Archean and Early Proterozoic Events Along the Snowbird Tectonic Zone in Northern Saskatchewan, Canada

Abstract

The Snowbird tectonic zone is a major boundary structure in the Canadian shield, separating rocks of the Rae and Hearne lithostructural domains. Field investigations along portions of the Snowbird tectonic zone exposed in Northern Saskatchewan have revealed a major granulite facies mylonite belt that records deformation and metamorphism at several intervals in the Archean and early Proterozoic. Early assemblages are dominated by granulite grade gneisses that were deformed in a major left-lateral strike-slip shear zone at ca. 3200 Ma. The major episode of deformation along this portion of the Snowbird tectonic zone occurred at ca. 2600 Ma, again at granulite facies in a dominantly right-lateral strike-slip shear zone. Little evidence of Proterozoic deformation is recorded within this region of the Snowbird tectonic zone itself, but neighboring rocks in the Rae province to the west preserve granulite grade right-lateral fabrics dated at ca. 1850 Ma. These constraints suggest that the Snowbird tectonic zone was a focus of major regional deformation throughout the middle and late Archean, but that regional deformation was partitioned outward to the surrounding Rae (and Hearne?) province rocks during the early Proterozoic. These data suggest that the Snowbird tectonic zone was not a major continental suture zone in the early Proterozoic.