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Fusion partielle d'un manteau métasomatisé par un liquide adakitique : approches géochimique et expérimentale de la genèse et de l'évolution des magmas de l'arrière-arc équatorien

Abstract : The Puyo cones, the Mera series and the Pan de Azúcar stratovolcano, three Plio-Quaternary formations located in the Ecuadorian volcanic rear-arc (Oriente), erupted silica-poor potassic lavas. The origin and the evolution of these magmas were constrained by geochemical modelling and an experimental melting study performed in a piston-cylinder device. First, the lherzolitic mantle wedge was metasomatized by 3-5% of silicic liquids generated by the melting of the subducted slab. Second, it partially melts (F = 1-4%) between 2-3 GPa and 1170-1400°C, leaving a garnet ± phlogopite-bearing residue. Whereas the Mera and Pan de Azúcar series differentiate by fractional crystallization, only a small variation of the degree of partial melting accounts for the whole Puyo series. The involvement of silicic liquids during the genesis of the Oriente lavas points to the influence of the subducted Carnegie Ridge in the volcanic rear-arc and suggests that the ridge was present in the Ecuadorian subduction zone before the lower Pleistocene.
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Submitted on : Wednesday, September 5, 2012 - 3:54:53 PM
Last modification on : Friday, April 5, 2019 - 8:12:29 PM
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  • HAL Id : tel-00728340, version 1

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Géraldine Hoffer. Fusion partielle d'un manteau métasomatisé par un liquide adakitique : approches géochimique et expérimentale de la genèse et de l'évolution des magmas de l'arrière-arc équatorien. Géochimie. Université Blaise Pascal - Clermont-Ferrand II, 2008. Français. ⟨NNT : 2008CLF21824⟩. ⟨tel-00728340⟩

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