CO₂+O₂地浸采铀后铀储层中残留铀的产状及成因机制对改进地浸采铀工艺及提高铀浸出效率具有重要意义，但国内外对这方面的研究却很少.鉴于此，以内蒙古钱家店铀矿床地浸开采前后钻孔岩心样品为研究对象，利用扫描电镜及能谱分析识别出3种残留铀产状类型：铀矿物、吸附态铀和含铀矿物，其中，铀矿物包括铀石及沥青铀矿两类，多分布在石英、长石等碎屑颗粒的溶孔中、碳质碎屑内部及边缘、高岭石内部及边缘以及高岭石包裹下的黄铁矿边缘，吸附态铀主要以被粘土矿物和碳质碎屑吸附的形式存在，而含铀矿物包括含铀独居石、含铀锆石以及含铀钛矿物等.对比地浸前后岩心样品中铀的产状变化发现：①与碎屑颗粒伴生的铀矿物中，观察到石英、长石、岩屑溶孔内部的铀矿物和与碳质碎屑伴生的铀矿物残留，未观察到云母解理缝内以及碎屑颗粒边缘的铀矿物残留；②与填隙物伴生的铀矿物中，观察到与黄铁矿和高岭石伴生的铀矿物残留，未观察到与菱铁矿相伴生的铀矿物残留；③高岭石与碳质碎屑吸附铀残留；④碎屑颗粒间的含铀矿物残留.以此为基础，探讨了地浸过程中赋矿层中铀残留的4种成因机制：①由于缺乏有效连通孔隙，浸出剂难以充分接触到碎屑颗粒内部铀矿物，导致碎屑颗粒内部铀矿物残留；②高岭石会堵塞流体运移通道使得与其伴生的铀矿物难以被浸出而残留；③高岭石自身结构具有吸附性且在酸性条件下稳定，导致其吸附的铀难以被浸出而残留，而富含碳质碎屑的区域由于其较强的还原能力、吸附能力以及其区域内较差的流通性导致其吸附的铀无法被浸出而残留；④含铀矿物不易与浸出剂反应导致铀无法浸出.研究表明赋矿层中铀的产状是影响其浸出的重要因素，成果将为改进地浸工艺、提高铀浸出效率提供矿物学方面依据.

The occurrence and genetic mechanism of residual uranium in uranium reservoirs after CO₂ + O₂ in-situ leaching of uranium are highly important for improving the in-situ leaching process and leaching efficiency of uranium, but few studies have been conducted in this field. Therefore, this work takes mineralized sandstones and drilling core samples after in-situ leaching of uranium as the research object in the Qian II block of the Qianjiadian uranium deposit in Inner Mongolia. Three types of residual uranium were identified via SEM-EDS analyses: uranium minerals, adsorbed uranium and minerals containing uranium. In the samples after in-situ leaching, uranium minerals include coffinite and pitchblende, which are mainly distributed in the dissolved pores of clastic particles or inside and around clay minerals such as kaolinite. The adsorbed uranium is adsorbed mainly by clay minerals and carbonaceous debris, whereas minerals containing uranium include mainly monazite containing uranium, zircon containing uranium and titanium minerals containing uranium. A comparison of the occurrence of uranium in the mineralized sandstones before and after in-situ leaching reveals the following. (1) In the types of uranium minerals associated with clastic particles, the residual uranium minerals inside the quartz, feldspar, rock debris and carbonaceous debris were observed, whereas no residual uranium minerals at the edge of clastic particles, or inside the mica joints were observed. (2) In the uranium minerals associated with interstitial material, residual uranium minerals associated with pyrite and kaolinite were observed, and no residual uranium minerals associated with siderite were observed.(3) Uranium adsorbed by kaolinite and carbonaceous debris was retained. (4) Minerals containing uranium retains between clastic particles. On the basis of above observations and analyses, four genetic mechanisms of uranium residue in uranium reservoirs during in-situ leaching are proposed. (1) Because of the lack of effective interconnected pores, the in-situ leaching solution has difficulty flowing through the uranium minerals inside the clastic particles, resulting in formation of the uranium residual uranium minerals.(2) Kaolinite can block fluid transport channels, making it difficult to leach uranium minerals associated. (3) Kaolinite has adsorption properties and is stable under acidic conditions, which makes it difficult for the adsorbed uranium to be leached out. Uranium cannot be leached in areas rich in carbonaceous debris because of its strong reduction ability, adsorption capacity and poor circulation in the area. (4) Minerals containing uranium have difficulty reacting with the leaching agent, which results in incomplete leaching. This research has shown that the occurrence of uranium in the mineralized sandstone is an important factor affecting its leaching, and the results provide a mineralogical basis for improving in-situ leaching processes and enhancing uranium leaching efficiency.