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SHRIMP U-Pb geochronology of the zircons from the Precambrian basement of the Qilian Block and its geological significances 总被引:6,自引:0,他引:6
Kuoan TUNG Huai-Jen YANG Houng-Yi YANG LIU DunYi ZHANG JianXin WAN YuSheng Chien-Yuan TSENG 《科学通报(英文版)》2007,52(19):2687-2701
Origin and tectonic evolution of the Qilian Precambrian basement on NW China were investigated using zircon U-Pb ages with collaborating stratigraphic and paleontological evidence. Zircon grains were separated from two schists, two granitic gneisses and one mylonized gneiss and dated with SHRIMP. Seventy percent of sixty-one detrital zircon ages from two schists ranges from 0.88 Ga to 3.09 Ga, mostly within 1.0 Ga to 1.8 Ga with a peak at 1.6 Ga to 1.8 Ga, and twenty percent varies from 2.0 Ga to 2.5 Ga. A few falls in the Archean and Neoproterozoic periods. The two granitic gneisses were dated 930±8 Ma and 918±14 Ma, whereas the mylonized granitic gneiss was dated 790±12 Ma. These ages represent two periods of magmatisms, which can be correlated with the early and late stages of magmatisms associated with the Jinningian movement on the Yangtze Blocks. The results from this and previous studies indicate that the ages of the Precambrian detrital zircons from the Qilian Block are widely distributed in the Proterozoic era, distinct from the North China Block which was stable in the Neo-Mesoproterozoic era. By contrast, the age histograms of the detrital zircons from the Qilian Block is similar to those from Precambrian basement of the Yangtze Craton. Therefore, it is suggested that the Qilian Block had a strong affinity toward the Yangtze Craton and might belong to the supercontinent Gondwana in the Neoproterozoic time. This inference is supported by Nd model age (TDM), stratigraphic, and paleontological evidence. It is further considered that the Qilian Block was rifted from the supercontinent Gondwana during late Sinian to form an isolated continent in the Proto-Tethyan Ocean, moving towards the Alaxa Block in the North China Craton. The part of Proto-Tethyan Ocean between the Qilian and Alaxa Blocks should correspond to the so-called Paleo-Qilian Ocean. Following the closure of the Paleo-Qilian Ocean in the early Paleozoic, the Qilian Block collided with the Alaxa Block to form the North Qilian Orogenic Belt. Based on this tectonic explanation, the North Qilian ophiolites should represent parts of lithosphere from the Proto-Tethyan Ocean. Lithological and geochronological evidence also indicates that the Qilian Block underwent continental reactivation possibly induced by the deep northward subduction of the North Qaidam Block in early Paleozoic time. 相似文献
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金鹤生 《湖南科技大学学报(自然科学版)》1991,(2)
通过对东特提斯地区有关地块编制地质时代——古纬度图,我们得出如下结论:①东特提斯开始形成于奥陶纪末——志留纪初;②东特提斯洋主体由特提斯——Ⅰ和特提斯——Ⅱ二支海槽组成,其间被中间地块或岛群断续分开;③藏北、藏南、帝汶等地块来自冈瓦纳,而中伊朗、塔里木、斯兰等地块(或岛)来自欧亚。这些结论也被各种地质资料所证实。图2,表12,参13。 相似文献
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本区奥陶系划分下统阿克萨依湖组,中统落石沟组(或兽形湖组),上统饮水河组。早奥陶世的腕足类、三叶虫及头足类的生物区系较复杂,与华北、藏南-滇西和扬子区关系较密切,属混生型。中晚奥陶世的头足类、三叶虫及腕足动物与藏南-滇西和扬子区接近,基本上属扬子区系。说明奥陶纪时亚洲大陆的海洋通道由早期南北向到中晚期近东西向的转变过程,即古特提斯海由早期萌发到中晚期雏形形成过程。 相似文献
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一百多年前,地质学家提出:大海的深度是永恒的吗?从那时起,特提斯海就成为世界地学界孜孜探求的热门研究课题,那么,它的持久魅力何在…… 相似文献
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