| Abstract: | As a comparison to airborne infrared (IR) flux measurements, ground-based sampling of fumarole and soil gases was used to characterize the quiescent degassing of CO2 from Oldoinyo Lengai volcano. Aerial and ground-based measurements are in good agreement: ???75% of the aerially measured CO2 flux at Lengai (0.05-0.06 ?? 1012 mol yr-1 or 6000-7200 tonnes CO2 d-1) can be attributed to seven large crater vents. In contrast to Etna and Vulcano Island, where 15-50% of the total CO2 flux emanates diffusely through the volcanic flanks, diffuse emissions were measured only within 500 m of the crater rim at Lengai, contributing < 2% of the total flux. The lack of extensive flank emissions may reflect the dimensions of the magma chamber and/or the lack of a shallow fluid flow system. Thermodynamic restoration of fumarole analyses shows that gases are the most CO2-rich and H2O-poor reported for any volcano, containing 64-74% CO2, 24-34% H2O, 0.88-1.0% H2, 0.1-0.4% CO and < 0.1% H2S, HCl, HF, and CH4. Volatile emissions of S, Cl, and F at Oldoiyno Lengai are estimated as 4.5, 1.5, and 1.0 ?? 107 mol yr-1, respectively. Accuracy of the airborne technique was also assessed by measuring the C emission rate from a coal-burning power plant. CO2 fluxes were measured within ??10% near the plant; however, poor resolution at increased distances caused an underestimation of the flux by a factor of 2. The relatively large CO2 fluxes measured for alkaline volcanoes such as Oldoinyo Lengai or Etna may indicate that midplate volcanoes represent a large, yet relatively unknown, natural source of CO2. |
| Genre: | Article |
| ProdID: | 70018953 |
| Citation Author: | Koepenick, K. W.; Brantley, S. L.; Thompson, J. M.; Rowe, G. L.; Nyblade, A. A.; Moshy, C. |
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| Citation End Page: | 13830 |
| Citation Issue: | 6 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Geophysical Research B: Solid Earth |
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| Citation Number Of Pages: | 12 |
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| Citation Search Results Text: | Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania; 1996; Article; Journal; Journal of Geophysical Research B: Solid Earth; Koepenick, K. W.; Brantley, S. L.; Thompson, J. M.; Rowe, G. L.; Nyblade, A. A.; Moshy, C. |
| Citation Start Page: | 13819 |
| Citation Volume: | 101 |
| Citation Year: | 1996 |
| Type: | citation/reference |
| Text: | Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania; 1996; Article; Journal; Journal of Geophysical Research B: Solid Earth; Koepenick, K. W.; Brantley, S. L.; Thompson, J. M.; Rowe, G. L.; Nyblade, A. A.; Moshy, C. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Mon, 1 Jan 1996 00:00 -0600 |
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