کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6439706 1638297 2016 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Resistivity structure and geochemistry of the Jigokudani Valley hydrothermal system, Mt. Tateyama, Japan
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Resistivity structure and geochemistry of the Jigokudani Valley hydrothermal system, Mt. Tateyama, Japan
چکیده انگلیسی
This study clarifies the hydrothermal system of Jigokudani Valley near Mt. Tateyama volcano in Japan by using a combination of audio-frequency magnetotelluric (AMT) survey and hot-spring water analysis in order to assess the potential of future phreatic eruptions in the area. Repeated phreatic eruptions in the area about 40,000 years ago produced the current valley morphology, which is now an active solfatara field dotted with hot springs and fumaroles indicative of a well-developed hydrothermal system. The three-dimensional (3D) resistivity structure of the hydrothermal system was modeled by using the results of an AMT survey conducted at 25 locations across the valley in 2013-2014. The model suggests the presence of a near-surface highly conductive layer of < 50 m in thickness across the entire valley, which is interpreted as a cap rock layer. Immediately below the cap rock is a relatively resistive body interpreted as a gas reservoir. Field measurements of temperature, pH, and electrical conductivity (EC) were taken at various hot springs across the valley, and 12 samples of hot-spring waters were analyzed for major ion chemistry and H2O isotopic ratios. All hot-spring waters had low pH and could be categorized into three types on the basis of the Cl−/SO 42 − concentration ratio, with all falling largely on a mixing line between magmatic fluids and local meteoric water (LMW). The geochemical analysis suggests that the hydrothermal system includes a two-phase zone of vapor-liquid. A comparison of the resistivity structure and the geochemically inferred structure suggests that a hydrothermal reservoir is present at a depth of approximately 500 m, from which hot-spring water differentiates into the three observed types. The two-phase zone appears to be located immediately beneath the cap rock structure. These findings suggest that the hydrothermal system of Jigokudani Valley exhibits a number of factors that could trigger a future phreatic eruption.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Volcanology and Geothermal Research - Volume 325, 1 October 2016, Pages 15-26
نویسندگان
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