Andréa Tommasi

Directrice de recherches
Geosciences Montpellier
UMR 5243 - CNRS/Univ. Montpellier

RESEARCH

PUBLICATIONS

My research themes couple geodynamics and petrophysics:

  • the interactions between plate tectonics and mantle convection :
  • Between 2009-2013 I coordinated the EC Marie Curie Initial Training Network CRYSTAL2PLATE - a training and career development platform associating 7 European research teams internationally recognized for their excellence in in Geodynamics, Petrophysics, Geochemistry, Petrology, Fluid Mechanics and Seismology. It reunited 10 PhD students and 2 postdocs whose projects focused on various aspects of the question: How does plate tectonics actually work? The CRYSTAL2PLATE Initial Training Network studied the interactions between lithospheric plates and the convecting mantle, analyzing (1) how plates modify or are affected by convection, (2) the role of the preexisting structure of the plates on the deformation distribution, (3) the coupling between chemical and physical processes at various scales in the mantle... These studies led to the publication of >20 articles (see the project publications list).

  • Between 2015-2019 I coordinated a second EC Marie Sklodowska-Curie Innovative Training Network CREEP (Complex RhEologies in Earth and industrial Processes) . CREEP associates 10 European research teams and 10 industrial partners. It provided training to 16 early stage researchers (PhD students) via a cross-disciplinary collaborative research program focused on the complex mechanical behaviour of Earth materials and their implications for geodynamic or industrial processes. These PhD projects cover a large spectra of applications of complex rheologies, from the deformation of the Earth surface and deep layers, to geothermal and petroleum exploration and industrial processes (see the project publications list).
  • the elementary processes resulting in strain heterogeneity and controlling recrystallization during viscoplastic (ductile) deformation :
  • In the frame of the ANR DREAM (2014-2018) we associated in-situ characterization by EBSD of the microstructure and texture (CPO) evolution during annealing and deformation experiments in the SEM Crystal Probe on analog materials (hexagonal ice and magnesium polycrystals) and numerical modelling of the viscoplastic deformation heterogeneity and of the recrystallization processes at the crystal and aggregate scales. This study is carried in collaboration with colleagues from Glaciology (IGE Grenoble) and Materials Sciences (LEM3 Metz et CEMEF Sophia-Antipolis). Here you can see a teaser for the in-situ deformation experiments (go to the end of the page to see the movies)!

  • This subject is also at the center of the activities of the CNRS INSIS-INSU Groupement de Recherches (GDR) Recristallisation et croissance des grains , which reunites academic and industrial researchers working on recrystallization phenomena from the Material and Earth Sciences communities in France.
  • the role of micro-scale dependent, time- and space-evolving rheologies on generating strain localization in the Earth :
  • The ERC Advanced RhEoVOLUTION, which started in November 2020, proposes a "revolution" in how we define rheology (the equations relating forces to deformation) in geodynamical models. It aims at predicting the onset and evolution of strain localization. Modeling spontaneous ductile strain localization has been impossible so far, because it depends on processes active at the mm scale that cannot be explicitly simulated in geodynamical models. The tools we designed and propose to develop in RhEoVOLUTION will make it possible. We will bridge scales and model how heterogeneity and anisotropy in the mechanical behavior of rocks control strain localization from the cm to the tens of km scale in the Earth. To do so, we will: 1. describe the heterogeneity of mechanical behavior of rocks deforming by dislocation creep by 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. For a brief introduction on points 1 and 2 see the talk given at the CIG workshop on Strain Localization in July 27th, 2020.

In addition, in a not so far away past (at least I would like to believe!), I have also worked on:

  • the effect of thermally-induced intraplate rheological heterogeneities on the mechanical behavior of a continental plate submitted to compression (continental collision) through the analysis of field examples (Neoproterozoic collisional belts of Brazil) and finite-element models;
  • the relationship between magmatism and deformation in the continental crust: coupling between granites emplacement and development of lithospheric scale strike-slip shear zones;
  • the partioning of the deformation in continental collisional belts: kinematic analysis of a neoproterozoic collisional belt of southern Brazil (field mapping and microstructural studies) showing a temporal and spatial partitioning of the deformation between tangential and strike-slip shear zones.