Late-stage structural evolution from near-bottom topographic and magnetic Surveys of Suda Seamount (West Pacific)

Abstract

The late-stage evolution of seamounts is widespread in the West Pacific and may control the distribution of manganese nodules on the lower seamount flanks and adjacent debris aprons. However, due to the paucity of near-bottom observational data, little research exists specifically focused on the late-stage evolution of seamount structures. To fill this knowledge gap, we systematically investigated the tectonic features and evolution of Suda Seamount based on rock samples, satellite gravity data, and high-resolution magnetic and topographic data surveyed by Autonomous Underwater Vehicle (AUV). We found that the central area of the seamount summit exhibits a negative magnetic anomaly related to a group of minor volcanic structures, while the collapse of volcanic structures on the northeast seamount flank is associated with an extensive positive magnetic anomaly. Surprisingly, a late-stage intrusive dyke with significantly high magnetic susceptibility originates from the lower part of a minor group of volcanic structures but cannot be clearly distinguished below the main summit volcanic structure (hereinafter referred to as the main mound complex). These results demonstrate that at least two late-stage periods of intense magmatic activity occurred during the evolution of the seamount, one centered on the main mound complex and one on the margin of the summit platform. By combining fine-scale topographic and satellite gravity data, we deduce that gravitational slip caused by magma intrusion along a fracture was the main cause of the seamount flank collapse. The late-stage processes resulted in a change in the seamount morphology and distributed clastic rock debris widely along the flanks, which contributed to the uneven distribution of manganese nodules along the lower seamount flanks and determined the distribution of subsequently formed nodules.