The 31-year-old defender has returned to his native Argentina after sustaining the injury when he fell awkwardly during the club's 4-2 Premier League win over Southampton on February 24.
"Colo has gone back to Argentina," Pardew was quoted as saying by local media.
"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."
Coloccini pledged to stay with Newcastle until the end of the season after seeking a move away in January.
He will now miss both legs of Newcastle's Europa League last 16 clash against Anzhi Makhachkala as well as a string of important Premier League matches for the side, who are 15th in the table.
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