Petrology, mineralogy and geochemistry of surficial uranium deposits

International Nuclear Information System (INIS)

Pagel, M.

1984-01-01

A comprehensive understanding of the petrology, mineralogy, and geochemistry of surficial uranium ore deposits is important for developing prospecting and evaluation strategies. Carnotite is the main uranium mineral and is found in those deposits that have the greatest potential uranium resources. The following uranium-bearing minerals have been reported to occur in surficial deposits: carnotite, tyuyamunite, soddyite, weeksite, haiweeite, uranophane, betauranophane, metaankoleite, torbernite, autunite, phosphuranylite, schroeckingerite, Pb-V-U hydroxide (unnamed mineral), uraninite and organourano complexes. The interrelationships between some of the minerals of the host rocks (especially the clays) are not well understood. (author)

Results of geochemical and mineralogical studies on uranium in Zechstein copper-bearing strata from Lubin-Polkowice area

International Nuclear Information System (INIS)

Bareja, E.

1977-01-01

The paper presents the results of geochemical and mineralogical studies on uranium in Zechstein copper-bearing strata from the Lubin-Polkowice area. It was found that particular lithofacial varietes of Zechstein copper-bearing strata are characterized by different concentration of uranium. The mineralogical studies made possible determination of the nature of uranium mineralization and the interdependence between uranium and lithology of copper-bearing strata. An interesting uranium mineralization was found in tectonic breccias which yield black blende and schroeckingerite as well as calcite, gypsum, pyrite, hematite and geothite. Secondary minerals such as schroeckingerite and geothite evidence intense weathering processes acting in the copper deposit. The highest value of geochemical background of uranium in the copper-bearing series is displayed by basel copper-bearing shales (so called pitch-black shales) - 68.10 x 10 -40 /0 U. Statistical distribution of that element is unimodal. Distribution of uranium is polymodal in basal sandstones of the copper-bearing series. The geochemical background of red-coloured sandstones (Rotliegendes) is low, equalling 0.39 x 10 40 /0 U, whilst that of gray-coloured sandstones (Zechstein) - 2.32 x 10 -40 /0 U. An anomallous population (344.0 x 10 -40 /0 U) found in the case of gray sandstones of the Lubin-Polkowice area evidences the effects of secondary processes on concentration of uranium. In sandstones occur black blende, carburanes as well as calcite, hematite and goethite. A bimodal distribution of uranium was found in carbonate series. Limestones are characterized by low value of geochemical background (Dsub(x1) = 0.78 x 10 -40 /0 U) whilst dolomites by markedly higher values of the background (Dsub(x2) = 2.73 x 10 -40 /0 U). (author)

Description and crystal structure of albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Mereiter, K. [Vienna Univ. of Technology (Austria). Inst. of Chemical Technologies and Analytics

2013-04-15

Albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O, triclinic, space group P anti 1, a = 13.569(2), b = 13.419(2), c = 11.622(2) Aa, α = 115.82(1), β = 107.61(1), γ = 92.84(1) (structural unit cell, not reduced), V = 1774.6(5) Aa{sup 3}, Z = 2, Dc = 2.69 g/cm{sup 3} (for 17.5 H{sub 2}O), is a mineral that was found in small amounts with schroeckingerite, NaCa{sub 3}F[UO{sub 2}(CO{sub 3}){sub 3}](SO{sub 4}).10H{sub 2}O, on a museum specimen of uranium ore from Joachimsthal (Jachymov), Czech Republic. The mineral forms small grain-like subhedral crystals (= 0.2 mm) that resemble in appearance liebigite, Ca{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]. ∝ 11H{sub 2}O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2V = 65(1) (λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO{sub 2} and H{sub 2}O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO{sub 2}(CO{sub 3}){sub 3}]{sup 4-} anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF{sub 2}(O{sub carbonate}){sub 3}(H{sub 2}O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO{sub 6}, CaF{sub 2}O{sub 2}(H{sub 2}O){sub 4}, CaFO{sub 3}(H{sub 2}O){sub 4} and CaO{sub 2}(H{sub 2}O){sub 6} coordination polyhedra. The crystal structure is built up from MgCa{sub 3}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].8H{sub 2}O layers parallel to (001) which