Geochronology And Geochemistry Of Qujia And Beijie Rocks Characteristics And Structural Significance

The object of this study is Qujia and Beijie truncation rock mass located in the north of zhaoye metallogenic belt,a famous gold production base in northwest jiaodong peninsula,and translocated in the archean jiaodong group metamorphic rock mass and linglong granite rock mass.On the basis of field geological survey,combined with u-pb dating,principal and trace elements,and combined with relevant geological data,this paper makes a detailed analysis on the chronologic,petrographic and geochemical characteristics of qujia and beijie rock masses.On this basis,it discusses the tectonic background and evolution process of the formation of Qujia and Beijie rock masses.In this study,both Qujia and Beijie blocks belong to the type I granites with high potassium,calcium and alkaline quasi-aluminum weak saturation.Zircon u-pb dating data show that the Qujia rock mass was formed at 128± 1.2ma and the Beijie rock mass at 127±1.2ma,all of which were formed in the early Mesozoic cretaceous.The rocks of Qu Jia and Beijie rock are characterized by high silicon,high aluminum,LILE enrichment,deficit HFSE,high Sr,low Y and Yb,high Sr/Y ratio,deficit HREE,and weak negative Eu anomaly,indicating that the two rocks are adakite.From the beginning of Jurassic,influenced by the expansion of the Pacific plate,the Paleo Pacific plate subducted towards the Eurasian plate,which triggered large-scale mantle magma basement invasion and brought huge thermal energy,resulting in partial melting of the thick lower crust and mixing with mantle source material,and finally forming Qujia and Beijie rocks.