Variations in thermal state revealed by the geochemistry of fumarolic gases and hot-spring waters of the Tateyama volcanic hydrothermal system, Japan
Variations in thermal state revealed by the geochemistry of fumarolic gases and hot-spring waters of the Tateyama volcanic hydrothermal system, Japan
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DOI：
10.1007/s00445-018-1264-7
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发表时间：
2019-01
影响因子：
3.5
通讯作者：
K. Seki;T. Ohba;Shinnosuke Aoyama;Y. Ueno;H. Sumino;W. Kanda;Muga Yaguchi;Toshiya Tanbo
中科院分区：
文献类型：
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作者：
K. Seki;T. Ohba;Shinnosuke Aoyama;Y. Ueno;H. Sumino;W. Kanda;Muga Yaguchi;Toshiya Tanbo
本研究报告了2015年和2016年在立山火山（日本中部）的次谷采集的温泉沃茨和火山气体的化学和同位素组成，以揭示底层热液系统的状态。我们从热液系统温度变化的角度讨论了地球化学数据时间变化的原因，并阐明了温泉沃茨水与喷气气体之间的关系。由深部岩浆提供的火山气体在到达浅部时分离成液相和气相。每个阶段形成以下三种类型的温泉水：（1）高阴离子浓度和同位素组成类似于岩浆水，（2）同位素组成低于第1类沃茨，Cl−/SO 42 −变化较大，（3）低Cl−和总阴离子浓度。1型和2型温泉的形成受岩浆成分HCl和SO2的影响。我们认为，第一类温泉是来自液相，而第二类温泉是来自气相的两相区。Cl−/SO 42 −的时间变化被认为是由液体和蒸汽分离的储层中的温度变化引起的，因为蒸汽和液相之间的HCl分配系数强烈依赖于温度。第三类温泉是从气相中提取的，其中HCl和SO2含量很低。我们认为，2型温泉的Cl−浓度可能是火山活动的一种衡量标准，因为它反映了潜水喷发发生的浅层两相区的热状态。
This study reports the chemical and isotopic compositions of hot-spring waters and fumarolic gases sampled in the Jigokudani Valley of Tateyama Volcano (central Japan) in 2015 and 2016 to reveal the state of the underlying hydrothermal system. We discuss the cause of temporal variations in geochemical data in terms of temperature change in the hydrothermal system and clarify the relationship between hot-spring waters and fumarolic gases. The volcanic gas supplied from deep-seated magma was separated into liquid and vapor phases when it reached a shallow depth. Each phase formed the following three types of hot-spring water: (1) high anion concentrations and isotopic compositions similar to magmatic water, (2) lower isotopic compositions compared to type-1 waters and large variations in Cl−/SO42−, and (3) low Cl−and total anion concentrations. The formation of type-1 and type-2 hot springs was influenced by magmatic components such as HCl and SO2. We consider that type-1 hot springs are derived from the liquid phase while type-2 hot springs are derived from the vapor phase of the two-phase zone. The temporal variations in Cl−/SO42−are considered to result from temperature changes in the reservoir where liquid and vapor separated, as the HCl partitioning coefficient between the vapor and liquid phases is strongly dependent on temperature. Type-3 hot springs are derived from the vapor phase, which is depleted in HCl and SO2. We propose that the Cl−concentration of type-2 hot springs could be a measure of volcanic activity because it reflects the thermal state of the shallow two-phase zone where phreatic eruptions occur.