Shallow crustal electrical structure of the Qingchengzi orefield in Liaodong area revealed by three-dimensional inversion of Magnetotelluric data

Abstract

Dense array Magnetotelluric sounding (MT) was applied in the study of the emergence of massive gold deposits relating to the tectonic activity responsible for the creation of the North China Craton. This study focuses on understanding the shallow crustal electrical structure characteristics (>1.5 km) of PbZn and AuAg deposits in the Qingchengzi orefield, through the analysis of shallow electrical resistivity distribution at depths less than 5 km, obtained by 3D inversion of full impedance at a frequency range of 320–0.107 Hz. The results showed that the electrical characteristics of Xiaotongjiapuzi and Taoyuan deposits in the 3D resistivity model are consistent with the known 2D resistivity model, and the Jianshanzi fault plays an important role in the gold mineralization, acting as a migration channel and precipitation zone for ore-forming materials. It is inferred that the fault extends at least 5 km deep with deep mineralization prospects. The strata of Liaohe Group in the north of the orefield, the intrusive granite in the south, and the NW-trending Jianshanzi and Yushanggou faults show distinguishable electrical properties, which are either high resistance, low resistance, or high and low resistance transition zone on the depth slice map. Furthermore, the Xinling rock mass has a NE trending extension, which confirms the inference that the Jianshanzi fault extends to a depth of 5 km into the crust.