ZIRCON U-Pb AGE OF THE DACHAZI SYENOGRANITE IN DUOBAOSHAN AREA, HEILONGJIANG PROVINCE: Geological implication

The geochronology with zircon SHRIMP U-Pb isotope of the Dachazi syenogranite, cropped in Duobaoshan area, Heilongjiang Province, is studied to find out its age and geological background. The result suggests that the zircon has significant zonal structure, with Th/U ratio of 0.41-0.99, which is a typical granitic magma-type zircon. Zircons in the syenogranite from 11 observation points are analyzed, obtaining the weighted average ²⁰⁶Pb/²³⁵U age of 345±3 Ma (n=11, SMWD=0.99), which represents the crystallizing age of the syenogranite, showing the formation age of Early Carboniferous. The analysis on the major elements and geochemistry shows that the syenogranite belongs to high potassium calc-alkaline series, genetically as A-type granite.