Metasomatism and sulfide mobility in lithospheric mantle beneath eastern Australia

Implications for mantle Re-Os chronology

William Powell*, Suzanne O'Reilly

*Corresponding author for this work

    Research output: Contribution to journalArticle

    40 Citations (Scopus)

    Abstract

    Spinel lherzolite xenoliths from Tertiary basaltic host magmas at Allyn River, eastern Australia reveal two distinct petrographic and geochemical types. One group is distinguished by xenoliths with undeformed, equilibrated microstructures and interstitial melt patches; The second group shows deformation and contains abundant fluid inclusions but no melt patches. Trace-element signatures of clinopyroxene in these xenoliths provide evidence for metasomatism by a silicate agent with hydrous component and by a carbonate-rich agent respectively. Melt patches in the undeformed xenoliths contain secondary minerals including clinopyroxene, olivine, feldspar, Mg- and Ca-rich carbonate, apatite, ilmenite and spinel. They are interpreted to represent volatile-rich melt captured shortly prior to entrainment in the host basalt. Sulfide globules, now recrystallised to discrete sulfide phases but inferred to be molten at lithospheric mantle T and P, are closely associated with the melt patches. The close association between sulfide and highly mobile, volatile-bearing fluid has important implications for the mobility of Re and Os, the use of their isotopes in dating mantle events, and the possible effect of volatile-bearing metasomatic agents on their composition.

    Original languageEnglish
    Pages (from-to)132-147
    Number of pages16
    JournalLithos
    Volume94
    Issue number1-4
    DOIs
    Publication statusPublished - Mar 2007

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