Cenozoic continental basalts with oceanic island basalt(OIB)- like geochemical compositions in the middle and eastern North China craton (NCC) are associated with the subduction of the Pacific slab. However, the geochronological and geochemical data of Cenozoic volcanic rocks in the western part of the North China craton are rarely reported.This paper reports for the first time the Cenozoic magmatism in Balongwula, northern Alxa block，western NCC. The basalts and dolerites in the Balongwula are constrained to the Eocene (37.2～36.5 Ma) by zircon U- Pb dating.These basalts and dolerites show high SiO2(50.38%～51.65%) and Al2O3(16. 9%～17. 5%) contents, are characterized by enrichment in light rare earthelements (LREEs) and large ion lithophile elements (LILEs), without negative Eu anomalies and Nb, Ta depletion, indicating an affinity with OIB. These rocks also display enriched isotopic compositions with initial 87Sr/86Sr ratios (0.7054～0.7057), εNd(t)(-7.2 to -6.7) and εHf(t) (-3.2 to -1.1). Geochemical analyses reveal that crustal contamination in these Cenozoic rocks has been negligible. Compared with the Cenozoic basalts in the eastern NCC,the Cenozoic basalts in the northern Alxa block have more enriched isotopic compositions and higher LILEs contents.The Cenozoic basalts and dolerites in the northern margin of the Alxa block were derived from the partial melting of garnet lherzolite that was metasomatized by subducted- related melts. During the Cenozoic, the extension of the lithosphere drove the upwelling of the asthenospheric mantle, leading to partial melting of the metasomatized enriched mantle,forming volcanic rocks with OIB- like geochemical features in the Alxa block.