Structural analysis of the Creignish Hills Mylonite Zone, Cape Breton Island, Nova Scotia: implications for Neoproterozoic core complex development along the northern Gondwanan margin?

Juxtaposition of low-grade over high-grade assemblages in several peri-Gondwanan basement blocks in central Cape Breton Island suggests that the Creignish Hills Mylonite Zone is part of a series of regional low-angle detachments with a core complex geometry. Similar ductile shear zones with easterly components of shear and low-angle pre-Carboniferous orientations also place low-grade over high-grade rocks in southern New Brunswick and the Cobequid Highlands of mainland Nova Scotia. Dated at ca. 565-540 and 605 Ma, respectively, they suggest repeated late Neoproterozoic detachment in the peri-Gondwanan arc(s). Detachment broadly coincides with the termination of arc magmatism and may reflect ridge-trench collision.