AMT在龙门山北段三堆地区地质填图中的应用

发布时间：2018-02-28 14:32

本文关键词： 音频大地电磁法电性结构 GOCAD 地质建模　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：研究区位于龙门山构造带北段的三堆镇地区。区内地表构造复杂,地表覆盖层发育,许多重点填图区域的地质地层单元、断裂构造等地表地质特征模糊,严重影响区域地质填图工作。特别是断层表现为脆韧性特征,在地表无明显的边界地质信息,深部延伸情况不明确;飞来峰群在地表的边界位置模糊、深部构造样式的展布特征不甚清楚等。基于以上原因,仅仅通过地表调查开展深部地质填图具有较大局限性,深部地质填图急需深部地球物理数据的支持。音频大地电磁法(AMT)勘探作为一种中浅部勘探技术,具有工作效率高、不受高阻层屏蔽和对低阻层分辨率较高等优点,因此在本地区采用音频大地电磁法(AMT)勘探地下结构。本文首先介绍了研究区的地质、地球物理特征;然后针对地面地质调查遇到的上述问题,结合研究区内的地质和物性资料,建立断层、褶皱和飞来峰等地电断面模型及测线深部粗结构模型,开展AMT正演模拟及反演计算,并分析电磁响应特征、探讨AMT法对典型地电模型的分辨能力;接着使用SSMT2000和MTSOFT-2D软件对实测AMT数据进行处理,获取测线深部2km以浅电阻率剖面图,结合研究区地质、物性资料对剖面进行地质地球物理综合解释;最后使用GOCAD软件完成AMT剖面局部约束下的深部地质建模。通过以上研究,取得如下主要成果:(1)研究区的岩层岩石电阻率测试结果表明,主要探测目标内部不同岩体、不同地层电性差异明显,满足进行电法勘探的物性基础,可以在测区合理布置测线,获取高质量数据,能够达到较好的勘探效果。(2)对音频大地电磁测深的数据进行处理后,对单点测深曲线以及视电阻率和相位断面进行定性研究,随后,选择非线性共轭梯度(NLCG)反演方法对大地电磁资料进行反演处理,结合地表地质填图资料对AMT反演结果进行解释,对梨树坝断层深部构造样式、莲花石飞来峰的地下展布有了清晰的认识。(3)GOCAD地质建模的结果表明在AMT数据的约束下能够解决梨树坝断层深部延伸情况、飞来峰构造深部样式及测区主要地层深部边界等地质问题,结果说明了音频大地电磁(AMT)探测成果能为深部地质调查及三维建模提供可靠参考资料。
[Abstract]:The study area is located in Sanduizhen area in the northern section of Longmen Mountain structural belt. The surface structure in the area is complicated, the surface overburden is developed, the geological stratigraphic units of many important mapping areas, the fault structure and other surface geological features are vague. It seriously affects the regional geological mapping. Especially, the fault shows brittle toughness, no obvious boundary geological information on the surface, the deep extension is not clear, the position of Feilai peak group in the boundary of the surface is fuzzy, the fault is characterized by brittleness and toughness, and there is no obvious boundary geological information on the surface. The distribution characteristics of deep structural styles are not very clear, etc. For the above reasons, it is more limited to carry out deep geological mapping only through surface survey. The deep geological mapping needs the support of the deep geophysical data. As a medium and shallow exploration technique, the Audio magnetotelluric (AMT) exploration has the advantages of high working efficiency, not being shielded by the high resistivity layer, and high resolution to the low resistivity layer, etc. Therefore, the Audio magnetotelluric method (AMT) is used to explore underground structures in this area. This paper first introduces the geological and geophysical characteristics of the study area, and then, in view of the above-mentioned problems encountered in the surface geological survey, combines the geological and physical data of the study area. The geoelectric cross section model such as fault, fold and Feilai peak and the coarse structure model in the depth of the survey line are established, the forward modeling and inversion calculation of AMT are carried out, and the characteristics of electromagnetic response are analyzed, and the resolution ability of the AMT method to typical geoelectric model is discussed. Then the SSMT2000 and MTSOFT-2D software are used to process the measured AMT data, and the shallow resistivity profile is obtained at the depth of 2 km. The geological geophysical comprehensive interpretation of the profile is carried out in combination with the geological and physical data of the study area. Finally, GOCAD software is used to complete the deep geological modeling under the local constraint of AMT profile. Through the above research, the following main results are obtained: 1) the resistivity test results of rock strata in the study area show that the main exploration targets are different rock masses. The difference of electrical properties in different strata is obvious, which satisfies the physical property foundation of electrical exploration, and can reasonably arrange the surveying lines in the survey area, obtain high quality data, and can achieve a better exploration effect. (2) after processing the data of Audio magnetotelluric sounding, Qualitative study on the single point bathymetric curve, apparent resistivity and phase section is carried out. Then, the nonlinear conjugate gradient inversion method is selected to process the magnetotelluric data, and the AMT inversion results are interpreted in combination with the surface geological mapping data. For the deep structural style of Lishuba fault, the underground distribution of Lianhuashifenglai peak is clearly understood. The results of geological modeling show that the deep extension of Lishuba fault can be solved under the constraint of AMT data. The geological problems such as the deep style of Feilefeng structure and the deep boundary of the main strata in the survey area are discussed. The results show that the detection results of Audio magnetotelluric (AMT) can provide reliable reference data for the deep geological survey and 3D modeling.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.325

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