北秦岭基底变质岩系流变特征与变形过程研究

The middle-lower crustal rheology information recorded and preserved in the orogen is not only crucial to deciphering the tectonic evolutionary history of orogenic belt, but also key to understanding the tectonic deformation, rheological mechanism and process of the continental lithosphere. A detailed study of middle-lower crustal rheological characteristics and processes on typical orogenic belt is significant to explore the rheology, growth, and deformation localization of continental lithosphere. The Qinling orogenic belt was formed by long-termed subduction-collision between the North China Block and the South China Block, and its metamorphic basement rocks, the Qinling complex, recorded the complete and complex rheology process during the orogeny. This project deals with the Qinling complex, and will focus on the Danfeng-Mangling, Qingyouhe, and Xiping-Wulichuan rheological cross sections. The outcrop-micro-lattice scale rheological characteristics will be obtained by field-based structural analysis, strain analysis, microtectonics, and fabrics. The application of microtectonics, crystallographic preferred orientations, and geothermometer constrains the deformation P-T conditions. The timing of deformation will be determined by hornblende, muscovite and biotite 40Ar/39Ar dating and zircon U-Pb dating, in order to establish the time frame of the tectonic deformation process of the Qinling complex. Based on the data of middle-lower crustal rheological characteristics, deformation P-T conditions, and time frame, this project will provide constraints of rheological mechanism and process on the tectonic evolutionary history of the Qinling orogenic belt.

造山带中丰富的中下地壳流变学信息是研究造山带构造演化、解决大陆岩石圈构造变形和探讨岩石圈流变机制与过程的关键。典型造山带中下地壳流变学特征与过程的精细解剖，对探讨大陆岩石圈流变学特性、形成过程及大陆变形局部化具有重要意义。秦岭造山带形成于华北板块和华南板块的长期俯冲碰撞过程，其中，北秦岭深变质基底岩系——秦岭杂岩记录和呈现了完整而复杂的流变作用和过程。本项目拟以秦岭杂岩为研究对象，通过野外构造解析、应变分析、显微构造和变形组构研究，讨论秦岭杂岩的露头-显微-晶格尺度流变学特征；综合显微构造、组构特征和矿物成分温压计，厘定构造变形的温度和压力条件；采用角闪石、白云母和黑云母40Ar/39Ar法、锆石U-Pb法，精确测定构造变形事件的时限，建立秦岭杂岩构造变形过程的年代学格架。最终，确定秦岭中下地壳流变学特征、变形条件和年代学框架信息，为秦岭造山带的构造演化过程提供有效的流变学机制与过程约束。

造山带中丰富的中下地壳流变学信息是研究造山带构造演化、解决大陆岩石圈构造变形和探讨岩石圈流变机制与过程的关键。典型造山带中下地壳流变学特征与过程的精细解剖，对探讨大陆岩石圈流变学特性、形成过程及大陆变形局部化具有重要意义。秦岭造山带形成于华北板块和华南板块的长期俯冲碰撞过程，其中，北秦岭深变质基底岩系——秦岭杂岩记录和呈现了完整而复杂的流变作用和过程。本项目以秦岭杂岩及其边界剪切带为研究对象，通过野外构造解析、应变分析、显微构造和变形组构研究，讨论秦岭杂岩的露头-显微-晶格尺度流变学特征；综合显微构造、组构特征和矿物成分温压计，厘定构造变形的温度和压力条件；采用角闪石、白云母和黑云母40Ar/39Ar法、锆石U-Pb法，精确测定构造变形事件的时限，建立秦岭杂岩构造变形过程的年代学格架。最终，确定秦岭中下地壳流变学特征、变形条件和年代学框架信息，为秦岭造山带的构造演化过程提供有效的流变学机制与过程约束。在本项目的支撑下，发表了标注SCI论文7篇，项目负责人获得了国家自然科学基金委优秀青年基金的资助。