肥东杂岩的锆石U-Pb年龄及其地质意义——兼论下扬子地区新元古代岩浆活动历史
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本文为国家自然科学基金项目(编号:41772228)的成果。


Zircon U-Pb Ages and Their Geological Significance of the Feidong Complex:Some Comments on Neoproterozoic Magmatism History in the Lower Yangtze Region
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    摘要:

    近年来在下扬子西缘地区厘定的一系列新元古代火成岩,为认识该区扬子板块新元古代岩浆活动历史与规律提供了窗口。结合本次与前人锆石UPb年代学数据,指示下扬子地区张八岭群、肥东杂岩与董岭杂岩内变火成岩的原岩时限分别为767~748 Ma、812~745 Ma和829~754 Ma。这些新元古代火成岩分别是峰期为750 Ma、800 Ma和825 Ma岩浆活动的产物。下扬子地区峰期为825 Ma的岩浆活动只出现在靠近江南造山带的南部。锆石年代学信息显示,下扬子地区还发生过峰期为840 Ma、2010 Ma和2454 Ma岩浆活动,但缺失1000~860 Ma的岩浆活动。通过区域对比表明,攀西—汉南弧没有延入下扬子地区。下扬子地区南部受到峰期为840 Ma的弧岩浆活动的影响。扬子板块上峰期为825 Ma的岩浆活动及早阶段的南华裂谷应是江南造山带后造山伸展的产物;而峰期为800 Ma和750 Ma的岩浆活动与相应的南华裂谷扩展,代表了Rodinia超大陆裂解的全面影响。

    Abstract:

    Objectives:Discovery of many Neoproterozoic igneous rocks in the Lower Yangtze region provides windows for understanding Neoproterozoic magmatism history and features in the Yangtze Plate. Methods:We used the LAICPMS zircon UPb method to date two gneiss samples from the Feidong Complex in the Lower Yangtze region. This and previous zircon UPb dating results from the Lower Yangtze region were analyzed for understanding the Neoproterozoic magmatic history in the region. Zircon age spectra for the Lower Yangtze region and other areas of the Yangtze Plate were then correlated for interpreting the magmatic events and their tectonic setting.Results:Zircon UPb dating for two orthogneiss samples from the Feidong Complex in the southern Zhangbaling Uplift gave protolith age of 805±9 Ma and 804±10 Ma (Neoproterozoic). This and previous zircon dating data demonstrate that protolith ages of metaigneous rocks in the Zhangbaling Group, Feidong Complex and Dongling Complex are 767~748 Ma, 812~745 Ma and 829~754 Ma respectively. The protolith ages of metavolcanic rocks in the Zhangbaling Group show a peak at 750 Ma whereas those of metaigneous rocks in the Feidong Complex exhibit clusters at 800 Ma and 750 Ma. The protolith ages of metavolcanic rocks in the Dongling Complex are 761~754 Ma whereas those of the metaplutons are 829~812 Ma with a peak at 825 Ma. The Neoproterozoic igneous rocks resulted from three phases of magmatism with peak ages of 750 Ma, 800 Ma and 825 Ma. The magmatism with the peak age of 825 Ma occurred only in the southern Lower Yangtze region next to the Jiangnan Orogen. Ages of captured, inherited and detrital zircons from the Neoproterozoic rocks suggest other three phases of magmatism with peak ages of 840 Ma, 2010 Ma and 2454 Ma and the absence of 1000 Ma~860 Ma magmatism in the Lower Yangtze region. Conclusions: Regional correlation demonstrates that the Panxi—Hannan Arc does not extend into the Lower Yangtze region. The southern Lower Yangtze region was affected by the arc magmatism with a peak age of 840 Ma and related to subduction of the South China Ocean. We propose that the magmatism clustering at 840 Ma and the associated Nanhua Rift were products of the postorogenic extension in the Jiangnan Orogen, and the magmatism clustering at 800 Ma and 750 Ma and propagation of the rift represent overall influence of the Rodinia breakup.

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李云剑,朱光,顾承串,张帅,刘程,牛漫兰,苏楠,肖世椰.2018.肥东杂岩的锆石U-Pb年龄及其地质意义——兼论下扬子地区新元古代岩浆活动历史[J].地质论评,64(3):551-568,[DOI].
LI Yunjian, ZHU Guang, GU Chengchuan, ZHANG Shuai, LIU Cheng, NIU Manlan, SU Nan, XIAO Shiye.2018. Zircon U-Pb Ages and Their Geological Significance of the Feidong Complex:Some Comments on Neoproterozoic Magmatism History in the Lower Yangtze Region[J]. Geological Review,64(3):551-568.

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  • 在线发布日期: 2018-05-20
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