POSTCOLLISIONAL OBLIQUE CONVERGENCE ALONG THE THELON TECTONIC ZONE, NORTH OF THE BATHURST FAULT, NWT, CANADA

The Thelon Tectonic Zone (TTZ) separates the Slave from the Churchill (Rae) structural provinces of the northwest Canadian Shield. Along the TTZ in the Tinney Hills-Overby Lake area, collision was initiated with northwestward overthrusting of granulite-facies gneiss onto the Slave province accompanied by thin-skinned shortening of the Proterozoic cover. In the succeeding transpressive stage, shortening structures assumed a SE-, rather than NW-, vergence; a deformation-front migrated westward into the Slave craton-edge, causing thick-skinned folding of the cover, probably including the detachment; and transpression was partitioned, in craton edge and allochthon, into zones of shortening, shortening + strike-slip, and strike-slip. Ductile deformation along the trace of the late NW-striking brittle Bathurst Fault occurred at this time; this zone links dextral NNE-trending transpressive zones, in which the shortening structures have opposite vergence (SE north of the fault, and NW to the south). The last episode of convergence, tectonic escape, may have been accomplished during brittle deformation on the Bathurst Fault. In the Slave Foreland and the reworked Slave craton-edge, the role of heterogeneous basement deformation is very important. The basement had a complex Archean structure, which was overprinted by systems of Proterozoic shear zones. The bulk strains accomplished by these are expressed as upright folds in the stratiform cover, causing characteristic synclines.