Strain localization is essential for the dynamics of the solid Earth. It is the rule rather than the exception in the lithosphere (the external layer of the solid Earth). Its first order expression is Plate Tectonics. However, after >50 years of the establishment of Plate Tectonics as the paradigm in Geodynamics, modelling spontaneous strain localization in ductile regime, which prevails in ~90% of the lithosphere, remains a challenge. As a consequence, we cannot predict: (1) when and where strain localization will develop, (2) the number and thickness of the shear zones accommodating this localized deformation, or (3) how the strain distribution will evolve through time.
Observations of ductile strain localization at various spatial scales in nature and experiments shows that heterogeneity in the mechanical behaviour is key for strain localization. This heterogeneity exists at all scales, but it is particularly well-developed at small scales, and it evolves in response to the mechanical fields. In the ERC RhEoVOLUTION, we posit that a poor representation of this heterogeneity and of its evolution with deformation is the locking point for generating strain localization in geodynamical models. The tools we design and develop in RhEoVOLUTION will bridge scales and unravel how heterogeneity and anisotropy in the mechanical behavior of rocks control strain localization in the Earth from the cm to the tens of km scale. To do so, we will:
1. describe the heterogeneity of mechanical behavior of rocks deforming by dislocation creep using stochastic parameterizations of the rheology;
2. constrain these parameterizations using experiments with in-situ follow-up of the microstructure and strain evolution and mesoscale models;
3. accelerate by orders of magnitude the calculation of the evolution of mechanical anisotropy during deformation using supervised machine-learning;
4. quantify feedbacks between the main processes producing strain localization by comparing the predictions of models parameterized to simulate these processes to observations in natural shear zones.
The aim of RhEoVOLUTION is to empower the geodynamics community with a robust framework and modelling tools for predicting self-consistent ductile strain localization and evolution of anisotropy over the large range of scales that characterize the deformation of the solid Earth, but also of ice caps and glaciers.
