* LME copper set to post biggest weekly loss in 2 mths * Zinc biggest weekly loser in Shanghai, London * Zinc surplus set to drag out as mine closures delayed * Coming up: U.S. CFTC commitment of traders data; 1930 GMT (Adds quotes, details; previous SINGAPORE) By Eric Onstad LONDON, Oct 12 (Reuters) - Copper fell on Friday on concern about demand in top metals consumer China ahead of trade and growth data next week as the market geared up for its biggest weekly loss in two months. Three-month copper on the London Metal Exchange shed 0.9 percent to $8,167.25 a tonne by 1020 GMT, reversing small gains in the previous session when prices rebounded after hitting their lowest in two weeks at $8,105 a tonne. Copper has drifted in a range of about $8,100-$8,400 a tonne for the past month as investors refocused on underlying demand amid sluggish global growth after the excitement of central bank stimulus measures that sent prices up around 10 percent. "There's quite a debate out there right now about the extent of the economic slowdown in China and what real impact this is having on metals demand," said Stephen Briggs, metals strategist at BNP Paribas in London. Chinese trade data, due to be released over the weekend, is expected to show copper imports rising in September from the previous month, but this may mostly be due to the arrival of term shipments booked last year, Standard Chartered Bank analyst Judy Zhu said. On Thursday, third quarter GDP data is expected to show China's economic growth slowed for a seventh straight quarter to the weakest level since the depths of the global financial crisis. Lacklustre demand in China, which accounts for about 40 percent of global copper consumption, has pressured prices, which are set to fall for the third week out of the past four, sliding about 1.6 percent on the LME. But Briggs believes copper prices will hold up during the quarter, even though the market is forecast to switch from deficit to surplus next year, due to further central bank stimulus, doubts about potential supply increases and a tight market outside of China where LME stocks are low. "Although I think it (the surplus) is going to happen, the market is going to need some proof of that and in the interim you can justify prices staying above $8,000," Briggs said. "I think there is a decent chance that we could get to $9,000 in November, December, but it's a fine call because there will be some downward pressure next year." On the Shanghai Futures Exchange, the most-traded January copper contract closed flat at 58,980 yuan ($9,400) a tonne and posted a 0.8 percent weekly fall, its biggest since the week of Aug. 5. "Shanghai copper is stifled today by a fall in Chinese equities and a lack of new reasons to cheer. Trading is also directionless ahead of upcoming China data with investors keeping to a range of 58,000-60,000 yuan," said CIFCO Futures analyst Zhou Jie. OVERSUPPLIED ZINC In other metals, zinc was due to be the biggest weekly loser among both LME and Shanghai metals. Shanghai zinc dropped 3 percent and the three-month LME contract was on track to shed 6.5 percent. "Fundamentally the zinc market remains oversupplied, and prospects for mine closures moving the market into deficit have been delayed," said analyst Ric Deverell of Credit Suisse in a note, saying an improvement in demand would be needed to support prices, which look vulnerable. "The outlook for premiums appears much stronger, but this could lead to weaker flat prices, with smelters relying more on premium revenue, as has been the case with aluminium." Minmetals Futures analyst Chen Yuan said: "Many Chinese zinc smelters have been taking up short positions on the futures market to lock in high prices during the recent rally." On Friday, LME zinc fell 1.3 percent to $1,940.75 per tonne. Three month aluminium lost 0.5 percent to $2,003.5 a tonne and nickel shed 1.8 percent to $17,408. Tin gave up 1.1 percent to $21,655 a tonne and lead fell 1.0 percent to $2,160.75. Metal Prices at 1023 GMT Comex copper in cents/lb, LME prices in $/T and SHFE prices in yuan/T Metal Last Change Pct Move End 2011 Ytd Pct move COMEX Cu 372.50 -2.70 -0.72 344.75 8.05 LME Alum 2002.25 -6.75 -0.34 2020.00 -0.88 LME Cu 8166.00 -73.50 -0.89 7600.00 7.45 LME Lead 2160.25 -22.75 -1.04 2034.00 6.21 LME Nickel 17407.00 -318.00 -1.79 18650.00 -6.66 LME Tin 21630.00 -270.00 -1.23 19200.00 12.66 LME Zinc 1941.50 -25.50 -1.30 1845.00 5.23 SHFE Alu 15460.00 -30.00 -0.19 15845.00 -2.43 SHFE Cu* 58960.00 -30.00 -0.05 55360.00 6.50 SHFE Zin 15210.00 -60.00 -0.39 14795.00 2.81 ** Benchmark month for COMEX copper * 3rd contract month for SHFE AL, CU and ZN SHFE ZN began trading on 26/3/07

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