Abstract:

Located in the Central Fujian Rift, the Meixian Pb-Zn deposit is a large volcanogenic massive sulfide Pb-Zn (-Ag) deposit. Based on a detailed field study, the authors identify Yanshanian porphyry granite (148.9±1.4 Ma, 152.0±2.1 Ma) in the Meixian deposit by LA-ICP-MS zircon U-Pb dating. Geochemical analyses show the porphyry granites have high SiO₂ and potassium abundances, moderate Al₂O₃, alkaline contents, and weak peraluminous. Chondrite-normalized REE distribution pattern display right skewed shapes showing fractionation between LREE and HREE with flat HREE pattern. These granites are enriched in large ion lithophile elements (LILEs) and high field strength elements(HFSEs) without obvious depletion in Nb-Ta, indicating that they were high-potassium calc-alkaline I-type granite formed in post-collision environment. Their parental magma were experienced strongly fractional crystallization of amphibole, biotite, plagioclase and some other accessory minerals. These porphyry granites are spatially associated with lead-zinc bodies, their magma are enriched in volatile component, large ion lithophile elements and have underwent high degree differentiation by fractional crystallization, indicating the Later Jurassic magmatism in the study area is very favorable for the skarn mineralization and extensively superimposed and reformed the earlier stage massive sulfur lead-zinc ore bodies.

Key words: zircon U-Pb dating, geochemistry, Yanshanian porphyry granite, Meixian Pb-Zn deposit, metallogenic effect