* LME/ShFE arb: http://tmsnrt.rs/2oQ5nm2
* Chinese zinc imports rise 21 pct in April, copper down 41 pct (Adds quotes, updates prices, changes dateline from MELBOURNE)
LONDON, May 23 (Reuters) - Zinc prices gained on Tuesday after imports of the metal into top consumer China rose, underlining a tightening supply situation, but copper dipped on indications of healthy supply.
Imports of refined zinc to China increased 21 percent in April to 47,469 tonnes year-on-year while shipments of ore and concentrates jumped 44 percent, customs data showed.
Some investors have been counting on shortages to emerge after a series of mine closures and suspensions last year, but evidence of tightness has been slow to emerge.
"Those import numbers showing that China's importing more in April could be evidence showing things are tightening up in China, which is the biggest consumer," said Robin Bhar, head of metals research at Societe Generale.
Copper imports in China, however, fell 41 percent, partly due to tighter credit.
"That reflects that the import arb (arbitrage) was essentially closed in the first quarter and has only fleetingly been opened from time to time," Bhar added.
* ZINC: London Metal Exchange benchmark zinc had climbed 0.9 percent to $2,657 a tonne by 1105 GMT, adding to gains in the previous session when it touched the highest since May 2 at $2,667. Shanghai Futures Exchange zinc added 1 percent to 22,370 yuan a tonne.
* COPPER: LME three-month copper slipped 0.3 percent to $5,687.
* COPPER SURPLUS: The global world refined copper market showed a 93,000 tonnes surplus in February, compared with a 55,000 tonnes surplus in January, the International Copper Study Group (ICSG) said in its latest monthly bulletin.
* LEAD - LME lead added 0.7 percent to $2,105.50.
* LEAD STOCKS: On-warrant LME lead stocks, those not earmarked for delivery, jumped by a quarter and nearby tightness in lead spreads dissolved. The cash over the three-month contract flipped to a $23.25 discount, the widest since July 2014, after having been at a $34.50 premium in late April. <CMPB0-3>
* NICKEL SOFTENS: LME nickel retreated 0.7 percent to $9,330 a tonne following hefty overnight gains.
(Editing by Ed Osmond)