* TSX down 73.31 pts, or 0.6 pct, to 12,406.39 * Index touches lowest in nearly 2 weeks * Miners, energy plays hurt by China growth fears * Viterra falls after deal details revealed * Potash Corp helps limit losses By Jon Cook TORONTO, March 20 (Reuters) - Toronto's main stock index was lower on Tuesday, with mining and energy issues hurt by fears about a slowdown in demand from top resources consumer China. Not even one of the year's largest takeover deals helped offset losses. Viterra's share price fell 0.2 percent to C$15.94 after Glencore said it's buying Viterra in a cash deal valuing the company at C$6.1 billion ($6.2 billion). Some Viterra investors had hoped the takeover of Canada's leading grain handler would spark multiple bids. Copper and other industrial metals prices slumped after BHP Billiton, the world's biggest miner, raised concerns about the possibility of a sharp slowdown in iron ore demand from powerhouse China. Earlier this month China cut its 2012 growth target to an eight-year low of 7.5 percent. "No one wants to hear that things are slowing," said Barry Schwartz, vice president and portfolio manager at Baskin Financial Services. "China lowering its growth GDP from the top end to the low end, one could expect to see a lower output of steel and lower inputs of iron ore." Canadian base metals mining shares fell 1.7 percent, led lower by major copper miner Teck Resources, which fell 2.2 percent to C$35.79. Inmet Mining dropped 2.8 percent to C$56.94. Gold miners were also hit, with Barrick Gold down 1 percent to C$42.66 and Goldcorp sliding 1.2 percent to C$42.84. At 11:35 a.m. (1535 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 73.31 points, or 0.6 percent, to 12,406.39, after hitting a two-week low at 12,336.89. All of the TSX's top 10 main sectors were down, led by energy shares which dropped 1.3 percent. Brent crude fell more than $2 a barrel on Tuesday after reports Iran would not close the strategically important Strait of Hormuz shipping lane. Top oil and gas producer Suncor Energy's shares fell 1.6 percent to C$32.92, while Canadian Natural Resources dropped 1.6 percent to C$34.92. Commodity prices weren't helped by mixed U.S. housing data on Tuesday, as starts fell in February, but permits for future construction jumped to their highest level since October 2008. A surge in Potash Corp's shares, up nearly 4 percent to C$46.41, helped limit losses. The world's top fertilizer producer was boosted after potash marketing consortium Canpotex said on Tuesday it has signed a contract with Sinofert Holdings to supply the Chinese fertilizer maker with 500,000 tonnes of potash in the second quarter of 2012. Canpotex is jointly owned by Potash, Mosaic Co and Agrium Inc, whose shares rose 2.2 percent to C$87.61.