Timing and kinematics of crustal movement in the Northern Superior superterrane: Insights from the Gull Rapids area of the Split Lake Block, Manitoba

Abstract

The Northern Superior superterrane in the northwestern Superior Province is characterized by an ancestry back to ca. 3.8 Ga and contains one of the largest and best-preserved high-grade terranes on Earth, the Pikwitonei Granulite Domain and its northeast extension, the Split Lake Block. This high-grade terrane occurs in the Superior Boundary zone, a complex transitional zone that bounds the northwestern margin of the Archean Superior Province and separates it from the Paleoproterozoic crust of the Trans-Hudson Orogen. Detailed structural and geochronological data from the exceptionally well-exposed Gull Rapids area at the eastern margin of the Split Lake Block shows evidence for both Neoarchean (Kenoran) and Paleoproterozoic (Trans-Hudson) deformation and metamorphism. More importantly, it indicates that the uplift of the Split Lake Block was achieved by shear zone movement in the Neoarchean, not in the Palaeoproterozoic, synchronous with peak metamorphism and dyke emplacement at ca. 2686 Ma. This indicates that uplift of the high-grade domains in the Northern Superior superterrane was neither related to its collision with the North Caribou superterrane at ca. 2.72 Ga, nor to the ca. 1.8 Ga Trans-Hudson orogeny. Instead, this uplift might have occurred during a major period of Superior-wide active tectonism toward the end of the Neoarchean Kenoran orogenesis.