The Syabru‐Bensi hydrothermal system in central Nepal: 2. Modeling and significance of the radon signature

摘要: The Syabru-Bensi hydrothermal system (SBHS), located in the Nepal Himalayas, is characterized by numerous hot (>30°C) springs and release of dry, cold (<35°C) CO2 associated with radon-222, detailed companion paper. In SBHS, radon fluxes on ground vary over 5–6 orders magnitude, reaching exceptional mean values 100 kg m−2 d−1 12 Bq m−2 s−1, respectively. This paper extends developing three quantitative models for signature based measurements radium concentrations spring waters effective concentration rocks soils. first model considers near-surface degassing from water, considered unlikely unless there exist currently unidentified large discharges water. second CO2, arising deeper sources, incorporating shallow sources as it percolates upward toward surface, more likely a percolation depth 100 m sufficient to account observed discharge. third peak gas zones assumes that gaseous can be transported kilometer-scale depths through fault network connected zones. latter affords possibility variations physical parameters at earthquake nucleation might detectable surface. Gas-dominated transport operate other locations Himalayas elsewhere may an important aspect coupled mechanisms seismically active orogens.