Relict 1.4 Ga oceanic crust in the Zambezi Valley, northern Zimbabwe: Evidence for Mesoproterozoic supercontinental fragmentation

Abstract

The Archean cratons of southern Africa are separated from one another by younger orogenic belts. It is widely believed that these deformation belts developed entirely within continental crust, but in the Zambezi belt of northern Zimbabwe, relict oceanic crust, i.e., ophiolite, has now been discovered. The zircon age of a plagiogranite dike within the ophiolite—1393 ± 22 Ma—makes this the oldest dated remnant of oceanic crust in Africa. Presence of the ophiolite is direct evidence for the rifting and/or assembly of continental fragments within Africa. The age of the ophiolite is consistent with its being a remnant of sea floor formed during the episode of continental fragmentation that immediately preceded the Grenville orogeny, the global event that marked the coalescence of the Late Proterozoic supercontinent of Rodinia.