Backward tracking of gas chemistry measurements at Erebus volcano

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Burgisser, Alain, Oppenheimer, Clive, Alletti, Marina, Kyle, Philip R., Scaillet, Bruno, Carroll, Michael R.
• Other Authors: Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Department of Geology, University of Cambridge UK (CAM), New Mexico Institute of Mining and Technology New Mexico Tech (NMT), Departimento di Scienze della Terra Camerino, Università degli Studi di Camerino (UNICAM), ANT- 0838817 from the Office of Polar Programs (National Science Foundation), European Project: 202844,EC:FP7:ERC,ERC-2007-StG,DEMONS(2008)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: Erebus volcano; eruptive mechanisms; thermodynamics; volcanic gas; geo; envir; Lava Lake; Antarc*; Antarctica
• Online Access: https://doi.org/10.1029/2012GC004243; https://hal-insu.archives-ouvertes.fr/insu-00771966/file/ggge2328.pdf; https://hal-insu.archives-ouvertes.fr/insu-00771966

International audience Erebus volcano in Antarctica offers an exceptional opportunity to probe the dynamics of degassing - its behavior is characterized by an active lava lake through which sporadic Strombolian eruptions occur. Here, we develop a framework for interpreting contrasting degassing signatures measured at high temporal resolution, which integrates physical scenarios of gas/melt separation into a thermodynamic model that includes new volatile solubility data for Erebus phonolite. In this widely applicable framework, the measured gas compositions are backtracked from surface to depth according to physical templates involving various degrees of separation of gas and melt during ascent. Overall, explosive signatures can be explained by large bubbles (gas slugs) rising slowly in equilibrium from at least 20 bars but at most a few hundred bars in a magmatic column closer to the stagnant end-member than the convecting end-member. The span of explosive signatures can be due to various departure depths and/or slug acceleration below a few tens of bars. Results also reveal that explosive gases last equilibrated at temperatures up to 300 degrees C colder than the lake due to rapid gas expansion just prior to bursting. This picture (individual rise of gas and melt batches from a single, potentially very shallow phonolitic source) offers an alternative to the conclusions of previous work based on a similar data set at Erebus, according to which differences between quiescent and explosive gas signatures are due to the decompression of two deep, volatile-saturated sources that mixed to various degrees (phonolite at 1-3 kbar and basanite at 5-8 kbar).