[S-GL23] 地球年代学・同位体地球科学

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

*可児 智美¹、三澤 啓司²、森川 徳敏³、風早 康平³、楠原 文武⁴、米田 成一⁵、寺門 靖高⁶ (1.熊本大学大学院自然科学研究科（理学）、2.極地研究所、3.地質調査所、4.電力中央研究所、5.国立科学博物館理工学研究部、6.神戸大学)

キーワード：Sr安定同位体、水、スラブ流体、沈み込み

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.