Physical property characteristics of rocks in Hanzhong and Ankang areas at the southern foot of Qinling Mountains and their application

Physical property parameters are the link between geophysics and geology and are crucial to the rational inversion of geophysical interpretation and inference. To systematically grasp the physical properties of rocks (minerals) in Hanzhong and Ankang areas to the south of the Qinling Mountains, improve interpretation accuracy, and serve basic geological research and the surveys and evaluation of mineral resources, this study collected 458 physical property points of rocks, 13 740 pieces of susceptibility data, and 458 sets of energy spectrum data in the hinterland of the Hanzhong and Ankang areas at the southern foot of the Qinling Mountains. Then, this study classified and made statistics of the physical properties of rocks. The results of magnetic susceptibility data show that the Paleoproterozoic basic and partial intermediate rock masses are ferromagnetic geological bodies in the study area, with an average magnetic susceptibility of greater than 4 000×10-5 SI, and gabbro has the highest magnetic susceptibility; the dominant magnetic strata in the area are the Paleoproterozoic Xixiang Group and the tuff in the Sinian Yaolinghe Formation, which have average magnetic susceptibility of mostly close to 1 000×10-5 SI, and the high magnetic susceptibility can reach more than 2 000×10-5 SI. According to laboratory testing, most of the magnetic geological bodies in the study area have induced magnetism, and a few tuffs, gabbros, and magnetite-bearing gabbros in the study area have strong remanence, which must be considered in the anomaly inversion. The physical property analysis based on energy spectrum parameters shows that the Paleozoic and Sinian metamorphic rocks in the study area have high radioactivity and highly variable content, among which black rocks (carbonaceous) generally have high radioactivity. As indicated by two examples of western Miaoba Village and the southeastern Shiquan County, magnetic, radioactive, and physical-property parameters are important for the interpretation of magnetic and radioactive data, and they establish a link between aerial magnetic and radioactive information and geological information, improving the reliability of interpretation.