Results 1 - 10 of 94
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[en] The first data on the discovery of Th–Sc mineralization in the pyritic complexes of the Southern Urals are presented. The minerals of Th (thorite) and Sc-containing thorium minerals are described. The conclusion is made that the Th–Sc mineralization formed due to crystallization of a residual melt in the local volume.
[en] Three cost estimating models developed by personnel of the Minerals Availability Field Office of the United States Bureau of Mines for use in developing an order-of-magnitude cost evaluation for the recovery of thorium from domestic deposits are described. The models can be used to calculate the cost, in 1977 dollars, for recovery of thorium contained in (1) thorite vein deposits similar to deposits at Wet Mountain, Colorado, and Lemhi Pass, Idaho, (2) fluviatile placer deposits similar to deposits found in the Piedmont Belt of North and South Carolina, and (3) massive carbonatite deposits similar to those found in the Powderhorn District of Colorado. The basic concepts of the cost models are discussed and a cost format, which can be used for applying the models to specific deposits, is presented
[en] In the central Alborz mountains the eastern portion of the Akapol batholith in Iran with its dikes is characterized in the Mejel valley by a series of radioactive anomalies (to 9000 cps). This area was geologically mapped and petrographic, radiometric and geochemical investigations were carried out. The magmatic relationships between the intrusion phases were investigated geologically, petrographically and petrochemically. It was found that all three intrusion phases could be interpreted as having been differentiated from an alkali magma. Going from the batholith to the peripherial zone and further to the dikes, crystallization proceeds from a basic-intermediate magma to an acid one. The SEE distribution in the magmatic rocks and their rockforming minerals support the evidence of the above mentioned magmatic differentiation. The distribution of uranium and thorium are likewise reflected in this differentiation series. The amount of thorium increases from the main body of the batholith (9 ppm) to the peripheral areas (42 ppm). With increasing differentiation uranium and thorium reach their highest concentration in the dikes. In the Mejel valley the aegirine-alkali granites appear to be the main bearer of the radioactivity with an average of 211 ppm U and 2452 ppm Th. In addition to the submicroscopic accessory minerals with their high procentage of U and Th, uranpyrochlore with an average of 15,67 wt% UO2 and thorite with an average of 44,31 wt% ThO2 were identified as the main sources of uranium and thorium in the aegirine-alkali granite dikes. (orig./HP)
[de]Der Akapol-Batholith des zentralen Alborz-Gebirges im Iran zeichnet sich an der oestlichen Seite mit seinen gangfoermigen Differentiationsprodukten durch eine Reihe von radioaktiven Anomalien (bis 9000 cps) im Mejel-Tal aus. Dieses Gebiet wurde geologisch kartiert sowie petrographisch, radiometrisch und geochemisch untersucht. Das Massiv ist von seinem Gesteinsrahmen im Mejel-Tal durch eine konkordante kontaktmetamorphe Marmorzone scharf abgegrenzt. Geologisch, petrographisch und petrochemisch wurden die magmatischen Zusammenhaenge zwischen drei Intrusionsphasen untersucht. Dabei stellte sich heraus, dass alle drei Intrusionen als Differentiationsfolge alkalischer Magmen aufzufassen sind, die vom Koerper zum Rand des Batholithen und weiter in den Gaengen sich durch Kristallisations-Differentiation von basisch-intermediaeren Gliedern zu sauren Differentiaten entwickeln. Die SEE-Verteilung in den magmatischen Gesteinen und in ihren gesteinsbildenden Mineralien unterstuetzt die Aussage ueber die obengenannte magmatische Spezialisierung. Die Verteilung von Uran und Thorium spiegelt sich ebenfalls in dieser Differentiationsabfolge wider. Der Th-Gehalt nimmt vom Koerper des Batholithen (9 ppm) zu der Randzone hin (42 ppm) zu. Bei zunehmender Differentiation in den Ganggesteinen erreichen Uran und Thorium ihre hoechste Konzentration. Als Haupttraeger der Radioaktivitaet im Mejel-Tal treten die Aegirinalkaligranite mit durchschnittlich 211 ppm U und 2452 ppm Th in Erscheinung. Neben den submikroskopischen Akzessorien mit ihrem hohen Anteil an U und Th in den gesteinsbildenden Mineralien wurden als Traeger des Urans Uranpyrochlor mit einem Gehalt von durchschnittlich 15,67 UO2 Gew.-% und des Thoriums Thorit mit einem Gehalt von 44,31 ThO2 Gew.-% in den Aegirinalkaligranitgaengen identifiziert. (orig./HP)
