TL;DR
Rio Tinto has begun a progressive restart of underground operations at Mongolia’s Oyu Tolgoi mine, a day after a seismic event caused a rockfall and halted production. Three employees were injured; two remained under treatment for non-life-threatening injuries, the company said. Rio has not disclosed lost output or a timetable for completing the restart.
Rio Tinto said Friday it had begun progressively restarting underground operations at Mongolia’s Oyu Tolgoi copper mine, one day after a seismic event triggered a rockfall that stopped production. Three employees were injured, with two still receiving treatment for non-life-threatening injuries, the company said.
Rio said the rockfall was confined to a temporary storage zone beside the production area. The company reported that safety reviews had been completed and that the incident caused no structural impact to the cave or its operating infrastructure. It did not state how much production was lost or when the restart would be complete.
The mine’s underground operation is a major part of Rio’s copper growth plans. In its October 14 production update, CEO Simon Trott said Oyu Tolgoi had been running at an annualized rate of about 450,000 tonnes during the third quarter. The company reported that copper production at the operation rose 27% year over year in the quarter and 29% in the first nine months of the year.
Rio’s wider copper production grew more slowly: consolidated output was 205,000 tonnes in the third quarter, little changed from a year earlier, while group production rose 1% in the first nine months. The Northern Miner reported that Rio shares fell 1.8% to $81.76 in New York trading Friday morning. That was a snapshot of the stock during the session, not a measure of the mine’s eventual financial impact.
Oyu Tolgoi’s Role in Rio’s Copper Plans
The incident interrupted an operation that has become a central source of Rio’s planned copper growth. The company has said it expects Oyu Tolgoi’s combined underground and open-pit operations to average about 500,000 tonnes of recoverable copper annually from 2028 through 2036. It also expects the mine to become the world’s fourth-largest copper mine by 2030. Those are company targets and forecasts, not outcomes established by the restart announcement.
The timing matters because the mine’s recent production growth contrasts with more limited growth across Rio’s copper business as a whole. Oyu Tolgoi’s underground expansion is therefore relevant to Rio’s ability to increase supply. A short interruption may have a different effect from a prolonged one, but Rio has not provided the production figures needed to estimate the impact.
There is also a workforce and safety dimension. While Rio described the injuries as non-life-threatening and said reviews were complete, two employees were still receiving treatment when the update was reported. The company’s account that the rockfall did not damage the cave or infrastructure addresses the reported physical impact on the mine; it does not provide further details about the cause of the seismic event or the workers’ recovery.
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Underground Expansion at Oyu Tolgoi
Oyu Tolgoi is in Mongolia’s South Gobi region. Rio Tinto manages the operation and owns 66%; the Mongolian government owns the remaining 34%. Open-pit mining began in 2011, concentrate production followed in 2013, and sustainable underground production began in March 2023.
The underground project matters because Rio says more than 80% of the deposit’s total value lies underground. The mine uses block caving: rock is removed beneath an orebody so the ore fractures and collapses under its own weight, after which broken material is collected and transported for processing. This method and the scale of the underground development help explain why safe, reliable access to the production area is important to the company’s growth plans.
Rio increased its stake from about 34% to 66% in December 2022, when it acquired the remaining minority interests in Turquoise Hill Resources. The ownership change preceded the start of sustainable underground production. Oyu Tolgoi has also faced border restrictions that, according to The Northern Miner’s report, recently curtailed copper concentrate exports by 70%, adding a separate challenge to the operation’s contribution to Rio’s copper business.
„The incident caused “no structural impact to the cave or its operating infrastructure.”“
— Rio Tinto, in a Friday statement
Restart Pace and Output Impact
Rio has not disclosed the volume of production lost, how long underground operations were fully stopped, or when the progressive restart is expected to finish. The company’s statement that there was no structural impact does not establish how quickly each part of the operation can return to its prior rate.
The reported injuries and the company’s account of the rockfall are the information available in the source report. Further details about the seismic event, the safety review’s findings, and the status of the injured employees beyond the two receiving treatment were not provided. The effect of the export restrictions on shipments and the mine’s overall sales was also not quantified in this update.
Updates on Safety and Production
The immediate next milestone is the completion of the progressive restart and Rio’s disclosure of whether underground output has returned to its previous operating rate. The company could also provide a clearer estimate of the interruption’s duration and production effect in a subsequent operating update.
Readers will also be watching for further information on the employees’ recovery and any findings Rio chooses to share from its safety reviews. Until the company supplies those details, the mine’s restart status is confirmed, but its pace, output impact and the full account of the incident remain open.
Key Questions
What happened at Oyu Tolgoi?
A seismic event triggered a rockfall on Thursday, stopping underground production at the Mongolian mine. Rio said the rockfall was confined to a temporary storage zone beside the production area.
Has Rio restarted production?
Rio said Friday that it had begun a progressive restart of underground operations. The company did not say when the restart would be complete or confirm that production had returned to its prior rate.
Were workers injured?
Yes. Rio said three employees were injured and two continued to receive treatment for non-life-threatening injuries at the time of its update.
Did the rockfall damage the mine?
Rio said the incident caused no structural impact to the cave or its operating infrastructure. It described the rockfall as confined to a temporary storage zone next to the production area.
How much copper production was lost?
Rio has not provided a figure for lost production or the duration of the stoppage. The reported rate of about 450,000 tonnes annually was the mine’s annualized operating rate during the third quarter, not an estimate of losses from the incident.
Source: northernminer.com
