Exploration of IOCG deposits in Queensland, Australia using geophysical models of Ernest Henry copper mine

The  Ernest Henry copper mine is one of the main Australian copper resources and a typical Iron Oxide Copper Gold (IOCG) deposit case. These deposits have specific geophysical signatures, e.g., considerable magnetic susceptibility and low resistivity due to magnetite mineralization. This research studies the geophysical models estimated via the inversion of magnetic and magnetotelluric in the Ernest Henry mine area. We also conducted these inversions in two other areas close to the Ernest  Henry mine, named A and B, which show magnetic anomalies similar to the Ernest Henry mine. Then, we compared the estimated models in these areas with those in  Ernest Henry's area. Three-dimensional inversion of magnetic data using the Li and Oldenburg algorithm revealed masses with magnetic susceptibilities higher than 0.019, 0.048, and 0.011 in SI units in the Ernest Henry, A and B areas, respectively. All the masses were extending from the surface to depths of one to three kilometres. Next, impedance analyses of magnetotelluric data indicated a two-dimensional behaviour of the Earth up to a frequency of 1 Hz in all the areas. Also,  we conducted two-dimensional inversions of these data along a profile for each area. A comparison of the estimated resistivities demonstrated a relatively conductive mass with a resistivity of less than 30 ohmm at depths of 5 km and beyond in all three areas. These models also demonstrated a decrease in the resistivity along the fault lines within the ranges, corresponding to the location of masses with relatively significant magnetic susceptibility identified during the magnetic data inversions. Geochemical analysis of copper grade variations in exploratory boreholes drilled in areas A and B indicated an increase in copper concentration exceeding 400 ppm in both areas. The structure of the estimated geophysical models in areas A and B and those estimated in the Ernest Henry area is similar. Besides, geochemical analysis of copper grade in exploratory boreholes drilled in areas A and B indicated an increase in copper concentration exceeding 400 ppm in both areas. Therefore, we deduce the possibility of IOCG copper mineralization deposits similar to the Ernst Henry mine in areas A and B. Meanwhile, since the concentrations of probable mineralizations have occurred along a fault zone in all the models, we suspect that the mineralization likely originated from hydrothermal solutions. These solutions spread from fault lines adjacent to highly resistive intrusive masses to the surface, causing the mineralization of magnetite and copper ores.