THE LIMPOPO METAMORPHIC BELT, SOUTH-AFRICA .1. GEOLOGICAL SETTING ANDRELATIONSHIP OF THE GRANULITE COMPLEX WITH THE KAAPVAAL AND ZIMBABWE CRATONS

The Limpopo granulite belt of southern Africa is subdivided into a Cen tral Zone, and a Southern and Northern Marginal Zones, The Central Zon e is characterized by a unique shelf-type supracrustal succession intr uded by a layered igneous complex, while the two marginal zones are ty pified by tectonically dismembered greenstone slivers, which are intim ately mixed with migmatized tonalitic gneisses. The Central Zone is se parated from the marginal zones by inward-dipping mylonitic shear zone s with strike-slip characteristics, while the two marginal zones are s eparated from the adjacent granite-greenstone cratons by inward-dippin g thrust zones. Geophysical, structural and metamorphic data all suppo rt a model that incorporates north-south-directed thrusting (D1) acros s the entire belt that resulted in the formation of the granulite terr ain exposed in the LB today. During subsequent uplift and unroofing of the thickened crust, rocks moved upwards and outwards onto the adjace nt granite-greenstone cratons along the inward directed shear zones (D 2) that bound the two marginal zones. This created a regional pop-up. High-grade rocks uplifted and thrusted onto the low-grade rocks of the two adjacent cratons suffered decompression and subsequent retrograde metamorphism, while the under-thrusted low grade rocks underwent prog rade metamorphism. The timing of thrusting in the marginal zones is co nstrained to a minimum age of about 2.627 Ga by the emplacement of syn tectonic chamockitic granitoids that clearly intrude D2 shear zones.