Zircon U-Pb age, geochemistry and genesis of acid intrusive rocks in the Yuejinshan skarn type copper-gold deposit, Wandashan block

Located in the southwest part of the Wandashan block, the Yuejinshan copper-gold deposit is a skarn type deposit, and its orebodies are hosted in skarns, granite porphyries and the tectonic fractures. The orebodies show lenticular or veined forms. LA-ICP-MS zircon U-Pb dating and geochemical data are reported for granite porphyries and granodiorites in the Yuejinshan coppergold deposit in order to constrain its formation time, petrogenesis and the minerogenetic geotectonic background. The zircon LAICP-MS U-Pb age dating results show that the petrogenic ages of granite porphyries and granodiorites respectively are(115.8±1.0) Ma and(126.9 ±1.7)Ma respectively, and the copper-gold mineralization age is consistent with petrogenetic age of granite porphyry. Geochemical study indicates that the granodiorites are peraluminous calc-alkaline granite. The chondrite-normalized REE patterns of granodiorites display LREE enrichment and HREE depletion, with a distinct Eu anomaly, and their magma came from the lower crust. The granite porphyries belong to peraluminous calc-alkaline granite. The REE patterns show that granite porphyries exhibit pronounced LREE enrichment and HREE depletion, enrichment of large-ion lithosphile elements (Rb, Ba, K, Sr) and incompatible elements (U, Th), and depletion of high field-strength elements (Ta, Nb, P, Ti) and HREE. The magma of granite porphyries came from crust-mantle mixture, and the copper-gold deposit formed in the collision of post-collision extensional tectonic setting. The metallogenic materials formed intermediate-acid magma heat source, and magmatism and mineralization took place in the extensional tectonics after the Pacific plate subduction.