Abstract

The paper reports geochemical and mineralogical data on ores of the Briketno-Zheltuhinskoe U–Mo–Re deposit, which is confined to the Visean paleochannel coal-bearing sandy sediments of the Moscow lignite basin. In addition to main ore elements (Re, Mo, U, and Se), the ores have elevated contents of the following metals (in order of decreasing abundance): Zr, Zn, Mn, Ni, As, Co, V, Pb, Y, Cu, and highly dispersed Tl and Ag. It was found that Re correlates positively with Mo, Ag, Zn, U, Se, and Co. The ores are incoherent and analytical scanning electron microscopy is the main method applied for their study. In order to clarify the speciation of U, Mo, and Re, sequential extraction experiments were performed. The main part of Re is associated with the organic and ion-exchange forms. Molybdenum is approximately equally distributed between the strongly bound (sulfide) and organic-related forms. Uranium mainly occurs in a weakly bound form and easily migrates with water. Authigenic minerals are mainly represented by pyrite, less common marcasite, and accessory sulfides (sphalerite, chalcopyrite, galena, etc.) and selenides (dzharkenite, clausthalite). Mo-minerals (containing up to 1.5 wt % Re) are represented by the tiny grains of molybdenite and jordisite. Uranium occurs as micron-size inclusions of uraninite (pitchblende) in colloform pyrite and is present as a macro-impurity in rhabdophane and zircon. The predominant part of U, Mo, and Re was found in adsorbed forms in carbonaceous, clayey, and strongly altered sulfide particles. Arkose and subordinate ash material together with heavy metals (Fe, Ni, Cu, Zn, Pb, U, Mo, Re), and also S and Se, were transported by river streams and accumulated in terrigenous sediments of shallow marine basin. These elements were adsorbed by plant detritus and, partly, by clay particles and iron oxyhydroxides/sulfides during diagenesis. The main economic U–Mo–Re ores were formed at the second, epigenetic stage, in the course of the lateral filtration of oxygenated groundwater through highly permeable sand horizons. This process was accompanied by the redeposition of U, Mo, Re, Se, Cu, Ni, and Zn from dispersed mineralization of the first stage at the reducing (plant detritus) and sorption (clay sediments) geochemical barriers. In this case, U, Mo, and Re were fixed in the mineral and, mainly, adsorbed forms. Significant contribution to the ore formation was likely provided by endogenous factors associated with activation of faults in the East European Platform (EEP) basement, epiplatform alkaline-basaltic magmatism, and the influx of deep fluids into the ore deposition zone.

中文翻译：

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俄罗斯板块石炭纪含煤砂中独特的R矿床：通讯2.矿石矿物学

摘要

本文报道了Briketno-Zheltuhinskoe U-Mo-Re矿床的矿石的地球化学和矿物学数据，该矿床仅限于莫斯科褐煤盆地的Visean古河道含煤砂质沉积物中。除了主要的矿石元素（Re，Mo，U和Se）外，矿石中以下金属的含量也有所增加（按含量递减的顺序）：Zr，Zn，Mn，Ni，As，Co，V，Pb， Y，Cu和高度分散的Tl和Ag。研究发现，Re与Mo，Ag，Zn，U，Se和Co呈正相关。矿石是非相干的，分析型扫描电子显微镜是研究的主要方法。为了阐明U，Mo和Re的形态，进行了顺序提取实验。Re的主要部分与有机和离子交换形式有关。钼在牢固结合的（硫化物）形式和与有机有关的形式之间近似均等地分布。铀主要以弱结合形式存在，并且容易与水一起迁移。自生矿物主要以黄铁矿，较少见的白铁矿和辅助硫化物（闪锌矿，黄铜矿，方铅矿等）和硒化物（铅锌矿，硅镁石）为代表。钼矿（含不超过1.5 wt％的Re）以辉钼矿和芒硝的细小晶粒为代表。铀是在黄铁矿中以微米级大小的铀矿（斜晶石）夹杂物形式存在的，在横纹石和锆石中以宏观杂质的形式存在。发现U，Mo和Re的主要部分以吸附形式存在于碳质，粘性和强烈变化的硫化物颗粒中。阿古斯和次要灰分材料以及重金属（铁，镍，铜，锌，铅，铀，钼，Re）S和Se以及S和Se都是通过河水运输的，并堆积在浅海盆地的陆源沉积物中。这些元素被植物碎屑吸附，部分被成岩过程中的粘土颗粒和羟基氧化铁/硫化铁吸附。主要的经济铀钼矿石是在表观生化的第二阶段形成的，这是通过高渗透性砂层对含氧地下水进行侧向过滤的过程。此过程伴随着还原，植物碎屑和吸附（粘土沉积物）地球化学屏障中第一阶段分散矿化过程中的U，Mo，Re，Se，Cu，Ni和Zn的重新沉积。在这种情况下，U，Mo和Re以矿物形式（主要是吸附形式）固定。