Geochemistry

Tectonics

Mantle (geology)

Lithosphere

Geomorphology

Geothermal gradient

Fault (geology)

Anomaly (physics)

Seismology

Plateau (mathematics)

Geothermal energy

Geology

Induced seismicity

Geothermal exploration

Physics

Petrology

Mathematics

Hydrothermal circulation

Condensed matter physics

Mathematical analysis

Geophysics

Meteoric water

Journal of Hydrology

• Thermal waters related with YGXFS are Na-HCO 3 , Ca-Na-HCO 3 and Na-HCO 3 -Cl types. • Fluid origin, water–rock interaction processes and reservoir temperatures are constrained. • Geothermal anomalies along the YGXFS correlate well with distribution of seismic activities. • Lithospheric thermal structure plays an important role in distribution of earthquakes. 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 (δ 18 O H2O , δD H2O , and δ 13 C 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-HCO 3 type with minor Ca-Na-HCO 3 and Na-HCO 3 -Cl types. The δ 18 O H2O (−18.7‰ to −14.5‰) and δD H2O (−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 δ 13 C DIC values (−4.3‰ to 5.9‰) and DIC contents of thermal waters reveals the involvement of CO 2 -bearing fluids from mantle and thermo-metamorphic decarbonation of crustal marine limestones in tectonic CO 2 outgassing 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 ( M s ≥ 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.

Fluid geochemistry and geothermal anomaly along the Yushu-Ganzi-Xianshuihe fault system, eastern Tibetan Plateau: Implications for regional seismic activity