The Fengli mafic intrusion crops out in the northern margin of the Lesser Xing’an Range. It predominantly consists of hornblendegabbro and gabbro. The hornblende gabbro contains large hornblende phenocrysts, which contain clinopyroxene and plagioclase inclusions. The Fengli mafic pluton yielded a crystallization age of 107±1. 0 Ma. They are characterized with homogeneous (87Sr/86Sr)i (0.7065) and εNd(t) (-0.17～0.14), which exclude the possibility of significant crustal contamination. Moreover, compared with the Early-Mesozoic mafic intrusions, Fengli pluton has relatively enriched Sr-Nd isotopic compositions. This could be resulted from the multi-stage Paleo-Asian Ocean and Paleo-Pacific subduction which leading to the enrichment and accumulation of the large ion lithophile elements and light rare earth elements. Whole rock major and trace element signatures suggest that Fengli mafic rocks were generated by low degree partial melting of depleted lithospheric mantle under spinel-facies conditions. Fengli mafic rocks have zircon δ18O values of 5.0‰ to 6.6‰ (average 5.8‰), slightly higher than the typical mantle zircon δ18O value, indicating that the parental magmas were likely derived from mantle wedge metasomatized by sedimentary melt and fluid from the subducted Paleo-oceanic plate. In addition, the occurrence of the hornblende in the rocks also indicates a high-H2O parental magma which experienced fluid metasomatism in the mantle source. In the latest Early-Cretaceous (110～100 Ma), the eastward narrowing of the distribution of igneous rocks, most of which are alkaline rocks, bimodal volcanic rocks and mafic rocks, reveals an intracontinental extensional environment resulted from the rollback of the Paleo-Pacific slab. Decompression partial melting of the lithospheric mantle induced the occurrence of the Fengli mafic rocks.