Quartz oxygen isotopes from Tick Hill area in Mount Isa Inlier: indication of a regional fluid overprint

• Published in: Australian journal of earth sciences 2022-04, Vol.69 (3), p.439-452
• Main Authors: Le, T. X., Dirks, P. H. G. M., Sanislav, I. V., Harris, C., Huizenga, J. M., Cocker, H. A., Manestar, G. N.
• Format: Article
• Language: English
• Subjects: gold deposit; Isan Orogeny; Mary Kathleen; Mount Isa; oxygen isotope; Tick Hill
• ISSN: 0812-0099; 1440-0952
• DOI: 10.1080/08120099.2022.1985608

At the Tick Hill gold deposit, δ 18 O quartz data for the mineralised lithologies and surrounding rocks are similar and fall within a narrow range of 10.5-13.7‰ V-SMOW. The highly mineralised quartzo-feldspathic mylonite has quartz δ 18 O (δ 18 O quartz ) values of 11.3-13.6‰, which are similar to values for the surrounding rocks both locally and regionally, i.e. δ 18 O quartz by itself does not provide a useful exploration tool. The δ 18 O quartz values from the Tick Hill area most likely reflect the late Isan hydrothermal overprint at 1525-1520 Ma. The origin of the altering fluids is unclear, as the δ 18 O quartz values overlap with reported δ 18 O values calculated for both metamorphic and igneous fluids. When combining the δ 18 O quartz results with δ 18 O calcite results available from the literature, a temperature of 350-550 °C was calculated, which is consistent with observed alteration assemblages associated with gold mineralisation. KEY POINTS The δ 18 O quartz values (10.5-13.7‰ V-SMOW) of Au-rich quartz-feldspar mylonite are indistinguishable from the altered host rocks both local and regional. The narrow range of δ 18 O quartz values for the rock units in the Tick Hill area and Mary Kathleen Domain most likely reflect a regional fluid overprint. The post-mineralised quartz-calcite veins yield higher δ 18 O quartz values (14.1-17‰), possibly reflecting (partial) re-equilibration of minerals locally formed in late cataclastic fault rocks.