Preliminary results of the 2023 geochemical exploration of volcanic volatiles at Deception Island (Antarctica): new inferences on the mantle heterogeneity

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• Antonio Caracausi, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Palermo, Italy
• Wednesday 27 November 2024, 14:00-15:00
• Wolfson Lecture Theatre.

If you have a question about this talk, please contact Adriano Gualandi.

Earth’s degassing, mostly related to magma dynamics and volcanic eruptions, provides the raw material for the formation of the atmosphere, which is essential for life. This fact is not evident in polar regions where there is still a lack of knowledge about the mantle beneath, due to the extreme conditions to work in these areas. In addition, for the mantle studies, the best samples come from active volcanic areas, thus increasing the mentioned difficulties related to potential emergencies in case of volcanic crisis.

Here I discuss the preliminary results of a geochemical survey of the volatiles emitted at Deception Island (DI) active volcano (Bransfield Strait, Antarctica). In 2023 we explored the gas emissions of the whole island and collected fluids emitted from fumaroles (T up to 104°C) and bubbling in seawater (< 10 m depth) along the Port Foster bay shore. We discover that the bubbling gases sampling is strongly conditioned by the tidal waves, which in turn reduces the time efficiency to finalize the gas collection. This increases the extreme difficulties in exploring and monitor this active volcano.

Two families of gases are distinguished in terms of chemical composition: CO2 and N2-rich, respectively. The helium (He) isotopic signature is in the range of the MORB mantle values (8.0±1Ra; Ra as the ratio in air). We also recognized the presence of an atmospheric component that is higher far from the bay shore. The CCO2 -He systematics explains the variation of the chemical and isotopic composition of pristine mantle volatiles due to magma degassing at depth and water-gas interaction in the shallow layers before reaching surface. Our study demonstrates that the C/3He and the delta13CCO2 of the mantle source feeding the DI volcanic gases is MORB -type. Furthermore, the N-isotopes indicate an N-rich-mantle relative to the average MORB mantle.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

This talk is included in these lists:

• Bullard Laboratories Wednesday Seminars
• Department of Earth Sciences seminars
• Wolfson Lecture Theatre

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