Origins of Gold, Uraninite, Pyrite, and Organic Matter in Conglomerates of Archean and Early Proterozoic Age

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9706279 Ohmoto The goal of this research is to develop a comprehensive model for the formation processes of gold-uranium deposits occurring in conglomerate beds of ~2.8 Ga to ~2.0 Ga and their paleoenvironments. The results of this study will lead to a better exploration model for this most important class of mineral deposits, and to a better understanding of the evolutionary history of the early EarthOs atmosphere and biosphere. The research goal will be achieved by seeking solutions to three major problems: (1) what are the origins of gold, uraninite, and pyrite: detrital, diagenetic, or hydrothermal?; (2) what are the origins of the fluids involved in dissolution/precipitation of gold, uraninite, and pyrite: oxygen-bearing ground water or high temperature hydrothermal fluid?; and (3) what are the origins of organic matter: indigenous microbial mats or extraneous petroleum? Solutions to these three problems will be sought from detailed and systematic investigations of a variety of minerals and organic matter in ore and country rocks in the Witwatersrand district, South Africa, and the Elliot Lake district, Canada. The investigations will focus on micro-scale variations in mineralogical characteristics (morphology, texture, abundance, paragenesis), chemical characteristics (major, trace, and rare earth elements), and stable isotopic characteristics (H, O, C, and S).