Chemical composition of acidic gases from fumarolic emissions at Deception Island volcano, Antarctica

AGUSTO, M.; GUERRIERO, L.; LAMBERTI, M.C.; FORTE, P.; MASSENZIO, A

Conferencia; SCAR Open Science Conference 2022; 2022

Deception Island (62°43´S, 60°57´W) is an active basaltic-andesitic volcano that forms part of the South Shetlands archipelago (Antarctica), in the Bransfield Strait. The island is the most active volcano in the region, where the most recent eruptions occurred between 1967 and 1970. This horseshoe-shaped island hosts a magmatic-hydrothermal system, developing areas with thermal anomalies and gas emissions mainly on the internal coast. The manifestations in Primero de Mayo bay constitute the largest fumarole field on the island. Previous studies have shown that gas emissions from this area are enriched in acid gases CO2 and H2S compared to other hydrothermal areas, where no species of S were detected. Previous samplings show vapor/gas ratios between 85 and 95%, with CO2 and H2S values up to 15% and 0.25%, respectively. The CO2/H2S ratios ranged between 25 and 90. The absence of magmatic gases (SO2-HCl-HF) suggests gas scrubbing by a hydrothermal reservoir. From January-March 2022, we took 40 samples of fumarolic gases by direct sampling alkaline trap (NaOH-Cd(OH)2) in 10 subaerial and submerged emission spots. The highest temperature gas emissions (90-100°C) were identified in Primero de Mayo bay and Mount Pond fumarolic fields. In comparison, the thermal areas of Cerro Caliente, Whalers Bay, Pendulum Cove and outer Stonethrow Ridge are characterized by steaming grounds with temperatures below 60°C.The results from a complete set of geochemical and isotopic data will allow identifying the different sources of fumarolic gases and the processes controlling the activity of the magmatic-hydrothermal system of Deception island.