Geochronology and Whole-rock Geochemistry of Intrusive Rocks from the Donglufang Cu-Mo Deposit in Western Margin of the Yangtze Block and Their Metallogenic Implications

The Donglufang Cu-Mo deposit is located in the western margin of the Yangtze Block.The deposit is characterized by porphyry Mo (-Cu) orebodies associated with quartz monzonite porphyry and skarn Cu orebodies.While previous research has mainly focused on the genesis of porphyry Mo mineralization, research on skarn Cu mineralization is relatively weak.In this paper, the zircon U-Pb geochronology and whole-rock geochemistry of Cu-mineralized quartz diorite porphyrite are studied on the basis of investigations of the exploration results of the deposit.The results show that the zircon U-Pb weighted average age of quartz diorite porphyrite is 82 Ma, indicating that it was formed in the Late Cretaceous, which is consistent with the W-Mo(Cu) mineralization age of the Late Cretaceous in the Geza arc.Quartz diorite porphyrite are high silica (SiO₂=60.74%–63.36%), alkali-rich(Na₂O+K₂O=7.03%–9.29%), metaluminous (A/CNK=0.63–0.86), displaying shoshonitic I-type granite characteristics.The rare earth elements have obvious right-leaning patterns and typical adakite affinity characteristics, which can be interpreted as the product of partial melting of the intermediate-mafic lower crust mix with mantle-derived magma.The nature of the magmatic source and the type of wall rocks determine the mineralization zoning of the Donglufang Deposit, with porphyry Mo(-Cu) mineralization occurring in the potassic zone of the deep quartz monzogranite porphyry, skarn Cu(-Mo) mineralization occurring in the contact zone, and vein Pb-Zn-Au-Ag mineralization occurring in the peripheral marble.The deposit constitutes a porphyry mineralization system with Mo(-Cu), Cu(-Mo), and Pb-Zn-Au-Ag mineralization.Our comparative study shows that the Late Cretaceous magmatic rocks and related mineralization in Geza arc extend southward to the western margin of Yangze Block, formed in the post-collision extensional setting.The degree of magmatic differentiation gradually decreases from north to south, and the contribution of mantle-derived magma gradually increased, resulting in obvious different mineralization style from north to south, i.e., from northern Xiuwacu W-Mo, Relin Mo-W, Hongshan and Tongchanggou Mo(-Cu), to southernmost Donglufang Cu(-Mo).