Campania Minera Antamina, a Peruvian subsidiary held jointly by
The syndicate consists of ABN-AMRO Bank, Australia & New Zealand Banking Group, the Bank of Montreal, Barclays Bank, the Canadian Imperial Bank of Commerce, Citibank, Deutsche Bank and the Bank of Nova Scotia.
The three Canadian partners also report that engineering giant Bechtel, which oversaw Antamina’s feasibility study, has been awarded the engineering, procurement and construction management contract for the project, and that contracts totalling US$250 million have been awarded for roads, mining equipment, engineering and camp construction.
In other news, the partners have reverted to a plan to transport concentrates via pipeline, rather than truck, from the mine site high in the Andes to the Pacific port of Huarmey, 300 km away. This change is expected to reduce cash-operating costs by more than 10% to about US35 cents per lb. and raise the total cost of the project by 7% to about US$2.35 billion, pending completion of further feasibility work. In addition to improving the project’s economics, the pipeline, which will follow the southern highway route around Huascaran National Park, is expected to bring environmental and safety benefits.
Situated at a 4,200-metre elevation, the Antamina skarn deposit hosts an estimated in-pit resource of 500 million tonnes grading 1.2% copper, 1% zinc and 0.03% molybdenum, plus 12 grams silver per tonne. A further 500 million tonnes of resources exist at similar grades.
There are six ore types at Antamina: copper with low (less than 25 parts per million) bismuth, which constitutes 38% of the total reserves, by weight; copper with high bismuth, which constitutes 11%; copper-zinc with low bismuth, 15%; copper-zinc with high bismuth, 27%; copper as bornite (rather than the predominant chalcopyrite) with low zinc, 3%; and bornite with high zinc, 6%.
The grades being mined will be slightly higher during the first 10 years of production, but this will be offset by a slightly higher stripping ratio during that period. Over 20 years, that ratio is expected to be 2.8-to-1, including 85 million tonnes of prestripping. Mining cash costs are projected at US70 cents per tonne of material mined.
Ore from the pit will pass, via a tunnel, to a 70,000-tonne-per-day concentrator facility consisting of a single semi-autogenous grinding mill, three 24-ft. ball mills, copper and zinc flotation cells, and a molybdenum-bismuth circuit.
The US$775-million concentrator facility will produce six concentrates: low-bismuth copper (grading about 30% copper); high-bismuth copper (30% copper); zinc (55%); molybdenum (52%); lead-bismuth; and bornite. The recovery rates for Antamina’s copper, zinc, moly and silver will be about 93%, 77%, 45% and 75%, respectively.
Bismuth tends to render copper brittle — a drawback that will be rectified by blending the various non-bornite-bearing ores to produce a copper concentrate with a final bismuth content no greater than 200 ppm.
Due to begin production in 2002, the Antamina open-pit mine expected to produce 600 million lbs. copper and 360 million lbs. zinc annually over a 20-year mine life.
The project will be one of the world’s largest and lowest-cost concentrate producers, shipping 1 million tonnes of copper concentrate and 500,000 tonnes of zinc concentrate during each of the first 10 years of the mine’s life.
Rio Algom and Noranda each own 37.5% of Compania Minera Antamina, while Teck owns the remaining 25%.
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