{"title":"Hydrochemical characteristics of carbonated waters and non-carbonated thermal waters of the Heyuan Deep Fault Zone in Guangdong, Southern China","authors":"Xianxing Huang , Linjun Xie , Yan Li , Guoping Lu","doi":"10.1016/j.geothermics.2025.103390","DOIUrl":null,"url":null,"abstract":"<div><div>This paper studied both carbonated geothermal waters and generic geothermal waters, to better understand deep groundwater circulations in deep fault-basin system in the Heyuan Deep Fault Zone. Uniquely occurring carbonated geothermal waters are not well known in their origin-evolution process, geologic settings of deep ground water systems, and their flow behaviors in response to the unique physicochemical properties. Through deep-borehole data, and field samplings of various isotope and aqueous geochemistry data, we characterized these carbonated and generic geothermal waters, and analyzed water-rock reactions in relevant silicate rocks. Carbonated waters have high contents of HCO<sub>3</sub><sup>−</sup> and dissolved CO<sub>2</sub>, and enhance their leaching effect in such a way consequently leading to much higher major ion concentrations than non-carbonated thermal waters. According to δD and δ<sup>18</sup>O data, both carbonated waters and non-carbonated waters are of local meteoric origin and recharge from the hilly areas scattering throughout the study area at elevations ranging from 492 to 602 m (masl). The δ<sup>13</sup>C results confirm that the high DIC contents in carbonated waters have their deep sources of both mantle and carbonate rock thermal metamorphism genesis. Thermal reservoir temperatures are estimated for water samples, yielding a temperature range of 48.2 to 134.8 °C, based on chalcedony and quartz geothermometers. A 3500-m-deep borehole for carbonated water has revealed the relatively low geothermal gradient (2.35 °C/100 m) in the carbonated water convergence zone, which is related to the localized depression of the granitic-igneous basement within the study area. Relatively low-temperature environments have formed in localized basement depressions with thick cover of sedimentary rocks, and thus have provided excellent storage condition for deep-derived CO<sub>2</sub> rising along deep faults, forming carbonated waters when combined with groundwater systems. The deep crustal groundwater flow was further examined for the crustal thermo-structure, showing the heat flow and temperature distribution in each layer of the crust. The findings and insights could provide further understanding of deep ground water flow systems and deep groundwater circulations. The implications involve effective exploitations and utilizations for carbonated water and non-carbonated thermal water. This study is the first of the kind to study the deep ground water systems including carbonated waters and non-carbonated thermal waters in deep fault-basin systems, in terms of the deep sourcing, ground-water circulation, and thermal structure of the deep crust, and deep groundwater circulation in deep fault settings.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"131 ","pages":"Article 103390"},"PeriodicalIF":3.9000,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geothermics","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0375650525001415","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
This paper studied both carbonated geothermal waters and generic geothermal waters, to better understand deep groundwater circulations in deep fault-basin system in the Heyuan Deep Fault Zone. Uniquely occurring carbonated geothermal waters are not well known in their origin-evolution process, geologic settings of deep ground water systems, and their flow behaviors in response to the unique physicochemical properties. Through deep-borehole data, and field samplings of various isotope and aqueous geochemistry data, we characterized these carbonated and generic geothermal waters, and analyzed water-rock reactions in relevant silicate rocks. Carbonated waters have high contents of HCO3− and dissolved CO2, and enhance their leaching effect in such a way consequently leading to much higher major ion concentrations than non-carbonated thermal waters. According to δD and δ18O data, both carbonated waters and non-carbonated waters are of local meteoric origin and recharge from the hilly areas scattering throughout the study area at elevations ranging from 492 to 602 m (masl). The δ13C results confirm that the high DIC contents in carbonated waters have their deep sources of both mantle and carbonate rock thermal metamorphism genesis. Thermal reservoir temperatures are estimated for water samples, yielding a temperature range of 48.2 to 134.8 °C, based on chalcedony and quartz geothermometers. A 3500-m-deep borehole for carbonated water has revealed the relatively low geothermal gradient (2.35 °C/100 m) in the carbonated water convergence zone, which is related to the localized depression of the granitic-igneous basement within the study area. Relatively low-temperature environments have formed in localized basement depressions with thick cover of sedimentary rocks, and thus have provided excellent storage condition for deep-derived CO2 rising along deep faults, forming carbonated waters when combined with groundwater systems. The deep crustal groundwater flow was further examined for the crustal thermo-structure, showing the heat flow and temperature distribution in each layer of the crust. The findings and insights could provide further understanding of deep ground water flow systems and deep groundwater circulations. The implications involve effective exploitations and utilizations for carbonated water and non-carbonated thermal water. This study is the first of the kind to study the deep ground water systems including carbonated waters and non-carbonated thermal waters in deep fault-basin systems, in terms of the deep sourcing, ground-water circulation, and thermal structure of the deep crust, and deep groundwater circulation in deep fault settings.
期刊介绍:
Geothermics is an international journal devoted to the research and development of geothermal energy. The International Board of Editors of Geothermics, which comprises specialists in the various aspects of geothermal resources, exploration and development, guarantees the balanced, comprehensive view of scientific and technological developments in this promising energy field.
It promulgates the state of the art and science of geothermal energy, its exploration and exploitation through a regular exchange of information from all parts of the world. The journal publishes articles dealing with the theory, exploration techniques and all aspects of the utilization of geothermal resources. Geothermics serves as the scientific house, or exchange medium, through which the growing community of geothermal specialists can provide and receive information.