The sub-index marked its lowest since Oct. 4 with sector-major BHP Group BHP.AX losing 0.8%. By Roushni Nair Oct 13 (Reuters) - Australian shares closed slightly lower on Thursday as weakness in energy and mining stocks outweighed gains in financials, with the focus shifting to U.S. inflation data due later in the day to gauge the extent of monetary tightening in the United States. Domestic energy stocks .AXEJ lost 0.9% as oil prices dropped on weakening global demand outlook.