华南岩石圈三维电性结构及构造意义

发布时间：2017-12-28 08:59

本文关键词：华南岩石圈三维电性结构及构造意义　出处：《吉林大学》2017年博士论文　论文类型：学位论文

【摘要】：华南大陆位于欧亚板块的东南部,处在全球现今三大重要板块——欧亚板块、太平洋板块与印度板块的汇聚拼合部位,是中国大陆及全球构造的重要组成部分,因此,建立华南大陆高精度三维结构模型具有重要的研究意义。论文依托国家专项“深部探测技术与实验研究”,围绕华南大陆岩石圈结构与构造问题开展研究,首次获得华南地区三维长周期大地电磁探测数据研究结果,基于获得的三维岩石圈电性结构模型对华南大陆的深部结构与状态进行系统剖析。通过对原始时间序列进行傅里叶变换、Robust估计、远参考、功率谱挑选等处理得到全部测点的大地电磁阻抗张量数据,经筛选获得385个高质量的大地电磁测深点。采用相位张量分解对维性信息进行分析,认为研究区整体二维性较好,仅局部及深部存在较强三维性。采用GB多频多测点分解法获得区域阻抗及电性主轴分布,分测线进行主轴统计,确定了研究区优势构造走向为NE向。采用感应矢量分析对高阻体高导体的平面特征进行定性分析,发现研究区深部可能存在线性分布的高导异常。应用Rhoplus分析对视电阻率和阻抗相位进行分析校正,并参照地质构造及视电阻率趋势对静态效应进行进一步评估。采用有效视电阻率进行一维正则化反演,获得了研究区岩石圈厚度分布。将各测线区域阻抗数据按照各自主轴方位角进行旋转,采用4种数据组合进行二维非线性共轭梯度反演。选用L曲线法确定最佳正则化因子,对不同数据组合的拟合情况进行评价。三维反演选用338个测点的全阻抗数据,在Tremissis数据平台上进行数据处理及模型构建,采用ModEM程序包进行三维反演,获得研究区岩石圈尺度的三维电性结构。对比二维三维反演结果,在电性特征上,东南沿海岩浆岩带反演结果一致,而华夏褶皱带与江南造山带差异较大。分析发现由于二维反演数据严重依赖于构造走向的确定,而华南地区复杂的地质构造使得这一分析结果存在较大不确定性,利用三维反演结果进行解释研究具有更大的合理性。研究区三维电性结构呈现纵向分层与横向分块特征,采用纵向圈层分析与横向地块分析相结合的手段对华南地区的电性结构进行综合研究。地壳整体以高阻特征为主,结构较为复杂。上地壳的电阻率分布格局反映了盆地深部与前寒武纪基底的耦合,下地壳电阻率的分布格局反映了新生麻粒岩相下地壳与古老地壳的组合。岩石圈地幔呈现明显的分区特征,扬子地块东缘江南造山带存在高阻体R1;华夏褶皱带存在高阻体R2、R3,其中R3越过上虞-政和-大浦断裂延伸入东南沿海岩浆岩带南段,高阻体R1、R2、R3通过线性延伸的低阻体C1、C2、C3衔接;东南沿海岩浆岩带北段存在低阻体C4,南北段为闽江断裂C5所分隔。根据岩石圈地幔的电阻率分布格局建立岩石圈尺度的构造框架。结合电性结构分析,研究了深大断裂的深部展布特征,讨论了华夏与扬子地块的接触关系。两大地块以东倾江绍断裂为界,华夏地块浅层向北西逆冲推覆,扬子在深部向华夏地块挤入。根据岩石圈厚度特征将华南地区岩石圈分为弱减薄型碎块岩石圈(Ⅰ型)和强减薄型的线性岩石圈(Ⅱ型)。弱减薄型碎块岩石圈厚度为130~150km,强减薄型线性岩石圈的厚度在80km左右。结合地幔捕掳体证据,对不同类型岩石圈地幔的物质结构进行分析,推测华南地区存在贫水、难熔的古老岩石圈地幔(Ⅰ型)和相对富水、新生的岩石圈地幔(Ⅱ型)。在物质结构基础上对上地幔热状态进行了大地热流对应分析,并根据高导区位置圈定了上地幔高热区域。
[Abstract]:Southern China, located in the southeastern part of the Eurasian plate in the world today, the three major sectors together spliced position of the Eurasian plate, the Pacific plate and India plate, is an important part of China, and global tectonics therefore, the establishment of Southern China, the high precision three-dimensional structure has important significance of constitutive model. Based on the national project "deep exploration technology and experimental research", focuses on the problems of Southern China continental lithosphere structure and tectonics, the first data research results in Southern China three long period magnetotelluric sounding, the 3D lithospheric electrical structure model of Southern China, the deep structure and based on system analysis. Through the processing of Fourier transform, Robust estimation, remote reference and power spectrum selection, we get the magnetotelluric impedance tensor data of all the measured points, and get 385 high-quality magnetotelluric sounding points. The phase tensor decomposition (phase tensor decomposition) is used to analyze the dimension of the information. It is considered that the overall two-dimensional character of the study area is better, but only the local and deep parts have strong three-dimensional character. The GB multi frequency and multi test point decomposition method is used to obtain the distribution of the main axis of the impedance and electrical properties of the region. The main shaft statistics are carried out by the measuring line, and the dominant structure of the study area is NE direction. The induction vector analysis is used to qualitatively analyze the plane characteristics of high resistance high conductor. It is found that there may be a high conductivity anomaly in the deep part of the study area. The Rhoplus analysis is used to analyze and correct the apparent resistivity and impedance phase, and the static effect is further evaluated according to the geological structure and the trend of apparent resistivity. The thickness distribution of the lithosphere in the study area is obtained by using the effective apparent resistivity for one dimensional regularization inversion. The impedance data of