Source Of Uranium Research Articles

Implications of Major and Trace Element Migration in Altered Granites for Hydrothermal Alteration and Granite-Related Uranium Mineralization in the Sanjiu Ore Field, South China

The recently discovered Sanjiu ore field (SJOF) is a granite-related uranium ore field located in the middle of Zhuguangshan (South China). The relationship between hydrothermal alteration of granite and uranium mineralization in the SJOF is crucial yet understudied. In this study, the major- and trace-element contents of granite samples (fresh granite, altered granite, and tectonites) with different uranium contents were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–mass spectrometry (ICP–MS). The analytical results show a relative increase in Si, S, Ca, Pb, Mo, and Sb content in altered granites and tectonites, relative to fresh granites. During the mineralization stage, the increase of the aforementioned elements is related to various hydrothermal alterations (e.g., silicification, carbonation, sulfation, etc.) and newly formed minerals (e.g., microfine crystalline quartz veins; calcite agglomerates or fine veins; and metal sulfides, such as pyrite). There is a concomitant relative decrease in Na, K, Al, Fe, Mg, and other elemental contents that may be due to mineralogical alteration processes, such as biotite to chlorite, feldspar-group minerals to clay minerals, and redox of Fe-bearing minerals. The LREE/HREE ratio in altered granites decreases significantly with the increase in uranium content, suggesting that a low LREE/HREE ratio may be a prospecting indicator. The normalized trace-element patterns of mineralized granite (ore) and the relatively high U content of fresh granite imply that granitic rocks may be the primary uranium source in the SJOF. The uranium mineralization is mainly concentrated in the redox zone that occurs at a depth of 100−300 m. The redox zone is characterized by the most developed hydrothermal alterations and enrichment of trace elements, including W, Mo, Sb, Li, and the HREE.

Role of alternative and nuclear energy in stimulating environmental sustainability: impact of government expenditures.

Environmental sustainability isfundamental to the survival of our planet and ourselves, as polluted air, water, and land severely affect communities and society to thrive and damage the quality of life. This study examined the role of alternative and nuclear energy in stimulating the environment sustainably while mediating the function of government expenditure and economic growth in the top three highest CO2 emitter countries. We apply advanced econometric methodologies for empirical analysis from 1981 to 2016 and find long-run relationships among the variables that suggest general government final consumption expenditure and economic growth are positively related to CO2 emissions. Moreover, alternative and nuclear energy and the square root of economic growth (EKC) improve environmental sustainability. The general government's final consumption expenditure and economic growth deteriorate environmental sustainability. Policymakers in the top three highest CO2 emitter countries are encouraged to adopt a comprehensive approach to access the compatibility of alternative and nuclear energy sources, changing the source of uranium from mined ore to seawater, encourage, tide, and include macroeconomic stabilization, public and private fiscal position goals with the environmental sustainability policies. Moreover, governments are suggested to incorporate green fiscal policies to address the global environmental challenges and promote a green economy. Aligning government expenditures with environmental goals, reflecting externalities in prices, broader fiscal reform by making fiscal space for clean and green investment is highly encouraged to achieve the sustainable development goals' target. Study limitations and directions for future research in the area are presented.

Importance of radon assessment in indoor Environment-a review

Radon is odourless, colourless indoor air pollutant from the radiation source of uranium. The source of radon in indoor are walls, floor and ceiling. Importance of radon detection at buildings are rare as it cannot be suspected until faced with an health issues. Concentration of radon in indoor environment depends on various factors. Lund disorders are the most commonly reported issue with radon exposure. This paper concentrates on the sources, factors influencing the radon dispersion and the health issues rise up with high radon exposure.

ПЕРСПЕКТИВИ УРАНОВОГО ЗРУДЕНІННЯ ПІВДЕННО-ЗАХІДНОГО СХИЛУ УКРАЇНСЬКОГО ЩИТА.

