Mining firm OZ Minerals announced that its board has approved the block cave expansion of its Carrapateena copper-gold mine located on the eastern margin of the Gawler Craton in South Australia.

Based on the pre-feasibility study, the Carrapateena block cave expansion project is estimated to cost A$1.25bn ($960m).

The company said that the block cave expansion would unlock Carrapateena’s potential to be a multi-generational, low quartile cash cost producing province.

The project is expected to boost production to 12 million tonnes per annum (Mtpa) and average copper production to approximately 110-120ktpa. Gold production is estimated to be ramped up to about 110-120koz.

As part of the expansion plan, Oz Minerals plans to start the block cave decline early works in the fourth quarter of this year.

In order to simplify planning, reduce execution threats, and maximise opportunities in value creation, the block cave expansion has been integrated into the existing operations plan of the Carrapateena project, taking it to take a whole of province development approach, the firm said.

The expansion project will involve converting the lower part of the current sub-level cave into a series of block caves.

Additionally, the company is targeting block cave 1 to begin operations by 2026, followed by block cave 2 by 2038.

OZ Minerals managing director and CEO Andrew Cole said: “The integration and acceleration of the Block Cave Expansion allows progressive de-risking of the Carrapateena Province in its sub level cave ramp-up to 4.7 to 5.0Mtpa from 2023 and transition from sub level cave to block cave, while preserving optionality at future major capital milestone decisions over the coming years.

“The accelerated program could bring forward commencement of block cave production by circa six months.”

Located in the highly prospective Gawler Craton in South Australia, the Carrapateena mine produced the first concentrate in late 2019 following securing final approvals in 2018.

Meanwhile, the company said it plans to take a final investment decision on the Prominent Hill expansion project in mid-2021 and on West Musgrave open pit project in 2022.