The Weixi–Qiaohou Fault (WQF) is considered an important zone of the western boundary of the Sichuan–Yunnan block, and its seismicity has attracted much attention after a series of moderate–strong earthquakes, especially the Yangbi Ms6.4 earthquake that occurred on 21 May 2021. In the present research, we investigate major and trace elements, as well as hydrogen and oxygen isotopes, of 10 hot springs sites located along the WQF, which are recharged by infiltrated precipitation from 1.9 to 3.1 km. The hydrochemical types of most analyzed geothermal waters are HCO3SO4-Na, SO4Cl-NaCa, and SO4-Ca, proving that they are composed of immature water and thus are characterized by weak water–rock reactions. The heat storage temperature range was from 44.1 °C to 101.1 °C; the circulation depth was estimated to range between 1.4 and 4.3 km. The results of annual data analysis showed that Na+, Cl−, and SO42− in hot springs decreased by 11.20% to 23.80% north of the Yangbi Ms5.1 earthquake, which occurred on 27 March 2017, but increased by 5.0% to 28.45% to the south; this might be correlated with the difference in seismicity within the fault zone. The results of continuous measurements of NJ (H1) and EYXX (H2) showed irregular variation anomalies 20 days before the Yangbi Ms6.4 earthquake. In addition, Cl− concentration is more sensitive to near-field seismicity with respect to Na+ and SO42−. We finally obtained a conceptual model on the origin of groundwater and the hydrogeochemical cycling process in the WQF. The results suggest that anomalies in the water chemistry of hot spring water can be used as a valid indicator of earthquake precursors.
Eight soil gas measurements were performed in the Liupanshan fault zone (LPSFZ) to observe the concentration and flux of soil gas radon (Rn) and CO2 in October 2017 and October 2018. By combining the historical strong earthquake background and modern seismic activity of the fault zone, the relation between the geochemical distribution characteristics of soil gas and the seismicity of the fault zone was studied herein. Furthermore, the strong seismic hazard potential of the fault zone was discussed. Results show that the concentration of soil gas Rn and CO2 considerably varies in the northern segment of the LPSFZ and is relatively stable in the southern segment. The spatial distribution of the concentration intensity and flux is strong in the north and weak in the south. However, the southern segment of the LPSFZ has a seismic gap that has not been ruptured by strong earthquakes with
Ms
≥
6.5
for the last 1400 years, whereas the seismic activity in the northern segment is relatively frequent, indicating that the fault zone locking degree of the southern segment is higher than that of the northern segment. This observation is completely consistent with the geochemical characteristic distribution of soil gas. Therefore, the southern segment of the LPSFZ should be considered a hazardous segment, where major or strong earthquakes can occur in the future.
Dengjiashan is a large‐scale Pb–Zn deposit discovered in the western part of the Xicheng ore field within the West Qinling metallogenic belt. Information regarding the distribution and occurrence of trace elements in ore minerals and mineralization, as well as the genesis of this deposit, remains scarce. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analysis and elemental mapping were used to determine the distribution and occurrence of trace elements in the sulfide minerals of the Dengjiashan deposit, as well as delineate the process of its genesis. Our results showed that the trace elements enriched in the different sulfides were significantly different. Sphalerite is the main carrier mineral of the scattered elements Cd, Ge and Ga. Based on the trace element content and ratio, principal component analysis and colour of the sphalerite and pyrite, the deposit likely formed in a medium‐temperature environment. The comparative analysis of trace elements from multiple deposits of different origins, combined with the geological characteristics and distribution of sulfide trace elements, suggests that Dengjiashan is a sedimentary exhalative (SEDEX)‐type deposit. As the metallogenic process had a closer relationship to medium‐low temperature hot brine and later tectonic metamorphic hydrothermal fluid, than with magmatic hydrothermal fluid, the deposit is likely of non‐magmatic SEDEX–hot brine superimposed transition origin. This study provides additional insight on the distribution of trace elements in the sulfide minerals of the Dengjiashan deposit, as well as the processes that led to its formation, and may further facilitate ongoing and future key metal prospecting and exploration efforts.
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