Geology Geochemistry And Formation Of Supergene Mineral Deposits In Deeply Weathered Terrain
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Geology, Geochemistry and Formation of Supergene Mineral Deposits in Deeply Weathered Terrain
This book provides a comprehensive overview of the major supergene mineral deposits formed in intensely weathered lateritic terrains. It discusses both contemporary and pre-existing supergene deposits, describing their geological, mineralogical and geochemical characteristics. Supergene processes of enrichment are those that occur under ambient near-surface conditions, compared to hypogene processes mostly at depth under higher temperatures and pressures. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. Descending meteoric waters oxidize the primary (hypogene) minerals and redistribute the chemical elements. Residual supergene enrichment occurs as a physical process when the predominant rock-forming minerals oxidize and dissolve, concentrating ore elements hosted in resistant stable minerals; absolute chemical enrichment occurs when the ore elements themselves are leached and migrate in groundwater and precipitate due changes in the pH, oxidation potential and chemical composition of water. These processes can enrich commercially important elements to produce orebodies formed entirely by supergene processes. These include Al (bauxite), Fe ore, Ni-Co laterites, kaolinite, REE (clay deposits), Nb and REE (on carbonatites), base metals (secondary sulfides and oxidate minerals including gossans), gold and surficial U (in calcretes).
Regional Studies and Specific Deposits
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.
Metals and Society
This book is a comprehensive overview of economic geology for the general geologist and anyone else interested in the minerals industry and the global supply of raw materials. It includes some thought-provoking statements and questions for discussion on globalisation and current practices in the minerals industry. In the second edition, all chapters have been extensively revised, and a new author has been added to increase coverage of some mineral deposits and topics. The economic issues surrounding the exploitation of mineral resources is discussed in three of the six chapters of the book. It deals with issues that are commonly addressed in current science reporting – the rate of exploitation of natural resources, the question of when or if these resources will be exhausted, the pollution and social disturbance that accompanies mining, the compromises and challenges that arise from the explosion in demand from China, India and other rapidly developing countries, and the moral issues that surround mining of metals in lesser-developed countries for consumption in the “first-world” countries. The book will be useful both as an introductory text for students in the earth sciences and a reference volume for students, teachers and researchers of geography, economics and the social sciences.