Fourth annual report for MCC 907-910 and MCC 912-913 Troy, 15 November 1991 to 14 November 1992

Abstract

Exploration during the year ended 14th November 1992 on Mineral Claims C907-910, 912-913 located to the north of Tennant Creek has largely been directed towards following up the discovery of a copper mineralised ironstone which was drilled in 1991. The main focus was to find if there was a high grade gold position associated with the ironstone. Although more copper mineralisation was found, no gold of significance was discovered, although the drilling programme was less extensive than planned due to drilling problems. Besides diamond and RC percussion drilling, exploration activities included downhole TEM, downhole 3 component magnetics, ground magnetics, grid gravity, IP, auger soil sampling, and soil gas analysis. Besides a wide selection of elements by ICP-MS, measurements on core included magnetic suceptability, specific gravity, thin section work and microprobing. Surface geochemistry and electrical geophysical techniques and gravity failed to detect the ironstone or mineralisation, primarily due to the ironstone's depth (+200m). Ground magnetics were able to be modelled in 3 dimensions to give a good idea of the shape of the ironstone and associated alteration system; downhole 3 component magnetometry supplemented this 3D interpretation. Diamond drilling found that the ironstone lode has a top of perhaps 200 metres below surface (possibly shallower) and has a steep northerly dip. The massive ironstone (variably chalcopyrite-bornite mineralised) has a chalcopyrite - bornite 'crackle vein' zone on its footwall and has an extensive vein feeder zone (carbonate, talc, magnetite, haematite) below it. The entire system is enveloped in a chlorite alteration zone and the ironstone itself is variably chlorite altered. The upper and lower parts of the ironstone has yet to be defined to any extent and hence there is still scope for a high grade gold position. The ironstone lode is located near the axis of a east-north-east plunging anticline developed in a sequence of haematitic silts and shales, which coarsen to wackes and arenites with depth. A strong east-west cleavage pervades the structure.