The geological position, composition and genesis of uranium mineralization of ore occurrences on the southwestern slope of the Ukrainian Shield are considered. In the Precambrian basement metamorphic rocks of the Dniester-Bug, Bug and ultrametamorphic rocks of the Golovanev, Pobuzh, Berdichev and Kirovograd complexes were established. On the southwestern slope of the Ukrainian Shield, 4 uranium occurrences and 4 radioactive anomalies have been discovered, studied and prospected. The uranium occurrences are localized along the regional unconformity surface of the Precambrian basement and platform cover. They are often confined to the nodes of the intersection of faults. The uranium occurrences are installed simultaneously both in the rocks of the basement and in the platform cover. The ore deposits form stockwork and vein segregations among the tectonized rocks of the Precambrian. In the rocks of the sedimentary cover they are discontinuous lenticular, subconcordant with the bedding of rocks. The uranium mineralization is vein-disseminated, represented by uraninite, pitchblende, coffinite, uranium black, casolite, etc. The uranium mineralization was caused by both endogenous and exogenous processes; several stages of uranium concentration have been established. The main source of uranium and associated elements was the low-temperature hydrothermal fluids of the “unconformity zone” faults of the Precambrian basement and sedimentary cover. A comparison is given and the similarity of the uranium mineralization of these occurrences with the rich uranium ores of the "zones of unconformity" of the Canadian and North Australian shields is given, which determines the significant prospects for uranium mineralization of the southwestern slope of the Ukrainian shield for the development of the uranium resource base of Ukraine.

The origin of uranium deposits related to the Huangmeijian A-type granite from the Lu-Zong volcanic basin, South China: Constraints from zircon U-Pb geochronology and mineral chemistry

Although most of granite-related uranium deposits in South China are spatially and genetically associated with S-type granites, few are related to A-type granites. In this study, we present whole-rock major and trace elements, zircon U-Pb geochronology, and mineral chemistry data for the Huangmeijiang A-type granite in the Lu-Zong volcanic basin (South China) to investigate the origin of uranium deposits related to this pluton. The uranium ore bodies mainly occur within the Jurassic Luoling formation close to the Huangmeijian pluton. Whole-rock and biotite geochemistry indicates that the F-rich alkaline magmas with relatively high fO2 prompted the partitioning of U into the fluids released from the Huangmeijian pluton with an affinity of A-type granites, which would set the stage for the later concentration of the U into the Jurassic Luoling formation. Thorite, zircon, apatite, and bastnäsite are the dominant accessory minerals that host U in this pluton. Backscattered electron (BSE) images suggest that some zircon and thorite grains can be divided into the unaltered domains and altered domains. The textural features are interpreted as a later hydrothermal event superimposed on the magmatic zircon and thorite. In situ LA-ICP-MS U-Pb dating on the unaltered domains and altered domains of zircon grains yielded weighted mean ages of 127.8 ± 1.0 Ma and 65.7 ± 5.3 Ma, respectively. The former age represents the emplacement age of the Huangmeijian pluton, and the latter one overlaps the timing of a uranium mineralization event (∼66.6 Ma) in this area. The altered domains of thorite and high-(U + Th) zircon grains have lower U contents than those of the unaltered domains, indicating that uranium was mobilized from thorite and zircon during fluid infiltration, which might be the main source of uranium for the ∼ 66.6 Ma uranium mineralization. Our study suggests that the Huangmeijian pluton was the primary source of uranium for the formation of uranium deposits in this area.

Appraising the factors favouring uranium mobilization and associated health risk assessment in groundwaters of north-western India

An attempt has been made in this study to evaluate the factors favoring the uranium mobilization into the groundwater of Northwest India using uranium isotope activity ratio (234U/238U), radon (222Rn) and environmental isotopes of water (2H, 18O and 3H). The values range from 23 - 597 µg/L for total uranium and 634–3210 Bq/m3 for radon and the corresponding annual effective dose is estimated to be 18.9–490 µSv/a and 6.2–31.5 μSv/a respectively. Uranium activity ratio (UAR) varies from 0.68 - 1.17 and maximum samples indicate secular equilibrium. Environmental isotopic data indicates that the source to groundwater is vertical percolation of rainwater in the case of shallow zone while regional flows from outcrop areas recharge the deep groundwater. A wide scatter is noticed in environmental 3H content (0.23–6.62 TU) indicating both fast and sluggish water flows. The UAR phase diagram suggests that leaching process controls the uranium mobilization into the groundwater. The correlations among UAR, uranium and Uexcess further indicate oxidative nature of leaching process. Statistical treatment of the obtained data along with available geochemical and isotope evidences suggest that source of uranium is common but the driving processes are different for shallow and deep zone. Influences of root zone CO2, oxic species from irrigation return flows and water level fluctuations are also evaluated. Low uranium, low UAR, low 3H and high 222Rn activity in deep zone suggest uranium being released from the roll front as well as transported from outcrop regions. This study highlights the application of uranium isotope ratio, radon and environmental isotopes in assessing vulnerability of alluvial aquifers towards uranium contamination.

