The new strategy will add 2.1 million ounces of gold production to the Tropicana business plan, extending mine life by about seven years to 2027.
Long Island will involve a strip-mining approach that minimises waste haulage distances by using in-pit backfill rather than trucking the material long distances to surface waste dumps.
The Long Island strategy is estimated to cost $18 million, while the ball mill installation will be worth $28 million.
"This project is in line with our approach of developing cost-effective brownfield projects with attractive payback periods that extend life and improve margins", said AngloGold Ashanti's Australian senior vice-president, Michael Erickson.
AU expects gold production at the Tropicana mine of as much as 492K oz.in 2018 and at least 530K oz.in 2019; gold production over the remaining life of the mine is forecast at ~4M oz.
Tropicana, which is jointly owned by AngloGold Ashanti Australia (70 per cent) and Independence Group, is the state's third largest gold mine, with production of 432,00oz past year.