Measurement of Water Dissolved in the Groundmass Glass in the Ejecta of the September 2004 Eruptions from the Asama Volcano, Central Japan

• MAKINO Kuniaki

  Department of Geology, Faculty of Science, Shinshu University

• TSUGANE Tatsuro

  Division of Environmental System Science, Graduate School of Science and Technology, Shinshu University

• SONEHARA Takafumi

  Division of Environmental System Science, Graduate School of Science and Technology, Shinshu University

• MIYAKE Yasuyuki

  Department of Geology, Faculty of Science, Shinshu University

Bibliographic Information

Other Title

• 浅間火山2004年9月の噴出物の石基ガラスの含水量測定
• アサマ カザン 2004ネン 9ガツ ノ フンシュツブツ ノ セッキ ガラス ノ ガン スイリョウ ソクテイ

Abstract

Infrared absorption spectra were taken to determine concentration of water dissolved in rhyolitic glass of pumice, scoria and andesite fragments ejected by the Asama 2004 September eruptions. As the groundmass in the fragments includes a lot of microlites of plagioclase and pyroxene, thickness of the volcanic glass itself is difficult to measure directly. However, an absorption peak, assigned to volcanic glass, is observed at 1,850cm^-1, and its peak intensity obtained by a curve-fitting method gives the net thickness of the glass. This net thickness provides the intensities of water per glass thickness without microlite contamination. The relationship between water concentration and two absorption peak-intensity (3,570, 1,630cm^-1) is derived from infrared analyses of the aphyric Wada obsidian, whose water content was determined by Karl Fischer titrator. Following the above procedure, the water contents in the glass of the pumice of the September 1st eruption, and scoria and andesite fragments of the September 23rd eruption are estimated to be 0.66, 0.1, 0.1-0.2wt%, respectively. The magma represented by the quenched marginal crust of the pumice preserves considerable amount of water (0.66wt%) for its shallow location beneath the crater floor, prior to the September 1st eruption. The tensile strength of the cap rock presumably kept sufficient pressure in the top of the magma column to dissolve water into the magma, whereas the magma providing the scoria and andesite fragments of the September 23rd eruption lost most of water.

Journal

• BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN

  BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN 51 (3), 151-159, 2006

  The Volcanological Society of Japan

Keywords

• Asama September eruptions
• ejecta
• Karl Fischer titrator
• infrared absorption
• water content

Details

• CRID: 1390282679281590784
• NII Article ID: 110004751971
• NII Book ID: AN10512786
• DOI: 10.18940/kazan.51.3_151
• ISSN: 21897182
• ISSN: 04534360
• NDL BIB ID: 8041516
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I8041516
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed