Abstract: The Yangmadian Mo deposit is located in western Liaoning province, eastern part of the Yanshan-Liaoning Mo (Cu) metallogenic belt. The Yangmadian granitic pluton associated with the molybdenum mineralization is composed of three main different lithofacies, porphyraceous granite, coarse-grained granite and fine-grained granite. Their major minerals include quartz (30%-45%), K-feldspar (35%-50%), plagioclase (15%-25%) and biotite (3%-5%). Orebodies of the Yangmadian Mo deposit occur mainly in the fine-grained granite, and minor in the coarse-grained granite and porphyraceous granite. Geochemical researches show that the pluton is rich in Si (w(SiO₂)=69.26%-76.44%), alkalis (w(Na₂O+K₂O)=7.87%-8.81%), poor in Ca (w(CaO)=0.36%-1.33%), Mg (w(MgO)=0.17%-0.61%), Fe (w(FeO_T)=1.47%-3.39%), potassic (K₂O/Na₂O=1.05-1.31) and metaluminous (A/CNK=0.90-1.00). The pluton is generally enriched in Large Ion Lithophile Element (LILE, such as K, Rb, Th and LREE), normal in High Field Strong Element (HFSE, such as Nb, Ta, Zr, Hf and HREE), slightly depleted in Medium REE, and displays a “V” shape chondrite-normalized REE patterns with strong negative Eu anomalies (δEu=0.26-0.76). Both evolution characters of the minerals and geochemical characters of the rocks indicate that the Yangmadian pluton were resulted from different degree fractional crystallization of the common parent magma, which derived from the part melting of lower crust materials under high-pressure granulite facies. The isotopic dating indicates that LA-ICP-MS zircon U-Pb ages are (192.1±1.9) Ma, (189.5±1.4) Ma, and (189.3±3.3) Ma for porphyraceous, coarse-grained and fine-grained granite, respectively. Based on comprehensive researches on existing geological data, it can be conclude that petrogeny and metallogeny of the Yangmadian pluton were resulted from the Early Jurassic reactivation of the residual mantle wedge induced by subduction of the Paleo-Asia Ocean in Paleozoic period.

Key words: porphyry molybdenum deposit, Early Jurassic, granite, geochemistry, Yanshan-Liaoning depression belt, North China