Rheological behaviour of the crust

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Western British Columbia was constructed by continued subduction of oceanic crust creating magmatic rocks near the margin (similar to what is happening today with the subduction of the Pacific plate beneath the western Cordillera and the consequent build up of volcanoes on the north American margin) and by the accretion of large fragments of rock ('terranes') to the margin. Generally, when terranes collide much of the displacement is taken up by relatively narrow zones of very high strain - consider, for example, the San Andreas Fault.  The purpose of this proposal is twofold: (1) To place constraints on the mechanisms of how rocks deform in these narrow zones, to determine how long-lived these zones are, and to determine the extent and geometry of these shear zones, and  (2) to place better timing constraints and understand the mechanisms that accommodated collision in west central British Columbia. This proposed research combines field mapping of deformed rocks found in collisional regimes, with microstructural analysis of rocks collected from the field, with geochronology (dating the rocks) to better understand the mechanisms of how rocks deform in zones of high strain. A smaller aspect of this proposal deals with experimental rock deformation and how we can use stress-strain data collected from the lab to better understand processes that occur in the Earth.