In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt
International audience Iron oxidation state and environment in magmas affect their phase diagram and their properties, including viscosity and density, which determine magma mobility and eruptive potential. In turn, magma composition, pressure, temperature and oxygen fugacity affect iron oxidation s...
Published in: | Contributions to Mineralogy and Petrology |
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ftccsdartic:oai:HAL:hal-02989564v1 2023-05-15T13:54:51+02:00 In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt Le losq, Charles Moretti, Roberto Oppenheimer, Clive Baudelet, François Neuville, Daniel Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP) Australian National University (ANU) Observatoire Volcanologique et Sismologique de Guadeloupe (OVSG) Institut de Physique du Globe de Paris University of Cambridge UK (CAM) Synchrotron SOLEIL (SSOLEIL) Centre National de la Recherche Scientifique (CNRS) 2020 https://hal.archives-ouvertes.fr/hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564/document https://hal.archives-ouvertes.fr/hal-02989564/file/CTMP-D-20-00018_R1.-HALpdf.pdf https://doi.org/10.1007/s00410-020-01701-4 en eng HAL CCSD Springer Verlag info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-020-01701-4 hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564/document https://hal.archives-ouvertes.fr/hal-02989564/file/CTMP-D-20-00018_R1.-HALpdf.pdf doi:10.1007/s00410-020-01701-4 info:eu-repo/semantics/OpenAccess ISSN: 0010-7999 EISSN: 1432-0967 Contributions to Mineralogy and Petrology https://hal.archives-ouvertes.fr/hal-02989564 Contributions to Mineralogy and Petrology, Springer Verlag, 2020, 175 (7), pp.64. ⟨10.1007/s00410-020-01701-4⟩ volcano XANES spectroscopy [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology info:eu-repo/semantics/article Journal articles 2020 ftccsdartic https://doi.org/10.1007/s00410-020-01701-4 2021-10-24T00:28:41Z International audience Iron oxidation state and environment in magmas affect their phase diagram and their properties, including viscosity and density, which determine magma mobility and eruptive potential. In turn, magma composition, pressure, temperature and oxygen fugacity affect iron oxidation state and coordination, potentially leading to complex feedbacks associated with magma ascent, degassing and eruption. While equilibrium experiments and models have led to a deep understanding of the role of iron in melts, our knowledge of the effects of disequilibrium processes on iron oxidation state and its structural role in lavas and magmas remains limited. Accordingly, we performed a series of dynamic disequilibrium experiments on a natural melt composition (a phonolite lava from Erebus volcano, Antarctica) at atmospheric pressure, in which oxygen fugacity and temperature were controlled and varied. During the experiments, we continuously measured iron oxidation and coordination using Fe K-edge dispersive X-ray Absorption Spectroscopy (XAS). We found that iron oxidation state changes in the phonolite melt are reversible and well reproduced by existing models. Changes in iron oxidation state are driven by joint diffusion of alkali cations and oxygen anions at magmatic temperatures (~ 1000 °C for Erebus phonolite). However, redox diffusion timescales are too slow for any significant oxygen exchange with the atmosphere at the lava/air interface or via air entrainment. Turning to iron coordination, while Fe 2+ and Fe 3+ are present mostly in an average five-fold coordination, complex coordination variations decoupled from redox changes were detected. The data suggest transitions between Fe 3+ in four-fold and six-fold coordination prior to reduction or as a consequence of oxidation. This questions the possible implication of Fe coordination changes in triggering crystallisation of magnetite nanolites upon magma ascent, and, through such crystallisation events, in promoting magma explosivity. Article in Journal/Newspaper Antarc* Antarctica Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Contributions to Mineralogy and Petrology 175 7 |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
volcano XANES spectroscopy [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology |
spellingShingle |
volcano XANES spectroscopy [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology Le losq, Charles Moretti, Roberto Oppenheimer, Clive Baudelet, François Neuville, Daniel In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
topic_facet |
volcano XANES spectroscopy [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology |
description |
International audience Iron oxidation state and environment in magmas affect their phase diagram and their properties, including viscosity and density, which determine magma mobility and eruptive potential. In turn, magma composition, pressure, temperature and oxygen fugacity affect iron oxidation state and coordination, potentially leading to complex feedbacks associated with magma ascent, degassing and eruption. While equilibrium experiments and models have led to a deep understanding of the role of iron in melts, our knowledge of the effects of disequilibrium processes on iron oxidation state and its structural role in lavas and magmas remains limited. Accordingly, we performed a series of dynamic disequilibrium experiments on a natural melt composition (a phonolite lava from Erebus volcano, Antarctica) at atmospheric pressure, in which oxygen fugacity and temperature were controlled and varied. During the experiments, we continuously measured iron oxidation and coordination using Fe K-edge dispersive X-ray Absorption Spectroscopy (XAS). We found that iron oxidation state changes in the phonolite melt are reversible and well reproduced by existing models. Changes in iron oxidation state are driven by joint diffusion of alkali cations and oxygen anions at magmatic temperatures (~ 1000 °C for Erebus phonolite). However, redox diffusion timescales are too slow for any significant oxygen exchange with the atmosphere at the lava/air interface or via air entrainment. Turning to iron coordination, while Fe 2+ and Fe 3+ are present mostly in an average five-fold coordination, complex coordination variations decoupled from redox changes were detected. The data suggest transitions between Fe 3+ in four-fold and six-fold coordination prior to reduction or as a consequence of oxidation. This questions the possible implication of Fe coordination changes in triggering crystallisation of magnetite nanolites upon magma ascent, and, through such crystallisation events, in promoting magma explosivity. |
author2 |
Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP) Australian National University (ANU) Observatoire Volcanologique et Sismologique de Guadeloupe (OVSG) Institut de Physique du Globe de Paris University of Cambridge UK (CAM) Synchrotron SOLEIL (SSOLEIL) Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Le losq, Charles Moretti, Roberto Oppenheimer, Clive Baudelet, François Neuville, Daniel |
author_facet |
Le losq, Charles Moretti, Roberto Oppenheimer, Clive Baudelet, François Neuville, Daniel |
author_sort |
Le losq, Charles |
title |
In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
title_short |
In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
title_full |
In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
title_fullStr |
In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
title_full_unstemmed |
In situ XANES study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
title_sort |
in situ xanes study of the influence of varying temperature and oxygen fugacity on iron oxidation state and coordination in a phonolitic melt |
publisher |
HAL CCSD |
publishDate |
2020 |
url |
https://hal.archives-ouvertes.fr/hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564/document https://hal.archives-ouvertes.fr/hal-02989564/file/CTMP-D-20-00018_R1.-HALpdf.pdf https://doi.org/10.1007/s00410-020-01701-4 |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
ISSN: 0010-7999 EISSN: 1432-0967 Contributions to Mineralogy and Petrology https://hal.archives-ouvertes.fr/hal-02989564 Contributions to Mineralogy and Petrology, Springer Verlag, 2020, 175 (7), pp.64. ⟨10.1007/s00410-020-01701-4⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-020-01701-4 hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564 https://hal.archives-ouvertes.fr/hal-02989564/document https://hal.archives-ouvertes.fr/hal-02989564/file/CTMP-D-20-00018_R1.-HALpdf.pdf doi:10.1007/s00410-020-01701-4 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1007/s00410-020-01701-4 |
container_title |
Contributions to Mineralogy and Petrology |
container_volume |
175 |
container_issue |
7 |
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