South Australia's Gawler Craton is known for its high exploration potential for iron oxide copper gold (IOCG) deposits. In addition to the giant Olympic Dam deposit, relatively recent discoveries at Prominent Hill and Carapateena and a large number of smaller prospects confirm the attractiveness of the Mesoproterozoic rocks near the eastern margin of the Craton. The challenge facing explorers is the thick and extensive sedimentary and volcanic cover that overlies those prospective basement rocks. The only way to image buried rocks is by integrated analysis of remotely measured geophysical data with geological knowledge. Deep reflection seismic data provides critical information on unit depths, thickness and geometries. Interpreted profiles along the 03GA-OD1 and transverse 03GA-OD2 reflection seismic lines centred on the Olympic Dam deposit provide the best available information on the crustal-scale 3D geometries in that area. These relationships are extended throughout a 600 km east-west by 510 km north-south subset of the eastern Gawler Craton, to a depth of 25 km below surface, using geologically-constrained 3D inversion of public domain gravity and magnetic data. Including geological constraints is critical to ensure that the 3D property models recovered using the inversions are consistent with all available geophysical and geological data. Geological constraints are developed from surface mapping, seismic profile interpretations on the Olympic Dam lines as well as the 08GA-C01 and 03GA-CU1 lines in the Curnamona Craton, and 2D potential field modelling. Where knowledge of the cover rocks exists, it is included as a constraint to enhance the resolution of features at depth.

The 2007 North Queensland seismic survey provided a new geodynamic framework and province architecture map for the North Queensland region. Coupled with this, companion geophysical studies provided new understandings of the subsurface of the region. A major focus of the geophysical investigations was the use of potential field inversions. These inversions allow for the mapping of units undercover, predict the extension of geometries away from seismic lines, and also provide a measure of alteration. The North Queensland region also allowed for the testing of both qualitative and quantitative methods to map alteration using geophysical inversions.

Hyperspectral airborne images from the Eastern Fold Belt of the Mount Isa Inlier, were validated as new tool for the detection of Iron oxide Cu-Au (IOCG) related alteration. High resolution mineral maps derived from hyperspectral imaging (4.5m/pixel) enables the recognition of various types of hydrothermal alteration patterns and the localisation of fluid pathways. Four different types of hydrothermal alteration patterns were identified with the hyperspectral mineral maps: (1) Metasomatic 1: White mica mineral maps were applied to map the spatial distribution of regional sodic-calcic alteration in metasedimentary successions of the Soldiers Cap Group in the Snake Creek Anticline. (2) Metasomatic 2: Alteration zoning is evident from albitised granites, assigned to the Williams-Naraku Suite, along the Cloncurry Fault show characteristic absorption features in the shortwave infrared range (SWIR) and can be detected with white mica mineral maps (white mica composition, white mica content, white mica crystallinity index).

The Broken Hill Exploration Initiative (BHEI) started in 1994 and is a joint effort between the New South Wales Department of Primary Industries - Mineral Resources, the South Australian Department of Primary Industry and Resources and the Commonwealth Government through Geoscience Australia. The aim of the BHEI is to provide a new generation of geoscientific data for the Curnamona Province, particularly the Broken Hill-Olary region, as a basis for more effective mineral exploration by industry. This initiative aims to provide the best possible knowledge and information-base for mineral and petroleum exploration investment in western New South Wales and eastern South Australia. The region will benefit from the application of new technologies and exploration methodologies to enhance knowledge of the geological controls of mineral deposit systems. BHEI conferences are held on a regular basis to highlight the geoscientific advances made during the life of the initiative. The contents of this Record are the extended abstracts of oral and poster papers presented at the BHEI conference that was held in Broken Hill on 26-28 September 2006.

Regional-scale constrained potential field inversions can be used to infer rock types, alteration, and structure. This is particularly valuable when basement is obscured by younger cover. The methods outlined in this study have been applied to a 150 km ? 150 km region around the giant Olympic Dam copper-uranium-gold deposit, where abundant haematite, sulphide, and magnetite alteration produces a strong potential field response despite thick cover. The results are used to develop the first 3D map of magnetite and haematite/sulphide alteration for the Olympic Cu-Au province, and shows that the alteration around known Cu-Au mineral occurrences can be detected using coarse regional-scale inversions. The provision of a reference model in the inversion formulation permits geological observations to be introduced into the inversion process, and to be used to guide the inversion towards more geologically reasonable outcomes. This allows hypotheses regarding 3D geological architecture to be tested rigorously for compatibility with potential field data. An iterative procedure of inversion followed by updating of the reference model allows 3D maps of alteration and structure to be created that are consistent with both the known geology and observed potential field data.

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Chemical alteration to certain end-member minerals, such as magnetite, pyrrhotite and pyrite, can produce density and magnetic susceptibility contrasts. These contrasts can be detected using gravity and magnetic surveys. Interpretation of alteration is made possibly by inverting the geophysical data (calculating subsurface properties from the survey results) and combining these inverse results with 3D geological mapping. An application of this method to

The Kangaroo Caves zinc-copper deposit in the Archaean Panorama District in the northern Pilbara Craton, Western Australia contains an Indicated and Inferred Mineral Resource of 6.3 million tonnes at 3.3% zinc and 0.5% copper. The Kangaroo Caves area is characterised by predominantly tholeiitic volcanic rocks of the Kangaroo Caves Formation, which is overlain by turbiditic sedimentary and volcanic rocks of the Soanesville Group. Zinc-copper mineralisation is hosted mainly by the regionally extensive Marker Chert, the uppermost unit of the Kangaroo Caves Formation, and structurally controlled by D1 synvolcanic faults. The upper area of the deposit is characterised by quartz-sphalerite ± pyrite ± baryte ± chalcopyrite, whereas the lower area contains mainly chlorite-pyrite-quartz-carbonate-sericite ± chalcopyrite ± sphalerite. Laser ablation inductively coupled plasma mass spectrometry analyses show that cobalt-nickel ratios in pyrite are significantly greater in the upper, zinc-rich area (median copper/nickel = 0.4) of the deposit than the lower, zinc-poor area (median copper/nickel = 5). Structural analysis of the Kangaroo Caves area combined with Leapfrog modelling of ore and trace element distribution shows that the deposit is predominantly an elongate sheet of zinc mineralisation (-1%), which plunges ~30° to the northeast and is approximately 1000 metres in length. The morphology of the Kangaroo Caves deposit was retained from its original formation, despite rotation during the D2 event. Variations in hydrothermal alteration assemblages, including the copper and nickel contents of pyrite within the deposit and underlying dacite, are interpreted to be the result of variations in the influx and mixing of seawater with upwelling volcanogenic fluids during zinc-copper mineralization. At the Kangaroo Caves area the cobalt-nickel ratio of pyrite can be used as an exploration vector towards high-grade zinc-copper mineralization.

An integrated package comprising geological, structural, geophysical, geochronological and geochemical data. The GIS encompasses the outcropping and covered portions of Palaeoproterozoic and Mesoproterozoic rocks straddling the NSW-SA border (the Broken Hill, Euriowie, Olary, Mount Painter and Mount Babbage Inliers). The GIS features recent data collected by the Broken Hill Exploration Initiative.