In WMC's continuing exploration of the area surrounding Arcoona Homestead and its underlying regional gravity structure, the completion of ground geophysical surveying has confirmed that closed magnetic highs exist at both Pearson Hill and Cocky Swamp; importantly, the Cocky Swamp anomaly has an associated gravity high, so it will probably be given priority for drilling. However, subsequent re-levelling of the grids at both prospects, using a newly available digital quartz pressure transducer, revealed that positive residual gravity features are present at each locality. During February 1979 an alternative drilling proposal was generated by the WMC geophysicists, to drill a stratigraphic test hole 8.5 km to the south-west of Arcoona Homestead at the Winjabbie Dam West prospect, where the interpretation of a new ground magnetic survey had produced a top of basement depth estimate of only about 300 m, versus 1000 m interpreted at the same time for the newly profiled Horse Well aeromagnetic anomaly. A precollar percussion drillhole was completed to 300 m at Winjabbie Dam West during April 1979, and the test was continued with diamond coring during September-November 1979 down to an interim total depth of 867.6 m, at which point the installed rig capacity was exhausted. Pre-Adelaidean basement was penetrated at 827.2 m depth, and drilling was stopped in ?banded iron formation containing veins and disseminations of chalcopyrite and bornite, which lies beneath a sequence of felsic volcanic tuffs and breccias. The drill core from the bottomhole 5.4 m thick interval below 861.6 m when assayed averaged 0.54% Cu, including 1 m @ 2.0% Cu, besides containing an average of 7 ppm U3O8. Early in 1980, a more powerful diamond rig was brought onto the WJD1 site, and this incomplete stratigraphic hole was deepened and completed at TD 1015 m. The aforesaid zone of copper mineralisation was found to continue deeper, to give a total intersection 61.4 m thick (from 861.6-923.0 m depth) that was shown to contain 0.4% Cu overall. This mineralisation is mainly chalcopyrite, with minor bornite in its upper part, and occurs within banded magnetite-chert-chlorite iron formation. Beneath the mineralised zone, pyrite is the predominant sulphide mineral present. Between June 1980 and February 1981, much additional drilling was carried out by WMC on its renewed EL 682. A previous drillhole at Oak Dam prospect, AD1, was deepened with the new diamond rig from 510.05 m to a total depth of 823.8 m, while elsewhere several precollar percussion drillholes were completed through the Stuart Shelf cover rocks at the Horse Well, Dromedary Dam, Burden Hill and Coorlay Ridge prospects, and further deep stratigraphic diamond drilling was undertaken at Cocky Swamp, Dromedary Dam and Heaton Hill. The drillhole at Heaton Hill (TD 1186.2 m) reached granitic gneiss basement at 1133 m depth. A notable highlight of the latest drilling was the intersection of significant mineralisation in hole AD1, with 3 m @ 0.63% Cu and 193 ppm U3O8 over the cored depth interval 534-537 m, plus 68 m @ 0.31% Cu and 680 ppm U3O8 from 600-668 m, that includes 10 m @ 0.46% Cu and 3700 ppm U3O8 from 625-635 m. This mineralisation comprises chalcopyrite plus uraninite in part, and occupyies haematitic breccias overlying granitic rocks. Because of this discovery, follow-up diamond drilling on the Oak Dam prospect is currently underway, at hole AD3 sited 1.6 km west of AD1. It is also now proposed to drill test the previously overlooked eastern gravity high of the Arcoona gravity structure.