Modeling outflow from the Ernest Henry Fe oxide Cu-Au deposit: implications for ore genesis and exploration

Cooling experiments (from 300 to 100 °C) using the 'spent fluids' predict early high-T (300-200 °C) Na-, Ca-, Fe-, and Mn-rich, magnetite-bearing hydrothermal associations, whereas with cooling to below 200 °C, and with progressive fluid-rock interaction, the system produces rhodochrosite-bearing, hematite-quartz-muscovite-barite-rich assemblages. These results show that the radical geochemical and mineralogical changes associated with cooling and progressive fluid influx are likely to be accompanied by major transformations in the geophysical expression (e.g., spectral and magnetic character) of the alteration in the outflow zone, and highlight the potential link between magnetite- and hematite-bearing IOCG hydrothermal systems.