Formation Of Uranium Deposits Research Articles

Uranium mobility and enrichment during hydrocarbon generation and accumulation processes: A review

Black shale serve as a new uranium sources and provide reducing agents for uranium deposits through hydrocarbon generation. However, the systematically interplay between the black shale and the formation of uranium deposits is not obscure. This paper provides a comprehensive summary and critical assessment of the depositional control factors of uranium in black shales, the extent of uranium migration during hydrocarbon generation, the enrichment of uranium in oil/gas reservoirs, and the relationship between crude oil-natural gas leakage and uranium. The study show that U-riched constituents within black shale persist through mechanisms of adsorption, reduction, complexation, and absorption within matrices rich in phosphates, iron, carbonate minerals, and organic matter. The U in black shale originates from continental weathering, volcanic eruptions, and seabed hydrothermal activities. The average U concentration in black shale is determined by the U content in atmosphere, while its relative content is controlled by the degree of anoxia during the geological historical periods.. Black shale prior to the Late Neoproterozoic period exhibits minimal migration with hydrocarbon substances, whereas black shale post the Late Neoproterozoic period demonstrates migration, with a migration rate ranging approximately between 55 and 75 %. However, the migrated uranium does not accumulate in (ancient) reservoirs. The correlation between hydrocarbon substances and sandstone-type uranium deposit is attributed to the oxygen uptake by hydrocarbons or the thermochemical sulfate reduction (TSR). The study has fundamental significance for further understand the interaction mechanisms between uranium and hydrocarbon substances.

Hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian basin, China

Groundwater is a key medium for the migration and enrichment of elements into ore bodies in sandstone-type uranium deposits, with anomalies of uranium elements and their associated components in water serving as indicators for exploring such deposits. The Erlian Basin, located in central-northern Inner Mongolia, is a crucial production area for sandstone-type uranium deposits in China. The groundwater flow system in the basin plays a significant role in the formation of uranium deposits. To study the hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian Basin, 269 groundwater samples were collected. Hydrogeochemical analysis methods, such as Piper diagrams, Gibbs diagrams, and contour maps, were employed to determine the distribution characteristics and occurrence forms of groundwater uranium in the study area. The primary water chemistry types in the study area were HCO3–Ca•Na, HCO3–Na, HCO3•SO4–Na, and SO4•HCO3–Na•Ca. The distribution range of uranium content in groundwater in the study area was 0.1–453 μg/L (average of 53.08 μg/L). A comprehensive analysis, based on the direction of groundwater flow and changes in the redox environment, suggested that the higher uranium values in groundwater were distributed in the runoff and discharge areas, with uranium anomaly points existing in areas with alternating oxidation and reduction zones. These uranium anomaly points were in good agreement with the known large uranium deposits of Nuheting, Qiharigetu, Daoersu, and others, thereby predicting six other uranium hydrochemical anomaly points as prospective areas for uranium mineralization. The pH value distribution range in the study area's groundwater was 6.8–9.1, and the redox potential (Eh) value range was -126–52 mV, indicating that uranium exists in groundwater in the form of UO2(CO3)34− and UO2(CO3)22−. An increase in bicarbonate (HCO3−) is conducive to uranium dissolution. The enrichment and occurrence forms of uranium in groundwater are influenced by the concentrations of Fe and (Ca2++Mg2+), with uranium precipitation and enrichment occurring as the groundwater evolves and changes in the redox environment. The uranium content in deep wells is higher than in nearby shallow wells, indicating that deep water circulation is beneficial for mineralization. The pH, Eh, HCO3−, Fe, and other hydrogeochemical indicators are indicative of uranium enrichment; thus, they can be considered as reference bases when exploring for potential uranium resources.

The use of lattice defects in quartz to determine provenance and conditions for the formation of sedimentary deposits (using the example of quartz from sedimentary rocks of the Central Kyzylkum)

