青藏高原东缘鲜水河断裂带南东段渐新世以来主要构造岩浆事件的岩石记录  

Petrological records of major tectono-magmatic events since Oligocene in the southeastern segment of Xianshuihe fault zone in the eastern margin of Tibetan Plateau

作　　者：唐渊[1,2] 王鹏[2] 邓红 刘宇平[2] 唐文清[2] TANG Yuan;WANG Peng;DENG Hong;LIU Yuping;TANG Wenqing(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Chengdu Center,China Geological Survey,Chengdu 610081,Sichuan,China;No.108 Geological Team,Sichuan Bureau of Geology and Mineral Exploration,Chengdu 611230,Sichuan,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质调查局成都地质调查中心,四川成都610081 [3]四川省地勘局一〇八地质队,四川成都611230

出　　处：《地质通报》2022年第7期1121-1143,共23页Geological Bulletin of China

基　　金：第二次青藏高原综合科学考察研究项目《典型地区岩石圈组成、演化与深部过程》(编号:2019QZKK0702);中国地质调查局项目《雅鲁藏布江下游水电开发区地质安全性评价》(编号:DD20211541);《三江造山带昌都—澜沧地区区域地质调查》(编号:DD20190053);《川(滇)藏铁路沿线区域地质调查》(编号:DD20160021)。

摘　　要：作为青藏高原东缘巴颜喀拉地块和川滇地块的分界线,鲜水河左行走滑断裂带被认为是调节藏东地壳物质大规模南东向挤出与地块旋转运动的东边界。研究鲜水河断裂带的构造变形特征和演化历史,对深入认识青藏高原东缘大陆变形过程具有十分重要的科学意义。针对鲜水河断裂带南东段的变形特征开展了野外露头-显微尺度的构造分析,并从该段发育的花岗质糜棱岩和淡色脉体中选取了5个样品开展锆石U-Pb测年,分别得到34.4±0.9 Ma、31.0±1.2 Ma、15.92±0.3 Ma、14.9±0.1 Ma和5.93±0.14 Ma的年龄;选取了2个花岗质糜棱岩样品开展白云母Ar-Ar测年,得到的坪年龄分别为17.21±0.30 Ma和3.21±0.16 Ma。结合前人获得的年龄数据,总结出鲜水河断裂带渐新世以来存在3个阶段的构造-岩浆作用过程。阶段Ⅰ:32~25 Ma,鲜水河断裂带的构造变形集中在地壳深部,表现为一定规模的岩浆作用和深熔作用;阶段Ⅱ:20~13 Ma,鲜水河断裂带的构造变形遍布整个地壳,表现为强烈的左行韧性剪切变形和大规模的岩浆作用;阶段Ⅲ:10 Ma~现今,变形集中在上地壳,表现为块体旋转和强烈隆升,地震活动性加强。综合分析认为,鲜水河断裂带渐新世以来的构造演化和现今地震活动性主要受印度-欧亚板块碰撞导致的青藏高原东缘向东挤出相关的陆内变形过程控制。As the boundary between the Bayan Kara and the Sichuan-Yunnan blocks on the eastern Tibetan Plateau,the Xianshuihe left strike-slip fault zone is considered to be the eastern boundary adjusting the large-scale southeastward extrusion of crustal materials beneath the plateau and the rotation of the blocks.The study of the structural deformation characteristics and evolution history of Xianshuihe fault zone is of great scientific significance to deeply understand the continental deformation process in the eastern margin of the Tibetan Plateau.Based on detailed outcrop-microscale structural analysis,the deformation characteristics of the southeast segment of Xianshuihe fault zone have been studied in this paper.Five samples of granitic mylonites and leucogranites were chosen for LA-ICP-MS zircon U-Pb dating,giving ages of 34.4±0.9 Ma,31.0±1.2 Ma,15.2±0.3 Ma,14.9±0.1 Ma and 5.93±0.14 Ma respectively.Two granitic mylonite samples were selected for Ar-Ar dating of muscovite.As a result,the plateau ages of the two samples are 17.21±0.30 Ma and 3.21±0.16 Ma.Based on the previous geochronological data and the results of this paper,three stages of tectonic evolution of Xianshuihe fault zone since Eocene are established.Ⅰ:ca.32~25 Ma,the deformation of Xianshuihe fault zone concentrated in the deep crust,showing weak magmatism and anatexis;Ⅱ:ca.20~13 Ma,the peak deformation period of left lateral strike slip of Xianshuihe fault zone,the deformation spread throughout the whole crust,showing a strong left lateral ductile shear deformation and large-scale magmatism.Ⅲ:ca.10 Ma,the deformation is concentrated in the upper crust,which is characterized by block rotation and strong uplift,fault weakening and strong seismicity.The tectonic evolution and seismicity of the Xianshuihe fault zone are constrained by the eastward extrusion of the eastern margin of the Tibetan Plateau since the collision of the Indian Eurasian Plate.

关 键 词：青藏高原东缘 鲜水河断裂带 花岗质糜棱岩 块体挤出 构造热年代学 地质调查工程 

分 类 号：P534.614[天文地球—古生物学与地层学] P546[天文地球—地质学]