BHP Billiton said Wednesday its boss Marius Kloppers will leave in May, weeks after the head of rival miner Rio Tinto resigned, with profits hit by weak commodity prices and cool Chinese demand. After nearly six years at the helm, South African Kloppers will be replaced by Andrew Mackenzie, the chief executive of non-ferrous business at the world\'s biggest miner. The departure of Kloppers, who led the firm through the global financial crisis, came on the same day BHP reported that first half net profit plunged 58 percent to US$4.2 billion. Chairman Jac Nasser gave credit to Kloppers for BHP outperforming rivals. Demands for change surfaced in November as Kloppers failed to finalise big deals -- including a bid for Rio Tinto -- while he lost his bonus over hefty US shale gas and oil purchases. However, the succession process had been expected to take a year or two. Scotland-born Mackenzie, 56, who has spent 30 years working in oil, gas, petrochemicals and minerals, joined BHP Billiton in November 2008. His appointment was \"very aggressive from a timing point-of-view,\" said IG Markets strategist Evan Lucas. \"We knew it was coming, but this shows BHP is looking to get on to the front foot with a division it has been keen to invest in over the last few years -- petroleum,\" he said. The departure of Kloppers comes after Rio chief executive Tom Albanese quit in January owing to $14.4 billion in impairment charges, while last Thursday it logged its first annual loss in 18 years. And in October Anglo American\'s US-born CEO Cynthia Carroll said she would step down owing to a weak performance as well as slumping platinum output on strike action in South Africa, which resulted in dozens of deaths. Anglo American on Friday posted an annual net loss of $1.49 billion -- its first in a decade -- after taking a $4.6 billion hit on the value of an iron-ore project in Brazil and platinum assets. A fall in commodity prices has hit the industry hard, with key market China in 2012 seeing its worst year of economic growth since 1999, although recent figures point to a strong pick-up this year. But Fat Prophets resource analyst David Lennox said after a run of poor results, sentiment had changed and mining appeared to have started 2013 on a firmer base. He pointed out that companies had reported a weakening of commodity prices but said they would likely take \"action to minimise their cost base and action to maximise the returns they are getting on their existing assets\". He added: \"You would have to suggest that probably we have seen the bottom of the worst of it but there will be another negative cycle at some point in the future.\" Despite the fall in commodity prices, BHP underlined it had fared better than others. Wednesday\'s results show underlying earnings of $9.8 billion for the July-December 2012 period, ahead of a consensus of $9.5 billion. Excluding one-off writedowns, earnings dropped 43 percent to $5.7 billion, in line with analyst forecasts. Revenues fell 14 percent to $32 billion, BHP said in a statement, declaring an interim dividend of 57 cents a share, up four percent from a year ago. BHP described the results as \"solid\" in a challenging half-year for the global resources industry but remained guarded about the future. \"Substantially lower commodity prices and resilient producer currencies, such as the Australian dollar and the Chilean peso, weighed on margins and profitability,\" it said. \"Measured economic stimulus has helped stabilise China\'s economy,\" the statement said. \"In the short term, we expect a general improvement in the global economy to support demand and prices for a number of commodities. However, the addition of low cost supply in many markets is expected to dampen the pricing upside.\" BHP Billiton shares fell 0.90 percent to $38.65.