Lithospheric thinning and reworking of Late Archean juvenile crust on the southern margin of the North China Craton: evidence from the Longwangzhuang Paleoproterozoic A‐type granites and their surrounding Cretaceous adakite‐like granites

Abstract

In the Longwangzhuang area along the southern margin of the North China Craton (NCC), a layer of Cretaceous K‐feldspar granites surrounds Paleoproterozoic granites. The Paleoproterozoic granites are enriched in sodic ferrogedrite and show low Al2O3 (12.3–13.0 wt%) and aluminum saturation index (ASI) (0.93–1.09) with high Zr (609–966 ppm), Y (47.2–96.7 ppm) and Nb (58.7–97.7 ppm) concentrations, resembling A‐type granites. The Cretaceous K‐feldspar granites have relatively high Sr (145–419 ppm), Ba (1252–1660 ppm), Sr/Y (19–127), La/Yb (36–56) ratios, but low Y (4.01–8.88 ppm) and Yb (0.46–0.99 ppm), geochemically resembling adakite‐like rocks. However, these Cretaceous adakite‐like K‐feldspar granites have rather low MgO (0.08–0.26 wt%), Al2O3 (13.6–14.5 wt%), Mg# (11–23), Cr (2.30–4.61 ppm) and high initial 86Sr/87Sr (0.7098–0.7118), as well as abundant K‐feldspar minerals, and are different from typical adakite. Zircon LA–ICP–MS geochronology shows that the two types of granites investigated in this study formed at 1616 ± 20 Ma and 140 ± 1 Ma, respectively. However, zircons from both the Paleoproterozoic and Cretaceous granites yield similar two‐stage Hf model ages at ca. 2.5–2.6 Ga, suggesting the reworking of Late Archean juvenile crust. The Paleoproterozoic A‐type granites show enriched Nd–Hf isotopic features but high whole‐rock oxygen isotopes. These rocks may have formed from partial melting of restitic crustal material during lithospheric thinning, along with extension and experienced crystal fractionation of plagioclase, apatite and magnetite. The Cretaceous adakite‐like K‐feldspar granites were formed by local anatexis of TTG rocks from the Taihua Group, with amphibole as the major residual phase. The local anatexis and accompanying migmatisation suggest crustal compression and possible transpression. Therefore, the lithospheric thinning in the NCC should have taken place after 140 Ma on the southern margin of the NCC. Copyright © 2012 John Wiley & Sons, Ltd.

Geochronology and geochemistry of the late Paleoproterozoic aluminous A-type granite in the Xiaoqinling area along the southern margin of the North China Craton: Petrogenesis and tectonic implications

“…1b). A great amount of late Paleoproterozoic to Mesoproterozoic intrusive magmatism had also developed in the southern margin of the NCC, including mafic dike swarms (e.g., Peng et al, 2004Peng et al, , 2005Peng et al, , 2008Wang et al, 2008;Hu et al, 2010;Bi et al, 2011;Peng, 2015), syenites and monzonites (e.g., Ren et al, 2000;Liu, 2011) and granitoid rocks (e.g., Hu and Lin, 1988;Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013;Deng et al, 2015), as well as extensive late Mesozoic granitic and mafic rocks (e.g., Gao et al, 2014a,b). Importantly, some rocks show an affinity to A-type granitoid, with wide emplacement ages from the late Paleoproterozoic to early Mesoproterozoic, such as the $1.62 Ga Longwangzhuang granite (Fig.…”

“…Importantly, some rocks show an affinity to A-type granitoid, with wide emplacement ages from the late Paleoproterozoic to early Mesoproterozoic, such as the $1.62 Ga Longwangzhuang granite (Fig. 1b, Hu and Lin, 1988;Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013), the $1.60 Ga Maping granite (Fig. 1b, Liu, 2011;Deng et al, 2015) and the $1.53 Ga Zhangjiaping granite (Fig.…”

“…However, regarding the tectonic evolution in the southern margin of the NCC, it is still unknown whether the final collision in the southern NCC was finished at $1.80 Ga or it remained an arc environment at that time (Hu and Lin, 1988;Chen et al, 1992;He et al, 2008He et al, , 2009He et al, , 2010, though the unique development of the 1.8-1.75 Ga Xiong'er Group volcanosedimentary series in the southern margin which is the oldest sedimentary record in the NCC after its final assembly at $1.85 Ga (Zhao et al, 2001(Zhao et al, , 2003(Zhao et al, , 2005Wilde et al, 2002). The recognition of the alkaline rock and alkaline-rich granite belt with an emplacement ages from Proterozoic to Cretaceous (Hu and Lin, 1988;Lu, 1989) can provide important insight into the tectonic evolution in the southern margin of the NCC, particularly for the identification of some late Proterozoic A-type granites in the alkaline rock belt (Lu et al, 2003;Bao et al, 2009;Liu, 2011;Wang et al, 2013).…”

Age and geochemistry of the early Mesoproterozoic A-type granites in the southern margin of the North China Craton: Constraints on their petrogenesis and tectonic implications

“…Hence, the generation of A-type granites has significant implications for secular evolution of continental crust (Collins et al, 1982;Bonin, 2007) and tectonics and geodynamics (Bonin, 2007). In recent decades, a Mesoproterozoic A-type granite belt has been recognized in the southern margin of the NCC, extending from Luonan, Shaanxi Province, to Luanchuan, Henan Province, mainly including the Longwangzhuang (e.g., Hu and Lin, 1988;Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013) and Maping A-type granites (e.g., Liu, 2011;Deng et al, 2015). These Mesoproterozoic A-type granites were attributed to be the products of anorogenic magmatism (Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013;Deng et al, 2015), although they originated from different source materials.…”

“…In recent decades, a Mesoproterozoic A-type granite belt has been recognized in the southern margin of the NCC, extending from Luonan, Shaanxi Province, to Luanchuan, Henan Province, mainly including the Longwangzhuang (e.g., Hu and Lin, 1988;Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013) and Maping A-type granites (e.g., Liu, 2011;Deng et al, 2015). These Mesoproterozoic A-type granites were attributed to be the products of anorogenic magmatism (Lu, 1989;Lu et al, 2003;Bao et al, 2009;Wang et al, 2013;Deng et al, 2015), although they originated from different source materials. The occurrence of these early Mesoproterozoic anorogenic magmatic rocks further indicates that the NCC was possibly involved in the breakup of the Columbia supercontinent (e.g., Bao et al, 2009;Deng et al, 2015).…”