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Geochemical study of the volcanic lake and thermal springs associated with the Rinjani Volcano. Study of the chemical and isotopic compositions of the volcanic lake and thermal springs associated with Rinjani (Segara Anak)(Lombok, Indonesia). Study of the CO2 flux at the surface of the lake. Interpretation of these data applied to a better understanding of the hydrothermal system. Forecasting of the geochemical change that would take place in case of magmatic eruption.
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Rinjani (3726 m) volcano is a complex volcano situated on the Lombok island. The island was constructed by several caldera-forming eruptions. The last major eruption has created the actual caldera filled with a 4 by 3 km wide lake (Segara Anak, child of the sea in local language). The maximum depth of the lake is 230 m. In the photo, we can see the Barujari cone (new cone) who concentrated all the historical activity. |
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Simulated natural color image obtained after processing 3 VNIR bands of ASTER satellite image. Data were recorded on April 28, 2002.
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ASTER data courtesy of NASA. http//asterweb.jpl.nasa.gov |
The volcano last erupted of October first 2004 with a small eruption localized on the North-West flank of the Barujari. |
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| Photo of the Barujari before and after the 2004 eruption | |
Several hot springs are discharging near the Barujari. The linear correlation between Na and Cl and between Mg and SO4 species. However no correlation exists between SO4 and Cl. These compositions can thus be interpreted as a mixing between two fluids of different origins, one with a neutral chloride composition and the second with magnesium sulfate composition. |
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| Correlation between Na and Cl | Correlation between Mg and SO4 |
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Chemical precipitates of Fe hydroxides suspended on the lake waters. |
Thermal plumes from the numerous hot springs discharging on the lake shore. | ||
| Theses two images show the discharge of hot springs in the lake | |||
This lake contains a large amout of dissolved bicarbonate (540ppm), much higher than CO2 concentration for water equilibrium with the CO2 concentration in the atmosphere. Preliminary mesurement of CO2 fluxes using the floating chamber method shows us a high level of diffusive CO2 degassing. |
Webmaster Benjamin Barbier
Last modification: january 25, 2006