Four Treasures Reference Database
Record No. 28096
Age dating of gem-quality zircon and sapphire from the New England gem fields, New South Wales, Australia, and its application to the geological origin of the sapphires
Journal Article
Abduriyim, A., Sutherland, F.L., Coldham, T.S. and Belousova, E. (2025) Age dating of gem-quality zircon and sapphire from the New England gem fields, New South Wales, Australia, and its application to the geological origin of the sapphires. Journal of Gemmology, Vol. 39, No. 7, pp. 656–671.
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gems, corundum, Australia.12, zircon, geology.11, New England District
Transparent pale yellow to brown zircon megacrysts occur with gem corundum in alluvial deposits linked to alkali basalts of the Inverell–Glen Innes District, New South Wales, Australia. Previous LA-ICP-MS analyses of zircons from Kings Plains, Mary Anne Gully, and Swan Brook showed chemical homogeneity and yielded two age groups: 216–174 Ma (Late Triassic–Early Jurassic) and 45–37.7 Ma (Eocene). New U-Pb dating of zircon inclusions in gem-quality blue sapphires produced concordant ages of 37 ± 1.7 Ma (Kings Plains) and 35.1 ± 1.6 Ma (Mary Anne Gully), matching the 38–33 Ma K-Ar ages of the Maybole volcanic suite and aligning with the younger zircon population. These results, together with gemmological and chemical evidence, demonstrate a genetic connection between sapphire crystallisation in the deep crust or mantle and subsequent transport to the surface by alkali basaltic magmas.