Extension orientale des roches volcaniques du Groupe de Wakeham et intrusion litée troctolitique de Musquaro, Province de Grenville, Basse-Côte-Nord, Québec

Abstract

A geological transect centered on La Romaine village in the eastern Grenville Province reveals a significant eastward extension of the Wakeham Group. A lithological assemblage of lapillistone, amphibolite, marble, and aluminous gneiss is locally mineralized and bears similarities with the 1.5 Ga supracrustal units newly recognized northwest of Musquaro Lake. These rocks are surrounded by granitic gneiss with recrystallized anorthosite enclaves. A practically undeformed 1 kmthick layered intrusion contains subvertical layers of peridotite, troctolite, and gabbro, with local Cu mineralization as well as various intrusive breccias. In the study area, two units record polyphase deformation with spectacular interference fold patterns: the eastern margin of the layered intrusion and a tonalitic gneiss of regional extent. Along with the anorthosite enclaves in the granitic gneiss, these units could be the expression of mafic magmatism and orogenesis of Labradorian age such as those found to the east in the Pinware terrane of Labrador.