Speculation over the power struggle at the top of global banking giant HSBC is likely to dominate early proceedings in London. Reports suggest that current chief executive Mike Geohegan will leave at the end of the year after failing to get the job of executive chairman.City traders suggest the FTSE 100 index will open around 25 points lower, following Wall Street's weak lead yesterday.Dana Petroleum's valiant rearguard action against the takeover bid by the Korea National Oil Corporation (KNOC) has failed. KNOC has declared its £18 a share offer wholly unconditional after almost two-thirds of Dana's shareholders backed the deal. The Koreans went hostile a month ago after Aberdeen-based Dana refused their advances, declaring the company worth far more than the £1.8bn on the table. Mining giant BHP Billiton has received the green light for development of the Macedon gas field in the Exmouth Sub-basin, Western Australia. Project costs will be in the region of US$1.5bn, of which BHP will pay 71.43%, in line with its project stake. Recoverable reserves for the Macedon field are between 400 and 750 billion cubic feet of gas.BHP's rival, Rio Tinto, meanwhile, is to plough US$230m into its operations at the Dampier Port in Western Australia to expand capacity. The expansion will result in an additional 5m tonnes annual capacity (Mt/a), taking total annual capacity for the Pilbara region to 230 Mt/a in the first quarter of 2012.