二连盆地西部白彦花地区砂岩型铀矿地质特征及控矿因素分析

Geological characteristics and prospecting factors of sandstone type uranium deposits in Baiyanhua area,Western Erlian Basin

白彦花铀矿为近几年二连盆地川井坳陷取得找矿新进展的矿区。通过煤田放射性异常钻孔筛选和地物化遥综合信息解译圈定了成矿有利地区,经钻探揭露发现了工业铀矿体。矿体在平面上呈近北西向展布,钻孔初步控制长度6.5 km,宽度200~800 m,产状平缓,铀矿体主要赋存在下白垩统赛汉组砂岩中,以平整的板状为主,矿石较疏松。铀的赋存形式以吸附态铀为主,其次铀矿物以铀石为主,赋存于矿化砂岩的填隙部位及碎屑物或矿物的解理中,交代黄铁矿、炭屑等;其余分散的铀被砂岩填隙物中的粘土矿物、碎屑物和矿物颗粒表面或裂隙面吸附。矿区主要蚀变类型包括褐铁矿化、赤铁矿化、高岭土化、绿泥石化和碳酸盐化等。含矿岩石地球化学特征表现为亏损高场强元素和重稀土元素,轻重稀土分异特征明显,Eu具有明显的负异常。铀矿体与坳陷内构造与沉积体系的形成密切相关,多种成矿有利条件相互耦合使其富集成矿。该认识深化了二连盆地川井坳陷的成矿认识,为下一步工作部署提供理论依据。

Baiyanhua uranium deposit is a new prospecting area in Chuanjing depression of Erlian basin in recent years.Through the screening of radioactive anomaly boreholes and the interpretation of geophysical and geochemical remote comprehensive information in the coalfield,the favorable metallogenic areas were delineated,and the industrial uranium ore bodies were discovered through drilling.The ore body is distributed in a nearly northwest direction on the plane.The initial control length of the borehole is 6.5 km,the width is 200~800 m,and the occurrence is gentle.The uranium ore body is mainly hosted in the sandstone of the Saihan Formation of the Lower Cretaceous,mainly in flat plate shape,and the ore is relatively loose.The occurrence form of uranium is mainly adsorbed uranium,and the uranium mineral is mainly uranium ore,which occurs in the fillings of mineralized sandstone and in the cleavage of clastic materials or minerals,replacing pyrite,carbon chips,etc;Partially dispersed uranium minerals are adsorbed by clay minerals,detritus and mineral particle surfaces or fracture surfaces in sandstone fillings.The main alteration types in the mining area include limonitization,hematite mineralization,kaolinization,chloritization and carbonation.The geochemical characteristics of ore bearing rocks are characterized by depletion of high field strength elements and heavy rare earth elements,obvious differentiation of light and heavy rare earth elements,and obvious negative anomaly of Eu.Uranium ore bodies are closely related to the formation of structures and sedimentary systems in the depression,and a variety of favorable metallogenic conditions are coupled to each other to enrich and mineralization.This understanding deepens the metallogenic understanding of Chuanjing Depression in Erlian Basin,and provides a theoretical basis for the next work deployment.