Interactions entre phénomènes tectoniques et magmatiques en contexte d'extension: l'exemple du segment de rift de Dabbahu

Abstract : In this thesis we quantify the interactions between tectonic and magmatic processes in the active Dabbahu rift segment, which experienced in 2005 a major rifting event. Here, we provide accurate constraints at this time scale by producing cosmogenic exposure ages of lavas surfaces and faults scarps, in order to decipher the morphological evolution of a rift depression, and to identify the processes that are responsible for the topography acquisition. The study is based on samples taken on two separate areas of the rift. The field areas were systematically mapped, and all lavas were chemically analysed in major and trace elements. The first studied focused the northern portion of the rift segment, where the lavas of the segment terminating volcano meets the neo-volcanic zone. This area allowed the influence of the presence of such volcanic edifice to be assessed. The second studied area is located at the middle of the segment, and covers the rift western margin up to the rift axis. The topography in this area is sensitive to the evolution in space and time of the location of the different axial magma reservoirs. Our results show that along the rift segment, topography develops during phases of low magmatic activity, and is inhibited during phases of lower magmatic activity. The 2005 appears to be an unusual event that represents about a tenth of the total intrusions necessary to build the depression. The maintaining of magmatic accretion at the axis seems to be the result of a relay between different magma reservoirs. The position of these reservoirs can vary between 0 and 15 km from both sides of the rift axis
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  • HAL Id : tel-01750376, version 1

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Sarah Medynski. Interactions entre phénomènes tectoniques et magmatiques en contexte d'extension: l'exemple du segment de rift de Dabbahu. Sciences de la Terre. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0121⟩. ⟨tel-01750376⟩

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