浙江大桥坞铀矿床斑岩体的“双层结构”与铀矿化

大桥坞斑岩型铀矿床产于中生代蒙山破火山口中一石英斑岩体的内外接触带及其隐爆角砾岩筒中。铀成矿主要与斑岩体的“双层结构”有关，即”双层结构”成矿模式。浅部石英斑岩为含矿岩体，深部花岗斑岩为矿源岩体。矿化以裂隙型、角砾型为主，矿体的形态主要呈细脉状、浸染状，与围岩界线不清。成岩物质来源于壳幔混源的富铀钙碱性岩浆。成矿物质主要来源于该深部富铀花岗岩浆冷凝结晶分异产生的富铀岩浆期后热液。其成矿过程主要是富铀岩浆期后热液流体沿断裂构造系统上升、运移，在浅部石英斑岩体内外接触带发生隐爆，成岩成矿。早期铀-赤铁矿化阶段形成贫铀矿化，晚期铀-金属硫化物矿化阶段，形成富铀矿化，两期叠加作用致富。

Relations Between"Two-Layer Structure"of the Porphyry Massif and Uranium Mineralization in Daqiaowu Uranium Deposit in Zhejiang Province

Daqiaowu uranium deposit oaurs in the contact Zone of quartz porphyry massif and explosive breccia chimney in the Mesozoic Mengshan caldera, belonging to porphyry type. Uranium oreforming has relations with "two-layer structure"of the porphyry massif, that is, ore-forming model of "two -layer structure". The shallow quartz porphyry is ore-bearing massif and the deep granite porphyry is ore-origimating one. Most mineralizations belong to fracture and breccia typer, and occur as little veined and disseminated. The shape of the ore-body is mainly vein-like, and the boundary of ore-body isn' t clear with country rocks, The material of rock - forming comes from uranium - rich calc - alkaline magma from deep in the crust or the mantle, and the material of ore -foming comes mainlg from hydrothermal solution and fluid after maginatic stage. uranium ore-forming process is that the uranium - rich hyolrothermal solution or fluid rise move explose and absorb from country rocks resulting in diagenetic mineralizafion in the contact zone of quariz porphyry massif in the shallow during uranium - rich granite magmafic crysfallizafion - differenfiafion in the deep. Eary stage is u - red iron froth,foming uranium - poor mineratization, and the late is u - polymetallic sulfide mineralization, forming uranium - rich mineralization, and the two stages of mineralizations superimpose to enrich.