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Trace element and Sr and Nd isotope geochemistry of peridotite xenoliths from the Eifel (West Germany) and their bearing on the evolution of the subcontinental lithosphere |
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| Authors: | H-G Stosch GW Lugmair |
| Institution: | 1Mineralogisch-Petrographisches Institut der Universität zu Köln, Zülpicher Str. 49, 5000 Köln 1F.R.G. 2Scripps Institution of Oceanography, A-012, University of California at San Diego, La Jolla, CA 92093U.S.A. |
| Abstract: | Peridotite xenoliths from the Eifel can be divided into incompatible element-depleted and -enriched members. The depleted group is restricted to dry lherzolites whereas the enriched group encompasses dry harzburgites, dry websterite and amphibole and/or phlogopite-bearing peridotites. Isotopically the depleted group is very diverse with143Nd/144Nd ranging from  0.51302 to 0.51355 and87Sr/86Sr from 0.7041 to 0.7019, thus occupying a field larger than expected for oceanic-type subcontinental mantle. These xenoliths are derived from a mantle which appears to have diverged from a bulk-earth Nd and Sr isotopic evolution path 2 Ga ago as a consequence of partial melting. The combination of high143Nd/144Nd with high87Sr/86Sr in some members of the depleted-xenoliths suite is likely to be the result of incipient reaction with incompatible element-enriched fluids in the mantle. In the enriched group such reactions have proceeded further and erased any pre-enrichment isotope memory resulting in a smaller isotopic diversity (143Nd/144Nd 0.51256–0.51273,87Sr/86Sr 0.7044–0.7032). An evaluation of Sm |
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