Application of Comprehensive Geophysical Exploration in the Lizichong Mining Area,Ailaoshan Tectonic Belt,Southwest Yunnan Province
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 Prov-ince.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 limita-tions 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 geo-physical results show that the mineralized bodies are mainly hosted in the metamorphic rock series in the Ailaos-han 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 ap-parent 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 de-formation 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 de-structive to the ore body.In the mining area,the positions with a good combination of IP anomalies and magnet-ic 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.
Ailaoshan metamorphic complex beltLizichong iron-copper deposithigh precision magnetic sur-veydual frequency induced polarization methodEH4 electromagnetic sounding
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