Hydrochemical calculations
Ratios of some components in hot water may have an effect on the deposition of travertine. The accumulation of bicarbonate content in the water tends to be limited to the concentration of calcium (Zhou et al., 2014). The ratios of\(\ \mathrm{\gamma}\)Ca/\(\mathrm{\gamma}\)HCO3 in the water samples of the Heinitang hot spring are not significantly different. The value of\(\text{\ \ }\mathrm{\gamma}\)Ca/\(\mathrm{\gamma}\)HCO3in the water samples S1, S2, S3, S4 and S6 is 0.44, that in S5 is 0.43 and that in S2* and S4* is 0.35 (Fig. 6a).
Fig. 6. Ratios of\(\mathrm{\gamma}\)Ca/\(\mathrm{\gamma}\)HCO3 (a) and\(\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca (b)
This indicates that the value of\(\text{\ \ }\mathrm{\gamma}\)Ca/\(\mathrm{\gamma}\)HCO3in hot water cannot be used to determine whether the precipitation of travertine occurs or not. Apart from the value of\(\text{\ \ }\mathrm{\gamma}\)Ca/\(\mathrm{\gamma}\)HCO3,\(\text{\ \ }\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca of hot springs is one of the important precipitation controlling factors, and precipitation of aragonite and calcite occurs easily when the value of\(\text{\ \ }\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca exceeds 1 (Folk, 1994; Rossi and Lozano, 2016). The values of\(\text{\ \ }\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca in S2* and S4* water samples are 0.46 and 0.47, respectively, and in other water samples the values are approximate 0.1 (Fig. 6b). They are significantly lower than 1. In addition, the precipitation of travertine also occurred near the Alhama-Jaraba hot spring in Spain when the values of\(\text{\ \ }\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca were around 0.7 (Asta et al., 2017). This indicates that the factor of\(\text{\ \ }\mathrm{\gamma}\)Mg/\(\mathrm{\gamma}\)Ca has little effect on the precipitation of travertine in the Heinitang and Alhama-Jaraba hot springs.
Precipitation of travertine easily occurs near the hot springs which are of HCO3-Ca type (Kpegli et al., 2015, Arenas et al., 2015). In an attempt to determine water types of the Heinitang hot springs in this paper, hydrochemical compositions of the water samples were plotted on the Piper diagrams (Piper, 1944). Concentration of carbonate is not plotted on the diagrams because of its low concentration in these water samples. All the water samples display a unique HCO3-Ca•Na type (Fig. 7). The result shows that the water types of the travertine-depositing water samples and the water samples that do not deposit travertine are the same. This indicates that the water type of hot springs cannot be used to determine whether the precipitation of travertine occurs or not.
Fig. 7. Piper diagram showing the Heinitang hot spring samples.