Genesis of Multifarious Uranium Mineralization in the Beaverlodge Area, Northern Saskatchewan, Canada

Abstract

The Beaverlodge area in Saskatchewan, Canada, hosts numerous fault-controlled uranium deposits that are geochemically and structurally complex because of multiple deformation events. Field, petrographic, and geochemical data indicate there are six distinct styles of uraninite mineralization, with five temporally distinct mineralization events. The earliest two styles of mineralization are hosted in cataclasite and veins that formed at ca. 2.29 Ga from 300°C fluids derived from retrograde metamorphic processes during late stages of the early Paleoproterozoic Arrowsmith orogen. The second style of mineralization is restricted to the albitized granite of the Gunnar deposit and formed between ca. 2.3 and 1.9 Ga from reducing magmatic-hydrothermal fluids near 300°C. However, uranium associated with this metasomatic style of mineralization is overprinted by the more significant breccia-vein and minor volcanic-type mineralization, thus the Gunnar deposit contains three styles of mineralization. Reactivation of major fault zones resulted in breccia-type mineralization, the dominant mineralizing event, at ca. 1.85 Ga, from Ca-Na-F-rich fluids at about 330°C during the postpeak Thelon-Taltson orogen and early stages of the Trans-Hudson orogen. Inversion followed by subsidence resulted in formation of the Martin Lake basin, a successor basin filled with ca. 5 km of arkose, conglomerates, siltstone, and alkaline mafic flows and sills that formed during back-arc extension following peak Trans-Hudson orogeny. Volcanic-style mineralization at 1.82 Ga. resulted from late exsolution of magmatic fluids from the alkaline mafic dikes. Overlying the Martin Lake basin are outliers of the Athabasca Formation associated with the last stage of uranium mineralization, at ca. 1.62 Ga, from oxidizing basinal brines near 230°C. Subsequent erosion of the Athabasca and Martin Lake basin rocks and weathering of the deposits resulted in secondary uranium minerals and late veins.Multiple stages of deformation and fluid overprinting suggest that uranium mineralization record progressively higher levels in the crust. Each successive event overprinted to varying degrees the previous events. Although the Beaverlodge area represents several distinct mineralizing events, the major event is the brecciatype that occurred at 1.85 Ga. The other styles of mineralization are minor, and their presence complicates both exploration and our understanding of ore deposit genesis in the area.

Structural controls and metallogenic model of polyphase uranium mineralization in the Kiggavik area (Nunavut, Canada)

“…U0 is observed in significantly mineralized brecciated rocks, and would have been an efficient and easily available source of U for basinal brines during their circulations in U0-mineralized basement structures. The presence of a pre-Thelon-basin source of uranium is comparable to what is described near the Athabasca basin: volcanic and metasomatic uranium in the western margin (Dieng et al 2013(Dieng et al , 2015 or magmatic and metamorphic uranium described in the eastern margin (Mercadier et al 2013).…”

Geochronology of Uraninite Revisited

“…The discrepancy observed between the two dating methods for the Foster Lake uraninite, with a much younger upper intercept 207 Pb/ 206 Pb age of 500 ± 140 Ma based on significantly discordant analyses may represent later fluid movement related to the Appalachian orogeny that overprinted the original mineralization age [68]. However, the secondary Pb-Pb age still retains the remineralization age of 1239 ± 170 Ma as the uraninite remained closed and did not incorporate U and/or Pb from external sources (i.e., aliquots simply moved along one discordia).…”