PMEL Publications Abstract
FY 2026
Multidisciplinary investigation of Healy submarine volcano (Kermadec arc, New Zealand) using AUV and submersible data: Structural control on magmatic and hydrothermal processes
Bagnasco, A., F. Caratori Tontini, C.E.J. de Ronde, S.L. Walker, L. Cocchi, A. Ghirotto, and E. Armadillo
Geophys. Res. Lett., 27, e2025GC012776, doi: 10.1029/2025GC012776, View open access article at AGU/Wiley (external link) (2026)
We present a comprehensive multidisciplinary investigation of the Healy submarine volcano in the southern Kermadec arc, northeast of New Zealand. We show the first results of sidescan-sonar data collected at a submarine arc volcano by an Autonomous Underwater Vehicle (AUV). We derive a seafloor geological map using visual observations including video and still photographs as well as samples collected by the manned submersible Pisces V, and integrate them with high-resolution bathymetric data, AUV magnetics, and hydrothermal plume geochemistry, to model the complex interplay of magmatic and tectonic processes and their control on the evolution of seafloor hydrothermal activity. Our results show that recent basaltic dikes, possibly associated with the onset of back-arc extension, preferentially intrude along structurally weakened sectors of the older caldera rim, particularly its southeastern walls, exploiting inherited structures that facilitate the upwelling of magma and fluids. Hydrothermal activity exhibits a similar spatial-temporal transition, shifting from older venting associated with arc magmatism around the caldera rim to more recent spatially diffuse venting linked to the emplacement of basaltic dikes and extensional fracturing. This relative spatial shift in magma, vent, and fluid distribution reflects the progressive reorganization of magmatic and hydrothermal activity within an arc-backarc transitional setting, making Healy a relevant case study for examining relative feedback among magmatic, structural, and hydrothermal processes.
Plain Language Summary. Healy is a submarine volcano located northeast of New Zealand. It is characterized by a set of younger volcanic reliefs overlapping an older caldera. Healy hosts a hydrothermal system, with several vents, that is, hot springs on the seafloor, at depths between 1,500 and 2,000 m. Detailed investigations at these depths are complicated by the difficulty of direct access. Here, we overcome these difficulties by presenting the results of an integrated study of near-seafloor data acquired by the Autonomous Underwater Vehicle Sentry and the Pisces V submersible. We derive a geological map from sidescan sonar data, which provides detailed images of the acoustic signature of the seafloor, making it possible to characterize the geology with 25 cm pixel resolution. By integrating these data with other geophysical information, we can obtain a model of the evolution of the Healy submarine volcano and its associated hydrothermal system. We infer that the evolution of the local tectono-magmatic setting has reorganized hydrothermal circulation, shifting it from older discharge along the caldera walls to present-day activity associated with younger volcanic reliefs that record ongoing extensional processes.