Collaborative study between Japan and Philippine on volcanic and geothermal history of Irosin caldera, south Luzon, Philippine

2011 Fiscal Year Final Research Report

• Project/Area Number: 21401005
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 海外学術
• Research Field: Geography
• Research Institution: Fukuoka University
• Principal Investigator: OKUNO Mitsuru 福岡大学, 理学部, 教授 (50309887)
• Co-Investigator(Kenkyū-buntansha): TAGUCHI Sachihiro 福岡大学, 理学部, 教授 (00108771) ; KOBAYASHI Tetsuo 鹿児島大学, 大学院・理工学研究科, 教授 (70112430)
• Co-Investigator(Renkei-kenkyūsha): MORIYA Ichio 金沢大学, 文学部, 名誉教授 (50052494) ; NAKAMURA Toshio 名古屋大学, 年代測定総合研究センター, 教授 (10135387) ; TAKASHIMA Isao 秋田大学, 工学資源学部, 名誉教授 (50163192)
• Project Period (FY): 2009 – 2011
• Keywords: イロシン / カルデラ / 年代測定 / 地熱変質 / 噴火史 / ボーリング掘削 / テフロクロノロジー / 火砕流

Research Abstract

Irosin caldera is located at the southeastern end of Luzon Island, Philippines. Bulusan volcano is a post-caldera cone. To reveal the sequence of the Irosin caldera eruption and the eruptive history of post-caldera volcanism, we conducted a collaborative project with PHIVOLCS. A small lava dome and ash-fall deposits were erupted as forerunners of the main caldera-forming eruption. The first stage of the caldera eruption was the plinian, which occurred shortly before the main ignimbrite eruption. The second stage of the eruption was the formation of the Irosin ignimbrite which can be divided into two units ; the lower fine unit and the upper coarse unit. The fine rhyolitic ash-fall deposit exposed in the summit crater of Inascan cone 80 km from the caldera is regarded as a co-ignimbrite ash-fall associated with the Irosin ignimbrite. Cummingtonite phenocrysts were identified in the Irosin ignimbrite and related deposits. Cored sediments obtained from the caldera are composed mainly of lahar deposits. Rhyolitic to andesitic ashes are intercalated with the sediments. One of them has similar petrographic characteristics with the Irosin ignimbrite. Recent volcanic ash from Bulusan volcano is composed of accessory materials, which involves gypsum. Chemistry and isotopic composition of hot springs distributed around Bulusan volcano suggests that all of the hot springs are dominant in HCO_3 suggesting a steam-heated type of water.

Research Products

• [Journal Article] Eruptions of Bulusan Volcano since November 2010 (2011)
  • Author(s): Okuno, M., Laguerta, E. P., Delos Reyes, P. J., Bornas, M. A. V., Mirabueno, M. H. T., Arpa, M. C. B., Bariso, E., Solidum, R. U. Jr., Taguchi, S., Torii, M. and Kobayashi, T.
  • Journal Title: The Journal of the Geological Society of Japan Volume: 117巻 Pages: XIV-XIV
  • Peer Reviewed
• [Journal Article] The Irosin co-ignimbrite ash-fall deposit : a widespread tephra marker in the Bicol arc, south Luzon, Philippines (2011)
  • Author(s): Mirabueno, M. H. T., Okuno, M., Torii, M., Danhara, T., Laguerta, E. P., Newhall, C. G. and Kobayashi, T.
  • Journal Title: Quaternary International Volume: Vol.246 Pages: 289-295
  • Peer Reviewed
• [Journal Article] テフラ編年学の多様な役割:フィリピン,中国,韓国,日本,アリューシャン列島の研究例
  • Author(s): 奥野充
  • Journal Title: 第四紀研究 Volume: 51巻(印刷中)
  • Peer Reviewed
• [Presentation] イロシンカルデラとブルサン火山の噴火史研究 (2012)
  • Author(s): 奥野充・Mirabueno, M. H. T.・Laguerta, E. P.・Delos Reyes, P. J.・Bornas, M. A. V.・高島勲・鳥井真之・檀原徹・小林哲夫, フィリピン
  • Organizer: 日本地理学会2012年春季学術大会
  • Place of Presentation: 首都大学東京
  • Year and Date: 2012-03-08
• [Presentation] The Irosin co-ignimbrite deposits : discovery of a widespread tephra in the Philippines. International Field Conference and Workshop on Tephrochronology (2010)
  • Author(s): Mirabueno, M. H. T., Okuno, M., Nakamura, T., Torii, M., Danhara, T., Laguerta, E. P., Newhall, C. G. and Kobayashi, T.
  • Organizer: Volcanism and Human Activity "Active Tephra in Kyushu, 2010"
  • Place of Presentation: Kirishima City, Kagoshima, Japan
  • Year and Date: 2010-05-11
• [Presentation] AMS radiocarbon dating for the Irosin ignimbrite and co-ignimbrite ash-fall, southern Luzon, Philippines (2009)
  • Author(s): Mirabueno, M. H. T., Okuno, M., Nakamura, T., Danhara, T., Laguerta, E. P., Newhall, C. G. and Kobayashi, T.
  • Organizer: 20th International Radiocarbon Conference
  • Place of Presentation: Big Island, Hawaii
  • Year and Date: 2009-06-02