590 workers will be temporarily laid off at Tara Mines in Meath today.
They voted to accept a deal over their terms and conditions during the closure.
60 employees will be kept on as part-time staff to carry out care and maintenance work.
Meath West TD Johnny Guirke says workers are concerned there's no date set for the re-opening of the mines:
"If workers don't have a return date, it is not temporary, it is permanent if they don't come out with a return date for workers".
Last month, Boliden Tara Mines said operations were to be temporarily suspended.
Tara Mines is the country's largest zinc mine and has been in operation since 1977. Boliden acquired the mine in 2004.
