STRUCTURES IN GRANITOID GNEISSES AND ASSOCIATED MIGMATITES CLOSE TO THE GRANULITE BOUNDARY OF THE LIMPOPO BELT, SOUTH-AFRICA

River platform exposures of quartzofeldspathic gneiss and associated migmatites occur close to the boundary of the Southern Marginal Zone of the Limpopo Belt with the adjacent low-grade granite-greenstone terrane of the Kaapvaal Craton. The complex gneisses and migmatites are described and are considered to represent the tectono-thermally reworked equivalents of the Pietersburg-Sutherland greenstone belts and early tonalitic and trondhjemitic intrusive granitoids. Structural features associated with the Hout River Shear Zone and the Limpopo Orogeny (approximately 2700-2650 Ma old), and which include subhorizontal overthrust fault slices produced as a result of lateral extrusion of rock material following transpressional displacement along a strike-slip fault or thrust zone, support structural, metamorphic and geophysical evidence suggesting southwestwards overthrusting of the high-grade Southern Marginal Zone rocks onto lower-grade rocks of the Kaapvaal Craton.