Spatial and temporal variations of gas geochemistry at Mt. Ontake, Japan
Author
dc.contributor.author
Kagoshima, Takanori
Author
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Sano, Yuji
Author
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Takahata, Naoto
Author
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Ishida, Akizumi
Author
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Tomonaga, Yama
Author
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Roulleau, Emilie
Author
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Pinti, Daniele L.
Author
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Fischer, Tobías P.
Author
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Lan, Tefang
Author
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Nishio, Yoshiro
Author
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Tsunogai, Urumu
Author
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Guo, Zhengfu
Admission date
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2017-11-21T15:07:22Z
Available date
dc.date.available
2017-11-21T15:07:22Z
Publication date
dc.date.issued
2016
Cita de ítem
dc.identifier.citation
Journal of Volcanology and Geothermal Research 325 (2016) 179–188
es_ES
Identifier
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10.1016/j.jvolgeores.2016.06.013
Identifier
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https://repositorio.uchile.cl/handle/2250/145703
Abstract
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This report describes spatial and temporal variations of helium, carbon, and nitrogen isotopes measured in CO2-rich bubbling gases from natural springs associated with Mt. Ontake (central Honshu, Japan) from November 1981 through September 2015. During the entire period, the He-3/He-4 ratio decreased concomitantly with increasing distance of the sampling site from the central cone. In contrast, the CO2/He-3 ratios and the delta C-13 values of CO2 increased with distance. These spatial trends became more pronounced after the September 27, 2014 Ontake eruption, suggesting reactivation of the volcano plumbing system with enhanced emission of magmatic volatiles, although the spatial trend of nitrogen isotopes disappeared. The 3He/4He ratios of the most proximal site to the central cone remained constant until 2000, apparently increasing from June 2003 through October 2014. They became constant soon after the eruption until September 2015. The ten-year He-3 enhancement might have been a precursor of the 2014 Ontake eruption. In contrast, delta C-13 values of CO2 at the same site remained constant through this period. The lack of delta C-13 anomaly might be attributable to 1) negligibly small amounts of magmatic CO2 introduced into the source of hot springs compared to ambient CO2 in the air-saturated aquifer, or 2) close resemblance of the carbon signature of magmatic CO2 to that of ambient CO2. Therefore its addition cannot change the overall delta C-13 value of the sampled hot springs. At distal sampling sites, no measurable change of helium, carbon, or nitrogen isotopes was observed in relation to the 2014 Ontake eruption, suggesting that the effect of this eruption on the Ontake hydrothermal system was geographically localized.
es_ES
Patrocinador
dc.description.sponsorship
Japan Society for the Promotion of Science
26900002