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西秦岭铀矿床含矿热液物理化学条件改变对铀沉淀影响 总被引:2,自引:0,他引:2
本文研究了西秦岭铀矿床含矿热液物理化学条件的改变对铀沉淀富集的影响。研究表明,铀在相对还原条件下迁移,而在相对氧化条件下沉淀富集。铀的沉淀富集主要发生在含矿热液的温度、压力和氧逸度大幅度降低,酸性增强及氧化-还原电位增高的物理化学条件下。 相似文献
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利用热力学方法计算了西秦岭铀矿床含矿热液中铀的迁移形式。结果表明,从含矿热液早阶段到主成矿作用发生之前,热液中的铀主要以「UO2(CO3)^0」形式迁移;在晚阶段残余热液中,铀的迁移形式改变为「UO2(SO4)^0」为主。铀迁移形式改变的原因与大气降水中SO^2-4离子的大量带入有关,表明含矿热液来自深部而非大气降水。 相似文献
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本文通过底苏和大梁子铅锌矿床硫铅及氢氧同位素,认为同生沉积成岩成矿阶段矿石硫来源于赋矿围岩或同生沉积成岩成矿阶段矿层,矿石铅主要来源于矿区地层,改造热液中的水主要来自大气降水,成矿热液属大气降水含热液。 相似文献
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利用山门银矿包裹体的测试数据,在分析研究其成矿热液理化特征的基础上,得出山门银矿床是在浅成低温、低压环境中,由以贫硫、低盐度,酸性大气降水为主的含矿热液,在低还原条件下形成的结论。 相似文献
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纳岭沟铀矿床是近年来在鄂尔多斯盆地北部发现的一个大型铀矿床。与典型层间氧化带砂岩型铀矿不同,纳岭沟铀矿床具有矿体呈板状、似层状产出与铀矿物以铀石为主等特点。文章通过扫描电镜与X衍射等方法对含矿层不同地球化学分带砂岩黏土矿物组合类型、相对含量的变化开展了系统的研究,为该区铀成矿模式与板状矿体的形成机制提供依据。研究结果表明,含矿层砂岩中黏土矿物以呈蜂窝状、片絮状产出的蒙脱石为主,其次为呈片状、书页状及蠕虫状产出的高岭石与呈叶片状、花朵状集合体产出的绿泥石,局部可见伊利石与蒙脱石向绿泥石转化而成的绿蒙混层;从二次还原绿色带→矿带与原生带,呈现蒙脱石、绿泥石明显减少,高岭石含量与w(TOC)、CH_4明显增加的趋势,说明二次还原绿色带与矿带之间存在E_h-pH突变界面;含矿层经历了弱碱性大气降水(含铀含氧)、酸性流体(有机酸与煤成气)、中-低温碱性热液油气与富Na~+、Ca~(2+)的弱碱性流体(盆地卤水)的共同作用,其中弱碱性大气降水与中-低温碱性热液混合而成的碱性-氧化成矿热液与下伏延安组煤系地层演化产生的酸性-还原流体(有机酸与煤成气)在相互接触面上因Eh-pH突变而造成铀石的沉淀,并在E_h-pH突变界面上形成板状矿体。 相似文献
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原生有机质及沥青的有机地球化学研究结果表明矿区存在微弱的热异常,地层中原生有机质含量极低,沥青是成矿过程中由含矿热液他地带来的迁移型流体烃,流体迁烃在迁移时发生轻烃组分的分馏。在成矿部位,含有硫酸盐,铅锌和流体烃的深湖热液与携带硫酸盐还原细菌的大气降水汇合,流体烃发生生物降解和水洗溶解并引起硫酸盐的生物还原,生成硫化氢,导致铅锌硫化物沉淀,形成矿床。 相似文献
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Transport and deposition of uranium in hydrothermal ore fluids as exemplified by Uranium Deposit 302 总被引:2,自引:0,他引:2
Uranium Deposit 302 is a large hydrothermal uranium deposit occurring in fault zones within a granite. Pitchblende is the
only primary uranium mineral found in the ore. The associated minerals include quartz, fluorite, hematite and pyrite.
