Kinematic Analysis And Metamorphic Character Of A Shear Zone In The Thelon Front, Artillery Lake Area, District of Mackenzie, N.W.T.

Abstract

<p>The Artillery Lake area is diagonally bisected by the north-northeasterly trending Thelon Front. The best single surface feature to represent the Thelon Front is the "straight zone" which is a zone of porphyroclastic metasediments that also contains the study area. Kinematic indicators observed in the study area include extensional shear surfaces, C&S fabric, mica "fish", asymmetrical porphyroclast tails, asymmetrical folds, microfaulted porphyroclasts and secondary quartz subgrain foliations. Kinematic analysis of these features has shown that right lateral simple shear displacements and "east-side-up" vertical shear displacements have been accommodated within the rocks of the study area. The displacement senses determined by kinematic analysis are consistent with the regional data indicating progressively deeper exposures of structural levels to the east which suggests vertical motions localized at the domain boundaries. The stretching lineation present in the area is a combination of passive and direct extensions due to sub-vertical motions in the shear zone. A transition from early-ductile to late-brittle feldspar deformation textures indicates that metamorphic conditions during initial deformation were at epidoteamphibolite facies and relaxed during the later stages of deformation to greenschist facies. </p>