| Summary: | The Black Bay Fault is a major Paleoproterozoic, NE-SW-trending, crustal-scale feature that separates different tectonometamorphic domains of the southern Rae craton in the Canadian Shield. This structure extends from the edge of Lake Athabasca northward for 100’s km into the Northwest Territories and was previously poorly constrained. Prior examination of the fault has been limited to small-scale studies in the Uranium City, SK vicinity. The Black Bay fault has previously been associated with rare-earth element and uranium mineralization in northern Saskatchewan, although this relationship is not fully understood. This thesis has focused on understanding the continuation of the Black Bay Fault into the Northwest Territories based on field mapping conducted as part of the GSC/NTGS GEM2 South Rae project. The observations are broken into three study areas: Tazin River, Insula-Labyrinth Lake and Dymond Lake. The Black Bay Fault has had a cryptic polyphase history. Overall the fault is observed to be a steep, west-dipping structure associated with a strong NE/SW-trending fabric, but there are major disruptions to this trend by two NW-SE-trending segments of this fault. Field observations indicate it was impacted by four main deformational events, D1 to D4. D1 produced sinistral transpression along the fault, resulting in the uplift of the western domains relative to the eastern domains, a steeply west-dipping, NNE-SSW-trending gneissosity and shallowly NE-plunging lineations. D1 is inferred to have occurred ca. 1910 Ma in associated with the Snowbird Orogeny and the collision of the Hearne craton onto the eastern edge of the Rae Craton. D2 is a regionally limited event which modified the geometry of the fault rather than producing deformation along its length and resulted in the development of a left-stepping bend in the fault around Labyrinth Lake and another larger bend around Dymond Lake. D2 fabrics are not observed along the southern extent of the Black Bay Fault. This event remains very poorly constrained but ...
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