PERTH (miningweekly.com) – Copper/gold miner Oz Minerals will bring forward the closure of its openpit operations at the Prominent Hill mine, in South Australia, from mid-2018 to the first quarter of the year.

About A$10-million will be saved through the accelerated plan, the company reported on Monday, as it released its September quarter results.

During the three months to September, Prominent Hill produced 28 880 t of copper and 29 264 oz of gold, compared with 28 163 t of copper and 32 136 oz of gold in the previous quarter.

MD and CEO Andrew Cole told shareholders that the underground operation at Prominent Hill performed strongly during the quarter, with production up 15%, and unit costs 21% lower than the previous quarter.

“The second decline broke through to the openpit in August, enabling productivity and efficiency gains at the underground works to increase production to 3.5-million tonnes to 4-million tonnes a year in 2019.”

Some 2.6-million tonnes of ore were milled during the quarter, a 7% increase on the previous quarter, despite a scheduled concentrator shutdown, which was completed on time and budget.

Some 63 720 t of concentrate was shipped from Prominent Hill during the quarter under review, containing 30 008 t of copper, 29 893 oz of gold and 205 895 oz of silver.

Meanwhile, Cole on Monday noted that work at the Carrapateena project, in Western Australia, had started, after board and government approvals for the airstrip and accommodation village.

“The Carrapateena project has seen considerable progress with key contracts finalised and orders placed for long lead items associated with the process plant,” Cole said.

He added that decline development is on plan with the second decline braking through to the boxcut, providing the primary ventilation circuit and enhancing access and egress.

An updated prefeasibility study estimated that the Carrapateena project could deliver 61 000 t/y of copper and 63 000 oz/y of gold over an estimated 20-year mine life, with project costs estimated at A$980-million.