Phosphoruscontrolled trace element distribution i

Authors: Wei Yang Yangting Lin Jialong Hao Jianchao Zhang Sen Hu Huaiwei Ni

Publish Date: 2016/03/04

Volume: 171, Issue: 3, Pages: 28-

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Abstract

To better understand the origin of oscillatory zoning in zircons distributions of REEs represented by Ce Sm Dy and Lu Y Ti Li and P in the igneous zircons QH from a felsic syenite in the Qinghu alkaline complex and metamorphic zircons DMP0614 from a banded granulite xenolith from Hannuoba basalts have been investigated with NanoSIMS The NanoSIMS analyses reveal well correlation between the trace element distributions and the cathodoluminescence dark–bright zonings of zircons The QH zircons with oscillatory zonings display large trace element variations within single grains by a factor up to 135 with Y and P ranging from 574 and 227 ppm in the bright zones to 7754 and 2464 ppm in the dark zones respectively By contrast the DMP0614 zircons without oscillatory zonings show much smaller trace element variations by a factor of 14 with Y ranging from 477 to 636 ppm and P from 331 to 467 ppm Such large trace element variations in oscillatory zonings cannot be produced by compositional fluctuation in the magma chambers The correlations between P and Y REEs Ce Sm Dy and Lu R 2  097 indicate xenotime substitution in zircons The oscillatory distribution of P in zircon could be formed by the fluctuation of P in the melt adjacent to the mineralmelt boundary either because P diffuses slower than Zr in the melt or due to surfacial interaction of melt with crystals Such a zoned distribution of P in turn controls the substitution types of phosphates in zircon developing oscillatory distributions of Y and REEs Our results indicate that apparent partition coefficients of Y and REEs between zircon and melt are controlled by P contents which may result in the large discrepancy in zircon partitioning dataWe thank Xianhua Li Hongfu Zhang Qiuli Li Yu Liu Guoqiang Tang for providing zircon samples Lu Feng Xuchao Zhao Yuchen Xu for assistances in the laboratory and Yun Liu for discussion Constructive comments from Qinzhu Yin Fang Huang Yan Luo Shuijiong Wang Liwei Deng and two anonymous reviewers are greatly appreciated This work was supported by the National Science Foundation of China Grants 41322022 41230209 41521062 41173012 41430105 and by CNSA Grant No TY3Q20110029

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