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Plume-lithosphere interactions in the generation of the basalts of the Kenya Rift, East Africa.

MacDonald, Raymond and Rogers, N. W. and Fitton, J. G. and Black, S. and Smith, M. (2001) Plume-lithosphere interactions in the generation of the basalts of the Kenya Rift, East Africa. Journal of Petrology, 42 (5). pp. 877-900.

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Abstract

Major and trace element and Sr–Nd–Pb isotopic data for mafic volcanic rocks are used to assess the number of mantle plumes contributing to the Tertiary–Holocene magmatism of the Kenya Rift Valley, current estimates of which vary from none to three. Rocks ranging in composition from nephelinite to hypersthene-normative basalt have been sampled from three lithospheric zones: the Tanzanian craton, the craton margin reworked during the late Proterozoic, and the Mozambique mobile belt. The magmas are interpreted as the products of variable degrees of partial melting within the spinel–garnet peridotite transition zone. Trace element and isotopic compositions from all three zones are broadly similar to those of oceanic island basalts, but there is considerable compositional variation, which is related to a strong overprint from the lithosphere on plume-derived melts. Sr and Nd isotopic ratios provide the only clear distinction between magmatic rocks from the three lithospheric domains. Within each setting, mafic magmatism has tended to become less silica undersaturated with time, and at any one locality magmatism has migrated towards the centre of the rift. Magmas may have formed as a result of the infiltration of plume-derived melts into the base of the lithosphere. The extent of interaction of inferred plume melts with the lithosphere has not varied systematically in time or space. The plume component appears to be similar to the source of oceanic island basalts.

Item Type: Article
Journal or Publication Title: Journal of Petrology
Uncontrolled Keywords: Kenya Rift Valley ; mantle plumes ; geochemistry ; metasomatism
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 21555
Deposited By: ep_ss_importer
Deposited On: 21 Jan 2009 11:17
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:48
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21555

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