Hydrogeochemical Characteristics and Geothermometry Applications of Thermal Waters in Coastal Xinzhou and Shenzao Geothermal Fields, Guangdong, China

Abstract

Two separate groups of geothermal waters have been identified in the coastal region of Guangdong, China. One is Xinzhou thermal water of regional groundwater flow system in a granite batholith and the other is thermal water derived from shallow coastal aquifers in Shenzao geothermal field, characterized by high salinity. The hydrochemical characteristics of the thermal waters were examined and characterized as Na-Cl and Ca-Na-Cl types, which are very similar to that of seawater. The hydrochemical evolution is revealed by analyzing the correlations of components versus Cl and their relative changes for different water samples, reflecting different extents of water-rock interactions and clear mixing trends with seawaters. Nevertheless, isotopic data indicate that thermal waters are all of the meteoric origins. Isotopic data also allowed determination of different recharge elevations and presentation of different mixing proportions of seawater with thermal waters. The reservoir temperatures were estimated by chemical geothermometries and validated by fluid-mineral equilibrium calculations. The most reliable estimates of reservoir temperature lie in the range of 148-162 ∘ C for Xinzhou and the range of 135-144 ∘ C for Shenzao thermal waters, based on the retrograde and prograde solubilities of anhydrite and chalcedony. Finally, a schematic cross-sectional fault-hydrology conceptual model was proposed.

Hydrochemical Characteristics and Temporal Variations of Geothermal Water Quality in Tangtou, Shandong, China

“…The variation of hot water exploitation in geothermal wells over the years is shown in Figure 11. It can be seen that the exploitation of geothermal water from 2005 to 2009 is maintained at 500 m 3 As can be seen from Figure 11, the content of the main chemical components in geothermal water varies obviously and shows certain fluctuation. On the whole, TDS, TH, Na + , Ca 2+ , Cl − , and K + showed a certain stage.…”

“…Generally speaking, Cl − is considered conservative due to the general lack of chlorine-bearing minerals (excluding halite) in aquifers [2,22]. Therefore, Cl − is usually considered as an important parameter in the analysis of geothermal water chemical characteristics [3,23]. The Cl − concentrations of geothermal water versus some major chemical components were illustrated in Figure 5.…”

“…Therefore, geothermal resources, as a clean and renewable resource, have aroused extensive exploration all over the world [1]. China is a country with abundant geothermal resources, which have a good prospect for development and utilization [2,3]. Geothermal water resources are the most widely recognized and utilized geothermal resources in the world.…”

The mechanism of high salinity geothermal water formed in karst low-temperature hydrothermal system

“…All the geothermal water samples are in the area of "Partially equilibrated or mature waters" (Fig. 4), which indicates that the geothermal water is in the imbalance state of water-rock interaction in the flow process, or the geothermal water is mixed with a small amount of shallow groundwater in the process of rising to the surface (Wang et al, 2018). Therefore, cationic geothermometers should be suitable in Yanchanghe geothermal field.…”

“…According to the relationship between TDS content and Na + /(Na + +Ca 2+ ), Cl -/(Cl -+HCO 3 -) in the water of rivers, lakes, and major oceans in the world, it divided the factors affecting river water chemical composition into three categories: atmospheric rainfall, water-rock interaction, and evaporation crystallization (Feth and Gibbs, 1971;Wang et al, 2018). Gibbs diagram can be used to determine the factors controlling TDS content in groundwater.…”