Special Conditions for the Formation of Large Exogenic Epigenetic Uranium Deposits

—For uranium deposits to form from oxidizing waters of surface origin, it is necessary to combine several conditions and processes of different ranks that make up a specific mineral system. Analysis of exogenic deposits of different scales and ore quality from different regions of the world showed that, among all the critical processes necessary for the formation of large deposits and vast provinces, global tectonic movements play a particular role. A geodynamic regime with moderate vertical differentiation of crustal blocks is most favorable for development of a hydrodynamic infiltration ore-forming system under near-surface conditions. An infiltration artesian system is capable of functioning for millions and tens of millions of years, which makes it possible to accumulate large uranium reserves at the geochemical reduction barrier. The required regime is typical of regions with a certain geotectonic position. For example, the peripheral regions of orogenic belts along tectonic plate boundaries, as well as the frames of some long-lived intraplate deep faults. In the same regions, the proximity of infiltration and expulsion hydrodynamic systems is possible. In local areas where groundwater of various origin and composition interact, conditions occur for particularly efficient uranium concentration in ores. Limitations on the productivity of a hydrodynamic infiltration ore-forming system are imposed by historical factors that predetermine the formation of the uranium source and lithological conditions for ore localization, as well as the climatic conditions of the time in which the system functioned and postore conditions determining the preservation of mineralization accumulated in the system. The revealed patterns be used to predict ancient provinces of exogenic uranium deposits.

Deep and crustal factors of thorium-uranium mineralization of the Golovanevskaya zone of Ukrainian Shield

The article discusses the features of the deep and crustal structure of the Golovanevskaya zone, the geochronological sequence of the main stages of its formation. The characteristic of thorium-uranium ore occurrences and deposits is given; and the main stages of their formation. The stages of successive concentrations of uranium and thorium in connection with the processes of sedimentation, volcanism, metamorphism, ultrametamorphism, and tectonic-magmatic activation are determined. The concentration of uranium and thorium was multi-stage and increased with each subsequent geological process. The deep and crustal sources of uranium and thorium, their ratio in the pre-ore main ore-generating stages of deposit formation are considered. It is shown that the formation of deposits became possible in the Proterozoic when neutral and alkaline water-potassium fluids replaced the deep acidic Archean fluids, and the formation of thorium-uranium rock complexes became possible in the crust. The totality of the data obtained is the basis for classifying the thorium-uranium mineralization as the metamorphogenic type. The presence in the Golovanevskaya zone of Lozovatsky, Yuzhny, Kalinovsky deposits, and numerous thorium-uranium ore occurrences determine this zone as promising for developing the thorium-uranium raw material base of the nuclear energy of Ukraine. Thorium-uranium mineralization is also genetically typical for the Kryvyi Rih-Inguletskaya, Orekhovo-Pavlograd interblock suture zones; detailed research is needed to determine their prospects. The confinement of thorium-uranium mineralization specifically to interblock zones is due to a combination of the following main regional features: the presence of Neoarchean thorium-uranium-bearing rock complexes; their metamorphism under conditions of granulite facies; intense ultrametamorphism; development of deep fluid-conducting faults; deep level of the erosional section, in which the products of the rare-metal and pyrite stages of thorium-uranium mineralization were exposed.

