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Les marges passives volcaniques : origine, structure et développement

Abstract : A passive margin is a non-active transition zone between the continental lithosphere and the oceanic lithosphere. Most of passive margins (>50%) show a strong magmatic development. These volcanic passive margins (VPMs) mark the lithospheric breakup over a melted mantle and they are typically characterized by a huge volume of intrusive and extrusive magmatism into the crust during ante-rift, syn-rift, and post-rift periods.Based on bibliographies, seismic data (IONGXT seismic reflection profiles, 3D seismic) and observations and results gained from fieldtrips on East and West Greenland coast, the objectives of this thesis were: (1) to better characterize the tectonic accommodation of the flexure of the upper crust which beneath inner SDRs and the signification of outer SDRs, and (3) to place the magmatic breakup on the scale of the fragmentation of a supercontinent.The main results obtained are: 1) the breakup of a supercontinent is always syn-magmatic. This breakup then propagates in a non-magmatic way (paper in preparation); 2) the outer SDRs are tectonically decoupled from an exhumed continental lower crust.The material of continental origin could exist deeply continuously across a transverse aseismic ridge such as the GIFR (paper submitted); 3) The crustal flexure is also accommodated by the magma that circulate in detachment faults beneath the inner SDRs. There is a decoupling at the extrados zone of the flexure which is accommodated by syn-tectonic magma injections in the form of laccoliths between inner SDRs and upper crust.
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Huixin Guan. Les marges passives volcaniques : origine, structure et développement. Sciences de la Terre. Université de Bretagne occidentale - Brest, 2018. Français. ⟨NNT : 2018BRES0068⟩. ⟨tel-02917958⟩

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