“Part of copper’s weakness can be explained by ongoing mine supply growth and broadening mining cost deflation, for example, from falling oil and steel prices as well as weakening producer currencies,” Carsten Menke, commodity analyst at Julius Baer, said in a CNBC article.

Citi also expects earnings of major miners to fall by 9% to 21% in 2015 and by 3% to 16% in 2016.

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Max Chen contributed to this article.