Xstrata Copper started underground mine production at its Ernest Henry operation 38 km northeast of Cloncurry in north Queensland in early December 2011, marking the site’s transition from open-pit mining, which is now complete, to underground mining and magnetite processing. The underground production start is a major milestone in an A$589-million project to extend Ernest Henry operations to at least 2024.
During the first phase of underground mining, ore is being trucked via a decline at a rate of approximately 3 million mt/y for processing at an on-site concentrator into concentrate containing about 25,000 mt/y of copper and 35,000 oz/y of gold. Second phase development is based on sinking of a hoisting shaft to a depth of 1,000 m. Following commissioning of the shaft in 2013, production will ramp up to 6 million mt/y of ore and 50,000 mt/y of copper and 70,000 oz/y of gold in concentrate.
Ernest Henry concentrate is trucked 157 km to Xstrata Copper’s Mount Isa smelter for smelting to anode. Anode is then railed to Townsville for refining to cathode at the company’s copper refinery.
The Ernest Henry orebody is an iron oxide-copper-gold deposit, with magnetite being the form of iron ore. Magnetite is liberated during the copper-gold concentrating process and was previously discarded as tailings. The Ernest Henry extension project included construction of a 1.2-million-mt/y magnetite concentrate plant, which was completed in February 2011. The new plant allows the magnetite to be recovered from the concentrator tailings stream and sold as an important by-product, reducing the amount of tailings sent to the on-site storage facility.
The first regular train-load of magnetite concentrate departed Cloncurry for Townsville April 30, 2011, and Xstrata Copper became Queensland’s first magnetite concentrate exporter June 15, when the first shipment of magnetite concentrate departed the Port of Townsville for Asia.