Xstrata said on Monday it is considering a major expansion of its thermal coal mining operations in northeastern Australia. The Anglo-Swiss company could invest US$ 13 billion at the Wandoan deposit in Queensland state. The area is being developed following the original, US$ 5.4 billion-scheme to mine 30 million tonnes of thermal coal a year from 2014; the expanded development would turn Wandoan into a four-pit, 100 million-metric tonnes a year prospect from the next decade.