Three-dimensional magnetic structure and genesis of the oceanic crust of the northern South China Sea

Abstract

• Magnetic inversion based on model weighting with variable inc and dec is developed. • Inversion method applied in the South China Sea northeast margin. • The distribution of magnetic bodies is north-to-south and east-to-west. • The tectonic patterns are due to the underplating activity in the oceanic crust . • The magnetic structure was disrupted, resulting in the magnetic quiet zone. The north continental margin of the South China Sea is an area conducive to examining the deep structure, tectonic evolution, and dynamic mechanisms of this region. As there is an influence of oblique magnetization in mid-latitude areas on the magnetic data pertaining to this area, this study develops and validates an inversion method for magnetic anomalies that accounts for inclination and declination. The inversion of the total magnetic intensity, ΔT , in the northern South China Sea was then used to reveal the distribution of magnetic bodies in this area. The inversion results show that there is significant tectonic zoning in the area under study, with north-to-south and east-to-west belts showing a pattern consistent with the main tectonic direction in this area. There are also distinct differences between the high magnetic anomaly belt in the continental margin and the magnetic inversion features of the magnetic quiet zone in the south. Combined with ocean-bottom seismology profiles and geothermal data, the observed phenomena may be closely related to magmatic underplating activity in the deep crust caused by plate subduction.