Formation age and tectonic environment of the Gantaohe Group, North China Craton: Geology, geochemistry, SHRIMP zircon geochronology and Hf-Nd isotopic systematics

Abstract

The Gantaohe Group is an important early Precambrian unit in the Trans-North China Orogen, North China Craton, and is mainly composed of greenschist-facies metabasalt, meta-sandstone and dolomitic marble. We report whole-rock geochemical compositions and SHRIMP zircon ages as well as LA-ICP-MS Hf-in-zircon isotopeic analyses for metabasalts from the Gantaohe Group. SHRIMP dating yielded a weighted mean 207 Pb/ 206 Pb age of 2087±16 Ma (MSWD=1.3) for magmatic zircons, but there are also abundant ca. 2.5 Ga inherited zircon xenocrysts. The magmatic zircons shows a large  Hf (t) variation in  Hf (t) from 7.17 to +0.45, suggesting an isotopically highly heterogeneous source for the metabasalt. Chemically all samples show no distinct Zr or Hf anomalies, and some samples show no Nd or Ta anomalies in a primitive mantle-normalized trace element variation diagram, and their whole-rock  Nd (t) values range from 4.0 to 0.8. We suggest that the basalt is formed by partial melting of a depleted mantle source, followed by significant crustal contamination. Field observations, the presence of abundant inherited zircon, as well as isotope and trace elements geochemistry support formation of the Gantaohe Group on top of a continental basement. These data and the regional geology lead us to conclude that the Trans-North China Orogen constituted an intracontinental rift during the Paleoproterozoic that was connected to the Eastern Block since the end of the Archean.

Neoarchean to Palaeoproterozoic tectonic evolution of the Trans‐North China Orogen, North China Craton: Evidence from zircon U–Pb geochronology, Lu–Hf isotopes, and geochemistry of the Zanhuang Complex

“…Histogram of zircon U–Pb ages from the Zanhuang Complex. Geochronological data are from Deng et al (2014), Du et al (2016a, 2016b), Li et al (2016, 2017), Liu et al (2012), Peng (2015), Peng et al (2017), Trap et al (2009), Wang et al (2013, 2015, 2017), Xiao and Wang (2011), Xiao et al (2013, 2014), Xie et al (2012), Yang et al (2011, 2013), and this study [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…The gneiss showed crystallization age of 2,606 ± 69 Ma (Trap et al, 2009). The Palaeoproterozoic magmatic rocks including the Xuting granite (Yang et al, 2011), diorite (Li et al, 2016), meta-basalt (Liu et al, 2012;Xie et al, 2012), gabbro and diabase (Peng et al, 2017), and mafic dykes (Peng, 2015) in the Western Zanhuang Domain were formed at 2,103-2,066 Ma. The ages of Palaeoproterozoic detrital zircons from the meta-sedimentary rocks in the Central Zanhuang Domain are 2,400-2,100 Ma from quartz-mica schists (Li et al, 2016), and 2,330-2,030 Ma from dolomite-calcite marble units (Tang et al, 2017;Tang, Santosh, Tsunogae, & Teng, 2016).…”

Tectonic Switching of the Trans‐North China Orogen in the Middle Paleoproterozoic: Insights From Mafic Magmatism in the Lüliang Complex

“…Contemporaneous or slightly later mafic and alkaline granitoid magmas with arc affinities have also been found in other adjacent complexes, including the 2.19 Ga gabbro (Wang et al, 2010) and the 2.11–2.05 Ga Lingyunkou potassic granite (Kröner et al, 2005; Zhao et al, 2011) in the Hengshan Complex, the 2.15 Ga mafic dyke (Peng et al, 2005) and the 2.17–2.10 potassic granites (Du et al, 2018; Wang & Wilde, 2002; Wilde et al, 2005) in the Wutai Complex, the 2.05–2.04 amphibolite (Tang et al, 2015) and the 2.08–2.02 gneissic granite (Guan et al, 2002; Tang et al, 2015) in the Fuping Complex, and the 2.09 Ga mafic dyke (Deng et al, 2014) and the 2.09–2.07 Xuting potassic granite (Du et al, 2016; Yang et al, 2011) in the Zanhuang Complex (Figure 12). On the surface, the upward fining sequence from conglomerates, sandy conglomerates, and quartzites in the bottom, to slates, dolomites, and marbles in the middle and upper parts were suggested to be deposited in extensional (back‐arc) basins, including the Doucun and Dongye subgroups in the Wutai Complex, the Wanzi Group in the Fuping Complex, the Lüliang and Lanhe groups in the Lüliang Complex, and the Gantaohe Group in the Zanhuang Complex (Figure 12; Du et al, 2010; Liu, Zhao, Sun, Zhang, et al, 2011; C. Liu et al, 2012; Ren et al, 2013; Wilde et al, 2004; Xie et al, 2012).…”

“…Tectonics (Figure 12; Du et al, 2010;Liu, Zhao, Sun, Zhang, et al, 2011;Ren et al, 2013;Wilde et al, 2004;Xie et al, 2012).…”

Zircon U–Pb ages and geochemistry of the late Archaean granitoids in the Zanhuang Complex: Records of an arc–continent collision event at the end of Archaean

“…The Guandu Group is mainly composed of amphibolite, marble, quartzite, and metapelite with a formation age of ~2.5 Ga or early Palaeoproterozoic (Deng et al, ; Wang et al, ; Yang et al, , ) and underwent greenschist facies to lower amphibolite facies metamorphism at 1.85–1.90 Ga (Trap et al, ; Xiao et al, ). The Gantaohe Group includes a large amount of mafic volcanic‐sedimentary rocks deposited between 2.1–1.9 Ga and has undergone greenschist‐facies metamorphism (BGMRHP, ; Du, Yang, Wyman, Nutman, Lu, Song, Zhao, et al, ; Liu et al, ; Xie et al, ; Yang et al, ).…”