the particular nature of tropically weathered terrains. The underlying theme is the recognition that regions between 35#N and 35#S in particular have a common history of deep chemical weathering and lateritization during the late Mesozoic and early Tertiary. This has had a profound and lasting effect, so that the surface geochemical expressions of mineralization throughout these regions have many similar features, with local modification due to more recent weathering under changed climates. The volume discusses the data derived from numerous research and case studies in terms of exploration and dispersion models based on the weathering and geomorphological history. The models permit valid comparisons between equivalent terrains that may be geographically widely separated and situated in quite different climatic environments. The basis of the volume is to view geochemical dispersion within the context of a genetic understanding of the evolution of landforms and the regolith ( i.e. landscape geochemistry ) and to develop exploration procedures based on this understanding. This book should be of interest to exploration geochemists, economic geologists, soil scientists, geomorphologists and environmental geochemists.

Contents

Preface. List of Contributors. Introduction. I: Characteristics of Tropically Weathered Terrains. Climate, Geomorphological Environment and Geochemical Dispersion Models (C.R.M. Butt and H. Zeegers). Chemical Weathering (J.-J. Trescases). The Ferruginous Laterites (D. Nahon and Y. Tardy). Soil Formation in Tropicallly Weathered Terrains (Y. Lucas and M. Chauvel). The Chemical Mobility and Transport of Elements in the Weathering Environment (M.R. Thornber). Physical Weathering and Dispersion (C.R.M. Butt). II: Gossan Formation and Gossan Surveys. The Mechanisms of Sulphide Oxidation and Gossan Formation (M.R. Thornber and G.F. Taylor). Gossan and Ironstone Surveys (G.F. Taylor and M.R. Thornber). III: Exploration in Areas of Low to Moderate Relief. Seasonally Humid Tropical Terrains ( Savannas ) (H. Zeegers and P. Lecomte). Humid Tropical Terrains ( Rainforests ) (P. Lecomte and H. Zeegers). Semi-Arid and Arid Terrains (C.R.M. Butt). IV: Exploration in Areas of Moderate to High Relief. Dissected Terrains and Tropical Mountains (C.R.M. Butt and H. Zeegers). V: Specific Commodities and Techniques. Diamond Exploration in Tropical Terrains (G.P. Gregory and A.J.A. Janse). Uranium Exploration in Tropical Terrains (F. Bianconi and K. Kogler). The Geochemistry of Gold in Lateritic Terrains (D.J. Gray, C.R.M. Butt and L.M. Lawrance). Heavy Mineral Surveys in Exploration of Lateritic Terrain (G. Friedrich, A. Marker and M. Kanig). VI: Synthesis and Conclusions. Summary and Procedural Recommendations. (H. Zeegers and C.R.M. Butt). Appendix 1: Sample Media used in Geochemical Exploration in Tropically Weathered Environments: Definitions and Use. Appendix 2: Sample Preparation and Analysis. Appendix 3: Profile Nomenclature and Glossary. Author Index. Place Index. Subject Index.

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