Rio Tinto is set to acquire 15 million shares in Canadian explorer Ivanhoe Mines, and increase its present stake in the company to 22.4 percent, reports say. Reports add that the deal permits Rio Tinto to be eligible for upto 44 percent stake in Ivanhoe Mines, and also acquire additional securities to maintain its proportional equity interest in Ivanhoe Mines, and acquire additional Ivanhoe Mines securities in certain defined circumstances and subject to certain limits. %% As per company announcements, both entities are in the process of firming details of the Oyu Tolgoi project, considered one of the world's largest untapped copper and gold deposits and is located in the Gobi desert. The joint venture of Rio Tinto and Ivanhoe Mines will be the largest foreign investment ever in Mongolia, reports say.