关键词: 锆石U-Pb年代学, 地球化学, 火山岩, 吉林中部

Abstract: The volcanic rocks in the Yitong area of central Jilin Province are located in the eastern segment of the northern margin of the North China plate. This paper presents zircon LA-ICP-MS U-Pb geochronology and geochemical data of the volcanic rocks in this area, aiming to explore their petrogenesis. The zircons in the andesite present euhedral-subhedral, and obvious magmatic oscillation zone, with Th/U ratios of 0.06-0.95, indicating their magmatic origin. Zircon dating results indicate that basaltic andesites were formed at (285±2) Ma, the Early Permian. The rock assemblage of the Early Permian volcanic rocks is basaltic andesite and andesite. The SiO2 mass fraction of the samples is 51.29%-58.91%, and the Mg# values are 39-66, belonging to the tholeiitic series, relatively enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs), and depleted in high field strength elements (HFSEs). Comprehensive studies suggest that the Early Permian volcanic magma originated from the depleted mantle wedge metasomatized by subducting fluids, and was formed in the active continental margin environment of the southward subduction of the Paleo-Asian Ocean. Combined with regional research results, it is believed that the northern margin of the North China plate was under the southward subduction of the Paleo-Asian Ocean in the Early Permian.

Key words: zircon U-Pb geochronology, geochemistry, volcanic rocks, central Jilin Province