Geochemical characteristics and LA-ICP-MS zircon U-Pb geochronology of the Shanqi intrusion in eastern North Huaiyang and their geological significance

The Shanqi quartz diorite in eastern North Huaiyang is characterized by medium contents of SiO₂ and Al₂O₃, and enrichment in alkali and low Mg^#, suggesting that it belongs to metaluminous alkaline series. It has high La_N/Yb_Nand LREE/HREE ratios, and is depleted in HREE relative to LREE, with a weak Ce negative anomaly. Relative enrichment in LREE shows high fractionation but HREE has no distinct fractionation. It is also enriched in LILE such as Rb,Ba,K and HFSE such as Zr,Hf,Y,but depleted significantly in Nb,Ta,Ti,P and U. LA-ICP-MS zircon U-Pb dating yields a ²⁰⁶Pb/²³⁸U age of 128.2 ± 3.3 Ma for the Shanqi intrusion, implying that it is early Early Cretaceous in age. The geochemical characteristics of the major and trace elements indicate that the Shanqi intrusion derived from the crust but contaminated with the mantle.