Abstract:

The LA-ICP-MS zircon U-Pb dating for three typical Mesozoic intrusions(AnjishanFuniushan rockmass, XiashuGaozi rockmass and Shima rockmass) in Ningzhen district yielded 109.1±1.9101.6±1.1 Ma, which represents the formation of these intrusions age and provides a precise formation time constraints for the intrusive rocks in the region. Copper polymetallic mineralization in Ningzhen district was related to the calcium alkaline magma activity around 100110 Ma in time, space and genesis, and both magmatism and mineralization in the area were continuous processes. Yanshanian intrusive rocks in Ningzhen district formed during the Early Cretaceous, while the calcalkaline intrusive rocks in Jiurui region and other regions formed in the Early Cretaceous; there are a difference of about 2535 Ma between both. Combined with the restrict from the Pacific plate activity characteristics since the Cretaceous to the petrogensis and metallogeny in the eastern China, the chronology data reveals that the magmatic activities in Yanshanian and metallogenetic response in Ningzhen region were the new diagenesismineralization events belonging to the largescale magmatic and metallogenic activities of the metallogenic belt in the middle and lower reaches of Yangtze River in the Mesozoic Era, as well as the geodynamic setting corresponds to the Mesozoic Era lithospheric thinning in eastern China. Lithospheric thinning of middle and the middle and lower reaches of Yangtze River started from 135 Ma, and might continue until around 100 Ma.

Key words:  Ningzhen district, Jiangsu, Yanshanian intrusive rocks, zircon U-Pb dating, mineralization belt of middle and lower reaches of Yangtze river, petrogensis and metallogeny