浙江大桥坞斑岩体“双层结构”与铀矿化

Two layer Structure of The Porphyry Massif and its Relation To Uranium Mineralization in Daqiaowu, Zhejiang Province

Daqiaowu uranium deposit , the porphyry type of uranium deposit, occurs in the contact zone of quartz porphyry and cryptoexplosion breccia massif in the Mesozoic mengshan caldera. The formation of uranium deposit is mainly related to the two layer structure of the porphyry massif . The quartz porphyry massif is ore-bearing massif and the granite porphyry massif which is under the quartz porphyry massif is the source massif of uranium. The type of veinlet like and dissemination like uranium mineralization mainly is fracture and breccia type. The morphology of ore body mainly is veinlet, and the boundary between ore-body and country rock isn't so clear. Diagenetic material is derived from uranium-rich calcium alkaline magma which is from the mixture of crust and mantle. The mineralization material is mainly derived from rich in uranium postmagmatic hydrothermal solution which is from the cooling and crystal fractionation of rich in uranium granite magma. Rich in uranium postmagmatic hydrothermal fluid rises, migrates along the fracture, and extracts the uranium from the wall rock. The cryptoexplosion is taken place when the hydrothermal fluid get the inner and outer contact zone of quartz porphyry. There are two mineralization stages: the early stage is the stage of uranium, hematite mineralization, and the late stage is the stage of uranium, metallic sulphide mineralization, and the uranium deposits are formed after the two stages of mineralization.