The role of geophysics in the discovery of the Gonneville PGE-NiCu-Co-Au Deposit, Julimar, Western Australia.

The Gonneville deposit is a significant new PGE-nickel copper-cobalt-gold sulphide deposit discovered by Chalice Mining in 2020. Located only 70 km northeast of Perth, Western Australia, it represents the first major discovery of a PGE-rich orthomagmatic sulphide deposit hosted in the Julimar Complex of the newly defined Western Yilgarn Ni-Cu-PGE Province. Geophysics has played a significant role in the targeting, discovery, delineation and understanding of the Gonneville deposit under shallow cover. Chalice staked the project in 2018 on the basis of a previously unrecognised, 26 km long, mafic-ultramafic intrusive complex interpreted from open-file aeromagnetic surveys. In 2019, a moving-loop electromagnetic (MLEM) survey undertaken over a discrete 1.6 km x 0.8 km magnetic anomaly detected multiple EM conductors, some of which were modelled to be consistent with a massive sulphide source. A maiden RC drilling program in March 2020 targeting the strongest MLEM conductor intersected massive, matrix and stringer sulphide mineralisation which reported 19 m @ 8.4 g/t Pd, 1.1 g/t Pt, 2.6% Ni, 1.0% Cu and 0.1% Co from 48 m downhole. Multiple high-grade massive-matrix-heavy disseminated sulphide zones have now been intersected in the Gonneville intrusion, along with widespread, low-grade disseminated sulphide mineralisation. The Gonneville intrusion has been surveyed with a wide variety of geophysical methods which include ground gravity, MLEM, downhole electromagnetic (DHEM), airborne magnetic, and airborne electromagnetic (AEM) surveys. DHEM has identified multiple conductors associated with known, and potentially mineralised zones. Gravity and magnetic survey data and inversions have improved the understanding of the geology and structure of the intrusion. A maiden AEM survey flown in late 2020 highlighted known mineralisation at Gonneville as well as identifying multiple new anomalies to the north within the broader Julimar Complex. Geophysical techniques will continue to provide a key role in exploring the Gonneville deposit including targeting extensions of known mineralisation as well as delineating new areas for continued exploration elsewhere within the Julimar Complex.