Hydrothermal iron deposits and associated sediments from submarine volcanoes off Vanuatu, southwest Pacific

Abstract

Four active submarine volcanoes lie in water less than 200 m deep off the island of Epi, in the eastern part of the New Hebrides arc. Near-surface samples are mostly gray or brown volcaniclastic silty sands and sandy silts dominated by volcanic glass. Five short cores, taken in and near two of the volcanoes, also include interbedded brick red silty beds up to 16 cm thick. These beds are predominantly amorphous iron oxide, containing up to 27.5% Fe. Their mineralogy and chemistry indicate that they are hydrothermal deposits, deposited as intermediate to late-stage precipitates from solutions associated with the volcanoes. Polymetallic sulphides may well occur on the seabed nearer the vents, or within the volcanic rocks surrounding the vents.