Ancient collisional continental margins in the Canadian Shield: geophysical signatures and derived crustal transects

Abstract

Paleomagnetic studies suggest that large-scale displacements of now contiguous terranes had occurred, thereby stimulating the search for appropriate sutures. Distinctive gravity signatures pointed to the presence of deep crustal breaks along boundaries between structural provinces, and seismic studies indicated differences in crustal thickness on either side. The breaks were interpreted as collisional sutures. Compelling evidence for plate collision comes from the Cape Smith Belt, where ophiolitic thrust sheets complete with a diagnostic sheeted dike complex and representing the oldest known example (1998 Ma) of oceanic crust in North America were identified. Geophysical transects across several suture zones provide insights into the large-scale crustal morphology of sutured margins. Examples include the Grenville Front, Labrador Trough, Cape Smith Belt, and Wopmay Orogen. -from Author