The Remarkable Chemistry of Sulfur in Hyper-Acid Crater Lakes: A Scientific Tribute to Bokuichiro Takano and Minoru Kusakabe

The composition of the gases released by El Chichón (Chiapas, Mexico) and Víti (Askja volcano, Iceland) volcanic lakes is examined by Multi‐GAS for the first time. Our results demonstrate that H2S and SO2 are degassed by these pH 2–3 lakes. We find higher CO2/H2S and H2/H2S ratios in the lakes' emissions (31–5,685 and 0.6–35, respectively) than in the fumarolic gases feeding the lakes (13–33 and 0.08–0.5, respectively), evidencing that only a fraction (0.2–5.4% at El Chichón) of the H2S(g) contributed by the subaquatic fumaroles ultimately reaches the atmosphere. At El Chichón, we estimate a H2S output from the crater lake of 0.02–0.06 t/day. Curiously, SO2 is also detected at trace levels in the gases released from both lakes (0.003–0.3 ppmv). We propose that H2S supplied into the lakes initiates a series of complex oxidation reactions, having sulfite as an intermediate product, and ultimately leading to SO2 production and degassing.

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“…followed by the rapid breakdown of thiosulfate (S 2 O 3 2− ) into sulfite (Delmelle & Bernard, ):

S_{2} {O_{3}}^{2 -}_{(aq)} = S ° + {SO}_{3}^{2 -}_{(aq)}

…”

Section: Discussionmentioning

confidence: 99%

Sulfur Degassing From Steam‐Heated Crater Lakes: El Chichón (Chiapas, Mexico) and Víti (Iceland)

Hasselle

Rouwet

Aiuppa

et al. 2018

Geophysical Research Letters

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“…At high-temperature magmatic conditions the following reaction applies (Giggenbach 1987;Delmelle and Bernard 2015):…”

Section: Magma Degassing From Bottom To Top Magma Degassingmentioning

confidence: 99%

Fluid Geochemistry and Volcanic Unrest: Dissolving the Haze in Time and Space

Rouwet

Hidalgo

Joseph

et al. 2017

Advances in Volcanology

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The heat and gas released by a degassing magma affects the overlying predominantly meteoric aquifers to form magmatic-hydrothermal systems inside the solid body of a volcano. This chapter reviews how fluid geochemical signals help to track the evolution throughout the various stages of volcanic unrest. A direct view into a degassing magma is possible at open-conduit degassing volcanoes. Nevertheless, in most cases gas is trapped (i.e. scrubbed) by abundant water, leading to the loss of the pure signal the magma ideally provides. Deciphering how magmatic gas rises through, reacts, and re-equilibrates with the liquids in the magmatic-hydrothermal system in time and space is the only way to trace back to the pure signal. The most indicative magmatic gas species (CO 2 , SO 2 -H 2 S, HCl and HF) are released as a function of their solubility in magma. The less soluble gas species are released early from a magma at higher pressure conditions (CO 2 ) (deeper), whereas the more soluble species are released later, at lower pressures (SO 2 , HCl and HF) (shallower depth). When these gases hit the water during their rise towards the surface, they will be more or less scrubbed. Depending on the chemical equilibria inside the magmatic-hydrothermal system (e.g. SO 2 -H 2 S conversion, acidity), the gas that eventually reaches the surface will carry the history of its rise from bottom to top. Tracking volcanic unrest implies a time frame; the kinetics of magma degassing throughout the liquid cocktail inside the volcano impose the maximum resolution the volcano provides and hence the monitoring time window to be adopted for each volcano. Gas-dominated systems are "faster" and require a higher monitoring frequency, water-dominated systems are slower and require a lower monitoring frequency. ResumenEl calor y gas liberados por la desgasificación del magma afecta los acuíferos de origen predominantemente meteórico para formar sistemas magmático-hidrotermales dentro el cuerpo sólido del volcán. Este capítulo revisa como la geoquímica de fluidos puede ayudar a trazar la evolución a través de las varias etapas de "unrest" volcánico. Una visión directa dentro de un magma en desgasificación es solo posible para volcanes de conducto abierto. Sin embargo, en la mayoría de las situaciones el gas queda atrapado (i.e. "scrubbing") en el agua, que conduce a la pérdida de la señal pura que el magma idealmente puede proporcionar. Descifrar como el magma sube a través de los líquidos, y reacciona y re-equilibra con ellos dentro el sistema magmático-hidrotermal, en un marco de tiempo y espacio, es la única manera para rastrear el origen de la señal del magma. La desgasificación de magma se da por cuatro procesos: (1) durante la subida de magma, (2) por la descompresión debido al eliminar una porción del edificio volcánico, (3) debido a la convección interna dentro la cámara magmática, o (4) después de "ebullición secundaria" siguiendo el enfriamiento y consecuente cristalización. Las especies gaseosas magmáti-cas más indicativas (CO 2 , ...

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“…Moreover, we assumed here that the stronger acid SO 2 stays in solution, whereas SO 2 is known to be released from acidic crater lakes (Shinohara et al 2015;Tamburello et al 2015;Gunawan et al 2016). Besides the extremely complex sulphur-speciation in crater lake environments (Delmelle & Bernard 2015; Henley 2015), how SO 2 behaves with respect to HCl in the aqueous acidic environment is not yet clear. Thus far, temporal variations of SO 4 /Cl ratios could only be interpreted in a qualitative way (e.g.…”

Section: Conclusion and Implications For Volcanic Surveillancementioning

confidence: 99%

HCl degassing from extremely acidic crater lakes: preliminary results from experimental determinations and implications for geochemical monitoring

Capaccioni

Rouwet

Tassi

2016

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Crater lakes are monitored to detect volcanic unrest starting from the assumption that they behave as condensers for magmatic gases. A further assumption is that acidic gases such as HCl are conservative once dissolved in water. This is not true for extremely acidic crater lakes, whose H + activity is high enough to induce Our experiments imply that: (i) the presence of very acidic gas species in fumaroles can be associated with a liquid-dominated feeding system, and (ii) dissolved in extremely acidic crater lakes, Cl 2 behaves as a non-conservative component.

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The Remarkable Chemistry of Sulfur in Hyper-Acid Crater Lakes: A Scientific Tribute to Bokuichiro Takano and Minoru Kusakabe

Cited by 40 publications

References 84 publications

Sulfur Degassing From Steam‐Heated Crater Lakes: El Chichón (Chiapas, Mexico) and Víti (Iceland)

Sulfur Degassing From Steam‐Heated Crater Lakes: El Chichón (Chiapas, Mexico) and Víti (Iceland)

Fluid Geochemistry and Volcanic Unrest: Dissolving the Haze in Time and Space

HCl degassing from extremely acidic crater lakes: preliminary results from experimental determinations and implications for geochemical monitoring

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