Mapping IOCG-related alteration using 3D gravity and magnetic inversion: an example from the Tennant Creek – Mount Isa region, northern Australia

Abstract

To support the Exploring for the Future (EFTF) initiative, identification of possible hydrothermal alteration systems associated with iron oxide copper-gold (IOCG) deposits has been carried out in the Tennant Creek–Mount Isa region of northern Australia. To identify the possible presence of IOCG-related alteration, gravity and magnetic intensity data were inverted to produce 3D models of density and magnetic susceptibility, respectively. The inversion models provide an indication of the volume and distribution of these physical properties within the subsurface. The models were used to define volumes with relatively high densities and high magnetic susceptibilities as proxies for magnetite-rich alteration, and volumes with high density and low magnetic susceptibility as proxies for hematite-rich alteration. Contact zones between these two sets of volumes are considered to be the most favourable areas for potential IOCG mineralisation. However, the inversion modelling inevitably will have mapped a number of false-positives, which will require more detailed inversion modelling and/or other data sets to discriminate these from true IOCG-related alteration.