Antofagasta first quarter copper output down 10.5 pct

LONDON, April 25 (Reuters) - Chilean-focused Antofagasta said first quarter copper production fell by 10.5 percent to 153,800 tonnes compared with the same quarter a year ago, mainly because of lower quality ore, but kept full-year output guidance unchanged.

The issue of ore quality in mature copper regions, especially Chile, the largest copper producing country, has been widely flagged.

It means more rock has to be processed to get the same amount of copper and adds to production costs for a mineral perceived to be in high demand as the world shifts to greater electrification.

Antofagasta CEO Ivan Arriagada said in a statement the company had expected to begin the year with poorer grades, but would move to higher quality ores and improve output as the year went on.

Full-year production guidance remains at 705,000-740,000 tonnes.

Net cash costs should also fall from $1.54 per pound of copper in the first quarter. Full-year guidance stays at $1.35/lb.

Analysts Bernstein said in a note the results were weaker than expected, but said it maintained its “outperform” rating as full-year guidance was maintained.

Antofagasta shares have fallen around 3 percent since the start of the year. (Reporting by Barbara Lewis Editing by Keith Weir)