Dec.16 (Bloomberg) -- (Corrects story published on Dec. 14 to say Marubeni will own 30 percent of the mine in second paragraph.)

Antofagasta Plc's (ANTO) board approved the $1.3 billion Antucoya copper project in Chile, which it says may boost the company's total output of the metal to 800,000 metric tons by 2015.

Japan's Marubeni Corp. (8002) will become a 30 percent owner in the project for $350 million, London-based Antofagasta said today in a statement to the London Stock Exchange. Marubeni is a shareholder in Antofagasta's Los Pelambres, Esperanza and El Tesoro mines in Chile.

Antofagasta is "confident" about long-term copper demand, Marcelo Awad, chief executive officer of Antofagasta's mining division, said in the statement. The company, which operates four copper mines in Chile, has a "strong pipeline" of projects to supply growing consumption of the metal, he said.

Antucoya will produce 80,000 tons a year of refined copper by dissolving the ore in acid, using a process known as heap- leach, the company said. Antucoya is 45 kilometers (28 miles) from the company's Michilla copper mine in the Atacama Desert.

Copper fell 2.4 percent to $3.3595 a pound at 8:26 a.m. in New York. Prices have dropped 24 percent this year because of concerns economies will slow, curbing demand.

Antofagasta expects its total output this year to reach about 640,000 tons, Francisco Veloso, vice president of corporate affairs, said Dec. 6.