A date with an O.C.C. (Oceanic core Complex)

For many years, the teaching of oceanic accretion processes in France has long focused on that of rapidly accreting ridges producing a Penrose-type lithosphere. Although often problematic in drawing a parallel with the structure of Alpine ophiolites (without real magmatic crust), themselves in the programs, it was nonetheless taught in high school. In the new high school programs of 2019, a small line has finally made it possible to include the teaching of the accretion processes of slow divergence zones. Although recognized for more than a decade by the scientific community, the key role of mantle exhumation, its serpentinization, detachment faults and the formation of complex oceanic cores can finally be taught. This finally lifts the veil on the absence in transatlantic seismic tomographies of low-velocity zones under the divergence axis. But also allows a better match between the field observations carried out by the classes during outings to mainland French ophiolitic spots and the concepts required for the baccalaureate (high school diploma). This presentation shows how it is possible to understand the functioning of a slow accretion zone by taking the very educational example of the complex oceanic cores of the mid-Atlantic zone.  By crossing data from oceanographic campaigns synthesized in the form of kml (Keyhole Markup Language), ocean topography with G.I.S. visualizers (Geographic Information System) like Google Earth and data and samples (macro and microscopic)  harvested from the sites, we show how high school students reconstruct the geodynamic and petrological mechanisms of slow accretion zones.