SHANGHAI, Sept. 22 (SMM) –Shanghai spot copper offers were quoted between premiums of positive RMB 100-250/mt today. Traded prices for standard-quality copper were between RMB 61,100-61,700/mt, and RMB 61,150-61,850/mt for high-quality copper. SHFE copper prices continued to slump by more than 3%, and spot copper supply remained ample, causing cargo-holders to push up premiums. Market transactions rose at first, and then fell. SHFE copper prices plummeted again at the tail of trading in the morning business, losing RMB 61,000/mt, keeping all market participants on the sidelines.