Lower crustal composition and crustal lineaments on the Vøring Margin, NE Atlantic: A review

Abstract

A prominent lower crustal high-velocity layer observed in the Vøring Basin, NE Atlantic, has been investigated with regard to composition and spatial link to crustal-scale lineaments. In the southernmost part of the basin the lower crustal layer is interpreted as eclogites, based on anomalously high P-wave velocities (8.4 km/s). In the remainder of the basin the layer is preferably interpreted as mafic intrusions emplaced during the last phase of rifting, but it cannot be excluded that the body consists of older (Caledonian?), mafic rocks. Direct link with high-grade Caledonian rocks to the east, and westwards to east Greenland, cannot be made, since these rocks are mainly of felsic composition. The crustal-scale lineaments inferred from wide-angle seismic data appear to represent the oceanward extension of post-Caledonian detachments. The spatial variation in the thickness of the layer is within the late-rifting magmatic hypothesis partly interpreted in terms of (pre-magmatic) variations in thickness of the lithosphere. In addition, lateral variations in extension, mantle upwelling and decompressional melting during the last phase of rifting may also have contributed.