湘黔桂新元古代拉伸纪晚期地层年代格架对比及关键地质事件初探  

Comparison of the geochronological frameworks and preliminary study on key geological events during the Neoproterozoic Late Tonian period in the Hunan-Guizhou-Guangxi area

作　　者：张嘉玮[1,2] 陈建书 吴滔 叶太平 陈明华 代雅然 邓小杰 牟军 ZHANG Jiawei;CHEN Jianshu;WU Tao;YE Taiping;CHEN Minghua;DAI Yaran;DENG Xiaojie;MU Jun(Guizhou Geological Survey,Bureau of Geology and Mineral Exploration and Development of Guizhou Province,Guiyang 550081,China;Technology Innovation Center of Mineral Resources Exploration Engineering in Bedrock Zone,Ministry of Natural Resources,Guiyang 550081,China;Guizhou Central Laboratory of Geology and Mineral Resources,Bureau of Geology and Mineral Exploration and Development of Guizhou Province,Guiyang 550018,China)

机构地区：[1]贵州省地质矿产勘查开发局贵州省地质调查院,贵州贵阳550081 [2]自然资源部基岩区矿产资源勘查工程技术创新中心,贵州贵阳550081 [3]贵州省地质矿产勘查开发局贵州省地质矿产中心实验室,贵州贵阳550018

出　　处：《地学前缘》2020年第4期1-16,共16页Earth Science Frontiers

基　　金：国家自然科学基金项目(41603039,41963006);贵州省地质矿产勘查开发局地质科研项目(黔地矿科合[2017]31,黔地矿科合[2019]22);贵州省科技计划项目(黔科合平台人才[2018]5626,黔科合[2016]平台人才5401,黔科合支撑[2019]2851);中国地质调查局地质调查工作项目(12120114068201)。

摘　　要：湘黔桂地区发育一套完整的新元古代拉伸纪晚期地层(下江群及其相当地层),是研究扬子克拉通与华夏板块碰撞拼接后华南大陆裂谷盆地演化的重要载体。本文报道了贵州省铜仁市万山区清水江组上部、平略组底部及中部变质凝灰岩和沉凝灰岩的年龄,分别为(763.8±5.5)Ma(N=24,MSWD=0.29)、(760.2±4.1)Ma(N=25,MSWD=0.39)、(759.1±3.9)Ma(N=26,MSWD=0.38)。通过对湘黔桂地区下江群及其相当地层中已有火山岩、火山碎屑沉积岩、含凝灰质岩石年龄的系统梳理与分析研究,进一步确定下江群其及相当地层的沉积时限在822~715 Ma,桂北丹洲群三门街组玄武岩是在武陵造山后伸展背景下湘黔桂地区裂谷最大裂陷时期的产物,清水江组与平略组内大量的火山物质可能来源于江南造山带东段800~760 Ma的中酸性喷出岩。结合地层、岩性、年代特征,本文恢复了湘黔桂盆地新元古代拉伸纪晚期的演化历史,并认为该套地层符合建立下江系条件。The Neoproterozoic Late Tonian stratum(the Xiajiang Group and its time-equivalent stratum)is well exposed in the Hunan-Guizhou-Guangxi area.It is an important research subject for studying the evolution of the rift basin in South China after the collision between the Yangtze Craton and the Cathaysia Block.Here,we report the zircon U-Pb ages of the tuffs and tuffite in the upper part of the Qingshuijiang Formation and the bottom and middle parts of the Pinglue Formation in the Wanshan area,Tongren City,Guizhou Province to be 763.8±5.5 Ma(N=24,MSWD=0.29),760.2±4.1 Ma(N=25,MSWD=0.39),and 759.1±3.9 Ma(N=26,MSWD=0.38),respectively.By compiling the area’s volcanic,volcanic-sedimentary and tuffeous rock ages,we further determined the deposition periods of the Xiajiang Group and its equivalence to be around 822-715 Ma.We propose that the basalt within the Sanmenjie Formation of the Danzhou Group in northern Guangxi formed in an extensional setting after the Wuling movement,as a result of maximum extension of the Hunan-Guizhou-Guangxi rift basin.A large amount of volcanic materials in the Qingshuijiang and Pinglue Formations are mainly sourced from the intermediate-acidic extrusive rocks(800-760 Ma)in the eastern section of the Jiangnan Orogen.Combined with regional stratigraphy,lithology and geochronology,we restore the Neoproterozoic Late Tonian evolutionary history of the Hunan-Guizhou-Guangxi basin and propose to establish the Xiajiang System.

关 键 词：板溪群 下江群 高涧群 丹洲群 拉伸纪 前寒武纪 扬子克拉通 江南造山带 

分 类 号：P534.3[天文地球—古生物学与地层学] P597.3[天文地球—地质学]