Research subject. The composition and distribution patterns of lattice defects in the clastic quartz of sedimentary rocks.Material and methods. Quartz collected from the core of two wells uncovering the Neogene, Paleogene and Cretaceous deposits in the rocks of the Central Kyzylkum. The registration and determination of the concentrations of lattice defects in detrital quartz were carried out by the EPR spectroscopy. Their stability in quartz under natural conditions was evaluated by comparing the concentrations of lattice defects in the near-surface and deep zones of quartz grains. The etching of quartz grains in HF was used to study the spatial location of lattice defects in the mineral. The genetic analysis of detrital quartz was carried out using the methods tested in the study of quartz from crystalline rocks.Results. The presence of substitutional Al, Ti, and Ge impurities, radiation induced E1-, Al–O−- and Ti-centers, as well as other paramagnetic centers possessing genetic information was found in quartz. The distribution of substitutional impurities in clastic quartz is close to their original distribution formed at the time of the mineral formation. This creates the prerequisites for identifying genetically similar quartz samples and attributing them to the certain provenance. The formation of sedimentary rocks of the Central Kyzylkum occurred due to two main provenance sources of terrigenous material. The expediency of using radiation induced centers with different thermal stability for studying the radiation prehistory of quartz and the conditions for the formation of uranium deposits is demonstrated.Conclusion. The clastic quartz of sedimentary deposits retains the main part of the genetically significant lattice defects formed during crystallisation. The most important of them are Al, Ti, and Ge isomorphic impurities. The regularities of their distribution, along with the distribution of radiation induced lattice defects in quartz, are able to carry information about the provenance of detrital material and the conditions of sedimentation and associated formation of mineral deposits.

Mesoproterozoic rift sedimentation, fluid events and uranium prospectivity in the Cariewerloo Basin, Gawler Craton, South Australia

ABSTRACTThe Cariewerloo Basin formed in the Mesoproterozoic following assembly of the Gawler Craton, South Australia, and was filled by arenaceous redbeds of the Pandurra Formation. While previous regional-scale work reveals a basin with similar size and sedimentary fill to the Proterozoic Athabasca and Kombolgie basins that host unconformity-related uranium deposits, few details of the Cariewerloo Basin are known. In this study, stratigraphy, petrography, lithogeochemistry, stable isotope geochemistry and 40Ar/39Ar geochronology are integrated to clarify the depositional history of the Pandurra Formation, and to assess fluid events in the basin that could be linked to the formation of uranium deposits. In the study area, the Pandurra Formation was deposited in two eastward-thickening packages that terminate at faulted basement uplifts, interpreted as half-grabens that formed in a continental rift system as the eastern Gawler Craton underwent extension. Deposition occurred between 1575 Ma (latest Hiltaba Suite age) and ca 1490 Ma, the 40Ar/39Ar age of diagenetic illite in the basal Pandurra. Diagenesis involving fluids having δ18O and δ2H values between –2.1 and 3.6‰, and between –66 and –8‰, respectively, occurred at around 150°C. Protracted diagenesis preferentially occurred in the upper Pandurra Formation based on petrography and Pearce Element Ratios that show complete replacement of detrital lithic and feldspathic grains by diagenetic phyllosilicates, and younger 40Ar/39Ar ages between ca 1330 and 1200 Ma that record fluid events later into basin history. Conversely, the basal Pandurra Formation shows better preservation of detrital grains, and older 40Ar/39Ar ages around 1450 Ma that suggest these strata became closed to fluid flow earlier in basin history. Although, based on O-isotope ratios, fluid–rock interaction did not occur in the Cariewerloo Basin to the same extent as that in the Athabasca or Kombolgie basins, it is possible that a uranium deposit formed where the upper Pandurra Formation was in contact with metasedimentary basement units outside the present basin margins.

Possible role of fluids free thermal convection processes in formation of uranium deposits in the Streltsovska ore field (Eastern Trans-Baikal Region)

This paper reports the preliminary results of computer simulation of the free thermal convection of fluids in a residual thermal field of a consolidated shallow magma chamber related to caldera formation. The deeply penetrating thermoconvective circulation of fluids provided conditions for mobilization and transportation of uranium from the vast area under the caldera to the ore deposition sites.

Behavior of isotope (18O/16O, 234U/238U) systems during the formation of uranium deposits of the “sandstone” type

The uneven character of the distribution of 18O/16O and 234U/238U values was established in the vertical cross section of the productive sequence of the Dybryn uranium deposit (Vitim uranium-ore region, Buryatia). Both a deficiency and an excess of 234U in relation to the equilibrium 234U/238U ratio in the vertical sequence may provide evidence for the extremely low rate of the infiltration water flow. The behavior of oxygen isotope characteristics for different size fractions of terrigenous rocks provides evidence for active uranium redistribution and openness of the isotope system of this element during interaction of terrigenous–sedimentary rocks with infiltration waters.

