南北构造带北段及邻区岩石圈力学强度与形变特征研究

The deformation features of lithosphere is a complex subject when referring to the study of continental dynamics, effective elastic thickness of the lithosphere (Te) and its anisotropy is a valid path to identify the deep tectonic deformation. .The north segment of North-South tectonic belt is an ideal research area for exploring the deformation characteristics of the continental lithosphere, where Tibet gradually move forward to the north-east, and records the history of blocks colliding and merging of Tibet as well as the severe tectonic deformation process since Indosinian times. Different blocks of the north and west sides of the North-South tectonic belt and different layers were selected in this research, meanwhile the multitaper spectral correlation method were applied to select different sliding windows to calculate the two-dimensional fine structure of the Te and its anisotropy in the study area. The geological and geophysical data of different blocks, and the metamorphic basement, cap rock composition, magma distribution, surface fault distribution, the effects of geothermal, density, wave velocity and electrical structure were combined to explore its impact on the mechanics strength of different lithosphere, meanwhile revealing structural diversity of different blocks. Comparing the Te anisotropy and seismic anisotropy along with the distribution characteristics of tectonic stress field in different blocks, analyzing vertical deformation model of lithosphere and the characteristics of deep material migration, this project revealing the differences in lithospheric deformation features of the north and west sides of the North-South tectonic belt, and providing a fundamental theory for the evolution and deep dynamics of the North-South tectonic belt.

岩石圈形变是大陆动力学研究面临的难题，岩石圈有效弹性厚度（Te）及其各向异性是解决深部构造变形的有效途径。贺兰-川滇南北构造带北段记录了青藏高原多个构造块体汇聚拼贴的历史，以及印支期以来强烈的陆内构造变形过程，是探讨大陆岩石圈形变特征的最佳场所。本研究拟选取南北构造带北段东、西两侧不同地块、不同圈层为研究对象，采用多窗口谱相关法，选取不同的滑动窗口，计算研究区岩石圈Te及其各向异性的二维精细结构；结合不同地块地质、地球物理资料，探讨变质基底、盖层岩石组成、岩浆分布、地表断裂、地热、密度、波速、电性结构等特征对不同岩石圈层力学强度的影响，揭示不同地块的构造活动性差异；对比不同地块Te各向异性与地震波各向异性和现今构造应力场的分布特征，分析壳幔变形模式，以及深部物质运移特征，揭示南北构造带北段东、西两侧岩石圈形变特征的差异性，为南北构造带形成演化的与深部动力学过程奠定理论基础。

南北构造带北段记录了青藏高原多个构造块体汇聚拼贴的历史，以及印支期以来强烈的陆内构造变形过程，它的深部构造及岩石圈形变特征是地球动力学研究的关键问题之一。岩石圈有效弹性厚度（Te）是研究岩石圈变形和动力学机制的有效途径。本项目以南北构造带北段及邻区不同块体为研究对象，系统开展了该区域岩石圈有效弹性厚度研究及有关地质问题的探讨。开展的主要工作和取得的主要认识如下：（1）基于重力异常和地形高程数据，采用Slepian多窗谱法反演了南北构造带北段及邻区的岩石圈Te及其各向异性；（2）与区域地质构造的对比分析显示，构造运动引起岩石圈块体之间发生相互作用，通过岩浆活动、断裂、褶皱等形式调整岩石圈内部物质组成和结构形态，这导致岩石圈Te值降低；（3）与地球物理属性的对比分析显示，研究区不同块体、不同岩石圈层的物质成分、结构形态和地球物理属性存在明显的差异，致使南北构造带北段东、西两侧岩石圈力学结构模式显著不同；（4）不同块体之间的相互作用会降低岩石圈的整体力学强度，同时下地壳中低速、低阻层的驰豫作用会将应力转移到上地壳，导致应力的相对积累增加，使脆性上地壳的稳定性极易破坏，容易发生地震。以上研究为南北构造带北段东、西两侧地块的深部结构特征和岩石圈形变特征的认识提供了重要的科学依据。在该项目资助下，发表会议论文4篇，撰写SCI论文4篇。