Tectono-Magmatic Processes of the Western Parece Vela Basin: Insights Derived From Seismic Imaging and Gravity Modeling

Abstract

The western Parece Vela Basin (PVB) contains three distinct geomorphological zones aligned with the seafloor spreading direction: the west abyssal hill zone, the central Chaotic Terrain zone, and the east abyssal hill zone. However, the tectono-magmatic processes responsible for the lateral geomorphologic variations remain enigmatic. By processing and analyzing new multi-channel seismic data and ship-borne gravity data across three zones, we characterize the structures of the oceanic crust and elucidate the tectono-magmatic processes involved in seafloor spreading. The west abyssal hill zone exhibits a wavy basement influenced by several normal faults with minor displacements, suggesting the presence of limited tectonic extension. The discontinuous seismic reflections from Moho are imaged in segments, with a crustal thickness of ∼5–7 km, indicating an abundant magma supply. The central Chaotic Terrain zone features three large-scale seafloor domes. Strong reflectors at different depths within the domes are interpreted as sills, suggesting the presence of multi-phase magmatic intrusions. Gravity modeling indicates that the crust at the apexes of the domes is roughly twice as thick as at the edges, showing that the domes were formed through variable magmatism. The east abyssal hill zone shows a flat basement devoid of faults, exhibits continuous sub-horizontal Moho reflections, and predominantly consists of oceanic crust thicker than 6 km. This suggests an abundant magma supply without extension. The findings indicate a dynamic tectono-magmatic process in the western PVB, characterized by an initial stable magma supply with limited tectonic extension, followed by fluctuations in magmatic activity, and ultimately a robust magma supply.