The Lanxiagou molybdenum deposit, situated in northern Hebei Province within the western Yan-Liao Metallogenic Belt, primarily hosts molybdenite within granitic gneisses, with only sporadic mineralization in granitic intrusions. The influence of magmatic activity on molybdenum mineralization remains a key research focus. Zircon U-Pb dating reveals the granitic intrusion formed at 134.9±0.94 Ma (Early Cretaceous), coeval with regional magmatic events. Geochemically, the Lanxiagou granite exhibits high SiO₂ (75.41%~76.21%), alkalis (Na₂O+K₂O=8.04%~8.73%), and Al₂O₃ (12.19%~12.64%) with low CaO (0.44%~0.85%), classifying as high-K calc-alkaline, weakly peraluminous granite. It displays enrichment in LILEs (Rb, Th, U) and LREEs, depletion in HREEs and HFSEs (Nb, P, Ti), and moderate Eu anomalies (δEu=0.31~0.40). EPMA analyses indicate crust-derived ferromagnesian biotite (high Mg, Fe, K; low Ca, Na) and albite (high Al, Na; low K, Ca). Mineralogical and geochemical signatures suggest a differentiated I-type granite with crystallization differentiation of biotite, plagioclase, and apatite. Zircon εHf(t) values (-18.16 to -14.76) and t_DM2(Hf) ages (2 570~2 117 Ma) indicate derivation from Paleoproterozoic lower crustal melting. The biotite in the intrusion exhibits relatively high oxygen fugacity (above the NNO buffer), with crystallization temperatures of 599~776℃, consolidation pressures of 164~260 MPa, and emplacement depths of 6.23~9.90 km, indicating formation under temperature and oxygen fugacity conditions favorable for molybdenum mineralization and significant exploration potential.