The Possible Source of Abnormally High Sodium Content in Low‐Salinity Geothermal Water

Abstract

The dissolution of sodium-containing minerals in high-temperature geothermal systems can cause Na + to exceed 400 mg/L with high salinity. But the Na + of low-salinity geothermal water is mostly less than 100 mg/L in medium-low temperature geothermal systems. However, geothermal water with Na + up to 325.4 mg/L and total dissolved solids less than 650 mg/L was found in the Huangshadong geothermal field, which is a typical medium-low temperature hydrothermal system in South China. The water chemistry results indicate that thermal groundwater is uniformly HCO 3 -Na type with high sodium content (average 240.06 mg/L). All the thermal groundwater and shallow groundwater have the same meteoric origin based on δD and δ 18 O. According to water chemical geothermometers and multicomponent mineral equilibrium (MME) method, the reservoir temperature is estimated to be 100 to 130 • C at a maximum depth of 2.43 km. The estimation of the Cl − mixed indicator suggests that geothermal water has mixed with 51% to 72% of shallow groundwater, resulting in the reduction of Na + content in real geothermal water (Na + up to 685.2 mg/L). The simulated results of water-rock interactions indicate that mineral dissolution and ion exchange have minor contributions to Na + enrichment in geothermal water. Hydrochemical simulations and Gibbs diagrams suggest an additional source of high sodium: granite fluid inclusions are fractured into geothermal water at high temperatures. Granite fluid inclusions may only account for 3% to 5% of geothermal water, but they provide the main source of Na + in geothermal water.

Application of Geochemical Modelling and Multiple Regression Analysis to Reassess Groundwater Evolution in Kaduna Basin, NW Nigeria

“…The electrical conductivity was excluded due to peculiarity with TDS. The TDS measures water's ionic content from rock mineral dissolution [104,105]. A significant relationship between TDS and some elements indicates a major elemental effect on the hydrochemistry of groundwater [106,107].…”

Geochemical and Isotopic Techniques Constraints on the Origin, Evolution, and Residence Time of Low‐enthalpy Geothermal Water in Western Wugongshan, SE China

“…9a), indicating cation exchange had occurred. In geothermal water, Na + deposited by clay minerals in the surrounding rock was exchanged for Ca 2+ and Mg 2+ , which increased Na + and decreased Ca 2+ and Mg 2+ (Mao et al, 2022). Samples of surface water and cold springs are concentrated near the origin and are not significantly affected by cation exchange processes.…”

The additional acceleration of geothermal water flow in the discharge section by the geothermal driving force

“…In this paper, a set of hydrochemical and isotopic data from a convective geothermal system is employed to assess the magnitude of the additional driving force in the discharge section and the effect on the velocity of groundwater flow in the Huangshadong geothermal field, South China. The hydrochemical characteristics of Huangshadong geothermal field and the sources of hydrochemical components have been discussed (Mao et al, 2022), but the distribution of temperature and flow velocity of geothermal water in Huangshadong geothermal field is rarely discussed. Here, we try to identify a quantitative method for evaluating geothermal driving forces and to provide new insights for their effects on the velocity of groundwater flow.…”