Frio Shear Zone: investigation of a major tectonic boundary in South Victoria Land, Antarctica

The Frio Shear Zone (FSZ) is a 4km wide, ductile shear zone, forming the boundary between two structural blocks, Walcott Block to the southwest and Dry Valleys Block to the northeast, in South Victoria Land, Antarctica. This boundary is thought to be very important as the two blocks it separates are characterised by different magmatic, metamorphic and tectonic histories. The study aimed to examine the nature of the FSZ structurally, and to document the extent of the differences across the shear zone determining the detailed relationships between the sedimentary rocks to the northeast and southwest. The FSZ was examined at Frio Peak and Chancellor Ridge area petrographically and structurally and the extent of the differences across the shear zone was documented. Detailed traverses along ridges where the rocks comprising the shear zone are exposed were undertaken with fieldwork mainly involving documenting lithologies, structural orientations and identifying localised phases of deformation within the main phase of shearing. A comprehensive suite of rocks across the shear zone was collected.