Jones announced in a letter to investors in mid-December that his firm planned to return the $300 million Tudor Futures Fund's cash to investors by the end of 2014, according to the source, who asked not to be identified because the information is private.

The fund, which Jones ran after launching it in 1984, posted investment gains in every year since its inception, the source said.

The source declined to provide details on the reasoning behind the Greenwich, Connecticut-based firm's decision to close the fund.

(Reporting by Sam Forgione; Editing by Leslie Adler)