Nd isotope mapping of a cryptic continental suture, Grenville Province of Ontario

Nd isotope data are presented for 70 Archean and Paleoproterozoic grey gneisses from the Grenville Parautochthonous belt in Ontario. These data constrain an age boundary which separates partially reworked Archean basement to the northwest from a Paleoproterozoic arc terrane to the southeast. This boundary is interpreted as a crustal-scale continental suture, but its exposure is cryptic due to metamorphic recrystallisation during the Grenville orogeny. Mesoproterozoic stitching plutons injected across the boundary suggest that it has a minimum age of 1.5Ga, and is probably a Paleoproterozoic structure. Archean basement northwest of the suture was intensely plutonised by the 1.75–1.7Ga Killarnean ensialic arc. Juvenile Paleoproterozoic basement southeast of the suture has a maximum crustal formation age of less than 2.0Ga. It is probably an accreted Penokean terrane which was reworked by the same Killarnean ensialic arc.