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Sample records for saleeite

  1. Alligator Rivers Analogue project. Geochemical modelling of secondary uranium ore formation. Final Report - Volume 11

    Energy Technology Data Exchange (ETDEWEB)

    Sverjensky, D. [The John Hopkins Univ, Dept of Earth and Planetary Sciences, Baltimore (United States); Bennett, D.G.; Read, D. [W.S. Atkins Science and Technology, Epsom Surrey, (United Kingdom)

    1992-12-31

    The purpose of the present study was to establish how the uranyl phosphate zone at the Koongarra site was formed. The overall approach taken in the present study employed theoretical chemical mass transfer calculations and models that permit investigation and reconstruction of the kinds of waters that could produce the uranyl phosphate zone. These calculations have used the geological and mineralogical data for the Koongarra weathered zone (Volumes 2, 8, and 9 of this series), to constrain the initial compositions and reactions undergone by groundwater during the formation of the uranyl phosphate zone. In carrying out these calculations the present-day analyses of Koongarra waters are used only as a guide to the possible initial composition of the fluids associated with the formation of the phosphate zone. Aqueous speciation, saturation state and chemical mass transfer calculations were carried out using the computer programs EQ3NR and EQ6 (Wolery, 1983; Wolery et al., 1984) and a thermodynamic database generated at The Johns Hopkins University over the last eight years which is tabulated in the Appendix 1 to Volume 12 of this series. Despite uncertainties in the thermodynamic characterisation of species, all the above calculations suggest that the uranyl phosphate zone at Koongarra has not formed from present-day groundwaters (Volume 12 of this series). The present-day groundwaters in the weathered zone (eg. at 13 m depth) appear to be undersaturated with respect to saleeite. Furthermore, as present-day groundwaters descend below the water table they rapidly lose their atmospheric oxygen imprint, as is typical of most groundwaters, and become even more reducing in character. Under these circumstances, the groundwaters become more undersaturated with respect to saleeite than the shallow groundwaters. Because much of the phosphate zone is currently below the water table, under saturated zone conditions, it is suggested in the present study that the uranyl phosphate

  2. The effect of remediation on water from a former Portuguese uranium mine area

    Science.gov (United States)

    Neiva, Ana; Carvalho, Paula; Antunes, Isabel; Santos, António; Cabral-Pinto, Marina

    2016-04-01

    The old Senhora das Fontes uranium mine consists of quartz veins containing autunite down to a depth of 40 m. But below, uraninite, Fe-saleeite and black uranium oxides occur in small veinlets or forming elongated nodules. The mine was exploited underground and was closed down in 1971. However, the ores from this mine and two others were treated by the heap-leach process in this area until 1982. Seven dumps containing 33,800 m3 of material were left in the area. The remediation process was carried out from May 2010 to January 2011. During this process, the relocation of the material deposited in dumps took place and was covered with erosion resisting covers. Groundwater and surface water were collected just before the remediation at November of 2009 and February 2010, in the wet season, at the beginning of the remediation, at May and June of 2010, and also after the remediation, at May and June of 2011, in the dry season. Ten wells, four springs and seven streams were chosen to collect water samples. However, some points were occasionally dry and a total of 113 water samples were obtained. The pH of groundwater and surface water was acid-to-alkaline, before, at the beginning and after the remediation, but decreased with the remediation, whereas Eh increased. In general, the uranium concentration was up to 116 μg/L in groundwater and up to 83 μg/L in surface water, before the remediation, in the wet season. The uranium water concentration increased up to 272 μg/L and 183 μg/L in the former and the latter, respectively, at the beginning of the remediation, in the dry season of 2010, due to remobilization of mine dumps and pyrite and chalcopyrite exposures, which caused the pH decrease. However, the uranium concentration decreased in groundwater and surface water at the north part of the mine area, after the remediation, in the dry season of 2011, but increased in both, particularly in groundwater up to 774 μg/L in the south and southwest parts of the area, due