Neoarchean–Paleoproterozoic magmatic–metamorphic events and its tectonic implications of the Zuoquan–Zanhuang metamorphic complexes in the North China Craton

Abstract

The global felsic continental crust mostly formed during the period of early to middle Neoarchean, and most of cratons worldwide are characterized by the well-developed tectono-thermal event of ca. 2.7 Ga. Abundant geochronological data indicated that the North China Craton (NCC) was predominated by the tectono-thermal event of ca. 2.5 Ga different from many other cratons. However, isotopic studies revealed that the ca. 2.5 Ga granitoids generally formed through reworking of 2.9–2.7 Ga continental materials, and more ca. 2.7 Ga magmatic rocks and zircons have been progressively identified in some areas of the NCC in recent years. These data, therefore, prompted geologists to reconsider the importance of the ca. 2.7 Ga tectono-thermal event in the NCC. The Zuoquan and Zanhuang metamorphic complexes are adjacent and both located in central NCC. Isotopic geochronology and rare earth element analyses of zircons in this study reveals two meaningful groups of magmatic ages, i.e., 2774–2700 Ma and 2519–2496 Ma, recorded in the two complexes. The older age group predominated in the Zuoquan complex which represented an early to middle Neoarchean magmatic event and were generally interpreted to be attributed to a mantle plume or superplume mechanisms. The ages of 2519–2496 Ma were commonly recorded by rocks in the Zanhuang area, representing a regional late Neoarchean magmatic event. Two groups of metamorphic ages (2519 Ma and 1854 Ma) were also recorded by the Zuoquan and Zanhuang metamorphic rocks, respectively. The former, accompanied by the late Neoarchean magmatic event, was probably related to underplating of mantle-derived magmas. The 1854 Ma metamorphic age represented another regional metamorphism in central NCC related to a collision process between the Eastern Block and Western Block.