Maximising the Value of Geophysical Data for Mineral Exploration: A Case Study from the Yilgarn Craton

Substantial investments are made in acquiring information for mineral exploration. However, quantifying critical data and developing an integrated workflow remains challenging. This study addresses these issues through a case study in the Yilgarn Craton, focusing on the Fortitude North prospect. In poorly outcropping regions, potential field geophysics are crucial for targeting drill holes in gold exploration, however, they typically do not directly image gold deposits. Any relationship between gold deposits and these datasets must involve other elements of the mineral system. We use a mineral system model based on Yilgarn Craton orogenic gold deposits which identifies iron-rich mafic hosts with magmatic magnetite as favourable sites for gold deposition. We performed gravity and magnetic inversions for the Laverton greenstone belt, mapping density and susceptibility ranges characteristic of doleritic host rocks containing magmatic magnetite. Areas matching these parameters constitute 14% of the total area and contains ~70% of known gold endowment. Sunrise Dam is excluded due to poor gravity data coverage, but its inclusion would potentially increase the contained endowment to ~90%. We tested various area reduction strategies in a ~465 km2 area around the Fortitude North prospect. Drilling the entire area to find a ~1Moz deposit is risky and expensive (100's M$). Applying the same density and susceptibility filter used for the Laverton belt reduce the search area by 81%. This could be further refined using ground magnetics for targeting drilling in areas where favourable hosts are cross-cut by structures (demagnetised zones). During this talk, we will present a scenario where our approach reduces the search space to 5%. We propose collecting 3D seismic (~millions $) to further target drilling (10's M$) in a cost-effective manner. This demonstrates a quantitative example of the value of regional geophysical data combined with simple mineral systems models in mineral exploration.