Abstract The Paleoproterozoic tectonic setting and spatial-temporal evolution of the northern North China and Central Orogenic belt constrain the assembly of the North China craton. Here we describe a new Paleoproterozoic mafic-ultramafic unit and intermediate-mafic intrusions located between the Khondalite belt and Central Orogenic belt, which we refer to as Donggouzi mafic-ultramafic complex. This complex is structurally complicated, and comprises a mixture of peridotite, amphibole pyroxenite, and websterite blocks, with associated alkali granitoid and gabbroic dikes, which were intruded into Paleoproterozoic granulites. Zircon U Pb geochronology of the granulite, intruding syenite and alkali granites together with the field observations constrain the formation of the Donggouzi mafic-ultramafic complex to between 1849 and 1845 Ma, i.e. 1.85 Ga. Geochemical and Sr Nd isotopic data indicate that the Paleoproterozoic mafic-ultramafic rocks were sourced from enriched metasomatized mantle by the fluid from a subduction slab. Emplacement of the complex occurred in a post-orogenic extensional setting, possibly associated with the collision along the northern margin of the North China craton at ca. 1.9–1.88 Ga. The ca. 1767 Ma gabbroic dike was emplaced in an intraplate extensional setting and experienced crustal contamination, which suggests that an upwelling mantle plume produced magmas that interacted with the lithosphere during the late Paleoproterozoic.

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古元古代洞沟子基性-超镁铁杂岩的地质、地球化学和年代学：对华北克拉通演化的启示

摘要 华北北部和中央造山带的古元古代构造背景和时空演化制约了华北克拉通的聚集。在这里，我们描述了一个新的古元古代基性-超镁铁质单元和位于孔达岩带和中央造山带之间的中基性侵入体，我们将其称为洞沟子基性-超镁铁质杂岩体。该杂岩体结构复杂，由橄榄岩、角闪石辉石岩和网橄榄石块体组成，伴生碱性花岗岩和辉长岩脉，侵入古元古代麻粒岩。麻粒岩、侵入正长岩和碱性花岗岩的锆石U Pb年代学以及野外观测将洞沟子基性-超基性杂岩的形成限制在1849-1845 Ma之间，即1.85 Ga。地球化学和 Sr Nd 同位素数据表明，古元古代基性-超镁铁质岩石来源于俯冲板片流体的富集交代地幔。复合体的就位发生在造山后的伸展环境中，可能与大约在华北克拉通北缘的碰撞有关。1.9–1.88 Ga。1767 Ma 辉长岩脉位于板内伸展环境中，并经历了地壳污染，这表明在晚古元古代，上涌的地幔柱产生了与岩石圈相互作用的岩浆。复合体的就位发生在造山后的伸展环境中，可能与大约在华北克拉通北缘的碰撞有关。1.9–1.88 Ga。1767 Ma 辉长岩脉位于板内伸展环境中，并经历了地壳污染，这表明在晚古元古代，上涌的地幔柱产生了与岩石圈相互作用的岩浆。复合体的就位发生在造山后的伸展环境中，可能与大约在华北克拉通北缘的碰撞有关。1.9–1.88 Ga。1767 Ma 辉长岩脉位于板内伸展环境中，并经历了地壳污染，这表明在晚古元古代，上涌的地幔柱产生了与岩石圈相互作用的岩浆。