鄂尔多斯盆地东胜砂岩型铀矿微量和稀土元素地球化学特征

鄂尔多斯盆地东胜砂岩型铀矿的微量和稀土元素能为铀矿勘查提供地球化学标志。以东胜铀矿层位侏罗系及其中铀矿化为对象,针对砂岩型铀矿石、铀矿化砂岩和围岩几类地质体进行元素地球化学对比研究。东胜砂岩型铀矿微量元素地球化学特征表明,Pb、Mo与U关系极为密切,它们在铀矿石中最富集,铀矿化砂岩中次富集,砂质和泥质围岩中不富集;Pb和Mo可以作为东胜铀矿床矿化的指示元素,Pb、U和Mo蛛网图上构成的"W"式样可作为东胜地区砂岩铀矿化的指示模型。铀矿石、铀矿化砂岩、砂岩以及泥岩表现出相似的REE地球化学特征和配分模式,推断其具有统一的物源、沉积环境和构造背景。部分铀矿石明显富集HREE,显然在沉积成岩后期经历了(热液)改造作用。东胜铀矿化经历了沉积成岩和热液改造作用两个成矿阶段。

Trace Element and REE Geochemical Characteristics of Sandstone-type Uranium Deposit in the Dongsheng Area of the Ordos Basin,China

This study examines the geochemical characteristics of the Dongsheng sandstone-type uranium deposit in the Ordos basin in order to find geochemical signals that are useful for uranium deposit exploration.Trace element analyses were carried out for uranium ores,uranium-mineralized sandstones,and non-mineralized country rock(sandstones and shales).The results indicate that Pb and Mo have close relationships with uranium mineralization,with the highest concentrations in the uranium ores,then in the uranium-mineralized sandstone,and lowest in country rocks.Therefore,Pb and Mo can be used as indicator elements for uranium mineralization.This is reflected by the "W" pattern(three peaks representing Pb,U and Mo) in the spider diagram.REE patterns suggest that the ores,mineralized sandstones and non-mineralized country rocks were initially formed from the same material sources,sedimentary environments and tectonic settings.The fact that some of the uranium ores are enriched in HREE relative to other uranium ores suggests two stages of uranium mineralization,a diagenetic stage overprinted by a hydrothermal mineralization.