Sm/Nd evidence for a major 1.5 Ga crust-forming event in the central Grenville province

The majority of gray gneisses from an 80 000 km2 area in the central (Quebec) Grenville province define a Sm-Nd isochron that yields an age of 1.53 ±0.07 Ga. Major element, trace element, and initial Nd isotopic data all point to a subduction-related (orogenic) source for this terrane. It is attributed to a major crustal extraction event that formed a mid-Proterozoic island arc. The age of the terrane agrees with published data from the eastern …