(Adds No. 4 shaft's output, Gold Fields, NUM quotes, detail)

JOHANNESBURG, Nov 14 (Reuters) - South Africa's Gold Fields <GFIJ.J> closed a shaft on Wednesday that produces some 500 ounces of gold a day at its Beatrix mine in South Africa after two miners were killed during a clash.

Gold Fields, the world's fourth-ranked gold producer, said it had temporarily shut the No. 4 shaft after three other miners were seriously injured when violence erupted between rival factions of the National Union of Mineworkers (NUM).

Gold Fields said it had taken the decision to stop the nightshift on Tuesday and dayshift on Wednesday at the shaft to ensure safety of its workers at the mine.

The incident occurred when about 750 members of the NUM met to elect a new leaders, Gold Fields said in a statement.

Gold Fields said police and Gold Fields security had stabilised the situation, and the top leadership at the NUM leaders had been notified.

"The loss in output is not material at the moment," Gold Fields spokeswoman Nerina Bodasing told Reuters.

"We hope that the shaft will be in working mode tonight but it all depends on the security and safety conditions," she added.

The entire Beatrix mine produces 600,000 ounces of gold yearly, out of the group's output of some 4 million ounces, Bodasing said.

The NUM's spokesman Lesiba Seshoka said the union had ordered an investigation into the causes of the fighting that led to the deaths of the miners. (Reporting by James Macharia, editing by Michael Roddy)

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