The move raises Xstrata's holding in Oakbridge to 78%.
Oakbridge operates the Bulga opencut and Baal Bone and South Bulga longwall mines in New South Wales. It is scheduled to begin longwall mining at Beltana - being developed off the highwall at Bulga - in May to replace the depleting South Bulga mine.
London-listed Xstrata said the transaction would not impact its consolidated revenue or EBIT because Oakbridge would continue to be classified as a subsidiary for accounting purposes.
However, attributable profit is expected to increase due to a reduction in the minority share of profit after tax.