In a reconstructed supercontinent assembly at ~0.9 Ga, the Grenville orogen extends from Scandinavia through North America and Antarctica to Australia. Part of it, the 2000 km long Grenville Province, exposed in the southeastern Canadian Shield, is large enough to allow a comprehensive view of its tectonic character. It has an orogen-parallel zonation: older, reworked crust, representing Archaean and Palaeoproterozoic orogens exposed in adjacent parts of the shield, is restricted to its northwest side; supracrustal and plutonic rocks of Grenvillian age (~1.3-0.95 Ga) are limited to the southeastern half. The latter lie on or within late Palaeoproterozoic and earlier Mesoproterozoic crust, which is the deformed, temporal equivalent of terranes that form a substantial part of the buried North American craton south of the shield. A pre-Grenvillian period of quiescence at ~1.5 Ga may have followed an earlier continental assembly. Grenvillian calc-alkaline igneous rocks, limited in volume and distribution, represent arc accretion that terminated with ocean closure by ~1.2 Ga. New crust was added after continent-continent collision and attendant crustal thickening by emplacement of large gabbro-anorthosite massifs of mantle origin, associated with, and in part responsible for, granitoid magma derived from the lower crust. This magmatism, beginning at ~1.18 Ga, was accompanied or followed by high-grade metamorphism, except in parts of the Grenvillian supracrustal terranes, and by low-angle, thrust-sense, ductile deformation directed toward the north and northwest. Ductile followed by brittle extensional deformation between 1.05 and 1.0 Ga, along with terminal thrust-uplift along the northwest margin of the orogen, represent the closing stages of tectonic activity, leading to unroofing and cooling by ~0.9 Ga. There is little evidence in the Grenville Province for supercontinent break-up until ~600 Ma.
