OZ Minerals has extended the mine life at the Prominent Hill copper-gold mine in South Australia to 2029 by making another addition to its underground reserves.
The miner has delivered an 18 per cent increase in the Prominent Hill underground ore reserve, lifting it to 39 million tonnes (Mt) at 1.7 per cent copper equivalent.
OZ explained that the increase would enable it to achieve an underground production rate of 3.5-4Mt a year from 2019 to continue through to 2029.
The underground ore reserve for copper and gold metal at Prominent hill has increased by 13 and 27 per cent respectively, OZ reported, driven by increased confidence in the mineral resource estimate, improved design inputs and lateral mining area expansions.
OZ has also grown its stockpiles at Prominent Hill by 25 per cent to 27Mt, with copper up 67 per cent and gold 34 per cent higher.
The growth in stockpiles was due to high volume, low strip mining from the open pit, according to OZ.
Once OZ closes the open pit at Prominent Hill in first quarter 2018, the company will maintain stockpile processing at full capacity until mid-2023, helping it to generate significant cash flows without open pit mining costs or other overheads.
OZ managing director Andrew Cole said Prominent Hill continued to develop its pedigree as a “strongly performing, long-life asset, with underground reserve life extending as the open pit draws to a close.”
“Our aim is to continue extending Prominent Hill underground mine life year on year. An estimated 80Mt of underground resource has not been converted to reserve, so there is significant potential for further extensions as we move forward,” Cole said.
“Stockpile processing will maintain the plant at full capacity to 2023, and with open pit related costs already incurred we are expecting substantial value to be realised through this period.”