羌塘地块深部电性结构研究及动力学意义
发布时间：2018-10-19 19:44
【摘要】：本文主要利用5条大地电磁剖面对青藏高原中北部羌塘地块及邻区深部电性结构开展详细研究探讨,并获得了该区域壳幔结构及动力学过程的一些新认识。大地电磁法资料处理时,首先分析了每个测点的二维偏离度、电性主轴方向、阻抗相位张量和趋肤深度等参数,再采用NLCG法对TE和TM两种模式的视电阻率和相位数据进行联合反演,最终获得了沿剖面5条测线的二维电性结构模型。基于这些电性结构模型,结合研究区域已有的地质和地球物理资料,我们对该区域深部电性结构及动力学过程取得了如下新认识：(1)羌塘地块垂向由浅至深大致可分为三个电性层：第一层为高阻层,电阻率值为几百至几千欧姆米；第二层为壳内高导层,电阻率值为几欧姆米,且高导层沿剖面分布不均匀；第三层为相对高阻层,电阻率值为几十至几百欧姆米。本研究还发现南羌塘地块存在壳内双层高导层,证实了青藏高原西部和中部南羌塘地块存在双层壳内高导层的观点。(2)横穿羌塘地块的三条大地电磁剖面反演结果显示：羌塘地块之下地电结构除具有上下分层的特性外,还有南北两分的特征。其中南羌塘地块之下高导层自羌中隆起附近向南倾斜；而北羌塘地块之下高导层形态类似于勺子形状,由金沙江缝合带之下靠近地表的深度向南倾斜,在北羌塘地块中部延伸至最大深度的下地壳或上地幔,并开始逐渐向上延伸,在羌中隆起附近到达近地表深度。南、北羌塘地块之下的壳内高导层均在羌中隆起附近向地表延伸,形成南北对冲的异常形态。基于此,认为在三叠纪时期,松潘-甘孜混杂岩沿金沙江缝合带向南俯冲,破坏并替代了几乎整个羌塘地块的地壳结构。羌塘地块壳内富水的混杂岩将有利于含水熔融的发生,进而解释班公湖-怒江缝合带两侧明显的地球物理差异。(3)根据羌塘地块壳内高导层的分布特征还可推断：在羌塘地块中西部,地壳流并非沿金沙江缝合带向东流动,而是在羌塘地块中部自西向东流动,并在高原东南部逐渐转为沿构造薄弱带流出。而在羌塘地块中部不断上涌的幔源岩浆为维持羌塘地块不变的海拔高度和不断东流的地壳流之间的平衡提供物质支持。(4)两条跨越班公湖-怒江缝合带的的大地电磁剖面的反演结果显示：壳内高导体在班公湖-怒江缝合带以南30～40km的位置(地表对应改则-色林错逆冲断裂)规模最大,并且具有南北对冲特征和向上地幔延伸的趋势。本人认为这一相互对冲的高导异常可能反映了中特提斯洋壳双向俯冲的残留痕迹。班公湖-怒江缝合带之下浅部与深部电性结构明显的错动说明了在新生代时期,班公湖-怒江缝合带两侧发生过强烈的逆冲推覆构造运动,使得班公湖-怒江缝合带上蛇绿岩发生构造侵位,进而导致浅部与深部构造错断,而南羌塘地块双层壳内高导层中的浅部高导层即为这一系列逆冲推覆构造所形成的构造滑脱面。(5)由卫星重、磁数据,发现羌塘地块中部双湖地堑具有由地表向下地壳延伸的趋势。通过比较羌塘地块各种地质事件发生的先后顺序,推测羌塘地块中部的双湖地堑是由于高原隆升至最大高度后,增厚的岩石圈地幔发生重力垮塌,进而形成了该南北向断裂。
[Abstract]:In this paper, five magnetotelluric profiles are used to study the deep electrical structures of the Qiangtang block and the adjacent region in the Qinghai-Tibet Plateau, and some new understandings of the structure and dynamic process of the shell structure are obtained. In the data processing of magnetotelluric method, the two-dimensional deviation, electrical principal axis direction, impedance phase tensor, skin depth and other parameters of each measuring point are analyzed, and the apparent resistivity and phase data of TE and TM modes are jointly inverted by NLCG method. Finally, a two-dimensional electrical structure model is obtained along section 5. Based on these electrical structural models, combined with the existing geological and geophysical data in the research area, we have obtained a new understanding of the deep electrical structure and dynamic process of the region: (1) the vertical direction of the Qiangtang plot can be divided into three electrical layers from shallow to deep: the first layer is the high resistance layer, the resistivity value is hundreds to thousands of ohms; the second layer is a high conductivity layer in the shell; the resistivity value is several ohms; and the high conductivity layer is not evenly distributed along the cross section; the third layer is a relatively high resistance layer, and the resistivity value is tens to hundreds of ohms. The present study also found that there are two layers of high conductivity in the shell of the southern Qiangtang block, and the view that the high conductivity layer in the double shell is present in the western part of the Tibetan Plateau and the southern Qiangtang block in the central part of the Qinghai-Tibet Plateau is proved. (2) The inversion results of three magnetotelluric cross sections across the Qiangtang block show that the electric structure under the Qiangtang block has the characteristics of two points of north and south besides the characteristics of upper and lower layers. wherein the high conductivity layer below the southern Qiangtang block is inclined to the south from the middle of the uplift; and the high conductivity layer below the northern Qiangtang block is similar to the spoon shape, the depth of the high conductivity layer below the north Qiangtang block is inclined to the south, and the middle part of the north Qiangtang block extends to the lower earth crust or the upper crust of the maximum depth, and begins to extend gradually upward, reaching a near surface depth in the vicinity of the ridge in the ridge. In the south and the northern Qiangtang block, the high conductivity layer in the shell extends to the earth surface in the vicinity of the uplift, thus forming the abnormal form of the north-south hedge. On the basis of this, it is believed that during the Triassic, Songpan-Ganzi hybrid rocks subducted to the south along the same suture zone, destroyed and replaced the crustal structure of almost the whole Qiangtang block. The water-rich mixed rock in the shell of the Qiangtang block will be beneficial to the occurrence of water-containing melting, and further explain the obvious geophysical