Technology enables penetration of mineral zone discovered 40 years ago
- A Broken Hill mining company has developed an innovative drilling technique to penetrate a difficult geological shear zone and access the long-untapped Centenary mineral deposit beneath the city.
- Initial drilling suggests the deposit could be substantially larger and richer in zinc than previously estimated, potentially growing from an earlier five-million-tonne resource to more than 10–20 million tonnes.
- If further drilling confirms the results, the deposit could provide a major long-term source of ore for Broken Hill’s existing processing plant, although significant technical and development challenges remain.
A large deposit of minerals was discovered in 1983 under an outback mining city’s streets, not far from existing operations.
Dubbed the “Centenary Zone” due to its discovery aligning with the 100th anniversary of the city’s founding, the then-mine operator was optimistic about what lay below but could not properly access it.
Patrick Walta, executive chair of Broken Hill Mines, which took over the mine in 2024, said the operator drilled about 13 holes more than a kilometre long from the surface into the deposit.
“They managed to hit the Centenary lode, which ultimately came out as an estimated resource of about 5 million tonnes, at eight or nine per cent zinc equivalent,” he said.
“But then you have this shear zone called the Glove-Vauxhall Shear, which is effectively a geological sequence that interrupts everything.”
Geologist Sandra Close described a shear zone as a natural deformation of rock that is difficult to penetrate.
“The rocks have been crushed, they’ve been pulverised, it’s several meters thick and very, very difficult to drill,” Dr Close said.
“If you …
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Original article and photo by "ABC News"
