We used a Multi-component Gas Analyser System (Multi-GAS) to measure,for the very first time, the composition (H2O, CO2, H2S, SO2) of thevolcanic gas plume issuing from the Boiling Lake, a vigorously degassing,hot (T ~ 80-90°C) volcanic lake in Dominica, West Indies. The Multi-GAS captured in-plume concentrations of H2O, CO2 and H2S were wellabove those typical of ambient atmosphere, while no volcanic SO2 wasdetected (<0.05 ppm). These were used to derive the Boiling Lake plumecharacteristic ratios of CO2/H2S (5.2±0.4) and H2O/CO2 (31.4±6).Assuming that other volcanic gas species (e.g., HCl, CO, H2, N2, etc.) areabsent in the plume, we recalculated a (air-free) composition for thesourcing volcanic gases of ~ 96.3% H2O, 3.1% CO2 and 0.6% H2S. Thishydrous gas composition is within the range of published gas compositionsin the Lesser Antilles region, and slightly more H2O-rich than obtainedfor the fumaroles of the nearby Valley of Desolation (~94.4%H2O, 4.7% CO2 and 0.8% H2S; CO2/H2S of ~5.7). We use our results,in tandem with the output of numerical simulations of gas scrubbing inthe lake-water (performed via the EQ3/6 software), to derive new constraintson the degassing mechanisms at this poorly studied (but potentiallyhazardous) volcanic lake.
|Number of pages||0|
|Journal||ANNALS OF GEOPHYSICS|
|Publication status||Published - 2013|
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