Geology Seminar Series

The Uranium City area of northern Saskatchewan records 1.5 Ga of geological history within the southern Rae Province of the Canadian Shield. Circa 3.0 and 2.6 Ga granitoids preceded a 2.37 Ga metamorphic event attributed to the Arrowsmith orogeny. The emplacement of 2.3 Ga post-orogenic granitoids overlapped initial deposition of the Paleoproterozoic Murmac Bay Group, which included a lower succession of basal conglomerate, quartzite, dolostone, iron formation, and basalt, and an upper component dominated by pelitic rocks deposited after 2.0 Ga. Widespread gabbros, considered cogenetic with the basalts, and komatiitic intrusive rocks cut the basement granitoids and lower Murmac Bay Group. Two thermotectonic events at 1.94-1.92 Ga and 1.91-1.90 Ga, attributed to the Taltson and Snowbird orogenies, respectively, produced east-west and overprinting northeast-trending regional fabrics and widespread shearing. The cumulative metamorphic gradient ranges from greenschist to granulite facies, and partial melting has led to the development of anatectic granites. Following a period of uplift and erosion, deformation attributed to the ca. 1.82 Ga Trans-Hudson orogeny produced intense brittle-ductile to brittle faulting and fracturing, which created accommodation space for deposition of the subsequently deformed but unmetamorphosed Martin Group, which comprises continental redbeds and intercalated basalts. Mafic dykes, considered cogenetic with the basalts, along with lamprophyres, and a variety of granitoid rocks were emplaced at about 1.82 Ga, coeval with an array of fluid alteration types and the Beaverlodge uranium deposits. Subsequent post-orogenic extension resulted in deposition of the 1.75-1.50 Ga Athabasca Supergroup, the northern extent of which unconformably overlies Murmac Bay Group quartzites at the southern extent of the Uranium City area. This talk illustrates the rocks, and some of the analytical methods used to better characterize and understand them, and shows how ideas and interpretations have changed since their initial description at the time of uranium production in the 1950 and 60s. Tectonic models to explain the geological record of the southern Rae Province continue to evolve.