New Varieties of Mantle Xenolith from the Massif Central, France

R. Hutchison, C. T. Williams, P. Henderson and S. J. B. Reed
Department of Mineralogy, British Museum (Natural History), London SW7 5BD
Department of Earth Sciences, Bullard Laboratories, Madingly Road, Cambridge CB3 0EZ

Abstract: Spinel lherzolite xenoliths from two localities in the Massif Central are undepleted in Al2O3, CaO, and Na2O. One suite from Tarreyres, is K2O depleted and amphibole-bearing whereas the other, from Monistrol d'Allier some 18 km away, is amphibole-free and has a higher mean K2O content of 0.035 wt.%. We present bulk major and minor element abundances in a harzburgite and a lherzolite from each locality and microprobe analyses of their constituent phases. Amphibole-bearing lherzolite and its pyroxenes are light-rare earth element (LREE) depleted, whereas amphibole-free lherzolite and its pyroxenes are LREE enriched. Both harzburgites and their pyroxenes are LREE enriched and one rock contains LREE enriched glass. The harzburgites are like harzburgite xenoliths from elsewhere but each lherzolite represents a previously unrecognized type of mantle in terms of the mineralogy and REE content. The implication for basalt genesis are briefly discussed.

Keywords: xenoliths • lherzolite • upper mantle • Massif Central • France

Mineralogical Magazine; December 1986 v. 50; no. 358; p. 559-565; DOI: 10.1180/minmag.1986.050.358.02
© 1986, The Mineralogical Society
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