Rio Tinto has won over the board of copper developer Turquoise Hill Resources with its $US3.3 billion ($4.84 billion) takeover offer in a major boost for the mining giant’s ambitions in Mongolia and perhaps its most important growth project.

The buyout of Turquoise Hill clears the way for Rio to work in partnership with the Mongolian government on development of the Oyu Tolgoi copper mine with a view to it becoming one of the world’s top five producers by 2030.