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Geochemistry of 24 Ma basalts from NE Egypt: source components and fractionation history

By
Chira Endress
Chira Endress
1
Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA
2
Department of Instruction and Learning, University of Pittsburgh, Pittsburgh PA 15260, USA
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Tanya Furman
Tanya Furman
1
Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA
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Mohamed Ali Abu El-Rus
Mohamed Ali Abu El-Rus
3
Geology Department, Assiut University, Assiut 71516, Egypt
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Barry B. Hanan
Barry B. Hanan
4
Department of Geological Sciences, San Diego State University, San Diego CA 92182, USA
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Published:
January 01, 2011

Abstract

Subalkaline basalts from NE Egypt represent an episode of magmatism at c. 24 Ma, coincident with widespread eruptive activity in northern Africa. New geochemical data provide insight into the mineralogical and isotopic characteristics of the underlying mantle. The basalts show little geochemical variation, with incompatible trace element abundances similar to those of ocean island basalts. They display fairly smooth primitive mantle-normalized incompatible trace element patterns. Trace element abundances and Sr–Nd–Pb–Hf isotopic signatures are consistent with contributions from two distinct source regions, one similar to the Afar plume and the other located within the metasomatized spinel-facies subcontinental lithosphere. Mixing of melts from these two domains was followed by minor crustal contamination during prolonged ascent or emplacement. Integrating the geochemical data with available tomographic information allows us to develop a framework for understanding mid-Tertiary magmatic activity throughout northern Africa. A model for this widespread volcanism involves ascent of upwelling mantle derived from the margins of the South African Superplume rooted at the core–mantle boundary and/or through small-scale convection at the 660 km discontinuity. Ascent of magmas to the surface was facilitated by pre-existing structures within the lithosphere, including those associated with incipient rifting of the Red Sea.

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Mineral chemistry data are available at http://www.geolsoc.org.uk/SUP18483.

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Geological Society, London, Special Publications

The Formation and Evolution of Africa: A Synopsis of 3.8 Ga of Earth History

D. J. J. Van Hinsbergen
D. J. J. Van Hinsbergen
University of Oslo, Norway
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S. J. H. Buiter
S. J. H. Buiter
Geological Survey of Norway
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T. H. Torsvik
T. H. Torsvik
University of Oslo
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C. Gaina
C. Gaina
Geological Survey of Norway
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S. J. Webb
S. J. Webb
University of the Witwatersrand, South Africa
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Geological Society of London
Volume
357
ISBN electronic:
9781862396050
Publication date:
January 01, 2011

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