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Determination of volatiles in magma by micro-gas-analysis of melt inclutions in phenocrysts

Research Project

Project/Area Number 63470031
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field 分析・地球化学
Research InstitutionOkayama University

Principal Investigator

KUSAKABE Minoru  Institute for Study of the Earth's Interior, Okayama University, Professor, 地球内部研究センター, 教授 (20015770)

Project Period (FY) 1988 – 1989
Project Status Completed (Fiscal Year 1989)
Budget Amount *help
¥5,100,000 (Direct Cost: ¥5,100,000)
Fiscal Year 1989: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1988: ¥4,400,000 (Direct Cost: ¥4,400,000)
Keywordsphenocryst / melt inclusions / magma / volatiles in magma / laser / quadrupole mass spectrometer / 斑晶中のガラス包有物 / レーザー溶融法
Research Abstract

The volatile compositions in maama can be obtained by micro-gas-analysis of glass inclusions in phenocrysts which can be regarded as a part of a "quenched magma". The system for gas extraction by laser heating followed by QMS analysis was assembled to determine H_2O and CO_2 contents in glasses on a 100 mum scale. A ND-YAG laser with a beam diameter of 10 mum And the energy of 7W was used to melt glasses in vacuum. The evolved gases were collected in a liquid air cold trap. CO_2 was separated from H_2O by trap work. In order to avoid the absorption of H_2O onto walls of the extraction line, H_2O was reduced to H_2 by reaction with a heated uranium metal. The resulting H_2 and CO_2 were determined by a statically operated QMS. The linear calibration curves were obtained in the range between 0.04-99 ng for H_2O and 0.01-18 ng for CO_2. The pit volume which released H_2O and CO_2 was estimated from the diameter and depth of the pit. The mass of the glass melted was calculated from the pit volume and the density of the glass. The gas concentrations were obtained by dividing the amount of H_2 and CO_2 determined by the mass of the glass melted.
Glassy margin of the Mariana Trough basalt (H_2O=1.37 wt% and CO_2=326 ppm) was used to test this technique. The amount of the evolved gases from each pit with a size ranging from 90 to 300 mum in diameter and from 15 to 110 mum in depth was between 30-120 ng for H_2O and between 0.08-1.2 ng for CO_2. The microanalysis showed 1.4<plus-minus>0.2 (S.E.) wt% for H_2O and 390<plus-minus>40 (S.E.) ppm for CO_2 based on 6 independent analyses. With the present technique, a melt inclusion with a diameter of ca. 150 mum can be analyzed, assuming the inclusion has the above gas composition.

Report

(3 results)
  • 1989 Annual Research Report   Final Research Report Summary
  • 1988 Annual Research Report
  • Research Products

    (5 results)

All Other

All Publications (5 results)

  • [Publications] 斎藤元治,日下部実: "火山噴火におけるマグマ中の揮発性物質の挙動-斑晶中のガラス包有物の分析に基づくアプロ-チ-" 火山(第2集). 34. 275-293 (1989)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] Genji Saitoh and Minoru Kusakabe: "Behavior of magmatic volatiles in volcanic eruptions based on glass inclusion analysis" Bull. Volcanol. Soc. Japan. 34(4). 275-293 (1989)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] 斎藤元治,日下部実: "火山噴火におけるマグマ中の揮発性物質の挙動ー斑晶中のガラス包有物の分析に基づくアプロ-チー" 火山(第2集). 34. 275-293 (1989)

    • Related Report
      1989 Annual Research Report
  • [Publications] 日下部実: 火山(第2集). 34. (1989)

    • Related Report
      1988 Annual Research Report
  • [Publications] 斎藤元治: 火山(第2集). 34. (1989)

    • Related Report
      1988 Annual Research Report

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Published: 1988-04-01   Modified: 2016-04-21  

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