Abstract:A lot of progress on Mesozoic lithospheric thinning has been made in eastern North China Craton, while the research of that in central North China remain weak. This study presents detailed LA-ICP-MS zircon U-Pb dating, major and trace element geochemical and Sr-Nd-Hf isotopic data for Ketou syenite within Huyanshan alkaline complex in central North China Craton. LA-ICP-MS zircon U-Pb dating shows that Ketou syenite was emplaced at the late stage (111 Ma) of Early-Cretaceous. These samples are all potassic-ultrapotassic and alkaline rocks. They are distinct positive Eu anomalies. They have high initial 87Sr/86Sr of 0.7058~0.7062, lower εNd (t) of -11.1 to -10.4 and zircon εHf(t) values of -12.2 to -5.2. Detailed research suggest that primitive magmas of Ketou syenite were derived from partial melting of enriched lithosphere mantle with phlogopite-bearing lithosphere mantle at spinel lherzolite zone. And primitive magmas have went through the process of assimilation and fractional crystallization (AFC). Combined with published data of magmatism in central North China, we infer that the late-Mesozoic magmatism in central North China can be subdivided into two stages: early one at 123~135 Ma for the peak magmatism, late one at 114 Ma for the last weak magmatism. Together with the source region for the late-Mesozoic magmatic rocks in central North China, it is indicated that the lithosphere mantle in central North China was enriched and heterogeneous, which was thinning at least from 138 to 111 Ma.