Name of the Project
Carrapateena block cave expansion.

Location
Gawler Craton, in South Australia.

Project Owner/s
OZ Minerals.

Project Description
The Carrapateena operation produced first concentrate in December 2019 and is now ramping up to an expected 4.25-million-tonne-a-year production rate by the end of 2020.

A prefeasibility study (PFS) on the Carrapteena block cave expansion has proposed the conversion of the lower portion of the current sublevel cave to a series of block caves.

The PFS has demonstrated that the Carrapateena block cave expansion can be built without impeding the operation of the sublevel cave, and without requiring major rework of the sublevel cave underground infrastructure, ensuring project delivery and return on the sublevel cave base case.

The PFS shows that replacing the lower half of the current sublevel cave with a block cave, and expanding the expected throughput from an estimated 4.7-million tonnes a year to 12-million tonnes a year, have the potential to create significantly more value than the sublevel cave alone.

A block cave conversion in the lower portion of the Carrapateena resource has the potential to nearly double average production to between 110 000 t/y and 120 000 t/y of copper, and between 110 000 oz/y and 120 000 oz/y of gold from 2026.

The block cave will leverage existing underground infrastructure, supported by expanded surface processing capability.

To achieve a rate of 12-million tonnes a year, a parallel process plant of 6.8-million tonnes a year has been designed to minimise brownfield interfaces and introduce energy load scheduling using the vertical roller mill as the primary surface-crushing option. The parallel process plant approach also allows for both plants to be run independently and for mine production to continue during plant shutdown periods.

Potential Job Creation
Not stated.

Net Present Value/Internal Rate of Return
The Block Cave 1 and 2 expansion is estimated to result in the net present value of the project increasing from A$600-million to A$770-million at a final investment decision in 2023, with an internal rate of return of 19%, after tax.

Capital Expenditure
Capital expenditure for both block caves is estimated at between A$1.2-billion and A$1.3-billion.

Planned Start/End Date
Block Cave 1 is expected to become operational by 2026, while Block Cave 2 will become operational by 2038.

Latest Developments
OZ Minerals has approved the block cave expansion at its Carrapateena operation in South Australia, while reporting increased production for the December 2020 quarter.

On January 29, OZ Minerals announced that the board had approved progressing the block cave expansion, given the successful ramp-up of the sublevel cave.

The block cave decline early works are now scheduled to begin in the fourth quarter of this year.

“The integration and acceleration of the block cave expansion allows for progressive derisking of the Carrapateena province in its sublevel cave ramp-up to 4.7-million tonnes to 5-million tonnes a year from 2023 and transition from sublevel cave to block cave, while preserving optionality at future major capital milestone decisions over the coming years. The accelerated programme could bring forward commencement of block cave production by circa six months,” MD Andrew Cole has said.

Key Contracts, Suppliers and Consultants
None stated.

Contact Details for Project Information
OZ Minerals, tel +61 8 8229 6600 or email info@ozminerals.com.