3D geometry of the Dugald River Shear Zone, Mount Isa Inlier, Australia

The Dugald River Shear Zone is a structurally complex, anastomosing shear zone that hosts high-grade Zn mineralisation within the Dugald River Slate. The Dugald River Zn-Pb-Ag mine is situated within the Mount Isa Inlier, Australia and developed through two phases of mineralisation with high-grade Zn mineralisation intimately associated with the development of the brittle-ductile Dugald River Shear Zone. The first phase of mineralisation occurred during the regionally extensive, D2 ductile fold and axial planar cleavage forming event and resulted in the development of a sulfide horizon. This horizon was a preferential site for strain partitioning during early D4 ductile deformation, which resulted in transposition-related concentration and thickening of a sulfide horizon marking the second phase of mineralisation. The Dugald River Shear Zone developed during D4 wherein strain rate incompatibilities between a ductile-deforming sulfide horizon and the brittle-deforming Dugald River Slate resulted in the development of a Riedel shear zone. A high-resolution 3D model of the shear zone was constructed from robust drilling and mapping datasets in which releasing and restraining bends highlight the thickening and thinning of ore lenses, respectively. The 3D model with detailed structural analysis and observations allows for predictive modelling of dilational zones within throughgoing Y-shears, which are prospective sites for remobilisation of high-grade Zn sulfides as the ore body developed coevally with progressive shearing.