East African rift systems

Extensive volcanism can be found in eastern Africa associated with the East African rift system. Helium isotope ratios measured in basalts from the Ethiopian Rift Valley and Afar, near the triple junction of Red Sea, Aden, and Ethiopian rift systems, are 6-17/ a (Marty et al., 1993, 1996 Scarsi and Craig, 1996). These values include MORB ratios as well as indications of both contributions from radiogenic He and high He/ He hotspots. To the south, the rift system divides into eastern and western branches. Xenoliths from Tanzanian vents in the eastern branch... 

Furman T. and Graham D. W. (1999) Erosion of lithospheric mantle beneath the East African rift system geochemical evidence from the Kivu volcanic province. Lithos 48, 237-262. 

We tested the sensitivity of the splitting to the scaling adopted. The orientation of the shear-wave polarizations will remain consistent, but the magnitude of the splitting could vary. What the modelling provides is a prediction of the pattern in splitting that should be observed around the edges of the keel. The results from seismic studies under way in the East African rift system (Nyblade, pers. comm. Stuart, pers. 

Furman T, Graham DW (1999) Erosion of lithospheric mantle beneath the East African Rift system geochemical evidence from the Kivu volcanic province. Lithos 48 237-262 Gasparon M, Hilton DR (1994) Crustal contamination processes traced by helium isotopes examples from the Sunda Arc, Indonesia. Earth Planet Sci Lett 126 15-22 Goes S, Spakman W., Bijwaard H (1999) A lower mantle source for central European volcanism. Science 286 1928-1931... 

The East African Rift System is an example for a large-scale zone of continental extension where two lithospheric plates slowly spread apart (at about 5 mm/year). The earthquake distribution is broader than at mid-ocean ridges, and the rift actually splits into an eastern and western branch when it encounters the relatively strong and deep-rooted Tanzanian Craton. Earthquakes have normal-faulting mechanisms with strikes parallel to the direction of the East African Rift... 

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