The Zhongdian copper polymetallic mineralization belt is located on the southern margin of Yidun Island Arc, which can be subdivided into the eastern and the western porphyry belts, respectively. In this paper, combined with previous published whole-rock geochemical data of the ore-bearing porphyries, zircon trace element and Hf-O isotope analyses are conducted on the Pulang and Disuga ore-bearing porphyries from the eastern belt and the Xuejiping ore-bearing porphyry from the western belt to identify their origin, evolution process and tectonic setting, and further explore the differences of the control factors for their copper mineralization. The results show that zircons from the Pulang, Disuga and Xuejiping ore-bearing porphyries are characterized by depletion of light rare earth elements and enrichment of heavy rare earth elements, with the average Th/U values of 0.19, 0.27 and 0.13, respectively. The zircon epsilon(Hf)(t) and delta O-18 values of the three ore-bearing porphyries are 0.31 +/- 0.6, 0.0 +/- 0.6 and 1.71 +/- 0.7, and 6.2 +/- 0.3 parts per thousand, 6.2% +/- 0.4 parts per thousand and 6.1% +/- 0.4 parts per thousand, respectively, indicating that they are all derived from mixed crust-mantle materials. However, there is a greater contribution of crustal material on the Pulang and Disuga porphyries than that of the Xuejiping porphyry. Whole-rock major and trace element variations together with the relationships of zircon Nb/Yb vs. Eu/Eu* and Th/Nb vs. Eu/Eu* reveal that the Pulang and Disuga porphyries underwent a higher degree of fractional crystallization than the Xuejiping porphyry. On the tectonic-background discrimination diagram of zircon trace elements, all the porphyries fall into volcanic arcs or arc-related orogenic environments. Combined with the whole rock Nb-Y and Rb-(Y+Nb) discrimination diagrams and their dated ages, it is suggested that the porphyries both in the eastern and the western porphyry belts were formed in a continental arc setting associated with the Late Triassic westward subduction of the Ganzi-Litang oceanic crust. The oxygen fugacities of the Pulang, Disuga and Xuejiping porphyries are estimated to be Delta FMQ+1.58, Delta FMQ+1.42, Delta FMQ+1.91 respectively by using the zircon oxygen fugacity meter (QFM is a quartz-iron peridotite-magnetite buffer). Combined with zircon Eu/Eu* values and whole-rock V/Sc ratios, all the porphyries have a relatively high oxygen fugacity, however, the oxygen fugacities of the Pulang and Disuga plutons are lower than that of the Xuejiping, which indicates that the level of oxygen fugacity is not proportional to the scale of mineralization under a relatively high oxygen fugacity condition. The crystalline temperatures of the three ore-bearing porphyries are 769 +/- 34 degrees C, 783 +/- 36 degrees C, 819 +/- 40 degrees C, respectively. Combined with the whole-rock Sr/Y ratios, it is found that the magmatic water contents of the Pulang and Disuga porphyries are higher than that of the Xuejiping porphyry. As a preliminary conclusion, higher water contents and higher differentiation degrees of magma may be the controlling factors for the development of more porphyry deposits in the eastern porphyry belt compared with the western porphyry belt, which suggests a greater mineralization prospecting potential for the eastern porphyry belt.
