Within a middle jurassic ignimbritic sequence at the Cerro Vanguardia Gold and Silver Mine, a fracture system hosts a swarm of epithermal, low-sulphidation veins of the sericite-andularia type. Veins are up to 10m thick, averaging 3.5m and dip from vertically to 60°. Detailed exploration established a resource base of 13Mt contained in 17 separate vein structures. A feasibility study defined 9.1Mt of open-pit mineable ore, grading 9.7g/t gold and 113g/t silver.
Total reserves at end-2005 attributable to Anglogold Ashanti were 6.0Mt grading 6.91g/t gold, equivalent to 41.8t of contained gold. Attributable measured, indicated and inferred resources totalled 32.6Mt at 3.14g/t gold, providing a further 102.2t of contained gold. In 2006, Cerro Vanguardia started a four-year exploration programme and started construction of a pilot plant for heap-leaching low-grade ore.
The annual production target was originally approx. 6t of gold and 60t of silver. During 2000, some 365,000 milled tonnes yielded 4,101kg of gold at a cash cost of $146/oz. Production fell to 193,000oz in 2002, recovered in 2003, and increased again in 2004. For 2005, AngloGold Ashanti reported its attributable 92.5% of production as 211,000oz, giving a total output of 228,100oz for the year at cash costs of US$171/oz and total production costs of US$277/oz.
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