Sample records for uranothorite
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Energetics of a uranothorite (Th 1–xU xSiO 4) solid solution
DOE Office of Scientific and Technical Information (OSTI.GOV)
Guo, Xiaofeng; Szenknect, Stephanie; Mesbah, Adel
High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO 4) x–(ThSiO 4) 1–x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO 4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. Furthermore, variations in unit cell parameters and negative excess volumesmore » of mixing, coupled with strongly exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.« less
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Energetics of a uranothorite (Th 1–xU xSiO 4) solid solution
Guo, Xiaofeng; Szenknect, Stephanie; Mesbah, Adel; ...
2016-10-11
High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO 4) x–(ThSiO 4) 1–x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO 4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. Furthermore, variations in unit cell parameters and negative excess volumesmore » of mixing, coupled with strongly exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.« less
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Purification of uranothorite solid solutions from polyphase systems
NASA Astrophysics Data System (ADS)
Clavier, Nicolas; Szenknect, Stéphanie; Costin, Dan Tiberiu; Mesbah, Adel; Ravaux, Johann; Poinssot, Christophe; Dacheux, Nicolas
2013-10-01
The mineral coffinite, nominally USiO4, and associated Th1-xUxSiO4 uranothorite solid solutions are of great interest from a geochemical point of view and in the case of the direct storage of spent nuclear fuels. Nevertheless, they clearly exhibit a lack in the evaluation of their thermodynamic data, mainly because of the difficulties linked with their preparation as pure phases. This paper thus presents physical and chemical methods aiming to separate uranothorite solid solutions from oxide additional phases such as amorphous SiO2 and nanometric crystallized Th1-yUyO2. The repetition of centrifugation steps envisaged in first place was rapidly dropped due to poor recovery yields, to the benefit of successive washings in acid then basic media. Under both static and dynamic flow rates (i.e. low or high rate of leachate renewal), ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy) analyses revealed the systematic elimination of Th1-yUyO2 in acid media and of SiO2 in basic media. Nevertheless, two successive steps were always needed to reach pure samples. On this basis, a first cycle performed in static conditions was chosen to eliminate the major part of the accessory phases while a second one, in dynamic conditions, allowed the elimination of the residual impurities. The complete purification of the samples was finally evidenced through the characterization of the samples by the means of PXRD (Powder X-Ray Diffraction), SEM (Scanning Electron Microscopy) observations and X-EDS (X-Ray Energy Dispersive Spectroscopy) analyses.
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Magmatic and hydrothermal R.E.E. fractionation in the Xihuashan granites (SE China)
NASA Astrophysics Data System (ADS)
Maruéjol, Patricia; Cuney, Michel; Turpin, Laurent
1990-11-01
The Xihuashan stock (South Jiangxi, China) is composed of cogenetic granitic units (granites Xe, γa, γc, γd and γb) and emplaced during the Yanshanian orogeny (153±0.2 Ma). They are two feldspars, Fe-rich biotite±garnet and slightly peraluminous granites. Primary accessory minerals are apatite 1, monazite, zircon, uranothorite±xenotime in granites Xe and γa, zircon, uranothorite, uraninite, betafite, xenotime 1; hydrothermal minerals are monazite altered into parisite and apatite 2, Y-rich parisite, yttroparisite, Y-rich fluorite and xenotime 2 in granites γc and γb. Petrographic observations, major element, REE, Y and Rb-Sr isotropic data point to a magmatic suite (granites Xe and γa → granites γc and γd → granite γb) distinct from hydrothermal Na-or K-alteration of γb. From granite Xe to granite γb, LREE, Eu, Th and Zr content are strongly depleted, while HREE, Y and U content increase. During K-alteration of γb, these variations are of minor importance. Major and accessory mineral evidences, geochemical and fluid inclusion results indicate two successive alteration fluids interacting with γb, (1) a late-magmatic F- and CO2-rich fluid and (2) a post-magmatic, aqueous and slightly saline fluid. The depletion of LREE and Th content and the increase in HREE, Y and U content correspond, in the magmatic suite to the early fractionation of monazite in the granites where there is no hydrothermal alteration (granites Xe and γe) and to the hydrothermal alteration of monazite into parisite and secondary apatite, intense new formation of yttroparisite, Y enrichment and U loss in the uranothorite and late crystallization of uraninite in the granites γc and γb. Moreover, simulated crystallization of monazite and temperature of monazite saturation show early fractionation of monazite from the magma in the less evolved granites (Xe and γe) and prevailing hydrothermal leaching of monazite in the most evolved granites (γc-γd and γb) related to a late-magmetic event. The slight variations of REE, Y, Th and U content in the K-altered granites compared to granite γb emphazes the distinct chemical nature of the successive hydrothermal fluids. Rb-Sr and Sm-Nd isotopic results point to a 30 Ma period of time between the late-magmatic and the post-magmatic fluid circulation.
