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Structure des croûtes profondes à déformation syn-magmatique en contexte extensif

Abstract : Seismic reflection profiles of Volcanic Passive Margins show a two-domain reflective lower crust. The particular reflectors are interpreted as mafic intrusions associated to the margin evolution.From those geophysical observations it is not possible to understand the consequences of mafic magma emplacement on the rheology and effective deformation of volcanic margins lower crust. This thesis explores two geologic examples of outcropping lower crusts affected by important volumes of magma during their extensional story: the Ivrea Zone (Italian Alps) and Seiland (Finmarkian Caledonides). An important field study associated to geochemical and isotopic analyses, and to Patersonapparatus deformation experiences led to (1) define a synthetic structure of an extensional lower crust affected by one or more major magmatic events and to indentify a ductile middle crust in the Ivrea Zone where roots the upper crust faults, (2) show the rheologic and deformation evolution of the lower crust in relation to magma emplacement timing, (3) characterize, from Seiland observations, the crustmantle interface in an extensional System. The whole study shows the complexity of the temporal, spatial and structural relationships between mafic rocks (as magma and as crystallised rock) and extensional deformation in the lower crust.
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Submitted on : Friday, January 31, 2020 - 4:54:11 PM
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Marie Bidault. Structure des croûtes profondes à déformation syn-magmatique en contexte extensif. Géophysique [physics.geo-ph]. Université de Bretagne occidentale - Brest, 2019. Français. ⟨NNT : 2019BRES0021⟩. ⟨tel-02463105⟩

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