Evidences from Helium Isotope for Groundwater Supplement,Circul ation and Mixing—Taking the Shiyanghe and Heihe river basins as an example
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摘要: 石羊河、黑河流域地下水氦同位素组成的研究表明，大部分样品的3He/4He具有大气降水特征，部分地区地下水4He同位素的过剩是基岩裂隙水和卤水的混合作用所致，祁连山前深大断裂带附近地下水的氮同位素具有明显的馒源氦特征，说明该断层的活动仍未停止。Abstract: Shiyanghe and Heihe rivers,situated in the east part of Hexi Corridor,Gansu province,are two typical rivers in the arid and semi-arid area. According to the groundwateic helium isotope composition,most samples collected from these two river basins are of meteoric characteristics. Theirδ3He values range from -93.8%-181.4%, but most of them are close to the atmosphere helium with δ3He ranging between-20-+200%3He/20Ne distribute in the range of 4.65×10-7-7.43×10-7, which is slightly higher than that of the air, indicating that their origin is mainly from the meteoric water. In the northwest of Wuwei basin,Shiyanghe river the He3/He4 values of groundwater is lower than atmosphere helium in 1-2 magnitude of orders,implying that the mixing of radiogenic helium from adjacent granite bodies in which abundant minerals containing U and Th are observed. The decay of U and Th can produce a large amount of 4He resulting in the excess of helium in the groundwater. The eminent accumulation of radiogenic helium shows that the circulation period of groundwater in this area could be 1000 years. Along the hidden fault in the front of the Qilian Mountains can observe the much higher 3He/4He values with δ3He ranging from 70%-180 %, indicating that the eminent contribution of mantle helium which implies that the Fault is still active.
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Key words:
- Shiyanghe river basin /
- groundwater /
- helium isotope /
- mixing
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