LITHOSPHERIC IMAGING OF THE CONGO – TANZANIA – BANGWEULU CRATON, THE ZIMBABWE – KAPPVAAL – NIASSA CRATON, AND THE TRANS-SOUTHERN AFRICAN OROGEN

Using two-dimensional (2D) radially-averaged power spectral analysis and 2D forward gravity modeling of satellite gravity data, we image the lithospheric structure (the depth to the upper crust, the depth to Moho, and the depth to the asthenosphere – lithosphere boundary) beneath the Congo – Tanzania – Bangweulu craton, the Zimbabwe – Kappvaal – Niassa craton, and the Trans-Southern African orogen. The latter underlies most of the basins of the Southwestern Branch (SWB) of the East African Rift System (EARS). We find the cratons, in general, to be underlain by thicker lithosphere reaching ~250 km compared to the Trans-Southern African orogen, which is underlain by lithosphere that is 150 – 200 km thick. Our findings suggest that the spatial extent of the Congo craton is much wider than what is exposed on the surface and is covered in the southeast by the Luffilian arc. Similarly, the geographic extent of the Bangweulu craton is wider than what is exposed on the surface with its southwestern limit covered by the Luffilian arc. The geographic extent of the Niassa craton is also redefined, and which is shown to have relatively thinner lithosphere (~ 200 km). In addition, the depths to LAB of Mesoproterozoic – Neoproterozoic orogenic belts, which are covered by the Karoo sediment are determined. The notable examples may be the lithospheric thickness of the Mesoproterozoic – Neoproterozoic Ghanzi – Chobe orogenic belt (~ 146 km) and the Neoproterozoic Damara orogenic belt (~ 146 km). The LAB estimates of these tectonic entities suggest that the SWB of the EARS as a whole are regionally controlled by the Trans-Southern Africa orogeny, while the development of individual basins are controlled by localized preexisting weaknesses. One notable example is the development of the Luangwa rift along the Mwembeshi shear zone, which is developed within a relatively thinner lithosphere that is in the range of (~ 150 – 200) km.