Thrust zones and shear zones of the margin of the Namaqua and Kheis mobile belts, southern Africa

Abstract

The Prieska area of the Cape Province of South Africa lies across the junction between two major Proterozoic low-angle shear/thrust zones. The first zone marks the margin to the Kheis mobile belt and carried Proterozoic schists and quartzitic sediments (the Matsap), together with Archaean basement, to the SE over a foreland of Proterozoic Transvaal sediments. The second, re-thrust the Matsap rocks to the NE, but also covered them with high-grade metamorphic rocks of the Namaqua belt. Later dextral strike-slip shear zone movements and large back-folds have enabled the SE-verging thrust zones to be traced well over 100 km on to the foreland, thus giving a minimum estimate of displacement. Both sets of shears are considered to represent A-type subduction zones some considerable distance from any oceanic suture.