南岭成矿带铀矿地质特征、成矿规律与全位成矿模式

Geological characteristics, metallogeny and geospatial mineralization model of uranium in the Nanling metallogenic belt

南岭成矿带是中国重要的铀矿基地,产出的铀矿床以花岗岩型为主,其次为碳硅泥岩型和少量砂岩型。本文通过搜集整理前人找矿勘查和科研成果,认为南岭成矿带多期多阶段构造演化为铀成矿作用提供了初始铀源、产铀花岗岩、断裂网络和含铀热液等有利的成矿条件。产铀花岗岩大多是由高硅、过铝、偏钾高碱的S型花岗岩,沿断裂分布的构造碎裂岩、蚀变岩和还原性地质体是有利的赋矿围岩。矿化与蚀变中心带发育沥青铀矿、黑色微晶玉髓、紫黑色萤石、胶状黄铁矿、赤铁矿、绿泥石等矿物组合。铀矿体形态多样,以中小规模、中低工业品位为主。南岭成矿带中新生代多阶段区域性拉张过程中形成了多阶段铀矿化。花岗岩型铀矿床分布于加里东隆起区花岗岩内部构造结和岩体接触带附近,矿体沿断裂与蚀变体一起赋存于氧化-还原界面和脆韧性构造转换面之间的"成矿壳层"内。南岭成矿带中新生代"空间全位"铀成矿模式显示,不同的构造层、不同的建造、不同的岩性及不同的部位均有铀成矿潜力,但由于具体成矿条件的不同组合而产出不同类型、不同规模、不同时间和不同强度的铀矿化。也就是说,难以排除某一空间部位不成矿的可能性。根据这一"全位"成矿的认识,从不同的角度对南岭成矿带中新生代铀成矿作用进行全面分析,找出尚未落实的"缺位",再根据工作区具体成矿条件指导铀矿找矿新突破。

Nanling metallogenic belt is an important uranium resource base of China.The granite type is the dominant uranium deposit type,with carbonaceous silicous-pelitic rock type and some sandstone type uranium deposits occurring as minor types.In this study,we compile and analyze the available literature on uranium prospecting,exploration and scientific research.We confirm that the favorable geological conditions for mineralization of uranium i.e.the initial source of uranium,uranium productive granitic massif,nets of fault junctures,uranium hydrothermal etc.were formed during the multi-stage tectonic evolution of Nanling metallogenic belt.Most of the uranium productive granitic massifs are the S-type granites characterized by high content of Si,peraluminous,meta-potassium and alkali.The favorable ore-bearing wallrocks are the cataclastic rocks,altered rocks and reductive geological bodies which are distributed along the faults.The mineral assemblage formed in the central zone of mineralization and alteration is composed of pitchblende,black microcrystalline chalcedony,purple black fluorite,colloidal pyrite,hematite,chlorite etc.Uranium ore bodies are mainly medium to small in scale,and of medium to low industrial grade.The research onmetallogenic regularity indicates that the multi-stage uranium mineralization occurred during the regional extension in the Meso-Cenozoic.Granite-type uranium deposits are distributed near the contact zones or in the internal tectonic junction of granite rock bodies from the Caledonian uplift area.The orebodies along the fracture and in the erosional geological bodies are distributed in the"metallogenic crust"between the oxidation-reduction interface and the transition plane of brittle and ductile structure.The"holomorphic space"uranium mineralization model shows that there could be potential mineralization places in different tectonic layers,formations,lithology and spaces.However,the types,scales,and metallogenic times of uranium deposits are different due to the diversity of metallogenic conditions in different sites implying thatno space can be excluded as a potential site for mineralization.Under this assumption,new uranium prospecting breakthroughscan be made based on the specific ore-forming conditions in the working areas.Summarising,the uranium mineralization in the Nanling metallogenic belt in Mesozoic-Cenozoic is comprehensively analyzed from different perspectivein this study based on the recognition of"holomorphic space mineralization".