云南红河-哀牢山断裂带隆升剥蚀的沉积响应：碎屑锆石双定年及磷灰石裂变径迹综合年代学研究

The Red River-Ailao Shan fault belt (RRAS), western Yunnan, is the largest Cenozoic structure in the southeastern margin of the Tibetan Plateau. It experienced structural uplift, subsidence and strike-slip deformation. A large number of previous studies paid much attention to the structural and thermal evolution of the metamorphic rocks along the RRAS. In view of our preliminary sedimentary and paleomagnetic researches, this project is planning to systematically collect metamorphic and granitic gravel samples with reference to the intraformational position of the Cenozoci conglomerate sediments lying in northeast of the Ailao Shan. 1) Same grains zircon double dating (fission track and U-Pb) will be conducted on the detrital zircon grains from the lower part of the sediments, allowing us to screen out the Ailao Shan-derived grains and reveal the uplift age information. We are about to use apatite fission track dating to reveal the latest uplift age of those components. 2) The zircon U-Pb dating will be conducted on single gravel samples from the upper section of the conglomerate sediments to make sure whether it is Ailao Shan-origined, and the following apatite fission track will possibly provide us the latest uplift age of the Ailao Shan. This multiple-dating research will not only reveal the Cenozoic uplift history of the Ailao Shan, but also provide us new sedimentary and thermochronological evidence for better understanding the Early Cenozoic ductile shear and regional uplift along the RRAS.

滇西红河-哀牢山断裂带是青藏高原东南缘规模最大的新生代构造，经历了隆升、下陷和走滑变形。前人开展了大量的研究，但是多集中在其中变质岩的构造和热演化方面。项目在前人成果及前期沉积学、古地磁年代学研究基础上，计划对哀牢山北东侧新生代砾岩地层中的变质岩、花岗岩砾石开展系统的分层采样测试研究。1）对新生代早期细粒砾石开展碎屑锆石双定年（裂变径迹及U-Pb）研究，筛选来自哀牢山的组分，提取其构造隆升年代信息，并尝试采用磷灰石裂变径迹方法揭示其对应的最新一期构造隆升发生的年代。2）对新生代晚期砾岩中单独砾石样品利用U-Pb年龄对比，判定其哀牢山属性，并通过磷灰石裂变径迹手段提取其构造隆升年代学信息。本项研究采用多定年手段综合分析哀牢山新生代隆升剥蚀历史，将为深入探讨红河-哀牢山断裂带早期韧性剪切及构造隆升活动历史提供新的沉积学及热年代学证据。