P-T conditions of metamorphic and hydrothermal events at Tick Hill gold deposit, Mount Isa, Queensland, Australia

• Published in: Australian journal of earth sciences Vol. 71; no. 4; pp. 538 - 552
• Main Authors: Le, T. X., Dirks, P. H. G. M., Sanislav, I. V., Huizenga, J. M., Cocker, H. A., Nguyen, G. T. T.
• Format: Journal Article
• Language: English
• Published: Hoboken Taylor & Francis 18.05.2024; Wiley Subscription Services, Inc
• Subjects: Amphibolite facies; Amphibolites; Barometers; Biotite; Bismuth; Calcium magnesium silicates; Chlorite; Deformation; Diopside; Feldspars; Garnet; Garnets; geobarometry; geothermometry; Gold; gold deposit; Inclusions; Inliers (landforms); Mary Kathleen; Metamorphism; Metamorphism (geology); Mineralization; Mount Isa; Plagioclase; Quartz; Rocks; Selenide; Selenides; Silver; Temperature changes; Thermometers; Tick Hill; Mount Isa
• ISSN: 0812-0099; 1440-0952
• DOI: 10.1080/08120099.2024.2320195

Tick Hill gold deposit is a unique gold mineralisation style in the Mary Kathleen Fold Belt in the Mount Isa Inlier. The gold at Tick Hill is generally pure without silver and was formed during two discrete metamorphic-deformation events (D 1 and D 3 ). Early gold was observed as inclusions or coarse grains hosted within D 1 peak-metamorphic diopside, scapolite and hornblende from the garnet-biotite-hornblende (tschemakite)-plagioclase (andesine)-quartz assemblage. Late gold is closely associated with bismuth selenide, chlorite, albite, sericite and K-feldspar, and formed during D 3 . The syn-D 1 garnet-plagioclase-hornblende-quartz-biotite assemblage was used to constrain the pressure and temperature (P-T) conditions of metamorphism and mineralisation using the garnet-plagioclase-hornblende-quartz barometer and the hornblende-plagioclase, garnet-biotite and garnet-hornblende thermometers. The results show that peak metamorphism at Tick Hill reached P-T conditions of 6.0-7.6 kbar and 720-760 °C. These P-T conditions together with gneissic and migmatisation textures recorded in different rock types at the Tick Hill area indicate that the peak metamorphism preserved in the area occurred at the amphibolite-granulite facies, compared with the amphibolite facies at the southern Mary Kathleen and Eastern Fold Belt. The D 3 chlorite, which formed during stage 2 to stage 4 mineralisation events, displays a wide range of compositions reflecting a gradual retrograde temperature change from ∼380 °C to ∼130 °C. The pressures during D 3 could not be reliably determined, but the presence of various Bi-selenides suggests that towards the waning stages of D 3 , the rocks may have been exhumed to a pressure less than 1 kbar.