Origin of Gold Metallogeny and Sources of Ore-Forming Fluids, Jiaodong Province, Eastern China

摘要

In this paper we use published isotopic ages for gold deposits and related rocks in the Jiaodong Peninsula (East Shandong Province) to investigate the origin of the large-scale gold metallogeny in the region, which contains world-class lode gold deposits. According to this database, metallogenic processes in this area occurred in the Mesozoic, with peak activities between 110 Ma and 130 Ma. In the Jiaodong gold province (JGP), the mineralizing events are coeval with or postdate Mesozoic granitoid intrusions. Both the Rb-Sr isochron ages and zircon SHRIMP age dating results suggest that Mesozoic granitoids were emplaced during several thermal events. The identification of inher-ited zircons coupled with I_(sr) ratios (>0.709) indicate that these granitoids were mainly sourced from the continental crust, by remelting or partial melting. I_(sr) values obtained from ores and fluid inclusions are generally higher than 0.709, and slightly higher than those for Mesozoic granitoids. This also indicates that both ore fluids and znetals were mainly sourced from the crust. Synthesis of the available data suggests that collision between the South and North China continents was probably the dominant factor responsible for the gold metallogeny in the JGP. Granitoid emplacement and large-scale gold metallogenesis can be related to three important stages in the geodynamic evolution of a collisional orogen (compression-crustal thickening-uplift, lithospheric delamination and transition to extension, and a final extension phase). The most important metallogenic phase occurred at the transition from collisional compression to extension tectonics.