Sm–Nd systematics of zircon
Sm–Nd systematics of zircon
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DOI：
10.1016/j.chemgeo.2004.07.004
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发表时间：
2004-11
期刊：
影响因子：
3.9
通讯作者：
Y. Amelin
中科院分区：
文献类型：
--
作者：
Y. Amelin
对19颗3.32 ~ 4.02 Ga锆石中的147Sm-143Nd和146sm - 142体系进行了研究，其中12颗已经进行了Lu-Hf分析。锆石中Nd含量为0.9 ~ 20ppm。Nd的回收率在13 ~ 446 pg之间。142 /144Nd和143nd /144Nd的分析精度随样品大小的变化在0.004% ~ 0.08% （2σm）之间。147sm /144Nd比值变化范围为0.4 ~ 1.2.143，nd /144Nd比值变化范围为0.5125 ~ 0.5346。对147sm - 143nd和U-Pb体系的综合解释表明，锆石中的轻稀土元素是高Sm/Nd（>1.6 ~ 2.0）的主组分和低Sm/Nd的次年轻组分的混合体。由于147sm /144Nd比值存在较大误差，从而导致了对古锆石的初始值的不确定度，因此无法以足够的精度和准确度测定古锆石的初始值。此外，蚀变较多的锆石中存在未知年龄和同位素组成的次生Nd，也会对[143Nd]值产生偏倚。147sm - 143nd体系更有希望作为锆石中次级、蚀变相关的稀土成分的测量指标。应用锆石146sm - 142体系确定早期陆相分异时间是有希望的。这将需要改进分析程序，以达到尽可能低的空白和最高的灵敏度。离子收率需要高达20-30%。
147Sm–143Nd and146Sm–142Nd systems were studied in nineteen 3.32–4.02 Ga zircon grains from Jack Hills metaconglomerate, 12 of which were previously analyzed for Lu–Hf. Nd concentrations in the zircons are 0.9–20 ppm.The amount of Nd recovered was between 13 and 446 pg. The analytical precision of142Nd/144Nd and143Nd/144Nd ratios varied between 0.004% and 0.08% (2σm) depending on the sample size. The147Sm/144Nd ratios vary from 0.4 to 1.2.143Nd/144Nd ratios are variably radiogenic, from 0.5125 to 0.5346. Combined interpretation of147Sm–143Nd and U–Pb systems shows that LREE in zircons are a mixture of a primary component with high Sm/Nd (>1.6–2.0), and a secondary, younger component with low Sm/Nd. Determination of initial ɛ143Nd of ancient zircons with a precision and accuracy sufficient for petrogenetic interpretations may not be possible because of large errors in the147Sm/144Nd ratio, which propagate to the uncertainty of ɛ143Nd. Additionally, the ɛ143Nd values are biased by the presence of secondary Nd of unknown age and isotopic composition in more altered zircons. The147Sm–143Nd system is more promising as a gauge for this secondary, alteration-related REE component in zircon. Application of the146Sm–142Nd system in zircon to determine the timing of early terrestrial differentiation is promising. It will require advancement of the analytical procedures to achieve the lowest possible blanks and maximum sensitivity. Ion yield as high as 20–30% will be required.