Behavior of uranium under conditions of interaction of rocks and ores with subsurface water     

B. I. Omel’yanenko  V. A. Petrov  V. V. Poluektov 《Geology of Ore Deposits》2007,49(5):378-391

The behavior of uranium during interaction of subsurface water with crystalline rocks and uranium ores is considered in connection with the problem of safe underground insulation of spent nuclear fuel (SNF). Since subsurface water interacts with crystalline rocks formed at a high temperature, the mineral composition of these rocks and uranium species therein are thermodynamically unstable. Therefore, reactions directed toward the establishment of equilibrium proceed in the water-rock system. At great depths that are characterized by hindered water exchange, where subsurface water acquires near-neutral and reducing properties, the interaction is extremely sluggish and is expressed in the formation of micro- and nanoparticles of secondary minerals. Under such conditions, the slow diffusion redistribution of uranium with enrichment in absorbed forms relative to all other uranium species is realized as well. The products of secondary alteration of Fe- and Ti-bearing minerals serve as the main sorbents of uranium. The rate of alteration of minerals and conversion of uranium species into absorbed forms is slow, and the results of these processes are insignificant, so that the rocks and uranium species therein may be regarded as unaltered. Under reducing conditions, subsurface water is always saturated with uranium. Whether water interacts with rock or uranium ore, the equilibrium uranium concentration in water is only ≤10^?8 mol/l. Uraninite ore under such conditions always remains stable irrespective of its age. The stability conditions of uranium ore are quite suitable for safe insulation of SNF, which consists of 95% uraninite (UO₂) and is a confinement matrix for all other radionuclides. The disposal of SNF in massifs of crystalline rocks at depths below 500 m, where reducing conditions are predominant, is a reliable guarantee of high SNF stability. Under oxidizing conditions of the upper hydrodynamic zone, the rate of interaction of rocks with subsurface water increases by orders of magnitude and subsurface water is commonly undersaturated with uranium. Uranium absorbed by secondary minerals, particularly by iron hydroxides and leucoxene, is its single stable species under oxidizing conditions. The impact of oxygen-bearing water leads to destruction of uranium ore. This process is realized simultaneously at different hypsometric levels even if the permeability of the medium is variable in both the lateral and vertical directions. As a result, intervals containing uranyl minerals and relics of primary uranium ore are combined in ore-bearing zones with intervals of completely dissolved uranium minerals. A wide halo of elevated uranium contents caused by sorption is always retained at the location of uranium ore entirely destroyed by weathering. Uranium ore commonly finds itself in the aeration zone due to technogenic subsidence of the groundwater table caused by open-pit mining or pumping out of water from underground mines. The capillary and film waters that interact with rocks and ores in this zone are supplemented by free water filtering along fractures when rain falls or snow is thawing. The interaction of uranium ore with capillary water results in oxidation of uraninite, accompanied by loosening of the mineral surface, formation of microfractures, and an increase in solubility with enrichment of capillary water in uranium up to 10^?4 mol/l. Secondary U(VI) minerals, first of all, uranyl hydroxides and silicates, replace uraninite, and uranium undergoes local diffusion redistribution with its sorption by secondary minerals of host rocks. The influx of free water facilitates the complete dissolution of primary and secondary uranium minerals, the removal of uranium at the sites of groundwater discharge, and its redeposition under reducing conditions at a greater depth. It is evident that the conditions of the upper hydrodynamic zone and the aeration zone are unfit for long-term insulation of SNF and high-level wastes because, after the failure of containers, the leakage of radionuclides into the environment becomes inevitable.  相似文献   

Early Paleozoic gabbro-granitoid associations in eastern segment of the Mongolian-Okhotsk foldbelt (Amur River basin): Age and tectonic position     

A. A. Sorokin  A. B. Kotov  E. B. Sal’nikova  N. M. Kudryashov  V. P. Kovach 《Stratigraphy and Geological Correlation》2007,15(3):241-257

Magmatic rocks of the Pikan and Un’ya massifs situated in eastern segment of the Mongolian-Okhotsk foldbelt are studied using isotopic-geochronological (U-Pb zircon dating) and geochemical methods. Two rock complexes different in age are recognized in the Pikan massif: the high-Al gabbro-tonalite association of the Middle Ordovician (468 ± Ma) and granodiorite-granite association of the Late Silurian-Early Devonian (415 ± 7 Ma). The Late Ordovician age (454 ± 5 Ma) is established for leucocratic granites of the Un’ya massif. As is suggested, the Pikan and Un’ya massifs are “allogenic blocks” detached from continental framework of the Mongolian-Okhotsk foldbelt and tectonically emplaced into the foldbelt structure at the last stage of its development.  相似文献   

