Integrated Analysis on Gravity and Magnetic Fields of the Hailar Basin, NE China: Implications for Basement Structure and Deep Tectonics

The Hailar Basin is one of the most representative basins among the Northeast China Basin Group, which is situated in the east of East Asia Orogene between the Siberia Plate and the North China Plate. Based on the detailed analysis of the Bouguer gravity anomaly, aeromagnetic anomaly as well as petrophysical data, we studied the features of gravity-magnetic fields in the basin and its neighboring areas. A combined approach of Wavelet Multi-scale Decomposition and Power Spectrum Analysis was adopted to quantitatively grade the gravity and magnetic anomalies into four levels. Accordingly, the apparent depths of the source fields can be assessed. The results reveal the crustal density and magnetic structures of the Hailar Basin. Low-order wavelet details of gravity-magnetic anomalies were carried out on studying basin basement structure. Seven major basement faults of the basin were identified, and the basement lithology was discussed and predicted. Three major uplifts and 14 depressions were delineated according to basement depth inversion by the Park method. High-order wavelet approximations of gravity-magnetic anomalies were carried out on studying deep tectonics of the basin. The average Moho depth of the study area is about 40 km, with a mantle uplift located in the northeast of the basin. The average depth of the Curie interface is about 19 km, while the uplift of the Curie interface is in the basin center and its east and west sides are depressions. Finally, inversion of Bouguer gravity anomalies was conducted on an across-basin GGT profile using the Wavelet Multi-scale Decomposition. The inversion results are consistent with those of GGT seismic inversion, suggesting that the Wavelet Multi-scale Decomposition can be applied to distinguish major crustal density interfaces.