Exploration for possible economic base and precious metal deposits in buried basement rocks, and for possible sedimentary uranium mineralisation in overlying Jurassic-Cretaceous Eromanga Basin sediments, within an area centred about 80 km east of Coober Pedy, has used geophysical and geochemical methods to delineate likely Cu-Au-U-REE drilling targets. Work commenced with compilation of a regional prospectivity review, and the reprocessing and interpretation of all available geophysical data. This was followed by the acquisition during September-October 2007 of a semi-detailed gravity survey (391 stations read at 2 km x 500 m spacing, infilled to 1 km x 500 m over features of interest). Several discrete gravity anomalies were discerned, lying within a prominent east-northeast trending structural corridor. Some of these anomalies coincide with basement magnetic highs, and were thought to have IOCG potential. Late in 2007 limited surface geochemical sampling was undertaken over these targets (5 x minus 80 mesh soil samples, plus 2 rock chip samples). No trace metal assay values of note were returned. During licence Year 2, Carbon Energy acquired a follow-up detailed gravity survey over three prioritised targets (817 stations read on three 400 m x 200 m grids, including some 200 m spaced infill station points). Two of these targets were thereby progressed to high rank status as IOCG prospects, but they appeared to lie at a considerable depth. Interpreted basement depths under post-Mesoproterozoic cover on the tenement, based on the results of inversion modelling of gravity and magnetic data, range from 60 m in the south-eastern corner to more than 1 km along the western and northern boundaries. During licence Year 3, further forward modelling and interpretation of the 2008 gravity survey data identified prospect BB1 as the most promising although still marginal strength IOCG target, with an interpreted depth of source body at 350 m. Prospect BB5 was also confirmed as a second drill-ready target, albeit with an ambiguous setting type and less well-defined shallow (50 m) to intermediate (500 m) source depth. Prospect BB2 was eliminated from drilling contention, as its geophysical properties seemed not to represent an IOCG target. An expert review of all existing exploration for the Balta Baltana region was commissioned from geological consultant David Tonkin early in 2010. His findings suggested that prospect BB5 represents a more attractive IOCG target in terms of gravity amplitude. The main density source at BB5 had been modelled at about 500-600 m depth, lying beneath three shallower E-W orientated basic dykes, but at this prospect the depth to crystalline basement is likely to be only around 100 m. Tonkin also recommended a revision to the existing target ranking, in view of his interpretation of the area's different basement geological characteristics (which appear more similar to those of the Cloncurry IOCG terrain in Queensland than to those associated with typical Olympic Domain rocks), and his dissatisfaction with the excessive basement depths estimated by previous geophysical modelling. The licensee's geophysical consultants Southern Geoscience were asked to consider if acquisition of additional close-spaced ground gravity over BB5 was warranted, in the light of Tonkin’s opinion. During this licence Year 4 period, lawful on-ground access to the tenement was precluded, as it required negotiations to be undertaken to complete a new Deed of Access between Energia and the Australian Commonwealth Department of Defence for this part of the Woomera Prohibited Area (WPA). A Deed of Access was subsequently approved by the Dept. of Defence, but with agreed access limited to a period of six months, due to developments that the Commonwealth and South Australia government authorities had recently announced, intended to further open the WPA for multiple co-existing forms of land usage. Early in licence Year 5, critical assessment of its prospect inventory by the licensee's consultants concluded that all existing geophysical targets appeared to be either of poor quality, or lay only partly on the tenement (prospect BB5), and had been accurately modelled to occur at significant depth. There were no obvious targets on the licence that would warrant the acquisition of more ground gravity data. Because of this adverse exploration outlook, the licensee decided to allow EL 3682 to expire without making application for renewal.