Delineation of the early Neoarchean (2.75 to 2.70 Ga) crustal growth and reworking processes in the southeast base of Taihang Mountain, North China Craton

Numerous studies suggest that various secular geologic and geochemical transitions occurred between ~3.2 Ga and 2.5 Ga. During this age-window, the ~2.70 Ga tectono-thermal event of the Neoarchean is by far the most influential, and is unusual in terms of coeval mafic-felsic magmatic rocks which wer...
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Numerous studies suggest that various secular geologic and geochemical transitions occurred between ~3.2 Ga and 2.5 Ga. During this age-window, the ~2.70 Ga tectono-thermal event of the Neoarchean is by far the most influential, and is unusual in terms of coeval mafic-felsic magmatic rocks which were interpreted to reflect widespread crustal accretion. Here we report the early Neoarchean TTG and potassic granite association preserved in the Yunmengshan area, Taihang Mountain, North China Craton (NCC). TTG and potassic granites emplaced at 2712 ± 65 to 2644 ± 25 Ma, followed by ~2.57 to 2.50 Ga metamorphism and partial anatexis. TTG has geochemical features corresponding to high-Al medium-pressure (MP) TTG. Their high CaO, low to moderate Al2O3/(FeOT + MgO), and positive ε Hf (t) values (+3.8 to +7.2) with T DM2 of 2.96 to 2.75 Ga, indicate that they formed by partial melting of juvenile low-K mafic rocks, representative of crustal accretion. Besides, TTG can be subdivided into two groups based on Eu anomalies. Those with Eu/Eu* 300 ppm plus elevated Sr/Y > 40, (La/Yb) N  > 12 and Eu/Eu* > 1.0). The high Eu/Eu*, Sr/Y and low Yb probably represent the contribution of amphibole fractionation and plagioclase accumulation during the magma evolution. The evidence favors an arc-related setting for the TTG. The early Neoarchean potassic granites are monzogranite to syenogranite, and formed shortly after TTG. They belong to high-K calc-alkaline to shoshonitic I-type granite, and display depleted and concave-upward REE patterns between middle and heavy REEs and higher Zr/Sm ratios (69.6 on average) than TTG (45.4). The calculated ε Hf (t) values are mainly positive (+1.4 to +7.0) with T DM2 from 3.03 Ga to 2.72 Ga, together with low Al2O3/(FeOT + MgO), low to moderate CaO and high K2O/Na2O ratios, indicating a high-K mafic crustal source with metapelite involvement. Meanwhile, we reviewed geochemical data of the early Neoarchean TTGs published in the NCC and other cratons abroad. The results show that samples from Trans-North China Orogen in NCC have lower Y contents, higher Sr/Y and (La/Yb)N ratios, and more depleted HREE tha... Ausführliche Beschreibung