* TSX up 8.75 points, or 0.7 percent at 12,940.21 * Energy and financials led 7 of 10 main groups higher * Materials and industrials dragged lower by gold miners, SNC-Lavalin By Solarina Ho TORONTO, Oct 16 (Reuters) - Canada's main stock index turned higher at midmorning on Wednesday, but gains were capped by weak materials stocks and a sharply lower earnings revision by SNC-Lavalin Group Inc. Most of the TSX tracked U.S. equity markets, which rose on optimism that a fiscal deal that would prevent the country from defaulting on its debt could be wrangled between Washington lawmakers at the eleventh-hour. "The U.S. market is popping up on the upside, so I guess they're optimistic, and it'll eventually drag us up," said Paul Hand, managing director at RBC Capital Markets. The heavily weighted financials and energy group were up 0.3 percent and 0.5 percent respectively. Brent crude oil prices rose above $110 a barrel, while U.S. crude rose to $101.72 per barrel on U.S. budget hopes. Meg Energy Corp rose 4.1 percent to C$35.72, while Encana Corp gained 0.9 percent to trade at C$18.47. The Toronto Stock Exchange's S&P/TSX composite index was up 8.75 points, or 0.7 percent at 12,940.21, at midmorning. Seven of the index's 10 main groups were in positive territory. Tempering advances was a 1 percent drop in materials stock. Gold miners in particular, retreated, with Agnico Eagle Mines Inc off 3.2 percent at C$24.93 and Goldcorp Inc off 1.9 percent at C$24.49. Bullion prices retreated as investors moved away from the safe-haven metal amid prospects of a last-minute U.S. debt deal. Still RBC's Hand said bullion prices have been very volatile of late. "Gold is becoming very hard to prognosticate," said Hand. SNC-Lavalin shares took a 5.2 percent hit to trade at C$41.84 after the Canadian engineering and construction firm said it slashing its fiscal 2013 outlook. The overall industrials group was off 0.4 percent.