江苏高淳铜多金属矿早白垩世侵入岩成因OA

The Gaochun Cu polymetallic deposit,located in the northern part of the Xuancheng ore concentration district within the Middle-Lower Yangtze River Metallogenic Belt,is a newly discovered mineralization area.This study focuses on diorite porphyry and quartz diorite porphyry exposed by drilling in the Gaochun mining area.Through zircon LA-ICP-MS U-Pb dating,whole-rock major and trace element analysis,zircon in-situ Hf isotopes,and whole-rock Sr-Nd isotope measurements,the formation age,magma source,and petrogenesis of the intrusive rocks are systematically investigated.The results show that the zircon U-Pb ages of diorite porphyry and quartz diorite porphyry are 134.1±2.0 Ma and 133.9±2.2 Ma,respectively,indicating they were products of Early Cretaceous magmatic activity.Geochemically,the rocks are characterized by high-K calc-alkaline and metaluminous affinity,enrichment in large ion lithophile elements(e.g.,Rb,Ba,Th),depletion in high field strength elements(e.g.,Nb,Ta,and Ti),significant fractionation of light and heavy rare earth elements,and weak Eu anomalies.Sr-Nd-Hf isotopic compositions suggest that the magmas were derived from mixing of an enriched mantle source and ancient crustal materials(Archean-Paleoproterozoic basement),accompanied by varying degrees of fractional crys-tallization and assimilation.Comparisons with intrusive rocks from the adjacent Chating ore district and the Tongling ore cluster indicate that the Gaochun intrusions are genetically linked to the first stage of crust-mantle interaction in the Middle-Lower Yangtze River Metallogenic Belt,formed in an intracontinental extensional setting following the subduction of the Paleo-Pacific Plate,involving magmatic underplating and mixing.This study provides new petro-geochemical evidence for understanding the deep magmatic-mineralization mechanisms in the Xuancheng ore cluster.