Influence of the oceanic crust structure on marine magnetic anomalies: Review and forward modelling

Marine magnetic anomaly strips are important for plate tectonic studies, thereby promoting the development of the geoscience revolution. Most previous studies typically consider a lava layer with vertical polarity boundaries as a simplified magnetic source layer. However, it cannot accurately explain the observed magnetic anomaly data; thus, complex oceanic crusts with multiple magnetic source layers, such as lava, dike, and gabbro layers, and various polarity boundary dip angles should be considered. To date, there is a lack of systematic understanding about how the dike and gabbro layers affect the total marine magnetic anomalies, particularly the effect of lava layers with different boundary inclinations on the intensity and polarity boundary of the magnetic anomaly. This study aimed to confirm the significance of these factors. Hence, we systematically simulated and analysed the magnetic anomaly characteristics with different inclination and magnetization settings for each layer using the forward modelling method and determined the impact of the complexity of the magnetic structure of the oceanic crust on the magnetic anomaly. Our results showed that the contributions of the dike and gabbro layers to the magnetic anomalies was up to 10%-30% and cannot be ignored. Moreover, the polarity transition point may shift with the inclination of the lava, dike, and gabbro layers but is insensitive to the magnetization of each layer. This study emphasizes the significance of the dike and gabbro layers and the inclination variations of different layers, which should be thoroughly studied. This study facilitates a reasonable interpretation of the magnetic structure of the oceanic crust and further refines the boundary of the magnetization zone with alternative polarity.