Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania
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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 x 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 x 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.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania |
| Series title | Journal of Geophysical Research B: Solid Earth |
| Volume | 101 |
| Issue | 6 |
| Year Published | 1996 |
| Language | English |
| Publisher | AGU |
| Contributing office(s) | Volcano Hazards Program |
| Description | 12 p. |
| First page | 13819 |
| Last page | 13830 |
| Google Analytic Metrics | Metrics page |