Zircon U-Pb age of granitoids in the Jiudian gold deposit,Shandong Province and its constraints on the magmatic activity patterns in the southern section of the Zhaoping fault

The Jiudian gold deposit from Shandong province is located in the south of the Zhaoping fault zone in Jiaodong Peninsula.It is a medium-sized gold deposit dominated by quartz-vein type mineralization.The granitoids in the district are widespread and of various types,but the formation ages and genesis of these granites have not been well studied,which limits the understanding of the metallogenic geodynamic background of this deposit.In this study,a detailed LA-ICP-MS zircon U-Pb dating of granite gneiss,garnet-bearing monzogranite,biotite monzogranite and granite pegmatite in Nos.4,6 and 12 veins of the Jiudian deposit shows that the granite gneiss age is 709.1±4.1 Ma(No.6),the garnet-bearing monzogranite is 164.1±1.9 Ma(No.4),the biotite monzogranite are 157.5±1.1 Ma(No.4)and 145.2±1.5 Ma(No.6),and the granitic pegmatite is 146.5±0.7 Ma(No.12).Combined with the geological characteristics and previous studies,it is indicated that there are three periods of magmatic activity in the Jiudian gold deposit:Neoproterozoic,Late Jurassic and Early Cretaceous.The Late Jurassic garnet-bearing monzogranite and biotite monzogranite are formed in lithosphere transition stage from extrusion to extend and they show characteristics of the S-type granite.They are not only the main host rocks of the deposit,but also may be the ore-forming rocks.