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spelling ftccsdartic:oai:HAL:insu-00717692v1 2023-05-15T16:39:22+02:00 Redox control of sulfur degassing in silicic magmas Scaillet, Bruno Clémente, Béatrice Evans, Bernard W. Pichavant, Michel Centre de Recherche sur la Synthèse et la Chimie des Minéraux (CRSCM) Centre National de la Recherche Scientifique (CNRS) Institut des Sciences de la Terre d'Orléans (ISTO) Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS) Department of Earth and Space Sciences Seattle University of Washington Seattle Department of Geological Sciences 1998 https://hal-insu.archives-ouvertes.fr/insu-00717692 https://hal-insu.archives-ouvertes.fr/insu-00717692/document https://hal-insu.archives-ouvertes.fr/insu-00717692/file/Scaillet-JGR-1998.pdf https://doi.org/10.1029/98JB02301 en eng HAL CCSD American Geophysical Union info:eu-repo/semantics/altIdentifier/doi/10.1029/98JB02301 insu-00717692 https://hal-insu.archives-ouvertes.fr/insu-00717692 https://hal-insu.archives-ouvertes.fr/insu-00717692/document https://hal-insu.archives-ouvertes.fr/insu-00717692/file/Scaillet-JGR-1998.pdf doi:10.1029/98JB02301 info:eu-repo/semantics/OpenAccess ISSN: 2169-9313 EISSN: 2169-9356 Journal of Geophysical Research : Solid Earth https://hal-insu.archives-ouvertes.fr/insu-00717692 Journal of Geophysical Research : Solid Earth, American Geophysical Union, 1998, 103 (B10), pp.23,937-23,949. ⟨10.1029/98JB02301⟩ [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology [SDE.MCG]Environmental Sciences/Global Changes info:eu-repo/semantics/article Journal articles 1998 ftccsdartic https://doi.org/10.1029/98JB02301 2021-10-24T16:16:36Z International audience Explosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an excess of sulfur relative to that calculated from melt degassing. If this excess sulfur is stored in a fluid phase, it implies a strong preference of sulfur for the fluid over the melt under oxidized conditions, with fluid/melt partition coefficients varying between 50 and 2612, depending on melt composition. Experimentally determined sulfur partition coefficients for a dacite bulk composition confirm this trend and show that in volcanic eruptions displaying excess gaseous sulfur, the magmas were probably fluid-saturated at depth. The experiments show that in more reduced silicic magmas, those coexisting only with pyrrhotite, the partition coefficient decreases dramatically to values around 1, because pyrrhotite locks up nearly all the sulfur of the magma. Reevaluation of the sulfur yields of some major historical eruptions in the light of these results shows that for oxidized magmas, the presence of 1-5 wt % fluid may indeed account for the differences observed between the petrologic estimate of the sulfur yield and that constrained from ice core data. Explosive eruptions of very large magnitude but involving reduced and cool silicic magmas, such as the Toba or the Bishop events, release only minor amounts of sulfur and could have consequently negligible long-term (years to centuries) atmospherical effects. This redox control on sulfur release diminishes as the melt composition becomes less silicic and as temperature increases, because both factors favor more efficient melt sulfur degassing owing to the increased diffusivity of sulfur in silicate melts under such conditions. Article in Journal/Newspaper ice core Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Journal of Geophysical Research: Solid Earth 103 B10 23937 23949
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 [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology
[SDE.MCG]Environmental Sciences/Global Changes
spellingShingle [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology
[SDE.MCG]Environmental Sciences/Global Changes
Scaillet, Bruno
Clémente, Béatrice
Evans, Bernard W.
Pichavant, Michel
Redox control of sulfur degassing in silicic magmas
topic_facet [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology
[SDE.MCG]Environmental Sciences/Global Changes
description International audience Explosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an excess of sulfur relative to that calculated from melt degassing. If this excess sulfur is stored in a fluid phase, it implies a strong preference of sulfur for the fluid over the melt under oxidized conditions, with fluid/melt partition coefficients varying between 50 and 2612, depending on melt composition. Experimentally determined sulfur partition coefficients for a dacite bulk composition confirm this trend and show that in volcanic eruptions displaying excess gaseous sulfur, the magmas were probably fluid-saturated at depth. The experiments show that in more reduced silicic magmas, those coexisting only with pyrrhotite, the partition coefficient decreases dramatically to values around 1, because pyrrhotite locks up nearly all the sulfur of the magma. Reevaluation of the sulfur yields of some major historical eruptions in the light of these results shows that for oxidized magmas, the presence of 1-5 wt % fluid may indeed account for the differences observed between the petrologic estimate of the sulfur yield and that constrained from ice core data. Explosive eruptions of very large magnitude but involving reduced and cool silicic magmas, such as the Toba or the Bishop events, release only minor amounts of sulfur and could have consequently negligible long-term (years to centuries) atmospherical effects. This redox control on sulfur release diminishes as the melt composition becomes less silicic and as temperature increases, because both factors favor more efficient melt sulfur degassing owing to the increased diffusivity of sulfur in silicate melts under such conditions.
author2 Centre de Recherche sur la Synthèse et la Chimie des Minéraux (CRSCM)
Centre National de la Recherche Scientifique (CNRS)
Institut des Sciences de la Terre d'Orléans (ISTO)
Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
Department of Earth and Space Sciences Seattle
University of Washington Seattle
Department of Geological Sciences
format Article in Journal/Newspaper
author Scaillet, Bruno
Clémente, Béatrice
Evans, Bernard W.
Pichavant, Michel
author_facet Scaillet, Bruno
Clémente, Béatrice
Evans, Bernard W.
Pichavant, Michel
author_sort Scaillet, Bruno
title Redox control of sulfur degassing in silicic magmas
title_short Redox control of sulfur degassing in silicic magmas
title_full Redox control of sulfur degassing in silicic magmas
title_fullStr Redox control of sulfur degassing in silicic magmas
title_full_unstemmed Redox control of sulfur degassing in silicic magmas
title_sort redox control of sulfur degassing in silicic magmas
publisher HAL CCSD
publishDate 1998
url https://hal-insu.archives-ouvertes.fr/insu-00717692
https://hal-insu.archives-ouvertes.fr/insu-00717692/document
https://hal-insu.archives-ouvertes.fr/insu-00717692/file/Scaillet-JGR-1998.pdf
https://doi.org/10.1029/98JB02301
genre ice core
genre_facet ice core
op_source ISSN: 2169-9313
EISSN: 2169-9356
Journal of Geophysical Research : Solid Earth
https://hal-insu.archives-ouvertes.fr/insu-00717692
Journal of Geophysical Research : Solid Earth, American Geophysical Union, 1998, 103 (B10), pp.23,937-23,949. ⟨10.1029/98JB02301⟩
op_relation info:eu-repo/semantics/altIdentifier/doi/10.1029/98JB02301
insu-00717692
https://hal-insu.archives-ouvertes.fr/insu-00717692
https://hal-insu.archives-ouvertes.fr/insu-00717692/document
https://hal-insu.archives-ouvertes.fr/insu-00717692/file/Scaillet-JGR-1998.pdf
doi:10.1029/98JB02301
op_rights info:eu-repo/semantics/OpenAccess
op_doi https://doi.org/10.1029/98JB02301
container_title Journal of Geophysical Research: Solid Earth
container_volume 103
container_issue B10
container_start_page 23937
op_container_end_page 23949
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