Tectonic evolution of the Bark Lake area, eastern Central Gneiss Belt, Ontario Grenville: Constraints from geology, geochemistry and uranium-lead geochronology

Detailed field mapping of lithology and structure was completed at the 1:25 000 scale in the Barry's Bay-Bark Lake region of Ontario, in the SE margin of the Central Gneiss Belt, in the immediate footwall of a crustal-scale ductile shear zone. The area is characterized by upper amphibolite- to granulite-facies, granodioritic orthogneiss that exhibits extensive migmatitic textures and a penetrative transposition foliation. Geochemistry results demonstrate calc-alkaline trends, typical of arc-derived magmas. U-Pb geochronology of 6 samples from the study area yield protolith crystallization ages at ∼1480 Ma. Penetrative ductile deformation was coeval with high-grade metamorphism and accompanying anatexis at ca. 1070–1040 Ma. Based on similar age and lithotectonic affinities of the Bark Lake area with the western Muskoka domain, this area is interpreted as representing the eastern extension of the Muskoka domain. These rocks are interpreted to have originated during the Mesoproterozoic in an Andean-type continental arc setting, on the southeast margin of pre-Grenvillian Laurentia.