关键词: 延边-东宁地区, 晚三叠世, 花岗岩, 地球化学, 古太平洋板块

Abstract:

Precise zircon U-Pb dating of the Taipingling pluton in Dongning area, Heilongjiang Province shows that the pluton was formed in the Late Triassic period, similar to those plutons at the Qishierdingzi, Naozhigou and Dahuanggou in Hunchun area. The Late Triassic granitoids in Yanbian-Dongning area are mainly composed of granodiorite and monzogranite. Their geochemical characteristics show they belong to medium K calcalkaline series, and have a tendency of evolving into highK calcalkaline series. They are enriched in LILE (Rb, Th, K, La,et al.), depleted in Sr, P, Ti and the HFSE (Nb, Ta, Zr, Hf,et al.). Ba shows a slight depletion compared with Rb and Th. The granitoids also show low I_sr，high ε_Nd(t) and young T_DM. Through studies on petrology, mineral assemblages and geochemistry, the formation of the granitoids is suggested to be related to the subduction of the oceanic crust, being an indication of the beginning of paleo-Pacific Oceanic plate subduction underneath the NE China.

Key words: Yanbian-Dongning area, Late Triassic, granite, geochemistry, plaeo-Pacific oceanic plate