日本地球惑星科学連合2019年大会

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[J] ポスター発表

セッション記号 A (大気水圏科学) » A-HW 水文・陸水・地下水学・水環境

[A-HW24] 同位体水文学 2019

2019年5月27日(月) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:安原 正也(立正大学地球環境科学部)、風早 康平(産業技術総合研究所活断層・火山研究部門)、大沢 信二(京都大学大学院理学研究科附属地球熱学研究施設(別府))、浅井 和由(株式会社 地球科学研究所)

[AHW24-P06] Geochemical characteristics and origin of groundwater in central to eastern Hokkaido

*中垣 優盛1 (1.千葉大学)

Japanese island arc is located in the subduction system where the groundwater migration/circulation is significant. Groundwater has chemical history of dissolved components that come from deep part. There are many reports about chemical composition of groundwater in Hokkaido. However, there is little geochemical research about chemical constituents derived from deep in the groundwater in Hokkaido. The relationship between geological features and chemical characteristics of groundwater remains unknown. This study focused on the geochemistry of deep fluid collected from hot springs in central to eastern Hokkaido area to understand the origin and underground geochemical processes by analyzing main and trace elements, hydrocarbon gas, and oxygen-hydrogen isotopes.

The concentrations of dissolved major elements such as Cl, suggested that groundwater in Hokkaido is mainly of seawater origin. The δ18O and δD values, however, indicate that the fluid also contains meteoric water. The redox condition of deep environment had changed the concentrations of Mn and SO4, and the weathering of sedimentary rocks had increased the amount of Si, respectively. Iodine was significantly enriched compared to seawater, resulting from the deposition of I-rich marine algae in the internal shallow water zone. Concentrations of trace elements such as Pb, Zn, and Li vary among sampling locations, which indicates elution of Pb and Zn by the weathering of minerals, and release of Li from clay minerals in high temperature environment.