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La déformation mécano-chimique dans la croûte supérieure terrestre . Exemples de processus couplés et de systèmes auto-organisés

Abstract : In the Earth's upper crust, deformation and compaction processes originate from interactions between mechanical and chemical processes. In such processes, the presence of water, in the pore space or at the grain contacts, is a necessary condition. Deformation processes as different as indented pebbles and grains, stylolites, dolomitization fronts, karsts, or compaction of aggregates in sedimentary basins or in fault zones may be observed. To understand such processes, I have pursued analytical and experimental studies at various scales. At the nanometer scale, I show that the interface between two minerals can trap a confined water film, whose stability depends on the coupling between an osmotic pressure and a Debye-Hückel double layer effect. At the microscopic scale, the contact between two grains under stress can self-organize in actual contacts that support the stress, and fluid inclusions. At this scale, the process of stress-enhanced dissolution (i.e. pressure solution creep) can be divided into three successive steps: 1) dissolution along the grain interface, controlled by stress; 2) diffusion of solutes towards the pore space; 3) precipitation of the free pore surface. The slowest of these steps imposes the overall deformation rate. At a mesoscopic scale, I propose a compaction model for sediments, where the rock is modeled as an aggregate of truncated spheres, representing individual grains. This model can fit porosity-depth data in quartz-rich sedimentary basins. Finally, at the macroscopic scale, when a reactive fluid circulates in a porous medium, a dissolution-transport instability can emerge, leading to the formation of unstable dissolution channels. I have reproduced experimentally this instability and showed that a reaction front can localize dissolution, and eventually deformation.
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https://tel.archives-ouvertes.fr/tel-00498542
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Submitted on : Wednesday, July 7, 2010 - 5:09:52 PM
Last modification on : Friday, July 17, 2020 - 5:08:15 PM
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  • HAL Id : tel-00498542, version 1

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Francois Renard. La déformation mécano-chimique dans la croûte supérieure terrestre . Exemples de processus couplés et de systèmes auto-organisés. Tectonique. Université Joseph-Fourier - Grenoble I, 1997. Français. ⟨tel-00498542⟩

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