粤北下庄矿田竹筒尖铀矿床铀镭平衡系数特征探讨

基于粤北下庄矿田竹筒尖铀矿床156个铀镭平衡系数样品,研究该地区铀镭平衡系数与铀含量、标高、岩性的变化关系,对这些变化关系进行综合整理分析,得出铀镭处于基本平衡略偏铀状态的分布特征。分析了铀镭平衡系数和铀含量之间的关系,当铀含量小于0.15%时,随着铀含量的逐渐增高,铀镭平衡系数减小,二者呈负相关关系;当铀含量大于0.15%时,铀镭平衡系数与铀含量的关系不明显。总结出铀镭平衡系数与标高的变化规律,由地表到深部,经历严重偏镭到偏铀再到基本平衡的过程。分析了铀镭平衡系数与硅化带、碎裂花岗岩、细粒黑云母花岗岩和中粒黑云母花岗岩的关系。上述成果为该地区物探编录和γ测井结果的准确计算、矿体边界的确定、铀矿资源量的估算提供了科学依据。     

论铀镭平衡问题

铀镭平衡系数是表征铀矿样品铀镭平衡状态的物理参数,对准确估算矿区的铀资源量,评价研究区的铀成矿潜力具有重要意义。本文从铀镭平衡系数的定义和计算方法出发,讨论了铀镭平衡系数在铀矿勘查过程中的作用和影响,以及不同类型铀矿床的铀镭平衡系数特征,强调造成铀镭不平衡的本质是在铀系的1个平衡周期内（约1.9 Ma）,发生了铀或镭的再分配,并分析了可能造成样品偏铀或偏镭的原因。     

地面伽马能谱测量在铀矿勘查中的应用——以黑龙江伊春威岭异常区为例

钍铀比、古铀量是伽马能谱测量中反映铀成矿信息的重要参数,可指示区域铀迁移路径、划分迁入富集区域,进一步提取铀成矿信息,判断铀成矿的可能性.这里以伊春威岭地区放射性异常为例,计算地面伽马能谱测量数据参数,对比铀含量与古铀量信息,进行方法有效性实验.实验表明:该区域内铀的迁出与迁入、淋失与富集被约束在糜棱岩化带内,存在二次...     

若尔盖铀矿田向阳沟铀镭平衡系数特征

铀镭平衡系数是衡量铀镭平衡状态的重要参数,不仅反映矿体所处的地球化学环境以及铀与镭的贫化、富集、迁移状况,也影响铀矿床储量计算的准确性和可靠性。通过计算了向阳沟矿床铀镭平衡系数,探讨了铀镭平衡系数与铀含量的关系,得出了向阳沟处于氧化—还原过渡带、矿床总体偏铀的结论,为修正该区测井解释结果、确定矿体边界、估算铀矿资源量以及预测成矿有利地段提供了科学依据。     

若尔盖铀矿田向阳沟铀镭平衡系数特征

铀镭平衡系数是衡量铀镭平衡状态的重要参数,不仅反映矿体所处的地球化学环境以及铀与镭的贫化、富集、迁移状况,也影响铀矿床储量计算的准确性和可靠性。通过计算了向阳沟矿床铀镭平衡系数,探讨了铀镭平衡系数与铀含量的关系,得出了向阳沟处于氧化—还原过渡带、矿床总体偏铀的结论,为修正该区测井解释结果、确定矿体边界、估算铀矿资源量以及预测成矿有利地段提供了科学依据。     

大气氡变化对航空伽马能谱测量的影响

笔者针对大气氡干扰伽马能谱测量的问题,研究了大气氡在气象变化时的规律,认为大气氡浓度变化易受气象因素控制,并对航空伽马能谱测量的总道和铀道产生较大的影响,根据下雨后3 h氡浓度逐渐趋于稳定的实验结果,在野外实际工作中,提出在一定气象条件下,其对航空伽马能谱测量的影响大小及需要采取的应对措施。     

地面伽马能谱测量在铀矿找矿中的应用研究--以黑龙江省嘉荫县磨石山地区为例

黑龙江省嘉荫县磨石山地区为火山岩分布区,为研究该地区的铀矿分布特征,采用地面伽马能谱测量方法对该地区进行测量,通过地面伽马能谱在该地区的应用,探讨了磨石山地区的铀异常分布特征,表明该方法在铀矿找矿中应用效果明显,为寻找铀矿提供了途径。     

铀矿石中铀镭平衡系数与铀含量关系探讨

铀镭平衡系数是描述铀系中铀镭平衡状态的一个参数。它不仅关系到铀矿床储量计算的可靠性,而且关系到寻找铀矿床的某些找矿方法的应用效果。因此有必要对它作进一步的探讨。铀镭平衡系数可由下式计算:     

