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DTSTART;TZID=Europe/Paris:20180305T140000
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CREATED:20180216T124525Z
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UID:14955-1520258400-1520262000@lmv.uca.fr
SUMMARY:VolcaPot: Sara Di Salvo et Yannick Le Moigne
DESCRIPTION:VolcaPot 5 Mars 2018 à 14h: deux présentations. \n\nSara Di Salvo:\n\nUnravel magmatic system dynamics through in situ isotopic micro-analyses: insights into the Campanian Ignimbrite activity (Campi Flegrei\, Italy) \nLarge compositional variations in ignimbrites reflect significant zoning in shallow magma reservoirs and represent an excellent source of information on magma storage conditions and volcanic evolutionary processes. Configuration of these magma chambers is still not clear\, so its knowledge represents an important task to better understand how emptying dynamics work during large explosive eruptions. \n The Campanian Ignimbrite (CI) eruption\, from Campi Flegrei volcanic field\, Italy\, represents a typical example of such events\, producing a voluminous pyroclastic sequence of trachytic to phonolitic magma around 39 ka ago. Great whole-rock geochemical variations are reported in literature and considerable isotopic dataset exists for products from medial CI outcrops\, suggesting Sr-isotope disequilibria. Nevertheless\, less is known about the isotopic variations in stratigraphic sections of CI from proximal outcrops\, despite its more detailed sequences in the field and the more remarkable heterogeneity of its components. In order to provide a complete picture of the compositional variability within the proximal CI sequences\, we have performed geochemical and isotopic micro-analyses on matrix glasses of all juvenile components of the proximal CI. Samples were collected along six different proximal CI outcrops from all the six stratigraphic units recognised for the proximal CI sequence. Our major and trace element data on matrix glasses and Sr-Nd isotopes point out a much larger geochemical heterogeneity than that already displayed by whole-rock data. \n Moreover\, our detailed micro-analytical data show a compositional complexity even at the micro-scale\, possibly revealing the presence of multiple magma components in the CI system interacting in a complex magmatic network. Recent hypotheses have suggested that the CI magma reservoir evolved by incremental addition of deeper recharge into a high-crystallinity region (i.e. crystal mush)\, from which crystal-poor melts were extracted. In this light\, the present work also contributes to better understand crystal mush systems linked to highly explosive eruptions\, through a detailed in situ isotopic micro-analytical study. \n  \n\nYannick Le Moigne\n\nInvestigating Canada’s deadliest volcanic eruption and mitigating future hazards \nTseax volcano is a small scoria cone associated with a 32 km-long basanite/hawaiite lava flow in NW British Columbia (Canada) and the site of one the youngest and deadliest volcanic eruptions in Canada. An eruption on the mid-1700s killed an estimated 2000 people of the Nisga’a Nation living in two villages near the volcano. A rich oral history has preserved detailed observational accounts of the eruption\, however\, the exact cause of the fatalities remains unclear. Moreover\, only a limited number of scientific studies exist for Tseax\, and thus many questions still need to be addressed.\n Field observations and petrophysical data are characteristics of a very low viscous lava flow and suggest a rapid expension of the flow. Our models show that a large volume and a low viscosity lava emitted during a short period of time could effectively reach the location of the two ancient Nisga’a villages and thus cause fatalities.\n The aim is to establish the sequence and duration of the volcanic events responsible for one Canada’s worst natural disasters through chemical and physical modelling of the eruption. \n 
URL:https://lmv.uca.fr/agenda/volcapot-sara-di-salvo-et-yannick-le-moigne/
CATEGORIES:VolcaPot
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