Lithium isotope systematics of Arima hot spring waters and groundwaters in Kii Peninsula

• DOI: 10.2343/geochemj.gj22015
• Publication Date: 2022-09-07T22:08:49Z
• Authors: Rofiqul Umam; Masaharu Tanimizu; Hitomi Nakamura; Yoshiro Nishio; Ryo Nakai; Naoto Sugimoto; Yasunori Mori; Yuuki Kobayashi; Akane Ito; Shigeyuki Wakaki; Kazuya Nagaishi; Tsuyoshi Ishikawa
• Keywords: Forearc; Slab; Fumarole; Peninsula

Slab-dehydrated fluid is considered to be involved in island arc magmatism. In this study, Li isotope ratios were determined for deep groundwater samples from the non-volcanic forearc region of SW Japan. The contribution slab-dehydrated Philippine Sea Plate (PHS) was investigated Arima area and eastern Kii Peninsula area, corresponding slab depths ~60 km 20-30 km, respectively. high-temperature thermal waters with high salinity called Arima-type clarified have low δ7Li values +1-+3‰. concentrations are thought result fluid-rock interactions at temperatures, which consistent characteristics fluid. On other hand, groundwaters showed a wide range +2 +29‰. Several had similar chemical property fluid: values, Cl/Li ratios, 87Sr/86Sr around 0.708-0.710. They distributed along Median Tectonic Line (MTL) within about 20 south MTL. These results indicate common supply fluids Japan PHS large faults, will useful indicator detect their contribution.