* TSX down 3 percent on day, 5.6 percent for week
* Energy sector sags as crude slides to $57.04
* RIM, Nortel help drag technology sector down
* Canwest drops 8.8 percent after quarterly results (Adds official closing numbers, details)
TORONTO, Nov 14 (Reuters) - The Toronto Stock Exchange's main index retreated broadly on Friday, led lower by weakness in energy and materials issues as gloomy U.S. retail sales data heightened worries about a deeper economic downturn.
Heavily weighted stocks that helped push the key index lower included EnCana Corp (ECA.TO) and Research in Motion RIM.TO.
The energy sector was a major source of weakness for the market, down 3.2 percent as the price of oil dropped to $57.04 a barrel on expectations of further weakness in demand as the euro zone slipped into a recession and on gloomy U.S. economic data. [ID:nSP399460] EnCana fell 5.8 percent to C$54.75.
The materials group was off 5.9 percent, helped lower by Agrium Inc (AGU.TO), which retreated 7.4 percent at C$40.49.
Potash Corp of Saskatchewan (POT.TO) was down 4.2 percent at C$86.12. Potash saw union workers ratify a new three-year contract this week at three of the company's Saskatchewan mines. [ID:nN14442189]
"Consumer confidence is still on the weak side in the U.S. Retail sales are also weaker than expected. Not any good reasons to be overly enthusiastic," said Francis Campeau, broker at MF Global Canada, in Montreal.
"The picture going forward still looks a bit bleak."
The S&P/TSX composite index .GSPTSE closed down 296.82 points, or 3.17 percent, at 9,055.96, with all but two of its 10 main groups in the red. Consumer staples rose 0.08 percent, while utilities were up 0.3 percent.
The index was down 5.6 for the week, it's weakest showing since Oct. 10.
The index sank lower as U.S. retailers suffered a record decline in October. While a separate report showed consumer sentiment improved in November, consumers were still on the defensive. [ID:nN14423234]
Investors were also locking in some profits following a 4.8 percent rise on Thursday, added Campeau.
The information technology group sank 6.7 percent as RIM fell 7.9 percent to C$49.37 and Nortel Networks NT.TO dropped 17.8 percent at 74 Canadian cents.
Canwest Global Communications CGS.TO, Canada's biggest media company, posted a steep quarterly loss on TV writedowns. [ID:nN14417750] Canwest sank 8.8 percent to 73 Canadian cents. ($1=$1.23 Canadian) (Reporting by Jennifer Kwan)