Based on a cutoff grade of 3 grams gold per tonne, the zones’ inferred resource is now pegged at 1.7 million tonnes grading 6.1 grams gold, or 331,917 oz. gold. When the cutoff is boosted to 5 grams, the tonnage drops to 683,976 million tonnes, while the grade climbs to 9.3 grams gold, or 204,269 oz.
A 1999 estimate of zone 118 indicated an inferred resource of 476,509 tonnes running 11 grams gold, or 167,927 oz. That estimate was based on just three holes.
The recent drilling was part of a year-long program. The zones remain open along strike and at depth, and Aurizon plans to test extensions to the zones in the third quarter. The holes will be drilled up to 1,500 metres east of a proposed shaft.
The two zones are 300-700 metres east of the West mine’s known reserves, downdip of the Principal zone, which is 500-1,000 metres below surface. The resource lies south of the Casa Berardi fault, except for area 117N, which is 20 metres north of the fault, 800-1,000 metres below surface.
Gold mineralization in the 400-by-500-metre 118 zone is associated with fine-grained arsenopyrite, pyrrothite and pyrite in quartz veins and veinlets, quartz stockworks and sulphide-rich stockworks.
In the 200-by-600-metre 120 zone, gold occurs in stacked quartz veins, quartz carbonate stockwork, and semi-massive sulphide lenses, north and south of the Casa Berardi fault.
In 2000, a feasibility study of the West Mine area indicated that reserves of 6.9 million tonnes averaging 6.7 grams gold could sustain annual production of 200,000 oz. gold over 7.5 years. Total cash costs were estimated to be US$145 per oz., and the capital cost, $121 million, mostly for underground development and the sinking of a 1,031-metre shaft.
The company intends to amend the study to include the new estimates.
A few hundred metres to the west, Aurizon is working to deepen the West mine’s ramp by 100 metres to the 550-metre level, and drift east some 450 metres into the 113 zone. The company expects to reach the zone in the fourth quarter.
Definition drilling and bulk sampling will attempt to confirm the 113 zone’s reserves, which are estimated at 4.1 million tonnes grading 7.4 grams gold per tonne.
The former producer comprises the East and West mines, which are joined by a 5-km-long underground track drift. Between 1988 and 1997, 3.75 million tonnes grading 6.7 grams were mined to produce 690,000 oz. gold.
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