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  

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

作　　者：蓝媛春 时毓[1,2] 唐源远 周予茜 翁伯寅 LAN Yuanchun;SHI Yu;TANG Yuanyuan;ZHOU Yuxi;WENG Boyin(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,China;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources,Guilin University of Technology,Guilin 541004,China)

机构地区：[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　　处：《高校地质学报》2024年第5期541-558,共18页Geological Journal of China Universities

基　　金：广西自然科学基金杰出青年基金项目(2019GXNSFFA245005);国家自然科学基金项目(42372083)联合资助。

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(T_(DM2))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。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-sedimentary 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(T_(DM2))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.

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 

分 类 号：P597[天文地球—地球化学] P736.44[天文地球—地质学]