Using along-strike variation in strain and kinematics to define the movement direction of curved transpressional shear zones: An example from northwestern Superior Province, Manitoba

摘要

A review of current understanding of structures in shear zones reveals that correlating the orientation of stretching lineations with movement direction, once a common practice based on the simple shear model, is not generally applicable to transpressional zones. It is difficult to determine the movement direction of a transpressional zone based on internal structures. We show that the movement direction can be better defined by considering the variation in strain geometry and kinematics of differently oriented and kinematically related shear zones or different segments of a curved shear zone. Application of this method to a shear zone in the northwestern Superior Province of Manitoba shows that the movement direction there is approximately north-south, in contrast to a commonly held view for similarly oriented shear zones in the Superior Province that the movement direction is approximately east-west.