扬子地块西缘中元古界登相营群年代学及地质意义  

Geochronology and tectonic significance of the Mesoproterozoic Dengxiangying Group in the western Yangtze Block

作　　者：刘璎 胡浩 易凯 智超[4] 张继彪 LIU Ying;HU Hao;YI Kai;ZHI Chao;ZHANG Jibiao(Lanzhou city University,Lanzhou,Gansu 730070,China;Changjiang Geophysical Exploration and Testing Company Limited,Wuhan,Hubei 430010,China;The fifth Geology Company of Hebei Geology&Minerals Bureau,Tangshan,Hebei 063000,China;Zhangye Geo-mine Survey Institute of Nonferrous Metal Geological Erploration,Zhangye,Gansu 734012,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]兰州城市学院,甘肃兰州730070 [2]长江地球物理探测(武汉)有限公司,湖北武汉430014 [3]河北省地质矿产勘查开发局第五地质大队,河北唐山063000 [4]甘肃省有色金属地质勘查局张掖矿产勘查院,甘肃张掖734012 [5]中国地质科学院地质研究所,北京100037

出　　处：《地质学报》2023年第8期2476-2494,共19页Acta Geologica Sinica

基　　金：兰州城市学院博士科研启动基金项目(编号LZCU-BS2019-08);兰州城市学院科研项目(编号LZCU-KJ/2021-036)联合资助的成果。

摘　　要：扬子板块西缘中元古界登相营群为一套与裂谷相关的沉积-火山岩序列,其年代学和构造背景对理解扬子板块前寒武纪构造演化具有重要意义。本文获得登相营群松林坪组、则姑组和朝王坪组火山岩LA-ICP-MS锆石U-Pb年龄分别为1166±6 Ma、1040±4 Ma和1020±4 Ma,精确限制了登相营群时代为1166~1020 Ma。松林坪组砂岩碎屑锆石年龄具有多峰值特征,地球化学特征表明砂岩物源主要来自酸性火山岩以及花岗岩。则姑组英安岩具有较高的Ga/Al比值和Zr、Hf、Ga和HREE含量以及高的锆石饱和温度,属于A型花岗岩系列,锆石εHf(t)值为~-15.1~-9.1,说明来自花岗质地壳物质的部分熔融。构造背景判别图解显示登相营群砂岩和英安岩形成于大陆裂谷盆地。结合前人的研究成果,笔者认为扬子地块西缘中元古代晚期构造属性为被动大陆边缘裂谷,新元古代早期构造动力学背景转为活动大陆边缘洋-陆俯冲,扬子板块应位于超大陆的边缘位置。Thelate Mesoproterozoic Dengxiangying Group in the western Yangtze Block is a rift-related sedimentary-volcanic sequence that is particularly important for the Precambrian tectonic evolution of the Yangtze Block.LA-ICP-MS zircon U-Pb dating of the Songlinping,the Zegu and the Chaowangping yielded zircon U-Pb ages of 1166±6 Ma,1040±4 Ma and 1020±4 Ma,respectively.The geochemical features of Songlinping sandstone samples indicate a predominantly felsic(granitic)source for the detritus.The Zegu dacites have high Zr,Hf,Ga,and HREE contents and Ga/Al ratios,and high calculated zircon saturation temperatures,thus resembling A-type granitoids.In addition,these rocks have negativeεHf(t)values(15.1~9.1),indicative of their derivation from partial melting of felsic continental crust.The geochemical discrimination diagrams suggest a continental rift setting for the Dengxiangying Group.Combined with previous studies,we concluded that the western Yangtze Block was located in an intra-continental rifting basin in a passive continental margin during the late Mesoproterozoic.An early-Neoproterozoic tectonic transformation from a continental-rifting basin to a compressional setting is suggested,and the Yangtze Block was in the peripheral rather in the center in the configuration of Rodinia.

关 键 词：扬子地块西缘 登相营群 锆石U-PB年龄 地球化学 大地构造背景 

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