Hydrothermal system of the Papandayan Volcano, West Java, Indonesia and its geochemistry evolution of thermal water after the November 2002 eruption

Abstract

Papandayan is a strato volcano situated in West Java, Indonesia. After the last magmatic eruption in 1772, only few phreatic explosions have been occurring. At the present time, the activity is centered in the northeast crater manifested by the presence of fumaroles and hot springs. In November 2002 an explosive eruption occurred and ejected ash and altered rocks. Study of the altered rocks revealed that an advanced argillic alteration took place in the hydrothermal system by an interaction between acid fl uids and rocks. Four zones of alteration have been formed as a limited extension along faults or across permeable structures at different levels beneath the active crater of the volcano. Two types of acid fl uids are distinguished in the crater of the Papandayan Volcano: (1) acid sulphate-chloride water with pH values between 1.6 and 4.6, and (2) acid sulphate water with pH values between 1.2 and 2.5. The samples collected after the eruption revealed an increase in the SO 4 / Cl and Mg / Cl ratios. This evolution is likely explained by an increase in the neutralization of acid fl uids which tends to show that water-rock interactions were more signifi cant after the eruption. The changes in chemistry observed in 2003 were the consequence of the opening of new fractures where unaltered or less altered volcanic rocks were in contact with the ascending acid water. The high δ 34 S values (9-17‰) observed in the acid sulphate-chloride water before the November 2002 eruption suggest that dissolved sulphates were mainly formed by the disproportionation of magmatic SO 2. On the other hand, the low δ 34 S values (-0.3-7 ‰) observed in acid sulphate-chloride water sampled after the eruption suggest that the origin of dissolved sulphates for these waters is the surfi cial oxidation of hydrogen sulphide.

Authigenic pyrite framboids in sedimentary facies of the Mount Wawel Formation (Eocene), King George Island, West Antarctica

“…Sulphate in the Eocene sedimentary environments of KGI could originate either from volcanic eruptions or from sea spray, or represent a mixture of the two sources. The d 34 S values for volcanic andesite−type rocks range from 0 ‰ to +20 ‰ (Torssander 1992;Marini et al 2002;Mazot et al 2007). The isotopic composition of sulphur in marine sulphate is close to +22 ‰ (Thode 1991), and similar values are ex− pected to have dominated the Paleogene marine water (Ayora et al 1995).…”

Sulfur dioxide emissions from Papandayan and Bromo, two Indonesian volcanoes

“…Magmatic degassing on Papandayan occurs mainly in two fumarolic zones, aligned in a northwestsoutheasterly direction and located in a deformed, horseshoeshaped eastern crater (Fig. 2) (Mazot et al, 2007(Mazot et al, , 2008.…”

Predicting topographic collapse following lava dome growth at Ibu volcano (North Maluku, Indonesia) using high-resolution PlanetScope images

“…The disaster following the lava dome collapse associated with Mt. Papandayan eruptions in West Java (Indonesia) caused approximately 2,000 fatalities in 1772 (Mazot et al 2006;Pratomo 2006); the Mt. Kerinci eruptions were triggered by lava dome growth in the crater in 2019 (ESDM 2019); Mt.…”