The Carrapateena copper-gold project is located on the eastern margin of the Gawler Craton in South Australia, approximately 160km from the Port Augusta.
Wholly owned by OZ Minerals, the mine is one of the biggest undeveloped copper projects in Australia and has the potential to produce 65,000t of copper and 67,000oz of gold a year over the mine’s 20-year life.
Phase one construction of the project commenced following the OZ Minerals’s Board approval for the development of the Carrapateena project in August 2017.
A feasibility study update, which was released in August 2017, estimated Carrapateena’s net present value at $916m. A feasibility study on the potential expansion of the bottom half of the operation into a block cave is in progress.
The project Carrapateena produced first concentrate in December 2019 and is currently working to mine and process a 91Mt ore resource using the sub-level cave system.It is now enhancing production to an estimated pace of 4.25Mtpa by the end of 2020, with throughput rates targeting 4.7–5.0Mtpa by 2023.
Carrapateena’s project development costs are expected to be in the range of $950-$980m as a result at first concentrate.
The Carrapateena block cave expansion feasibility study stage 1 is expected to be completed by the end of 2021.
The Carrapateena copper-gold deposit was discovered by Rudy Gomez in 2005. OZ Minerals acquired the project from Rudy Gomez (58%), Teck Australia (34%) and minorities (8%) in May 2011.
Carrapateena location, geology and reserves
The project is located at Pernatty Station and its associated infrastructure is situated within Oakden Hills station.
Carrapateena is an iron oxide-copper-gold (IOCG) ore deposit located approximately 250km south-east of OZ Minerals’ Prominent Hill mine. It comprises four exploration licences spread across a 1,070km² area in central South Australia.
With a 300m diameter and a vertical depth of 1,000m, the cylindrical-shaped Carrapateena deposit is located within the eastern margin of the Gawler Craton and hosted by the Carrapateena Breccia Complex (CBC), which is overlain by 470m of Stuart Shelf sediments.
The mineralisation at Carrapateena is dominated by coarse-grained disseminated chalcopyrite with common occurrences of sulphide vein-fill and blebs.
As of June 2019, the Carrapateena mine was estimated to contain 91Mt of probable ore reserves grading at 1.6% copper, 0.67g/t of gold and 8g/t of silver.
The Carrapateena mineral resource was estimated to be 970Mt grading at 0.5% copper, 0.2g/t gold and 3g/t silver.
Recovery and ore processing at Carrapateena mine
A block caving method involving two 500m-high lifts will be employed at the underground copper and gold mine for ore extraction.
The block cave mine will be accessed through two declines, including a main access and a production access decline. The main access decline will be developed by a tunnel boring machine, while the drill and blast method will be applied to develop the production access decline.
Ore will be primarily crushed underground, and the material will be delivered to the processing plant via a conveyor. Approximately 16 load haul dump loaders will be used to transport ore to the surface.
The processing plant is expected to process 12.4Mt of pre-crushed ore a year to produce copper-gold concentrate using conventional methods of grinding and flotation. The obtained concentrate will pass through three stages of cleaner flotation before being filtered and finally packed in containers for transportation by the Adelaide to Darwin railway to the port in Adelaide.
Tailings will be stored in a storage facility being constructed approximately 2km south-east of the concentrator plant.
Carrapateena plant ramp-up continues to progress well with strong throughput rates achieved, including a daily record of 15,022t milled and periods exceeding 15 days at an average rate of 12,000tpd over the nameplate.
Mine construction and infrastructure facilities
The underground mining project includes the construction of two block caves (lifts), a ventilation system capable of delivering 1,200m³ of air per second to the mine, access roads, the processing plant, a 50km-long transmission line, in addition to other amenities at the mine site.
The mine will be accessible from the Stuart Highway via a 50km-long access road. Water supplies for the mining, ore processing and other site activities will be supplied from a newly developed bore field.
The power will be provided by the existing Electranet 132kV line at Mount Gunson, with emergency back-up power to be supplied from a 20MW diesel-fired power generation facility.
An accommodation village to house both construction and operation workers with a capacity of 2,000 people has been constructed.
Contractors involved in Carrapateena
AMC Mining Consultants, GR Engineering, AECOM, SMEC and Golder Associates were involved in preparing the pre-feasibility study of the project.
Intract Indigenous Contractors and McMahon Services were awarded a $2.9m contract to construct an exploration accommodation camp for the Carrapateena mining project.
GR Engineering Services was awarded a contract in February 2019 for engineering, procurement and construction (EPC) for the project.
ElectraNet executed a transmission connection agreement with OZ Minerals to provide 55MW of electricity for 20 years. Ventia was responsible for the design, capital works and procurement of the associated transmission line and substation, under a contract with ElectraNet.
A joint venture of AUSENCO and Downer provided capital and an operationally efficient plant.
KBR was selected to provide project management services for the project in October 2017.
In April 2018, Downer EDI was awarded a $660m contract by OZ Minerals for the next-phase development of the Carrapateena underground mine.