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, and produced its 1 millionth ounce on schedule in December 2015, just over two years after pouring first gold, and its 2 millionth ounce nearly three years later in January 2018.
The large-scale, open pit operation features a modern processing plant which uses conventional carbon-in-leach technology and includes high pressure grinding rolls (HPGR) for energy-efficient comminution. Mining is carried out under an alliance-style contract with Macmahon.
In 2017 Tropicana produced 322,000 oz (AGAA's 70% share) as a result of a 10% increase in mill throughput to 5.3 Mtpa. By year-end optimisation and expansion of the processing plant had lifted processing capacity to 7.5 Mtpa. A fines pulp circuit was commissioned in November 2017, further improving efficiency by minimising downtime during maintenance shutdowns. This is expected to increase annual mill runtimes by approximately 1.5%.
Following the introduction of a 600t face shovel to the mining fleet, mining rates increased to more than 90 Mtpa in 2017, enabling the resumption of grade streaming – the preferential treatment of higher grade ore while low-to-medium grade ore is stockpiled – in the second half of the year. Mining in 2017 focused on the Havana 3 and Tropicana 2 pits.
In December the Tropicana Joint Venture partners announced a commitment to the Long Island mining strategy and approval for an additional ball mill in the processing plant, to further lift plant throughput to 8.1 Mtpa and increase gold recovery.
Total cash costs benefited from higher gold production and lower unit mining costs at Tropicana, dropping by 6% to $743/oz in 2017.
Ongoing mining efficiencies at Tropicana as part of the site’s Operational Excellence initiatives are expected to reduce mining costs by 5%-10% in 2018.
At Tropicana the focus in 2018 and beyond will be on implementation of the Long Island strategy, which adds 2.1 million ounces to Tropicana’s business plan, extending mine life by approximately seven years to 2027. It also brings forward 200,000oz into 2017-2019.
The Long Island strategy has been driven by finding a more cost-efficient way to mine waste in pit cutbacks. It involves using a strip-mining approach that minimises waste haulage distances by using in-pit backfill, essentially optimising haulage over the life of mine.
The approach comprises eight stages with three major decision points providing flexibility to tailor the approach at each decision point depending on market conditions.
Phase One comprises mining of the Havana South pit and a cutback of the Boston Shaker pit, using the completed Tropicana pit as the first backfill location.
Mining rates will increase to between 95-107 Mtpa over the next two years through the Long Island development, peaking at 107 Mtpa in 2019 and continuing at that rate for about four years.
The project was enhanced by the decision to install a 6MW ball mill in the processing plant, enabling throughput to be lifted to 8.1 Mtpa and matched to the increased mining rate.Through a reduction in grind size baseline metallurgical gold recovery will be improved by up to 3% to approximately 92%.
Gold production (100%) is forecast to be between 478,000oz and 492,000oz in 2018 and between 530,000oz–548,000oz in 2019, or about 4Moz over the remaining life of the mine.
This does not include potential future underground production from mineralisation at the Boston Shaker ore body, which remains open at depth. A prefeasibility study on underground mining will be commissioned in 2018 with the aim of defining an underground Ore Reserve by the end of the 2018 calendar year. The PFS will include infill drilling and mining studies. The target is to delineate underground reserves at +3 g/t to displace stockpiled mill feed after 2021.
The Long Island strategy was underpinned by an increase in the Ore Reserve to 66.59 Mt grading 1.91 g/t gold for a total of 4.08 Moz. Including gold produced to date, Tropicana has delivered a 72% increase in Ore Reserves since the project was approved in November 2010.