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<p>Hot springs emerging along fault zones provide valuable evidence of fluid circulation, fault activity, and possible seismic precursors. In the seismically active Central Tianshan Mountains (CTM), a variety of indicators from 17 hot springs were analysed between 2017 and 2023 to identify potential geochemical signals associated with seismic events. Analyses of major and trace elements, hydrogen and oxygen isotopes, strontium isotopes, silica (SiO<sub>2</sub>), and dissolved gases indicate meteoric recharge at depths of 1.3–4.1&#xa0;km, Na-Cl-dominated compositions primarily derived from evaporite dissolution, and additional inputs from deep fluids, with reservoir temperatures ranging from 13.45 to 96.69&#xa0;°C. Helium isotope ratios (0.02–0.05 Ra) measured in spring waters indicate a predominantly crustal origin. Springs located within the central sections of the North Tianshan and South Tianshan fault zones exhibit the deepest circulation pathways and correlate with areas with the highest seismic activity. This finding confirms that water-rock interactions have a measurable influence on fault activity. Continuous monitoring from 2021 to 2023 captured pre-seismic multi-index hydrogeochemical anomalies occurring 1–4 months before the 2023 Shaya <i>M</i><sub>S</sub>6.1 and 2024 Wushi <i>M</i><sub>S</sub>7.1 earthquakes (<i>M</i><sub>S</sub>: Surface wave Magnitude). These anomalies included abrupt declines in Na<sup>+</sup>, Cl<sup>-</sup>, and SO<sub>4</sub><sup>2-</sup> concentrations (13.3–99.3%) and shifts in isotope signatures (δD, δ<sup>18</sup>O, δ<sup>13</sup>C<sub>DIC</sub>), which are interpreted as indicators of stress-induced microfracturing and fluid mixing. The negative abnormal post-seismic fluctuations may indicate subsequent fault healing and hydrological reorganisation. This study presents the first identified relationship between variations in multiple hydrochemical indicators in hot springs of the CTM and seismic activity. The integration of multiple elemental and isotopic analyses provides a more comprehensive framework for understanding fault processes, fluid circulation, and pre-seismic anomalies.</p>

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Hot spring geochemistry in the central Tianshan mountains: unveiling fault Activity, fluid Circulation, and Pre-seismic anomalies

  • 期刊论文

  • 发表日期：

    2026年1月5日

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  • Gaoyuan Xing,
  • Yucong Yan,
  • Ying Li,
  • Xiaocheng Zhou,
  • Zhaojun Zeng,
  • Le Hu,
  • Chang Lu,
  • Zhaofei Liu,
  • Zihan Gao,
  • Jia Ren,
  • Fan Zhang,
  • Miao He,
  • Jiao Tian,
  • Yuwen Wang,
  • Shihan Cui,
  • Bingyu Yao,
  • Chengguo Wang,
  • Kayimu Saimaiernaji

摘要

Hot springs emerging along fault zones provide valuable evidence of fluid circulation, fault activity, and possible seismic precursors. In the seismically active Central Tianshan Mountains (CTM), a variety of indicators from 17 hot springs were analysed between 2017 and 2023 to identify potential geochemical signals associated with seismic events. Analyses of major and trace elements, hydrogen and oxygen isotopes, strontium isotopes, silica (SiO2), and dissolved gases indicate meteoric recharge at depths of 1.3–4.1 km, Na-Cl-dominated compositions primarily derived from evaporite dissolution, and additional inputs from deep fluids, with reservoir temperatures ranging from 13.45 to 96.69 °C. Helium isotope ratios (0.02–0.05 Ra) measured in spring waters indicate a predominantly crustal origin. Springs located within the central sections of the North Tianshan and South Tianshan fault zones exhibit the deepest circulation pathways and correlate with areas with the highest seismic activity. This finding confirms that water-rock interactions have a measurable influence on fault activity. Continuous monitoring from 2021 to 2023 captured pre-seismic multi-index hydrogeochemical anomalies occurring 1–4 months before the 2023 Shaya MS6.1 and 2024 Wushi MS7.1 earthquakes (MS: Surface wave Magnitude). These anomalies included abrupt declines in Na+, Cl-, and SO42- concentrations (13.3–99.3%) and shifts in isotope signatures (δD, δ18O, δ13CDIC), which are interpreted as indicators of stress-induced microfracturing and fluid mixing. The negative abnormal post-seismic fluctuations may indicate subsequent fault healing and hydrological reorganisation. This study presents the first identified relationship between variations in multiple hydrochemical indicators in hot springs of the CTM and seismic activity. The integration of multiple elemental and isotopic analyses provides a more comprehensive framework for understanding fault processes, fluid circulation, and pre-seismic anomalies.