The East African Rift, magma genesis and astheno-lithospheric dynamics.

Abstract

The complexity of magmas associated with intracontinental rifts is typified by the volcanic rocks of the Great Rift Valley of East Africa. The magmas were evolved from continental tholeiites rich in incompatible elements, through alkaline products to transitional magmas relatively low in incompatible elements, which characterize a proto-oceanic stage. This evolutionary sequence requires modifications to the accepted model for generating continental intraplate magmas in terms of astheno-lithosphere dynamics. New average compositions of first volcanic cycle tholeiites for Zaire are given.-R.A.H.