Micro-cartographie P-T-» dans les roches métamorphiques. Applications aux Alpes et à l'Himalaya

Abstract : The study of the lithosphere dynamics such as vertical and horizontal material transport processes requires the detailed reconstruction of the geodynamic evolution of the mountain belts. These geodynamic models are classically constrained using pressure-temperature-time-deformation (P-T-t-e) paths unravelled from textural and chemical study of metamorphic rocks fragments. Metamorphic rocks are made by mosaic of local thermodynamic equilibria involving minerals that grew at different temporal, pressure, and temperature conditions. The topic of this thesis is the reconstruction of pressure-temperature paths by combining direct techniques such as pseudosection computed by energy minimization and inverse techniques such as multi-equilibrium, in space, i.e. two-dimensions, using a micro-mapping approach. The use of chemical images and thermodynamic modelling requires user-friendly programs freely available for the community. In this thesis, we first propose a set of programs and a new solid solution model for chlorite and also two application examples are proposed in the Alps and the Himalaya. We propose a set of programs written in Matlab (1) for microprobe image processing and the computation of pressure temperature maps: XMapTools, (2) for multi-equilibrium calculations using different thermodynamic data and solid solution models: PT-lines, MultiPlot and Meamp. A new solid solution model for chlorite is presented including a di-trioctahedral chlorite end-member. This model can be used to calculate pseudosection phase diagrams and for fluid-rock interaction modelling. Thermodynamic modelling and micro-mapping techniques are used together to add new constraints to the geodynamic models of subduction-collision mountain belts. In the French Western Alps, P-T-e and P-T-t paths are recovered for some metamorphic units in which the available estimates were only based on the occurrence of index minerals. These new thermobarometric and radiometric data indicate a strong coupling between the exhumation of the oceanic accretionary wedge and the continental subducting plate. In The Himalaya, we studied a new eclogite occurrence and we propose a detailed and continuous P-T path calculated using our newly created program XMapTools.
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Submitted on : Wednesday, March 20, 2013 - 11:54:30 AM
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  • HAL Id : tel-00799283, version 1



Pierre Lanari. Micro-cartographie P-T-» dans les roches métamorphiques. Applications aux Alpes et à l'Himalaya. Sciences de la Terre. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENU033⟩. ⟨tel-00799283⟩



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