Temporal change of 236U/238U and 235U/238U isotopic ratios in atmospheric deposition in Tokyo and Akita from 1963 to 1979

We examine the temporal changes of 236U/238U and 235U/238U in atmospheric deposition from samples collected in Tokyo and Akita from 1963 to 1979 and elucidate the spatial distribution and historical changes of the anthropogenic sources of uranium in Japan. The 236U/238U ratio of atmospheric deposition in Tokyo peaked in 1963 and again during the 1970s, while the corresponding 235U/238U ratios of atmospheric deposition during the second peak period were lower than that of natural uranium. The 236U/238U ratios of atmospheric deposition in Akita samples peaked in 1963. The 235U/238U ratios in Akita samples were almost identical to that of the natural uranium ratios. These results suggest that the peak of 236U/238U in 1963 corresponds to what is recognized as representative for global fallout. The increase of 236U/238U and the decrease of 235U/238U observed simultaneously in the 1970s indicate that depleted uranium has subsequently been released into the environment around Tokyo. The cumulative deposition density of 236U for atmospheric fallout samples collected in Tokyo from 1968 to 1979 is an order of magnitude larger than that of the global fallout, suggesting that the depleted uranium in the 1970s is a major component of 236U in Tokyo and should be considered as an end-member when using 236U as an environmental tracer in the industrial city. This knowledge can facilitate future research using 236U as an effective environmental tracer.

Petrographic and geochemical implications for ore genesis and mineralogical composition studies of the Tarat formation hosted sandstone uranium deposit in the Tamari Prospect from Arlit, Niger

The ongoing uranium mining activities coupled with mines development in SOMAIR open pit mine at Arlit led to the discovery of a new prospect called Tamari prospect endowed with a potential uranium ore deposit and have been subjected to a very few scientific studies but their characteristics still need to be examined in further detail investigation in order to determine the mineralogical composition, ore genesis and geochemical characteristics of the deposit. Based on detailed studies using optical microscopy, backscattered electron imaging, electron-microprobe and high resolution elemental mapping, the authors have established that detrital, authigenic and uranium ore-stage minerlization are associated with the deposit. Previous studies on the deposits documented two stages of uranium deposits one close to 190 Ma and the other close to 150 Ma. The dominant uranium ore minerals occur as uraninite. Pyrite and galena are the most dominant sulfide minerals associated with the uranium mineralization and therefore, chemical composition analysis shows that pyrite contains an average U concentration up to of 7.62 wt% and galena has an average of 27.16 wt%. The association U–Zr–Pb present in the zircon and monazite indicates that the geochemical environment responsible for this correlation should be that with a large association with lithophile elements which occur in monazite and zircon minerals that could possibly be the potential source of uranium. The impregnation of organic matter with U–Ti oxide indicates a synsedimentary or early source of uranium. Uraninite contains a high concentration of Zr (av. 5.77 wt%) suggesting a probable succession of fluid circulation that would allow either the deposition of two generations of uraninites or mineralization leaching. The excellent positive correlation of U, Fe, Ca and Mn in the mineralized pole of U–Ti oxides is related to the presence of high concentrations of complexing ligands such as carbonate, oxalate, hydroxide, fulvic and humic acids in the deposits. Uranium mineralization occurs as Iriginite (U–Mo) and the powellite (Pb–MoO4) cemented the quartz grains and kaolinite highlights a late fluid circulation.

Trace metal accumulation in agricultural soils from mineral phosphate fertiliser applications in European long‐term field trials

AbstractMineral phosphate (P) fertilisers are the main suspected sources of uranium (U) and cadmium (Cd) input to agricultural soils. This study was set up to survey the general long‐term impact of P fertilisers on concentrations of Cd, U and other trace metals in European soils. A total of 218 soil samples was collected from 15 long‐term (3–78 years, median 18 years) P trials at 11 locations with a pairwise comparison of topsoil composition between the fertilised and corresponding unfertilised soils. Aqua regia soil extraction detected the effects of fertilisation more sensitively than the HF (real total) soil extraction. Statistically significant differences in aqua regia soluble metals due to fertiliser application were detected more frequently for U (10 of 15 trials) than for Cd (4 of 15 trials). The concentrations of U and Cd in soil linearly increased with cumulative applied P across all soils and sites; a total addition of 1 ton P ha−1 increased the mean topsoil (23 cm depth) concentrations by 0.11 mg U kg−1 soil (0.09–0.12 mg U kg−1, 95% CI) and 0.03 (0.02–0.04) mg Cd kg−1 soil. These results correspond with mass balance predictions (1 ton P ha−1; +0.15 mg U kg−1 soil and +0.02 mg Cd kg−1 soil) based on previously determined average trace element concentrations in European fertilisers. Data thus suggests that, on average among trials, losses of Cd from soil are undetectable. In contrast, about 30% of the theoretical U input from fertilisers is lost in the same trials. This study provides data to better evaluate the modelled trace metal accumulations in soil and to evaluate the prevailing metal limits in mineral fertilisers.Highlights U and Cd accumulation in agricultural soils correlates with cumulative mineral P‐fertiliser dose. Accumulation of fertiliser‐derived U is more often detectable compared to Cd. Due to its accumulation potential, U accumulation should be monitored. Aqua regia soluble concentrations better detect metal accumulation in soil than real total concentrations.

