This paper presents U-Pb geochronology, whole-rock geochemistry, and zircon Lu-Hf isotopic analyses of Middle Triassic pyroxene diorite and Late Jurassic gabbro in the Kaiyuan region, along the northern margin of the North China Block. The study investigates the petrogenesis of these igneous rocks and modification of the lithospheric mantle of the North China Craton by subduction of the Paleo-Asian Ocean plate and the Paleo-Pacific plate. Zircon U-Pb dating indicates that the Middle Triassic pyroxene diorite formed at 243 ± 1 Ma, classifying it as a calc-alkaline, sub-aluminous rock. This gabbro shows geochemical characteristics typical of arc magmatic rocks, with enrichment in large ion lithophile elements (Rb and Ba) and depletion in high field strength elements (Nb and Ta), without significant Eu anomalies. The enriched zircon Hf isotopic composition (εHf(t) = -14.7 to - 8.9) suggests that the pyroxene diorite originated from partial melting of an enriched lithospheric mantle. For the Late Jurassic gabbro, zircon U-Pb dating yields an age of 160 ± 1 Ma, also categorizing it as a calc-alkaline, sub-aluminous rock. Similar to the Middle Triassic gabbro, the Late Jurassic gabbro is enriched in large ion lithophile elements (Rb and Ba) and depleted in high field strength elements (Nb, Ta, Zr, and Hf), with negative εHf(t) values (-10.6 to -7.7). These geochemical and isotopic characteristics indicate that the gabbro primarily originated from partial melting of an enriched mantle modified by subduction-related fluids. Integrating previous studies, this paper proposes that the Middle Triassic pyroxene diorite formed during the post-collision extensional phase following the final closure of the Paleo-Asian Ocean, while the Late Jurassic gabbro formed in a tectonic environment related to the subduction of the Paleo-Pacific. The prolonged subduction of the Paleo-Asian and Paleo-Pacific Oceans has imparted enriched mantle characteristics to the lithospheric mantle beneath the northern margin of the North China Craton.