JOHANNESBURG (miningweekly.com) – Joint venture (JV) partners AngloGold Ashanti and Independence Group have committed to the initial phase of the Long Island strategy, which will ultimately add 2.1-million ounces to the Tropicana mine’s business plan and will extend the operation’s mine life by seven years to 2027.
The brownfield project at the Tropicana mine, in Western Australia, is based on a more cost-effective approach to mine waste and involves using a strip-mining approach that minimises waste haulage by using in-pit backfill, rather than trucking material over long distances to surface waste dumps.
Phase 1 of the strategy comprises mining the Havana South pit and a cutback of the Boston Shaker pit, which uses the completed Tropicana pit as the first backfill location.
AngloGold, which owns 70% of the JV and is also the operator, said on Thursday that the Long Island strategy would increase Tropicana’s mining rate to between 95-million tonnes and 107-million tonnes a year. The installation of a 600-t face shovel last year had lifted the mining rate to about 90-million tonnes.
The JV partners would add a second 600-t shovel with up to five additional Caterpillar 793 trucks and supporting ancillary equipment to manage the additional movement increase.
Mining contractor Macmahon would provide the additional fleet.
AngloGold said that the capital expenditure required for the Long Island strategy was estimated at A$18-million and related primarily to the expansion of the accommodation camp and heavy vehicle workshop infrastructure.
To enable throughput to match the increased mining rate, the JV has also approved the installation of an additional 6 MW ball mill at a cost of A$28-million. The second ball mill would increase the throughput rate of the processing plant to about 8.1-million tonnes a year and improve gold recovery by up to 3% to about 92%.
The increased throughput would bring forward gold production, while the improved recovery rate would add about 160 000 oz to the recovered gold over the life of the mine.
The new ball mill would be commissioned in the final quarter of 2018. The investment would have a payback period of less than a year, AngloGold reported.
The processing plant currently has a throughput rate of about 7.6-million tonnes a year and was expanded through a range of optimisation projects from the initial nameplate capacity of 5.8-million tonnes a year.
The Long Island strategy is underpinned by continued exploration success, with the ore reserve having increased to 66.59-million tons grading 1.91 g/t for 4.08-million ounces.
The remaining life-of-mine production of Tropicana excludes the potential future underground mineralisation at the Boston Shaker orebody, which AngloGold is currently studying. A scoping study is under way and will be advanced to a prefeasibility study next year.
“This project validates the innovative ideas developed by our site team and technical specialists, and also gives us an excellent base from which to investigate adding additional value through underground mining opportunities and regional exploration,” comments AngloGold Ashanti senior VP for Australia, Michael Erickson.