Electrical characteristics and metallogenic prediction of Baishawo rare metal deposit in northeast Hunan Province
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摘要: 花岗伟晶岩型稀有金属矿床是最重要的稀有金属矿床类型之一。连云山东部新发现了白沙窝伟晶岩型矿床,初步评估白沙窝矿床深部稀有金属资源潜力巨大,但该矿床的矿产开采程度很低,围绕深部隐伏花岗伟晶岩脉的研究程度不高。通过研究白沙窝伟晶岩型矿床的深部电性结构特征,探讨稀有金属成矿模型及赋矿载体的空间分布,阐明矿脉就位关系,旨为稀有金属找矿预测提供依据。通过可控源音频大地电磁法(CSAMT)在白沙窝岩体东南方向开展深部隐伏岩(矿)体的探测工作,采用共轭梯度法反演实测3条探测剖面数据,探测深部隐伏岩(矿)体,并结合钻孔信息和元素地球化学异常特征信息进行综合分析,揭示隐伏岩脉的分布及成矿特征。研究结果表明,隐伏伟晶岩脉主要位于冷家溪群中,集中分布在花岗岩体顶部及构造裂隙周围,埋深在50~300 m;伟晶岩脉的成矿地球物理标志为深部高阻体侵入浅部低阻体中的高阻脉状地质体。研究成果为白沙窝矿床后续勘查工作提供了科学依据,揭示了伟晶岩脉的形成机理,并为湘东北及华南地区的稀有金属勘查提供了可靠的物探预测技术和经验。Abstract:
Objective The aim of this study is to characterize the deep electrical structure of the Baishawo pegmatite-type deposits, explore the spatial distribution of rare metal mineralization models and ore-conferring carriers, and elucidate the relationship between the location of ore veins to provide a basis for prediction in rare metal mineral exploration. Methods Through the controlled-source audio-geomagnetic method (CSAMT) and the conjugate gradient method of inverse measurement of three exploration profiles, deep hidden rock (ore) bodies were detected. Then, by combining these results with the information from drill holes and elemental geochemical anomalies, a comprehensive analysis was carried out to reveal the distribution of the hidden dikes and the mineralization characteristics. Results The study showed that the concealed pegmatite veins are mainly located in the Lengjiaxi Group, where they are concentrated on the top of the granite body and around tectonic fissures and have burial depths ranging from 50 to 300 m. The geophysical signature of pegmatite vein mineralization is a high-resistance vein-like geologic body intruded from a deep high-resistance body into a shallow low-resistance body. Conclusion The determined distribution and burial depth of concealed pegmatite veins, identified potential concealed veins in the study area, and geophysical characteristics of the pegmatite vein mineralization provide a basis for understanding the formation mechanism of fracture zone-constrained pegmatite veins. Significance The research results provide a scientific basis for follow-up exploration of the Baishawo deposit, reveal the formation mechanism of the pegmatite veins, and provide reliable physical exploration and prediction technology and experience useful for rare metal exploration in northeast Hunan and south China. -
Key words:
- pegmatite /
- Lianyunshan mountain /
- CSAMT /
- lithium-beryllium-niobium-tantalum deposit /
- rare metal
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图 1 湘东北地区地质简图
a—华南构造划分图(Chen and Jahn,1998);b—湘东北地区大地构造图(许德如等,2009)
Figure 1. Generalized geological map of northeast Hunan Province in the Jiangnan Orogen Belt
(a) Tectonic division map of South China (Chen and Jahn, 1998); (b) Geotectonic map of northeast Hunan (Xu et al., 2009)
图 2 白沙窝矿床测线布置图(据曹创华等,2020修改)
Figure 2. Map of CSAMT survey line layout in the research area (modified after Cao et al., 2020)
图 3 测线实测数据和二维反演模型数据
a—测线L1中170号点的视电阻率曲线;b—测线L1中170号点的相位曲线;c—测线L2中870号点的视电阻率曲线;d—测线L2中870号点的相位曲线
Figure 3. Data of line measurement and two-dimensional inversion model
(a) Apparent resistivity curve at point 170 in Line 1; (b) Phase curve at point 170 in Line 1; (c) Apparent resistivity curve at point 870 in Line 2; (d) Phase curve at point 870 in Line 2
图 6 白沙窝矿床测线L1—L3的电性结构和地质解释图
a—测线L1电性结构图;b—测线L1地质解释图;c—测线L2电性结构图;d—测线L2地质解释图;e—测线L3电性结构图;f—测线L3地质解释图
Figure 6. L1–L3 electrical structure and geological interpretation map of the Baishawo mining area
(a) Electrical structure diagram of measuring Line 1; (b) Geological interpretation map of survey Line 1; (c) Electrical structure diagram of measuring Line 2; (d) Geological interpretation map of survey Line 2; (e) Electrical structure diagram of measuring Line 3; (f) Geological interpretation map of survey Line 3
图 7 钻孔地质剖面与地球化学元素解译图
a—ZK201钻孔地质剖面图; b—测线L3元素地球化学异常特征图(Wen et al.,2021)
Figure 7. Comprehensive geological and geochemical results interpretation map
(a) Geological profile of drill hole ZK201; (b) Characterization of L3 elemental geochemical anomalies in the survey line (Wen et al., 2021)
表 1 白沙窝矿床主要地层与岩浆岩物性参数
Table 1. Physical parameters of main strata and magmatic rocks in the Baishawo mining area
地质体类型 样品数量 电阻率/(Ω·m) 最小值 最大值 平均值 地层 第四系 532 1.21 211.12 112.22 冷家溪群 388 118.66 1988.31 886.53 花岗岩 白沙窝岩体 331 5633.23 33552.83 24388.22 含矿体 伟晶岩 111 4568.66 26953.77 17683.41 -
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