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    安徽庐江-枞阳矿集区典型铜、铁矿床三维电性结构特征

    The three-dimensional electrical characteristics of the typical iron and copper deposits in the Lujiang-Zongyang ore concentration area

    • 摘要: “玢岩型”铁矿和斑岩型铜矿是庐江—枞阳矿集区两个主要矿床类型,以往研究主要集中在矿床学、岩石学、年代学和地球化学等方面,地球物理工作开展相对较少。随着找矿深度不断加大,地球物理的作用越来越大。为建立典型矿床地球物理探测的解释“标尺”,笔者选择泥河铁矿和沙溪铜矿为研究对象,开展三维音频大地电磁测深工作,获得了典型铜、铁矿床及围岩的三维电性结构模型。结果显示,玢岩(泥河)铁矿电性主体表现为层状结构,由浅至深主要为低阻的沉积层、高阻火山岩、相对低阻的蚀变带以及相对高阻的次火山岩,赋存于次火山岩体顶部穹隆状的磁铁矿主要表现为高阻特征。斑岩(沙溪)铜矿电性主体表现为块状(或纵向带状)结构,浅表为低阻沉积盖层,深部主要为相对高阻的沉积地层和高阻斑岩体,赋存于岩体内或围岩接触带的矿体则为中等电阻特征。为便于模型的实用,笔者将两类矿床的复杂电性模型转化为简化的概念电性模型,为寻找类似矿床提供快速对比“标尺”。

       

      Abstract: The porphyrite iron and porphyry copper ore deposits are the major deposit categories in the Lujiang-Zongyang ore concentration area. However, previous researches were mostly focused on mineralogy, petrology, geochronology and geochemistry, but paid less attention to geophysics. As the exploration depth is increasing, geophysical methods become more important. In order to develop the interpretation 'scaleplate' of the geophysical exploration for typical deposits, the authors took the Nihe iron and Shaxi copper ore deposits as the research subjects, and obtained the three-dimensional electrical models of the orebodies and the surrounding rocks through the audio-magnetotelluric sounding. The results indicate that the major structure of the porphyrite (Nihe) iron deposit is composed of several layers including low resistivity sedimentary rocks, high resistivity volcanic rocks, relatively low resistivity alteration zone and relatively high resistivity intrusive of subvolcanic rocks from shallow place to the depth. In addition, the magnetite body, which exists as a dome on the top of the mass, presents the characteristics of high resistivity. For the porphyry (Shaxi) copper deposit, the major electrical characteristics are the massive (or longitudinal belt) structures composed of the shallow sedimentary rocks with low resistivity, the deep sedimentary rocks with relatively high resistivity, and the porphyry mass with high resistivity. In addition, the orebodies, which exist in the mass or the contact zone between the mass and surrounding rocks, present electrical characteristics of medium resistivity. The orebodies hosted in the mass (or in the contact zone with surrounding rocks) present medium-resistivity. For the practicability of the models, the authors converted the inversion results with complex electrical structures into two facilitate models, which would be used as the comparative 'scaleplate' for the discovery of the similar deposits.

       

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