河北沽源460铀矿床主矿段矿体空间定位机制

Emplacement mechanism of orebodies in main ore block of No.460 uranium deposit in Guyuan,Hebei Province

460矿床构造几何学和运动学特征研究表明,460矿床构造格架是在大致自北西而南东的构造应力作用下,F45断裂带右行扭动并与F’45相互作用所形成。结合主矿段容矿构造产状和分布特征,提出矿区北西向反S形或弧形张-张扭性断裂是F45断裂的派生构造,是矿床定位的决定性因素;由陡倾断裂和缓倾地层组成的"断裂-地层圈闭"是矿床定位的另一重要因素。铀成矿作用与晚侏罗世—早白垩世火山作用没有直接的成因联系,而是与区域上强烈构造活动时期的构造活动密切相关。次流纹斑岩的侵入和两次铀成矿作用在时间上与区域上的强烈构造运动时期相对应,是区域构造演化不同阶段的产物,二者没有必然的因果关系。

A study of geometric and kinematic features of structures in No. 460 uranium deposit indicates that the structural framework of No. 460 uranium deposit was formed by the dextral strike-slip of the fault zone F45 and its reaction with F＇45 under the action of tectonic stress from northwest to southeast. According to the attitude and distribution of ore-hosting structures in the main ore block, the authors have reached the conclusion that the NW-trending reversed s-shaped or arc-shaped tensile to tensio-shear faults in the mineralized area, which serve as branch faults of the F45 fault zone, are the decisive factors for the emplacement of uranium mineralization, and that the ＂fault-strata trap＂, constructed by steep-inclined faults and gentle-inclined strata, is another significant factor. Uranium mineralization had no direct genetic relation to Late Jurassic to Early Cretaceous volcanism, but was closely related to regional tectonic activities during the strong structural movement. The intrusion of subrhyolite-porphyry and two uranium mineralization events were all produced by regional tectonic evolution at different stages and had no necessary genetic relation because they respectively corresponded to one of the strong structural movements in this region.