欢迎访问《高校地质学报》官方网站,今天是
分享到:

高校地质学报 ›› 2024, Vol. 30 ›› Issue (05): 541-558.DOI: 10.16108/j.issn1006-7493.2023057

• • 上一篇    下一篇

桂东鹰扬关群变质沉积岩锆石年代学、地球化学特征及其地质意义

蓝媛春1, 2,时 毓1, 2*,唐源远1, 2,周予茜1, 2,翁伯寅1, 2   

  1. 1. 桂林理工大学 广西隐伏金属矿产勘查重点实验室,桂林 541004;
    2. 桂林理工大学 有色金属矿产勘查与资源高效利用协同创新中心,桂林 541004
  • 出版日期:2024-10-20 发布日期:2024-10-20

Zircon Geochronology, Geochemical Characteristics and Geological Significance of Meta-Sedimentary Rocks in the Yingyangguan Group, Eastern Guangxi

LAN Yuanchun1,2,SHI Yu1,2*,TANG Yuanyuan1,2,ZHOU Yuxi1,2,WENG Boyin1,2   

  1. 1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;
    2. Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources,
    Guilin University of Technology, Guilin 541004, China
  • Online:2024-10-20 Published:2024-10-20

摘要: 文章对桂东鹰扬关群的新元古代浅变质沉积岩进行了岩石地球化学、锆石U-Pb定年及锆石Lu-Hf同位素分析。研究显示,鹰扬关群变质沉积岩具有中等的成分成熟度和风化淋滤程度,其稀土配分模式与后太古宙澳大利亚页岩(PAAS)变化一致,具中等的Eu负异常。微量元素蛛网图显示部分样品存在U亏损现象且Co、Ni含量较南岭其他地区偏高,指示源区含有较多的中基性组分。变质沉积岩是鹰扬关群构造混杂岩基质的组成部分,碎屑锆石U-Pb定年结果给出了构造混杂岩基质部分的最大沉积年龄(660 Ma)。结合前人研究成果认为,鹰扬关群构造混杂岩形成于新元古代中后期,此后又遭受了早中生代构造热事件的改造。物源分析结果显示,鹰扬关群新元古代变质沉积岩以长英质物源为主,结合锆石的阴极发光图像特征、锆石U-Pb年代学特征、Hf同位素二阶段模式年龄(TDM2)和相关区域地质资料,推测变质沉积岩中的中基性组分主要来源于区内以及邻近的地体,鹰扬关群与华夏板块具有亲缘性。结合区域构造演化特征,推断鹰扬关群新元古代变质沉积岩沉积于造山后伸展的裂谷盆地中。

关键词: 变质沉积岩, 锆石U-Pb年龄, Lu-Hf同位素, 新元古代, 桂东鹰扬关群

Abstract: This study presents new geochemical, zircon U-Pb and Lu-Hf isotopic data for the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group in eastern Guangxi. Geochemical data show that the meta-sedimentary rocks of the Yingyangguan Group have moderate composition maturity and weathering extent, and their rare earth element (REE) patterns are similar to that of the Post-Archaean Australian Shale (PAAS), with moderate Eu negative anomalies. The trace element distributions diagram shows that some samples are depleted in U, with higher Co and Ni contents compared with those of the meta-sedimentary rocks in the Nanling range, suggesting that the provenance was mostly intermediate to mafic rocks. The matrix of the Yingyangguan tectonic mélange contains a component of meta-sedimentary rocks. The detrital zircon U-Pb dating results give a maximum depositional age (660 Ma) of the matrix part of the tectonic mélange. Combined with previous results, we suggest that the Yingyangguan tectonic mélange was formed in the Middle-Late Neoproterozoic, and resulted from reworking by the Early Mesozoic thermal events. Provenance analysis reveals that the Neoproterozoic meta-edimentary rocks of the Yingyangguan Group are mainly of felsic components, combined with zircon cathodoluminescence image characteristics, zircon U-Pb geochronological characteristics, Hf model age of the second stage (TDM2) and relevant regional geological data, we suggest that the intermediate to mafic provenance in the meta-sedimentary rocks mainly originated from the Yingyangguan area or the adjacent terranes, suggesting a close affinity of the Yingyangguan Group with the Cathaysia Block. Combined with the characteristics of regional tectonic evolution, it is inferred that the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group were deposited in a post-orogenic extension rift basin.

Key words: meta-sedimentary rocks, zircon U-Pb ages, Lu-Hf isotopes, the Neoproterozoic, the Yingyangguan Group in eastern Guangxi

中图分类号: