Exploration undertaken by Western Mining Corp. in a search for possible economic Mount Gunson - type stratiform copper mineralisation that could have formed within a sequence of buried Adelaidean metasediments of the eastern Stuart Shelf which in part subcrop on EL 233, initially comprised ground geophysical surveys aimed at delineating several interpreted regional magnetic and gravity anomalies, followed by targeted deep stratigraphic/exploratory drilling at two confirmed prospects. Approximately 70% of EL 233 is covered by poorly consolidated Recent to Tertiary evaporitic and lacustrine sediments of Lake Torrens, which WMC had estimated as being up to 300 m thick. The north-northwest trending Torrens Hinge Zone (THZ), a major basement-penetrating structural feature bordering the Stuart Shelf, was believed to underlie the western margin of the lake. Existing deep drillhole stratigraphic information was restricted to that derived from the Clarence River Basin Oil Co.'s Woomera 1 located at Phillips Pond, on the Arcoona Plateau west of the THZ, which bottomed at 611.28 m within the Late Middle Proterozoic Pandurra Formation. One favoured exploration model being addressed by WMC on the basis of the Woomera 1 stratigraphy was the possibility of copper mineralisation occurring at the Pandurra Formation - Whyalla Sandstone unconformity. Early in 1976, 5 traverses totalling 56 line km of ground magnetic and gravity readings taken at 100 m station intervals were laid out across semi-coincident 4000 gamma regional magnetic and 0 mGal regional gravity highs (named the Torrens prospect) mapped as extending over part of that lake adjacent to the north-eastern side of Andamooka Island, about 8 km from Crombie Ridge. Interpretation of the resulting ground magnetic profiles TR1 and TR2 placed the top of a discrete 2000nT magnetic source body at between 500 and 550 m depth, and showed that it dips south-eastwards to 800-900 m deep over a distance of about 5 km. This model fits with the expectation that, heading eastwards across the THZ, the flat-lying shallow marine platformal sediments of the Stuart Shelf should thicken, change facies and become much more folded and faulted. Three single-point electrosoundings, performed to determine the depth to bedrock under the north-western margin of the lake, indicated that it lies at 40-50 m depth. Subsequently, a rotary airblast, cased precollar hole was drilled to 58 m depth during November 1976, after the completion of which, vertical diamond hole TD1 was drilled to a total depth of 498 m during December 1976-January 1977 from a site on the shoreline of Andamooka Island located nearest to the shallow point of the target magnetic body. Down to a depth of 412.7 m that corresponds to the base of the Tregolana Shale, this drillhole passed through relatively shallow (10-15 degrees) dipping, recognisably Adelaidean strata, but below this depth the sedimentary rocks intersected are very brecciated and have an overall steeper dip of ~30 degrees. A very brecciated and altered chemical sedimentary unit was encountered at the bottom of TD1, over the depth interval 422.75-498 m. It exhibits abundant chlorite, fluorite, pyrite and magnetite, and was found to contain up to 0.29% Cu and 27 % Fe. To follow up another potential target on EL 233, a ground magnetic and gravity survey was conducted during January 1977 along 5 traverses located on the north-western main shoreline of the lake, close to Conan Ridge. However, apparently coinciding regional magnetic and gravity anomalies that had previously been seen at this Red Dam prospect were downgraded by WMC when the new gravity data did not record any appreciable increase in the Bouguer anomaly strength. Later in 1977, more traverses of ground geophysics were acquired in the West Well area on the north-eastern shoreline of Lake Torrens, and the results enabled that particular prospect to be confirmed for drilling. Stratigraphic/exploratory test hole WWD1 was spudded there during January 1978.