Mr Mackenzie has 30 years' experience working in oil and gas, petrochemicals and minerals, and had previously held senior positions at BP and Rio Tinto before joining BHP in 2008.

BBC: Marius Kloppers

Investors seemed less concerned by the risks of digging up minerals, more by potential political obstacles in the wake of the Canadian government's intervention to block BHP Billiton's hostile takeover of Potash Corporation.

ECONOMIST: Boom time for miners in a resource-hungry region