二连盆地铀矿床成矿类型及时空分布特征

Metallogenic Types and Spatiotemporal Distribution Characteristics of Uranium Deposits in Erlian Basin

二连盆地具有铀矿床成矿类型多的特点,其表现在产出部位、层位、沉积相等均有一定的差异,而探讨不同类型铀矿床的划分及时空分布特征等,对铀矿勘探具有重要的指导意义。以含矿岩性、构造位置、水文地质结构、铀产出层位、沉积相及铀成因类型等条件为依据,将二连盆地铀矿床类型划分为了两个大类4个亚类,各亚类铀矿床产于特定的构造、层位、沉积相、水文地质等环境之中。二连盆地铀矿床成矿时代主要集中于晚白垩世至古近纪末期,受断陷盆地性质的影响,铀成矿年龄多集中于地层沉积间断期;在沉积间断期盆地内的地层出露、古地貌、古水文地质等条件决定了铀成矿作用的发生及规模,而在沉积期,上覆泥岩地层的发育,易阻断铀的成矿作用。综合二连盆地不同类型铀矿床时空分布特征,提出了应从识别沉积间断期的地层出露、沉积相展布、地下水动力等铀成矿环境入手,在不同的断陷构造部位应注重相应层位、相应沉积相、相应类型铀矿床的勘查。

There are many genetic types of uranium deposits in Erlian Basin,which are different in the occurrence position,horizon and sedimentary faces.The division and spatiotemporal distribution characteristics of different types are of great significance for uranium exploration.Based on the study of ore bearing lithology,structural location,hydrogeological structure,uranium producing horizon,sedimentary facies and uranium genetic type,the types of uranium deposits in Erlian Basin were divided into two categories and four subcategories.Each subcategory of uranium deposits occurs in a specific environment of structure,horizon,sedimentary facies and hydrogeology.The metallogenic age of uranium deposits in Erlian basin is mainly from Late Cretaceous to the end of Paleogene.Influenced by the nature of faulted down basin,the uranium mineralization age was mainly concentrated in the interval of stratum sedimentation.The occurrence and scale of uranium mineralization were determined by the strata outcroping,paleogeomorphology and paleohydrogeology of the basin during the period of sedimentary discontinuity.However,the development of overlying mudstone strata blocked the formation of uranium mineralization.Based on the spatial and temporal distribution characteristics of different types of uranium deposits in Erlian Basin,it was suggested that the uranium metallogenic environment should be recognized from the aspects of strata outcropping,sedimentary facies distribution,groundwater dynamics,etc.,and that the exploration of corresponding strata,sedimentary facies and types of uranium deposits should be focused on the different fault subsidence structural positions.