Backfill assumptions were “probably miscalculated” following May’s seismic events at the Kakula mine in the Democratic Republic of Congo, Ivanhoe Mines CEO Marna Cloete told delegates at the London Indaba mining investment conference on Wednesday June 26.
“Assumptions [about] how [the] backfill would [behave] — and [the fact that it replaced] pillars — were probably miscalculated,” Cloete told attendees.
She said the company will apply new mining methods across its entire “massive mining district”, including the Kansoko and Kamoa operations.
Production at the Kakula underground mine, which is part of the Kamoa-Kakula copper complex in the DRC, was suspended on May 20 after seismic activity in its eastern section. This prompted the Canadian miner to cut its 2025 copper production guidance by 28% to 370,000-420,000 tonnes of copper in concentrates, from 520,000-580,000 tonnes.
Speaking publicly about the technical challenges, Cloete said the seismic event occurred “in a section where we had a mature level of extraction,” referring to “a shallow, thick ore body” — a type of deposit she noted has few recent parallels.
“There haven’t been many discoveries like Kamoa-Kakula in the past couple of years,” she said.
District-wide mining overhaul
The technical issues have forced Ivanhoe to rethink its mining approach across the entire complex, according to the CEO.
“We are going to have to mine based more on a geological understanding [of] what’s ahead of us, [leaving] much larger pillars, and then also mining out to the [periphery] and then retreat mining back,” she said.
The company will “re-engineer our life of mine plan” not only for Kakula but for “the entire Kamoa-Kakula complex” because the seismic event “really changes our understanding of the geology of the region,” she added.
“So we will also go and do the same at Kansoko and the same at Kamoa,” Cloete said, referring to other mines in what she called “a massive mining district.”
Kansoko is an early-stage underground mine, while Kamoa includes multiple ore bodies under development — both are parts of the broader Kamoa-Kakula copper project in the DRC, according to Ivanhoe Mines’ project documentation and technical reports published in 2023.
‘We had to let the eastern side flood’
The seismic events forced the company to let the eastern side of the Kakula mine flood due to damages to infrastructure.
“We had to take a decision to let the eastern side of the mine flood,” Cloete said, adding that electricity supply to pumps was connected to side walls “that basically just kept falling off.”
Ivanhoe is managing underground water inflows of approximately 4,000 liters per second using about 4,400 liters per second of temporary underground pumps. They have also ordered four high-capacity surface pumps (650 liters per second each, totaling 2,600 liters per second) to be installed via shafts later this year.
Cloete credited Chinese partner Zijin (alongside CITIC Metal) for swiftly procuring this additional dewatering equipment, according to an Ivanhoe Mines operational update published on May 26.
“We should have the [the eastern side of the] mine dewatered by the end of the year,” Cloete said.
Restarting on the western side of Kakula; relying on surface stockpiles
The seismic event affected 30% of the Kakula resource, with “20% of that in the eastern zone” that flooded, according to Cloete. She expressed optimism about recovery, however: “The experts reckon we will be able to recover a good portion of that once we get through.”
The company restarted mining on the western side of Kakula on June 7 after a stabilization of underground water levels, according to an operational update.
Ivanhoe is also relying on surface stockpiles to maintain production. “We luckily have stockpiles on surface that we’re currently milling,” Cloete said. “We’ve moved some of our crews to our other mining areas where there’s scope to increase [and] open up new mining faces.”
‘We went through the stages of grief’
Reflecting on the impact of the crisis, Cloete said: “You can imagine, you’re a human being… we all went through the stages of grief because it’s our [mine], we discovered it. It’s been such a phenomenal growth story.”
But she said the incident was “not a failure” but rather “a temporary glitch” and “a lesson for us.”
The company is applying these lessons beyond the immediate crisis, according to the CEO.
“We’ve already started applying the same lessons to Platreef [in South Africa], the same lessons to Kipushi, getting people with fresh eyes to look at what we’ve done, what our designs are, so that we do not repeat the same mistake,” she said.
The Kipushi zinc-copper-germanium-silver-lead mine in the DRC is a high-grade zinc operation. Its 800,000-tonne-per-year concentrator was completed in May 2024, with first production of concentrate achieved the following month.
Fourth largest copper discovery ever
Despite the operational challenges, Ivanhoe expects to commission its blister copper smelter in early September, with “first anode expected in October,” Cloete said.
The smelter, which will operate at an initial capacity of approximately 250,000 tonnes per year, is expected to “reduce our logistic charges by about 50%,” according to a June 11 operational update.
While acknowledging the significant challenges, Cloete remained optimistic about the long-term prospects.
“I’m bullish on Kamoa-Kakula. If you look at just what it is in the great scheme of things, it’s the fourth largest copper discovery ever,” she said. “It’s just one of those mining complexes that will stand the test of time. This would be one chapter in a very thick book.”
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