Following the first public announcement on 18/11/1976 by Western Mining Corp. of its giant Olympic Dam copper, gold and uranium discovery on Roxby Downs Station, Newmont Pty Ltd began a detailed assessment of the Stuart Shelf region of South Australia. Although the latter company did not yet know the nature of the mineralisation or controlling host strata at Olympic Dam, it swiftly made application to the SA Department of Mines for the grant of exploration licences over available ground located north-west of Olympic Dam, selecting areas occupying a trend that lay to the east of the Torrens Hinge Zone (THZ). The subject Codna Hill area was chosen because it covered coincident broad regional gravity and magnetic anomalies that are situated close to the intersection of an east-northeast trending geophysical lineament and the THZ. Newmont entered into a 50:50 joint venture partnership with BHP subsidiary Dampier Mining Co. early in 1977, and EL 327 was granted to both companies in the middle of that year along with six other Exploration Licences covering adjoining ground in the Anna Creek - Mount Woods region which looked to have a similar geophysical character, and which lay over a linear crustal feature that appeared to link major copper deposits further south (Olympic Dam, Mount Gunson and Moonta-Wallaroo). Within the Newmont-Dampier exploration project area, the target sought was of Olympic Dam type, i.e. large tonnage, low grade primary Cu-U mineralisation occurring in or near to a crystalline basement host. Initial field activities commenced in August 1977, with the acquisition of detailed ground magnetic and gravity surveys over regional geophysical anomalies, which in the case of EL 327 comprised the Mount Allalone gravity anomaly. A prospect grid was surveyed there and reconnaissance hand-held magnetometer readings were taken at 250 m intervals along three 8 km long traverses. No discrete magnetic highs were identified associated with these traverses. Solo Geophysics were contracted next to take gravity readings at 250 m x 250 m grid spacing over the Mount Allalone anomaly, and the resulting values from 116 stations defined a broad high. A preferred drill site was picked by Newmont's chief geophysicist for conducting an initial stratigraphic test. Drilling was begun in early November 1977, when vertical rotary mud hole SR11 was carried to 103.9 m, at which depth the hole was abandoned due to sticking drill pipe. A second twin hole, SR12, commenced drilling close by immediately afterwards, but realising progress proved very difficult, necessitating a change of drilling method and contractor. This hole took until May 1978 to reach a depth of 399.0 m, and was terminated there within inferred Permian strata. Diamond coring was conducted in SR12 (NQ and BQ respectively between 98.89-154.5 m and from that depth to hole TD), with reasonable core recoveries obtained throughout. Later scintillometer scans of the recovered drill core gave very low radioactivity responses (2-4 counts per second combined U/Th). While the ground geophysical surveys and drilling were underway and during the months following, Newmont carried out office-based regional basin studies to inform its stratabound, African Copperbelt style epigenetic mineralisation model. Using stratigraphic data from water wells and other boreholes, it estimated that 500-600 m thickness of Recent to Palaeozoic cover sediments might exist at the Mount Allalone prospect. An in-house study of 1:100,000 scale aerial photomosaics and Landsat images was performed to map lineaments over a wide prospective belt running northward along the Torrens Hinge Zone from Moonta to the northern end of the Stuart Range Project acreage, and the aforementioned prominent NNW-trending lineament was clearly identified. Additional lineaments were also seen to pass through the Mount Allalone feature; a prominent ENE trending gravity/magnetic high, and a nearby subsidiary ERTS imaged lineament running parallel about 25 km west of the major Mount Gunson - Olympic Dam lineament zone. Important stratigraphic drilling planned for adjacent Project licences, which would determine if deeper drilling should be attempted on EL 327, was delayed for nine months during 1978 by unseasonally wet weather in the SA Outback, but early in 1979 three deep diamond holes were begun from existing precollared sites on ELs 341 and 355, aiming to penetrate the as-yet still untested basement that now was assumed to lie below 1 km -1500 m depth.