[S-GL34] Geochronology and Isotope Geology

[SGL34-P03] Stable Sr isotopes of saline water from non-volcanic Arima-type spring in Japan: Sr isotope fractionation during fluid generation from subducting carbonate?

*Tomomi Kani¹, Keiji Misawa², Noritoshi Morikawa³, Kohei Kazahaya³, Fumitake Kusuhara⁴, Yasutaka Terakado⁵ (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 (AIST) , 4.Central Research Institute of Electric Power Industry , 5.Graduate School of Human Development and Environment, Kobe University )

Keywords:slab-fluid, subduction, geofluid, water

Stable Sr isotope values (δ⁸⁸Sr) of saline water, which were sampled from Arima-type springs in Japan, were analyzed by TRITON TIMS with correction of isotope fractionation during mass spectrometry with ⁸⁷Sr-⁸⁴Sr double spike. The saline water samples were collected from Arima hot spring in Hyogo prefecture and Kashio mineral spring in Nagano prefecture. The Arima-type saline water possibly originated deep fluids derived from subducting slab rather than palaeoseawater buried in an aquifer, based on oxygen, hydrogen, helium and carbon isotopic compositions. The new obtained δ⁸⁸Sr values (0.11) of the saline water samples from Arima hot spring in this work are lower than those of surrounding Rokko granitoids and tuff (0.2) and the Phanerozoic mean of carbonates (0.16). The obtained δ⁸⁸Sr value (0.13) of the Kashio saline water is low as much as that of Arima saline water. The low δ⁸⁸Sr of Arima-type saline water indicate Sr isotope fractionation during fluid extraction from subducting oceanic plate with marine carbonates.