CENOZOIC MAGMATISM THROUGHOUT EAST-AFRICA RESULTING FROM IMPACT OF A SINGLE PLUME

The geology of northern and central Africa is characterized by broad p lateaux, narrower swells and volcanism occurring from similar to 45 My r ago to the present. The greatest magma volumes occur on the >1,000-k m-wide Ethiopian and east African plateaux, which are transected by th e Red Sea, Gulf of Aden and east African rift systems, active since th e late Oligocene epoch. Evidence for one or more mantle plumes having impinged beneath the plateaux comes from the dynamic compensation infe rred from gravity studies, the generally small degrees of extension ob served and the geochemistry of voluminous eruptive products(1-4). Here we present a model of a single large plume impinging beneath the Ethi opian plateau that takes into account lateral flow and ponding of plum e material in pre-existing zones of lithospheric thinning(5), We show that this single plume can explain the distribution and timing of magm atism and uplift throughout east Africa. The thin lithosphere beneath the Mesozoic-Palaeogene rifts and passive margins of Africa and Arabia guides the lateral flow of plume material west to the Cameroon volcan ic line and south to the Comoros Islands. Our results demonstrate the strong control that the lithosphere exerts on the spatial distribution of plume-related melting and magmatism.