BASE metals on the London Metal Exchange (LME) have closed mostly lower, but kept in recent ranges amid quiet trade. Although LME three-month aluminium on Monday closed 0.9 per cent higher at $US1,817 a metric ton, the LME's flagship metal copper fell alongside most others in the LME complex. LME three-month copper closed 0.4 per cent down from Friday's settlement at $US7,245 a ton, while LME three-month nickel fell 0.6 per cent to close at $US13,950 a ton. Fresh jitters regarding when the US may start to withdraw its commodity-supportive bond-buying program weighed on demand expectations and dented prices. Copper prices slumped on Friday as a pair of Federal Reserve officials indicated that the central bank may reduce the pace of its bond purchases in the near future. The comments spooked investors just two days after the bank's policymaking committee decided to stick to its $US85-billion-a-month bond-buying program. The Fed's stimulus efforts have buoyed expectations for growth and for metal demand, as the metals are used in several industrial applications. Traders also say the cash the stimulus injected into the financial system has also lifted investor demand for alternative assets, such as commodities. LME Metals were also feeling the weight of a weaker euro against the US dollar, which dampens the appeal of US dollar-denominated assets to buyers holding Europe's common currency. The losses came despite upbeat economic data from China, the world's top industrial metal consumer, accounting for about 40 per cent of global copper demand. HSBC's preliminary gauge of China's manufacturing sector showed activity strengthened in September, reaching a six-month high. This lent prices some support as an indicator of robust demand, but other figures were mixed and overall the data failed to lift base metal prices. "Metal prices continue to show themselves immune to good economic data," said Commerzbank. Both new orders and export orders have improved, which points to better economic dynamism and thus also to higher demand for metals. Even so, imports of refined and raw copper into China in August had risen from a year ago, but fell considerably from July's reading.