The goal of the interdisciplinary MACIV project is to obtain new information about the crustal and lithospheric structures and ongoing volcanic processes beneath the French Massif Central (FMC) that occupies a strategic position in the French geological and geographical landscape, having recorded a varied geological history from the end of the Proterozoic to the present, i.e., nearly 600 Ma. We specifically aim to improve our understanding of the impact of the lithological-structural inheritance from the Variscan history and the role of present-day geodynamics on the FMC Cenozoic intraplate volcanism.

Intraplate volcanism is difficult to explain using standard features of plate tectonics, such as subduction at convergent boundaries or upwelling at rifted margins, responsible for most volcanism on Earth. Instead, other mechanisms are proposed, including upwelling mantle plumes, small asthenospheric convection cells, shear-driven upwelling of the asthenosphere, or slab tear (e.g., Merle & Michon, 2001, Dezes et al., 2004 ; Davies and Davies, 2009 ; Conrad et al., 2011). The relative importance of these mechanisms is still vigorously debated and likely varies from one geological setting to the next. Particularly, intraplate volcanism and magmatism in Western Europe are only understood in broad terms. The European volcanic provinces, and the FMC specifically, exhibit clear links with the Cenozoic rift systems and the European Variscan belt, but the specific role of each structure on their origin, dynamics, and morphology is still poorly documented. The current activity of the Eifel volcanic region (Germany), a system similar to the FMC, reminds us of the severe natural hazards (e.g., potential VEI 6 eruption of the Laacher See volcano in a populated area) that remain difficult to assess in these dormant regions. Here we propose an ambitious geophysical project mainly based on multi-scale seismic imaging and monitoring of the FMC region that will constrain the 3D structure of the lithosphere with an increased resolution across the volcanic province. This project will shed light on the magmatic plumbing system from the mantle to volcanoes and will document the relationship between inherited Variscan structures and emplacement of the different volcanic edifices and their morphology. By doing so, this project will fill a knowledge gap in this region and will allow us to tackle fundamental scientific questions about mantle dynamics, crustal extension, and volcanism in the Alpine foreland, with first-order societal implications in terms of natural resources and hazards.

Updated on 11 janvier 2024