The 31-year-old, who has returned to his homeland of Argentina temporarily, suffered a back injury during the Magpies' 4-2 victory over Southampton a fortnight ago.
"Colo has gone back to Argentina," Pardew told The Chronicle. "There's no treatment he can have, he's broken two of the bones in his back. We think it's going to be anything between three and seven weeks. He's gone back for a week."
Meanwhile, the North-East outfit are preparing to take on Anzhi Makhachkala in the Europa League final 16 tonight.