(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. * At 9:43 a.m. ET (13:43 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 99.22 points, or 0.48%, at 20,454.79. * The materials sector, 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. * The energy sector dipped 0.2% as oil prices were dented by a warning from the International Energy Agency that the Delta variant of the coronavirus could hurt fuel demand. * The financials sector slipped 0.4%. The industrials sector fell 0.2%. * On the TSX, 79 issues were higher, while 146 issues declined for a 1.85-to-1 ratio to the downside, with 12.94 million shares traded. * The largest percentage gainer on the TSX was Ats Automation Tooling Systems, which jumped 5.7% to extend gains into a second session after the company posted bumper quarterly results. * Northland Power fell 7.5%, the most on the TSX, after its revenue missed estimates. The second-biggest decliner was Endeavour Silver, down 5.8%, tracking weakness in precious metals. * The most heavily traded shares by volume were Bombardier B , Well Health Technologies, and Nevada Copper . * The TSX posted 18 new 52-week highs and three new lows. * Across all Canadian issues, there were 72 new 52-week highs and 9 new lows, with total volume of 28.48 million shares. (Reporting by Ambar Warrick, Editing by Sherry Jacob-Phillips)