As part of a final feasibility study,
The Vancouver-based company hopes to revive Aljustrel, based on an operation treating 1.5 million tonnes of zinc-rich ore annually, beginning in late 2000. Capital costs are estimated in the range of US$40-50 million, though this amount could be reduced by European grants.
The final feasibility study is examining the mining of higher-grade zinc and copper zones in the Feitais and Moinho deposits, two of five zoned massive sulphide deposits at Aljustrel.
The latest resource estimates calculated by Steffan Robertson & Kirsten (SRK) are based on data from 342 diamond drill holes and 964 underground channel samples. Feitais and Moinho are now reported to host a total resource (in all categories) of 141.3 million tonnes of 2.79% zinc, 0.97% lead and 0.51% copper, plus 35 grams silver and 0.6 gram gold per tonne, at a zero cutoff grade. Both remain open downdip and down-plunge.
The zinc zone boasts a resource (in all categories) totalling 60.15 million tonnes grading 4.41% zinc, 0.31% copper, 1.45% lead, 49.67 grams silver and 0.69 gram gold, based on a 3% zinc cutoff grade. At a 4.5% cutoff grade, the total falls to 20.26 million tonnes of 5.9% zinc, 0.26% copper, 1.89% lead, 65.08 grams silver and 0.76 gram gold.
The copper zone totals 9.7 million tonnes of 1.03% zinc, 2.07% copper, 0.32% lead, 15.33 grams silver and 0.37 gram gold at a 1.5% cutoff grade.
The final bankable feasibility study is expected to be completed in the first quarter of 2000. It will include an evaluation of various development proposals, including the copper zone.
EuroZinc intends to begin mining at Feitais, where most of the recent drilling has been focused. This work was aimed at boosting the existing resource of 13 million tonnes grading 5.9% zinc, 2.02% lead and 0.24% copper, plus silver grading about 60 grams.
The final study will include an updated minable reserve for Feitais, as well as the results of pilot-plant metallurgical studies.
More than 1,000 tonnes of ore have been treated at an on-site pilot plant. While not all results are in hand, EuroZinc reports that zinc recoveries of 82-84% have been obtained from a zinc concentrate containing 48-50% zinc. Lead recovery of 58-60% was obtained with a lead concentrate grade of 49-51% lead. The silver recovery to the lead concentrate is projected to be 36-38%. Bench-scale tests on the copper mineralization have resulted in a 90% copper recovery from stockwork-type mineralization, to a concentrate grading 25% copper.
EuroZinc says the recoveries are consistent with prefeasibility projections. More tests are planned to evaluate the potential to enhance precious metals recoveries.
After the final feasibility study is completed and project financing arranged, EuroZinc will have acquired a 75% interest in the project from a Portuguese state-owned mining company.
In addition to developed deposits, the Aljustrel project includes a modern 3,500-tonne-per-day mill, tailings disposal facility, roads, rail and a deep-water port.
Aljustrel operated for several years in the early 1990s. However, low recoveries (about 40% for zinc) and inefficient mining methods, combined with low metal prices, forced its closure.
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