Geochronology and geochemistry of the Paleoproterozoic Yinyugou Group in the southern North China Craton: Implications for provenance and tectonic evolution

Abstract

The Paleoproterozoic Yinyugou Group in the southern North China Craton is a littoral facies sedimentary sequence which is mainly composed of feldspar quartzites and mica schists with minor carbonate rocks. U-Pb isotopic dating of detrital zircons bracket the depositional age of the Yinyugou Group at ∼2.43–2.30Ga. Chemical Index of Alteration (CIA) values of most feldspar quartzite and schist samples are lower than 75, indicating generally weak to moderate source weathering conditions for the Yinyugou rocks. The majority of the studied Yinyugou samples give a large range of Index of Compositional Variability (ICV) values of 0.93–2.59, revealing a chemically immature source which deposited in an active continental margin setting. Chondrite-normalized REE patterns and discrimination diagrams involving La, Th, Hf, Co and Sc reveal that the Yinyugou Group dominantly received detritus from felsic sources with minor contribution from mafic igneous rocks. U-Pb ages of detrital zircons from the Yinyugou Group can be divided into two groups: 2.90–2.40Ga and 3.50–3.20Ga, with a predominant age peak at ∼2.50Ga. The 3.50–3.20Ga detrital zircons have negative εHf(t) values ranging from −11.2 to −3.8 and old crustal model ages (TDMC) of 4246 to 3909Ma, indicating a mature crustal source. Most ∼2.50Ga zircons show sub-depleted mantle positive εHf(t) values and TDMC ages mainly ranging from 3.10 to 2.70Ga, representing the time when juvenile materials were extracted from the depleted mantle. Taking all these data into account, the Yinyugou Group was most likely deposited in a back-arc setting. In combination with previous studies on other Paleoproterozoic volcanic-sedimentary sequences and magmatic rocks in the NCC, a cycle of subduction (collision)-extension (rift)-subduction processes is proposed to explain the tectonic evolution of the NCC during Paleoproterozoic.