碎屑锆石U⁃Pb定年地层划分对比应用探讨——以新元古界梵净山群“淘金河组”为例  

Comparative Application of Detrital Zircon U-Pb Dating for Stratigraphic Delineation:The"Taojinhe Formation"of the Neoproterozoic Fanjingshan Group as an example

作　　者：代雅然 陈建书 张嘉玮[1] 李海波 刘纬鹏 王坤 DAI YaRan;CHEN JianShu;ZHANG JiaWei;LI HaiBo;LIU WeiPeng;WANG Kun(Guizhou Geological Survey,Bureau of Geology and Mineral Exploration and Development of Guizhou Province,Guiyang 550081,China;Guizhou Administrative Bureau of Fanjingshan National Nature Reserve,Tongren,Guizhou 554400,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,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,贵阳550081 [2]贵州梵净山国家级自然保护区管理局,贵州铜仁554400 [3]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵阳550081

出　　处：《沉积学报》2024年第6期2006-2019,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41603039)。

摘　　要：【目的】前寒武纪经历了多期次构造热事件、构造复杂、变形变质严重,给地层划分对比及客观地层层序的建立带来不便与困难。【方法】以江南造山带西段新元古界梵净山群出露最老的淘金河组为研究对象,开展碎屑锆石形态学对比、U-Pb定年、分析该层位的物质来源及沉积大地构造背景,并将梵净山地层进行多维定标分析对比。【结果】“淘金河组”锆石颗粒自形程度高,代表短距离搬运,源岩为花岗岩、辉绿岩、正长岩/二长岩和玄武岩,碎屑锆石年龄峰值为875 Ma、1862 Ma和2513 Ma,经锆石地球化学数据分析,“淘金河组”沉积于汇聚背景。【结论】“淘金河组”与其上覆地层余家沟组之上的肖家河组锆石年龄图谱相似,物源相同;结合其他地层地质特征,指出桃树林一带梵净山群“淘金河组”与肖家河组可能为同一地层单元。[Objective]Precambrian stratigraphy has undergone multiple tectonic events,complex tectonics,severe deformation,and metamorphism,making it inconvenient and difficult to compare the strata and establish an objective stratigraphic sequence.[Methods]This study selected the Taojinhe Formation,the oldest outcrop of the Neoproterozoic Fanjingshan Group in the western part of the Jiangnan orogen as a research object,and we collected sandstone samples carry out comparing detrital zircon morphology,U-Pb dating,rock,and mineral identification and analysis of the material origin and sedimentary geotectonic settings of this formation,as well as for multidimensional scaling analysis and comparison of the stratigraphy of the Fanjingshan Group.[Results]The sample rocks are mainly composed of detrital particles and fillers;the detrital particles are mainly quartz,feldspar and cutting and subangular to sub-rounded with average sortability.The fillers are mainly mica,silica,and iron,and the mica is mainly sericite and white mica.The zircon grains of the"Taojinhe Formation"are angular,representing short-distance transport,and the source rocks are granite,diabase,Syenite/Monzonite,and basalt,with detrital zircon peak ages of 875 Ma,1862 Ma,and 2513 Ma.Based on the zircon geochemical data analysis,the"Taojinhe Formation"was deposited in a convergent background.U/Nb values of"Taojinhe Formation"zircon range from 25-700,with one mantle-sourced zircon and 98 arc-sourced zircons.Using U/Yb values to compare with Hf,all zircons were in the continental source range,and the Sc(average value 385.1)and Sc/Yb values(average 1.1)also show island arc magmatic features.Conversely,the zircons have high U/Nb,Sc/Yb,and U/Yb values,relatively low Nb/Yb values,and U/Nb>20,suggesting that the zircons were formed in a subduction environment.In contrast,the zircons of the Yujiagou Formation are mostly elliptical,suggesting long-distance transport and deposition in a disseminated background,and the source rocks are granites,diorites,basalts,alkalites,and

关 键 词：前寒武纪 碎屑锆石 U-PB定年 梵净山群 地层对比 

分 类 号：P597[天文地球—地球化学]