Plutonism in the southern Abitibi Subprovince; a tectonic and petrogenetic framework

Studies of plutonic rocks in Archean terranes such as the southern Abitibi subprovince have been an important component in the development of an accretionary tectonic model for the Superior province. In the southern Abitibi subprovince, pretectonic ( approximately 2.75-2.70 Ga), low K, tholeiitic calc-alkaline, dioritic to tonalitic plutons (e.g., Bourlamaque batholith; Flavrian pluton) are associated with volcanism and are interpreted to be derived from both partial melting of hydrated mantle during oceanic arc formation and fractionation of tholeiitic to calc-alkaline basalt-andesite. Pretectonic, synvolcanic tholeiitic intrusions (e.g., Dundonald sill, Kamiskotia gabbroic complex: 2.72-2.70 Ga) show in situ fractionation trends, and locally, have mixed magma textures with contemporaneous calc-alkaline granitoids. They are believed to be derived from a midocean ridge basalt (MORB)-like depleted mantle, with little evidence for contamination by an older crustal component. Pre- to syntectonic ( approximately 2.72-2.69 Ga) porphyry and tonalite plutons (e.g., Timmins porphyries, Round Lake batholith) have geochemical characteristics typical of Archean tonalite-trondhjemite suites considered to be derived from melting of basaltic rocks at high metamorphic grades. Late to post-tectonic (