This paper focusses on the mechanism of transport and deposition of uranium in hydrothermal oreforming solutions responsible
for the deposit. It is concluded that uranium might be not only oxidized in a relatively reducing environment, but also reduced
in a relatively oxidizing environment, depending on the speciation of uranium in the solutions. The formation of pitchblende
is closely related to uranium reduction at the stage of uranium mineralization. 相似文献
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毛洋头火山岩铀(银、钼)矿床的控矿因素及成因 总被引:6,自引:1,他引:6
毛尖头铀矿床,是产于早白垩世晚期火山中的火山岩型矿床。基底构造和岩浆活化对矿床的形成起明显的控制作用,研究认为,该矿床成矿热液早期为岩浆水,晚期为大气降水;成矿元素U,Ag,Mo有不同来源;其中早期矿化热液中的铀主要来自次火山热液或次火山岩,而晚期成矿热液的铀主要来自基底岩石; 相似文献
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水溶液的pH值对铀沉淀的影响 总被引:2,自引:0,他引:2
形成酸性或碱性含铀溶液,而后又发生中和作用,这是形成铀矿床的一对极有利的条件。接近中性的水介质有利于铀的沉淀。中和作用是各种铀沉淀作用的触发钮。由中和作用引起的铀的还原沉淀作用称为中和还原作用。铀的还原沉淀是在水-铀比电位值△Eh_水~U<0的条件下发生的(△Eh_水~U=Eh_水-Eh_0~U)。铀的还原沉淀不仅是依靠Eh_水的降低,同时与Eh_水~U的回升或下降速率有关。花岗岩铀矿床中往往不存在强烈的还原剂,热液上升过程中,一般很难提高它的还原能力,这时中和还原作用就显得格外重要。这是研究铀矿成矿机制和富矿条件的一条新线索。 相似文献
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Vikt. L. Barsukov 《Geochemistry International》2006,44(12):1191-1214
By means of computer modeling, it was shown that the pre-uranium quartz and quartz-sulfide veins of the Schlema deposit with
their typomorphic assemblages could be formed at the expense of cooling of hot pore solutions from the Aue granite cupola
underlying the mineralized zones. As was shown previously [1], the ore metal content of these pore solutions changes with
decreasing temperature and pressure in the granite-water system and an increase in the intensity of granite “flushing” with
a water phase. The dependence of the composition of precipitated material on the proportions of chlorides and carbon dioxide
in the pore solutions was evaluated in the models. It was shown that silica mobilization from the granite and redeposition
were accompanied by the oxidation of ferrous iron in the granite and extraction of sulfide sulfur in molal amounts similar
to or even higher than those of silica. This provided conditions for uranium migration after these stages and formation of
hydrothermal uranium ores.
Original Russian Text ? Vikt.L. Barsukov. 2006, published in Geokhimiya, 2006, No. 12, pp. 1290–1314. 相似文献
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The solubility of methane in formation water and water content in the coexisting gas phase were measured under the conditions of high temperature and high pressure, using an ultra-high-pressure fluid PVT system, where the experimental temperature reached up to 453 K and pressure reached up to 130 MPa. Experimental results show the following (1) The two phases of gas and liquid still exhibit an obvious interphase interface even under high temperatures and pressures. (2) When temperatures exceed 353 K, the solubility of methane in formation water increases as the temperature and pressure rise. The growth rate of solubility is faster under a relatively low temperature and pressure, and slower at a relatively high temperature and pressure, but the solubility will not increase without limit. In this experiment, the solubility of methane in formation water reached its peak when the temperature was at 453 K and the pressure at 130 MPa. (3) Water content in the coexisting gas phase increases as temperature rises, with a smaller increase at relatively low temperatures and a much greater increase at relatively high temperatures but decreases with the increasing pressure, more rapidly under low pressure and more slowly under high pressure. The solubility of methane in formation water and the water content in the coexisting gas phase are controlled by both temperature and pressure, but using classic calculation models, these two parameters under high temperatures and pressures are inconsistent with our experimental data. Therefore, the study is significant and highlights other possible effects on solubility and condensate water content. Additionally, an example from the Yinggehai Basin in the South China Sea, where the temperature and the pressure are high, demonstrates the influence of solubility and phase behaviour on natural gas migration, its formation and the distribution of gas reservoirs. 相似文献
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湘西北地区位于扬子陆块东南缘,在其寒武系纽芬兰统海相磷块岩的微孔隙中发现nm~μm级晶质铀矿。文章通过扫描电镜对铀矿的空间占位进行微区解剖,确定铀以超显微状态(1~4μm)的晶质铀矿形式存在于方硫镍矿中。认为超显微晶质铀矿和辉砷镍矿是同沉积鲕粒状磷块岩在较高的温压条件下,通过海底喷流气水溶液强溶蚀改造并发生结晶时,以超显微包体的形式存在于方硫镍矿中;随着温度、压力的下降,包体中富铀溶液出现过饱和,晶质铀矿从富铀溶液中结晶析出,以独立矿物晶质铀矿的形式呈超显微状态存在于方硫镍矿中。晶质铀矿在中高温热液成矿作用中以超显微状态呈立方体、八面体、立方体与八面体的聚形以及块状体产出,对认识天然条件下晶质铀矿生成的物理化学条件具有重要意义。同时,晶质铀矿呈超显微状态存在的实例对该类型铀矿存在形式的发现和研究具有重要启迪,为揭示扬子陆块东南缘的陆缘裂陷中海底喷流成矿示踪提供了依据。 相似文献
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本文以621与670地区为例,概述了钠长石与水云母型铀矿产出的地质背景及成矿前期岩石的蚀变特征,综合分析了这两类蚀变岩型铀矿矿石结构构造、矿物成分、共生元素、成矿温度、成矿时间、流体成分及放射性场等方面的差异性。探讨了这两类铀矿不同的成因机制:钠长石型铀矿成矿物质主要来自围岩,铀以碳酸铀酰络离子[UO2(CO3)3]4形式搬运,铀的析出富集主要由溶液成分、碱度发生突变所引起;而水云母型铀矿成矿物质主要来自富铀的火山期后热液,铀以钼酸钠酰络离子[UO2(MoO4)2]2形式迁移,铀沉淀富集主要由溶液温度、压力降低所引起。 相似文献