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Corundum (sapphire) and zircon relationships, Lava Plains gem fields, NE Australia: integrated mineralogy, geochemistry, age determination, genesis and geographical typing
journal contribution
posted on 2023-05-18, 15:58 authored by Sutherland, FL, Coenraads, RR, Abduriyim, A, Sebastien MeffreSebastien Meffre, Hoskin, PWO, Giuliani, G, Beattie, R, Wuhrer, R, Sutherland, GBGem 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 (δ18O 4.5–5.6%) and crustal (δ18O 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.
History
Publication title
Mineralogical MagazineVolume
79Pagination
545-581ISSN
0026-461XDepartment/School
School of Natural SciencesPublisher
Mineralogical SocietyPlace of publication
41 Queens Gate, London, England, Sw7 5HrRights statement
Copyright 2015 The Mineralogical SocietyRepository Status
- Restricted