BHP has reported an underground block cave (BC) resource at its Olympic Dam integrated copper, uranium, gold and silver mine in South Australia, as part of its operational review to September 30, 2026.
The Olympic Dam BC resource is 10,730 Mt at 0.59% Cu, 0.19 kg/t U3O8, 0.21 g/t Au, and 1 g/t Ag. This considers a non-selective underground block caving scenario, reporting all material within a continuous shape designed to capture material generally above 0.35% Cu, where all material was deemed to have reasonable prospects of eventual economic extraction. As such, zero-grade waste material was included as internal dilution to account for the non-selective nature of block caving.
As mining studies progress, the constraint (and therefore the reported Olympic Dam resource) may change; block-cave mining remains at an early stage of assessment, and its potential development timeframe is not yet known, BHP stated.
The inclusion of an underground bulk mining method provides an updated total classified underground mineral resource for Olympic Dam, estimated to contain 88.1 Mt of Cu, 2.8 Mt of U3O8, 103 Moz of Au and 498 Moz of Ag.
The BC resource report comes alongside the existing underground sub-level open stoping (SLOS) mineral resource at the mine.
These changes reflect the application of updated mining scenarios for the Olympic Dam Deposit: selective sub-level open stoping for higher-grade material and bulk underground mining, such as block caving, for large continuous volumes. Together, these scenarios support assessment of future mining options as studies progress, BHP said.
It is assumed that the SLOS resource would be extracted prior to block caving (with zero grade backfill material replacing mineralisation). Future mining studies are required and may determine that some areas of the deposit are more economically amenable to block caving without extraction of the selective SLOS resource component, in which case, some of the SLOS resource may convert to block cave resource in future.
A maximum depth threshold of -1,500 m from surface level (~-1,400 mRL) for block caving was applied to the BC resource. This threshold was applied based on benchmarking of deposits of similar style and tenor to account for modifying factors, such as economic and geotechnical factors relating to the reasonable prospects for economic extraction of deep block cave mining. Beyond this depth there are uncertainties on management of geotechnical conditions, heat and ventilation. Future mining studies may refine these assumptions and considerations. No depth constraint exists for reporting of the SLOS resource.
The Olympic Dam operation consists of an underground mine, mineral processing plant, copper smelter and refinery, as well as associated infrastructure.
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