Large-scale organization of carbon dioxide discharge in the Nepal Himalayas

Frédéric Girault (1) , Laurent Bollinger (2) , Mukunda Bhattarai (3) , Bharat Prasad Koirala (3) , Christian France-Lanord (4) , Sudhir Rajaure (3) , Jérôme Gaillardet (1) , Monique Fort (5) , Soma Nath Sapkota (3) , Frédéric Perrier (1)

1 IPGP - Institut de Physique du Globe de Paris
2 DAM/DIF - DAM Île-de-France
3 National Seismic Centre, Nepal
4 CRPG - Centre de Recherches Pétrographiques et Géochimiques
5 PRODIG - Pôle de recherche pour l'organisation et la diffusion de l'information géographique

Gaseous carbon dioxide (CO 2) and radon-222 release from the ground was investigated along the Main Central Thrust zone in the Nepal Himalayas. From 2200 CO 2 and 900 radon-222 flux measurements near 13 hot springs from western to central Nepal, we obtained total CO 2 and radon discharges varying from 10 À3 to 1.6 mol s À1 and 20 to 1600 Bq s À1 , respectively. We observed a coherent organization at spatial scales of ≈ 10 km in a given region: low CO 2 and radon discharges around Pokhara (midwestern Nepal) and in the Bhote Kosi Valley (east Nepal); low CO 2 but large radon discharges in Lower Dolpo (west Nepal); and large CO 2 and radon discharges in the upper Trisuli Valley (central Nepal). A 110 km long CO 2-producing segment, with high carbon isotopic ratios, suggesting metamorphic decarbonation, is thus evidenced from 84.5°E to 85.5°E. This spatial organization could be controlled by geological heterogeneity or large Himalayan earthquakes.

Mots clés: Nepal Himalayas; Carbon dioxide

Domaines: Géographie; Physique des Hautes Energies - Expérience [hep-ex]

Frédéric Girault, Laurent Bollinger, Mukunda Bhattarai, Bharat Prasad Koirala, Christian France-Lanord, et al.. Large-scale organization of carbon dioxide discharge in the Nepal Himalayas. Geophysical Research Letters, 2014, 41 (18), p.1-9. ⟨10.1002/2014GL060873⟩. ⟨hal-01201563⟩