Mantle Serpentinization at Rifted Margins: insights from West Iberia and the Tyrrhenian Sea using seismic imaging and Vp tomography

Major sites of currently active serpentinization production are slow and ultra-slow mid-ocean ridges (MORs). At magma-poor margins, serpentinization takes place during mantle exhumation at the Continent Ocean Transition (COT), a phase occurring after continental breakup and before the establishment of a steady-state oceanic ridge. During this process, mantle rocks become intensely serpentinized as they interact with seawater that percolates through cracks and faults. However, the precise sequence of serpentinization formation in these regions remains still a topic of debate.

In this study, we examine two well-known examples of mantle exhumation: the West Iberia margin, using the FRAME-P3 profile, and the Tyrrhenian back-arc basin, analyzed through the MEDOC-6 profile. Both profiles were recently acquired with high-resolution multi-channel seismic (MCS) data and are complemented by previously modelled wide-angle seismic (WAS) data. This integration significantly enhances the P-wave velocity model, providing a more detailed and refined view of the basement structure and challenging previous interpretations. The improved model offers better velocity resolution, particularly in regions with complex subsurface structures, and delivers a comprehensive characterization of the transition zone between the oceanic crust and exhumed mantle.

This analysis revealed unprecedented details such as the extent of serpentinization and the detection of a continuous reflector indicative of a hydration front. They also highlight significant fluid-rock interactions and serpentinization processes in the region. In addition, the time-migrated MCS seismic section provides a detailed view of the tectonostratigraphic framework of the COT transition.