AngloGold Ashanti’s Australia region produced 554,000oz in 2020 compared to 614,000oz in 2019, as the completion of grade streaming and a lower proportion of open pit ore in the mill feed resulted in a 17% drop in year-on-year attributable production at Tropicana, in line with the mine plan.
At Sunrise Dam production was steady at 256,000oz as the mine focused on a strategy to fill the mill with the best quality ore through a programme of underground exploration and development to build orebody knowledge and add to the Ore Reserve.
The strategy involves maximising the extraction of the Vogue orebody, which is currently the primary source of underground ore, and providing mining flexibility by developing an alternate mining area. Vogue will contribute 80% of underground ore over the next two years, with multiple ore sources making up the remaining 20% of mill feed.
Mill throughput remained consistent at 4.0Mt for 2020 and metallurgical recovery is benefiting from the float ultra-fine grind circuit that was implemented in 2018.Pre-stripping of the Golden Delicious open pit, 12km from the Sunrise Dam processing plant, began in the December quarter 2020.
Ore production from Golden Delicious is scheduled to begin in the June quarter of 2021 and the open pit is expected to deliver approximately 136,000oz over a 2.7-year life of mine. From the second half of 2021, Golden Delicious ore will totally displace the low-grade stockpile mill feed, enabling grade streaming to be applied through 2022.
Tropicana produced 298,000oz for the year compared to 360,000oz in 2019. Production was lower year-on-year as planned. Up until June 2020, ore production from the open pits exceeded plant capacity, allowing higher-grade ore to be preferentially treated, while lower-grade ore was accumulated on stockpiles.
With the completion of the Tropicana pit and stage one of the Havana pit (Havana cutbacks 1, 2 and 3) mid-way through the year, this grade streaming process ceased, in line with the mine plan.The Boston Shaker underground mine started commercial production on time and on budget in September 2020.
When the underground mine reaches its full production rate of 1.1Mtpa in the second half of 2021, it will contribute 100,000oz annually to gold production. The mine will achieve payback in three years.Waste stripping for stage 2 of the Havana pit began in the second half of 2020 and while waste stripping is underway, mill feed will be made up of ore from the Boston Shaker underground mine, the Boston Shaker open pit and stockpiles.
The Tropicana processing plant continued to perform well in 2020, with throughput and metallurgical recoveries higher than the previous year. Further efficiency improvements are planned for 2021 to increase throughput from 8.8Mtpa to 9Mtpa in the second half.