* TSX ends up 43.48 points, or 0.3 pct, to 13,789.63
* Three of 10 main sectors end in positive territory (Updates with details, comments)
By Claire Sibonney
TORONTO, March 18 (Reuters) - Toronto's main stock index closed at a one-week high on Friday, as a Group of Seven intervention to weaken the soaring yen and a ceasefire declaration in Libya provided some investor optimism and helped lift mining issues.
The materials sector, up 1.1 percent, led the gainers. Gold and base-metal miners advanced despite a pullback in copper prices. Gold rose more than 1 percent as the United Nations' authorization of a no-fly zone in Libya boosted bullion's status as a safe haven. [GOL/] [MET/L]
Muammar Gaddafi's government said it was declaring a unilateral ceasefire in its offensive to crush Libya's revolt as Western warplanes prepared to enforce the no-fly zone. [ID:nLDE72H00K]
Barrick Gold Corp (ABX.TO) jumped 2.3 percent to C$48.87, and Goldcorp (G.TO) gained 2.1 percent to C$46.76. Ivanhoe Mines surged 4 percent to C$25.84.
Meanwhile, Japan bought billions of U.S. dollars to restrain the yen, as did other Group of Seven central banks, including the Bank of Canada, as the G7 moved to calm markets made nervous by Japan's nuclear crisis. [ID:nL3E7EH3HN]
"The fact that the Japanese market rallied overnight and the fact that the situation there is somewhat under control, plus the ceasefire in Libya, that's all added to some optimism in the markets," said Elvis Picardo, an analyst and strategist at Global Securities in Vancouver.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE closed up 43.48 points, or 0.32 percent, at 13,789.63. Only three of the 10 main sectors finished higher positive, including financials, up 0.1 percent, and industrials, up 0.5 percent.
The TSX pulled back from a broader rally earlier in the day, with energy stocks turning negative in choppy trading as oil prices slipped [O/R]. It reached as high as 13,875.70, its strongest level since March 10.
"There are so many moving parts to the market here, but I think essentially it boils down to a justifiable reluctance to leave long positions over the weekend and that's mainly on the account of concerns about the ongoing nuclear situation in Japan," added Picardo, noting the energy sector has been exceptionally unsteady in recent weeks.
Among financials, insurers outperformed after a recent selloff tied to exposure to Japan.
Manulife Financial (MFC.TO) gained 2.4 percent to C$16.82, while Sun Life Financial (SLF.TO) climbed 0.7 percent to C$30.47.
($1=$0.98 Canadian) (Reporting by Claire Sibonney; editing by Rob Wilson)