滇西地区地壳与上地幔电性结构及其构造意义研究

The study area is located in the binding site of the Tengchong block and the Baoshan block of Yunnan Burma Thailand plate. It is located in the southeast margin of the Qinghai Tibet Plateau and the southern section of the North South seismic belt of China, and it has always been attention by Chinese and foreign geologists for intense activities of geological structure and the unique of deep crust structure. It has made a great progress in surface geological research after years of research. There are significant differences of major scientific problems of the cognize and relationship between deep crust mantle structure in western Yunnan, especially the Bangong Nujiang suture zone extension in western Yunnan and the contact relationship of Tengchong block and the Baoshan block, such as the Bangong Nujiang suture zone extends along the Nu River or the Longling Ruili fault zone, or underneath the Tengchong block. The project will focus on these problems, to carry out comprehensive geological and geophysical study of the measurement and interpretation of magnetotelluric profile, combined with atlas of remote sensing interpretation, the controlled source audio frequency magnetotelluric and geological data of the surface. The project will build a multiscale model of the crust and upper mantle structure on the basis of magnetotelluric sounding interpretation. The research results have important significance for solving geological structure problem of the extension of the Bangong Nujiang suture zone in western Yunnan and contact relationship of the Tengchong block and the Baoshan block . At the same time, it has important reference value to the study of the Longling earthquake zone electrical structure and geological line selection of railway.

研究区位于滇缅泰亚板块的腾冲地块与保山地块结合部位，它既是青藏高原的东南缘，又位于中国南北地震带南段，地质构造活动强烈，地壳深部结构独特，历来为中外地质学家所注目。经过多年研究，地表地质研究有长足进展。但有关滇西地区深部壳幔结构认识与相互间关系等重大科学问题的看法，特别是班公湖-怒江缝合带滇西段的延伸、腾冲地块和保山地块的接触关系等问题存在着很大分歧，如班公湖-怒江缝合带是沿怒江还是龙陵-瑞丽断裂延伸，还是被腾冲地块压在下面。项目将围绕这些问题，开展以大地电磁剖面测量与解释为主，结合遥感解译、可控源音频大地电磁和地表地质资料对比分析等综合地质地球物理方法研究，建立一个以大地电磁解释为主的多尺度地壳与上地幔结构模型。研究成果对于解决班公湖-怒江缝合带滇西段延伸、腾冲地块和保山地块接触关系等地质构造难题具有重要指导意义，同时对龙陵地震区电性结构与灾害地震研究以及铁路地质选线也具有重要参考价值。

项目对青藏高原东缘特别是三江地区地壳上地幔电性结构研究进展进行了收集和整理，系统地对研究区地壳上地幔电性结构、区域电性孕震环境及弱物质流通道等方面进行了梳理和分析，归纳总结建立了青藏高原东缘六种壳幔电性结构类型；完善了大地电磁二、三维倾子正演模拟和电性参数约束反演方法研究；对噪声干扰下多种张量阻抗分解方法的稳定性进行对比分析，实现了基于相位张量分解估算稳定电性主轴方向估算算法以及“二次方程”法视电阻率曲线校正；在高黎贡山斜向碰撞造山带及邻区实施了盈江芒章—镇康流水和腾冲马站—昌宁更戛两条大地电磁测深剖面，初步建立起腾冲地块和保山地块深部地壳高阻—低阻—中高阻层状电性结构模型，发现腾冲地块与保山地块结合部高黎贡山斜向碰撞造山带深部存在高阻楔形电性结构，证实腾冲中基性火山岩区上地壳底部存在多个尚未固结的岩浆囊，推测龙陵Ms7.3级和Ms7.4级地震震源区存在隐伏震源断裂；在此基础上，结合大瑞铁路黄草坝断裂CSAMT、遥感地质解译及钻探等成果，对高黎贡山隧道地质选线进行了研究，研究表明：龙陵—瑞丽断裂带深处存在丁青—怒江碰撞缝合带，浅部黄草坝断裂是一条起阻水隔热作用的分界断裂，其与区域断裂深循环系统共同控制研究区地下热水的补给、径流和排泄条件，为高黎贡山隧道方案成立的重要和关键工程地质条件。滇西地区深部电性结构研究对揭示研究区岩石圈结构和构造格局提供了重要依据，同时对龙陵—腾冲地震区的构造关系和发震机理研究及重大工程实施具有重要指导意义。