The delineation of Coronet West by detailed underground DHEM

Abstract

The Coronet Nickel mine is located at Kambalda, 60 km south of Kalgoorlie in Western Australia. The ore shoots currently being mined extend to depths of up to 600 m. Extensional exploration from underground drilling platforms is routinely used to discover ore shoots outside existing reserves. This drilling is expensive, and limited drilling positions often provide poor drilling angles sub-parallel to the mineralised contact. Such holes however, make excellent geophysical platforms and the highly conductive nickel sulphide orebodies provide excellent geophysical targets. The intersection of a significant thickness of high tenor massive nickel sulphide west of existing reserves prompted an extensive underground drilling program. This yielded numerous, subgrade intersections, and the extent of the economic mineralisation remained unknown. Further drilling would have been very expensive and was only possible at very poor drill angles. Drillhole electromagnetic (DHEM) surveying of the initial holes confirmed the presence of many conductors, and EM modelling resulted in the development of a very detailed and tightly constrained geological model. On the strength of this model and the geological information, a decision was made to develop out to this ore shoot named Coronet West. This decision was proven correct when ore was intersected within 1m of the position predicted by the DHEM. Subsequent mining has shown the ore shoot to be comparable in size and attitude to that predicted by the geophysics model.