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EARTHQUAKE ›› 2025, Vol. 45 ›› Issue (2): 49-66.doi: 10.12196/j.issn.1000-3274.2025.02.004

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Study on Hydrogeochemical Characteristics of Lujiang Tangchi Hot Spring in Anhui Province

WANG Jun1,2, ZHOU Xiao-cheng3, PEI Hong-yun1, WANG Shi-xian4, YANG Yuan-yuan1, LI Jun-hui1, MA Li4   

  1. 1. Anhui Earthquake Agency, Hefei 230031, China;
    2. Anhui Mengcheng National Geophysical Observatory, Mengcheng 233527, China;
    3. Insitiute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China;
    4. Hefei Earthquake Monitoring Center Station, Anhui Earthquake Agency, Hefei 231200, China
  • Received:2024-04-03 Accepted:2024-10-23 Published:2025-09-05

Abstract: This paper takes the chemical characteristics and isotopic composition of the water about Lujiang Tangchi hot spring well in the Tanlu fault zone as the research object, and the chemical composition content of the hot spring water was sampled and tested from 2021 to 2023, and the hydrogen and oxygen isotopes of the hot spring water were monitored from January to October in 2023, and a model of hydrochemical migration of the hot springs in Lujiang Tangchi is built. The results show that: ① The chemical type of hot spring water is Na-SO4. ② The values of the stable isotopes (δD and δ18O) are -59.6‰~-63.9‰ and -8.79‰~-9.79‰, respectively, distributing deviate the atmospheric precipitation line. It shows that Tangchi Hot Spring in Lujiang County is also supplied by deep underground hot water, and its recharge elevation is 1.3 km. ③ The major elements come from the water-rock reaction of granite and tuff. ④ The Na-K-Mg triangle diagram show that the hot spring water samples are mainly partially mature water and the degree of water-rock reaction is high. ⑤ The temperature of the thermal reservoir is estimated to be 92.19℃ and the cycle depth is 1.524 km by using SiO2 thermometer. ⑥ The hot spring is formed by the infiltration of rainfall into the atmosphere, heating by a deep heat source, and moving up along the fault zone to supply, which is a good correlation between the fluid geochemical characteristics and the seismic activity of the surrounding area. The sodium ions, chloride ions and sulfate ions in the hot spring were obviously abnormal 28~113 days before the M4.2 earthquake in Changzhou, Jiangsu. Meanwhile, the hydrogen and oxygen isotopes also showed synchronous abnormal changes before the 2023 M5.5 earthquake in Pingyuan, Shandong. Therefore, the continuous monitioring of fluid geochemical variations in Lujiang Tangchi hot spring could provide an effective indicator for judging the seismic risk near the Tanlu fault zone in the future.

Key words: Lujiang Tangchi hot spring, Hydrogeochemistry, Hydrogen and oxygen isotopes, Abnormal features, The 2021 Changzhou M4.2 earthquake

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