[S-GL23] Geochronology and Isotope Geology

[SGL23-P04] Stable Sr isotope composition (δ^88/86Sr) of Arima saline water

*Tomomi Kani¹, Keiji Misawa², Noritoshi Morikawa³, Kohei Kazahaya³, Fumitake Kusuhara⁴, Shigekazu Yoneda⁵, Yasutaka Terakado⁶ (1.Department of Earth and Environmental Sciences, Kumamoto University, 2.National Institute of Polar Research, 3.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, 4.Central Research Institute of Electric Power Industry, 5.National Museum of Nature and Science, 6.Graduate School of Human Development and Environment, Kobe University)

Keywords:Stable Sr isotope, water, slab-fluid, subduction

Stable Sr isotope values (δ⁸⁸Sr) of nonvolcanic Arima-type spring water with high salinity were analyzed by TRITONTIMS with correction of isotope fractionation during mass spectrometry with ⁸⁷Sr-⁸⁴Sr double spike. The Arima-type saline water possibly originated from slab-fluid because their oxygen, hydrogen and carbon isotopic compositions are magmatic/hydrothermal. The obtained δ⁸⁸Sr values of the saline water samples from Arima hot spring which range from +0.122‰ to +0.153‰ are lighter than those of surrounding Rokko granites and Arima rhyolitic welded tuff, suggestingthe Sr isotope composition of the saline water is not disturbed by the local rocks. The lighter Sr enriched signature of the saline water can be explained by isotope fractionation during fluid extraction from subducting slab with marine carbonates as a Sr source.