滇西南哀牢山构造带李子冲矿区综合物探的应用研究

doi:10.19657/j.geoscience.1000-8527.2024.084

摘要/Abstract

摘要：

云南省金平县李子冲铁铜矿区地处扬子板块与印支板块交接部位的哀牢山构造带南段,其外围已发现大量的铁铜矿床(点),是云南重要的铁铜矿产基地。但研究区高山植被覆盖严重,地形起伏较大,地质构造复杂,岩浆活动强烈,找矿困难。为克服单一勘探方法找矿的局限性,选择高精度磁法、双频激电法和EH4电磁测深法对矿区进行综合地球物理勘探,结合地质调查资料,对矿区构造、隐伏岩体及矿化体的深部延伸情况进行解译,并总结找矿信息。综合物探结果表明,矿化体主要在哀牢山群变质岩系产出,与基性侵入岩和花岗闪长岩体关系密切,并伴有多种矿化现象;铁矿化区显示高磁、低视电阻率、高视幅频率特征,铜矿化区则具有低磁、低视电阻率、高视幅频率特征。根据磁力线突变或弯曲变形的磁异常现象和低视电阻率的激电异常及EH4剖面测量解译结果,推测矿区可能存在形成时间较早的北西向张性断裂和形成时间较晚的北东向剪性断裂,近北西向断裂有利于成矿而近北东向断裂对矿体具有破坏作用。对矿区内激电异常与磁异常整体套合较好且EH4电磁测深揭露深部具有成矿潜力的位置进行工程验证,结果显示,矿体在深部具有一定程度的延伸,近北西向断裂构造及其次级构造是主要的赋矿区域,相对低缓的磁异常区域深部可能存在新的铁铜矿化体,有扩大储量的可能,这对下一步地质勘查工作具有指导意义。

关键词: 哀牢山变质杂岩带, 李子冲铁铜矿, 高精度磁法, 双频激电法, EH4电磁测深

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

中图分类号:

于慧敏, 沈晓丽, 苏虎虎, 贾文臣, 张宝林, 苏捷. 滇西南哀牢山构造带李子冲矿区综合物探的应用研究[J]. 现代地质, 2024, 38(04): 1054-1066.

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.

图/表 11

图1 哀牢山构造带区域地质图(a)(修改自文献[34])和哀牢山变质杂岩带南段地质图(b) 1. 哀牢山群凤港组、阿龙组和小羊街组;2.哀牢山群乌都坑组;3.瑶山群;4.洗马塘组;5.永宁镇组;6.三叠系个旧组一段;7.三叠系个旧组二段;8.三叠系个旧组三段;9.中三叠统未分层;10.上三叠统火把冲组;11.闪长花岗片麻岩;12.片麻状黑云花岗岩;13.黑云花岗岩;14.基性-超基性岩;15.电、磁法研究区域;16.矿区;17.铜矿化点;18.铁矿化点

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

图2 哀牢山变质杂岩带李子冲铁铜矿岩(矿)石照片

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

图3 哀牢山变质带李子冲矿区磁法圆滑-化极磁法平面图((a)—(d)对应图1中的磁法研究区域A—D)

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

图4 哀牢山变质杂岩带李子冲矿区激电扫面视幅频率(%)图((a)—(d)对应图1中的电法研究区域A—D)

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

图5 哀牢山变质杂岩带李子冲矿区激电扫面视电阻率(Ω·m)图 ((a)—(d)对应图1中的电法研究区域A—D)

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

图6 哀牢山变质杂岩带李子冲矿区A分区EH4测深剖面位置及断层分布

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

图7 哀牢山变质杂岩带李子冲矿区A分区的EH4电磁测深断面图 ((a)—(d)为图6中A分区EH4电磁测线MQ-1—MQ-4断面图)

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

图8 滇东南遥感解译图(据文献[4,43]修改)

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

图9 李子冲矿区构造体系图 1. 推测压剪性构造带;2.张性构造带;3.旋转方向

Fig.9 Tectonic system map of the Lizichong mining area

图10 李子冲矿区A分区探槽剖面图(据红河州中科矿业有限责任公司资料修编)

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

图11 李子冲矿区A分区钻孔及矿化体剖面简图 (据红河州中科矿业有限责任公司资料修编)

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

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