Fumarolic composition at Deception Island volcano, Antarctica: insights into the magmatic-hydrothermal system by means of Multigas measurements

NUÑEZ, N.; SÁNCHEZ, H.; GUERRIERO, L.; VESGA-RAMÍREZ, A.; LAMBERTI, M.C.; FORTE, P.; MASSENZIO, A.; AGUSTO, M.; GÓMEZ, M.

Arequipa

Workshop; 14th Field Workshop on Volcanic Gases; 2022

Commission on the Chemistry on Volcanic Gases

Deception Island is an active volcano located to the southwest of the South Shetland Islands, in the Bransfield Strait. Its last eruptions took place in the 1960s and 1970s, and the volcano currently exhibits significant hydrothermal activity. Most hydrothermal sites in Deception island present steaming grounds and soil diffuse degassing. Primero de Mayo bay (Fumarole Bay, in English toponymy) also hosts a fumarolic field with three main fumaroles on the shoreline: F1, F2 and F3, that are periodically exposed according to the tide levels.During the 2021-2022 Argentine Antarctic Summer Expedition, a portable Multigas was used for the first time, to measure CO2, H2S and SO2 gas concentrations in five thermal areas of Deception Island. Measurements were conducted placing the Multigas at fixed locations, in close proximity to the fumaroles, usually for an hour or more.Multigas measurements detected CO2 and H2S as the dominant acidic gas species in Primero de Mayo bay and Whalers Bay. CO2/H2S ratios were obtained by calculating the slopes of the best fit regression lines. CO2/H2S ratios at Primero de Mayo bay showed an average of 72 and 110.8 for F2 and F3 (with R2 between 0.5 and 0.7 in both cases), whereas at Whalers Bay the CO2/H2S ratio was 30.6 (R2 = 0.5). Moreover, the occasional presence of SO2 was also detected on Primero de Mayo bay.Furthermore, the results of this survey were combined with those of a soil diffuse degassing study, which allowed estimating CO2 and H2S outputs at Primero de Mayo bay (≈1.3 t/day and 14.5 kg/day, respectively) and at Whalers Bay (≈140 kg/day and 5 kg/day, respectively).