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[en] Dequartzification and Na-metasomatism are the first postsolidus transformations in episyenitisation of granites in uraniferous ore deposits. The same transformations have been discovered in granitoids in contact with peralcaline phonolite; these metasomatized granitoids are true fenites. This connection between episyenites and fenites, involve that deep CO2-rich fluids are active in the genesis of these metasomatites; this leads one to propose a close relationship between undersaturated alkali-magmatism and U and therefore a deep, possibly mantellic source, for a part of U. In a first stage, the U which is carried by such magmas or derived products and associated fluids, will be preconcentrated near main crustal distensive faulting; then, by remobilization under usual hydrothermal processes, ore bodies can be generated. This U-alkalinity connection is probably valid for other magma types (as leucogranitic, for instance), when intruding in such setting, just as fluids can be acting on various lithologies: so, different types of uraniferous deposits are related in this comprehensive model. It also explains the localization of episyenites (often near main crustal lineaments) and their frequent association with lamprophyres
[fr]
Les transformations postsolidus premieres (dequartzification, metasomatose sodique...), caracteristiques de l'episyenitisation des granites en contexte uranifere, ont ete retrouvees au contact d'une phonolite peralcaline, dans des granitoides qui se revelent etre de veritables fenites. Ce parallelisme episyenite-fenite implique que des fluides a CO2 d'origine profonde, jouent un role important dans la genese de ces metasomatites et conduit a proposer une liaison entre magmatisme alcalin sous-sature et U, donc une origine profonde voire mantellique, pour une part de celui-ci. L'U porte par de tels magmas ou produits derives et fluides associes, serait preconcentre au voisinage d'accidents de type distensif, puis concentre par le relais de circuits hydrothermaux classiques en des gisements de types divers. Cette liaison alcalinite - U concerne d'autres types de magmas (par exemple, leucogranitiques) mis en place dans des contextes similaires, de meme que le jeu des fluides peut s'exercer sur des lithologies variees: ce modele reunit donc des gites uraniferes actuellement consideres comme tres differents. Il donne en outre, une signification a la localisation des episyenites (souvent a proximite de lineaments importants) et a leur frequente association avec des lamprophyresJournal
Comptes Rendus des Seances de l'Academie des Sciences. Serie 2; ISSN 0249-6305; 
; CODEN CRSUD; v. 302(5); p. 227-232
; CODEN CRSUD; v. 302(5); p. 227-232
[en] The optical and X-ray spectrum microanalysis methods have been used to investigate U-Ni-Co-V-Mo mineral associations in Lower Paleozoic carboniferous siliceous shales. A specific mineral association is found in fracture and cataclasis zones. The association is presented by sulfides and sulfosalts, Fe, Co, Ni, molybdenite, uraninite, Fe, V, Mn oxides. Enrichement with metals is observed in the latter which characterizes zones of Late Paleozoic hydrothermal accumulation
[ru]
Journal
Doklady Akademii Nauk SSSR; ISSN 0002-3264; ; v. 259(1); p. 192-194
; v. 259(1); p. 192-194
[en] A quantitative and precise method for determination of dissolved M (nmol)/kg level in seawater has been developed and used to study the distribution of Mn in the northeast Pacific. Mn concentrations in the surface mixed layer decrease from 1.0 to 0.6 nmol/kg between the central gyre and the western boundary of the California Current, then increase to values from 2 to 6 nmol/kg near the coastal boundary (in contrast to the distribution of 210Pb). Particulate Mn in the surface waters accounts for only about 1% of the total. Vertical distributions of Mn are characterized by surface maxima, minima near 300 m, maxima at mid-depth coinciding with the oxygen minimum and the labile nutrient maxima, and concentrations in Pacific bottom waters of approximately 0.2 nmol/kg. The oceanic distribution of Mn appears to be dominated by external inputs superimposed upon ovberall scavenging which can lead to Mn maxima in (1) the surface waters due to riverine and atmospheric sources; (2) the deep ocean as a result of hydrothermal injection and/or sediment resuspension; and (3) the oxygen minimum region resulting from in-situ breakdown of organic matter, in-situ MnO2 reduction, and/or advective-diffusive transport of dissolved Mn from anoxic slope sediments. (orig.)
