Degassing of soil gas radon and its implication to fault activity in the western margin of the Ordos Block, China

Abstract

Soil gas radon (Rn) serves as an effective indicator for assessing fault activity in fault zones. Measurement of Rn degassing at the active faults was conducted twice in 2017 and 2018 to assess fault activity in the western margin of the Ordos block. The concentration and flux values of Rn ranged from 0.41 to 40.93 kBq m⁻³ and 5.17 to 140.33 mBq m⁻² s⁻¹, respectively. The compression of the Tibetan Plateau has led to higher Rn concentration and flux in the southern part compared with the northern part. The fault activity is evaluated by the index of I_Rn calculated from Rn concentrations. The Haiyuan arcuate tectonic region exhibited the most intensive fault activity, followed by the Yinchuan Basin and Jilantai-Linhe Basin. These findings enhance our understanding of the relationship between fault activity and Rn emission and provide a significant geochemical reference for the fault activity.