Geological and geophysical parameters of mid-plate volcanism

Abstract

Volcanism occurs mainly at oceanic ridges and subduetion zones, but also takes place within continental plates. Mid-plate Cenozoic volcanism is widespread in Africa, where it is alkaline in composition and characteristically associated with uplift and faulting. There is a clear time correlation between the pause at ca. 45 Ma in the African apparent polar wander path and the outbreak of volcanism at ca. 35 Ma, suggesting that the slowing or coming to rest of the plate may be an important antecedent to the outbreak of volcanism. Moreover, the Cenozoic volcanism is almost completely restricted spatially to non-cratonic areas. Cratons in Africa are characterized geologically by tectonic stability for at least the past 1200 M,and geophysically by low elevations, heat flow less than 45 mW m-2, lithospheric thicknesses greater than 200 km higher than average seismic velocities. In contrast, non- cratonic regions have undergone tectono-thermal events within the past 1200 Ma, stand higher, have greater heat flow and lower lithospheric thicknesses and seismic velocities.