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南海东北部陆缘是研究南海深部结构、构造演化与动力学机制的关键区域。鉴于该区磁测数据受低磁纬度斜磁化和剩磁影响,本文采用等效源技术与磁异常模量反演相结合的策略,基于实测磁异常进行三维磁性结构反演。反演结果显示,区内具有显著的南北分块,东西分带的构造分区特点,磁性体的延展方向表现为东西向、北东向和北西向三组,与区内的主要构造方向一致。陆缘区高值磁异常带与其南侧的磁静区磁性反演特征存在明显差异,前者表现为沿北东向延伸的强磁性体,其平面展布范围约500km*60km,深度超过25km,结合最新的地球物理研究成果,认为可能与板块俯冲有关的地壳深部岩浆底侵活动密切相关。后者表现为浅部呈东西条带状展布的弱磁性体,而其深部下地壳及上地幔顶部为宽缓的磁性层,显示出类似于洋壳的磁性结构,推测可能与古洋壳有关。
The continental margin in northeastern South China Sea is a key area for studying the deep structure, tectonic evolution and dynamics of the South China Sea. In view of the fact that the magnetic data in this area is affected by the oblique magnetization and remanent magnetization at low magnetic latitudes, a three-dimensional magnetic structure inversion based on the measured magnetic anomalies is carried out by using a combination of equivalent source technologies and magnetic anomalous modulus inversion. The inversion results show that there are significant north-south blocks and structural zonation of east-west zoning in the area. The extension directions of the magnetic bodies are three groups of east-west, north-east and north west, which are consistent with the main tectonic directions in the area. There is a significant difference between the magnetic anomaly zone in the marginal zone and the magnetostatic zone in the south. The former shows a ferromagnetic body extending along the NE direction with a plane distribution range of about 500 km * 60 km and a depth of over 25 km. Combined with the latest geophysical research results, it is concluded that there is a close correlation between the magmatic underplating and the deep crustal intrusion associated with plate subduction. The latter is characterized by a weak magnetic body with east-west striped distribution in the shallow part, and a wide magnetic layer at the top of the deep lower crust and the upper mantle, which shows the magnetic structure similar to that of the oceanic crust, which may be related to the paleo-oceanic crust .