【作者】 郑军；

【导师】 魏文博；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2011， 硕士

【摘要】 本论文以在华北鄂尔多斯地区所采集的35-40号大地电磁剖面数据为依托。在室内系统运用了先进的数据处理方法,完成了大地电磁数据处理工作,得到了可靠的MT响应。采用先进的二维反演算法,获得了研究区域具有较高可信度的二维电性结构模型。大地电磁场观测数据的阻抗张量分解结果表明,研究区域的地下介质电性结构近似为二维结构,电性主轴方位近南北向,这说明鄂尔多斯块体的主构造方向为近南北向。沿剖面范围内分布着多个电性异常带与畸变带,与区域构造资料对比,这些电性梯度带和畸变带的位置与区域内的深大断裂带相吻合,这些断裂带同时也是研究区域内各构造单元的边界断裂带。鄂尔多斯块体内部岩石圈范围内电性结构大致可以分为三层,即上、下为高阻层,中间为高导层,表层低阻层可能是新生代或中新生代的沉积层。研究区域中下地壳普遍发育有30欧姆米以下的高导层,高导体在鄂尔多斯块体内发育最为广泛和连续,以东西埋深小,中间埋深大特点为主,北部高导体在厚度和规模上大于南部,鄂尔多斯块体中南部上地幔发育圆环状高导体,圆环中心为一高阻体。鄂尔多斯西缘过渡带中下地壳普遍发育高导体,产状水平,规模较大,电阻率值相对较高。祁连快体东部,阿拉善块体东部以及吕梁地块下地壳高导体发育较少。鄂尔多斯块体莫霍面埋深在40-45公里,岩石圈厚度在120-150公里之间。鄂尔多斯块体内部中下地壳的高导体很可能是由于含盐流体或是局部熔融和含盐流体共同作用的结果,他们与鄂尔多斯块体内部的隐伏断层不无关系。鄂尔多斯块体东西两侧断裂带附近的的下地壳和上地幔高导体很可能是部分熔融和流体的共同作用,岩石部分熔融或者水分析出的热源来自于块体的运动,摩擦生热,并造成岩层的破碎,形成一系列断层,上地幔物质向上涌,形成壳幔混合物。鄂尔多斯最北端结晶基底是孔兹岩,孔兹岩是含石墨富铝的片岩、片麻岩夹大理岩和石英岩的区域变质岩组合,所以鄂尔多斯北部块体内部的下地壳的高导体可能是由石墨导致。沿着鄂尔多斯西缘褶断带的低阻体发育连续,且规模巨大,青藏高原的塑性的物质可能沿此逃逸。更多还原

【Abstract】 The thesis based on the No.35-40 magnetotelluric profiles data which is collected in Ordos region. In the Lab, we systemic used the advanced data processing methods, and completed the work of MT data processing to obtain a reliable MT response. After used the advanced two-dimensional inversion algorithm, we finally got the high confidence two-dimensional electrical structural model of the studies region.As the decomposition of the magnetotelluric impedance tensor show the underground electrical structure of research area is approximately a two-dimensional structure,in which electrical axis is nearly east-west direction,thus indicating the main structure of Ordos region is north-south direction.With MT sounding response analyzed.The research results show that there are distributed number of anomalous zone and electrical distortion zone, the position of the electric gradient and distortion zones roughly coincides with the major fault line delineated by regional geological data. These fault zones simultaneously are also to be the each tectonic element’s dividing line fault zone in the study area. The internal electrical structure of the lithosphere in Ordos block can be divided into three layers, contain the upper and lower layer of high resistance, and the middle layer of high conductivity, the surface layer conductive bed possibly is the Cainozoic Era or Cainozoic Era’s deposit formation. Study area generally development the high-conductivity layer below 30 Oumu Mi in lower crust. The high-conductivity layer development extensively and continuously within Erods block,which the main feature is:the depth in East and West are small,by contrast the middle of the profile are large.The thickness and scale of the high conductivity layer in north of the Erods block larger than the south of the Erdos block.The circle of high conductivity body development in the middle and south Erdos block,which center is a high resistivity.The east of alashan block、qilian block and the north and south lvliang upheaval in west of north china development few high conductivity body in lower crust which scale is not large. Transition zone in the western margin of Ordos widespread development of high conductive body with relatively high resistivity values and a large scale in lower crust,which occurrence is level.The depth of Moho surface is nrarly 40-45 Km in Erdos block,and the thickness of the lithosphere is 120-150Km.The Saline fluid and Partial melting interaction with the saline fluid are the reason for the high conductive layer development at the internal Erdos block, which are impossible irrelated with the buried fault in the Erdos block.The most possible reasons for high conductivity larer which developmente in lower crust and upper mantle in the fault belt located in both sides of the Erdos block are partial melting and fluid interaction.The heat source of the rock particl and the water move out of the rock is the block movement,which made fiction product heat and cause fragmentation of rock,which forming a series of fault.Material in upper mantle upwelling forming crust-mantle mixture.The crustle base in north Erdos block is khondalite,which is aluminum-rich schist with graphite gneiss folder、marble and quartzite combination of regional metamorphic rocks.So the high conductivity body in the internal north of the Erdos block maybe due to the Graphite.the low resistivity body in the western margin of Ordos fold belt which the material in Tibetan Plateau escaped development continuously,which scale is large.更多还原