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NASA Astrophysics Data System (ADS)
Lira, Raul; Ripley, Edward M.
1990-03-01
The Rodeo de Los Molles rare earth element (REE) and thorium deposit is located in granitic rocks of the Las Chacras-Piedras Coloradas Batholith, in the southern block of the Eastern Pampean Ranges, Central Argentina. Mineralization occurs within an elongate (2 km × 0.6 km) body of alkalifeldspar granite (alaskite) localized along the northeastern edge of a composite batholith. The surrounding lithology is predominantly a biotite monzogranite. Both the alaskite and localized areas of quartz alkalifeldspar syenite within the alaskite have been produced by hydrothermal alteration of a late-crystallizing phase of the monzogranite. REE minerals are primarily of the cerium group and include britholite and allanite, both partially replaced by bastnaesite or thorbastnaesite. These minerals occur as nodules with quartz, fluorite, aegirine-augite, sphene, and Fe-Ti oxides within aplitic to pegmatoidal quartz alkalifeldspar syenite. Uranothorite, along with a second generation of fluorite and minor amounts of MnBa oxides, occurs in the alaskite as nodules, or within quartz-lined miarolitic cavities, but is not found with the Ce-mineralization. Studies of fluid inclusions contained in quartz and fluorite indicate a complex history of open-system fluid migration and interaction with monzogranite host rocks. Fluids responsible for REE mineralization and quartz deposition, along with initial alteration of the monzogranite to alaskite and quartz alkalifeldspar syenite, were of relatively high temperature (T h of fluid inclusions in quartz = 356-535°C) and moderate salinity (15-25 eq. wt% NaCl). Mixed CO 2H 2O fluids (XCO 2 = .13-.07) found as both primary and secondary inclusions within fluorite are representative of fluids involved in the replacement of britholite-allanite by bastnaesite and sphene, aegirine-augite, and plagioclase by calcite. Minimum pressures of mineral deposition estimated from H 2OCO 2NaCl phase relations range from 1 to 2 kbars. Secondary aqueous fluid inclusions in quartz define a trend of low salinity-high temperature to high salinity-low temperature, thought to be a result of hydration reactions occurring in alaskite and quartz alkali-feldspar syenite. The highest salinity fluids (35-37 eq. wt% NaCl) detected in the area are associated with the formation of uranothorite and late fluorite. Multiple periods of hydrothermal fluid introduction are consistent with recent geological data that indicate that the batholith is composed of several stock-like bodies. The location of the mineralized area near the top of the magma chamber, the presence of numerous miarolitic cavities, and the bulk composition of inclusion fluids (Na ≥ K > Ca) suggest that the fluids responsible for REE and Th mineralization were of magmatic origin.
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Reconnaissance for uranium and thorium in Alaska, 1954
Matzko, John J.; Bates, Robert G.
1957-01-01
During 1954 reconnaissance investigations to locate minable deposits of uranium and thorium in Alaska were unsuccessful. Areas examined, from which prospectors had submitted radioactive samples, include Cap Yakataga, Kodiak Island, and Shirley Lake. Unconcentrated gravels from the beach at Cape Yakataga average about 0.001 percent equivalent uranium. Uranothorianite has been identified by X-ray diffraction data and is the principal source of radioactivity in the Cape Yakataga beach sands studied; but the zircon, monazite, and uranothorite are also radioactive. The black, opaque uranothorianite generally occurs as minute euhedral cubs, the majority of which will pass through a 100-mesh screen. The bedrock source of the radioactive samples from Kodiak Island was not found; the maximum radioactivity of samples from the Shirley Lake area was equivalent to about 0.02 percent uranium. Radiometric traverses of the 460-foot level of the Garnet shaft of the Nixon Fork mine in the Nixon Fork mining district indicated a maximum of 0.15 mr/hr. In the Hot Springs district, drill hole concentrates of gravels examined contained a maximum of 0.03 percent equivalent uranium. A radioactivity anomaly noted during the Survey's airborne reconnaissance of portions of the Territory during 1954 is located in the Fairhaven district. A ground check disclosed that the radioactivity was due to accessory minerals in the granitic rock.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Haruna, I. V., E-mail: vela_hi@yahoo.co.uk; Orazulike, D. M.; Ofulume, A. B.
