BHP Group (ASX:BHP), via a wholly-owned unit, entered into a long-term silver streaming agreement with Wheaton Precious Metals International, a wholly-owned unit of Wheaton Precious Metals, for an upfront payment of $4.3 billion at completion, according to a Tuesday Australian bourse filing.

BHP will deliver silver to Wheaton calculated by reference to its share of silver produced at the Antamina mine in Peru, in which BHP is a shareholder through its 33.75% investment in Compañía Minera Antamina. The agreement is effective April 1.

BHP will deliver the equivalent of 33.75% of the silver produced by Antamina. After 100 million ounces of silver have been delivered to Wheaton, BHP will then deliver the equivalent of 22.5% of the silver produced by Antamina over the remaining life of mine.

Wheaton will also pay BHP 20% of the spot silver price at the time of delivery for each ounce of silver delivered to the former under the deal.