Commodity trading giant Glencore
The deal includes Mercuria's marketing agreement for coal from the Koornfontein mine and future output from the Optimum mine.
Glencore will begin marketing OCH's coal in June next year, the sources said.
Glencore will shortly make a formal offer to all remaining OCH shareholders, they said.
Glencore was not immediately available for comment.
(Reporting by Jacqueline Cowhig; Editing by Anthony Barker)