Zircon U-Pb Ages of Volcanic and Sedimentary Rocks of the Wudang Group in the Qinling Orogenic Belt within Western Henan Province
Zircon U-Pb Ages of Volcanic and Sedimentary Rocks of the Wudang Group in the Qinling Orogenic Belt within Western Henan Province
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发表时间：
2008
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通讯作者：
Zhu Xiyan
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作者：
Zhu Xiyan
广泛分布于南秦岭地块的武当群变质沉积—火山层序被认为是武当地块的基底岩，是秦岭造山带东部重要的岩石单元。然而，武当群的形成年代一直存在争议。为了确定武当群的形成时间，作者报道了用LA-ICP-MS技术测定的锆石U-Pb年龄。样品由群上部阳平组的一个变质沉积岩样品和群下部双台组的四个变质火山岩样品组成。测年结果表明，阳平组的沉积源主要来自新元古代（~860~640 Ma）和古元古代（~2260~1800 Ma），其次是晚太古代和中元古代的地壳物质，与扬子地块有亲缘关系。沉积应该发生在640 Ma之后。变质长英质火山岩形成于~730 ~ ~780 Ma之间，峰值在（755±6）Ma，与武当地区内双台组新元古代基性变质火山岩同时发生，可能与罗丁尼亚超大陆的分裂有关。
Metamorphosed sedimentary-volcanic sequences of the Wudang Group widely distributed in the South Qinling Block are considered to be basement rocks of the Wudang Terrain and important rock units in the eastern part of the Qinling Orogenic Belt.Nevertheless,there exists controversy over the formation age of the Wudang Group.To determine the formation time of the Wudang Group,the authors reported zircon U-Pb ages obtained by the LA-ICP-MS technique in this paper.The samples were composed of a meta-sedimentary rock sample collected from the Yangping Formation in the upper part of the Group,and four meta-volcanic rock samples from the Shuangtai Formation in the lower part of the Group.Dating results demonstrate that sedimentary sources of the Yangping Formation originated mainly from Neoproterozoic(～860～640 Ma)and Paleoproterozoic(～2260～1800 Ma),and subordinately from Late Archean and Mesoproterozoic crustal materials,with an affinity to the Yangtze Block.Sedimentation should have occurred later than 640 Ma.Metamorphosed felsic volcanic rocks were formed between ～730 Ma and ～780 Ma,with the peak at(755±6)Ma,being simultaneous with the metamorphosed Neoproterozoic mafic volcanic rocks of the Shuangtai Formation within the Wudang Terrain and probably related to the breakup of the supercontinent Rodinia in petrogenesis.