High-resolution magnetic, sidescan, and water column constraints on the tectono-magmatic and hydrothermal evolution of Healy submarine volcano, Kermadec arc, New Zealand

Here we present a multidisciplinary, high-resolution investigation of Healy submarine volcano, located in the southern Kermadec arc, New Zealand, combining magnetic, sidescan, and hydrothermal plume datasets to constrain the structure and evolution of its magmatic–hydrothermal system.

Near-seafloor magnetic and sidescan sonar data acquired by the Autonomous Underwater Vehicle (AUV) Sentry have been integrated with shipborne magnetic and gravity measurements, multibeam bathymetry, acoustic backscatter, and hydrothermal plume observations, as well as seafloor imagery and in situ temperature measurements collected by the Pisces V submersible, to develop a detailed geological and geophysical characterization of the volcano.

High-resolution sidescan sonar data reveal fine-scale volcanic and tectonic structures, including lava flow textures, fracture networks, and cone morphology providing context for interpreting magnetic anomalies and hydrothermal plume results. Magnetic ‘lows’ are spatially associated with older, caldera-related structures and demarcate zones of ancient hydrothermal discharge, consistent with the loss of magnetite due to hydrothermal alteration. By contrast, younger basaltic cones emplaced along NNE–SSW-trending lineaments exhibit relatively high magnetization signatures and host the currently active hydrothermal venting, characterized by directly observed low-temperature discharge, while hydrothermal plume data (e.g. turbidity anomalies) suggest the possible presence of higher-temperature venting. Taken together, the spatial distribution of volcanic facies, structural lineaments, magnetization patterns, and hydrothermal activity suggests a temporal evolution in magma emplacement and fluid pathways. This evolution is consistent with a transition from caldera-related, arc-dominated volcanism toward more localized basaltic magmatism exploiting extensional structures, which may reflect the early development of back-arc extension.

Our results highlight the important role of multi-sensor, high-resolution surveys in developing robust conceptual models of submarine volcanic systems, and demonstrate how combined gravity, magnetic, sidescan, and hydrothermal plume investigations are prerequisites for understanding hydrothermal processes and related resources in remote deep-sea environments.