(Corrects to make clear 11,000 set to be fired, not 20,000)
* Gold Fields Beatrix mine back up, dismissal ultimatum looms
* Amplats says to hold off on further dismissals
* AngloGold to decide on ultimatum next week
JOHANNESBURG, Oct 18 (Reuters) - Striking miners at one of Gold Fields' South African operations returned to work on Thursday, but the bullion producer still looked set to fire more than 11,000 others taking part in the worst wildcat walkout since the end of apartheid.
More than 80,000 miners have downed tools in the country since August in often violent strikes that are hitting growth and investor confidence in Africa's biggest economy, and raising questions about President Jacob Zuma's leadership.
Gold Fields, the world's fourth-largest bullion producer and second-biggest in Africa, said all of the 9,000 workers at its Beatrix mine were now back at work after responding to a dismissal ultimatum.
Eleven thousand strikers at its KDC West operations in Carletonville, 40 km (25 miles) west of Johannesburg, have until 1200 GMT to return to work or face immediate dismissal. Gold Fields has said it may issue a similar ultimatum to those striking at KDC East.
More and more mines in South Africa have resorted to mass dismissals to tackle the strikes gripping the sector. Around 15,000 workers have been sacked in the last two weeks, although experts say it is more a hard-ball negotiating tactic than outright dismissal.
"It's largely a tactical move," said a labour lawyer, who asked not to be named as he is involved in talks to resolve the strikes. "They don't expect to be able to run a mine with a completely new labour force."
While most of the workers will be rehired when the protests end, weeks of wildcat strikes have pushed some already struggling shafts into the red.
Anglo American Platinum (Amplats) said it would not fire any wildcat strikers at its relatively profitable Union and Amandelbult mines for now as it sought to engage unions to resolve the disputes.
The world's No. 1 platinum producer also said it was open to discussing the fate of the 12,000 miners already dismissed at its Rustenburg operations, which are known to be struggling.
"While it remains our stated position that we will not reinstate the 12,000 dismissed Rustenburg employees, we have agreed with our recognised unions that we are willing to discuss their status as part of this engagement," it said, without elaborating.
Attendance at those mines remains below 20 percent.
AngloGold Ashanti, the world's third-largest gold producer, said it would make a decision next week on whether to issue an ultimatum to workers. (Reporting by Sherilee Lakmidas, Agnieszka Flak and Ed Cropley; Editing by Ed Cropley and Pravin Char)