Resources giant Rio Tinto has increased its stake in Canadian miner Ivanhoe Mines to 49 per cent.
Rio Tinto said it had acquired an additional 3.7 million shares in the Toronto-listed Ivanhoe.
The purchase - bought for $C73,075,000 ($A72,537,047) at a price per share of $C19.75 - increases Rio Tinto's ownership by 0.5 per cent.
It is the current maximum permitted shareholding in Ivanhoe Mines.
The two companies are involved in a joint venture to develop the colossal $US4.5 billion ($A4.6 billion) Oyu Tolgoi copper, gold and silver project in the Gobi Desert in Mongolia.
Commercial output is slated to start in the first half of 2013.