Geophysical correlations in the Ungava Bay area

Abstract

We used gravity and magnetic data to extend geological features across Ungava Bay and Hudson Strait, from northern Quebec and Labrador to Baffin Island. Tectonic domains identified on land were extended offshore by visual inspection of the potential fields. The boundaries identified on colour shaded relief maps were drawn on the original marine magnetic profiles to verify the robustness of the conclusions. Our interpretation in Ungava Bay remains speculative but gives some insight into the architecture of the northeastern Canadian Shield. Onshore, where trends are well marked, the magnetic fabric of the Superior Province reappears east of the New Quebec Orogen in the western core zone. Geochronology and geochemical data also suggest the affinity of the western core zone with the Superior Province. On the gravity map, the New Quebec Orogen appears to vanish offshore. A major trend in magnetic and gravity gradients can be followed offshore possibly as far north as Hudson Strait. It has been identified as the extension of the George River and Moonbase shear zones. The De Pas Batholith is associated with a linear trend west of this shear zone. To the east, several features appear distinctly in the magnetic map. A narrow northwest-trending anomaly can be followed from Quebec all the way to Baffin Island. On land, this feature marks the western limit of the Lake Harbour Group. Two wide north-trending bands that can be followed from the Torngat Orogen all the way to Baffin Island are interpreted as the extensions of the Lac Lomier Complex and Tasiuyak Domain.