(Adds portfolio manager comment, details; updates prices to close)
* TSX ends down 315.94 points, or 2.37 percent, at 13,042.83
* Ten declining stocks for every rising issue
By Alastair Sharp
TORONTO, Dec 7 (Reuters) - Canada's main stock index took its biggest one-day loss in 10 weeks on Monday, pummeled by slumping energy stocks as oil prices fell to their lowest in almost seven years following OPEC's decision to keep crude production high.
Oil ministers from the Organization of the Petroleum Exporting Countries dropped any reference to the group's output ceiling for the first time in decades on Friday, highlighting disagreement among members about how to accommodate Iranian barrels once Western sanctions are lifted.
"Everybody was hoping against hope on Friday that OPEC would come to its senses and manage their business a little bit better than they have been," said John Kinsey, portfolio manager at Caldwell Securities Ltd.
Brent and U.S. crude settled at or near February 2009 lows, and Canada's heavyweight oil and gas sector tumbled 5.9 percent.
Canadian Natural Resources fell 6.2 percent to C$28.80 and Suncor Energy Inc declined 3.5 percent to C$34.77.
The slump appeared contagious, with financials off 1.8 percent and materials stocks losing 3.3 percent as gold and copper prices also pulled back.
"The banks, I guess because of the loans they have to the oil companies, are all down quite a bit," Kinsey said. "The minerals, not to be left out, are having sympathy pains and they're all down too."
The Toronto Stock Exchange's S&P/TSX composite index closed down 315.94 points, or 2.37 percent, at 13,042.83. That was its sharpest one-day loss since Sept. 28.
At one point it touched 13,018.70, its lowest since Sept. 29.
Declining issues outnumbered advancers by almost 10 to 1, with 47 stocks hitting fresh 52-week lows.
Diversified miner Teck Resources Ltd declined 9.4 percent to C$4.99, while gold futures fell 1.2 percent to $1,071 an ounce and copper prices declined 1.2 percent to $4,557.15 a tonne.
Air Canada, which stands to benefit from lower fuel costs, rose 2.6 percent to C$10.59, and smaller rival WestJet Airlines Ltd advanced 0.9 percent to C$20.51.
HudBay Minerals Inc stock fell 11.4 percent to C$5.43 after its chief executive was named to replace Goldcorp Inc's CEO after he retires next year. Goldcorp stock slipped 3.2 percent to C$16.49.
U.S. crude prices settled down 5.8 percent at $37.65 a barrel, while Brent crude lost 5.3 percent to $40.74. (Editing by Meredith Mazzilli and James Dalgleish)