Urad Middle Banner (Wulatezhongqi) in Inner Mongolia is tectonically located in the northwestern margin of North China Craton, belonging to the LangshanBaiyan Obo epicontinental rifting. Regionally, maficultramafic intrusions are distributed discontinuously along central Inner Mongolia, forming a 400kmlong, 30kmwide magmatic belt. This belt hosts lots of CuNi (PGE) deposits/ occurrences, with the smallmedium sized Kebu CuNi deposit occurring in the Kebu massif. The Kebu massif, cropping out over an area of 45km2, consists of gabbro and olive facies. The gabbro facies is dominant litholgical facies for massif, whereas the olive facies hosts the main orebodies. The two facies occur together and present a transition relation. In this study, LAICPMS UPb dating of zircons yielded an age of 2581±18Ma (MSWD=23) for the Kebu plagioharzburgite, suggesting a Late Permain magmatic event. Geochemical analysis results show that the maficultramafic rocks from the Kebu massif belong to the tholetiitic series. These rocks are relatively enriched in large ion lithophile elements (eg. Rb, Sr, Ba,) and depleted in high field strength elements (eg. Nb, Ta, Zr, Hf, Ti), with rightinclined REE distribution pattern and (La/Yb)N value of 247~1129. According to the Fo and Ni values of olivine which contains the highest Fo, MgO and FeO contents of parent magma were estimated to 101% and 121% respectively, indicating that the parent magma of the Kebu intrusion is a highMgO tholetiitic basalt. The comprehensive analysis shows that the Kebu maficultramafic intrusion might form in the postcollisional tectonic setting, with magmatic source consisting of asthenospheric material and mantle wedge material, both of which were contaminated by previously subducted fluids. Crystallization fractionation of Fe and Mgrich minerals (such as olivine and pyroxene) and contamination of Sirich crust material might have played a key role in Ssaturation and subsequent sulfide segregation.