FMG and Guinea's biggest bauxite exporter, SMB-Winning, were the last two companies in the running for the rights to develop the blocks, Reuters reported citing three sources.
The blocks became available earlier this year after Beny Steinmetz's BSG Resources did a deal with Guinea.
Rio Tinto, Chinalco and the government own blocks three and four.
The better-than-expected US data eased recession fears but the gold price remains above US$1,500 an ounce, worth more than $1,506/oz on the spot market earlier.
Key market futures were mixed as concerns continue over US-China trade tensions.
China's week-long national day holiday finishes today.
Australia-based gold miner St Barbara (ASX: SBM) was one of the top gainers on the S&P/ASX200 at the time of writing, up 3.6%.
Barrick Gold (TSX: ABX) had closed 2.7% higher in Toronto on Friday.