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Radon signature of CO2 flux constrains the depth of degassing: Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas).

Authors :
Girault, Frédéric
Viveiros, Fátima
Silva, Catarina
Thapa, Sandeep
Pacheco, Joana E.
Adhikari, Lok Bijaya
Bhattarai, Mukunda
Koirala, Bharat Prasad
Agrinier, Pierre
France-Lanord, Christian
Zanon, Vittorio
Vandemeulebrouck, Jean
Byrdina, Svetlana
Perrier, Frédéric
Source :
Scientific Reports; 10/22/2022, Vol. 12 Issue 1, p1-16, 16p
Publication Year :
2022

Abstract

Substantial terrestrial gas emissions, such as carbon dioxide (CO<subscript>2</subscript>), 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 CO<subscript>2</subscript> 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 CO<subscript>2</subscript>, and Syabru-Bensi Hydrothermal System (SBHS, Central Nepal) with metamorphic CO<subscript>2</subscript>. At both sites, radon fluxes reach exceptionally high values (> 10 Bq m<superscript>−2</superscript> s<superscript>−1</superscript>) systematically associated with large CO<subscript>2</subscript> fluxes (> 10 kg m<superscript>−2</superscript> day<superscript>−1</superscript>). The significant radon‒CO<subscript>2</subscript> 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‒CO<subscript>2</subscript> coupling is a powerful tool to ascertain gas sources and monitor active sites. The exceptionally high radon discharge from FLFF during quiescence (≈ 9 GBq day<superscript>−1</superscript>) suggests significant radon output from volcanoes worldwide, potentially affecting atmosphere ionisation and climate. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
20452322
Volume :
12
Issue :
1
Database :
Complementary Index
Journal :
Scientific Reports
Publication Type :
Academic Journal
Accession number :
159897481
Full Text :
https://doi.org/10.1038/s41598-022-14653-5