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Key alteration minerals associated with epithermal and porphyry Cu–Au mineralisation have been successfully identified using HyMap airborne hyperspectral imagery in a regolith-dominated terrain in the southern Gawler Ranges, South Australia. Alteration assemblages were mapped using Spectral Feature Fitting, a spectral matching algorithm, identifying the spatial distribution of localised advanced argillic and broader argillic alteration. X-ray diffraction (XRD) analysis was undertaken to independently identify the mineralogy of 57 surface soil and rock samples collected from the study area. This analysis confirmed the presence of key alteration minerals including alunite, pyrophyllite and dickite. The integration of spectral and XRD analytical techniques allowed interpretation of mineralogical patterns across the landscape. This study demonstrates that it is possible to identify surface alteration related to potential mineralisation using airborne hyperspectral imagery and semi-quantitative XRD even in a weathered regolith-dominated terrain.KEY POINTS Advanced argillic and argillic alteration identified through hyperspectral image analysis in a regolith-dominated terrain X-ray diffraction used to validate the presence of advanced argillic alteration minerals alunite, pyrophyllite and dickite in the landscape Relationship of advanced argillic and argillic alteration interpreted in two key landscape features in the context of a porphyry mineral system Demonstrates potential for detection of alteration signatures with airborne hyperspectral imagery in regolith-dominated terrains elsewhere. Refereed/Peer-reviewed

A first pass workflow for placing cover sequence materials into four broad lithological groups using A-CNK-FM (Al2O3-CaO + Na2O + K2O-Fe2O3+MgO) and A-CN-K (Al2O3-CaO + Na2O-K2O) ternary diagrams in conjunction with the SiO2 vs Al2O3, Fe2O3 and CaO plus the Ca versus Sr XY diagrams has been derived from lithological logging and laboratory whole-rock geochemistry of 2346 samples. These lithological groups include siliciclastics (quartz sands and clays), weathered material, carbonate lithologies (marine limestone, pedogenic carbonate and compositions intermediate between the two end members) and ferruginous lithologies (including ferricrete and ferruginous sediments). Depositional, weathering and groundwater processes influence sample geochemistry during or after the formation of the material and will influence where the sample will plot on the geochemical diagrams used in this study. Geochemical data for discrete lithologies targeted during sampling (e.g. carbonate lithologies) clusters on diagrams used in the geochemical workflow, whereas data from targeted stratigraphic horizons (e.g. basement-cover interface) are more variable. The ability to characterise rock types that are texturally defined using the geochemical workflow is limited. For instance, the geochemistry of diamictite/conglomerate samples is dependent on the matrix versus clast content and composition as well as the source rock and catchment area. This workflow has the potential to be applied in a mineral exploration environment for rapid interpretation of real-time geochemical (e.g. portable XRF) data to gain an understanding of background geochemistry and geochemical signatures that may be related to underlying mineralisation.Key points A workflow for broad lithogeochemcial characterisation of cover sequence materials has been developed. Uses commonly collected major element plus strontium data acquired by laboratory or portable techniques. Categorises materials into siliciclastics, weathered material, carbonate lithologies and ferruginous lithologies. Applications include a mineral exploration environment for interpretation of large geochemical datasets to understand geology and mineralisation vectors. Refereed/Peer-reviewed

Exploration and mining companies in Australia are faced with the challenge of locating deep ore deposits buried under hundreds of metres of cover sequence. This research aimed to investigate how the integration of hyperspectral remote sensing and surface geochemistry can be used to identify potentially economic mineralisation under cover. While each of these methods are individually mature, their combination for the purpose of mineral exploration is novel. A variety of methods including classification of spatial data and radiometric imagery, hyperspectral alteration mineral mapping and lithogeochemical analysis produced useful results that might benefit exploration specifically in the study area. Further, the methods developed might benefit the wider Australian and international minerals industry, especially in areas where there is no obvious expression of alteration at the surface. Refereed/Peer-reviewed