铀石-沥青铀矿稠密韵律生长环带及其成因意义

本语文报道某铀矿床中铀石与沥青铀矿交互生成多达２０环稠密韵律生长环带,结合该矿床物气液包裹体研究资料和文献资料,探讨生成这一罕见奇特结构的介质物理化学条件及机制。该结构具有指示成矿流体ｐＨ－Ｆｈ状态和ＳｉＯ２活度演化的标型意义。     

粤北下庄335矿床成矿时代的厘定——来自LA-ICP-MS沥青铀矿U-Pb年龄的制约

文章采用LA-ICP-MS测试技术对下庄矿田335矿床的沥青铀矿开展了U-Pb微区定年工作.335矿床沥青铀矿的成分特征及微观形貌特征显示,本区沥青铀矿在初始形成之后受到过后期的一些地质事件的影响.本次获得沥青铀矿的最大年龄为(93.5±1.2) Ma.结合华南岩石圈伸展发生的时间、辉绿岩脉对铀矿的控制作用及矿区内辉绿...     

Uranium Behavior in the Process of Primary Pitchblende Ores Alteration by the Post‐ore Hydrothermal Solutions: An Application to Assessment of Uranium Migration from Underground Spent Nuclear Fuel Repositories

It has been shown that the main uranium ore mineral, pitchblende (uranium dioxide), is a natural analog of synthetic uraninite (also uranium dioxide), which constitutes 96% of spent nuclear fuel (SNF). Geochronological studies of the U‐Pb isotope systems in unaltered pitchblende from the orebodies reveal that these systems remained completely closed over the entire period (approximately 135 Ma) since the formation of the deposits. The bulk of the primary uranium ores within the Streltsovskoye ore field was influenced to various degrees by post‐ore hydrothermal solutions that led to pitchblende spherulites being replaced by pseudomorphs of an amorphous phase with a U‐Si composition; this phase also re‐precipitated in veinlets proximal to the pitchblende pseudomorphs. A technique specially developed by the authors was used to carry out quantitative counts of the abundance of uranium minerals by calculating the uranium mass balance in one of the orebodies subjected to hydrothermal alteration. The calculations reveal minimal uranium loss from the orebody. Uranium liberated in the process of the pseudomorphic replacement of pitchblende was immediately fixed, in situ, in the newly formed coffinite‐like amorphous U‐Si phase as a result of the development of an efficient geochemical barrier that prevented the long‐distance migration of uranium. In assessing the long‐term safety of underground SNF repositories, the results of the present study give us confidence that SNF uraninite, in terms of the preservation of its integrity as a mineral phase, provides for the reliable long‐term isolation of uranium, transuranium elements, and fission products that are “sealed” in the uraninite matrix. In the case of the mineral transformation of the uraninite matrix by hydrothermal solutions, the liberated uranium would be efficiently immobilized by the newly formed amorphous U‐Si phase.     

某铀钨矿床中钨矿化特征及其成因研究

铀钨矿床是一种新矿床类型。其主要矿物是白钨矿和沥青铀矿，它们既有共生，也有伴生。钨以白钨矿细脉、分散状微粒白钨矿和吸附状等形式产出。钨与铀的成矿过程可划分为六个阶段。矿岩时差较大。钨来源于已固结的花岗石，它是由地下热水或热卤水从已固结的花岗岩中浸取出来的。钨（铀）矿化是在低温条件下，在有利的构造岩性中沉淀富集而成的，不是岩浆热液矿床     

Experimental study on reduction of U (VI) by an anaerobic bacterium, <Emphasis Type="Italic">Shewanella putrefaciens</Emphasis>: Application to sandstone-hosted interlayer oxidation-zone type uranium deposits,China

An experimental study on reduction of U (VI) by anaerobic bacteria, Shewanella putrefaciens, is first reported here in China. The experimental conditions were: 35°C and pH= 7.0-7.4, corresponding to a physicochemical environments in which the sandstone-hosted interlayer oxidation-zone type uranium deposit formed in Northwest China’s Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural environment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2-4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water environments and for underground dissolving extraction of the sandstone-hosted uranium ores.     

桂北沙子江铀矿床成矿年代学研究：沥青铀矿U-Pb同位素年龄及其地质意义

苗儿山矿田为中南地区五大铀矿田之一,其内分布有我国最大规模碳硅泥岩型的铲子坪铀矿床及诸多花岗岩型铀矿床,沙子江矿床为矿田内重要的花岗岩型铀矿床之一。沥青铀矿是理想的铀矿床直接定年样品,同时,也是U-Pb同位素研究的理想矿物。本次研究以沥青铀矿为对象进行U-Pb同位素分析,获得了沙子江矿床早、晚两期铀成矿作用的年代分别为104.4Ma和53.0±6.4Ma,结合铲子坪矿床主成矿期年代74.1±9.9Ma,它们可能分别代表了苗儿山矿田3期主要铀成矿作用的时代。沙子江矿床等时线拟合所得高的初始Pb值反映了该期成矿作用之前存在铀的预富集作用。3期成矿作用与华南地区基性脉岩年代数据统计反映的岩石圈伸展期次相对应,暗示了铀成矿受控于华南岩石圈伸展这一大的动力学环境。     

粤北地区302矿床沥青铀矿的形成时代、地球化学特征及其成因研究

302铀矿床位于诸广山岩体东南部,是中国花岗岩型铀矿床中规模较大、埋藏较深的矿床。研究表明,沥青铀矿的U-Pb和Sm-Nd等时线年龄分别为(68.7±2.7)Ma和(70±11)Ma,与华南花岗岩型铀矿床的主成矿期一致。沥青铀矿低的εNd(t)值(-11.3～-13.1)、古老的Nd模式年龄(1.76～1.88Ga)以及它们的微量元素和稀土元素组成都与赋矿围岩油洞岩体,尤其与长江岩体十分相似,表明铀源可能主要来源于赋矿花岗岩体,尤其是长江岩体。     

电子探针化学测年法在晶质铀矿/沥青铀矿定年研究中的应用现状

简要介绍近年发展起来的各种微区测年方法及其优缺点,重点介绍不同时期电子探针化学测年法在晶质铀矿/沥青铀矿定年研究中的发展状况及前人使用的分析测试条件,并展望了该方法在晶质铀矿/沥青铀矿定年研究中的应用前景及可能存在的问题。通过系统研究,认为该方法在铀矿物定年研究中将大有作为,尤其是在微小铀矿物（〈10μm）和多期次、多阶段铀矿体的微区定年研究中更能显示其优越性。     

某沥青铀矿石堆浸性能的研究

简要介绍了铀矿床的类型和铀矿石的分选方法,重点介绍了某火山岩型铀矿床硬岩类原生沥青铀矿石的实验室溶浸试验。试验结果表明,该沥青铀矿石在用天然铁锰矿石为氧化剂的条件下,经过123d实验室溶浸试验,铀浸出率可达78.92%。