Formation of the composition and quality of carbonate mineral water of the Elburgan water bearing complex (Essentuki Town)     

K. E. Pit’eva  M. A. Fortygina  A. V. Mikheev 《Moscow University Geology Bulletin》2007,62(4):277-285

The problems of underground water formation in the Elburgan water bearing stratum in conditions close to a marine sedimentation basin are considered in this article. As well, we consider variations in water composition under the influence of mixing with ground waters during water pumping for commercial purposes, and the deterioration of water quality caused by a decrease in the mineralization of mixture, considered with respect to the degree of mineralization accepted for waters used for medical purposes.  相似文献   

Geochemistry and age of metamorphic rocks of the Khavyven Highland,eastern Kamchatka     

I. A. Tararin  Z. G. Badredinov  S. I. Dril’ 《Geochemistry International》2007,45(9):882-899

The metamorphic rocks of the Khavyven Highland in eastern Kamchatka were determined to comprise two complexes of metavolcanic rocks that have different ages and are associated with subordinate amounts of metasediments. The complex composing the lower part of the visible vertical section of the highland is dominated by leucocratic amphibole-mica (±garnet) and epidote-mica (±garnet) crystalline schists, whose protoliths were andesites and dacites and their high-K varieties of the island-arc calc-alkaline series. The other complex, composing the upper part of the vertical section, consists of spilitized basaltoids transformed into epidote-amphibole and phengite-epidote-amphibole green schists, which form (together with quartzites, serpentinized peridotites, serpentinites, and gabbroids) a sea-margin ophiolitic association. The high LILE concentrations, high K/La, Ba/Th, Th/Ta, and La/Nb ratios, deep Ta-Nb minima, and low (La/Yb)_N and high ⁸⁷Sr/⁸⁶Sr ratios of the crystalline schists of the lower unit are demonstrated to testify to their subduction nature and suggest that their protolithic volcanics were produced in the suprasubduction environment of the Ozernoi-Valaginskii (Achaivayam-Valaginskii) island volcanic arc of Campanian-Paleogene age. The green schists of the upper unit show features of depleted MOR tholeiitic melts and subduction melts, which cause the deep Ta-Nb minima, and low K/La and ⁸⁷Sr/⁸⁶Sr ratios suggesting that the green schists were formed in a marginal basin in front of the Ozernoi-Valaginskaya island arc. Recently obtained K-Ar ages in the Khavyven Highland vary from 32.4 to 39.3 Ma and indicate that the metamorphism of the protolithic rocks occurred in the Eocene under the effect of collision and accretion processes of the arc complexes of the Ozernoi-Valaginskii and Kronotskii island arcs with the Asian continent and the closure of forearc oceanic basins in front of them. The modern position of the collision suture that marks the fossil subduction zone of the Ozernoi-Valaginskii arc and is spatially restricted to the buried Khavyven uplift in the Central Kamchatka Depression, which is characterized by well-pronounced linear gravity anomalies.  相似文献   

Corundum-group minerals in rocks of the Khibiny alkaline pluton,Kola Peninsula     

Yu. A. Mikhailova  N. G. Konopleva  V. N. Yakovenchuk  G. Yu. Ivanyuk  Yu. P. Men’shikov  Ya. A. Pakhomovsky 《Geology of Ore Deposits》2007,49(7):590-598

Five minerals of the corundum group have been identified in the Khibiny pluton with certainty. Corundum proper and karelianite occur only in hornfels after volcanic and sedimentary rocks. Xenoliths of hornfels mark the ring faults that bound foidalite within the field of foyaite. Hematite occurs in hydrothermally altered nepheline syenite and crosscutting hydrothermal veins related to the ring faults. Minerals of the ilmenite-pyrophanite series are present in all rocks of the pluton, including veins. Accessory ilmenite in foyaite varies from the manganese variety and pyrophanite in the inner and outer parts of the pluton to manganese-free ilmenite in zone of the Main Ring Fault. In xenoliths of volcanic rocks and alkaline ultramafic rocks, ilmenite is enriched in magnesium. The zoning in distribution of the above-mentioned minerals and the character of variation in their compositions from margins of the pluton to its center are consistent with the petrochemical zoning formed as a result of foyaite alteration of near ring faults.  相似文献   

Construction of a depth-velocity model using migration methods of seismic section transformation     

