共和盆地西缘柔起岗地区变质岩系LA-ICP-MS锆石U-Pb年龄 —原岩最大沉积时代及物源研究
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国家自然科学基金项目(面上项目,重点项目,重大项目)


LA-ICP-MS Zircon Age of the Metamorphism Rocks in Rouqigang Area of Western Gonghe Basin-Maximum Depositional Ages of Protoliths and Provenance Feature
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    摘要:

    共和盆地西缘原划古元古代金水口岩群中发育一套低级变质的灰色绢云石英片岩、绢云石英岩及黑云石英片岩组合,该套变质岩系原岩沉积时代及变质基底构造属性存在争议。本文对采自青海省兴海县柔起岗地区的两件片岩样品开展了系统的岩石学及LA-ICP-MS锆石 U-Pb年代学研究,对其原岩沉积时代、沉积物源及基底构造亲缘性进行了探讨。结果表明,该套片岩两件样品的碎屑锆石U-Pb年龄谱可明显分为新元古代和古元古代两个主年龄谱以及中元古代的两个次年龄谱,新元古代主年龄谱分别为688-908 Ma和711-841 Ma,峰值年龄为788 Ma和780 Ma,古元古代主年龄谱分别为1871-2174 Ma和1832-2194 Ma,峰值年龄为2140 Ma和2072 Ma,中元古代两个次年龄谱分别为1520-1638 Ma和1271-1276 Ma,峰值年龄为1635 Ma和1275 Ma。片岩最小碎屑锆石年龄值688 Ma限定了其原岩的最大沉积时代。塔洞片岩碎屑锆石U-Pb年龄谱特征表明其碎屑物质来源较为复杂,物源主体来自周邻造山带的西秦岭、东昆仑和柴达木盆地北缘构造带的前寒武纪块体,扬子板块对其沉积物源亦有部分贡献,而华北板块没有对其提供沉积物源。更为重要的是,该套片岩锆石U-Pb年龄谱突出显示新元古代早期的构造-岩浆-热事件年龄信息,而没有华北板块典型的1850 Ma 和2500 Ma左右的特征,结合区域资料认为西秦岭源区基底与东昆仑地块、柴达木盆地北缘、祁连地块等一样表现出扬子板块的构造亲缘性,源区基底固结时代为新元古代早期。

    Abstract:

    Paleoproterozoic Jinshuikou Group in the west of the West Qinling composed by serite-quartz schist、chlorite-sericite-quartz schist and biotite quartz schist , underwent greenschist facies metamorphism, which have a lot of debate about the deposition time and the tectonics property of metamorphic basement. With two schist samples of the Jinshuikou Group in Rouqigang area of Qinghai province as the research object,this paper used the LA-ICP-MS zircon U–Pb isotopic geochronologic methods to study the formation age,sedimentary source of Jinshuikou Group and metamorphic basement affinity. Detrital zircon U-Pb age spectrum of two schist samples can be divided into two major age spectrums of Neoproterozoic and Paleoproterozoic, and two minor age spectrum of Mesoproterozoic. Neoproterozoic age spectrums are group 688-908Ma and 711-841 Ma,with peak value of 788 Ma and 780 Ma; Paleoproterozoic age spectrums are group 1871-2174 Ma and 1832-2194 Ma, with peak value of 2140Ma and 2072Ma;Mesoproterozoic age spectrums are group 1520-1638 Ma and 1271-1276 Ma, with peak value of 1635 Ma and 1275 Ma.The age group information indicates that the sedimentary sources of Jinshuikou Group is much more complicated and characterized by obvious diversity. Its sources mainly might have come from the East Kunlun orogenic belt and the North Qaidam tectonic belt, and some from Yangtze plate, but without North China plate. More importantly, the U-Pb age spectrum of the schist`zircon highlight about the 780Ma age of Neoproterozoic, but without representative 1850Ma age and 2500Ma age of North China plate. In combination with regional data, the West Qinling basement, whose crystallization time is Early Neoproterozoic, is identical to the East kunlun block、the North Qaidam、Qilian block ,which all express tectonic affinity to Yangtze plate.

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李瑞保,裴先治,杨栓海,王伟峰,魏立勇,孙雨,李飞,刘满年,赵长存,李佐臣,杨高学,陈力子.2016.共和盆地西缘柔起岗地区变质岩系LA-ICP-MS锆石U-Pb年龄 —原岩最大沉积时代及物源研究[J].地质学报,90(1):93-114.
liruibao, Pei Xianzhi, Yang Shuahai, Wang Weifeng, Wei Liyong, Sun Yu, Li Fei, Liu Mannian, Zhao Changcun, Li Zuochen, Yang Gaoxue, CHEN Lizi.2016. LA-ICP-MS Zircon Age of the Metamorphism Rocks in Rouqigang Area of Western Gonghe Basin-Maximum Depositional Ages of Protoliths and Provenance Feature[J]. Acta Geologica Sinica,90(1):93-114.

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  • 收稿日期:2014-12-18
  • 最后修改日期:2015-03-31
  • 录用日期:2015-04-01
  • 在线发布日期: 2016-01-18
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