Uranium mineralization associated with albitization in a Paleoproterozoic granite: Example of the Saraya granite, (Eastern Senegal, West Africa)

The uranium mineralization occurrences hosted within the Saraya episyenites (hydrothermally altered granites) were discovered between 1985 and 1960 during an airborne regional survey conducted by prospectors from the Commissariat à l'Energie Atomique (C.E.A). Following this discovery, a strategic and tactical exploration program led by the Compagnie Générale des Matières Nucléaires (COGEMA) was undertaken between 1974 and 1984, which significantly contributed to the improved delineation of these occurrences. Recent investigations carried out by AREVA from 2008 to 2010 have facilitated the collection of fresh materials from drill core samples of mineralized zones, along with detailed petro-mineralogical and geochemical studies.

Our results show that the uranium mineralization developed from peraluminous leucogranitic granites, initially characterized by albitization is associated with dequartzification during the episyenitization phase. This dequartzification resulted in the formation of vugs that were subsequently filled by chlorite, uranium minerals, including coffinite, uraninite, and other uranium oxides, along with Ti-oxides (rutile and anatase). Post ore-stage alteration led to the development of carbonate minerals and argillization, in association with the leaching of the primary uranium mineralization, as well as the remobilization of carbonaceous matter. Enrichment in Medium Rare Earth Elements (MREE) and Heavy Rare Earth Elements (HREE), as well as in yttrium, was also observed within the mineralized facies.

This mineralization event is part of a broader event spanning from the Paleoproterozoic to the Mesoproterozoic, which also affected other uranium provinces in central Ukraine, Canada, China, Australia, India, southern Morocco, and Guyana (Cuney et al., 2008).