Investigation of the Crystal Chemistry of Pb Uranyl Oxide Hydrate Minerals Using a CCD-Based X-Ray Area Detector

9804723燃烧六价铀（铀酰）矿物在铀矿床的氧化部分中很常见，对于了解铀矿床中的水-岩石相互作用、环境中锕系元素的流动性、铀矿和尾矿的风化以及地质处置库中乏核燃料的蚀变都很重要。本研究将集中在铅铀氧化物水合物矿物发生在前寒武纪铀矿床的风化部分，以及在风化的尾矿，从这些资源的利用。这些结构复杂的矿物包含几个不同的片铀酰多面体，铅阳离子和水分子位于层间位置。初步工作表明，这些矿物在某些结构类型中表现出相当大的成分变异性，并导致假设铀酰多面体中的阴离子取代可能是允许层间含量变化的电荷平衡机制。铅铀酰氧化物水合物矿物vandendriesscheite，fourmarierite，curite，richetite，sayrite，wlsendorfite将使用广泛的晶体学研究，微探针分析和矿物类似物的合成进行研究。这些研究将提供这些复杂矿物的晶体化学可变性的细节。调查结果将用于扩展铀酰矿物的结构层次，并了解这些和其他低温矿物的结构和共生关系。

9804723BurnsHexavalent uranium (uranyl) minerals are common in the oxidized portions of U deposits, and are important for understanding water-rock interactions in U deposits, the mobility of actinides in the environment, the weathering of U mine and mill tailings, and the alteration of spent nuclear fuel in a geological repository. This study will focus on Pb uranyl oxide hydrate minerals that occur in the weathered portions of Precambrian U deposits, as well as in weathered mine tailings that result from the utilization of such resources. These structurally complex minerals contain several different sheets of uranyl polyhedra, with Pb cations and water molecules located in interlayer positions. Preliminary work has demonstrated that these minerals show considerable compositional variability within some of the structure types, and led to the hypothesis that anionic substitution in the sheets of uranyl polyhedra may be the charge-balancing mechanism that permits variation of the interlayer content. The Pb uranyl oxide hydrate minerals vandendriesscheite, fourmarierite, curite, richetite, sayrite, and wlsendorfite will be investigated using extensive crystallographic studies, microprobe analysis, and the synthesis of mineral analogues. These studies will provide the details of the crystal-chemical variability of these complex minerals. The results of the investigations will be used to extend the structural hierarchy of uranyl minerals, and to develop an understanding of the relationship between the structures and paragenesis of these and other low-temperature minerals.