* The most heavily traded shares by volume were Bombardier B , Well Health Technologies , and Nevada Copper . Adds details and updates prices Aug 12 (Reuters) - Canada's main stock index retreated from a record high on Thursday, as major gold miners weighed the most while energy shares were pulled down by concerns over slow demand recovery in the global crude market. * The materials sector .GSPTTMT, which includes precious and base metals miners and fertilizer companies, lost 1.1% as gold prices retreated from recent gains made on signs of slowing U.S. consumer inflation.