Gravity and magnetic correlation analysis based on the second-order vertical derivative of gravity anomaly and normalized source strength of magnetic anomaly with noise disturbance: A case of Xiangshan uranium orefields
WANG Yanguo1,2, TIAN Ye1, DENG Juzhi1,2, GE Kunpeng1,2
1. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang, Jiangxi 330013, China; 2. School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang, Jiangxi 330013, China
Abstract：Comprehensive processing and interpretation of gravity and magnetic data can be employed to reduce multi-solutions and improve geological interpretation reliability.The gravity and magnetic correspondence analysis method is a commonly adopted method for joint quantitative interpretation of gravity and magnetic anomalies.However, the method is affected by remanent magnetization to cause spurious information, and thus the practicality is low.Therefore, this paper derives Poisson's formula of gravity and magnetic anomalies based on the expressions of the second-order vertical derivative of gravity anomaly and normalized source strength of magnetic anomaly.Additionally, a new gravity and magnetic correspondence analysis is proposed, and the effectiveness of the new method can be improved through noise disturbance.This method features clear physical meaning, easy implementation, and no need for reduction to the magnetic pole, and it is less influenced by the background field of gravity and magnetics.The model tests show that the conventional correspondence analysis method only yields sound results when the gravity and magnetics are totally the same source, and spurious information will be produced when the gravity and magnetic sources are different.The proposed method can reflect whether the gravity and magnetic sources are the same source and location and can obtain good results under complex situations.Meanwhile, by applying the new method to process and interpret gravity and magnetic data of Xiangshan uranium orefield in Jiangxi, the location and scale of three types of gravity and magnetic rocks at the same source are accurately reflected, including porphyroclastic lava, rhyodacite, and granite porphyry. Additionally, the main rock types of ancient volcanic eruptions are reflected and an ancient volcanic crater with porphyroclastic lava is inferred on basis of the strong negative and positive correlation characteristics of large-scale distribution.The uranium orefields in Xiangshan area are mainly distributed in the transition zone between a strong positive correlation and a strong negative correlation, which further reveals the close relationship between the distribution of uranium orefields and the contact surface of lithology.The results can provide a data basis for exploring deep uranium orefields in Xiangshan.
王彦国, 田野, 邓居智, 葛坤朋. 基于噪声扰动下重力二阶垂向导数与归一化磁源强度的重磁相关性分析——以相山铀矿田为例[J]. 石油地球物理勘探, 2023, 58(5): 1231-1243.
WANG Yanguo, TIAN Ye, DENG Juzhi, GE Kunpeng. Gravity and magnetic correlation analysis based on the second-order vertical derivative of gravity anomaly and normalized source strength of magnetic anomaly with noise disturbance: A case of Xiangshan uranium orefields. Oil Geophysical Prospecting, 2023, 58(5): 1231-1243.
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