Ulkan-Dzhugdzhur ore-bearing anorthosite-rapakivi granite-peralkaline granite association, Siberian Craton: Age, tectonic setting, sources, and metallogeny

The paper systematizes and integrates the results of geological, isotopic geochronological, and geochemical studies of the igneous rocks that make up the Ulkan-Dzhugdzhur anorthosite-rapakivi granite-peralkaline granite association and related mineralization. This association is a typical example of anorogenic igneous rocks that formed in the within-plate geodynamic setting most likely under effect of the mantle superplume, which was active in the territory of the Siberian Craton 1.75–1.70 Ga ago. The igneous rock association formed in a discrete regime that reflected the pulsatory evolution of a sublithospheric mantle source. The prerift (1736–1727 Ma) and rift proper (1722–1705 Ma) stages and a number of substages are distinguished. All igneous rocks pertaining to this association have mixed mantle-crustal origin. Basic rocks crystallized from the OIB-type basaltic magma, which underwent crustal contamination at various depths. Felsic rocks are products of mantle and crustal magma mixing. The contribution of mantle component progressively increased in a time-dependent sequence: moderately alkaline subsolvus granite → moderately alkaline and alkaline hypersolvus granites → peralkaline hypersolvus granite. All endogenic deposits in the studied district are related to a single source represented by the mantle plume and its derivatives. The Fe-Ti-apatite deposits hosted in anorthosite formed as a result of intense lower crustal contamination of basaltic magma near the Moho discontinuity and two stages of fractional crystallization at lower and upper crustal depth levels. The rare-metal deposits are genetically related to peralkaline granite. Formation of uranium deposits was most likely caused by Middle Riphean rejuvenation of the region, which also involved rocks of the Ulkan-Dzhugdzhur association.

The effects of deformation and permeability variation in controlling the formation of uranium deposits in the Alligator Rivers region, Northern Territory, Australia

The effects of deformation and permeability variation in controlling the formation of uranium deposits in the Alligator Rivers region, Northern Territory, Australia

Characterization of extracellular minerals produced during dissimilatory Fe(III) and U(VI) reduction at 100 °C by Pyrobaculum islandicum

In order to gain insight into the significance of biotic metal reduction and mineral formation in hyperthermophilic environments, metal mineralization as a result of the dissimilatory reduction of poorly crystalline Fe(III) oxide, and U(VI) reduction at 100 degrees C by Pyrobaculum islandicum was investigated. When P. islandicum was grown in a medium with poorly crystalline Fe(III) oxide as an electron acceptor and hydrogen as an electron donor, the Fe(III) oxide was reduced to an extracellular, ultrafine-grained magnetite with characteristics similar to that found in some hot environments and that was previously thought to be of abiotic origin. Furthermore, cell suspensions of P. islandicum rapidly reduced the soluble and oxidized form of uranium, U(VI), to extracellular precipitates of the highly insoluble U(IV) mineral, uraninite (UO(2)). The reduction of U(VI) was dependent on the presence of hydrogen as the electron donor. These findings suggest that microbes may play a key role in metal deposition in hyperthermophilic environments and provide a plausible explanation for such phenomena as magnetite accumulation and formation of uranium deposits at ca. 100 degrees C.

Chlorites: occurrence, genesis and crystal chemistry – introduction

The crystal chemistry and mechanisms of chlorite formation (more particularly the ferrous varieties) are currently attracting growing interest in various fields of application. In oil prospection, this interest is linked to the origin and formation of diagenetic chlorite rims that preserve the quality of sandy reservoirs down to unusual depths of burial. In the nuclear industry, the use of iron containers for the storage of radioactive waste is likely to produce ferrous chlorites by interaction with the clayey barrier within which the waste is stored. The ditrioctahedral and tri-trioctahedral chlorites are also some of the best clay mineral markers of hydrothermal activity leading to the formation of uranium deposits underlying the Proterozoic unconformity that make up the largest current economic reserves.The high chemical and structural variability of chlorite is an obstacle in understanding its mechanism of formation, transformation and alteration. This also applies to the determination of the thermodynamic parameters that are required for digital models based on thermo-kinetic laws.

Reduction of Fe(III), Mn(IV), and toxic metals at 100 degrees C by Pyrobaculum islandicum.

