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Geoscience ›› 2017, Vol. 31 ›› Issue (01): 1-10.

• Mineral Deposit and Petrology • Previous Articles     Next Articles

Formation and Metamorphic Ages of the Banded Iron Formation in Fangmayu of Miyun, Beijing: Zircon SHRIMP U-Pb Dating

SHI Zhiqiang1,2(), SHI Yuruo2()   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
    2. Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037,China
  • Received:2016-06-06 Revised:2016-10-23 Online:2017-02-10 Published:2017-03-16

Abstract:

This paper reports zircon SHRIMP U-Pb ages for magnetite-garnet-plagioclase gneiss from host rocks in the Fangmayu iron deposit, Miyun of Beijing. Zircon 207Pb/206Pb ages of the gneiss we mainly obtained are (1 817±13) Ma and (2 456±6) Ma, respectively. Based on the cathodoluminescence images of zircons, together with the petrography of rocks, the ages represent two stages of metamorphism of the banded magnetic quartzite, corresponding to similar ages of two large-scale metamorphic events (namely ca. 2.44 Ga and ca. 1.82 Ga) reported from the eastern block of North China Craton. Then, we also found some owning oscillatory zoning zircons with 207Pb/206Pb age of (2 529±8) Ma, which represent the age of the detrital zircon from the magnetite-garnet-plagioclase gneiss. It also indirectly constrains that the banded iron formation was formed between (2 456±6) to (2 529±8) Ma, most likely at the end of Neoarchean by combining previous research data. The results also provide further detailed information for research of early tectonic evolution of North China Craton and iron deposits (BIF) in China.

Key words: BIF, zircon, SHRIMP U-Pb dating, North China Craton, metamorphic event, Fangmayu iron deposit, Miyun of Beijing

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