铀矿找矿中α径迹测量方法的影响因素研究

我国于1974年开始将核径迹探测技术应用于铀矿勘探,其中α径迹测量是寻找深部隐伏铀矿的有效方法之一.本文对氡浓度大小、探杯尺寸、杯内表面放射性沉积物以及杯内底面固体放射性元素等对α径迹测量结果的影响进行了理论研究,建立了α径迹测量中不同装置结构及不同放射性元素对α径迹密度影响的理论公式,为该方法应用于铀矿勘探以及环境氡浓度测量提供理论参考依据.同时结合实验对比测量,进一步对理论公式进行验证,α径迹测量结果与理论计算所得结果吻合较好.研究结果表明：探测器上α径迹主要来源于氡,探杯尺寸不应小于氡致α径迹的最大有效探测尺寸.此外,放射性沉积物放出的α射线对测量结果有重要积极贡献,在铀矿勘探中,从提高探测灵敏度和减小测量结果不确定度的角度来看,其影响越大越好.在大多数测量装置尺寸下,探杯内底面以下的固态α放射性元素对径迹密度影响较小或无影响,实际测量时可将其忽略.     

含金石英脉的展布规律及其形成机制——涡旋作用

对国内外5个石英脉型金矿床的研究表明,矿田中的含金石英脉往往成群出现,并呈弧形帚状分布,帚状脉群的收敛端方向一致地显示为逆时针旋转方向。这一规律可能与科里奥利力产生的涡旋作用有关。     

大板金矿“港湾成矿”模式探讨

自 8 0年代末 ,辽宁西部排山楼金矿发现以来 ,对于同韧性剪切带型金矿床的赋存规律一直引起广大地质工作者的重视。通过对大板、老虎沟、樱桃沟等金矿的初步研究表明 ,采用微观和宏观相互结合、相互映衬的指导思想 ,针对韧性剪切带动力机制进行思考 ,认为闾山造山带中北北东向和东西向两个方向的剪切带为一期韧性剪切构造作用的产物 ,形成时间为印支末期—燕山早期 ,其区域构造样式为共轭式韧性剪切带 ,呈网结状。含金矿液的沉淀作用一般发生于韧性剪切带的网结点处附近 ,较大型的金矿床应赋存于韧性剪切带中刚性体周围 ,尤其是首尾等“港湾”处 ,即“港湾成矿”。     

Spatial and temporal variability of surface water and groundwater before and after the remediation of a Portuguese uranium mine area

The old Senhora das Fontes uranium mine, in central Portugal, consists of quartz veins which penetrated along fracture shear zones at the contact between graphite schist and orthogneiss. The mine was exploited underground until a depth of 90 m and was closed down in 1971. The ores from this mine and two others were treated in the mine area by the heap-leach process which ended in 1982. Seven dumps containing a total of about 33,800 m³ of material and partially covered by natural vegetation were left in the mine area. A remediation process took place from May 2010 to January 2011. The material deposited in dumps was relocated and covered with erosion resisting covers. Surface water and groundwater were collected in the wet season just before the remediation, in the following season at the beginning of the remediation and also after the remediation in the following dry season. Before, at the beginning and after the remediation, surface water and groundwater have an acid-to-alkaline pH, which decreased with the remediation, whereas Eh increased. In general, before the remediation, uranium concentration was up to 83 μg/L in surface water and up to 116 μg/L in groundwater, whereas at the beginning of the remediation it increases up to 183 μg/L and 272 μg/L in the former and the latter, respectively, due to the remobilization of mine dumps and pyrite and chalcopyrite exposures, responsible for the pH decrease. In general, after the remediation, the U concentration decreased significantly in surface water and groundwater at the north part of the mine area, but increased in both, particularly in the latter up to 774 μg/L in the south and southwest parts of this area, attributed to the remobilization of sulphides that caused mobilization of metals and arsenic which migrated to the groundwater flow. Uranium is adsorbed in clay minerals, but also in goethite as indicated by the geochemical modelling. After the remediation, the saturation indices of oxyhydroxides decrease as pH decreases. The remediation also caused decrease in Cd, Co, Cr, Ni, Pb, Zn, Cu, As, Sr and Mn concentrations of surface water and groundwater, particularly in the north part of the mine area, which is supported by the speciation modelling that shows the decrease of most dissolved bivalent species. However, in general, after the remediation, Th, Cd, Al, Li, Pb, Sr and As concentrations increased in groundwater and surface water at south and southwest of the mine area. Before and after the remediation, surface water and groundwater are contaminated in U, Cd, Cr, Al, Mn, Ni, Pb, Cu and As. Remediation caused only some improvement at north of the mine area, because at south and southwest part, after the remediation, the groundwater is more contaminated than before the remediation.     

