Crust-mantle interactions through time & subduction(s)

– Understanding the chemical and lithological evolution of the mantle and its interactions with core and crust through time using the chemical, isotopic, and petrological characteristic of igneous rocks, their minerals and inclusions in minerals. This objective is achieved through three different approaches : 1/ the study of melt inclusions and host minerals of mantle-derived (komatiites) and crustal (TTGs, gabbro and granites) rocks originated from 4.4 Ga till now ; 2/ the study of lavas from ocean islands and their xenoliths (eg Society Islands in French Polynesia), produced by plumes originating from the deep mantle and carrying material recycled by ancient subductions ; 3/ the effects of mantle metasomatism, in particular involving C-bearing agents, on mantle chemistry, lithology, and rheology (e.g., Tibet Plateau, kimberlites). In the framework of ERC Synergy project MEET (Monitoring Earth Evolution Through Time) we plan I : to monitor the compositional evolution of the terrestrial mantle and crust from the Hadean to the present time, and II : to use geodynamic modelling to relate Aim I outcomes to the evolution of mantle convection, crustal production, plate tectonics, and the surface environment.

– Investigating more precisely the nature of the subduction wedge and the mantle beneath the Alps. This will be done In the framework of both the Alparray and the CIFALP2 projects, lead by the team “Ondes” and the RGF Alps. We will combine a fine petrological approach coupled with an experimental petrophysical approach in collaboration with colleagues from ISTep (Paris Sorbonne) that will allow us to refine the petrophysical characteristics of the main alpine rocks. These data will then be injected into synthetic seismic models and compared with actual seismic data. Discussions are underway with our colleagues from the team “Ondes” and researchers at the LIG (Laboratoire d’Informatique de Grenoble) to process these models using Artificial Intelligence

– Couplings between reaction, deformation and fluid flow in context such as subduction zones Mineralogical reactions modify the density, porosity and fluid pressure in the lithosphere. These parameters play a key role for reaction itself but also for deformation and fluid flow. These interconnected processes will be studied with : 1) the determination of reaction kinetics and transport properties at high pressure, under anisotropic stress and in confined environments to evaluate the role of reaction for deformation in metamorphic conditions, 2) the experimental reproduction of transport processes involving the couplings between reaction, deformation and fluid flow (reactive porosity waves). These studies require experimental and numerical developments and also involve collaborations with the teams “Cycle sismique et déformations transitoires” and “Mécanique des failles” for a comparison with geophysical data collected in natural systems. The application to the serpentine system will be developed by combining a structural, petrological and mineralogical approach based on the example of Oman and New Caledonia. Indeed, our work in recent years suggests that the serpentinization of the mantle corner of these two ophiolitic systems was initiated very early during the subduction infancy and continued during the decompression/exhumation of the mantle. They are therefore privileged locations for understanding the coupling between deformation, fluid circulation, and mineralogical changes.

Contacts :
– A. Sobolev
– A-L. Auzende
– C. Cordier
– E. Janots
– V. Batanova
– B. Malvoisin
– F. Brunet