Geology, Geochemistry and Formation of Supergene Mineral Deposits in Deeply Weathered Terrain

This book provides a comprehensive overview of all major supergene mineral deposits. It discusses both contemporary and classic mineral deposits, drawing on an extensive database that provides the geological, mineralogical, and geochemical characteristics of supergene mineral deposits. Supergene processes or enrichment are those that occur comparatively near to the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary (hypogene) minerals and redistribute the chemical elements. Supergene enrichment occurs when elements that have been leached from the oxidized rock or ore migrate downward in groundwater and react to changes in the pH, oxidation potential, and chemical composition of water or interact with substrate rock. In these environments, commercially important chemical elements can be enriched to produce an orebody formed entirely by supergene processes. This includes Al (bauxite), Fe (pig iron), Li (brines or evaporites), U (calcretes), REE (clay deposits), base metals (secondary sulfides or gossans), silver, and gold.