Distribution Study of U,V, Mo,and Zr in Different Sites of Lakes Van and Hazar,River and Seawater Samples by ICP‐MS

The aim of this study is to investigate the concentrations of U, Th, V, Mo, and Zr in natural waters taken from Turkey. Among these water species, Lake Van is the largest soda lake and the fourth largest closed basin on Earth. The water samples were collected from 51 locations between 2008 and 2009. The inductively coupled plasma‐MS was used for determinations. The obtained U and Zr concentrations are in the range of 37–110 µg L^?1 and 17–78 µg L^?1 in Lake Van and 0.53–0.81 µg L^?1 and 0.15–0.19 µg L^?1 in Lake Hazar, respectively. The concentration of uranium in other studied waters varies from the lowest 0.09 µg L^?1 in Tigris (Dicle) river to the highest 4.0 µg L^?1 in Mediterranean Sea water. Mean Mo and V concentrations in the studied water samples were found to be in ranges of 0.1–17 and 2.7–113 µg L^?1, respectively. The obtained highest U concentration in Lake Van correlates with the highest Mo and Zr levels compared to the Lake Hazar and river waters. These results imply that there is a young occurrence of uranium minerals around Lake Van. It is concluded that there is about 50.000 ton of uranium in Lake Van water.     

The oxygen isotopic composition of uranium minerals: A review

Uranium ore is an essential material in the preparation of nuclear fuel for civilian as well as military uses. Uranium is first extracted from uranium-bearing minerals using a variety of reagents, and is precipitated from solutions as yellow cake prior to isotope enrichment processes. The disintegration of the former Eastern Bloc in the 1990s and frequent unrest in the Middle East have underscored the need for better characterizing source uranium ores for forensic and attribution purposes.The world's major deposits of U occur in several distinctly different geological environments. Fourteen principal types of U deposits and rocks with elevated uranium contents are recognized with more than 40 subtypes. Combining our own analysis and literature data, we have amassed over 250 oxygen isotope data from 13 major U-producing countries, which vary widely from − 32 to + 11‰. However, interpreting the oxygen isotopic composition of uraninite in terms of the composition of the fluid from which it precipitated, or interacted with, requires knowledge of the fractionation factor and temperature of interactions, which are not always available. Since each deposit type occurs within a unique geologic setting and is generally formed from chemically distinct fluids, the chemical compositions of the uranium ores are also distinct: uranium deposits that form in igneous rocks have higher trace element compositions relative to sandstone-hosted deposits. Our data shows that one of the most useful techniques for distinguishing between uranium ore is to use a combination of δ¹⁸O values and rare-earth elements (e.g., La/Yb ratios). These methods may allow investigators to trace uranium ore back to the source.     

中国热液铀矿成矿理论体系

在总结前人大量研究成果的基础上,笔者尝试对我国的热液铀矿成矿理论体系作一简要概括。在成矿的＂源-运-导-集-存＂基本规律问题上,此体系大体包含以下10个方面：（1）硅化带成矿类型;（2）矿-岩时差;（3）碱交代作用;（4）成矿壳层;（5）4种铀矿类型（花岗岩型、火山岩型、碳硅泥岩型、砂岩型）统一构造-热液成矿;（6）铀成矿预富集序列;（7）花岗岩岩浆演化链的解耦;（8）绢英岩化高温富矿类型;（9）玄武岩事件;（10）幔汁成岩成矿论。     

Advances in understanding the Kombolgie Subgroup and unconformity-related uranium deposits in the Alligator Rivers Uranium Field and how to explore for them using lithogeochemical principles

