Deep crustal structure imaging of gravity and magnetic anomalies in the Xisha Trough, China

Abstract

The deep structure of the Xisha Trough (China) is of great significance for describing its tectonic attributes. In this paper, the multi-scale segmentation for anomaly separation and the iteration method for downward continuation are used to obtain the information about high-resolution gravity anomaly and magnetic-source gravity anomaly, which is then conducted with apparent density imaging inversion. According to the analysis of anomalous characteristics, it is considered that the aeromagnetic anomaly in the Xisha Trough (China) should be caused by the reverse magnetization of big tilting angle. The magnetic anomaly is conducted with magnetic-source gravity conversion and apparent density imaging inversion, whose results show that the apparent density imaging of magnetic-source gravity has a good comparability with the apparent density imaging of the Bouguer gravity anomaly; thus, it can reflect the homology characteristics of gravity and magnetism in trough center. At the same time, the Moho bathymetric map of the Xisha Trough (China) based on gravity anomaly inversion indicates that the crusts on the north and south sides of the trough have similar structures. The homology characteristics of gravity and magnetism and the similar and comparable characteristics of crustal structure can reflect that the trough is a typical extensional rift structure and also reveal that the processes of mantle upwelling, crust thinning, generation of tensional fault, and basalt eruption occur in the trough evolution.