SHRIMP U-Pb Dating of the Gaoshanjiao Granodiorite in the Yinkeng Ore-field of the South Jiangxi Region and Its Relations to Mineralization

The Gaoshanjiao granodiorite intrusion is located in the east section of the Nanling region at the conjunction of the Nanling W-E striking structure and the Pacific Ocean rim NNE structure belt. The Gaoshanjiao granodiorite occurs within the Yinkeng Au-Ag-Zn-Pb-Cu ore-field and the magmatism is genetically related with the mineralization. This paper is based on the studies of regional geology and deposit geology, by using the SHRIMP zircon U-Pb dating method, to accurately date the Gaoshanjiao intrusion. Determination results show that the formation age of Gaoshanjiao granodiorite is (161±1) Ma, with the captured zircon age of (422±4) Ma. The Gaoshanjiao intrusion occurred in the early Yanshanian period and not the early Cretaceous period as previously reported elsewhere. According to the ore deposit geology data, it is considered that the polymetallic mineralization is simultaneous with the magmatic activity and granodiaorite forming. The magmatism and mineralization occurs in the transitioning period from the Middle Jurassic epoch to the late Jurassic epoch (J₂/J₃ transition period is 160 Ma), and may be associated with the structural dynamic mechanical background of the lithosphere large extension. The Yinkeng Au-polymetallic deposit and the same metallogenic-series with famous W deposit in southern Jiangxi Province and the metallogenic age of Au are basically concordant with that of W/Sn where the ore-forming processes are mainly concentrated in the period of 150-165 Ma.