The Alligator Rivers Uranium Field (ARUF) includes the mined and unmined Jabiluka, Ranger, Koongarra and Nabarlek unconformity-related uranium deposits and several small prospects including the newly discovered King River prospect. Uranium mineralisation is hosted by a variety of metamorphosed Nimbuwah Domain lithologies that are unconformably overlain by the Kombolgie Subgroup, a basin package of unmetamorphosed arenites and mafic volcanics. All of the uranium deposits and prospects preserve an identical alteration assemblage that is subdivided into a distal and proximal alteration zone. The distal alteration zone comprises an assemblage of sericite and chlorite that replace albite and amphibole. In some cases, this alteration can be traced >1000 m from the proximal alteration zone that is dominated by uraninite, hematite, chlorite and sericite. Uranium precipitated in the basement as uraninite at 1680 Ma at around 200°C from a fluid having δ¹⁸O_fluid values of 3.0±2.8‰ and δD_fluid values of ?28±13‰ VSMOW reflecting an evolved marine source. These geochemical properties are indistinguishable from those recorded by diagenetic illite and chlorite that were collected from the Kombolgie Subgroup sandstones across the ARUF. The illite and chlorite formed in diagenetic aquifers, and where these aquifers intersected favourable basement rocks, such as those containing graphite or other reductants, U was precipitated as uraninite. Therefore, it is proposed that the Kombolgie Subgroup is the source for fluids that formed the deposits. A post-ore alteration assemblage dominated by chlorite, but also comprising quartz±dolomite±sulfide veins cut the uranium mineralisation at all deposits and has historically been recorded as part of the syn-ore mineralisation event. However, these minerals formed anywhere between 1500 to 630 Ma from fluids that have distinctly lower δ¹⁸O_fluid values around 1.5‰ and lower δD_fluid values around ?45‰ reflecting a meteoric water origin. Despite unconformity-related uranium deposits having a large alteration halo, they remain difficult to find. The subtle alteration of albite to sericite several hundred metres from mineralisation occurs in isolation of any increase in trace elements such as U and radiogenic Pb and can be difficult or impossible to identify in hand specimen. Whole rock geochemical data indicate that Pearce Element Ratio (PER) analysis and General Element Ratio (GER) analysis may vector into this subtle alteration because it does not rely on an increase in trace elements to identify proximity to ore. PER and GER plots, Al/Ti vs (2Ca + Na + K)/Ti, Na/Al vs (Na + K)/Al, K/Al vs (Na + K)/Al and (Fe + Mg)/Al vs (Na + K)/Al provide a visual guide that readily distinguish unaltered from altered samples. A plot of (Na + K)/Al and (Fe + Mg)/Al on the x-axis against the concentration of trace elements on the y-axis reveals that U, Pb, Mo, Cu, B, Br, Ce, Y, Li, Ni, V and Nd are associated with the most intensely altered samples. The lithogeochemical vectors should aid explorers searching for uranium mineralisation in a prospective basin environment, but exploration must first focus on the characteristics of the basin to assess its mineralisation potential. A holistic model that describes the evolution of the Kombolgie Subgroup from deposition through diagenesis to formation of the uranium deposits in the underlying basement rocks is presented and has application to other basins that are considered prospective for unconformity-related uranium deposits. The model outlines that explorers will need to consider the thickness of the sedimentary pile, its lithological composition relative to depositional setting, the depth to which the sediments were buried during diagenesis and the degree of diagenesis achieved, which may be time dependant, before deciding on the prospectivity of the basin.     

二连盆地中部古河道砂岩型铀矿成矿特征

笔者通过对铀源、赛汉组上段沉积建造、构造演化等的分析认为,二连盆地中部具备古河道砂岩型铀矿成矿条件;古河道形态与规模、河道内沉积微相、潜水一层间氧化是铀矿床定位的“三要素”,其不同的组合方式构成了不同的古河道砂岩型铀矿成矿模式。据此,指出二连盆地中部具有较好的古河道找矿远景。     

新疆冰草沟矿床铀、磷相关性研究

北天山褶皱带博格达复背斜南翼二叠系含磷砂岩、粉砂岩,华力西晚期安山玢岩中发育大量铀异常矿化点,冰草沟矿床在该区铀、磷成矿特征研究程度较高。通过对冰草沟矿床铀、磷矿化特征、赋存部位与矿体空间关系进行对比,结合铀、磷化学成因与成矿期联系,认为铀、磷矿为同体共生关系,在该区具综合找矿意义。