SEISMIC STUDIES IN THE LIMPOPO BELT

The structure of the Archaean Limpopo Belt of southern Africa has been investigated by means of a deep seismic reflection profile and the recording of the traveltimes of mining-induced tremors at regional distances. Interpretation of the traveltimes suggests that a seismic low-velocity zone exists in the upper mantle of the northern Kaapvaal Craton and Limpopo Belt, beginning at a depth of about 42 km. The seismic reflection profile provides evidence for a northward dip of the contact between the Kaapvaal Craton and the Southern Marginal Zone of the Limpopo Belt. No mid-crustal decollement zone is detected. The tectonic model of Van Reenen et al. (1990) is in accord with these observations. The lower crust is essentially seismically transparent, and no reflection Moho is observed.