Diversified miner Rio Tinto and Chile’s State-owned Empresa Nacional de Minería, or Enami, have signed a binding agreement to form a joint venture (JV) for the development of the Salares Altoandinos lithium project in Chile’s Atacama region, the companies said in a statement.

The deal cements Rio Tinto’s position as the controlling partner in the project, with the Anglo-Australian miner set to acquire a 51% interest. The agreement follows Rio’s nomination as preferred partner on May 23.

As part of the transaction, Rio Tinto will contribute up to $425-million in cash and non-cash resources, including its proprietary direct lithium extraction (DLE) technology. The funding will be staged, beginning with sole funding of a prefeasibility study and further technical work, subject to progress through JV investment milestones.

The companies expect the transaction to close in the first half of 2026, pending regulatory approvals and other customary conditions.

“We are continuing to execute our strategy of building a world-class lithium portfolio to position Rio Tinto as a global leader in the responsible supply of critical minerals essential to the energy transition,” said Rio Tinto Minerals CE Sinead Kaufmann.

“The Salares Altoandinos project represents a significant opportunity to develop a large-scale, long-life, low-cost lithium brine resource.

"We are committed to the highest environmental standards and to ensuring any potential development is guided by transparent, respectful, and ongoing engagement with local communities in Chile’s Atacama region," said Kaufmann.

The agreement marks another step in Rio Tinto’s efforts to expand in lithium. In March, Rio Tinto completed its $6.7-billion acquisition of Arcadium Lithium, giving it access to the company's vertically integrated global lithium operations, including decades of commercial DLE experience, a capability few other major producers possess at scale.

At its Rincon project in Argentina, acquired in 2022 for $825-million, Rio built a pilot‑scale DLE plant of 3 000  t/y, with commissioning completed by late 2024. The company approved a $2.5-billion investment to boost capacity to 60 000 t/y by 2028.

In Chile, Rio also secured a near‑$900-million investment to take a 49.99% stake in partnership with State miner Codelco. The project will deploy DLE at scale.