Specificity in magma preparation processes for large caldera-forming eruptions

2023 Fiscal Year Final Research Report

• Project/Area Number: 20H02001
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Hokkaido University
• Principal Investigator: Kuritani Takeshi 北海道大学, 理学研究院, 教授 (80397900)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: カルデラ / 珪長質マグマ / マグマ溜まり / 火山岩 / U-Th放射非平衡

Outline of Final Research Achievements

Regarding the question of why catastrophic caldera-forming eruptions occur, petrological and geochemical analyses, including U-Th disequilibrium analyses, were conducted on eruptive products from some representative caldera volcanoes in Japan, with the aim of clarifying the uniqueness and factors behind the preparation of huge felsic magmas. As a result, an interesting commonality was found in all the studied caldera volcanoes: the voluminous felsic magmas responsible for the caldera-forming eruptions consisted of the main long-lived (>400 kyrs) felsic magmas and additional magmas that were generated intermittently in younger periods.

Free Research Field

火成岩岩石学・地球化学

Academic Significance and Societal Importance of the Research Achievements

破局的噴火の発生要因の理解は、地球科学の枠組みに収まらず、気候環境や防災面の観点から人類共通の課題でもある。巨大カルデラ形成噴火の研究における主な問題点は、(1) 膨大な量のマグマが生成・蓄積するメカニズムは何か？(2) 噴火を引き起こすメカニズムは何か？(3) 現在形成されつつある巨大マグマ溜りをどのように検知するか？という点であるが、本研究ではこのうち(1)に関わる、巨大カルデラ火山のマグマ系の発達過程を根源的に理解するための手がかりが得られたといえる。