b'Conferences and eventsNewsThe Oak Dam discoveryKatherine McKenna (BHP)The Oak Dam discovery is an iron oxide copper-gold (IOCG) mineral system discovered in 2018 by the BHP Metals Exploration team. It is located in South Australia 65 km south south-east of Olympic Dam deposit. The project had originally been identified and drilled by WMC in the 1980s. The Discovery hole, AD23, was drilled in April 2018 and produced a discovery intersection of 425 m at 3.04% Cu (with associated gold and uranium), which included 180 m at just over 6% Cu. Use of the historical geophysical data including airborne gravity and magnetics, together with historical drilling and a mineral systems approach, led the exploration team to formulate a hypothesis. More detailed geophysical data wasFigure 1.MT resistivity inversion model across the Duketon greenstone belt.undertaken to aid in supporting the proposed systems model and allow for a more confident targeting. required. Athree-dimensional pseudo-lithological model was constructed based on integrated interpretation of the geophysical and geological data. As well as more conventional Its a story about good old fashion explorationmodel building based on forward modelling and geologically geoscience, Katherine McKenna. constrained interpretation of the potential fields data, the airborne electromagnetic data was used for geological mapping and to provide additional structural information, based in part on Deeper understanding of the Duketon Gold projectthe interpreted dips of extensive stratigraphic conductors. through integration of district scale resistivity data Radiometric data was also effective for refining geological boundaries, and classification of rock types. The regional Tom Hoskin* (Moombarriga Geoscience) and Celia Guergouzframework developed during this phase of the work pointed to (Regis Resources) the possibility of a second mineralisation phase involved in the The Duketon Belt is a greenstone belt with significantgenetic model, highlighted areas of further interest for detailed known gold resources located on the boundary of theexploration work, and complemented the geodata input for a eastern Yilgarn Craton (Kalgoorlie and Kurnalpi Terranes) andmachine learning based targeting exercise. The model and the Burtville Terrane. Regis Resources own the vast majoritytargeting outcomes are used in the recognition of prospective of exploration and mining leases over the belt, operating threeareas and helped to discover several prospects, including production centres fed by numerous satellite deposits. Registhe Siriema Cu-(Ni-PGE) deposit, about 1.5 km south continue to develop satellite projects across the belt as wellof Vermelhos mine.as extending existing projects underground. Moombarriga Geoscience acquired 513 magnetotelluric soundings for RegisThe end result of the geophysical modelling Resources during two field seasons between 2018 and 2020,needsto be usable for the exploration geologist, providing deep electrical resistivity models across much of theJames Reid.belt. These models are compared with existing geophysical and geological data for the belt, to develop a model for the mineral system of the Duketon Belt.Interpretation of regional geophysical data for copper exploration, Cura Valley, BrazilJames Reid*, Scott Napier, Jean-Philippe Paiement, Glenn Pears (Mira Geoscience) and Pablo Mejia (Ero Copper Corp.)Regional airborne geophysical data, including SkyTEMairborne electromagnetics, airborne gravity, aeromagneticsand radiometrics, have been interpreted to produce a 3D model of the Cura Valley, Bahia, Brazil. The Cura Valley is host to several operating mines and Cu deposits, including Pilar, Vermelhos and Surubim. Cu-(Ni-PGE) sulphide mineralisationFigure 2.SOM classification of regional airborne radiometric data.is associated with mafic-ultramafic rocks exhibiting broad alteration and possibly associated with regional-scale structures.Geophysical response and exploration methods for Airborne electromagnetics and airborne gravity surveys wereCallie-style targets in Tanami, NT, Australiaoriginally conducted with the aim of direct detection of mineralisation or favourable host rocks. However, significantTim Dohey*, Alan Hawkins, Andrew Crawford and David Maidment differences between the existing geological mapping and the(Newmont Corporation)new geophysical data were immediately recognised. In order to find new deposits, a revised interpretation of the geometry of theCallie is a world-class vein-hosted orogenic gold deposit Precambrian units, major structures and intrusive sequences waslocated 650 km NW of Alice Springs, within a conformable FEBRUARY 2022 PREVIEW 20'