江西崇仁新元古代岛弧型斜长角闪岩的年代学、地球化学及其构造意义  

Geochronology and Geochemistry of the Chongren Neoproterozoic Arc-type Amphibolites and Their Tectonic Implications

作　　者：周永智 王岳军[1,2] 张玉芝[1] ZHOU Yong-zhi;WANG Yue-jun;ZHANG Yu-zhi(School of Earth Sciences and Geological Engineering, Sun Yat-Sen University, Guangzhou 510275 , China;Guangdong Provincial Key Lab. of Geological Processes and Mineral Resource Survey, Guangzhou 510275 , China)

机构地区：[1]中山大学地球科学与地质工程学院,广州510275 [2]广东省地质过程与矿产资源探查重点实验室,广州510275

出　　处：《矿物岩石地球化学通报》2019年第4期840-854,共15页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家重点基础研究发展计划项目(2014CB440901);国家自然科学基金项目(41372198,41402165);中山大学高校基本业务费资助课题

摘　　要：为了解赣中周潭群的构造属性和华夏陆块的演化历史,本文对崇仁地区的斜长角闪岩开展了锆石U-Pb年代学和地球化学研究。结果表明,崇仁地区斜长角闪岩形成年龄为(870±9) Ma,其SiO2含量为51. 22%~53. 11%,MgO为6. 16%~6. 74%,TiO2为1. 23%~1. 40%,原岩为拉斑玄武岩。崇仁地区斜长角闪岩LaN/YbN值为1. 85~2. 12,GdN/YbN值为1. 10~1. 17,与E-MORB相比富集大离子亲石元素。样品亏损高场强元素,具有明显的Nb-Ta异常、Nb/La=0. 50~0. 72。样品的εNd(t)值为5. 1~6. 0,其源区为受俯冲组分改造的地幔楔,其构造背景为弧后盆地。结合前人在华夏陆块的工作,推测崇仁相山新元古代~870 Ma斜长角闪岩与北侧的弋阳周潭群火山岩指示了华夏内部新元古代弧后盆地的存在。In order to understand the tectonic setting of the Zhoutan Group and the Neoproterozoic evolution history of the Cathaysia Block,we have carried out a study on the zircon U-Pb geochronology and whole-rock elemental and Sr-Nd isotopical geochemistry of the Chongren amphibolites in this paper. The results show that the representative sample of the Chongren amphibolites has a zircon U-Pb age of(870±9) Ma. These amphibolites have SiO_2 contents ranging from 51. 22% to53. 11%,MgO contents varying from 6. 16% to 6. 74% and TiO_2 contents varying from 1. 23% to 1. 40%,respectively.Their protolith could be tholeiite. They have relative flat REE-normalized pattern with LaN/YbNvalues varying from 1. 85 to 2. 12 and GdN/YbNvalues varying from 1. 10 to 1. 17. They are relatively enriched in large ion lithophile elements and depleted high field strength elements with obvious Nb-Ta anomalies and Nb/Ta values of 0. 50-0. 72 comparing to those of the E-MORB. In addition,they have εNd(t) values ranging from 5. 1 to 6. 0,suggesting that they could be derived from the metasomatized mantle wedge by subduction components and formed in a tectonic setting of back-arc basin.Based on our data and other available data of the Neoproterozoic(~ 870 Ma) Chongren amphibolites and volcanic rocks of the Zhoutan Group in the Yiyang area,it is proposed that there could be a Neoproterozoic back-arc basin in the Yiyang-Chongren area within the Cathaysia Block.

关 键 词：锆石U-PB定年 新元古代 斜长角闪岩 弧后盆地 周潭群 华夏陆块 

分 类 号：P597[天文地球—地球化学]