The Corrugated Hills Continental Flood Basalt: a c. 2.17 Ga flood basalt province related to breakup of the Superior craton

Abstract

Abstract This study documents a major continental flood basalt province in the central Labrador Trough that produced voluminous mafic magmatism along the palaeo-rifted margin of the Superior craton. This area, representing a preserved magma volume of approximately 25 000 km 3 , is characterized by classic ‘traps’ topography with columnar-jointed flows and sills separated by thin clastic sedimentary layers. A gabbroic sill near the bottom of the sequence yielded a U–Pb zircon age of 2166 ± 4 Ma, and another near the middle of the sequence yielded a 2171 ± 3 Ma U–Pb zircon age. These ages overlap in time with published ages of mafic dyke swarms that radiate outwards into the adjacent Superior craton, namely the Biscotasing (2172–2167 Ma) and Payne River (2170–2160 Ma) dykes, as well as the Otish sills (2172–2162 Ma) and Tasiataq (2170 Ma) dyke. Our data suggest that these central Labrador magmas, named the Corrugated Hills Continental Flood Basalt, were emplaced near or above a mantle plume head, leading to thermal uplift and then rifting of the Superior craton margin. Field relationships suggest that these magmas were erupted through thinned Archean crust as a rift-related continental flood basalt suite. The Corrugated Hills Continental Flood Basalt province represents remnants of one of the oldest continental flood basalt provinces on Earth.