TORONTO, Sept 19 (Reuters) - Canada's main stock index opened lower on Friday, hurt by moderate declines across a broad selection of sectors led by heavyweight resource and financial stocks. The Toronto Stock Exchange's S&P/TSX composite index was down 36.90 points, or 0.24 percent, at 15,428.64 shortly after the open. It is on track for a 0.7 percent decline for the week. (Reporting by Alastair Sharp Editing by W Simon)