文章基本信息

标题：Extreme lithium isotopic fractionation in three zircon standards (Plešovice, Qinghu and Temora)
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作者：Yu-Ya Gao ; Xian-Hua Li ; William L. Griffin 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
期号：1
DOI：10.1038/srep16878
语种：English
出版社：Springer Nature
摘要：To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5–20 μm wide in which [Li] is 5 to 20 times higher than in the core. Up to ~20‰ isotopic fractionation is observed on a small scale in the rims of a single zircon grain. The measured δ⁷Li values range from –14.3 to 3.7‰ for Plešovice, –22.8 to 1.4‰ for Qinghu and –4.7 to 16.1‰ for Temora zircon. The [Li] and δ⁷Li are highly variable at the rims, but relatively homogenous in the cores of the grains. From zircon rim to core, [Li] decreases rapidly, while δ⁷Li increases, suggesting that the large isotopic variation of Li in zircons could be caused by diffusion. Our data demonstrate that homogeneous δ⁷Li in the cores of zircon can retain the original isotopic signatures of the magmas, while the bulk analysis of Li isotopes in mineral separates and in bulk-rock samples may produce misleading data.