each line area are rotated according to the azimuth of each axis, and the two dimensional nonlinear conjugate gradient inversion is carried out by 4 kinds of data combinations. The L curve method was used to determine the best regularization factor, and the fitting of different data combinations was evaluated. Three dimensional inversion is based on 338 impedance data. The data processing and model building are carried out on the Tremissis data platform. The three-dimensional electrical structure of the lithospheric scale in the study area is obtained by using ModEM package for 3D inversion. Compared with the results of two-dimensional three-dimensional inversion, the inversion results of the magmatic rocks in the southeast coastal areas are consistent in the electrical characteristics, but the difference between the Huaxia fold belt and the Jiangnan orogenic belt is great. It is found that the two-dimensional inversion data is heavily dependent on the determination of the structural trend. The complicated geological structure in Southern China area makes the analysis result uncertain. The three-dimensional electrical structure in the study area is vertically stratified and laterally partitioned. The electrical structure of Southern China area is comprehensively studied by means of the combination of vertical circle analysis and transverse plot analysis. The whole crust is characterized by high resistance, and the structure is more complex. The resistivity distribution pattern of the upper crust reflects the coupling between the deep part of the basin and the Precambrian basement. The distribution pattern of the resistivity of the lower crust reflects the combination of the new granulite facies and the lower crust with the ancient crust. The lithospheric mantle show the partition characteristics of the Yangtze block of eastern margin of the Jiangnan orogenic belt has the high resistance body R1; China fold belt of existing high resistivity body R2, R3, R3 - across Shangyu Zhenghe Dapu fault extends into the southeast coast of Southern magmatite belt, high resistance R1, R2, R3 by linear extension of the low C1, C2, C3 resistance and cohesion; southeast coastal magmatite belt of low resistance C4, separated by the North-South Minjiang fault C5. The tectonic framework of the lithosphere scale is established according to the distribution pattern of the resistivity of the lithosphere mantle. Combined with the electrical structure analysis, the deep distribution characteristics of the deep fault are studied, and the contact relationship between the Huaxia and the Yangtze block is discussed. The two major blocks are bound to the east of the JIANGSHAO fault, and the shallow layer of the Huaxia block is thrust into the northwestern thrust, and the Yangtze is squeezed into the Huaxia massif in the deep. The lithosphere in Southern China area is divided into weakly reduced lithospheric lithosphere (type I) and strongly reduced linear lithosphere (type II) according to the thickness of the lithosphere. The thickness of the weakly reduced lithosphere is 130~150km, and the thickness of the strongly thinned linear lithosphere is about 80km. Combined with the evidence of mantle traps, we analyzed the material structure of different types of lithospheric mantle, and concluded that there are water poor and refractory ancient lithospheric mantle (type I) and relatively water rich and new lithospheric mantle (type II) in Southern China area. The thermal state of the upper mantle is analyzed on the basis of the material structure, and the upper mantle high heat region is delineated according to the position of the high guide area.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P631.325

【相似文献】