* TSX ends down 246.13 points, or 1.8 pct, at 13,638.58
* All 10 main sectors lower
* China data, Spain debt downgrade stoke growth concerns (Updates to close, adds details, comments)
By Claire Sibonney
TORONTO, March 10 (Reuters) - Toronto's main stock index retreated for a fourth-straight session on Thursday, chalking up its biggest drop in seven months as it reacted to disappointing economic data from China and a Spanish debt downgrade.
The index's powerhouse energy and materials sectors led the slide, down 2.6 percent and 2.8 percent, respectively, undermined by a sharp early drop in oil and metals prices, although some commodity prices regained ground on reports of unrest in oil-rich Saudi Arabia.
Commodities priced in U.S. dollars such as oil, gold, and copper fell as the greenback rallied on safe-haven buying after Moody's cut Spain's credit rating. Also, figures that showed China ran a trade deficit in February underscored concerns about the robustness of global economic growth. [O/R] [GOL/] [MET/L]
Among the biggest decliners, Suncor Energy (SU.TO), plunged 3.5 percent to C$41.67, fellow oil company Canadian Natural Resources (CNQ.TO) dropped 3 percent to C$44.94, and Barrick Gold Corp (ABX.TO) declined 1.7 percent to C$49.13.
"We're seeing some flight to safety and out of risky assets, so that's putting a lot of pressure on stocks today, said Youssef Zohny, portfolio manager at Van Arbor Asset Management in Vancouver.
"Overall it's mostly macro factors driving the market, all negative."
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE ended down 246.13 points, or 1.8 percent, at 13,638.58. The index was at its lowest point since Feb. 1 and all 10 of its main sectors were lower. The heavyweight financial group fell 1.3 percent.
During the day, the TSX declined more than 2 percent, its biggest fall since August.
Zohny said the index's close below the 50-day moving average of 13,696 signaled the biggest danger to the market's eight-month rally so far.
"The next few weeks will determine if the uptrend has been severely disabled and we're in a larger correction, but that's not necessarily the case yet," he said. "We'll need a couple more weeks to sort what's happening in the Middle East as well as overseas in Asia."
($1=$0.98 Canadian) (Reporting by Claire Sibonney; editing by Peter Galloway)