OZ Minerals Ltd. said Nov. 12 that an updated estimate increased underground reserves at its Prominent Hill operation in South Australia by 2%, extending the life of the mine by another year to 2030 at an underground production rate of up to 4 million tonnes per year planned from 2019.
Prominent Hill hosts proven and probable reserves totaling 69 Mt grading 1.0% copper, 0.6 g/t gold and 3 g/t silver, representing 660,000 tonnes of copper, 1.3 million ounces of gold and 6 Moz of silver.
The estimate comprises underground and open pit material and uses a net smelter return cutoff of A$52/t for in situ ore and A$16/t for stockpiled ore.
Measured, indicated and inferred copper resources at Prominent Hill total 130 Mt grading 1.1% copper, 0.6 g/t gold and 3 g/t silver, decreasing 7% from the previous estimate primarily due to mining depletion. Prominent Hill also hosts gold resources of 20 Mt grading 1.2 g/t gold, 0.1% copper and 2 g/t silver.
OZ Minerals also reported an initial resource estimate for the Fremantle Doctor zone at its preproduction-stage Carrapateena property.
Fremantle Doctor hosts inferred resources of 104 Mt grading 0.7% copper, 0.5 g/t gold and 3 g/t silver, using a 0.4% copper cutoff, representing 800,000 tonnes of copper, 1.6 Moz of gold and 10 Moz of silver.
The company, which will consider the Fremantle Doctor resource in broader planning for Carrapateena, also restated resources and reserves at Carrapateena due to limited drilling activity over the past year.
Carrapateena hosts reserves of 79 Mt grading 1.8% copper, 0.7 g/t gold and 8.5 g/t silver, with resources of 134 Mt grading 1.5% copper, 0.6 g/t gold and 6.5 g/t silver.
An updated resource estimate for Carrapateena is anticipated in the first quarter of 2019, with reserves to be updated in the fourth quarter of 2019 on the start of production.
OZ Minerals also plans to update resources at West Musgrave, Antas, Pedra Branca and CentroGold and Pantera through 2019.
