Mineralogy, geochemistry and diagenetic evolution of continental clastic proterozoic basins. The example of the Jotnian in the Baltic shield. Implications on the genesis of unconformity related U-deposits

The Satakunta and Muhos basins in Finland are Mesoproterozoic (Jotnian in Fennoscandia, Riphean in Russia) clastic basins unconformably overlying Paleoproterozoic metamorphic basements. These basins share similarities with the Athabasca (Canada) and Kombolgie (Australia) basins, which are associated with large unconformity-related uranium deposits. The aim of the study is to characterize their mineralogy and geochemistry and to compare them to the mineralized basins. The samples for this study have been taken from existing drill cores stored at the Loppi drill core depot of the Geological Survey of Finland. Geological setting, characteristics of the basement and the sediments, sandstone geochemical characteristics are reported. Degree of the sediments' maturity, pH and redox conditions, P-T conditions of the thermal events and evidence of hydrothermal alteration are discussed. It is concluded that extreme immaturity of Satakunta and Muhos basin sediments, strong silicification and weak diagenetic fluid circulation are unfavourable for significant U-deposit associated to them