Rio Tinto has approved a $US108 million ($146 million) investment to explore the prospect of underground mining at the Kennecott copper operations in the United States.
The underground mining investment will target early orebody access and orebody characterisation studies for underground mining, building upon a $US25 million investment in early 2020 to complete Kennecott’s pre-feasibility study.
According to Rio Tinto, underground mining will occur at the same time as open pit operations to increase copper output.
Rio Tinto copper chief executive Bold Baatar said an underground development at Kennecott would bolster the company’s copper supply for electric vehicles and renewables.
“Kennecott holds a range of options to extend our supply of copper and other critical materials, to meet the strong demand being driven by electric vehicles and renewable power technologies,” he said.
“The operation is uniquely positioned to supply these emerging markets, with one of only two operating smelters in the United States that also processes concentrates from third parties, a long history delivering high quality products and significant resources that are yet to be developed.”
The Kennecott copper operations has a declared mineral resource of 20 million tonnes at 3.65 per cent copper and 1.62 grams per tonne of gold.
Rio Tinto plans to extends existing infrastructure from previous underground projects to access the site’s North Rim Skarn orebody.
Kennecott’s feasibility study work is slated for completion in 2024 and will assist Rio Tinto in assessing underground development options.
The project is comprised of around 15,000 feet of lateral development and 1000 feet of vertical development and other infrastructure.
Rio Tinto will also trial underground battery electric vehicles at Kennecott to cut carbon emissions.
The electric vehicles will be supplied by Sandvik Mining and Rock Solutions, and will include a battery-electric haul truck and loader that will determine performance and suitability for future underground mining fleets.
Pre-feasibility studies are also underway to extend Kennecott’s open pit beyond 2032.
The Kennecott mine produced 33,700 tonnes of copper in the June 2021 quarter.