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Contemporaneous formation of vein-hosted and stratabound gold mineralization at the world-class Dead Bullock Soak mining camp, Australia

Stuart Perazzo, Stephen Turner, Sandra Occhipinti, Christopher McFarlane, John Miller, Crystal LaFlamme, Nicolas Thébaud, Laura Petrella

We investigate the relative and absolute timing associated with the formation of the world-class Dead Bullock Soak (DBS) mining camp. The study area is situated in the Paleoproterozoic Granites-Tanami Gold Province in the Northern Territory, Australia, and consists of five orogenic gold deposits, including the Callie deposit with a resource of 14.2 Moz Au. At DBS, the ore is hosted in Paleoproterozoic metasedimentary rocks and consists of two contrasting styles of mineralization, vein-hosted and stratabound. The vein-hosted mineralization consists of visible gold in quartz, chlorite, carbonate veins preferentially hosted in finely laminated, decarbonized siltstones. In contrast, the stratabound mineralization consists of free gold associated with arsenopyrite concentrated in bedding-parallel sulfide-rich layers, hosted in iron-rich siltstones. This study combines structural and petrographic analysis with detailed U–Pb geochronological data on hydrothermal and metamorphic xenotime and monazite to constrain the relative and isotopic timing of ore formation in the DBS mining camp. The results of this study show that both mineralization styles developed within a series of NE-trending and SE-dipping vein corridors or structural pathways, associated with the development of axial planar fabric related to small-scale F2 folds. U–Pb geochronology shows that both mineralization styles formed at c. 1805 Ma, approximately 35 m.y. after peak metamorphism at c. 1840 Ma. A post-mineralization hydrothermal event is locally remobilizing gold and yields an age of c. 1790 Ma, which provides a minimum age for gold deposition.