The floor of the Central Atlantic Ocean hides surprising tectonic and magmatic structures. 10 million years ago a rapid change in the relative movements between South American and African plates brought up a narrow 3-4 km high – 300 km long transverse ridge. It is the worldwide longest exposure of continuous oceanic crust section known. We sampled the upper mantle rocks exposed along the base of the whole lithospheric section. These rocks are residues of the partial melting process that generated the oceanic magmatic crust along the Mid Atlantic Ridge. A 20 My long melting history can be drawn trough major and trace element distribution in the residual mantle minerals. Modelling the Rare Earth Element patterns of the residual clinopyroxenes suggest a deeper than known origin of the oceanic Mid Ocean Ridge Basalts and a rapid-low aggregative migration of the partial melts throughout the melting region. Surprisingly we discovered that the transverse ridge we were studying is topped by carbonatic-coralline structures drown by the thermal subsidence of the oceanic crust. Are these sink islands new candidates for the lost Atlantide?
Laboratoire Pierre Süe