In a search for possible economic repetitions of Cattlegrid and MG14 - style copper sulphide mineralisation, or for any buried analogues to Western Mining Corp.'s recently discovered copper deposits on Roxby Downs Station, ongoing exploratory work...
In a search for possible economic repetitions of Cattlegrid and MG14 - style copper sulphide mineralisation, or for any buried analogues to Western Mining Corp.'s recently discovered copper deposits on Roxby Downs Station, ongoing exploratory work undertaken in the Mount Gunson area has included: - stepout percussion drilling at Cattlegrid to look for orebody extensions; - deep stratigraphic percussion drilling at MG11, Elizabeth Creek, Wirrapa and Lake Dutton; - a deep stratigraphic test, by diamond drilling, of the strongly dipolar aeromagnetic anomaly 'A' located 5 km north of Lucas Hill, sourced by an interpreted flat-lying tabular body (vertical DDH LH1 to TD 788 m, including 232 m RC precollared, drilled during February-April 1978). This drillhole failed to reach pre-Adelaidean basement; - continuing interpretations of regional Landsat, gravity and aeromagnetic data; - acquisition and processing of a 2300 line km low level aeromagnetic survey, flown by Geoex Pty Ltd during August 1978 at 300 m flight line spacing and 100 m mean terrain clearance; - follow-up of selected geochemical and geophysical anomalies by percussion drilling and ground magnetic and gravity surveys; - the conduct of trial IP surveys aimed at mapping the limits of the Tapley Hill Formation and possibly locating any significant accumulations of sulphide mineralisation within this unit; - the conduct of a trial seismic reflection survey aimed at mapping unconformities bounding the Tapley Hill Formation, and delineating the geometry of block fault structures that might have controlled its deposition and facies; - detailed petrographic studies of drill core samples of the 'McLeay Beds', Tapley Hill Formation and Pandurra Formation; - compilation of bedrock lithology, structure contour (Hiatus 3, pre- and post- Tapley Hill Formation erosion surfaces) and isopach maps (Tapley Hill Formation, Yudnapinna Beds, Yudnapinna Beds / Whyalla Sandstone, Whyalla Sandstone and Tregolana Shale); and - resampling of drill cuttings for previously unattempted assays, and their relogging. Percussion drilling undertaken late in 1977 at the South Windabout prospect, 6 km away from Cattlegrid, gave encouraging results when 3 of 13 holes encountered >1% Cu over thicknesses of up to 5 m at the top of the Tapley Hill Formation. Another single hole drilled on the Cattlegrid Extension grid at this time also had >2% Cu over 1 m. However, DDH LW66 completed in September 1978 returned the best intercept so far made in the brownfields exploration programme, when drill core cut in the upper Tapley Hill Formation between 46 and 48 m depth assayed 4.18% Cu and 32 g/t Ag. The predominantly chalcocite mineralisation has a supergene type, fracture-filling habit, and lies within an oxidised shale sequence.
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