Petrogenesis and geochronology of the granulite facies gneissic suite hosting the Katanning Gold Deposit, Yilgarn Craton, Southwest Western Australia

Understanding the formation of high metamorphic grade sequences from Archean Cratons is necessary for modelling Craton formation and evolution. In this study, we undertake a detailed review of the 1.28 Moz Au Katanning Gold Deposit granulite-facies host sequence, located in the southwestern Yilgarn Craton, Western Australia. To elucidate the nature of this granulite-facies gold deposit, a detailed geochemical, petrographic, and geochronological investigation was undertaken of its host gneissic sequence to establish a petrogenetic model of its formation. The high-grade metamorphic rocks that host gold mineralisation at the Katanning Gold Deposit can be divided into nine major lithological associations. These rocks are interpreted as mafic to felsic protoliths resembling modern BADR sequences which is consistent with extensional magmatism in a back arc setting. Zircon U-Pb dating yielded magmatic ages of a felsic and mafic gneiss at 2711 +/- 4 Ma and 2703 +/- 3 Ma, respectively, which are contemporaneous with the latest Archean volcanic events in the western Yilgarn Craton. The U-Pb ages of metamorphic zircon across four samples yielded a combined age of 2651 +/- 2 Ma, interpreted as the time of peak metamorphic conditions of similar to 700-900 degrees C and similar to 5-7 kbar for the entire sequence. Indicating rapid (c. 30 Myr) burial, marked by the maximum depositional age of a metasedimentary gneiss (2683 +/- 8 Ma) to granulite facies metamorphism, potentially implicating inversion of a closed back arc rift. This study provides a regional context for tectonic evolution of the southwestern Yilgarn Craton, reflecting on the role of high-grade metamorphism in Archean Cratons, and serves as a rare, detailed investigation into a large granulite-facies gold deposit.