Shares in Australia's Padbury Mining Ltd plunged as trading in the stock resumed after its plans for a deal to build a $6.5 billion iron ore port and rail network collapsed within a month of being announced. Padbury, a small explorer, surprised markets on April 11 when it said it had lined up more than $6 billion in funding from unnamed investors to build an iron ore port and rail line in Western Australia, a project that had been stuck on the drawing board for two decades. Padbury's announcement triggered a spike in its shares and the Australian Securities Exchange slammed a halt on trading until the company provided more details on the deal.