The chief executive of mining giant Rio Tinto, Tom Albanese (pictured), has resigned after the company announced a $14 billion write-down.
The write-down relates to the company's aluminium and coal-mining businesses.
Mr Albanese has been replaced by Sam Walsh, chief executive of Rio's iron ore business.
In a statement, Rio Tinto chairman Jan du Plessis said the scale of the write-down was "unacceptable".
The impairments include approximately $3 billion relating to Rio Tinto Coal Mozambique, which only began shipping coal in June last year.
"The Rio Tinto board fully acknowledges that a write-down of this scale in relation to the relatively recent Mozambique acquisition is unacceptable," Mr du Plessis said.
"We are also deeply disappointed to have to take a further substantial write-down in our aluminium businesses, albeit in an industry that continues to experience significant adverse changes globally."
Doug Ritchie, who led the acquisition and integration of the Mozambique coal assets in his previous role as Energy chief executive, has also stepped down by mutual agreement, the company said.
The write-downs will be included in Rio Tinto's full-year results due on February 14.
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