Geochronology and geochemistry ofca. 2.48 Ga granitoid gneisses from theYudongzi Complexin the north‐westernYangtze Block,China

Abstract

The Early Precambrian magmatism in the Archean–Palaeoproterozoic basement Yudongzi Complex is critical for understanding the early crustal formation and evolutionary history of the Yangtze Block in the South China Craton. In this paper, combined zircon UPb geochronological, zircon Hf isotopic, and whole‐rock geochemical studies are carried out on the granitoid gneisses from the Yudongzi Complex, north‐western Yangtze Block. The magmatic zircons from the granitoid gneiss yield a UPb upper intercept age of 2,477±18 Ma, interpreted as the crystallization age of the granitoid gneiss. The granitoid gneiss samples are characterized by high Al2O3 contents, moderate to high Sr/Y, (La/Yb)N and Na2O/K2O ratios, no obvious Eu and Sr anomalies, and depleted Nb, Ta, and Ti values that are similar to those of Archean trondhjemite–tonalite–granodiorite (TTG) suites, indicating that the investigated rocks belonging to TTG‐series rocks. They display pronounced enriched‐LREE patterns with high La/Yb values and relatively high Zr/Sm and Eu/Eu* but low Nb/Ta and Dy/Yb ratios, implying that these rocks were formed by partial melting within amphibolite‐facies conditions with mainly residual amphibole, garnet, and accessory rutile in the magma source. These rocks also display apparently low MgO, Mg#, Ni, and Cr contents, suggesting derivation from partial melting of thickened ancient lower crust. Zircon εHf(t) values from the granitoid gneiss sample vary from −10.1 to −6.9 with TDM2 of ca. 3.59–3.40 Ga, what demonstrates their crustal source nature as well. Thus, taking all these factors together, we propose that the ca. 2.48 Ga granitoid gneisses in the Yudongzi Complex might have been produced by partial melting of ancient crust material under amphibolite‐facies conditions, with primarily residual assemblages of amphibole, garnet, and attached rutile. Taking together our new data and such from previous studies, the Yangtze Block has been probably involved into a significant reworking of ancient crust event during the Early Palaeoproterozoic time.

Tectonic affinity and geological significance of the Feidong Complex in the northeastern margin of the Yangtze Craton: Evidence from zircon U–Pb and Lu–Hf isotopes of the basement rocks

“…Recent research has also reported magmatism at ca. 2.5 Ga in the northern margin of the Yangtze Craton, predominantly exposed in the Douling Complex (Hu et al, 2013; Wu et al, 2014), Yudongzi Complex (Chen et al, 2019; Hui et al, 2019; Zhou et al, 2018), Jiamiao Complex (Tian et al, 2022), Jinpan Complex (Zhang et al, 2022), Xishui Complex (Zhao et al, 2021) and Susong Complex (Wang et al, 2020, 2021). The magmatic rocks of this period are characterised by negative ε Hf (t) values, with corresponding two‐stage Hf model ages (T DM2 ) ranging from 2.7 to 3.7 Ga (Figure 8f).…”

“…In recent years, Early Paleoproterozoic (ca. 2.50–2.45 Ga) magmatism and metamorphism have been documented in the northern margin of the Yangtze Craton (Chen et al, 2019, 2023; Hui et al, 2017, 2019; Tian et al, 2022; Wu et al, 2014; Zhang et al, 2022; Zhang, Zheng, et al, 2020; Zhao et al, 2021; Zhou et al, 2018), collectively indicating the development of a subduction system during this period in the northern margin of the Yangtze Craton (Zhang, Zheng, et al, 2020). The arc‐related magmatism in the Early Paleoproterozoic (ca.…”

Geochronology and geochemistry of basalts from the Yingchuan Formation, eastern Jiangnan Orogen: Implications for the Neoproterozoic tectonic evolution of the South China Block

“…Located between the Yangtze Block and the Cathaysia Block, the Jiangnan Orogen is an NNE‐ trending belt extending for 1500 km from north‐eastern Guizhou Province to northern Jiangxi Province and southern Anhui Province (Figure 1a) (Shu et al, 1995, Shu, 2012, Shu et al, 2019; Charvet et al, 1996; Zhao & Cawood, 1999; Zhou et al, 2004; Wang et al, 2007; Wang, Wyman, et al, 2010; Dong et al, 2012; Zhang & Wang, 2019; Dong et al, 2021, 2022). The oldest metamorphic basement rocks in the Yangtze Block are exposed in the Kongling and Yudongzi area, including 3.4–3.2 Ga and 2.9–2.8 Ga TTG gneisses and 3.2 Ga migmatites (Gao, Jie, et al, 2011; Hui et al, 2017; Hui et al, 2019; Li et al, 2014; Qiu et al, 2000; Zhang et al, 2006; Zheng et al, 2006). In the Cathaysia Block, the metamorphic basement rocks have a Neoproterozoic age and are exposed in the north‐eastern part (including southern Zhejiang Province, northern/western Fujian Province and eastern Jiangxi Province), and the south‐western part of the Cathaysia Block (Yu et al, 2008).…”