Slumping export demand stalled manufacturing in some of Asia's biggest economies, and in the euro zone the sector contracted at its fastest pace in two years last month, data and surveys showed. Benchmark three-month copper on the London Metal Exchange was $7,826 per tonne in official rings, from $7,885 at the close. It hit a four-week high on Wednesday and trade volumes shot up to almost double the 50-day moving average, amplified by short covering. Copper, used widely in manufacturing, particularly in China, bucked a generally positive trend of stock markets, which still basked in the major central banks' move to ease a global liquidity crunch. China's official purchasing managers' index for November fell to 49, dipping below the 50 mark that separates growth from contraction for the first time in nearly three years. The weaker-than-expected China PMI reading came one day after Beijing lowered banks' reserve requirements by 50 basis points to try to ease credit strains. "That move came earlier, and was more substantive than we had anticipated," said Duncan Hobbs, senior commodities and mining analyst at Macquarie. "Our concern was what was it that the Chinese authorities can see that markets as a whole cannot yet see. That was unveiled today with the PMI data, that's the key driver behind today's market retreat." A weaker dollar helped stem further losses. A weak dollar boosts commodities such as base metals priced in the greenback as it makes such assets cheaper for holders of other currencies. Key for the near-term economic outlook will be whether European leaders are able to agree on credible action to tackle the debt crisis at a European Union summit on Dec 9. "Until we get greater clarity, markets will continue to trade in much the way we have seen recently, which is indiscriminately of the individual market fundamentals and taking their cues from economic data and political news flow," Hobbs said. However, fundamentals played some part in copper and tin's losses on Thursday. Workers at Chile's giant Collahuasi mine ended a two-day labour stoppage that disrupted output, the operator and union of the world's No. 3 copper mine said on Wednesday. Tin was the biggest loser among the base metals after breakaway Indonesian smelters shipped metal in contravention of the industry's self-imposed ban on shipments from the world's top exporter. Three-month tin was $20,350 per tonne in official rings, from $20,900 at the close on Wednesday. Smelters in Indonesia's main tin producing region of Bangka island stopped shipments from Oct. 1 in an effort to push benchmark tin prices above $23,000 a tonne. "The ITA's tin export moratorium is now looking increasingly fragile and a normalization of the Indonesian export flow before the year end is becoming more likely," Credit Suisse said in a note. Headline inventories of the metal in LME-monitored warehouses at 12,150 tonnes are the lowest in 13 months and have shrunk by around half since AReuters Three-month lead was $2,085 in rings from $2,110. Inventories of lead in LME-monitored warehouses fell 575 tonnes to 369,250 tonnes as cancelled warrants, or new orders, jumped to nearly 6,000 tonneS into Singapore and 7,000 in Johor.