二连盆地巴彦乌拉铀矿床氧化带发育样式与岩石地球化学特征

Oxidation Zone Developing Pattern and Petrogeochemical Characteristics of Bayanwula Uranium Deposit in Erlian Basin

砂岩型铀矿床的形成受氧化带空间展布、规模及强度的影响,对其氧化带发育样式及其岩石地球化学特征的精细解剖,有助于揭示区域铀成矿规律,为下一步勘探提供理论依据。巴彦乌拉铀矿床是二连盆地发现的大型砂岩型铀矿床,文章通过钻孔岩心观察、连井剖面、样品薄片鉴定以及环境指标分析,认为巴彦乌拉铀矿床铀元素的富集程度主要由后生氧化作用的发育程度决定,宏观上,矿体赋存在赛汉组上段古河谷砂体中,受由北向南的潜水-层间氧化作用控制;微观上,铀矿化的富集与矿物组合、岩石地球化学特性及特征元素的分布呈现出明显的规律性。不同的氧化带样式决定了铀矿体的产出部位和形态,而铀含量增高的地方恰好为ΔEh、S_(全)、S^(2-)、C_(有)、CO_(2)、Fe_(2)O_(3)等环境指标的增高部位,表明铀成矿与岩石地球化学障密切相关。

The formation of sandstone type uranium deposit is affected by the spatial distribution,scale and intensity of the oxidation zone.Detail analysis on the developing pattern of the oxidation zone and its petrogeochemical characteristics will benefit the establishment of regional uranium metallogenic pattern and provide theoretical basis for further exploration.Based on the field drilling core observation,cross-borehole profile,thin section identification and environmental index sample analysis in the large scale Bayanwula uranium deposit in Erlian Basin,the uranium enrichment level was found mainly determined by the developing level of epigenous oxidation.Macroscopically,the ore body exists in the sand body of paleo valley in the upper member of Saihan Formation and controlled by phreatic interlayer oxidation from north to south.In microscopic level,the uranium enrichment,mineral assemblage,geochemical characteristics and indicative elements distribution can be divided into full oxidation subzone,weak oxidation subzone,weak reduction subzone and reduction zone and the oxidation zone presents vertical,lateral and vertical superimposed lateral modes in space.