Genesis of Sr Isotopes in Groundwater of Hebei Plain

To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of ⁸⁷Sr/⁸⁶Sr ratio was studied. It is shown that ⁸⁷Sr/⁸⁶Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to ⁴He_exc and a negative correlation to δ¹⁸O and δD. The groundwater is divided into three groups to discuss the relation between ⁸⁷Sr/⁸⁶Sr ratio and Sr²⁺ content: ① moderate Sr²⁺ content and higher ⁸⁷Sr/⁸⁶Sr ratio (water Ⅰ); ② lower Sr²⁺ content and higher ⁸⁷Sr/⁸⁶Sr ratio (water Ⅱ); and ③ higher Sr²⁺ content and lower ⁸⁷Sr/⁸⁶Sr ratio (water Ⅲ), that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater (Q₄–Q₁) originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate dissolution, with lower ⁸⁷Sr/⁸⁶Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate ⁸⁷Sr/⁸⁶Sr ratio. However, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies.