Radon gas is a widespread environmental contaminant and the second leading cause of lung cancer , but current mapping does not satisfactorily correlate high risk areas with hypothesized near-surface sources. We investigate more explanatory subsurface geogenic sources by sampling springs, which provide the opportunity to study deep groundwater and gas geochemistry. This study sampled springs near major faults in the Canadian Kootenays and Rockies to investigate radon’s geogenic sources by evaluating the co-occurrence of dissolved radon and carbon dioxide (CO2) in the context of their geochemistry and isotopic composition, and estimating groundwater circulation depths using geothermometry. Dissolved gases at Kootenay sites align with a two-end-member relationship, but spring water types differ geographically, suggesting distinct sources of water and dissolved gases. This distinction is further supported by a weak correlation (r2 = 0.19) between dissolved radon and groundwater circulation depth, attributed to differences in radon travel time given its short half-life (3.8 days). However, dissolved CO2 in springs and 13CCO2 concentrations are strongly correlated (r2 = 0.93). 13CCO2 approaches a mantle signature (-6 ‰) as CO2 concentration increases with calculated circulation depth, suggesting that CO2 in some springs is mantle- derived. Since mantle-derived CO2 tends to co-occur with radon (r2 = 0.8 3), it is likely that radon gas origin is related to geogenic processes. Mantle-derived CO2 is typically produced at significant depth, which implies rapid CO2 and radon transport and could be consistent with buoyant free-phase gas transport along deep geologic structures.