Metamorphism of basement rocks in the Central Zone of the North China Craton: implications for Paleoproterozoic tectonic evolution

Lithological, structural, metamorphic and geochronological data for the North China Craton enable its division into the Western and Eastern Blocks of Archean to Paleoproterozoic age separated by a north–south trending Paleoproterozoic orogenic belt: the Central Zone. The Central Zone is divisible into a series of low- to medium-grade granite–greenstone belts and high-grade metamorphic terrains containing reworked Archean material and late Archean to Paleoproterozoic juvenile igneous and sedimentary rocks which developed in intra-continental magmatic arc and intra-arc basin environments bordering the western margin of the Eastern Block. The basement rocks from the Central Zone, regardless of their protolith age, composition and metamorphic grade, record a metamorphic history characterized by nearly isothermal decompression (M2) and then retrogressive cooling (M3) following peak metamorphism (M1). The decompression textures are represented by worm-like hyperstheneplagioclase symplectites or clinopyroxeneorthopyroxeneplagioclase coronas in mafic granulites, hornblende:cummingtoniteplagioclase symplectites in amphibolites, and cordierite coronas and cordieriteorthopyroxene or cordieritespinel symplectites in pelitic rocks. The cooling textures are shown by hornblendeplagioclase symplectites in mafic granulites, chloriteepidotemica retrogressive rims around garnet or hornblende grains in amphibolites, and biotiteK-feldspar9muscovite9magnetite replacing garnet, cordierite and sillimanite in pelitic gneisses. These textura