Currently, Rio Tinto subsidiary Simfer holds a 95-per cent stake and the International Finance Corporation (IFC), a member of the World Bank Group, holds the remaining 5 per cent.

Last year, Rio Tinto and China's state-owned aluminum giant Chinalco signed a memorandum of understanding to form a joint venture, in which Rio Tinto's 95-per cent interest in Simfer would be transferred to the new JV.

Chalco will acquire a 47-per cent interest in the new JV by providing $1.35 billion on an effective ongoing earn-in basis

Once Chinalco has invested its $1.35 billion, the effective stakes owned by Rio Tinto and Chinalco in the Simandou project will be 50.35 per cent and 44.65 per cent respectively with the International Finance Corporation retaining its original 5-per cent holding.

Under the agreement, Chinalco will fund the ongoing development work over the next two to three years.

Rio Tinto settled a long-running dispute over Guinea's huge Simandou iron ore field, and as part of the April 2011 settlement, the government of Guinea has the right to take a stake of up to 35 per cent gradually over the next 20 years in the project, including 15 per cent at no cost.