The cenozoic volcanic rocks in eastern part of Liaoning-Jinn district consist mainly of basaltS which contain abundant mantle-derived xenoliths. The rocks of ultramafic inclusions are composed mostly of spinel lherzolites and a small amount of websterites. It order to study the origin of xenoliths

the concentrations of several trace elements （REE

Rb

Sr

Ba

Th

U

Hf

Sc

Cr

Fe

Co and Ni） have been studied by NAA. According to geochemical characteristics of REE and other trace elements

there are two types of spinel lherzolite inclusions. The first type is refractory residues left after partial melting of the upper mantle and the second type is metasomatizing refractory residues. It applies that even within a small volume beneath the area studied the upper mantle is inhomogeneous. But websterites inclusions are formed by segregation of basaltic melt derived from high degree of melting of mantle source rocks.