Sheffield MD Bruce McFadzean says signing is a major milestone toward development of Thunderbird.
The JV is expected to get the Kwinana plant into production next year.
The parties will work on development and financing plans, with Macquarie to lend financial advice.
The JV is subject to approval by the Foreign Investment Review Board, which could pose a challenge.
Tripartite pact forged for Cloncurry exploration.
Hexagon to go it alone at McIntosh as Mineral Resources throws in towel.