Application of Comprehensive Geophysical Exploration in the Lizichong Mining Area, Ailaoshan Tectonic Belt, Southwest Yunnan Province

doi:10.19657/j.geoscience.1000-8527.2024.084

Abstract

Abstract:

The Lizichong iron-copper deposit is located in the southern section of the Ailaoshan tectonic belt, between the Yangtze Plate and the Indian Plate in Yunnan Province. A large number of iron-copper deposits have been found in the periphery of this area, making it an important iron-copper mineral base in Yunnan Province. However, this study area is covered by alpine vegetation and has large topographic variations, complex geological structures, intense magmatic activities, making ore exploration challenging. To overcome the limitations of a single exploration method, we used high-precision magnetic method, dual-frequency IP methods, and EH4 electromagnetic sounding methods to conduct a comprehensive geophysical exploration in the mining area. Combined with a geological survey, the deep extension of the structure, buried magmatic rock and mineralized body in the mining area were interpreted, and the prospecting information was summarized. Comprehensive geophysical results show that the mineralized bodies are mainly hosted in the metamorphic rock series in the Ailaoshan Group and are closely related to the basic intrusive rocks and the granodiorite porphyry rock with various types of mineralization. The iron-mineralized area shows high magnetism, low apparent resistivity and high apparent amplitude frequency, while the copper-mineralized area is characterized by low magnetism, low apparent resistivity and high apparent amplitude frequency. According to the magnetic anomalies of abrupt or bending deformation of magnetic field lines, IP anomalies of low apparent resistivity and the measurement and interpretation results of EH4 profiles, there may be earlier-formed NW-trending tensile faults and subsequently-formed NE-trending shear faults. The NW-trending fault is conducive to mineralization, while the NE-trending fault is destructive to the ore body. In the mining area, the positions with a good combination of IP anomalies and magnetic anomalies, and deep ore-forming potential revealed by EH4 electromagnetic sounding have been verified by engineering operations. The results show that the ore body, to some extent, extends into the deep, and that the NW-trending fault and its secondary structure are the main ore-bearing area. There may be new iron-copper mineralization bodies in the deeper locations with relatively low and gentle magnetic anomalies, which have the potential to expand the reserve. This has significance for further geological exploration.

Key words: Ailaoshan metamorphic complex belt, Lizichong iron-copper deposit, high precision magnetic survey, dual frequency induced polarization method, EH4 electromagnetic sounding

CLC Number:

YU Huimin, SHEN Xiaoli, SU Huhu, JIA Wenchen, ZHANG Baolin, SU Jie. Application of Comprehensive Geophysical Exploration in the Lizichong Mining Area, Ailaoshan Tectonic Belt, Southwest Yunnan Province[J]. Geoscience, 2024, 38(04): 1054-1066.

Figures/Tables 11

Fig.1 Geological sketch (a) (modified after ref.[34])and geological map of the southern section of the Ailaoshan Metamorphic Complex Belt (AMCB) (b)

Fig.2 Photographs of rocks and ores from the Lizichong iron-copper deposit in the AMCB

Fig.3 Magnetic map of the Lizichong ore district in the AMCB after smoothing and reduction to the pole of the original data

Fig.4 IP apparent amplitude frequency (%) maps of the Lizichong copper-iron ore district in the AMCB

Fig.5 IP apparent resistivity (Ω·m) maps of the Lizichong copper-iron ore district in the AMCB

Fig.6 Location and fault distribution of the EH4 sounding profile for zone A of the Lizichong mining area in theAMCB

Fig.7 EH4 electromagnetic sounding profiles for the Lizichong copper-iron ore district in the AMCB

Fig.8 Remote sensing interpretation map of southeastern Yunnan (modified after refs.[4,43])

Fig.9 Tectonic system map of the Lizichong mining area

Fig.10 Profile view of section A of the channel in the Lizichong mining area

Fig.11 Profile of the borehole and mineralized body in zone A of the Lizichong mining area

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