TORONTO, March 26 (Reuters) - Canada's main stock index fell on Wednesday, led by a sharp selloff in gold mining shares and broad declines in most other sectors, after comments from President Barack Obama revived worries about the crisis in Ukraine. The Toronto Stock Exchange's S&P/TSX composite index unofficially closed down 115.39 points, or 0.81 percent, at 14,184.10. Seven of the 10 main sectors on the index were in the red. (Reporting by John Tilak; Editing by Leslie Adler)