Brine samples from the wells in the Kashio mineral spring (an “Arima-type” hot spring at Ooshika-Mura, central Japan) were analyzed to determine the original chemical and isotopic compositions of the deep brine end-member before its dilution by meteoric water and to elucidate the origin of the end-member. The trends of variation between Cl, δD, and δ 18 O indicated the existence of a two-component mixing system and a systematic variation in the mixing ratio, which were mentioned in previous studies. By carefully tracking the variation in tritium ( 3 H) and atmospheric noble gas in the brine, the Cl concentration in the end-member was determined to be 24,000 mg/L. This value is consistent with the result of previous studies. Based on the estimated composition and other related data, we inferred that the end-member originated from slab-derived fluid, which in turn may have undergone oxygen isotope exchange reactions with minerals. Although both the Arima and Kashio brines are considered to be derived from fluid dehydrated from the Philippine Sea slab, the chemical and isotopic compositions of the Kashio end-member are different from those of the Arima end-member. In particular, the Kashio end-member is characterized by low Cl concentration (~ 40% lower than that in the Arima end-member), low hydrogen isotope ratio, and low 3 He/ 4 He ratio (1.4 Ra). These results indicate that the chemical and isotopic compositions of the slab-derived fluid are different for each location. The significant difference in δD could reflect the difference in the dehydration depth. Finally, the low temperature and relatively low 3 He/ 4 He ratio of the brine end-member could be explained by its long residence time within the crust.

中文翻译：

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日本中部Kashio矿泉板片源深层卤水的原始成分及形成过程

对 Kashio 矿泉（日本中部大鹿村的“Arima 型”温泉）井中的盐水样品进行了分析，以确定在被大气水稀释之前深部盐水端元的原始化学和同位素组成并阐明端元的起源。Cl、δD 和 δ 18 O 之间的变化趋势表明存在双组分混合系统和混合比的系统变化，这在之前的研究中已经提到。通过仔细跟踪盐水中氚 ( 3 H) 和大气惰性气体的变化，确定端部中的 Cl 浓度为 24,000 mg/L。该值与以往研究的结果一致。根据估计的成分和其他相关数据，我们推断端元起源于板片衍生流体，进而可能与矿物发生了氧同位素交换反应。尽管 Arima 和 Kashio 卤水都被认为来自菲律宾海板块脱水的流体，但 Kashio 端元的化学和同位素组成与 Arima 端元不同。特别是，Kashio 端元的特点是低 Cl 浓度（比 Arima 端元低约 40%）、低氢同位素比和低 3 He/4 He 比（1.4 Ra）。这些结果表明板片衍生流体的化学和同位素组成在每个位置都不同。δD 的显着差异可以反映脱水深度的差异。最后，