One of Australia's top five gold mines, Tropicana transitioned from large scale open pit mining to a combination of open pit and underground mining in 2020 when the Boston Shaker underground mine started ore production.
The site has produced more than 5Moz since it began operations.
Open pit mining uses conventional drill and blast methodology with total annual movement of ore and waste of approximately 90 Mtpa. The open pit mining strategy at Tropicana has been designed to optimise cash flow, NPV and delivery of ore. This strategy resulted in the decision in 2021 to go ahead with a final cutback of the Havana pit. The Havana cutback will generate a further 32 million tonnes of ore for 1.4Moz of gold, extending mine life from 2027 to 2030.
Open pit ore production rates were expected to rise in the second half of 2024 as the Havana 4 cutback strip ratio decreased. The Havana pit will be the main source of open pit ore.
A pre-feasibility study on mining underground ore beneath the Havana pit was completed in 2023 and a feasibility study initiated to focus on operational readiness and detailed design. It is anticipated that construction of the access decline will start in the second quarter of 2024.
The Boston Shaker underground mine achieved steady state production of 1.4 Mt of ore per annum in early 2022 and is scheduled to rise to approximately 2 Mtpa. Underground mining uses mechanised jumbo development and open stoping methods. Monthly underground ore production rates were expected to lift to 175,000 tonnes from 165,000t in mid-2024, once ventilation constraints were resolved.
The processing plant has a throughput capacity of ~9 Mtpa. The crushing circuit consists of a primary gyratory crusher feeding a set of secondary cone crushers and tertiary high pressure grinding rolls. A 14MW ball mill and a 6MW ball mill operating in parallel complete the circuit.
Exploration at the site remains focused on testing for extensions of underground mineralisation at Boston Shaker, Tropicana and Havana and on regional targets in the northern corridor, as well as the Bushwacker target to the south of the mine.
Construction of a renewable energy facility at Tropicana started in the second half of 2023 and is on schedule for completion in early 2025. The facility comprises four 6MW wind turbines, a 24MW solar farm and a 14MW battery storage system. It will integrate 62MW of clean energy into Tropicana's existing 54MW gas-fired power system, reducing the site's diesel and gas consumption for power generation by 96% and 50% respectively, slashing carbon emissions by more than 65,000t annually over a 10-year period.
