流体混合对砂岩型铀矿成矿作用的影响

The influence of fluid mixing on the mineralization of sandstone type uranium deposits

探讨不同类型盆地中不同来源、不同组成、不同性质的流体混合对砂岩型铀矿成矿的影响。流体混合不但改变流体的物理化学条件,更重要的是改变流体的化学组成,导致流体化学平衡的破坏,引起流体卸载成矿。不同构造背景下形成的盆地、流体特征及其对砂岩型铀矿成矿的影响不同。铀—油—煤共存盆地中,浅表层含铀氧化性流体与油气有关的有机还原性流体相互作用对铀成矿起重要的控制作用;挤压构造环境下的盆地,在形成过程中造山带流体与盆地深源流体混合对成矿的影响很大;而伸展背景下的断陷盆地或裂谷盆地,往往伴随有深部岩浆和热流体的活动,应重视热液对砂岩型铀矿的改造、叠加富集的作用。

The influence of different sources, compositions and properties of fluid mixing in different types of basins on the sandstone type uranium deposits was discussed in this paper. Fluid mixing changes physical and chemical conditions of the fluid and, what is more important, changes the chemical composition of the fluid, leading to the destruction of fluid chemical equilibrium and causing unloading mineralization of the fluid. In basins formed in different tectonic backgrounds, the impacts of fluid characteristics on the sandstone type uranium mineralization are different. In the uranium-oil-coal coexistent basin, the interaction between the uraniumbearing oxidizing fluid in the shallow layer and the organic reducing fluids associated with oil and gas plays an important controlling role in uranium mineralization, whereas in the basin Under the tectonic environment, the mixing of orogenic belt fluid and basin deep source fluid exerts great influence on mineralization. However, in the rift basin under the extension environment, there often occur deep magmatic and hydrothermal fluid activities, and hence attention should be paid to the transformation and superposition enrich- ment role of the thermal fluid on sandstone type uranium deposits.