Aim of the project
Tracking how metamorphic transformations and associated changes in material properties affect the mechanical behaviour of rocks
Left: Relationship between seismicity and metamorphic reactions under Tibet (Yamato et al., 2022)
Right: Rupture of a "butterfly" glass caused by the presence of a NiS ball © wintech-group
Why ?
Solid-state chemical reactions are responsible for the alteration of the mechanical properties of materials. They appear to be a first order control of many geological processes (e.g. seismicity induced by olivine phase transitions in the Earth mantle and by polymorphic transformations of quartz in the continental crust) but are also an issue beyond material sciences (e.g. glass spontaneous breakage due to α - β of nickel sulphide inclusions, lithium battery wear, issue with ceramic sintering).
Serpentinized harzburgites (Andréani et al., 2007)
Transformations in the lab
Geological reactions are usually much more complex than simple phase transitions because they imply equilibrium between multiple reactants and products, with non-instantaneous kinetics, and deformation stages. This is the case for reactions such as peridotite hydration beneath the oceanic seafloor, subsequent serpentine dehydration in subduction zones, and eclogitization of the continental crust during collision.
Whether rheological changes, volume changes (∆V) or enthalpy budget (∆H) are dominant processes needs to be addressed and quantified
Quantifying the impact and the timing of reaction-induced changes on force and energy balances at any scale remains a real challenge and requires the development of new modeling tools able to bridge scales from laboratory to nature
The intimate feedbacks between reaction and strain are still enigmatic and their significance at natural time scales unknown, mainly due to a lack in numerical tools to untangle the feedbacks: this is what METROLOGY aims to address. Reaction-deformation experiments in the laboratory as well as numerical simulations will be performed in association with different institutes in Paris (ENS & ISTeP, Sorbonne University) and Lyon (LGL-TPE).
∆H and ∆V associated with the reaction, kinetics, overstepping, and strength contrast between reactants and products are responsible for a shift in deformation modes from ductile to brittle. However, the mechanical processes operating during the reaction are still enigmatic and the position of the expected switch to unstable behaviour for high ∆V or high ∆H reactions is actually not constrained.