HR: 1400h
AN: V43A-01    [Abstracts]
TI: Carbon Dioxide Degassing at the Crater Lake of Kelud Volcano, Eastern Java (Indonesia): Using CO₂ Fluxes to Know the Input of Steam and Brine From the Hydrothermal System
AU: * Mazot, A
EM: amazot@geofisica.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autónoma, Ciudad Universitaria, Mexico, D.F 04510, Mexico
AU: Bernard, A
EM: abernard@ulb.ac.be
AF: Department of Earth and Environmental Sciences,Université Libre de Bruxelles, 50 Avenue F.Roosevelt, Brussels, 1050, Belgium
AB: The last eruption of Kelud volcano was occurred in 1990 and it contains a crater lake. Periodical surveys are carried out in geochemistry since 1993 to understand the hydrothermal system of this volcano. The lake contains near neutral waters with a pH of 6: a part of CO₂ is dissolved as bicarbonates, and another part of CO₂ escape through the lake as bubbles and by diffusion to the surface. From 2001 to 2006, measurements of CO₂ flux emitted by the surface of the lake were performed by using the accumulation chamber method modified in order to work at the surface of a crater lake. Two statistical methods were used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach permit to quantify the different degassing processes that are acting at the lake surface: one corresponding to CO₂ fluxes resulting from rising bubbles close to the lake shore (from 2633 to 9072 g/m²/d); the second corresponding to CO₂ fluxes from rising bubbles in the middle of the lake (from 478 to 945 g/m²/d); and the last corresponding to equilibrium diffusion of dissolved CO₂ at the water-air surface (from 151 to 209 g/m²/d). Total CO₂ emission rate estimated by stochastic simulation ranges from 105 t/d for 2001 to 35 t/d for 2006. Thermal energy released by the lake was estimated by using physical characteristics of the lake and meteorological data (wind speed, rainfall rate). The results of gases analysis and CO₂ fluxes have provided a new constraint in the quantification of the input of steam and brine from the hydrothermal system. The thermal flux decreased from 200 MW (2001) to 60 MW (2006) and estimated inflow steam from 12 to 4 kg/s and inflow brine from 429 to 235 kg/s.
DE: 8400 VOLCANOLOGY
DE: 8410 Geochemical modeling (1009, 3610)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8430 Volcanic gases
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly