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Gold in 2000
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Archean Rare-Metal Pegmatites in Zimbabwe and Western Australia
Lithium-cesium-tantalum (LCT) pegmatites are important resources for rare metals. For Cs, only the LCT pegmatites with the zeolite group mineral pollucite at Bikita (Zimbabwe Craton) and Tanco (Superior Province Craton) are of commercial importance. Common characteristics of world-class LCT pegmatite deposits include their Meso- to Neoarchean age and geological setting within greenstone belt lithologies on Archean Cratons. This study presents the first coherent and comparative scientific investigation of five major LCT pegmatite systems from the Yilgarn, Pilbara and Zimbabwe Craton. For the evaluation of their Cs potential and of the genetic concepts of pollucite formation, the pegmatites from Wodgina, Londonderry, Mount Deans and Cattlin Creek were compared to the Bikita pollucite mineralization. The integration of the new data (e.g., geochronological and radiogenic isotope data) into the complex geological framework: 1) enhances our knowledge of the formation of LCT pegmatite systems, and 2) will contribute to the further exploration of additional world-class LCT pegmatite deposits, which 3) may host massive pollucite mineralisations.
Ore Deposits in an Evolving Earth
Ore deposits form by a variety of natural processes that concentrate elements into a volume that can be economically mined. Their type, character and abundance reflect the environment in which they formed and thus they preserve key evidence for the evolution of magmatic and tectonic processes, the state of the atmosphere and hydrosphere, and the evolution of life over geological time. This volume presents 13 papers on topical subjects in ore deposit research viewed in the context of Earth evolution. These diverse, yet interlinked, papers cover topics including: controls on the temporal and spatial distribution of ore deposits; the sources of fluid, gold and other components of orogenic gold deposits; the degree of oxygenation in the Neoproterozoic ocean; bacterial immobilization of gold in the semi-arid near-surface environment; and mineral resources for the future, including issues of resource estimation, sustainability of supply and the criticality of certain elements to society.
