Gold transport and deposition efficiency in orogenic gold systems A study of Bonanza Au mineralization in the world-class Callie deposit (Northern Territory, Australia)

Orogenic gold deposits commonly concentrate gold in veins with grades often superior to 100 ppm Au. The deposition of elevated concentration of gold remains poorly understood considering the overall low Au-solubility in hydrothermal solutions. This thesis addresses this knowledge gap through a multiscale and multidisciplinary study of the world-class Callie deposit (Northern Territory, Australia) that contains two contrasted styles of orogenic gold mineralisation respectively: very-high-grade (up to 10,000 g/t) gold veins and lower-grade (~2 g/t) sulfide-rich stratabound horizons. This investigation shows that both colloidal gold transport and deposition mechanism efficienly contribute to the formation of high-grade mineralisation.