Three dimensional strain distribution and deformation temperature interpreted from quartz microstructures and petrofabrics in the Okanagan Valley shear zone, southern Canadian Cordillera

Date created: 
Quartz crystallographic preferred orientations (CPOs)
Quartz recrystallization mechanisms
Deformation temperatures
Okanagan Valley shear zone (OVsz)
Shuswap metamorphic complex

The Eocene Okanagan Valley shear zone (OVsz) is a ~1-1.5 km thick, <30° west-dipping, extensional ductile to brittle detachment that facilitated exhumation of the southwestern Shuswap metamorphic complex in the southern Canadian Cordillera. A predominantly top-to-the-WNW sense of shear is confirmed by meso- and micro-shear-sense indicators. Quartz a-axis patterns obtained from crystallographic preferred analysis suggest general plane strain conditions with some constriction in the upper 150m of the shear zone. Deformation temperatures derived from recrystallization mechanisms and crystallographic orientations of quartz progressively increase from ~280 to >650 ° down the exposed structural section. The observed telescoping of isotherms in the immediate footwall of the OVsz is interpreted to be the result of detachment-parallel penetrative general shear flow in predominantly plane strain deformation during progressive exhumation. This thesis discusses the possible processes that could have been responsible for this intense compression of isotherms in the immediate footwall of the OVsz.

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Senior supervisor: 
Dan Gibson
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.