Mapping discontinuous sulphide-rich harzburgite bodies using geophysical inversion techniques: A case study from a Ni–Cu deposit

The Ni–Cu sulphide mineralisation investigated in this study is hosted within a steeply dipping, differentiated ultramafic sill composed primarily of tremolite schist and lenticular bodies of harzburgite. The harzburgite contains net-textured sulphides and occasional massive sulphide veins, with mineralisation dominated by pyrrhotite, chalcopyrite, and pentlandite. Physical property measurements indicate that the mineralised sill is both more conductive and magnetically susceptible than the surrounding country rocks, making it a viable target for geophysical inversion.

This study integrates airborne magnetic data, ground and downhole electromagnetic (EM) surveys, and audio-frequency magnetotelluric (AMT) data to map discontinuous sulphide-rich harzburgite bodies. Magnetic and EM modelling techniques were used to delineate high-conductance zones, which were integrated with geological models to highlight potential extensions of mineralised pods. AMT inversion further confirmed the geometry of the mineralised intrusion. The results demonstrate the value of combining multiple geophysical methods to guide drilling and improve targeting of discontinuous sulphide-rich bodies within ultramafic systems.