Abstract:The Shanggusi porphyry molybdenum deposit is located in the easternmost part of all the known molybdenum deposits in the East Qinling with an outcrop area about 1.5km². Disseminated molybdenite mineralization occurred in the marginal fine-grain porphyry granite and the periphery granitic pegmatite in the east and south part of the Shanggusi granite porphyry, and some fracture-filling molybdenite mineralization occurred in the hornstone of the southern Shanggusi granite porphyry as well. The main rock-forming mineral phase assemblage of the Shanggusi molybdenum-bearing granite porphyry contains quartz, alkaline feldspar and plagioclase, and the chemical compositions of the granite porphyry are characterized by enriched silicon and alkali, depleted iron and magnesium. The Shanggusi granite porphyry bears the typical high-temperature granular quartz, of which different extents of resorption have taken place with features of harbour-like, skeletal, and dendritic quartz. The dissolved quartz is filled with or included by alkaline feldspar and plagioclase, resulting from the fast disequilibrium crystallization after the high-temperature quartz-bearing granitic porphyry magma rapidly intruded at shallow levels. The spherical, ellipsoidal and plastic flow state of the mafic magmatic enclaves, and irregular, lamellar-shaped biotite-enriched regions in the porphyry body are compelling evidence for the magmatic mixing/ mingling. Fluids exsolution and transportation phenomenon are well preserved by some significant structures in the Shanggusi porphyry, including (but not limited to) the alteration miarolitic cavities, interconnected miarolitic cavities, cavities, the sulfide alteration prominence and the vertical snake-curved mica-enriched regions. The fine-grained granite porphyry and the granitic pegmatite, generated by the undercooled crystallization of the marginal porphyritic magma and rapid crystal growth of its front supersaturated melts respectively, by which the ore-forming fluids were trapped, resulted in the disseminated mineralization. The Shanggusi porphyry molybdenum deposit provides a coupled mineralization example of crust-derived magma and deep ore-bearing fluid, which correspond to the orthomagmatic subsystem and peri-pegmatite subsystem in the metallogenic system of transmagmatic fluid theory. Therefore, a large ore deposition may exist within the unexposed portion of the Shanggusi porphyry body.