赣南地区寒武系牛角河组碎屑锆石U-Pb年龄和Hf同位素特征及其地质意义  

Zircon U-Pb Ages and Hf Isotope Features of Rocks from Niujiaohe Formation of Cambrian in the Southern Jiangxi Area and Their Geological Implications

作　　者：徐文坦 马虎超 陆丽娜[2] 张雷 周博文[3,4] 郭坤一 胡海燕[5] XU Wentan;MA Huchao;LU Lina;ZHANG Lei;ZHOU Bowen;GUO Kunyi;HU Haiyan(Chengdu University of Technology,Chengdu,Sichuan 610059;Institute of Disaster Prevention,Beijing 101601;Chinese Academy of Geological Sciences,Beijing 100037;Nanjing Institute of Geology and Mineral Resources,Nanjing,Jiangsu 210016;Chongqing Chuandongnan Geotechnical Investigation and Design Institute,Chongqing 400038)

机构地区：[1]成都理工大学,四川成都610059 [2]防灾科技学院,北京101601 [3]中国地质科学院,北京100037 [4]南京地质矿产研究所,江苏南京210016 [5]重庆川东南地质工程勘察设计院,重庆400038

出　　处：《地质与勘探》2019年第2期542-561,共20页Geology and Exploration

基　　金：中央高校基本科研业务费专项资金创新团队项目;中国地质调查局地质调查项目(编号:ZY20160109;12120115030101)联合资助

摘　　要：通过对赣南地区寒武纪牛角河组变余长石石英砂岩锆石U-Pb年代学和Hf同位素分析表明,牛角河组地层沉积年龄晚于556Ma。LA-ICP-MS U-Pb数据结果显示550～600Ma、700～900Ma、900～1100Ma、1500Ma和2500Ma为五个主要年龄峰值,其中900～1100Ma和700～900Ma两个峰值最显著,表明Rodinia超大陆的裂解聚合在华南地区的响应为赣南地区寒武纪地层提供了主要物源,该物源曾遭受泛非运动的影响,进一步说明华夏地块与冈瓦纳大陆具有一定亲缘性。此次工作中3568Ma锆石的捕获,说明华夏地块可能存在太古宙结晶基底。对具有不同年龄峰值的锆石进行稀土元素分析,其结果表明研究区锆石具有重稀土富集、强Ce正异常、弱或不明显的Eu负异常的地球化学特征,与岩浆锆石特征相似,指示其物源区以岩浆岩为主。此外,Lu-Hf同位素分析显示源区锆石除少数源于新生地壳物质组分熔融产生的岩浆,大多结晶于古老地壳部分熔融产生的岩浆;综合锆石年代学结果,暗示华南地区存在强烈的古元古代到新元古代岩浆活动,其中中元古代末期-新元古代的岩浆事件最甚;而新太古代为一个重要的新生地壳生长时期。U-Pb dating and Hf isotope analysis of detrital zircon grains from Niujiaohe Formation rocks in the southern Jiangxi area suggest that the sedimentary time of Niujiaohe Formation is 566 Ma. LA-ICP-MS U-Pb dating has five peaks: 550 ~ 600 Ma,700 ~ 900 Ma,900 ~ 1100 Ma,1500 Ma and2500 Ma,of which 900 ~ 1100 Ma and 700 ~ 900 Ma are most notable. It implies that the response of South China block to Rodinia supercontinent provided the main source of the Cambrian strata in this area. The source of the area has been affected by pan-African movements,further demonstrating that the Cathaysia block has a certain affinity with Gondwana. The capture of the zircon age at 3568 Ma indicates that the Cathaysia block may have an Archean crustal basement. These zircons show the characteristics of heavy rare earth enrichment,strong Ce positive anomalies,weak or inconsiderable Eu negative anomalies,and similarity to magmatic zircons,indicating that the source resulted from magmatic rocks. Lu-Hf isotope data indicate that a small number of zircons in the source region were crystallized in the magma which were produced by the melting of neo-crustal material components,and most of them were crystallized in the magma produced by the partial melting of ancient crust components. Combined with zircon age data,there was a notable magmatic event during the Neoproterozoic and Paleoproterozoic in southern China,especially the Late Mesoproterozoic-Neoproterozoic time. The Neoarchean is an important period for growth of new crust.

关 键 词：锆石U-Pb定年 HF同位素 物源分析 地壳生长 牛角河组 寒武系 赣南地区 

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