JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-GL Geology

[S-GL34] Geochronology and Isotope Geology

convener:Takahiro Tagami(Graduate School of Science, Kyoto University), Yuji Sano(Division of Ocean and Earth Systems, Atmosphere and Ocean Research Institute, University of Tokyo)

[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.