Mantle metasomatism beneath western Victoria, Australia

II. Isotopic geochemistry of Cr-diopside lherzolites and Al-augite pyroxenites

W. L. Griffin*, Suzanne Y. O'Reilly, Stabel A.

*Corresponding author for this work

Research output: Contribution to journalArticle

121 Citations (Scopus)

Abstract

Cr-diopside spinel lherzolite xenoliths from Victoria show metasomatic introduction of amphibole ± mica ± apatite, accompanied by enrichments in Sr, LREE and other incompatible elements. The metasomatism can be related to fluids emanating from crystallizing basaltic magmas now represented by dykes of pyroxenite. Abundant garnet and spinel metapyroxenites are products of an older magmatic episode; igneous-textured wehrlite series xenoliths represent a younger (Recent ?) episode. Sr-Nd isotopic compositions of the lherzolites spread into the "enriched mantle" field (ε{lunate}Nd < 0, ε{lunate}Sr > 0). Nd isotopic systematics suggest a maximum age for LREE enrichment of <700 Ma. At 300-500 Ma, the metapyroxenites define a mixing hyperbola with the lherzolites, most of which have ε{lunate}Sr > 0 at this time. More detailed mixing models require a third (apatite-rich component with present-day ε{lunate}Sr and ε{lunate}Nd ≈0). The least-modified metapyroxenites have very unradiogenic Nd and unsupported radiogenic Sr, suggesting a large component of older recycled crustal material. The origin of the "apatite component" is uncertain.

Original languageEnglish
Pages (from-to)449-459
Number of pages11
JournalGeochimica et Cosmochimica Acta
Volume52
Issue number2
DOIs
Publication statusPublished - 1988

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