V026-06
Investigation of Magmatic and Hydrothermal Processes at Erebus Volcano, Antarctica

Thursday, 10 December 2020: 19:20
Virtual
Tehnuka Ilanko, University of Waikato, Earth & Ocean Sciences, Hamilton, New Zealand, Clive Oppenheimer, Department of Geography, University of Cambridge, Cambridge, United Kingdom, Tobias P Fischer, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, United States, Aaron Curtis, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States, Alain Burgisser, Institut de Sciences de la Terre, Université Savoie Mont Blanc, Le Bourget du Lac, France, Hyunwoo Lee, School of Earth & Environmental Sciences, Seoul National University, Seoul, South Korea, Yuji Sano, Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan and Philip R Kyle, Department of Earth & Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM, United States
Recorded Presentation
Abstract:
The geochemistry of gas emissions measured at active volcanoes reflects the interplay of complex subsurface and atmospheric processes. Interpretation of observed gas compositions is, therefore, not straightforward, but a combination of lab and field approaches can further our understanding of these mechanisms and their effects on volcanic activity.

Here, we examine magmatic and hydrothermal processes at Erebus volcano, Antarctica. Degassing from its lava lake and associated vents in the summit crater, and from low-temperature vents and diffuse sources on and around the summit cone, allows us to map spatial variations in gas chemistry. We report measurements of lava lake and high-temperature vent emissions made using open-path FTIR spectroscopy in the field. Our data shed light on magma transport and gas separation dynamics that relate directly to observed lava lake activity and eruptive style (e.g. bubble bursts [1]). We also collected gas samples from low-temperature degassing sources. These are easily identified thanks to the ambient climate and include warm ground, and vents in ice towers or ice caves. We analysed samples from these sites for gas molecular and isotopic (carbon and nitrogen) compositions.

We identify cyclic changes in degassing via the lava lake, a pattern also evident in emissions from small hot vents within the summit crater. Analyses of periodicity in different gas species enable us to distinguish between redox- and solubility-dominated changes in gas chemistry associated with shallow magma transport [2]. The dynamic morphology of vents in the summit crater, and differences between their gas compositions, suggest complex shallow plumbing systems, with segregated magmatic or gas-only pathways that can shift observably within timescales of days. Gases at low-temperature sites reflect the interaction of magmatic gas with the volcanic edifice [3]: compositions are dominated by air, potentially entrained through the flanks of the volcano, while carbon isotope data suggest interaction with a hydrothermal system fed by snow and ice melt.

[1] Ilanko et al. 2015, GeoResJ

[2] Ilanko et al. 2015, Bull. Volcanol.

[3] Ilanko et al. 2019, J. Volcanol. Geotherm. Res.

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