Zircon U–Pb age, trace element and Hf isotope composition of Kongling terrane in the Yangtze Craton: refining the timing of Palaeoproterozoic high‐grade metamorphism
Zircon U–Pb age, trace element and Hf isotope composition of Kongling terrane in the Yangtze Craton: refining the timing of Palaeoproterozoic high‐grade metamorphism
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DOI：
10.1111/j.1525-1314.2009.00826.x
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发表时间：
2009-08
影响因子：
3.4
通讯作者：
Y.‐B. Wu;Shang Gao;H. Gong;H. Xiang;W. Jiao;S. Yang;Ys Liu;H. Yuan
中科院分区：
文献类型：
--
作者：
Y.‐B. Wu;Shang Gao;H. Gong;H. Xiang;W. Jiao;S. Yang;Ys Liu;H. Yuan
对扬子北方空岭斜长角闪岩和一套变质沉积岩进行了锆石U-Pb年龄、微量元素和Hf同位素组成分析。锆石具有明显的形态特征和化学特征。斜长角闪岩中的锆石大多呈振荡分带，Th/U和176 Lu/177 Hf比值高，形成温度高，微量元素含量高，Eu负异常明显，重稀土元素富集，表明其为岩浆成因。锆石的207 Pb/206 Pb加权平均年龄为2857 ± 8 Ma，代表岩浆原岩的年龄。另外两个样品中的锆石是变质的。低Th/U比值，低微量元素含量，HREE含量（33.8 ≥ LuN≥2213; 14.7 ≤ LuN/SmN ≤ 354）和176 Lu/177 Hf比值（0.000030-0.001168）变化较大。结果表明，锆石形成于石榴子石的存在下，并处于上角闪岩相条件下。变质锆石的207 Pb/206 Pb加权平均年龄为2010 ± 13 Ma。这些结果与以前获得的古元古代变质年龄相结合，建议c。2.0 Ga古元古代扬子板块碰撞事件，可能是哥伦比亚超大陆组装的结果。两个样品中锆石的加权平均两阶段Hf模式年龄（TDM 2）分别为3217 ± 110和2943 ± 50 Ma，表明它们的原岩主要来自太古宙地壳。
U–Pb age, trace element and Hf isotope compositions of zircon were analysed for a metasedimentary rock and two amphibolites from the Kongling terrane in the northern part of the Yangtze Craton. The zircon shows distinct morphological and chemical characteristics. Most zircon in an amphibolite shows oscillatory zoning, high Th/U and 176Lu/177Hf ratios, high formation temperature, high trace element contents, clear negative Eu anomaly, as well as HREE‐enriched patterns, suggesting that it is igneous. The zircon yields a weighted mean 207Pb/206Pb age of 2857 ± 8 Ma, representing the age of the magmatic protolith. The zircon in the other two samples is metamorphic. It has low Th/U ratios, low trace element concentrations, variable HREE contents (33.8 ≥ LuN≥2213; 14.7 ≤ LuN/SmN ≤ 354) and 176Lu/177Hf ratios (0.000030–0.001168). The data indicate that the zircon formed in the presence of garnet and under upper amphibolite facies conditions. The metamorphic zircon yields a weighted mean 207Pb/206Pb age of 2010 ± 13 Ma. These results combined with previously obtained Palaeoproterozoic metamorphic ages suggest a c. 2.0 Ga Palaeoproterozoic collisional event in the Yangtze Craton, which may result from the assembly of the supercontinent Columbia. The zircon in two samples yields weighted mean two‐stage Hf model (TDM2) ages of 3217 ± 110 and 2943 ± 50 Ma, respectively, indicating that their protoliths were mainly derived from Archean crust.