Beebyn-W11 has estimated resources of 20.5Mt at a grade of 61.3% iron.
Securing control of all mining, hauling, logistics and port operations boosts Fenix's portfolio of Mid West iron ore projects, which includes the Iron Ridge and Shine iron ore mines.
Under the terms of the transaction Fenix will give Sinosteel an initial upfront payment of $5 million and then another $5 million once mining approvals were achieved.
A fixed $2 per tonne base royalty payment will also apply as well as a variable profit share royalty.
That will be based on actual revenue received for Beebyn-W11 shipments.
Fenix chairman John Welborn said he was delighted to be expanding such a mutually successful partnership with a right-to-mine agreement.
"From the inception of Fenix's production from Iron Ridge, Sinosteel have been a valued partner both as an off-taker and a provider of infrastructure," he said.
"Our unique road, rail and port infrastructure and capabilities provide an advantage which enables the efficient monetisation of high-quality regional deposits which for too long have been stranded."
Welborn said Fenix's Mid West operations had significant scale potential.