difference between the two sides of the Bangong Lake-Nujiang suture zone. (3) According to the distribution characteristics of the high conductivity layer in the shell of the Qiangtang block, it can be concluded that in the west and west of the Qiangtang block, the earth's crust flow does not flow eastward along the north-west suture zone, but flows eastward from west to east in the middle part of the Qiangtang block, and gradually turns out along the structural weakness zone in the southeast part of the plateau. In the middle of the Qiangtang block, the flood-source magma poured into the middle of the northern Qiangtang block provides material support for maintaining the constant altitude of the Qiangtang block and the constant flow of the earth's crust. (4) The inversion results of the magnetotelluric cross section of the two suture zones across the Bangong Lake-Nujiang River show that the height of the high conductor in the shell is the largest in the 30 ~ 40km south of the Bangong Lake-Nujiang suture zone (corresponding to the change of the surface corresponding to the reverse impact of the color forest). and has a trend of north-south hedge characteristics and up-and-down extension. I believe that this one-sided high anomaly may reflect the vestiges of a two-way dive in the Tethys oceanic crust. The obvious misinterpretation of shallow part and deep electrical structure under Bangong Lake-Nujiang suture zone shows that there has been a strong reverse thrust-over tectonic movement on both sides of Bangong Lake-Nujiang suture zone during the Cenozoic era, so that the ophiolite in Bangong Lake-Nujiang suture belt has tectonic invasion position. in addition, that shallow part and the deep structure are staggered, and the shallow part high-permeability layer in the high-permeability layer in the double-layer shell of the south Qiangtang block is the structure slip surface formed by the series of reverse punching and pushing-over structure. (5) From the satellite weight and magnetic data, it is found that the double-lake graben in the middle of the Qiangtang block has a tendency to extend downward from the earth's surface. By comparing the sequence of various geological events in the Qiangtang block, it is estimated that the two-lake graben in the middle part of the Qiangtang block is due to the high plateau uplift to the maximum height, and the thickened lithospheric surface is collapsed and the north-south fault is formed.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.325
本文编号：2282169
[Abstract]:In this paper, five magnetotelluric profiles are used to study the deep electrical structures of the Qiangtang block and the adjacent region in the Qinghai-Tibet Plateau, and some new understandings of the structure and dynamic process of the shell structure are obtained. In the data processing of magnetotelluric method, the two-dimensional deviation, electrical principal axis direction, impedance phase tensor, skin depth and other parameters of each measuring point are analyzed, and the apparent resistivity and phase data of TE and TM modes are jointly inverted by NLCG method. Finally, a two-dimensional electrical structure model is obtained along section 5. Based on these electrical structural models, combined with the existing geological and geophysical data in the research area, we have obtained a new understanding of the deep electrical structure and dynamic process of the region: (1) the vertical direction of the Qiangtang plot can be divided into three electrical layers from shallow to deep: the first layer is the high resistance layer, the resistivity value is hundreds to thousands of ohms; the second layer is a high conductivity layer in the shell; the resistivity value is several ohms; and the high conductivity layer is not evenly distributed along the cross section; the third layer is a relatively high resistance layer, and the resistivity value is tens to hundreds of ohms. The present study also found that there are two layers of high conductivity in the shell of the southern Qiangtang block, and the view that the high conductivity layer in the double shell is present in the western part of the Tibetan Plateau and the southern Qiangtang block in the central part of the Qinghai-Tibet Plateau is proved. (2) The inversion results of three magnetotelluric cross sections across the Qiangtang block show that the electric structure under the Qiangtang block has the characteristics