Himalayan-type escape tectonics along the Superior Boundary Zone in Manitoba, Canada

Abstract

The Superior Boundary Zone separates the Neoarchean Superior Province to the southeast from the Paleoproterozoic Reindeer Zone of the Trans-Hudson Orogen to the northwest. In northern Manitoba, late convergence along the zone in the Paleoproterozoic has previously been interpreted in terms of a promontory model, where the Superior Province indents the Reindeer Zone towards the northwest. We present a modified promontory model that includes a WNW transport direction of the Superior Province and lateral escape of a segment of the Superior Province (the Split Lake Block) along the northern margin of the promontory. The model is based on the kinematics of an array of shear zones along the Superior Boundary Zone that are interpreted as having been active concurrently. Tectonic escape of the Split Lake Block occurred in a manner similar to the extrusion and rotation of the Indochina block along the eastern margin of the Himalayas, but at a much smaller scale. Our model explains shear zone kinematics, but also the curvilinear nature of some of the shear zones and a high component of along-strike stretch along one of the shear zones.