Magma chamber decompression during explosive caldera-forming eruption of Aira caldera
Magma chamber decompression during explosive caldera-forming eruption of Aira caldera
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DOI：
10.1038/s43247-021-00272-x
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发表时间：
2021-09-29
影响因子：
7.9
通讯作者：
Conway, Chris E.
中科院分区：
文献类型：
--
作者：
Geshi, Nobuo;Yamasaki, Tadashi;Conway, Chris E.
根据对石英湾中水含量的分析，3万年前日本爱乐火山喷发的原生岩浆期早期的大规模岩浆室减压导致了强烈的地面变形和火山口坍塌。岩浆室的减压是火山口坍塌的基本条件。尽管理论模型预测了火山口坍塌前岩浆室的减压，但以前的研究很少证明岩浆室的减压程度。在这里，我们测定了大约30,000年前艾拉火山形成火山喷发的火山碎屑沉积物中的石英玻璃包裹体和包裹体中的水分含量，并将这些数据用于计算岩浆室内的减压。我们发现，在火山口坍塌前大约50公里(3)的岩浆提取过程中，压力从140-260兆帕下降到20-90兆帕。在灾难性的火山口坍塌开始之前，岩浆的提取可能导致了火山口中心的下沉。我们认为，这种变形导致顶板岩石破裂和坍塌进入岩浆室，导致大量褐沸石喷发。
Substantial magma chamber decompression during the early plinian stage of the eruption of Aira volcano, Japan, 30,000 years ago caused intense ground deformation and caldera collapse, according to analyses of water content in quartz embaymentsDecompression of a magma chamber is a fundamental condition of caldera collapse. Although theoretical models have predicted the decompression of magma chambers before caldera collapse, few previous studies have demonstrated the amount of magma chamber decompression. Here, we determine water content in quartz glass embayments and inclusions from pyroclastic deposits of a caldera-forming eruption at Aira volcano approximately 30,000 years ago and apply this data to calculate decompression inside the magma chamber. We identify a pressure drop from 140-260 MPa to 20-90 MPa during the extraction of around 50 km(3) of magma prior to the caldera collapse. The magma extraction may have caused down-sag subsidence at the caldera center before the onset of catastrophic caldera collapse. We propose that this deformation resulted in the fracturing and collapse of the roof rock into the magma chamber, leading to the eruption of massive ignimbrite.