Mechanisms of oxidation and degassing in the Takanoobane rhyolite lava of Aso Volcano, Japan

Kuniyuki Furukawa, Koji Uno, Isoji Miyagi

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Vertical variation of the oxidation state as recorded by Fe-Ti oxides of Takanoobane rhyolite lava (TR lava) is revealed on the basis of petrographic and rock magnetic studies. Petrographic observations of the interior of TR lava showed that Fe-Ti oxides are preferentially oxidized along the flow structure that is characterized by the light-colored band composed of aggregates of deformed minute cavities, whereas both the top and bottom parts of the lava are not oxidized. Rock magnetic studies measuring thermal demagnetization of a three-component isothermal remanent magnetization (IRM) and magnetic susceptibility revealed that hematite of a highly oxidized state is formed preferentially along the light-colored band, consistent with the petrographic observations. The observed preferential oxidation of the light-colored band is adequately explained by post-eruptive degassing of hydrogen from the interior of the lava, rather than migration of atmospheric oxygen into the hot interior of the cooling lava against the back-streaming volcanic gas. The magmatic volatiles emitted from the interior can be transported effectively through the light-colored band and microcracks which ubiquitously develop nearly vertical to the flow direction. The degassing mechanism should be limited to highly viscous silicic lavas such as rhyolite because the mechanism requires development of the flow structure and the microcracks as the pathways for gases. These structures are achieved only in highly viscous silicic lavas.

Original languageEnglish
Pages (from-to)348-354
Number of pages7
JournalJournal of Volcanology and Geothermal Research
Volume198
Issue number3-4
DOIs
Publication statusPublished - Dec 15 2010

Fingerprint

rhyolite
Volcanoes
degassing
Degassing
Microcracks
lava
Flow structure
volcanoes
Oxides
Japan
Volcanic Eruptions
volcano
Rocks
oxidation
Demagnetization
Oxidation
Magnetic susceptibility
microcracks
microcrack
flow structure

Keywords

  • Aso
  • Fe-Ti oxide
  • Lava
  • Oxidation
  • Oxygen fugacity
  • Rhyolite

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Mechanisms of oxidation and degassing in the Takanoobane rhyolite lava of Aso Volcano, Japan. / Furukawa, Kuniyuki; Uno, Koji; Miyagi, Isoji.

In: Journal of Volcanology and Geothermal Research, Vol. 198, No. 3-4, 15.12.2010, p. 348-354.

Research output: Contribution to journalArticle

@article{6214fb0f1bd54584b157a4ff307132fe,
title = "Mechanisms of oxidation and degassing in the Takanoobane rhyolite lava of Aso Volcano, Japan",
abstract = "Vertical variation of the oxidation state as recorded by Fe-Ti oxides of Takanoobane rhyolite lava (TR lava) is revealed on the basis of petrographic and rock magnetic studies. Petrographic observations of the interior of TR lava showed that Fe-Ti oxides are preferentially oxidized along the flow structure that is characterized by the light-colored band composed of aggregates of deformed minute cavities, whereas both the top and bottom parts of the lava are not oxidized. Rock magnetic studies measuring thermal demagnetization of a three-component isothermal remanent magnetization (IRM) and magnetic susceptibility revealed that hematite of a highly oxidized state is formed preferentially along the light-colored band, consistent with the petrographic observations. The observed preferential oxidation of the light-colored band is adequately explained by post-eruptive degassing of hydrogen from the interior of the lava, rather than migration of atmospheric oxygen into the hot interior of the cooling lava against the back-streaming volcanic gas. The magmatic volatiles emitted from the interior can be transported effectively through the light-colored band and microcracks which ubiquitously develop nearly vertical to the flow direction. The degassing mechanism should be limited to highly viscous silicic lavas such as rhyolite because the mechanism requires development of the flow structure and the microcracks as the pathways for gases. These structures are achieved only in highly viscous silicic lavas.",
keywords = "Aso, Fe-Ti oxide, Lava, Oxidation, Oxygen fugacity, Rhyolite",
author = "Kuniyuki Furukawa and Koji Uno and Isoji Miyagi",
year = "2010",
month = "12",
day = "15",
doi = "10.1016/j.jvolgeores.2010.09.015",
language = "English",
volume = "198",
pages = "348--354",
journal = "Journal of Volcanology and Geothermal Research",
issn = "0377-0273",
publisher = "Elsevier",
number = "3-4",

}

TY - JOUR

T1 - Mechanisms of oxidation and degassing in the Takanoobane rhyolite lava of Aso Volcano, Japan

AU - Furukawa, Kuniyuki

AU - Uno, Koji

AU - Miyagi, Isoji

PY - 2010/12/15

Y1 - 2010/12/15

N2 - Vertical variation of the oxidation state as recorded by Fe-Ti oxides of Takanoobane rhyolite lava (TR lava) is revealed on the basis of petrographic and rock magnetic studies. Petrographic observations of the interior of TR lava showed that Fe-Ti oxides are preferentially oxidized along the flow structure that is characterized by the light-colored band composed of aggregates of deformed minute cavities, whereas both the top and bottom parts of the lava are not oxidized. Rock magnetic studies measuring thermal demagnetization of a three-component isothermal remanent magnetization (IRM) and magnetic susceptibility revealed that hematite of a highly oxidized state is formed preferentially along the light-colored band, consistent with the petrographic observations. The observed preferential oxidation of the light-colored band is adequately explained by post-eruptive degassing of hydrogen from the interior of the lava, rather than migration of atmospheric oxygen into the hot interior of the cooling lava against the back-streaming volcanic gas. The magmatic volatiles emitted from the interior can be transported effectively through the light-colored band and microcracks which ubiquitously develop nearly vertical to the flow direction. The degassing mechanism should be limited to highly viscous silicic lavas such as rhyolite because the mechanism requires development of the flow structure and the microcracks as the pathways for gases. These structures are achieved only in highly viscous silicic lavas.

AB - Vertical variation of the oxidation state as recorded by Fe-Ti oxides of Takanoobane rhyolite lava (TR lava) is revealed on the basis of petrographic and rock magnetic studies. Petrographic observations of the interior of TR lava showed that Fe-Ti oxides are preferentially oxidized along the flow structure that is characterized by the light-colored band composed of aggregates of deformed minute cavities, whereas both the top and bottom parts of the lava are not oxidized. Rock magnetic studies measuring thermal demagnetization of a three-component isothermal remanent magnetization (IRM) and magnetic susceptibility revealed that hematite of a highly oxidized state is formed preferentially along the light-colored band, consistent with the petrographic observations. The observed preferential oxidation of the light-colored band is adequately explained by post-eruptive degassing of hydrogen from the interior of the lava, rather than migration of atmospheric oxygen into the hot interior of the cooling lava against the back-streaming volcanic gas. The magmatic volatiles emitted from the interior can be transported effectively through the light-colored band and microcracks which ubiquitously develop nearly vertical to the flow direction. The degassing mechanism should be limited to highly viscous silicic lavas such as rhyolite because the mechanism requires development of the flow structure and the microcracks as the pathways for gases. These structures are achieved only in highly viscous silicic lavas.

KW - Aso

KW - Fe-Ti oxide

KW - Lava

KW - Oxidation

KW - Oxygen fugacity

KW - Rhyolite

UR - http://www.scopus.com/inward/record.url?scp=78649634792&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78649634792&partnerID=8YFLogxK

U2 - 10.1016/j.jvolgeores.2010.09.015

DO - 10.1016/j.jvolgeores.2010.09.015

M3 - Article

VL - 198

SP - 348

EP - 354

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

SN - 0377-0273

IS - 3-4

ER -