Abstract The Siziwangqi region of Inner Mongolia lies along the northern margin of the North China Craton. It consists of diverse suites of Precambrian and Phanerozoic rock units including relicts of the Paleo-Asian Ocean, arc magmatic rocks, amphibolites, and TTG (tonalite–trondhjemite–granodiorite). The amphibolite rocks in the Siziwangqi area occur as enclaves embedded in granodiorite. Geochemical, Lu–Hf isotopic, and zircon U–Pb geochronological analyses on amphibolite enclaves from Siziwangqi indicate end Archean subduction-related mantle metasomatism accompanied by partial melting. U-Pb zircon dating of amphibolite reveals a protolith age of 2503 ± 6 Ma with an inherited zircon age of ∼ 2549 Ma. Geochemical data indicate that the amphibolites range in composition from subalkaline basalt through basaltic–andesite and andesite, all with island arc affinities. The eHf(t) values for the amphibolites range from ＋2.7 to ＋11.4 and their TDM1 model ages range from 2681 to 2517 Ma and peak at 2625 Ma, suggesting dominant late Neoarchean mantle input. This study shows that the amphibolite protoliths likely formed by partial melting of spinel-bearing lherzolites from a depleted mantle, which had been metasomatized by subduction-related fluids.

中文翻译：

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华北克拉通北部与俯冲有关的地幔交代和部分熔融：来自内蒙古四子王旗角闪岩飞地的见解

摘要 内蒙古四子王旗地区位于华北克拉通北缘。它由不同的前寒武纪和显生宙岩石单元组成，包括古亚洲洋遗迹、弧形岩浆岩、角闪岩和 TTG（透长岩-长闪长岩-花岗闪长岩）。四子王旗地区的角闪岩以镶嵌在花岗闪长岩中的飞地形式出现。对四子王旗角闪岩飞地的地球化学、Lu-Hf 同位素和锆石 U-Pb 年代学分析表明，太古宙末期俯冲相关地幔交代伴随着部分熔融。角闪岩的 U-Pb 锆石测年显示原岩年龄为 2503 ± 6 Ma，继承的锆石年龄约为 2549 Ma。地球化学数据表明角闪岩的组成范围从亚碱性玄武岩到玄武岩-安山岩和安山岩，都具有岛弧亲和力。角闪岩的 eHf(t) 值范围为 +2.7 至 +11.4，其 TDM1 模型年龄范围为 2681 至 2517 Ma，峰值为 2625 Ma，表明新太古代晚期地幔输入占主导地位。这项研究表明，角闪石原岩很可能是由贫化地幔中含尖晶石的二辉石部分熔融形成的，地幔已被俯冲相关的流体交代。