The Aurora Vent Field at the Transition From Magmatic Accretion to Tectonic Extension on Gakkel Ridge: Constraints From Microseismicity and Aeromagnetic Observations

The Aurora hydrothermal vent field (AVF) is the first confirmed active vent system on the Arctic Ocean seafloor, located at the western end of the ultraslow spreading Gakkel Ridge. It marks a distinctive endmember among ridge‐axis hydrothermal systems, where volcanic construction and ultramafic influence co‐exist. The region's perennial ice cover and remoteness have left the crustal and lithospheric structure, including the underlying subseafloor processes, largely unconstrained. In 2023, the RV Polarstern PS137 expedition investigated how lithosphere forms in this region and how it interacts with the AVF's hydrothermal system. Here, we present results from a ∼11‐month passive seismic data set, recorded by a network of eight ice‐going ocean bottom seismometers and complemented by a coincident aeromagnetic survey. Together, these data reveal a transition from magmatic to non‐volcanic spreading between the Western Volcanic Zone and the Lena Trough. With the AVF located at its onset, seismicity and magnetic anomaly patterns are consistent with progressively thicker and colder lithosphere and reduced melt supply toward the Lena Trough. A localized and likely thermally controlled gap in seismicity may indicate a small gabbroic intrusion northeast of the AVF that could provide a heat source for the hydrothermal system. Abundant seismicity surrounding the AVF indicates that tectonic processes continuously influence the lithosphere, whereas evidence for transient magmatic activity near the vent field is limited. These findings suggest that the AVF represents a long‐lived hydrothermal system and provide new insights into the geological controls on hydrothermal systems at ultraslow spreading ridges.