Geology of the Thelon tectonic zone in the Moraine Lake area, District of Mackenzie, Northwest Territories: The definition and significance of lithologic, structural and metamorphic changes across the boundary between the Slave and Churchill structural provinces.

摘要

The boundary between the Slave and Churchill structural provinces separates polydeformed, Proterozoic granulite-facies gneisses and granitoid rocks of the Churchill Province from the Archean Slave Province that was metamorphosed and weakly deformed as a result of juxtaposition at ca. 1.96 Ga.;West- to west-northwest-directed, post-granulite-facies ductile thrusts in the rocks east of the Slave - Churchill boundary exhumed granulites from depths of 20-25 km, tectonically buried the eastern margin of the Slave Province and juxtaposed the Slave and Churchill structural provinces. The metamorphic effect of thrusting on the Slave Province was a medium-grade, medium-pressure metamorphism defined as M;Subsequent to ductile thrusting in the granulite terrane, the Slave - Churchill boundary and rocks on both sides of the boundary were deformed in a 15-km-wide north-northeasterly-striking ductile shear zone. Kinematic indicators in the zone demonstrate that the sense of shear is dextral transcurrent. M;Kinematic transition from thrusting to transcurrent displacement is consistent with a model of progressive, heterogeneous strain that resulted from continued approximately east-west shortening across and along the north-northeasterly-striking margin of the Slave Province. Post-thrusting transcurrent displacement became significant when shortening could no longer be accommodated by crustal thickening.;West of the boundary, the Slave Province includes Archean supracrustal gneisses and granitoid gneisses that were metamorphosed in the Archean (M;Thrusting and exhumation of granulite-facies rocks in the Churchill Province was the result of a collision between the Slave craton and an Archean terrain to the east that is in part preserved as the Queen Maud Block. This model suggests that the Slave - Churchill boundary is more analogous to a structure like the Main Central Thrust of the Himalayas than to a suture between collided continents.