Fluid geochemistry and geothermal anomaly along the Yushu-Ganzi-Xianshuihe fault system, eastern Tibetan Plateau: implications for regional seismic activity
Fluid geochemistry and geothermal anomaly along the Yushu-Ganzi-Xianshuihe fault system, eastern Tibetan Plateau: implications for regional seismic activity
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DOI：
10.1016/j.jhydrol.2022.127554
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发表时间：
2022-02
影响因子：
6.4
通讯作者：
Wei Liu;L. Guan;Yi Liu;Xian-gang Xie;Maoliang Zhang;Biying Chen;Sheng Xu;Y. Sano
中科院分区：
文献类型：
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作者：
Wei Liu;L. Guan;Yi Liu;Xian-gang Xie;Maoliang Zhang;Biying Chen;Sheng Xu;Y. Sano
然而，在区域尺度上，控制热液循环的过程和因素仍然较少，地热异常与地震活动之间的关系尚不清楚。利用热液化学(DIC) δ18OH2O、δDH2O和δ13C)综合数据，识别热液流体的成因、循环路径和储层性质，揭示流体循环与地震活动的关系。温泉水以na - hco3型为主，其次为ca - na - hco3型和Na-HCO3-Cl型。δ18OH2O（- 18.7‰~ - 14.5‰）和δDH2O（- 142‰~ - 110‰）值反映了大气水的补给，这些大气水沿YGXFS渗透至2 ~ 6 km深度，在地表排放之前与深部流体混合。基于δ 13cdic值（−4.3‰~ 5.9‰）和热水DIC含量的物质平衡模型揭示了地幔含co2流体和地壳海相灰岩热变质脱碳化作用参与了活动断裂构造释气。热水石英地温计测得的储层温度（85 ~ 336℃）沿YGXFS由东南向西北递减。值得注意的是，从储层温度的空间分布来看，强度≥6级的强震震中多位于地热异常过渡带。结合地质和地球物理资料，我们认为地壳热结构的非均质性和深部流体的上升流可能是温泉分布和地震高频率的重要原因。
Hydrothermal activity and seismicity are abundant along the Yushu-Ganzi-Xianshuihe fault system (YGXFS) in the eastern Tibetan Plateau. However, the processes and factors that control hydrothermal fluid circulation at a regional scale remain less constrained, and the relationship between geothermal anomaly and seismic activity is poorly known. In this study, we report an integrated dataset of thermal water chemistry (δ18OH2O, δDH2O, and δ13C of dissolved inorganic carbon (DIC)) to identify the origin, circulation path, and reservoir properties of hydrothermal fluids and then reveal the relationship between fluid circulation and seismic activity. The thermal waters are mainly classified as Na-HCO3type with minor Ca-Na-HCO3and Na-HCO3-Cl types. The δ18OH2O(−18.7‰ to −14.5‰) and δDH2O(−142‰ to −110‰) values indicate recharge of meteoric waters, which infiltrated along the YGXFS to 2–6 km depths and underwent mixing with deep fluids prior to their discharge at the surface. A mass balance model based on δ13CDICvalues (−4.3‰ to 5.9‰) and DIC contents of thermal waters reveals the involvement of CO2-bearing fluids from mantle and thermo-metamorphic decarbonation of crustal marine limestones in tectonic CO2outgassing from the active fault. The estimated reservoir temperatures (85–336 °C) based on silica geothermometer of the thermal waters decrease from southeast to northwest along the YGXFS. Notably, the epicenters of strong earthquakes (Ms ≥ 6) are mostly located in the transition zone of geothermal anomalies according to spatial distribution of the reservoir temperatures. Combined with geological and geophysical information, we suggest that the heterogeneity of crustal thermal structure and the upwelling of deep fluids may play an essential role in the distribution of thermal springs and the high frequency of earthquakes along the YGXFS.