It has recently been noted that a diversity of hyperthermophilic microorganisms have the ability to reduce Fe(III) with hydrogen as the electron donor, but the reduction of Fe(III) or other metals by these organisms has not been previously examined in detail. When Pyrobaculum islandicum was grown at 100 degrees C in a medium with hydrogen as the electron donor and Fe(III)-citrate as the electron acceptor, the increase in cell numbers of P. islandicum per mole of Fe(III) reduced was found to be ca. 10-fold higher than previously reported. Poorly crystalline Fe(III) oxide could also serve as the electron acceptor for growth on hydrogen. The stoichiometry of hydrogen uptake and Fe(III) oxide reduction was consistent with the oxidation of 1 mol of hydrogen resulting in the reduction of 2 mol of Fe(III). The poorly crystalline Fe(III) oxide was reduced to extracellular magnetite. P. islandicum could not effectively reduce the crystalline Fe(III) oxide minerals goethite and hematite. In addition to using hydrogen as an electron donor for Fe(III) reduction, P. islandicum grew via Fe(III) reduction in media in which peptone and yeast extract served as potential electron donors. The closely related species P. aerophilum grew via Fe(III) reduction in a similar complex medium. Cell suspensions of P. islandicum reduced the following metals with hydrogen as the electron donor: U(VI), Tc(VII), Cr(VI), Co(III), and Mn(IV). The reduction of these metals was dependent upon the presence of cells and hydrogen. The metalloids arsenate and selenate were not reduced. U(VI) was reduced to the insoluble U(IV) mineral uraninite, which was extracellular. Tc(VII) was reduced to insoluble Tc(IV) or Tc(V). Cr(VI) was reduced to the less toxic, less soluble Cr(III). Co(III) was reduced to Co(II). Mn(IV) was reduced to Mn(II) with the formation of manganese carbonate. These results demonstrate that biological reduction may contribute to the speciation of metals in hydrothermal environments and could account for such phenomena as magnetite accumulation and the formation of uranium deposits at ca. 100 degrees C. Reduction of toxic metals with hyperthermophilic microorganisms or their enzymes might be applied to the remediation of metal-contaminated waters or waste streams.

The roles of organic matter in the formation of uranium deposits in sedimentary rocks

Because reduced uranium species have a much smaller solubility than oxidized uranium species and because of the strong association of organic matter (a powerful reductant) with many uranium ores, reduction has long been considered to be the precipitation mechanism for many types of uranium deposits. Organic matter may also be involved in the alterations in and around tabular uranium deposits, including dolomite precipitation, formation of silicified layers, iron-titanium oxide destruction, dissolution of quartz grains, and precipitation of clay minerals. The diagenetic processes that produced these alterations also consumed organic matter. Consequently, those tabular deposits that underwent the more advanced stages of diagenesis, including methanogenesis and organic acid generation, display the greatest range of alterations and contain the smallest amount of organic matter. Because of certain similarities between tabular uranium deposits and Precambrian unconformity-related deposits, some of the same processes might have been involved in the genesis of Precambrian unconformity-related deposits. Hydrologic studies place important constraints on genetic models of various types of uranium deposits. In roll-front deposits, oxidized waters carried uranium to reductants (organic matter and pyrite derived from sulfate reduction by organic matter). After these reductants were oxidized at any point in the host sandstone, uranium minerals were reoxidized and transported further down the flow path to react with additional reductants. In this manner, the uranium ore migrated through the sandstone at a rate slower than the mineralizing ground water. In the case of tabular uranium deposits, the recharge of surface water into the ground water during flooding of lakes carried soluble humic material to the water table or to an interface where humate precipitated in tabular layers. These humate layers then established the chemical conditions for mineralization and related alterations. In the case of Precambrian unconformity-related deposits, free thermal convection in the thick sandstones overlying the basement rocks carried uranium to concentrations of organic matter in the basement rocks.

A Model for Formation of Uranium Deposits in Volcanic Rocks: ABSTRACT

Uranium is found in widespread occurrences and several commercial concentrations in volcanic rocks of western North America. Mineral exploration and estimates of potential resources in this frontier geologic environment have been hampered by the lack of a viable genetic model. Geologic, geophysical, and geochemical aspects of numerous deposits are compared and synthesized, and a genetic model is presented that integrates these features. The model includes uranium migration during caldera evolution, and subsequent ground water and diagenetic effects. The comparison and model are enhanced by the availability of large chemical data sets for several example areas, and statistical properties are discussed. Exploration for these deposits should involve close attention to detailed volcanic geology, rock permeability, and trace element chemistry. Significant deposits exist in the intrusive, intra-caldera, outflow, and volcaniclastic environments. The variety of potential host environments is large, and this has presented a bewildering array to the explorationist and to the commodity specialist. Lithogeochemical exploration proves to be more successful than stream sediment studies. End_of_Article - Last_Page 931------------

Environments of Formation of Uranium Deposits: ABSTRACT

Environments of Formation of Uranium Deposits: ABSTRACT