Genesis and metallogenic characteristic of Dongnan Cu-Mo deposit associated granitoids: LA-ICP-MS zircon U-Pb dating and isotope constraint from Zijinshan ore field in southeastern China

The Dongnan Cu-Mo deposit, located in the southeast of the Zijinshan ore field (the largest porphyry-epithermal system in Southeast China), represents the complex magmatic and metallogenesis events in the region. The petrogenesis and metallogenesis of granitoids from the deposit are not determined, especially the interactions between ore-bearing (granodiorite porphyry) and barren samples (granodiorite and diorite). In the paper, the whole rock geochemical features shared a similar affinity to the middle-lower content and revealed that they derived from partial melting of the Cathaysian basement with the contribution of mantle materials, even represented that they generated in the plate subduction; LA-ICP-MS zircon U-Pb ages show that these granodiorites, granodioritic porphyry and diorite, were generated during 114-103 Ma. The ore-bearing samples mostly presented epsilon(Hf)(t) of negative values (peak value is -4 to -3) with old two-stage Hf model ages (t(DM)(2)) (peak value is 1.10-1.15 Ga), while the barren sample showed slightly negative epsilon(Hf)(t) (peak value is -1 to 0) values with young t(DM)(2) (peak value is 1.00-1.05 Ga). The value of zircon Ce4+/Ce3+ ratio mostly higher than 450 was first verified for the ore-bearing samples in the Dongnan Cu-Mo deposit, and the values of ore-bearing were found to be higher than those from the barren, which suggests that the ore-bearing formed in more oxidized parental magma with higher oxygen fugacity. Based on the geochemical characteristic of the element and isotope, we concluded that the Early Cretaceous multi-phases magmatic activities, low melting temperature and low pressure of pluton, and high oxygen fugacity of zircon, were the favorable conditions for metallogenesis of Dongnan Cu-Mo deposit.