An exploration and deposit access drive was commenced from the Tritton underground infrastructure towards the Budgerygar deposit during FY2021.
A resource definition diamond drilling program has commenced to upgrade the quality of the Mineral Resource and to enable mine planning and scheduling to commence. Mining is due to commence from the Budgerygar deposit in late FY2022.
Ore from Budgerygar will supplement mine production, replacing the declining production coming from the deeper parts of the Tritton deposit.
Budgery Deposit Open Pit
The Budgery deposit is approximately 20 kilometres south of the Tritton ore processing plant, close to the Hermidale township. It is located within the same geological setting as the Tritton and Murrawombie deposits and again, displays similar characteristics.
Significant exploration drilling has been conducted to support a concept study for an open-pit project, however additional resource drilling, metallurgy studies, environmental studies and native title negotiations are required before a pre-feasibility study can be completed.
The conceptual open-pit would mine a combination of oxide and sulphide ore types with the treatment method for the near-surface oxide portion of the ore body requiring additional technical work. One option for the treatment of the oxide ore is by heap-leaching, a process with which the Tritton Copper Operations is very familiar. A second option is treatment through the Tritton ore processing plant with a sulphidisation pre-treatment. Both of these possibilities will be considered.
The Budgery mineralised system is significant and known to continue at depth. There has been limited drilling completed at depth, and this presents an opportunity to increase the Mineral Resource down-dip from the current reported Mineral Resource, which extends some 250 metres vertically. Options for selective underground mining of possible deposit extensions will be tested as drilling information becomes available.
Murrawombie Open Pit
The expansion of the old Murrawombie Open Pit, which entails a small push back of the eastern wall to increase the pit depth, will allow Aeris to mine an estimated additional 1.6 million tonnes of ore.
The pit expansion project has secured Local and State Government approvals and, from a regulatory perspective, can proceed at any time.
Production from the Murrawombie Open Pit has historically been scheduled to start after the completion of the Murrawombie Underground to avoid complex operational interactions. However, options to mine in parallel with Murrawombie Underground is being investigated.
It is now expected that the push-back of the Murrawombie Open Pit will commence in FY2022.
Waste mined from the pit expansion will be used for site rehabilitation and closure works. Use of the pit waste as capping for the adjacent heap leach pads substantially reduces the closure cost for the Murrawombie mine site.
Avoca Tank Underground
Avoca Tank is a small, high-grade deposit located five kilometres to the north of the Murrawombie mine site. The current planned life of mine for Avoca Tank is approximately four years, including construction, however there is a realistic expectation that exploration drilling may increase the size and life of the deposit. Avoca Tank has multiple lenses of mixed chalcopyrite and pyrite mineralisation, and it is likely that the complex structural character has contributed to its high grades. The deposit is unusual for the region due to its vertical dip, and it has an uncharacteristically high gold content at 0.8g/t.
As a small scale, high-grade mine Avoca Tank is planned to be mined as a supplementary ore source to top-up production from the larger Tritton and Murrawombie mines. Planned production rates are modest at 350,000 tonne per year, consistent with the size of the deposit. The high grade of the ore will be an important sweetener of the processing plant head grade.
The pre-feasibility study that describes the project was completed in 2014. Execution planning and additional studies have been completed to better define the project. A major change compared to the pre-feasibility study was the decision to access the deposit via a two-kilometre-long decline from the Hartmans pit, rather than develop a new box cut pit and portal. The reduction in environmental impact due to the design change was significant. Capital development work on Avoca Tank project commenced in the first half of FY2022.