云开地块北缘构造混杂岩的岩石成因探讨

发布时间：2018-04-17 10:30

本文选题：云开群 + 构造混杂岩　；参考：《岩石学报》2017年03期

【摘要】：华南云开地块北缘的信宜贵子地区见大量变玄武岩与变沉积岩混杂产出。变玄武岩多以构造岩块或透镜体产出,地球化学以中等Mg#、富钠贫钾为特征,属亚碱性的拉斑玄武岩系列。轻稀土元素中等富集,无Eu异常,微量元素以富Nb、显著的Sr-Nb-Ta弱亏损为特征。143Nd/144Nd变化于0.512513~0.512655之间,对应的εNd(t)值介于2.89~4.90之间。构造环境判别表明,变玄武岩原岩可能为弧后盆地玄武岩。2个变玄武岩样品的锆石U-Pb年龄为1031±28Ma、1025±39Ma。变沉积岩基质以片岩、变砂岩和石英岩为主,表现为陆缘碎屑沉积特征。2个石英岩样品的碎屑锆石U-Pb年龄显示变沉积岩原岩具有~1.0Ga的物源峰,其最年轻锆石为777Ma和571Ma,原岩沉积时间大致为南华纪-震旦纪。本次研究认为,信宜贵子构造混杂岩是Grenville期弧后盆地玄武岩与新元古代晚期陆缘碎屑沉积物构造混杂堆积的结果,构造混杂的时间可能为奥陶纪-志留纪。
[Abstract]:A large number of metabalts and sedimentary rocks are mixed up in the Xinyi Guizi area of the northern margin of the Yunkai block in South China.Metamorphic basalts are mainly tectonic blocks or lenticular rocks, and their geochemistry is characterized by moderate Mg#1, rich in sodium and poor potassium, and belongs to the subalkaline tholeiite series.Light rare earth elements are moderately enriched and have no EU anomaly. The trace elements are rich in NB, marked by weak depletion of Sr-Nb-Ta. The variation of 0.143 ND / 144ND is between 0.512513 and 0.512655, and the corresponding 蔚 Ndct) is between 2.89 and 4.90.The tectonic environment indicates that the metabalts may be basalts in the back-arc basin. The zircon U-Pb age of two metabalt samples is 1031 卤28Ma1025 卤39Ma.The metamorphic rock matrix is dominated by schist, metamorphic sandstone and quartzite, which is characterized by clastic sedimentary characteristics of continental margin. The U-Pb age of clastic zircon of two quartz samples shows that the source rock of metamorphic rocks has a provenance peak of 1.0 Ga.The youngest zircon is 777Ma and 571Ma.The sedimentary time of the original rocks is about Nanhua-Sinian.It is considered that the tectonic melange in Xinyi Guizi basin is the result of the tectonic mixing of basalt and clastic sediments in the late Neoproterozoic continental margin in the Grenville back arc basin, and the time of tectonic confounding may be Ordovician-Silurian.
【作者单位】：中国地质调查局武汉地质调查中心;中国地质调查局花岗岩成岩成矿地质研究中心;
【基金】：中国地质调查局项目(12120114039201、121201009000150011、121201009000150015)资助
【分类号】：P581

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