A Discussion on global tectonics in Proterozoic times - Tectonics of the North Atlantic Proterozoic dyke swarm

The Proterozoic North Atlantic dyke swarm occurs in Scotland, East and West Greenland, and Labrador, over an area of at least 250000 km2, and includes two dominant dyke sets which in West Greenland strike NNE-SSW, and ESE-WNW. The intrusive relations of the two sets, and their association with ductile shear zones and other lateral displacements of country rocks, show the dykes to represent a conjugate swarm emplaced along shear fractures, rather than along tensional openings. The mechanical behaviour of the Proterozoic lithosphere is considered in the context of the regional fracture system.