Basaltic volcanism in Ethiopia: Constraints on continental rifting and mantle interactions
Middle to late Cenozoic mafic lavas from the Ethiopian volcanic province exhibit considerable chemical and isotopic diversity that is linked to eruption age and eruption location. These variations provide a geochemical framework in which continental rifting can be examined. Trace element and Sr, Nd, and Pb isotopic data are interpreted to indicate involvement of up to two depleted and two enriched mantle reservoirs throughout Cenozoic rift development in Ethiopia. Superimposed on the characteristics imparted by varying degrees of melting of these distinct reservoirs are the effects of crystal fractionation and, in some instances, crustal contamnation. Initial stages of Oligocene rifting and volcanism, as manifested by the rift-bounding plateau flood basalts, are attributed to asthenospheric upwelling and melting of a heterogeneous, enriched subcontinental lithospheric mantle. Mildly alkaline lavas were produced from an enriched source with characteristics similar to those of the inferred source of other mantle/minus/derived lavas and xenoliths from east Africa (LoNd array, EMI to HIMU). Contemporaneous tholeiitic lavas were derived from a source similar to that producing oceanic basalts from Samoa and the Society Islands (EMII). As lithospheric thinning and rifting continued into the Miocene, upwelling depleted asthenosphere (depleted OIB reservoir, PREMA) interacted with the lithospheric sources producing lavas with hybrid elemental and isotopic characteristics (11-6 Ma plateau and rift margin basalts).
- Research Organization:
- Geology Department, Miami University, Oxford, Ohio(US); Los Alamos National Laboratory, New Mexico; Berkeley Geochronology Center, California; Geology Department, Franklin and Marshall College, Lancaster, Pennsylvania
- OSTI ID:
- 5940569
- Journal Information:
- J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Journal Issue: B6 Vol. 94:B6; ISSN JGREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580202* -- Geophysics-- Volcanology-- (1980-1989)
AFRICA
BASALT
CENOZOIC ERA
CHEMICAL COMPOSITION
CONTINENTAL CRUST
DEVELOPING COUNTRIES
EARTH CRUST
EARTH MANTLE
ETHIOPIA
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
ISOTOPE RATIO
LAVA
MAGMATISM
RIFT ZONES
ROCKS
VOLCANIC ROCKS
VOLCANISM