Ivanhoe Mines and Rio Tinto received a boost on Tuesday after Mongolia removed an obstacle to the construction of a $4bn copper and gold mine.

The decision to repeal a tax on windfall profits also fulfils the conditions for the Anglo-Australian miner to invest a further $388m in Ivanhoe, doubling its stake to almost 20 per cent. Rio bought 10 per cent of the Canadian group three years ago for $303m.