has named its copper and coal division head, Jean-Sébastien Jacques, as its chief executive, replacing the veteran Sam Walsh and signaling a shift in strategy for the Anglo-Australian mining company. Mr. Walsh, 66, was placed at the helm three years ago after the abrupt ousting of Tom Albanese. But the company has run into further trouble with the downturn in commodities prices. Mr. Jacques, 44, praised by analysts for running tough assignments like Rio’s Oyu Tolgoi project in Mongolia, will be the first executive in decades with a copper background to run a group that depends on iron ore.