【作者】 胡亮；

【导师】 吴柏林；

【作者基本信息】 西北大学 ， 矿物学、岩石学、矿床学， 2010， 硕士

【摘要】 研究区主要的蚀变类型有绿色化、碳酸盐化、氧化蚀变、漂白现象等,与东胜矿床中铀的富集现象一起构成了本区较为独特的一系列流体作用现象。对其地质地球化学特征及成因的研究探讨,为该区铀的富集及成因提供了十分丰富的认识。认为早期形成铀矿化的古层间氧化带在强还原性环境下,经二次还原作用改造形成了控矿的绿色蚀变带,二者皆具有低有机碳,低∑S,高Th／U的特征。铀矿化岩石其有机碳、在各蚀变阶段中最高,Th／U最低。分布于延安组顶部的漂白现象是表生氧化岩石在还原性环境下经还原改造形成,其Th／U比值高, TFe含量低。总之,绿色蚀变和漂白现象及铀矿化的形成处于一种相对较强的还原性环境,而这种环境与本区大规模发生的油气逸散作用有关。通过对“钙化木”中方解石及含矿层中方解石脉体的包裹体进行激光拉曼光谱探针测试成份、均一法测温度等的测试,认为蚀变流体主要含有天然气成分,而且这种流体为来源于沉积盆地内的低温热流体。对其它蚀变类型石英增生边和方解石胶结物的包裹体研究认为含有较多的盐水包裹体组成,流体具有常温大气水组成的特点。综合认为,本区各蚀变的流体组成由大气水、低温热液及逸散油气等成份混合组成。通过选择透镜状碳酸盐及”钙化木”中方解石进行碳、氧同位素分析其碳质来源与油气等有机质流体作用有关；黄铁矿中硫同位素数据分析表明,黄铁矿硫源具有生物细菌-煤质共同作用的特点；白色化岩石中高岭石氢氧同位素说明曾遭受热液作用而非风化成因；流体包裹体的氢氧同位素研究表明,成矿溶液地下水来源于表生浅层的大气降水。综合分析得出了东胜铀矿区各蚀变的形成为“大气降水-逸散油气-煤质有机酸-低温热液”混合流体作用系列结果的认识。进一步在实验室通过对天然气还原氧化砂岩含铀溶液的模拟研究表明,在天然气的作用下,氧化砂岩中的粘土矿物发生了一定的类型转化,并同时出现了铀的沉淀现象,这一结果很好地说明了东胜矿床铀富集及各蚀变发生的机理。更多还原

【Abstract】 The main types of the rock alteration in study area include green alteration, carbonatization,oxidation alteration,bleaching phenomenon.Together with uranium enrichment in Dongsheng deposit,forms a unique series of fluid phenomenon. The paper deals with geological-geochemical characteristics and genesis to provide a rich understanding in generation and accumulation of uranium.Under strong reducing environment condition, the early interlayer oxidation zone was reformed and formed ore-controlling green alteration zone after twice deoxidizations. These two systems both have low organic carbon, low∑S, high Th /U. Uranium mineralizated rocks have the highest organic carbon and the lowest Th/U. The bleaching phenomenon on the top of Yan’an Formation was formed after hypergene oxydic rocks’reduction and reformation in reducing environment. The bleaching rocks have high Th /U and low TFe.In short, green alteration, bleaching phenomenon and uranium mineralizating are formed in a relatively strong environment which relates to large scale hydrocarbon dissipation in this area.The inclusions in the calcite in "calcified wood" to observe and test the composition by the Laser Raman Microprobe, the temperature is tested with the inclusion homogenization method. The results showed that the fluid mainly contained gas component and derived from hydrothermal fluids in the sedimentary basin. Based on the fluid inclusions study in the secondary concrescence of quartz edge and calcite cements in other types of rock alterations, it is found that inclusions have lots of saltwater inclusions and fluid composed with normal temperature atmospheric water. It is concluded that the alterated fluid in this area consists of atmospheric water, epithermal and dissipation hydrocarbon.Based on the carbon and oxygen isotope analyzing in lenticular carbonate and "calcified wood", it is found that carbon source relates fluid action of organic matter; Sulfur isotope analysis in pyrite showed that sulfur source has the characteristic between the biological bacteria and coal; The hydrogen and oxygen isotope in kaolinite showed that it suffered hydrothermal activity rather than weathering; The hydrogen and oxygen isotope in fluid inclusion showed groundwater of mineralizing fluid rooted in hypergene superficial atmospheric precipitation. It is concluded that, the formation of Dongsheng deposit is the result of mixed fluid action by " atmospheric precipitation-dissipation hydrocarbon-coal organic acids-epithermal".Combined with experiment on bleaching and green sandstone by fluid, proved that the clay minerals of oxidation sandstone have changed and precipitated of uranium at the same time under the gas action, it is a good model to explain enrichment of uranium in Dongsheng deposits and the alteration mechanisms.更多还原