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<p>Mt. Changbai volcano, one of the largest and most hazardous active volcanoes in the world, poses destructive threats to neighboring communities and thus should be monitored proactively. The analysis of bubbling gases in volcanic hydrothermal systems offers valuable insights into subsurface magmatic activities and serves as a critical tool in global volcano surveillance. There are two hydrothermal group springs named Julong Springs and Jinjiang Springs on the Mt. Changbai cone of which the gas geochemistry should be further investigated before efficient monitoring strategies are proposed. Here, chemical and isotopic characteristics of degassing CO<sub>2</sub>, <sup>222</sup>Rn, and He from the two springs are systematically investigated. The results show that these two springs exhibit similar C–He isotopic signatures typically of magmatic provenance while they are largely different in gas compositions and fluxes. The Julong Springs exhibit significantly higher CO<sub>2</sub> and radon concentrations coupled with elevated radon flux compared to the Jinjiang Springs. However, He concentration and CO<sub>2</sub> flux at the Julong Springs are depleted relative to the Jinjiang Springs, which are diagnostic signatures of residual degassing. In combination with previous geophysical data, we believe that excess <sup>222</sup>Rn at the Julong Springs is sourced from a shallow-crustal magma pocket given <sup>222</sup>Rn’s short half-life. Such a pocket is decoupled from its main magma chamber at present due to the lack of recharges, and the degassing intensity is receding gradually as the magma cools down. However, the emitted gases at the Jinjiang Springs originate directly from the main magma chamber with a larger volume of magma and more extensive magmatism. Therefore, gas geochemistry of the two springs on Mt. Changbai volcano can be a distinctive tool to identify subsurface magmatic activities at the different depths. The integrated monitoring at both sites enables dynamic assessment of magmatic unrest processes and enhances eruption forecasting capabilities. The findings highlight the necessity of conducting volcanic gas geochemistry investigations prior to the application of gas monitoring.</p> Graphical abstract <p></p>

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CO2, 222Rn, and He degassing from hydrothermal springs on the cone of Mt. Changbai with implications for volcano monitoring

  • 期刊论文

  • 发表日期：

    2025年7月9日

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  • Le Hu,
  • Xiaodong Pan,
  • Guangpei Zhong,
  • Guohui Gu,
  • Zhaofei Liu,
  • Ying Li,
  • Mengmeng Li

摘要

Mt. Changbai volcano, one of the largest and most hazardous active volcanoes in the world, poses destructive threats to neighboring communities and thus should be monitored proactively. The analysis of bubbling gases in volcanic hydrothermal systems offers valuable insights into subsurface magmatic activities and serves as a critical tool in global volcano surveillance. There are two hydrothermal group springs named Julong Springs and Jinjiang Springs on the Mt. Changbai cone of which the gas geochemistry should be further investigated before efficient monitoring strategies are proposed. Here, chemical and isotopic characteristics of degassing CO2, 222Rn, and He from the two springs are systematically investigated. The results show that these two springs exhibit similar C–He isotopic signatures typically of magmatic provenance while they are largely different in gas compositions and fluxes. The Julong Springs exhibit significantly higher CO2 and radon concentrations coupled with elevated radon flux compared to the Jinjiang Springs. However, He concentration and CO2 flux at the Julong Springs are depleted relative to the Jinjiang Springs, which are diagnostic signatures of residual degassing. In combination with previous geophysical data, we believe that excess 222Rn at the Julong Springs is sourced from a shallow-crustal magma pocket given 222Rn’s short half-life. Such a pocket is decoupled from its main magma chamber at present due to the lack of recharges, and the degassing intensity is receding gradually as the magma cools down. However, the emitted gases at the Jinjiang Springs originate directly from the main magma chamber with a larger volume of magma and more extensive magmatism. Therefore, gas geochemistry of the two springs on Mt. Changbai volcano can be a distinctive tool to identify subsurface magmatic activities at the different depths. The integrated monitoring at both sites enables dynamic assessment of magmatic unrest processes and enhances eruption forecasting capabilities. The findings highlight the necessity of conducting volcanic gas geochemistry investigations prior to the application of gas monitoring.

Graphical abstract