Losses in LME copper triggered a steep sell-off in other metals, with the most-traded August copper contract on the Shanghai Futures Exchange hitting limit down of 4 percent at 50,530 yuan ($8,200) a tonne on Thursday The most active aluminium and zinc contracts on the Shanghai Futures Exchange fell to their lowest in more than four years, lead hit another contract trough and LME nickel tumbled to the weakest since July 2009.