Structural Architecture and Spatial-Temporal Distribution of the Archean Domains in the Eastern North China Craton

Globally, the Archean domains are composed of tonalite–trondhjemite–granodiorite (TTG) gneisses, diorites and granites, and supracrustal successions (commonly greenstone belts), which metamorphosed to greenschist facies, but less commonly up to granulite facies. However, the Archean domains in the Eastern North China craton were mostly metamorphosed to high-grades. For example, the majority of the Anshan-Qingyuan region was built at 2570–2500 Ma with a few 3800–3000 Ma rocks, and it suffered high-amphibolite to granulite facies metamorphism with anticlockwise P-T-paths at ~2480 Ma. The majority of the Huai’an-Zunhua region formed at 2560–2500 Ma with a few ~3300 Ma rocks, and it also experienced high-amphibolite to granulite facies metamorphism with anticlockwise P-T-path at ~2480 Ma, but its west part (the Huai’an-Chengde area) was overprinted by a ~1950–1800 Ma metamorphism up to high-pressure granulite facies with clockwise P-T-paths. The Archean rocks of the Anshan-Qingyuan and Huai’an-Zunhua regions were strongly deformed, and the supracrustal rocks occur as relic bodies with varied scales up to kilometers intruded by the TTG gneisses-dominated plutons. They show quite different architecture from the typical dome-and-keel structure, which likely formed under significant vertical tectonism. Based on the spatial-temporal distribution of different rock series and the spatial distribution of varied metamorphic grades of the Neoarchean in different regions of the Eastern North China craton, we propose that the craton can be divided into four blocks, i.e., the Lushan-Jiaobei, Zhongtiao-Taishan, Liaonan-Qingyuan, and Wutai-Zunhua blocks. This spatial-temporal distribution of the Neoarchean blocks approves a horizontal growth of crust, which is also supported by the chemistry of the igneous rocks; however, the presence of mafic rocks from primitive mantle and the anatexis in high-grade regions may indicate the coexisting of vertical growth of the crust. These Archean high-grade regions may be the exhumed lower crust of arc-like terrains produced by the Archean-style subduction, i.e., a mantle-wedge-weak ‘hot’ flat subduction with significant mantle upwelling under the arc crust, resulting in their amalgamation at ~2480 Ma.