The offtake agreement, announced earlier this week, will see Golden West supply Valin with up to 4.5 million tonnes of direct shipping ore annually over 15 years, largely from its Wiluna West project.
The $26.64 million share placement will give Valin an 11.4% stake in Golden West's issued capital through the issue of 14.4 million shares at $1.85.
In a letter to Golden West shareholders, Portman said it was "surprised" Golden West had entered into an off-take agreement at such an early stage of its Wiluna West project.
"Wiluna West is still an exploration asset without a detailed feasibility study and without any access to existing infrastructure that would allow any ore to get to market," Portman said.
"Portman is also surprised that Golden West has summarised a pricing schedule which is purported to apply before the commencement of operations at Oakajee Port, as it has not outlined an alternative rail and port system from which it would propose to ship ore from Wiluna West before Oakajee becomes operational."
Portman also said that if Golden West's plans to issue 5 million shares to purchase the Joyners Find tenements and up to 50 million shares and options by way of a placement were approved, then shareholders interests in Golden West could be diluted by up to 39%.
Golden West will hold a shareholding meeting on August 29, where Portman - which holds a 19.9% stake in Golden West - will look to remove executive chairman Con Markopoulos and director Michael Wilson, replacing them with Richard Mehan as a non-executive director and Paul Piercy as an independent, non-executive chairman.
Portman has previously denied it is trying to gain control of the company or that it will launch a takeover bid for Golden West, saying the reason for nominating Mehan and Piercy is to boost the iron ore experience on Golden West's board.
Yesterday, Golden West appointed former chief operating officer for Rio Tinto iron ore, David Rose, as its new chief executive officer.
Shares in Portman have slipped 2c to $18, while Golden West remains unchanged at $1.65.
