In separate announcements in June 2011, Xstrata Copper reported it has begun prefeasibility studies for expansions at Cía. Minera Doña Inés de Collahuasi, where it has 44% ownership, and at its 100%-owned Lomas Bayas mine. Both mines are located in northern Chile. The Collahuasi study is considering expansion of production of copper in concentrates from 500,000 mt/y to either 800,000 mt/y or 1 million mt/y. The Lomas Bayas study is considering expansion of production from 75,000 mt/y of copper cathodes to a combined production of 140,000 mt/y of copper cathodes and copper in concentrates.
Xstrata acquired its interests in Collahuasi and Lomas Bayas when it acquired Falconbridge in August 2006.
Collahuasi: The Collahuasi prefeasibility study (PFS) is considering construction of either one or two new grinding lines to allow plant throughput to increase to either 270,000 or 380,000 mt/d of ore. A decision will be taken in the second half of 2011 on whether to complete studies on the options of either one or two new grinding lines. The PFS is scheduled for completion in the first half of 2012. Project commissioning is tentatively planned for 2017.
The Collahuasi open-pit operation is the world’s fourth largest copper mine. Cía. Minera Dona Inés de Collahuasi is a joint venture of Xstrata (44%), Anglo American (44%) and a group of Japanese companies headed by Mitsui & Co. (12%).
Collahuasi is based on two major porphyry copper deposits, Ujina and Rosario, located at altitudes of 4,000 m to 4,800 m above sea level. Mine life is projected at more than 50 years. Both copper sulphide and copper oxide ores are processed to produce copper concentrates and cathodes, respectively.
Collahuasi facilities include the Ujina and Rosario open-pit mines, a permanent accommodation complex, the concentrator, a solvent extraction-electrowinning plant, and a 200-km pipeline to transport concentrate from the mine to the port of Punta Patache, 60 km south of Iquique. As of mid-2010, mineral resources totaled 7.1 billion mt at an average grade of 0.82% copper and 269 ppm molybdenum, using a 0.34% copper cutoff grade.
Lomas Bayas: Xstrata’s Lomas Bayas PFS is assessing possible investment of $1.6 billion to expand annual production to 140,000 mt of copper in the form of concentrates and cathodes and to extend the life of the Lomas Bayas operation to 2039. The project would include a 70,000-mt/d concentrator that would use seawater in its operations. The PFS will include new drilling, metallurgical tests and geomechanical studies, and is scheduled for completion at the end of 2012. Subject to positive feasibility studies and government and company approvals, Xstrata estimates the Lomas Bayas sulphide project could start production in 2017.
The current Lomas Bayas sulphide resource totals 435 million mt grading 0.39% copper at a 0.2% copper cut-off grade, plus molybdenum, gold and silver credits. Associated with the potential sulphide pit are 408 million mt of leachable oxide and mixed mineral resources at an average grade of 0.26% copper.