Basinal fluid flow systems and their relationships with mineralization - driving forces, paths and traps

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Many mineral deposits formed from circulation of geologic fluids in sedimentary basins. Understanding the operation mechanisms of these fluid flow systems, including their driving forces, paths and reaction with various lithologies and/or fluids leading to precipitation of ore minerals (traps), is important for mineral exploration. The primary goal of my research is to enhance our understanding of these basinal mineralization systems and to establish tools or geologic criteria that can help identify favorable locations for mineralization. The proposed research focuses on uranium mineralization associated with the Athabasca Basin in northern Saskatchewan, which contains the richest uranium deposits in the world. Since the first discovery of this type of uranium deposits (named unconformity-type because they occur near the unconformity between the basin and its basement) in the Athabasca Basin nearly 50 years ago, extensive studies have been carried out and a comprehensive mineralization model (called the diagenetic-hydrothermal model) has been established. Generations of geoscientists have been continuously making effort to improve the mineralization model in order to better guide exploration and increase the success rate. In my previous Discovery Grant, my research team has found evidence suggesting that the uranium mineralization in the Athabasca Basin may have taken place at much shallower depths ( 5km), and that the limited distribution of uranium-rich fluids, rather than the availability of reducing agents required to precipitate uraninite (as implied in the conventional exploration model), was the key factor determining whether or not and where uranium deposits may form. Furthermore, it was found that fluid flow related to uranium mineralization was controlled by reactivated basement faults, not only because these faults may be used as conduits, but also because they can control the location of fluid convection cells and can episodically provide the driving force for fluid flow that can explain the ingress and egress flow patterns demonstrated by the mineralization features. Based on these findings, we propose to carry out new research to further delineate the timing of uranium mineralization and basinal brine (parent of the ore-forming fluid) development, the possible paths of the brine from the upper part to the basal part of the basin and the basement, the hydrodynamic relationships between the basinal brine and basement faults (both shallow- and deep-seated), and physical and chemical traps that promote channeling of uranium-rich fluids and their reaction with reducing agents (either in fluid or rock). The results will refine the mineralization model to better guide exploration. The research is important for Canada as the second largest uranium producer in the world and one of the leading countries in uranium geology study.