The Tropicana Mine, the first greenfields gold discovery to be brought into production in Australia for more than a decade, poured first gold on September 26, 2013, ahead of schedule and on budget.
Innovation has been incorporated into the design of Tropicana’s mining and processing systems, from the start of exploration through to environmental management and closure planning.
The mine was officially opened in March 2014 by the then Western Australian Minister for Mines and Petroleum, the Hon. Bill Marmion.
In 2020, Tropicana achieved several major milestones, starting underground production at Boston Shaker and pouring its 3 millionth ounce of gold.
The Boston Shaker underground mine transitioned into commercial production in September 2020 on schedule, below the A$105.7 million budget and importantly, with no safety incidents. Boston Shaker will deliver approximately 1.1 million tonnes of ore per annum at an estimated grade of 3.5 grams/tonne, contributing approximately 100,000 ounces per annum to gold production over a seven year mine life.
The first production stope was fired in June 2020 and the design production rate expected to be achieved in March 2021.
Importantly the Boston Shaker mineralisation extends down-dip and remains open at depth, limited only by drilling information.
Tropicana produced its 3 millionth ounce in March 2020, just seven years after pouring first gold.During this period ore has been sourced from the Tropicana, Havana, Havana South and Boston Shaker pits, which have been mined as a series of cutbacks, sequenced and scheduled to maximise value at a mining rate that delivers the best mining unit cost for the scale of the operation.
Late in 2018 a second ball mill was added to the Tropicana processing plant increasing throughput capacity to more than 8 Mtpa, and providing flexibility to balance throughput and recovery. The modern processing plant uses conventional carbon-in-leach technology and includes high pressure grinding rolls (HPGR) for energy-efficient comminution.
Up until June 2020 ore production from the open pits exceeded the plant capacity, allowing higher grade ore to be preferentially treated (grade streaming) while lower grade ore was accumulated on stockpiles.
During the second half of 2019 and the first half of 2020, the Tropicana pit and Havana pit were completed, in line with the mine plan. As a result, grade streaming came to an end and stockpiled ore is currently being used to supplement the mill feed from the Havana South and Boston Shaker pits.
A decision was made in the June 2020 quarter to invest in the next cutback of the Havana pit (Stage 2) which will allow access to the deeper Havana open pit ore from 2022 onwards. While this cutback is being completed, mill feed will be sourced from the Boston Shaker open pit, supplemented by approximately 4 Mtpa of low grade (0.85 – 1.05 g/t) stockpiled ore, resulting in a lower milled grade over the period. The lower grade will be partially offset by the Boston Shaker underground mine.
The plan remains for annual gold production (at 100%) in 2020 and 2021 to be between 400,000-450,000 oz lifting to between 450,000–500,000 oz from 2022 onwards as the portion of stockpiled ore in the mill feed is replaced by both Boston Shaker underground ore and an increasing contribution of ore from the Havana pit as the cutback progresses.
Significant potential remains to unlock known extensions of mineralisation beneath the Tropicana and Havana open pits and the extensions at depth of the Boston Shaker underground mineralisation.
In the second half of 2020 development of the Tropicana underground exploration drive commenced. This drive is well positioned to also provide production access to the Tropicana underground reserve should the drilling prove successful. Underground diamond drilling is scheduled for the December 2020 quarter to improve orebody confidence.
Final trade-off studies are currently being completed on the Havana Stage 3 open pit cut-back and Havana underground to determine the optimal open pit – underground interface. A decision on the way forward for Havana Stage 3 is expected to be made during 2021.
Regional exploration continued through 2020 with encouraging results from a number of prospects.Recent operational excellence work at Tropicana included the successful trial of autonomous open pit blast hole drilling which demonstrated that significant productivity gains could be achieved. As a result, five platform drill rigs have been converted to autonomous operation.