群馬県万座地域主要源泉の溶存成分濃度経年変化

概要

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Long-term changes in temperature, pH and major element chemistry during 1969 and 1999 were investigated for the three hot springs, Manza-Yubatake, Okumanza and Manza-Karabuki, in the Manza hot spring area located in the western foot of Kusatsu-Shirane volcano, Gunma, Japan. At Manza-Yubatake and Okumanza, water temperatures have been decreasing for at least these 60 years except occasionally small irregular changes probably accompanied by the change of volcanic activity of Kusatsu-Shirane volcano. The concentrations of dissolved components of Manza-Karabuki water have widely fluctuated obviously related with volcanic activities, while the water temperature has rarely been fluctuated. The waters of the three hot springs show similar ratios among the concentration of the analyzed dissolved components except calcium and sulfate ions, which are possibly controlled by the solubility of gypsum. The similarity of chemical composition and the highest concentration of dissolved species in the Manza-Karabuki waters indicate that Manza-Yubatake and Okumanza waters are formed by the mixing between local meteoric water and the Manza-Karabuki water, which has the closest chemical composition to the primitive hydrothermal fluids related to the volcanic activity in the Manza area.
日本地球化学会の論文
2002-03-10