Hydrothermal and magmatic contributions to surface waters in the Aso caldera, southern Japan: Implications for weathering processes in volcanic areas
Hydrothermal and magmatic contributions to surface waters in the Aso caldera, southern Japan: Implications for weathering processes in volcanic areas
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DOI：
10.1016/j.chemgeo.2021.120612
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发表时间：
2021-11
期刊：
影响因子：
3.9
通讯作者：
G. Romero-Mujalli;J. Hartmann;T. Hosono;P. Louvat;K. Okamura;P. Delmelle;T. Amann;M. Böttcher
中科院分区：
文献类型：
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作者：
G. Romero-Mujalli;J. Hartmann;T. Hosono;P. Louvat;K. Okamura;P. Delmelle;T. Amann;M. Böttcher
热液流体在火山地区原生矿物溶解中的作用，全球范围内硅酸盐风化的热点，没有很好的量化。本研究的目的是确定热液的贡献，从阿索破火山口，日本南部的溶质的横向出口。系统地讨论了与热液有关的贡献的一套指标。沿破火山口的两条主要河流采集了沿着的泉水、地下水和河水样品，分析了它们的常量和微量元素浓度，以及水（δ2 H和δ 18 O）、溶解无机碳（δ 13 C）和硫酸盐（δ 34 S和δ 18 O）的稳定同位素组成。研究区的热泉与岩浆成因的大量硫酸盐贡献有关。相比之下，非热泉的水化学反映了地表水-土壤的相互作用。特别地，非热液沃茨具有比热液沃茨显著更高的硒与硫酸盐的比率。硒与硫酸盐的比例可以区分阿索流域中两种不同的硫源：受硫化物氧化影响或受SO2反硝化反应控制的热液沃茨和非热液硫酸盐。总体而言，结果表明，热液沃茨强烈影响硫预算，占67至91%的总硫酸盐通量在破火山口出口。岩浆CO2和SO2的溶解贡献了该火山区观测到的风化通量的60%以上。这表明，在估算区域和全球尺度的地球化学收支时，应考虑岩浆气体和热液流体。然而，岩浆活动的时间变化及其对沃茨化学的影响必须在今后的工作中进行调查。
The role of hydrothermal fluids in the dissolution of primary minerals in volcanic areas, hotspots of silicate weathering at the global scale, is not well quantified. This study aims to determine the hydrothermal contribution to the lateral export of solutes from the Aso caldera, southern Japan. A set of indicators for the hydrothermally related contribution is systematically discussed. Spring, groundwater and river water samples were collected along the two main rivers of the caldera, and their major and trace element concentrations, as well as the stable isotopic compositions of water (δ2Η and δ18O), dissolved inorganic carbon (δ13C), and sulphate (δ34S and δ18O) were analysed. Hydrothermal springs in the study area are associated with a substantial sulphate contribution of magmatic origin. In contrast, the hydrochemistry of non-hydrothermal springs reflects surface water-soil interactions. In particular, non-hydrothermal waters have significantly higher selenium to sulphate ratios than hydrothermal waters. The selenium to sulphate ratios allow to distinguish two different sulphur sources in the Aso catchment: hydrothermal waters impacted by the oxidation of sulphides or controlled by disproportionation reactions of SO2, and non-hydrothermal sulphate. Overall, the results show that hydrothermal waters strongly influence the sulphur budget, accounting for 67 to 91% of the total sulphate flux at the caldera outlet. The dissolution of magmatic CO2and SO2contribute to >60% of the observed weathering fluxes in this volcanic area. This suggests that magmatic gases and hydrothermal fluids should be considered for the estimation of biogeochemical budgets at the regional and global scales. However, the temporal variation of the magmatic activity and its effect on the chemistry of waters have to be investigated in future work.