Geochemical Characteristics and Prospecting Significance of Perdu Rhyolite Porphyry in Madaokou Molybdenum Deposit, Chicheng County

There are some Large and medium-sized uranium-molybdenum deposits such as Zhangmajing (460) and Daguangchang (534) and several uranium-molybdenum mineralization sites have been found around the Guyuan Mesozoic volcanic faulted basin in Zhangjiakou. Uranium-molybdenum deposits (mineralization bodies) mostly occur in the perdu rhyolite porphyry under the volcanic strata of the Zhangjiakou Formation of the Early Cretaceous. Madaokou molybdenum deposit which lie in volcanic basin edge is been found in recent years, based on the analysis of rock geochemical and formation age of perdu rhyolitic porphyry, conclude that the formation age of Madaokou perdu rhyolite porphyry is similar to 460, 534 uranium deposits, are all formed in the Early Cretaceous; Compared with the ore-bearing gray perdu rhyolite porphyry to ore-free porphyry of Madaokou area, the ore-free porphyry has obvious alkali metasomatism, and the contents of SiO₂ and Mo are significantly reduced, while the contents of K₂O and Na₂O are significantly increased. The content of Mo element in Madaokou porphyry mass is similar to or close to 460 and 534 porphyry mass, while U element is significantly lower than 460 and 534 porphyry mass, which is close to the average value of granite in North China platform. Indicating that Madaokou mining area is a single molybdenum deposit, non-uranium molybdenum deposit type, which is also consistent with the current prospecting status. The perdu rhyolite porphyry is the main source of ore-forming material, the type of ore deposit belongs to alkali metasomatic hydrothermal deposit. The perdu rhyolite porphyry can be used as an important target geological body for mineral exploration.