MECHANISM OF EMPLACEMENT OF THE CANNIBAL CREEK GRANITE WITH SPECIAL REFERENCE TO TIMING AND DEFORMATION HISTORY OF THE AUREOLE

The ovoid Cannibal Creek Granite consists of a minor phase emplaced during the regional D3 deformation and a major phase emplaced during the regional D4 deformation. It possesses an intense contact-parallel foliation on its margin and in the adjacent porphyroblastic schist that formed through partitioning of the shearing component of deformation against the crystallized pluton margin during synchronous E-W D4 shortening. During this process a pre-existing shallow S3 foliation was updomed around the pluton and re-used/reactivated by D4 shear, with associated dissolution of quartz, resulting in the formation of an ovoid closed foliation around the pluton. Thus the granite is located within a domal-shaped, approximately N-S-trending, pluton-scale F43 antiform that formed synchronous with emplacement. Three successive stages of porphyroblast growth record the history of processes operating during progressive emplacement and the structures that developed. Space problems were solved through upward movement of the rocks above the granite due to movement on the S4 cleavage as well as on pre-existing subvertical bedding and cleavages, and by reactivation of steep D2 faults.