关键词: 温泉, 水化学, 同位素, 碱性, 云南

Abstract:

The Wangjiazhuang hot spring is located in the Liuchang Township in Xiangyun County of Yunnan, China. The water samples YMD10-1 (from the Wangjia geothermal well) and YMD10-2 (from the Julong hot spring well) range in TDS from 1.49 to 1.65 g/L. The cation and anion are predominated by Na⁺and $HCO_{3}^{-}$ and the hot water is of HCO₃-Na type. The pH values of the water samples are 10.8 and 7, respectively. Because of the high $p_{co_{2}}$ in the YMD10-2 sample, the pH value measured in the field is lower than expected. The pH values measured in laboratory are 8 and 7.6, respectively, which are mainly affected by the diffe-rence in $p_{co_{2}}$, resulting in changes in the carbonate compositions in the water samples. δ ²H and δ ¹⁸O data of the hot water samples indicate that the hot spring is of meteoric origin. The recharge altitude of the hot water is estimated as 2 845-2 865 m, the temperature of the geothermal reservoir as 89-92 ℃, and the depth of the groundwater circulation as approximately 3 808-3 898 m. The age of the hot spring is estimated as 319-447 a with the ²²⁶Ra-²²²Rn method. After receiving recharge from infiltration of precipitation in the surrounding mountain areas, the groundwater undergoes deep circulation and is heated by heat flow, and flows up along the fault zone through the Quaternary sediments and emerges on the lad surface. The alkalinity of the hot spring is attributed to the reaction of feldspar with water and CO₂, resulting in high concentrations of $HCO_{3}^{-}$, and hydro-lysis of $HCO_{3}^{-}$ in solution possibly consumes H⁺ to produce OH^-. The Wangjiazhuang hot spring is used to produce alkali by local people due to high contents of Na⁺, $HCO_{3}^{-}$ and $CO_{3}^{2-}$ in the hot water.

Key words: hot spring, hydrochemistry, isotope, alkalinity, Yunnan