Uranium Exploration, Deposit and Resources: The Key of Nuclear Power Plant Development Program in Indonesia

Uranium deposit in Indonesia was found in almost all Indonesian Archipelago, mainly in Kalimantan, Sulawesi, Sumatera, Papua, Bangka Belitung and Riau islands. Uranium exploration activities started in the 1960s to recent, conducted in many exploration stages. The exploration in prospects area are completed with drilling activities to delineate the mineralization zone and continued to resources estimation. In Kalan Area, the research had been completed with underground/tunneling mining. The uranium resources are classified into discovered or undiscovered based on exploration stages, and conventional or unconventional based on sources of primary/secondary/by-product mineral production. The resources are calculated from Kalan Area and its surroundings (Kalimantan) with addition of Mamuju Area (West Sulawesi) and Sibolga Area (North Sumatera). Uranium identified resource in Indonesia is 13,503 tU while the undiscovered is 62,330 tU. Meanwhile, categorized by uranium source, the conventional and unconventional resources are 48,388 tU and 27,445 tU respectively. The uranium resources categories should be increased and completed with feasibility study to increase the resources to reserve classification. The exploration, deposit, and resources are the key to ensure the readiness of developing nuclear power plants in Indonesia, where one of them is Experimental Power Reactor (EPR) or Reaktor Daya Eksperimental (RDE) with domestic uranium fuel.

Deciphering anthropogenic uranium sources in the equatorial northwest Pacific margin

This work reports the first high-resolution deposition records of anthropogenic uranium (236U and 233U) in a sediment core taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial northwest Pacific Ocean. Two notable peaks were observed in both profiles of 236U and 233U concentrations, with a narrower peak in 1951–1957 corresponding to close-in Pacific Proving Grounds (PPG) signal, and a broader peak in 1960s–1980s corresponding to the global fallout from nuclear weapons testing. 236U and 233U areal cumulative inventories in the studied sediment core are (2.79 ± 0.20) ∙ 1012 atom ∙ m−2 and (3.12 ± 0.41) ∙ 1010 atom ∙ m−2, respectively, about 20–30% of reported 233U and 236U inventories from the direct global fallout deposition. The overall 233U/236U atomic ratios obtained in this work vary within (0.3–3.5) ∙ 10−2, with an integrated 233U/236U atomic ratio of (1.12 ± 0.17) ∙ 10−2. The contribution from global fallout and close-in PPG fallout to 236U in the sediment core is estimated to be about 69% and 31%, respectively. We believe the main driving process for anthropogenic uranium deposition in the Philippine sediment is continuous scavenging of dissolved 236U from the surface seawater by sinking particles.

Roles of dispersed organic matters in sandstone-type uranium mineralization: A review of geological and geochemical processes

Among uranium deposits in sedimentary basins, sandstone-type uranium deposits are epigenetic. The development scales of sandstone-type uranium deposits are controlled by tectonic events, provenance, sand bodies, uranium sources, and reducing media, including that reducing media control the scales of redox transition zone. Dispersed organic matter (DOM) within sandstones, e.g., carbonaceous debris (CD), is one of the important reducing media. The characteristics of organic petrology and element of CD are similar in those of coals, being grouped into type III kerogen. However, the origin of CD within sandstones is unclear. Uranium occurs in uranium-bearing matter and uranium mineral, and coexists with CD in space. Adsorption, complexation, and reduction of organic matter are responsible for the mobility and precipitation of uranium in sediments. The adsorption and complexation capacity of DOM is the most intensive at the stage of immaturity to low maturity, and decreases with the increasing coalification. The reduction capacity is linked to organic matter maturity. Besides, porous macerals could provide the channels for uranium-bearing fluid migration and the space for uranium preconcentration. Under certain physical and chemical conditions, uranium-bearing fluid could permeate into macerals, and react, i.e., trapping followed by reduction. Nevertheless, the coordination characteristics of uranium within uranium-bearing DOM should be further investigated. Uranium enrichment concurrently alters organic matter, causing an increase in organic matter maturity and anisotropy through the effects of radiogenic heat or α-irradiation-induced crosslinking. However, α-irradiation-induced crosslinking should be the primary way. Besides, contributions of CD to uranium mineralization should be reckoned.

