川滇地块东部断裂带的右行走滑变形研究：对青藏高原物质向东挤出的制约

The Chuandian Block is a key area to study the eastern extrusion process of the Tibet plateau. Since Oligocene to early Miocene (~32-20Ma), the Xianshuihe fault, it is the NE boundary fault of the Chuandian Block, had experienced stronger metamorphic events. At the same time, some synchronous migmatite occurred along the fault. However, the movement characteristics of the block during this period are still unknown. In eastern Chuandian block, there are several faults which show sinistral strike-slip in the late Cenozoic. However, our latest research discovered a stronger dextral strike-slip deformation occurred on these faults. The dextral deformation formed a ductile shear zone along the Anninghe fault, and affected the spatial distribution of the 35-20Ma large rare-earth ore. It is necessary further to confirm and to study the strong transformed dextral deformation along these faults. This project focuses on the structural geometries, the kinematics, the chronologies of the dextral deformation, and pays close attention to the regional tectono- thermal events coinstantaneous the dextral deformation. This study will get a preliminary understanding of the kinematic mechanism of the dextral deformation, as well as its basic constraint of the eastern extrusion of the Tibet plateau.

青藏高原东南缘的川滇地块是研究高原物质向东挤出的关键区域。渐新世-早中新世（~32 -20Ma），沿着川滇地块北东边界的鲜水河断裂带发生了强烈的变质事件，形成沿断裂带展布的混合岩。但此时川滇地块的运动特征尚不清楚。在川滇地块东部发育数条近南北走向的断裂带，新生代晚期以来表现为左行走滑。最新资料显示在左行走滑之前，这些断裂带可能经历了强烈的右行走滑变形，形成沿安宁河断裂带分布的糜棱岩，并影响了35-20Ma大型稀土矿床的空间分布。这期右行走滑已经被左行走滑强烈改造，需要进一步证实和研究。项目将以川滇地块东部数条断裂带的右行走滑变形为研究对象，查明其详细的几何学、运动学、年代学、及其伴生的构造热事件。探讨这期右行走滑变形的动力学机制及对青藏高原物质向东挤出的制约。

板块构造所面临的巨大挑战来自如何认识发生在远离板块边界的造山行为及深部控制因素、浅部表现特征。青藏高原东缘如何聚集并形成绵延千公里的山脉。青藏高原东南缘的川滇地块是研究青藏高原物质向东挤出方式、深部控制机理、浅部表现特征及其伴生灾害、环境效应的关键区域。项目从构造地质学传统研究方法切入，聚焦渐新世-早中新世以来，川滇地块的边界断层活动历史及伴生强烈的构造-热事件，并将研究内容辐射到青藏高原东缘重要边界断裂带的活动构造特征、构造地貌演化等方面。目前获得了重要成果包括：（1）在青藏高原东南缘的川滇地块中部，即川西北次级地块与滇东南次级地块之间的扬子地块的边界上、基于运动学和年代学两方面的数据，发现了渐新世-早中新世右行走滑的变形证据。（2）基于青藏高原东缘不同块体挤出过程的差异性对比研究，识别出巴颜喀拉和川滇地块在渐新世-早中新世发生了向北东方向的挤压。在晚中新世~10Ma以来二者表现出不同深部过程和挤出方式。基于以上的研究，建立青藏高原东缘新生代以来的演化模型。本项目将其概况为两期变形机制，期间存在一重要的构造体制转折。且青藏高原东缘并不存在从南向北的顺序扩展与隆升。（3）聚焦块体相东挤出引起的地貌效应，创新地构建了内外动力耦合的机制及其对地貌的控制作用。