Noble gases in shallow aquifers preserve signatures of boiling events beneath Weishan volcano of Wudalianchi volcanic field, northeast China

Shuai Wang, Xuelian Huang, Tao Wen, Xun Wang, He Wang, Yongjie Han, Zhiwei Li, Jian Kuang, Shihua Qi

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The study on whether there is a magma chamber under Wudalianchi is a hot topic recently, as it holds great significances for the theory of plate tectonics, early warning of volcano eruption and geothermal exploration. There is no near surface geothermal abnormality reported in Weishan, the widely used and well-studied tool, geochemistry of geothermal fluids and geothermal gases, cannot be applied to this area. To reveal the thermal conditions under Weishan, we conducted a study about the abundances and isotope ratios of dissolved noble gases in shallow groundwater and springs of Weishan. The concentrations of noble gases display obvious Ne excesses and mass-dependent differentiation, the isotopic ratios indicate that Ne, Ar, Kr, and Xe are atmosphere-derived noble gases (ANGs). We apply the closed-system equilibrium (CE) model to process the data of noble gases, and indicate that the excess ANGs are not caused by the increased hydrostatic pressure or diffusive influx. Neither meltwater mixing nor oxygen consumption alone could generate sufficient noble gas excesses in our samples. Based on the reconstructed abundances of noble gases in vapor phases produced at different boiling temperatures, which are calculated according to the boiling model established on Henry's law, we conclude that the abundances of noble gases in these samples were influenced by vapor–liquid partition caused by underground boiling. The diagrams of 84Kr/36Ar, 20Ne/36Ar and 130Xe/36Ar confine the temperature range where the boiling events occur in ∼100 °C–300 °C. We argued that the excess ANGs in shallow groundwater are geochemical evidence of boiling events, which seems to be continuously happening during the time range confined by the young groundwater in basalt aquifer and old groundwater in sandstone aquifer. Our findings also corroborate the recent results of geophysical survey works that a potential magma chamber exists under Weishan area. We suggest that noble gases dissolved in shallow aquifers represent a reliable geochemical tool to unveil subsurface geothermal state, where no near-surface thermal anomaly occurs.

Original languageEnglish (US)
Article number128246
JournalJournal of Hydrology
Volume612
DOIs
StatePublished - Sep 2022

Keywords

  • Noble gases
  • Rayleigh distillation
  • Shallow aquifer
  • Wudalianchi volcanoes

ASJC Scopus subject areas

  • Water Science and Technology

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