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Basaltic magmatism and the geodynamics of the East African rift system

Rogers, N. W. (2006). Basaltic magmatism and the geodynamics of the East African rift system. In: Yirgu, G.; Ebinger, C. J. and Maguire, P. K. H. eds. The Afar Volcanic Province within the East African Rift System. Special Publication (259). London: Geological Society of London, pp. 77–93.

URL: http://www.geolsoc.org.uk
DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1144/GSL.SP.2006.259.01.08
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Abstract

The major and trace element and radiogenic isotope compositions of basalts from throughout the East African rift system are reviewed in the context of constraints from previous geophysical studies. The data indicate the presence of two mantle plumes, the East African and Afar plumes, which dynamically support the East African and Ethiopian plateaus. Rifting across the plateaus is accompanied by the generation of large volumes of basaltic magma and associated evolved derivatives. Relatively few matic magmas have an unambiguous Afar mantle plume signature, notably the MgO-rich picrites and ankaramites from the 29-31 Ma Ethiopian traps, and the most recent basalts (< 5 Ma) from Afar. The Eocene Amaro basalts from southern Ethiopia also have a plume source but their lower source temperatures and isotopic characteristics are distinct from those of Afar. The remaining basalts from the Ethiopian rift, and throughout the Kenya and Western rifts, have a lithospheric source region as reflected in both radiogenic isotope and trace element characteristics. The Amaro basalts are suggested as the first manifestations of magmatism from the East African plume; subsequent magmatic activity being represented by progressively younger episodes further south through Turkana, Kenya and into Northern. Tanzania, as the African plate migrated north. Despite their clear lithospheric characteristics, U-series data on geologically recent basalts from the axis of the Kenya rift show that they were generated in a dynamic melting regime. Melting is effected when lithospheric mantle heats up and becomes incorporated into the convecting mantle, hence leading to greater degrees, of lithospheric thinning than are indicated by extension across individual rift basins.

Item Type: Book Chapter
Copyright Holders: 2006 Geological Society of London
ISBN: 1-86239-196-3, 978-1-86239-196-3
Extra Information: International Conference on East African Rift Systems: Geodynamics, Resources and Environment; Addis Ababa, Ethipia; Jun 2004; ISSN 0305-8719
Keywords: Main Ethiopian rift; Plume-lithosphere interactions; Afar mantle plume; Flood basalts; Kenya rift; Melt generation; Isotopic variations; Volcanic province; Red-sea; Series disequilibria;
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 16078
Depositing User: Nick Rogers
Date Deposited: 14 May 2009 16:26
Last Modified: 17 Jan 2013 16:14
URI: http://oro.open.ac.uk/id/eprint/16078
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