Remobilization of silicic intrusion by mafic magmas during the 2010 Eyjafjallajökull eruption

• Published in: Solid Earth
• Main Authors: Sigmarsson, Olgeir, Vlastélic, Ivan, Andreasen, R., Bindeman, I., Devidal, Jean-Luc, Moune, Séverine, Keiding, J.K., Larsen, G., Höskuldsson, A., Thordarson, T.
• Other Authors: Laboratoire Magmas et Volcans (LMV), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS), University of Iceland Reykjavik, Imperial College London, University of Oregon Eugene, German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), University of Edinburgh (Edin.)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology; Eyjafjallajökull; Iceland
• Online Access: https://insu.hal.science/insu-02949513; https://insu.hal.science/insu-02949513/document; https://insu.hal.science/insu-02949513/file/se-2-271-2011.pdf; https://doi.org/10.5194/se-2-271-2011

International audience Injection of basaltic magmas into silicic crustal holding chambers and subsequent magma mingling or mixing is a process that has been recognised since the late seventies as resulting in explosive eruptions. Detailed reconstruction and assessment of the mixing process caused by such intrusion is now possible because of the exceptional time-sequence sample suite available from the tephra fallout of the 2010 summit eruption at Eyjafjallajökull volcano in South Iceland. Fallout from 14 to 19 April contains three glass types of basaltic, intermediate, and silicic compositions recording rapid magma mingling without homogenisation, involving evolved FeTi-basalt and silicic melt with composition identical to that produced by the 1821–1823 AD Eyjafjallajökull summit eruption. The time-dependent change in the magma composition suggests a binary mixing process with changing end-member compositions and proportions. Beginning of May, a new injection of primitive basalt was recorded by deep seismicity, appearance of Mg-rich olivine phenocrysts together with high sulphur dioxide output and presence of sulphide crystals. Thus, the composition of the basaltic injection became more magnesian and hotter with time provoking changes in the silicic mixing end-member from pre-existing melt to the solid carapace of the magma chamber. Finally, decreasing proportions of the mafic end-member with time in the erupted mixed-magma demonstrate that injections of Mg-rich basalt was the motor of the 2010 Eyjafjallajökull explosive eruption, and that its decreasing inflow terminated the eruption. Significant quantity of silicic magma is thus still present in the interior of the volcano. Our results show that detailed sampling during the entire eruption was essential for deciphering the complex magmatic processes at play, i.e. the dynamics of the magma mingling and mixing. Finally, the rapid compositional changes in the eruptive products suggest that magma mingling occurs on a timescale of a few hours to days whereas the ...