* Massive, quake-proof copper mines dodge harm following 8.2 quake
* Some concerns closed ports could curb supply
* Copper prices rise to over three-week high
(Adds analyst quotes, context, refineries) SANTIAGO, April 2 (Reuters) - Copper operations in Chile, the world's top producer, were unscathed by a major earthquake that struck the mineral-rich north on Tuesday night and prompted the evacuations of some workers. Several ports that ship metals from the Andean country remained closed on Wednesday following a tsunami evacuation, suggesting some trade flows might be temporarily interrupted.
Copper prices rose to their highest in more than three weeks on Wednesday on concerns that supplies could be affected following the 8.2 magnitude quake. Chile supplies one-third of the world's red metal. But none of the quake-proofed mines in the Andean country reported structural damage following the earthquake, which killed six and triggered the tsunami that pounded the shore.
"I think the impact this time around is close to zero," said Juan Carlos Guajardo, the head of mining think tank CESCO. "Ports are the most exposed, but they didn't suffer either because the tsunami was very small." Any major damage could have been catastrophic for Chile, where copper accounts for over one-half of export revenue and about 15 percent of gross domestic product. Still, power cuts following the quake may have dented output, although most mines can quickly activate back-up generators. "Up until now, the fall in electricity generation in (the Northern SING grid) averages around 350 megawatts," said Pedro Fuenzalida, a mining and energy analyst with LarrainVial in Santiago. "That leads us to estimate that to date roughly 1,000 tonnes in copper output have been lost." (Map showing area of quake: http://link.reuters.com/hyk28v Graphic of Chile copper mines: http://link.reuters.com/gaq87v) The massive Collahuasi mine, a partnership between Glencore Xstrata Plc and Anglo American Plc, located relatively close to the epicenter, evacuated workers, but said the deposit and port were intact and that mining operations should return to normal on Wednesday. Chilean state-run miner Codelco and global miner BHP Billiton said their mines and ports were experiencing no problems with copper shipments. SQM , which has extraction rights to some of the world's biggest reserves of nitrates, iodine and lithium in the north, said they had not suffered damage at their operations, but a few facilities had power cut. ENAP, the state-owned oil company, said it had halted operations and evacuated workers at its Aconcagua and Bio Bio refineries but operations were returning to normal. Chile's fuel supply was unaffected by the quake, the company added. The northern ports of Arica, Patache, Iquique, Mejillones and Tocopilla were closed or only partially operating, according to the Chilean army. China is the world's top consumer of metals and many of the ships on Chile's Pacific coast cross the ocean to Asia. "Any delay, based on the premise that there indeed wasn't major damage to ports, should be overcome within a few days," Fuenzalida, the analyst, added. The CESCO/CRU copper conference that kicks off next week in the capital, Santiago, where the quake was not felt, was set to proceed as normal.
(Additional reporting by Fabian Cambero and Felipe Iturrieta; Editing by Sofina Mirza-Reid and Jeffrey Benkoe)