Zircon O and Lu-Hf isotopes in Tasmanian Devonian Granites

The Tasmanian Devonian granites were emplaced during the Tabberabberan Orogeny when the East and West Tasmania Terranes collided. The primary aim of this study is to determine zircon O and Lu-Hf isotope constraints on, and relationships between, the magmas forming these granites. A second aim is to determine if these zircon isotopic compositions can be used to inform granite-related ore endowment. Several granites (n = 11 in East Tasmania Terrane, n = 1 West Tasmania Terrane) were previously dated by U-Pb geochronology using SHRIMP, and the zircon pits from the dating analyses were targeted firstly in O and later in Lu-Hf isotope analyses. The magmatic zircon δ18OVSMOW results ranged from mantle-like values (<5.7‰) to values like supracrustal rocks (~12‰). The zircon δ18O results for Tombstone Creek, Lisle and Mt Stronach granites are similar and the most mantle-like. The Tombstone Creek zircon εHfi results are significantly lower than those of Lisle and Mt Stronach, indicating distinct mantle-derived melt sources from which the zircons crystallized. The magmatic zircon δ18O and εHfi results revealed two distinct paths of infracrustal to upper crustal rock εHfi– δ18O melt evolution: one “high εHf” path linking the results from the Lisle, Mt Stronach, Hazards, Henbury, Lottah, Gipps Creek and Royal George granites, and the other “low εHf” path linking those from Tombstone Creek, Meredith, Poimena, Bicheno and Ansons Bay granites. The paths are statistically different and modeled results are consistent with mixing of Mathinna Supergroup rocks with different infracrustal/mantle-like components. The latter components may be different isotopically defined mantle domains or different mixtures of lower crust and mantle. The high εHf group of granites are strongly associated with granite-related Au, Sn, and Sn–W ore deposits. Citation: Colin L. Jones, Evan A. Orovan, Sebastien Meffre, Jay Thompson, Elena A. Belousova, Matthew J. Cracknell, John Everard, Ralph Bottrill, Simon Bodorkos, David R. Cooke, Zircon O and Lu-Hf isotope evidence of mantle and supracrustal origins of Tasmanian Devonian granites, Gondwana Research, Volume 110, 2022, Pages 1-12, ISSN 1342-937X, ttps://doi.org/10.1016/j.gr.2022.06.004.