Mid-Proterozoic deformational and intrusive events along the Grenville Front in the Sudbury-Killarney area, Ontario, and their implications

The Grenville Front marks the northwest boundary of the Grenville structural province. At its exposed southwest end, it is associated with several granitoid intrusions (the Chief Lake Batholith, the Bell Lake Granite, and the Killarney Granite of the Killarney Igneous Complex), which clearly postdate the last obvious deformation to have affected their Huronian host strata. These granitoid rocks were emplaced at shallow depths. The Killarney Granite has a crystallization age of 1742 Ma. The Chief Lake Batholith, having a zircon age of 1713 Ma and a Rb-Sr age of 1750 Ma, may be correlative with the Killarney Granite. The Bell Lake Granite, having a crystallization age of 1471 Ma, marks a second period of granite emplacement. Movements during the Grenvillian event (roughly 1200 to 1000 Ma) resulted in shearing of all these rocks; several zones of mylonites were produced, cumulatively totalling about 0.5 km in thickness, and intrusive contacts were modified or destroyed. -from Author