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Upper-mantle heterogeneities beneath the Nyos volcano (Cameroon) from the study of ultramafic xenoliths

Abstract:

Volcanic deposits from the lake Nyos (Cameroon) contain ultrabasic xenoliths: lherzolites, harzburgites and websterites, sometimes containing amphibole. Major and trace element compositions of clinopyroxene and amphibole allow the recognition of an old depletion event followed by two episodes of incompatible-element enrichment. One is high in light rare-earth elements, while the other one is low in these elements, but high in U and Th. Their relative chronology is not yet established. © 2004 Académie des sciences. Publié par Elsevier SAS. Tous droits réservés.