Spatial Distribution of Rn, CO2, Hg, and H2 Concentrations in Soil Gas Across a Thrust Fault in Xinjiang, China

Abstract

Spatial distribution characteristics and origin of soil gasses were discussed in this study. We also examine the correlation between the spatial variation of soil gasses and fault activity, based on the measurements of Rn, Hg, H 2 , and CO 2 concentrations in the eastern segment of the BLT fault zone in the southern Tianshan Mountains, Xinjiang, China. The results show that the Rn and CO 2 concentrations on the hanging wall were higher than those near the fault zone and on the footwall of the fault. Moreover, the Hg and H 2 concentrations on the footwall were also higher than those near the fault and on the hanging wall of the fault. The main factors affecting the variations in soil gas spatial distribution were gaseous origin structure of the crust, fault activity, fault fracture degree, stratigraphic lithology, and the cover layer. The results of active structural fault mapping show that the BLT fault has been active since the Late Quaternary and the thrust has broken the fault surface. Under the influence of tectonic compressive stress, the tension zone was formed on the hanging wall of the fault and fractures were developed. This result is consistent with the characteristics of soil gas concentrations measured in this study, indicating that the concentrations of Rn, Hg, H 2 , and CO 2 are closely related to the fault activity. These findings can be applied to identify seismic precursors from gas monitoring data of the studied area.

Soil Degassing From the Xianshuihe–Xiaojiang Fault System at the Eastern Boundary of the Chuan–Dian Rhombic Block, Southwest China

“…Previous studies and field observations have demonstrated that faults and/or fractures are highly permeable pathways for gas migration from gas sources, which retain the signatures of gas sources in the soil cover (e.g. Fu et al, 2005;Ciotoli et al, 2014Ciotoli et al, , 2016Sciarra et al, 2015Sciarra et al, , 2017Sciarra et al, , 2018Sciarra et al, , 2020Yuce et al, 2017;Xiang et al, 2020). Gas anomalies are well-correlated with earthquakes (e.g.…”

Native H2 Exploration in the Western Pyrenean Foothills

“…Soil gas monitoring (e.g., 222 Rn, He, CH 4 , CO 2 , O 2 , COS, CS 2 , H 2 S, and light hydrocarbons) combined with geophysical methods enables large areas survey and has already been applied with great success for targeting mineral, geothermal, and hydrocarbons resources (Disnar & Gauthier, 1988; Gao et al., 2011; Hinkle et al., 1990; McCarthy & Reimer, 1986; Noble et al., 2013; Pereira et al., 2010; Polito et al., 2002). Furthermore, the geochemical characteristics and behavior of soil gases ( 222 Rn, Hg, He, H 2 , H 2 S, and CO 2 ) in volcanic and seismically active areas have been widely investigated for correlating geochemical variations with faults and earthquake activities (Ciotoli et al., 1999, 2007; Y. Li et al., 2013; Lombardi & Voltattorni, 2010; Wiersberg & Erzinger, 2008; Xiang et al., 2020).…”

“…Furthermore, the geochemical characteristics and behavior of soil gases ( 222 Rn, Hg, He, H 2 , H 2 S, and CO 2 ) in volcanic and seismically active areas have been widely investigated for correlating geochemical variations with faults and earthquake activities (Ciotoli et al, 1999(Ciotoli et al, , 2007; Y. Li et al, 2013;Lombardi & Voltattorni, 2010;Wiersberg & Erzinger, 2008;Xiang et al, 2020).…”