Geochronology and petrogenesis of gray gneisses from the Taihua Complex at Xiong'er in the southern segment of the Trans-North China Orogen: Implications for tectonic transformation in the Early Paleoproterozoic

Episodic crustal growth in the southern segment of the Trans-North China Orogen across the Archean-Proterozoic boundary

“…The Taihua Complex in the Xiaoqinling area was traditionally regarded as a meta-volcanic sedimentary sequence, and was further subdivided into the Lower and Upper Taihua "Groups" according to rock types (Qi, 1992;Guan, 1996;Ding, 1996), similar to those in the Lushan and Xiong'er areas (Huang et al, 2010(Huang et al, , 2012. The Upper Taihua "Group" consists of quartzite, metapelitic gneiss and schist, marble and iron formation, whereas the Lower Taihua "Group" consists of meta-basic volcanic rocks (amphibolite) and intermediate to felsic gneisses (biotite-plagioclase gneiss and plagioclase-amphibole gneiss), with minor granulites (Qi, 1992;Ding, 1996).…”

“…However, it still remains unknown whether or not the southern segment of the TNCO (Fig. 1a) also underwent such a long-lived subduction, though available data indicate that the Taihua and Dengfeng Complexes experienced a series of magmatic events from the Late Archean to Early Paleoproterozoic (Wan et al, 2006;Diwu et al, 2007Diwu et al, , 2011Liu et al, 2009Liu et al, , 2012aHuang et al, 2010Huang et al, , 2012.…”

“…There are many published chronological and geochemical investigations on the Taihua Complex in the Xiong'er (Diwu et al, 2007;Huang et al, 2012) and Lushan (Wan et al, 2006;Liu et al, 2009;Xu et al, 2009;Huang et al, 2010) areas, but very few reliable geochronological and geochemical studies have been done on the Taihua Complex in the Xiaoqinling area (Fig. 1b) even though it is the largest outcrop of Precambrian basement in the southern segment of the TNCO.…”

“…On the basis of Sm-Nd isochrons, depleted mantle Nd model ages, Ar-Ar dating, and single-grain zircon evaporation Pb-Pb ages, it has been suggested that the Taihua Complex in the Xiaoqinling area was comparable with other areas (BGMR, 1982;Qi, 1992;Zhou et al, 1998). However, in situ zircon U-Pb dates for the Taihua Complex in the Lushan and Xiong'er areas showed different crystallization ages (Diwu et al, 2007;Liu et al, 2009;Huang et al, 2010Huang et al, , 2012, and it is important to examine whether or not rocks in the Xiaoqinling area can be correlated with either of these areas.…”

2.24 Ga mafic dykes from Taihua Complex, southern Trans-North China Orogen, and their tectonic implications

“…Although the tectonic model that the North China Craton was formed by the amalgamation between the Western Eastern Blocks of the NCC along the TransNorth China Orogen (TNCO) has been accepted by most scholars ( Fig. 1a; Diwu et al, 2014;Huang et al, 2012;Kusky et al, 2007;Yu et al, 2013;Zhao et al, 2001Zhao et al, , 2005, controversies still have been arised as to the formation of the TNCO: (1) some researchers suggested that the final amalgamation resulted from a westward subduction at ∼2.5 Ga (later modified to 2.3-2.2 Ga) (Kusky and Li, 2003;Kusky, 2011;Li and Kusky, 2007;Zhai and Liu, 2003); (2) some others proposed a eastward subduction with the final amalgamation at ∼1.85 Ga (Zhao et al, 2001(Zhao et al, , 2003(Zhao et al, , 2005; (3) the others suggested a westward subduction with two Paleoproterozoic Zhao et al, 2005); Abbreviations for metamorphic complexes: NH, Northern Hebei; XH, Xuanhua; HA, Huai'an; HS, Hengshan; FP, Fuping; WT, Wutai; LL, Lvliang; ZH, Zanhuang; ZT, Zhongtiao; DF, Dengfeng; TH, Taihua. (b) Geological distribution of the Taihua Complex in the southern NCC and the location of the Zhaiwa Mo deposits (after Li et al, 2014). on the above studies, meanwhile, most of these rocks studied are mainly distributed in the northern part of the TNCO, with studies of contemporary rocks in the southern part of the TNCO rare, which in turn limits our understanding of the tectonic evolution of the TNCO in the Palaeoproterozoic.…”