b'FeatureImaging the supergene search space with ANTboth the cover and basement due to physical processes that mayBackground: Alford East geologybe important for holistic mineral exploration. This method has been widely used over the past 20 years in studies of depth ofThe Alford East project area lies within the eastern Gawler sedimentary cover (Beard et al. 2022), magmatic systems (Lietal.Craton, which is host to iron oxide copper-gold deposits of 2023), active faulting (Mordret et al. 2019), lithospheric andthe Olympic Cu-Au Province (Skirrow et al. 2007, 2018; Reid continental scale structure (Bensen and Ritzwoller 2008; Saygin2019). Hematite breccia deposits such as Olympic Dam, and Kennett 2010; Ward et al. 2013; Hoggard et al. 2020) andProminent Hilland Carrapateena occur in continuum of mineral exploration (Hollis et al. 2018; Li et al. 2020; Chen etal.Cu-Au-U deposit types that includes deposits that formed at 2021; Ryberg et al. 2022). Recent advances in the sensitivity ofhighertemperaturessuch as the Hillside deposit (Conor etal. ANT seismometers mean that the cover-basement interface can2010; Ismail et al. 2014). The Alford East project lies in the now be imaged with great precision (Beard et al. 2022; Oliviersouthern region of the Olympic Cu-Au Province, near to the et al. 2022). However, it has been less certain if these seismictownship of Wallaroo on Yorke Peninsula, a historical copper methods can image variation within the cover sedimentarymining centre (Figure 2).units, and especially to image variation in weathering intensityThe basement geology of Alford East project area consists of that might indicate the presence of supergene zones with higherPalaeoproterozoic metasedimentary and metavolcanics rocks prospectivity to host economic mineralisation. (Wallaroo Group) intruded by and structurally interleaved with Recently, Fleet Space Technologies partnered with Thor EnergyA- to I-type granites (Conor et al. 2010). Primary copper-gold PLC to investigate the use of ANT for imaging the weatheredmineralisation in the region is structurally controlled, associated zones of primary sulphide-enriched rocks in the eastern Gawlerwith sheared metavolcanic rocks of the Wallaroo Group, Craton. Here we provide a brief overview of the project andmetasomatic rocks of the Oorlano Metasomatite, and Hiltaba the resulting ANT 3D velocity models and discuss the utility ofSuite granites. Cambrian and Cenozoic sedimentary rocks for this method for detecting highly weathered basement zonesa cover sequence across much of Yorke Peninsula (Zang 2006). across covered terranes. With the intensity of weathering thatIn the Alford East region, cover is generally thin, ranging from the Australian continent in particular has been subject to, since5to50 m.at least the Mesozoic, but principally during the Paleogene (Hill et al. 2008; Bourman et al. 2010), the likelihood that supergene enriched zones exist in other covered areas of Australia is high, and a method that can screen for zones of possible supergene enrichment will be a useful addition to the mineral explorationtool kit.Background: Supergene processesOxide ore occurs within soft and relatively easily mined saprolite and is often amenable to simpler metallurgical treatment compared to sulphide from deeper, hypogene ore. Mineralogically, supergene copper occurs as oxide minerals such as chrysocolla, malachite and azurite, or sulphide mineralssuch as chalcocite, which is an important aspect of many Andean porphyry deposits such as Escondida (Sillitoe 2005). Other elements are also often concentrated by weathering and deep oxidation. In examples from the Andean copper porphyry systems, weathering also releases low-grade refractory gold, making this also amenable to metallurgical processing and concentration (Sillitoe 2005). Where basement rocks are enriched in accessory phases that contain rare earth elements (REE), such as monazite, zircon or xenotime, REE may also be enriched by acidic weathering. The REE may then be found as either adsorbed ions on clays, as colloids, or as secondary REE minerals such as xenotime, or apatite (Cocker2014; Wu et al. 2023).Supergene oxide ore forms by electrochemical oxidation of sulphide-bearing bedrock in acidic conditions due to interaction between groundwaters, rocks and Fe- and S-oxidising bacteria (Sillitoe 2005). In such environments, copper is leached and transferred downward to the reduced environment, beneath the water table, forming zones of supergene enrichment and ideally, economic ore. The structure of the basement rock system is an important control on movement of groundwatersFigure 2. Location of the Alford East project on exploration licenses of Thor and formation of supergene enrichment, with structuresEnergy PLC (Els 6529, 5984), in the eastern Gawler Craton of South Australia. Location of ANT survey is shown, and the inset shows the location within South providing a focus for movement of groundwaters into theAustralia. a. Simpli\x1ded surface geology of the Alford East region. b. Total magnetic deeper parts of the orebody and outwards into cover unitsintensity image. c. Interpreted crystalline basement geology. Geological and (Arabpour et al. 2021). geophysical data from Geological Survey of South Australia, via SARIG.40 PREVIEWAPRIL 2024'