Geophysical investigation of the Mado Megamullion oceanic core complex: implications for the end of back-arc spreading

Abstract Detachment faulting is one of the main styles seafloor spreading at slow to intermediate mid-ocean ridges. However, we have limited insight into its role in back-arc basin formation. We surveyed a remnant center Philippine Sea and determined detailed features formation processes Mado Megamullion (Mado MM) oceanic core complex (OCC). This was undertaken context evolution, based on shipborne bathymetry, magnetics, gravity with radiometric age dating rock samples collected. The MM OCC has typical morphology prominent corrugations domed surface positive anomalies, suggesting that there been an exposure lower crust mantle materials by detachment fault. downdip side continues relict axial rift valley, which indicated formed end opening. rate decreased once when direction changed after six million years stable trench perpendicular spreading. then further immediately prior formed. existence other OCC-like structures neighboring segment previously reported OCCs along Parece Vela Rift melt-poor, tectonic-dominant widespread phenomenon terminal phase decrease later stage consistent previous numerical modeling because retreat. In Izu–Bonin–Mariana arc system, rotation axis resultant segmentation enhanced lithosphere cooling constrained upwelling, caused final evolution.