Sept 12 (Reuters) - Australian shares fell on Tuesday, dragged by declines in heavyweight financials stocks, while cautious investors awaited a key U.S. inflation data later in the week for cues on the U.S. Federal Reserve's rate hike trajectory. MET/LIRONORE/ The gold sub-index increased 0.5%, with sector heavyweights St Barbara SBM.AX and Northern Star Resources NST.AX climbing 1.4% and 0.8%, respectively. In corporate news, Santos STO.AXconducted a debt offering and successfuly priced a $850 million senior unsecured fixed rate bond.