扬子陆块三峡地区莲沱组砂岩中碎屑锆石U-Pb年龄、Hf同位素组成及其地质意义  

Detrital Zircon Compositions of U-Pb Ages and Hf Isotope for Sandstone of Liantuo Formation from Three Gorges Area, Yangtze Block and Its Geological Significance

作　　者：徐琼 江拓[1] 侯林春[4] 赵小明[1,3] 童喜润[1] 散飞雪 邱啸飞[1,2,3] Xu Qiong;Jiang Tuo;Hou Linchun;Zhao Xiaoming;Tong Xirun;San Feixue;Qiu Xiaofei(Wuhan Center of Chitia Geological Survey,Wuhan 430205,China;Institute of Geological Survey,China University of Geosciences,Wuhan 430074,China;Hubei Key Laboratory of Paleontology and Geological Environment Evolution,Wuhan 430205,China;School of Geography and Information Engineering,China University of Geosciences,Wuhan 430074,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质大学地质调查研究院,湖北武汉430074 [3]古生物与地质环境演化湖北省重点实验室,湖北武汉430205 [4]中国地质大学地理与信息工程学院,湖北武汉430074 [5]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2021年第4期1217-1230,共14页Earth Science

基　　金：湖北省重点实验室开放基金项目(No.KLPE-202013);国家自然科学基金项目(No.41303026);中国地质调查局地质调查项目(Nos.DD20190374,DD20190385)。

摘　　要：对扬子陆块三峡地区黄牛岩剖面莲沱组顶部砂岩中的120颗碎屑锆石进行了U-Pb定年和Lu-Hf同位素分析.结果显示,黄牛岩剖面莲沱组中碎屑锆石的年龄谱具有~880~800 Ma、~2 000 Ma、~2 500 Ma及~2 700 Ma的峰值,其中最年轻的碎屑锆石年龄为724±8 Ma.结合前人对该地区莲沱组顶部凝灰岩开展的年代学工作,将莲沱组顶部砂岩沉积时代限定为724~714 Ma.莲沱组砂岩沉积时间与其中最年轻的碎屑锆石U-Pb年龄接近,反映了其源区地壳物质的快速再循环.碎屑锆石Hf同位素两阶段模式年龄(T_(DM2))集中在~3.7~3.1 Ga、~2.5~2.0 Ga和~1.3~1.0 Ga,反映其物源区存在古-中太古代、古元古代以及中元古代末期的初生地壳生长.对比近年来三峡地区不同剖面莲沱组砂岩中已报道的碎屑锆石年龄和Hf同位素数据,黄牛岩剖面的莲沱组碎屑锆石年龄和Hf同位素组成与之以北的王丰岗剖面均存在明显差异,说明莲沱组沉积期两者的陆源物质供给区有较大差别.In this study,120 detrital zircons from the sandstone at the top of the Liantuo Formation in the Huangniuyan Section of the Three Gorges area were measured for U-Pb dating and Lu-Hf isotopic compositions. The U-Pb ages of the zircons from the Huangniuyan Section cluster at ~800-880 Ma, ~2 000 Ma, ~2 500 Ma, ~2 700 Ma, among which the youngest zircon age is724±8 Ma. According to the previous geochronological study of tuff on the top of the Liantuo Formation, the sedimentary age of the sandstone in the upper most part of the Liantuo Formation is limited to ~724-714 Ma. The sedimentary time of the Liantuo sandstone is close to the U-Pb age of the youngest detrital zircon, which may reflect a rapid recycling of crustal materials. The Hf isotopic two-stage model ages(T_(DM2)) of zircon are concentrated at ~3.7-3.1 Ga, ~2.5-2.0 Ga and ~1.3-1.0 Ga, which indicates that the provenance of the sandstone has juvenile crustal growth in the Paleo-Mesoarchean, Paleoproterozoic and Late Mesoproterozoic. By comparing the detrital zircon U-Pb ages and Hf isotopic data from different sections of the Liantuo Formation in the nucleus of the Yangtze craton reported in recent years, it is suggested that the Huangniuyan Section has distinct detrital zircon U-Pb ages and Hf isotopic compositions compared with the Wangfenggang Section, revealing different provenance between them.

关 键 词：扬子陆块 莲沱组 碎屑锆石 U-PB年龄 HF同位素 岩石学 

分 类 号：P581[天文地球—岩石学]