Shear zones of the Limpopo Belt and adjacent granitoid-greenstone terranes: implications for late Archaean collision tectonics in southern Africa

Abstract

Granulite metamorphism in the > 2.65 Ga Limpopo Belt of southern Africa is related to crustal thickening, due to late Archaean collision tectonics. The Central Zone of the belt is a major thrust sheet of distinctive lithological, structural and isotopic character, separated from adjacent terranes by crustal-scale shear zones, and the Northern and Southern Marginal Zones are up-thrust deep-level granulite facies terranes of the adjacent cratons. Geometrically the marginal zones are mirror images and the Limpopo Belt is essentially symmetrical in N–S section. Conventionally regarded as a N–S collisional orogeny, the gross structural and lithological differences between the Central Zone and the marginal zones, kinematic data from shear zones and geophysical data showing the three-dimensional geometry of the Central Zone are here used to suggest that the direction of emplacement of the Central Zone was also the collision direction. This was from northeast to southwest, with the upthrust, outwardly directed, marginal zones developing in mechanical response to this collision.