Abstract: The Cenozoic volcanic rocks in Tumen river valley are located on the east of Tianchi volcano, Changbai Mountains, Jilin Province, Northeast China. The volcanic rocks in Tumen river valley are a suit of sodic tholeiitic basaltic rock which have characteristic of effusive eruption. The magma of the Cenozoic volcanic rocks in Tumen river came from upper mantle. In this paper, we discussed the magmas source characteristics of the volcanic rocks by the way of studying on the trace-element, REE, Sr and Nd isotopic data. The results show that the volcanic rocks have the characteristic of higher ε_Sr(3.5～9.1)and lower ε_Nd(-3.3～0.3) relatively and the compositions of magma source are mostly close to that of primitive mantle substance. The magmas experienced assimilation and contamination of the crustal materials to different degrees during their ascending through the lithosphere. But the magma's Sr and Nd isotopic characteristics mainly inherit the character of source mantle area. Integrating all the data on tectonic surrounding, geophysics and isotopic geochemistry, we think that the deep subduction of western Pacific plate is the key mechanism for the interaction of crust-mantle in the source mantle area.

Key words: Cenozoic volcanic rocks, Sr, Nd isotope, geochemistry characteristic of source mantle area, Tumen river valley

摘要： 图们江流域火山岩是一套以溢流式喷发为特征的、钠质拉斑系列为主的玄武质岩石。通过对火山岩的微量元素、REE和Sr、Nd同位素地球化学研究,探讨图们江流域火山岩的岩浆源区特征。结果显示:图们江流域火山岩具有相对高ε_Sr(3.5～9.1)和低ε_Nd(-3.3～0.3)特征,火山岩的岩浆源区成分接近于似原始地幔,岩浆上升过程中受到不同程度壳源物质的同化混染。但火山岩的Sr、Nd同位素值更多地继承了源区物质的特征。结合长白山区的大地构造背景、地球物理资料和火山岩的同位素地球化学特征,认为西太平洋板块深俯冲作用是导致东北亚大陆弧后扩张、岩石圈地幔熔融和岩浆喷发的主导机制。

关键词: 新生代火山岩, Sr、Nd同位素, 岩浆源区特征, 长白山区图们江流域