An inaugural exploration licence covering land in the Roxby Downs Station and Andamooka Station holdings was taken up by Western Mining Corp. (WMC) to document the stratigraphic section present in the northern portion of the Stuart Shelf tectonic region, and to investigate the base metal potential of largely flat-lying Cambrian and Precambrian metasediments believed to be present in the subsurface on this previously unexplored ground. It was intended to undertake geophysical surveys and drilling, to gather information intended primarily to ascertain whether suitable environments exist there for the formation of economic stratiform copper deposits, perhaps of the Mount Gunson / Cattle Grid deposit style, which is spatially associated with the Proterozoic Pandurra Formation - Whyalla Sandstone unconformity. At the outset of exploration field work, a refraction/reflection seismic survey was conducted by WMC near Olympic Dam [i.e. the original water storage geographical feature] on Roxby Downs Station during May 1975, to help define the likely depth to top of pre-Adelaidean basement, and thus constrain the depth required to be attained in test stratigraphic drilling. Two refraction lines, one north-south 5 km long, the other east-west 6.5 km long, plus a 1 line km continuous reflection profile, were shot and recorded in the vicinity of this particular dam by contractor the South Australian Department of Mines (SADM). The survey results were interpreted by the Department's Chief Geophysicist, Mr B.E. Milton (cf. RB 790). The survey proved to be a technical success, by clearly demonstrating the existence of seismic velocity contrasts in the Marinoan quartzites, sandstones and shales of the Tent Hill Formation, while the continuous reflection profile laid out east of the dam defined a possible basement reflective seismic event at ~291 +/- 34 m vertical depth. In addition to the seismic survey work, one 24 km long ground magnetic traverse that passed directly through the Olympic Dam locality was acquired along 321.5 degrees True direction, to provide detailed magnetic data to enable a calculation of depth to the top of a magnetic anomaly interpreted as originating from basement rocks. However, the resulting ground magnetic data yielded a profile that was almost identical to that produced by earlier BMR 4-mile regional airborne magnetic data. This similarity was interpreted as indicating that the source of the magnetic anomaly lay at considerable depth, i.e. within ?Cleve Metamorphics crystalline basement. 7 vertical percussion holes with a total penetration of 330 m were drilled by WMC during July 1975, in a search for groundwater which it was hoped could supply both its planned diamond drilling project and Roxby Downs Station needs. Only hole RDP1 found water, but of a quantity insufficient to provide drilling requirements for exploratory hole RDD1 then already underway. During June-July 1975, vertical stratigraphic diamond drillhole RDD1 was completed at the Roxby Downs prospect to a total depth of 411 m, from a site 400 m west of Olympic Dam, to test a coincident magnetic and gravity high that was inferred to represent a geophysical response of a kind that could be caused by buried basic volcanic rocks (possibly Roopena Volcanics). After passing through the Stuart Shelf Cambrian and Adelaidean metasedimentary cover sequence comprising (from the surface downwards) Andamooka Limestone, Arcoona Quartzite, Corraberra Sandstone and Woomera / Tregolana Shale, probable basement was reached at 335.73 m depth, when the hole passed from a very thin layer of medium grained red sandstone with heavy mineral cross-bedding into what appeared to be a coarse grained, red haematitic amygdaloidal basic volcanic rock. The NQ/BQ drill core was chip sampled at nominal 2 m intervals during early August, and these samples were sent for laboratory assaying to determine the diagnostic trace metal contents of the strata encountered. Significant copper mineralisation was reported in the assay results from sampling of the bottommost unit drilled, together with elevated gold and silver, e.g. 1.02% Cu, 0.29 ppm Au and 3.7 ppm Ag on average over the depth interval 353-391 m, with higher grade thick (to 18 m) zonal intercepts within this interval variously attaining maximum values of 1.32% Cu, 0.45 ppm Au and 5.1 ppm Ag. In view of these good results, the RDD1 diamond core was resampled using half-core splits to get a more representative assay; this yielded average values of 1.047% Cu, 91 ppm Mo, 11.34% Fe and 4.0 ppm Ag over the same depth interval 353-391 m, including peak values of 1.382% Cu, 145 ppm Mo and 5.9 ppm Ag over the interval 359-367 m. The stratigraphy of RDD1 was re-interpreted following receipt of the drill core assay results, to have ?Whyalla Sandstone as the very thin sandy horizon unconformably overlying ?Pandurra Formation at 335.73 m depth, and the core recovered from below this depth was re-logged to produce a different geological description of the mineralised ?Pandurra unit, viz. "red altered fragmental rock composed of angular quartz fragments set in a sericite-quartz-haematite matrix". The host material composition was studied via X ray diffraction determination of its mineralogy, and rock bulk density measurements were made. During late August 1975, vertical stratigraphic