Journal
Earth and Planetary Science Letters; ISSN 0012-821X; ; v. 49(1); p. 45-56
; v. 49(1); p. 45-56
[en] A photooxidative system for deep desulfurization of model diesel fuel was explored. Nanoparticles of anatase titania (TiO2) were synthesized via sol-gel hydrothermal method. The TiO2 was further modified with bimetallic Cu-Fe using wet-impregnation method followed by calcination process in order to extend the activity region of the photocatalyst to visible-light. A series of bimetallic 2.2 wt % Cu-Fe/ TiO2 photocatalysts with different Cu:Fe mass compositions were characterized for their physical, chemical and optical properties using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance UV-visible spectroscopy (DR-UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmet-Teller (BET) surface area analysis. The performance of the photocatalysts was evaluated for photooxidation of dibenzothiophene (DBT) as the sulfur species from model oil in the presence of hydrogen peroxide, H2O2 under 500 W visible light illumination. The highest sulfur conversion of 82.36 % was observed for photocatalyst with 10:1Cu:Fe mass composition. (author)
Journal
Malaysian Journal of Analytical Sciences; ISSN 1394-2506; ; v. 20(4); p. 713-725
; v. 20(4); p. 713-725
[en] The formation of hydrothermal uranium concentrations in the Hercynian crystalline basement took place mainly during the Permian. Most of these deposits are spatially and genetically associated with Carboniferous peraluminous leucogranites. They are found either in the central or marginal parts of these granites or in the immediately surrounding metamorphic rocks. Taking the Saint-Sylvestre uranium district as an example it is shown that the incidence and size of ore deposits are strongly influenced by magmatic to late-magmatic processes of uranium concentration in structurally well-defined lineaments. The Permian basins may have provided the formation waters which remobilised or deposited uranium in these structures. The Permian hydrothermal uranium concentrations have in general been remobilised several times, in some cases destroying evidence of the first phase of deposition
[fr]
Le Permien represente la periode majeure pour la formation des concentrations d'uranium hydrothermales dans le socle hercynien. Ces gisements d'uranium sont pour la plupart associes spatialement et genetiquement a des leucogranites peralumineux carboniferes, indifferemment dans leur partie interne, leur peripherie ou encore dans l'encaissant metamorphique immediat. L'exemple du massif de Saint-Sylvestre montre que la localisation et l'importance des gisements sont fortement controlees par les processus de concentration magmatique a tardi-magmatique de l'uranium dans des zones lineamentaires structuralement bien definies. Les bassins permiens ont pu fournir les eaux de formations qui ont conduit a la remobilisation ou au depot de l'uranium dans ces structures. Les concentrations hydrothermales permiennes ont generalement subi une ou plusieurs phases importantes de remobilisation ayant pu, dans certains cas, effacer les evidences de la premiere phase de depotJournal
[en] On the basis of study of temperatures of hydrocarbon precipitation from hydrothermal solutions a conclusion is made on similar temperature conditions of the formation of pitchblende and solid bitumens (anthraxolite, kerite). It is shown that at the temperatures of about 180-200 deg C a coprecipitation of pitchblende and solid bitumens from hydrocarbon-aqueous emulsions takes place, at that, bitumens at first pass through liquid-viscous state and later consolidate, undergoing polymerization and oxidation (sulphuration)
[ru]
Journal
Doklady Akademii Nauk Ukrainskoi SSR. Seriya B, Geologicheskie, Khimicheskie i Biologicheskie Nauki; ISSN 0201-8454; ; (no.5); p. 31-34
; (no.5); p. 31-34
[en] Reduced form exciting factors of governing mineralization are discussed. It is indicated that metallogenic conditions of hydrothermal uranium deposits of reduced form exciting factors governing mineralization are ore-forming solution flow into metallogenic space; Eh decreases significantly, and reach reducing condition of mineral deposit. The exciting factors of governing mineralization are divided into internal reduction subclass and environment reduction subclass. Then emphases on the classification, characteristic, formation condition, representative deposits and prospecting significance in this paper. The environment reduction index is put forward to evaluate reducing power of surrounding rock. (authors)
Journal
Journal of East China Institute of Technology. Natural Science; ISSN 1674-3504; ; v. 31(3); p. 217-222
; v. 31(3); p. 217-222
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