Sequential separation and selective extraction of uranium and thorium from monazite sulfate leach liquor using dipropylamine extractant

Monazite mineral is the main source of uranium and thorium, which are mainly associated with rare earth elements (REEs). So, their separation is the crucial task to satisfy their application for nuclear fuel. Dipropylamine was used for the first time in the selective extraction and separation of uranium and thorium from Monazite sulfate leach liquor. The extraction of thorium (98%) was achieved using dipropylamine in kerosene at pH 1; it was followed by selective extraction of uranium (97%) by Dipropylamine at pH 3. The thermodynamic analysis demonstrated that uranium (VI) and thorium (IV) extraction by dipropylamine is an exothermic process. From the stripped liquor (1 M H2SO4), Th and U were precipitated as oxalate and peroxide, respectively, for technological application. Thus, marketable pure thorium and uranium products were prepared in addition to rare earth concentrate.

Assessing Uranium Pollution Levels in the Rietspruit River, Far West Rand Goldfield, South Africa.

The Rietspruit is located in Gauteng Province, South Africa, within the Witwatersrand Basin. The basin is noted for its vast gold deposit. The river extends for about 60 km before joining the Vaal River. The aim of this study was to determine the concentration of uranium in the Rietspruit and the factors that influenced the concentration of U at each of the sites. The source of uranium in the river is the discharge from the gold mine and the mine wastes. Inductively coupled plasma mass spectrometry was used for water and sediment analysis in order to determine the concentration of U. High concentration of U was found in the river water and sediment, which is above the permissible limit of U. The water is used for irrigation of farmlands, cattle watering and for human consumption despite the high concentration of uranium in it. Ingestion of uranium is dangerous to human health. Due to the toxic nature of uranium, consumption of the water for domestic use and agriculture purpose must be discouraged.

Alkaline leaching characteristics of uranium from Lincang coal: Correlation with the dissolution of coal humic substances

The characteristics involving the leachability of uranium from coal by utilizing sodium carbonate-bicarbonate mixtures and the role of coal humic substances dissolution in the leaching procedure were investigated. Alkaline leaching is an effective method to extract uranium from coal without reducing the usability of coal. Under the optimum leaching condition, viz. liquid/solid (L/S) ratio = 20: 1 and [CO32−]/[HCO3−] ratio = 2: 1, the leaching efficiency increases from 80.50 ± 0.24% at 10 °C to 96.29 ± 0.70% at 90 °C with the leaching agent concentration of 0.6 mol/L. As the primary form of uranium in the coal, the organic-bound uranium decreases by 64.95 ± 3.25 mg/kg after leaching at ambient temperature of 25 °C, and is the main source of the alkaline-leached uranium. Besides, the uranium is linearly and significantly correlated with the dissolved organic carbon (DOC) in the leachate (R2 = 0.916, p < 0.01) before the leaching equilibrium. The fluorescence excitation-emission matrix (EEM) analysis, coupled with parallel factor (PARAFAC), peak-picking and fluorescence regional integration (FRI) analysis, shows that the leaching concentration of uranium is closely correlated with the fluorescence components represented humic acid (HA)-like substances in leachate, with R2 values around 0.8 and p < 0.05. Thus, we hypothesize that the dissolution of HA-like substances can be the key factor for the alkaline leaching of uranium from the coal.