Zing-Monkin area, located in the northern part of Adamawa Massif, is underlain by extensive exposures of moderately radioactive granodiorites, anatectic migmatites, equigranular granites, porphyritic granites and highly radioactive fine-grained granites with minor pegmatites. Selected major and trace element petrochemical investigations of the rocks show that a progression from granodiorite through migmatite to granites is characterised by depletion of MgO, CaO, Fe{sub 2}O{sub 3,} Sr, Ba, and Zr, and enrichment of SiO{sub 2} and Rb. This trend is associated with uranium enrichment and shows a chemical gradation from the more primitive granodiorite to the more evolved granites. Electron microprobe analysis showsmore » that the uranium is content in uranothorite and in accessories, such as monazite, titanite, apatite, epidote and zircon. Based on petrochemical and mineralogical data, the more differentiated granitoids (e.g., fine-grained granite) bordering the Benue Trough are the immediate source of the uranium prospect in Bima Sandstone within the Trough. Uranium was derived from the granitoids by weathering and erosion. Transportation and subsequent interaction with organic matter within the Bima Sandstone led to precipitation of insoluble secondary uranium minerals in the Benue Trough.« less
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Orgün, Y; Altinsoy, N; Sahin, S Y; Güngör, Y; Gültekin, A H; Karahan, G; Karacik, Z
2007-06-01
This paper represents the first reports on the natural and anthropogenic radionuclides in Kestanbol granitic pluton and surrounding rocks, and coastal region of the Ezine town. To assess the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate and the external hazard index were calculated, and in situ gamma dose rates were measured. The high-activity concentrations were measured in the pluton and sands, which was originated mainly from the pluton, due to the presence of zircon, allanite, monazite, thorite, uranothorite and apatite. The average activity concentrations of (238)U, (232)Th and (40)K are 174.78, 204.69 and 1171.95 Bq kg(-1) for pluton, and 290.36, 532.04 and 1160.75 Bq kg(-1) for sands, respectively. (137)Cs in Ezine region ranged from 0-6.57 Bq kg(-1). The average absorbed dose rate for the granitic and sand samples were calculated to be 251.6 and 527.92 nGy h(-1), respectively. The maximum contribution to the total absorbed gamma dose rate in air was due to the (232)Th (52.3% for pluton and 67.1% for sands). The Raeq activities of the pluton and sands are higher than the recommended maximum value of 370 Bq kg(-1) criterion limit of Raeq activity for building materials.
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Slack, J.F.; Aleinikoff, J.N.; Belkin, H.E.; Fanning, C.M.; Ransom, P.W.
2008-01-01
Small polycrase-titanite veins 0.1-2 mm thick cut the tourmalinite feeder zone in the deep footwall of the Sullivan Pb-Zn-Ag deposit, southeastern British Columbia. Unaltered, euhedral crystals of polycrase and titanite 50-100 ??m in diameter are variably replaced by a finer-grained alteration-induced assemblage composed of anhedral polycrase and titanite with local calcite, albite, epidote, allanite, and thorite or uranothorite (or both). Average compositions of the unaltered and altered polycrase, as determined by electron-microprobe analysis, are (Y0.38 REE0.49 Th0.10 Ca0.04 Pb0.03 Fe0.01U0.01) (Ti1.48 Nb0.54 W0.04 Ta0.02)O6 and (Y0.42 REE0.32 Th0.15 U0.06 Ca0.04 Pb0.01 Fe0.01) (Ti1.57 Nb0.44 W0.04 Ta0.02)O6, respectively. The unaltered titanite has, in some areas, appreciable F (to 0.15 apfu), Y (to 0.40 apfu), and Nb (to 0.13 apfu). SHRIMP U-Pb geochronology of eight grains of unaltered polycrase yields a weighted 207Pb/206Pb age of 1413 ?? 4 Ma (2??) that is interpreted to be the age of vein formation. This age is 50-60 m.y. younger than the ca. 1470 Ma age of synsedimentary Pb-Zn-Ag mineralization in the Sullivan deposit, which is based on combined geological and geochronological data. SHRIMP ages for altered polycrase and titanite suggest later growth of minerals during the ???1370-1320 Ma East Kootenay and ???1150-1050 Ma Grenvillian orogenies. The 1413 ?? 4 Ma age for the unaltered polycrase in the veins records a previously unrecognized post-ore (1370 Ma) mineralizing event in the Sullivan deposit and vicinity. The SHRIMP U-Pb age of the polycrase and high concentrations of REE, Y, Ti, Nb, and Th in the veins, together with elevated F in titanite and the absence of associated sulfides, suggest transport of these high-field-strength elements (HFSE) by F-rich and S-poor hydrothermal fluids unrelated to the fluids that formed the older Fe-Pb-Zn-Ag sulfide ores of the Sullivan deposit. Fluids containing abundant REE, HFSE, and F may have been derived from a geochemically specialized magma such as those that form alkaline granites, pegmatites, or carbonatites. In an alternative model. preferred here, these fluids were associated with a rift-related, crustal metasomatic event in the region. Determination of a Mesoproterozoic age for the polycrase-titanite veins establishes the first known occurrence of pre-Grenvillian REE-rich mineralization in the Belt-Purcell basin.