Petrogenesis and tectonic setting of 2. 2 ∼ 2. 1 Ga granites in Wutai area, North China Craton

2. 2 similar to 2. 0Ga magmatism widely occurs in the Trans-North China Orogen (TNCO), which is vital for unveiling the Paleoproterozoic tectonic evolution on the North China Craton (NCC). This paper presents the whole rock geochemical data, zircon U-Pb ages and Hf isotopes of Paleoproterozoic Dawaliang, Wangjiahui and Lianhuashan granitoids in Wutai area. SHRIMP U-Pb zircon dating of Dawaliang porphyritic granite sample yields an age of 2170 +/- 17Ma. One sample from Wangjiahui monzonitic granitic gneiss obtains a LA-ICPMS zircon U-Pb age of 2101 +/- 6Ma, and 3 samples from Lianhuashan granite gets zircon U-Pb ages of 2117 +/- 6Ma, 2110 +/- 4Ma and 2143 +/- 15Ma, respectively. Dawaliang granite is high in SiO2 and K2O +Na2O, low in CaO, and enriched in REEs (except Eu), Zr, Nb, Ga and Y, and depleted in Sr. Meanwhile, all samples of Dawaliang granite have high Ga/Al values and Zr + Nb + Y + Ce contents with whole rock zircon saturation temperature as high as 876 similar to 986 degrees C, which is identical with the features of the A-type granite. Wangjiahui and Lianhuashan granites enrich in SiO2, K2O and Na2O, and deplete in MgO and CaO, on the other hand, the granites show minor to intensive differentiation on REEs with obviously negative Eu abnormity. Three plutons (Dawaliang, Wangjiahui and Lianhuashan granites) have high Nb and Y concentrations, so they show the features of post-collision and within plate granite. Zircon epsilon(Hf)(t) values in all samples are lower than that in depleted mantle, and meanwhile, one and two stage Hf model ages are 2. 4 similar to 2. 6Ga and 2. 45 similar to 2. 75Ga, respectively, which are much older than the zircon U-Pb ages of the granites. Combining petrology, geochemistry and isotope in the samples, we propose that the Paleoproterozoic granites are derived from the partial melting by the Late Archean TTG gneisses under the extensional environment. Considering the 2. 2 similar to 2. 0Ga magmatism along the TNCO exhibits two stages of 2. 2 similar to 2. 1Ga and 2. 1 similar to 2. 0Ga in different regions, in which 2. 2 similar to 2. 1 Ga magma represent the early stage and some granites at this stage show the features of A-type granite and form the bimodal magmatic assemblages with the coeval mafic rocks. Therefore, we deduce that the middle of Paleoproterozoic magmatism is related with the intracontinental rift in the NCC.