Galiano already owns 45% of Asanko, which produced 170,000 ounces of gold in 2022 and is one of Ghana's biggest gold mines.
Johannesburg-based Gold Fields has been reviewing its investment in Asanko, in which the government of Ghana holds 10%, saying it needs to fall under the control of one investor.
"It is clear that the committed path forward for the Asanko mine requires consolidated ownership, and Gold Fields is pleased to realise value for its holding now," Gold Fields interim CEO Martin Preece said in a statement.
Gold Fields, which owns 9.8% of Galiano, will increase its shareholding in the Canada-listed miner with additional shares worth $20 million as part of the Asanko deal.
Galiano said in a separate statement that the elimination of the joint venture structure "will streamline operational and financial decision making" at Asanko, its flagship asset.
In March, Gold Fields and AngloGold Ashanti agreed to merge their Tarkwa and Iduapriem mines in Ghana to create Africa's biggest gold mine, which would produce 900,000 ounces annually over the first five years of the merger.
The proposed transaction is still under consideration by the Ghanaian authorities.
Ghana is currently the second biggest contributor after Australia to the output of Gold Fields, which also has operations in South Africa, Peru and Chile.
(Reporting by Nelson Banya; Editing by Alexander Smith)
