Tectospheric structure beneath southern Africa

P-wave and S-wave delay times from the broadband data of the southern Afric a seismic experiment have been inverted to obtain three-dimensional images of velocity perturbations in the mantle beneath southern Africa. High veloc ity mantle roots appear to extend to depths of at least 250 km, and locally to depths of 300 km beneath the Kaapvaal and Zimbabwe cratons. Thick roots are confined to tile Archean cratons, with Ilo evidence for similar struct ures beneath the adjacent Proterozoic mobile belts. The Kaapvaal craton was modified ca, 2.05 Ga by the Bushveld magmatic event, which affected a broa d swath of cratonic mantle beneath and to the west of the exposed Bushveld Complex. The mantle beneath the extended Bushveld province is characterized by seismic velocities lower than those observed in regions of undisturbed cratonic mantle. The mantle beneath the Limpopo Belt, an Archean collisiona l zone sandwiched between the Kaapvaal and Zimbabwe cratons, exhibits a cra tonic signature.