Abstract Khondalite Belt is located in the northwestern part of North China Craton, and is a typical continent-to-continent collisional orogen, along which the Yinshan Block collided with the Ordos Block at 1.95–1.85 Ga. However, this model was mainly relied on high-grade metamorphic records in the Khondalite Belt, whether the extensively exposed low-grade rocks were also involved in such collision remains poorly constrained. Erdaowa Group is an important lithological unit of the belt and consists of extensive low-grade metamorphic rock assemblages (i.e. greenschist to amphibolite facies), and provide crucial insights into understanding the issue. Based on petrological and geochemical characteristics, low-grade metamorphic rocks of Erdaowa Group show a large affinity to bimodal volcanic sequence characterized by basaltic and acidic endmembers. Meta-mafic rocks were derived from partial melting of lithospheric mantle with minor contamination of crustal materials, whereas meta-acidic rocks were generated from the middle-to-lower crust. Geochemical data of both rock assemblages show depletion of HFSE and enrichment of LILE, indicative of a subduction-related magmatic arc environment. U-Pb zircon dating results indicated that these rocks erupted at 2465 ± 42 Ma, and experienced metamorphism at 1940–1861 Ma. In combination with available petrological, geochemical and geochronological data, we infer that arc magmatism was developed at a back-arc basin area of a ~2.45 Ga active continental margin along southern Yinshan Block. Together with those high-grade metamorphic rocks, these low-grade rocks were also incorporated into the final collisional event at ~1.95–1.90 Ga.

中文翻译：

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二道洼群低品位变质岩年代学、地球化学及其对华北克拉通古元古代孔达岩带构造演化的意义

摘要 孔达岩带位于华北克拉通西北部，是典型的陆-陆碰撞造山带，印山地块与鄂尔多斯地块在1.95~1.85 Ga相撞。孔达岩带的高品位变质记录，大范围出露的低品位岩石是否也参与了这种碰撞，目前尚不清楚。二道洼群是该带的重要岩性单元，由广泛的低品位变质岩组合（即绿片岩至角闪岩相）组成，为理解该问题提供了重要的见解。从岩石学和地球化学特征来看，二道洼群低品位变质岩与以玄武质和酸性端元为特征的双峰火山层序具有较大的亲和力。变基性岩来源于岩石圈地幔部分熔融，地壳物质受到轻微污染，而变酸性岩来源于中下地壳。两种岩石组合的地球化学数据显示 HFSE 耗尽和 LILE 富集，表明与俯冲相关的岩浆弧环境。U-Pb 锆石测年结果表明，这些岩石在 2465±42 Ma 喷发，并在 1940-1861 Ma 发生变质作用。结合现有的岩石学、地球化学和地质年代学数据，我们推断弧岩浆作用是在沿银山地块南部约 2.45 Ga 活动大陆边缘的弧后盆地区域发育的。与那些高品位变质岩一起，这些低品位岩石也被纳入了~1.95-1.90 Ga的最终碰撞事件中。