(Adds details, updates prices)
* TSX down 52.04 points, or 0.35 percent, to 14,635.42
* Eight of the TSX's 10 main groups moved lower
TORONTO, Aug 22 (Reuters) - Canada's main stock index fell on Monday as lower oil and metal prices weighed on energy and mining stocks, while Alimentation Couche-Tard Inc jumped after the convenience store operator bought a U.S. chain in an expansion move.
The energy group retreated 1.2 percent, with oil prices falling as China ramped up exports of refined products, U.S. oil producers added rigs for an eighth straight week and prospects emerged for increased exports from Iraq and Nigeria.
Canadian Natural Resources fell 1.5 percent to C$41.15 and Suncor Energy Inc lost 0.7 percent to C$36.28.
The materials group, which includes precious and base metal miners and fertilizer companies, lost 1.2 percent, as gold hit a two-week low and copper fell to its lowest in five weeks.
Barrick Gold Corp fell 1.4 percent to C$26.10 and Goldcorp Inc shed 1.9 percent to C$23.12, while diversified miner Teck Resources Ltd lost 1.7 percent to C$19.97.
At 10:08 a.m. EDT (1408 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 52.04 points, or 0.35 percent, to 14,635.42.
Decliners were outnumbering gainers by around 3-to-1 and eight of the index's 10 main groups were in negative territory, with consumer staples and healthcare sectors boosted by big moves in single stocks.
Couche-Tard jumped rose 6.8 percent to C$66.35 after the convenience store operator said it would buy U.S. chain CST Brands Inc in a roughly $4.4 billion deal.
Couche-Tard also said it would sell some Canadian CST assets to Parkland Fuel Corp, whose shares rose 12.1 percent to C$28.30.
Valeant Pharmaceuticals International Inc advanced 6.1 percent to C$39.21 after naming a new chief financial officer.
The financials group slipped 0.5 percent, just ahead of the start of earnings season for the country's biggest banks.
Industrials fell 0.4 percent, while technology stocks lost 0.5 percent.
Canadian wholesale trade increased by 0.7 percent in June from May, the third consecutive monthly gain, Statistics Canada said.
Declining issues outnumbered advancing ones on the TSX by 179 to 57, for a 3.14-to-1 ratio on the downside.
The index was posting 4 new 52-week highs and 2 new lows. (Reporting by Alastair Sharp; Editing by Bernadette Baum)