Natural springs containing volcanic and magmatic components occur in association with these activities. However, features of deeply originated fluids and solutes were less documented from fields, where active volcanic and magmatic activities are not distributed. To characterize the presence of deep components and identify their major pathways 28 groundwater samples (~ 1230 m deep) were collected from hot spring sites located at western coast of Kumamoto, southwestern Japan, where the typical subduction related magmatisms are absent. The samples were measured for dissolved ion concentrations and stable isotope ratios (δ²H_H2O, δ¹⁸O_H2O, δ¹³C_DIC and δ³⁴S_SO4) that were compared with data of 33 water samples from vicinity surface systems. The groundwaters were classified into three types based on major hydrochemistry: high Cl⁻ fluid, low concentration fluid, and high HCO₃⁻ fluid. Our data set suggests that the high Cl⁻ fluid was formed by saline water mixing with aquifer waters of meteoric origin and subsequently evolved by reverse cation exchange. The low concentration fluid is identical to regional aquifer water of meteoric origin that was subjected to cation exchange. The high HCO₃⁻ fluid showed the highest HCO₃⁻ concentrations (~ 3,888 mg/l) with the highest δ¹³C_DIC (up to − 1.9‰). Based on our carbon mixing model and observed δ²H_H2O and δ¹⁸O_H2O shifts, it is suggested that dissolved carbon of mantle origin and small fraction of fluids generated in deep crust were transported towards surface through structural weakness under open tectonic setting. These deeply derived components were then mixed with waters in the surface systems and diluted. Their impacts on surface hydrological systems were limited in space except few locations, where deeply connected pathways are anticipated along active structural deformations.

含有火山和岩浆成分的天然泉水与这些活动有关。然而，在没有活跃火山和岩浆活动分布的野外，深源流体和溶质的特征记录较少。为了表征深部成分的存在并确定其主要途径，从位于日本西南部熊本西海岸的温泉地点收集了 28 个地下水样品（~ 1230 m 深），那里没有典型的俯冲相关岩浆活动。测量样品的溶解离子浓度和稳定同位素比率（δ ² H _H2O、δ ¹⁸ O _H2O、δ ¹³ C _DIC和 δ ³⁴ S_SO4 ) 与来自邻近地表系统的 33 个水样的数据进行了比较。根据主要水化学将地下水分为三种类型：高Cl ^-流体、低浓度流体和高HCO ₃ ^-流体。我们的数据集表明，高Cl ^-流体是由咸水与来自大气层的含水层水混合形成的，随后通过反向阳离子交换演变而来。低浓度流体与经过阳离子交换的大气来源的区域含水层水相同。高 HCO ₃ ^-流体显示出最高的 HCO ₃ ^-浓度 (~ 3,888 mg/l) 和最高的 δ ¹³ C _DIC（最高 - 1.9‰）。基于我们的碳混合模型和观察到的 δ ² H _H2O和 δ ¹⁸ O _H2O位移，表明地幔来源的溶解碳和深部地壳中产生的小部分流体在开放构造环境下通过结构弱点向地表输送。然后将这些深层衍生的成分与地表系统中的水混合并稀释。除了少数几个地点外，它们对地表水文系统的影响在空间上是有限的，在这些地点预计会沿着活动的结构变形形成深度连接的路径。