南秦岭勉略构造带略阳三岔子地区金家河千枚岩沉积物源分析：碎屑锆石U-Pb年代学证据  

Despositional Provenance Analysis of the Jinjiahe Phyllite from Sanchazhi Area(Lueyang County) in Mianlue Tectonic Belt of South Qinling,Shaanxi:Evidence from Detrital Zircon U-Pb Dating

作　　者：弓晨 裴先治[1,2] 李瑞保[1,2] 李佐臣[1,2] 裴磊[1,2] 刘成军[1,2] 高峰[1,2] 陈有炘[1,2] 王盟[1,2] 赵少伟[1,2] GONG Chen;PEI Xianzhi;LI Ruibao;LI Zuochen;PEI Lei;LIU Chenjun;GAO Feng;CHEN Youxin;WANG Meng;ZHAO Shaowei(School of Earth Sciences and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Key Laboratory of Western China's Mineral Resources and Geological Engineering,Ministry of Education,Xi'an 710054,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《西北地质》2019年第4期28-52,共25页Northwestern Geology

基　　金：国家自然科学基金项目“扬子地块西北缘碧口群构造属性及与Rodinia超大陆聚合裂解关系”（41872233）;陕西省自然科学基金“勉略宁地区中新元古代中酸性侵入岩构造属性研究”（2019JM 312）;中央高校基本科研业务费资助项目“西昆仑麻扎康西瓦构造带构造属性及向西延展研究”（310827161006）

摘　　要：南秦岭勉略构造带略阳三岔子地区发育一套灰-灰黑色含碳绢云石英千枚岩和灰白色绢云石英千枚岩夹灰黑色含砾绢云千枚岩、白云质灰岩、硅质岩以及碳硅质板岩的岩石组合。为探讨其形成时代及沉积物源,笔者对其中的含砾绢云白云质石英千枚岩、绢云白云质石英千枚岩进行岩石学及LA-ICP-MS碎屑锆石U-Pb年代学研究。所获得的碎屑锆石年龄可以分为3组:新元古代年龄组(678~966 Ma),该段有明显峰值,峰值年龄分别为781 Ma、865 Ma;中元古代年龄组(1122~1432 Ma);古元古代-太古代年龄组(1944~2824 Ma)。2件变质碎屑岩的碎屑锆石最小年龄组分别为678~736 Ma(平均年龄为725 Ma)、771~775 Ma(平均年龄为773 Ma)。综合研究认为该沉积地层沉积时代不早于南华纪,其沉积物源主要为勉略构造带内、碧口微地块、扬子地块西北缘汉南-米仓山杂岩新元古代岩浆岩,其沉积事件对应于新元古带中晚期(800 Ma~)勉略构造带及扬子地块西北缘后碰撞-裂解阶段。A set of rock assemblage is exposed in the Sanchazi area,Mianlue tectonic belt of Southern Qinling orogenic belt,which is consist of gray-black carbonaceous sericite-quartz-phyllite,gray-white sericite-quartz-phyllite,intercalated with gravelly sericite-phyllite,dolomitic limestone,siliceous rock and carbon-siliceous slate.In order to explore their formation age and provenance,we conducted LA-ICP-MS U-Pb dating on detrital zircons from the gravelly sericite-dolomite-quartz-phyllite and sericite-dolomite-quartz-phyllite in Jinjiahe area.The obtained zircon U-Pb ages can be divided into three groups:Neoproterozoic age group(678~966Ma),with main age peak at 781Ma for sample ML1259-TW3 and 865Ma for sample ML1261-TW1,respectively;Mesoproterozoic age group(1122~1432Ma):and Palaeoproterozoic-Archaean age group(1944~2824Ma).The minimum age groups of detrital zircons for two metamorphic detrital rocks are 678~736Ma(average age of 725Ma)and 771~775Ma(average age of 773Ma),respectively.Combined with the regional geological records,we propose that the provenance of clastic debris in the sedimentary strata was mainly sourced from the Neoproterozoic magmatic rocks within the Mianlue tectonic belt,the Bikou block,and the Hannan-Micangshan complex in the northwestern margin of the Yangtze block.The maximum depositional age of the studied meta-sedimentary rocks is not later than Nanhua Period,and it may give insights into the post-collision-cracking stage of the Mianlue tectonic belt and the northwestern margin of the Yangtze block during the mid-late Neoproterozoic period(800Ma~).

关 键 词：南秦岭 勉略构造带 碎屑锆石 关家沟组 锆石LA-ICP-MS U-Pb定年 

分 类 号：P542.3[天文地球—构造地质学]