LA-ICP-MS zircon U-Pb dating of Mesozoic granite in Miaoxibei uplift, Bohai Sea area, and its geological significance

For the purpose of better understanding of the formation, evolution and tectonic environment of the first unmetamorphosed granite oil pool in Bohai Sea area, the authors carried out a study of granite buried hill of Miaoxibei uplift. Based on petrography, LA-ICP-MS zircon U-Pb ages and whole-rock major and trace elements, the authors investigated the petrogenesis, magma source and tectonic setting. LA-ICP-MS zircon U-Pb data of the granite yielded weighted age of 155.4±2.5Ma, the granite is of cale-alkaline suite with positive Eu anomaly, both samples have the characteristics of depletion of heavy rare earth elements and en-richment of light rare earth elements, and the granite is strongly enriched in large ion lithophile elements (LILEs, e.g., Pb, Sr) but depleted in high field strength elements (HFSEs, e.g. Th, Nb, Zr). It is thus held that the crust experienced shortening and thickening rapidly because of the pressure of Yangtze plate and the Jiamusi Mongolia block during the early Middle Jurassic, and that, due to the rising temperature, the lower crust was subjected to partial melting, which eventually surged and invaded, resulting in the formation of peraluminous S-type granite in the Miaoxibei uplift buried hill.