Geological Features And Tectonic Setting Of Intermediateacidic Dykes In Taerqi, Inner Mongolia

From the angle of geochemistry,They can be divided into basic,neutral and acidic dykes.After the geological field work,we found that they intrude in middle Jurassic granite and late Jurassic Manketouebo group and Manitu group.According to causes and formation age,some of them accompanied by fractures dykes due to regional dykes,some of granite pophyry,diorite porphyrite closely related to Mesozoic volcano,and they belongs to specificity.Explored the age,petrogenesis and tectonic setting of intermediate-acidic dykes in Taerqi regions through studying zircon U-Pb age and geochemical features of them. The zircon U-Pb age indicades that some of those intermediate dykes and acidic dykes were formed in Early Cretaceous 141.4 ~ 136.0Ma and 136.5 ~ 126.4Ma. The analysis of geo-chemical data show that those intermediate dykes is characterized by medium silicon,alkali-rich, quasi-aluminous(A/CNK=0.8~0.92), Which belongs to high-k calc-alkaline weakly quasi-aluminous series,and most of them exists obvious Eu negative anomaly;Those acidic dykes is characterized by high silicon, alkali-rich, weakly peraluminous(A/CNK=1.03~1.24), Which belongs to high-k calc-alkaline seriesand,most of them have no Eu negative anomaly.Synthesizing regional geological data analysis show that some of intermediate dykesare similar to Taerqi Manitu volcanic rocks, some of those acidic dykes are similar to Taerqi Baiyingaolao volcanic rocks and granite porphyry and they may be the products of two stages of magma activities,and those dykes formed in extensional tectonic environment.