Mengyin komatiites are characterized by typical spinifex texture,high MgO,low TiO_2,and unde- pleted Al.They show positive Rb,Ba,Sr and U anomalies,depleted LREE,flat HREE and low total REE content.There occurs fractionation of HFSE from REE,and Nb/Nb~* is positive.These data indicate that the source of komatiites is depleted in LREE and enriched in HFSE.Fractionation of HFSE from REE also shows that the plume could not have come from the mantle source area where olivine,pyroxene and garnet or majoritite were dominant.The latest Sm-Nd isotopic data of Mengyin komatiites not only prove that komatiites were de- rived from a prolonged depleted mantle but also indicate that the plume only underwent very insignificant assimi- lation of old continental crust.It is inferred that such a magmatic event might have constituted a component part of the continental growth in late Archean.