The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Abstract: More than 721 submarine hydrothermal fields have been identified worldwide, but our knowledge of hydrothermal activity beneath the ice-covered ocean remains scarce. The JASMInE project, led by China in 2021, has detected the first hydrothermal plume anomalies above a neovolcanic ridge at 100°E along the Gakkel Ridge in deep Arctic Ocean. This study investigates the mineralogical and geochemical characteristics of a sediment core (~ 4475 m water depth) from a central valley located approximately 40 km to the west of the neovolcanic ridge. Detailed analysis, including core scanning, mineralogy and major and trace element geochemistry, revealed that the components of the 369 cm long core is complex. It consists mainly of iceberg-debris, pelagic sediments, authigenic materials and hydrothermal plume fall-out components. In the top 85 cm of the core, there are event layers (H1-H3) characterised by elevated concentrations of Fe, Mn, Cu, Zn, Pb, U, P and V. In particular, the H2 layer contains very coarse sand volcanic glass and abundant Fe-Mn-(oxyhydr)oxides. It has an iron content of up to 15.2%, accompanied by positive Eu and negative Ce anomalies. Based on a comprehensive analysis of the Eu/Eu*-Fe/(Fe+Mn+Al) and Al-Mg-Fe plots, we suggest that these event layers record the distal subsidence of hydrothermal plume material and are related to the volcanic eruption process of the adjacent neovolcanic ridge. Evidence of hydrothermal activity buried in deep-sea sediments, first revealed in this study, provides a new perspective for exploring the pattern of submarine hydrothermal activity in ice-covered ocean.

ice-covered ocean, hydrothermal event, sediment core, major and trace elements