フィリピン共和国,イロシン火砕流堆積物とそれに伴う降下火山灰の岩石記載的特徴  [in Japanese] Petrography of Irosin Ignimbrite and Co-ignimbrite Ash Fall Deposits, Southeast Luzon, Philippines  [in Japanese]

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Author(s)

    • 奥野 充 OKUNO Mitsuru
    • 福岡大学理学部・産学官連携研究機関国際火山噴火史情報研究所 Faculty of Science, also AIG Collaborative Research Institute for International Study on Eruptive History and Informatics, Fukuoka University
    • 鳥井 真之 TORII Masayuki
    • 熊本大学大学院自然科学研究科附属減災型社会システム実践研究教育センター The Implementation Research and Education System Center for Reducing Disaster Risk, Kumamoto University
    • 小林 哲夫 KOBAYASHI Tetsuo
    • 鹿児島大学大学院理工学研究科(理学系) Graduate School of Science and Engineering (Science Course), Kagoshima University

Abstract

 Irosin ignimbrite (41 cal kBP) and its related deposits were the first widespread tephra recognized in the Philippines. This paper describes petrographic properties such as the particle composition and refractive index of the volcanic glass, in order to understand the nature of the eruption that emplaced these deposits. Green hornblende, cummingtonite, and biotite were observed in most of the samples analyzed, but green hornblende was not observed in some pumice clasts from the ignimbrite. However, it occurred in the matrix of the ignimbrite, co-ignimbrite ash, and plinian pumice samples. These results are probably due to small amounts of green hornblende phenocryst in the pumice fragments. The coexistence of cummingtonite and biotite in pumice indicates differences in crystallization conditions within the magma reservoir. A basal ash from the Malobago lava dome that preceded the ignimbrite eruption contains isolated crystals of orthopyroxene and irregular glass shards. The pumiceous deposit within the caldera shows slightly different petrographic properties (e.g. wider range of refractive index) from the other samples, which supports the interpretation of Irosin ignimbrite being reworked within the caldera.

Journal

  • Journal of Geography (Chigaku Zasshi)

    Journal of Geography (Chigaku Zasshi) 123(1), 143-152, 2014

    Tokyo Geographical Society

Codes

  • NII Article ID (NAID)
    130003395489
  • NII NACSIS-CAT ID (NCID)
    AN00322536
  • Text Lang
    JPN
  • ISSN
    0022-135X
  • NDL Article ID
    025300758
  • NDL Call No.
    Z15-169
  • Data Source
    NDL  J-STAGE 
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