The new joint venture, the Chinalco Rio Tinto Exploration Co Ltd, will be 51% owned by the Chinese firm and will concentrate on copper exploration as its "immediate priority", with coal and potash to be considered at a later stage, Rio Tinto said.

Chinalco has sought to diversify its business away from aluminum, and its listed unit Chalco has already agreed to invest $1.35bn in the Simandou iron ore deposit in Guinea, another joint project with Rio Tinto.

Rio Tinto has been anxious to rebuild ties with Chinalco after rejecting a $19.5bn investment bid from the Chinese firm in 2009. Chinalco remains Rio Tinto's largest shareholder, with a 9% stake.

Under the joint venture agreement, which is subject to Chinese regulatory approval, Chinalco will nominate three directors to CRTX, including the chairman and chief financial officer, while Rio will appoint two directors, including a general manager responsible for day-to-day operations.