Mayank Bansal, CFA
Mayank Bansal is a CFA Charterholder and heads the Equity Research team at Kapitales Research, with over 5 years of experience analysing global equity markets. He leads fundamental, data-driven research combining rigorous financial analysis with macro trends.
Rio Tinto Halts Underground Mining at Mongolia's Oyu Tolgoi Following Seismic Activity
Highlights
Introduction
Rio Tinto Limited (ASX: RIO) has halted underground work at Oyu Tolgoi, its copper-gold mine in Mongolia. The miner disclosed the pause in a brief media release dated 30 October. The release said the halt follows procedure and will remain in place until a safety review has been completed. Rio Tinto had not lodged a separate ASX announcement on the matter at the time of writing.
What the Company Has Disclosed
According to Rio Tinto, the event took place at about 6:00 PM local time on 29 October. A rock fault zone on the site experienced seismic activity, which made the underground mine vibrate. The release did not say whether any equipment or infrastructure was damaged.
The company reported no fatalities. It said three employees had sustained injuries, without giving details of their condition.
The release did not indicate how long the safety review might take. It also made no mention of the open pit operations at the site.
Why the Underground Mine Matters
Rio Tinto has pointed to Oyu Tolgoi as a source of recent growth. In its third quarter production report, lodged with the ASX on 14 October, the company listed its interest in the mine at 66% and said copper growth there had helped lift its year-to-date copper equivalent output.
That report showed Oyu Tolgoi produced 113.5 thousand tonnes of copper in concentrates in the September quarter on a 100% basis. That was 27% above the same quarter a year earlier, while output for the first nine months of 2026 rose 29% to 312.0 thousand tonnes.
Rio Tinto attributed the third quarter increase to the ongoing underground ramp-up and better recoveries. Underground ore treated reached 3.77 million tonnes in the quarter, compared with 3.26 million tonnes in the June quarter. The mine also produced 123.6 thousand ounces of gold in concentrates over the three months, on a 100% basis.
Ramp-Up Targets Already in Place
In the same October report, Rio Tinto said the ramp-up remained on track to deliver roughly 500,000 tonnes a year of copper on average from 2028 to 2036, on a 100% basis. The company was developing Panel 0 and Panel 2 North, with Panel 2 South to follow.
It noted that Mongolia's government had agreed in June 2026 to start resolving the transfer of Panel 1's Entrée licence, a panel Rio Tinto expects will be the last to enter production.
At that time, Rio Tinto left its 2026 group copper production guidance of 800 to 870 thousand tonnes unchanged. The latest release did not refer to production, guidance or the ramp-up schedule.
How the Shares Traded
Rio Tinto shares were at AU$146.84 (bid) in morning trade, down 1.9% on the previous close. About 641,000 shares had changed hands by that point.
What Investors Should Watch
Conclusion
For now, Rio Tinto has confirmed only the basic facts: a seismic event, no fatalities, a procedural pause underground and three employees injured, according to Rio Tinto. It has not put a timeframe on the review.
Investors will look to the company's next disclosure for clarity on when underground mining at Oyu Tolgoi can resume.
Note- All data presented is based on information available at the time of writing.
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