Palaeoproterozoic granites accompanied with granulite‐facies gneisses can be recognized in the Kuandian area, northern Jiao‐Liao‐Ji Belt (JLJB). This study highlights two episodes of Palaeoproterozoic magmatism, identified by granites and biotite monzogranitic gneisses herein. Zircon grains from biotite monzogranitic gneiss with homogeneous oscillatory zoning yielded a U–Pb age of 2,153 ± 16 Ma, in accordance with the age of zircon cores from the monzogranitic gneiss. Zircon grains from the two granites yielded upper intercept ages of 1,892 ± 38 Ma and 1,859 ± 36 Ma respectively. Monzogranitic gneiss samples are enriched in Th, Rb, Pb, U, and REE, but depleted in Sr and P. They have high 1,000 × Ga/Al ratios versus Zr, Ce, Nb, Y contents, which are usually interpreted as the features of classical A‐type granite that originated in a lithospheric extension setting. The ~1.89–1.86 Ga granite samples have relatively high Al, Rb, Th, U and low Sr, Zr, and Hf contents. These features, combined with the observation of minor apatite grains under the microscope are similar with the I‐type granites. In situ zircon Lu–Hf isotopic analyses revealed that ~1.89–1.86 Ga granite had a similar range and T_DM2 ages with the monzogranitic gneiss, but with much lower ε_Hf(t) values. The monzogranitic gneiss may have originated from an Archean crust, while the later granite may be derived from melting of the partial melting of the monzogranitic gneiss or the Archean crust that generated the monzogranitic gneiss. The ~1.89–1.86 Ga granites, together with the coeval S‐type granites in the JLJB, represent an orogeny process that may involve a Palaeoproterozoic subduction.

中文翻译：

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胶辽冀带宽甸地区两种古元古代花岗岩的地球化学，锆石U-Pb定年和Lu-Hf同位素特征：对区域构造背景的启示

在胶辽纪地带北部（JLJB）的宽甸地区，可以看到古元古代花岗岩和花岗质片麻岩。这项研究强调了古元古代岩浆作用的两次发作，这是由本文中的花岗岩和黑云母独生片麻岩识别的。黑云母单斜生片麻岩中的锆石晶粒具有均一的振荡带，其U–Pb年龄为2,153±16 Ma，与单斜生片麻岩中锆石芯的年龄一致。来自这两个花岗岩的锆石晶粒的截距年龄分别为1,892±38 Ma和1,859±36 Ma。Monzogranitic片麻岩样品富含Th，Rb，Pb，U和REE，但富含Sr和P。与Zr，Ce，Nb，Y含量相比，它们具有高1,000×Ga / Al比。通常被解释为起源于岩石圈伸展背景下的经典A型花岗岩的特征。〜1.89–1.86 Ga花岗岩样品具有较高的Al，Rb，Th，U和较低的Sr，Zr和Hf含量。这些特征，再加上在显微镜下观察到的细小的磷灰石晶粒，与I型花岗岩相似。原位锆石Lu-Hf同位素分析表明，〜1.89-1.86 Ga花岗岩具有相似的射程和T_DM2会随着单线片麻岩而老化，但_εHf（t）值要低得多。独生岩片麻岩可能起源于太古宙地壳，而后来的花岗岩可能来自于独生岩片麻岩或部分产于独生岩片麻岩的太古代壳的熔融。约1.89–1.86的Ga花岗岩以及JLJB中的同期S型花岗岩代表了造山过程，可能涉及古元古代俯冲。