The African upper mantle and its relationship to tectonics and surface geology

摘要: SUMMARY This paper focuses on the upper-mantle velocity structure of African continent and its relationship to surface geology. The distribution seismographs earthquakes providing seismograms for this study results in good fundamental higher mode path coverage by a large number relatively short propagation paths, allowing us image SV-wave speed structure, with horizontal resolution several hundred kilometres vertical ∼50 km, depth about 400 km. difference mantle between Archean Pan-African terranes is apparent our shear wave model. High-velocity (4–7 per cent) roots exist beneath cratons. Below West African, Congo Tanzanian Cratons, these extend 225–250 km depth, but Kalahari Craton, high root extends only ∼170 With exception Damara Belt that separates any high-speed lid below too thin be resolved long-period technique. underlain speeds, similar those observed Craton. Extremely low speeds occur bottom model Afar region. temperature upper determined from Large variations at 125 temperatures west Africa all southern warm terrane northern Africa. At 175 cool occurs Congo, Cratons anomalously zone northcentral region surrounding Red Sea. All volcanic centres are located above regions mantle. profiles were fit geotherm determine thickness lithosphere. Thick lithosphere exists cratonic areas; independent evidence thick comes locations diamondiferous kimberlites. Almost diamond where 175–200 thick, they largely absent thickest appears thicker