Clermont Auvergne MSCA PF Master Class: Hosting Offer on Ultra-fast Ascent of CO2-rich Magmas (project BASANITE)

Ultra-fast ascent of CO2-rich magmas from the mantle to the surface: Experimental developments and application to basanites in the French Massif Central (see the uploaded file for details on the host institution and the research laboratory).

There is increasing evidence that the primary magmas at the origin of low-silica alkaline volcanism, such as basanites, are very rich in CO2 and that they can rise rapidly, directly from the mantle to the Earth’s surface. Such volcanic systems are numerous in intraplate oceanic and continental settings, including the French Massif Central (FMC), and are remarkable for the abundance of large mantle-derived xenoliths. These volcanic systems are of great magmatological interest because they provide an open window on the upper mantle, enabling us to get a closer look at the composition of primary magmas, the conditions of partial melting in the mantle, the magmatic processes operating at depth or the deep CO2 cycle.

This project aims to develop a general scheme for the eruption of CO2-rich basanitic magmas, from their roots in the mantle to the surface, by coupling experimental petrology, physical modeling and the analysis (Raman, EPMA, LA-ICPMS, SIMS) of natural samples from the FMC. We have just documented exceptional CO2 contents (up to 4.8 wt%) in melt inclusions of Bas-Vivarais basanites, making FMC the perfect target for studying low-silica alkaline volcanism in a continental intraplate setting (Buso et al., 2025. Melt inclusions reveal massive carbon dioxide emissions from continental intraplate volcanism. Communications Earth & Environment, 6: 1002). The project is very broad and there are various research directions that could be developed as part of a postdoctoral fellowship, including the following(other directions are possible depending on the postdoctoral fellow's interests and areas of expertise):

- characterize the storage conditions and the state of the magma in the deeper parts of the volcanic system, and better constrain the pressures of olivine crystallization and melt inclusion entrapment.

- study experimentally how magma reacts to rapid decompression during ascent and apply the experimental results to natural samples to determine the conditions of ascent of basanitic magmas from the FMC.

- characterize the composition of primary magmas in FMC basanites and their storage depth in the mantle by studying melt inclusions and host olivines, and deduce the melting conditions in the mantle (nature of sources, pressure, temperature).