Understanding the Burial and Migration Characteristics of Deep Geothermal Water Using Hydrogen, Oxygen, and Inorganic Carbon Isotopes

Abstract

Geothermal water samples taken from deep aquifers within the city of Kaifeng at depths between 800 and 1650 m were analyzed for conventional water chemical compositions and stable isotopes. These results were then combined with the deuterium excess parameter (d value), and the contribution ratios of different carbon sources were calculated along with distributional characteristics and data on the migration and transformation of geothermal water. These results included the conventional water chemical group, hydrogen, and oxygen isotopes (δD-δ 18 O), dissolved inorganic carbon (DIC) and associated isotopes (δ 13 C DIC ). The results of this study show that geothermal water in the city of Kaifeng is weakly alkaline, water chemistry mostly comprises a HCO 3 -Na type, and the range of variation of δD is between −76.12‰ and −70.48‰, (average: −74.25‰), while the range of variation of δ 18 O is between −11.08‰ and −9.41‰ (average: −10.15‰). Data show that values of d vary between 1.3‰ and 13.3‰ (average: 6.91‰), while DIC content is between 91.523 and 156.969 mg/L (average: 127.158 mg/L). The recorded range of δ 13 C DIC was between −10.160‰ and −6.386‰ (average: −9.019‰). The results presented in this study show that as depth increases, so do δD and δ 18 O, while d values decrease and DIC content and δ 13 C DIC gradually increase. Thus, δD, δ 18 O, d values, DIC, and δ 13 C DIC can all be used as proxies for the burial characteristics of geothermal water. Because data show that the changes in d values and DIC content are larger along the direction of geothermal water flow, so these proxies can be used to indicate migration. This study also shows demonstrates that the main source of DIC in geothermal water is CO 2 thathas a biological origin in soils, as well as the dissolution of carbonate minerals in surrounding rocks. Thus, as depth increases, the contribution of soil biogenic carbon sources to DIC decreases while the influence of carbonate dissolution on DIC increases.

Factors Controlling of Thermal Water Hydrogeochemical Characteristics in Tatun Volcano Group, Taiwan

“…The variation in the geochemical component of thermal water is considered a key element in volcanic activity [1][2][3]. Based on the water chemistry of springs, we can determine the origin of thermal water [4,5], the degree of mixing between the thermal fluid and shallow groundwater [6,7], migration of the geothermal water [8,9], evaluate the geothermal potential [10,11], and establish a conceptual model of the thermal system [12][13][14]. Moreover, there are studies investigating the reservoir temperature through hydrogeochemistry in Mexico, Spain, and China [2,15,16].…”

Isotopes in Hydrology and Hydrogeology

“…The last contribution to this section is related to the geothermal system [12]. Wang et al [12] discuss the evolutionary process of geothermal water in Henan province (North China Plain).…”

“…The last contribution to this section is related to the geothermal system [12]. Wang et al [12] discuss the evolutionary process of geothermal water in Henan province (North China Plain). Through a conventional water chemical group, hydrogen and oxygen isotopes (δ 2 H and δ 18 O), dissolved inorganic carbon (DIC), and associated isotopes (δ 13 C DIC ), authors demonstrate that the primary source of DIC in geothermal water is CO 2 , which has a biological origin in soils, as well as the dissolution of carbonate minerals in surrounding rocks.…”

Stable isotope study of rainfall, river drainage and hot springs of the kerguelen archipelago, SW Indian Ocean

“…Stable isotope values and the chemical composition will be used to "fingerprint" surface and geothermal water, such as sources, recharge and transition processes taking place in underground aquifers such as rainfall or seawater recharge and temperature changes (c.f. Barbieri, 2019;Wang et al, 2018). We complemented the chemical composition and stable isotope values for fluids with stable isotope values for minerals (kaolinite, aragonite, pyrite and native sulfur) precipitated in thermal springs.…”