The output of the other, Falconbridge, complements the coal, copper and zinc businesses of its purchaser, Xstrata.

ECONOMIST: How to make sense of the current plethora of mining deals

Last month two people were killed and buildings set alight in Espinar, in the southern highlands, in a protest against Xstrata, an Anglo-Swiss company that owns a copper mine at Tintaya and is building another nearby.

ECONOMIST: The president and the protesters fall out

Glencore and Xstrata, the world's biggest exporter of thermal coal which also produces copper, nickel and zinc, agreed last year on a merger that would create an industry giant.

NPR: Glencore Sees Sharp Fall In 2012 Earnings

Citing uncertainty about the tax, Xstrata, a Swiss-based company, has suspended further exploration in Queensland, where it mines copper.

ECONOMIST: A rare rich-world leader for whom a budget brings good news

Glencore said China is reviewing its proposed merger with Xstrata with a focus on whether the combined company would exert too much influence on China's copper market.

WSJ: What's News