扬子克拉通拉伸系莲沱组年代框架与沉积过程  

Chronological framework and sedimentary evolution process of the Neoproterozoic Liantuo Formation in the Yangtze Craton

作　　者：王玉冲 旷红伟[2] 柳永清[2] 赵峰华[1] 彭楠[2] 陈骁帅 祁柯宁 刘海 东归霖 WANG Yuchong;KUANG Hongwei;LIU Yongqing;ZHAO Fenghua;PENG Nan;CHEN Xiaoshuai;QI Kening;LIU Hai;DONG Guilin(College of Geosciences and Surveying Engineering,China University of Mining and Technology,Beijing 100083,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei,Anhui 230009,China;Central South Institute of Metallurgical Geology,Yichang,Hubei 443003,China)

机构地区：[1]中国矿业大学(北京),地球科学与测绘工程学院,北京100083 [2]中国地质科学院地质研究所,北京100037 [3]合肥工业大学,资源与环境工程学院,安徽合肥230009 [4]湖北冶金地质研究所(中南冶金地质研究所),湖北宜昌443003

出　　处：《地质学报》2023年第12期3922-3942,共21页Acta Geologica Sinica

基　　金：国家重点研发计划项目(编号2022YFF0800302,2016YFC0601001);中国地质调查局项目(编号DD20221649);国家自然科学基金项目(编号42072135);北京科委国际创新资源合作项目(编号Z201100008320007)联合资助的成果。

摘　　要：扬子克拉通保存的独特拉伸纪晚期碎屑岩建造为研究新元古代中期演化提供了绝佳素材,内部丰富的凝灰岩夹层和同位素年龄也为扬子克拉通新元古代中期演化提供有效的年代学约束。然而扬子克拉通拉伸系莲沱组内部演化缺少年代学约束,制约了拉伸纪晚期扬子克拉通的沉积演化研究。本研究通过野外地质调查,采用LA-ICP-MS技术获取莲沱组底界(神农架)凝灰岩锆石U-Pb谐和年龄为763.1±6.2 Ma,莲沱组下部陆相地层中获得(鹤峰)的凝灰岩锆石U-Pb谐和年龄761.8±7.1 Ma,莲沱组中下部海陆过渡段获得通山(764.1±3.5 Ma)、长阳(751.5±6.3 Ma)、神农架(752.1±6.5 Ma)三组凝灰岩锆石U-Pb谐和年龄。莲沱组顶部海相地层获得729.6±9.2 Ma(皖南休宁组)、722.4±4.5 Ma(神农架)凝灰岩锆石U-Pb谐和年龄,以及城口龙潭河组凝灰岩锆石U-Pb谐和年龄(712.4±6.4 Ma)。这些凝灰岩锆石年龄数据和地层序列表明:820~770 Ma扬子克拉通普遍处于暴露剥蚀环境,770~750 Ma开始沉积陆相-海陆过渡相莲沱组,750 Ma之后扬子克拉通过渡到海相沉积环境并持续到成冰纪。建立的莲沱组与邻区地层对比格架表明扬子克拉通拉伸纪晚期演化受控于罗迪尼亚超大陆裂解过程,与深部地幔柱诱导的伸展裂谷、岩浆地幔柱冷却密切关联。本研究为扬子克拉通拉伸纪晚期地层提供有效年代学约束,揭示了扬子克拉通新元古代中期沉积演化与构造背景演化的协同关系,为扬子克拉通在罗迪尼亚裂解过程中的演化提供有效数据支撑。The unique clastic formation preserved in the Yangtze Craton provides excellent material for studying the mid-Neoproterozoic evolution,and the abundantzircon U-Pb ages of tuff interlayers within also provide effective geochronological constraints for the mid-Neoproterozoic evolution of the Yangtze Craton.However,the evolution of the Liantuo Formation in the Yangtze Craton still lacks geochronological constraints,which restricts study of sedimentary evolution of the Yangtze Craton in the late Tonian.In this study,field geological investigation and LA-ICP-MS technology were used to obtain 763.1±6.2 Ma(Shennongjia)tuff zircon U-Pb concordant age at the bottom boundary of the Liantuo Formation,761.8±7.1 Ma(Hefeng)tuff zircon U-Pb concordant age in lower part of the Liantuo Formation,764.1±3.5 Ma(Tongshan),751.5±6.3 Ma(Changyang),752.1±6.5 Ma(Shennongjia)of tuff zircon U-Pb concordant ages in marine-terrestrial strata of middle and lower part of the Liantuo Formation,729.6±9.2 Ma(Xiuning Formation),722.4±4.5 Ma(Shennongjia)tuff zircon U-Pb concordant ages in marine strata of upper part of Liantuo Formation,and 712.4±6.4 Ma tuff zircon U-Pb concordant age in middle part of the Longtanhe Formation.These data and stratigraphic sequence show that:820~770 Ma Yangtze Craton was exposed to erosional environment,terrestrial deposit began~770 Ma,after 750 Ma Yangtze Craton completely transitioned to marine deposit that continued until Cryogenian.The strata framework during the late Tonian shows that the evolution of Yangtze was controlled by Rodinia supercontinent breakup process,and may be closely related to deep mantle plume induced extensional rift,magmatic mantle plume cooling.This study provides effective geochronological constraints for the late Tonian strata in the Yangtze Craton,reveals synergistic relationship between sedimentary evolution and tectonic background of Yangtze Craton during the mid-Neoproterozoic,provides effective data support for evolution of Yangtze Craton during Rodinia breakup.

关 键 词：扬子克拉通 拉伸纪晚期 莲沱组 锆石U-PB年龄 年代框架 沉积过程 

分 类 号：P597.3[天文地球—地球化学] P512.2[天文地球—地质学] P534.3