( Taylor) The Perseverance Gold Copper Deposit - A New Peak Mines Challenge

摘要

The Perseverance deposit is the most southerly known economic copper/gold deposit within the Cobar gold fi eld. The deposit is situated approximately 12 km to the south-southeast of Cobar and is essentially blind to surface with the top of economic mineralisation occurring 750 m below ground level.Based on the December 2010 resource estimate (inclusive of reserves and net of depletion) the deposit contains 3 011 000 tonnes at 6.1 g/t Au and 0.90 per cent Cu (590 000 oz of gold and 28 000 tonnes of copper). The deposit is comprised of four principal lenses, the Perseverance, Hulk, Zone B, and Hercules lenses. In excess of 90 per cent of the known resource tonnes are contained within the Perseverance and Hulk lenses.The deposit is shear related and hosted within lower Devonian rocks of the Cobar Basin. The competency contrast of rhyolites juxtaposed against sediments by the Peak-Perseverance shear is the principal control on mineralisation. Both the Perseverance and Hulk lenses are primarily hosted by brecciated rhyolites juxtaposed against Chesney formation sediments across the Peak- Perseverance shear. This faulted rhyolite sediment contact roughly defi nes the global orientation of the deposit. The Perseverance lens continues within the shear for up to several hundred metres beyond the extent of the faulted rhyolite sediment contact. Mineralisation within the shear beyond the faulted rhyolite contact zone is hosted by sheared silicifi ed sediments. The Perseverance lens remains open at depth and to the south. The Zone B and Hercules lenses, which are signifi cantly less important in tonnage terms, are hosted by rhyolite breccias within the main body of the rhyolite and appear to be only tenuously related to the Peak-Perseverance shear. Within the Perseverance lens, the presence of northeast trending high grade breccia veins developed oblique to the north-south trending shear system has led to the development of steeply north plunging high grade ore shoots within a globally north-south trending mineralised domain. These high grade shoots have limited horizontal continuity but signifi cant down plunge extent. The presence of coarse gold and the resulting strongly skewed nature of the gold grades, in conjunction with controls on mineralisation which are not parallel to the mineralised domain, has led to predictive diffi culties regarding stope performance. Strong heterogeneity of the gold content of the ore and geological controls on mineralisation which are not parallel to the global trend of the mineralisation impose a set of diffi culties which sound geological control is helping overcome.