Late Neoarchean to early Paleoproterozoic tectonic evolution of the southern North China Craton: Evidence from geochemistry, zircon geochronology and Hf isotopes of felsic gneisses from the Taihua complex

Abstract

The Archean-Paleoproterozoic Taihua Complex, extending from east to west along the southern margin of the North China Craton (NCC), is an ideal window to understand the tectonic evolution of the early Earth. Here we present new data on petrology, zircon geochronology, whole-rock geochemistry and isotopes of TTGs, granitic gneisses and felsic leucosomes of migmatites from the Taihua complex in the Xiaoqinling area. Zircon LA-ICP-MS analyses of rocks yield the formation ages of 2564–2503 Ma for TTGs, 2481–2476 Ma for felsic leucosomes and 2359–2334 Ma for granitic gneisses, respectively. The zircon Lu-Hf isotopes suggest that crustal growth occurred in the late Neoarchean and crustal reworking occurred in the end of Neoarchean and the early Paleoproterozoic. The TTG gneisses are characterized by high Na2O/K2O, La/Yb, Sr/Y and low Nb/Ta ratios, and they were likely generated by partial melting of subducted juvenile oceanic crust with garnet or amphibole in residuals, a mechanism similar to the slab melting model. Both the felsic leucosomes and granitic gneisses have high SiO2 contents and various Hf isotopic compositions, and they probably were formed in an extensional setting, attributing to partial melting as well as mixing of the preexisting TTG suite.Statistically, we report a major transitional phase in the tectonic milieu of the southern NCC from compression to extension during the late Neoarchean (ca. 2.57–2.42 Ga). The compressional tectonics can be attributed to amalgamation of micro-continental blocks during the late Neoarchean (ca. 2.57–2.5 Ga) as the leading period of crustal growth and associated multistage TTG magmatism. In contrast, the extensional phase occurred during the end of Neoarchean (ca. 2.5–2.42 Ga) that may represent the end of cratonic stabilization period and formation of large amounts of K-rich granitic rocks, widespread high-grade metamorphism and migmatites. Additionally, the formation of a large amount of crust-derived granites and mafic dykes during the early Paleoproterozoic in southern NCC reflect another stage (ca. 2.36–2.24 Ga) of crustal extension, which represents an episode of initial worldwide rifting events probably linking to the great oxygen event (GOE). Therefore, the present study proposes a new profile on multi-stage crustal growth/reworking and craton stabilization during Neoarchean-Paleoproterozoic period along the southern NCC, and provides useful insights on complex and heterogeneous evolutionary processes of early Earth.