Geostatistical analysis of uranium concentrations in North-Western part of Ogun State, Nigeria

Several statistical techniques have been adopted in the analysis and interpretation of radiometric survey data set with little attention to the geostatistical approach. In this study, the geostatistical technique was used to analyse an airborne uranium data set in the North-western part of Ogun state to deduce the autocorrelation level of uranium with the corresponding geological composition through the geostatistical model fitting. Twelve uranium lithological (UL) units were identified and analysed using variogram and kriging. Three variogram models namely; spherical, exponential and gaussian, were utilised. The variogram results showed that the three models fit in the interpretation of uranium data in the order of Spherical < Gaussian < Exponential models for all the UL units except at UL6 which had range (R) values of 4227.3 m, 5318.2 m and 5636.4 m for Gaussian, Spherical and Exponential models, respectively. The Nugget-Sill ratios (NSR) were in the range of 3.57–18.97% for the three models across the 12 UL units. These results indicate strong spatial autocorrelation/dependency of uranium concentration on geological composition. The ordinary kriging estimator revealed that the weathered basement formation has the highest uranium concentration compared to basement and sedimentary formations across the study area. The coefficient of variation results also revealed homogeneity in the uranium source across the UL units. The geostatistics technique is a useful mathematical tool in the analysis and interpretation of uranium concentration in the North-western part of Ogun State.

Uraninite from the Guangshigou Pegmatite-Type Uranium Deposit in the North Qinling Orogen, Central China: Its Occurrence, Alteration and Implications for Post-Caledonian Uranium Circulation

The Guangshigou deposit is the largest pegmatite-type uranium deposit in the Shangdan domain of the North Qinling Orogenic Belt, which is characterized by the enrichment of uraninite hosted in biotite granitic pegmatites. At Guangshigou, uraninite commonly occurs as mineral inclusions in quartz, K-feldspar and biotite or in interstices of these rock-forming minerals with magmatic characteristics (e.g., U/Th &lt; 100, high ThO2, Y2O3 and REE2O3 contents and low concentrations of CaO, FeO and SiO2). It crystallized at 407.6 ± 2.9 Ma from fractionated calc-alkaline high-K pegmatitic melts under conditions of 470–700 °C and 2.4–3.4 kbar as deduced by the compositions of coexisting peritectic biotite. The primary uranium mineralization took place during the Late Caledonian post-collisional extension in the North Qinling Orogen. After this magmatic event, uraninite has experienced multiple episodes of fluid-assisted metasomatism, which generated an alteration halo of mineral assemblages. The alteration halo (or radiohalo) was the result of the combined effects of metamictization and metasomatism characterized by an assemblage of goethite, coffinite and an unidentified aluminosilicate (probably clay minerals) around altered uraninite. This fluid-assisted alteration was concomitant with the albitization of K-feldspar subsequently followed by the coffinitization of uraninite during the major period of 84.9–143.6 Ma, as determined by U-Th-Pb chemical ages. Further investigations revealed that the metasomatic overprinting on uraninite initially and preferentially took place along microcracks or cavities induced by metamictization and promoted their amorphization, followed by the release of U and Pb from structure and the incorporation of K, Ca and Si from the fluids, finally resulting in various degrees of uraninite coffinitization. The released U and Pb were transported by alkali-rich, relatively oxidizing fluids and then re-precipitated locally as coffinite and an amorphous U-Pb-rich silicate under low to moderate temperature conditions (85–174 °C). The compositional changes in primary uraninite, its structure amorphization together with the paragenetic sequence of secondary phases, therefore, corroborate a combined result of intense metamictization of uraninite and an influx of alkali–metasomatic fluids during the Late Mesozoic Yanshanian magmatic event in the region. Hence, the remobilization and circulation of uranium in the North Qinling Orogen was most likely driven by post-Caledonian magmatism and hydrothermal activities related to large-scale tectonic events. In this regards, Paleozoic pegmatite-type uranium mineralization may represent a significant uranium source for Mesozoic hydrothermal mineralization identified in the Qinling Orogenic Belt.

Occurrence of uranopolycrase in pegmatite related to a Jurassic granite pluton in Cheongwon, South Korea: mineral chemistry and texture of a potential source of uranium and radon in a granite aquifer

Occurrence of uranopolycrase in pegmatite related to a Jurassic granite pluton in Cheongwon, South Korea: mineral chemistry and texture of a potential source of uranium and radon in a granite aquifer