Isotope Fractionation and HCl Partitioning During Evaporative Degassing from Active Crater Lakes

<p>Some active volcanoes host thermal springs with ultra- (1<pH<2) and even hyper- (pH < 1) acidic waters with composition corresponding to a mixture of HCl and H2SO4 acids and with cations where Al and Fe are often the major components. Such springs sometimes are known as inferred drainages from active crater lakes (e.g., Rios Agrio at Poas and Copahue volcanoes). However, there are a number of acidic volcano-hydrothermal systems of Cl-SO4 composition at volcanoes without crater lakes. &#160;At least ten groups of manifestation of this type are known for Kuril Islands. Several groups of acid volcanic springs including the famous Tamagawa springs are described in Japan.&#160; Most of the acid Cl-SO4 volcano-hydrothermal systems are characteristic for island volcanoes, probably due to specific hydrological conditions of small volcanic islands. Maybe most known are coastal acid springs at Satsuma Iwojima volcano, Ryukyu arc, Japan. The accepted idea about the origin of such systems is scrubbing (dissolution) of magmatic HCl, HF and SO2 by groundwaters above magmatic conduits.&#160; If so, the composition of acid springs must reflect the state of activity of a volcano. This review describes case histories that are known from the literature and from authors&#8217; studies. Most of the volcanoes hosting acid systems show frequent phreatic activity. We show that &#160;in contrast to crater lakes (Poas, Ruapehu, Copahue, White Island), acid springs on slopes of active volcanoes generally do not response on the preparing or ongoing volcanic eruptions. The aquifers and flow paths of the acid waters in volcanic edifices can be not associated with active conduits but with other degassing magmatic bodies and/or with deeper aquifers. One of the examples of such a complicated system is Ebeko volcano with Yuryevskye springs in Kuril Islands. These springs have a hydrochemical record since 1950s, and during this period Ebeko volcano had at least 10 strong phreatic eruptions.</p>

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Eruptive activity of Planchón-Peteroa volcano for period 2010-2011, Southern Andean Volcanic Zone, Chile

Andean geology ◽

10.5027/andgeov43n1-a02 ◽

2015 ◽

Vol 43 (1) ◽

pp. 20 ◽

Cited By ~ 8

Author(s):

Felipe Aguilera ◽

Oscar Benavente ◽

Francisco Gutiérrez ◽

Jorge Romero ◽

Ornella Saltori ◽

...

Keyword(s):

Fall Deposit ◽

Tephra Fall ◽

Crater Lakes ◽

Active Crater ◽

Maule Earthquake ◽

Magmatic Reservoir ◽

Eruptive Period ◽

Main Component ◽

Thickness Variable ◽

Fall Deposits

Planchón-Peteroa volcano started a renewed eruptive period between January 2010 and July 2011. This eruptive period was characterized by the occurrence of 4 explosive eruptive phases, dominated by low-intensity phreatic activity, which produced almost permanent gas/steam columns (200-800 m height over the active crater). Those columns presented frequently scarce ash, and were interrupted by phreatic explosions that produced ash columns 1,000-3,000 m height in the more intense periods. Eruptive plumes were transported in several directions (NW, N, NE, E and SE), but more than half of the time the plume axis was 130-150° E, and reached a distance up to 638 km from the active crater. Tephra fall deposits identified in the NW, N, NE, E and SE flanks covered an area of 1,265 km2, thickness variable from 4 m (SE border of active crater) to ~0.5 cm 36.8 km SE and ~8 km NW from active crater, respectively, corresponding to a minimum volume of 0.0088 km3. Tephra fall deposit is exclusively constituted of no juvenile fragments including: lithics fragments as main component, quartz and plagioclase crystals, some oxidized lithics, and occasional presence of Fe oxide, and less frequently Cu minerals, as single fragments. We present new field-based measurements data of the geochemistry of gas/water from fumaroles and acid crater lakes, and fall deposit analysis, that integrated with the eruptive record and GOES satellite data, suggests that the eruptive period 2010-2011 has been related to an increasing of heat and mass transfer from hydrothermal-magmatic reservoirs, which would have been favoured by the formation and/or reactivation of cracks after 8.8 Mw Maule earthquake in February 2010. This process also allowed the ascent of fluids from a shallow hydrothermal source, dominated by reduced species as H2S and CH4, during the entire eruptive period, and the release of more oxidizing fluids from a deep magmatic reservoir, dominated by acid species as SO2, HCl and HF, increasing strongly after the end of the eruptive period, probably since October 2011. The eruptive period was scored with a magnitude of 3.36, corresponding to a VEI 1-2.

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Sulfur isotopic effects in the disproportionation reaction of sulfur dioxide in hydrothermal fluids: implications for the δ 34 S variations of dissolved bisulfate and elemental sulfur from active crater lakes

Journal of Volcanology and Geothermal Research ◽

10.1016/s0377-0273(99)00161-4 ◽

2000 ◽

Vol 97 (1-4) ◽

pp. 287-307 ◽

Cited By ~ 109

Author(s):

M. Kusakabe ◽

Y. Komoda ◽

B. Takano ◽

T. Abiko

Keyword(s):

Sulfur Dioxide ◽

Elemental Sulfur ◽

Hydrothermal Fluids ◽

Disproportionation Reaction ◽

Crater Lakes ◽

Active Crater ◽

Isotopic Effects

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Oxygen isotope fractionation between gypsum and its formation waters: Implications for past chemistry of the Kawah Ijen volcanic lake, Indonesia

American Mineralogist ◽

10.2138/am-2020-7298 ◽

2020 ◽

Vol 105 (5) ◽

pp. 756-763

Author(s):

Sri Budhi Utami ◽

Vincent J. van Hinsberg ◽

Bassam Ghaleb ◽

Arnold E. van Dijk

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Historical Record ◽

Oxygen Isotopic Composition ◽

Volcanic Lake ◽

Oxygen Isotope Fractionation ◽

Crater Lakes ◽

Oxygen Isotopic ◽

Fractionation Factors ◽

Kawah Ijen

Abstract Gypsum (CaSO4·2H2O) provides an opportunity to obtain information from both the oxygen isotopic composition of the water and sulfate of its formation waters, where these components are commonly sourced from different reservoirs (e.g., meteoric vs. magmatic). Here, we present δ18O values for gypsum and parent spring waters fed by the Kawah Ijen crater lake in East Java, Indonesia, and from these natural samples derive gypsum-fluid oxygen isotope fractionation factors for water and sulfate group ions of 1.0027 ± 0.0003‰ and 0.999 ± 0.001‰, respectively. Applying these fractionation factors to a growth-zoned gypsum stalactite that records formation waters from 1980 to 2008 during a period of passive degassing, and gypsum cement extracted from the 1817 eruption tephra fall deposit, shows that these fluids were in water-sulfate oxygen isotopic equilibrium. However, the 1817 fluid was >5‰ lighter. This indicates that the 1817 pre-eruption lake was markedly different, and had either persisted for a much shorter duration or was more directly connected to the underlying magmatic-hydrothermal system. This exploratory study highlights the potential of gypsum to provide a historical record of both the δ18Owater and δ18Osulfate of its parental waters, and provides insights into the processes acting on volcanic crater lakes or any other environment that precipitates gypsum.

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