Qingyuan area in northern Liaoning,located at the eastern segment of the northern margin of the North China Craton,is one of the typical areas to study the paleo-Pacific ocean tectonic domain.The petrogenesis and tectonic setting of Mesozoic magmatic rocks in the study area are of great significance for understanding the evolution of the paleo-Pacific tectonic domain.This study focuses on the zircon U-Pb geochronology and geochemistry of gabbronorite,quartz diorite and granodiorite in the Xiajiapu area of Qingyuan.Zircon U-Pb dating results show that gabbronorite,quartz diorite and granodiorite were emplaced in the(163.8±2.4)Ma,(169.9±2.2)Ma and 169.9-167.3 Ma respectively.Geochemical characteristics of Gabbronorite and quartz diorite show that they have low SiO2 content,high Al2O3 content and high Mg#value,which are typical of the calc-alkaline series.Samples are weakly enriched in LREEs and enriched in LILEs(e.g.,Rb,Ba,K,Sr)and depleted in HFSEs(e.g.,Nb,Ta,),and Eu shows weak positive or no anomaly;Granodiorite shows a high content of SiO2,Al2O3 and total-alkali,which is typical of the high-K calc-alkaline I-type granite.Samples have high Sr/Yb values and weak Eu negative anomalies,and they are enriched in LREEs and LILEs(e.g.,Rb,K and Ba)and depleted in HREEs and HFSEs(e.g.,Nb,Ta).Based on these data,we conclude that primary magma of gabbronorite and quartz diorite is likely derived from partial melting of lithospheric mantle,which is metasomatized by fluid from subducted oceanic slab.Granodiorite is derived mainly from partial melting of mafic rocks in lower crust,which is metasomatized by fluid.Combining with regional tectonic evolution and spatial distribution of magmatic activity,we suggest that the origin of Middle Jurassic intrusive rocks in Xiajiapu area,Qingyuan,northern Liaoning might be related to the subduction of paleo-Pacific plate.
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