Temporal changes in the chemistry of lake water within Yugama Crater, Kusatsu-Shirane Volcano, Japan: Implications for the evolution of the magmatic hydrothermal system
Temporal changes in the chemistry of lake water within Yugama Crater, Kusatsu-Shirane Volcano, Japan: Implications for the evolution of the magmatic hydrothermal system
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DOI：
10.1016/j.jvolgeores.2008.06.015
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发表时间：
2008-12-10
影响因子：
2.9
通讯作者：
Nogami, Kenji
中科院分区：
文献类型：
--
作者：
Ohba, Takeshi;Hirabayashi, Jun-ichi;Nogami, Kenji
日本草津白根火山汤间火山口内湖水的化学成分和温度在1966年至2005年期间有明显波动。1966 ~ 1981年水温较低，Cl-和SO 42-浓度逐渐降低。这些趋势是由密封带的生长所解释的，该密封带形成于脱气岩浆周围的热岩区域和地下水饱和的冷地壳之间。封闭带的作用是限制岩浆挥发分的释放。1982年和1983年，汤间火山口内发生了几次蒸汽驱动的爆炸性喷发。火山爆发后，湖水温度升高，SO 42-和阳离子浓度显着增加，虽然没有增加CI-记录。这些变化归因于密封区的破坏。地下水与岩浆房周围的热岩区域（包括密封带）的相互作用增加，产生了富含阳离子和硫酸盐的流体，并将其输送到Yugama湖。1990年，火山地区发生了大量地震。此时，湖水中的CI-浓度迅速增加，而水体pH值下降。这些变化的原因是地下水通过破裂的密封带侵入。侵入水与热岩内部靠近熔融岩浆的区域发生相互作用，热岩中的Cl以HCl的形式溶出到水中，富含HCl的水被输送到汤间湖，导致Cl-浓度升高，pH值降低。1996 ~ 2005年，热岩-水相互作用后HCl从热岩中被提取的顺序再次出现。虽然相互作用的程度比1982 - 1995年的前一个序列小得多，导致没有发生重大喷发。(c)2008 Elsevier B. V.保留所有权利。
The chemical composition and temperature of lake water within Yugama Crater, Kusatsu-Shirane Volcano, Japan, have fluctuated markedly over the period 1966 to 2005. From 1966 to 1981, water temperature was relatively low, and CI- and SO42- concentrations gradually decreased. These trends are explained by the growth of a sealing zone that formed between the region of hot rock surrounding the degassing magma and cool crust saturated with groundwater. The sealing zone acted to restrict the emission of magmatic volatiles. In 1982 and 1983, several steam-driven explosive eruptions occurred within Yugama Crater. Following the eruptions, lake temperature increased and SO42- and cation concentrations increased markedly, although no increase in CI- was recorded. These changes are attributed to a breach of the sealing zone. The increased interaction of groundwater with the hot rock region surrounding the magma chamber, including the sealing zone, produced a cation- and sulfate-rich fluid that was transported to Yugama Lake. A large number of earthquakes occurred in the region of the volcano in 1990. At this time, CI- concentrations in lake water increased rapidly, while water pH dropped. These changes are explained by the invasion of groundwater through the breached sealing zone. The invading water interacted with the inner region of hot rock close to the molten magma, and CI stored in the hot rock was leached to the water as HCI The HCI-enriched water was then transported to Yugama Lake, resulting in the observed increase in CI- concentration and decrease in pH.The sequence of hot rock-water interaction followed by the extraction of HCI from hot rock recurred in 1996 to 2005, although the degree of the interaction was much smaller than the former sequence in 1982 to 1995, resulting in no occurrence of significant eruptions. (c) 2008 Elsevier B.V. All rights reserved.