Petrogenesis of the granite porphyry related to the Jiudingshan Cu-Mo deposit in western Yunnan: Constraints from LA-ICP-MS zircon U-Pb chronology, Sr-Nd-Hf isotopes and petrogeochemistry

Abstract: In this study, the authors carried out a comprehensive research including zircon U-Pb dating, petrogeochemical investigation and Sr-Nd-Hf isotope analysis of the granite porphyry related to the Jiudingshan Cu-Mo deposit in western Yunnan. LA-ICP-MS zircon U-Pb chronology indicates that the porphyry was emplaced at 34.5?34.9 Ma, consistent with or slightly earlier than the formation of the Cu-Mo deposit (33.9?35.3 Ma) and similar in time to the peak of Cenozoic alkali-rich magmatic activity (45?30 Ma) in western Yunnan, indicating that they were formed by the ore-forming process in the period of late-collisional transformation (40?26 Ma). The granite porphyry is silica-rich (SiO2=62.86%?71.57%), potassium-rich (K2O/Na2O=1.64?2.78) and alkali-rich (K2O+Na2O = 8.98%?11.28%), belonging to shoshonitic series peraluminous granite, with the characteristics of LREE enrichment, HREE depletion, and weak negative Eu anomaly (δEu=0.82?0.93). The porphyry is enriched in LILEs such as Rb, Ba, Th and U, and depleted in HFSEs such as Nb, Ta, Zr and U. Sr?Nd?Hf isotopes imply that the magma originated from the EMII which was contaminated by crustal materials in the process of magmatic upwelling to form a potassium-rich ore-bearing magma with mixed sources of the crust and the mantle.