OZ Minerals considers Carrapateena block cave to up production

Core samples at Carrapateena. Image: OZ Minerals.

OZ Minerals has completed a scoping study that suggests converting a section of the in-development Carrapateena project in South Australia to a block cave will significantly increase production.

The company’s plans refer to converting a portion of the copper-gold mine’s lower sub-level cave into a block cave from 2026.

Block caving is a relatively new form of underground hard rock mining that involves using natural stress factors to break up rock formations by inducing deliberate caving.

The method can significantly cut drilling and blasting costs while heightening productivity in the right circumstances.

Northparkes Mines in New South Wales was the first company to use this process in Australia at its copper-gold operation and has another block cave in development.

OZ Minerals reported that introducing block caving at Carrapateena could double mine throughput from 4.25 million tonnes a year to 10-12 million tonnes. The move would increase Carrapateena’s average copper production to 105,000–125,000 tonnes a year and reduce all-in sustaining costs (AISC) to $US0.90–0.95 per pound.

The expansion could also increase Carrapateena’s overall tonnes from 84 million at an average 1.8 per cent copper and 0.7 grams of gold per tonne to 145 million tonnes at 1.2 per cent copper and 0.5 grams of gold per tonne over a 20-year period.

OZ Minerals is working on a pre-feasibility study (PFS) for the expansion, which it expects to complete by mid-2020.

“The potential for the Carrapateena block cave expansion to progressively unlock the Carrapateena life of province more broadly via a controlled, methodical and incremental approach is particularly attractive as it manages risk and capital expenditure whilst enhancing value for shareholders and other stakeholders” OZ Minerals chief executive officer Andrew Cole said.

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