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DTSTART;TZID=Europe/Paris:20191018T180000
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CREATED:20191003T072637Z
LAST-MODIFIED:20191003T072637Z
UID:20736-1571421600-1571428800@lmv.uca.fr
SUMMARY:Soutenance de thèse de Swetha Venugopal
DESCRIPTION:Swetha Venugopal soutiendra sa thèse le vendredi 18\noctobre à 9h (heure locale de Vancouver ; 18h à Clermont) dans la salle\nn°2020 à la bibliothèque de l’Université Simon Fraser (Vancouver\, Canada). \nVous trouverez\nci-dessous le titre et le résumé de la thèse. \nTitre : From magmatic sources to volcanic gas emissions: insight from the\nGaribaldi Volcanic Belt\, western Canada \nJury: \nDirector: Tim Druitt (UCA)\nDirectrice: Severine Moune (UCA)\nDirector: Glyn Williams-Jones (SFU) \nExaminatrice: Gwenn Flowers (SFU)\nExaminatrice: Nathalie Vigouroux-Callibiot (Douglas College) \nRapporteur: Brendan Dyck (SFU)\nRapporteur: Jacob Lowenstern (USGS) \nRésumé: \nVolcanoes are the surficial representation of the complex interplay of\nmagmatic\, crustal\, and hydrothermal processes operating below the Earth’s\nsurface. Studying volcanic deposits provides a unique snapshot into the\ncomposition of the deep mantle source. Melt inclusions\, which are small\npockets of magma trapped inside growing crystals\, preserve multi-faceted\nrecords of magma petrogenesis. Additionally\, the magma at depth contains a\nsignificant proportion of dissolved magmatic gases. Once these gases\nbecome saturated in the magma\, they exsolve into a separate vapour phase\nand ascend quickly to the surface\, where they are released as volcanic\ngases. The composition of gases at the surface can provide valuable\ninsight into the composition of the magma at depth\, as well as the\nshallow-level hydrothermal system. Volcanic gases are an important factor\ncontrolling whether an eruption is gentle and effusive\, or violent and\nexplosive. A greater amount of gas that separates at depth can trigger\nlarge\, explosive eruptions (Devine et al.\, 1998; Shinohara\, 2008).\nTherefore\, gas detection at the surface is an essential monitoring tool\nfor eruption forecasting. In this thesis\, I begin with an in-depth look\ninside glassy and crystallized olivine-hosted melt inclusions and assess\nthe nature of micron-scale solid phases occupying the vapour bubble. From\nhere\, major\, volatile and trace element compositions of olivine-hosted\nmelt inclusions from every centre along the Garibaldi Volcanic Belt (GVB)\nreveals a north to south transition from an enriched mantle signature\, to\na subduction-modified depleted mantle source. Finally\, the recent\nre-discovery of fumaroles beneath the summit glacier of Mount Meager has\nprompted the first MultiGAS survey in the GVB. The plumes are H2S\, CO2 and\nH2O rich\, and hot enough to melt through the overlying ice. Can the\nbasaltic magma\, represented by melt inclusions\, produce the volcanic gases\ncurrently emitted at the surface? To test this\, two different gas\nmodelling software (SolEx and MagmaSat) are used\, along with original and\nrecalculated (with the bubble components) as input parameters. The\nresulting molar ratios are compared with MultiGAS ratios of fumaroles.\nOverall\, SolEx closed-system degassing using recalculated melt inclusions\nyields the best approximation to MultiGAS ratios. This thesis addresses a\ncompositional knowledge gap within the GVB. By understanding both the\ndistinct magmatic sources underlying the arc\, as well as the composition\nof volcanic gases emanating from summit fumaroles\, we gain a broad and\ncomprehensive geochemical overview of the Garibaldi Volcanic Belt.
URL:https://lmv.uca.fr/agenda/soutenance-de-these-de-swetha-venugopal/
ATTACH;FMTTYPE=image/jpeg:https://lmv.uca.fr/wp-content/uploads/2019/10/Swetha-Defence-poster.jpg
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