UPDATE 1-Miner Antogafasta's Q4 copper output up 15 pct

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LONDON, Jan 31 (Reuters) - London-listed Chilean miner Antofagasta (ANTO.L) said on Thursday its copper output in the fourth quarter rose 15 percent on the previous quarter due to higher throughput and better ore grades.

The firm said copper production in the three months to end December was 115,400 tonnes, up from 100,600 tonnes in the previous quarter. Full-year output fell 8 percent year on year to 428,100 tonnes.

The main driver of improved copper output in the last three months of the year was the flagship Los Pelambres mine, where output shot up 22.5 percent due to increased plant throughput and improved ore grades.

On an annual basis, however, weaker production was due to lower average ore grades at Los Pelambres during the year, it added.

Group cash costs for 2007 fell 21 percent to 31.6 cents per pound due to improved by-product credits and reduced tolling charges.

Molybdenum output at its Los Pelambres mine rose to a record 10,200 tonnes for the year, up 4 percent.

The shares, which have shed about 10 percent so far this year, fell 1.5 percent to 6.46 pounds by 1015 GMT, compared with a 0.7 percent increase in the UK mining index .FTNMX1770. (Reporting by Eric Onstad, editing by Will Waterman)