Unravelling the magma source and plumbing systems beneath the submarine volcanoes of Bransfield Strait (Antarctica) with stable and noble gas isotopes

Abstract Oxygen and hydrogen isotope geochemistry, together with helium, neon and argon isotope systematics, are powerful tools for tracing magma sources and magma plumbing system processes beneath volcanic systems. Characterising them is crucial for understanding volcanic systems behaviour and improving volcanic hazard assessment. This is particularly relevant for Antarctic active submarine volcanoes, where limited accessibility and arduous weather conditions hinder detailed studies despite their potential hazards, especially in the Bransfield Strait, the Antarctic region hosting the highest concentration of infrastructure. Here we present a novel database of oxygen and hydrogen isotope ratios measured in volcanic rocks, glass, clinopyroxene and olivine, as well as helium, neon and argon isotope ratios measured in their melt and fluid inclusions, from the submarine volcanoes Edifice C, Three Sisters, Orca and Gebra Seamount, located at the centre of the Bransfield Strait. Oxygen and helium isotope ratios are consistent with a magma source influenced by subduction of the Phoenix Plate. Hydrogen isotope ratios are consistent with magma degassing involving recycled sediment-fluid components. These results support previously proposed models of sub-slab mantle flow beneath the Bransfield Strait and provide a new stable isotope dataset improving understanding of submarine volcanism at this challenging region.