Rio Tinto will spend an additional $170m to develop its Simandou iron ore mine project in Guinea.
The investment, which bolsters $650m already spent, will be used to optimise the mine's design and infrastructure, rail system and port facilities, as well as enabling further work on drilling operations.
Rio Tinto chief executive iron ore division Sam Walsh said Simandou will be the largest integrated iron ore mine and infrastructure project developed in Africa.
The total cost of developing the mine has been estimated at around $6bn.
The mine is expected to produce 95 million tons of iron ore annually, and mining operations will be launched within five years.
Last week, Rio Tinto signed a $1.35bn deal with Aluminum Corporation of China (Chinalco) for a joint venture (JV) to develop the Simandou project.
According to the agreement, Chinalco will acquire a 47% interest in the JV by providing $1.35bn through sole funding of ongoing development work over the next two to three years.