High‐Resolution Magnetic Signature of Lava Flows, Hydrothermal Field and Fossil Lava Lakes on the Equatorial East Pacific Rise

Abstract

Lava flows and associated basalt‐hosted hydrothermal fields and fossil lava lakes are ubiquitous on the fast‐spreading East Pacific Rise (EPR), but their detailed magnetic signature is not well documented. We analyze high‐resolution bathymetric and magnetic data collected by an Autonomous Underwater Vehicle (AUV) over the eastern slope of the EPR at 2°13′S. These high resolution deep‐sea magnetic data, with an altitude of 5 m and line spacing of 10 m, suggest that three successive lava flows exist in the study area. Magnetic lows reveal void spaces and collapsed lava lakes, respectively, distributed in the younger and older part of each lava flow. A small‐scale hydrothermal field lies at the limit of the two lava flows, bearing a low magnetization. Forward modeling shows that the depth of alteration zone and void space is shallower than 10 m, confirming that the cooling lava flow sustains the hydrothermal field. Such high‐resolution magnetic data, combined with high‐resolution bathymetry and other data, pave the way for deep‐sea studies in volcanology comparable to those conducted on land.