BHP has reported an underground block cave resource at its Olympic Dam copper, uranium, gold and silver mine in South Australia as part of its September quarter operational review. The block cave resource is 10,730 million tonnes at 0.59 percent copper, 0.19 kilograms per tonne of uranium oxide, 0.21 grams per tonne of gold and 1 gram per tonne of silver, reported within a continuous shape capturing material generally above 0.35 percent copper and including zero grade waste as internal dilution, reflecting the non-selective nature of block caving.
Together with the existing sub-level open stoping resource of 1.59 billion tonnes grading 1.56 percent copper, the updated classified underground resource at Olympic Dam 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. BHP assumes the higher grade stoping resource would be extracted before any block caving, and applied a maximum depth threshold of 1,500 metres below surface for the cave resource on geotechnical, heat and ventilation grounds.
The disclosure is an option, not a plan. BHP said block cave mining remains at an early stage of assessment, its potential development timeframe is not yet known, and mining studies may change the reported resource. Australian Mining reported that BHP is targeting Copper South Australia production of about 500,000 tonnes a year by 2035 and up to 650,000 tonnes by 2040, has more than 2 billion dollars of projects in execution in the province, and expects to give more detail at a site visit in November. A smelter and refinery expansion final investment decision is targeted for 2027 and a separate mine and concentrator growth project, including assessment of a 10 million tonne block cave, for 2029.
The long term resource sits against a weaker quarter. Copper South Australia production fell 16 percent year on year to 60,700 tonnes, mainly on an underground conveyor failure at Carrapateena that took seven weeks to repair, and BHP held full year guidance for the province at 290,000 to 320,000 tonnes. Group copper output for the quarter is covered in the updated BHP production story from October 19.