U-Pb dating of zircons from Al-rich paragneisses of Jingshan Group in Shandong peninsula and its geological significance
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    Abstract:

    Al-rich paragneisses in Jingshan Group are extensively distributed in the early Precambrian metamorphic basement of Shandong peninsula, southeast part of the North China Craton. Zircons separated from Al-rich paragneisses are divided into three main types based on cathodoluminescence (CL) and in situ U-Pb dating, i.e., inherited (magmatic or detrital) zircon, HP metamorphic zircon and retrogressive zircon. The inherited zircon records two group 207Pb/206Pb ages of ~2 650 Ma and ~2 100 Ma, indicating two magmatic-thermal events occurring in Neoarchean and Paleoproterozoic epochs and the existence of Paleoproterozoic protoliths of Al-rich paragneisses. In contrast, the homogeneous HP metamorphic zircon records younger 207Pb/206Pb ages ranging from 1 900 Ma to 1 850 Ma, which represent peak HP granulite-facies metamorphic times of Al-rich paragneisses in Jingshan Group . The retrogressive zircon records the youngest 207Pb/206Pb ages of 1 840~1 820 Ma, which represent late medium-and low-granulites-facies retrograde metamorphic times of Al-rich paragneisses in Jingshan Group. These results indicate that the Paleoproterozoic protoliths of Al-rich paragneisses, together with their TTG rocks and mafic rocks, were subducted to coeval Paleoproterozoic HP metamorphism (1 900~1 850 Ma), followed by late medium-and low-granulites-facies retrogression (1 840~1 820 Ma). This new result has very important significance for deep discussion of the genetic mechanism and geodynamic model of the HP granulites distributed in the southeast part of the North China Craton.

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刘平华,刘福来,王舫,刘建辉,2011,山东半岛荆山群富铝片麻岩锆石U-Pb定年及其地质意义[J].岩石矿物学杂志,30(5):829~843. LIU Ping-hua, LIU Fu-lai, WANG Fang, LIU Jian-hui,2011,U-Pb dating of zircons from Al-rich paragneisses of Jingshan Group in Shandong peninsula and its geological significance[J]. Acta Petrologica et Mineralogica,30(5):829~843.

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  • Received:March 10,2011
  • Revised:July 15,2011
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