La-Ce and Sm-Nd isotopic systematics of early Proterozoic leucogranite with tetrad REE pattern
La-Ce and Sm-Nd isotopic systematics of early Proterozoic leucogranite with tetrad REE pattern
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DOI：
10.1016/j.chemgeo.2010.07.003
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发表时间：
2010-09-01
期刊：
影响因子：
3.9
通讯作者：
Song, Yong Sun
中科院分区：
文献类型：
--
作者：
Lee, Seung-Gu;Asahara, Yoshihiro;Song, Yong Sun
我们报告的La-Ce和Sm-Nd同位素数据的浅色花岗岩四重稀土元素（REE）模式在Imweon地区在东北部的Yeongnam地块，韩国。浅色花岗岩是由石英、钾长石、斜长石、白云母、黑云母、石榴子石和硅线石等变质沉积物部分熔融形成的强过铝质（A/CNK = 1.18-1.79）S型花岗岩。浅色花岗岩的稀土元素配分模式有三种类型：一种为M型四元配分模式，具较大的负Eu异常;另一种为V型配分模式，具正Eu异常;第三种为地壳型配分模式，具轻稀土富集、重稀土亏损的配分模式。浅色花岗岩的锆石U-Pb年龄和Sm-Nd、Rb-Sr全岩年龄为1853 ± 15 Ma ~ 1859 ± 14 Ma（2 σ），1833 +/- 220 Ma（2 σ），含钕（Nd）（1.83 Ga）= -6.6 +/- 5.5（2 sigma）和1740 +/- 71 Ma（2 sigma），初始Sr-87/Sr-86 = 0.755 +/- 0.050（2 sigma）。这些值表明，浅色花岗岩是由地壳物质部分熔融形成的岩浆侵位的。在Ce（Ce）-Nd（Nd）图解中，具有四分稀土配分模式的浅色花岗岩的Ce、Nd同位素组成为正Nd（Nd）、Nd（Ce），而不具有四分稀土配分模式的浅色花岗岩的Ce、Nd同位素组成为负Nd（Nd）、正Nd（Ce）。稀土元素四分体模式的浅色花岗岩的初始Ce同位素值为-2.31
We report La-Ce and Sm-Nd isotopic data for leucogranites having tetrad rare earth element (REE) patterns at Imweon area in the northeastern Yeongnam Massif, South Korea. The leucogranites are strongly peraluminous (A/CNK = 1.18-1.79) S-type granite generated by the partial melting of metasediments, which consist of quartz, K-feldspar, plagioclase, muscovite, biotite, garnet and sillimanite. The leucogranites have three types of chondrite-normalized REE patterns: one showing a tetrad REE pattern of M-type with a large negative Eu anomaly, another with slightly V-shaped REE pattern with a positive Eu anomaly, and third with an REE pattern of crustal type with an LREE-enriched and HREE-depleted pattern. U-Pb zircon ages and, Sm-Nd and Rb-Sr whole-rock ages from the leucogranites are 1853 +/- 15 Ma - 1859 +/- 14 Ma (2 sigma), 1833 +/- 220 Ma (2 sigma) with epsilon(Nd)(1.83 Ga) = -6.6 +/- 5.5 (2 sigma) and 1740 +/- 71 Ma (2 sigma) with initial Sr-87/Sr-86 = 0.755 +/- 0.050 (2 sigma), respectively. These values suggest that the leucogranites were emplaced from magma formed by partial melting of the crustal material. In the epsilon(Ce)-epsilon(Nd) diagram, the present Ce and Nd isotopic compositions of the leucogranites with a tetrad REE pattern are plotted in the positive epsilon(Nd) and epsilon(Ce) field whereas those of the leucogranites without tetrad REE pattern are in the negative epsilon(Nd) and positive epsilon(Ce) field. The initial Ce isotope values of the leucogranites with a tetrad REE pattern are plotted in a range of -2.31