Characteristics of Magnetic Anomalies and Geological Significance in the Southern Hongshigang Area of the Eastern Tianshan Mountains, China

In recent years, the emphasis of metal mineral exploration has gradually shifted to the hidden deposits in the covered areas where the rock mass is not exposed. However, it is difficult to obtain the information of underground abnormal bodies in the early investigation work because of the thick overlying layer. The Mafic and ultramafic rock mass outlying in the Hongshigang area of the Eastern Tianshan Cu-Ni metallogenic belt shows good prospecting potential. The 1∶50 000 aeromagnetic data and gravity data show that there is a high magnetic and high gravity coupling anomaly in the southern Quaternary covered area, which has not been investigated yet. Therefore, this study conducted high-precision ground magnetic survey work in the southern Hongshigang area and used magnetic anomaly reduced to the pole, vertical first derivative, normalized total gradient method, two-dimensional profile simulation, and three-dimensional magnetic anomaly inversion methods to conduct preliminary exploration and research on the underground anomalous bodies in the area. It was found that there are five significant magnetic anomalies in the investigation area, and the average magnetic susceptibility of the hidden anomalous bodies is about 6000 × 10⁻⁵ SI, with a depth of about 200-300 meters. There are five main small anomalous bodies, which strike nearly southwest-northeast and dip to the north. Combined with geological data and rock physical properties, the anomalous bodies in this area may be mafic and ultramafic rock bodies with high magnetic susceptibility. Magnetic anomalies are used to indicate the Huangshan-Jingerquan faults in the southwest-northeast direction which are consistent with the inferred position of predecessors and the secondary fault in the investigated area, which could provide a favorable metallogenic environment for copper-nickel deposits. Therefore, the underground anomalous bodies in the southern Hongshigang area have great prospecting potential for copper-nickel deposits, and this study provides reliable geophysical data for subsequent exploration work in the area.