Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

• Published in: Earth and Planetary Science Letters
• Main Authors: Oppenheimer, Clive, Moretti, Roberto, Kyle, Philip R., Eschenbacher, Al, Lowenstern, Jacob B., Hervig, Richard L., Dunbar, Nelia W.
• Other Authors: University of Cambridge UK (CAM), Institut des Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Université de Tours (UT)-Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Napoli (INGV), Istituto Nazionale di Geofisica e Vulcanologia, Centro Interdipartimentale di Ricerca in Ingegneria Ambientale (CIRIAM), Seconda Università degli Studi di Napoli = Second University of Naples, New Mexico Institute of Mining and Technology New Mexico Tech (NMT), Volcano Hazards Team, United States Geological Survey Reston (USGS), ASU School of Earth and Space Exploration (SESE), Arizona State University Tempe (ASU), ANT-0538414 and ANT-0838817 from the Office of Polar Programs (National Science Foundation)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: CO2 fluxing; degassing; Strombolian eruptions; lava lake; melt inclusions; redox; [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology; [SDE.MCG]Environmental Sciences/Global Changes; Lava Lake; Antarc*; Antarctica
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00707142; https://hal-insu.archives-ouvertes.fr/insu-00707142/document; https://hal-insu.archives-ouvertes.fr/insu-00707142/file/Oppenheimer-EPSL-2011.pdf; https://doi.org/10.1016/j.epsl.2011.04.005

International audience Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4 kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer).