Girault F., Viveiros F., Silva C., Thapa S., Pacheco J. E., Adhikari L. B., Bhattarai M., Koirala B. P., Agrinier P., France-Lanord C., Zanon V., Vandemeulebrouck J., Byrdina Svetlana, Perrier F. (2022). Radon signature of CO2 flux constrains the depth of degassing : Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas). Scientific Reports - Nature, 12 (1), 10837 [16 p.]. ISSN 2045-2322.
Titre du document
Radon signature of CO2 flux constrains the depth of degassing : Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas)
Année de publication
2022
Auteurs
Girault F., Viveiros F., Silva C., Thapa S., Pacheco J. E., Adhikari L. B., Bhattarai M., Koirala B. P., Agrinier P., France-Lanord C., Zanon V., Vandemeulebrouck J., Byrdina Svetlana, Perrier F.
Source
Scientific Reports - Nature, 2022,
12 (1), 10837 [16 p.] ISSN 2045-2322
Substantial terrestrial gas emissions, such as carbon dioxide (CO2), are associated with active volcanoes and hydrothermal systems. However, while fundamental for the prediction of future activity, it remains difficult so far to determine the depth of the gas sources. Here we show how the combined measurement of CO2 and radon-222 fluxes at the surface constrains the depth of degassing at two hydrothermal systems in geodynamically active contexts: Furnas Lake Fumarolic Field (FLFF, Azores, Portugal) with mantellic and volcano-magmatic CO2, and Syabru-Bensi Hydrothermal System (SBHS, Central Nepal) with metamorphic CO2. At both sites, radon fluxes reach exceptionally high values (> 10 Bq m(-2) s(-1)) systematically associated with large CO2 fluxes (> 10 kg m(-2) day(-1)). The significant radon-CO2 fluxes correlation is well reproduced by an advective-diffusive model of radon transport, constrained by a thorough characterisation of radon sources. Estimates of degassing depth, 2580 +/- 180 m at FLFF and 380 +/- 20 m at SBHS, are compatible with known structures of both systems. Our approach demonstrates that radon-CO2 coupling is a powerful tool to ascertain gas sources and monitor active sites. The exceptionally high radon discharge from FLFF during quiescence (approximate to 9 GBq day(-1)) suggests significant radon output from volcanoes worldwide, potentially affecting atmosphere ionisation and climate.
Plan de classement
Sciences du milieu [021]
;
Hydrologie [062]
;
Géophysique interne [066]
Description Géographique
PORTUGAL ; NEPAL ; HIMALAYA ; ACORES
Localisation
Fonds IRD [F B010085365]
Identifiant IRD
fdi:010085365
