Polymetamorphism and structures in the Superior Province near the Grenville Front in south-central Quebec

Abstract

Abstract Polymetamorphic metabasalts and metasediments of the Villebon area are interpreted as a sequence representing the top slice of oceanic crust covered by a layer of island-arc volcanic products and turbidites in a back-arc environment during pre-Kenoran times. They were folded and metamorphosed during the Kenoran Orogeny. During the Aphebian, renewed sedimentation took place on an Atlantic-type continental edge, whereafter during the Hudsonian Orogeny part of the Superior craton slid on top of the sediment wedge over a low rheidity migmatized layer. Later westward thrusting of Grenvillian deposits, together with their basement, caused tilting and steepening of preexisting Kenoran and Hudsonian structures. The decollement plane, previously mapped as the Grenville Front, is a Hudsonian Feature; the true Grenville Front is probably located more eastward.