Explosive style, magma degassing and evolution in the Chaimilla eruption, Villarrica volcano, Southern Andes

Article Article scientifique Article Explosive style, magma degassing and evolution in the Chaimilla eruption, Villarrica volcano, Southern Andes eng 2015 author Pioli Laura 685658 author Scalisi Rosalinda 679584 author Costantini Licia 638056 author Di Muro A. author Bonadonna Costanza 0000-0002-2368-2193 636612 author Clavero J. 10.1007/s00445-015-0976-1 0258-8900 http://link.springer.com/10.1007/s00445-015-0976-1 Villarrica (Chile) is a basaltic stratovolcano, currently in an open-conduit condition. It now has relatively frequent Strombolian and effusive eruptions, but it had large explosive eruptions in prehistoric times. Among them, the most recent eruption was Chaimilla, which occurred about 3100 years ago and produced deposits that indicate complex,multiphase eruptive dynamics. Significant differences in mineralogy and glass compositions of the erupted scoria suggest the eruption was fed by two distinct magma batches with similar bulk compositions but distinct crystallization and degassing histories. The lower sequence scoria has a complex crystal assemblage with several crystal populations produced by mixing between a relatively degassed magma containing Fo 75-79 olivine, normally or reversely zoned plagioclase (An70-94) and augite (type 1 magma), and a subordinate volume of more-primitive and more volatile-rich magma rising from depth (type 2 magma) and carrying normally zoned plagioclase and higher-Mg (Fo81-85) olivine crystals. Type 2 magma was the main component emitted during the larger and more explosive eruptive phase that deposited the upper sequence. The Chaimilla eruption occurred under closed-vent conditions and was fed by water-rich magmas. Whencompared with the petrological features of the magma currently erupted at Villarrica, which has slightly more evolved bulk compositions, lower crystal content and lower water content,these results suggest that the evolution in eruptive style of the volcano from highly explosive to a lava lake/Strombolian activity corresponds to significant changes in the shallow plumbing system (which is now at much shallower depths);these plumbing-system changes were not associated with significant changes in the parental magma compositions. Dewey 550 Swiss National Science Foundation Two phase flow regimes in low viscosity magmas CH Project funding Swiss National Science Foundation Characterization of the dynamics and the products of basaltic explosive volcanism CH Project funding 42 Département des sciences de la Terre 154 false 667 Physical Volcanology and Geological Risk Bulletin of volcanology 77:93 e3e267a4-4807-436e-afad-86ab12f58a81 Article (Published version) Restricted art%3A10.1007%2Fs00445-015-0976-1.pdf 3253622 application/pdf restrictedAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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Explosive style, magma degassing and evolution in the Chaimilla eruption, Villarrica volcano, Southern Andes	Bulletin of volcanology			2015	709	1

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Scalisi, Rosalinda