Neoarchean to Paleoproterozoic continental growth in the southeastern margin of the North China Craton: Geochemical, zircon U–Pb and Hf isotope evidence from the Huoqiu complex
Neoarchean to Paleoproterozoic continental growth in the southeastern margin of the North China Craton: Geochemical, zircon U–Pb and Hf isotope evidence from the Huoqiu complex
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DOI：
10.1016/j.gr.2014.08.011
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发表时间：
2015-10
影响因子：
6.1
通讯作者：
Lei Liu;Xiaoyong Yang;M. Santosh;S. Aulbach
中科院分区：
文献类型：
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作者：
Lei Liu;Xiaoyong Yang;M. Santosh;S. Aulbach
霍邱杂岩位于华北陆块东南缘，以新太古代灰色片麻岩、斜长角闪岩和大量变质沉积岩为主。在这里，我们报告的出现新太古代古元古代岩石的钻孔岩心样品。片麻岩的成分类似于TTG（英云闪长岩-奥长花岗岩-花岗闪长岩），与斜长角闪岩的空间组合关系密切。地球化学特征，如高Sr/Y和（La/Yb）N与陡峭的稀土元素模式和微量元素建模表明，这些岩石是由部分熔融的含水变玄武岩（斜长角闪岩）在加厚的镁铁质大陆地壳的基础上，留下一个金红石榴辉岩残留物。岩浆锆石LA-MC-ICP-MS U-Pb年龄为2.76- 2.71Ga。随后，广泛的混合岩化作用发生在1.91-1.82 Ga，产生了大量的混合岩和高钾花岗岩。斜长角闪岩和片麻岩中锆石颗粒的Hf同位素组成显示εHf（t）值分别为2.4-15.5和− 3.0-1.5。该片麻岩的tDM 2（Hf）模式年龄为2.87 ~ 3.14Ga，与斜长角闪岩的tDM 1（Hf）年龄（2.84- 3.16Ga）在分析不确定度范围内一致，表明该片麻岩是由斜长角闪岩部分熔融形成的，是新太古代古陆壳大规模改造的证据。花岗岩中锆石颗粒的Hf同位素组成分为两类。老岩群（1916 ± 42 Ma）的εHf（t）值和tDM 2（Hf）模式年龄分别为− 10.5-2.4和2.40-3.20 Ga，而年轻岩群（1823 ± 41 Ma）的εHf（t）值变化较大，范围为− 18.1 ~ 12.5，tDM 2（Hf）模式年龄为1.70-3.59 Ga。年轻组中的一对锆石U-Pb年龄和tDM 2值一致，表明1.82 ~ 1.91Ga期间年轻地壳来自亏损地幔源的增生作用。然而，占主导地位的Hf同位素特征与先存大陆地壳的改造是一致的。因此，我们推断，只有有限的增生的少年地壳发生在这段时间内，古元古代（1.82至1.91 Ga）构造在东南边缘的NCC见证了广泛的改造旧大陆地壳。
The Huoqiu complex in the southeastern margin of the North China Craton (NCC) is dominated by Neoarchean gray gneisses, amphibolites and voluminous metasediments. Here we report the occurrence of Neoarchean to Paleoproterozoic rocks from drill-core samples. The gneisses are similar to TTG (tonalite–trondhjemite–granodiorite) in composition and show close spatial association with amphibolites. Geochemical characteristics such as high Sr/Y and (La/Yb)Nwith steep REE patterns and trace element modeling suggest that these rocks were generated by partial melting of hydrous meta-basalts (amphibolites) at the base of a thickened mafic continental crust, leaving a rutile-bearing eclogite residue. LA-MC-ICP-MS U–Pb age data from magmatic zircon grains show protolith emplacement ages of 2.76–2.71 Ga. Subsequently, widespread migmatization took place at 1.91–1.82 Ga, generating voluminous migmatites and high-K granites. Hf isotopic compositions of zircon grains from the amphibolite and gneiss show εHf(t) values of 2.4–15.5 and − 3.0–1.5, respectively. The tDM2(Hf) model ages of the gneisses range from 2.87 to 3.14 Ga, and are identical to the tDM1(Hf) ages of amphibolites (2.84–3.16 Ga) within analytical uncertainty, suggesting that the gneisses formed by partial melting of amphibolite, and attest to large-scale reworking of the ancient continental crust during Neoarchean. The zircon grains from the granites define two groups with regard to their Hf isotopic composition. The older group (1916 ± 42 Ma) has εHf(t) values and tDM2(Hf) ages of − 10.5–2.4 and 2.40–3.20 Ga, respectively, whereas the younger one (1823 ± 41 Ma) shows a large variation in εHf(t) values ranging from − 18.1 to 12.5, with tDM2(Hf) model ages of 1.70–3.59 Ga. A couple of zircon grains from the younger group display consistent U–Pb ages and tDM2, indicating accretion of juvenile crust from depleted mantle sources during 1.82 to 1.91 Ga. However, the dominant Hf isotope features are consistent with the reworking of preexisting continental crust. We therefore infer that only limited accretion of juvenile crust occurred during this time, and that the Paleoproterozoic (1.82 to 1.91 Ga) tectonics in the southeastern margin of the NCC witnessed extensive reworking of older continental crust.