The uranium mineralization potential and diagenetic fluid histories of the Proterozoic Yeneena, Sibley and Sioux Basins.

摘要

The genesis of uranium deposits depends largely on the development of diagenetic aquifers and fluid geochemistry, which are related to the diagenetic history of a sedimentary basin. The purpose of this thesis is to determine the diagenetic histories of the Mesoproterozoic Yeneena, Paleoproterozoic Sibley, and Paleoproterozoic Sioux Basins and through comparison with the diagenetic histories of the uranium-rich Paleoproterozoic Athabasca Basin in Canada and Kombolgie Sub-basin in Australia, evaluate the potential of the Yeneena, Sibley and Sioux Basins to host unconformity-type uranium mineralization.; Fluids present during late diagenesis in the Mesoproterozoic Yeneena Basin in Western Australia were approximately 225°C and stable isotopic compositions indicate derivation of the fluids from a mixed meteoric and seawater source, similar to the fluids associated with peak diagenesis and uranium mineralization in the Athabasca Basin and Kombolgie Sub-basin. However, petrographic studies and isotope analyses of mobile Pb indicate that the basal Coolbro sandstone in the Yeneena Basin has remained closed to significant volumes of fluids and thus downgrades the potential for significant unconformity-type uranium mineralization in the area.; Peak diagenetic fluids in the Sibley Basin in Ontario were approximately 150°C and had a dominately meteoric origin, which is in contrast to the higher temperature and mixed meteoric and seawater origin of fluids associated with peak diagenesis and uranium mineralization in the Athabasca Basin and Kombolgie Sub-basin. The temperatures and chemistry of diagenetic fluids, the absence of mobile radiogenic Pb, and thin, segmented diagenetic paleoaquifers in the Sibley Basin are consistent with the basin having a low potential to host significant unconformity-type uranium deposits in the area studied.; Pore waters that were present during peak diagenesis in the Sioux Basin in Minnesota had temperatures of approximately 200°C and stable isotopic compositions consistent with a meteoric source and evaporated seawater. Although peak diagenetic fluids were similar to those associated with peak diagenesis and uranium mineralization in the Athabasca Basin and Kombolgie Sub-basin, leachable Pb isotopic compositions indicate a common source of Pb and thin, discontinous diagenetic paleoaquifers are consistent with a low potential for economic unconformity-type uranium mineralization in the Sioux Basin.