* TSX down 136.45 points at 12,598.96
* Nine of 10 main sectors lower
* Materials, energy groups lead retreat (Adds details, quote)
TORONTO, Nov 16 (Reuters) - Toronto's main stock index tumbled on Tuesday morning as global economic fears boosted the U.S. dollar, weighing on commodity prices and the index's hefty resource sectors.
A strong U.S. dollar, bolstered in part by concerns about sovereign debt problems in Europe, helped drag oil prices down more than $1 to below $84 a barrel as investors cut their exposure to commodities. [O/R]
Canadian Natural Resources (CNQ.TO) slid 2 percent to C$38.78, while Suncor Energy (SU.TO) gave back 1.9 percent to C$33.77. TransCanada Corp (TRP.TO) sank 3.4 percent to C$35.72.
The three big energy companies were the most influential movers on the downside. The broader energy group was down 1.7 percent.
Apart from euro zone debt concerns, investor sentiment was also bruised by worries over fiscal tightening by China. [ID:nL3E6MG081] [MKTS/GLOB]
As well, in U.S. economic data, core producer prices unexpectedly fell in October in their largest decline in more than four years, underscoring the U.S. Federal Reserve's concerns about the low inflation environment. [ID:nN16103144]
"We've had weakness in the commodity sector globally in terms of the resource patch," said Andrew Pyle, a portfolio manager at ScotiaMcLeod.
"We had some weak producer price numbers out of the States this morning and that has kind of put a somber note on that sector." [ID:nLDE6AF1QZ]
At 10:56 a.m. (1556 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 136.45 points, or 1.07 percent, at 12,598.96. Nine of the index's 10 main groups were lower.
"It's pretty broad based at this point. Most sectors are being hit -- obviously resources are being weighed upon ... it's really more general macro news that's moving the markets," said Pyle.
The telecoms sector eked out a 0.04 percent gain.
The materials group, home to mining companies, was down 1.9 percent. Cameco Corp (CCO.TO), slumped 5.4 percent to C$33.99, while Teck Resources TCKb.TO was off 2.8 percent at C$47.98. NovaGold Resources Inc (NG.TO) tumbled 5 percent to C$13.56.
Copper prices skidded on China tightening fears, while gold hit a two-week low, partly on the stronger greenback. [MET/L] [GOL/]
In company news, Nexen Inc NXY.TO sank 4 percent to C$21.48. The oil firm said on Tuesday it expects capital spending of C$2.4 billion to C$2.7 billion next year and said it was pressing forward with plans to restart an exploration program in the Gulf of Mexico. [ID:nSGE6AF05F]
Shares of fertilizer giant Potash (POT.TO) were down 0.7 percent at C$137.58. Russia's Phosagro expressed interest in the company after BHP Billiton (BHP.AX) withdrew its $39 billion takeover offer. [ID:nLDE6AF0WJ]
($1=$1.01 Canadian) (Reporting by Solarina Ho and Jennifer Kwan; editing by Rob Wilson)