Imaging a mantle plume beneath the French Massif Central

Teleseismic tomography is now widely recognised as a very powerful tool for studying the velocity structure of the lithosphere-asthenosphere system on both local and regional scales. A prime objective is to identify velocity perturbations and to constrain their location and intensity. Here we use the arrival times of P-waves from teleseismic events, recorded by a dense network of mobile and permanent stations within the French Massif Central, to derive a 3D P-velocity model for an area of 425 km × 300 km. Combined with knowledge of the basement geology of the area and the timing and geochemical characteristics of Tertiary-Quaternary volcanic activity, we consider that the velocity model provides unequivocal evidence for the ascent of a thermally and chemically anomalous mantle plume beneath the Massif Central during Tertiary times. Our model is consistent with regional Bouger gravity anomalies, documented patterns of Neogene-Recent uplift and deformation fabrics within lithosphere-derived mantle xenoliths exhumed by the volcanics.