Since 1970’s isotope and trace element studies of Cenozoic basalts provide evidenceof a heterogeneous mantle with a two-layer structure.J.B.Schilling and S.S.Sun etal.first proposed a two-layer model for the mantle and accounted with the conceptof“plume”for the mixing between the lower mantle and the depleted upper mantle,aswell as the differences in isotopes and trace elements among basalts.Especially since R.K.O’nions pointed out the negative correlation between Nd/Sr isotopes in oceanic basalts,many authors have justified such a correlation by using a two-component mixing model