Publication Date:
2021-01-12
Description:
The South Sandwich Volcanic Arc is one of the most remote and enigmatic arcs on Earth. Sporadic observations from rare cloudfree
satellite images—and even rarer in situ reports—provide glimpses into a dynamic arc system characterised by persistent gas
emissions and frequent eruptive activity. Our understanding of the state of volcanic activity along this arc is incomplete compared
to arcs globally. To fill this gap, we present here detailed geological and volcanological observations made during an expedition
to the South Sandwich Islands in January 2020.We report the first in situ measurements of gas chemistry, emission rate and carbon
isotope composition from along the arc. We show that Mt. Michael on Saunders Island is a persistent source of gas emissions,
releasing 145±59 t day−1 SO2 in a plume characterised by a CO2/SO2 molar ratio of 1.8 ± 0.2. Combining this CO2/SO2 ratio with
our independent SO2 emission rate measured near simultaneously, we derive a CO2 flux of 179 ± 76 t day−1. Outgassing from low
temperature (90–100 °C) fumaroles is pervasive at the active centres of Candlemas and Bellingshausen, with measured gas
compositions indicative of interaction between magmatic fluids and hydrothermal systems. Carbon isotope measurements of dilute
plume and fumarole gases from along the arc indicate a magmatic δ13C of − 4.5 ± 2.0‰. Interpreted most simply, this result
suggests a carbon source dominated by mantle-derived carbon. However, based on a carbon mass balance from sediment core
ODP 701, we show that mixing between depleted upper mantle and a subduction component composed of sediment and altered
crust is also permissible.We conclude that, although remote, the South Sandwich Volcanic Arc is an ideal tectonic setting in which
to explore geochemical processes in a young, developing arc.
Description:
This expedition was funded by public donations raised by Quark Expeditions Ltd., by the Government of South Georgia and the South Sandwich Islands (GSGSSI) and by individual contributions. This work was carried out under RAP 2019/025 issued by GSGSSI. EJL was supported by a Leverhulme Early Career Fellowship. A.A. and M.B. acknowledge funding from Miur (Grant N. 2017LMNLAW). K.W. acknowledges support from the Mount Everest Foundation (20-06)
Description:
Published
Description:
id 3
Description:
4V. Processi pre-eruttivi
Description:
6V. Pericolosità vulcanica e contributi alla stima del rischio
Description:
1IT. Reti di monitoraggio e sorveglianza
Description:
JCR Journal
Keywords:
South Sandwich Volcanic Arc
;
Volcanic gas emissions
;
Volcanic activity
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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