An 18% growth in underground ore reserves to 39 Mt @ 1.7% copper equivalent has extended OZ Minerals’ Prominent Hill mine life significantly. This will see an expected underground production rate of 3.5-4.0 Mt/y from 2019 to continue through to 2029. Underground ore reserves for copper and gold metal have increased by ~13 and ~27% respectively, driven by increased confidence in the Mineral Resource estimate, improved design inputs and lateral (across and along strike) mining area expansions.

OZ Minerals Managing Director and Chief Executive Officer, Andrew Cole, said: “Prominent Hill continues 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 80 Mt of underground Resource has not been converted to Reserve, so there is significant potential for further extensions as we move forward. 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.”

The Prominent Hill processing plant has been operating since February 2009 and comprises a conventional crushing, grinding and flotation circuit to recover copper, gold and silver to produce a high quality concentrate. The plant can process approximately 10 Mt/y subject to the ore blend. The current life of mine schedule has the plant running at that capacity until May 2020 when open pit copper ore stocks are depleted.

From then until 2023, throughput will be approximately nine to 1o Mt/y with a high proportion of stockpiled open pit gold ore. On exhaustion of gold ore stocks the plant will be fed with underground ore alone.