What was the topic of the argument that led to the great schism?

East-West Schism, also called Schism of 1054, event that precipitated the final separation between the Eastern Christian churches (led by the patriarch of Constantinople, Michael Cerularius) and the Western church (led by Pope Leo IX). The mutual excommunications by the pope and the patriarch in 1054 became a watershed in church history. The excommunications were not lifted until 1965, when Pope Paul VI and Patriarch Athenagoras I, following their historic meeting in Jerusalem in 1964, presided over simultaneous ceremonies that revoked the excommunication decrees.

Explanation:

might be agreeing to participate ethically with other european nations in the slave trade

or notifying other european nations when taking possession   of african territories