Saudi Arabian Mining Co's (Maaden) 9.25 billion riyals ($2.47 billion) initial public offering, the Middle East's largest ever mining IPO, was more than two times oversubscribed, advisers of the sale said.

The IPO, which was open only to Saudi investors, defied a "challenging" context marked by the global downturn, Rupert Fane, head of equity syndicate at JP Morgan, told Reuters by telephone.

"If you have a $2.5 billion transaction ... that was over two times covered for both (retail and institutional) tranches ... is a huge success against that backdrop," he said.

He could not disclose more details pending the official release of the final results.

JP Morgan was appointed sole bookrunner and financial adviser for the 10-day sale which closed on Monday.

"This is the first IPO we have done in Saudi Arabia," Fane said, declining to give details on other issues his company is currently working on in the Middle East.

Shares in Maaden will begin trading by end-July, Fane said.

Maaden offered 462.5 million worth of shares -- equivalent to 50 percent of its share capital -- at 20 riyals each.

The IPO is to cover some of the costs of projects led by the company, mainly a 720,000-tonne aluminium smelter with Rio Tinto and a 3-million tonnes phosphate and by-products plant with Saudi Basic Industries Corp (Sabic).

Fane said the smelter will export 70 percent of its output and the bauxite mines in the kingdom can cover 30 years of production.

The phosphate plant, due to start production in 2010, will account for 10 percent of global trade in diammonium phosphate, Fane said.

The other 50 percent of Maaden's capital is held by the state-run Public Investment Fund. Maaden estimates its total investments at 60 billion riyals, including phosphate, bauxite, gold and industrial minerals. The investments are part of government plans to diversify an economy that heavily depends on oil. - Reuters