of two points of north and south besides the characteristics of upper and lower layers. wherein the high conductivity layer below the southern Qiangtang block is inclined to the south from the middle of the uplift; and the high conductivity layer below the northern Qiangtang block is similar to the spoon shape, the depth of the high conductivity layer below the north Qiangtang block is inclined to the south, and the middle part of the north Qiangtang block extends to the lower earth crust or the upper crust of the maximum depth, and begins to extend gradually upward, reaching a near surface depth in the vicinity of the ridge in the ridge. In the south and the northern Qiangtang block, the high conductivity layer in the shell extends to the earth surface in the vicinity of the uplift, thus forming the abnormal form of the north-south hedge. On the basis of this, it is believed that during the Triassic, Songpan-Ganzi hybrid rocks subducted to the south along the same suture zone, destroyed and replaced the crustal structure of almost the whole Qiangtang block. The water-rich mixed rock in the shell of the Qiangtang block will be beneficial to the occurrence of water-containing melting, and further explain the obvious geophysical difference between the two sides of the Bangong Lake-Nujiang suture zone. (3) According to the distribution characteristics of the high conductivity layer in the shell of the Qiangtang block, it can be concluded that in the west and west of the Qiangtang block, the earth's crust flow does not flow eastward along the north-west suture zone, but flows eastward from west to east in the middle part of the Qiangtang block, and gradually turns out along the structural weakness zone in the southeast part of the plateau. In the middle of the Qiangtang block, the flood-source magma poured into the middle of the northern Qiangtang block provides material support for maintaining the constant altitude of the Qiangtang block and the constant flow of the earth's crust. (4) The inversion results of the magnetotelluric cross section of the two suture zones across the Bangong Lake-Nujiang River show that the height of the high conductor in the shell is the largest in the 30 ~ 40km south of the Bangong Lake-Nujiang suture zone (corresponding to the change of the surface corresponding to the reverse impact of the color forest). and has a trend of north-south hedge characteristics and up-and-down extension. I believe that this one-sided high anomaly may reflect the vestiges of a two-way dive in the Tethys oceanic crust. The obvious misinterpretation of shallow part and deep electrical structure under Bangong Lake-Nujiang suture zone shows that there has been a strong reverse thrust-over tectonic movement on both sides of Bangong Lake-Nujiang suture zone during the Cenozoic era, so that the ophiolite in Bangong Lake-Nujiang suture belt has tectonic invasion position. in addition, that shallow part and the deep structure are staggered, and the shallow part high-permeability layer in the high-permeability layer in the double-layer shell of the south Qiangtang block is the structure slip surface formed by the series of reverse punching and pushing-over structure. (5) From the satellite weight and magnetic data, it is found that the double-lake graben in the middle of the Qiangtang block has a tendency to extend downward from the earth's surface. By comparing the sequence of various geological events in the Qiangtang block, it is estimated that the two-lake graben in the middle part of the Qiangtang block is due to the high plateau uplift to the maximum height, and the thickened lithospheric surface is collapsed and the north-south fault is formed.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.325
【参考文献】
相关期刊论文 前9条
1 张乐天;金胜;魏文博;叶高峰;段书新;董浩;张帆;谢成良;;青藏高原东缘及四川盆地的壳幔导电性结构研究[J];地球物理学报;2012年12期
2 郭良辉;孟小红;石磊;陈召曦;;优化滤波方法及其在中国大陆布格重力异常数据处理中的应用[J];地球物理学报;2012年12期
3 赵文津;吴珍汉;史大年;熊嘉育;薛光琦;宿和平;胡道功;叶培盛;;国际合作INDEPTH项目横穿青藏高原的深部探测与综合研究[J];地球学报;2008年03期
4 郑洪伟;李廷栋;高锐;赵大鹏;贺日政;;印度板块岩石圈地幔向北俯冲到羌塘地体之下的远震P波层析成像证据[J];地球物理学报;2007年05期
5 迟效国,李才,金巍;藏北羌塘地区新生代火山作用与岩石圈构造演化[J];中国科学(D辑:地球科学);2005年05期
6 马晓冰,孔祥儒,刘宏兵,闫永利;青藏高原东北部地区地壳电性结构特征[J];地球物理学报;2005年03期
7 潘桂棠,朱弟成,王立全,廖忠礼,耿全如,江新胜;班公湖—怒江缝合带作为冈瓦纳大陆北界的地质地球物理证据[J];地学前缘;2004年04期
8 孙洁,晋光文,白登海,王立凤;青藏高原东缘地壳、上地幔电性结构探测及其构造意义[J];中国科学(D辑:地球科学);2003年S1期
9 熊绍柏,刘宏兵;青藏高原西部的地壳结构[J];科学通报;1997年12期
，本文编号：2282169
本文链接：https://www.wllwen.com/shoufeilunwen/jckxbs/2282169.html
