Testing the Big Mantle Wedge Hypothesis to Explain Intra-Continental Volcanism

• Applicant: Enrico Marzotto, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry ; Geology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559893073

Identifying the source of intraplate volcanism is one of the most challenging scientific problems in geoscience. In the classical view, intraplate volcanism is caused by hot and buoyant mantle plumes that rise from the core-mantle boundary. The origin of such plumes is still enigmatic and the classical view, although explaining well intra-oceanic volcanism (e.g. Hawaii), fails to explain intra-continental volcanism, such as seen in the European Cenozoic Rift System (ECRiS) and its volcanic landforms in France and Germany. Intra-continental volcanism is atypical because it features: sporadic activity, lack of age progression and heat flux anomalies, low 3He/4He ratio, and the presence of sub-lithospheric structures rising from a cold region located in the mantle transition zone (MTZ). A recent hypothesis suggests that ECRiS intra-continental volcanism might be caused by hydrous plumes originating from the flux melting of the subducted oceanic crust, now stagnating in the MTZ beneath Europe. This geological setting is called Big Mantle Wedge (BMW). Here, I propose to test the BMW hypothesis by: 1) implementing variable thermal conductivity in a geodynamic software to compute the thermo-mechanical evolution of subducting slabs; 2) investigating the effect of temperature dependent parameters on slab stagnation in the MTZ; 3) modelling slab dehydration in the MTZ. This project will: (a) provide a unique method to compute heat transport inside the slab; (b) advance our knowledge of the deep-Earth water cycle; (c) provide impactful insight to model the nucleation of plumes from the MTZ, beneath Europe and elsewhere.

• DFG Programme: Research Grants