The offer is not associated with Chinese regulatory approvals or funding conditions.
Baosteel Resources International chairman Zhihao Dai said: "Our compelling Offer provides Aquila shareholders with an opportunity to realise certain value for their Aquila shares at a significant premium to the Aquila share price prior to the announcement of the Offer."
"At the same time, Baosteel believes the transaction, if successful, provides a genuine opportunity for the development of greenfield resources for the benefit of both Australia and China."
Aurizon managing director and CEO Lance Hockridge said: "The Offer is the first step in a potential pathway to co-investment in resources and greenfield infrastructure, representing a great opportunity to co-develop world-class rail and port infrastructure in Australia, and in the process generate new jobs, boost national exports and deliver to government significant royalty revenue."
In May, Baosteel and Aurizon have made an A$1.4bn ($1.3bn) joint offer for Aquila Resources.
On completion of the deal, Baosteel Resources International will have 85% stake in Aquila and Aurizon will hold the remaining stake.
