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Nd, Pb, and Sr isotope composition of Late Mesozoic to Quaternary intra-plate magmatism in NE-Africa (Sudan, Egypt): high-μ signatures from the mantle lithosphere.
- Source :
- Contributions to Mineralogy & Petrology; Dec2008, Vol. 156 Issue 6, p765-784, 20p, 1 Chart, 8 Graphs, 1 Map
- Publication Year :
- 2008
-
Abstract
- The isotopic composition of mafic small-volume intra-plate magmatism constrains the compositions of the sub-continental mantle sources. The Nd, Pb, and Sr isotope signatures of widespread late Mesozoic to Quaternary intra-plate magmatism in NE Africa (Sudan, South Egypt) are surprisingly uniform and indicate the presence of a high-μ (μ = <superscript>238</superscript>U/<superscript>204</superscript>Pb) source in the mantle. The rocks are characterized by small ranges in the initial isotopic composition of Nd, Pb, and Sr and most samples fall within ε Nd ca. 3–6, <superscript>206</superscript>Pb/<superscript>204</superscript>Pb ca. 19.5–20.5, <superscript>207</superscript>Pb/<superscript>204</superscript>Pb ca. 15.63–15.73, <superscript>208</superscript>Pb/<superscript>204</superscript>Pb ca. 39–40 and <superscript>87</superscript>Sr/<superscript>86</superscript>Sr ca. 0.7028–0.7034. We interpret this reservoir as lithospheric mantle that formed beneath the Pan-African orogens and magmatic arcs from asthenospheric mantle, which was enriched in trace elements (U, Th, and light REE). Combining our new data set with published data of intra-plate magmatic rocks from the Arabian plate indicates two compositionally different domains of lithospheric mantle in NE-Africa–Arabia. The two domains are spatially related to the subdivision of the Pan-African orogen into a western section dominated by reworked cratonic basement (NE-Africa; high-μ lithospheric mantle) and an eastern section dominated by juvenile Pan-African basement (easternmost NE-Africa and Arabia; moderate μ lithospheric mantle). The compositions of the Pan-African lithospheric mantle and the MORB-type mantle of the Red Sea and Gulf of Aden spreading centers could explain the Nd–Pb-Sr isotopic compositions of the most pristine Afar flood basalts in Yemen and Ethiopia by mixtures of the isotopic composition of regional lithospheric and asthenospheric sources. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00107999
- Volume :
- 156
- Issue :
- 6
- Database :
- Complementary Index
- Journal :
- Contributions to Mineralogy & Petrology
- Publication Type :
- Academic Journal
- Accession number :
- 34649711
- Full Text :
- https://doi.org/10.1007/s00410-008-0314-0