CANADA STOCKS-Argentine default, Valeant outlook fuel TSX selloff

* TSX down 194.09 points, 1.25 percent, at 15,330.73 * Nine of the 10 main index sectors decline * Valeant tumbles 7 percent after cutting outlook By John Tilak TORONTO, July 31 (Reuters) - Canada's main stock index tumbled on Thursday after a default by Argentina stoked worries about other emerging-market economies, while shares of Valeant Pharmaceuticals International dropped sharply after the drugmaker cut its outlook. Also unsettling the market, geopolitical tensions rem