青藏高原东南缘金河—箐河断裂带右旋走滑变形的证据及构造意义

The Study of the Dextral Oblique-slip Deformation of the Jinhe–Qinghe Fault,Southeast Tibet,and Its Tectonic Significance

青藏高原东南缘新生代以来的演化是认识高原向东扩展的关键。位于该区的金河—箐河断裂带总体呈NE向展布,现今表现为左行走滑特征。最新的野外地质调查发现,金河—箐河断裂带的北段发育一套具有典型韧性剪切变形特征的糜棱岩,其原岩为泥盆纪的火山凝灰岩和中—上元古界的流纹质火山岩。剪切带的显微构造特征及岩层的变形特征指示断裂带发生了右旋剪切变形。对剪切带内特征矿物显微构造分析,结合EBSD测试限定整条韧性剪切带的变形温度为~400℃。目前对这期右行走滑的时代缺乏研究,结合区域相关资料,推断其可能发生在晚始新世—早中新世。这对于完善和认识青藏高原东南缘新生代早期的构造变形具有重要意义。

The Cenozoic geological evolution of the southeastern margin of the Tibetan Plateau is a key issue to understanding the eastwards material propagation processes of Tibetan Plateau.The Jinhe–Qinghe fault zone,striking in NE direction,shows left-lateral strike-slipping now.However,the latest field geological survey discovered the northern segment of the Jinhe–Qinghe fault zone had experienced ductile shear deformation.The protoliths of the mylonite of the shear zone are volcanic tuff and rhyolitic volcanics.The meso-and micro-structure characteristics indicate dextral oblique-slip deformation.Microstructure analysis of these deformed minerals,such as quartz and feldspars,combined with the EBSD testing,suggests that the deformation temperature is^400℃.Under reviewing the regional geological studies,this paper suggests that the dextral oblique-slip deformation might occur during Late Eocene to Early Miocene.It also needs further researches.This study might provide a new aspect and have a great significance to understanding the Early Cenozoic deformation and material propagation processes of the Southeast Tibet.