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 Margaret Creek area was chosen because it covered coincident broad regional gravity and magnetic anomalies that are situated close to the southern edge of the Phillipson Trough. Newmont entered into a 50:50 joint venture partnership with BHP subsidiary Dampier Mining Co. early in 1977, and EL 305 was granted to both companies in March along with two other Exploration Licences covering adjoining ground in the Danae Hill and Coolawarra areas which looked to have a similar geophysical character, and which lay to the west of 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 April 1977, with the acquisition of detailed ground magnetic and gravity surveys over the McDouall Peak gravity anomaly in the west of EL 305. A prospect grid was surveyed there and reconnaissance hand-held magnetometer readings were taken at 250 m intervals along three 10 km long principal traverses. Solo Geophysics were contracted during July 1977 to take gravity readings at 250 m x 2000 m station spacing (140 readings collected). Interpretation of the resulting magnetic and gravity data indicated that crystalline basement occurs at shallow depth, so it was decided not to drill test this anomaly. Attention shifted to the Hawks Nest gravity anomaly situated 24 km to the SSE. Ground magnetic surveying conducted there by Newmont in September 1977 along two 8 km long traverses spaced 2.5 km apart defined a sharp 1400 gamma peak coinciding with the gravity high, and this was thought to reflect banded iron formation units present in the Cleve Metamorphics at this locality, because such rocks outcrop to the west of the grid. To better define the anomaly and provide a selection of drill sites, Solo Geophysics read 76 gravity stations at Hawks Nest, also at 250 m station intervals, during the month. Exploratory/stratigraphic percussion hole SR7 was drilled vertically at Hawks Nest to a total depth of 67.2 m during October 1977. The hole was stopped within fresh chloritic schist, after passing through a weathered basement section that probably extends from ~35 m to 65.7 m depth. A second hole, SR9, also sited on the flank of the Hawks Nest anomaly, was drilled to 71.4 m total depth during November 1977. It bottomed in a lithic plagioclase-quartz wacke having a chlorite-sericite matrix. This was thought to be part of a ?Cretaceous pebble horizon overlying basement. A third stratigraphic drillhole at Hawks Nest, SR15, was afterwards precollared to 85.8 m depth at a site 7 km to the west-northwest of SR9. It encountered a hard, fine grained pale greenish-brown quartzite at 84.2 m, which was correlated with the unit at the base of SR9 as a downdip facies equivalent. Newmont decided to return to hole SR9 and deepen it with a diamond cored tail to obtain samples of the underlying basement, to help determine if any prospective Proterozoic rocks are present at Hawks Nest. This extension drilling at SR9 took place in December 1977, with 19.1 m of coring done down to 90.5 m depth. The entire core lithology consists of a slightly pyritic, metamorphosed coarse grained litharkosic wacke, in which the pebbles have been stretched along the foliation. Newmont considered this rock to be part of the Cleve Metamorphics. The diamond rig was shifted back to SR15 to deepen it also, with an additional 25.7 m of coring completed to TD 111.5 m. This showed that the ?Cretaceous or ?Permian sandstone sequence there continues to 104.3 m depth, before transitioning into a dark grey, medium grained arkosic wacke similar to the rock types seen at the bottom of SR9. The rock contains 2-3% disseminated pyrite as grains averaging ~1 mm diameter. Laboratory semi-quantitative emission spectroscopic chemical analyses were made of selected core samples collected at 10 cm intervals from the lower part of both drillholes, but the results were uninteresting, apart from slightly anomalous lead (highest values 100 ppm and 300 ppm Pb) in samples from the interval 69.5-89.5 m in hole SR9. All of the drill cuttings and cores from the three exploratory holes were scanned using a hand-held gamma ray spectrometer, but readings averaged only 1-2 counts per second of combined U/Th radiation. Because the Hawks Nest anomaly appeared to be underlain at shallow depth by the Cleve Metamorphics, the JV partners decided that further exploration there was not warranted. However, a recent re-evaluation of regional geophysical anomalies within the licence area had identified a distinct circular aeromagnetic anomaly situated 5 km north-northeast from the Mirikata Tracking Station, which it was thought could have exploration potential. Consequently, application was made to SADME for an extension of tenure period for six months, from March to September 1978, to allow for making an investigation of this feature. Ground magnetic readings and a detailed gravity survey of 126 stations were acquired on it during April 1978, over a 250 m x 2500 m grid of three principal lines pegged as an extension of the McDouall Peak grid. The magnetic anomaly appeared to be caused by two sources - a low-order NW trending anomaly possibly, caused by BIF or a basic dyke, and an unusually sharp 2000 gamma anomaly crossing this at right angles. A low order gravity trend was defined coinciding with the NW trending magnetic anomaly, but the NE trending magnetic anomaly had no gravity expression, and was discounted as a target. Subsequent considerations of this feature's geophysical character and of the licence's overall prospectivity downgraded both when, in the light of the wider drilling results that they had so far obtained, the partners concluded that Proterozoic basement was unlikely to exist there, nor within the JV's other tenements located too far west of the Torrens Hinge Zone and the major tectonic lineament belt. Therefore tenure of EL 305 was surrendered during July 1978.