Importance of Long-Term Shallow Degassing of Basaltic Magma on the Genesis of Massive Felsic Magma Reservoirs: a Case Study of Aso Caldera, Kyushu, Japan

DOI PDF PDF 研究データあり 被引用文献4件 参考文献146件 オープンアクセス
  • Isoji Miyagi
    Geological Survey of Japan , AIST 1-1-1-7 Higashi, Tsukuba, Ibaraki 305-8567, JAPAN
  • Hideo Hoshizumi
    Geological Survey of Japan , AIST 1-1-1-7 Higashi, Tsukuba, Ibaraki 305-8567, JAPAN
  • Taichi Suda
    Geological Survey of Japan , AIST 1-1-1-7 Higashi, Tsukuba, Ibaraki 305-8567, JAPAN
  • Genji Saito
    Geological Survey of Japan , AIST 1-1-1-7 Higashi, Tsukuba, Ibaraki 305-8567, JAPAN
  • Yasuo Miyabuchi
    Center for Water Cycle, Marine Environment and Disaster Management, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, JAPAN
  • Nobuo Geshi
    Geological Survey of Japan , AIST 1-1-1-7 Higashi, Tsukuba, Ibaraki 305-8567, JAPAN

書誌事項

公開日
2023-02-01
資源種別
journal article
権利情報
  • https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model
DOI
  • 10.1093/petrology/egad009
公開者
Oxford University Press (OUP)

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説明

<jats:title>Abstract</jats:title><jats:p>This paper presents the chemical composition (including H2O and CO2) of matrix glass, melt inclusions in phenocrysts, and their host minerals in eruptive products from Aso caldera. We found a group of melt inclusions with clearly lower potassium (0.6–2 wt % K2O at 50–70 wt % SiO2) than previously reported high-K2O whole-rock compositions (3–5 wt % K2O at 55–70 wt % SiO2). While most of the high-K2O intermediate to felsic melt inclusions are vapor undersaturated and show the features of H2O, CO2, and K2O accumulation, the low-K2O basaltic melt already has higher H2O and CO2. We reconcile this discrepancy with a model in which (1) the volatile-rich basalt magmas degas near the surface, (2) migrate back to depths of $\ge$12 km in the crust, and (3) crystallize feldspar and quartz to produce high-K2O felsic melt, (4) magma mixing among the undegassed, degassed, and evolved magmas. By crystallization, about five times as much low-K2O basaltic magma is required to produce high-K2O felsic magma. The quantity of felsic magma ejected from 270 ka (Aso-1) to 90 ka (Aso-4) requires a basalt magma supply rate of 18 to 31 km3/ka. This magma supply rate is comparable to or less than the present-day production rate of degassed magma (73 km3/ka) at an active center of Aso, Nakadake. These findings suggest volcanic gas flux monitoring has the potential to be a ‘basalt usage meter’ during the dormant period of caldera volcanoes.</jats:p>

収録刊行物

  • Journal of Petrology

    Journal of Petrology 64 (3), egad009-, 2023-02-01

    Oxford University Press (OUP)

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