The Central Afar region as an analogue for the development of oceanic plateaus?

Abstract

Oceanic plateaus are traditionally considered as oceanic crust thickened by magmatic processes. In the last decades, however, continental material significantly older than the surrounding oceanic crust has been recovered from drillings on oceanic plateaus (e.g. Rio Grande Rise, Mauritius and Mascarene Plateau, Elan Bank), leading to numerous questions about the origin of these structures.The Central Afar region is part of the Afro-Arabian Rift System. It witnessed the eruption of the Ethiopian Flood Basalts approx. 30 My ago followed by rifting. Mapping, plate kinematic modelling and geophysical data show that, despite important extension, the area features relatively thick crust. This crust is characterized by important magmatic underplating, intrusions, and volcanic material with isolated continental fragments. Therefore, it might represent an analogue for the development of oceanic plateaus. Numerous rift jumps and magma-compensated thinning linked to the presence of the Afar hotspot can explain the structure of the Central Afar. Unlike Central Afar, the Danakil Depression in northern Afar shows more classical structures and will probably develop into a magma-rich margin. The Afar depression thus constitute a unique example of the early development of different types of passive margins and oceanic plateaus.