Accretion and indentation tectonics at the southern edge of the Kaapvaal craton during the Kibaran (Grenville) orogeny

Abstract

A comparison of the lithologic, geochronologic, and kinematic features of the ∼1Ga orogens in southern Africa (Namaqua-Natal belt) and the Heimefrontfjella (East Antarctica) shows that the three areas originally constituted a contiguous belt that evolved within a prolonged, consistently northeast-oriented stress regime (African azimuths). An early northeast- or southwest-directed thrusting event has been identified along the entire belt. A later episode of transcurrent shearing can account for both the emplacement of extensive late-tectonic granitoid plutons in Natal and for the development of the Koras and Sinclair basins in Namaqualand and Namibia. The geometry and sense of movement of the later shear zones are functions of the varying orientation of the adjacent Archean cratonic margin and a prolonged period of northeast-directed plate convergence. Consequently, the craton is interpreted as a southwest-directed indenter during the Grenville orogeny.