Identification and Application of Audio Magnetotellurics to the Deep Buried Structure:A Case Study of Lijiawan Manganese Deposit at Songtao County in Guizhou Province
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摘要: 面对国家级整装勘查区——贵州铜仁松桃锰矿整装勘查区深部找矿难度加大的现状,特别是隐伏构造的识别对于第二空间(500~2 000m深度)找矿至关重要的问题,鉴于当前锰矿床后期保存条件的研究需要,利用音频大地电磁法对深部隐伏构造的识别很有必要。以区内岩石物性特征为基础,结合“大塘坡式”锰矿地质模型,建立了初步的正演模型,比较了正演TE、TM两支理论正演曲线,TM模式视电阻率响应较TE模式纵向分辨率强;对比了两支曲线在断层上下盘的响应特征。贵州省松桃县李家湾锰矿实测数据的不同反演结果表明:以一维Occam-TE反演作为初始模型的二维NLCG-TE反演能较好地反映真实的电断面结构。通过剖面电性结构特征分析,为查明“大塘坡式”锰矿深部构造格架及其对含锰岩系的破坏程度提供了地球物理依据,为进一步“攻深找盲”工程部署提供参考。
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关键词:
- 音频大地电磁法 /
- 隐伏构造 /
- 正演 /
- 非线性共轭梯度 /
- 贵州省松桃县李家湾锰矿
Abstract: Songtao manganese mine integrated exploration zone belongs to a part of the national integrated exploration area.Facing the present situation of difficulty in deep prospecting,the buried structure identification for second space(depth from 500 to 2000meters)is very important.For the study of preservation conditions of current manganese deposit,it is necessary to recognize the deep buried structure by AMT.In this paper,with the physical properties in this area as the foundation,combined with 'Datangpo type' manganese deposit model,we established the initial geoelectric forwarding model,and then,calculated the forward computation curves of TE and TM mode.By contrast,we found that the TM mode outperforms the TE mode in the vertical resolution.Also we compared the response characteristics of the two curves in the hanging walls and footwalls of the fault.Through the different inversions of real data in Lijiawan manganese deposit,it can better reflect the morphology when NLCG-TE inversion,whose initial model is Occam-TE data measure the geoelectric section.Finally,the electric profile analysis of the structural characteristics provides geophysical evidence for the identification of deep buried structure and the extent of damage about a series of strata with manganese,also offers reference for deployment of deep exploration.
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