* No reason given for CEO's departure
* Third platinum boss to leave this year
* Shares fall over 6 percent
(Adds details, background, analyst comments, shares)
LONDON, Oct 8 (Reuters) - The chief executive of Aquarius Platinum , the world's fourth-largest platinum miner, has resigned with immediate effect, the company said on Monday, giving no reason for his departure after more than a decade at the company.
The news sent London-listed shares in Aquarius, the third major platinum miner to lose its chief executive this year, down 6.3 percent to 44.5 pence at 0750 GMT, underperforming a 1.4 percent drop in the broader mining sector .
Aquarius has been hit along with the rest of the South Africa-focused platinum sector by labour unrest and soaring costs. It was forced to temporarily suspend operations at its Kroondal mine last month.
"Stuart Murray has pretty much been the face of Aquarius Platinum," Nomura analysts said in a morning note.
"After an extremely difficult last three years for the company there will be plenty of speculation surrounding whether or not there is more bad news to come."
A replacement for Murray - who was also chairman of the miner's principal, South African subsidiary - will be considered "in due course", it said in a statement, adding that he will continue at Aquarius until Mar. 31 to facilitate an "orderly handover".
Since August nearly 50 people have been killed in labour conflict in the crucial South African mining sector after strikes for higher wages started in the platinum industry, causing the worst social unrest in the country since the end of apartheid in 1994.
The miner, which in August reported a full-year loss for the 12 months ended June 30, also said that Jean Nel, formerly commercial director, would become its chief operating officer.
(Reporting by Clara Ferreira-Marques; editing by Sarah Young)
((email@example.com)(+44 207 542 3214)(Reuters Messaging: firstname.lastname@example.org))