Girault, F., Perrier, F., Crockett, R. G. M., Bhattarai, M., Koirala, B. P., France-Lanord, C., Agrinier, P., Ader, M., Fluteau, F., Gréau, C. and Moreira, M. (2014) The Syabru-Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes. Journal of Geophysical Research: Solid Earth. 119(5), pp. 4017-4055. 2169-9313.
| Item Type: | Article |
|---|---|
| Abstract: | The Syabru-Bensi hydrothermal system (SBHS), located at the Main Central Thrust zone in central Nepal, is characterized by hot (30–62°C) water springs and cold (<35°C) carbon dioxide (CO2) degassing areas. From 2007 to 2011, five gas zones (GZ1–GZ5) were studied, with more than 1600 CO2 and 850 radon flux measurements, with complementary self-potential data, thermal infrared imaging, and effective radium concentration of soils. Measurement uncertainties were evaluated in the field. CO2 and radon fluxes vary over 5 to 6 orders of magnitude, reaching exceptional maximum values of 236 ± 50 kg m−2 d−1 and 38.5 ± 8.0 Bq m−2 s−1, with estimated integrated discharges over all gas zones of 5.9 ± 1.6 t d−1 and 140 ± 30 MBq d−1, respectively. Soil-gas radon concentration is 40 × 103 Bq m−3 in GZ1–GZ2 and 70 × 103 Bq m−3 in GZ3–GZ4. Strong relationships between CO2 and radon fluxes in all gas zones (correlation coefficient R = 0.86 ± 0.02) indicate related gas transport mechanisms and demonstrate that radon can be considered as a relevant proxy for CO2. CO2 carbon isotopic ratios (δ13C from −1.7 ± 0.1 to −0.5 ± 0.1‰), with the absence of mantle signature (helium isotopic ratios R/RA < 0.05), suggest metamorphic decarbonation at depth. Thus, the SBHS emerges as a unique geosystem with significant deep origin CO2 discharge located in a seismically active region, where we can test methodological issues and our understanding of transport properties and fluid circulations in the subsurface. |
| Uncontrolled Keywords: | CO2, radon, gas fluxes, accumulation chamber, hydrothermal system, Nepal Himalayas |
| Subjects: |
G Geography. Anthropology. Recreation > GB Physical geography > GB651 Hydrology. Water > GB980 Ground and surface waters Q Science > QE Geology > QE500 Dynamic and structural geology |
| Creators: | Girault, Frédéric, Perrier, Frédéric, Crockett, Robin G M, Bhattarai, Mukunda, Koirala, Bharat Prasad, France-Lanord, Christian, Agrinier, Pierre, Ader, Magali, Fluteau, Frédéric, Gréau, Claire and Moreira, Manuel |
| Publisher: | American Geophysical Union |
| Faculties, Divisions and Institutes: | Faculties > Faculty of Arts, Science & Technology > Environmental Science |
| Date: | 12 May 2014 |
| Date Type: | Publication |
| Page Range: | pp. 4017-4055 |
| Journal or Publication Title: | Journal of Geophysical Research: Solid Earth |
| Volume: | 119 |
| Number: | 5 |
| Language: | English |
| DOI: | https://doi.org/10.1002/2013JB010301 |
| ISSN: | 2169-9313 |
| Status: | Published / Disseminated |
| Refereed: | Yes |
| URI: | http://nectar.northampton.ac.uk/id/eprint/6651 |
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