Corundum (sapphire) and zircon relationships, Lava Plains gem fields, NE Australia : integrated mineralogy, geochemistry, age determination, genesis and geographic typing

F. L. Sutherland, R. R. Coenraads, A. Abduriyim, S. Meffre, P. W. O. Hoskin, G. Giuliani, R. Beattie, R. Wuhrer, G. B. Sutherland

    Research output: Contribution to journalArticlepeer-review

    26 Citations (Scopus)

    Abstract

    Gem minerals at Lava Plains, northeast Queensland, offer further insights into mantle-crustal gemformation under young basalt fields. Combined mineralogy, U-Pb age determination, oxygen isotope and petrological data on megacrysts and meta-aluminosilicate xenoliths establish a geochemical evolution in sapphire, zircon formation between 5 to 2 Ma. Sapphire megacrysts with magmatic signatures (Fe/Mg ~100-1000, Ga/Mg 3-18) grew with ~3 Ma micro-zircons of both mantle (δ180 4.5-5.6‰) and crustal (δ180 9.5-10.1‰) affinities. Zircon megacrysts (3±1 Ma) show mantle and crustal characteristics, but most grew at crustal temperatures (600-800°C). Xenolith studies suggest hydrous silicate melts and fluids initiated from amphibolized mantle infiltrated into kyanite+sapphire granulitic crust (800°C, 0.7 GPa). This metasomatized the sapphire (Fe/Mg ~50-120, Ga/Mg ~3-11), left relict metastable sillimanite-corundum-quartz and produced minerals enriched in high field strength, large ion lithophile and rare earth elements. The gem suite suggests a syenitic parentage before its basaltic transport. Geographical trace-element typing of the sapphire megacrysts against other eastern Australian sapphires suggests a phonolitic involvement.
    Original languageEnglish
    Pages (from-to)545-581
    Number of pages37
    JournalMineralogical Magazine
    Volume79
    Issue number3
    DOIs
    Publication statusPublished - 2015

    Keywords

    • Australia
    • basalt
    • corundum
    • gemstone genesis
    • lithosphere
    • sapphires
    • trace elements
    • zircon

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