Post-Taltson sedimentary and intrusive history of the southern Rae Province along the northern margin of the Athabasca Basin, Western Canadian Shield

Abstract

The southern Rae Province of the western Canadian Shield underwent extensive reworking during Paleoproterozoic time. Widespread granitic plutonism and poorly defined metamorphism resulting from the ca. 2.5 to 2.3 Ga Arrowsmith Orogen was followed by more intense thermotectonic overprints attributed to the 1.99–1.92 Ga Taltson Orogen in the west and ca. 1.91–1.90 Ga tectonic activity associated with the Snowbird Tectonic Zone in the east. The Thluicho Lake Group is a fining-upwards, conglomerate–arkose–argillite succession deposited in an intermontane setting towards the end of the Taltson Orogen. Following deposition, the Thluicho Lake Group underwent two phases of regional folding and greenschist-facies metamorphism marking the latest Taltson and Snowbird overprints, respectively, prior to the emplacement of extensive 1.82 Ga mafic dykes. These depositional constraints support correlation of the Thluicho Lake Group with the lithologically similar Nonacho Group in the Northwest Territories, whereas petrological similarities and coeval emplacement ages indicate that the mafic dykes represent a southeastward extension of the Sparrow dykes. Mafic volcanic rocks geochemically linked to the dykes are intercalated within the Martin Group, a continental redbed succession deposited in trans-tensional basin settings, indicating that deposition was ongoing at 1.82 Ga. Similarities in age, lithological association and depositional setting suggest that the Martin Group is broadly correlative with the Baker Lake Group of the lower Dubawnt Supergroup in Nunavut. Widespread lamprophyre dykes of the type that fed minette volcanic rocks of the Christopher Island Formation in the Baker Lake Group are also spatially associated with the Martin Group. The broadly coeval Hudson granites, which extend over much of the same ground as the lamprophyres in Nunavut, also appear to have analogs in the southern Rae Province. The formation of widespread trans-tensional basins, together with extensive dyke emplacement, implies a period of intense brittle to brittle–ductile deformation throughout the western Churchill Province at about 1.83–1.82 Ga. This deformation is attributed to a broadly east-west stress regime imposed by accretion of the Nahanni-Fort Simpson Terrane to the west, combined with terminal collision in the Trans-Hudson Orogen to the east.