坑内伽马能谱测量在红山地区铀矿找矿中的应用

论述了坑内伽马能谱测量在盆地内寻找近地表铀矿以及预测深部铀矿可能发育部位的应用实例.坑内伽马能谱测量数据经过多参数组合处理和微弱信息提取,分析了坑内伽马能谱放射性异常与铀矿体位置的关系,异常特征在浅地表工业铀矿体上方表现为铀异常区和铀迁移富集中心,在深部铀矿体上方表现为铀高场向铀低场过渡的梯度带.因此,对于寻找盆地内近地表铀矿以及预测深部铀矿可能的发育部位,坑内伽马能谱测量可以作为一种寻找铀矿的有效方法.     

GP-1型γ射线谱仪能谱漂移的手动补偿装置及其在铀镭平衡破坏样品分析中的应用

为解决GP-1型γ射线谱仪能谱漂移的问题,在前置放大器与主放大器之间加一个螺旋电位器,使之可手动连续调节信号幅度,确保谱仪在运行中系数不变。叙述了B-γ-γ能谱法测铀、镭、钍的原理及含量的计算公式,并用改进了的GP-1型γ射线谱仪测定了铀镭平衡破坏样品中的铀,镭、钍含量。本工作相化学方法分析的结果是符合的。     

Uranium-series disequilibrium in Australian soils and its effect on aerial gamma-ray surveys

Measurements of U and ²²⁶Ra in 445 soil samples collected from areas throughout Australia show that these soils have a mean U content of 2.0 mg kg⁻¹ and activity ratio (U/²²⁶Ra) of 1.09. There is a wide spread in individual values but, overall, more soils are U-rich than ²²⁶Ra-rich. Some indications of regional disequilibrium were found, with ²²⁶Ra-rich soils being noted in the Southern Cross-Kambalda area (WA), in south-eastern Eyre Peninsula (SA) and in an area north of Cobar (NSW). Uranium-rich soils were found in two Carboniferous volcanic terrains in north-eastern Queensland. The spread in activity ratio values indicates that disequilibrium will contribute to the noise in U channel data obtained by aerial gamma-ray surveying. The combination of statistical noise from low count rates (reflecting the low U concentrations in soils) and U-²²⁶Ra disequilibrium combine to give variances of 40–60% in typical U channel data. Data appearance can be improved to some extent by appropriate filtering.     

中国东部全新世火山的镭-钍同位素年代学

活火山是指1万年来有过喷发历史的全新世火山。火山的高分辨年代学对火山灾害评估和火山分类具有重要意义。对于缺乏历史记载的全新世火山,直接对火山岩进行同位素定年很困难。本文利用具有高时间分辨率的镭-钍-铀非平衡确定中国东部年轻火山的年龄。根据镭-钍-铀同位素,海南岛的马鞍岭和雷虎岭是全新世火山（马鞍岭：4.3ka;雷虎岭：4.7ka）;镜泊湖火山（4.9ka）也是全新世火山;龙岗火山存在晚更新世和全新世活动（7.0ka,15.0ka）;大兴安岭阿尔山和诺敏河Ra/Th非平衡消失但²³⁰Th/²³⁸U非平衡显著,属于晚更新世喷发（阿尔山：63ka;诺敏河：71ka）。海南岛的马鞍岭火山、雷虎岭火山和东北地区的龙岗火山、镜泊湖火山,是4座活火山。至于东北地区的阿尔山和诺敏河火山是否是活火山,有待测试更多样品的Ra/Th同位素。五大连池老黑山和火烧山有历史喷发记录,这与它们都存在显著Ra/Th非平衡一致。五大连池老黑山和火烧山的岩浆滞留年龄分别小于4.2ka和3.2ka,岩浆上升速率>18~23m/y。

     

Uranium-series disequilibrium in tuffs from Yucca Mountain,Nevada, as evidence of pore-fluid flow over the last million years

