[H-TT18] 環境トレーサビリティー手法の開発と適用

[HTT18-P09] Geochemical characteristics of hydrothermal fluids observed along Median Tectonic Line in Mie-Prefecture, Japan.

*Umam Rofiqul¹、谷水 雅治¹、杉本 直人¹、仲井 涼¹、森 康則² (1.Kwansei Gakuin University、2.Mie Prefecture Health and Environmental Research Institute, Japan)

キーワード：Groundwater、Geofluid、Median Tectonic Line、Mass spectrometry、Hot spring

Island arc magmatism is considered to be triggered by the addition of fluids dehydrated from subducting slab. The relationship among volcanism, hydrothermal ore forming, and hot spring in island arc is therefore important to understand distribution of geofluid in the area. We investigated hot spring in Mie-prefecture to estimate their origin. Various types of hot spring are observed in that area, and their origin and characteristics are estimated from dissolved trace element concentrations and their isotope systematics.

We investigated the ratios of ¹¹B/¹⁰B and ⁷Li/⁶Li of hot spring water samples as well as ¹⁸O/¹⁶O and D/H isotope ratios of water. Resultant ¹⁸O/¹⁶O-D/H ratios of water were mainly plotted along the fractionation trend of meteoric water and a mixing trend with seawater, but some samples have isotopic shifts toward heavy ¹⁸O/¹⁶O ratios, which indicate interactions with rocks under high temperature. Their ¹¹B/¹⁰B and ⁷Li/⁶Li ratios showed very low values for some samples, which suggest that the fluids are originated from deeper part of the earth crust. In addition, a decoupling between the two isotope systems is observed.