* TSX off 47.61 points, or 0.38 pct, at 12,527.18 * 9 of 10 main sectors weaker * Centerra skids 19 pct after mine forecast slashed By Jennifer Kwan TORONTO, March 27 (Reuters) - Toronto's main stock index sank on Tuesday morning, led lower by energy and materials shares on weaker commodity prices after having climbed to a three-week peak on hopes that the Federal Reserve would take further action to stimulate the U.S. economy. The key sectors on the downside were the hefty energy group, down 0.8 percent, and materials, lower by 0.7 percent as the price of oil, gold and base metals retreated. Big names on the downside included Centerra, which plummeted 19 percent to C$13.05 as the Canadian miner slashed its forecast for 2012 production at its flagship mine in Kyrgyzstan by about a third due to ice movement in the pit, a decline sure to weigh on the fragile economy of the Central Asian state. Also lower was Cenvous, down 1 percent at C$36.20, and Suncor Energy, which dropped 1.2 percent at C$32.74 as the price of oil fell. First Quantum sank 1.8 percent to C$18.85. Marcus Xu, director of equity investments at Genus Capital Management in Vancouver, said it's no surprise to see the market give back a bit after its recent run-up. "If you have a negative view on the market going forward profit-taking might kick in," he said. At around 11:15 a.m. (1515 GMT), the Toronto Stock Exchange's S&P/TSX composite index was off 47.61 points, or 0.38 percent, at 12,527.18. It had climbed to a high of 12,603.71 shortly after the open, its strongest level since Mar. 5, on lingering effects of comments by U.S. Fed chairman Ben Bernanke. Bernanke said on Monday the U.S. economy needs to grow more quickly to get unemployment down, leading investors to take on more risk on hopes the central bank could conduct another round of quantitative easing. Elsewhere in company news, Canadian Pacific Railway, down 0.5 percent at C$78.49, was in the spotlight as an investor day meeting is being held in Toronto at which CP will lay out more details of a multi-year plan to improve its performance and the company's defense in a proxy battle with U.S. activist shareholder William Ackman. Enbridge Inc, up 0.3 percent at C$38.36, said it and Enterprise Products Partners LP will more than double the capacity of the Seaway Pipeline and expand another line from Illinois, further easing a major oil glut in the United States.