Completion of the transaction, expected by mid-year, will see Japan’s Sumitomo move to 28% ownership, with Freeport retaining the balance. The latter is selling assets to reduce its heavy debt load. Analysts said the sale implied a total value for the mine of US$7.7 billion. One said: “To us [that] appears a very, very generous price”.

“It equates to US$77,000/t of annual capacity or almost four-times what Antofagasta paid for its 50% stake in Zaldivar, a transaction that was itself considered punchy.”

For its part Freeport expects to book about a $550 million gain on the deal.