Africa output growth boosts Glencore Xstrata copper output

* $900 mln iron ore project approved in Mauritania

* Zinc output down 18 pct, nickel's falls 15 pct

* Koniambo nickel output below expectations (Adds approval of Mauritania iron ore project, details)

By Silvia Antonioli

LONDON, May 6 (Reuters) - Miner Glencore Xstrata met market forecasts with a 24 percent increase in copper production in the first quarter of 2014 mainly due to output expansion at its African operations and to higher grades at its South American (Frankfurt: SS7.F - news) mines.

Glencore said the performance of its marketing division was overall "strong and in line with expectations" without elaborating further.

Among diversified miners, Glencore Xstrata (Other OTC: GLCNF - news) has the biggest exposure to copper, which accounted for almost half of its earnings last year.

The mining company produced 382,000 tonnes in the three months, up almost a quarter from 308,000 tonnes in the same period a year ago.

The increase was driven by the expansion at the Mutanda mine in the Democratic Republic of Congo and the Ernest Henry mine in Australia and improved production at the Collahuasi and Antamina mines in South America.

African copper (LSE: ACU.L - news) production rose 27 percent to 106,400 tonnes, boosted by growth at the Mutanda, Mopani and Katanga operations.

The miner expects growth from the Mutanda mine to accelerate as it completes its next expansion phase.

"Glencore's African copper assets remain its strongest source of high quality revenue growth, in our view," Bernstein Research analysts said in a note.

"Today's results reinforce our thesis for Glencore Xstrata, predicated on its high copper exposure and the increasing benefit of its high-grade African copper assets. We reiterate our outperform rating."

Glencore said the Askaf North iron ore project in Mauritania has been approved. Construction of the greenfield project is expected to cost $900 million and production should start in early 2017.

ZINC, NICKEL OUTPUT FALL

Coal, which made up about 13 percent of Glencore's earnings last year, saw a 4 percent total output increase to 34.1 million tonnes, as its Colombian Cerrejón mine recovered from a strike which hit production last year and helped by productivity improvements and expansion projects in Australia.

Output of zinc, another key source of revenue for the group, fell by 18 percent mainly due to the end of mine life closures of the Perseverance and Brunswick (Munich: BWI.MU - news) mines in Canada in June 2013.

Nickel production fell 15 percent after the XNA mine in Australia and the Falcondo mine in the Dominican Republic conducted maintenance last year.

The Koniambo nickel mine in New Caledonia, which Glencore inherited from Xstrata, produced below expectation due to various factors including power availability and extended maintenance stoppages.

Glencore is now reviewing the annual production expectations from Koniambo in light of the quarterly operational performance and the start-up experiences to date.

Glencore Xstrata shares were down almost 1 percent by 0756 GMT versus a 1.5 percent fall in the UK-listed mining sector . (Editing by Jason Neely)