Lithosphere-asthenosphere structure and impact on serpentinization processes and topography across the plate boundary between Iberia and Europe

Abstract

The tectonic evolution of the plate boundary between Iberia and Europe since the Variscan and more clearly since the Mesozoic rifting is at the origin of heterogeneities of densities and structure, in the crust and the mantle, which have an impact on the distribution of the current stresses and post-orogenic uplift in the Pyrenees. Here, we investigate the lithosphere structure across the Pyrenees and Western Europe using LitMod2D that integrates geophysical and petrological data sets to produce the thermal, density, and seismic velocity structure of the lithosphere and upper mantle. Of particular interest is the chemical composition of the mantle, including the degree of serpentinization near the North Pyrenean Fault (>10 km), and the shape of the lithosphere-asthenosphere boundary at a larger scale (>100 km). The topography and geophysical constraints, including LAB geometry, Vs, Vp data are well reproduced for a weak fertile Phanerozoic lithosphere. Our results suggest that accounting for serpentinization allows fitting second-order gravity and seismological features in the lithosphere, but not topography which is controlled to first-order by high lateral variability in crustal thickness and lithosphere strength.