关键词: 延边地区, 中生代, 火山岩, 捕虏晶, Sr-Nd同位素

Abstract: The pyroxenite xenoliths and amphibole xenocrysts occur in Middle Jurassic and Early Cretaceous volcanic rocks from Yanbian area. The pyroxenite xenoliths, showing cumulate texture, are composed of augites. The augites are similar to those of clinopyroxene (Cpx) megacrysts in Cenozoic basalts from Eastern China in chemical composition. The amphibole xenocrysts are pargasite and magnesium-hastingsite which are similar to those in the amphibolewebsterite xenoliths from Late Mesozoic basalt. The P-T estimated results show that the pyroxenite xenoliths and amphibole xenocrysts could be from the depth of 25~37 km. The (^{87Sr/86Sr)_i ratios and ε_Nd(t) values of Mesozoic volcanic rocks in Yanbian area are 0.7043~0.7050 and 2.33~4.71, respectively, which implies the magma source could be composed of a suite of the depleted and newly accreted mantle material. On the basis of abovementioned characteristics, it is suggested that the primary magma of Mesozoic volcanic rocks in Yanbian area could be derived from the partial melting of newly accreted material in the crustmantle transitional zone. The accretion event could take place in the Neoproterozoic.}