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Devenir d'une lithosphère en subduction dans le manteau terrestre : Etude de sa déformation et des flux mantelliques associés

Abstract : In this thesis, I provide a tighter constraint on the range of possible viscosity ratio between the slab and the surrounding mantle that mainly controls slab deformation and mantle flow associated. To quantify the viscosity contrast between the slab and surrounding mantle, I used the rheological dependence of the geometrical response of a viscous subducting slab, subjected to mantle flow induced by slab motion. By combining results from analogue experiments, semi-analytic solutions and 3D numerical methods, I was able to quantify the fate of a subducting slab in the mantle. The comparison of these model results, with geophysical data (mainly seismic tomography and earthquake distributions on a selection of subduction zones) indicated that the viscosity contrast between the slab and upper mantle is small and should not exceed 100. According to this weak slab prediction, the geometry of a subducting slab was observed to ultimately evolve into a "jellyfish" like shape. The weak slab prediction also provides a new explanation of the seismic anomalies observed in the deep mantle. Additionally, in order to support the observed slab penetration into the lower mantle, combined with the assumption of a weak slab, it was also possible to constrain the density contrast and the viscosity structure of the mantle, in particular, the ratio of upper to lower mantle viscosity.
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https://tel.archives-ouvertes.fr/tel-00583031
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Submitted on : Monday, April 4, 2011 - 4:49:11 PM
Last modification on : Thursday, January 14, 2021 - 11:39:28 AM
Long-term archiving on: : Thursday, March 30, 2017 - 9:11:54 AM

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  • HAL Id : tel-00583031, version 1

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Christelle Loiselet. Devenir d'une lithosphère en subduction dans le manteau terrestre : Etude de sa déformation et des flux mantelliques associés. Géologie appliquée. Université Rennes 1, 2009. Français. ⟨tel-00583031⟩

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