庐枞矿集区矾山—将军庙地区AMT三维反演及地质结构解释

Subsurface electrical structure of the Fanshan-Jiangjunmiao region in the Lujiang-Zongyang Ore District derived from 3-D inversion of audio-magnetotelluric data

庐江—枞阳矿集区是长江中下游成矿带内的一个重要的多矿种成矿区.为揭示矾山—将军庙地区的地质结构以指导找矿,首先,在庐枞矿集区北部的矾山—将军庙地区开展了三维音频大地电磁数据采集工作,采用Rhoplus方法进行AMT数据死频带校正保证数据质量,利用相位张量分析地下介质的维性特征;其次,利用模块化三维反演并行代码ModEM开展了实测数据的三维反演,获得了一个典型的具有双层结构特征的火山岩盆地三维地下电性模型;最后通过电性模型及其他地质资料的综合解释,依据反演模型中近地表的低阻层和深部的高阻隆起区,分别勾画出了火山岩地层的厚度和深部侵入岩的分布范围,并在小岭地区发现地表浅部下方存在一个含矿次级火山机构的高导体.

The Lujiang-Zongyang ore district is an important polymetallic ore depodit in the Middle and Lower Reach of Yangtze metallogenetic belt.In order to reveal the geological structure of theFanshan-Jiangjunmiao area,part of the Lujiang-Zongyang ore district,a 3-D audio magnetotelluric（AMT）data acquisition was carried out.The Rhoplus technique was applied to correct the distortion data caused by AMT high-frequency dead-band in to guarantee the data quality,and the dimensional characteristics of underground media were analyzed using the phase tensor method.Then,a 3-D inversion of the data was carried out by a modular code which is referred to as ModEM.Through 3-D inversion,a high-resolution 3-D electrical resistivity model was established.The study area is a two-layer structure of a volcanic basin.Combining with geological data available,the 3-D inversion results show that the main features in the electrical resistivity model corresponded well to the known geological features and the near-surface conductive layers and high-resistivity uplift zones at depth,which delineate the thickness of volcanic formation and distribution of intrusions.Meanwhile,a near-surface high-conductive body was found beneath the Xiaoling Mountain,which was considered to be an ore-bearing secondary volcanic edifice.