Our knowledge of melt generation, migration and extraction in the Earth mantle beneath mid-oceanic ridges is mostly derived from geodynamic numerical models constrained by geological and geophysical observations at sea and field investigations of ophiolites. High resolution observations are mostly restrained to the oceanic crust and the shallow part of the mantle. Here we use a > 200 km-long seismic reflection section to image with high-resolution the sub-oceanic lithosphere within the Western Somali Basin where spreading ceased ~120 Ma ago. The location of the failed spreading axis is inferred from both seismic data and gravity data. Four groups of strong reflections are imaged down to depths of more than 30 km below the top of the oceanic crust. The deepest reflectors, within the mantle, may result from frozen melt bodies which may be relicts of a paleo melt channel system located at the base of the lithosphere and feeding the failed ridge axis. Another possibility is that some of the deepest reflectors correspond to melt bodies injected into major shear zones along the Davie fracture zone, which has been reactivated during a Late Cretaceous volcanic event. The shallowest group of reflectors, located below a 8-5 km thick oceanic crust, is interpreted as marking a fossil melt-rich crust mantle transition zone up to 3 km thick. This interpretation implies a poorly efficient extraction of melt out of the mantle, which is favored by the combination of a slow spreading rate and a high magma budget.