diamond drillhole RDD2 was completed by WMC at the Roxby Downs South prospect to a total depth of 513 m, from a site ~2 km east of Appendicitis Dam, to test a coincident magnetic and gravity high that was inferred to underlie a similar but more shallowly lying stratigraphic section than had been encountered in RDD1. Due to the copper discovery made in that particular hole, the target for RDD2 was to intersect stratiform copper mineralisation formed in a comparable setting above probable, but as yet not found, altered basic volcanic rocks [to accord with Douglas Haynes' original metallogenetic model for Stuart Shelf copper mineralisation, which was adopted in 1972 by WMC]. The hole was percussion precollared to 120 m depth, and then diamond cored through the Stuart Shelf Adelaidean strata until reaching an unconformity at 437 m depth, whereupon the hole passed from quartzite into a thin horizon of dolomite. This in turn was underlain with sharp unconformity at 439.64 m by non-magnetic ?Pandurra Formation red-bed shales, gritty sandstones and conglomerates commonly showing heavy mineral banding. No copper mineralisation was seen, and no assay values of note were returned from drill core sampling done at 2 m intervals. The third quarter of tenure of EL 190 was partly devoted to obtaining improved geophysical coverage in the Roxby Downs prospect area. A three-line prospect grid totalling 70 km was laid out and levelled around a baseline connecting drillholes RDD1 and RDD2. Then a seismic refraction survey was shot during November 1975, recording 40.94 line km of spread along two of the transverse grid lines. Following this, ground magnetic and gravity surveys were read over the grid during December 1975, with coinciding readings taken at 90 m station spacings. This detailed gravity data permitted more precise definition of the amplitude of the Roxby Downs gravity anomaly (20 mGal, compared to the 8 mGal that was estimated from the former regional gravity data acquired at 4 mile spacing by the SADM). In addition, downhole geophysical logging was performed on 30/10/1975 through the entirety of the two open diamond drillholes by contractor SADM, with gamma ray and neutron tools being run to confirm the anomalous subsurface radioactivity which WMC had earlier detected, when it had gamma ray logged hole RDD1 during September with its own wireline tool. A planned programme of selective diamond drilling to define the extent and strength of copper mineralisation discovered by RDD1 was begun in mid-December 1975, initially via percussion precollaring of a pattern of ten vertical holes (RP8 - RP15, plus RP 17 and RP18, for 865 m) centred on that location. An addition percussion hole, RP16, was drilled to 50 m depth at Sunday Well in an unsuccessful search for potable and/or drilling supply groundwater. Two diamond cored holes, RD3 and RD4, were next completed for a total penetration of 734.35 m (561.5 m cored). RD3 was sited 400 m south-east of RDD1, while RD4 was sited 400 m north-west of it. No definite Pandurra Formation was intersected below the Woomera / Tregolana Shale horizon in either case. Both holes were terminated within granite basement, which gave disappointing copper assays (2 m @ 0.57% Cu in RD3, and a maximum of only 0.123% Cu in RD4), and had undetectable levels of uranium. Also during this quarter, the results of assaying the RDD1 drill core for uranium were received, for rocks penetrated below 335 m depth: an average uranium content of 72 ppm (0.16 lb/ton) U was measured for the 59 m thick interval 335.87-395.00 m. During the fourth quarter of licence Year 1, diamond drillhole RD5, located about 1 km north of RDD1, was completed to a total depth of 461.66 m, but was terminated prematurely due to difficult drilling conditions. The hole entered pre-?Pandurra Formation altered granite basement at 325.74 m depth, and therein found a thick occurrence of chalcocite-haematite mineralisation that provided a much-needed stimulus for WMC's exploration effort. Assaying of the split drill core returned 96 m @ 1.00% Cu and 3.8 ppm Ag from the depth interval 364-460 m, including 34 m @ 1.25% Cu and 3.8 ppm Ag from 364-398 m. Uranium assay values were low (40-60 ppm U). No significant values were obtained for Ni, Co, Mn, Mo, Pb, Zn, Sn or Au. The iron content of the entire copper-mineralised basement intercept (which remained open-ended at the hole's TD) averaged 4.08% Fe. Diamond drillhole RD6 was also started in this period, from a site located 400 m north-east of RDD1, and at 2/5/1976 was at 403 m depth. It encountered some basic or andesitic volcanic rocks interlayered with fragmental haematitic units, immediately beneath the Woomera (Tregolana) Shale, between 326.48 and 354.14 m depth. These volcanic rocks were the first such encountered by WMC's drilling, and were found to contain slightly anomalous Ni, Co, Cu, Pb and Zn. In further geophysical work, data were interpreted for the seismic refraction profiles that had been acquired during the previous quarter in an attempt to follow laterally the seismic break the SADM had detected at Olympic Dam, which WMC formerly had thought must originate from the basement rocks. However, the new seismic data made it apparent that this particular event is caused by the unconformity between the Pandurra Formation and the Woomera Shale.