Low-temperature hydrothermal anomalies and deep-sea explosive volcanic activity have been found on the 85° E axial volcanic ridge of the ultraslow-spreading Gakkel Ridge, Arctic ocean. Seafloor optical survey and volcanic glasses during the JASMInE voyage in 2021 are used to discuss the coupling of volcanic and hydrothermal activity in this region.Through seafloor optical survey, the thickest (up to 10 cm) volcaniclastic deposits and bacterial mats zone of about 2 km is mainly distributed on the northern flank of Oden volcano, revealing that the origin of hydrothermal activity is related to explosive volcanoes.Compared with ridges sample of effusive eruption, the lower Mg# (63-66) of the Oden volcano sample indicates that magma go through high crystallization evolution and the balanced saturation in CO₂, which is contrary to rapid eruption, show that there was a higher degassing before eruption and the magma chamber is located in a shallow area.Oden volcano samples show a trend of high H₂O/Ce, high Cl/Nb and Cl-excess (up to 150 ppm), indicating that shallow magma chamber is not only the trigger of explosive eruption, but also the driven force of hydrothermal activity. Our research show that explosive eruption and hydrothermal activity in study region are different results caused by the same factor.Explosive eruptions enhance the permeability of the crust, providing channels and heat for hydrothermal activity, while hydrothermal activity affects the composition of lava.The study contributes to our understanding of the driving force of explosive volcanism and hydrothermal activity and enriches the complex geological backgrounds and the habitats of a small scale in magmatic zone, which expand the understanding of deep-sea multi-sphere cycling.

Gakkel Ridge, hydrothermal activities, explosive eruption, carbon dioxide degassing