We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

中文翻译：

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冀北赤城回生榴辉岩锆石U-Pb定年及Lu-Hf同位素

我们报告了赤城地区两个回生榴辉岩样品的锆石 U-Pb 年龄和 Lu-Hf 同位素数据。赤城回生榴辉岩中的变质锆石分为两组：一组为轻稀土贫化、重稀土曲线平坦的特征，无明显Eu异常，可能形成于榴辉岩相变质条件下；第二组富含HREE，Eu呈轻微负异常，表明它们可能在角闪岩相变质条件下形成。ε 的锆石 Lu-Hf 同位素赤城榴辉岩的Hf跨度较大，为6.0～18.0，表明榴辉岩原岩的岩浆可能与部分地壳成分混合。赤城榴辉岩的榴辉岩相变质峰值可能发生在 348.5-344.2 Ma，角闪岩的逆行变质作用可能发生在约 325.0 马。红旗营子杂岩可能经历多期变质事件，主要包括太古宙晚期（2494～2448 Ma）、古元古代晚期（1900～1734 Ma，峰龄1824.6 Ma）和显生宙（495～234 Ma，峰龄323.7 Ma）。因此，赤城榴辉岩的变质事件（348.5-325 Ma）与红旗营子杂岩的显生宙变质事件一致。