P. S. Vasil’ev 《Moscow University Geology Bulletin》2007,62(1):49-54

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Changing poverty distribution in Bolivia: the role of rural–urban migration and urban services     

Greg O’Hare  Sara Rivas 《GeoJournal》2007,68(4):307-326

Bolivia is a country with high levels of poverty and inequality among its peoples and regions. For the nation and its urban and rural areas, trends in the social and spatial distribution of poverty (and extreme poverty) are identified from 1976 to 2003 using UBN data with minor support where appropriate from poverty lines. The main survey between 1992 and 2001 uses composite and selected UBN to track detailed poverty change for the country’s nine departments, its ten largest cities and a selection of other smaller urban and rural municipalities. Because of rising background increases in population in the various surveyed administrative units, many instances of relative reductions in poverty are accompanied by rising absolute increases. Marked spatial variations in poverty and development in the country over the last several decades are identified as the main driver for the country’s quickening pace of rural–urban migration. As a result, the paper concludes by assessing two different but closely related views. One investigation tests the notion that because more poor people have been living in Bolivia’s cities than in its rural areas since the mid to late 1990s, rapid rural–urban migration has simply shifted the locus of poverty from the countryside to the cities in a process called, the ‘urbanisation of poverty.’ A second, more challenging, investigation assesses the view that the flow of poor rural people to the better serviced urban areas of Bolivia has actually acted to alleviate national poverty levels.  相似文献   

Hydrothermally altered hyaloclastites at the Earth’s surface in the rift zone of Iceland: Problem of the biochemogenic accumulation of trace elements     

A. R. Geptner  T. A. Ivanovskaya  E. V. Pokrovskaya  S. M. Lyapunov  A. T. Savichev  A. V. Gorbunov  N. V. Gor’kova 《Lithology and Mineral Resources》2007,42(5):453-476

Results of the mineral and chemical study of surface-altered hyaloclastites from the Theistareykir and Nämafjall geothermal zones, the North Iceland rift, are considered. The paper scrutinizes the composition of hydrothermally altered rocks mainly consisting of clay minerals related to the transformation of bedrock hyaloclastites. The clay minerals also make up slope talus or proluvial deltas around highlands. The major clay minerals in areas of the present-day fumarole activity are kaolinite and smectite, while the redeposited talus-proluvial sediments are mainly composed of smectites. The studied rocks contain framboids, globules, rods, and other structures with morphology and size similar to those of mineralized bacteria. The local concentration of Ag in proluvial deposits is attributed to the intense bacterial activity. It is supposed that elevated contents of some trace elements could be related to an intense microbiotic influence.  相似文献   

Urban effect on the formation of the Moskva River environmental state (historical aspect)     

N. M. Shchegol’kova 《Water Resources》2007,34(2):217-228

Results of long-term monitoring of water quality parameters of the Moskva River section within the limits of the city are generalized. The dynamics in quality parameters of the water entering the city wastewater treatment plants, purified effluents of the treatment plants, and river water is analyzed. A relationship between the concentration of organic matter in the river water at the exit from the city and WWTP capacity is demonstrated. Periods of unfavorable environmental state of the river in terms of oxygen regime are singled out based on oxygen regime dynamics. Variations in the river self-purification process are shown. It is stated that purified effluents of the WWTP are a component of the city hydrological system.  相似文献   

Dynamics of the radiation belt formed by solar protons during magnetic storms     

L. L. Lazutin  S. N. Kuznetsov  A. N. Podorol’skii 《Geomagnetism and Aeronomy》2007,47(2):175-184

Experimental proofs of the existence of the formation and destruction mechanisms of solar proton belts in the inner magnetosphere at a rapid change in the penetration boundary of solar protons are presented. An analysis of the measurements of solar protons and alpha-particles on board the Coronas-F low-altitude polar satellite during the magnetic storms in October–November 2003 is performed. During this period, formation and destruction of the belts of solar cosmic rays was observed several times. The compression of the magnetosphere during a storm makes possible the direct penetration of solar protons deep into the inner magnetosphere. The proton trajectories outside the penetration boundary are open, and the preliminary captured particles can easily leave the magnetosphere. During the recovery of the magnetospheric configuration, when the penetration boundary goes away from the Earth, the solar protons and alpha-particles with relatively low velocity of the magnetic drift remain stably captured, whereas the particles of higher energies follow the motion of the penetration boundary. That is why the energy range of the captured protons is limited from above in contrast to the effect of injection during ineffective SC in the low-energy region.  相似文献