Geochronology and Genesis of the Helegang Xilikete Granitic Plutons from the Southern Margin of the Eastern East Kunlun Orogenic Belt and Their Tectonic Significance
Geochronology and Genesis of the Helegang Xilikete Granitic Plutons from the Southern Margin of the Eastern East Kunlun Orogenic Belt and Their Tectonic Significance
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发表时间：
2013
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通讯作者：
Chen Guocha
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作者：
Chen Guocha
东昆仑造山带东段南缘出露了大量晚古生代—中生代岩体，其成因和物源区特征一直是地质学家研究的热点。本研究对该地区和勒冈希里克特岩体进行了岩相学、LA-ICPMS锆石U-Pb年代学和岩石地球化学特征的详细研究。结果表明，岩体具有特征性。 Sr/Y和La/Yb比值较高，Na2O和Sr含量较高，轻稀土和重稀土分异明显，Eu正负异常轻微，Yb和Y含量较低。这些特征表明岩体与埃达克岩相似。岩石属于准铝质或弱过铝质高钾钙碱花岗岩，富LILE，贫HFSE，Mg#和Cr、Ni含量和Nb/Ta值与大陆地壳相似。另外，岩石中含有大量的镁铁质包体和暗色微粒包体，表明它们是玄武质岩浆底侵作用到下地壳的产物。岩体的锆石同位素年龄约为（225±5）Ma，代表其形成年龄。结合地球化学特征，该年龄可能暗示东东部地区当时的昆仑造山带正处于碰撞到碰撞后的过渡时期。
There are plenty of Late Paleozoic-Mesozoic plutons outcropped in the southern margin of the eastern part of the East Kunlun Orogenic Belt,and their genesis and features of source region have long been the hot topic among geologists.This study carried out the detailed investigation over petrography,LA-ICPMS zircon U-Pb chronology and litho-geochemical characteristics for the Helegang Xilikete plutons in the area.The results show that the plutons are characteristic of high Sr/Y and La/Yb ratios,high Na2O and Sr contents,apparent differentiation between LREE and HREE,slight positive and negative anomalies of Eu,and low contents of Yb and Y.All this features indicate that the plutons are similar to adakitic rocks.The rocks are classified to metaluminous or weak peraluminous high-K calc-alkali granitoid and enriched in LILE and depleted in HFSE,with high Mg#and Cr,Ni in content,and Nb/Ta value similar to that of continental crust.In addition,the rocks contain a lot of mafic enclaves and dark micro-grained enclaves indicate they were the product of underplating of basaltic magma into lower crust.The zircon isotopic age of the plutons is about(225±5)Ma,representing their forming age.In combination with geochemical features,the age may imply that the eastern part of East Kunlun Orogenic Belt stayed in the transitional period from collision to post-collision at that time.