July 31 (Reuters) - Canada's main stock index was flat on Tuesday as gains in the materials sector countered losses in the energy sector following a drop in oil prices.
* At 9:38 a.m. ET (1338 GMT), the Toronto Stock Exchange's S&P/TSX Composite index .GSPTSE was up 7.2 points, or 0.04 percent, at 16,352.67.
* Six of the index's 11 major sectors were lower, with energy .SPTTEN down 0.3 percent. Oil prices fell after a survey showed OPEC's output hit a 2018 high in July, reigniting concerns about supply swamping demand. U.S. crude CLc1 prices were down 1.6 percent a barrel, while Brent crude LCOc1 lost 0.9 percent. O/R
* The materials sector .GSPTTMT , which includes precious and base metals miners, added 0.7 percent, boosted by shares of First Quantum Minerals FM.TO , which jumped 3.5 percent after posting quarterly results. Financials .SPTTFS slipped 0.2 percent.
* The Unites States and China are trying to restart talks aimed at averting a full-blown trade war between the world's two largest economies, according to a report. Canada's economy grew by 0.5 percent in May, the biggest rise in a year, as industries recovered from a combination of bad weather and maintenance shutdowns in April, according to Statistics Canada data. Producer prices grew by 0.5 percent in June from May on higher prices for primary non-ferrous metal products, as well as motorized and recreational vehicles. The Canadian dollar dipped against the greenback as trade uncertainty and lower oil prices offset robust data. On the TSX, 121 issues were higher, while 116 issues declined for a 1.04-to-1 ratio favouring gainers, with 10.75 million shares traded.
* The top percentage gainer on the TSX was First Quantum Minerals followed by shares of Lundin Mining LUN.TO , which rose 2.4 percent after a rating upgrade.
* WestJet Airline WJA.TO fell 10.5 percent, the top laggard on the TSX, followed by shares of Shopify Inc SHOP.TO , down 4.4 percent after results. The most heavily traded shares by volume were Cequence Energy CQE.TO and Nemaska Lithium NMX.TO .
* The TSX posted one new 52-week highs and four new lows.
* Across all Canadian issues, there were seven new 52-week highs and eight new lows, with total volume of 19.33 million shares.