Rio Tinto halts underground operations at major copper mine

Rio Tinto Group has suspended underground operations at its massive Oyu Tolgoi copper mine in Mongolia.

A rockfall triggered by a seismic event on Thursday led to three workers being injured, the company said in a statement on Friday. Operations are paused as Rio carries out a safety review, it said.

Shares in the miner fell as much as 2.9% in Sydney.

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Oyu Tolgoi is one of the world’s biggest copper and gold mines, and 80% of its value lies deep underground. It’s running at an annualised output rate of 450 000 tons of copper per year, according to the latest operational update.

While it was too early be conclusive, the incident was “unlikely to have long-term impacts on production expectations,” Jefferies LLC analysts including Christopher LaFemina said in a note Friday. “Surface operations of milling and open-pit mining continue.”

The mine doesn’t have its own smelter, and is a major supplier of semi-processed ores to processing plants in northern China. Disruptions could cause strain on the already scarce supply of feedstock. Rio Tinto owns 66% of Oyu Tolgoi.

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