PERTH (miningweekly.com) – Diversified metals miner Independence Group is on track to bring forward over 200 000 oz of gold production at its Tropicana gold joint venture (JV), in Western Australia, between 2017 and 2019, with the re-introduction of grade streaming.

Independence, which owns 30% of Tropicana in a JV with AngloGold, stated on Monday that mill throughput had successfully increased from the nameplate capacity of 5.8-million tonnes to 7.5-million tonnes a year, with potential to increase further to between 7.6-million and 7.7-million tonnes by the end of 2017 with the completion of plant improvements.

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 in 2015.

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.

Independence MD Peter Bradford said that grade streaming, through the continuation of the accelerated mine plan, would result in elevated mill head grades of up to 2.4 g/t in 2019.

Meanwhile, Bradford noted that potential also existed to extend the mine life at Tropicana through to 2027 to 2030, with the matter currently being investigated through the Long Island feasibility study.

The study was based on a strip mining strategy designed to significantly reduce waste mining costs and unlock the mineral resource potential. The plan consists of three key decision points over the life of the mine, with eight planned strips.

Subject to the decision to proceed with the Long Island mine plan in December this year, mining rates at Tropicana will increase slightly through 2018 to a maximum of 105-million tonnes a year during 2019.

This increase will require the introduction of a second 600-t face shovel and an increase in the haul truck fleet over time. The Long Island plan capital cost has been estimated at A$18-million.

“We are seeing positive outcomes with the Long Island study and making good progress in identifying how to unlock additional value from the Tropicana mineral resource through improved mining efficiencies and lower unit mining costs, through implementation of a strip-mining approach with in-pit dumping of waste and the use of larger face shovels as the primary waste mining tool,” Bradford said.