[en] Nodules of thorium-rich hydrocarbon are recorded in sandstone sequences from several basins. The hydrocarbon nodules contain mineral inclusions, particularly of thorite or monazite. There is evidence both for accretion of hydrocarbons around detrital heavy mineral grains and for epigenetic growth by interaction of hydrocarbons with thorium-bearing fluids. Both mechanisms depend upon the precipitation of solid hydrocarbons induced by irradiation from thorium. The nodules exhibit aggressive replacement of other grains, a characteristic of radioanomalous hydrocarbons. The occurrence of the nodules is dependent upon an appropriate (plutonic) source for the thorium, but given this constraint they are important evidence for hydrocarbon migration pathways. (author)
[en] Radioactive albitites at the northern contact of the Ilimaussaq intrusion are poor in thorium compared with uranium. They may have a high content of niobium. During field work in 1979 radioactive albitites were discovered at Sdr. Siorarssuit in the quartzites bordering the south-western contact of the intrusion. A preliminary account of the radioactive albitites at Agpat and Sdr. Siorarssuit is presented. (author)
[en] The paper deals with the analysis of sequence of formation and paragenetic relationship of coffinite with minerals of the zircon group from the crystal chemistry viewpoint. In different by genesis uranium ore deposits the coffinite, zircon and apatite association (more seldom with uraninite and thorite), is known. Coffinite under hydrothermal mineral formation is unable to metasomatically substitute zricon. In the isostructural silicates triad: zircon-thorite-coffinite a limited isomorphism is permissible in the zircon-thorite pair, it has not been observed in the zircon-coffinite pair. The specific features of paragenetic relationship of the zircon group minerals is explained by crystal-chemistry data. It is considered that uranium is the so called f-element. In its bond with anions electrons of f-level which are absent in Zr4+ and Th4+ participate. This fact can be the reason of isomorphism absence of between Zr4+ and U4+ while it to some extent is manifested by the Zr4+-Th4+ pair
[en] This paper documents additional results of laboratory studies, including SEM-EDS and isotope analyses, and discusses mineral associations in the following: 1. selected mafic, felsic, hybrid and ore grade rocks; 2. mineralized gneissic and white heterogenous pegmatites; 3. mineralized pegmatites associated with quartzite and with pyrite-bearing biotite gneisses; 4. mineralized migmatites associated with microcline pegmatites; 5. pegmatites associated with mafic skarn and biotite gneisses. Mineralization occurs in primary and secondary minerals. Uranium mineralization occurs in contact zones between microcline pegmatite and paragneisses, as well as between paleosome and neosome phases. Radioactive REE-bearing occurrences are common at contacts between the pegmatite and mafic skarn
[en] Detailed characterization of Th–REE mineralization confined to terrigenous deposits of the Shatak complex is presented. For the first time the veinlet xenotime mineralization, unknown in the scientific literature, as well as diverse unidentified Th–REE compounds of variable composition were described in terrigenous deposits. It was concluded that permanent Th and REE admixtures and rare-earth minerals and thorite, respectively, as well as the occurrence of paragenetic intergrowths of Th and REE minerals of variable composition, are evidence that Th–REE mineralization crystallized as a result of the influence of the fluid phase on the sedimentary substrate upon magmatic melt intrusion into the frame rocks. The superimposed dynamothermal greenschist-facies metamorphism led to decay of metastable Th–REE phases without affecting significantly the redistribution of thorium and rare earth elements.