Geochronology of the Gold and Sulfide Mineralization of the Archean Witwatersrand Basin

University Of Arizona, Tucson AZ

Investigators

Abstract

EAR-0308656 Ruiz The Witwatersrand Archean basin has been at the center of Earth-system debates ranging from the oxygen content of the Archean atmosphere to the flux of gold from the mantle. At the heart of these debates is the question of whether sulfide, gold and uranium minerals were introduced into the basin as detrital grains of sedimentary origin or precipitates from hydrothermal fluids. Our recent Re-Os dating study produced convincing isochrons indicating a ca. 3.01 Ga old age. This age requires a detrital origin since the grains are older than the basin, and may support a very reduced--oxygen poor--atmosphere during the Archean. The work, however, is considered controversial due to the limited number of samples studied. This award will expand the set of analyses to more completely characterize gold and sulfide mineralization and answer questions such as the relationship of gold extraction to consolidation of the Kaapvaal craton and the mantle gold flux. Broader impacts include education of a graduate student and international collaboration with the private sector. Placer Dome and Anglogold corporations will provide access, logistic, and some scientific support.