Rio Tinto shareholders have taken up a healthy 96.97% of the shares offered to them as part of the miner's $15.2bn fully underwritten rights issue. The group received valid acceptances in respect of 508.58m of the £7.1bn of shares available in London. Underwriters Credit Suisse and J.P. Morgan Cazenove will seek subscribers for the remaining 15.88m shares.The details of the Australian issue are not yet available.Rio's biggest shareholder Chinalco, which holds about 9% of the group, has taken up its full entitlement. Terms of the rights were 21 New Rio Tinto shares for every 40 existing shares at 1,400 pence per share, a 48% discount, and 21 New Rio Tinto Limited Shares offered for every 40 existing shares at A$28.29 each. Rio launched the cash call and announced a merger of its West Australia iron ore assets with those of bitter rival BHP Billiton last month after scrapping its controversial $19.5bn refinancing deal with Chinalco.