Samples of tuff from boreholes drilled into fault zones in the Exploratory Studies Facility (ESF) and relatively unfractured rock of the Cross Drift tunnels, at Yucca Mountain, Nevada, have been analysed by U-series methods. This work is part of a project to verify the finding of fast flow-paths through the tuff to ESF level, indicated by the presence of ‘bomb’ ³⁶Cl in pore fluids. Secular radioactive equilibrium in the U decay series, (i.e. when the radioactivity ratios ²³⁴U/²³⁸U, ²³⁰Th /²³⁴U and ²²⁶Ra/²³⁰Th all equal 1.00) might be expected if the tuff samples have not experienced radionuclide loss due to rock-water interaction occurring within the last million years. However, most fractured and unfractured samples were found to have a small deficiency of ²³⁴U (weighted mean ²³⁴U/²³⁸U=0.95±0.01) and a small excess of ²³⁰Th (weighted mean ²³⁰Th/²³⁴U 1.10±0.02). The ²²⁶Ra/²³⁰Th ratios are close to secular equilibrium (weighted mean=0.94±0.07). These data indicate that ²³⁴U has been removed from the rock samples in the last ∼350 ka, probably by pore fluids. Within the precision of the measurement, it would appear that ²²⁶Ra has not been mobilized and removed from the tuff, although there may be some localised ²²⁶Ra redistribution as suggested by a few ratio values that are significantly different from 1.0. Because both fractured and unfractured tuffs show approximately the same deficiency of ²³⁴U, this indicates that pore fluids are moving equally through fractured and unfractured rock. More importantly, fractured rock appears not to be a dominant pathway for groundwater flow (otherwise the ratio would be more strongly affected and the Th and Ra isotopic ratios would likely also show disequilibrium). Application of a simple mass-balance model suggests that surface infiltration rate is over an order of magnitude greater than the rate indicated by other infiltration models and that residence time of pore fluids at ESF level is about 400 a. Processes of U sorption, precipitation and re-solution are believed to be occurring and would account for these anomalous results but have not been included in the model. Despite the difficulties, the U-series data suggest that fractured rock, specifically the Sundance and Drill Hole Wash faults, are not preferred flow paths for groundwater flowing through the Topopah Spring tuff and, by implication, rapid-flow, within 50 a, from the surface to the level of the ESF is improbable.     

厦门火烧屿裸露岩石的铀放射系不平衡

用HPGey谱方法测定了厦门火烧屿裸露岩石天然放射性核素40K、228Ra、228Th、238U、226Ra和210Pb含量,对其铀系不平衡关系进行了讨论,发现钍系核素228Ra和228Th基本上是平衡的,而大部分样品226Ra相对于238U、210Pb相对于226Ra亏损.由此推论,水体作用下岸边岩石中226Ra直接进入水体,可以是海水中226Ra的一个来源;岸边岩石中222Rn逸出后,衰变为210Pb再进入水体,可以是海水中210Pb的一个来源.     

水－岩反应的铀系不平衡判别

天然体系中水－岩反应的铀系不平衡判别,是基于水－岩反应使岩石中天然铀衰变系子体核素＾２３４Ｕ,＾２２６Ｒｂ和六价铀的选择性溶失,造成原始放射性平衡遭到不同程度破坏,因而可利用现今测得的岩石中３组核素放射性活度比值Ａ（＾２３４Ｕ）／Ａ（＾２３８Ｕ）,Ａ（＾２３０Ｔｈ）／Ａ（＾２３４Ｕ）和Ａ（＾２２６Ｒａ）／Ａ（＾２３０Ｔｈ）反演判别该岩石曾经历了近代水－岩反应的大致强度和出现,持续时间,这是近十余年     

高分辨电感耦合等离子体质谱法测定铀矿石样品中234U/238U、230Th/232Th和228Ra/226Ra同位素比值 

采用氢氟酸-硝酸-盐酸混合酸密闭消解含铀矿石样品,用阴离子交换树脂、阳离子交换树脂和锶特效树脂逐级分离富集铀、钍和镭。使用高分辨电感耦合等离子体质谱(HR-ICPMS)测定分离纯化液中234U/238U2、30Th/232Th和228Ra/226Ra同位素。比值的测量精密度取决于比值的大小和对应核素浓度的大小。对质量浓度为10 ng/mL天然铀测量液,234U/238U的测量精密度优于1.2%;对230Th质量浓度为0.6ng/mL且230Th和232Th质量浓度接近的测量液,230Th/232Th的测量精密度为1.2%;对228Ra质量浓度为0.48 pg/mL且228Ra和226Ra质量浓度接近的测量液,228Ra/226Ra的测量精密度为4.0%。     

Evidence for the stability of the potential nuclear waste host,sphene, over geological time,from uranium-lead ages and uranium-series measurements

