北京云蒙山地区侵入岩体SHRIMP锆石U-Pb年龄、地球化学特征及其地质意义
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中国地质调查局项目(DD20160345,1212011121075,12120114020901)


Zircon SHRIMP U-Pb ages and geochemical characteristics of the granitoids in Yunmengshan area of Beijing and their geological significance
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    摘要:

    位于华北克拉通北缘的云蒙山地区花岗岩类研究对认识该区域由挤压到拉张的构造背景转换的时间和机制有重要意义。本文在对云蒙山地区长园岩体、官山岩体和云蒙山岩体的岩相学特征及其与周围岩体的关系研究基础上,对这些花岗岩体进行了SHRIMP 锆石U-Pb测年和主微量元素分析。结合前人研究结果,认为云蒙山地区在晚侏罗世-早白垩世期间主要有162~151 Ma和151~141 Ma两期岩浆活动,从早到晚岩浆酸性逐渐增加,反映岩浆源区从幔源物质到壳源物质的转变,随着晚侏罗世-早白垩世时期的挤压作用,地壳逐渐增厚,后期形成的岩浆更加具有壳源特征,甚至出现了中等分异的花岗岩。通过限定相关岩浆活动的时间,得出云蒙山地区从挤压到拉张的转换时间为141~129 Ma,本文研究的花岗岩类形成的构造背景是强挤压陆内造山环境,表明岩浆侵位于该区岩石圈大规模减薄之前。伴随中酸性岩浆上移侵位,残留相的密度越来越大,具备了后期下地壳发生拆沉的一些条件。

    Abstract:

    The granitoids in Yunmengshan area, located on the northern margin of the North China Craton, are important for understanding the formation time and mechanism of the tectonic background transition in this area. In this paper, the authors present zircon SHRIMP U-Pb ages and geochemical characteristics of the granitoids in Changyuan pluton, Guanshan pluton and Yunmengshan pluton. The results, in combination with available zircon U-Pb ages, show two magmatic periods in Yunmengshan area:162~151 Ma and 151~141 Ma. Compared with the second period, samples from the first magmatism period are higher in Mg# but lower in SiO2, which indicates that they evolved from the mantle source to the crust source during Late Jurassic-Early Cretaceous compression episode, accompanied by crustal thickening, even with some exposed moderately-fractionated granitoids. The transition from compression to extension in the study area lasted for 12 Ma, i.e., from 141 Ma to 129 Ma. The granitoids from Yunmengshan area were formed in a compressional environment before decratonization, and the thickened crust possessed the condition for later delamination.

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康月蓝,石玉若,2018,北京云蒙山地区侵入岩体SHRIMP锆石U-Pb年龄、地球化学特征及其地质意义[J].岩石矿物学杂志,37(3):379~394. KANG Yue-lan, SHI Yu-ruo,2018,Zircon SHRIMP U-Pb ages and geochemical characteristics of the granitoids in Yunmengshan area of Beijing and their geological significance[J]. Acta Petrologica et Mineralogica,37(3):379~394.

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  • 收稿日期:2017-06-08
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  • 在线发布日期: 2018-05-25
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