The biggest former Yugoslav republic is following Hungary and Poland, where officials boosted gold reserves in 2018 to create a bulwark against crisis.
The deal comes as a relief to the sector, where officials were fearful of a repeat of a five-month platinum strike in 2014-2015 which crippled production and hurt the economy.
Eramet earlier predicted the FID would be made at the earliest in the fourth quarter of this year, but the decision has been slightly delayed due to the change in Argentina's government.