A sphene-based, glass-ceramic material is being investigated as a potential host for Canadian nuclear fuel recycle waste. The ability of sphene to retain certain radionuclides over geological time is examined using observed properties and age measurements of natural sphenes.The long-term stability of sphene is determined by comparing UThPb isotopic age data for sphene, from the literature, with ages determined for zircon and other minerals. Better internal agreement is found between UThPb sphene ages than for zircon ages indicating the resistance of sphene to daughter radionuclide loss over periods as long as 3000 Ma. Excellent agreement was observed between sphene ages and the estimated age of crystallization of the host rocks or vein infillings, except where subsequent metamorphim had reset the sphene age. Complete lead loss was generally found to accompany high-grade metamorphic conditions when temperatures exceeded ∼ 500°C.Stability over shorter periods of geological time was found for vein infilling and mineral separates of sphene using uranium-series disequilibrium analysis. Conditions of secular equilibrium in the decay chain ²³⁸U-²³⁴U-²³⁰Th-²²⁶Ra were observed for most of the 21 sphenes studied indicating that no radionuclide migration had occurred over periods as long as the last 1 Ma. Exceptions to this were four sphenes that had ²³⁴U deficiencies between 6 and 24% and two sphenes that showed ²²⁶Ra/²³⁰Rh disequilibrium. No correlation was found between the extent of radiation damage suffered by the sphenes and the presence of uranium-series disequilibrium. The presence of alteration products in three sphenes did correlate, however, with measured disequilibrium, indicating that some ²³⁴U and ²²⁶Ra had been lost or gained by these samples in the last 1 Ma and 8 ka, respectively.     

Capabilities and constraints of the Pb-Pb dating of metamorphogenic minerals using the step-leaching method

Based on particular examples, this paper considers the capabilities and constraints of the step-leaching Pb-Pb dating (PbSL) of metamorphogenic minerals. It was shown that stepwise leaching allows the separation of fractions enriched in uranogenic and thorogenic Pb isotopes, which can be used for the determination of mineral ages and the time of crystallization of coexisting equilibrium and, occasionally, disequilibrium monazites. The presence of monazite in a mineral is indicated by a high Th/U ratio similar to that of monazite. The main limitation of the method is related to the presence in minerals of both disequilibrium domains of the mineral matrix and disequilibrium monazite microinclusions. By the example of minerals studied, we discussed three scenarios for the development of the U-Th-Pb isotopic systems of metamorphogenic minerals.     

Uranium geochemistry and dating of Pacific island apatite

Uranium-series disequilibrium dating of island phosphate deposits is evaluated in terms of known associated coral ages, uranium geochemistry, and stratigraphic sequences as well as the concordance between the geochronometers ²³⁴U/²³⁸U, ²³⁰Th/²³⁴U and ²²⁶Ra/²³⁸U. U(VI) is the predominant oxidation state of uranium in island phosphorites and by analogy to the youngest surficial deposits, most of the uranium initially bound is in the form of U(VI) sorbed by surfaces from seawater. Insular deposits contain more organic matter than even very young ocean floor samples and this leads to a greater probability of reduction of available recoil uranium than occurs in marine deposits. As a consequence, R(VI) ? R(T) ? R(VI), where R represents the ²³⁴U/²³⁸U activity ratio. This situation is completely opposite from that observed for marine-origin phosphorites. We determined that a fraction of U(VI) in ancient insular phosphorites is very labile and lost to alkaline carbonate solutions with a uranium activity ratio even more depleted in ²³⁴U than the bulk R(VI).Most younger samples appear to have no more discordance between ²³⁴U/²³⁸U, ²³⁰Th/²³⁴U and ²²⁶Ra/²³⁸U than marine phosphorites of similar apparent age. Young, surficial atoll-rim apatite cements and unconsolidated phosphorites date in the range of 1500–8000 years B.P., consistent with the concept of partial submergence of low-lying coral islands prior to 2000 years B.P. Sub-surficial samples in the same environment date older at about 20,000 years B.P. Violation of the closed system assumption occurs in at least 6 out of 13 ancient (> 800,000 year) samples. Uranium-series disequilibrium dating of insular apatite shows some promise as a recorder of climatic/sea level events, but the assumptions necessary for valid ages must be carefully evaluated for each occurrence.     

锾法找铀矿的初步试验结果

本文从化探角度出发,讨论了鑀在岩、矿石和土壤中的分市特征及其与铀成矿作用之间的关系。以鑀和铀、镭之间,其衰变成因联系和不同的地球化学性质为基础,对锾法在寻找铀矿中的应用进行了初步探讨。通过在湘西,湘南四种不同类型的20个铀矿床(点)上的大量综合对比,证明了它不仅对铀、镭放射性平衡破坏研究有其独特之处,并且可以推测出成矿过程中的地球化学变化,从而解释铀矿床的成因,评价异常点、带,因此是铀矿普查勘探攻深找盲的一种有效手段。它具有野外工作方法简便、显示直观、影响因素少和便于综合对比等优点。由于氧化还原反应广泛参加了铀矿床的形成和破坏,所以在其它方法(如伽玛、铀量、氡及其子体测量)反映不明显的情况下,鑀法仍有较好的显示。