PERTH (miningweekly.com) – Gold production from the Tropicana mine, in Western Australia, is expected to improve considerably next year, when grade streaming is reintroduced.

Gold major AngloGold Ashanti, which owns 70% of Tropicana, and its joint venture (JV) partner Independence Group, which owns a 30% stake in the project, reported on Thursday that the mine would produce at a rate of between 450 000 oz/y and 490 000 oz/y from the second half of 2017.

Grade streaming, which involves the preferential treatment of higher grade ore and stockpiling of low- and medium-grade ore, was adopted at Tropicana in its first three years of operation and came to an end last year.

The Tropicana bankable feasibility study envisaged a production rate of 320 000 oz/y over the initial three-year gold streaming period. The mine produced 296 000 oz in the first nine months of 2016.

To resume grade streaming for at least the next two calendar years, a 600-t shovel has been introduced to accelerate mining rates and the processing plant throughput has been increased from 5.8-million tonnes a year to 7.5-million tonnes a year. Further tuning of the circuit is anticipated to increase throughput to 7.9-million tonnes a year over the next 12 months.

“We’ve adopted an innovative, holistic approach that demonstrates the quality of this asset and the enhanced returns it will deliver to stakeholders,” said AngloGold Ashanti senior VP for Australia, Michael Erickson.

Independence MD Peter Bradford highlighted a number of work programmes that had been concluded during 2016 to optimise the gold mine. These included the completion of a resource definition exploration programme that resulted in the mineral resource and ore reserve increasing to 8-million ounces and 3.8-million ounces of contained gold respectively, the expansion of the processing plant and implementing modifications to the mining schedule and fleet to allow for the restart of an accelerated mining rate.

“Although this remains a work in progress, these work programmes have demonstrated the significant value that can be unlocked. To date, the work programmes have identified the potential to deliver more than a 75% increase to the Tropicana net present value, when compared on a like-for-like basis to our business plan at the start of 2016. This is a great achievement, which demonstrates the quality of the Tropicana gold mine.”

Bradford said that significant value remained to be captured from the ongoing Long Island study, which would be completed by mid-2017. The study would determine the longer term mining rate of Tropicana.

“The final study will include the addition of a Boston Shaker resource update and Havana South. This will likely extend the mine life through to 2027 or 2030,” he added.

Long Island mining could potentially start in 2019, thereafter average gold production was expected to be between 400 000 oz/y and 450 000 oz/y.

The Long Island study is based on strip mining of the depth extensions of the Tropicana mineralised system and using the completed Tropicana pit as an initial void into which waste will be backfilled. The proposed backfilling, in conjunction with strip mining, is expected to reduce the cost of mining waste.