PERTH (miningweekly.com) – Takeover target Oz Minerals has reported ore reserve increases at its Prominent Hill underground operation, in South Australia, and its West Musgrave project, in Western Australia.

In its annual mineral resource and ore reserve updates, Oz Minerals reported a near 23% increase to the Prominent Hill underground ore reserve, which now stands at 59-million tonnes at 1.4% copper equivalent, extending the mine life by two years to at least 2038.

The project has a total resource estimate of some 180-million tonnes, containing 1.6-million tonnes of copper, 4.5-million ounces of gold and 14-million ounces of silver.

At West Musgrave, Oz Minerals reported a near 7% increase in the ore reserve compared with the September feasibility study and positive investment decision, with the ore reserve now standing at 270-million tonnes grading 0.34% copper and 0.31% nickel, supporting a 24-year mine life to 2040.

The A$1.7-billion West Musgrave copper/nickel project is expected to produce an average of 35 000 t/y of nickel and 41 000 t/y of copper in the first five years of operations, and some 27 000 t/y of  nickel and 33 000 t/y of copper in the remaining mine life.

Meanwhile, Oz Minerals on Wednesday said that the mineral resource tonnage at Carrapateena decreased by 5%, and with no change to the copper grade, this resulted in a 5% decrease in copper metal. Ore reserve tonnes at the operation reduced to 190-million tonnes, with copper and gold metal down some 13%.

Furthermore, decreases to the Pedra Branca mineral resource and ore reserve were primarily due to mining depletion and an increase to reporting cut-off as a result of increased project cost. The decrease in mineral resource has been partially offset by additional tonnes as a result of extensional drilling.

The mineral resource tonnes have decreased by some 5% with copper grade stable and copper metal down some 6%. The ore reserve as at the end of June 2022 is 4-million tonnes at 2% copper and 0.5 g/t gold compared to the end of June 2021 5-million tonnes at 2.1% copper and 0.5 g/t gold.

A maiden mineral resource estimate of 5.8-million tonnes at 2.1% copper and 0.35 g/t gold at Santa Lúcia was released in September 2021. Additional drilling has been completed and an updated mineral resource estimate is expected to be completed imminently.

A maiden mineral resource estimate for Pantera has been released estimating a mineral resource of 20-million tonnes at 1.2% copper and 0.2 g/t gold.