The significance of the silicification zones for the formation of unconformity-related uranium deposits in the Athabasca basin, Saskatchewan

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It is becoming increasingly difficult to discover new uranium deposits in the Athabasca Basin due to the increasing depth of undiscovered mineralization, which necessitates an even better understanding of their formation conditions and setting. One feature of these deposits that has never been systematically studied is the silicification zone, or "cap", present immediately above the deposits in the Athabasca Group sandstones. The purpose of this project is to ascertain what the role, if any, this silicification played in the formation of the unconformity-related uranium deposits and to establish how it can affect exploration efforts. To achieve these goals, the project will focus on two main topics: (1) Establishing the three-dimensional spatial extent of the silicification zone. This will be done using drill logs available at AREVA and in the public domain. Two main possibilities are: the silicification zone is strictly local and situated directly above a deposit, or it occurs on a regional scale and is not directly related to a deposit. (2) Establishing the physical and chemical conditions of formation and the temporal relationship between the silicification zone and the deposits' formation. This will be achieved using mostly mineralogical and geochemical methods, in particular stable isotopes on quartz overgrowths and quartz filling pore space, using Secondary Ion Mass Spectrometry (SIMS), and fluid inclusions. It is anticipated that the findings of this project will help relate, spatially and temporally, the silicification zone with style and intensity of alteration, desilicification, structural setting, petrology, and most importantly, uranium deposition. The area studied will primarily be the Martin Lake U prospect, which exhibits well-developed silicification zones, with possible extension to the McArthur River Zone 2 and Centennial deposits. Once the significance of the silicification for uranium deposition has been established, the results will be assessed, in conjunction with AREVA geologists, in terms of increased exploration efficiency.