Geochemistry of the Yaochong granite in Dabie orogenic belt and its geological implications

Located in the Qinling-Dabie orogenic belt, the Yaochong granite body mainly consists of biotite granite and granite porphyry. According to the geochemical analysis, Yaochong granites have the following data: SiO₂=71.28%~77.24%, K₂O=3.81%~5.28%, Na₂O=3.76%~5.03%, Al₂O₃=11.61%~14.6%, and A/CNK=0.96~1.03. The rocks are enriched in LREE, depleted in HREE with negative Eu anomalies, enriched in Rb, U, Hf, Y and depleted in Ba, Nb, Ta, Ti, which indicates that Yaochong granites belong to metaluminous to peraluminous, high-K calc-alkaline I-type granite. According to zircon Hf isotope analysis, the ε_Hf(t) values of the granite range from-30 to-22.8, lying below the depleted mantle line. The t_DM2 values range from 2.21Ga to 2.60Ga, which indicates that the granite resulted from the lower crust of Yangtze block. The components of the granite porphyry are similar to those of Neoproterozoic TTG magmatic rocks. Yaochong granites were emplaced after the major collisional period of the North China block and Yangtze block, in a post-collisional tectonic setting under the regional extension mechanism. The geodynamic setting was the transformation of the tectonic regime of the late Jurassic-Early Cretaceous period.