Aeromagnetic characteristics and fracture structure framework of the eastern part of the western Qinling orogen

According to the latest high-precision 1:50000 aeromagnetic data, the authors analyzed the aeromagnetic characteristics and geological origin of the eastern section of the western Qinling orogenic belt in detail based on gravity data, inferred newly and corrected the fracture plane position, and discussed the geological significance of ore-controlling role of fractures and some typical faults. The research shows that the main factor of forming gentle negative magnetic background seems to be Paleozoic Devonian, Carboniferous, Permian, and Mesozoic Triassic carbonate rocks-sedimentary clastic rocks, whereas all kinds of widespread intrusive rocks are the main factor for complex changes and different patterns of superimposed anomaly. The whole area's basic structural framework is formed by NWW-EW trending, NNE-NE trending and NW trending deep and major faults. The deep NWW-EW trending fault was the earliest formed main fault; its aeromagnetic features seem to be the boundaries of different magnetic fields or striking magnetic gradient belts, resulting from the NS-trending subduction and collision of North China and Yangtze plate in Neoproterozoic-Triassic along Shangdan, Mianxian, Lueyang suture zone and forming a boundary of the primary tectonic units in this region. In particular, it played a decisive role in controlling polymetallic mineralization in Devonian. The NNENE trending deep and major faults might have been the product of strong intracontinental orogenic stage of Qinling Mountain in Late Triassic -Cenozoic by the vertical accretion hyperplasia action and exerted obvious cutting, traction or blocking effects on the NWW-EW and NW faults, with the continuous linear aeromagnetic gradient characterized by good torsional or magnetic field change. They served as the limit of secondary tectonic unit in the region, and played a guiding role in the migration of deep ore source materials.