A magnetotectonic study correlating late Archean deformation in northwestern Ontario

Abstract

Late Archean lamprophyre dikes crop out on both sides of the Quetico–Shebandowan subprovince boundary. They post date F1 folds in late Archean rocks (2690 Ma) but their intrusion overlapped with the waning phase of S1 development. S1 developed to varying degrees or is absent in some dikes. Nevertheless, the dikes show a cryptic tectonic fabric in the ferromagnetic minerals revealed by anisotropy of magnetic susceptibility (AMS). This is parallel to S1 in the host metamorphic rocks. Thus, the S1 fabric-forming episode may be correlated from one subprovince to the other using the dike swarm as a chronological marker.