Geochemical characteristics and zircon U-Pb dating of the Yangjiawan plutonin the eastern part of North Huaiyang and their geological significances

The Yangjiawan pluton in the eastern part of North Huaiyang, which consists mainly of quartz diorite, contains medium contents of SiO₂, Al₂O₃ and ALK, low Mg^#, suggesting that the Yangjiawan pluton is characteristic of metaluminous high-k calc alkaline series rock. The pluton has low REE content, relatively high(La/Yb)_N and LREE/HREE ratios and weak Ce negative anomaly, with strong fractionation between LREE and HREE, enrichment in large ion lithophile elements(Rb, Ba, K)and high field strength elements(Zr, Hf, Y). Low negative anomalies of Nb, Ta, Ti, P and U indicate depletion in HFSE and enrichment in LILE. LA-ICP-MS zircon U-Pb dating for the Yangjiawan pluton firstly yielded an age of 139.6±2.2 Ma, which belongs to middle Yanshanian period and can represent the rock-forming age of the Yangjiawan pluton. Our study shows that the Yangjiawan pluton should be the product of early Cretaceous magmatic activity.