Rio Tinto has increased its copper mineral resources by 20 million metric tons (mt) to 106 million mt at the Kennecott Utah Copper Bingham Canyon mine. The mineral resource addition, known as the North Rim Skarn, increases contained metal in mineral resources by 730,000 mt copper, 1 million oz gold and 13 million oz silver over the 2010 year-end mineral resource estimate.

The North Rim Skarn is a high-grade copper-gold skarn deposit located approximately 300 m below the current Bingham Canyon pit and is expected to be developed by underground methods. This deposit was initially explored by a surface and underground drilling program that was completed in the mid-1980s. Further surface drilling has more recently been completed with the combined data set of 35 surface and 71 underground drill holes (total lengths of 39,127 m and 13,001 m, respectively) forming the basis for this new resource estimate.

“While establishing this high grade underground resource at Kennecott Utah Copper is substantial in itself, it points the way to the significant underground potential of the asset,” said Andrew Harding, chief executive, Rio Tinto Copper.

Rio Tinto has committed $165 million to complete the next stage of exploration and development studies by 2014. This pre-feasibility program includes final shaft rehabilitation, an access decline from the pit and further underground exploration drilling. This investment follows the approval for $238 million to advance studies extending the open-pit life to 2028 and the purchase associated long-lead time equipment.