Petrologic and geochemical exploration of the plumbing systems under submarine volcanoes Edifice C, Three Sisters and Orca (Bransfield Strait, Antarctica)

Submarine volcanism represents one of the most abundant forms of volcanic activity on Earth, yet it remains poorly studied due to the limited accessibility. In Antarctica, the remoteness and arduous climate conditions have restricted research on submarine volcanoes to only a few regions, particularly the Bransfield Strait. This back-arc basin, separating the South Shetland Islands from the Antarctic Peninsula, hosts numerous submarine volcanic edifices along its main axis. An eruption from these volcanoes could both impact the local ecosystem, potentially disrupting the Antarctic trophic chain, and pose a direct hazard to nearby scientific stations, as the shallow water depths increase the likelihood of explosive hydrovolcanic eruptions and tsunami triggering. Previous geochemical studies of volcanic rocks collected along the basin have characterised the relationship between magma compositions and their geodynamic setting, however, the magmatic plumbing systems of these submarine volcanic edifices are still poorly known. To address this gap, this work presents a petrological and geochemical study of juvenile volcanic samples from three of the seven main submarine volcanoes: Edifice C, Three Sisters and Orca. The results identify the magmatic storage regions at maximum depths of 12–17 km, consistent with previous geophysical estimates, and magma temperatures of up to 1130–1180 °C, matching magmas of similar compositions. Magmas rapidly ascended (from hours to days) beneath the three volcanoes. This research represents the first approach to decipher the magmatic plumbing systems of these submarine volcanoes, providing essential parameters for a strengthening hazard assessment in this region.