Birth of an oceanic spreading center at a magma-poor rift system

Morgane Gillard (1) , Daniel Sauter (1) , Julie Tugend (1) , Simon Tomasi (1) , Marie-Eva Epin (1) , Gianreto Manatschal (1)

1 IPGS - Institut de physique du globe de Strasbourg

Oceanic crust is continuously created at mid-oceanic ridges and seafloor spreading represents one of the main processes of plate tectonics. However, if oceanic crust architecture, composition and formation at present-day oceanic ridges are largely described, the processes governing the birth of a spreading center remain enigmatic. Understanding the transition between inherited continental and new oceanic domains is a prerequisite to constrain one of the last major unsolved problems of plate tectonics, namely the formation of a stable divergent plate boundary. In this paper, we present newly released high-resolution seismic reflection profiles that image the complete transition from unambiguous continental to oceanic crusts in the Gulf of Guinea. Based on these high-resolution seismic sections we show that onset of oceanic seafloor spreading is associated with the formation of a hybrid crust in which thinned continental crust and/or exhumed mantle is sandwiched between magmatic intrusive and extrusive bodies. This crust results from a polyphase evolution showing a gradual transition from tectonic-driven to magmatic-driven processes. The results presented in this paper provide a characterization of the domain in which lithospheric breakup occurs and enable to define the processes controlling formation of a new plate boundary.

Domaines: Géophysique [physics.geo-ph]

Morgane Gillard, Daniel Sauter, Julie Tugend, Simon Tomasi, Marie-Eva Epin, et al.. Birth of an oceanic spreading center at a magma-poor rift system. Scientific Reports, 2017, 7 (1), ⟨10.1038/s41598-017-15522-2⟩. ⟨hal-01661168⟩