Rio Tinto and its partners gave the greenlight to a $5.3bn (£3.7bn) expansion of its Oyu Tolgoi mine in Mogolia today.
The move demonstrates the mining giant's confidence that low copper prices will stage a turnaround in a few years time.
The London-listed company, the Mongolian government and Turquoise Hill Resources, approved the next stage in the development of the mine, which will start producing in 2020.
Once at full capacity, Oyu Tolgoi is expected to pump out 500,000 tonnes of copper per year, nearly triple current levels.
Rio Tinto's deputy chief executive, Jean-Sébastien Jacques, said: "Today's investment takes it to another level and will transform Oyu Tolgoi into one of the most significant copper mines globally, unlocking 80 per cent of its value."
"Long-term copper fundamentals remain strong and production from the Oyu Tolgoi underground will commence at a time when copper markets are expected to face a structural deficit."
Copper is currently trading at multi-year lows due to the global oversupply, however a dearth of big discoveries means industry insiders, analysts and commentators expect a rebound in the next few years.
Oyu Tolgoi has previously been described by analysts as the best undeveloped copper project globally, and probably the best undeveloped asset in the industry.
Rio Tinto's shares fell 1.3 per cent to 2,086.5p per share in early morning trading.