Schism

A split or separation within a group or organization, typically caused by discord.

A formal division or split within a religious body.

"The schism between Sunnis and Shias happened quite early in Islamic history."

A split within Christianity whereby a group no longer recognizes the Bishop of Rome as the head of the Church, but shares essentially the same beliefs with the Church of Rome. In other words, a political split without the introduction of heresy.