Mineralization processes of the Mount Garnet Zinc deposit, NE Queensland (Australia): Insights from garnet geochemistry and U-Pb geochronology

The Mount Garnet Zinc deposit in NE Queensland, Australia, is located in the region of voluminous magmatism associated with the formation of Palaeozoic continental arcs of Gondwana. Ore-forming events of this deposit are related to the intrusion of the Kennedy Igneous Association (KIA) – a large suite of igneous rocks spanning Late Carboniferous to Early Permian in age – into the Silurian limestone (Chillagoe Formation) in the Hodgkinson Province (Mossman Orogen). Petrographic observations and in situ major and trace element analysis reveal the sequence of garnet growth and fluid-rock interaction during skarn formation. Three types of garnets are identified, Grt I (including IA and IB) and Grt II. Grt IB is related to Zn-Pb mineralization. All garnets have elevated Sn and W and the highest levels of W and Sn are observed in Grt II. Garnet U-Pb ages of Grt IB provide the first direct geochronological result of hydrothermal minerals in the Mount Garnet region. New data argues that the base metal mineralization may take place during early Permian period and be sourced from the Claret Creek Supersuite. Sn-W mineralization may be associated with the O’Briens Creek Supersuite.