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

RESEARCH

PUBLICATIONS

CV

My research themes couple geodynamics and petrophysics:

• relations between the mantle flow and the anisotropy of its physical properties
  • multi-scale numerical models of the development of olivine crystalographic orientations and seismic anisotropy in the upper mantle, which were applied to the study of:
    • upper mantle deformation and seismic anisotropy due to the asthenospheric drag beneath an oceanic plate
    • the effect of a continuous vertical variation of the LPO on the measured anisotropy as well as the frequency dependence of this later
    • the deformation of the lithospheric (and sublithospheric) mantle in continental collision zones, rifts, and lithospheric-scale shear zones
    • seismic anisotropy associated with salt diapirism
  • numerical models and experimental measurements of the anisotropy of thermal diffusivity in the upper mantle
  • strain-induced mechanical anisotropy in the upper mantle: effect of the preexisting structure of the lithosphere on continental rifting
  • relation between deformation and the anisotropy of electrical conductivity inferred in the upper mantle by long-period MT measurements
  • flow and seismic anisotropy in the deep mantle (actualités INSU)
  • the interactions between deformation and fluid/melt transport in the mantle (actualités INSU)

the interactions between plate tectonics and mantle convection - I coordinate the EC Marie Curie Initial Training Network CRYSTAL2PLATE

CRYSTAL2PLATE is a coherent 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 will provide to 10 PhD students and 2 postdocs between April 2009 and March 2013: (1) state-of-the-art concepts and leading-edge techniques essential to study complex natural systems via the research projects, courses, and scientific exchanges within and beyond the network; (2) essential career-management skills via courses and practical activities aimed to develop their organisational, management, and networking skills; (3) an understanding of the impact of research results for the private sector and an insight of the enterprise world via exchanges and visits to the industrial partners; (4) new possibilities of career development via professional contacts in academia and industry.

How does plate tectonics actually work? To answer this question, the CRYSTAL2PLATE Initial Training Network will study the interactions between lithospheric plates and the convecting mantle. The research projects will investigate: (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, in particular through partial melting, fluids percolation, and fluid-rock reactions. Linking chemical and physical processes in the mantle requires understanding the relation of crystal-scale processes to the large-scale dynamics. Crystal- and rock-scale processes, such as viscous and elastic deformation, melt transport and reactions, modify the composition, microstructure, and physical properties of mantle rocks, which are the key for interpreting geophysical observations in terms of temperature, composition, and deformation in the mantle. On the other hand, small-scale processes depend on the large-scale temperature, stress, and pressure structure in the mantle. Understanding the interactions between physical and chemical processes at various scales in the mantle is thus fundamental to comprehend its dynamics and hence the onset of plate tectonics.

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: analysis of the rheological effect of the emplacement of large volume of magmas in the continental crust;
• 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.