Evolution of the East African rift: Drip magmatism, lithospheric thinning and mafic volcanism

Tanya Furman, Wendy R. Nelson, Linda Elkins-Tanton

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The origin of the Ethiopian-Yemeni Oligocene flood basalt province is widely interpreted as representing mafic volcanism associated with the Afar mantle plume head, with minor contributions from the lithospheric mantle. We reinterpret the geochemical compositions of primitive Oligocene basalts and picrites as requiring a far more significant contribution from the metasomatized subcontinental lithospheric mantle than has been recognized previously. This region displays the fingerprints of mantle plume and lithospheric drip magmatism as predicted from numerical models. Metasomatized mantle lithosphere is not dynamically stable, and heating above the upwelling Afar plume caused metasomatized lithosphere with a significant pyroxenite component to drip into the asthenosphere and melt. This process generated the HT2 lavas observed today in restricted portions of Ethiopia and Yemen now separated by the Red Sea, suggesting a fundamental link between drip magmatism and the onset of rifting. Coeval HT1 and LT lavas, in contrast, were not generated by drip melting but instead originated from shallower, dominantly anhydrous peridotite. Looking more broadly across the East African Rift System in time and space, geochemical data support small volume volcanic events in Turkana (N. Kenya), Chyulu Hills (S. Kenya) and the Virunga province (Western Rift) to be derived ultimately from drip melting. The removal of the gravitationally unstable, metasomatized portion of the subcontinental lithospheric mantle via dripping is correlated in each case with periods of rapid uplift. The combined influence of thermo-mechanically thinned lithosphere and the Afar plume together thus controlled the locus of continental rift initiation between Africa and Arabia and provide dynamic support for the Ethiopian plateau.

Original languageEnglish (US)
JournalGeochimica et Cosmochimica Acta
DOIs
StateAccepted/In press - Jul 30 2015

Fingerprint

thinning
magmatism
volcanism
Melting
mantle
lithosphere
mantle plume
Oligocene
Numerical models
plume
melting
Heating
picrite
pyroxenite
flood basalt
asthenosphere
Chemical analysis
peridotite
rifting
upwelling

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Evolution of the East African rift : Drip magmatism, lithospheric thinning and mafic volcanism. / Furman, Tanya; Nelson, Wendy R.; Elkins-Tanton, Linda.

In: Geochimica et Cosmochimica Acta, 30.07.2015.

Research output: Contribution to journalArticle

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