The numbers were part of the company’s latest operational update, and while the block-cave resource is not an ore reserve or an approved mine plan, and block caving remains in the early stages of assessment, it adds a potentially significant underground mining option to BHP’s broader copper ambitions.
The longer-term growth plans sit against a more challenging start to the 2027 financial year (FY27). Copper production in South Australia fell 16 per cent year on year to 60,700 tonnes, primarily due to an underground conveyor failure at Carrapateena.
BHP installed a replacement belt within seven weeks, with the conveyor progressively ramping up through September before returning to full capacity. The company maintained its FY27 Copper South Australia production guidance of 290–320 kilotonnes.
“Copper production was lower in the first quarter, reflecting planned grade declines and scheduled maintenance, alongside temporary disruptions from severe weather in Chile, stops for safety and the conveyor failure at Carrapateena,” BHP chief executive officer Brandon Craig said.
“We are building the next phase of growth in copper and potash. We continued to strengthen one of the world’s largest copper portfolios, from funding the Escondida New Concentrator in Chile to growing our resource base and long-term production potential at Copper South Australia, while also expanding our copper growth pipeline across the Americas.”
BHP announced an expanded mineral resource base at Olympic Dam ahead of a site visit in November, during which the company is expected to reveal further details about its copper strategy.
The updated resource reflects two potential underground mining approaches at Olympic Dam. BHP expects selective sub-level open stoping to remain suited to higher-grade material, while a bulk underground method such as block caving could provide access to much larger volumes of lower-grade mineralisation.
The existing sub-level open stoping resource contains 1.59 billion tonnes grading 1.56 per cent copper, compared with the newly reported block-cave resource of 10.73 billion tonnes at 0.59 per cent. BHP has assumed that the higher-grade resource would be mined before any future cave development.
The new block-cave mineral resource comprises 10.73 billion tonnes grading 0.59 per cent copper, 0.19kg/t uranium oxide, 0.21g/t gold and 1g/t silver.
Combined with Olympic Dam’s existing sub-level open stoping resource, the updated classified underground resource is estimated to contain 88.1 million tonnes of copper, 2.8 million tonnes of uranium oxide, 103 million ounces of gold and 498 million ounces of silver.
Those figures represent contained metal rather than recoverable production. The block-cave resource has not been converted into an ore reserve, and BHP said further mining studies could change its reported dimensions.
Although the contained-metal figures do not represent recoverable production, the new resource provides a geological foundation for BHP to assess bulk underground mining as part of Olympic Dam’s longer-term expansion. Further details on the company’s Copper South Australia strategy are expected during a site visit in November.
The block-cave studies form part of a much wider investment program. BHP has more than $2 billion in Copper South Australia projects in execution, including the 1.3 km-deep haul shaft at Prominent Hill and a new underground access tunnel into Olympic Dam’s Southern Mine Area.
In July, BHP awarded China Nerin Engineering a design-and-supply contract covering key processing facilities for the proposed Olympic Dam smelter and refinery expansion.
The expansion remains under study, with BHP targeting a potential final investment decision in 2027. A separate mine and concentrator growth project, which includes assessment of a 10-million-tonne block cave, is targeting a potential final investment decision in 2029.
Copper South Australia comprises the Olympic Dam, Prominent Hill and Carrapateena underground mines, which supply a centralised smelter and refinery at Olympic Dam. BHP is also advancing the Ankata exploration project, formerly known as Oak Dam.
“Copper South Australia is a globally significant province and we are working at pace to unlock its full potential and supply more of the copper the world needs,” BHP asset president for Copper South Australia Anna Wiley said earlier this year.