As ore grades decline and trucking becomes economically unviable, the world’s largest open-pit copper mine is going underground.
Chile’s massive Chuquicamata, which began production in 1915, is forecast to be unprofitable before the end of the decade.
In an effort to avoid closure, state-owned Codelco has already invested nearly 4 billion US dollars to transform it into the world’s largest underground mine. The company will dig more than 1,000 kilometres of tunnels below the pit and plans to replace dump trucks with an in-pit crushing and conveying (IPCC) system. Trucks currently drive more than 10 kilometres to bring lower-grade ore from the bottom of the world’s second-deepest open pit to the surface.
Codelco believes the mine’s untapped deposits are equal to more than half of all copper extracted there over the past century. The company is confident an underground mine at Chuquicamata can produce more than 300,000 tonnes of copper per year for another 50 years. The open-pit mine produced 443,000 tonnes in 2011.